Periportal low attenuation associated with liver metastasis from colorectal cancer: evaluation using multi-detector-row CT with pathological correlation.

PubMed

Takaji, Ryo; Matsumoto, Shunro; Kiyonaga, Maki; Yamada, Yasunari; Mori, Hiromu; Iwashita, Yukio; Ohta, Masayuki; Inomata, Masafumi; Hijiya, Naoki; Moriyama, Masatsugu; Takaki, Hajime; Fukuzawa, Kengo; Yonemasu, Hirotoshi

2017-01-01

Periportal low attenuation (PPLA) associated with metastatic liver cancer is occasionally seen on multi-detector-row CT (MDCT). The purpose of this study was to investigate the MDCT patterns of the PPLA and to correlate it with pathological findings. We retrospectively reviewed the MDCT images of 63 patients with metastatic liver cancers from colorectal adenocarcinoma. On MDCT scans, PPLA associated with liver metastasis was visualized in six patients with colorectal cancer. In these six patients who had undergone surgical resection, the radiologic-pathologic correlation was analyzed. All patients underwent a single contrast-enhanced MDCT within 1 month before surgical resection. The six liver cancers were pathologically proven to be moderately differentiated adenocarcinoma. We assessed the PPLA on MDCT concerning the distribution patterns and contrast enhancement with pathological correlation. In five of the patients, the PPLA extended to the hilar side from metastatic liver cancer. Pathologically, there was no cancer invasion into the intra-hepatic periportal area; however, massive lymphedema and fibrosis occurred in all six cases. PPLA on the hilar and peripheral sides of hepatic metastasis from colorectal cancer may be present suggesting lymphedema and fibrosis of portal tracts not always indicating cancer infiltration.

Pitfalls in 16-detector row CT of the coronary arteries.

PubMed

Nakanishi, Tadashi; Kayashima, Yasuyo; Inoue, Rintaro; Sumii, Kotaro; Gomyo, Yukihiko

2005-01-01

Recently developed 16-detector row computed tomography (CT) has been introduced as a reliable noninvasive imaging modality for evaluating the coronary arteries. In most cases, with appropriate premedication that includes beta-blockers and nitroglycerin, ideal data sets can be acquired from which to obtain excellent-quality coronary CT angiograms, most often with multiplanar reformation, thin-slab maximum intensity projection, and volume rendering. However, various artifacts associated with data creation and reformation, postprocessing methods, and image interpretation can hamper accurate diagnosis. These artifacts can be related to pulsation (nonassessable segments, pseudostenosis) as well as rhythm disorders, respiratory issues, partial volume averaging effect, high-attenuation entities, inappropriate scan pitch, contrast material enhancement, and patient body habitus. Some artifacts have already been resolved with technical advances, whereas others represent partially inherent limitations of coronary CT angiography. Familiarity with the pitfalls of coronary angiography with 16-detector row CT, coupled with the knowledge of both the normal anatomy and anatomic variants of the coronary arteries, can almost always help radiologists avoid interpretive errors in the diagnosis of coronary artery stenosis. (c) RSNA, 2005.

[New methods for the evaluation of bone quality. Assessment of bone structural property using imaging.

PubMed

Ito, Masako

Structural property of bone includes micro- or nano-structural property of the trabecular and cortical bone, and macroscopic geometry. Radiological technique is useful to analyze the bone structural property;multi-detector row CT(MDCT)or high-resolution peripheral QCT(HR-pQCT)is available to analyze human bone in vivo . For the analysis of hip geometry, CT-based hip structure analysis(HSA)is available as well as DXA-based HSA. These structural parameters are related to biomechanical property, and these assessment tools provide information of pathological changes or the effects of anti-osteoporotic agents on bone.

Quantification of myocardial blood flow using dynamic 320-row multi-detector CT as compared with ¹⁵O-H₂O PET.

PubMed

Kikuchi, Yasuka; Oyama-Manabe, Noriko; Naya, Masanao; Manabe, Osamu; Tomiyama, Yuuki; Sasaki, Tsukasa; Katoh, Chietsugu; Kudo, Kohsuke; Tamaki, Nagara; Shirato, Hiroki

2014-07-01

This study introduces a method to calculate myocardium blood flow (MBF) and coronary flow reserve (CFR) using the relatively low-dose dynamic 320-row multi-detector computed tomography (MDCT), validates the method against (15)O-H₂O positron-emission tomography (PET) and assesses the CFRs of coronary artery disease (CAD) patients. Thirty-two subjects underwent both dynamic CT perfusion (CTP) and PET perfusion imaging at rest and during pharmacological stress. In 12 normal subjects (pilot group), the calculation method for MBF and CFR was established. In the other 13 normal subjects (validation group), MBF and CFR obtained by dynamic CTP and PET were compared. Finally, the CFRs obtained by dynamic CTP and PET were compared between the validation group and CAD patients (n = 7). Correlation between MBF of MDCT and PET was strong (r = 0.95, P < 0.0001). CFR showed good correlation between dynamic CTP and PET (r = 0.67, P = 0.0126). CFRCT in the CAD group (2.3 ± 0.8) was significantly lower than that in the validation group (5.2 ± 1.8) (P = 0.0011). We established a method for measuring MBF and CFR with the relatively low-dose dynamic MDCT. Lower CFR was well demonstrated in CAD patients by dynamic CTP. • MBF and CFR can be calculated using dynamic CTP with 320-row MDCT. • MBF and CFR showed good correlation between dynamic CTP and PET. • Lower CFR was well demonstrated in CAD patients by dynamic CTP.

Evaluation of organ doses in CT examinations with an infant anthropomorphic phantom.

PubMed

Fujii, K; Akahane, K; Miyazaki, O; Horiuchi, T; Shimada, A; Nagmatsu, H; Yamauchi, M; Yamauchi-Kawaura, C; Kawasaki, T

2011-09-01

The aim of this study is to evaluate organ doses in infant CT examinations with multi-detector row CT scanners. Radiation doses were measured with radiophotoluminescence glass dosemeters set in various organ positions within a 1-y-old child anthropomorphic phantom and organ doses were evaluated from the measurement values. Doses for tissues or organs within the scan range were 28-36 mGy in an infant head CT, 3-11 mGy in a chest CT, 5-11 mGy in an abdominal-pelvic CT and 2-14 mGy in a cardiac CT. The doses varied by the differences in the types of CT scanners and scan parameters used at each medical facility. Compared with those for children of various ages, the doses in an infant CT protocol were found to be similar to or slightly smaller than those in a paediatric CT for 5- or 6-y-old children.

[Chronic pancreatitis: which is the role of 320-row CT for the staging?].

PubMed

Stabile Ianora, Amato Antonio; Rubini, Giuseppe; Lorusso, Filomenamila; Ambriola, Angela; Rella, Leonarda; Di Crescenzo, Vincenzo; Moschetta, Marco

2013-01-01

The purpose of this study was to evaluate the diagnostic potential of multi-planar and volumetric reconstructions obtained from isotropic data by using 16-slice computed tomography (CT) in the diagnosis and staging of chronic pancreatitis. In a group of 42 patients CT images were evaluated searching for alterations in morphology and structure of the pancreas, alterations of the Wirsung duct, dilatation of the bile ducts, fluid collections, and vascular involvement of the digestive tract. The disease was then staged in mild, moderate and severe and correlated with the clinical staging. CT allowed the recognition of chronic pancreatitis in all cases. The staging was correct in 25/42 patients, with an accuracy rate of 59.5%. In the staging of moderate and severe forms, CT correlation with clinical and laboratory data was valid, but in mild forms it appeared less significant. Multi-detector CT is accurate in the recognition of moderate, advanced forms of chronic pancreatitis and in the identification of its complications, while it is poorly correlated with the clinical staging in mild forms of the disease.

Influence of detector collimation and beam pitch for identification and image quality of ground-glass attenuation and nodules on 16- and 64-detector row CT systems: experimental study using chest phantom.

PubMed

Ohno, Yoshiharu; Koyama, Hisanobu; Kono, Astushi; Terada, Mari; Inokawa, Hiroyasu; Matsumoto, Sumiaki; Sugimura, Kazuro

2007-12-01

The purpose of the present study was to determine the influence of detector collimation and beam pitch for identification and image quality of ground-glass attenuation (GGA) and nodules on 16- and 64-detector row CTs, by using a commercially available chest phantom. A chest CT phantom including simulated GGAs and nodules was scanned with different detector collimations, beam pitches and tube currents. The probability and image quality of each simulated abnormality was visually assessed with a five-point scoring system. ROC-analysis and ANOVA were then performed to compare the identification and image quality of either protocol with standard values. Detection rates of low-dose CTs were significantly reduced when tube currents were set at 40mA or less by using detector collimation 16 and 64x0.5mm and 16 and 32mmx1.0mm for low pitch, and at 100mA or less by using detector collimation 16 and 64x0.5mm and 16 and 32mmx1.0mm for high pitch (p<0.05). Image qualities of low-dose CTs deteriorated significantly when tube current was set at 100mA or less by using detector collimation 16 and 64x0.5mm and 16 and 32x1.0mm for low pitch, and at 150mA or less by using detector collimation 16 and 64x0.5mm and 16 and 32x1.0mm for high pitch (p<0.05). Detector collimation and beam pitch were important factors for the image quality and identification of GGA and nodules by 16- and 64-detector row CT.

Comparison of CT and MRI in diagnosis of cerebrospinal leak induced by multiple fractures of skull base

PubMed Central

Wang, Xuhui; Xu, Minhui; Liang, Hong; Xu, Lunshan

2011-01-01

Background Multiple basilar skull fracture and cerebrospinal leak are common complications of traumatic brain injury, which required a surgical repair. But due to the complexity of basilar skull fracture after severe trauma, preoperatively an exact radiological location is always difficult. Multi-row spiral CT and MRI are currently widely applied in the clinical diagnosis. The present study was performed to compare the accuracy of cisternography by multi-row spiral CT and MRI in the diagnosis of cerebrospinal leak. Methods A total of 23 patients with multiple basilar skull fracture after traumatic brain injury were included. The radiological and surgical data were retrospectively analyzed. 64-row CT (mm/row) scan and three-dimensional reconstruction were performed in 12 patients, while MR plain scan and cisternography were performed in another 11 patients. The location of cerebrospinal leak was diagnosed by 2 experienced physicians majoring neurological radiology. Surgery was performed in all patients. The cerebrospinal leak location was confirmed and repaired during surgery. The result was considered as accurate when cerebrospinal leak was absent after surgery. Results According to the surgical exploration, the preoperative diagnosis of the active cerebrospinal leak location was accurate in 9 out of 12 patients with CT scan. The location could not be confirmed by CT because of multiple fractures in 2 patients and the missed diagnosis occurred in 1 patient. The preoperative diagnosis was accurate in 10 out of 11 patients with MRI examination. Conclusions MRI cisternography is more advanced than multi-row CT scan in multiple basilar skull fracture. The combination of the two examinations may increase the diagnostic ratio of active cerebrospinal leak. PMID:22933941

Electrocardiographically gated 16-section CT of the thorax: cardiac motion suppression.

PubMed

Hofmann, Lars K; Zou, Kelly H; Costello, Philip; Schoepf, U Joseph

2004-12-01

Thirty patients underwent 16-section multi-detector row computed tomographic (CT) angiography of the thorax with retrospective electrocardiographic gating. Institutional review board approval was obtained for retrospective analysis of CT scan data and records; patient informed consent was not required. Images reconstructed at six different time points (0%, 20%, 40%, 50%, 60%, 80%) within the R-R interval on the electrocardiogram were analyzed by two radiologists for diagnostic quality, to identify suitable reconstruction intervals for optimal suppression of cardiac motion. Five regions of interest (left coronary artery, aortic root, ascending and descending aorta, pulmonary arteries) were evaluated. Best image quality was achieved by referencing image reconstruction to middiastole (50%-60%) for the left coronary artery, aortic root, and ascending aorta. The pulmonary arteries are best displayed during mid- to late diastole (80%). (c) RSNA, 2004

Imaging in chronic obstructive pulmonary disease.

PubMed

Shaker, Saher B; Dirksen, Asger; Bach, Karen S; Mortensen, Jann

2007-06-01

Chronic obstructive pulmonary disease (COPD) is divided into pulmonary emphysema and chronic bronchitis (CB). Emphysema is defined patho-anatomically as "permanent enlargement of airspaces distal to the terminal bronchiole, accompanied by the destruction of their walls, and without obvious fibrosis" (1). These lesions are readily identified and quantitated using computed tomography (CT), whereas the accompanying hyperinflation is best detected on plain chest X-ray, especially in advanced disease. The diagnosis of CB is clinical and relies on the presence of productive cough for 3 months in 2 or more successive years. The pathological changes of mucosal inflammation and bronchial wall thickening have been more difficult to identify with available imaging techniques. However, recent studies using Multi-detector row CT (MDCT) reported more reproducible assessment of air wall thickening.

Estimation of regional lung expansion via 3D image registration

NASA Astrophysics Data System (ADS)

Pan, Yan; Kumar, Dinesh; Hoffman, Eric A.; Christensen, Gary E.; McLennan, Geoffrey; Song, Joo Hyun; Ross, Alan; Simon, Brett A.; Reinhardt, Joseph M.

2005-04-01

A method is described to estimate regional lung expansion and related biomechanical parameters using multiple CT images of the lungs, acquired at different inflation levels. In this study, the lungs of two sheep were imaged utilizing a multi-detector row CT at different lung inflations in the prone and supine positions. Using the lung surfaces and the airway branch points for guidance, a 3D inverse consistent image registration procedure was used to match different lung volumes at each orientation. The registration was validated using a set of implanted metal markers. After registration, the Jacobian of the deformation field was computed to express regional expansion or contraction. The regional lung expansion at different pressures and different orientations are compared.

Temporal resolution measurement of 128-slice dual source and 320-row area detector computed tomography scanners in helical acquisition mode using the impulse method.

PubMed

Hara, Takanori; Urikura, Atsushi; Ichikawa, Katsuhiro; Hoshino, Takashi; Nishimaru, Eiji; Niwa, Shinji

2016-04-01

To analyse the temporal resolution (TR) of modern computed tomography (CT) scanners using the impulse method, and assess the actual maximum TR at respective helical acquisition modes. To assess the actual TR of helical acquisition modes of a 128-slice dual source CT (DSCT) scanner and a 320-row area detector CT (ADCT) scanner, we assessed the TRs of various acquisition combinations of a pitch factor (P) and gantry rotation time (R). The TR of the helical acquisition modes for the 128-slice DSCT scanner continuously improved with a shorter gantry rotation time and greater pitch factor. However, for the 320-row ADCT scanner, the TR with a pitch factor of <1.0 was almost equal to the gantry rotation time, whereas with pitch factor of >1.0, it was approximately one half of the gantry rotation time. The maximum TR values of single- and dual-source helical acquisition modes for the 128-slice DSCT scanner were 0.138 (R/P=0.285/1.5) and 0.074s (R/P=0.285/3.2), and the maximum TR values of the 64×0.5- and 160×0.5-mm detector configurations of the helical acquisition modes for the 320-row ADCT scanner were 0.120 (R/P=0.275/1.375) and 0.195s (R/P=0.3/0.6), respectively. Because the TR of a CT scanner is not accurately depicted in the specifications of the individual scanner, appropriate acquisition conditions should be determined based on the actual TR measurement. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

SimDoseCT: dose reporting software based on Monte Carlo simulation for a 320 detector-row cone-beam CT scanner and ICRP computational adult phantoms

NASA Astrophysics Data System (ADS)

Cros, Maria; Joemai, Raoul M. S.; Geleijns, Jacob; Molina, Diego; Salvadó, Marçal

2017-08-01

This study aims to develop and test software for assessing and reporting doses for standard patients undergoing computed tomography (CT) examinations in a 320 detector-row cone-beam scanner. The software, called SimDoseCT, is based on the Monte Carlo (MC) simulation code, which was developed to calculate organ doses and effective doses in ICRP anthropomorphic adult reference computational phantoms for acquisitions with the Aquilion ONE CT scanner (Toshiba). MC simulation was validated by comparing CTDI measurements within standard CT dose phantoms with results from simulation under the same conditions. SimDoseCT consists of a graphical user interface connected to a MySQL database, which contains the look-up-tables that were generated with MC simulations for volumetric acquisitions at different scan positions along the phantom using any tube voltage, bow tie filter, focal spot and nine different beam widths. Two different methods were developed to estimate organ doses and effective doses from acquisitions using other available beam widths in the scanner. A correction factor was used to estimate doses in helical acquisitions. Hence, the user can select any available protocol in the Aquilion ONE scanner for a standard adult male or female and obtain the dose results through the software interface. Agreement within 9% between CTDI measurements and simulations allowed the validation of the MC program. Additionally, the algorithm for dose reporting in SimDoseCT was validated by comparing dose results from this tool with those obtained from MC simulations for three volumetric acquisitions (head, thorax and abdomen). The comparison was repeated using eight different collimations and also for another collimation in a helical abdomen examination. The results showed differences of 0.1 mSv or less for absolute dose in most organs and also in the effective dose calculation. The software provides a suitable tool for dose assessment in standard adult patients undergoing CT examinations in a 320 detector-row cone-beam scanner.

SimDoseCT: dose reporting software based on Monte Carlo simulation for a 320 detector-row cone-beam CT scanner and ICRP computational adult phantoms.

PubMed

Cros, Maria; Joemai, Raoul M S; Geleijns, Jacob; Molina, Diego; Salvadó, Marçal

2017-07-17

This study aims to develop and test software for assessing and reporting doses for standard patients undergoing computed tomography (CT) examinations in a 320 detector-row cone-beam scanner. The software, called SimDoseCT, is based on the Monte Carlo (MC) simulation code, which was developed to calculate organ doses and effective doses in ICRP anthropomorphic adult reference computational phantoms for acquisitions with the Aquilion ONE CT scanner (Toshiba). MC simulation was validated by comparing CTDI measurements within standard CT dose phantoms with results from simulation under the same conditions. SimDoseCT consists of a graphical user interface connected to a MySQL database, which contains the look-up-tables that were generated with MC simulations for volumetric acquisitions at different scan positions along the phantom using any tube voltage, bow tie filter, focal spot and nine different beam widths. Two different methods were developed to estimate organ doses and effective doses from acquisitions using other available beam widths in the scanner. A correction factor was used to estimate doses in helical acquisitions. Hence, the user can select any available protocol in the Aquilion ONE scanner for a standard adult male or female and obtain the dose results through the software interface. Agreement within 9% between CTDI measurements and simulations allowed the validation of the MC program. Additionally, the algorithm for dose reporting in SimDoseCT was validated by comparing dose results from this tool with those obtained from MC simulations for three volumetric acquisitions (head, thorax and abdomen). The comparison was repeated using eight different collimations and also for another collimation in a helical abdomen examination. The results showed differences of 0.1 mSv or less for absolute dose in most organs and also in the effective dose calculation. The software provides a suitable tool for dose assessment in standard adult patients undergoing CT examinations in a 320 detector-row cone-beam scanner.

Non-invasive detection of aortic and coronary atherosclerosis in homozygous familial hypercholesterolemia by 64 slice multi-detector row computed tomography angiography

USDA-ARS?s Scientific Manuscript database

Homozygous familial hypercholesterolemia (HoFH) is a rare disorder characterized by the early onset of atherosclerosis, often at the ostia of coronary arteries. In this study we document for the first time that aortic and coronary atherosclerosis can be detected using 64 slice multiple detector row ...

Assessment of temporal resolution of multi-detector row computed tomography in helical acquisition mode using the impulse method.

PubMed

Ichikawa, Katsuhiro; Hara, Takanori; Urikura, Atsushi; Takata, Tadanori; Ohashi, Kazuya

2015-06-01

The purpose of this study was to propose a method for assessing the temporal resolution (TR) of multi-detector row computed tomography (CT) (MDCT) in the helical acquisition mode using temporal impulse signals generated by a metal ball passing through the acquisition plane. An 11-mm diameter metal ball was shot along the central axis at approximately 5 m/s during a helical acquisition, and the temporal sensitivity profile (TSP) was measured from the streak image intensities in the reconstructed helical CT images. To assess the validity, we compared the measured and theoretical TSPs for the 4-channel modes of two MDCT systems. A 64-channel MDCT system was used to compare TSPs and image quality of a motion phantom for the pitch factors P of 0.6, 0.8, 1.0 and 1.2 with a rotation time R of 0.5 s, and for two R/P combinations of 0.5/1.2 and 0.33/0.8. Moreover, the temporal transfer functions (TFs) were calculated from the obtained TSPs. The measured and theoretical TSPs showed perfect agreement. The TSP narrowed with an increase in the pitch factor. The image sharpness of the 0.33/0.8 combination was inferior to that of the 0.5/1.2 combination, despite their almost identical full width at tenth maximum values. The temporal TFs quantitatively confirmed these differences. The TSP results demonstrated that the TR in the helical acquisition mode significantly depended on the pitch factor as well as the rotation time, and the pitch factor and reconstruction algorithm affected the TSP shape. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

A Multi-Source Inverse-Geometry CT system: Initial results with an 8 spot x-ray source array

PubMed Central

Baek, Jongduk; De Man, Bruno; Uribe, Jorge; Longtin, Randy; Harrison, Daniel; Reynolds, Joseph; Neculaes, Bogdan; Frutschy, Kristopher; Inzinna, Louis; Caiafa, Antonio; Senzig, Robert; Pelc, Norbert J.

2014-01-01

We present initial experimental results of a rotating-gantry multi-source inverse-geometry CT (MS-IGCT) system. The MS-IGCT system was built with a single module of 2×4 x-ray sources and a 2D detector array. It produced a 75 mm in-plane field-of-view (FOV) with 160 mm axial coverage in a single gantry rotation. To evaluate system performance, a 2.5 inch diameter uniform PMMA cylinder phantom, a 200 μm diameter tungsten wire, and a euthanized rat were scanned. Each scan acquired 125 views per source and the gantry rotation time was 1 second per revolution. Geometric calibration was performed using a bead phantom. The scanning parameters were 80 kVp, 125 mA, and 5.4 us pulse per source location per view. A data normalization technique was applied to the acquired projection data, and beam hardening and spectral nonlinearities of each detector channel were corrected. For image reconstruction, the projection data of each source row were rebinned into a full cone beam data set, and the FDK algorithm was used. The reconstructed volumes from upper and lower source rows shared an overlap volume which was combined in image space. The images of the uniform PMMA cylinder phantom showed good uniformity and no apparent artefacts. The measured in-plane MTF showed 13 lp/cm at 10% cutoff, in good agreement with expectations. The rat data were also reconstructed reliably. The initial experimental results from this rotating-gantry MS-IGCT system demonstrated its ability to image a complex anatomical object without any significant image artefacts and to achieve high image resolution and large axial coverage in a single gantry rotation. PMID:24556567

Paleoradiology: advanced CT in the evaluation of nine Egyptian mummies.

PubMed

Hoffman, Heidi; Torres, William E; Ernst, Randy D

2002-01-01

Axial thin-collimation state-of-the-art spiral computed tomography (CT) was combined with sagittal and coronal reformatting, three-dimensional (3D) reconstruction, and virtual "fly-through" techniques to nondestructively study nine Egyptian mummies. These techniques provided important paleopathologic and historical information about mummification techniques, depicted anatomy in the most informative imaging plane, illustrated the soft-tissue preservation and physical appearance of mummies in superb detail, and generated an intriguing virtual tour through hollow mummified remains without harming the specimens themselves. Images generated with these methods can help archaeologists and Egyptologists understand these fascinating members of mankind and can serve as adjunct visual aids for laypersons who are interested in mummies. CT has emerged as the imaging modality of choice for the examination of Egyptian mummies due to its noninvasive cross-sectional nature and inherently superior contrast and spatial resolution. As multi-detector row CT and postprocessing tools evolve, the capabilities and applications of CT will continue to proliferate, attesting to the expanded versatility and utility of CT as a noninvasive research tool in the multidisciplinary study of Egyptian mummies. Copyright RSNA, 2002

Development and performance evaluation of an experimental fine pitch detector multislice CT scanner.

PubMed

Imai, Yasuhiro; Nukui, Masatake; Ishihara, Yotaro; Fujishige, Takashi; Ogata, Kentaro; Moritake, Masahiro; Kurochi, Haruo; Ogata, Tsuyoshi; Yahata, Mitsuru; Tang, Xiangyang

2009-04-01

The authors have developed an experimental fine pitch detector multislice CT scanner with an ultrasmall focal spot x-ray tube and a high-density matrix detector through current CT technology. The latitudinal size of the x-ray tube focal spot was 0.4 mm. The detector dimension was 1824 channels (azimuthal direction) x 32 rows (longitudinal direction) at row width of 0.3125 mm, in which a thinner reflected separator surrounds each detector cell coupled with a large active area photodiode. They were mounted on a commercial 64-slice CT scanner gantry while the scan field of view (50 cm) and gantry rotation speed (0.35 s) can be maintained. The experimental CT scanner demonstrated the spatial resolution of 0.21-0.22 mm (23.8-22.7 lp/cm) with the acrylic slit phantom and in-plane 50%-MTF 9.0 lp/cm and 10%-MTF 22.0 lp/cm. In the longitudinal direction, it demonstrated the spatial resolution of 0.24 mm with the high-resolution insert of the CATPHAN phantom and 0.34 mm as the full width at half maximum of the slice sensitivity profile. In low-contrast detectability, 3 mm at 0.3% was visualized at the CTDI(vol) of 47.2 mGy. Two types of 2.75 mm diameter vessel phantoms with in-stent stenosis at 25%, 50%, and 75% stair steps were scanned, and the reconstructed images can clearly resolve the stenosis at each case. The experimental CT scanner provides high-resolution imaging while maintaining low-contrast detectability, demonstrating the potentiality for clinical applications demanding high spatial resolution, such as imaging of inner ear, lung, and bone, or low-contrast detectability, such as imaging of coronary artery.

Respiratory-gated segment reconstruction for radiation treatment planning using 256-slice CT-scanner during free breathing

NASA Astrophysics Data System (ADS)

Mori, Shinichiro; Endo, Masahiro; Kohno, Ryosuke; Minohara, Shinichi; Kohno, Kazutoshi; Asakura, Hiroshi; Fujiwara, Hideaki; Murase, Kenya

2005-04-01

The conventional respiratory-gated CT scan technique includes anatomic motion induced artifacts due to the low temporal resolution. They are a significant source of error in radiotherapy treatment planning for the thorax and upper abdomen. Temporal resolution and image quality are important factors to minimize planning target volume margin due to the respiratory motion. To achieve high temporal resolution and high signal-to-noise ratio, we developed a respiratory gated segment reconstruction algorithm and adapted it to Feldkamp-Davis-Kress algorithm (FDK) with a 256-detector row CT. The 256-detector row CT could scan approximately 100 mm in the cranio-caudal direction with 0.5 mm slice thickness in one rotation. Data acquisition for the RS-FDK relies on the assistance of the respiratory sensing system by a cine scan mode (table remains stationary). We evaluated RS-FDK in phantom study with the 256-detector row CT and compared it with full scan (FS-FDK) and HS-FDK results with regard to volume accuracy and image noise, and finally adapted the RS-FDK to an animal study. The RS-FDK gave a more accurate volume than the others and it had the same signal-to-noise ratio as the FS-FDK. In the animal study, the RS-FDK visualized the clearest edges of the liver and pulmonary vessels of all the algorithms. In conclusion, the RS-FDK algorithm has a capability of high temporal resolution and high signal-to-noise ratio. Therefore it will be useful when combined with new radiotherapy techniques including image guided radiation therapy (IGRT) and 4D radiation therapy.

Subtraction coronary CT angiography using second-generation 320-detector row CT.

PubMed

Yoshioka, Kunihiro; Tanaka, Ryoichi; Muranaka, Kenta; Sasaki, Tadashi; Ueda, Takanori; Chiba, Takuya; Takeda, Kouta; Sugawara, Tsuyoshi

2015-06-01

The purpose of this study was to explore the feasibility of subtraction coronary computed tomography angiography (CCTA) by second-generation 320-detector row CT in patients with severe coronary artery calcification using invasive coronary angiography (ICA) as the gold standard. This study was approved by the institutional board, and all subjects provided written consent. Twenty patients with calcium scores of >400 underwent conventional CCTA and subtraction CCTA followed by ICA. A total of 82 segments were evaluated for image quality using a 4-point scale and the presence of significant (>50 %) luminal stenosis by two independent readers. The average image quality was 2.3 ± 0.8 with conventional CCTA and 3.2 ± 0.6 with subtraction CCTA (P < 0.001). The percentage of segments with non-diagnostic image quality was 43.9 % on conventional CCTA versus 8.5 % on subtraction CCTA (P = 0.004). The segment-based diagnostic accuracy for detecting significant stenosis according to ICA revealed an area under the receiver operating characteristics curve of 0.824 (95 % confidence interval [CI], 0.750-0.899) for conventional CCTA and 0.936 (95 % CI 0.889-0.936) for subtraction CCTA (P = 0.001). The sensitivity, specificity, positive predictive value, and negative predictive value for conventional CCTA were 88.2, 62.5, 62.5, and 88.2 %, respectively, and for subtraction CCTA they were 94.1, 85.4, 82.1, and 95.3 %, respectively. As compared to conventional, subtraction CCTA using a second-generation 320-detector row CT showed improvement in diagnostic accuracy at segment base analysis in patients with severe calcifications.

Differentiation of benign and malignant ampullary obstruction by multi-row detector CT.

PubMed

Angthong, Wirana; Jiarakoop, Kran; Tangtiang, Kaan

2018-05-21

To determine useful CT parameters to differentiate ampullary carcinomas from benign ampullary obstruction. This study included 93 patients who underwent abdominal CT, 31 patients with ampullary carcinomas, and 62 patients with benign ampullary obstruction. Two radiologists independently evaluated CT parameters then reached consensus decisions. Statistically significant CT parameters were identified through univariate and multivariate analyses. In univariate analysis, the presence of ampullary mass, asymmetric, abrupt narrowing of distal common bile duct (CBD), dilated intrahepatic bile duct (IHD), dilated pancreatic duct (PD), peripancreatic lymphadenopathy, duodenal wall thickening, and delayed enhancement were more frequently in ampullary carcinomas observed (P < 0.05). Multivariate logistic regression analysis using significant CT parameters and clinical data from univariate analysis, and clinical symptom with jaundice (P = 0.005) was an independent predictor of ampullary carcinomas. For multivariate analysis using only significant CT parameters, abrupt narrowing of distal CBD was an independent predictor of ampullary carcinomas (P = 0.019). Among various CT criteria, abrupt narrowing of distal CBD and dilated IHD had highest sensitivity (77.4%) and highest accuracy (90.3%). The abrupt narrowing of distal CBD and dilated IHD is useful for differentiation of ampullary carcinomas from benign entity in patients without the presence of mass.

Low-contrast detectability in volume rendering: a phantom study on multidetector-row spiral CT data.

PubMed

Shin, Hoen-Oh; Falck, Christian V; Galanski, Michael

2004-02-01

To cope with the increasing amount of CT data, there is growing interest in direct volume-rendering techniques (VRT) as a diagnostic tool. The aim of this phantom study was to analyze the low-contrast detectability (LCD) of VRT compared with multi-planar reformations (MPR). Soft tissue lesions were simulated by spheres of different diameters (3-8 mm). The average lesion density was 15 HU compared with a background density of 35 HU. Two different CT protocols with 40 and 150 mAs were performed on a multi-detector row CT. The scanning parameters were as following: 140 kV; 2x0.5-mm slice collimation; pitch 2 (table movement per rotation/single slice collimation), and reconstruction with 0.5-mm slice thickness at 0.5-mm interval. A B30 kernel was used for reconstruction. The VRT was performed by mapping Hounsfield values to gray levels equal to a CT window (center: 60 HU; window: 370 HU ). A linear ramp was applied for the opacity transfer function varying the maximum opacity between 0.1 and 1.0. A statistical method based on the Rose model was used to calculate the detection threshold depending on lesion size and image noise. Additionally, clinical data of 2 patients with three liver lesions of different sizes and density were evaluated. In VRT, LCD was most dependent on object size. Regarding lesions larger than 5 mm, VRT is significantly superior to MPR (p<0.05) for all opacity settings. In lesions sized 3-5 mm a maximum opacity level approximately 40-50% showed a near equivalent detectability in VRT and MPR. For higher opacity levels VRT was superior to MPR. Only for 3-mm lesions MPR performed slightly better in low-contrast detectability (p<0.05). Compared with MPR, VRT shows similar performance in LCD. Due to noise suppression effects, it is suited for visualization of data with high noise content.

Development of a fast multi-line x-ray CT detector for NDT

NASA Astrophysics Data System (ADS)

Hofmann, T.; Nachtrab, F.; Schlechter, T.; Neubauer, H.; Mühlbauer, J.; Schröpfer, S.; Ernst, J.; Firsching, M.; Schweiger, T.; Oberst, M.; Meyer, A.; Uhlmann, N.

2015-04-01

Typical X-ray detectors for non-destructive testing (NDT) are line detectors or area detectors, like e.g. flat panel detectors. Multi-line detectors are currently only available in medical Computed Tomography (CT) scanners. Compared to flat panel detectors, line and multi-line detectors can achieve much higher frame rates. This allows time-resolved 3D CT scans of an object under investigation. Also, an improved image quality can be achieved due to reduced scattered radiation from object and detector themselves. Another benefit of line and multi-line detectors is that very wide detectors can be assembled easily, while flat panel detectors are usually limited to an imaging field with a size of approx. 40 × 40 cm2 at maximum. The big disadvantage of line detectors is the limited number of object slices that can be scanned simultaneously. This leads to long scan times for large objects. Volume scans with a multi-line detector are much faster, but with almost similar image quality. Due to the promising properties of multi-line detectors their application outside of medical CT would also be very interesting for NDT. However, medical CT multi-line detectors are optimized for the scanning of human bodies. Many non-medical applications require higher spatial resolutions and/or higher X-ray energies. For those non-medical applications we are developing a fast multi-line X-ray detector.In the scope of this work, we present the current state of the development of the novel detector, which includes several outstanding properties like an adjustable curved design for variable focus-detector-distances, conserving nearly uniform perpendicular irradiation over the entire detector width. Basis of the detector is a specifically designed, radiation hard CMOS imaging sensor with a pixel pitch of 200 μ m. Each pixel has an automatic in-pixel gain adjustment, which allows for both: a very high sensitivity and a wide dynamic range. The final detector is planned to have 256 lines of pixels. By using a modular assembly of the detector, the width can be chosen as multiples of 512 pixels. With a frame rate of up to 300 frames/s (full resolution) or 1200 frame/s (analog binning to 400 μ m pixel pitch) time-resolved 3D CT applications become possible. Two versions of the detector are in development, one with a high resolution scintillator and one with a thick, structured and very efficient scintillator (pitch 400 μ m). This way the detector can even work with X-ray energies up to 450 kVp.

Whole brain CT perfusion deficits using 320-detector-row CT scanner in TIA patients are associated with ABCD2 score.

PubMed

Mehta, Bijal K; Mustafa, Ghulam; McMurtray, Aaron; Masud, Mohammed W; Gunukula, Sameer K; Kamal, Haris; Kandel, Amit; Beltagy, Abdelrahman; Li, Ping

2014-01-01

Transient ischemic attacks (TIA) are cerebral ischemic events without infarction. The uses of CT perfusion (CTP) techniques such as cerebral blood volume (CBV), time to peak (TTP), mean transit time (MTT) and cerebral blood flow (CBF) provide real time data about ischemia. It has been shown that CTP changes occur in less sensitive CTP scanners in patients with TIA. Larger detector row CTP (whole brain perfusion studies) may show that CTP abnormalities are more prevalent than previously noted. It is also unclear if these changes are associated with TIA severity. To demonstrate that TIA patients are associated with perfusion deficits using whole brain 320-detector-row CT perfusion, and to determine an association between ABCD2 score and perfusion deficit using whole brain perfusion. We retrospectively reviewed all TIA patients for CTP deficits from 2008-2010. Perfusion imaging was reviewed at admission; and it was determined if a perfusion deficit was present along with vascular territory involved. Of 364 TIA patients, 62 patients had CTP deficits. The largest group of patients had MCA territory involved with 48 of 62 patients (77.42%). The most common perfusion abnormality was increased TTP with 46 patients (74.19%). The ABCD2 score was reviewed in association with perfusion deficit. Increased age >60, severe hypertension (>180/100 mmHg), patients with speech abnormalities, and duration of symptoms >10 min were associated with a perfusion deficit but history of diabetes or minimal/moderate hypertension (140/90-179/99 mmHg) was not. There was no association between motor deficit and perfusion abnormality. Perfusion deficits are found in TIA patients using whole brain CTP and associated with components of the ABCD2 score.

Coronary artery calcium: a multi-institutional, multimanufacturer international standard for quantification at cardiac CT.

PubMed

McCollough, Cynthia H; Ulzheimer, Stefan; Halliburton, Sandra S; Shanneik, Kaiss; White, Richard D; Kalender, Willi A

2007-05-01

To develop a consensus standard for quantification of coronary artery calcium (CAC). A standard for CAC quantification was developed by a multi-institutional, multimanufacturer international consortium of cardiac radiologists, medical physicists, and industry representatives. This report specifically describes the standardization of scan acquisition and reconstruction parameters, the use of patient size-specific tube current values to achieve a prescribed image noise, and the use of the calcium mass score to eliminate scanner- and patient size-based variations. An anthropomorphic phantom containing calibration inserts and additional phantom rings were used to simulate small, medium-size, and large patients. The three phantoms were scanned by using the recommended protocols for various computed tomography (CT) systems to determine the calibration factors that relate measured CT numbers to calcium hydroxyapatite density and to determine the tube current values that yield comparable noise values. Calculation of the calcium mass score was standardized, and the variance in Agatston, volume, and mass scores was compared among CT systems. Use of the recommended scanning parameters resulted in similar noise for small, medium-size, and large phantoms with all multi-detector row CT scanners. Volume scores had greater interscanner variance than did Agatston and calcium mass scores. Use of a fixed calcium hydroxyapatite density threshold (100 mg/cm(3)), as compared with use of a fixed CT number threshold (130 HU), reduced interscanner variability in Agatston and calcium mass scores. With use of a density segmentation threshold, the calcium mass score had the smallest variance as a function of patient size. Standardized quantification of CAC yielded comparable image noise, spatial resolution, and mass scores among different patient sizes and different CT systems and facilitated reduced radiation dose for small and medium-size patients.

Computer-aided detection of acute pulmonary embolism with 64-slice multi-detector row computed tomography: impact of the scanning conditions and overall image quality in the detection of peripheral clots.

PubMed

Dewailly, Marion; Rémy-Jardin, Martine; Duhamel, Alain; Faivre, Jean-Baptiste; Pontana, François; Deken, Valérie; Bakai, Anne-Marie; Remy, Jacques

2010-01-01

To evaluate the performance of a computer-aided detection (CAD) system for diagnosing peripheral acute pulmonary embolism (PE) with a 64-slice multi-detector row computed tomography (CT). Two radiologists investigated the accuracy of a software aimed at detecting peripheral clots (PECAD prototype, version 7; Siemens Medical Systems, Forchheim, Germany) by applying this tool for the analysis of the pulmonary arterial bed of 74 CT angiograms obtained with 64-slice dual-source CT (Definition; Siemens Medical Systems). These cases were retrospectively selected from a database of CT studies performed on the same CT unit, with a similar collimation (64 x 0.6 mm) and similar injection protocols. Patient selection was based on a variety of (1) scanning conditions, namely, nongated (n = 30), electrocardiography-gated (n = 30), and dual-energy CT angiograms (n = 14), and (2) image quality (IQ), namely, scans of excellent IQ (n = 53) and lower IQ due to lower levels of arterial enhancement and/or presence of noise (n = 21). The standard of truth was based on the 2 radiologists' consensus reading and the results of CAD. The software detected 80 of 93 peripheral clots present in the 21 patients (42 segmental and 38 subsegmental clots). The overall sensitivity (95% confidence interval) of the CAD tool was 86% (77%-92%) for detecting peripheral clots, 78% (64.5%-88%) at the segmental level and 97% (85.5%-99.9%) at the subsegmental level. Assuming normal vascular anatomy with 20 segmental and 40 subsegmental arteries, overall specificity and positive and negative predictive values (95% confidence interval) of the software were 91.8% (91%-92.6%), 18.4% (15%-22.4%), and 99.7% (99.5%-99.8%), respectively. A mean of 5.4 false positives was found per patient (total, 354 false positives), mainly linked to the presence of perivascular connective tissue (n = 119; 34%) and perivascular airspace consolidation (n = 97; 27%). The sensitivities (95% confidence interval) for the CAD tool were 91% (69.8%-99.3%) for dual-energy, 87% (59.3%-93.2%) for electrocardiography-gated, and 87% (73.5%-95.3%) for nongated scans (P > 0.05). No significant difference was found in the sensitivity of the CAD software when comparing the scans according to the scanning conditions and image quality. The evaluated CAD software has a good sensitivity in detecting peripheral PE, which is not influenced by the scanning conditions or the overall image quality.

Role of Computer Aided Diagnosis (CAD) in the detection of pulmonary nodules on 64 row multi detector computed tomography.

PubMed

Prakashini, K; Babu, Satish; Rajgopal, K V; Kokila, K Raja

2016-01-01

To determine the overall performance of an existing CAD algorithm with thin-section computed tomography (CT) in the detection of pulmonary nodules and to evaluate detection sensitivity at a varying range of nodule density, size, and location. A cross-sectional prospective study was conducted on 20 patients with 322 suspected nodules who underwent diagnostic chest imaging using 64-row multi-detector CT. The examinations were evaluated on reconstructed images of 1.4 mm thickness and 0.7 mm interval. Detection of pulmonary nodules, initially by a radiologist of 2 years experience (RAD) and later by CAD lung nodule software was assessed. Then, CAD nodule candidates were accepted or rejected accordingly. Detected nodules were classified based on their size, density, and location. The performance of the RAD and CAD system was compared with the gold standard that is true nodules confirmed by consensus of senior RAD and CAD together. The overall sensitivity and false-positive (FP) rate of CAD software was calculated. Of the 322 suspected nodules, 221 were classified as true nodules on the consensus of senior RAD and CAD together. Of the true nodules, the RAD detected 206 (93.2%) and 202 (91.4%) by the CAD. CAD and RAD together picked up more number of nodules than either CAD or RAD alone. Overall sensitivity for nodule detection with the CAD program was 91.4%, and FP detection per patient was 5.5%. The CAD showed comparatively higher sensitivity for nodules of size 4-10 mm (93.4%) and nodules in hilar (100%) and central (96.5%) location when compared to RAD's performance. CAD performance was high in detecting pulmonary nodules including the small size and low-density nodules. CAD even with relatively high FP rate, assists and improves RAD's performance as a second reader, especially for nodules located in the central and hilar region and for small nodules by saving RADs time.

Measuring coronary calcium on CT images adjusted for attenuation differences.

PubMed

Nelson, Jennifer Clark; Kronmal, Richard A; Carr, J Jeffrey; McNitt-Gray, Michael F; Wong, Nathan D; Loria, Catherine M; Goldin, Jonathan G; Williams, O Dale; Detrano, Robert

2005-05-01

To quantify scanner and participant variability in attenuation values for computed tomographic (CT) images assessed for coronary calcium and define a method for standardizing attenuation values and calibrating calcium measurements. Institutional review board approval and participant informed consent were obtained at all study sites. An image attenuation adjustment method involving the use of available calibration phantom data to define standard attenuation values was developed. The method was applied to images from two population-based multicenter studies: the Coronary Artery Risk Development in Young Adults study (3041 participants) and the Multi-Ethnic Study of Atherosclerosis (6814 participants). To quantify the variability in attenuation, analysis of variance techniques were used to compare the CT numbers of standardized torso phantom regions across study sites, and multivariate linear regression models of participant-specific calibration phantom attenuation values that included participant age, race, sex, body mass index (BMI), smoking status, and site as covariates were developed. To assess the effect of the calibration method on calcium measurements, Pearson correlation coefficients between unadjusted and attenuation-adjusted calcium measurements were computed. Multivariate models were used to examine the effect of sex, race, BMI, smoking status, unadjusted score, and site on Agatston score adjustments. Mean attenuation values (CT numbers) of a standard calibration phantom scanned beneath participants varied significantly according to scanner and participant BMI (P < .001 for both). Values were lowest for Siemens multi-detector row CT scanners (110.0 HU), followed by GE-Imatron electron-beam (116.0 HU) and GE LightSpeed multi-detector row scanners (121.5 HU). Values were also lower for morbidly obese (BMI, > or =40.0 kg/m(2)) participants (108.9 HU), followed by obese (BMI, 30.0-39.9 kg/m(2)) (114.8 HU), overweight (BMI, 25.0-29.9 kg/m(2)) (118.5 HU), and normal-weight or underweight (BMI, <25.0 kg/m(2)) (120.1 HU) participants. Agatston score calibration adjustments ranged from -650 to 1071 (mean, -8 +/- 50 [standard deviation]) and increased with Agatston score (P < .001). The direction and magnitude of adjustment varied significantly according to scanner and BMI (P < .001 for both) and were consistent with phantom attenuation results in that calibration resulted in score decreases for images with higher phantom attenuation values. Image attenuation values vary by scanner and participant body size, producing calcium score differences that are not due to true calcium burden disparities. Use of calibration phantoms to adjust attenuation values and calibrate calcium measurements in research studies and clinical practice may improve the comparability of such measurements between persons scanned with different scanners and within persons over time.

Pulmonary arterial hypertension in children: diagnosis using ratio of main pulmonary artery to ascending aorta diameter as determined by multi-detector computed tomography.

PubMed

Caro-Domínguez, Pablo; Compton, Gregory; Humpl, Tilman; Manson, David E

2016-09-01

The ratio of the transverse diameter of the main pulmonary artery (MPA) to ascending aorta as determined at multi-detector CT is a tool that can be used to assess the pulmonary arterial size in cases of pulmonary arterial hypertension in children. To establish a ratio of MPA to ascending aorta diameter using multi-detector CT imaging suggestive of pulmonary arterial hypertension in children. We hypothesize that a defined ratio of MPA to ascending aorta is identifiable on multi-detector CT and that higher ratios can be used to reliably diagnose the presence of pulmonary arterial hypertension in children. We calculated the multi-detector CT ratio of MPA to ascending aorta diameter in 44 children with documented pulmonary arterial hypertension by right heart catheterization and in 44 age- and gender-matched control children with no predisposing factors for pulmonary arterial hypertension. We compared this multi-detector-CT-determined ratio with the MPA pressure in the study group, as well as with the ratio of MPA to ascending aorta in the control group. A threshold ratio value was calculated to accurately identify children with pulmonary arterial hypertension. Children with documented primary pulmonary arterial hypertension have a significantly higher ratio of MPA to ascending aorta (1.46) than children without pulmonary arterial hypertension (1.11). A ratio of 1.3 carries a positive likelihood of 34 and a positive predictive value of 97% for the diagnosis of pulmonary arterial hypertension. The pulmonary arteries were larger in children with pulmonary arterial hypertension than in a control group of normal children. A CT-measured ratio of MPA to ascending aorta of 1.3 should raise the suspicion of pulmonary arterial hypertension in children.

High resolution micro-CT of low attenuating organic materials using large area photon-counting detector

NASA Astrophysics Data System (ADS)

Kumpová, I.; Vavřík, D.; Fíla, T.; Koudelka, P.; Jandejsek, I.; Jakůbek, J.; Kytýř, D.; Zlámal, P.; Vopálenský, M.; Gantar, A.

2016-02-01

To overcome certain limitations of contemporary materials used for bone tissue engineering, such as inflammatory response after implantation, a whole new class of materials based on polysaccharide compounds is being developed. Here, nanoparticulate bioactive glass reinforced gelan-gum (GG-BAG) has recently been proposed for the production of bone scaffolds. This material offers promising biocompatibility properties, including bioactivity and biodegradability, with the possibility of producing scaffolds with directly controlled microgeometry. However, to utilize such a scaffold with application-optimized properties, large sets of complex numerical simulations using the real microgeometry of the material have to be carried out during the development process. Because the GG-BAG is a material with intrinsically very low attenuation to X-rays, its radiographical imaging, including tomographical scanning and reconstructions, with resolution required by numerical simulations might be a very challenging task. In this paper, we present a study on X-ray imaging of GG-BAG samples. High-resolution volumetric images of investigated specimens were generated on the basis of micro-CT measurements using a large area flat-panel detector and a large area photon-counting detector. The photon-counting detector was composed of a 010× 1 matrix of Timepix edgeless silicon pixelated detectors with tiling based on overlaying rows (i.e. assembled so that no gap is present between individual rows of detectors). We compare the results from both detectors with the scanning electron microscopy on selected slices in transversal plane. It has been shown that the photon counting detector can provide approx. 3× better resolution of the details in low-attenuating materials than the integrating flat panel detectors. We demonstrate that employment of a large area photon counting detector is a good choice for imaging of low attenuating materials with the resolution sufficient for numerical simulations.

CT features and common causes of arc of Riolan expansion: an analysis with 64-detector-row computed tomographic angiography

PubMed Central

Xie, Yuanliang; Jin, Chaolin; Zhang, Shutong; Wang, Xiang; Jiang, Yanping

2015-01-01

Objective: To study the manifestations of arc of Riolan expansion (ARE) using multi-detector computed tomography angiography (MDCTA). Materials and methods: The manifestations and clinical data of 626 consecutive mesentery CTA images were retrospectively analyzed. The 47 cases with ARE and 47 patients without expansion were involved. The average diameter of arc of Riolan was measured. Two radiologists after reaching consensus analyzed the shapes of mesenteric artery, CT findings and the occurrence and causes of ARE. Results: The mean diameter of arc of Riolan was 1.2 mm, 4.6 mm, 2.5 mm, 2.3 mm, 1.9 mm, 2.5 mm, and 2.0 mm at baseline and following obstruction of superior mesenteric artery (SMA), stenosis of SMA, obstruction of inferior mesenteric artery (IMA), stenosis of IMA, colon cancer, and active ulcerative colitis, respectively. The expansion of arc of Riolan was the most significant following obstruction of SMA. The diameters of arc of Riolan were significantly different between the upward flow group and the downward or the two-way flow groups, and between the colon tumor group and the active ulcerative colitis group. CT findings such as bowel wall thickening, contrast enhancement, intestinal obstruction, marginal artery expansion, lymph node enlargement varied and were help to identify the cause of ARE. Conclusions: ARE often suggests the occurrence of obstructed intestinal feeding artery or intestinal lesions. MDCTA can clearly display the situation of arc of Riolan and collateral circulation, and together with CT symptoms, can guide the selection of diagnosis and treatment schemes in clinic. PMID:26064208

[Evaluation of Slavic continuity for electrocardiograph (ECG)-gated non-helical scan using multi detector-row computed tomography with 64 data acquisition system].

PubMed

Shiotani, Masataka; Ogawa, Masato; Watanabe, Ryo; Shinohara, Tamotsu

2012-01-01

Multi detector-row computed tomography with 64 data acquisition systems are widely used for coronary CT angiography with an electrocardiograph (ECG) gated helical scan (HS). Step and shoot with ECG gated non-helical scan (snap shot pulse: SSP) could reduce exposure dose but banding artifact-like discontinuity was observed between adjacent slabs on volume rendering (VR) and curved planner reconstruction (CPR). Therefore, we investigated the factors that influence continuity of VR and CPR images by calculating image properties of Z-axis direction of slab. The observer performance studies were performed for evaluating continuity of simulated blood vessels of VR and CPR images at simulated heart rates: 50, 55, 57 and 60 beat per minute (bpm). As a result, the value of SD at both slab edges in SSP were 20.5% lower than middle part of slab and differences of value of SD were up to 4.4 between adjacent slab edges. Slice thickness of both slab edges were 20.3% thinner than that of the peripheral part of slab. At the border of the adjacent slab, the position of the simulated blood vessel was shifted. VR images of SSP at 57 bpm was indicated as the highest score and HS was significantly superior to SSP at 55 and 60 bpm (p<0.05). In CPR images, there were no significant differences at all simulated heart rates. In conclusion, we considered that VR images of SSP were influenced heart rates except 57 bpm (resonance case) and there was little difference of visibility for discontinuity of both CPR images obtained by SSP and HS.

Features of cranio-maxillofacial trauma in the massive Sichuan earthquake: analysis of 221 cases with multi-detector row CT.

PubMed

Chu, Zhi-gang; Yang, Zhi-gang; Dong, Zhi-hui; Chen, Tian-wu; Zhu, Zhi-yu; Deng, Wen; Xiao, Jia-he

2011-10-01

In a massive earthquake, cranio-maxillofacial trauma was common. The present study was to determine the features of cranio-maxillofacial trauma sustained in the massive Sichuan earthquake by multi-detector row computed tomography (MDCT). The study included 221 consecutive patients (123 males and 98 females; age range, 1-83 years; median age, 35 years) with cranio-maxillofacial trauma in the Sichuan earthquake, who underwent cranio-maxillofacial MDCT scans. The image data were retrospectively reviewed focusing on the injuries of the cranio-maxillofacial soft tissue, facial bones and cranium. All patients had soft tissue injuries frequently with foreign bodies. Ninety-seven (43.9%) patients had fractures (1.5 involved sites per patient, range from 1 to 8) including single cranial fractures in 36 (37.1%) cases, single maxillofacial fractures were seen in 48 (49.5%) and cranio-maxillofacial fractures in 13 (13.4%). Single bone fracture was more common than multiple bone fractures (p<0.05). Nasal, ethmoid bones and the orbits were the most commonly involved sites of the craniofacial region. Thirty-eight (17.2%) patients had intracranial injuries, the commonest being subarachnoid haemorrhage and the commonest sites were the temporal and frontal regions. Coexisting intracranial injuries were more common in patients with cranial fractures than in patients with maxillofacial fractures (p<0.05). Our results indicate that the cranio-maxillofacial trauma arising from the massive Sichuan earthquake had some characteristic features, and a significant number of individuals had the potential for combined cranial and maxillofacial injuries, successful management of which required a multidisciplinary approach. Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.

Role of Computer Aided Diagnosis (CAD) in the detection of pulmonary nodules on 64 row multi detector computed tomography

PubMed Central

Prakashini, K; Babu, Satish; Rajgopal, KV; Kokila, K Raja

2016-01-01

Aims and Objectives: To determine the overall performance of an existing CAD algorithm with thin-section computed tomography (CT) in the detection of pulmonary nodules and to evaluate detection sensitivity at a varying range of nodule density, size, and location. Materials and Methods: A cross-sectional prospective study was conducted on 20 patients with 322 suspected nodules who underwent diagnostic chest imaging using 64-row multi-detector CT. The examinations were evaluated on reconstructed images of 1.4 mm thickness and 0.7 mm interval. Detection of pulmonary nodules, initially by a radiologist of 2 years experience (RAD) and later by CAD lung nodule software was assessed. Then, CAD nodule candidates were accepted or rejected accordingly. Detected nodules were classified based on their size, density, and location. The performance of the RAD and CAD system was compared with the gold standard that is true nodules confirmed by consensus of senior RAD and CAD together. The overall sensitivity and false-positive (FP) rate of CAD software was calculated. Observations and Results: Of the 322 suspected nodules, 221 were classified as true nodules on the consensus of senior RAD and CAD together. Of the true nodules, the RAD detected 206 (93.2%) and 202 (91.4%) by the CAD. CAD and RAD together picked up more number of nodules than either CAD or RAD alone. Overall sensitivity for nodule detection with the CAD program was 91.4%, and FP detection per patient was 5.5%. The CAD showed comparatively higher sensitivity for nodules of size 4–10 mm (93.4%) and nodules in hilar (100%) and central (96.5%) location when compared to RAD's performance. Conclusion: CAD performance was high in detecting pulmonary nodules including the small size and low-density nodules. CAD even with relatively high FP rate, assists and improves RAD's performance as a second reader, especially for nodules located in the central and hilar region and for small nodules by saving RADs time. PMID:27578931

Exact consideration of data redundancies for spiral cone-beam CT

NASA Astrophysics Data System (ADS)

Lauritsch, Guenter; Katsevich, Alexander; Hirsch, Michael

2004-05-01

In multi-slice spiral computed tomography (CT) there is an obvious trend in adding more and more detector rows. The goals are numerous: volume coverage, isotropic spatial resolution, and speed. Consequently, there will be a variety of scan protocols optimizing clinical applications. Flexibility in table feed requires consideration of data redundancies to ensure efficient detector usage. Until recently this was achieved by approximate reconstruction algorithms only. However, due to the increasing cone angles there is a need of exact treatment of the cone beam geometry. A new, exact and efficient 3-PI algorithm for considering three-fold data redundancies was derived from a general, theoretical framework based on 3D Radon inversion using Grangeat's formula. The 3-PI algorithm possesses a simple and efficient structure as the 1-PI method for non-redundant data previously proposed. Filtering is one-dimensional, performed along lines with variable tilt on the detector. This talk deals with a thorough evaluation of the performance of the 3-PI algorithm in comparison to the 1-PI method. Image quality of the 3-PI algorithm is superior. The prominent spiral artifacts and other discretization artifacts are significantly reduced due to averaging effects when taking into account redundant data. Certainly signal-to-noise ratio is increased. The computational expense is comparable even to that of approximate algorithms. The 3-PI algorithm proves its practicability for applications in medical imaging. Other exact n-PI methods for n-fold data redundancies (n odd) can be deduced from the general, theoretical framework.

[Evaluation of Dose Reduction of the Active Collimator in Multi Detector Row CT].

PubMed

Ueno, Hiroyuki; Matsubara, Kosuke

The purpose of this study was to evaluate the performance of active collimator by changing acquisition parameters and obtaining dose profiles in z-axis direction. Dose profiles along z-axis were obtained using XRQA2 Gafchromic film. As a result, the active collimator reduced overranging about 55% compared to that without the active collimator. In addition, by changing the combination of X-ray beam width (32 mm, 40 mm), pitch factor (1.4, 0.6), and the X-ray tube rotation time (0.5 s/rot, 1.0 s/rot), the overranging changed from 19.4 to 34.9 mm. Although the active collimator is effective for reducing overranging, it is necessary to adjust acquisition parameters by taking the properties of the active collimator for acquisition parameters, especially setting beam width, into consideration.

Subjective and objective comparisons of image quality between ultra-high-resolution CT and conventional area detector CT in phantoms and cadaveric human lungs.

PubMed

Yanagawa, Masahiro; Hata, Akinori; Honda, Osamu; Kikuchi, Noriko; Miyata, Tomo; Uranishi, Ayumi; Tsukagoshi, Shinsuke; Tomiyama, Noriyuki

2018-05-29

To compare the image quality of the lungs between ultra-high-resolution CT (U-HRCT) and conventional area detector CT (AD-CT) images. Image data of slit phantoms (0.35, 0.30, and 0.15 mm) and 11 cadaveric human lungs were acquired by both U-HRCT and AD-CT devices. U-HRCT images were obtained with three acquisition modes: normal mode (U-HRCT N : 896 channels, 0.5 mm × 80 rows; 512 matrix), super-high-resolution mode (U-HRCT SHR : 1792 channels, 0.25 mm × 160 rows; 1024 matrix), and volume mode (U-HRCT SHR-VOL : non-helical acquisition with U-HRCT SHR ). AD-CT images were obtained with the same conditions as U-HRCT N . Three independent observers scored normal anatomical structures (vessels and bronchi), abnormal CT findings (faint nodules, solid nodules, ground-glass opacity, consolidation, emphysema, interlobular septal thickening, intralobular reticular opacities, bronchovascular bundle thickening, bronchiectasis, and honeycombing), noise, artifacts, and overall image quality on a 3-point scale (1 = worst, 2 = equal, 3 = best) compared with U-HRCT N . Noise values were calculated quantitatively. U-HRCT could depict a 0.15-mm slit. Both U-HRCT SHR and U-HRCT SHR-VOL significantly improved visualization of normal anatomical structures and abnormal CT findings, except for intralobular reticular opacities and reduced artifacts, compared with AD-CT (p < 0.014). Visually, U-HRCT SHR-VOL has less noise than U-HRCT SHR and AD-CT (p < 0.00001). Quantitative noise values were significantly higher in the following order: U-HRCT SHR (mean, 30.41), U-HRCT SHR-VOL (26.84), AD-CT (16.03), and U-HRCT N (15.14) (p < 0.0001). U-HRCT SHR and U-HRCT SHR-VOL resulted in significantly higher overall image quality than AD-CT and were almost equal to U-HRCT N (p < 0.0001). Both U-HRCT SHR and U-HRCT SHR-VOL can provide higher image quality than AD-CT, while U-HRCT SHR-VOL was less noisy than U-HRCT SHR . • Ultra-high-resolution CT (U-HRCT) can improve spatial resolution. • U-HRCT can reduce streak and dark band artifacts. • U-HRCT can provide higher image quality than conventional area detector CT. • In U-HRCT, the volume mode is less noisy than the super-high-resolution mode. • U-HRCT may provide more detailed information about the lung anatomy and pathology.

Entrance surface dose measurements using a small OSL dosimeter with a computed tomography scanner having 320 rows of detectors.

PubMed

Takegami, Kazuki; Hayashi, Hiroaki; Yamada, Kenji; Mihara, Yoshiki; Kimoto, Natsumi; Kanazawa, Yuki; Higashino, Kousaku; Yamashita, Kazuta; Hayashi, Fumio; Okazaki, Tohru; Hashizume, Takuya; Kobayashi, Ikuo

2017-03-01

Entrance surface dose (ESD) measurements are important in X-ray computed tomography (CT) for examination, but in clinical settings it is difficult to measure ESDs because of a lack of suitable dosimeters. We focus on the capability of a small optically stimulated luminescence (OSL) dosimeter. The aim of this study is to propose a practical method for using an OSL dosimeter to measure the ESD when performing a CT examination. The small OSL dosimeter has an outer width of 10 mm; it is assumed that a partial dose may be measured because the slice thickness and helical pitch can be set to various values. To verify our method, we used a CT scanner having 320 rows of detectors and checked the consistencies of the ESDs measured using OSL dosimeters by comparing them with those measured using Gafchromic™ films. The films were calibrated using an ionization chamber on the basis of half-value layer estimation. On the other hand, the OSL dosimeter was appropriately calibrated using a practical calibration curve previously proposed by our group. The ESDs measured using the OSL dosimeters were in good agreement with the reference ESDs from the Gafchromic™ films. Using these data, we also estimated the uncertainty of ESDs measured with small OSL dosimeters. We concluded that a small OSL dosimeter can be considered suitable for measuring the ESD with an uncertainty of 30 % during CT examinations in which pitch factors below 1.000 are applied.

Limitations of Airway Dimension Measurement on Images Obtained Using Multi-Detector Row Computed Tomography

PubMed Central

Oguma, Tsuyoshi; Hirai, Toyohiro; Niimi, Akio; Matsumoto, Hisako; Muro, Shigeo; Shigematsu, Michio; Nishimura, Takashi; Kubo, Yoshiro; Mishima, Michiaki

2013-01-01

Objectives (a) To assess the effects of computed tomography (CT) scanners, scanning conditions, airway size, and phantom composition on airway dimension measurement and (b) to investigate the limitations of accurate quantitative assessment of small airways using CT images. Methods An airway phantom, which was constructed using various types of material and with various tube sizes, was scanned using four CT scanner types under different conditions to calculate airway dimensions, luminal area (Ai), and the wall area percentage (WA%). To investigate the limitations of accurate airway dimension measurement, we then developed a second airway phantom with a thinner tube wall, and compared the clinical CT images of healthy subjects with the phantom images scanned using the same CT scanner. The study using clinical CT images was approved by the local ethics committee, and written informed consent was obtained from all subjects. Data were statistically analyzed using one-way ANOVA. Results Errors noted in airway dimension measurement were greater in the tube of small inner radius made of material with a high CT density and on images reconstructed by body algorithm (p<0.001), and there was some variation in error among CT scanners under different fields of view. Airway wall thickness had the maximum effect on the accuracy of measurements with all CT scanners under all scanning conditions, and the magnitude of errors for WA% and Ai varied depending on wall thickness when airways of <1.0-mm wall thickness were measured. Conclusions The parameters of airway dimensions measured were affected by airway size, reconstruction algorithm, composition of the airway phantom, and CT scanner types. In dimension measurement of small airways with wall thickness of <1.0 mm, the accuracy of measurement according to quantitative CT parameters can decrease as the walls become thinner. PMID:24116105

Heart CT scan

MedlinePlus

... Computed tomography scan - heart; Calcium scoring; Multi-detector CT scan - heart; Electron beam computed tomography - heart; Agatston ... table that slides into the center of the CT scanner. You will lie on your back with ...

Influence of detector collimation on SNR in four different MDCT scanners using a reconstructed slice thickness of 5 mm.

PubMed

Verdun, F R; Noel, A; Meuli, R; Pachoud, M; Monnin, P; Valley, J-F; Schnyder, P; Denys, A

2004-10-01

The purpose of this paper is to compare the influence of detector collimation on the signal-to-noise ratio (SNR) for a 5.0 mm reconstructed slice thickness for four multi-detector row CT (MDCT) units. SNRs were measured on Catphan test phantom images from four MDCT units: a GE LightSpeed QX/I, a Marconi MX 8000, a Toshiba Aquilion and a Siemens Volume Zoom. Five-millimetre-thick reconstructed slices were obtained from acquisitions performed using detector collimations of 2.0-2.5 mm and 5.0 mm, 120 kV, a 360 degrees tube rotation time of 0.5 s, a wide range of mA and pitch values in the range of 0.75-0.85 and 1.25-1.5. For each set of acquisition parameters, a Wiener spectrum was also calculated. Statistical differences in SNR for the different acquisition parameters were evaluated using a Student's t-test (P<0.05). The influence of detector collimation on the SNR for a 5.0-mm reconstructed slice thickness is different for different MDCT scanners. At pitch values lower than unity, the use of a small detector collimation to produce 5.0-mm thick slices is beneficial for one unit and detrimental for another. At pitch values higher than unity, using a small detector collimation is beneficial for two units. One manufacturer uses different reconstruction filters when switching from a 2.5- to a 5.0-mm detector collimation. For a comparable reconstructed slice thickness, using a smaller detector collimation does not always reduce image noise. Thus, the impact of the detector collimation on image noise should be determined by standard deviation calculations, and also by assessing the power spectra of the noise. Copyright 2004 Springer-Verlag

Helical cone beam CT with an asymmetrical detector.

PubMed

Zamyatin, Alexander A; Taguchi, Katsuyuki; Silver, Michael D

2005-10-01

If a multislice or other area detector is shifted to one side to cover a larger field of view, then the data are truncated on one side. We propose a method to restore the missing data in helical cone-beam acquisitions that uses measured data on the longer side of the asymmetric detector array. The method is based on the idea of complementary rays, which is well known in fan beam geometry; in this paper we extend this concept to the cone-beam case. Different cases of complementary data coverage and dependence on the helical pitch are considered. The proposed method is used in our prototype 16-row CT scanner with an asymmetric detector and a 700 mm field of view. For evaluation we used scanned body phantom data and computer-simulated data. To simulate asymmetric truncation, the full, symmetric datasets were truncated by dropping either 22.5% or 45% from one side of the detector. Reconstructed images from the prototype scanner with the asymmetrical detector show excellent image quality in the extended field of view. The proposed method allows flexible helical pitch selection and can be used with overscan, short-scan, and super-short-scan reconstructions.

Multi-detector CT imaging in the postoperative orthopedic patient with metal hardware.

PubMed

Vande Berg, Bruno; Malghem, Jacques; Maldague, Baudouin; Lecouvet, Frederic

2006-12-01

Multi-detector CT imaging (MDCT) becomes routine imaging modality in the assessment of the postoperative orthopedic patients with metallic instrumentation that degrades image quality at MR imaging. This article reviews the physical basis and CT appearance of such metal-related artifacts. It also addresses the clinical value of MDCT in postoperative orthopedic patients with emphasis on fracture healing, spinal fusion or arthrodesis, and joint replacement. MDCT imaging shows limitations in the assessment of the bone marrow cavity and of the soft tissues for which MR imaging remains the imaging modality of choice despite metal-related anatomic distortions and signal alteration.

Determining contrast medium dose and rate on basis of lean body weight: does this strategy improve patient-to-patient uniformity of hepatic enhancement during multi-detector row CT?

PubMed

Ho, Lisa M; Nelson, Rendon C; Delong, David M

2007-05-01

To prospectively evaluate the use of lean body weight (LBW) as the main determinant of the volume and rate of contrast material administration during multi-detector row computed tomography of the liver. This HIPAA-compliant study had institutional review board approval. All patients gave written informed consent. Four protocols were compared. Standard protocol involved 125 mL of iopamidol injected at 4 mL/sec. Total body weight (TBW) protocol involved 0.7 g iodine per kilogram of TBW. Calculated LBW and measured LBW protocols involved 0.86 g of iodine per kilogram and 0.92 g of iodine per kilogram calculated or measured LBW for men and women, respectively. Injection rate used for the three experimental protocols was determined proportionally on the basis of the calculated volume of contrast material. Postcontrast attenuation measurements during portal venous phase were obtained in liver, portal vein, and aorta for each group and were summed for each patient. Patient-to-patient enhancement variability in same group was measured with Levene test. Two-tailed t test was used to compare the three experimental protocols with the standard protocol. Data analysis was performed in 101 patients (25 or 26 patients per group), including 56 men and 45 women (mean age, 53 years). Average summed attenuation values for standard, TBW, calculated LBW, and measured LBW protocols were 419 HU +/- 50 (standard deviation), 443 HU +/- 51, 433 HU +/- 50, and 426 HU +/- 33, respectively (P = not significant for all). Levene test results for summed attenuation data for standard, TBW, calculated LBW, and measured LBW protocols were 40 +/- 29, 38 +/- 33 (P = .83), 35 +/- 35 (P = .56), and 26 +/- 19 (P = .05), respectively. By excluding highly variable but poorly perfused adipose tissue from calculation of contrast medium dose, the measured LBW protocol may lessen patient-to-patient enhancement variability while maintaining satisfactory hepatic and vascular enhancement.

Inter-algorithm lesion volumetry comparison of real and 3D simulated lung lesions in CT

NASA Astrophysics Data System (ADS)

Robins, Marthony; Solomon, Justin; Hoye, Jocelyn; Smith, Taylor; Ebner, Lukas; Samei, Ehsan

2017-03-01

The purpose of this study was to establish volumetric exchangeability between real and computational lung lesions in CT. We compared the overall relative volume estimation performance of segmentation tools when used to measure real lesions in actual patient CT images and computational lesions virtually inserted into the same patient images (i.e., hybrid datasets). Pathologically confirmed malignancies from 30 thoracic patient cases from Reference Image Database to Evaluate Therapy Response (RIDER) were modeled and used as the basis for the comparison. Lesions included isolated nodules as well as those attached to the pleura or other lung structures. Patient images were acquired using a 16 detector row or 64 detector row CT scanner (Lightspeed 16 or VCT; GE Healthcare). Scans were acquired using standard chest protocols during a single breath-hold. Virtual 3D lesion models based on real lesions were developed in Duke Lesion Tool (Duke University), and inserted using a validated image-domain insertion program. Nodule volumes were estimated using multiple commercial segmentation tools (iNtuition, TeraRecon, Inc., Syngo.via, Siemens Healthcare, and IntelliSpace, Philips Healthcare). Consensus based volume comparison showed consistent trends in volume measurement between real and virtual lesions across all software. The average percent bias (+/- standard error) shows -9.2+/-3.2% for real lesions versus -6.7+/-1.2% for virtual lesions with tool A, 3.9+/-2.5% and 5.0+/-0.9% for tool B, and 5.3+/-2.3% and 1.8+/-0.8% for tool C, respectively. Virtual lesion volumes were statistically similar to those of real lesions (< 4% difference) with p >.05 in most cases. Results suggest that hybrid datasets had similar inter-algorithm variability compared to real datasets.

Quantitative colorectal cancer perfusion measurement using dynamic contrast-enhanced multidetector-row computed tomography: effect of acquisition time and implications for protocols.

PubMed

Goh, Vicky; Halligan, Steve; Hugill, Jo-Ann; Gartner, Louise; Bartram, Clive I

2005-01-01

To determine the effect of acquisition time on quantitative colorectal cancer perfusion measurement. Dynamic contrast-enhanced computed tomography (CT) was performed prospectively in 10 patients with histologically proven colorectal cancer using 4-detector row CT (Lightspeed Plus; GE Healthcare Technologies, Waukesha, WI). Tumor blood flow, blood volume, mean transit time, and permeability were assessed for 3 acquisition times (45, 65, and 130 seconds). Mean values for all 4 perfusion parameters for each acquisition time were compared using the paired t test. Significant differences in permeability values were noted between acquisitions of 45 seconds and 65 and 130 seconds, respectively (P=0.02, P=0.007). There was no significant difference for values of blood volume, blood flow, and mean transit time between any of the acquisition times. Scan acquisitions of 45 seconds are too short for reliable permeability measurement in the abdomen. Longer acquisition times are required.

Comparison of the Diagnostic Image Quality of the Canine Maxillary Dentoalveolar Structures Obtained by Cone Beam Computed Tomography and 64-Multidetector Row Computed Tomography

PubMed Central

Soukup, Jason W.; Drees, Randi; Koenig, Lisa J.; Snyder, Christopher J.; Hetzel, Scott; Miles, Chanda R.; Schwarz, Tobias

2016-01-01

Summary The objective of this blinded study was to validate the use of cone beam computed tomography (CT) for imaging of the canine maxillary dentoalveolar structures by comparing its diagnostic image quality with that of 64-multidetector row CT. Sagittal slices of a tooth-bearing segment of the maxilla of a commercially purchased dog skull embedded in methyl methacrylate were obtained along a line parallel with the dental arch using a commercial histology diamond saw. The slice of tooth-bearing bone that best depicted the dentoalveolar structures was chosen and photographed. The maxilla segment was imaged with cone beam CT and 64-multidetector row CT. Four blinded evaluators compared the cone beam CT and 64-multidetector row CT images and image quality was scored as it related to the anatomy of dentoalveolar structures. Trabecular bone, enamel, dentin, pulp cavity, periodontal ligament space, and lamina dura were scored. In addition, a score depicting the evaluators overall impression of the image was recorded. Images acquired with cone beam CT were found to be significantly superior in image quality to images acquired with 64-multidetector row CT overall, and in all scored categories. In our study setting, cone beam CT was found to be a valid and clinically superior imaging modality for the canine maxillary dentoalveolar structures when compared to 64-multidetector row CT. PMID:26415384

Numerical Analysis of Organ Doses Delivered During Computed Tomography Examinations Using Japanese Adult Phantoms with the WAZA-ARI Dosimetry System.

PubMed

Takahashi, Fumiaki; Sato, Kaoru; Endo, Akira; Ono, Koji; Ban, Nobuhiko; Hasegawa, Takayuki; Katsunuma, Yasushi; Yoshitake, Takayasu; Kai, Michiaki

2015-08-01

A dosimetry system for computed tomography (CT) examinations, named WAZA-ARI, is being developed to accurately assess radiation doses to patients in Japan. For dose calculations in WAZA-ARI, organ doses were numerically analyzed using average adult Japanese male (JM) and female (JF) phantoms with the Particle and Heavy Ion Transport code System (PHITS). Experimental studies clarified the photon energy distribution of emitted photons and dose profiles on the table for some multi-detector row CT (MDCT) devices. Numerical analyses using a source model in PHITS could specifically take into account emissions of x rays from the tube to the table with attenuation of photons through a beam-shaping filter for each MDCT device based on the experiment results. The source model was validated by measuring the CT dose index (CTDI). Numerical analyses with PHITS revealed a concordance of organ doses with body sizes of the JM and JF phantoms. The organ doses in the JM phantoms were compared with data obtained using previously developed systems. In addition, the dose calculations in WAZA-ARI were verified with previously reported results by realistic NUBAS phantoms and radiation dose measurement using a physical Japanese model (THRA1 phantom). The results imply that numerical analyses using the Japanese phantoms and specified source models can give reasonable estimates of dose for MDCT devices for typical Japanese adults.

The effects of once-weekly teriparatide on hip structure and biomechanical properties assessed by CT.

PubMed

Ito, M; Oishi, R; Fukunaga, M; Sone, T; Sugimoto, T; Shiraki, M; Nishizawa, Y; Nakamura, T

2014-03-01

Once-weekly administration of 56.5 μg teriparatide improved cortical bone parameters and biomechanical parameters at the proximal femur by CT geometry analysis. The aim of this study was to evaluate the effects of weekly administration of teriparatide [human PTH (1-34)] on bone geometry, volumetric bone mineral density (vBMD), and parameters of bone strength at the proximal femur which were longitudinally investigated using computed tomography (CT). The subjects were a subgroup of a recent, randomly assigned, double-blind study (578 subjects) comparing the anti-fracture efficacy of a once-weekly subcutaneous injection of 56.5 μg teriparatide with placebo (TOWER trial). Sixty-six ambulatory postmenopausal women with osteoporosis were enrolled at 15 study sites having multi-detector row CT, and included women injected with teriparatide (n = 29, 74.2 ± 5.1 years) or with placebo (n = 37, 74.8 ± 5.3 years). CT data were obtained at baseline and follow-up scans were performed at 48 and 72 weeks. The data were analyzed to obtain cross-sectional densitometric, geometric, and biomechanical parameters including the section modulus (SM) and buckling ratio (BR) of the femoral neck, inter-trochanter, and femoral shaft. We found that once-weekly teriparatide increased cortical thickness/cross-sectional area (CSA) and total area, and improved biomechanical properties (i.e., decreasing BR) at the femoral neck and shaft. Teriparatide did not change the cortical perimeter. Our longitudinal analysis of proximal femur geometry by CT revealed that once-weekly administration of 56.5 μg teriparatide improved cortical bone parameters at the femoral neck and shaft and also improved biomechanical parameters.

Comparison of standard- and low-tube voltage 320-detector row volume CT angiography in detection of intracranial aneurysms with digital subtraction angiography as gold standard.

PubMed

Sun, Gang; Ding, Juan; Lu, Yang; Li, Min; Li, Li; Li, Guo-ying; Zhang, Xu-ping

2012-03-01

The aim of this study was to prospectively assess the effect of low-tube voltage (80 kVp) 320-detector row volume computed tomographic (CT) angiography (L-VCTA) in the detection of intracranial aneurysms, with three-dimensional (3D) spin digital subtraction angiography (DSA) as the gold standard. Forty-eight patients with clinically suspected subarachnoid hemorrhages were divided into two groups. One group underwent L-VCTA and DSA, while the other group underwent conventional-tube voltage (120 kVp) volume CT angiography (C-VCTA) and DSA. Vascular enhancement, image quality, detection accuracy of aneurysms, and radiation dose were compared between the two groups. For objective image quality, the L-VCTA group had higher mean vessel attenuation, correlated with higher image noise and lower signal-to-noise ratio, than the C-VCTA group. For subjective image quality, there were no significant differences between the two groups regarding scores for arterial enhancement, depiction of small arterial detail, interference of venous structures, and overall image quality scores. The mean effective dose for the L-VCTA group was significantly lower than for the C-VCTA group (0.56 ± 0.25 vs 1.84 ± 0.002 mSv), with a reduction of radiation dose of 69.73%. With 3D DSA as the reference standard, the sensitivity, specificity, and accuracy in the L-VCTA and C-VCTA groups were 94.12%, 100%, 94.4% and 100%, 100%, and 100%, respectively. In both groups, there were significant correlations for maximum aneurysm diameter measurements between volume CT angiography and 3D DSA; no statistical difference in the mean maximum diameter of each aneurysm was measured between volume CT angiography and 3D DSA. L-VCTA is helpful in detecting intracranial aneurysms, with results similar to those of 3D DSA, but at a lower radiation dose than C-VCTA. Copyright © 2012 AUR. Published by Elsevier Inc. All rights reserved.

[Comparison of radiation dose reduction of prospective ECG-gated one beat scan using 320 area detector CT coronary angiography and prospective ECG-gated helical scan with high helical pitch (FlashScan) using 64 multidetector-row CT coronary angiography].

PubMed

Matsutani, Hideyuki; Sano, Tomonari; Kondo, Takeshi; Fujimoto, Shinichiro; Sekine, Takako; Arai, Takehiro; Morita, Hitomi; Takase, Shinichi

2010-12-20

A high radiation dose associated with 64 multidetector-row computed tomography (64-MDCT) is a major concern for physicians and patients alike. A new 320 row area detector computed tomography (ADCT) can obtain a view of the entire heart with one rotation (0.35 s) without requiring the helical method. As such, ADCT is expected to reduce the radiation dose. We studied image quality and radiation dose of ADCT compared to that of 64-MDCT in patients with a low heart rate (HR≤60). Three hundred eighty-five consecutive patients underwent 64-MDCT and 379 patients, ADCT. Patients with an arrhythmia were excluded. Prospective ECG-gated helical scan with high HP (FlashScan) in 64 was used for MDCT and prospective ECG-gated conventional one beat scan, for 320-ADCT. Image quality was visually evaluated by an image quality score. Radiation dose was estimated by DLP (mGy･cm) for 64-MDCT and DLP.e (mGy･cm) for 320-ADCT. Radiation dose of 320-ADCT (208±48 mGy･cm) was significantly (P<0.0001) lower than that of 64-MDCT (484±112 mGy･cm), and image quality score of 320-ADCT (3.0±0.2) was significantly (P=0.0011) higher than that of 64-MDCT (2.9±0.4). Scan time of 320-ADCT (1.4±0.1 s) was also significantly (P<0.0001) shorter than that of 64-MDCT (6.8±0.6 s). 320-ADCT can achieve not only a reduction in radiation dose but also a superior image quality and shortening of scan time compared to 64-MDCT.

Comparison of the Diagnostic Image Quality of the Canine Maxillary Dentoalveolar Structures Obtained by Cone Beam Computed Tomography and 64-Multidetector Row Computed Tomography.

PubMed

Soukup, Jason W; Drees, Randi; Koenig, Lisa J; Snyder, Christopher J; Hetzel, Scott; Miles, Chanda R; Schwarz, Tobias

2015-01-01

The objective of this blinded study was to validate the use of cone beam computed tomography (C) for imaging of the canine maxillary dentoalveolar structures by comparing its diagnostic image quality with that of 64-multidetector row CT Sagittal slices of a tooth-bearing segment of the maxilla of a commercially purchased dog skull embedded in methylmethacrylate were obtained along a line parallel with the dental arch using a commercial histology diamond saw. The slice of tooth-bearing bone that best depicted the dentoalveolar structures was chosen and photographed. The maxillary segment was imaged with cone beam CT and 64-multidetector row CT. Four blinded evaluators compared the cone beam CT and 64-multidetector row CT images and image quality was scored as it related to the anatomy of dentoalveolar structures. Trabecular bone, enamel, dentin, pulp cavity, periodontal ligament space, and lamina dura were scored In addition, a score depicting the evaluators overall impression of the image was recorded. Images acquired with cone beam CT were found to be significantly superior in image quality to images acquired with 64-multidetector row CT overall, and in all scored categories. In our study setting cone beam CT was found to be a valid and clinically superior imaging modality for the canine maxillary dentoalveolar structures when compared to 64-multidetector row CT.

Reduction of thoracic aorta motion artifact with high-pitch 128-slice dual-source computed tomographic angiography: a historical control study.

PubMed

Nakagawa, Junichiro; Tasaki, Osamu; Watanabe, Yoshiyuki; Azuma, Takeo; Ohnishi, Mitsuo; Ukai, Isao; Tahara, Kenichi; Ogura, Hiroshi; Kuwagata, Yasuyuki; Hamasaki, Toshimitsu; Shimazu, Takeshi

2013-01-01

Electrocardiogram-gated imaging combined with multi-detector row computed tomography (MDCT) has reduced cardiac motion artifacts, but it was not practical in the emergency setting. The purpose of this study was to evaluate the ability of a high-pitch, 128-slice dual-source CT (DSCT) scanner to reduce motion artifacts in patients admitted to the emergency room. This study comprised 100 patients suspected of having thoracic aorta lesions. We examined 47 patients with the 128-slice DSCT scanner (DSCT group), and 53 patients were examined with a 64-slice MDCT scanner (MDCT group). Six anatomic areas in the thoracic aorta were evaluated. Computed tomography images in the DSCT group were distinct, and significant differences were observed in images of all areas between the 2 groups except for the descending aorta. The high-pitch DSCT scanner can reduce motion artifacts of the thoracic aorta and enable radiological diagnosis even in patients with tachycardia and without breath hold.

Comparison Study of Regularizations in Spectral Computed Tomography Reconstruction

NASA Astrophysics Data System (ADS)

Salehjahromi, Morteza; Zhang, Yanbo; Yu, Hengyong

2018-12-01

The energy-resolving photon-counting detectors in spectral computed tomography (CT) can acquire projections of an object in different energy channels. In other words, they are able to reliably distinguish the received photon energies. These detectors lead to the emerging spectral CT, which is also called multi-energy CT, energy-selective CT, color CT, etc. Spectral CT can provide additional information in comparison with the conventional CT in which energy integrating detectors are used to acquire polychromatic projections of an object being investigated. The measurements obtained by X-ray CT detectors are noisy in reality, especially in spectral CT where the photon number is low in each energy channel. Therefore, some regularization should be applied to obtain a better image quality for this ill-posed problem in spectral CT image reconstruction. Quadratic-based regularizations are not often satisfactory as they blur the edges in the reconstructed images. As a result, different edge-preserving regularization methods have been adopted for reconstructing high quality images in the last decade. In this work, we numerically evaluate the performance of different regularizers in spectral CT, including total variation, non-local means and anisotropic diffusion. The goal is to provide some practical guidance to accurately reconstruct the attenuation distribution in each energy channel of the spectral CT data.

Novel imaging detailing the origins of a pneumothorax.

PubMed

Nakanishi, Kozo; Goto, Hidenori; Ito, Tomokazu; Nagata, Yasuhito; Hayashi, Shinichi; Ishihara, Toshihiro

2018-01-01

This is a prospective clinical study aimed at introducing a method to visualise the location of an air leak and to identify the bulla responsible on three-dimensional (3-D) cine CT. In 10 patients with spontaneous pneumothorax, dynamic 320-detector row CT was performed with injection of 0.9% saline into the affected pleural cavity via a preplaced chest tube. In eight cases, 3-D cine CT thoracography revealed the location of the air leak and the bulla responsible (7 cases: air stream sign; 1 case: repeated collapse and expansion of a bulla with the patient's breathing). Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Submillisievert median radiation dose for coronary angiography with a second-generation 320-detector row CT scanner in 107 consecutive patients.

PubMed

Chen, Marcus Y; Shanbhag, Sujata M; Arai, Andrew E

2013-04-01

To (a) use a new second-generation wide-volume 320-detector row computed tomographic (CT) scanner to explore optimization of radiation exposure in coronary CT angiography in an unselected and consecutive cohort of patients referred for clinical purposes and (b) compare estimated radiation exposure and image quality with that from a cohort of similar patients who underwent imaging with a previous first-generation CT system. The study was approved by the institutional review board, and all subjects provided written consent. Coronary CT angiography was performed in 107 consecutive patients with a new second-generation 320-detector row unit. Estimated radiation exposure and image quality were compared with those from 100 consecutive patients who underwent imaging with a previous first-generation scanner. Effective radiation dose was estimated by multiplying the dose-length product by an effective dose conversion factor of 0.014 mSv/mGy ⋅ cm and reported with size-specific dose estimates (SSDEs). Image quality was evaluated by two independent readers. The mean age of the 107 patients was 55.4 years ± 12.0 (standard deviation); 57 patients (53.3%) were men. The median body mass index was 27.3 kg/m(2) (range, 18.1-47.2 kg/m(2)); however, 71 patients (66.4%) were overweight, obese, or morbidly obese. A tube potential of 100 kV was used in 97 patients (90.6%), single-volume acquisition was used in 104 (97.2%), and prospective electrocardiographic gating was used in 106 (99.1%). The mean heart rate was 57.1 beats per minute ± 11.2 (range, 34-96 beats per minute), which enabled single-heartbeat scans in 100 patients (93.4%). The median radiation dose was 0.93 mSv (interquartile range [IQR], 0.58-1.74 mSv) with the second-generation unit and 2.67 mSv (IQR, 1.68-4.00 mSv) with the first-generation unit (P < .0001). The median SSDE was 6.0 mGy (IQR, 4.1-10.0 mGy) with the second-generation unit and 13.2 mGy (IQR, 10.2-18.6 mGy) with the first-generation unit (P < .0001). Overall, the radiation dose was less than 0.5 mSv for 23 of the 107 CT angiography examinations (21.5%), less than 1 mSv for 58 (54.2%), and less than 4 mSv for 103 (96.3%). All studies were of diagnostic quality, with most having excellent image quality. Three of four image quality indexes were significantly better with the second-generation unit compared with the first-generation unit. The combination of a gantry rotation time of 275 msec, wide volume coverage, iterative reconstruction, automated exposure control, and larger x-ray power generator of the second-generation CT scanner provides excellent image quality over a wide range of body sizes and heart rates at low radiation doses. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13122621/-/DC1. RSNA, 2013

WE-E-18C-01: Multi-Energy CT: Current Status and Recent Innovations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pelc, N; McCollough, C; Yu, L

2014-06-15

Conventional computed tomography (CT) uses a single polychromatic x-ray spectrum and energy integrating detectors, and produces images whose contrast depends on the effective attenuation coefficient of the broad spectrum beam. This can introduce errors from beam hardening and does not produce the optimal contrast-to-noise ratio. In addition, multiple materials can have the same effective attenuation coefficient, causing different materials to be indistinguishable in conventional CT images. If transmission measurements at two or more energies are obtained, even with polychromatic beams, more specific information about the object can be obtained. If the object does not contain materials with k-edges in themore » spectrum, the x-ray attenuation can be well-approximated by a linear combination of two processes (photoelectric absorption and Compton scattering) or, equivalently, two basis materials. For such cases, two spectral measurements suffice, although additional measurements can provide higher precision. If K-edge materials are present, additional spectral measurements can allow these materials to be isolated. Current commercial implementations use varied approaches, including two sources operating a different kVp, one source whose kVp is rapidly switched in a single scan, and a dual layer detector that can provide spectral information in every reading. Processing of the spectral information can be performed in the raw data domain or in the image domain. The process of calculating the amount of the two basis functions implicitly corrects for beam hardening and therefore can lead to improvements in quantitative accuracy. Information can be extracted to provide material specific information beyond that of conventional CT. This additional information has been shown to be important in several clinical applications, and can also lead to more efficient clinical protocols. Recent innovations in x-ray sources, detectors, and systems have made multi-energy CT much more practical and improved its performance. In addition, this is a very active area of research and further improvements are expected through further technological improvements. Learning Objectives: Basic principles of multi-energy CT Current implementations of mutli-energy CT Data and image analysis methods in multi-energy CT Current clinical applications of dual energy CT5. recent innovations and anticipated advances in multi-energy CT.« less

Postmortem dynamic cerebral angiography for detecting aneurysm and bleeding sites in cases of subarachnoid hemorrhage.

PubMed

Inokuchi, Go; Yajima, Daisuke; Hayakawa, Mutsumi; Motomura, Ayumi; Chiba, Fumiko; Torimitsu, Suguru; Makino, Yohsuke; Iwase, Hirotaro

2014-12-01

One of the advantages of postmortem imaging is its ability to obtain diagnostic findings in a non-destructive manner when autopsy is either difficult or may destroy forensic evidence. In recent years, efforts have been made to incorporate computed tomography (CT) based postmortem angiography into forensic pathology; however, it is not currently clear how well the modality can determine sites of bleeding in cases of subarachnoid hemorrhage. Therefore, in this study, we investigated the utility of postmortem cerebral angiography using multi-detector row CT (MDCT) by injecting a contrast medium through a catheter inserted into the internal carotid and vertebral arteries of 10 subarachnoid hemorrhage cases. While postmortem MDCT angiography (PMCTA) was capable of detecting aneurysms in a non-destructive manner, it was sometimes difficult to identify the aneurysm and bleeding sites because of a large amount of contrast medium leaking into the extravascular space. To overcome this problem, we developed the novel contrast imaging method "dynamic cerebral angiography," which involves scanning the same area multiple times while injecting contrast medium to enable real-time observation of the contrasted vasculature. Using multiphase contrast images acquired by this method, we successfully captured the moment when contrast medium leaked from the hemorrhage site. This method will be useful for identifying exact bleeding sites on PMCTA.

Broad ligament hernia successfully treated by laparoscopy: Case report and review of literature.

PubMed

Matsunami, Masatoshi; Kusanagi, Hiroshi; Hayashi, Ken; Yamada, Shigetoshi; Kano, Nobuyasu

2014-11-01

We report a case of a 36-year-old woman with a history of caesarean section who presented with small bowel obstruction. Abdominal multi-detector CT showed discontinuity of the small bowel near the broad ligament on the left. We made a provisional diagnosis of an internal hernia through a defect in the broad ligament and performed laparoscopic exploration, which revealed a viable ileal loop incarcerated by the broad ligament. Multi-detector CT may be useful for diagnosing this type of defect preoperatively, whereby open surgery can be avoided. © 2014 Japan Society for Endoscopic Surgery, Asia Endosurgery Task Force and Wiley Publishing Asia Pty Ltd.

Implementation of GPU accelerated SPECT reconstruction with Monte Carlo-based scatter correction.

PubMed

Bexelius, Tobias; Sohlberg, Antti

2018-06-01

Statistical SPECT reconstruction can be very time-consuming especially when compensations for collimator and detector response, attenuation, and scatter are included in the reconstruction. This work proposes an accelerated SPECT reconstruction algorithm based on graphics processing unit (GPU) processing. Ordered subset expectation maximization (OSEM) algorithm with CT-based attenuation modelling, depth-dependent Gaussian convolution-based collimator-detector response modelling, and Monte Carlo-based scatter compensation was implemented using OpenCL. The OpenCL implementation was compared against the existing multi-threaded OSEM implementation running on a central processing unit (CPU) in terms of scatter-to-primary ratios, standardized uptake values (SUVs), and processing speed using mathematical phantoms and clinical multi-bed bone SPECT/CT studies. The difference in scatter-to-primary ratios, visual appearance, and SUVs between GPU and CPU implementations was minor. On the other hand, at its best, the GPU implementation was noticed to be 24 times faster than the multi-threaded CPU version on a normal 128 × 128 matrix size 3 bed bone SPECT/CT data set when compensations for collimator and detector response, attenuation, and scatter were included. GPU SPECT reconstructions show great promise as an every day clinical reconstruction tool.

Over-exposure correction in knee cone-beam CT imaging with automatic exposure control using a partial low dose scan

NASA Astrophysics Data System (ADS)

Choi, Jang-Hwan; Muller, Kerstin; Hsieh, Scott; Maier, Andreas; Gold, Garry; Levenston, Marc; Fahrig, Rebecca

2016-03-01

C-arm-based cone-beam CT (CBCT) systems with flat-panel detectors are suitable for diagnostic knee imaging due to their potentially flexible selection of CT trajectories and wide volumetric beam coverage. In knee CT imaging, over-exposure artifacts can occur because of limitations in the dynamic range of the flat panel detectors present on most CBCT systems. We developed a straightforward but effective method for correction and detection of over-exposure for an Automatic Exposure Control (AEC)-enabled standard knee scan incorporating a prior low dose scan. The radiation dose associated with the low dose scan was negligible (0.0042mSv, 2.8% increase) which was enabled by partially sampling the projection images considering the geometry of the knees and lowering the dose further to be able to just see the skin-air interface. We combined the line integrals from the AEC and low dose scans after detecting over-exposed regions by comparing the line profiles of the two scans detector row-wise. The combined line integrals were reconstructed into a volumetric image using filtered back projection. We evaluated our method using in vivo human subject knee data. The proposed method effectively corrected and detected over-exposure, and thus recovered the visibility of exterior tissues (e.g., the shape and density of the patella, and the patellar tendon), incorporating a prior low dose scan with a negligible increase in radiation exposure.

Simultaneous profile measurements of medium- and high-Z impurity concentrations (nZ/ne) , Te , ΔZeff and n e2Zeff in MCF plasmas from multi-energy x-rays

NASA Astrophysics Data System (ADS)

Maddox, Jacob; Delgado-Aparicio, Luis; Pablant, Novimir; Rutman, Max; Hill, Ken; Bitter, Manfred; Reinke, Matthew; Rice, John

2016-10-01

Novel energy resolved measurements of x-ray emissions were used to characterize impurity concentrations, electron temperature, and ΔZeff in a variety of Alcator C-Mod plasmas. A PILATUS2 detector programmed in a multi-energy configuration and used in a pinhole camera geometry provides the capability to function similar to a pulse height analyzer (PHA) but with full plasma profile views and sufficient spatial ( 1 cm), energy ( .5 keV), and temporal ( 10 ms) resolution. Each of the PILATUS2's 100k (487x195) pixels can be set to an energy threshold, which sorts x-ray emissions into energy bins by counting only photons with energy above the threshold energy. By setting every 13th pixel row to the same energy bin and the 12 interjacent pixel rows to different energy bins on the PILATUS2 detector gives 38 poloidal sightlines (487 rows/13 energy bins). The number of photons detected in each energy bin depends on (nZ/ne) , Te, and ne2Zeff, so that these plasma parameters can be extracted by fitting the data to an emission model, which includes free-free, free-bound, and bound-bound emissions from a De/H background plasma with perturbing medium and high-Z impurities, like intrinsic Mo, Fe, and Cu or injected W. Also, radial electron temperature profiles were measured during LHRF and ICRF and compared to Thomson scattering and ECE.

CT liver volumetry using three-dimensional image data in living donor liver transplantation: Effects of slice thickness on volume calculation

PubMed Central

Hori, Masatoshi; Suzuki, Kenji; Epstein, Mark L.; Baron, Richard L.

2011-01-01

The purpose was to evaluate a relationship between slice thickness and calculated volume on CT liver volumetry by comparing the results for images with various slice thicknesses including three-dimensional images. Twenty adult potential liver donors (12 men, 8 women; mean age, 39 years; range, 24–64) underwent CT with a 64-section multi-detector row CT scanner after intra-venous injection of contrast material. Four image sets with slice thicknesses of 0.625 mm, 2.5 mm, 5 mm, and 10 mm were used. First, a program developed in our laboratory for automated liver extraction was applied to CT images, and the liver boundary was obtained automatically. Then, an abdominal radiologist reviewed all images on which automatically extracted boundaries were superimposed, and edited the boundary on each slice to enhance the accuracy. Liver volumes were determined by counting of the voxels within the liver boundary. Mean whole liver volumes estimated with CT were 1322.5 cm3 on 0.625-mm, 1313.3 cm3 on 2.5-mm, 1310.3 cm3 on 5-mm, and 1268.2 cm3 on 10-mm images. Volumes calculated for three-dimensional (0.625-mm-thick) images were significantly larger than those for thicker images (P<.0001). Partial liver volumes of right lobe, left lobe, and lateral segment were also evaluated in a similar manner. Estimated maximum differences in calculated volumes of lateral segment was −10.9 cm3 (−4.6%) between 0.625-mm and 5-mm images. In conclusion, liver volumes calculated on 2.5-mm or thicker images were significantly smaller than volumes calculated on three-dimensional images. If a maximum error of 5% in the calculated graft volume is within the range of having an insignificant clinical impact, 5-mm thick images are acceptable for CT volumetry. If not, three-dimensional images could be essential. PMID:21850689

An ancient Roman bowl embedded in a soil sample: surface shaded three dimensional display using data from a multi-detector CT.

PubMed

De Maeseneer, M; Buls, N; Cleeren, N; Lenchik, L; De Mey, J

2006-01-01

We present an unusual application of multidetector CT and shaded surface rendering in the investigation of a soil sample, containing an ancient Roman bronze bowl. The CT findings were of fundamental importance in helping the archaeologists study the bronze bowl from the soil sample.

Evaluation of a metal artifact reduction algorithm applied to post-interventional flat detector CT in comparison to pre-treatment CT in patients with acute subarachnoid haemorrhage.

PubMed

Mennecke, Angelika; Svergun, Stanislav; Scholz, Bernhard; Royalty, Kevin; Dörfler, Arnd; Struffert, Tobias

2017-01-01

Metal artefacts can impair accurate diagnosis of haemorrhage using flat detector CT (FD-CT), especially after aneurysm coiling. Within this work we evaluate a prototype metal artefact reduction algorithm by comparison of the artefact-reduced and the non-artefact-reduced FD-CT images to pre-treatment FD-CT and multi-slice CT images. Twenty-five patients with acute aneurysmal subarachnoid haemorrhage (SAH) were selected retrospectively. FD-CT and multi-slice CT before endovascular treatment as well as FD-CT data sets after treatment were available for all patients. The algorithm was applied to post-treatment FD-CT. The effect of the algorithm was evaluated utilizing the pre-post concordance of a modified Fisher score, a subjective image quality assessment, the range of the Hounsfield units within three ROIs, and the pre-post slice-wise Pearson correlation. The pre-post concordance of the modified Fisher score, the subjective image quality, and the pre-post correlation of the ranges of the Hounsfield units were significantly higher for artefact-reduced than for non-artefact-reduced images. Within the metal-affected slices, the pre-post slice-wise Pearson correlation coefficient was higher for artefact-reduced than for non-artefact-reduced images. The overall diagnostic quality of the artefact-reduced images was improved and reached the level of the pre-interventional FD-CT images. The metal-unaffected parts of the image were not modified. • After coiling subarachnoid haemorrhage, metal artefacts seriously reduce FD-CT image quality. • This new metal artefact reduction algorithm is feasible for flat-detector CT. • After coiling, MAR is necessary for diagnostic quality of affected slices. • Slice-wise Pearson correlation is introduced to evaluate improvement of MAR in future studies. • Metal-unaffected parts of image are not modified by this MAR algorithm.

Performance of today’s dual energy CT and future multi energy CT in virtual non-contrast imaging and in iodine quantification: A simulation study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faby, Sebastian, E-mail: sebastian.faby@dkfz.de; Kuchenbecker, Stefan; Sawall, Stefan

2015-07-15

Purpose: To study the performance of different dual energy computed tomography (DECT) techniques, which are available today, and future multi energy CT (MECT) employing novel photon counting detectors in an image-based material decomposition task. Methods: The material decomposition performance of different energy-resolved CT acquisition techniques is assessed and compared in a simulation study of virtual non-contrast imaging and iodine quantification. The material-specific images are obtained via a statistically optimal image-based material decomposition. A projection-based maximum likelihood approach was used for comparison with the authors’ image-based method. The different dedicated dual energy CT techniques are simulated employing realistic noise models andmore » x-ray spectra. The authors compare dual source DECT with fast kV switching DECT and the dual layer sandwich detector DECT approach. Subsequent scanning and a subtraction method are studied as well. Further, the authors benchmark future MECT with novel photon counting detectors in a dedicated DECT application against the performance of today’s DECT using a realistic model. Additionally, possible dual source concepts employing photon counting detectors are studied. Results: The DECT comparison study shows that dual source DECT has the best performance, followed by the fast kV switching technique and the sandwich detector approach. Comparing DECT with future MECT, the authors found noticeable material image quality improvements for an ideal photon counting detector; however, a realistic detector model with multiple energy bins predicts a performance on the level of dual source DECT at 100 kV/Sn 140 kV. Employing photon counting detectors in dual source concepts can improve the performance again above the level of a single realistic photon counting detector and also above the level of dual source DECT. Conclusions: Substantial differences in the performance of today’s DECT approaches were found for the application of virtual non-contrast and iodine imaging. Future MECT with realistic photon counting detectors currently can only perform comparably to dual source DECT at 100 kV/Sn 140 kV. Dual source concepts with photon counting detectors could be a solution to this problem, promising a better performance.« less

Analysis of in-plane signal-to-noise ratio in computed tomography

NASA Astrophysics Data System (ADS)

Hara, Takanori; Ichikawa, Katsuhiro; Sanada, Shigeru; Ida, Yoshihiro

2008-03-01

The purposes of this study are to analyze signal-to-noise ratio (SNR) changes for in-plane (axial plane) position and in-plane direction in X-ray computed tomography (CT) system and to verify those visual effects by using simulated small low-contrast disc objects. Three-models of multi detector-row CT were employed. Modulation transfer function (MTF) was obtained using a thin metal wire. Noise power spectrum (NPSs) was obtained using a cylindrical water phantom. The measurement positions were set to center and off-centered positions of 64mm, 128mm and 192mm. One-dimensional MTFs and NPSs for the x- and y-direction were calculated by means of a numerical slit scanning method. SNRs were then calculated from MTFs and NPSs. The simulated low-contrast disc objects with diameter of 2 to 10mm and contrast to background of 3.0%, 4.5% and 6.0% were superimposed on the water phantom images. Respective simulated objects in the images are then visually evaluated in degree of their recognition, and then the validity of the resultant SNRs are examined. Resultant in-plane SNRs differed between the center and peripheries and indicated a trend that the SNR values increase in accordance with distance from the center. The increasing degree differed between x- and y-direction, and also changed by the CT systems. These results suggested that the peripheries region has higher low-contrast detectability than the center. The properties derived in this study indicated that the depiction abilities at various in-plane positions are not uniform in clinical CT images, and detectability of the low contrast lesion may be influenced.

Pacemaker-induced Metallic Artifacts in Coronary Computed Tomography Angiography: Clinical Feasibility of Single Energy Metal Artifact Reduction Technique.

PubMed

Takayanagi, Tomoya; Arai, Takehiro; Amanuma, Makoto; Sano, Tomonari; Ichiba, Masato; Ishizaka, Kazumasa; Sekine, Takako; Matsutani, Hideyuki; Morita, Hitomi; Takase, Shinichi

2017-01-01

Coronary computed tomography angiography (CCTA) in patients with pacemaker suffers from metallic lead-induced artifacts, which often interfere with accurate assessment of coronary luminal stenosis. The purpose of this study was to assess a frequency of the lead-induced artifacts and artifact-suppression effect by the single energy metal artifact reduction (SEMAR) technique. Forty-one patients with a dual-chamber pacemaker were evaluated using a 320 multi-detector row CT (MDCT). Among them, 22 patients with motion-free full data reconstruction images were the final candidates. Images with and without the SMEAR technique were subjectively compared, and the degree of metallic artifacts was compared. On images without SEMAR, severe metallic artifacts were often observed in the right coronary artery (#1, #2, #3) and distal anterior descending branch (#8). These artifacts were effectively suppressed by SEMAR, and the luminal accessibility was significantly improved in #3 and #8. While pacemaker leads often cause metallic-induced artifacts, SEMAR technique reduced the artifacts and significantly improved the accessibility of coronary lumen in #3 and #8.

Multi-energy CT based on a prior rank, intensity and sparsity model (PRISM).

PubMed

Gao, Hao; Yu, Hengyong; Osher, Stanley; Wang, Ge

2011-11-01

We propose a compressive sensing approach for multi-energy computed tomography (CT), namely the prior rank, intensity and sparsity model (PRISM). To further compress the multi-energy image for allowing the reconstruction with fewer CT data and less radiation dose, the PRISM models a multi-energy image as the superposition of a low-rank matrix and a sparse matrix (with row dimension in space and column dimension in energy), where the low-rank matrix corresponds to the stationary background over energy that has a low matrix rank, and the sparse matrix represents the rest of distinct spectral features that are often sparse. Distinct from previous methods, the PRISM utilizes the generalized rank, e.g., the matrix rank of tight-frame transform of a multi-energy image, which offers a way to characterize the multi-level and multi-filtered image coherence across the energy spectrum. Besides, the energy-dependent intensity information can be incorporated into the PRISM in terms of the spectral curves for base materials, with which the restoration of the multi-energy image becomes the reconstruction of the energy-independent material composition matrix. In other words, the PRISM utilizes prior knowledge on the generalized rank and sparsity of a multi-energy image, and intensity/spectral characteristics of base materials. Furthermore, we develop an accurate and fast split Bregman method for the PRISM and demonstrate the superior performance of the PRISM relative to several competing methods in simulations.

Evaluation of simethicone-coated cellulose as a negative oral contrast agent for abdominal CT.

PubMed

Sahani, Dushyant V; Jhaveri, Kartik S; D'souza, Roy V; Varghese, Jose C; Halpern, Elkan; Harisinghani, Mukesh G; Hahn, Peter F; Saini, Sanjay

2003-05-01

Because of the increased clinical use of computed tomography (CT) for imaging the abdominal vasculature and urinary tract, there is a need for negative contrast agents. The authors undertook this study to assess the suitability of simethicone-coated cellulose (SCC), which is approved for use as an oral contrast agent in sonography, for use as a negative oral contrast agent in abdominal CT. This prospective study involved 40 adult patients scheduled to undergo abdominal CT for the evaluation of hematuria. Prior to scanning, 20 subjects received 800 mL of SCC and 20 received 800 mL of water as an oral contrast agent. Imaging was performed with a multi-detector row helical scanner in two phases, according to the abdominal CT protocol used for hematuria evaluation at the authors' institution. The first, "early" phase began an average of 15 minutes after the ingestion of contrast material; the second, "late" phase began an average of 45 minutes after the ingestion of contrast material. Blinded analysis was performed by three abdominal radiologists separately, using a three-point scale (0 = poor, 1 = acceptable, 2 = excellent) to assess the effectiveness of SCC for marking the proximal, middle, and distal small bowel. Average scores for enhancement with SCC and with water were obtained and compared. Statistical analysis was performed with a Wilcoxon signed-rank test. SCC was assigned higher mean scores than water for enhancement in each segment of the bowel, both on early-phase images (0.8-1.35 for SCC vs 0.6-1.1 for water) and on late-phase images (1.1-1.4 vs 0.81-0.96). Bowel marking with SCC, particularly in the jejunum and ileum, also was rated better than that with water in a high percentage of patients. The differences between the scores for water and for SCC, however, were not statistically significant (P > .05). SCC is effective as a negative oral contrast agent for small bowel marking at CT.

Initial Simulated FFR Investigation Using Flow Measurements in Patient-specific 3D Printed Coronary Phantoms.

PubMed

Shepard, Lauren; Sommer, Kelsey; Izzo, Richard; Podgorsak, Alexander; Wilson, Michael; Said, Zaid; Rybicki, Frank J; Mitsouras, Dimitrios; Rudin, Stephen; Angel, Erin; Ionita, Ciprian N

2017-02-11

Accurate patient-specific phantoms for device testing or endovascular treatment planning can be 3D printed. We expand the applicability of this approach for cardiovascular disease, in particular, for CT-geometry derived benchtop measurements of Fractional Flow Reserve, the reference standard for determination of significant individual coronary artery atherosclerotic lesions. Coronary CT Angiography (CTA) images during a single heartbeat were acquired with a 320×0.5mm detector row scanner (Toshiba Aquilion ONE). These coronary CTA images were used to create 4 patient-specific cardiovascular models with various grades of stenosis: severe, <75% (n=1); moderate, 50-70% (n=1); and mild, <50% (n=2). DICOM volumetric images were segmented using a 3D workstation (Vitrea, Vital Images); the output was used to generate STL files (using AutoDesk Meshmixer), and further processed to create 3D printable geometries for flow experiments. Multi-material printed models (Stratasys Connex3) were connected to a programmable pulsatile pump, and the pressure was measured proximal and distal to the stenosis using pressure transducers. Compliance chambers were used before and after the model to modulate the pressure wave. A flow sensor was used to ensure flow rates within physiological reported values. 3D model based FFR measurements correlated well with stenosis severity. FFR measurements for each stenosis grade were: 0.8 severe, 0.7 moderate and 0.88 mild. 3D printed models of patient-specific coronary arteries allows for accurate benchtop diagnosis of FFR. This approach can be used as a future diagnostic tool or for testing CT image-based FFR methods.

Combined anatomical and functional imaging using coronary CT angiography and myocardial perfusion SPECT in symptomatic adults with abnormal origin of a coronary artery.

PubMed

Uebleis, C; Groebner, M; von Ziegler, F; Becker, A; Rischpler, C; Tegtmeyer, R; Becker, C; Lehner, S; Haug, A R; Cumming, P; Bartenstein, P; Franz, W M; Hacker, M

2012-10-01

There has been a lack of standardized workup guidelines for patients with congenital abnormal origin of a coronary artery from the opposite sinus (ACAOS). We aimed to evaluate the use of cardiac hybrid imaging using multi-detector row CT (MDCT) for coronary CT angiography (Coronary CTA) and stress-rest myocardial perfusion SPECT (MPS) for comprehensive diagnosis of symptomatic adult patients with ACAOS. Seventeen symptomatic patients (12 men; 54 ± 13 years) presenting with ACAOS underwent coronary CTA and MPS. Imaging data were analyzed by conventional means, and with additional use of 3D image fusion to allocate stress induced perfusion defects (PD) to their supplying coronary arteries. An anomalous RCA arose from the left anterior sinus in eight patients, an abnormal origin from the right sinus was detected in nine patients (5 left coronary arteries, LCA and 4 LCx). Five of the 17 patients (29%) demonstrated a reversible PD in MPS. There was no correlation between the anatomical variants of ACAOS and the presence of myocardial ischemia. Image fusion enabled the allocation of reversible PD to the anomalous vessel in three patients (two cases in the RCA and the other in the LCA territory); PD in two patients were allocated to the territory of artery giving rise to the anomalies, rather than the anomalies themselves. In a small cohort of adult symptomatic patients with ACAOS anomaly there was no relation found between the specific anatomical variant and the appearance of stress induced myocardial ischemia using cardiac hybrid imaging.

Dose profiles for lung and breast regions at prospective and retrospective CT coronary angiography using optically stimulated luminescence dosimeters on a 64-detector CT scanner.

PubMed

Funama, Yoshinori; Taguchi, Katsuyuki; Utsunomiya, Daisuke; Oda, Seitaro; Murasaki, Hiroo; Yamashita, Yasuyuki; Awai, Kazuo

2012-01-01

The purpose of our study was to acquire dose profiles at critical organs of lung and breast regions using optically stimulated luminescence (OSL) dosimeters; assess the actual radiation dose delivered at retrospective and prospective computed tomography coronary angiography (CTCA). Using a chest CT phantom we applied a prospectively-gated step-and-shoot- and a retrospectively-gated helical mode on a 64-detector row CT scanner. Retrospective scan mode was used with and without electrocardiogram (ECG) based tube current modulation. OSL dosimeters were used to measure dose profiles. In the both scan modes we acquired dose profiles and determined the mean and maximum dose in left lung and in left breast regions. In prospective mode, the mean dose was 21.53 mGy in left lung- and 23.59 mGy in left breast region. With respect to the retrospective mode, the mean dose with tube current modulation was 38.63 mGy for left lung- and 46.02 mGy for left breast region, i.e. 0.56 and 0.55 times lower than the mean dose without modulation. The OSL dosimeter is useful for measurement of the actual radiation dose along z-axis at lung and breast regions in the prospective and the retrospective CTCA. Copyright © 2011 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Energy-discriminating X-ray computed tomography system utilizing a cadmium telluride detector

NASA Astrophysics Data System (ADS)

Sato, Eiichi; Abderyim, Purkhet; Enomoto, Toshiyuki; Watanabe, Manabu; Hitomi, Keitaro; Takahasi, Kiyomi; Sato, Shigehiro; Ogawae, Akira; Onagawa, Jun

2010-07-01

An energy-discriminating K-edge X-ray computed tomography (CT) system is useful for increasing contrast resolution of a target region utilizing contrast media and for reducing the absorbed dose for patients. The CT system is of the first-generation type with a cadmium telluride (CdTe) detector, and a projection curve is obtained by translation scanning using the CdTe detector in conjunction with an x-stage. An object is rotated by the rotation step angle using a turntable between the translation scans. Thus, CT is carried out by repeating the translation scanning and the rotation of an object. Penetrating X-ray photons from the object are detected by the CdTe detector, and event signals of X-ray photons are produced using charge-sensitive and shaping amplifiers. Both the photon energy and the energy width are selected by use of a multi-channel analyzer, and the number of photons is counted by a counter card. Demonstration of enhanced iodine K-edge X-ray CT was carried out by selecting photons with energies just beyond the iodine K-edge energy of 33.2 keV.

Investigating the effect of characteristic x-rays in cadmium zinc telluride detectors under breast computerized tomography operating conditions

PubMed Central

Glick, Stephen J.; Didier, Clay

2013-01-01

A number of research groups have been investigating the use of dedicated breast computerized tomography (CT). Preliminary results have been encouraging, suggesting an improved visualization of masses on breast CT as compared to conventional mammography. Nonetheless, there are many challenges to overcome before breast CT can become a routine clinical reality. One potential improvement over current breast CT prototypes would be the use of photon counting detectors with cadmium zinc telluride (CZT) (or CdTe) semiconductor material. These detectors can operate at room temperature and provide high detection efficiency and the capability of multi-energy imaging; however, one factor in particular that limits image quality is the emission of characteristic x-rays. In this study, the degradative effects of characteristic x-rays are examined when using a CZT detector under breast CT operating conditions. Monte Carlo simulation software was used to evaluate the effect of characteristic x-rays and the detector element size on spatial and spectral resolution for a CZT detector used under breast CT operating conditions. In particular, lower kVp spectra and thinner CZT thicknesses were studied than that typically used with CZT based conventional CT detectors. In addition, the effect of characteristic x-rays on the accuracy of material decomposition in spectral CT imaging was explored. It was observed that when imaging with 50-60 kVp spectra, the x-ray transmission through CZT was very low for all detector thicknesses studied (0.5–3.0 mm), thus retaining dose efficiency. As expected, characteristic x-ray escape from the detector element of x-ray interaction increased with decreasing detector element size, approaching a 50% escape fraction for a 100 μm size detector element. The detector point spread function was observed to have only minor degradation with detector element size greater than 200 μm and lower kV settings. Characteristic x-rays produced increasing distortion in the spectral response with decreasing detector element size. If not corrected for, this caused a large bias in estimating tissue density parameters for material decomposition. It was also observed that degradation of the spectral response due to characteristic x-rays caused worsening precision in the estimation of tissue density parameters. It was observed that characteristic x-rays do cause some degradation in the spatial and spectral resolution of thin CZT detectors operating under breast CT conditions. These degradations should be manageable with careful selection of the detector element size. Even with the observed spectral distortion from characteristic x-rays, it is still possible to correctly estimate tissue parameters for material decomposition using spectral CT if accurate modeling is used. PMID:24187383

Usefulness of multidetector-row CT (MDCT) for the diagnosis of non-occlusive mesenteric ischemia (NOMI): assessment of morphology and diameter of the superior mesenteric artery (SMA) on multi-planar reconstructed (MPR) images.

PubMed

Woodhams, Reiko; Nishimaki, Hiroshi; Fujii, Kaoru; Kakita, Satoko; Hayakawa, Kazushige

2010-10-01

The purpose of this study was to assess the efficacy of multidetector-row CT (MDCT) for the diagnosis of non-occlusive mesenteric ischemia (NOMI) by analyzing morphology and diameter of superior mesenteric artery (SMA). We assessed whether MDCT was as useful as angiography for the diagnosis of NOMI. Four patients who were diagnosed with NOMI were retrospectively analyzed. All patients had 8-row MDCT followed by laparotomy. Two of them underwent angiography after MDCT. The morphology and diameter of SMA of these cases was analyzed on multi-planar reconstructed (MPR) images. The mean diameter of SMA of NOMI cases was compared to that of 13 control cases. MPR images of all NOMI cases showed irregular narrowing of the SMA, spasm of the arcades of SMA, and poor demonstration of intramural vessels. MPR images of two patients who had angiography were concordant with their angiograms. The mean diameter of SMA of NOMI patients was 3.4±1.1mm, which was statistically smaller than that of 13 control patients, 6.0±1.5mm (P<0.05, Wilcoxon rank sum tests). Angiography has been recognized essential for the diagnosis of NOMI. This study shows the possibility of MDCT to be an equivalently useful modality compared to angiography for the diagnosis of NOMI by interpreting morphologic appearance and diameter of SMA. Introduction of MDCT in the decision tree of NOMI treatment may bring the benefit of prompt diagnosis and subsequent early and efficient initiation of therapy, which may improve the mortality. Copyright © 2009 Elsevier Ireland Ltd. All rights reserved.

Stomach arteriovenous malformation resected by laparoscopy-assisted surgery: A case report.

PubMed

Hotta, Masahiro; Yamamoto, Kazuhito; Cho, Kazumitsu; Takao, Yoshimune; Fukuoka, Takeshi; Uchida, Eiji

2016-05-01

Arteriovenous malformations of the stomach are an uncommon cause of upper GI bleeding. We report a case of stomach arteriovenous malformation in an 85-year-old Asian man who presented with massive hematemesis. Initial esophagogastroduodenoscopy did not detect this lesion, but contrast multi-detector CT confirmed GI bleeding. Multi-detector CT revealed a mass of blood vessels underlying the submucosa that arose from the right gastroepiploic artery. Repeat esophagogastroduodenoscopy showed that the lesion was a submucosal tumor with erosion and without active bleeding in the lower body of the stomach on the greater curvature. We performed partial gastrectomy via laparoscopy-assisted surgery. The histopathological diagnosis was arteriovenous malformation. © 2016 Japan Society for Endoscopic Surgery, Asia Endosurgery Task Force and John Wiley & Sons Australia, Ltd.

Acquiring 4D Thoracic CT Scans Using Ciné CT Acquisition

NASA Astrophysics Data System (ADS)

Low, Daniel

One method for acquiring 4D thoracic CT scans is to use ciné acquisition. Ciné acquisition is conducted by rotating the gantry and acquiring x-ray projections while keeping the couch stationary. After a complete rotation, a single set of CT slices, the number corresponding to the number of CT detector rows, is produced. The rotation period is typically sub second so each image set corresponds to a single point in time. The ciné image acquisition is repeated for at least one breathing cycle to acquire images throughout the breathing cycle. Once the images are acquired at a single couch position, the couch is moved to the abutting position and the acquisition is repeated. Post-processing of the images sets typically resorts the sets into breathing phases, stacking images from a specific phase to produce a thoracic CT scan at that phase. Benefits of the ciné acquisition protocol include, the ability to precisely identify the phase with respect to the acquired image, the ability to resort images after reconstruction, and the ability to acquire images over arbitrarily long times and for arbitrarily many images (within dose constraints).

Evaluation of prosthetic valve thrombosis by 64-row multi-detector computed tomography. .

PubMed

Tarzia, Vincenzo; Bortolussi, Giacomo; Rubino, Maurizio; Gallo, Michele; Bottio, Tomaso; Gerosa, Gino

2015-03-01

Multi-detector computed tomography (MDCT), combined with retrospective electrocardiographic gating, permits cardiac imaging with high accuracy. Recent advances in MDCT have seemed to respond adequately to the need for a non-invasive and reliable assessment of the coronary artery lumen. Two patients with prosthetic aortic valves (one bioprosthetic, one mechanical) presented at the authors' institution with dyspnea and syncopal episodes. MDCT was performed to evaluate thrombus characteristics and exclude coronary artery disease (CAD). Based on the MDCT coronary artery assessment, neither patient underwent preoperative invasive coronary angiography, abolishing the risk of any iatrogenic thrombus fragmentation and subsequent embolization. One patient underwent surgical treatment without complications, while medical therapy was successful in the other case. MDCT can be used for the accurate imaging of thrombi on prosthetic aortic valves, and to correctly assess possible CAD.

A high-resolution imaging technique using a whole-body, research photon counting detector CT system

NASA Astrophysics Data System (ADS)

Leng, S.; Yu, Z.; Halaweish, A.; Kappler, S.; Hahn, K.; Henning, A.; Li, Z.; Lane, J.; Levin, D. L.; Jorgensen, S.; Ritman, E.; McCollough, C.

2016-03-01

A high-resolution (HR) data collection mode has been introduced to a whole-body, research photon-counting-detector CT system installed in our laboratory. In this mode, 64 rows of 0.45 mm x 0.45 mm detector pixels were used, which corresponded to a pixel size of 0.25 mm x 0.25 mm at the iso-center. Spatial resolution of this HR mode was quantified by measuring the MTF from a scan of a 50 micron wire phantom. An anthropomorphic lung phantom, cadaveric swine lung, temporal bone and heart specimens were scanned using the HR mode, and image quality was subjectively assessed by two experienced radiologists. High spatial resolution of the HR mode was evidenced by the MTF measurement, with 15 lp/cm and 20 lp/cm at 10% and 2% modulation. Images from anthropomorphic phantom and cadaveric specimens showed clear delineation of small structures, such as lung vessels, lung nodules, temporal bone structures, and coronary arteries. Temporal bone images showed critical anatomy (i.e. stapes superstructure) that was clearly visible in the PCD system. These results demonstrated the potential application of this imaging mode in lung, temporal bone, and vascular imaging. Other clinical applications that require high spatial resolution, such as musculoskeletal imaging, may also benefit from this high resolution mode.

Carotid stenosis assessment with multi-detector CT angiography: comparison between manual and automatic segmentation methods.

PubMed

Zhu, Chengcheng; Patterson, Andrew J; Thomas, Owen M; Sadat, Umar; Graves, Martin J; Gillard, Jonathan H

2013-04-01

Luminal stenosis is used for selecting the optimal management strategy for patients with carotid artery disease. The aim of this study is to evaluate the reproducibility of carotid stenosis quantification using manual and automated segmentation methods using submillimeter through-plane resolution Multi-Detector CT angiography (MDCTA). 35 patients having carotid artery disease with >30 % luminal stenosis as identified by carotid duplex imaging underwent contrast enhanced MDCTA. Two experienced CT readers quantified carotid stenosis from axial source images, reconstructed maximum intensity projection (MIP) and 3D-carotid geometry which was automatically segmented by an open-source toolkit (Vascular Modelling Toolkit, VMTK) using NASCET criteria. Good agreement among the measurement using axial images, MIP and automatic segmentation was observed. Automatic segmentation methods show better inter-observer agreement between the readers (intra-class correlation coefficient (ICC): 0.99 for diameter stenosis measurement) than manual measurement of axial (ICC = 0.82) and MIP (ICC = 0.86) images. Carotid stenosis quantification using an automatic segmentation method has higher reproducibility compared with manual methods.

A High-Resolution Time-of-Flight Clinical PET Detection System Using a Gapless PMT-Quadrant-Sharing Method

NASA Astrophysics Data System (ADS)

Wong, Wai-Hoi; Li, Hongdi; Zhang, Yuxuan; Ramirez, Rocio; An, Shaohui; Wang, Chao; Liu, Shitao; Dong, Yun; Baghaei, Hossain

2015-10-01

We developed a high-resolution Photomultiplier-Quadrant-Sharing (PQS) PET system for human imaging. This system is made up of 24 detector panels. Each panel (bank) consists of 3 ×7 detector blocks, and each block has 16 ×16 LYSO crystals of 2.35 ×2.35 ×15.2 mm3. We used a novel detector-grinding scheme that is compatible with the PQS detector-pixel-decoding requirements to make a gapless cylindrical detector ring for maximizing detection efficiency while delivering an ultrahigh spatial-resolution for a whole-body PET camera with a ring diameter of 87 cm and axial field of view of 27.6 cm. This grinding scheme enables two adjacent gapless panels to share one row of the PMTs to extend the PQS configuration beyond one panel and thus maximize the economic benefit (in PMT usage) of the PQS design. The entire detector ring has 129,024 crystals, all of which are clearly decoded using only 576 PMTs (38-mm diameter). Thus, each PMT on average decodes 224 crystals to achieve a high crystal-pitch resolution of 2.44 mm ×2.44 mm. The detector blocks were mass-produced with our slab-sandwich-slice technique using a set of optimized mirror-film patterns (between crystals) to maximize light output and achieve high spatial and timing resolution. This detection system with time-of-flight capability was placed in a human PET/CT gantry. The reconstructed image resolution of the system was about 2.87 mm using 2D-filtered back-projection. The time-of-flight resolution was 473 ps. The preliminary images of phantoms and clinical studies presented in this work demonstrate the capability of this new PET/CT system to produce high-quality images.

A comparative study of FDG PET/CT and enhanced multi-detector CT for detecting liver metastasis according to the size and location.

PubMed

Park, Jung Mi; Kim, Il Young; Kim, Sang Won; Lee, Sang Mi; Kim, Hyun Gi; Kim, Shin Young; Shin, Hyung Chul

2013-04-01

The aim of this study was to compare the diagnosability between (18)F-fluorodeoxyglucose (FDG) PET/CT and enhanced multi-detector CT (MDCT) for the detection of liver metastasis (LM) according to the size and location in liver and to evaluate standard maximum standardized uptake values (SUVmax) of all liver metastatic lesions. One hundred two consecutive patients with malignancy who underwent both FDG PET/CT and MDCT for LM evaluation were retrospectively reviewed. Among them, 56 patients with LM were enrolled in this study. LM was confirmed by follow-up imaging studies after at least 6 months or by histopathology. FDG PET/CT and MDCT images were visually analyzed using three-point scale by the consensus of two radiologists and two nuclear medicine physicians. The size and location (central vs. sub-capsular) of the all liver lesions were evaluated using MDCT images. Furthermore, SUVmax of all liver lesions on FDG PET/CT images were calculated. A total of 146 liver lesions were detected by FDG PET/CT and MDCT and 142 of the lesions were diagnosed as LM. The detection rates of MDCT and FDG PET/CT for LM by visual analysis were 77 and 78%, respectively. There was no significant difference of detection rate according to the overall location and size of the lesions. However, FDG PET/CT was more sensitive than MDCT for detecting small and sub-capsular LM. The detection rate of FDG PET/CT for LM was 68% by the cutoff SUVmax of 2.7. Although the diagnosabilities of MDCT and FDG PET/CT for detecting LM were comparable, FDG PET/CT is superior to MDCT for detecting small LM located in the sub-capsular portion of liver.

Performance evaluation of a compact PET/SPECT/CT tri-modality system for small animal imaging applications

NASA Astrophysics Data System (ADS)

Wei, Qingyang; Wang, Shi; Ma, Tianyu; Wu, Jing; Liu, Hui; Xu, Tianpeng; Xia, Yan; Fan, Peng; Lyu, Zhenlei; Liu, Yaqiang

2015-06-01

PET, SPECT and CT imaging techniques are widely used in preclinical small animal imaging applications. In this paper, we present a compact small animal PET/SPECT/CT tri-modality system. A dual-functional, shared detector design is implemented which enables PET and SPECT imaging with a same LYSO ring detector. A multi-pinhole collimator is mounted on the system and inserted into the detector ring in SPECT imaging mode. A cone-beam CT consisting of a micro focus X-ray tube and a CMOS detector is implemented. The detailed design and the performance evaluations are reported in this paper. In PET imaging mode, the measured NEMA based spatial resolution is 2.12 mm (FWHM), and the sensitivity at the central field of view (CFOV) is 3.2%. The FOV size is 50 mm (∅)×100 mm (L). The SPECT has a spatial resolution of 1.32 mm (FWHM) and an average sensitivity of 0.031% at the center axial, and a 30 mm (∅)×90 mm (L) FOV. The CT spatial resolution is 8.32 lp/mm @10%MTF, and the contrast discrimination function value is 2.06% with 1.5 mm size cubic box object. In conclusion, a compact, tri-modality PET/SPECT/CT system was successfully built with low cost and high performance.

Reproducible Simulation of Respiratory Motion in Porcine Lung Explants.

PubMed

Biederer, J; Plathow, C; Schoebinger, M; Tetzlaff, R; Puderbach, M; Bolte, H; Zaporozhan, J; Meinzer, H-P; Heller, M; Kauczor, H-U

2006-11-01

To develop a model for exactly reproducible respiration motion simulations of animal lung explants inside an MR-compatible chest phantom. The materials included a piston pump and a flexible silicone reconstruction of a porcine diaphragm and were used in combination with an established MR-compatible chest phantom for porcine heart-lung preparations. The rhythmic inflation and deflation of the diaphragm at the bottom of the artificial thorax with water (1 - 1.5 L) induced lung tissue displacement resembling diaphragmatic breathing. This system was tested on five porcine heart-lung preparations using 1.5T MRI with transverse and coronal 3D-GRE (TR/TE = 3.63/1.58, 256 x 256 matrix, 350 mm FOV, 4 mm slices) and half Fourier T2-FSE (TR/TE = 545/29, 256 x 192, 350 mm, 6 mm) as well as multiple row detector CT (16 x 1 mm collimation, pitch 1.5, FOV 400 mm, 120 mAs) acquired at five fixed inspiration levels. Dynamic CT scans and coronal MRI with dynamic 2D-GRE and 2D-SS-GRE sequences (image frequencies of 10/sec and 3/sec, respectively) were acquired during continuous "breathing" (7/minute). The position of the piston pump was visually correlated with the respiratory motion visible through the transparent wall of the phantom and with dynamic displays of CT and MR images. An elastic body splines analysis of the respiratory motion was performed using CT data. Visual evaluation of MRI and CT showed three-dimensional movement of the lung tissue throughout the respiration cycle. Local tissue displacement inside the lung explants was documented with motion maps calculated from CT. The maximum displacement at the top of the diaphragm (mean 26.26 [SD 1.9] mm on CT and 27.16 [SD 1.5] mm on MRI, respectively [p = 0.25; Wilcoxon test]) was in the range of tidal breathing in human patients. The chest phantom with a diaphragmatic pump is a promising platform for multi-modality imaging studies of the effects of respiratory lung motion.

Assessing vertebral fracture risk on volumetric quantitative computed tomography by geometric characterization of trabecular bone structure

NASA Astrophysics Data System (ADS)

Checefsky, Walter A.; Abidin, Anas Z.; Nagarajan, Mahesh B.; Bauer, Jan S.; Baum, Thomas; Wismüller, Axel

2016-03-01

The current clinical standard for measuring Bone Mineral Density (BMD) is dual X-ray absorptiometry, however more recently BMD derived from volumetric quantitative computed tomography has been shown to demonstrate a high association with spinal fracture susceptibility. In this study, we propose a method of fracture risk assessment using structural properties of trabecular bone in spinal vertebrae. Experimental data was acquired via axial multi-detector CT (MDCT) from 12 spinal vertebrae specimens using a whole-body 256-row CT scanner with a dedicated calibration phantom. Common image processing methods were used to annotate the trabecular compartment in the vertebral slices creating a circular region of interest (ROI) that excluded cortical bone for each slice. The pixels inside the ROI were converted to values indicative of BMD. High dimensional geometrical features were derived using the scaling index method (SIM) at different radii and scaling factors (SF). The mean BMD values within the ROI were then extracted and used in conjunction with a support vector machine to predict the failure load of the specimens. Prediction performance was measured using the root-mean-square error (RMSE) metric and determined that SIM combined with mean BMD features (RMSE = 0.82 +/- 0.37) outperformed MDCT-measured mean BMD (RMSE = 1.11 +/- 0.33) (p < 10-4). These results demonstrate that biomechanical strength prediction in vertebrae can be significantly improved through the use of SIM-derived texture features from trabecular bone.

Initial simulated FFR investigation using flow measurements in patient-specific 3D printed coronary phantoms

NASA Astrophysics Data System (ADS)

Shepard, Lauren; Sommer, Kelsey; Izzo, Richard; Podgorsak, Alexander; Wilson, Michael; Said, Zaid; Rybicki, Frank J.; Mitsouras, Dimitrios; Rudin, Stephen; Angel, Erin; Ionita, Ciprian N.

2017-03-01

Purpose: Accurate patient-specific phantoms for device testing or endovascular treatment planning can be 3D printed. We expand the applicability of this approach for cardiovascular disease, in particular, for CT-geometry derived benchtop measurements of Fractional Flow Reserve, the reference standard for determination of significant individual coronary artery atherosclerotic lesions. Materials and Methods: Coronary CT Angiography (CTA) images during a single heartbeat were acquired with a 320x0.5mm detector row scanner (Toshiba Aquilion ONE). These coronary CTA images were used to create 4 patientspecific cardiovascular models with various grades of stenosis: severe, <75% (n=1); moderate, 50-70% (n=1); and mild, <50% (n=2). DICOM volumetric images were segmented using a 3D workstation (Vitrea, Vital Images); the output was used to generate STL files (using AutoDesk Meshmixer), and further processed to create 3D printable geometries for flow experiments. Multi-material printed models (Stratasys Connex3) were connected to a programmable pulsatile pump, and the pressure was measured proximal and distal to the stenosis using pressure transducers. Compliance chambers were used before and after the model to modulate the pressure wave. A flow sensor was used to ensure flow rates within physiological reported values. Results: 3D model based FFR measurements correlated well with stenosis severity. FFR measurements for each stenosis grade were: 0.8 severe, 0.7 moderate and 0.88 mild. Conclusions: 3D printed models of patient-specific coronary arteries allows for accurate benchtop diagnosis of FFR. This approach can be used as a future diagnostic tool or for testing CT image-based FFR methods.

Size-based emphysema cluster analysis on low attenuation area in 3D volumetric CT: comparison with pulmonary functional test

NASA Astrophysics Data System (ADS)

Lee, Minho; Kim, Namkug; Lee, Sang Min; Seo, Joon Beom; Oh, Sang Young

2015-03-01

To quantify low attenuation area (LAA) of emphysematous regions according to cluster size in 3D volumetric CT data of chronic obstructive pulmonary disease (COPD) patients and to compare these indices with their pulmonary functional test (PFT). Sixty patients with COPD were scanned by a more than 16-multi detector row CT scanner (Siemens Sensation 16 and 64) within 0.75mm collimation. Based on these LAA masks, a length scale analysis to estimate each emphysema LAA's size was performed as follows. At first, Gaussian low pass filter from 30mm to 1mm kernel size with 1mm interval on the mask was performed from large to small size, iteratively. Centroid voxels resistant to the each filter were selected and dilated by the size of the kernel, which was regarded as the specific size emphysema mask. The slopes of area and number of size based LAA (slope of semi-log plot) were analyzed and compared with PFT. PFT parameters including DLco, FEV1, and FEV1/FVC were significantly (all p-value< 0.002) correlated with the slopes (r-values; -0.73, 0.54, 0.69, respectively) and EI (r-values; -0.84, -0.60, -0.68, respectively). In addition, the D independently contributed regression for FEV1 and FEV1/FVC (adjust R sq. of regression study: EI only, 0.70, 0.45; EI and D, 0.71, 0.51, respectively). By the size based LAA segmentation and analysis, we evaluated the Ds of area, number, and distribution of size based LAA, which would be independent factors for predictor of PFT parameters.

Differentiation of nonneoplastic and neoplastic gallbladder polyps 1 cm or bigger with multi-detector row computed tomography.

PubMed

Park, Ko Woon; Kim, Seong Hyun; Choi, Seong Ho; Lee, Won Jae

2010-01-01

To evaluate useful computed tomographic features to differentiate nonneoplastic and neoplastic gallbladder polyps 1 cm or bigger. Thirty-one patients with 32 nonneoplastic polyps and 67 patients with 73 neoplastic polyps 1 cm or bigger underwent unenhanced and dual-phase (arterial and portal venous phases) multi-detector row computed tomography. Gallbladder polyps were diagnosed by cholecystectomy. Computed tomographic features including size (1.5 cm), surface (smooth or irregular), shape (pedunculated or sessile), accompanying wall thickening, basal indentation, perception on unenhanced images, and enhancement pattern between 2 groups were compared using univariate and multivariate analyses. On univariate analysis, age 55 years or older (P = 0.0019), size bigger than 1.5 cm (P < 0.0001), irregular surface (P = 0.0033), sessile shape (P = 0.0016), accompanying wall thickening (P = 0.0056), basal indentation (P = 0.0236), and perception on unenhanced images (P < 0.0001) were significantly more frequent in neoplastic polyps as compared with nonneoplastic polyps. On multivariate analysis, size bigger than 1.5 cm (P = 0.0260), sessile shape (P = 0.0397), and perception on unenhanced images (P < 0.0001) were statistically significant. Size bigger than 1.5 cm, sessile shape, and perception on unenhanced images are the main factors that differentiate neoplastic from nonneoplastic gallbladder polyps 1 cm or bigger.

A CMOS ASIC Design for SiPM Arrays

PubMed Central

Dey, Samrat; Banks, Lushon; Chen, Shaw-Pin; Xu, Wenbin; Lewellen, Thomas K.; Miyaoka, Robert S.; Rudell, Jacques C.

2012-01-01

Our lab has previously reported on novel board-level readout electronics for an 8×8 silicon photomultiplier (SiPM) array featuring row/column summation technique to reduce the hardware requirements for signal processing. We are taking the next step by implementing a monolithic CMOS chip which is based on the row-column architecture. In addition, this paper explores the option of using diagonal summation as well as calibration to compensate for temperature and process variations. Further description of a timing pickoff signal which aligns all of the positioning (spatial channels) pulses in the array is described. The ASIC design is targeted to be scalable with the detector size and flexible to accommodate detectors from different vendors. This paper focuses on circuit implementation issues associated with the design of the ASIC to interface our Phase II MiCES FPGA board with a SiPM array. Moreover, a discussion is provided for strategies to eventually integrate all the analog and mixed-signal electronics with the SiPM, on either a single-silicon substrate or multi-chip module (MCM). PMID:24825923

Estimation of absorbed doses from paediatric cone-beam CT scans: MOSFET measurements and Monte Carlo simulations.

PubMed

Kim, Sangroh; Yoshizumi, Terry T; Toncheva, Greta; Frush, Donald P; Yin, Fang-Fang

2010-03-01

The purpose of this study was to establish a dose estimation tool with Monte Carlo (MC) simulations. A 5-y-old paediatric anthropomorphic phantom was computed tomography (CT) scanned to create a voxelised phantom and used as an input for the abdominal cone-beam CT in a BEAMnrc/EGSnrc MC system. An X-ray tube model of the Varian On-Board Imager((R)) was built in the MC system. To validate the model, the absorbed doses at each organ location for standard-dose and low-dose modes were measured in the physical phantom with MOSFET detectors; effective doses were also calculated. In the results, the MC simulations were comparable to the MOSFET measurements. This voxelised phantom approach could produce a more accurate dose estimation than the stylised phantom method. This model can be easily applied to multi-detector CT dosimetry.

A general tool for the evaluation of spiral CT interpolation algorithms: revisiting the effect of pitch in multislice CT.

PubMed

Bricault, Ivan; Ferretti, Gilbert

2005-01-01

While multislice spiral computed tomography (CT) scanners are provided by all major manufacturers, their specific interpolation algorithms have been rarely evaluated. Because the results published so far relate to distinct particular cases and differ significantly, there are contradictory recommendations about the choice of pitch in clinical practice. In this paper, we present a new tool for the evaluation of multislice spiral CT z-interpolation algorithms, and apply it to the four-slice case. Our software is based on the computation of a "Weighted Radiation Profile" (WRP), and compares WRP to an expected ideal profile in terms of widening and heterogeneity. It provides a unique scheme for analyzing a large variety of spiral CT acquisition procedures. Freely chosen parameters include: number of detector rows, detector collimation, nominal slice width, helical pitch, and interpolation algorithm with any filter shape and width. Moreover, it is possible to study any longitudinal and off-isocenter positions. Theoretical and experimental results show that WRP, more than Slice Sensitivity Profile (SSP), provides a comprehensive characterization of interpolation algorithms. WRP analysis demonstrates that commonly "preferred helical pitches" are actually nonoptimal regarding the formerly distinguished z-sampling gap reduction criterion. It is also shown that "narrow filter" interpolation algorithms do not enable a general preferred pitch discussion, since they present poor properties with large longitudinal and off-center variations. In the more stable case of "wide filter" interpolation algorithms, SSP width or WRP widening are shown to be almost constant. Therefore, optimal properties should no longer be sought in terms of these criteria. On the contrary, WRP heterogeneity is related to variable artifact phenomena and can pertinently characterize optimal pitches. In particular, the exemplary interpolation properties of pitch = 1 "wide filter" mode are demonstrated.

Coronary Events and Anatomy After Arterial Switch Operation for Transposition of the Great Arteries: Detection by 16-Row Multislice Computed Tomography Angiography in Pediatric Patients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oztunc, Funda, E-mail: foztunc@yahoo.com; Baris, Safa, E-mail: safabaris@hotmail.co; Adaletli, Ibrahim, E-mail: iadaletli@yahoo.com

2009-03-15

The purpose of this study was to evaluate the feasibility of multislice computed tomographic (MSCT) angiography as a noninvasive method for detecting ostial, proximal, and middle segment coronary stenosis or occlusion and anatomy in patients with transposition of the great arteries who had undergone arterial switch operation (ASO). Sixteen-detector-row MSCT angiography was performed in 16 patients treated with ASO for transposition of the great arteries. The median age was 10.3 years (range, 6.2-16.3 years). Sixteen-detector-row MSCT angiography was performed in 16 patients who had undergone ASO. CT imaging was performed in the craniocaudal direction from 2 cm above the carinamore » up to the heart basis. Noninvasive assessment of coronary artery stenosis and anatomy were investigated by MSCT angiography. Two patients were excluded from the study because of artifacts. Of 14 evaluated patients, 1 patient had ostial stenosis (7.1%). A coronary artery anatomy variant was present in six patients: left main artery (LMA) and right coronary artery (RCA) originating from the right sinus as a single orifice (n = 2); left circumflex artery (LCX) originating from the RCA (n = 1); LMA and RCA, after branching to the LCX, originating separately from the right sinus (n = 1); and LMA (n = 1) and left anterior descending artery (LADA; n = 1) originating directly from the right sinus. Intramural bridging in the LAD (n = 2) was detected. Five patients were normal. In conclusion, MSCT angiography, as a noninvasive, feasible technique for assessing coronary stenosis or occlusion and anatomy, can be used in the follow-up of patients who have undergone ASO.« less

A tetrahedron beam computed tomography benchtop system with a multiple pixel field emission x-ray tube.

PubMed

Xu, Xiaochao; Kim, Joshua; Laganis, Philip; Schulze, Derek; Liang, Yongguang; Zhang, Tiezhi

2011-10-01

To demonstrate the feasibility of Tetrahedron Beam Computed Tomography (TBCT) using a carbon nanotube (CNT) multiple pixel field emission x-ray (MPFEX) tube. A multiple pixel x-ray source facilitates the creation of novel x-ray imaging modalities. In a previous publication, the authors proposed a Tetrahedron Beam Computed Tomography (TBCT) imaging system which comprises a linear source array and a linear detector array that are orthogonal to each other. TBCT is expected to reduce scatter compared with Cone Beam Computed Tomography (CBCT) and to have better detector performance. Therefore, it may produce improved image quality for image guided radiotherapy. In this study, a TBCT benchtop system has been developed with an MPFEX tube. The tube has 75 CNT cold cathodes, which generate 75 x-ray focal spots on an elongated anode, and has 4 mm pixel spacing. An in-house-developed, 5-row CT detector array using silicon photodiodes and CdWO(4) scintillators was employed in the system. Hardware and software were developed for tube control and detector data acquisition. The raw data were preprocessed for beam hardening and detector response linearity and were reconstructed with an FDK-based image reconstruction algorithm. The focal spots were measured at about 1 × 2 mm(2) using a star phantom. Each cathode generates around 3 mA cathode current with 2190 V gate voltage. The benchtop system is able to perform TBCT scans with a prolonged scanning time. Images of a commercial CT phantom were successfully acquired. A prototype system was developed, and preliminary phantom images were successfully acquired. MPFEX is a promising x-ray source for TBCT. Further improvement of tube output is needed in order for it to be used in clinical TBCT systems.

32. TYPICAL BRYANT ITEMS FROM THE 1930S; TOP ROW LEFT ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

32. TYPICAL BRYANT ITEMS FROM THE 1930S; TOP ROW LEFT TO RIGHT: PORCELAIN CASED SWITCH, ROTARY SWITCH, SHORTING PLUG TO BYPASS FUSE; SECOND ROW: BRASS INCANDESCENT LAMP SURFACE RECEPTACLE, INCANDESCENT LAMPHOLDER WITH ADAPTER FOR GLASS GLOBE; THIRD ROW: PORCELAIN BASE ROTARY SWITCH, APPLIANCE BREAKER WITH COVER REMOVED, APPLIANCE BREAKER - Bryant Electric Company, 1421 State Street, Bridgeport, Fairfield County, CT

Craniofacial and dental malformations in Costello syndrome: A detailed evaluation using multi-detector row computed tomography.

PubMed

Takahashi, Masashi; Ohashi, Hirofumi

2013-06-01

Costello syndrome is a rare multiple congenital anomaly syndrome caused by heterozygous germline HRAS mutations, which is characterized by intellectual disability, growth retardation, distinctive facies, loose skin, cardiomyopathy and a preposition to malignancies. Although teeth abnormalities have been encountered in nearly two-thirds of the patients in literature, the evaluation tended to be limited to the extent which can be obtained from physical examination. We investigated detailed craniofacial, oral and dental findings in four patients with Costello syndrome. In this study, images reconstructed by multi-detector row computed tomography (MDCT) were used as substitutes for dental cast study and panoramic and lateral cephalometric radiograph studies to evaluate dental arches, tooth size, relationships between craniofacial and dental structures, and hypodontia. All four patients showed true/relative macrocephaly with facial bone hypoplasia and gingival hypertrophy. Occlusal attrition, malocclusion, small dental arches, microdontia, and convex face were noted in three patients. In addition, one patient showed dental caries, conic tooth and gingivitis, and another patient showed hypodontia. Our study suggests that craniofacial and dental abnormalities are common in Costello syndrome patients and comprehensive dental care should be provided from early infancy. To our knowledge, this is the first study of thorough craniofacial and dental evaluation by using MDCT in Costello syndrome. MDCT is a useful tool for precise evaluation of craniofacial and oral manifestations in patients with congenital anomaly/intellectual disability syndromes. © 2012 The Authors. Congenital Anomalies © 2012 Japanese Teratology Society.

Robust x-ray based material identification using multi-energy sinogram decomposition

NASA Astrophysics Data System (ADS)

Yuan, Yaoshen; Tracey, Brian; Miller, Eric

2016-05-01

There is growing interest in developing X-ray computed tomography (CT) imaging systems with improved ability to discriminate material types, going beyond the attenuation imaging provided by most current systems. Dual- energy CT (DECT) systems can partially address this problem by estimating Compton and photoelectric (PE) coefficients of the materials being imaged, but DECT is greatly degraded by the presence of metal or other materials with high attenuation. Here we explore the advantages of multi-energy CT (MECT) systems based on photon-counting detectors. The utility of MECT has been demonstrated in medical applications where photon- counting detectors allow for the resolution of absorption K-edges. Our primary concern is aviation security applications where K-edges are rare. We simulate phantoms with differing amounts of metal (high, medium and low attenuation), both for switched-source DECT and for MECT systems, and include a realistic model of detector energy 0 resolution. We extend the DECT sinogram decomposition method of Ying et al. to MECT, allowing estimation of separate Compton and photoelectric sinograms. We furthermore introduce a weighting based on a quadratic approximation to the Poisson likelihood function that deemphasizes energy bins with low signal. Simulation results show that the proposed approach succeeds in estimating material properties even in high-attenuation scenarios where the DECT method fails, improving the signal to noise ratio of reconstructions by over 20 dB for the high-attenuation phantom. Our work demonstrates the potential of using photon counting detectors for stably recovering material properties even when high attenuation is present, thus enabling the development of improved scanning systems.

Determination of calibration parameters of a VRX CT system using an “Amoeba” algorithm

PubMed Central

Jordan, Lawrence M.; DiBianca, Frank A.; Melnyk, Roman; Choudhary, Apoorva; Shukla, Hemant; Laughter, Joseph; Gaber, M. Waleed

2008-01-01

Efforts to improve the spatial resolution of CT scanners have focused mainly on reducing the source and detector element sizes, ignoring losses from the size of the secondary-ionization charge “clouds” created by the detected x-ray photons, i.e., the “physics limit.” This paper focuses on implementing a technique called “projective compression.” which allows further reduction in effective cell size while overcoming the physics limit as well. Projective compression signifies detector geometries in which the apparent cell size is smaller than the physical cell size, allowing large resolution boosts. A realization of this technique has been developed with a dual-arm “variable-resolution x-ray” (VRX) detector. Accurate values of the geometrical parameters are needed to convert VRX outputs to formats ready for optimal image reconstruction by standard CT techniques. The required calibrating data are obtained by scanning a rotating pin and fitting a theoretical parametric curve (using a multi-parameter minimization algorithm) to the resulting pin sinogram. Excellent fits are obtained for both detector-arm sections with an average (maximum) fit deviation of ~0.05 (0.1) detector cell width. Fit convergence and sensitivity to starting conditions are considered. Pre- and post-optimization reconstructions of the alignment pin and a biological subject reconstruction after calibration are shown. PMID:19430581

Determination of calibration parameters of a VRX CT system using an "Amoeba" algorithm.

PubMed

Jordan, Lawrence M; Dibianca, Frank A; Melnyk, Roman; Choudhary, Apoorva; Shukla, Hemant; Laughter, Joseph; Gaber, M Waleed

2004-01-01

Efforts to improve the spatial resolution of CT scanners have focused mainly on reducing the source and detector element sizes, ignoring losses from the size of the secondary-ionization charge "clouds" created by the detected x-ray photons, i.e., the "physics limit." This paper focuses on implementing a technique called "projective compression." which allows further reduction in effective cell size while overcoming the physics limit as well. Projective compression signifies detector geometries in which the apparent cell size is smaller than the physical cell size, allowing large resolution boosts. A realization of this technique has been developed with a dual-arm "variable-resolution x-ray" (VRX) detector. Accurate values of the geometrical parameters are needed to convert VRX outputs to formats ready for optimal image reconstruction by standard CT techniques. The required calibrating data are obtained by scanning a rotating pin and fitting a theoretical parametric curve (using a multi-parameter minimization algorithm) to the resulting pin sinogram. Excellent fits are obtained for both detector-arm sections with an average (maximum) fit deviation of ~0.05 (0.1) detector cell width. Fit convergence and sensitivity to starting conditions are considered. Pre- and post-optimization reconstructions of the alignment pin and a biological subject reconstruction after calibration are shown.

Dual- and Multi-Energy CT: Principles, Technical Approaches, and Clinical Applications

PubMed Central

Leng, Shuai; Yu, Lifeng; Fletcher, Joel G.

2015-01-01

In x-ray computed tomography (CT), materials having different elemental compositions can be represented by identical pixel values on a CT image (ie, CT numbers), depending on the mass density of the material. Thus, the differentiation and classification of different tissue types and contrast agents can be extremely challenging. In dual-energy CT, an additional attenuation measurement is obtained with a second x-ray spectrum (ie, a second “energy”), allowing the differentiation of multiple materials. Alternatively, this allows quantification of the mass density of two or three materials in a mixture with known elemental composition. Recent advances in the use of energy-resolving, photon-counting detectors for CT imaging suggest the ability to acquire data in multiple energy bins, which is expected to further improve the signal-to-noise ratio for material-specific imaging. In this review, the underlying motivation and physical principles of dual- or multi-energy CT are reviewed and each of the current technical approaches is described. In addition, current and evolving clinical applications are introduced. © RSNA, 2015 PMID:26302388

Computed Tomography Assessment of Hepatic Metastases of Breast Cancer with Revised Response Evaluation Criteria in Solid Tumors (RECIST) Criteria (Version 1.1): Inter-Observer Agreement.

PubMed

Ghobrial, Fady Emil Ibrahim; Eldin, Manal Salah; Razek, Ahmed Abdel Khalek Abdel; Atwan, Nadia Ibrahim; Shamaa, Sameh Sayed Ahmed

2017-01-01

To assess inter-observer agreement of revised RECIST criteria (version 1.1) for computed tomography assessment of hepatic metastases of breast cancer. A prospective study was conducted in 28 female patients with breast cancer and with at least one measurable metastatic lesion in the liver that was treated with 3 cycles of anthracycline-based chemotherapy. All patients underwent computed tomography of the abdomen with 64-row multi- detector CT at baseline and after 3 cycles of chemotherapy for response assessment. Image analysis was performed by 2 observers, based on the RECIST criteria (version 1.1). Computed tomography revealed partial response of hepatic metastases in 7 patients (25%) by one observer and in 10 patients (35.7%) by the other observer, with good inter-observer agreement (k=0.75, percent agreement of 89.29%). Stable disease was detected in 19 patients (67.8%) by one observer and in 16 patients (57.1%) by the other observer, with good agreement (k=0.774, percent agreement of 89.29%). Progressive disease was detected in 2 patients (7.2%) by both observers, with perfect agreement (k=1, percent agreement of 100%). The overall inter-observer agreement in the CT-based response assessment of hepatic metastasis between the two observers was good ( k =0.793, percent agreement of 89.29%). We concluded that computed tomography is a reliable and reproducible imaging modality for response assessment of hepatic metastases of breast cancer according to the RECIST criteria (version 1.1).

Characterizing trabecular bone structure for assessing vertebral fracture risk on volumetric quantitative computed tomography

NASA Astrophysics Data System (ADS)

Nagarajan, Mahesh B.; Checefsky, Walter A.; Abidin, Anas Z.; Tsai, Halley; Wang, Xixi; Hobbs, Susan K.; Bauer, Jan S.; Baum, Thomas; Wismüller, Axel

2015-03-01

While the proximal femur is preferred for measuring bone mineral density (BMD) in fracture risk estimation, the introduction of volumetric quantitative computed tomography has revealed stronger associations between BMD and spinal fracture status. In this study, we propose to capture properties of trabecular bone structure in spinal vertebrae with advanced second-order statistical features for purposes of fracture risk assessment. For this purpose, axial multi-detector CT (MDCT) images were acquired from 28 spinal vertebrae specimens using a whole-body 256-row CT scanner with a dedicated calibration phantom. A semi-automated method was used to annotate the trabecular compartment in the central vertebral slice with a circular region of interest (ROI) to exclude cortical bone; pixels within were converted to values indicative of BMD. Six second-order statistical features derived from gray-level co-occurrence matrices (GLCM) and the mean BMD within the ROI were then extracted and used in conjunction with a generalized radial basis functions (GRBF) neural network to predict the failure load of the specimens; true failure load was measured through biomechanical testing. Prediction performance was evaluated with a root-mean-square error (RMSE) metric. The best prediction performance was observed with GLCM feature `correlation' (RMSE = 1.02 ± 0.18), which significantly outperformed all other GLCM features (p < 0.01). GLCM feature correlation also significantly outperformed MDCTmeasured mean BMD (RMSE = 1.11 ± 0.17) (p< 10-4). These results suggest that biomechanical strength prediction in spinal vertebrae can be significantly improved through characterization of trabecular bone structure with GLCM-derived texture features.

Effects of pure and hybrid iterative reconstruction algorithms on high-resolution computed tomography in the evaluation of interstitial lung disease.

PubMed

Katsura, Masaki; Sato, Jiro; Akahane, Masaaki; Mise, Yoko; Sumida, Kaoru; Abe, Osamu

2017-08-01

To compare image quality characteristics of high-resolution computed tomography (HRCT) in the evaluation of interstitial lung disease using three different reconstruction methods: model-based iterative reconstruction (MBIR), adaptive statistical iterative reconstruction (ASIR), and filtered back projection (FBP). Eighty-nine consecutive patients with interstitial lung disease underwent standard-of-care chest CT with 64-row multi-detector CT. HRCT images were reconstructed in 0.625-mm contiguous axial slices using FBP, ASIR, and MBIR. Two radiologists independently assessed the images in a blinded manner for subjective image noise, streak artifacts, and visualization of normal and pathologic structures. Objective image noise was measured in the lung parenchyma. Spatial resolution was assessed by measuring the modulation transfer function (MTF). MBIR offered significantly lower objective image noise (22.24±4.53, P<0.01 among all pairs, Student's t-test) compared with ASIR (39.76±7.41) and FBP (51.91±9.71). MTF (spatial resolution) was increased using MBIR compared with ASIR and FBP. MBIR showed improvements in visualization of normal and pathologic structures over ASIR and FBP, while ASIR was rated quite similarly to FBP. MBIR significantly improved subjective image noise (P<0.01 among all pairs, the sign test), and streak artifacts (P<0.01 each for MBIR vs. the other 2 image data sets). MBIR provides high-quality HRCT images for interstitial lung disease by reducing image noise and streak artifacts and improving spatial resolution compared with ASIR and FBP. Copyright © 2017 Elsevier B.V. All rights reserved.

Chromatic Modulator for a High-Resolution CCD or APS

NASA Technical Reports Server (NTRS)

Hartley, Frank; Hull, Anthony

2008-01-01

A chromatic modulator has been proposed to enable the separate detection of the red, green, and blue (RGB) color components of the same scene by a single charge-coupled device (CCD), active-pixel sensor (APS), or similar electronic image detector. Traditionally, the RGB color-separation problem in an electronic camera has been solved by use of either (1) fixed color filters over three separate image detectors; (2) a filter wheel that repeatedly imposes a red, then a green, then a blue filter over a single image detector; or (3) different fixed color filters over adjacent pixels. The use of separate image detectors necessitates precise registration of the detectors and the use of complicated optics; filter wheels are expensive and add considerably to the bulk of the camera; and fixed pixelated color filters reduce spatial resolution and introduce color-aliasing effects. The proposed chromatic modulator would not exhibit any of these shortcomings. The proposed chromatic modulator would be an electromechanical device fabricated by micromachining. It would include a filter having a spatially periodic pattern of RGB strips at a pitch equal to that of the pixels of the image detector. The filter would be placed in front of the image detector, supported at its periphery by a spring suspension and electrostatic comb drive. The spring suspension would bias the filter toward a middle position in which each filter strip would be registered with a row of pixels of the image detector. Hard stops would limit the excursion of the spring suspension to precisely one pixel row above and one pixel row below the middle position. In operation, the electrostatic comb drive would be actuated to repeatedly snap the filter to the upper extreme, middle, and lower extreme positions. This action would repeatedly place a succession of the differently colored filter strips in front of each pixel of the image detector. To simplify the processing, it would be desirable to encode information on the color of the filter strip over each row (or at least over some representative rows) of pixels at a given instant of time in synchronism with the pixel output at that instant.

[Measurement of scatter radiation on MDCT equipment using an OSL dosimeter].

PubMed

Tomita, Hironobu; Morozumi, Kunihiko

2004-11-01

The recent introduction of multi-detector row computed tomography (MDCT) has made it possible to scan the entire abdomen within approximately 10 sec in procedures such as interventional radiology computed tomography (IVRCT), which are associated with operator exposure. Therefore, anxious patients and patients who are not able to remain still can be examined with an assistant. In the present study, radiation exposure to the assistant was estimated, and the distribution of scattered radiation near the gantry was measured using an optically stimulated luminescence (OSL) dosimeter. Simultaneous measurements were obtained using a direction storage (DIS) dosimeter for reference. The maximum value of 1.47 mSv per examination was obtained at the point closest to the gantry's center (50 cm from the center at a height of 150 cm above the floor) . In addition, scattered radiation decreased as the measurement point was moved further from the gantry's center, falling below the limit of detection (0.1 mSv or less) at 200 cm and at the sides of the gantry. OSL dosimeters are also employed as personal dosimeters, permitting reliable values to be obtained easily. They were found to be an effective tool for the measurement of scattered radiation, as in the present study, helping to provide better understanding of the distribution of scattered radiation within the CT room.

Contour variations of the body and tail of the pancreas: evaluation with MDCT.

PubMed

Omeri, Ahmad Khalid; Matsumoto, Shunro; Kiyonaga, Maki; Takaji, Ryo; Yamada, Yasunari; Kosen, Kazuhisa; Mori, Hiromu; Miyake, Hidetoshi

2017-06-01

To analyze morphology/contour variations of the pancreatic body and tail in subjects free of pancreatic disease. We retrospectively reviewed triple-phase, contrast-enhanced multi-detector row computed tomography (3P-CE-MDCT) examinations of 449 patients who had no clinical or CT evidence of pancreatic diseases. These patients were evaluated for morphologic/contour variations of the pancreatic body and tail, which were classified into two types. In Type I, a portion of normal pancreatic parenchyma protrudes >1 cm in maximum diameter from the body or tail (Ia-anteriorly; Ib-posteriorly). Type II was defined as a morphologic anomaly of the pancreatic tail (IIa-globular; IIb-lobulated; IIc-tapered; IId-bifid). Thirty-eight (8.5%) out of 449 patients had body or tail variations. Of those, 23 patients showed Type I variant: Ia in 21 and Ib in two. Type II variant was identified in 15 patients: IIa in eight, IIb in two, IIc in two and IId in three. Protrusion of the anterior surface of the normal pancreas, especially in the tail, was the most frequently occurring variant. Recognizing the types and subtypes of morphology/contour variations of the pancreatic body and tail could help prevent misinterpretation of normal variants as pancreatic tumors on unenhanced MDCT.

PET/CT alignment calibration with a non-radioactive phantom and the intrinsic 176Lu radiation of PET detector

NASA Astrophysics Data System (ADS)

Wei, Qingyang; Ma, Tianyu; Wang, Shi; Liu, Yaqiang; Gu, Yu; Dai, Tiantian

2016-11-01

Positron emission tomography/computed tomography (PET/CT) is an important tool for clinical studies and pre-clinical researches which provides both functional and anatomical images. To achieve high quality co-registered PET/CT images, alignment calibration of PET and CT scanner is a critical procedure. The existing methods reported use positron source phantoms imaged both by PET and CT scanner and then derive the transformation matrix from the reconstructed images of the two modalities. In this paper, a novel PET/CT alignment calibration method with a non-radioactive phantom and the intrinsic 176Lu radiation of the PET detector was developed. Firstly, a multi-tungsten-alloy-sphere phantom without positron source was designed and imaged by CT and the PET scanner using intrinsic 176Lu radiation included in LYSO. Secondly, the centroids of the spheres were derived and matched by an automatic program. Lastly, the rotation matrix and the translation vector were calculated by least-square fitting of the centroid data. The proposed method was employed in an animal PET/CT system (InliView-3000) developed in our lab. Experimental results showed that the proposed method achieves high accuracy and is feasible to replace the conventional positron source based methods.

320-Row wide volume CT significantly reduces density heterogeneity observed in the descending aorta: comparisons with 64-row helical CT.

PubMed

Yamashiro, Tsuneo; Miyara, Tetsuhiro; Honda, Osamu; Kamiya, Ayano; Tanaka, Yuko; Murayama, Sadayuki

2014-01-01

The aim of this study was to compare density heterogeneity on wide volume (WV) scans with that on helical CT scans. 22 subjects underwent chest CT using 320-WV and 64-helical modes. Density heterogeneity of the descending aorta was evaluated quantitatively and qualitatively. At qualitative assessment, the heterogeneity was judged to be smaller on WV scans than on helical scans (p<0.0001). Mean changes in aortic density between two contiguous slices were 1.64 HU (3.40%) on WV scans and 2.29 HU (5.19%) on helical scans (p<0.0001). CT density of thoracic organs is more homogeneous and reliable on WV scans than on helical scans. Copyright © 2013 Elsevier Ltd. All rights reserved.

Experimental flat-panel high-spatial-resolution volume CT of the temporal bone.

PubMed

Gupta, Rajiv; Bartling, Soenke H; Basu, Samit K; Ross, William R; Becker, Hartmut; Pfoh, Armin; Brady, Thomas; Curtin, Hugh D

2004-09-01

A CT scanner employing a digital flat-panel detector is capable of very high spatial resolution as compared with a multi-section CT (MSCT) scanner. Our purpose was to determine how well a prototypical volume CT (VCT) scanner with a flat-panel detector system defines fine structures in temporal bone. Four partially manipulated temporal-bone specimens were imaged by use of a prototypical cone-beam VCT scanner with a flat-panel detector system at an isometric resolution of 150 microm at the isocenter. These specimens were also depicted by state-of-the-art multisection CT (MSCT). Forty-two structures imaged by both scanners were qualitatively assessed and rated, and scores assigned to VCT findings were compared with those of MSCT. Qualitative assessment of anatomic structures, lesions, cochlear implants, and middle-ear hearing aids indicated that image quality was significantly better with VCT (P < .001). Structures near the spatial-resolution limit of MSCT (e.g., bony covering of the tympanic segment of the facial canal, the incudo-stapedial joint, the proximal vestibular aqueduct, the interscalar septum, and the modiolus) had higher contrast and less partial-volume effect with VCT. The flat-panel prototype provides better definition of fine osseous structures of temporal bone than that of currently available MSCT scanners. This study provides impetus for further research in increasing spatial resolution beyond that offered by the current state-of-the-art scanners.

Multisource inverse-geometry CT. Part II. X-ray source design and prototype

PubMed Central

Neculaes, V. Bogdan; Caiafa, Antonio; Cao, Yang; De Man, Bruno; Edic, Peter M.; Frutschy, Kristopher; Gunturi, Satish; Inzinna, Lou; Reynolds, Joseph; Vermilyea, Mark; Wagner, David; Zhang, Xi; Zou, Yun; Pelc, Norbert J.; Lounsberry, Brian

2016-01-01

Purpose: This paper summarizes the development of a high-power distributed x-ray source, or “multisource,” designed for inverse-geometry computed tomography (CT) applications [see B. De Man et al., “Multisource inverse-geometry CT. Part I. System concept and development,” Med. Phys. 43, 4607–4616 (2016)]. The paper presents the evolution of the source architecture, component design (anode, emitter, beam optics, control electronics, high voltage insulator), and experimental validation. Methods: Dispenser cathode emitters were chosen as electron sources. A modular design was adopted, with eight electron emitters (two rows of four emitters) per module, wherein tungsten targets were brazed onto copper anode blocks—one anode block per module. A specialized ceramic connector provided high voltage standoff capability and cooling oil flow to the anode. A matrix topology and low-noise electronic controls provided switching of the emitters. Results: Four modules (32 x-ray sources in two rows of 16) have been successfully integrated into a single vacuum vessel and operated on an inverse-geometry computed tomography system. Dispenser cathodes provided high beam current (>1000 mA) in pulse mode, and the electrostatic lenses focused the current beam to a small optical focal spot size (0.5 × 1.4 mm). Controlled emitter grid voltage allowed the beam current to be varied for each source, providing the ability to modulate beam current across the fan of the x-ray beam, denoted as a virtual bowtie filter. The custom designed controls achieved x-ray source switching in <1 μs. The cathode-grounded source was operated successfully up to 120 kV. Conclusions: A high-power, distributed x-ray source for inverse-geometry CT applications was successfully designed, fabricated, and operated. Future embodiments may increase the number of spots and utilize fast read out detectors to increase the x-ray flux magnitude further, while still staying within the stationary target inherent thermal limitations. PMID:27487878

Multisource inverse-geometry CT. Part II. X-ray source design and prototype

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neculaes, V. Bogdan, E-mail: neculaes@ge.com; Caia

2016-08-15

Purpose: This paper summarizes the development of a high-power distributed x-ray source, or “multisource,” designed for inverse-geometry computed tomography (CT) applications [see B. De Man et al., “Multisource inverse-geometry CT. Part I. System concept and development,” Med. Phys. 43, 4607–4616 (2016)]. The paper presents the evolution of the source architecture, component design (anode, emitter, beam optics, control electronics, high voltage insulator), and experimental validation. Methods: Dispenser cathode emitters were chosen as electron sources. A modular design was adopted, with eight electron emitters (two rows of four emitters) per module, wherein tungsten targets were brazed onto copper anode blocks—one anode blockmore » per module. A specialized ceramic connector provided high voltage standoff capability and cooling oil flow to the anode. A matrix topology and low-noise electronic controls provided switching of the emitters. Results: Four modules (32 x-ray sources in two rows of 16) have been successfully integrated into a single vacuum vessel and operated on an inverse-geometry computed tomography system. Dispenser cathodes provided high beam current (>1000 mA) in pulse mode, and the electrostatic lenses focused the current beam to a small optical focal spot size (0.5 × 1.4 mm). Controlled emitter grid voltage allowed the beam current to be varied for each source, providing the ability to modulate beam current across the fan of the x-ray beam, denoted as a virtual bowtie filter. The custom designed controls achieved x-ray source switching in <1 μs. The cathode-grounded source was operated successfully up to 120 kV. Conclusions: A high-power, distributed x-ray source for inverse-geometry CT applications was successfully designed, fabricated, and operated. Future embodiments may increase the number of spots and utilize fast read out detectors to increase the x-ray flux magnitude further, while still staying within the stationary target inherent thermal limitations.« less

Radiation dose of digital tomosynthesis for sinonasal examination: comparison with multi-detector CT.

PubMed

Machida, Haruhiko; Yuhara, Toshiyuki; Tamura, Mieko; Numano, Tomokazu; Abe, Shinji; Sabol, John M; Suzuki, Shigeru; Ueno, Eiko

2012-06-01

Using an anthropomorphic phantom, we have investigated the feasibility of digital tomosynthesis (DT) of flat-panel detector (FPD) radiography to reduce radiation dose for sinonasal examination compared to multi-detector computed tomography (MDCT). A female Rando phantom was scanned covering frontal to maxillary sinus using the clinically routine protocol by both 64-detector CT (120 kV, 200 mAs, and 1.375-pitch) and DT radiography (80 kV, 1.0 mAs per projection, 60 projections, 40° sweep, and posterior-anterior projections). Glass dosimeters were used to measure the radiation dose to internal organs including the thyroid gland, brain, submandibular gland, and the surface dose at various sites including the eyes during those scans. We compared the radiation dose to those anatomies between both modalities. In DT radiography, the doses of the thyroid gland, brain, submandibular gland, skin, and eyes were 230 ± 90 μGy, 1770 ± 560 μGy, 1400 ± 80 μGy, 1160 ± 2100 μGy, and 112 ± 6 μGy, respectively. These doses were reduced to approximately 1/5, 1/8, 1/12, 1/17, and 1/290 of the respective MDCT dose. For sinonasal examinations, DT radiography enables dramatic reduction in radiation exposure and dose to the head and neck region, particularly to the lens of the eye. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Effects of dose reduction on multi-detector computed tomographic images in evaluating the maxilla and mandible for pre-surgical implant planning: a cadaveric study.

PubMed

Koizumi, Hiroshi; Sur, Jaideep; Seki, Kenji; Nakajima, Koh; Sano, Tsukasa; Okano, Tomohiro

2010-08-01

To assess effects of dose reduction on image quality in evaluating maxilla and mandible for pre-surgical implant planning using cadavers. Six cadavers were used for the study using multi-detector computed tomography (CT) operated at 120 kV and the variable tube current of 80, 40, 20 and 10 mA. A slice thickness of 0.625 mm and pitch 1 were used. Multi-planar images perpendicular and parallel to dentitions were created. The images were evaluated by five oral radiologists in terms of visibility of the anatomical landmarks including alveolar crest, mandibular canal, floors of the maxillary sinus and nasal cavity, contours/cortical layer of jaw bones and the details of trabecular bone. Observers were asked to determine the quality of the images in comparison with 80 mA images based on the criteria: excellent, good, fair or non-diagnostic. The average scores of all observers were calculated for each specimen in all exposure conditions. The 40 mA images could visualize such landmarks and were evaluated to be same or almost equivalent in quality to the 80 mA images. Even the 20 mA images could be accepted just for diagnostic purpose for implant with substantial deterioration of the image quality. The 10 mA images may not be accepted because of the obscured contour caused by image noise. Significant dose reduction by lowering mA can be utilized for pre-surgical implant planning in multi-detector CT.

The Dosepix detector—an energy-resolving photon-counting pixel detector for spectrometric measurements

NASA Astrophysics Data System (ADS)

Zang, A.; Anton, G.; Ballabriga, R.; Bisello, F.; Campbell, M.; Celi, J. C.; Fauler, A.; Fiederle, M.; Jensch, M.; Kochanski, N.; Llopart, X.; Michel, N.; Mollenhauer, U.; Ritter, I.; Tennert, F.; Wölfel, S.; Wong, W.; Michel, T.

2015-04-01

The Dosepix detector is a hybrid photon-counting pixel detector based on ideas of the Medipix and Timepix detector family. 1 mm thick cadmium telluride and 300 μm thick silicon were used as sensor material. The pixel matrix of the Dosepix consists of 16 x 16 square pixels with 12 rows of (200 μm)2 and 4 rows of (55 μm)2 sensitive area for the silicon sensor layer and 16 rows of pixels with 220 μm pixel pitch for CdTe. Besides digital energy integration and photon-counting mode, a novel concept of energy binning is included in the pixel electronics, allowing energy-resolved measurements in 16 energy bins within one acquisition. The possibilities of this detector concept range from applications in personal dosimetry and energy-resolved imaging to quality assurance of medical X-ray sources by analysis of the emitted photon spectrum. In this contribution the Dosepix detector, its response to X-rays as well as spectrum measurements with Si and CdTe sensor layer are presented. Furthermore, a first evaluation was carried out to use the Dosepix detector as a kVp-meter, that means to determine the applied acceleration voltage from measured X-ray tubes spectra.

[Study of radiation dose to the eye lens by multi-detector row computed tomography of the temporal bone].

PubMed

Hirakuri, Ayaka; Numasawa, Kanako; Takeishi, Hideki; Satomura, Minato; Takeda, Hiromitsu; Harada, Kuniaki; Asanuma, Osamu; Sakata, Motomichi

2012-01-01

The exposure of the eye lens caused by multi-detector row computed tomography (MDCT) of the temporal bone is a serious problem. Our aim was to evaluate the radiation dose to the eye lens by different scan baselines (orbitomeatal line; OML, acanthiomeatal line; AML) and examine the difference of the depiction of the temporal bone structures. Measurement of the exposure to the eye lens was performed by means of MDCT of the temporal bone with a radio-photoluminescence glass dosimeter using a rand phantom. Moreover, we studied only one volunteer (58-year-old male) who had no symptom and was not suspected of having any ear abnormalities with a two scan baseline. Visualization of the major anatomical structures of the temporal bone (the tympanic portion of the facial nerve canal, the body of the incus, stapes superstructures, vestibule etc.) was performed on the volunteer. The average absorbed dose was 6.42 mGy by the OML and 1.59 mGy by the AML, respectively. With regard to visualization of the temporal bone structures, all structures were of equal quality with the two scan baseline. With the AML line, the radiation dose to the eye lens was reduced to 75%. Therefore, the authors recommended an AML for use for MDCT of the temporal bone. In clinical practice, the optimization of scanning factor (kVp, mAs etc.) and the use of the radio-protection should be implemented for radiation dose reduction of the eye lens by MDCT of the temporal bone.

Preliminary experimental results from a MARS Micro-CT system.

PubMed

He, Peng; Yu, Hengyong; Thayer, Patrick; Jin, Xin; Xu, Qiong; Bennett, James; Tappenden, Rachael; Wei, Biao; Goldstein, Aaron; Renaud, Peter; Butler, Anthony; Butler, Phillip; Wang, Ge

2012-01-01

The Medipix All Resolution System (MARS) system is a commercial spectral/multi-energy micro-CT scanner designed and assembled by the MARS Bioimaging, Ltd. in New Zealand. This system utilizes the state-of-the-art Medipix photon-counting, energy-discriminating detector technology developed by a collaboration at European Organization for Nuclear Research (CERN). In this paper, we report our preliminary experimental results using this system, including geometrical alignment, photon energy characterization, protocol optimization, and spectral image reconstruction. We produced our scan datasets with a multi-material phantom, and then applied ordered subset-simultaneous algebraic reconstruction technique (OS-SART) to reconstruct images in different energy ranges and principal component analysis (PCA) to evaluate spectral deviation among the energy ranges.

Comparison of computed tomography pulmonary angiography and point-of-care tests for pulmonary thromboembolism diagnosis in dogs.

PubMed

Goggs, R; Chan, D L; Benigni, L; Hirst, C; Kellett-Gregory, L; Fuentes, V L

2014-04-01

To evaluate the feasibility of CT pulmonary angiography for identification of naturally occurring pulmonary thromboembolism in dogs using predefined diagnostic criteria and to assess the ability of echocardiography, cardiac troponins, D-dimers and kaolin-activated thromboelastography to predict the presence of pulmonary thromboembolism in dogs. Twelve dogs with immune-mediated haemolytic anaemia and evidence of respiratory distress were prospectively evaluated. Dogs were sedated immediately before CT pulmonary angiography using intravenous butorphanol. Spiral CT pulmonary angiography was performed with a 16 detector-row CT scanner using a pressure injector to infuse contrast media through peripheral intravenous catheters. Pulmonary thromboembolism was diagnosed using predefined criteria. Contemporaneous tests included echocardiography, arterial blood gas analysis, kaolin-activated thromboelastography, D-dimers and cardiac troponins. Based on predefined criteria, four dogs were classified as pulmonary thromboembolism positive, three dogs were suspected to have pulmonary thromboembolism and the remaining five dogs had negative scans. The four dogs identified with pulmonary thromboembolism all had discrete filling defects in main or lobar pulmonary arteries. None of the contemporaneous tests was discriminant for pulmonary thromboembolism diagnosis, although the small sample size was limiting. CT pulmonary angiography can be successfully performed in dogs under sedation, even in at-risk patients with respiratory distress and can both confirm and rule out pulmonary thromboembolism in dogs. © 2014 British Small Animal Veterinary Association.

Multi-detector CT angiography of the aortic valve—Part 2: disease specific findings

PubMed Central

Ganeshan, Arul

2014-01-01

The aortic valve and adjacent structures should be routinely evaluated on all thoracic cross-sectional imaging studies. Echocardiography and magnetic resonance imaging (MRI) are the main imaging techniques used for assessment of the aortic valve and related pathology but multi-detector computed tomography (MDCT) can offer valuable complimentary information in some clinical scenarios. MDCT is the definite means of assessing aortic valvular calcification, acute aortic syndrome and for non-invasive assessment of the coronary arteries. MDCT also has an emerging role in the planning and follow-up of trans-catheter aortic valve replacement. This article reviews the spectrum of aortic valve disease highlighting the key MDCT imaging features. PMID:25202663

The relevance of image quality indices for dose optimization in abdominal multi-detector row CT in children: experimental assessment with pediatric phantoms

NASA Astrophysics Data System (ADS)

Brisse, H. J.; Brenot, J.; Pierrat, N.; Gaboriaud, G.; Savignoni, A.; DeRycke, Y.; Neuenschwander, S.; Aubert, B.; Rosenwald, J.-C.

2009-04-01

This study assessed and compared various image quality indices in order to manage the dose of pediatric abdominal MDCT protocols and to provide guidance on dose reduction. PMMA phantoms representing average body diameters at birth, 1 year, 5 years, 10 years and 15 years of age were scanned in a four-channel MDCT with a standard pediatric abdominal CT protocol. Image noise (SD, standard deviation of CT number), noise derivative (ND, derivative of the function of noise with respect to dose) and contrast-to-noise ratio (CNR) were measured. The 'relative' low-contrast detectability (rLCD) was introduced as a new quantity to adjust LCD to the various phantom diameters on the basis of the LCD1% assessed in a Catphan® phantom and a constant central absorbed dose. The required variations of CTDIvol16 with respect to phantom size were analyzed in order to maintain each image quality index constant. The use of a fixed SD or CNR level leads to major dose ratios between extreme patient sizes (factor 22.7 to 44 for SD, 31.7 to 51.5 for CNR2.8%), whereas fixed ND and rLCD result in acceptable dose ratios ranging between factors of 2.9 and 3.9 between extreme phantom diameters. For a 5-9 mm rLCD1%, adjusted ND values range between -0.84 and -0.11 HU mGy-1. Our data provide guidance on dose reduction on the basis of patient dimensions and the required rLCD (e.g., to get a constant 7 mm rLCD1% for abdominal diameters of 10, 13, 16, 20 and 25 cm, tube current-time product should be adjusted in order to obtain CTDIvol16 values of 6.2, 7.2, 8.8, 11.6 and 17.7 mGy, respectively).

In Vivo Evaluation of Chemical Composition of Eight Types of Urinary Calculi Using Spiral Computerized Tomography in a Chinese Population.

PubMed

Huo, Jun; Liu, Zhong-Yuan; Wang, Ke-Feng; Xu, Zhen-Qun

2015-09-01

This study was conducted to evaluate the chemical composition of eight types of urinary calculi using spiral computerized tomography (CT) in vivo. From October 2011 to February 2013, upper urinary tract calculi were obtained from 122 patients in the department of urinary surgery of the First Affiliated Hospital of Soochow University. All patients were scanned with a 64-detector row helical CT scanner using 6.50 mm collimation before ureterorenoscopy. Data from the preoperative spiral CT scans and postoperative chemical composition of urinary calculi were collected. The chemical composition analysis indicates that there were five types of pure calculi and three types of mixed calculi, including 39 calcium oxalate calculi, 12 calcium phosphate calculi, 10 calcium carbonate calculi, 8 magnesium ammonium phosphate calculi, 6 carbonated apatite, 21 uric acid/ammonium urate calculi, 10 uric acid/calcium oxalate calculi, and 16 calcium oxalate/calcium phosphate calculi. There were significant differences in the mean CT values among the five types of pure calculi (P < 0.001). Furthermore, we also observed significant differences in the mean CT values among three types of mixed calculi (P < 0.001). Significant differences in the mean CT values were also found among eight types of urinary calculi (P < 0.001). However, no statistically significant difference was observed between the mean CT values of magnesium ammonium phosphate calculi and uric acid/calcium oxalate calculi (P = 0.262). Our findings suggest that spiral CT could be a promising tool for determining the chemical composition of upper urinary tract calculi. © 2014 Wiley Periodicals, Inc.

Patient-related factors influencing detectability of coronary arteries in 320-row CT angiography in infants with complex congenital heart disease.

PubMed

Yamasaki, Yuzo; Kawanami, Satoshi; Kamitani, Takeshi; Sagiyama, Koji; Shin, Seitaro; Hino, Takuya; Nagata, Hazumu; Yabuuchi, Hidetake; Nagao, Michinobu; Honda, Hiroshi

2018-05-05

To investigate the performance of second-generation 320-row computed tomographic (CT) angiography (CTA) in detecting coronary arteries and identify factors influencing visibility of the coronary arteries in infants with complex congenital heart disease (CHD). Data of 60 infants (aged 0-2 years, median 2 months) with complex CHD who underwent examination using 320-row CTA with low-dose prospective electrocardiogram-triggered volume target scanning were reviewed. The coronary arteries of each infant were assessed using a 0-4-point scoring system based on the number of coronary segments with a visible course. Clinical parameters, the CT value in the ascending aorta, image noise, and the radiation dose were subjected to univariate and multivariate analyses. The mean coronary score for all examinations was 2.6 ± 1.5 points. The mean attenuation in the ascending aorta was 306.7 ± 66.2 HU and the mean standard deviation was 21.7 ± 4.4. The mean effective radiation dose was 1.27 ± 0.39 mSv. Multivariate regression analysis showed significant correlations between coronary score and body weight (p < 0.05) and between coronary score and the CT value in the ascending aorta (p < 0.02). Second-generation 320-row CTA with prospective electrocardiogram-triggered volume target scanning and hybrid iterative reconstruction allows good visibility of the coronary arteries in infants with complex CHD. Body weight and the CT value in the ascending aorta are important factors influencing the visibility of the coronary arteries in infants.

Diagnosing Early Ischemic Changes with the Latest-Generation Flat Detector CT: A Comparative Study with Multidetector CT.

PubMed

Maier, I L; Leyhe, J R; Tsogkas, I; Behme, D; Schregel, K; Knauth, M; Schnieder, M; Liman, J; Psychogios, M-N

2018-05-01

One-stop management of mechanical thrombectomy-eligible patients with large-vessel occlusion represents an innovative approach in acute stroke treatment. This approach reduces door-to-reperfusion times by omitting multidetector CT, using flat detector CT as pre-mechanical thrombectomy imaging. The purpose of this study was to compare the diagnostic performance of the latest-generation flat detector CT with multidetector CT. Prospectively derived data from patients with ischemic stroke with large-vessel occlusion and mechanical thrombectomy were analyzed in this monocentric study. All included patients underwent multidetector CT before referral to our comprehensive stroke center and flat detector CT in the angiography suite before mechanical thrombectomy. Diagnosis of early ischemic signs, quantified by the ASPECTS, was compared between modalities using cross tables, the Pearson correlation, and Bland-Altman plots. The predictive value of multidetector CT- and flat detector CT-derived ASPECTS for functional outcome was investigated using area under the receiver operating characteristic curve analysis. Of 25 patients, 24 (96%) had flat detector CT with sufficient diagnostic quality. Median multidetector CT and flat detector CT ASPECTSs were 7 (interquartile range, 5.5-9 and 4.25-8, respectively) with a mean period of 143.6 ± 49.5 minutes between both modalities. The overall sensitivity was 85.1% and specificity was 83.1% for flat detector CT ASPECTS compared with multidetector CT ASPECTS as the reference technique. Multidetector CT and flat detector CT ASPECTS were strongly correlated ( r = 0.849, P < .001) and moderately predicted functional outcome (area under the receiver operating characteristic curve, 0.738; P = .007 and .715; P = .069, respectively). Determination of ASPECTS on flat detector CT is feasible, showing no significant difference compared with multidetector CT ASPECTS and a similar predictive value for functional outcome. Our findings support the use of flat detector CT for emergency stroke imaging before mechanical thrombectomy to reduce door-to-groin time. © 2018 by American Journal of Neuroradiology.

INTERIOR SECOND FLOOR EAST END LOOKING WEST AT NORTH ROW ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

INTERIOR SECOND FLOOR- EAST END LOOKING WEST AT NORTH ROW OF MUSHROOM COLUMNS. - Colt Fire Arms Company, South Armory Building, 36-150 Huyshope Avenue, 17-170 Van Dyke Avenue, 49 Vredendale Avenue, Hartford, Hartford County, CT

An X-Ray computed tomography/positron emission tomography system designed specifically for breast imaging.

PubMed

Boone, John M; Yang, Kai; Burkett, George W; Packard, Nathan J; Huang, Shih-ying; Bowen, Spencer; Badawi, Ramsey D; Lindfors, Karen K

2010-02-01

Mammography has served the population of women who are at-risk for breast cancer well over the past 30 years. While mammography has undergone a number of changes as digital detector technology has advanced, other modalities such as computed tomography have experienced technological sophistication over this same time frame as well. The advent of large field of view flat panel detector systems enable the development of breast CT and several other niche CT applications, which rely on cone beam geometry. The breast, it turns out, is well suited to cone beam CT imaging because the lack of bones reduces artifacts, and the natural tapering of the breast anteriorly reduces the x-ray path lengths through the breast at large cone angle, reducing cone beam artifacts as well. We are in the process of designing a third prototype system which will enable the use of breast CT for image guided interventional procedures. This system will have several copies fabricated so that several breast CT scanners can be used in a multi-institutional clinical trial to better understand the role that this technology can bring to breast imaging.

Defining the optimal cut-off values for liver enzymes in diagnosing blunt liver injury.

PubMed

Koyama, Tomohide; Hamada, Hirohisa; Nishida, Masamichi; Naess, Paal A; Gaarder, Christine; Sakamoto, Tetsuya

2016-01-25

Patients with blunt trauma to the liver have elevated levels of liver enzymes within a short time post injury, potentially useful in screening patients for computed tomography (CT). This study was performed to define the optimal cut-off values for serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in patients with blunt liver injury diagnosed with contrast enhanced multi detector-row CT (CE-MDCT). All patients admitted from May 2006 to July 2013 to Teikyo University Hospital Trauma and Critical Care Center, and who underwent abdominal CE-MDCT within 3 h after blunt trauma, were retrospectively enrolled. Using receiver operating characteristic (ROC) curve analysis, the optimal cut-off values for AST and ALT were defined, and sensitivity and specificity were calculated. Of a total of 676 blunt trauma patients 64 patients were diagnosed with liver injury (Group LI+) and 612 patients without liver injury (Group LI-). Group LI+ and LI- were comparable for age, Revised Trauma Score, and Probability of survival. The groups differed in Injury Severity Score [median 21 (interquartile range 9-33) vs. 17 (9-26) (p < 0.01)]. Group LI+ had higher AST than LI- [276 (48-503) vs. 44 (16-73); p < 0.001] and higher ALT [240 (92-388) vs. 32 (16-49); p < 0.001]. Using ROC curve analysis, the optimal cut-off values for AST and ALT were set at 109 U/l and 97 U/l, respectively. Based on these values, AST ≥ 109 U/l had a sensitivity of 81%, a specificity of 82%, a positive predictive value of 32%, and a negative predictive value of 98%. The corresponding values for ALT ≥ 97 U/l were 78, 88, 41 and 98%, respectively, and for the combination of AST ≥ 109 U/l and/or ALT ≥ 97 U/l were 84, 81, 32, 98%, respectively. We have identified AST ≥ 109 U/l and ALT ≥ 97 U/l as optimal cut-off values in predicting the presence of liver injury, potentially useful as a screening tool for CT scan in patients otherwise eligible for observation only or as a transfer criterion to a facility with CT scan capability.

Demonstration of iodine K-edge imaging by use of an energy-discrimination X-ray computed tomography system with a cadmium telluride detector.

PubMed

Abudurexiti, Abulajiang; Kameda, Masashi; Sato, Eiichi; Abderyim, Purkhet; Enomoto, Toshiyuki; Watanabe, Manabu; Hitomi, Keitaro; Tanaka, Etsuro; Mori, Hidezo; Kawai, Toshiaki; Takahashi, Kiyomi; Sato, Shigehiro; Ogawa, Akira; Onagawa, Jun

2010-07-01

An energy-discrimination K-edge X-ray computed tomography (CT) system is useful for increasing the contrast resolution of a target region by utilizing contrast media. The CT system has a cadmium telluride (CdTe) detector, and a projection curve is obtained by linear scanning with use of the CdTe detector in conjunction with an X-stage. An object is rotated by a rotation step angle with use of a turntable between the linear scans. Thus, CT is carried out by repetition of the linear scanning and the rotation of an object. Penetrating X-ray photons from the object are detected by the CdTe detector, and event signals of X-ray photons are produced with use of charge-sensitive and shaping amplifiers. Both the photon energy and the energy width are selected by use of a multi-channel analyzer, and the number of photons is counted by a counter card. For performing energy discrimination, a low-dose-rate X-ray generator for photon counting was developed; the maximum tube voltage and the minimum tube current were 110 kV and 1.0 microA, respectively. In energy-discrimination CT, the tube voltage and the current were 60 kV and 20.0 microA, respectively, and the X-ray intensity was 0.735 microGy/s at 1.0 m from the source and with a tube voltage of 60 kV. Demonstration of enhanced iodine K-edge X-ray CT was carried out by selection of photons with energies just beyond the iodine K-edge energy of 33.2 keV.

Spectral performance of a whole-body research photon counting detector CT: quantitative accuracy in derived image sets

NASA Astrophysics Data System (ADS)

Leng, Shuai; Zhou, Wei; Yu, Zhicong; Halaweish, Ahmed; Krauss, Bernhard; Schmidt, Bernhard; Yu, Lifeng; Kappler, Steffen; McCollough, Cynthia

2017-09-01

Photon-counting computed tomography (PCCT) uses a photon counting detector to count individual photons and allocate them to specific energy bins by comparing photon energy to preset thresholds. This enables simultaneous multi-energy CT with a single source and detector. Phantom studies were performed to assess the spectral performance of a research PCCT scanner by assessing the accuracy of derived images sets. Specifically, we assessed the accuracy of iodine quantification in iodine map images and of CT number accuracy in virtual monoenergetic images (VMI). Vials containing iodine with five known concentrations were scanned on the PCCT scanner after being placed in phantoms representing the attenuation of different size patients. For comparison, the same vials and phantoms were also scanned on 2nd and 3rd generation dual-source, dual-energy scanners. After material decomposition, iodine maps were generated, from which iodine concentration was measured for each vial and phantom size and compared with the known concentration. Additionally, VMIs were generated and CT number accuracy was compared to the reference standard, which was calculated based on known iodine concentration and attenuation coefficients at each keV obtained from the U.S. National Institute of Standards and Technology (NIST). Results showed accurate iodine quantification (root mean square error of 0.5 mgI/cc) and accurate CT number of VMIs (percentage error of 8.9%) using the PCCT scanner. The overall performance of the PCCT scanner, in terms of iodine quantification and VMI CT number accuracy, was comparable to that of EID-based dual-source, dual-energy scanners.

Multi-detector thoracic CT findings in cerebro-costo-mandibular syndrome: rib gaps and failure of costo-vertebral separation.

PubMed

Watson, Tom Anthony; Arthurs, Owen John; Muthialu, Nagarajan; Calder, Alistair Duncan

2014-02-01

Cerebro-costo-mandibular syndrome (CCMS) describes a triad of mandibular hypoplasia, brain dysfunction and posterior rib defects ("rib gaps"). We present the CT imaging for a 2-year-old girl with CCMS that highlights the rib gap defects and shows absent transverse processes with abnormal fusion of the ribs directly to the vertebral bodies. We argue that this is likely to relate to abnormal lateral sclerotome development in embryology, with the failure of normal costo-vertebral junctions compounding impaired thoracic function. The case also highlights the use of CT for specific indications in skeletal dysplasia.

Design and performance of a multi-pinhole collimation device for small animal imaging with clinical SPECT and SPECT-CT scanners

PubMed Central

DiFilippo, Frank P.

2008-01-01

A multi-pinhole collimation device is developed that uses the gamma camera detectors of a clinical SPECT or SPECT-CT scanner to produce high resolution SPECT images. The device consists of a rotating cylindrical collimator having 22 tungsten pinholes with 0.9 mm diameter apertures and an animal bed inside the collimator that moves linearly to provide helical or ordered-subsets axial sampling. CT images also may be acquired on a SPECT-CT scanner for purposes of image co-registration and SPECT attenuation correction. The device is placed on the patient table of the scanner without attaching to the detectors or scanner gantry. The system geometry is calibrated in-place from point source data and is then used during image reconstruction. The SPECT imaging performance of the device is evaluated with test phantom scans. Spatial resolution from reconstructed point source images is measured to be 0.6 mm full width at half maximum or better. Micro-Derenzo phantom images demonstrate the ability to resolve 0.7 mm diameter rod patterns. The axial slabs of a Micro-Defrise phantom are visualized well. Collimator efficiency exceeds 0.05% at the center of the field of view, and images of a uniform phantom show acceptable uniformity and minimal artifact. The overall simplicity and relatively good imaging performance of the device make it an interesting low-cost alternative to dedicated small animal scanners. PMID:18635899

Design and performance of a multi-pinhole collimation device for small animal imaging with clinical SPECT and SPECT CT scanners

NASA Astrophysics Data System (ADS)

Di Filippo, Frank P.

2008-08-01

A multi-pinhole collimation device is developed that uses the gamma camera detectors of a clinical SPECT or SPECT-CT scanner to produce high-resolution SPECT images. The device consists of a rotating cylindrical collimator having 22 tungsten pinholes with 0.9 mm diameter apertures and an animal bed inside the collimator that moves linearly to provide helical or ordered-subsets axial sampling. CT images also may be acquired on a SPECT-CT scanner for purposes of image co-registration and SPECT attenuation correction. The device is placed on the patient table of the scanner without attaching to the detectors or scanner gantry. The system geometry is calibrated in-place from point source data and is then used during image reconstruction. The SPECT imaging performance of the device is evaluated with test phantom scans. Spatial resolution from reconstructed point source images is measured to be 0.6 mm full width at half maximum or better. Micro-Derenzo phantom images demonstrate the ability to resolve 0.7 mm diameter rod patterns. The axial slabs of a Micro-Defrise phantom are visualized well. Collimator efficiency exceeds 0.05% at the center of the field of view, and images of a uniform phantom show acceptable uniformity and minimal artifact. The overall simplicity and relatively good imaging performance of the device make it an interesting low-cost alternative to dedicated small animal scanners.

Energy-discrimination X-ray computed tomography system utilizing a silicon-PIN detector and its application to 2.0-keV-width K-edge imaging

NASA Astrophysics Data System (ADS)

Hagiwara, Osahiko; Watanabe, Manabu; Sato, Eiichi; Matsukiyo, Hiroshi; Osawa, Akihiro; Enomoto, Toshiyuki; Nagao, Jiro; Sato, Shigehiro; Ogawa, Akira; Onagawa, Jun

2011-05-01

Demonstration of narrow-energy-width computed tomography (CT) was carried out by means of energy-discrimination. An X-ray CT system is of a first-generation type and consists of an X-ray generator, a turntable, a translation stage, a two-stage controller, a silicon-PIN detector system with amplifiers, a multi-channel analyzer (MCA), a counter card (CC), and a personal computer (PC). CT is accomplished by repeating the translation and the rotation of an object, and projection curves of the object are obtained by the translation of the moving object. Both photon-energy level and energy width are determined by the MCA, and the pulses of the discriminated event signal from the MCA are counted by CC in conjunction with PC. The maximum count rate was approximately 300 cps (counts per second) with energy widths of 2.0 keV, and energy-discrimination CT was carried out with a photon-energy resolution of 0.15 keV. To perform iodine K-edge CT, X-ray photons with an energy range from 33.2 to 35.2 keV were used. Next, to carry out cerium K-edge CT, an energy range from 40.3 to 42.3 keV was selected.

A tetrahedron beam computed tomography benchtop system with a multiple pixel field emission x-ray tube

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Xiaochao; Kim, Joshua; Laganis, Philip

2011-10-15

Purpose: To demonstrate the feasibility of Tetrahedron Beam Computed Tomography (TBCT) using a carbon nanotube (CNT) multiple pixel field emission x-ray (MPFEX) tube. Methods: A multiple pixel x-ray source facilitates the creation of novel x-ray imaging modalities. In a previous publication, the authors proposed a Tetrahedron Beam Computed Tomography (TBCT) imaging system which comprises a linear source array and a linear detector array that are orthogonal to each other. TBCT is expected to reduce scatter compared with Cone Beam Computed Tomography (CBCT) and to have better detector performance. Therefore, it may produce improved image quality for image guided radiotherapy. Inmore » this study, a TBCT benchtop system has been developed with an MPFEX tube. The tube has 75 CNT cold cathodes, which generate 75 x-ray focal spots on an elongated anode, and has 4 mm pixel spacing. An in-house-developed, 5-row CT detector array using silicon photodiodes and CdWO{sub 4} scintillators was employed in the system. Hardware and software were developed for tube control and detector data acquisition. The raw data were preprocessed for beam hardening and detector response linearity and were reconstructed with an FDK-based image reconstruction algorithm. Results: The focal spots were measured at about 1 x 2 mm{sup 2} using a star phantom. Each cathode generates around 3 mA cathode current with 2190 V gate voltage. The benchtop system is able to perform TBCT scans with a prolonged scanning time. Images of a commercial CT phantom were successfully acquired. Conclusions: A prototype system was developed, and preliminary phantom images were successfully acquired. MPFEX is a promising x-ray source for TBCT. Further improvement of tube output is needed in order for it to be used in clinical TBCT systems.« less

Myocardial perfusion in patients with suspected coronary artery disease: comparison between 320-MDCT and rubidium-82 PET.

PubMed

Dantas, Roberto Nery; Assuncao, Antonildes Nascimento; Marques, Ismar Aguiar; Fahel, Mateus Guimaraes; Nomura, Cesar Higa; Avila, Luiz Francisco Rodrigues; Giorgi, Maria Clementina Pinto; Soares, Jose; Meneghetti, Jose Claudio; Parga, Jose Rodrigues

2018-06-01

Despite advances in non-invasive myocardial perfusion imaging (MPI) evaluation, computed tomography (CT) multiphase MPI protocols have not yet been compared with the highly accurate rubidium-82 positron emission tomography ( 82 RbPET) MPI. Thus, this study aimed to evaluate agreement between 82 RbPET and 320-detector row CT (320-CT) MPI using a multiphase protocol in suspected CAD patients. Forty-four patients referred for MPI evaluation were prospectively enrolled and underwent dipyridamole stress 82 RbPET and multiphase 320-CT MPI (five consecutive volumetric acquisitions during stress). Statistical analyses were performed using the R software. There was high agreement for recognizing summed stress scores ≥ 4 (kappa 0.77, 95% CI 0.55-0.98, p < 0.001) and moderate for detecting SDS ≥ 2 (kappa 0.51, 95% CI 0.23-0.80, p < 0.001). In a per segment analysis, agreement was high for the presence of perfusion defects during stress and rest (kappa 0.75 and 0.82, respectively) and was moderate for impairment severity (kappa 0.58 and 0.65, respectively). The 320-CT protocol was safe, with low radiation burden (9.3 ± 2.4 mSv). There was a significant agreement between dipyridamole stress 320-CT MPI and 82 RbPET MPI in the evaluation of suspected CAD patients of intermediate risk. The multiphase 320-CT MPI protocol was feasible, diagnostic and with relatively low radiation exposure. • Rubidium-82 PET and 320-MDCT can perform MPI studies for CAD investigation. • There is high agreement between rubidium-82 PET and 320-MDCT for MPI assessment. • Multiphase CT perfusion protocols are feasible and with low radiation. • Multiphase CT perfusion protocols can identify image artefacts.

Multi-port, optically addressed RAM

NASA Technical Reports Server (NTRS)

Johnston, Alan R. (Inventor); Nixon, Robert H. (Inventor); Bergman, Larry A. (Inventor); Esener, Sadik (Inventor)

1989-01-01

A random access memory addressing system utilizing optical links between memory and the read/write logic circuits comprises addressing circuits including a plurality of light signal sources, a plurality of optical gates including optical detectors associated with the memory cells, and a holographic optical element adapted to reflect and direct the light signals to the desired memory cell locations. More particularly, it is a multi-port, binary computer memory for interfacing with a plurality of computers. There are a plurality of storage cells for containing bits of binary information, the storage cells being disposed at the intersections of a plurality of row conductors and a plurality of column conductors. There is interfacing logic for receiving information from the computers directing access to ones of the storage cells. There are first light sources associated with the interfacing logic for transmitting a first light beam with the access information modulated thereon. First light detectors are associated with the storage cells for receiving the first light beam, for generating an electrical signal containing the access information, and for conducting the electrical signal to the one of the storage cells to which it is directed. There are holographic optical elements for reflecting the first light beam from the first light sources to the first light detectors.

What are the potential advantages and disadvantages of volumetric CT scanning?

PubMed

Voros, Szilard

2009-01-01

After the introduction and dissemination of 64-slice multislice computed tomography systems, cardiovascular CT has arrived at a crossroad, and different philosophies lead down different paths of technologic development. Increased number of detector rows in the z-axis led to the introduction of dynamic, volumetric scanning of the heart and allows for whole-organ imaging. Dynamic, volumetric "whole-organ" scanning significantly reduces image acquisition time; "single-beat whole-heart imaging" results in improved image quality and reduced radiation exposure and reduced contrast dose. It eliminates helical and pitch artifacts and allows for simultaneous imaging of the base and apex of the heart. Beyond coronary arterial luminal imaging, such innovations open up the opportunity for myocardial perfusion and viability imaging and coronary arterial plaque imaging. Dual-source technology with 2 x-ray tubes placed at 90-degree angles provides heart rate-independent temporal resolution and has the potential for tissue characterization on the basis of different attenuation values at different energy levels. Refined detector technology allows for improved low-contrast resolution and may be beneficial for more detailed evaluation of coronary arterial plaque composition. The clinical benefit of each of these technologies will have to be evaluated in carefully designed clinical trials and in everyday clinical practice. Such combined experience will probably show the relative benefit of each of these philosophies in different patient populations and in different clinical scenarios.

Validation of multi-detector computed tomography as a non-invasive method for measuring ovarian volume in macaques (Macaca fascicularis).

PubMed

Jones, Jeryl C; Appt, Susan E; Werre, Stephen R; Tan, Joshua C; Kaplan, Jay R

2010-06-01

The purpose of this study was to validate low radiation dose, contrast-enhanced, multi-detector computed tomography (MDCT) as a non-invasive method for measuring ovarian volume in macaques. Computed tomography scans of four known-volume phantoms and nine mature female cynomolgus macaques were acquired using a previously described, low radiation dose scanning protocol, intravenous contrast enhancement, and a 32-slice MDCT scanner. Immediately following MDCT, ovaries were surgically removed and the ovarian weights were measured. The ovarian volumes were determined using water displacement. A veterinary radiologist who was unaware of actual volumes measured ovarian CT volumes three times, using a laptop computer, pen display tablet, hand-traced regions of interest, and free image analysis software. A statistician selected and performed all tests comparing the actual and CT data. Ovaries were successfully located in all MDCT scans. The iliac arteries and veins, uterus, fallopian tubes, cervix, ureters, urinary bladder, rectum, and colon were also consistently visualized. Large antral follicles were detected in six ovaries. Phantom mean CT volume was 0.702+/-SD 0.504 cc and the mean actual volume was 0.743+/-SD 0.526 cc. Ovary mean CT volume was 0.258+/-SD 0.159 cc and mean water displacement volume was 0.257+/-SD 0.145 cc. For phantoms, the mean coefficient of variation for CT volumes was 2.5%. For ovaries, the least squares mean coefficient of variation for CT volumes was 5.4%. The ovarian CT volume was significantly associated with actual ovarian volume (ICC coefficient 0.79, regression coefficient 0.5, P=0.0006) and the actual ovarian weight (ICC coefficient 0.62, regression coefficient 0.6, P=0.015). There was no association between the CT volume accuracy and mean ovarian CT density (degree of intravenous contrast enhancement), and there was no proportional or fixed bias in the CT volume measurements. Findings from this study indicate that MDCT is a valid non-invasive technique for measuring the ovarian volume in macaques.

4. VIEW NORTHWEST, INTERIOR OF GATEHOUSE, SHOWING ROW OF GATE ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. VIEW NORTHWEST, INTERIOR OF GATEHOUSE, SHOWING ROW OF GATE OPERATING MECHANISMS; HEIGHT OF STEMS INDICATES FOREGROUND GATE IS OPEN - Norwich Water Power Company, Headgates, West bank of Shetucket River opposite Fourteenth Street, Greenville section, Norwich, New London County, CT

Role of Multi Detector Computed Tomography (MDCT) in Preoperative Staging of Pancreatic Carcinoma.

PubMed

Singhal, Soumil; Prabhu, Nirmal Kumar; Sethi, Pulkit; Moorthy, Srikanth

2017-05-01

Pancreatic carcinoma is one of the leading causes of cancer related death in advanced countries and has shown rising trends in developing countries like India. Increase in the incidence has been linked to risk factors like lifestyle modification associated with increased alcohol consumption and rapid urbanization. Most patients at the time of diagnosis present with an advanced condition. Surgical resection offers the only chance for cure in them and imaging plays a crucial role in the early diagnosis of the condition. To compare the staging of pancreatic carcinoma by MDCT (Multi Detector Computed Tomography) with surgery in a preoperative setting in a tertiary referral centre in Kerala. A cross-sectional observational study was performed between November 2014 and October 2016, 25 patients (12 men, 13 women), with a mean age of 54.2 years, were evaluated. MDCT was performed using 16 slice, 64 slice and 256 slice multi detector CT machines. The gold standard for diagnosis was histopathology and operative data. All statistical analysis was done using IBM SPSS version 20.0. Validity parameters like sensitivity, specificity, accuracy and Positive Predictive Value (PPV) / Negative Predictive Value (NPV) were computed for MDCT with respect to surgery. Of the 25 patients who were evaluated for surgery, 15 (60%) cases were classified as resectable tumours, 3 (12%) as borderline resectable and 7 (28%) as unresectable tumours. CT showed a sensitivity of 82.3% with a specificity of 87.5%. However, for assessing vascular invasion, CT showed sensitivity and specificity of 100% and 93.3% respectively. Three (12%) patients in the study who were classified as borderline resectable pancreatic tumours underwent surgery. Contrast-enhanced multiphase pancreatic imaging using MDCT plays a pivotal role in diagnosing and assessing resectability and vascular invasion of pancreatic tumours. It is very useful for determining borderline resectable tumours pre-operatively, which aids for better treatment planning.

Cardiac imaging with multi-sector data acquisition in volumetric CT: variation of effective temporal resolution and its potential clinical consequences

NASA Astrophysics Data System (ADS)

Tang, Xiangyang; Hsieh, Jiang; Taha, Basel H.; Vass, Melissa L.; Seamans, John L.; Okerlund, Darin R.

2009-02-01

With increasing longitudinal detector dimension available in diagnostic volumetric CT, step-and-shoot scan is becoming popular for cardiac imaging. In comparison to helical scan, step-and-shoot scan decouples patient table movement from cardiac gating/triggering, which facilitates the cardiac imaging via multi-sector data acquisition, as well as the administration of inter-cycle heart beat variation (arrhythmia) and radiation dose efficiency. Ideally, a multi-sector data acquisition can improve temporal resolution at a factor the same as the number of sectors (best scenario). In reality, however, the effective temporal resolution is jointly determined by gantry rotation speed and patient heart beat rate, which may significantly lower than the ideal or no improvement (worst scenario). Hence, it is clinically relevant to investigate the behavior of effective temporal resolution in cardiac imaging with multi-sector data acquisition. In this study, a 5-second cine scan of a porcine heart, which cascades 6 porcine cardiac cycles, is acquired. In addition to theoretical analysis and motion phantom study, the clinical consequences due to the effective temporal resolution variation are evaluated qualitative or quantitatively. By employing a 2-sector image reconstruction strategy, a total of 15 (the permutation of P(6, 2)) cases between the best and worst scenarios are studied, providing informative guidance for the design and optimization of CT cardiac imaging in volumetric CT with multi-sector data acquisition.

Role of enhanced multi-detector-row computed tomography before urgent endoscopy in acute upper gastrointestinal bleeding.

PubMed

Miyaoka, Youichi; Amano, Yuji; Ueno, Sayaka; Izumi, Daisuke; Mikami, Hironobu; Yazaki, Tomotaka; Okimoto, Eiko; Sonoyama, Takayuki; Ito, Satoko; Fujishiro, Hirofumi; Kohge, Naruaki; Imaoka, Tomonori

2014-04-01

Multi-detector-row computed tomography (MDCT) has been reported to be a potentially useful modality for detection of the bleeding origin in patients with acute upper massive gastrointestinal (GI) bleeding. The purpose of this study is to investigate the efficacy of MDCT as a routine method for detecting the origin of acute upper GI bleeding prior to urgent endoscopy. Five hundred seventy-seven patients with acute upper GI bleeding (514 nonvariceal patients, 63 variceal patients) who underwent urgent upper GI endoscopy were retrospectively analyzed. Patients were divided into three groups: enhanced MDCT, unenhanced MDCT, and no MDCT before endoscopy. The diagnostic accuracy of MDCT for detection of the bleeding origin was evaluated, and the average procedure times needed to endoscopically identify the bleeding origin were compared between groups. Diagnostic accuracy among endoscopists was 55.3% and 14.7% for the enhanced MDCT and unenhanced MDCT groups, respectively. Among nonvariceal patients, accuracy was 50.2% in the enhanced MDCT group, which was significantly better than that in the unenhanced MDCT group (16.5%). In variceal patients, accuracy was significantly better in the enhanced MDCT group (96.4%) than in the unenhanced MDCT group (0.0%). These accuracies were similar to those achieved by expert radiologists. The average procedure time to endoscopic detection of the bleeding origin in the enhanced MDCT group was significantly faster than that in the unenhanced MDCT and no-MDCT groups. Enhanced MDCT preceding urgent endoscopy may be an effective modality for the detection of bleeding origin in patients with acute upper GI bleeding. © 2013 Journal of Gastroenterology and Hepatology Foundation and Wiley Publishing Asia Pty Ltd.

Comparison of image features calculated in different dimensions for computer-aided diagnosis of lung nodules

NASA Astrophysics Data System (ADS)

Xu, Ye; Lee, Michael C.; Boroczky, Lilla; Cann, Aaron D.; Borczuk, Alain C.; Kawut, Steven M.; Powell, Charles A.

2009-02-01

Features calculated from different dimensions of images capture quantitative information of the lung nodules through one or multiple image slices. Previously published computer-aided diagnosis (CADx) systems have used either twodimensional (2D) or three-dimensional (3D) features, though there has been little systematic analysis of the relevance of the different dimensions and of the impact of combining different dimensions. The aim of this study is to determine the importance of combining features calculated in different dimensions. We have performed CADx experiments on 125 pulmonary nodules imaged using multi-detector row CT (MDCT). The CADx system computed 192 2D, 2.5D, and 3D image features of the lesions. Leave-one-out experiments were performed using five different combinations of features from different dimensions: 2D, 3D, 2.5D, 2D+3D, and 2D+3D+2.5D. The experiments were performed ten times for each group. Accuracy, sensitivity and specificity were used to evaluate the performance. Wilcoxon signed-rank tests were applied to compare the classification results from these five different combinations of features. Our results showed that 3D image features generate the best result compared with other combinations of features. This suggests one approach to potentially reducing the dimensionality of the CADx data space and the computational complexity of the system while maintaining diagnostic accuracy.

Energy-Discriminative Performance of a Spectral Micro-CT System

PubMed Central

He, Peng; Yu, Hengyong; Bennett, James; Ronaldson, Paul; Zainon, Rafidah; Butler, Anthony; Butler, Phil; Wei, Biao; Wang, Ge

2013-01-01

Experiments were performed to evaluate the energy-discriminative performance of a spectral (multi-energy) micro-CT system. The system, designed by MARS (Medipix All Resolution System) Bio-Imaging Ltd. (Christchurch, New Zealand), employs a photon-counting energy-discriminative detector technology developed by CERN (European Organization for Nuclear Research). We used the K-edge attenuation characteristic of some known materials to calibrate the detector’s photon energy discrimination. For tomographic analysis, we used the compressed sensing (CS) based ordered-subset simultaneous algebraic reconstruction techniques (OS-SART) to reconstruct sample images, which is effective to reduce noise and suppress artifacts. Unlike conventional CT, the principal component analysis (PCA) method can be applied to extract and quantify additional attenuation information from a spectral CT dataset. Our results show that the spectral CT has a good energy-discriminative performance and provides more attenuation information than the conventional CT. PMID:24004864

Added Value of Coronal Reformations for Duty Radiologists and for Referring Physicians or Surgeons in the CT Diagnosis of Acute Appendicitis

PubMed Central

Lee, Kyoung Ho; Hahn, Seokyung; Lee, Kyung Won; Lee, Hak Jong; Kim, Tae Jung; Kang, Sung-Bum; Shin, Joong Ho; Park, Byung Joo

2006-01-01

Objective To assess the added value of coronal reformation for radiologists and for referring physicians or surgeons in the CT diagnosis of acute appendicitis. Materials and Methods Contrast-enhanced CT was performed using 16-detector-row scanners in 110 patients, 46 of whom had appendicitis. Transverse (5-mm thickness, 4-mm increment), coronal (5-mm thickness, 4-mm increment), and combined transverse and coronal sections were interpreted by four radiologists, two surgeons and two emergency physicians. The area under the receiver operating characteristic curve (Az value), sensitivity, specificity (McNemar test), diagnostic confidence and appendiceal visualization (Wilcoxon signed rank test) were compared. Results For radiologists, the additional coronal sections tended to increase the Az value (0.972 vs. 0.986, p = 0.076) and pooled sensitivity (92% [95% CI: 88, 96] vs. 96% [93, 99]), and enhanced appendiceal visualization in true-positive cases (p = 0.031). For non-radiologists, no such enhancement was observed, and the confidence for excluding acute appendicitis declined (p = 0.013). Coronal sections alone were inferior to transverse sections for diagnostic confidence as well as appendiceal visualization for each reader group studied (p < 0.05). Conclusion The added value of coronal reformation is more apparent for radiologists compared to referring physicians or surgeons in the CT diagnosis of acute appendicitis. PMID:16799269

Dose reduction in paediatric MDCT: general principles.

PubMed

Paterson, A; Frush, D P

2007-06-01

The number of multi-detector array computed tomography (MDCT) examinations performed per annum continues to increase in both the adult and paediatric populations. Estimates from 2003 suggested that CT contributed 17% of a radiology department's workload, yet was responsible for up to 75% of the collective population dose from medical radiation. The effective doses for some CT examinations today overlap with those argued to have an increased risk of cancer. This is especially pertinent for paediatric CT, as children are more radiosensitive than adults (and girls more radiosensitive than boys). In addition, children have a longer life ahead of them, in which radiation induced cancers may become manifest. Radiologists must be aware of these facts and practise the ALARA (as low as is reasonably achievable) principle, when it comes to deciding CT protocols and parameters.

Assessment of image quality in soft tissue and bone visualization tasks for a dedicated extremity cone-beam CT system.

PubMed

Demehri, S; Muhit, A; Zbijewski, W; Stayman, J W; Yorkston, J; Packard, N; Senn, R; Yang, D; Foos, D; Thawait, G K; Fayad, L M; Chhabra, A; Carrino, J A; Siewerdsen, J H

2015-06-01

To assess visualization tasks using cone-beam CT (CBCT) compared to multi-detector CT (MDCT) for musculoskeletal extremity imaging. Ten cadaveric hands and ten knees were examined using a dedicated CBCT prototype and a clinical multi-detector CT using nominal protocols (80 kVp-108mAs for CBCT; 120 kVp- 300 mAs for MDCT). Soft tissue and bone visualization tasks were assessed by four radiologists using five-point satisfaction (for CBCT and MDCT individually) and five-point preference (side-by-side CBCT versus MDCT image quality comparison) rating tests. Ratings were analyzed using Kruskal-Wallis and Wilcoxon signed-rank tests, and observer agreement was assessed using the Kappa-statistic. Knee CBCT images were rated "excellent" or "good" (median scores 5 and 4) for "bone" and "soft tissue" visualization tasks. Hand CBCT images were rated "excellent" or "adequate" (median scores 5 and 3) for "bone" and "soft tissue" visualization tasks. Preference tests rated CBCT equivalent or superior to MDCT for bone visualization and favoured the MDCT for soft tissue visualization tasks. Intraobserver agreement for CBCT satisfaction tests was fair to almost perfect (κ ~ 0.26-0.92), and interobserver agreement was fair to moderate (κ ~ 0.27-0.54). CBCT provided excellent image quality for bone visualization and adequate image quality for soft tissue visualization tasks. • CBCT provided adequate image quality for diagnostic tasks in extremity imaging. • CBCT images were "excellent" for "bone" and "good/adequate" for "soft tissue" visualization tasks. • CBCT image quality was equivalent/superior to MDCT for bone visualization tasks.

Technical Note: FreeCT_wFBP: A robust, efficient, open-source implementation of weighted filtered backprojection for helical, fan-beam CT.

PubMed

Hoffman, John; Young, Stefano; Noo, Frédéric; McNitt-Gray, Michael

2016-03-01

With growing interest in quantitative imaging, radiomics, and CAD using CT imaging, the need to explore the impacts of acquisition and reconstruction parameters has grown. This usually requires extensive access to the scanner on which the data were acquired and its workflow is not designed for large-scale reconstruction projects. Therefore, the authors have developed a freely available, open-source software package implementing a common reconstruction method, weighted filtered backprojection (wFBP), for helical fan-beam CT applications. FreeCT_wFBP is a low-dependency, GPU-based reconstruction program utilizing c for the host code and Nvidia CUDA C for GPU code. The software is capable of reconstructing helical scans acquired with arbitrary pitch-values, and sampling techniques such as flying focal spots and a quarter-detector offset. In this work, the software has been described and evaluated for reconstruction speed, image quality, and accuracy. Speed was evaluated based on acquisitions of the ACR CT accreditation phantom under four different flying focal spot configurations. Image quality was assessed using the same phantom by evaluating CT number accuracy, uniformity, and contrast to noise ratio (CNR). Finally, reconstructed mass-attenuation coefficient accuracy was evaluated using a simulated scan of a FORBILD thorax phantom and comparing reconstructed values to the known phantom values. The average reconstruction time evaluated under all flying focal spot configurations was found to be 17.4 ± 1.0 s for a 512 row × 512 column × 32 slice volume. Reconstructions of the ACR phantom were found to meet all CT Accreditation Program criteria including CT number, CNR, and uniformity tests. Finally, reconstructed mass-attenuation coefficient values of water within the FORBILD thorax phantom agreed with original phantom values to within 0.0001 mm(2)/g (0.01%). FreeCT_wFBP is a fast, highly configurable reconstruction package for third-generation CT available under the GNU GPL. It shows good performance with both clinical and simulated data.

Monoenergetic reconstructions for imaging of coronary artery stents using spectral detector CT: In-vitro experience and comparison to conventional images.

PubMed

Hickethier, Tilman; Baeßler, Bettina; Kroeger, Jan Robert; Doerner, Jonas; Pahn, Gregor; Maintz, David; Michels, Guido; Bunck, Alexander C

Accurate assessment of coronary stents using non-invasive CT imaging remains challenging despite new stent materials and improvements in CT technology. Virtual monoenergetic (monoE) images reconstructed from dual energy CT acquisitions potentially decrease artifacts caused by coronary stents. A novel spectral detector technology provides monoE and conventional images simultaneously for all conducted scans. The purpose of our study was to systematically investigate the influence of different monoE reconstructions on the visualization of coronary stent lumen in comparison to conventional images. Ten different coronary stents (diameter 3.0 mm) embedded in plastic tubes filled with contrast agent (500 HU) were scanned with a 128-row spectral detector CT (IQon, Philips, 120 kV, 125 mAs). Images were reconstructed (0.67 mm slice thickness, 0.35 mm increment) with a stent-specific conventional reconstruction kernel and 6 different monoE settings (60, 70, 80, 90, 100, 150 keV). Image quality for each stent and reconstruction was quantified using established parameters: image noise (standard deviation (SD) within a standardized ROI), in-stent attenuation difference (mean attenuation difference between stented and non-stented lumen) and visible lumen diameter (mean visible diameter of the stented tube). Image noise was significantly lower in all monoE data dets compared to conventional images (conventional: 13.41, 60 keV: 11.62, 70 keV: 11.67, 80 keV: 11.69, 90 keV: 11.71, 100 keV: 11.75, 150 keV: 11.80 HU SD; p < 0.01). The in-stent attenuation difference was significantly smaller in monoE data with higher keV levels than in conventional images (conventional: 148.18, 60 keV: 154.13 p = 0.036, 70 keV: 143.43 p = 0.109, 80 keV: 137.25 p = 0.052, 90 keV: 133.02 p = 0.043, 100 keV: 130.12 p = 0.039, 150 keV: 123.99 HU p = 0.035). The visible lumen diameter was significantly greater in monoE data with higher keV levels than in conventional images (conventional: 0.65, 60 keV: 0.68 p = 0.542, 70 keV: 0.71 p = 0.053, 80 keV: 0.74 p < 0.01, 90 keV: 0.77 p < 0.01, 100 keV: 0.82 p < 0.01, 150 keV: 0.87 mm p < 0.01). In comparison to conventional CT images, well-established parameters for objective assessment of CT image quality for coronary stents are significantly improved by utilization of monoE reconstructions with adequate keV levels derived from data acquired on a novel spectral detector CT platform. Copyright © 2017 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.

The development, validation and application of a multi-detector CT (MDCT) scanner model for assessing organ doses to the pregnant patient and the fetus using Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Gu, J.; Bednarz, B.; Caracappa, P. F.; Xu, X. G.

2009-05-01

The latest multiple-detector technologies have further increased the popularity of x-ray CT as a diagnostic imaging modality. There is a continuing need to assess the potential radiation risk associated with such rapidly evolving multi-detector CT (MDCT) modalities and scanning protocols. This need can be met by the use of CT source models that are integrated with patient computational phantoms for organ dose calculations. Based on this purpose, this work developed and validated an MDCT scanner using the Monte Carlo method, and meanwhile the pregnant patient phantoms were integrated into the MDCT scanner model for assessment of the dose to the fetus as well as doses to the organs or tissues of the pregnant patient phantom. A Monte Carlo code, MCNPX, was used to simulate the x-ray source including the energy spectrum, filter and scan trajectory. Detailed CT scanner components were specified using an iterative trial-and-error procedure for a GE LightSpeed CT scanner. The scanner model was validated by comparing simulated results against measured CTDI values and dose profiles reported in the literature. The source movement along the helical trajectory was simulated using the pitch of 0.9375 and 1.375, respectively. The validated scanner model was then integrated with phantoms of a pregnant patient in three different gestational periods to calculate organ doses. It was found that the dose to the fetus of the 3 month pregnant patient phantom was 0.13 mGy/100 mAs and 0.57 mGy/100 mAs from the chest and kidney scan, respectively. For the chest scan of the 6 month patient phantom and the 9 month patient phantom, the fetal doses were 0.21 mGy/100 mAs and 0.26 mGy/100 mAs, respectively. The paper also discusses how these fetal dose values can be used to evaluate imaging procedures and to assess risk using recommendations of the report from AAPM Task Group 36. This work demonstrates the ability of modeling and validating an MDCT scanner by the Monte Carlo method, as well as assessing fetal and organ doses by combining the MDCT scanner model and the pregnant patient phantom.

Reducing image noise in computed tomography (CT) colonography: effect of an integrated circuit CT detector.

PubMed

Liu, Yu; Leng, Shuai; Michalak, Gregory J; Vrieze, Thomas J; Duan, Xinhui; Qu, Mingliang; Shiung, Maria M; McCollough, Cynthia H; Fletcher, Joel G

2014-01-01

To investigate whether the integrated circuit (IC) detector results in reduced noise in computed tomography (CT) colonography (CTC). Three hundred sixty-six consecutive patients underwent clinically indicated CTC using the same CT scanner system, except for a difference in CT detectors (IC or conventional). Image noise, patient size, and scanner radiation output (volume CT dose index) were quantitatively compared between patient cohorts using each detector system, with separate comparisons for the abdomen and pelvis. For the abdomen and pelvis, despite significantly larger patient sizes in the IC detector cohort (both P < 0.001), image noise was significantly lower (both P < 0.001), whereas volume CT dose index was unchanged (both P > 0.18). Based on the observed image noise reduction, radiation dose could alternatively be reduced by approximately 20% to result in similar levels of image noise. Computed tomography colonography images acquired using the IC detector had significantly lower noise than images acquired using the conventional detector. This noise reduction can permit further radiation dose reduction in CTC.

Feasibility and accuracy of dual-layer spectral detector computed tomography for quantification of gadolinium: a phantom study.

PubMed

van Hamersvelt, Robbert W; Willemink, Martin J; de Jong, Pim A; Milles, Julien; Vlassenbroek, Alain; Schilham, Arnold M R; Leiner, Tim

2017-09-01

The aim of this study was to evaluate the feasibility and accuracy of dual-layer spectral detector CT (SDCT) for the quantification of clinically encountered gadolinium concentrations. The cardiac chamber of an anthropomorphic thoracic phantom was equipped with 14 tubular inserts containing different gadolinium concentrations, ranging from 0 to 26.3 mg/mL (0.0, 0.1, 0.2, 0.4, 0.5, 1.0, 2.0, 3.0, 4.0, 5.1, 10.6, 15.7, 20.7 and 26.3 mg/mL). Images were acquired using a novel 64-detector row SDCT system at 120 and 140 kVp. Acquisitions were repeated five times to assess reproducibility. Regions of interest (ROIs) were drawn on three slices per insert. A spectral plot was extracted for every ROI and mean attenuation profiles were fitted to known attenuation profiles of water and pure gadolinium using in-house-developed software to calculate gadolinium concentrations. At both 120 and 140 kVp, excellent correlations between scan repetitions and true and measured gadolinium concentrations were found (R > 0.99, P < 0.001; ICCs > 0.99, CI 0.99-1.00). Relative mean measurement errors stayed below 10% down to 2.0 mg/mL true gadolinium concentration at 120 kVp and below 5% down to 1.0 mg/mL true gadolinium concentration at 140 kVp. SDCT allows for accurate quantification of gadolinium at both 120 and 140 kVp. Lowest measurement errors were found for 140 kVp acquisitions. • Gadolinium quantification may be useful in patients with contraindication to iodine. • Dual-layer spectral detector CT allows for overall accurate quantification of gadolinium. • Interscan variability of gadolinium quantification using SDCT material decomposition is excellent.

ARGUS/LLNL IR Camera Calibration and Characterization

DTIC Science & Technology

1989-11-01

122 of the 244 rows, once every 1/60 second. The even-numbered detector rows, beginning with row zero , are read out in one field; the odd-numbered...Radiometrically, a very cold reference scene is desirable because the absolute signal level of the reference scene is subtracted from all subsequent...to have effectively zero radiant energy within the spectral passband of the sensor, and so may be ignored. 1.3 LABORATORY EQUIPMENT CONFIGURATION The

Evaluation of the accuracy of linear measurements on multi-slice and cone beam computed tomography scans to detect the mandibular canal during bilateral sagittal split osteotomy of the mandible.

PubMed

Freire-Maia, B; Machado, V deC; Valerio, C S; Custódio, A L N; Manzi, F R; Junqueira, J L C

2017-03-01

The aim of this study was to compare the accuracy of linear measurements of the distance between the mandibular cortical bone and the mandibular canal using 64-detector multi-slice computed tomography (MSCT) and cone beam computed tomography (CBCT). It was sought to evaluate the reliability of these examinations in detecting the mandibular canal for use in bilateral sagittal split osteotomy (BSSO) planning. Eight dry human mandibles were studied. Three sites, corresponding to the lingula, the angle, and the body of the mandible, were selected. After the CT scans had been obtained, the mandibles were sectioned and the bone segments measured to obtain the actual measurements. On analysis, no statistically significant difference was found between the measurements obtained through MSCT and CBCT, or when comparing the measurements from these scans with the actual measurements. It is concluded that the images obtained by CT scan, both 64-detector multi-slice and cone beam, can be used to obtain accurate linear measurements to locate the mandibular canal for preoperative planning of BSSO. The ability to correctly locate the mandibular canal during BSSO will reduce the occurrence of neurosensory disturbances in the postoperative period. Copyright © 2016 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Imaging of acute mesenteric ischemia using multidetector CT and CT angiography in a porcine model.

PubMed

Rosow, David E; Sahani, Dushyant; Strobel, Oliver; Kalva, Sanjeeva; Mino-Kenudson, Mari; Holalkere, Nagaraj S; Alsfasser, Guido; Saini, Sanjay; Lee, Susanna I; Mueller, Peter R; Fernández-del Castillo, Carlos; Warshaw, Andrew L; Thayer, Sarah P

2005-12-01

Acute mesenteric ischemia, a frequently lethal disease, requires prompt diagnosis and intervention for favorable clinical outcomes. This goal remains elusive due, in part, to lack of a noninvasive and accurate imaging study. Traditional angiography is the diagnostic gold standard but is invasive and costly. Computed tomography (CT) is readily available and noninvasive but has shown variable success in diagnosing this disease. The faster scanning time of multidetector row CT (M.D.CT) greatly facilitates the use of CT angiography (CTA) in the clinical setting. We sought to determine whether M.D.CT-CTA could accurately demonstrate vascular anatomy and capture the earliest stages of mesenteric ischemia in a porcine model. Pigs underwent embolization of branches of the superior mesenteric artery, then imaging by M.D.CT-CTA with three-dimensional reconstruction protocols. After scanning, diseased bowel segments were surgically resected and pathologically examined. Multidetector row CT and CT angiography reliably defined normal and occluded mesenteric vessels in the pig. It detected early changes of ischemia including poor arterial enhancement and venous dilatation, which were seen in all ischemic animals. The radiographic findings--compared with pathologic diagnoses-- predicted ischemia, with a positive predictive value of 92%. These results indicate that M.D.CT-CTA holds great promise for the early detection necessary for successful treatment of acute mesenteric ischemia.

Correctness of multi-detector-row computed tomography for diagnosing mechanical prosthetic heart valve disorders using operative findings as a gold standard.

PubMed

Tsai, I-Chen; Lin, Yung-Kai; Chang, Yen; Fu, Yun-Ching; Wang, Chung-Chi; Hsieh, Shih-Rong; Wei, Hao-Ji; Tsai, Hung-Wen; Jan, Sheng-Ling; Wang, Kuo-Yang; Chen, Min-Chi; Chen, Clayton Chi-Chang

2009-04-01

The purpose was to compare the findings of multi-detector computed tomography (MDCT) in prosthetic valve disorders using the operative findings as a gold standard. In a 3-year period, we prospectively enrolled 25 patients with 31 prosthetic heart valves. MDCT and transthoracic echocardiography (TTE) were done to evaluate pannus formation, prosthetic valve dysfunction, suture loosening (paravalvular leak) and pseudoaneurysm formation. Patients indicated for surgery received an operation within 1 week. The MDCT findings were compared with the operative findings. One patient with a Björk-Shiley valve could not be evaluated by MDCT due to a severe beam-hardening artifact; thus, the exclusion rate for MDCT was 3.2% (1/31). Prosthetic valve disorders were suspected in 12 patients by either MDCT or TTE. Six patients received an operation that included three redo aortic valve replacements, two redo mitral replacements and one Amplatzer ductal occluder occlusion of a mitral paravalvular leak. The concordance of MDCT for diagnosing and localizing prosthetic valve disorders and the surgical findings was 100%. Except for images impaired by severe beam-hardening artifacts, MDCT provides excellent delineation of prosthetic valve disorders.

Event sequence detector

NASA Technical Reports Server (NTRS)

Hanna, M. F. (Inventor)

1973-01-01

An event sequence detector is described with input units, each associated with a row of bistable elements arranged in an array of rows and columns. The detector also includes a shift register which is responsive to clock pulses from any of the units to sequentially provide signals on its output lines each of which is connected to the bistable elements in a corresponding column. When the event-indicating signal is received by an input unit it provides a clock pulse to the shift register to provide the signal on one of its output lines. The input unit also enables all its bistable elements so that the particular element in the column supplied with the signal from the register is driven to an event-indicating state.

High resolution multidetector CT aided tissue analysis and quantification of lung fibrosis

NASA Astrophysics Data System (ADS)

Zavaletta, Vanessa A.; Karwoski, Ronald A.; Bartholmai, Brian; Robb, Richard A.

2006-03-01

Idiopathic pulmonary fibrosis (IPF, also known as Idiopathic Usual Interstitial Pneumontis, pathologically) is a progressive diffuse lung disease which has a median survival rate of less than four years with a prevalence of 15-20/100,000 in the United States. Global function changes are measured by pulmonary function tests and the diagnosis and extent of pulmonary structural changes are typically assessed by acquiring two-dimensional high resolution CT (HRCT) images. The acquisition and analysis of volumetric high resolution Multi-Detector CT (MDCT) images with nearly isotropic pixels offers the potential to measure both lung function and structure. This paper presents a new approach to three dimensional lung image analysis and classification of normal and abnormal structures in lungs with IPF.

Interior micro-CT with an offset detector

PubMed Central

Sharma, Kriti Sen; Gong, Hao; Ghasemalizadeh, Omid; Yu, Hengyong; Wang, Ge; Cao, Guohua

2014-01-01

Purpose: The size of field-of-view (FOV) of a microcomputed tomography (CT) system can be increased by offsetting the detector. The increased FOV is beneficial in many applications. All prior investigations, however, have been focused to the case in which the increased FOV after offset-detector acquisition can cover the transaxial extent of an object fully. Here, the authors studied a new problem where the FOV of a micro-CT system, although increased after offset-detector acquisition, still covers an interior region-of-interest (ROI) within the object. Methods: An interior-ROI-oriented micro-CT scan with an offset detector poses a difficult reconstruction problem, which is caused by both detector offset and projection truncation. Using the projection completion techniques, the authors first extended three previous reconstruction methods from offset-detector micro-CT to offset-detector interior micro-CT. The authors then proposed a novel method which combines two of the extended methods using a frequency split technique. The authors tested the four methods with phantom simulations at 9.4%, 18.8%, 28.2%, and 37.6% detector offset. The authors also applied these methods to physical phantom datasets acquired at the same amounts of detector offset from a customized micro-CT system. Results: When the detector offset was small, all reconstruction methods showed good image quality. At large detector offset, the three extended methods gave either visible shading artifacts or high deviation of pixel value, while the authors’ proposed method demonstrated no visible artifacts and minimal deviation of pixel value in both the numerical simulations and physical experiments. Conclusions: For an interior micro-CT with an offset detector, the three extended reconstruction methods can perform well at a small detector offset but show strong artifacts at a large detector offset. When the detector offset is large, the authors’ proposed reconstruction method can outperform the three extended reconstruction methods by suppressing artifacts and maintaining pixel values. PMID:24877826

Performance evaluation of a modular detector unit for X-ray computed tomography.

PubMed

Guo, Zhe; Tang, Zhiwei; Wang, Xinzeng; Deng, Mingliang; Hu, Guangshu; Zhang, Hui

2013-04-18

A research prototype CT scanner is currently under development in our lab. One of the key components in this project is the CT detector. This paper describes the design and performance evaluation of the modular CT detector unit for our proposed scanner. It consists of a Photodiode Array Assembly which captures irradiating X-ray photons and converts the energy into electrical current, and a mini Data Acquisition System which performs current integration and converts the analog signal into digital samples. The detector unit can be easily tiled together to form a CT detector. Experiments were conducted to characterize the detector performance both at the single unit level and system level. The noise level, linearity and uniformity of the proposed detector unit were reported and initial imaging studies were also presented which demonstrated the potential application of the proposed detector unit in actual CT scanners.

Sample size requirements for estimating effective dose from computed tomography using solid-state metal-oxide-semiconductor field-effect transistor dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trattner, Sigal; Cheng, Bin; Pieniazek, Radoslaw L.

2014-04-15

Purpose: Effective dose (ED) is a widely used metric for comparing ionizing radiation burden between different imaging modalities, scanners, and scan protocols. In computed tomography (CT), ED can be estimated by performing scans on an anthropomorphic phantom in which metal-oxide-semiconductor field-effect transistor (MOSFET) solid-state dosimeters have been placed to enable organ dose measurements. Here a statistical framework is established to determine the sample size (number of scans) needed for estimating ED to a desired precision and confidence, for a particular scanner and scan protocol, subject to practical limitations. Methods: The statistical scheme involves solving equations which minimize the sample sizemore » required for estimating ED to desired precision and confidence. It is subject to a constrained variation of the estimated ED and solved using the Lagrange multiplier method. The scheme incorporates measurement variation introduced both by MOSFET calibration, and by variation in MOSFET readings between repeated CT scans. Sample size requirements are illustrated on cardiac, chest, and abdomen–pelvis CT scans performed on a 320-row scanner and chest CT performed on a 16-row scanner. Results: Sample sizes for estimating ED vary considerably between scanners and protocols. Sample size increases as the required precision or confidence is higher and also as the anticipated ED is lower. For example, for a helical chest protocol, for 95% confidence and 5% precision for the ED, 30 measurements are required on the 320-row scanner and 11 on the 16-row scanner when the anticipated ED is 4 mSv; these sample sizes are 5 and 2, respectively, when the anticipated ED is 10 mSv. Conclusions: Applying the suggested scheme, it was found that even at modest sample sizes, it is feasible to estimate ED with high precision and a high degree of confidence. As CT technology develops enabling ED to be lowered, more MOSFET measurements are needed to estimate ED with the same precision and confidence.« less

Sample size requirements for estimating effective dose from computed tomography using solid-state metal-oxide-semiconductor field-effect transistor dosimetry

PubMed Central

Trattner, Sigal; Cheng, Bin; Pieniazek, Radoslaw L.; Hoffmann, Udo; Douglas, Pamela S.; Einstein, Andrew J.

2014-01-01

Purpose: Effective dose (ED) is a widely used metric for comparing ionizing radiation burden between different imaging modalities, scanners, and scan protocols. In computed tomography (CT), ED can be estimated by performing scans on an anthropomorphic phantom in which metal-oxide-semiconductor field-effect transistor (MOSFET) solid-state dosimeters have been placed to enable organ dose measurements. Here a statistical framework is established to determine the sample size (number of scans) needed for estimating ED to a desired precision and confidence, for a particular scanner and scan protocol, subject to practical limitations. Methods: The statistical scheme involves solving equations which minimize the sample size required for estimating ED to desired precision and confidence. It is subject to a constrained variation of the estimated ED and solved using the Lagrange multiplier method. The scheme incorporates measurement variation introduced both by MOSFET calibration, and by variation in MOSFET readings between repeated CT scans. Sample size requirements are illustrated on cardiac, chest, and abdomen–pelvis CT scans performed on a 320-row scanner and chest CT performed on a 16-row scanner. Results: Sample sizes for estimating ED vary considerably between scanners and protocols. Sample size increases as the required precision or confidence is higher and also as the anticipated ED is lower. For example, for a helical chest protocol, for 95% confidence and 5% precision for the ED, 30 measurements are required on the 320-row scanner and 11 on the 16-row scanner when the anticipated ED is 4 mSv; these sample sizes are 5 and 2, respectively, when the anticipated ED is 10 mSv. Conclusions: Applying the suggested scheme, it was found that even at modest sample sizes, it is feasible to estimate ED with high precision and a high degree of confidence. As CT technology develops enabling ED to be lowered, more MOSFET measurements are needed to estimate ED with the same precision and confidence. PMID:24694150

Medipix-based Spectral Micro-CT.

PubMed

Yu, Hengyong; Xu, Qiong; He, Peng; Bennett, James; Amir, Raja; Dobbs, Bruce; Mou, Xuanqin; Wei, Biao; Butler, Anthony; Butler, Phillip; Wang, Ge

2012-12-01

Since Hounsfield's Nobel Prize winning breakthrough decades ago, X-ray CT has been widely applied in the clinical and preclinical applications - producing a huge number of tomographic gray-scale images. However, these images are often insufficient to distinguish crucial differences needed for diagnosis. They have poor soft tissue contrast due to inherent photon-count issues, involving high radiation dose. By physics, the X-ray spectrum is polychromatic, and it is now feasible to obtain multi-energy, spectral, or true-color, CT images. Such spectral images promise powerful new diagnostic information. The emerging Medipix technology promises energy-sensitive, high-resolution, accurate and rapid X-ray detection. In this paper, we will review the recent progress of Medipix-based spectral micro-CT with the emphasis on the results obtained by our team. It includes the state- of-the-art Medipix detector, the system and method of a commercial MARS (Medipix All Resolution System) spectral micro-CT, and the design and color diffusion of a hybrid spectral micro-CT.

Segmentation of pelvic structures for planning CT using a geometrical shape model tuned by a multi-scale edge detector

PubMed Central

Martínez, Fabio; Romero, Eduardo; Dréan, Gaël; Simon, Antoine; Haigron, Pascal; De Crevoisier, Renaud; Acosta, Oscar

2014-01-01

Accurate segmentation of the prostate and organs at risk in computed tomography (CT) images is a crucial step for radiotherapy (RT) planning. Manual segmentation, as performed nowadays, is a time consuming process and prone to errors due to the a high intra- and inter-expert variability. This paper introduces a new automatic method for prostate, rectum and bladder segmentation in planning CT using a geometrical shape model under a Bayesian framework. A set of prior organ shapes are first built by applying Principal Component Analysis (PCA) to a population of manually delineated CT images. Then, for a given individual, the most similar shape is obtained by mapping a set of multi-scale edge observations to the space of organs with a customized likelihood function. Finally, the selected shape is locally deformed to adjust the edges of each organ. Experiments were performed with real data from a population of 116 patients treated for prostate cancer. The data set was split in training and test groups, with 30 and 86 patients, respectively. Results show that the method produces competitive segmentations w.r.t standard methods (Averaged Dice = 0.91 for prostate, 0.94 for bladder, 0.89 for Rectum) and outperforms the majority-vote multi-atlas approaches (using rigid registration, free-form deformation (FFD) and the demons algorithm) PMID:24594798

Zonal wavefront sensor with reduced number of rows in the detector array.

PubMed

Boruah, Bosanta R; Das, Abhijit

2011-07-10

In this paper, we describe a zonal wavefront sensor in which the photodetector array can have a smaller number of rows. The test wavefront is incident on a two-dimensional array of diffraction gratings followed by a single focusing lens. The periodicity and the orientation of the grating rulings of each grating can be chosen such that the +1 order beam from the gratings forms an array of focal spots in the detector plane. We show that by using a square array of zones, it is possible to generate an array of +1 order focal spots having a smaller number of rows, thus reducing the height of the required detector array. The phase profile of the test wavefront can be estimated by measuring the displacements of the +1 order focal spots for the test wavefront relative to the +1 order focal spots for a plane reference wavefront. The narrower width of the photodetector array can offer several advantages, such as a faster frame rate of the wavefront sensor, a reduced amount of cross talk between the nearby detector zones, and a decrease in the maximum thermal noise. We also present experimental results of a proof-of-concept experimental arrangement using the proposed wavefront sensing scheme. © 2011 Optical Society of America

Ultra-high spatial resolution multi-energy CT using photon counting detector technology

NASA Astrophysics Data System (ADS)

Leng, S.; Gutjahr, R.; Ferrero, A.; Kappler, S.; Henning, A.; Halaweish, A.; Zhou, W.; Montoya, J.; McCollough, C.

2017-03-01

Two ultra-high-resolution (UHR) imaging modes, each with two energy thresholds, were implemented on a research, whole-body photon-counting-detector (PCD) CT scanner, referred to as sharp and UHR, respectively. The UHR mode has a pixel size of 0.25 mm at iso-center for both energy thresholds, with a collimation of 32 × 0.25 mm. The sharp mode has a 0.25 mm pixel for the low-energy threshold and 0.5 mm for the high-energy threshold, with a collimation of 48 × 0.25 mm. Kidney stones with mixed mineral composition and lung nodules with different shapes were scanned using both modes, and with the standard imaging mode, referred to as macro mode (0.5 mm pixel and 32 × 0.5 mm collimation). Evaluation and comparison of the three modes focused on the ability to accurately delineate anatomic structures using the high-spatial resolution capability and the ability to quantify stone composition using the multi-energy capability. The low-energy threshold images of the sharp and UHR modes showed better shape and texture information due to the achieved higher spatial resolution, although noise was also higher. No noticeable benefit was shown in multi-energy analysis using UHR compared to standard resolution (macro mode) when standard doses were used. This was due to excessive noise in the higher resolution images. However, UHR scans at higher dose showed improvement in multi-energy analysis over macro mode with regular dose. To fully take advantage of the higher spatial resolution in multi-energy analysis, either increased radiation dose, or application of noise reduction techniques, is needed.

Ultra-High-Resolution Computed Tomography of the Lung: Image Quality of a Prototype Scanner.

PubMed

Kakinuma, Ryutaro; Moriyama, Noriyuki; Muramatsu, Yukio; Gomi, Shiho; Suzuki, Masahiro; Nagasawa, Hirobumi; Kusumoto, Masahiko; Aso, Tomohiko; Muramatsu, Yoshihisa; Tsuchida, Takaaki; Tsuta, Koji; Maeshima, Akiko Miyagi; Tochigi, Naobumi; Watanabe, Shun-Ichi; Sugihara, Naoki; Tsukagoshi, Shinsuke; Saito, Yasuo; Kazama, Masahiro; Ashizawa, Kazuto; Awai, Kazuo; Honda, Osamu; Ishikawa, Hiroyuki; Koizumi, Naoya; Komoto, Daisuke; Moriya, Hiroshi; Oda, Seitaro; Oshiro, Yasuji; Yanagawa, Masahiro; Tomiyama, Noriyuki; Asamura, Hisao

2015-01-01

The image noise and image quality of a prototype ultra-high-resolution computed tomography (U-HRCT) scanner was evaluated and compared with those of conventional high-resolution CT (C-HRCT) scanners. This study was approved by the institutional review board. A U-HRCT scanner prototype with 0.25 mm x 4 rows and operating at 120 mAs was used. The C-HRCT images were obtained using a 0.5 mm x 16 or 0.5 mm x 64 detector-row CT scanner operating at 150 mAs. Images from both scanners were reconstructed at 0.1-mm intervals; the slice thickness was 0.25 mm for the U-HRCT scanner and 0.5 mm for the C-HRCT scanners. For both scanners, the display field of view was 80 mm. The image noise of each scanner was evaluated using a phantom. U-HRCT and C-HRCT images of 53 images selected from 37 lung nodules were then observed and graded using a 5-point score by 10 board-certified thoracic radiologists. The images were presented to the observers randomly and in a blinded manner. The image noise for U-HRCT (100.87 ± 0.51 Hounsfield units [HU]) was greater than that for C-HRCT (40.41 ± 0.52 HU; P < .0001). The image quality of U-HRCT was graded as superior to that of C-HRCT (P < .0001) for all of the following parameters that were examined: margins of subsolid and solid nodules, edges of solid components and pulmonary vessels in subsolid nodules, air bronchograms, pleural indentations, margins of pulmonary vessels, edges of bronchi, and interlobar fissures. Despite a larger image noise, the prototype U-HRCT scanner had a significantly better image quality than the C-HRCT scanners.

Quantitative colorectal cancer perfusion measurement by multidetector-row CT: does greater tumour coverage improve measurement reproducibility?

PubMed

Goh, V; Halligan, S; Gartner, L; Bassett, P; Bartram, C I

2006-07-01

The purpose of this study was to determine if greater z-axis tumour coverage improves the reproducibility of quantitative colorectal cancer perfusion measurements using CT. A 65 s perfusion study was acquired following intravenous contrast administration in 10 patients with proven colorectal cancer using a four-detector row scanner. This was repeated within 48 h using identical technical parameters to allow reproducibility assessment. Quantitative tumour blood volume, blood flow, mean transit time and permeability measurements were determined using commercially available software (Perfusion 3.0; GE Healthcare, Waukesha, WI) for data obtained from a 5 mm z-axis tumour coverage, and from a 20 mm z-axis tumour coverage. Measurement reproducibility was assessed using Bland-Altman statistics, for a 5 mm z-axis tumour coverage, and 20 mm z-axis tumour coverage, respectively. The mean difference (95% limits of agreement) for blood volume, blood flow, mean transit time and permeability were 0.04 (-2.50 to +2.43) ml/100 g tissue; +8.80 (-50.5 to +68.0) ml/100 g tissue/min; -0.99 (-8.19 to +6.20) seconds; and +1.20 (-5.42 to +7.83) ml/100 g tissue/min, respectively, for a 5 mm coverage, and -0.04 (-2.61 to +2.53) ml/100 g tissue; +7.40 (-50.3 to +65.0) ml/100 g tissue/min; -2.46 (-12.61 to +7.69) seconds; and -0.23 (-8.31 to +7.85) ml/100 g tissue/min, respectively, for a 20 mm coverage, indicating similar levels of agreement. In conclusion, increasing z-axis coverage does not improve reproducibility of quantitative colorectal cancer perfusion measurements.

CT colonography: automated measurement of colonic polyps compared with manual techniques--human in vitro study.

PubMed

Taylor, Stuart A; Slater, Andrew; Halligan, Steve; Honeyfield, Lesley; Roddie, Mary E; Demeshski, Jamshid; Amin, Hamdam; Burling, David

2007-01-01

To prospectively investigate the relative accuracy and reproducibility of manual and automated computer software measurements by using polyps of known size in a human colectomy specimen. Institutional review board approval was obtained for the study; written consent for use of the surgical specimen was obtained. A colectomy specimen containing 27 polyps from a 16-year-old male patient with familial adenomatous polyposis was insufflated, submerged in a container with solution, and scanned at four-section multi-detector row computed tomography (CT). A histopathologist measured the maximum dimension of all polyps in the opened specimen. Digital photographs and line drawings were produced to aid CT-histologic measurement correlation. A novice (radiographic technician) and an experienced (radiologist) observer independently estimated polyp diameter with three methods: manual two-dimensional (2D) and manual three-dimensional (3D) measurement with software calipers and automated measurement with software (automatic). Data were analyzed with paired t tests and Bland-Altman limits of agreement. Seven polyps (

PET/CT: underlying physics, instrumentation, and advances.

PubMed

Torres Espallardo, I

Since it was first introduced, the main goal of PET/CT has been to provide both PET and CT images with high clinical quality and to present them to radiologists and specialists in nuclear medicine as a fused, perfectly aligned image. The use of fused PET and CT images quickly became routine in clinical practice, showing the great potential of these hybrid scanners. Thanks to this success, manufacturers have gone beyond considering CT as a mere attenuation corrector for PET, concentrating instead on design high performance PET and CT scanners with more interesting features. Since the first commercial PET/CT scanner became available in 2001, both the PET component and the CT component have improved immensely. In the case of PET, faster scintillation crystals with high stopping power such as LYSO crystals have enabled more sensitive devices to be built, making it possible to reduce the number of undesired coincidence events and to use time of flight (TOF) techniques. All these advances have improved lesion detection, especially in situations with very noisy backgrounds. Iterative reconstruction methods, together with the corrections carried out during the reconstruction and the use of the point-spread function, have improved image quality. In parallel, CT instrumentation has also improved significantly, and 64- and 128-row detectors have been incorporated into the most modern PET/CT scanners. This makes it possible to obtain high quality diagnostic anatomic images in a few seconds that both enable the correction of PET attenuation and provide information for diagnosis. Furthermore, nowadays nearly all PET/CT scanners have a system that modulates the dose of radiation that the patient is exposed to in the CT study in function of the region scanned. This article reviews the underlying physics of PET and CT imaging separately, describes the changes in the instrumentation and standard protocols in a combined PET/CT system, and finally points out the most important advances in this hybrid imaging modality. Copyright © 2016 SERAM. Publicado por Elsevier España, S.L.U. All rights reserved.

320-row CT renal perfusion imaging in patients with aortic dissection: A preliminary study.

PubMed

Liu, Dongting; Liu, Jiayi; Wen, Zhaoying; Li, Yu; Sun, Zhonghua; Xu, Qin; Fan, Zhanming

2017-01-01

To investigate the clinical value of renal perfusion imaging in patients with aortic dissection (AD) using 320-row computed tomography (CT), and to determine the relationship between renal CT perfusion imaging and various factors of aortic dissection. Forty-three patients with AD who underwent 320-row CT renal perfusion before operation were prospectively enrolled in this study. Diagnosis of AD was confirmed by transthoracic echocardiography. Blood flow (BF) of bilateral renal perfusion was measured and analyzed. CT perfusion imaging signs of AD in relation to the type of AD, number of entry tears and the false lumen thrombus were observed and compared. The BF values of patients with type A AD were significantly lower than those of patients with type B AD (P = 0.004). No significant difference was found in the BF between different numbers of intimal tears (P = 0.288), but BF values were significantly higher in cases with a false lumen without thrombus and renal arteries arising from the true lumen than in those with thrombus (P = 0.036). The BF values measured between the true lumen, false lumen and overriding groups were different (P = 0.02), with the true lumen group having the highest. Also, the difference in BF values between true lumen and false lumen groups was statistically significant (P = 0.016), while no statistical significance was found in the other two groups (P > 0.05). The larger the size of intimal entry tears, the greater the BF values (P = 0.044). This study shows a direct correlation between renal CT perfusion changes and AD, with the size, number of intimal tears, different types of AD, different renal artery origins and false lumen thrombosis, significantly affecting the perfusion values.

Reduction of the unnecessary dose from the over-range area with a spiral dynamic z-collimator: comparison of beam pitch and detector coverage with 128-detector row CT.

PubMed

Shirasaka, Takashi; Funama, Yoshinori; Hayashi, Mutsukazu; Awamoto, Shinichi; Kondo, Masatoshi; Nakamura, Yasuhiko; Hatakenaka, Masamitsu; Honda, Hiroshi

2012-01-01

Our purpose in this study was to assess the radiation dose reduction and the actual exposed scan length of over-range areas using a spiral dynamic z-collimator at different beam pitches and detector coverage. Using glass rod dosimeters, we measured the unilateral over-range scan dose between the beginning of the planned scan range and the beginning of the actual exposed scan range. Scanning was performed at detector coverage of 80.0 and 40.0 mm, with and without the spiral dynamic z-collimator. The dose-saving ratio was calculated as the ratio of the unnecessary over-range dose, with and without the spiral dynamic z-collimator. In 80.0 mm detector coverage without the spiral dynamic z-collimator, the actual exposed scan length for the over-range area was 108, 120, and 126 mm, corresponding to a beam pitch of 0.60, 0.80, and 0.99, respectively. With the spiral dynamic z-collimator, the actual exposed scan length for the over-range area was 48, 66, and 84 mm with a beam pitch of 0.60, 0.80, and 0.99, respectively. The dose-saving ratios with and without the spiral dynamic z-collimator for a beam pitch of 0.60, 0.80, and 0.99 were 35.07, 24.76, and 13.51%, respectively. With 40.0 mm detector coverage, the dose-saving ratios with and without the spiral dynamic z-collimator had the highest value of 27.23% with a low beam pitch of 0.60. The spiral dynamic z-collimator is important for a reduction in the unnecessary over-range dose and makes it possible to reduce the unnecessary dose by means of a lower beam pitch.

Performance and applications of GaAs:Cr-based Medipix detector in X-ray CT

NASA Astrophysics Data System (ADS)

Kozhevnikov, D.; Chelkov, G.; Demichev, M.; Gridin, A.; Smolyanskiy, P.; Zhemchugov, A.

2017-01-01

In the recent years, the method of single photon counting X-ray μ-CT is being actively developed and applied in various fields. Results of our studies carried out using the MARS μ-CT scanner equipped with GaAs Medipix-based camera are presented. The procedure of mechanical alignment of the scanner is described, including direct and indirect measurements of the spatial resolution. The software chain for data processing and reconstruction has been developed and reported. We demonstrate the possibility to apply the scanner for research in geology and medicine and provide demo images of geological samples (chrome spinellids, titanium magnetite ore) and medical samples (atherosclerotic plaque, abdominal aortic aneurysm). The first results of multi-energy scans using GaAs:Cr-based camera are shown.

CFD simulation of hemodynamics in sequential and individual coronary bypass grafts based on multislice CT scan datasets.

PubMed

Hajati, Omid; Zarrabi, Khalil; Karimi, Reza; Hajati, Azadeh

2012-01-01

There is still controversy over the differences in the patency rates of the sequential and individual coronary artery bypass grafting (CABG) techniques. The purpose of this paper was to non-invasively evaluate hemodynamic parameters using complete 3D computational fluid dynamics (CFD) simulations of the sequential and the individual methods based on the patient-specific data extracted from computed tomography (CT) angiography. For CFD analysis, the geometric model of coronary arteries was reconstructed using an ECG-gated 64-detector row CT. Modeling the sequential and individual bypass grafting, this study simulates the flow from the aorta to the occluded posterior descending artery (PDA) and the posterior left ventricle (PLV) vessel with six coronary branches based on the physiologically measured inlet flow as the boundary condition. The maximum calculated wall shear stress (WSS) in the sequential and the individual models were estimated to be 35.1 N/m(2) and 36.5 N/m(2), respectively. Compared to the individual bypass method, the sequential graft has shown a higher velocity at the proximal segment and lower spatial wall shear stress gradient (SWSSG) due to the flow splitting caused by the side-to-side anastomosis. Simulated results combined with its surgical benefits including the requirement of shorter vein length and fewer anastomoses advocate the sequential method as a more favorable CABG method.

Transcatheter Arterial Embolization Therapy for a Hypoplastic Pelvic Kidney with a Single Vaginal Ectopic Ureter to Control Incontinence: The Usefulness of Three-Dimensional CT Angiography Using Multidetector-Row Helical CT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kudoh, Kouichi, E-mail: cdk70770@par.odn.ne.jp; Kadota, Masataka; Nakayama, Yoshiharu

2003-09-15

A girl with continuous urinary incontinence was successfully treated by angiographic embolization of a hypoplastic pelvic kidney with a single unilateral vaginal ectopic opening of the ureter. For this intervention, CT angiography was useful for detecting the corresponding renal artery of the hypoplastic kidney.

Role of multidetector computed tomography in evaluating incidentally detected breast lesions.

PubMed

Moschetta, Marco; Scardapane, Arnaldo; Lorusso, Valentina; Rella, Leonarda; Telegrafo, Michele; Serio, Gabriella; Angelelli, Giuseppe; Ianora, Amato Antonio Stabile

2015-01-01

Computed tomography (CT) does not represent the primary method for the evaluation of breast lesions; however, it can detect breast abnormalities, even when performed for other reasons related to thoracic structures. The aim of this study is to evaluate the potential benefits of 320-row multidetector CT (MDCT) in evaluating and differentiating incidentally detected breast lesions by using vessel probe and 3D analysis software with net enhancement value. Sixty-two breast lesions in 46 patients who underwent 320-row chest CT examination were retrospectively evaluated. CT scans were assessed searching for the presence, location, number, morphological features, and density of breast nodules. Net enhancement was calculated by subtracting precontrast density from the density obtained by postcontrast values. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of CT were calculated for morphological features and net enhancement. Thirty of 62 lesions were found to be malignant at histological examination and 32 were found to be benign. When morphological features were considered, the sensitivity, specificity, accuracy, PPV, and NPV of CT were 87%, 100%, 88%, 100%, and 50%, respectively. Based on net enhancement, CT reached a sensitivity, specificity, accuracy, PPV, and NPV of 100%, 94%, 97%, 94%, and 100%, respectively. MDCT allows to recognize and characterize breast lesions based on morphological features. Net enhancement can be proposed as an additional accurate feature of CT.

Investigation of ultra low-dose scans in the context of quantum-counting clinical CT

NASA Astrophysics Data System (ADS)

Weidinger, T.; Buzug, T. M.; Flohr, T.; Fung, G. S. K.; Kappler, S.; Stierstorfer, K.; Tsui, B. M. W.

2012-03-01

In clinical computed tomography (CT), images from patient examinations taken with conventional scanners exhibit noise characteristics governed by electronics noise, when scanning strongly attenuating obese patients or with an ultra-low X-ray dose. Unlike CT systems based on energy integrating detectors, a system with a quantum counting detector does not suffer from this drawback. Instead, the noise from the electronics mainly affects the spectral resolution of these detectors. Therefore, it does not contribute to the image noise in spectrally non-resolved CT images. This promises improved image quality due to image noise reduction in scans obtained from clinical CT examinations with lowest X-ray tube currents or obese patients. To quantify the benefits of quantum counting detectors in clinical CT we have carried out an extensive simulation study of the complete scanning and reconstruction process for both kinds of detectors. The simulation chain encompasses modeling of the X-ray source, beam attenuation in the patient, and calculation of the detector response. Moreover, in each case the subsequent image preprocessing and reconstruction is modeled as well. The simulation-based, theoretical evaluation is validated by experiments with a novel prototype quantum counting system and a Siemens Definition Flash scanner with a conventional energy integrating CT detector. We demonstrate and quantify the improvement from image noise reduction achievable with quantum counting techniques in CT examinations with ultra-low X-ray dose and strong attenuation.

Image reconstruction in cone-beam CT with a spherical detector using the BPF algorithm

NASA Astrophysics Data System (ADS)

Zuo, Nianming; Zou, Yu; Jiang, Tianzi; Pan, Xiaochuan

2006-03-01

Both flat-panel detectors and cylindrical detectors have been used in CT systems for data acquisition. The cylindrical detector generally offers a sampling of a transverse image plane more uniformly than does a flat-panel detector. However, in the longitudinal dimension, the cylindrical and flat-panel detectors offer similar sampling of the image space. In this work, we investigate a detector of spherical shape, which can yield uniform sampling of the 3D image space because the solid angle subtended by each individual detector bin remains unchanged. We have extended the backprojection-filtration (BPF) algorithm, which we have developed previously for cone-beam CT, to reconstruct images in cone-beam CT with a spherical detector. We also conduct computer-simulation studies to validate the extended BPF algorithm. Quantitative results in these numerical studies indicate that accurate images can be obtained from data acquired with a spherical detector by use of our extended BPF cone-beam algorithms.

Systems for Lung Volume Standardization during Static and Dynamic MDCT-based Quantitative Assessment of Pulmonary Structure and Function

PubMed Central

Fuld, Matthew K.; Grout, Randall; Guo, Junfeng; Morgan, John H.; Hoffman, Eric A.

2013-01-01

Rationale and Objectives Multidetector-row Computed Tomography (MDCT) has emerged as a tool for quantitative assessment of parenchymal destruction, air trapping (density metrics) and airway remodeling (metrics relating airway wall and lumen geometry) in chronic obstructive pulmonary disease (COPD) and asthma. Critical to the accuracy and interpretability of these MDCT-derived metrics is the assurance that the lungs are scanned during a breath-hold at a standardized volume. Materials and Methods A computer monitored turbine-based flow meter system was developed to control patient breath-holds and facilitate static imaging at fixed percentages of the vital capacity. Due to calibration challenges with gas density changes during multi-breath xenon-CT an alternative system was required. The design incorporated dual rolling seal pistons. Both systems were tested in a laboratory environment and human subject trials. Results The turbine-based system successfully controlled lung volumes in 32/37 subjects, having a linear relationship for CT measured air volume between repeated scans: for all scans, the mean and confidence interval of the differences (scan1-scan2) was −9 ml (−169, 151); for TLC alone 6 ml (−164, 177); for FRC alone, −23 ml (−172, 126). The dual-piston system successfully controlled lung volume in 31/41 subjects. Study failures related largely to subject non-compliance with verbal instruction and gas leaks around the mouthpiece. Conclusion We demonstrate the successful use of a turbine-based system for static lung volume control and demonstrate its inadequacies for dynamic xenon-CT studies. Implementation of a dual-rolling seal spirometer has been shown to adequately control lung volume for multi-breath wash-in xenon-CT studies. These systems coupled with proper patient coaching provide the tools for the use of CT to quantitate regional lung structure and function. The wash-in xenon-CT method for assessing regional lung function, while not necessarily practical for routine clinical studies, provides for a dynamic protocol against which newly emerging single breath, dual-energy xenon-CT measures can be validated. PMID:22555001

Systematic implementation of spectral CT with a photon counting detector for liquid security inspection

NASA Astrophysics Data System (ADS)

Xu, Xiaofei; Xing, Yuxiang; Wang, Sen; Zhang, Li

2018-06-01

X-ray liquid security inspection system plays an important role in homeland security, while the conventional dual-energy CT (DECT) system may have a big deviation in extracting the atomic number and the electron density of materials in various conditions. Photon counting detectors (PCDs) have the capability of discriminating the incident photons of different energy. The technique becomes more and more mature in nowadays. In this work, we explore the performance of a multi-energy CT imaging system with a PCD for liquid security inspection in material discrimination. We used a maximum-likelihood (ML) decomposition method with scatter correction based on a cross-energy response model (CERM) for PCDs so that to improve the accuracy of atomic number and electronic density imaging. Experimental study was carried to examine the effectiveness and robustness of the proposed system. Our results show that the concentration of different solutions in physical phantoms can be reconstructed accurately, which could improve the material identification compared to current available dual-energy liquid security inspection systems. The CERM-base decomposition and reconstruction method can be easily used to different applications such as medical diagnosis.

Automated continuous quantitative measurement of proximal airways on dynamic ventilation CT: initial experience using an ex vivo porcine lung phantom.

PubMed

Yamashiro, Tsuneo; Tsubakimoto, Maho; Nagatani, Yukihiro; Moriya, Hiroshi; Sakuma, Kotaro; Tsukagoshi, Shinsuke; Inokawa, Hiroyasu; Kimoto, Tatsuya; Teramoto, Ryuichi; Murayama, Sadayuki

2015-01-01

The purpose of this study was to evaluate the feasibility of continuous quantitative measurement of the proximal airways, using dynamic ventilation computed tomography (CT) and our research software. A porcine lung that was removed during meat processing was ventilated inside a chest phantom by a negative pressure cylinder (eight times per minute). This chest phantom with imitated respiratory movement was scanned by a 320-row area-detector CT scanner for approximately 9 seconds as dynamic ventilatory scanning. Obtained volume data were reconstructed every 0.35 seconds (total 8.4 seconds with 24 frames) as three-dimensional images and stored in our research software. The software automatically traced a designated airway point in all frames and measured the cross-sectional luminal area and wall area percent (WA%). The cross-sectional luminal area and WA% of the trachea and right main bronchus (RMB) were measured for this study. Two radiologists evaluated the traceability of all measurable airway points of the trachea and RMB using a three-point scale. It was judged that the software satisfactorily traced airway points throughout the dynamic ventilation CT (mean score, 2.64 at the trachea and 2.84 at the RMB). From the maximum inspiratory frame to the maximum expiratory frame, the cross-sectional luminal area of the trachea decreased 17.7% and that of the RMB 29.0%, whereas the WA% of the trachea increased 6.6% and that of the RMB 11.1%. It is feasible to measure airway dimensions automatically at designated points on dynamic ventilation CT using research software. This technique can be applied to various airway and obstructive diseases.

CT perfusion imaging of the liver and the spleen in patients with cirrhosis: Is there a correlation between perfusion and portal venous hypertension?

PubMed

Talakić, Emina; Schaffellner, Silvia; Kniepeiss, Daniela; Mueller, Helmut; Stauber, Rudolf; Quehenberger, Franz; Schoellnast, Helmut

2017-10-01

To correlate hepatic and splenic CT perfusion parameters with hepatic venous pressure gradient (HVPG) measurements in patients with cirrhosis. Twenty-one patients with cirrhosis (males, 17; females, 4; mean ± SD age, 57 ± 7 years) underwent hepatic and splenic perfusion CT on a 320-detector row volume scanner as well as invasive measurement of HVPG. Different CT perfusion algorithms (maximum slope analysis and Patlak plot) were used to measure hepatic arterial flow (HAF), portal venous flow (PVF), hepatic perfusion index (HPI), splenic arterial flow (SAF), splenic blood volume (SBV) and splenic clearance (SCL). Hepatic and splenic perfusion parameters were correlated with HVPG, and sensitivity and specificity for detection of severe portal hypertension (≥12 mmHg) were calculated. The Spearman correlation coefficient was -0.53 (p < 0.05) between SAF and HVPG, and -0.68 (p < 0.01) between HVPG and SCL. Using a cut-off value of 125 ml/min/100 ml for SCL, sensitivity for detection of a HVPG of ≥12 mmHg was 94%, and specificity 100%. There was no significant correlation between hepatic perfusion parameters and HVPG. CT perfusion in patients with cirrhosis showed a strong correlation between SCL and HVPG and may be used for detection of severe portal hypertension. • SAF and SCL are statistically significantly correlated with HVPG • SCL showed stronger correlation with HVPG than SAF • 125 ml/min/100 ml SCL-cut-off yielded 94 % sensitivity, 100 % specificity for severe PH • HAF, PVF and HPI showed no statistically significant correlation with HVPG.

Multislice spiral CT simulator for dynamic cardiopulmonary studies

NASA Astrophysics Data System (ADS)

De Francesco, Silvia; Ferreira da Silva, Augusto M.

2002-04-01

We've developed a Multi-slice Spiral CT Simulator modeling the acquisition process of a real tomograph over a 4-dimensional phantom (4D MCAT) of the human thorax. The simulator allows us to visually characterize artifacts due to insufficient temporal sampling and a priori evaluate the quality of the images obtained in cardio-pulmonary studies (both with single-/multi-slice and ECG gated acquisition processes). The simulating environment allows both for conventional and spiral scanning modes and includes a model of noise in the acquisition process. In case of spiral scanning, reconstruction facilities include longitudinal interpolation methods (360LI and 180LI both for single and multi-slice). Then, the reconstruction of the section is performed through FBP. The reconstructed images/volumes are affected by distortion due to insufficient temporal sampling of the moving object. The developed simulating environment allows us to investigate the nature of the distortion characterizing it qualitatively and quantitatively (using, for example, Herman's measures). Much of our work is focused on the determination of adequate temporal sampling and sinogram regularization techniques. At the moment, the simulator model is limited to the case of multi-slice tomograph, being planned as a next step of development the extension to cone beam or area detectors.

Improving Spectral Results Using Row-by-Row Fourier Transform of Spatial Heterodyne Raman Spectrometer Interferogram.

PubMed

Barnett, Patrick D; Strange, K Alicia; Angel, S Michael

2017-06-01

This work describes a method of applying the Fourier transform to the two-dimensional Fizeau fringe patterns generated by the spatial heterodyne Raman spectrometer (SHRS), a dispersive interferometer, to correct the effects of certain types of optical alignment errors. In the SHRS, certain types of optical misalignments result in wavelength-dependent and wavelength-independent rotations of the fringe pattern on the detector. We describe here a simple correction technique that can be used in post-processing, by applying the Fourier transform in a row-by-row manner. This allows the user to be more forgiving of fringe alignment and allows for a reduction in the mechanical complexity of the SHRS.

Performance simulation of an x-ray detector for spectral CT with combined Si and Cd[Zn]Te detection layers

NASA Astrophysics Data System (ADS)

Herrmann, Christoph; Engel, Klaus-Jürgen; Wiegert, Jens

2010-12-01

The most obvious problem in obtaining spectral information with energy-resolving photon counting detectors in clinical computed tomography (CT) is the huge x-ray flux present in conventional CT systems. At high tube voltages (e.g. 140 kVp), despite the beam shaper, this flux can be close to 109 Mcps mm-2 in the direct beam or in regions behind the object, which are close to the direct beam. Without accepting the drawbacks of truncated reconstruction, i.e. estimating missing direct-beam projection data, a photon-counting energy-resolving detector has to be able to deal with such high count rates. Sub-structuring pixels into sub-pixels is not enough to reduce the count rate per pixel to values that today's direct converting Cd[Zn]Te material can cope with (<=10 Mcps in an optimistic view). Below 300 µm pixel pitch, x-ray cross-talk (Compton scatter and K-escape) and the effect of charge diffusion between pixels are problematic. By organising the detector in several different layers, the count rate can be further reduced. However this alone does not limit the count rates to the required level, since the high stopping power of the material becomes a disadvantage in the layered approach: a simple absorption calculation for 300 µm pixel pitch shows that the required layer thickness of below 10 Mcps/pixel for the top layers in the direct beam is significantly below 100 µm. In a horizontal multi-layer detector, such thin layers are very difficult to manufacture due to the brittleness of Cd[Zn]Te. In a vertical configuration (also called edge-on illumination (Ludqvist et al 2001 IEEE Trans. Nucl. Sci. 48 1530-6, Roessl et al 2008 IEEE NSS-MIC-RTSD 2008, Conf. Rec. Talk NM2-3)), bonding of the readout electronics (with pixel pitches below 100 µm) is not straightforward although it has already been done successfully (Pellegrini et al 2004 IEEE NSS MIC 2004 pp 2104-9). Obviously, for the top detector layers, materials with lower stopping power would be advantageous. The possible choices are, however, quite limited, since only 'mature' materials, which operate at room temperature and can be manufactured reliably should reasonably be considered. Since GaAs is still known to cause reliability problems, the simplest choice is Si, however with the drawback of strong Compton scatter which can cause considerable inter-pixel cross-talk. To investigate the potential and the problems of Si in a multi-layer detector, in this paper the combination of top detector layers made of Si with lower layers made of Cd[Zn]Te is studied by using Monte Carlo simulated detector responses. It is found that the inter-pixel cross-talk due to Compton scatter is indeed very high; however, with an appropriate cross-talk correction scheme, which is also described, the negative effects of cross-talk are shown to be removed to a very large extent.

Geographic Distribution of CT, MRI and PET Devices in Japan: A Longitudinal Analysis Based on National Census Data.

PubMed

Matsumoto, Masatoshi; Koike, Soichi; Kashima, Saori; Awai, Kazuo

2015-01-01

Japan has the most CT and MRI scanners per unit population in the world; however, the geographic distribution of these technologies is currently unknown. Moreover, nothing is known of the cause-effect relationship between the number of diagnostic imaging devices and their geographic distribution. Data on the number of CT, MRI and PET devices and that of their utilizations in all 1829 municipalities of Japan was generated, based on the Static Survey of Medical Institutions conducted by the government. The inter-municipality equity of the number of devices or utilizations was evaluated with Gini coefficient. Between 2005 and 2011, the number of CT, MRI and PET devices in Japan increased by 47% (8789 to 12945), 19% (5034 to 5990) and 70% (274 to 466), respectively. Gini coefficient of the number of devices was largest for PET and smallest for CT (p for PET-MRI difference <0.001; MRI-CT difference <0.001). For all three modalities, Gini coefficient steadily decreased (p for 2011-2005 difference: <0.001 for CT; 0.003 for MRI; and <0.001 for PET). The number of devices in old models (single-detector CT, MRI<1.5 tesla, and conventional PET) decreased, while that in new models (multi-detector CT, MRI≥1.5 tesla, and PET-CT) increased. Gini coefficient of the old models increased or remained unchanged (increase rate of 9%, 3%, and -1%; p for 2011-2008 difference <0.001, 0.072, and 0.562, respectively), while Gini coefficient of the new models decreased (-10%, -9%, and -10%; p for 2011-2008 difference <0.001, <0.001, and <0.001 respectively). Similar results were observed in terms of utilizations. The more abundant a modality, the more equal the modality's distribution. Any increase in the modality made its distribution more equal. The geographic distribution of the diagnostic imaging technology in Japan appears to be affected by spatial competition derived from a market force.

Monte Carlo simulations in multi-detector CT (MDCT) for two PET/CT scanner models using MASH and FASH adult phantoms

NASA Astrophysics Data System (ADS)

Belinato, W.; Santos, W. S.; Paschoal, C. M. M.; Souza, D. N.

2015-06-01

The combination of positron emission tomography (PET) and computed tomography (CT) has been extensively used in oncology for diagnosis and staging of tumors, radiotherapy planning and follow-up of patients with cancer, as well as in cardiology and neurology. This study determines by the Monte Carlo method the internal organ dose deposition for computational phantoms created by multidetector CT (MDCT) beams of two PET/CT devices operating with different parameters. The different MDCT beam parameters were largely related to the total filtration that provides a beam energetic change inside the gantry. This parameter was determined experimentally with the Accu-Gold Radcal measurement system. The experimental values of the total filtration were included in the simulations of two MCNPX code scenarios. The absorbed organ doses obtained in MASH and FASH phantoms indicate that bowtie filter geometry and the energy of the X-ray beam have significant influence on the results, although this influence can be compensated by adjusting other variables such as the tube current-time product (mAs) and pitch during PET/CT procedures.

Unenhanced 320-row multidetector computed tomography of the brain in children: comparison of image quality and radiation dose among wide-volume, one-shot volume, and helical scan modes.

PubMed

Jeon, Sun Kyung; Choi, Young Hun; Cheon, Jung-Eun; Kim, Woo Sun; Cho, Yeon Jin; Ha, Ji Young; Lee, Seung Hyun; Hyun, Hyejin; Kim, In-One

2018-04-01

The 320-row multidetector computed tomography (CT) scanner has multiple scan modes, including volumetric modes. To compare the image quality and radiation dose of 320-row CT in three acquisition modes - helical, one-shot volume, and wide-volume scan - at pediatric brain imaging. Fifty-seven children underwent unenhanced brain CT using one of three scan modes (helical scan, n=21; one-shot volume scan, n=17; wide-volume scan, n=19). For qualitative analysis, two reviewers evaluated overall image quality and image noise using a 5-point grading system. For quantitative analysis, signal-to-noise ratio, image noise and posterior fossa artifact index were calculated. To measure the radiation dose, adjusted CT dose index per unit volume (CTDI adj ) and dose length product (DLP) were compared. Qualitatively, the wide-volume scan showed significantly less image noise than the helical scan (P=0.009), and less streak artifact than the one-shot volume scan (P=0.001). The helical mode showed significantly lower signal-to-noise ratio, with a higher image noise level compared with the one-shot volume and wide-volume modes (all P<0.05). The CTDI adj and DLP were significantly lower in the one-shot volume and wide-volume modes compared with those in the helical scan mode (all P<0.05). For pediatric unenhanced brain CT, both the wide-volume and one-shot volume scans reduced radiation dose compared to the helical scan mode, while the wide-volume scan mode showed fewer streak artifacts in the skull vertex and posterior fossa than the one-shot volume scan.

Image quality and artefact generation post-cerebral aneurysm clipping using a 64-row multislice computer tomography angiography (MSCTA) technology: A retrospective study and review of the literature.

PubMed

Zachenhofer, Iris; Cejna, Manfred; Schuster, Antonius; Donat, Markus; Roessler, Karl

2010-06-01

Computed tomography angiography (CTA) is a time and cost saving investigation for postoperative evaluation of clipped cerebral aneurysm patients. A retrospective study was conducted to analyse image quality and artefact generation due to implanted aneurysm clips using a new technology. MSCTA was performed pre- and postoperatively using a Philips Brilliance 64-detector-row CT scanner. Altogether, 32 clipping sites were analysed in 27 patients (11 female and 16 male, mean ages 52a, from 24 to 72 years). Clip number per aneurysm was 2.3 mean (from 1 to 4), 54 clips were made of titanium alloy and 5 of cobalt alloy. Altogether, image quality was rated 1.8 mean, using a scale from 1 (very good) to 5 (unserviceable) and clip artefacts were rated 2.4 mean, using a 5 point rating scale (1 no artefacts, 5 unserviceable due to artefacts). A significant loss of image quality and rise of artefacts was found when using cobalt alloy clips (1.4 versus 4.2 and 2.1 versus 4.0). In 72% of all investigations, an excellent image quality was found. Excluding the cobalt clip group, 85% of scans showed excellent image quality. Artefacts were absent or minimal (grade 1 or 2) in 69% of all investigations and in 81% in the pure titanium clip group. In 64-row MSCTA of good image quality with low artefacts, it was possible to detect small aneurysm remnants of 2mm size in individual patients. By using titanium alloy clips, in our study up to 85% of postoperative CTA images were of excellent quality with absent or minimal artefacts in 81% and seem adequate to detect small aneurysm remnants. Copyright 2010 Elsevier B.V. All rights reserved.

Marrow Adipose Tissue Quantification of the Lumbar Spine by Using Dual-Energy CT and Single-Voxel 1H MR Spectroscopy: A Feasibility Study

PubMed Central

Daley, Scott M.; Kalra, Mannudeep K.; Brown, J. Keenan; Miller, Karen K.; Torriani, Martin

2015-01-01

Purpose To test the performance of dual-energy computed tomography (CT) in the assessment of marrow adipose tissue (MAT) content of the lumbar spine by using proton (hydrogen 1 [1H]) magnetic resonance (MR) spectroscopy as a reference standard and to determine the influence of MAT on the assessment of bone mineral density (BMD). Materials and Methods This study was institutional review board approved and complied with HIPAA guidelines. Written informed consent was obtained. Twelve obese osteopenic but otherwise healthy subjects (mean age ± standard deviation, 43 years ± 13) underwent 3-T 1H MR spectroscopy of the L2 vertebra by using a point-resolved spatially localized spectroscopy sequence without water suppression. The L2 vertebra was scanned with dual-energy CT (80 and 140 kV) by using a dual-source multi–detector row CT scanner with a calibration phantom. Mean basis material composition relative to the phantom was estimated in the L2 vertebra. Volumetric BMD was measured with and without correction for MAT. Bland-Altman 95% limits of agreement and Pearson correlation coefficients were calculated. Results There was excellent agreement between 1H MR spectroscopy and dual-energy CT, with a mean difference in fat fraction of −0.02 between the techniques, with a 95% confidence interval of −0.24, 0.20. There was a strong correlation between marrow fat fraction obtained with 1H MR spectroscopy and that obtained with dual-energy CT (r = 0.91, P < .001). The presence of MAT led to underestimation of BMD, and this bias increased with increasing MAT content (P < .001). Conclusion Dual-energy CT can be used to assess MAT content and BMD of the lumbar spine in a single examination and provides data that closely agree and correlate with 1H MR spectroscopy data. © RSNA, 2015 PMID:25988401

SU-E-I-33: Establishment of CT Diagnostic Reference Levels in Province Nova Scotia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tonkopi, E; Abdolell, M; Duffy, S

2015-06-15

Purpose: To evaluate patient radiation dose from the most frequently performed CT examinations and to establish provincial diagnostic reference levels (DRLs) as a tool for protocol optimization. Methods: The study investigated the following CT examinations: head, chest, abdomen/pelvis, and chest/abdomen/pelvis (CAP). Dose data, volume CT dose index (CTDIvol) and dose-length product (DLP), were collected from 15 CT scanners installed during 2004–2014 in 11 hospital sites of Nova Scotia. All scanners had dose modulation options and multislice capability (16–128 detector rows). The sample for each protocol included 15 average size patients (70±20 kg). Provincial DRLs were calculated as the 75th percentilemore » of patient dose distributions. The differences in dose between hospitals were evaluated with a single factor ANOVA statistical test. Generalized linear modeling was used to determine the factors associated with higher radiation dose. A sample of 36 abdominal studies performed on three different scanners was blinded and randomized for an assessment by an experienced radiologist who graded the imaging quality of anatomic structures. Results: Data for 900 patients were collected. The DRLs were proposed using CTDIvol (mGy) and DLP (mGy*cm) values for CT head (67 and 1049, respectively), chest (12 and 393), abdomen/pelvis (16 and 717), and CAP (14 and 1034). These DRLs were lower than the published national data except for the head CTDIvol. The differences between the means of the dose distributions from each scanner were statistically significant (p<0.05) for all examinations. A very weak correlation was found between the dose and the scanner age or the number of slices with Pearson’s correlation coefficients of 0.011–0.315. The blinded analysis of image quality demonstrated no clinically significant difference except for the noise category. Conclusion: Provincial DRLs were established for typical CT examinations. The variations in dose between the hospitals suggested a large potential for optimization of examinations. Radiology Research Foundation grant.« less

NOTE: A BPF-type algorithm for CT with a curved PI detector

NASA Astrophysics Data System (ADS)

Tang, Jie; Zhang, Li; Chen, Zhiqiang; Xing, Yuxiang; Cheng, Jianping

2006-08-01

Helical cone-beam CT is used widely nowadays because of its rapid scan speed and efficient utilization of x-ray dose. Recently, an exact reconstruction algorithm for helical cone-beam CT was proposed (Zou and Pan 2004a Phys. Med. Biol. 49 941 59). The algorithm is referred to as a backprojection-filtering (BPF) algorithm. This BPF algorithm for a helical cone-beam CT with a flat-panel detector (FPD-HCBCT) requires minimum data within the Tam Danielsson window and can naturally address the problem of ROI reconstruction from data truncated in both longitudinal and transversal directions. In practical CT systems, detectors are expensive and always take a very important position in the total cost. Hence, we work on an exact reconstruction algorithm for a CT system with a detector of the smallest size, i.e., a curved PI detector fitting the Tam Danielsson window. The reconstruction algorithm is derived following the framework of the BPF algorithm. Numerical simulations are done to validate our algorithm in this study.

A BPF-type algorithm for CT with a curved PI detector.

PubMed

Tang, Jie; Zhang, Li; Chen, Zhiqiang; Xing, Yuxiang; Cheng, Jianping

2006-08-21

Helical cone-beam CT is used widely nowadays because of its rapid scan speed and efficient utilization of x-ray dose. Recently, an exact reconstruction algorithm for helical cone-beam CT was proposed (Zou and Pan 2004a Phys. Med. Biol. 49 941-59). The algorithm is referred to as a backprojection-filtering (BPF) algorithm. This BPF algorithm for a helical cone-beam CT with a flat-panel detector (FPD-HCBCT) requires minimum data within the Tam-Danielsson window and can naturally address the problem of ROI reconstruction from data truncated in both longitudinal and transversal directions. In practical CT systems, detectors are expensive and always take a very important position in the total cost. Hence, we work on an exact reconstruction algorithm for a CT system with a detector of the smallest size, i.e., a curved PI detector fitting the Tam-Danielsson window. The reconstruction algorithm is derived following the framework of the BPF algorithm. Numerical simulations are done to validate our algorithm in this study.

Performance evaluation of a 64-slice CT system with z-flying focal spot.

PubMed

Flohr, T; Stierstorfer, K; Raupach, R; Ulzheimer, S; Bruder, H

2004-12-01

The meanwhile established generation of 16-slice CT systems enables routine sub-millimeter imaging at short breath-hold times. Clinical progress in the development of multidetector row CT (MDCT) technology beyond 16 slices can more likely be expected from further improvement in spatial and temporal resolution rather than from a mere increase in the speed of volume coverage. We present an evaluation of a recently introduced 64-slice CT system (SOMATOM Sensation 64, Siemens AG, Forchheim, Germany), which uses a periodic motion of the focal spot in longitudinal direction (z-flying focal spot) to double the number of simultaneously acquired slices. This technique acquires 64 overlapping 0.6 mm slices per rotation. The sampling scheme corresponds to that of a 64 x 0.3 mm detector, with the goal of improved longitudinal resolution and reduced spiral artifacts. After an introduction to the detector design, we discuss the basics of z-flying focal spot technology (z-Sharp). We present phantom and specimen scans for performance evaluation. The measured full width at half maximum (FWHM) of the thinnest spiral slice is 0.65 mm. All spiral slice widths are almost independent of the pitch, with deviations of less than 0.1 mm from the nominal value. Using a high-resolution bar pattern phantom (CATPHAN, Phantom Laboratories, Salem, NY), the longitudinal resolution can be demonstrated to be up to 15 lp/cm at the isocenter independent of the pitch, corresponding to a bar diameter of 0.33 mm. Longitudinal resolution is only slightly degraded for off-center locations. At a distance of 100 mm from the isocenter, 14 lp/cm can be resolved in the z-direction, corresponding to a bar diameter of 0.36 mm. Spiral "windmill" artifacts presenting as hyper- and hypodense structures around osseous edges are effectively reduced by the z-flying focal spot technique. Cardiac scanning benefits from the short gantry rotation time of 0.33 s, providing up to 83 ms temporal resolution with 2-segment ECG-gated reconstruction.

Review on the characteristics of radiation detectors for dosimetry and imaging

NASA Astrophysics Data System (ADS)

Seco, Joao; Clasie, Ben; Partridge, Mike

2014-10-01

The enormous advances in the understanding of human anatomy, physiology and pathology in recent decades have led to ever-improving methods of disease prevention, diagnosis and treatment. Many of these achievements have been enabled, at least in part, by advances in ionizing radiation detectors. Radiology has been transformed by the implementation of multi-slice CT and digital x-ray imaging systems, with silver halide films now largely obsolete for many applications. Nuclear medicine has benefited from more sensitive, faster and higher-resolution detectors delivering ever-higher SPECT and PET image quality. PET/MR systems have been enabled by the development of gamma ray detectors that can operate in high magnetic fields. These huge advances in imaging have enabled equally impressive steps forward in radiotherapy delivery accuracy, with 4DCT, PET and MRI routinely used in treatment planning and online image guidance provided by cone-beam CT. The challenge of ensuring safe, accurate and precise delivery of highly complex radiation fields has also both driven and benefited from advances in radiation detectors. Detector systems have been developed for the measurement of electron, intensity-modulated and modulated arc x-ray, proton and ion beams, and around brachytherapy sources based on a very wide range of technologies. The types of measurement performed are equally wide, encompassing commissioning and quality assurance, reference dosimetry, in vivo dosimetry and personal and environmental monitoring. In this article, we briefly introduce the general physical characteristics and properties that are commonly used to describe the behaviour and performance of both discrete and imaging detectors. The physical principles of operation of calorimeters; ionization and charge detectors; semiconductor, luminescent, scintillating and chemical detectors; and radiochromic and radiographic films are then reviewed and their principle applications discussed. Finally, a general discussion of the application of detectors for x-ray nuclear medicine and ion beam imaging and dosimetry is presented.

Evaluation of a metal artifacts reduction algorithm applied to postinterventional flat panel detector CT imaging.

PubMed

Stidd, D A; Theessen, H; Deng, Y; Li, Y; Scholz, B; Rohkohl, C; Jhaveri, M D; Moftakhar, R; Chen, M; Lopes, D K

2014-01-01

Flat panel detector CT images are degraded by streak artifacts caused by radiodense implanted materials such as coils or clips. A new metal artifacts reduction prototype algorithm has been used to minimize these artifacts. The application of this new metal artifacts reduction algorithm was evaluated for flat panel detector CT imaging performed in a routine clinical setting. Flat panel detector CT images were obtained from 59 patients immediately following cerebral endovascular procedures or as surveillance imaging for cerebral endovascular or surgical procedures previously performed. The images were independently evaluated by 7 physicians for metal artifacts reduction on a 3-point scale at 2 locations: immediately adjacent to the metallic implant and 3 cm away from it. The number of visible vessels before and after metal artifacts reduction correction was also evaluated within a 3-cm radius around the metallic implant. The metal artifacts reduction algorithm was applied to the 59 flat panel detector CT datasets without complications. The metal artifacts in the reduction-corrected flat panel detector CT images were significantly reduced in the area immediately adjacent to the implanted metal object (P = .05) and in the area 3 cm away from the metal object (P = .03). The average number of visible vessel segments increased from 4.07 to 5.29 (P = .1235) after application of the metal artifacts reduction algorithm to the flat panel detector CT images. Metal artifacts reduction is an effective method to improve flat panel detector CT images degraded by metal artifacts. Metal artifacts are significantly decreased by the metal artifacts reduction algorithm, and there was a trend toward increased vessel-segment visualization. © 2014 by American Journal of Neuroradiology.

Thoracic Injuries in earthquake-related versus non-earthquake-related trauma patients: differentiation via Multi-detector Computed Tomography.

PubMed

Dong, Zhi-Hui; Yang, Zhi-Gang; Chen, Tian-Wu; Chu, Zhi-Gang; Deng, Wen; Shao, Heng

2011-01-01

Massive earthquakes are harmful to humankind. This study of a historical cohort aimed to investigate the difference between earthquake-related crush thoracic traumas and thoracic traumas unrelated to earthquakes using a multi-detector Computed Tomography (CT). We retrospectively compared an earthquake-exposed cohort of 215 thoracic trauma crush victims of the Sichuan earthquake to a cohort of 215 non-earthquake-related thoracic trauma patients, focusing on the lesions and coexisting injuries to the thoracic cage and the pulmonary parenchyma and pleura using a multi-detector CT. The incidence of rib fracture was elevated in the earthquake-exposed cohort (143 vs. 66 patients in the non-earthquake-exposed cohort, Risk Ratio (RR) = 2.2; p<0.001). Among these patients, those with more than 3 fractured ribs (106/143 vs. 41/66 patients, RR=1.2; p<0.05) or flail chest (45/143 vs. 11/66 patients, RR=1.9; p<0.05) were more frequently seen in the earthquake cohort. Earthquake-related crush injuries more frequently resulted in bilateral rib fractures (66/143 vs. 18/66 patients, RR= 1.7; p<0.01). Additionally, the incidence of non-rib fracture was higher in the earthquake cohort (85 vs. 60 patients, RR= 1.4; p<0.01). Pulmonary parenchymal and pleural injuries were more frequently seen in earthquake-related crush injuries (117 vs. 80 patients, RR=1.5 for parenchymal and 146 vs. 74 patients, RR = 2.0 for pleural injuries; p<0.001). Non-rib fractures, pulmonary parenchymal and pleural injuries had significant positive correlation with rib fractures in these two cohorts. Thoracic crush traumas resulting from the earthquake were life threatening with a high incidence of bony thoracic fractures. The ribs were frequently involved in bilateral and severe types of fractures, which were accompanied by non-rib fractures, pulmonary parenchymal and pleural injuries.

Thoracic Injuries in earthquake-related versus non-earthquake-related trauma patients: differentiation via Multi-detector Computed Tomography

PubMed Central

Dong, Zhi-hui; Yang, Zhi-gang; Chen, Tian-wu; Chu, Zhi-gang; Deng, Wen; Shao, Heng

2011-01-01

PURPOSE: Massive earthquakes are harmful to humankind. This study of a historical cohort aimed to investigate the difference between earthquake-related crush thoracic traumas and thoracic traumas unrelated to earthquakes using a multi-detector Computed Tomography (CT). METHODS: We retrospectively compared an earthquake-exposed cohort of 215 thoracic trauma crush victims of the Sichuan earthquake to a cohort of 215 non-earthquake-related thoracic trauma patients, focusing on the lesions and coexisting injuries to the thoracic cage and the pulmonary parenchyma and pleura using a multi-detector CT. RESULTS: The incidence of rib fracture was elevated in the earthquake-exposed cohort (143 vs. 66 patients in the non-earthquake-exposed cohort, Risk Ratio (RR) = 2.2; p<0.001). Among these patients, those with more than 3 fractured ribs (106/143 vs. 41/66 patients, RR = 1.2; p<0.05) or flail chest (45/143 vs. 11/66 patients, RR = 1.9; p<0.05) were more frequently seen in the earthquake cohort. Earthquake-related crush injuries more frequently resulted in bilateral rib fractures (66/143 vs. 18/66 patients, RR = 1.7; p<0.01). Additionally, the incidence of non-rib fracture was higher in the earthquake cohort (85 vs. 60 patients, RR = 1.4; p<0.01). Pulmonary parenchymal and pleural injuries were more frequently seen in earthquake-related crush injuries (117 vs. 80 patients, RR = 1.5 for parenchymal and 146 vs. 74 patients, RR = 2.0 for pleural injuries; p<0.001). Non-rib fractures, pulmonary parenchymal and pleural injuries had significant positive correlation with rib fractures in these two cohorts. CONCLUSIONS: Thoracic crush traumas resulting from the earthquake were life threatening with a high incidence of bony thoracic fractures. The ribs were frequently involved in bilateral and severe types of fractures, which were accompanied by non-rib fractures, pulmonary parenchymal and pleural injuries. PMID:21789386

Fiber optic crossbar switch for automatically patching optical signals

NASA Technical Reports Server (NTRS)

Bell, C. H. (Inventor)

1983-01-01

A system for automatically optically switching fiber optic data signals between a plurality of input optical fibers and selective ones of a plurality of output fibers is described. The system includes optical detectors which are connected to each of the input fibers for converting the optic data signals appearing at the respective input fibers to an RF signal. A plurality of RF to optical signal converters are arranged in rows and columns. The output of each of the optical detectors are each applied to a respective row of optical signal converted for being converters back to an optical signal when the particular optical signal converter is selectively activated by a dc voltage.

Detectability index of differential phase contrast CT compared with conventional CT: a preliminary channelized Hotelling observer study

NASA Astrophysics Data System (ADS)

Tang, Xiangyang; Yang, Yi; Tang, Shaojie

2013-03-01

Under the framework of model observer with signal and background exactly known (SKE/BKE), we investigate the detectability of differential phase contrast CT compared with that of the conventional attenuation-based CT. Using the channelized Hotelling observer and the radially symmetric difference-of-Gaussians channel template , we investigate the detectability index and its variation over the dimension of object and detector cells. The preliminary data show that the differential phase contrast CT outperforms the conventional attenuation-based CT significantly in the detectability index while both the object to be detected and the cell of detector used for data acquisition are relatively small. However, the differential phase contrast CT's dominance in the detectability index diminishes with increasing dimension of either object or detector cell, and virtually disappears while the dimension of object or detector cell approaches a threshold, respectively. It is hoped that the preliminary data reported in this paper may provide insightful understanding of the differential phase contrast CT's characteristic in the detectability index and its comparison with that of the conventional attenuation-based CT.

Integrated circuit detector technology in abdominal CT: added value in obese patients.

PubMed

Morsbach, Fabian; Bickelhaupt, Sebastian; Rätzer, Susan; Schmidt, Bernhard; Alkadhi, Hatem

2014-02-01

The purpose of this article was to assess the effect of an integrated circuit (IC) detector for abdominal CT on image quality. In the first study part, an abdominal phantom was scanned with various extension rings using a CT scanner equipped with a conventional discrete circuit (DC) detector and on the same scanner with an IC detector (120 kVp, 150 effective mAs, and 75 effective mAs). In the second study part, 20 patients were included who underwent abdominal CT both with the IC detector and previously at similar protocol parameters (120 kVp tube current-time product and 150 reference mAs using automated tube current modulation) with the DC detector. Images were reconstructed with filtered back projection. Image quality in the phantom was higher for images acquired with the IC compared with the DC detector. There was a gradually increasing noise reduction with increasing phantom sizes, with the highest (37% in the largest phantom) at 75 effective mAs (p < 0.001). In patients, noise was overall significantly (p = 0.025) reduced by 6.4% using the IC detector. Similar to the phantom, there was a gradual increase in noise reduction to 7.9% in patients with a body mass index of 25 kg/m(2) or lower (p = 0.008). Significant correlation was found in patients between noise and abdominal diameter in DC detector images (r = 0.604, p = 0.005), whereas no such correlation was found for the IC detector (r = 0.427, p = 0.060). Use of an IC detector in abdominal CT improves image quality and reduces image noise, particularly in overweight and obese patients. This noise reduction has the potential for dose reduction in abdominal CT.

SU-E-J-97: Evaluation of Multi-Modality (CT/MR/PET) Image Registration Accuracy in Radiotherapy Planning.

PubMed

Sethi, A; Rusu, I; Surucu, M; Halama, J

2012-06-01

Evaluate accuracy of multi-modality image registration in radiotherapy planning process. A water-filled anthropomorphic head phantom containing eight 'donut-shaped' fiducial markers (3 internal + 5 external) was selected for this study. Seven image sets (3CTs, 3MRs and PET) of phantom were acquired and fused in a commercial treatment planning system. First, a narrow slice (0.75mm) baseline CT scan was acquired (CT1). Subsequently, the phantom was re-scanned with a coarse slice width = 1.5mm (CT2) and after subjecting phantom to rotation/displacement (CT3). Next, the phantom was scanned in a 1.5 Tesla MR scanner and three MR image sets (axial T1, axial T2, coronal T1) were acquired at 2mm slice width. Finally, the phantom and center of fiducials were doped with 18F and a PET scan was performed with 2mm cubic voxels. All image scans (CT/MR/PET) were fused to the baseline (CT1) data using automated mutual-information based fusion algorithm. Difference between centroids of fiducial markers in various image modalities was used to assess image registration accuracy. CT/CT image registration was superior to CT/MR and CT/PET: average CT/CT fusion error was found to be 0.64 ± 0.14 mm. Corresponding values for CT/MR and CT/PET fusion were 1.33 ± 0.71mm and 1.11 ± 0.37mm. Internal markers near the center of phantom fused better than external markers placed on the phantom surface. This was particularly true for the CT/MR and CT/PET. The inferior quality of external marker fusion indicates possible distortion effects toward the edges of MR image. Peripheral targets in the PET scan may be subject to parallax error caused by depth of interaction of photons in detectors. Current widespread use of multimodality imaging in radiotherapy planning calls for periodic quality assurance of image registration process. Such studies may help improve safety and accuracy in treatment planning. © 2012 American Association of Physicists in Medicine.

A MAPS Based Micro-Vertex Detector for the STAR Experiment

DOE PAGES

Schambach, Joachim; Anderssen, Eric; Contin, Giacomo; ...

2015-06-18

For the 2014 heavy ion run of RHIC a new micro-vertex detector called the Heavy Flavor Tracker (HFT) was installed in the STAR experiment. The HFT consists of three detector subsystems with various silicon technologies arranged in 4 approximately concentric cylinders close to the STAR interaction point designed to improve the STAR detector’s vertex resolution and extend its measurement capabilities in the heavy flavor domain. The two innermost HFT layers are placed at radii of 2.8 cm and 8 cm from the beam line. These layers are constructed with 400 high resolution sensors based on CMOS Monolithic Active Pixel Sensormore » (MAPS) technology arranged in 10-sensor ladders mounted on 10 thin carbon fiber sectors to cover a total silicon area of 0.16 m 2. Each sensor of this PiXeL (“PXL”) sub-detector combines a pixel array of 928 rows and 960 columns with a 20.7 μm pixel pitch together with front-end electronics and zero-suppression circuitry in one silicon die providing a sensitive area of ~3.8 cm 2. This sensor architecture features 185.6 μs readout time and 170 mW/cm 2 power dissipation. This low power dissipation allows the PXL detector to be air-cooled, and with the sensors thinned down to 50 μm results in a global material budget of only 0.4% radiation length per layer. A novel mechanical approach to detector insertion allows us to effectively install and integrate the PXL sub-detector within a 12 hour period during an on-going multi-month data taking period. The detector requirements, architecture and design, as well as the performance after installation, are presented in this paper.« less

Imaging the Parasinus Region with a Third-Generation Dual-Source CT and the Effect of Tin Filtration on Image Quality and Radiation Dose.

PubMed

Lell, M M; May, M S; Brand, M; Eller, A; Buder, T; Hofmann, E; Uder, M; Wuest, W

2015-07-01

CT is the imaging technique of choice in the evaluation of midface trauma or inflammatory disease. We performed a systematic evaluation of scan protocols to optimize image quality and radiation exposure on third-generation dual-source CT. CT protocols with different tube voltage (70-150 kV), current (25-300 reference mAs), prefiltration, pitch value, and rotation time were systematically evaluated. All images were reconstructed with iterative reconstruction (Advanced Modeled Iterative Reconstruction, level 2). To individually compare results with otherwise identical factors, we obtained all scans on a frozen human head. Conebeam CT was performed for image quality and dose comparison with multidetector row CT. Delineation of important anatomic structures and incidental pathologic conditions in the cadaver head was evaluated. One hundred kilovolts with tin prefiltration demonstrated the best compromise between dose and image quality. The most dose-effective combination for trauma imaging was Sn100 kV/250 mAs (volume CT dose index, 2.02 mGy), and for preoperative sinus surgery planning, Sn100 kV/150 mAs (volume CT dose index, 1.22 mGy). "Sn" indicates an additional prefiltration of the x-ray beam with a tin filter to constrict the energy spectrum. Exclusion of sinonasal disease was possible with even a lower dose by using Sn100 kV/25 mAs (volume CT dose index, 0.2 mGy). High image quality at very low dose levels can be achieved by using a Sn100-kV protocol with iterative reconstruction. The effective dose is comparable with that of conventional radiography, and the high image quality at even lower radiation exposure favors multidetector row CT over conebeam CT. © 2015 by American Journal of Neuroradiology.

Processing of CT sinograms acquired using a VRX detector

NASA Astrophysics Data System (ADS)

Jordan, Lawrence M.; DiBianca, Frank A.; Zou, Ping; Laughter, Joseph S.; Zeman, Herbert D.

2000-04-01

A 'variable resolution x-ray detector' (VRX) capable of resolving beyond 100 cycles/main a single dimension has been proposed by DiBianca, et al. The use of detectors of this design for computed-tomography (CT) imaging requires novel preprocessing of data to correct for the detector's non- uniform imaging characteristics over its range of view. This paper describes algorithms developed specifically to adjust VRX data for varying magnification, source-to-detector range and beam obliquity and to sharpen reconstructions by deconvolving the ray impulse function. The preprocessing also incorporates nonlinear interpolation of VRX raw data into canonical CT sinogram formats.

TU-H-CAMPUS-IeP2-03: Development of 3D Printed Coronary Phantoms for In-Vitro CT-FFR Validation Using Data from 320- Detector Row Coronary CT Angiography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ionita, C; Rudin, S; Bednarek, D

Purpose: To validate Computed Tomography Fractional Flow Reserve (CT-FFR) measurements with accurate 3D printed coronary phantoms. Methods: DICOM data from four phases in two patients imaged with a standard 320 × 0.5mm coronary CT acquisition (70–80% cardiac cycle) underwent semi-automated segmentation using a research workstation. Both patients had a >50% stenosis from the clinical image interpretation. Each volume was saved as a Stereo Lithographic (STL) file with 250 micron resolution. The 3D geometries were qualitatively assessed; the best of the four phases was 3D printed using a Stratasys Eden260V printer in Tango+, a rubber-like material that roughly emulates mechanical propertiesmore » of human vasculature. We connected the model to a programmable pump and measured the pressure drop using pressure sensors embedded proximal and distal to the arterial stenosis. Next, the STL files used for the 3D printed models were uploaded in the ANSYS meshing tool (ICEM CFD 16.1). A standard meshing process was applied and the meshed geometry was directly imported in the ANSYS Fluent for Computational Flow Dynamics simulations. The CFD simulations were used to calculate the CT-FFR and compared to the bench top FFR measured in the 3D printed phantoms. Results: FFR-CT measurements and phantoms were completed in within an hour after the segmentation. Patient 1 had a 60% stenosis that resulted in a CT-FFR of 0.68. The second case had a 50% stenosis and a CT-FFR of 0.75. The average bench top FFR measurements were 0.72 and 0.80, respectively. Conclusion: This pilot investigation demonstrated the use of a bench-top coronary model for CT-FFR validation. The measurements and the CFD simulations agreed within 6%. Project supported by Support: Toshiba America Medical Systems Corp.and NIH grant R01-EB002873. Project supported by Toshiba America Medical Systems Corp.and partial support from NIH grant R01-EB002873.« less

A prototype optical-CT system for PRESAGE 3D dosimeter readout

NASA Astrophysics Data System (ADS)

Miles, Devin; Yoon, Paul; Kodra, Jacob; Adamovics, John; Oldham, Mark

2017-05-01

This work introduces the Duke Integrated-lens Optical Scanner (DIOS), a prototype optical-CT system designed for convenient and low-cost readout of PRESAGE 3D dosimeters. A key novelty of the DIOS is the incorporation of a multi-purpose light-collimating tank (the LC-tank). The LC-tank collimates light from a point source, maintains parallel ray geometry through a dosimeter mounted inside the tank, and refocuses emergent light onto a CCD detector. A second purpose is to dramatically reduce the amount of refractive matched fluid required in prior optical-CT scanners. This is achieved by substituting large quantities of refractive-matched fluid with solid RI-matched polyurethane. The advantages of DIOS include eliminating the need for expensive telecentric lenses, and eliminating the impracticality of large volumes of RI matched fluid. The DIOS is potentially more susceptible to stray-light artifacts. Preliminary phantom testing shows promising agreement between PRESAGE/DIOS readout and prior commissioned optical-CT scanners, as well as with Eclipse dose calculations.

Analysis of deep inferior epigastric perforator (DIEP) arteries by using MDCTA: Comparison between 2 post-processing techniques.

PubMed

Saba, Luca; Atzeni, Matteo; Ribuffo, Diego; Mallarini, Giorgio; Suri, Jasjit S

2012-08-01

Our purpose was to compare two post-processing techniques, Maximum-Intensity-Projection (MIP) and Volume Rendering (VR) for the study of perforator arteries. Thirty patients who underwent Multi-Detector-Row CT Angiography (MDCTA) between February 2010 and May 2010 were retrospectively analyzed. For each patient and for each reconstruction method, the image quality was evaluated and the inter- and intra-observer agreement was calculated according to the Cohen statistics. The Hounsfield Unit (HU) value in the common femoral artery was quantified and the correlation (Pearson Statistic) between image quality and HU value was explored. The Pearson r between the right and left common femoral artery was excellent (r=0.955). The highest image quality score was obtained using MIP for both observers (total value 75, with a mean value 2.67 for observer 1 and total value of 79 and a mean value of 2.82 for observer 2). The highest agreement between the two observers was detected using the MIP protocol with a Cohen kappa value of 0.856. The ROC area under the curve (Az) for the VR is 0.786 (0.086 SD; p value=0.0009) whereas the ROC area under the curve (Az) for the MIP is 0.0928 (0.051 SD; p value=0.0001). MIP showed the optimal inter- and intra-observer agreement and the highest quality scores and therefore should be used as post-processing techniques in the analysis of perforating arteries. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Intramural location and size of arterial calcification are associated with stenosis at carotid bifurcation.

PubMed

Yamada, Shigeki; Oshima, Marie; Watanabe, Yoshihiko; Ogata, Hideki; Hashimoto, Kenji; Miyake, Hidenori

2014-06-01

The purpose of this study was to investigate the association between internal carotid artery (ICA) stenosis and intramural location and size of calcification at the ICA origins and the origins of the cervical arteries proximal to the ICA. A total of 1139 ICAs were evaluated stenosis and calcification on the multi-detector row CT angiography. The intramural location was categorized into none, outside and inside location. The calcification size was evaluated on the 4-point grading scale. The multivariate analyses were adjusted for age, serum creatinine level, hypertension, hyperlipidemia, diabetes mellitus, smoking and alcohol habits. Outside calcification at the ICA origins showed the highest multivariate odds ratio (OR) for the presence of ICA stenosis (30.0) and severe calcification (a semicircle or more of calcification at the arterial cross-sectional surfaces) did the second (14.3). In the subgroups of >70% ICA stenosis, the multivariate OR of outside location increased to 44.8 and that of severe calcification also increased to 32.7. Four of 5 calcified carotid plaque specimens extracted by carotid endarterectomy were histologically confirmed to be calcified burdens located outside the internal elastic lamia which were defined as arterial medial calcification. ICA stenosis was strongly associated with severe calcification located mainly outside the carotid plaque. Outside calcification at the ICA origins should be evaluated separately from inside calcification, as a marker for the ICA stenosis. Additionally, we found that calcification at the origins of the cervical arteries proximal to the ICA was significantly associated with the ICA stenosis. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Combination of CT scanning and fluoroscopy imaging on a flat-panel CT scanner

NASA Astrophysics Data System (ADS)

Grasruck, M.; Gupta, R.; Reichardt, B.; Suess, Ch.; Schmidt, B.; Stierstorfer, K.; Popescu, S.; Brady, T.; Flohr, T.

2006-03-01

We developed and evaluated a prototype flat-panel detector based Volume CT (fpVCT) scanner. The fpVCT scanner consists of a Varian 4030CB a-Si flat-panel detector mounted in a multi slice CT-gantry (Siemens Medical Solutions). It provides a 25 cm field of view with 18 cm z-coverage at the isocenter. In addition to the standard tomographic scanning, fpVCT allows two new scan modes: (1) fluoroscopic imaging from any arbitrary rotation angle, and (2) continuous, time-resolved tomographic scanning of a dynamically changing viewing volume. Fluoroscopic imaging is feasible by modifying the standard CT gantry so that the imaging chain can be oriented along any user-selected rotation angle. Scanning with a stationary gantry, after it has been oriented, is equivalent to a conventional fluoroscopic examination. This scan mode enables combined use of high-resolution tomography and real-time fluoroscopy with a clinically usable field of view in the z direction. The second scan mode allows continuous observation of a timeevolving process such as perfusion. The gantry can be continuously rotated for up to 80 sec, with the rotation time ranging from 3 to 20 sec, to gather projection images of a dynamic process. The projection data, that provides a temporal log of the viewing volume, is then converted into multiple image stacks that capture the temporal evolution of a dynamic process. Studies using phantoms, ex vivo specimens, and live animals have confirmed that these new scanning modes are clinically usable and offer a unique view of the anatomy and physiology that heretofore has not been feasible using static CT scanning. At the current level of image quality and temporal resolution, several clinical applications such a dynamic angiography, tumor enhancement pattern and vascularity studies, organ perfusion, and interventional applications are in reach.

Four-arm variable-resolution x-ray detector for CT target imaging

NASA Astrophysics Data System (ADS)

DiBianca, Frank A.; Gulabani, Daya; Jordan, Lawrence M.; Vangala, Sravanthi; Rendon, David; Laughter, Joseph S.; Melnyk, Roman; Gaber, M. W.; Keyes, Gary S.

2005-04-01

The basic VRX technique boosts spatial resolution of a CT scanner in the scan plane by two or more orders of magnitude by reducing the angle of incidence of the x-ray beam with respect to the detector surface. A four-arm Variable-Resolution X-ray (VRX) detector has been developed for CT scanning. The detector allows for "target imaging" in which an area of interest is scanned at higher resolution than the remainder of the subject, yielding even higher resolution for the focal area than that obtained from the basic VRX technique. The new VRX-CT detector comprises four quasi-identical arms each containing six 24-cell modules (576 cells total). The modules are made of individual custom CdWO4 scintillators optically-coupled to custom photodiode arrays. The maximum scan field is 40 cm for a magnification of 1.4. A significant advantage of the four-arm geometry is that it can transform quickly to the two-arm, or even the single-arm geometry, for comparison studies. These simpler geometries have already been shown experimentally to yield in-plane CT detector resolution exceeding 60 cy/mm (<8μ) for small fields of view. Geometrical size and resolution limits of the target VRX field are calculated. Two-arm VRX-CT data are used to simulate and establish the feasibility of VRX CT target imaging. A prototype target VRX-CT scanner has been built and is undergoing initial testing.

Carotid artery stents on CT angiography: in vitro comparison of different stent designs and sizes using 16-, 64- and 320-row CT scanners.

PubMed

Lettau, Michael; Kotter, Elmar; Bendszus, Martin; Hähnel, Stefan

2014-10-01

CT angiography (CTA) is an increasingly used method for evaluation of stented vessel segments. Our aim was to compare the appearance of different carotid artery stents in vitro on CTA using different CT scanners. Of particular interest was the measurement of artificial lumen narrowing (ALN) caused by the stent material within the stented vessel segment to determine whether CTA can be used to detect in-stent restenosis. CTA appearances of 16 carotid artery stents of different designs and sizes (4.0 to 11.0 mm) were investigated in vitro. CTA was performed using 16-, 64- and 320-row CT scanners. For each stent, artificial lumen narrowing (ALN) was calculated. ALN ranged from 18.77% to 59.86%. ALN in different stents differed significantly. In most stents, ALN decreased with increasing stent diameter. In all but one stents, ALN using sharp image kernels was significantly lower than ALN using medium image kernels. Considering all stents, ALN did not significantly differ using different CT scanners or imaging protocols. CTA evaluation of vessel patency after stent placement is possible, but is considerably impaired by ALN. Investigators should be informed about the method of choice for every stent and stent manufacturers should be aware of potential artifacts caused by their stents during noninvasive diagnostic methods such as CTA. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Electronic noise in CT detectors: Impact on image noise and artifacts.

PubMed

Duan, Xinhui; Wang, Jia; Leng, Shuai; Schmidt, Bernhard; Allmendinger, Thomas; Grant, Katharine; Flohr, Thomas; McCollough, Cynthia H

2013-10-01

The objective of our study was to evaluate in phantoms the differences in CT image noise and artifact level between two types of commercial CT detectors: one with distributed electronics (conventional) and one with integrated electronics intended to decrease system electronic noise. Cylindric water phantoms of 20, 30, and 40 cm in diameter were scanned using two CT scanners, one equipped with integrated detector electronics and one with distributed detector electronics. All other scanning parameters were identical. Scans were acquired at four tube potentials and 10 tube currents. Semianthropomorphic phantoms were scanned to mimic the shoulder and abdominal regions. Images of two patients were also selected to show the clinical values of the integrated detector. Reduction of image noise with the integrated detector depended on phantom size, tube potential, and tube current. Scans that had low detected signal had the greatest reductions in noise, up to 40% for a 30-cm phantom scanned using 80 kV. This noise reduction translated into up to 50% in dose reduction to achieve equivalent image noise. Streak artifacts through regions of high attenuation were reduced by up to 45% on scans obtained using the integrated detector. Patient images also showed superior image quality for the integrated detector. For the same applied radiation level, the use of integrated electronics in a CT detector showed a substantially reduced level of electronic noise, resulting in reductions in image noise and artifacts, compared with detectors having distributed electronics.

Multi-national findings on radiation protection of children.

PubMed

Rehani, Madan M

2014-10-01

This article reviews issues of radiation protection in children in 52 low-resource countries. Extensive information was obtained through a survey by the International Atomic Energy Agency (IAEA); wide-ranging information was available from 40 countries and data from the other countries pertained to frequency of pediatric CT examinations. Of note is that multi-detector CT (MDCT) was available in 77% of responses to the survey, typically nodal centers in these countries. Nearly 75% of these scanners were reported to have dose displays. The pediatric CT usage was lower in European facilities as compared to Asian and African facilities, where usage was twice as high. The most frequently scanned body part was the head. Frequent use of 120 kVp was reported in children. The ratio of maximum to minimum CT dose index volume (CTDIvol) values varied between 15 for abdomen CT in the age group 5-10 years and 100 for chest CT in the age group <1 year. In 8% of the CT systems, CTDI values for pediatric patients were higher than those for adults in at least one age group and for one type of examination. Use of adult protocols for children was associated with CTDIw or CTDIvol values in children that were double those of adults for head and chest examination and 50% higher for abdomen examination. Patient dose records were kept in nearly half of the facilities, with the highest frequency in Europe (55% of participating facilities), and in 49% of Asian, 36% of Latin American and 14% of African facilities. The analysis of the first-choice examinations in seven clinical conditions showed that practice was in accordance with guidelines for only three of seven specified clinical conditions.

Performance simulation of an x-ray detector for spectral CT with combined Si and Cd[Zn]Te detection layers.

PubMed

Herrmann, Christoph; Engel, Klaus-Jürgen; Wiegert, Jens

2010-12-21

The most obvious problem in obtaining spectral information with energy-resolving photon counting detectors in clinical computed tomography (CT) is the huge x-ray flux present in conventional CT systems. At high tube voltages (e.g. 140 kVp), despite the beam shaper, this flux can be close to 10⁹ Mcps mm⁻² in the direct beam or in regions behind the object, which are close to the direct beam. Without accepting the drawbacks of truncated reconstruction, i.e. estimating missing direct-beam projection data, a photon-counting energy-resolving detector has to be able to deal with such high count rates. Sub-structuring pixels into sub-pixels is not enough to reduce the count rate per pixel to values that today's direct converting Cd[Zn]Te material can cope with (≤ 10 Mcps in an optimistic view). Below 300 µm pixel pitch, x-ray cross-talk (Compton scatter and K-escape) and the effect of charge diffusion between pixels are problematic. By organising the detector in several different layers, the count rate can be further reduced. However this alone does not limit the count rates to the required level, since the high stopping power of the material becomes a disadvantage in the layered approach: a simple absorption calculation for 300 µm pixel pitch shows that the required layer thickness of below 10 Mcps/pixel for the top layers in the direct beam is significantly below 100 µm. In a horizontal multi-layer detector, such thin layers are very difficult to manufacture due to the brittleness of Cd[Zn]Te. In a vertical configuration (also called edge-on illumination (Ludqvist et al 2001 IEEE Trans. Nucl. Sci. 48 1530-6, Roessl et al 2008 IEEE NSS-MIC-RTSD 2008, Conf. Rec. Talk NM2-3)), bonding of the readout electronics (with pixel pitches below 100 µm) is not straightforward although it has already been done successfully (Pellegrini et al 2004 IEEE NSS MIC 2004 pp 2104-9). Obviously, for the top detector layers, materials with lower stopping power would be advantageous. The possible choices are, however, quite limited, since only 'mature' materials, which operate at room temperature and can be manufactured reliably should reasonably be considered. Since GaAs is still known to cause reliability problems, the simplest choice is Si, however with the drawback of strong Compton scatter which can cause considerable inter-pixel cross-talk. To investigate the potential and the problems of Si in a multi-layer detector, in this paper the combination of top detector layers made of Si with lower layers made of Cd[Zn]Te is studied by using Monte Carlo simulated detector responses. It is found that the inter-pixel cross-talk due to Compton scatter is indeed very high; however, with an appropriate cross-talk correction scheme, which is also described, the negative effects of cross-talk are shown to be removed to a very large extent.

New technology in the management of liver trauma

PubMed Central

Chatoupis, Konstantinos; Papadopoulou, Glikeria; Kaskarelis, Ioannis

2013-01-01

The liver is the second most frequently injured solid organ in patients with blunt abdominal trauma. Hence the diagnosis and clinical assessment of hepatic trauma is of great importance because of the relationship of the liver to high morbidity and mortality. Multi detector-row computed tomography is the main diagnostic modality for the examination of hepatic parenchyma and other associated organ injuries, such as acute or delayed complications. Based on clinical and radiological findings, the majority of patients are managed conservatively, with the most important criterion of surgical therapy being hemodynamic instability. Radiologists must demonstrate a high knowledge of imaging recommendations and standardization of reporting to enable the selection of the appropriate treatment algorithm. Transcatheter embolization therapy is a method of great potential for the management of patients with traumatic hepatic injuries. PMID:24714662

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schambach, Joachim; Anderssen, Eric; Contin, Giacomo

For the 2014 heavy ion run of RHIC a new micro-vertex detector called the Heavy Flavor Tracker (HFT) was installed in the STAR experiment. The HFT consists of three detector subsystems with various silicon technologies arranged in 4 approximately concentric cylinders close to the STAR interaction point designed to improve the STAR detector’s vertex resolution and extend its measurement capabilities in the heavy flavor domain. The two innermost HFT layers are placed at radii of 2.8 cm and 8 cm from the beam line. These layers are constructed with 400 high resolution sensors based on CMOS Monolithic Active Pixel Sensormore » (MAPS) technology arranged in 10-sensor ladders mounted on 10 thin carbon fiber sectors to cover a total silicon area of 0.16 m 2. Each sensor of this PiXeL (“PXL”) sub-detector combines a pixel array of 928 rows and 960 columns with a 20.7 μm pixel pitch together with front-end electronics and zero-suppression circuitry in one silicon die providing a sensitive area of ~3.8 cm 2. This sensor architecture features 185.6 μs readout time and 170 mW/cm 2 power dissipation. This low power dissipation allows the PXL detector to be air-cooled, and with the sensors thinned down to 50 μm results in a global material budget of only 0.4% radiation length per layer. A novel mechanical approach to detector insertion allows us to effectively install and integrate the PXL sub-detector within a 12 hour period during an on-going multi-month data taking period. The detector requirements, architecture and design, as well as the performance after installation, are presented in this paper.« less

Measuring radiation dose in computed tomography using elliptic phantom and free-in-air, and evaluating iterative metal artifact reduction algorithm

NASA Astrophysics Data System (ADS)

Morgan, Ashraf

The need for an accurate and reliable way for measuring patient dose in multi-row detector computed tomography (MDCT) has increased significantly. This research was focusing on the possibility of measuring CT dose in air to estimate Computed Tomography Dose Index (CTDI) for routine quality control purposes. New elliptic CTDI phantom that better represent human geometry was manufactured for investigating the effect of the subject shape on measured CTDI. Monte Carlo simulation was utilized in order to determine the dose distribution in comparison to the traditional cylindrical CTDI phantom. This research also investigated the effect of Siemens health care newly developed iMAR (iterative metal artifact reduction) algorithm, arthroplasty phantom was designed and manufactured that purpose. The design of new phantoms was part of the research as they mimic the human geometry more than the existing CTDI phantom. The standard CTDI phantom is a right cylinder that does not adequately represent the geometry of the majority of the patient population. Any dose reduction algorithm that is used during patient scan will not be utilized when scanning the CTDI phantom, so a better-designed phantom will allow the use of dose reduction algorithms when measuring dose, which leads to better dose estimation and/or better understanding of dose delivery. Doses from a standard CTDI phantom and the newly-designed phantoms were compared to doses measured in air. Iterative reconstruction is a promising technique in MDCT dose reduction and artifacts correction. Iterative reconstruction algorithms have been developed to address specific imaging tasks as is the case with Iterative Metal Artifact Reduction or iMAR which was developed by Siemens and is to be in use with the companys future computed tomography platform. The goal of iMAR is to reduce metal artifact when imaging patients with metal implants and recover CT number of tissues adjacent to the implant. This research evaluated iMAR capability of recovering CT numbers and reducing noise. Also, the use of iMAR should allow using lower tube voltage instead of 140 KVp which is used frequently to image patients with shoulder implants. The evaluations of image quality and dose reduction were carried out using an arthroplasty phantom.

Adrenal and nephrogenic hypertension: an image quality study of low tube voltage, low-concentration contrast media combined with adaptive statistical iterative reconstruction.

PubMed

Li, Zhen; Li, Qiong; Shen, Yaqi; Li, Anqin; Li, Haojie; Liang, Lili; Hu, Yao; Hu, Xuemei; Hu, Daoyu

2016-09-01

The aim of this study was to investigate the effect of using low tube voltage, low-concentration contrast media and adaptive statistical iterative reconstruction (ASIR) for reducing the radiation and iodine contrast doses in adrenal and nephrogenic hypertension patients. A total of 148 hypertension patients who were suspected for adrenal lesions or renal artery stenoses were assigned to two groups and. Group A (n=74) underwent a low tube voltage, low molecular weight dextran enhanced multi-detector row spiral CT (MDCT) (80 kVp, 270 mg I/mL contrast agent), and the raw data were reconstructed with standard filtered back projection (FBP) and ASIR at four different levels of blending (20%, 40%, 60% and 80%, respectively). The control group (Group B, n=74) underwent conventional MDCT (120 kVp, 370 mg I/mL contrast agent), and the data were reconstructed with FBP. The CT values, standard deviation (SD), signal-noise-ratio (SNR) and contrast-noise-ratio (CNR) were measured in the renal vessels, normal adrenal tissue, adrenal neoplasms and subcutaneous fat. The volume CT dose index (CTDIvol ) and dose length product (DLP) were recorded, and an effective dose (ED) was obtained. Two-tailed independent t-tests, paired Chi-square tests and Kappa consistency tests were used for statistical analysis of the data. The CTDIvol , DLP and total iodine dose in group A were decreased by 47.8%, 49.0% and 26.07%, respectively, compared to group B (P<.001). In the qualitative quality analysis, the radiologists rated the 60% ASIR the highest. The mean value of noise (SD) was significantly lower in the 40%, 60% and 80% ASIR-A groups compared with FBP-B for all comparisons. Compared to FBP-B, CNR was significantly higher, with 40%, 60% and 80% ASIR in renal artery stems (P<.05). Compared with FBP-B, a significant increase in the SNR of 40%, 60%, or 80% ASIR was observed in all cases (P<.05). Compared with conventional protocols, the use of low tube voltage, low-concentration contrast media and 60% ASIR provides similar enhancement and image quality with a reduced radiation dose and contrast iodine dose. © 2016 John Wiley & Sons Ltd.

Ultra-High-Resolution Computed Tomography of the Lung: Image Quality of a Prototype Scanner

PubMed Central

Kakinuma, Ryutaro; Moriyama, Noriyuki; Muramatsu, Yukio; Gomi, Shiho; Suzuki, Masahiro; Nagasawa, Hirobumi; Kusumoto, Masahiko; Aso, Tomohiko; Muramatsu, Yoshihisa; Tsuchida, Takaaki; Tsuta, Koji; Maeshima, Akiko Miyagi; Tochigi, Naobumi; Watanabe, Shun-ichi; Sugihara, Naoki; Tsukagoshi, Shinsuke; Saito, Yasuo; Kazama, Masahiro; Ashizawa, Kazuto; Awai, Kazuo; Honda, Osamu; Ishikawa, Hiroyuki; Koizumi, Naoya; Komoto, Daisuke; Moriya, Hiroshi; Oda, Seitaro; Oshiro, Yasuji; Yanagawa, Masahiro; Tomiyama, Noriyuki; Asamura, Hisao

2015-01-01

Purpose The image noise and image quality of a prototype ultra-high-resolution computed tomography (U-HRCT) scanner was evaluated and compared with those of conventional high-resolution CT (C-HRCT) scanners. Materials and Methods This study was approved by the institutional review board. A U-HRCT scanner prototype with 0.25 mm x 4 rows and operating at 120 mAs was used. The C-HRCT images were obtained using a 0.5 mm x 16 or 0.5 mm x 64 detector-row CT scanner operating at 150 mAs. Images from both scanners were reconstructed at 0.1-mm intervals; the slice thickness was 0.25 mm for the U-HRCT scanner and 0.5 mm for the C-HRCT scanners. For both scanners, the display field of view was 80 mm. The image noise of each scanner was evaluated using a phantom. U-HRCT and C-HRCT images of 53 images selected from 37 lung nodules were then observed and graded using a 5-point score by 10 board-certified thoracic radiologists. The images were presented to the observers randomly and in a blinded manner. Results The image noise for U-HRCT (100.87 ± 0.51 Hounsfield units [HU]) was greater than that for C-HRCT (40.41 ± 0.52 HU; P < .0001). The image quality of U-HRCT was graded as superior to that of C-HRCT (P < .0001) for all of the following parameters that were examined: margins of subsolid and solid nodules, edges of solid components and pulmonary vessels in subsolid nodules, air bronchograms, pleural indentations, margins of pulmonary vessels, edges of bronchi, and interlobar fissures. Conclusion Despite a larger image noise, the prototype U-HRCT scanner had a significantly better image quality than the C-HRCT scanners. PMID:26352144

Empirical projection-based basis-component decomposition method

NASA Astrophysics Data System (ADS)

Brendel, Bernhard; Roessl, Ewald; Schlomka, Jens-Peter; Proksa, Roland

2009-02-01

Advances in the development of semiconductor based, photon-counting x-ray detectors stimulate research in the domain of energy-resolving pre-clinical and clinical computed tomography (CT). For counting detectors acquiring x-ray attenuation in at least three different energy windows, an extended basis component decomposition can be performed in which in addition to the conventional approach of Alvarez and Macovski a third basis component is introduced, e.g., a gadolinium based CT contrast material. After the decomposition of the measured projection data into the basis component projections, conventional filtered-backprojection reconstruction is performed to obtain the basis-component images. In recent work, this basis component decomposition was obtained by maximizing the likelihood-function of the measurements. This procedure is time consuming and often unstable for excessively noisy data or low intrinsic energy resolution of the detector. Therefore, alternative procedures are of interest. Here, we introduce a generalization of the idea of empirical dual-energy processing published by Stenner et al. to multi-energy, photon-counting CT raw data. Instead of working in the image-domain, we use prior spectral knowledge about the acquisition system (tube spectra, bin sensitivities) to parameterize the line-integrals of the basis component decomposition directly in the projection domain. We compare this empirical approach with the maximum-likelihood (ML) approach considering image noise and image bias (artifacts) and see that only moderate noise increase is to be expected for small bias in the empirical approach. Given the drastic reduction of pre-processing time, the empirical approach is considered a viable alternative to the ML approach.

Coronary Artery Disease: Analysis of Diagnostic Performance of CT Perfusion and MR Perfusion Imaging in Comparison with Quantitative Coronary Angiography and SPECT-Multicenter Prospective Trial.

PubMed

Rief, Matthias; Chen, Marcus Y; Vavere, Andrea L; Kendziora, Benjamin; Miller, Julie M; Bandettini, W Patricia; Cox, Christopher; George, Richard T; Lima, João; Di Carli, Marcelo; Plotkin, Michail; Zimmermann, Elke; Laule, Michael; Schlattmann, Peter; Arai, Andrew E; Dewey, Marc

2018-02-01

Purpose To compare the diagnostic performance of stress myocardial computed tomography (CT) perfusion with that of stress myocardial magnetic resonance (MR) perfusion imaging in the detection of coronary artery disease (CAD). Materials and Methods All patients gave written informed consent prior to inclusion in this institutional review board-approved study. This two-center substudy of the prospective Combined Noninvasive Coronary Angiography and Myocardial Perfusion Imaging Using 320-Detector Row Computed Tomography (CORE320) multicenter trial included 92 patients (mean age, 63.1 years ± 8.1 [standard deviation]; 73% male). All patients underwent perfusion CT and perfusion MR imaging with either adenosine or regadenoson stress. The predefined reference standards were combined quantitative coronary angiography (QCA) and single-photon emission CT (SPECT) or QCA alone. Results from coronary CT angiography were not included, and diagnostic performance was evaluated with the Mantel-Haenszel test stratified by disease status. Results The prevalence of CAD was 39% (36 of 92) according to QCA and SPECT and 64% (59 of 92) according to QCA alone. When compared with QCA and SPECT, per-patient diagnostic accuracy of perfusion CT and perfusion MR imaging was 63% (58 of 92) and 75% (69 of 92), respectively (P = .11); sensitivity was 92% (33 of 36) and 83% (30 of 36), respectively (P = .45); and specificity was 45% (25 of 56) and 70% (39 of 56), respectively (P < .01). When compared with QCA alone, diagnostic accuracy of CT perfusion and MR perfusion imaging was 82% (75 of 92) and 74% (68 of 92), respectively (P = .27); sensitivity was 90% (53 of 59) and 69% (41 of 59), respectively (P < .01); and specificity was 67% (22 of 33) and 82% (27 of 33), respectively (P = .27). Conclusion This multicenter study shows that the diagnostic performance of perfusion CT is similar to that of perfusion MR imaging in the detection of CAD. © RSNA, 2017 Online supplemental material is available for this article.

Fast Confocal Raman Imaging Using a 2-D Multifocal Array for Parallel Hyperspectral Detection.

PubMed

Kong, Lingbo; Navas-Moreno, Maria; Chan, James W

2016-01-19

We present the development of a novel confocal hyperspectral Raman microscope capable of imaging at speeds up to 100 times faster than conventional point-scan Raman microscopy under high noise conditions. The microscope utilizes scanning galvomirrors to generate a two-dimensional (2-D) multifocal array at the sample plane, generating Raman signals simultaneously at each focus of the array pattern. The signals are combined into a single beam and delivered through a confocal pinhole before being focused through the slit of a spectrometer. To separate the signals from each row of the array, a synchronized scan mirror placed in front of the spectrometer slit positions the Raman signals onto different pixel rows of the detector. We devised an approach to deconvolve the superimposed signals and retrieve the individual spectra at each focal position within a given row. The galvomirrors were programmed to scan different focal arrays following Hadamard encoding patterns. A key feature of the Hadamard detection is the reconstruction of individual spectra with improved signal-to-noise ratio. Using polystyrene beads as test samples, we demonstrated not only that our system images faster than a conventional point-scan method but that it is especially advantageous under noisy conditions, such as when the CCD detector operates at fast read-out rates and high temperatures. This is the first demonstration of multifocal confocal Raman imaging in which parallel spectral detection is implemented along both axes of the CCD detector chip. We envision this novel 2-D multifocal spectral detection technique can be used to develop faster imaging spontaneous Raman microscopes with lower cost detectors.

A new timing detector for the CT-PPS project

NASA Astrophysics Data System (ADS)

Arcidiacono, R.; Cms; TOTEM Collaborations

2017-02-01

The CT-PPS detector will be installed close to the beam line on both sides of CMS, 200 m downstream the interaction point. This detector will measure forward scattered protons, allowing detailed studies of diffractive hadron physics and Central Exclusive Production. The main components of the CT-PPS detector are a silicon tracking system and a timing system. In this contribution we present the proposal of an innovative solution for the timing system, based on Ultra-Fast Silicon Detectors (UFSD). UFSD are a novel concept of silicon detectors potentially able to obtain the necessary time resolution (∼20 ps on the proton arrival time). The use of UFSD has also other attractive features as its material budget is small and the pixel geometries can be tailored to the precise physics distribution of protons. UFSD prototypes for CT-PPS have been designed by CNM (Barcelona) and FBK (Trento): we will present the status of the sensor productions and of the low-noise front-end electronics currently under development and test.

High-definition multidetector computed tomography for evaluation of coronary artery stents: comparison to standard-definition 64-detector row computed tomography.

PubMed

Min, James K; Swaminathan, Rajesh V; Vass, Melissa; Gallagher, Scott; Weinsaft, Jonathan W

2009-01-01

The assessment of coronary stents with present-generation 64-detector row computed tomography scanners that use filtered backprojection and operating at standard definition of 0.5-0.75 mm (standard definition, SDCT) is limited by imaging artifacts and noise. We evaluated the performance of a novel, high-definition 64-slice CT scanner (HDCT), with improved spatial resolution (0.23 mm) and applied statistical iterative reconstruction (ASIR) for evaluation of coronary artery stents. HDCT and SDCT stent imaging was performed with the use of an ex vivo phantom. HDCT was compared with SDCT with both smooth and sharp kernels for stent intraluminal diameter, intraluminal area, and image noise. Intrastent visualization was assessed with an ASIR algorithm on HDCT scans, compared with the filtered backprojection algorithms by SDCT. Six coronary stents (2.5, 2.5, 2.75, 3.0, 3.5, 4.0mm) were analyzed by 2 independent readers. Interobserver correlation was high for both HDCT and SDCT. HDCT yielded substantially larger luminal area visualization compared with SDCT, both for smooth (29.4+/-14.5 versus 20.1+/-13.0; P<0.001) and sharp (32.0+/-15.2 versus 25.5+/-12.0; P<0.001) kernels. Stent diameter was higher with HDCT compared with SDCT, for both smooth (1.54+/-0.59 versus1.00+/-0.50; P<0.0001) and detailed (1.47+/-0.65 versus 1.08+/-0.54; P<0.0001) kernels. With detailed kernels, HDCT scans that used algorithms showed a trend toward decreased image noise compared with SDCT-filtered backprojection algorithms. On the basis of this ex vivo study, HDCT provides superior detection of intrastent luminal area and diameter visualization, compared with SDCT. ASIR image reconstruction techniques for HDCT scans enhance the in-stent assessment while decreasing image noise.

Development of an iterative reconstruction method to overcome 2D detector low resolution limitations in MLC leaf position error detection for 3D dose verification in IMRT.

PubMed

Visser, R; Godart, J; Wauben, D J L; Langendijk, J A; Van't Veld, A A; Korevaar, E W

2016-05-21

The objective of this study was to introduce a new iterative method to reconstruct multi leaf collimator (MLC) positions based on low resolution ionization detector array measurements and to evaluate its error detection performance. The iterative reconstruction method consists of a fluence model, a detector model and an optimizer. Expected detector response was calculated using a radiotherapy treatment plan in combination with the fluence model and detector model. MLC leaf positions were reconstructed by minimizing differences between expected and measured detector response. The iterative reconstruction method was evaluated for an Elekta SLi with 10.0 mm MLC leafs in combination with the COMPASS system and the MatriXX Evolution (IBA Dosimetry) detector with a spacing of 7.62 mm. The detector was positioned in such a way that each leaf pair of the MLC was aligned with one row of ionization chambers. Known leaf displacements were introduced in various field geometries ranging from  -10.0 mm to 10.0 mm. Error detection performance was tested for MLC leaf position dependency relative to the detector position, gantry angle dependency, monitor unit dependency, and for ten clinical intensity modulated radiotherapy (IMRT) treatment beams. For one clinical head and neck IMRT treatment beam, influence of the iterative reconstruction method on existing 3D dose reconstruction artifacts was evaluated. The described iterative reconstruction method was capable of individual MLC leaf position reconstruction with millimeter accuracy, independent of the relative detector position within the range of clinically applied MU's for IMRT. Dose reconstruction artifacts in a clinical IMRT treatment beam were considerably reduced as compared to the current dose verification procedure. The iterative reconstruction method allows high accuracy 3D dose verification by including actual MLC leaf positions reconstructed from low resolution 2D measurements.

Geometric correction methods for Timepix based large area detectors

NASA Astrophysics Data System (ADS)

Zemlicka, J.; Dudak, J.; Karch, J.; Krejci, F.

2017-01-01

X-ray micro radiography with the hybrid pixel detectors provides versatile tool for the object inspection in various fields of science. It has proven itself especially suitable for the samples with low intrinsic attenuation contrast (e.g. soft tissue in biology, plastics in material sciences, thin paint layers in cultural heritage, etc.). The limited size of single Medipix type detector (1.96 cm2) was recently overcome by the construction of large area detectors WidePIX assembled of Timepix chips equipped with edgeless silicon sensors. The largest already built device consists of 100 chips and provides fully sensitive area of 14.3 × 14.3 cm2 without any physical gaps between sensors. The pixel resolution of this device is 2560 × 2560 pixels (6.5 Mpix). The unique modular detector layout requires special processing of acquired data to avoid occurring image distortions. It is necessary to use several geometric compensations after standard corrections methods typical for this type of pixel detectors (i.e. flat-field, beam hardening correction). The proposed geometric compensations cover both concept features and particular detector assembly misalignment of individual chip rows of large area detectors based on Timepix assemblies. The former deals with larger border pixels in individual edgeless sensors and their behaviour while the latter grapple with shifts, tilts and steps between detector rows. The real position of all pixels is defined in Cartesian coordinate system and together with non-binary reliability mask it is used for the final image interpolation. The results of geometric corrections for test wire phantoms and paleo botanic material are presented in this article.

Image Based Mango Fruit Detection, Localisation and Yield Estimation Using Multiple View Geometry

PubMed Central

Stein, Madeleine; Bargoti, Suchet; Underwood, James

2016-01-01

This paper presents a novel multi-sensor framework to efficiently identify, track, localise and map every piece of fruit in a commercial mango orchard. A multiple viewpoint approach is used to solve the problem of occlusion, thus avoiding the need for labour-intensive field calibration to estimate actual yield. Fruit are detected in images using a state-of-the-art faster R-CNN detector, and pair-wise correspondences are established between images using trajectory data provided by a navigation system. A novel LiDAR component automatically generates image masks for each canopy, allowing each fruit to be associated with the corresponding tree. The tracked fruit are triangulated to locate them in 3D, enabling a number of spatial statistics per tree, row or orchard block. A total of 522 trees and 71,609 mangoes were scanned on a Calypso mango orchard near Bundaberg, Queensland, Australia, with 16 trees counted by hand for validation, both on the tree and after harvest. The results show that single, dual and multi-view methods can all provide precise yield estimates, but only the proposed multi-view approach can do so without calibration, with an error rate of only 1.36% for individual trees. PMID:27854271

Investigation of energy weighting using an energy discriminating photon counting detector for breast CT

PubMed Central

Kalluri, Kesava S.; Mahd, Mufeed; Glick, Stephen J.

2013-01-01

Purpose: Breast CT is an emerging imaging technique that can portray the breast in 3D and improve visualization of important diagnostic features. Early clinical studies have suggested that breast CT has sufficient spatial and contrast resolution for accurate detection of masses and microcalcifications in the breast, reducing structural overlap that is often a limiting factor in reading mammographic images. For a number of reasons, image quality in breast CT may be improved by use of an energy resolving photon counting detector. In this study, the authors investigate the improvements in image quality obtained when using energy weighting with an energy resolving photon counting detector as compared to that with a conventional energy integrating detector. Methods: Using computer simulation, realistic CT images of multiple breast phantoms were generated. The simulation modeled a prototype breast CT system using an amorphous silicon (a-Si), CsI based energy integrating detector with different x-ray spectra, and a hypothetical, ideal CZT based photon counting detector with capability of energy discrimination. Three biological signals of interest were modeled as spherical lesions and inserted into breast phantoms; hydroxyapatite (HA) to represent microcalcification, infiltrating ductal carcinoma (IDC), and iodine enhanced infiltrating ductal carcinoma (IIDC). Signal-to-noise ratio (SNR) of these three lesions was measured from the CT reconstructions. In addition, a psychophysical study was conducted to evaluate observer performance in detecting microcalcifications embedded into a realistic anthropomorphic breast phantom. Results: In the energy range tested, improvements in SNR with a photon counting detector using energy weighting was higher (than the energy integrating detector method) by 30%–63% and 4%–34%, for HA and IDC lesions and 12%–30% (with Al filtration) and 32%–38% (with Ce filtration) for the IIDC lesion, respectively. The average area under the receiver operating characteristic curve (AUC) for detection of microcalcifications was higher by greater than 19% (for the different energy weighting methods tested) as compared to the AUC obtained with an energy integrating detector. Conclusions: This study showed that breast CT with a CZT photon counting detector using energy weighting can provide improvements in pixel SNR, and detectability of microcalcifications as compared to that with a conventional energy integrating detector. Since a number of degrading physical factors were not modeled into the photon counting detector, this improvement should be considered as an upper bound on achievable performance. PMID:23927337

Inter- and intrascanner variability of pulmonary nodule volumetry on low-dose 64-row CT: an anthropomorphic phantom study

PubMed Central

Xie, X; Willemink, M J; Zhao, Y; de Jong, P A; van Ooijen, P M A; Oudkerk, M; Greuter, M J W

2013-01-01

Objective: To assess inter- and intrascanner variability in volumetry of solid pulmonary nodules in an anthropomorphic thoracic phantom using low-dose CT. Methods: Five spherical solid artificial nodules [diameters 3, 5, 8, 10 and 12 mm; CT density +100 Hounsfield units (HU)] were randomly placed inside an anthropomorphic thoracic phantom in different combinations. The phantom was examined on two 64-row multidetector CT (64-MDCT) systems (CT-A and CT-B) from different vendors with a low-dose protocol. Each CT examination was performed three times. The CT examinations were evaluated twice by independent blinded observers. Nodule volume was semi-automatically measured by dedicated software. Interscanner variability was evaluated by Bland–Altman analysis and expressed as 95% confidence interval (CI) of relative differences. Intrascanner variability was expressed as 95% CI of relative variation from the mean. Results: No significant difference in CT-derived volume was found between CT-A and CT-B, except for the 3-mm nodules (p<0.05). The 95% CI of interscanner variability was within ±41.6%, ±18.2% and ±4.9% for 3, 5 and ≥8 mm nodules, respectively. The 95% CI of intrascanner variability was within ±28.6%, ±13.4% and ±2.6% for 3, 5 and ≥8 mm nodules, respectively. Conclusion: Different 64-MDCT scanners in low-dose settings yield good agreement in volumetry of artificial pulmonary nodules between 5 mm and 12 mm in diameter. Inter- and intrascanner variability decreases at a larger nodule size to a maximum of 4.9% for ≥8 mm nodules. Advances in knowledge: The commonly accepted cut-off of 25% to determine nodule growth has the potential to be reduced for ≥8 mm nodules. This offers the possibility of reducing the interval for repeated CT scans in lung cancer screenings. PMID:23884758

Dual-contrast agent photon-counting computed tomography of the heart: initial experience.

PubMed

Symons, Rolf; Cork, Tyler E; Lakshmanan, Manu N; Evers, Robert; Davies-Venn, Cynthia; Rice, Kelly A; Thomas, Marvin L; Liu, Chia-Ying; Kappler, Steffen; Ulzheimer, Stefan; Sandfort, Veit; Bluemke, David A; Pourmorteza, Amir

2017-08-01

To determine the feasibility of dual-contrast agent imaging of the heart using photon-counting detector (PCD) computed tomography (CT) to simultaneously assess both first-pass and late enhancement of the myocardium. An occlusion-reperfusion canine model of myocardial infarction was used. Gadolinium-based contrast was injected 10 min prior to PCD CT. Iodinated contrast was infused immediately prior to PCD CT, thus capturing late gadolinium enhancement as well as first-pass iodine enhancement. Gadolinium and iodine maps were calculated using a linear material decomposition technique and compared to single-energy (conventional) images. PCD images were compared to in vivo and ex vivo magnetic resonance imaging (MRI) and histology. For infarct versus remote myocardium, contrast-to-noise ratio (CNR) was maximal on late enhancement gadolinium maps (CNR 9.0 ± 0.8, 6.6 ± 0.7, and 0.4 ± 0.4, p < 0.001 for gadolinium maps, single-energy images, and iodine maps, respectively). For infarct versus blood pool, CNR was maximum for iodine maps (CNR 11.8 ± 1.3, 3.8 ± 1.0, and 1.3 ± 0.4, p < 0.001 for iodine maps, gadolinium maps, and single-energy images, respectively). Combined first-pass iodine and late gadolinium maps allowed quantitative separation of blood pool, scar, and remote myocardium. MRI and histology analysis confirmed accurate PCD CT delineation of scar. Simultaneous multi-contrast agent cardiac imaging is feasible with photon-counting detector CT. These initial proof-of-concept results may provide incentives to develop new k-edge contrast agents, to investigate possible interactions between multiple simultaneously administered contrast agents, and to ultimately bring them to clinical practice.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, K; Li, X; Liu, B

Purpose: To accurately measure CT bow-tie profiles from various manufacturers and to provide non-proprietary information for CT system modeling. Methods: A GOS-based linear detector (0.8 mm per pixel and 51.2 cm in length) with a fast data sampling speed (0.24 ms/sample) was used to measure the relative profiles of bow-tie filters from a collection of eight CT scanners by three different vendors, GE (LS Xtra, LS VCT, Discovery HD750), Siemens (Sensation 64, Edge, Flash, Force), and Philips (iBrilliance 256). The linear detector was first calibrated for its energy response within typical CT beam quality ranges and compared with an ionmore » chamber and analytical modeling (SPECTRA and TASMIP). A geometrical calibration process was developed to determine key parameters including the distance from the focal spot to the linear detector, the angular increment of the gantry at each data sampling, the location of the central x-ray on the linear detector, and the angular response of the detector pixel. Measurements were performed under axial-scan modes for most representative bow-tie filters and kV selections from each scanner. Bow-tie profiles were determined by re-binning the measured rotational data with an angular accuracy of 0.1 degree using the calibrated geometrical parameters. Results: The linear detector demonstrated an energy response as a solid state detector, which is close to the CT imaging detector. The geometrical calibration was proven to be sufficiently accurate (< 1mm in error for distances >550 mm) and the bow-tie profiles measured from rotational mode matched closely to those from the gantry-stationary mode. Accurate profiles were determined for a total of 21 bow-tie filters and 83 filter/kV combinations from the abovementioned scanner models. Conclusion: A new improved approach of CT bow-tie measurement was proposed and accurate bow-tie profiles were provided for a broad list of CT scanner models.« less

Cochlear Implant Electrode Localization Using an Ultra-High Resolution Scan Mode on Conventional 64-Slice and New Generation 192-Slice Multi-Detector Computed Tomography.

PubMed

Carlson, Matthew L; Leng, Shuai; Diehn, Felix E; Witte, Robert J; Krecke, Karl N; Grimes, Josh; Koeller, Kelly K; Bruesewitz, Michael R; McCollough, Cynthia H; Lane, John I

2017-08-01

A new generation 192-slice multi-detector computed tomography (MDCT) clinical scanner provides enhanced image quality and superior electrode localization over conventional MDCT. Currently, accurate and reliable cochlear implant electrode localization using conventional MDCT scanners remains elusive. Eight fresh-frozen cadaveric temporal bones were implanted with full-length cochlear implant electrodes. Specimens were subsequently scanned with conventional 64-slice and new generation 192-slice MDCT scanners utilizing ultra-high resolution modes. Additionally, all specimens were scanned with micro-CT to provide a reference criterion for electrode position. Images were reconstructed according to routine temporal bone clinical protocols. Three neuroradiologists, blinded to scanner type, reviewed images independently to assess resolution of individual electrodes, scalar localization, and severity of image artifact. Serving as the reference standard, micro-CT identified scalar crossover in one specimen; imaging of all remaining cochleae demonstrated complete scala tympani insertions. The 192-slice MDCT scanner exhibited improved resolution of individual electrodes (p < 0.01), superior scalar localization (p < 0.01), and reduced blooming artifact (p < 0.05), compared with conventional 64-slice MDCT. There was no significant difference between platforms when comparing streak or ring artifact. The new generation 192-slice MDCT scanner offers several notable advantages for cochlear implant imaging compared with conventional MDCT. This technology provides important feedback regarding electrode position and course, which may help in future optimization of surgical technique and electrode design.

Characterisation of a neutron diffraction detector prototype based on the Trench-MWPC technology

NASA Astrophysics Data System (ADS)

Buffet, J. C.; Clergeau, J. F.; Cuccaro, S.; Guérard, B.; Mandaroux, N.; Marchal, J.; Pentenero, J.; Platz, M.; Van Esch, P.

2017-12-01

The Trench Multi-Wire-Proportional-Chamber is a new type of MWPC which has been designed to fulfill the requirements of the 2D curved neutron detector under development for the XtremeD neutron diffractometer, under construction at ILL. In this design, anode wires are mounted orthogonally to a stack of metallic cathode plates which are insulated from each other by ceramic spacers. A row of teeth is spark-eroded along the edge of the cathode plates so that anode wires appear to be stretched along trenches machined across a segmented cathode plane. This design was tested on a prototype detector module mounted in a vessel filled with a mixture of 3He-Ar-CO2 at 7 bar. The detector configuration as well as measurements performed on this prototype at ILL neutron test beam line are presented. Results show that the Trench-MWPC design provides uniform amplification gain across the detection area despite the absence of the top cathode wires used to balance the electric field in standard Cathode-Anode-Cathode MWPC configurations. The presence of cathode trench side-walls surrounding anode wires minimises the spread of neutron-induced charge across electrodes, allowing for detector operation at reduced amplification gain without compromising the signal to noise per electrode. Pulse-height spectra acquired under various neutron flux conditions demonstrated that the Trench-MWPC design minimises space-charge effects, thanks to its low amplification gain combined with the fast collection of ions by cathode trench side-walls surrounding anode wires. Measurements also showed that this space-charge effect reduction results in a high local count-rate of ~100 kHz at 10% count loss when irradiating the detector with a small 5 mm × 5 mm neutron beam.

Ultrahigh-resolution CT and DR scanner

NASA Astrophysics Data System (ADS)

DiBianca, Frank A.; Gupta, Vivek; Zou, Ping; Jordan, Lawrence M.; Laughter, Joseph S.; Zeman, Herbert D.; Sebes, Jeno I.

1999-05-01

A new technique called Variable-Resolution X-ray (VRX) detection that dramatically increases the spatial resolution in computed tomography (CT) and digital radiography (DR) is presented. The technique is based on a principle called 'projective compression' that allows the resolution element of a CT detector to scale with the subject or field size. For very large (40 - 50 cm) field sizes, resolution exceeding 2 cy/mm is possible and for very small fields, microscopy is attainable with resolution exceeding 100 cy/mm. Several effects that could limit the performance of VRX detectors are considered. Experimental measurements on a 16-channel, CdWO4 scintillator + photodiode test array yield a limiting MTF of 64 cy/mm (8(mu) ) in the highest-resolution configuration reported. Preliminary CT images have been made of small anatomical specimens and small animals using a storage phosphor screen in the VRX mode. Measured detector resolution of the CT projection data exceeds 20 cy/mm (less than 25 (mu) ); however, the final, reconstructed CT images produced thus far exhibit 10 cy/mm (50 (mu) ) resolution because of non-flatness of the storage phosphor plates, focal spot effects and the use of a rudimentary CT reconstruction algorithm. A 576-channel solid-state detector is being fabricated that is expected to achieve CT image resolution in excess of that of the 26-channel test array.

Radiological protection in computed tomography and cone beam computed tomography.

PubMed

Rehani, M M

2015-06-01

The International Commission on Radiological Protection (ICRP) has sustained interest in radiological protection in computed tomography (CT), and ICRP Publications 87 and 102 focused on the management of patient doses in CT and multi-detector CT (MDCT) respectively. ICRP forecasted and 'sounded the alarm' on increasing patient doses in CT, and recommended actions for manufacturers and users. One of the approaches was that safety is best achieved when it is built into the machine, rather than left as a matter of choice for users. In view of upcoming challenges posed by newer systems that use cone beam geometry for CT (CBCT), and their widened usage, often by untrained users, a new ICRP task group has been working on radiological protection issues in CBCT. Some of the issues identified by the task group are: lack of standardisation of dosimetry in CBCT; the false belief within the medical and dental community that CBCT is a 'light', low-dose CT whereas mobile CBCT units and newer applications, particularly C-arm CT in interventional procedures, involve higher doses; lack of training in radiological protection among clinical users; and lack of dose information and tracking in many applications. This paper provides a summary of approaches used in CT and MDCT, and preliminary information regarding work just published for radiological protection in CBCT. © The International Society for Prosthetics and Orthotics Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Trabecular bone class mapping across resolutions: translating methods from HR-pQCT to clinical CT

NASA Astrophysics Data System (ADS)

Valentinitsch, Alexander; Fischer, Lukas; Patsch, Janina M.; Bauer, Jan; Kainberger, Franz; Langs, Georg; DiFranco, Matthew

2015-03-01

Quantitative assessment of 3D bone microarchitecture in high-resolution peripheral quantitative computed tomography (HR-pQCT) has shown promise in fracture risk assessment and biomechanics, but is limited to the distal radius and tibia. Trabecular microarchitecture classes (TMACs), based on voxel-wise clustering texture and structure tensor features in HRpQCT, is extended in this paper to quantify trabecular bone classes in clinical multi-detector CT (MDCT) images. Our comparison of TMACs in 12 cadaver radii imaged using both HRpQCT and MDCT yields a mean Dice score of up to 0.717+/-0.40 and visually concordant bone quality maps. Further work to develop clinically viable bone quantitative imaging using HR-pQCT validation could have a significant impact on overall bone health assessment.

Development of adaptive noise reduction filter algorithm for pediatric body images in a multi-detector CT

NASA Astrophysics Data System (ADS)

Nishimaru, Eiji; Ichikawa, Katsuhiro; Okita, Izumi; Ninomiya, Yuuji; Tomoshige, Yukihiro; Kurokawa, Takehiro; Ono, Yutaka; Nakamura, Yuko; Suzuki, Masayuki

2008-03-01

Recently, several kinds of post-processing image filters which reduce the noise of computed tomography (CT) images have been proposed. However, these image filters are mostly for adults. Because these are not very effective in small (< 20 cm) display fields of view (FOV), we cannot use them for pediatric body images (e.g., premature babies and infant children). We have developed a new noise reduction filter algorithm for pediatric body CT images. This algorithm is based on a 3D post-processing in which the output pixel values are calculated by nonlinear interpolation in z-directions on original volumetric-data-sets. This algorithm does not need the in-plane (axial plane) processing, so the spatial resolution does not change. From the phantom studies, our algorithm could reduce SD up to 40% without affecting the spatial resolution of x-y plane and z-axis, and improved the CNR up to 30%. This newly developed filter algorithm will be useful for the diagnosis and radiation dose reduction of the pediatric body CT images.

Grating Oriented Line-Wise Filtration (GOLF) for Dual-Energy X-ray CT

NASA Astrophysics Data System (ADS)

Xi, Yan; Cong, Wenxiang; Harrison, Daniel; Wang, Ge

2017-12-01

In medical X-ray Computed Tomography (CT), the use of two distinct X-ray source spectra (energies) allows dose-reduction and material discrimination relative to that achieved with only one source spectrum. Existing dual-energy CT methods include source kVp-switching, double-layer detection, dual-source gantry, and two-pass scanning. Each method suffers either from strong spectral correlation or patient-motion artifacts. To simultaneously address these problems, we propose to improve CT data acquisition with the Grating Oriented Line-wise Filtration (GOLF) method, a novel X-ray filter that is placed between the source and patient. GOLF uses a combination of absorption and filtering gratings that are moved relative to each other and in synchronization with the X-ray tube kVp-switching process and/or the detector view-sampling process. Simulation results show that GOLF can improve the spectral performance of kVp-switching to match that of dual-source CT while avoiding patient motion artifacts and dual imaging chains. Although significant flux is absorbed by this pre-patient filter, the proposed GOLF method is a novel path for cost-effectively extracting dual-energy or multi-energy data and reducing radiation dose with or without kVp switching.

Grating Oriented Line-Wise Filtration (GOLF) for Dual-Energy X-ray CT

PubMed Central

Xi, Yan; Cong, Wenxiang; Harrison, Daniel

2017-01-01

In medical X-ray Computed Tomography (CT), the use of two distinct X-ray source spectra (energies) allows dose-reduction and material discrimination relative to that achieved with only one source spectrum. Existing dual-energy CT methods include source kVp-switching, double-layer detection, dual-source gantry, and two-pass scanning. Each method suffers either from strong spectral correlation or patient-motion artifacts. To simultaneously address these problems, we propose to improve CT data acquisition with the Grating Oriented Line-wise Filtration (GOLF) method, a novel X-ray filter that is placed between the source and patient. GOLF uses a combination of absorption and filtering gratings that are moved relative to each other and in synchronization with the X-ray tube kVp-switching process and/or the detector view-sampling process. Simulation results show that GOLF can improve the spectral performance of kVp-switching to match that of dual-source CT while avoiding patient motion artifacts and dual imaging chains. Although significant flux is absorbed by this pre-patient filter, the proposed GOLF method is a novel path for cost-effectively extracting dual-energy or multi-energy data and reducing radiation dose with or without kVp switching. PMID:29333113

Scout-view Assisted Interior Micro-CT

PubMed Central

Sen Sharma, Kriti; Holzner, Christian; Vasilescu, Dragoş M.; Jin, Xin; Narayanan, Shree; Agah, Masoud; Hoffman, Eric A.; Yu, Hengyong; Wang, Ge

2013-01-01

Micro computed tomography (micro-CT) is a widely-used imaging technique. A challenge of micro-CT is to quantitatively reconstruct a sample larger than the field-of-view (FOV) of the detector. This scenario is characterized by truncated projections and associated image artifacts. However, for such truncated scans, a low resolution scout scan with an increased FOV is frequently acquired so as to position the sample properly. This study shows that the otherwise discarded scout scans can provide sufficient additional information to uniquely and stably reconstruct the interior region of interest. Two interior reconstruction methods are designed to utilize the multi-resolution data without a significant computational overhead. While most previous studies used numerically truncated global projections as interior data, this study uses truly hybrid scans where global and interior scans were carried out at different resolutions. Additionally, owing to the lack of standard interior micro-CT phantoms, we designed and fabricated novel interior micro-CT phantoms for this study to provide means of validation for our algorithms. Finally, two characteristic samples from separate studies were scanned to show the effect of our reconstructions. The presented methods show significant improvements over existing reconstruction algorithms. PMID:23732478

Patient- and cohort-specific dose and risk estimation for abdominopelvic CT: a study based on 100 patients

NASA Astrophysics Data System (ADS)

Tian, Xiaoyu; Li, Xiang; Segars, W. Paul; Frush, Donald P.; Samei, Ehsan

2012-03-01

The purpose of this work was twofold: (a) to estimate patient- and cohort-specific radiation dose and cancer risk index for abdominopelvic computer tomography (CT) scans; (b) to evaluate the effects of patient anatomical characteristics (size, age, and gender) and CT scanner model on dose and risk conversion coefficients. The study included 100 patient models (42 pediatric models, 58 adult models) and multi-detector array CT scanners from two commercial manufacturers (LightSpeed VCT, GE Healthcare; SOMATOM Definition Flash, Siemens Healthcare). A previously-validated Monte Carlo program was used to simulate organ dose for each patient model and each scanner, from which DLP-normalized-effective dose (k factor) and DLP-normalized-risk index values (q factor) were derived. The k factor showed exponential decrease with increasing patient size. For a given gender, q factor showed exponential decrease with both increasing patient size and patient age. The discrepancies in k and q factors across scanners were on average 8% and 15%, respectively. This study demonstrates the feasibility of estimating patient-specific organ dose and cohort-specific effective dose and risk index in abdominopelvic CT requiring only the knowledge of patient size, gender, and age.

6. Historic American Buildings Survey James Rainey, Photographer May 7, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

6. Historic American Buildings Survey James Rainey, Photographer May 7, 1936 STAIRS FROM ROOM OF SECRETARY OF STATE SECOND FLOOR (Looking North) - Old State House, Main Street & Central Row, Hartford, Hartford County, CT

Explosive Detection in Aviation Applications Using CT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martz, H E; Crawford, C R

2011-02-15

CT scanners are deployed world-wide to detect explosives in checked and carry-on baggage. Though very similar to single- and dual-energy multi-slice CT scanners used today in medical imaging, some recently developed explosives detection scanners employ multiple sources and detector arrays to eliminate mechanical rotation of a gantry, photon counting detectors for spectral imaging, and limited number of views to reduce cost. For each bag scanned, the resulting reconstructed images are first processed by automated threat recognition algorithms to screen for explosives and other threats. Human operators review the images only when these automated algorithms report the presence of possible threats.more » The US Department of Homeland Security (DHS) has requirements for future scanners that include dealing with a larger number of threats, higher probability of detection, lower false alarm rates and lower operating costs. One tactic that DHS is pursuing to achieve these requirements is to augment the capabilities of the established security vendors with third-party algorithm developers. A third-party in this context refers to academics and companies other than the established vendors. DHS is particularly interested in exploring the model that has been used very successfully by the medical imaging industry, in which university researchers develop algorithms that are eventually deployed in commercial medical imaging equipment. The purpose of this paper is to discuss opportunities for third-parties to develop advanced reconstruction and threat detection algorithms.« less

MT3825BA: a 384×288-25µm ROIC for uncooled microbolometer FPAs

NASA Astrophysics Data System (ADS)

Eminoglu, Selim; Gulden, M. Ali; Bayhan, Nusret; Incedere, O. Samet; Soyer, S. Tuncer; Ustundag, Cem M. B.; Isikhan, Murat; Kocak, Serhat; Turan, Ozge; Yalcin, Cem; Akin, Tayfun

2014-06-01

This paper reports the development of a new microbolometer Readout Integrated Circuit (ROIC) called MT3825BA. It has a format of 384 × 288 and a pixel pitch of 25μm. MT3825BA is Mikro-Tasarim's second microbolometer ROIC product, which is developed specifically for resistive surface micro-machined microbolometer detector arrays using high-TCR pixel materials, such as VOx and a-Si. MT3825BA has a system-on-chip architecture, where all the timing, biasing, and pixel non-uniformity correction (NUC) operations in the ROIC are applied using on-chip circuitry simplifying the use and system integration of this ROIC. The ROIC is designed to support pixel resistance values ranging from 30 KΩ to 100 KΩ. MT3825BA is operated using conventional row based readout method, where pixels in the array are read out in a row-by-row basis, where the applied bias for each pixel in a given row is updated at the beginning of each line period according to the applied line based NUC data. The NUC data is applied continuously in a row-by-row basis using the serial programming interface, which is also used to program user configurable features of the ROIC, such as readout gain, integration time, and number of analog video outputs. MT3825BA has a total of 4 analog video outputs and 2 analog reference outputs, placed at the top and bottom of the ROIC, which can be programmed to operate in the 1, 2, and 4-output modes, supporting frames rates well above 60 fps at a 3 MHz pixel output rate. The pixels in the array are read out with respect to reference pixels implemented above and below actual array pixels. The bias voltage of the pixels can be programmed over a 1.0 V range to compensate for the changes in the detector resistance values due to the variations coming from the manufacturing process or changes in the operating temperature. The ROIC has an on-chip integrated temperature sensor with a sensitivity of better than 5 mV / K, and the output of the temperature sensor can be read out the output as part of the analog video stream. MT3825BA can be used to build a microbolometer FPAs with an NETD value below 100 mK using a microbolometer detector array fabrication technology with a detector resistance value up to 100 KΩ, a high TCR value (< 2 % / K), and a sufficiently low pixel thermal conductance (Gth ≤ 20 nW / K). MT3825BA measures 13.0 mm × 13.5 mm and is fabricated on 200 mm CMOS wafers. The microbolometer ROIC wafers are engineered to have flat surface finish to simplify the wafer level detector fabrication and wafer level vacuum packaging (WLVP). The ROIC runs on 3.3 V analog and 1.8 V digital supplies, and dissipates less than 85 mW in the 2-output mode at 30 fps. Mikro-Tasarim provides tested ROIC wafers and offers compact test electronics and software for its ROIC customers to shorten their FPA and camera development cycles.

Novel scintillation detector design and performance for proton radiography and computed tomography.

PubMed

Bashkirov, V A; Schulte, R W; Hurley, R F; Johnson, R P; Sadrozinski, H F-W; Zatserklyaniy, A; Plautz, T; Giacometti, V

2016-02-01

Proton computed tomography (pCT) will enable accurate prediction of proton and ion range in a patient while providing the benefit of lower radiation exposure than in x-ray CT. The accuracy of the range prediction is essential for treatment planning in proton or ion therapy and depends upon the detector used to evaluate the water-equivalent path length (WEPL) of a proton passing through the object. A novel approach is presented for an inexpensive WEPL detector for pCT and proton radiography. A novel multistage detector with an aperture of 10 × 37.5 cm was designed to optimize the accuracy of the WEPL measurements while simplifying detector construction and the performance requirements of its components. The design of the five-stage detector was optimized through simulations based on the geant4 detector simulation toolkit, and the fabricated prototype was calibrated in water-equivalent millimeters with 200 MeV protons in the research beam line of the clinical proton synchrotron at Loma Linda University Medical Center. A special polystyrene step phantom was designed and built to speed up and simplify the calibration procedure. The calibrated five-stage detector was tested in the 200 MeV proton beam as part of the pCT head scanner, using a water phantom and polystyrene slabs to verify the WEPL reconstruction accuracy. The beam-test results demonstrated excellent performance of the new detector, in good agreement with the simulation results. The WEPL measurement accuracy is about 3.0 mm per proton in the 0-260 mm WEPL range required for a pCT head scan with a 200 MeV proton beam. The new multistage design approach to WEPL measurements for proton CT and radiography has been prototyped and tested. The test results show that the design is competitive with much more expensive calorimeter and range-counter designs.

Novel scintillation detector design and performance for proton radiography and computed tomography

PubMed Central

Schulte, R. W.; Hurley, R. F.; Johnson, R. P.; Sadrozinski, H. F.-W.; Zatserklyaniy, A.; Plautz, T.; Giacometti, V.

2016-01-01

Purpose: Proton computed tomography (pCT) will enable accurate prediction of proton and ion range in a patient while providing the benefit of lower radiation exposure than in x-ray CT. The accuracy of the range prediction is essential for treatment planning in proton or ion therapy and depends upon the detector used to evaluate the water-equivalent path length (WEPL) of a proton passing through the object. A novel approach is presented for an inexpensive WEPL detector for pCT and proton radiography. Methods: A novel multistage detector with an aperture of 10 × 37.5 cm was designed to optimize the accuracy of the WEPL measurements while simplifying detector construction and the performance requirements of its components. The design of the five-stage detector was optimized through simulations based on the geant4 detector simulation toolkit, and the fabricated prototype was calibrated in water-equivalent millimeters with 200 MeV protons in the research beam line of the clinical proton synchrotron at Loma Linda University Medical Center. A special polystyrene step phantom was designed and built to speed up and simplify the calibration procedure. The calibrated five-stage detector was tested in the 200 MeV proton beam as part of the pCT head scanner, using a water phantom and polystyrene slabs to verify the WEPL reconstruction accuracy. Results: The beam-test results demonstrated excellent performance of the new detector, in good agreement with the simulation results. The WEPL measurement accuracy is about 3.0 mm per proton in the 0–260 mm WEPL range required for a pCT head scan with a 200 MeV proton beam. Conclusions: The new multistage design approach to WEPL measurements for proton CT and radiography has been prototyped and tested. The test results show that the design is competitive with much more expensive calorimeter and range-counter designs. PMID:26843230

Improving depiction of temporal bone anatomy with low-radiation dose CT by an integrated circuit detector in pediatric patients: a preliminary study.

PubMed

He, Jingzhen; Zu, Yuliang; Wang, Qing; Ma, Xiangxing

2014-12-01

The purpose of this study was to determine the performance of low-dose computed tomography (CT) scanning with integrated circuit (IC) detector in defining fine structures of temporal bone in children by comparing with the conventional detector. The study was performed with the approval of our institutional review board and the patients' anonymity was maintained. A total of 86 children<3 years of age underwent imaging of temporal bone with low-dose CT (80 kV/150 mAs) equipped with either IC detector or conventional discrete circuit (DC) detector. The image noise was measured for quantitative analysis. Thirty-five structures of temporal bone were further assessed and rated by 2 radiologists for qualitative analysis. κ Statistics were performed to determine the agreement reached between the 2 radiologists on each image. Mann-Whitney U test was used to determine the difference in image quality between the 2 detector systems. Objective analysis showed that the image noise was significantly lower (P<0.001) with the IC detector than with the DC detector. The κ values for qualitative assessment of the 35 fine anatomical structures revealed high interobserver agreement. The delineation for 30 of the 35 landmarks (86%) with the IC detector was superior to that with the conventional DC detector (P<0.05) although there were no differences in the delineation of the remaining 5 structures (P>0.05). The low-dose CT images acquired with the IC detector provide better depiction of fine osseous structures of temporal bone than that with the conventional DC detector.

Recent micro-CT scanner developments at UGCT

NASA Astrophysics Data System (ADS)

Dierick, Manuel; Van Loo, Denis; Masschaele, Bert; Van den Bulcke, Jan; Van Acker, Joris; Cnudde, Veerle; Van Hoorebeke, Luc

2014-04-01

This paper describes two X-ray micro-CT scanners which were recently developed to extend the experimental possibilities of microtomography research at the Centre for X-ray Tomography (www.ugct.ugent.be) of the Ghent University (Belgium). The first scanner, called Nanowood, is a wide-range CT scanner with two X-ray sources (160 kVmax) and two detectors, resolving features down to 0.4 μm in small samples, but allowing samples up to 35 cm to be scanned. This is a sample size range of 3 orders of magnitude, making this scanner well suited for imaging multi-scale materials such as wood, stone, etc. Besides the traditional cone-beam acquisition, Nanowood supports helical acquisition, and it can generate images with significant phase-contrast contributions. The second scanner, known as the Environmental micro-CT scanner (EMCT), is a gantry based micro-CT scanner with variable magnification for scanning objects which are not easy to rotate in a standard micro-CT scanner, for example because they are physically connected to external experimental hardware such as sensor wiring, tubing or others. This scanner resolves 5 μm features, covers a field-of-view of about 12 cm wide with an 80 cm vertical travel range. Both scanners will be extensively described and characterized, and their potential will be demonstrated with some key application results.

Comparison of ring artifact removal methods using flat panel detector based CT images

PubMed Central

2011-01-01

Background Ring artifacts are the concentric rings superimposed on the tomographic images often caused by the defective and insufficient calibrated detector elements as well as by the damaged scintillator crystals of the flat panel detector. It may be also generated by objects attenuating X-rays very differently in different projection direction. Ring artifact reduction techniques so far reported in the literature can be broadly classified into two groups. One category of the approaches is based on the sinogram processing also known as the pre-processing techniques and the other category of techniques perform processing on the 2-D reconstructed images, recognized as the post-processing techniques in the literature. The strength and weakness of these categories of approaches are yet to be explored from a common platform. Method In this paper, a comparative study of the two categories of ring artifact reduction techniques basically designed for the multi-slice CT instruments is presented from a common platform. For comparison, two representative algorithms from each of the two categories are selected from the published literature. A very recently reported state-of-the-art sinogram domain ring artifact correction method that classifies the ring artifacts according to their strength and then corrects the artifacts using class adaptive correction schemes is also included in this comparative study. The first sinogram domain correction method uses a wavelet based technique to detect the corrupted pixels and then using a simple linear interpolation technique estimates the responses of the bad pixels. The second sinogram based correction method performs all the filtering operations in the transform domain, i.e., in the wavelet and Fourier domain. On the other hand, the two post-processing based correction techniques actually operate on the polar transform domain of the reconstructed CT images. The first method extracts the ring artifact template vector using a homogeneity test and then corrects the CT images by subtracting the artifact template vector from the uncorrected images. The second post-processing based correction technique performs median and mean filtering on the reconstructed images to produce the corrected images. Results The performances of the comparing algorithms have been tested by using both quantitative and perceptual measures. For quantitative analysis, two different numerical performance indices are chosen. On the other hand, different types of artifact patterns, e.g., single/band ring, artifacts from defective and mis-calibrated detector elements, rings in highly structural object and also in hard object, rings from different flat-panel detectors are analyzed to perceptually investigate the strength and weakness of the five methods. An investigation has been also carried out to compare the efficacy of these algorithms in correcting the volume images from a cone beam CT with the parameters determined from one particular slice. Finally, the capability of each correction technique in retaining the image information (e.g., small object at the iso-center) accurately in the corrected CT image has been also tested. Conclusions The results show that the performances of the algorithms are limited and none is fully suitable for correcting different types of ring artifacts without introducing processing distortion to the image structure. To achieve the diagnostic quality of the corrected slices a combination of the two approaches (sinogram- and post-processing) can be used. Also the comparing methods are not suitable for correcting the volume images from a cone beam flat-panel detector based CT. PMID:21846411

Review of Fusion Systems and Contributing Technologies for SIHS-TD (Examen des Systemes de Fusion et des Technologies d’Appui pour la DT SIHS)

DTIC Science & Technology

2007-03-31

Unlimited, Nivisys, Insight technology, Elcan, FLIR Systems, Stanford photonics Hardware Sensor fusion processors Video processing boards Image, video...Engineering The SPIE Digital Library is a resource for optics and photonics information. It contains more than 70,000 full-text papers from SPIE...conditions Top row: Stanford Photonics XR-Mega-10 Extreme 1400 x 1024 pixels ICCD detector, 33 msec exposure, no binning. Middle row: Andor EEV iXon

Solitary pulmonary nodules: Comparison of dynamic first-pass contrast-enhanced perfusion area-detector CT, dynamic first-pass contrast-enhanced MR imaging, and FDG PET/CT.

PubMed

Ohno, Yoshiharu; Nishio, Mizuho; Koyama, Hisanobu; Seki, Shinichiro; Tsubakimoto, Maho; Fujisawa, Yasuko; Yoshikawa, Takeshi; Matsumoto, Sumiaki; Sugimura, Kazuro

2015-02-01

To prospectively compare the capabilities of dynamic perfusion area-detector computed tomography (CT), dynamic magnetic resonance (MR) imaging, and positron emission tomography (PET) combined with CT (PET/CT) with use of fluorine 18 fluorodeoxyglucose (FDG) for the diagnosis of solitary pulmonary nodules. The institutional review board approved this study, and written informed consent was obtained from each subject. A total of 198 consecutive patients with 218 nodules prospectively underwent dynamic perfusion area-detector CT, dynamic MR imaging, FDG PET/CT, and microbacterial and/or pathologic examinations. Nodules were classified into three groups: malignant nodules (n = 133) and benign nodules with low (n = 53) or high (n = 32) biologic activity. Total perfusion was determined with dual-input maximum slope models at area-detector CT, maximum and slope of enhancement ratio at MR imaging, and maximum standardized uptake value (SUVmax) at PET/CT. Next, all indexes for malignant and benign nodules were compared with the Tukey honest significant difference test. Then, receiver operating characteristic analysis was performed for each index. Finally, sensitivity, specificity, and accuracy were compared with the McNemar test. All indexes showed significant differences between malignant nodules and benign nodules with low biologic activity (P < .0001). The area under the receiver operating characteristic curve for total perfusion was significantly larger than that for other indexes (.0006 ≤ P ≤ .04). The specificity and accuracy of total perfusion were significantly higher than those of maximum relative enhancement ratio (specificity, P < .0001; accuracy, P < .0001), slope of enhancement ratio (specificity, P < .0001; accuracy, P < .0001), and SUVmax (specificity, P < .0001; accuracy, P < .0001). Dynamic perfusion area-detector CT is more specific and accurate than dynamic MR imaging and FDG PET/CT in the diagnosis of solitary pulmonary nodules in routine clinical practice. © RSNA, 2014.

MicroCT with energy-resolved photon-counting detectors

PubMed Central

Wang, X; Meier, D; Mikkelsen, S; Maehlum, G E; Wagenaar, D J; Tsui, BMW; Patt, B E; Frey, E C

2011-01-01

The goal of this paper was to investigate the benefits that could be realistically achieved on a microCT imaging system with an energy-resolved photon-counting x-ray detector. To this end, we built and evaluated a prototype microCT system based on such a detector. The detector is based on cadmium telluride (CdTe) radiation sensors and application-specific integrated circuit (ASIC) readouts. Each detector pixel can simultaneously count x-ray photons above six energy thresholds, providing the capability for energy-selective x-ray imaging. We tested the spectroscopic performance of the system using polychromatic x-ray radiation and various filtering materials with Kabsorption edges. Tomographic images were then acquired of a cylindrical PMMA phantom containing holes filled with various materials. Results were also compared with those acquired using an intensity-integrating x-ray detector and single-energy (i.e. non-energy-selective) CT. This paper describes the functionality and performance of the system, and presents preliminary spectroscopic and tomographic results. The spectroscopic experiments showed that the energy-resolved photon-counting detector was capable of measuring energy spectra from polychromatic sources like a standard x-ray tube, and resolving absorption edges present in the energy range used for imaging. However, the spectral quality was degraded by spectral distortions resulting from degrading factors, including finite energy resolution and charge sharing. We developed a simple charge-sharing model to reproduce these distortions. The tomographic experiments showed that the availability of multiple energy thresholds in the photon-counting detector allowed us to simultaneously measure target-to-background contrasts in different energy ranges. Compared with single-energy CT with an integrating detector, this feature was especially useful to improve differentiation of materials with different attenuation coefficient energy dependences. PMID:21464527

MicroCT with energy-resolved photon-counting detectors.

PubMed

Wang, X; Meier, D; Mikkelsen, S; Maehlum, G E; Wagenaar, D J; Tsui, B M W; Patt, B E; Frey, E C

2011-05-07

The goal of this paper was to investigate the benefits that could be realistically achieved on a microCT imaging system with an energy-resolved photon-counting x-ray detector. To this end, we built and evaluated a prototype microCT system based on such a detector. The detector is based on cadmium telluride (CdTe) radiation sensors and application-specific integrated circuit (ASIC) readouts. Each detector pixel can simultaneously count x-ray photons above six energy thresholds, providing the capability for energy-selective x-ray imaging. We tested the spectroscopic performance of the system using polychromatic x-ray radiation and various filtering materials with K-absorption edges. Tomographic images were then acquired of a cylindrical PMMA phantom containing holes filled with various materials. Results were also compared with those acquired using an intensity-integrating x-ray detector and single-energy (i.e. non-energy-selective) CT. This paper describes the functionality and performance of the system, and presents preliminary spectroscopic and tomographic results. The spectroscopic experiments showed that the energy-resolved photon-counting detector was capable of measuring energy spectra from polychromatic sources like a standard x-ray tube, and resolving absorption edges present in the energy range used for imaging. However, the spectral quality was degraded by spectral distortions resulting from degrading factors, including finite energy resolution and charge sharing. We developed a simple charge-sharing model to reproduce these distortions. The tomographic experiments showed that the availability of multiple energy thresholds in the photon-counting detector allowed us to simultaneously measure target-to-background contrasts in different energy ranges. Compared with single-energy CT with an integrating detector, this feature was especially useful to improve differentiation of materials with different attenuation coefficient energy dependences.

Study of Image Quality From CT Scanner Multi-Detector by using Americans College of Radiology (ACR) Phantom

NASA Astrophysics Data System (ADS)

Mulyadin; Dewang, Syamsir; Abdullah, Bualkar; Tahir, Dahlang

2018-03-01

In this study, the image quality of CT scan using phantom American College of Radiology (ACR) was determined. Scanning multidetector CT is used to know the image quality parameters by using a solid phantom containing four modules and primarily from materials that are equivalent to water. Each module is 4 cm in diameter and 20 cm in diameter. There is white alignment marks painted white to reflect the alignment laser and there are also “HEAD”, “FOOT”, and “TOP” marks on the phantom to help align. This test obtains CT images of each module according to the routine inspection protocol of the head. Acceptance of image quality obtained for determination: CT Number Accuracy (CTN), CT Number Uniformity and Noise, Linearity CT Number, Slice Technique, Low Contrast Resolution and High Contrast Resolution represent image quality parameters. In testing CT Number Accuracy (CTN), CT Uniform number and Noise are in the range of tolerable values allowed. In the test, Linearity CT Number obtained correlation value above 0.99 is the relationship between electron density and CT Number. In a low contrast resolution test, the smallest contrast groups are visible. In contrast, the high resolution is seen up to 7 lp/cm. The quality of GE CT Scan is very high, as all the image quality tests obtained are within the tolerance brackets of values permitted by the Nuclear Power Control Agency (BAPETEN). Image quality test is a way to get very important information about the accuracy of snoring result by using phantom ACR.

Functional Imaging of the Lungs with Gas Agents

PubMed Central

Kruger, Stanley J.; Nagle, Scott K.; Couch, Marcus J.; Ohno, Yoshiharu; Albert, Mitchell; Fain, Sean B.

2015-01-01

This review focuses on the state-of-the-art of the three major classes of gas contrast agents used in magnetic resonance imaging (MRI) – hyperpolarized (HP) gas, molecular oxygen, and fluorinated gas – and their application to clinical pulmonary research. During the past several years there has been accelerated development of pulmonary MRI. This has been driven in part by concerns regarding ionizing radiation using multi-detector computed tomography (CT). However, MRI also offers capabilities for fast multi-spectral and functional imaging using gas agents that are not technically feasible with CT. Recent improvements in gradient performance and radial acquisition methods using ultra-short echo time (UTE) have contributed to advances in these functional pulmonary MRI techniques. Relative strengths and weaknesses of the main functional imaging methods and gas agents are compared and applications to measures of ventilation, diffusion, and gas exchange are presented. Functional lung MRI methods using these gas agents are improving our understanding of a wide range of chronic lung diseases, including chronic obstructive pulmonary disease (COPD), asthma, and cystic fibrosis (CF) in both adults and children. PMID:26218920

[Clinical application of high-pitch excretory phase images during dual-source CT urography with stellar photon detector].

PubMed

Sun, Hao; Xue, Hua-dan; Jin, Zheng-yu; Wang, Xuan; Chen, Yu; He, Yong-lan; Zhang, Da-ming; Zhu, Liang; Wang, Yun; Qi, Bing; Xu, Kai; Wang, Ming

2014-10-01

To retrospectively evaluate the clinical feasibility of high-pitch excretory phase images during dual-source CT urography with Stellar photon detector. Totally 100 patients received dual-source CT high-pitch urinary excretory phase scanning with Stellar photon detector [80 kV, ref.92 mAs, CARE Dose 4D and CARE kV, pitch of 3.0, filter back projection reconstruction algorithm (FBP)] (group A). Another 100 patients received dual-source CT high-pitch urinary excretory phase scanning with common detector(100 kV, ref.140 mAs, CARE Dose 4D, pitch of 3.0, FBP) (group B). Quantitative measurement of CT value of urinary segments (Hounsfield units), image noise (Hounsfield units), and effective radiation dose (millisievert) were compared using independent-samples t test between two groups. Urinary system subjective opacification scores were compared using Mann-Whitney U test between two groups. There was no significant difference in subjective opacification score of intrarenal collecting system and ureters between two groups (all P>0.05). The group A images yielded significantly higher CT values of all urinary segments (all P<0.01). There was no significant difference in image noise (P>0.05). The effective radiation dose of group A (1.1 mSv) was significantly lower than that of group B (3.79 mSv) (P<0.01). High-pitch low-tube-voltage during excretory phase dual-source CT urography with Stellar photon detector is feasible, with acceptable image noise and lower radiation dose.

High resolution collimator system for X-ray detector

DOEpatents

Eberhard, Jeffrey W.; Cain, Dallas E.

1987-01-01

High resolution in an X-ray computerized tomography (CT) inspection system is achieved by using a collimator/detector combination to limit the beam width of the X-ray beam incident on a detector element to the desired resolution width. In a detector such as a high pressure Xenon detector array, a narrow tapered collimator is provided above a wide detector element. The collimator slits have any desired width, as small as a few mils at the top, the slit width is easily controlled, and they are fabricated on standard machines. The slit length determines the slice thickness of the CT image.

A resource for the assessment of lung nodule size estimation methods: database of thoracic CT scans of an anthropomorphic phantom◊

PubMed Central

Gavrielides, Marios A.; Kinnard, Lisa M.; Myers, Kyle J.; Peregoy, Jennifer; Pritchard, William F.; Zeng, Rongping; Esparza, Juan; Karanian, John; Petrick, Nicholas

2010-01-01

A number of interrelated factors can affect the precision and accuracy of lung nodule size estimation. To quantify the effect of these factors, we have been conducting phantom CT studies using an anthropomorphic thoracic phantom containing a vasculature insert to which synthetic nodules were inserted or attached. Ten repeat scans were acquired on different multi-detector scanners, using several sets of acquisition and reconstruction protocols and various nodule characteristics (size, shape, density, location). This study design enables both bias and variance analysis for the nodule size estimation task. The resulting database is in the process of becoming publicly available as a resource to facilitate the assessment of lung nodule size estimation methodologies and to enable comparisons between different methods regarding measurement error. This resource complements public databases of clinical data and will contribute towards the development of procedures that will maximize the utility of CT imaging for lung cancer screening and tumor therapy evaluation. PMID:20640011

Comparison of quantitatively analyzed dynamic area-detector CT using various mathematic methods with FDG PET/CT in management of solitary pulmonary nodules.

PubMed

Ohno, Yoshiharu; Nishio, Mizuho; Koyama, Hisanobu; Fujisawa, Yasuko; Yoshikawa, Takeshi; Matsumoto, Sumiaki; Sugimura, Kazuro

2013-06-01

The objective of our study was to prospectively compare the capability of dynamic area-detector CT analyzed with different mathematic methods and PET/CT in the management of pulmonary nodules. Fifty-two consecutive patients with 96 pulmonary nodules underwent dynamic area-detector CT, PET/CT, and microbacterial or pathologic examinations. All nodules were classified into the following groups: malignant nodules (n = 57), benign nodules with low biologic activity (n = 15), and benign nodules with high biologic activity (n = 24). On dynamic area-detector CT, the total, pulmonary arterial, and systemic arterial perfusions were calculated using the dual-input maximum slope method; perfusion was calculated using the single-input maximum slope method; and extraction fraction and blood volume (BV) were calculated using the Patlak plot method. All indexes were statistically compared among the three nodule groups. Then, receiver operating characteristic analyses were used to compare the diagnostic capabilities of the maximum standardized uptake value (SUVmax) and each perfusion parameter having a significant difference between malignant and benign nodules. Finally, the diagnostic performances of the indexes were compared by means of the McNemar test. No adverse effects were observed in this study. All indexes except extraction fraction and BV, both of which were calculated using the Patlak plot method, showed significant differences among the three groups (p < 0.05). Areas under the curve of total perfusion calculated using the dual-input method, pulmonary arterial perfusion calculated using the dual-input method, and perfusion calculated using the single-input method were significantly larger than that of SUVmax (p < 0.05). The accuracy of total perfusion (83.3%) was significantly greater than the accuracy of the other indexes: pulmonary arterial perfusion (72.9%, p < 0.05), systemic arterial perfusion calculated using the dual-input method (69.8%, p < 0.05), perfusion (66.7%, p < 0.05), and SUVmax (60.4%, p < 0.05). Dynamic area-detector CT analyzed using the dual-input maximum slope method has better potential for the diagnosis of pulmonary nodules than dynamic area-detector CT analyzed using other methods and than PET/CT.

Obsidian provenance determination by using the beam stability controlled BSC-XRF and the PIXE-alpha portable spectrometers of the LANDIS laboratory of the LNS-INFN and IBAM-CNR in Catania (Italy)

NASA Astrophysics Data System (ADS)

Pappalardo, L.; Bracchitta, D.; Palio, O.; Pappalardo, G.; Rizzo, F.

2012-04-01

About 1300 obsidian artefacts coming from various archaeological sites of Sicily were analyzed by using the BSC-XRF (Beam Stability Controlled - X-ray Fluorescence) and PIXE-alpha (Particle Induced X-ray Emission, using low energy alpha particles) portable spectrometers developed at the Landis laboratory at the LNS-INF and IBAM-CNR in Catania (Italy). The portable BSC-XRF system allows the non-destructive analysis of the Rb, Sr, Y, Zr and Nb trace concentrations, which are considered to be characteristic of the obsidian samples and consequently are indicative of the provenance quarries. Quantitative data on Rb, Sr, Y, Zr, Nb trace element concentrations where deduced through the use of a method that makes use of a multi parameter linear regression, previously The portable PIXE-alpha spectrometer allows the quantitative determination of the matrix major elements, from Na to Zn. In the present work the two instrumental devices are presented. The data are from: Milena (Cl), Ustica (Pa), Rocchicella (Ct), Poggio dell'Acquila (Ct), San Marco (Ct), Villaggio del Petraro* (Sr) and Licodia Eubea* (Ct). Results on compositional data for trace elements and major elements allowed to identify Lipari and Pantelleria islands as the only two sources of the analysed samples. Analyses carried out on vitreous artefact found in Rocchicella, showed for the first time that the Palagonite was used as row material. *Preliminary data. Topic of conference: Application of XRS in archaeometry Kind of presentation: oral

Vision 20/20: Single photon counting x-ray detectors in medical imaging

PubMed Central

Taguchi, Katsuyuki; Iwanczyk, Jan S.

2013-01-01

Photon counting detectors (PCDs) with energy discrimination capabilities have been developed for medical x-ray computed tomography (CT) and x-ray (XR) imaging. Using detection mechanisms that are completely different from the current energy integrating detectors and measuring the material information of the object to be imaged, these PCDs have the potential not only to improve the current CT and XR images, such as dose reduction, but also to open revolutionary novel applications such as molecular CT and XR imaging. The performance of PCDs is not flawless, however, and it seems extremely challenging to develop PCDs with close to ideal characteristics. In this paper, the authors offer our vision for the future of PCD-CT and PCD-XR with the review of the current status and the prediction of (1) detector technologies, (2) imaging technologies, (3) system technologies, and (4) potential clinical benefits with PCDs. PMID:24089889

Pediatric chest HRCT using the iDose4 Hybrid Iterative Reconstruction Algorithm: Which iDose level to choose?

NASA Astrophysics Data System (ADS)

Smarda, M.; Alexopoulou, E.; Mazioti, A.; Kordolaimi, S.; Ploussi, A.; Priftis, K.; Efstathopoulos, E.

2015-09-01

Purpose of the study is to determine the appropriate iterative reconstruction (IR) algorithm level that combines image quality and diagnostic confidence, for pediatric patients undergoing high-resolution computed tomography (HRCT). During the last 2 years, a total number of 20 children up to 10 years old with a clinical presentation of chronic bronchitis underwent HRCT in our department's 64-detector row CT scanner using the iDose IR algorithm, with almost similar image settings (80kVp, 40-50 mAs). CT images were reconstructed with all iDose levels (level 1 to 7) as well as with filtered-back projection (FBP) algorithm. Subjective image quality was evaluated by 2 experienced radiologists in terms of image noise, sharpness, contrast and diagnostic acceptability using a 5-point scale (1=excellent image, 5=non-acceptable image). Artifacts existance was also pointed out. All mean scores from both radiologists corresponded to satisfactory image quality (score ≤3), even with the FBP algorithm use. Almost excellent (score <2) overall image quality was achieved with iDose levels 5 to 7, but oversmoothing artifacts appearing with iDose levels 6 and 7 affected the diagnostic confidence. In conclusion, the use of iDose level 5 enables almost excellent image quality without considerable artifacts affecting the diagnosis. Further evaluation is needed in order to draw more precise conclusions.

Modeling and measurement of the detector presampling MTF of a variable resolution x-ray CT scanner.

PubMed

Melnyk, Roman; DiBianca, Frank A

2007-03-01

The detector presampling modulation transfer function (MTF) of a 576-channel variable resolution x-ray (VRX) computed tomography (CT) scanner was evaluated in this study. The scanner employs a VRX detector, which provides increased spatial resolution by matching the scanner's field of view (FOV) to the size of an object being imaged. Because spatial resolution is the parameter the scanner promises to improve, the evaluation of this resolution is important. The scanner's pre-reconstruction spatial resolution, represented by the detector presampling MTF, was evaluated using both modeling (Monte Carlo simulation) and measurement (the moving slit method). The theoretical results show the increase in the cutoff frequency of the detector presampling MTF from 1.39 to 43.38 cycles/mm as the FOV of the VRX CT scanner decreases from 32 to 1 cm. The experimental results are in reasonable agreement with the theoretical data. Some discrepancies between the measured and the modeled detector presampling MTFs can be explained by the limitations of the model. At small FOVs (1-8 cm), the MTF measurements were limited by the size of the focal spot. The obtained results are important for further development of the VRX CT scanner.

Modeling and measurement of the detector presampling MTF of a variable resolution x-ray CT scanner

PubMed Central

Melnyk, Roman; DiBianca, Frank A.

2007-01-01

The detector presampling MTF of a 576-channel variable resolution x-ray (VRX) CT scanner was evaluated in this study. The scanner employs a VRX detector, which provides increased spatial resolution by matching the scanner’s field of view (FOV) to the size of an object being imaged. Because spatial resolution is the parameter the scanner promises to improve, the evaluation of this resolution is important. The scanner’s pre-reconstruction spatial resolution, represented by the detector presampling MTF, was evaluated using both modeling (Monte Carlo simulation) and measurement (the moving slit method). The theoretical results show the increase in the cutoff frequency of the detector presampling MTF from 1.39 cy/mm to 43.38 cy/mm as the FOV of the VRX CT scanner decreases from 32 cm to 1 cm. The experimental results are in reasonable agreement with the theoretical data. Some discrepancies between the measured and the modeled detector presampling MTFs can be explained by the limitations of the model. At small FOVs (1–8 cm), the MTF measurements were limited by the size of the focal spot. The obtained results are important for further development of the VRX CT scanner. PMID:17369872

Peripheral Quantitative CT (pQCT) Using a Dedicated Extremity Cone-Beam CT Scanner

PubMed Central

Muhit, A. A.; Arora, S.; Ogawa, M.; Ding, Y.; Zbijewski, W.; Stayman, J. W.; Thawait, G.; Packard, N.; Senn, R.; Yang, D.; Yorkston, J.; Bingham, C.O.; Means, K.; Carrino, J. A.; Siewerdsen, J. H.

2014-01-01

Purpose We describe the initial assessment of the peripheral quantitative CT (pQCT) imaging capabilities of a cone-beam CT (CBCT) scanner dedicated to musculoskeletal extremity imaging. The aim is to accurately measure and quantify bone and joint morphology using information automatically acquired with each CBCT scan, thereby reducing the need for a separate pQCT exam. Methods A prototype CBCT scanner providing isotropic, sub-millimeter spatial resolution and soft-tissue contrast resolution comparable or superior to standard multi-detector CT (MDCT) has been developed for extremity imaging, including the capability for weight-bearing exams and multi-mode (radiography, fluoroscopy, and volumetric) imaging. Assessment of pQCT performance included measurement of bone mineral density (BMD), morphometric parameters of subchondral bone architecture, and joint space analysis. Measurements employed phantoms, cadavers, and patients from an ongoing pilot study imaged with the CBCT prototype (at various acquisition, calibration, and reconstruction techniques) in comparison to MDCT (using pQCT protocols for analysis of BMD) and micro-CT (for analysis of subchondral morphometry). Results The CBCT extremity scanner yielded BMD measurement within ±2–3% error in both phantom studies and cadaver extremity specimens. Subchondral bone architecture (bone volume fraction, trabecular thickness, degree of anisotropy, and structure model index) exhibited good correlation with gold standard micro-CT (error ~5%), surpassing the conventional limitations of spatial resolution in clinical MDCT scanners. Joint space analysis demonstrated the potential for sensitive 3D joint space mapping beyond that of qualitative radiographic scores in application to non-weight-bearing versus weight-bearing lower extremities and assessment of phalangeal joint space integrity in the upper extremities. Conclusion The CBCT extremity scanner demonstrated promising initial results in accurate pQCT analysis from images acquired with each CBCT scan. Future studies will include improved x-ray scatter correction and image reconstruction techniques to further improve accuracy and to correlate pQCT metrics with known pathology. PMID:25076823

Missed rib fractures on evaluation of initial chest CT for trauma patients: pattern analysis and diagnostic value of coronal multiplanar reconstruction images with multidetector row CT.

PubMed

Cho, S H; Sung, Y M; Kim, M S

2012-10-01

The objective of this study was to review the prevalence and radiological features of rib fractures missed on initial chest CT evaluation, and to examine the diagnostic value of additional coronal images in a large series of trauma patients. 130 patients who presented to an emergency room for blunt chest trauma underwent multidetector row CT of the thorax within the first hour during their stay, and had follow-up CT or bone scans as diagnostic gold standards. Images were evaluated on two separate occasions: once with axial images and once with both axial and coronal images. The detection rates of missed rib fractures were compared between readings using a non-parametric method of clustered data. In the cases of missed rib fractures, the shapes, locations and associated fractures were evaluated. 58 rib fractures were missed with axial images only and 52 were missed with both axial and coronal images (p=0.088). The most common shape of missed rib fractures was buckled (56.9%), and the anterior arc (55.2%) was most commonly involved. 21 (36.2%) missed rib fractures had combined fractures on the same ribs, and 38 (65.5%) were accompanied by fracture on neighbouring ribs. Missed rib fractures are not uncommon, and radiologists should be familiar with buckle fractures, which are frequently missed. Additional coronal imagescan be helpful in the diagnosis of rib fractures that are not seen on axial images.

Statistical iterative reconstruction for streak artefact reduction when using multidetector CT to image the dento-alveolar structures.

PubMed

Dong, J; Hayakawa, Y; Kober, C

2014-01-01

When metallic prosthetic appliances and dental fillings exist in the oral cavity, the appearance of metal-induced streak artefacts is not avoidable in CT images. The aim of this study was to develop a method for artefact reduction using the statistical reconstruction on multidetector row CT images. Adjacent CT images often depict similar anatomical structures. Therefore, reconstructed images with weak artefacts were attempted using projection data of an artefact-free image in a neighbouring thin slice. Images with moderate and strong artefacts were continuously processed in sequence by successive iterative restoration where the projection data was generated from the adjacent reconstructed slice. First, the basic maximum likelihood-expectation maximization algorithm was applied. Next, the ordered subset-expectation maximization algorithm was examined. Alternatively, a small region of interest setting was designated. Finally, the general purpose graphic processing unit machine was applied in both situations. The algorithms reduced the metal-induced streak artefacts on multidetector row CT images when the sequential processing method was applied. The ordered subset-expectation maximization and small region of interest reduced the processing duration without apparent detriments. A general-purpose graphic processing unit realized the high performance. A statistical reconstruction method was applied for the streak artefact reduction. The alternative algorithms applied were effective. Both software and hardware tools, such as ordered subset-expectation maximization, small region of interest and general-purpose graphic processing unit achieved fast artefact correction.

Solid state VRX CT detector

NASA Astrophysics Data System (ADS)

DiBianca, Frank A.; Melnyk, Roman; Sambari, Aniket; Jordan, Lawrence M.; Laughter, Joseph S.; Zou, Ping

2000-04-01

A technique called Variable-Resolution X-ray (VRX) detection that greatly increases the spatial resolution in computed tomography (CT) and digital radiography (DR) is presented. The technique is based on a principle called 'projective compression' that allows the resolution element of a CT detector to scale with the subject or field size. For very large (40 - 50 cm) field sizes, resolution exceeding 2 cy/mm is possible and for very small fields, microscopy is attainable with resolution exceeding 100 cy/mm. Preliminary results from a 576-channel solid-state detector are presented. The detector has a dual-arm geometry and is comprised of CdWO4 scintillator crystals arranged in 24 modules of 24 channels/module. The scintillators are 0.85 mm wide and placed on 1 mm centers. Measurements of signal level, MTF and SNR, all versus detector angle, are presented.

Time-multiplexed, optically-addressed, gigabit optical crossbar switch

NASA Technical Reports Server (NTRS)

Lang, Robert J. (Inventor); Cheng, Li-Jen (Inventor); Maserjian, Joseph (Inventor)

1994-01-01

A time-multiplexed, optically-addressed, crossbar switch (38) is provided using a two-dimensional, optically-addressed, reflective spatial light modulator (O-SLM) (20). Since the optical addressing is time-multiplexed, only N addressing lines are required for an N.times.N crossbar, rather than the N.sup.2 lines needed in the prior art. This reduction in addressing lines makes possible the development of enormous crossbar switches, such as 100.times.100, for the first time. In addition, since data paths remain entirely in the optics domain, data speeds can reach the multi-gigabit level. In the switch, a row (40) of N inputs (42) at the read wavelength is spread over one axis of the O-SLM. The light is refocused along the other axis to an output array (48) of detectors (50), so that each input has the potential to talk to any one output. The O-SLM is normally off, i.e., non-reflective, so that the output is, in the absence of an input signal, zero. A one-dimensional array (52) of lasers (54) at the write wavelength is imaged onto the O-SLM. Each laser scans across an entire row of the O-SLM; where the laser is on, it turns on a portion of the O-SLM and establishes a connection between a particular input and a particular output. A full row is scanned in a time much shorter than the response time of the O-SLM, so that state of the O-SLM is capacitively stored and dynamically refreshed. The scanning is accomplished by tuning the wavelength of the laser and passing it through a grating, which sweeps the beam in space.

Multi-detector CT features of acute intestinal ischemia and their prognostic correlations.

PubMed

Moschetta, Marco; Telegrafo, Michele; Rella, Leonarda; Stabile Ianora, Amato Antonio; Angelelli, Giuseppe

2014-05-28

Acute intestinal ischemia is an abdominal emergency occurring in nearly 1% of patients presenting with acute abdomen. The causes can be occlusive or non occlusive. Early diagnosis is important to improve survival rates. In most cases of late or missed diagnosis, the mortality rate from intestinal infarction is very high, with a reported value ranging from 60% to 90%. Multi-detector computed tomography (MDCT) is a fundamental imaging technique that must be promptly performed in all patients with suspected bowel ischemia. Thanks to the new dedicated reconstruction program, its diagnostic potential is much improved compared to the past and currently it is superior to that of any other noninvasive technique. The increased spatial and temporal resolution, high-quality multi-planar reconstructions, maximum intensity projections, vessel probe, surface-shaded volume rending and tissue transition projections make MDCT the gold standard for the diagnosis of intestinal ischemia, with reported sensitivity, specificity, positive and negative predictive values of 64%-93%, 92%-100%, 90%-100% and 94%-98%, respectively. MDCT contributes to appropriate treatment planning and provides important prognostic information thanks to its ability to define the nature and extent of the disease. The purpose of this review is to examine the diagnostic and prognostic role of MDCT in bowel ischemia with special regard to the state of art new reconstruction software.

SU-E-I-15: Quantitative Evaluation of Dose Distributions From Axial, Helical and Cone-Beam CT Imaging by Measurement Using a Two-Dimensional Diode-Array Detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chacko, M; Aldoohan, S; Sonnad, J

2015-06-15

Purpose: To evaluate quantitatively dose distributions from helical, axial and cone-beam CT clinical imaging techniques by measurement using a two-dimensional (2D) diode-array detector. Methods: 2D-dose distributions from selected clinical protocols used for axial, helical and cone-beam CT imaging were measured using a diode-array detector (MapCheck2). The MapCheck2 is composed from solid state diode detectors that are arranged in horizontal and vertical lines with a spacing of 10 mm. A GE-Light-Speed CT-simulator was used to acquire axial and helical CT images and a kV on-board-imager integrated with a Varian TrueBeam-STx machine was used to acquire cone-beam CT (CBCT) images. Results: Themore » dose distributions from axial, helical and cone-beam CT were non-uniform over the region-of-interest with strong spatial and angular dependence. In axial CT, a large dose gradient was measured that decreased from lateral sides to the middle of the phantom due to large superficial dose at the side of the phantom in comparison with larger beam attenuation at the center. The dose decreased at the superior and inferior regions in comparison to the center of the phantom in axial CT. An asymmetry was found between the right-left or superior-inferior sides of the phantom which possibly to angular dependence in the dose distributions. The dose level and distribution varied from one imaging technique into another. For the pelvis technique, axial CT deposited a mean dose of 3.67 cGy, helical CT deposited a mean dose of 1.59 cGy, and CBCT deposited a mean dose of 1.62 cGy. Conclusions: MapCheck2 provides a robust tool to measure directly 2D-dose distributions for CT imaging with high spatial resolution detectors in comparison with ionization chamber that provides a single point measurement or an average dose to the phantom. The dose distributions measured with MapCheck2 consider medium heterogeneity and can represent specific patient dose.« less

A preliminary study for conducting a rational assessment of radon exposure levels.

PubMed

Jeon, Hyung-Jin; Kang, Dae-Ryoung; Go, Sang-Baek; Park, Tae-Hyun; Park, Si-Hyun; Kwak, Jung-Eun; Lee, Cheol-Min

2017-06-01

The aim of this study was to determine the factors that go into a highly reliable estimate of radon exposure levels for use in setting up the case-control study. To this end, the present study conducted a multi-faceted investigation of the distribution of radon concentrations in the bedrooms and living rooms of 400 households in the target areas during the winter months from December 2014 to February 2015. We determined that taking the mean value of the radon concentration levels detected in the bedroom and living room as the representative value of residential concentration is appropriate, given the usability of previous research data and the difference in the concentration levels between the two. In terms of detector placement, we found that detectors should not inconvenience residents or be affected by an air current. Further, we found that housing type should distinguish between regular housing (single-detached, row, and multiplex housing) and apartments but that the building type was not a key factor in the assessment of radon exposure levels. Houses should be classified into those constructed with soil (red clay) and those with constructed with general building materials for the assessment of radon exposure levels.

Evaluation of an adaptive detector collimation for prospectively ECG-triggered coronary CT angiography with third-generation dual-source CT.

PubMed

Messerli, Michael; Dewes, Patricia; Scholtz, Jan-Erik; Arendt, Christophe; Wildermuth, Simon; Vogl, Thomas J; Bauer, Ralf W

2018-05-01

To investigate the impact of an adaptive detector collimation on the dose parameters and accurateness of scan length adaption at prospectively ECG-triggered sequential cardiac CT with a wide-detector third-generation dual-source CT. Ideal scan lengths for human hearts were retrospectively derived from 103 triple-rule-out examinations. These measures were entered into the new scanner operated in prospectively ECG-triggered sequential cardiac scan mode with three different detector settings: (1) adaptive collimation, (2) fixed 64 × 0.6-mm collimation, and (3) fixed 96 × 0.6-mm collimation. Differences in effective scan length and deviation from the ideal scan length and dose parameters (CTDIvol, DLP) were documented. The ideal cardiac scan length could be matched by the adaptive collimation in every case while the mean scanned length was longer by 15.4% with the 64 × 0.6 mm and by 27.2% with the fixed 96 × 0.6-mm collimation. While the DLP was almost identical between the adaptive and the 64 × 0.6-mm collimation (83 vs. 89 mGycm at 120 kV), it was 62.7% higher with the 96 × 0.6-mm collimation (135 mGycm), p < 0.001. The adaptive detector collimation for prospectively ECG-triggered sequential acquisition allows for adjusting the scan length as accurate as this can only be achieved with a spiral acquisition. This technique allows keeping patient exposure low where patient dose would significantly increase with the traditional step-and-shoot mode. • Adaptive detector collimation allows keeping patient exposure low in cardiac CT. • With novel detectors the desired scan length can be accurately matched. • Differences in detector settings may cause 62.7% of excessive dose.

Assessment of image quality and low-contrast detectability in abdominal CT of obese patients: comparison of a novel integrated circuit with a conventional discrete circuit detector at different tube voltages.

PubMed

Euler, A; Heye, T; Kekelidze, M; Bongartz, G; Szucs-Farkas, Z; Sommer, C; Schmidt, B; Schindera, Sebastian T

2015-03-01

To compare image quality and low-contrast detectability of an integrated circuit (IC) detector in abdominal CT of obese patients with conventional detector technology at low tube voltages. A liver phantom with 45 lesions was placed in a water container to mimic an obese patient and examined on two different CT systems at 80, 100 and 120 kVp. The systems were equipped with either the IC or conventional detector. Image noise was measured, and the contrast-to-noise-ratio (CNR) was calculated. Low-contrast detectability was assessed independently by three radiologists. Radiation dose was estimated by the volume CT dose index (CTDIvol). The image noise was significantly lower, and the CNR was significantly higher with the IC detector at 80, 100 and 120 kVp, respectively (P = 0.023). The IC detector resulted in an increased lesion detection rate at 80 kVp (38.1 % vs. 17.2 %) and 100 kVp (57.0 % vs. 41.0 %). There was no difference in the detection rate between the IC detector at 100 kVp and the conventional detector at 120 kVp (57.0 % vs. 62.2 %). The CTDIvol at 80, 100 and 120 kVp measured 4.5-5.2, 7.3-7.9 and 9.8-10.2 mGy, respectively. The IC detector at 100 kVp resulted in similar low-contrast detectability compared to the conventional detector with a 120-kVp protocol at a radiation dose reduction of 37 %.

AN EVALUATION OF THE BASIC CHARACTERISTICS OF A PLASTIC SCINTILLATING FIBRE DETECTOR IN CT RADIATION FIELDS.

PubMed

Terasaki, Kento; Fujibuchi, Toshioh; Toyoda, Takatoshi; Yoshida, Yutaka; Akasaka, Tsutomu; Nohtomi, Akihiro; Morishita, Junji

2016-12-01

The ionisation chamber for computed tomography (CT) is an instrument that is most commonly used to measure the computed tomography dose index. However, it has been reported that the 10 cm effective detection length of the ionisation chamber is insufficient due to the extent of the dose distribution outside the chamber. The purpose of this study was to estimate the basic characteristics of a plastic scintillating fibre (PSF) detector with a long detection length of 50 cm in CT radiation fields. The authors investigated position dependence using diagnostic X-ray equipment and dependencies for energy, dose rate and slice thickness using an X-ray CT system. The PSF detector outputs piled up at a count rate of 10 000 counts ms -1 in dose rate dependence study. With calibration, this detector may be useful as a CT dosemeter with a long detection length except for the measurement at high dose rate. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Dose reduction in 64-row whole-body CT in multiple trauma: an optimized CT protocol with iterative image reconstruction on a gemstone-based scintillator.

PubMed

Geyer, Lucas L; Körner, Markus; Harrieder, Andreas; Mueck, Fabian G; Deak, Zsuzsanna; Wirth, Stefan; Linsenmaier, Ulrich

2016-01-01

Evaluation of potential dose savings by implementing adaptive statistical iterative reconstruction (ASiR) on a gemstone-based scintillator in a clinical 64-row whole-body CT (WBCT) protocol after multiple trauma. Dose reports of 152 WBCT scans were analysed for two 64-row multidetector CT scanners (Scanners A and B); the main scanning parameters were kept constant. ASiR and a gemstone-based scintillator were used in Scanner B, and the noise index was adjusted (head: 5.2 vs 6.0; thorax/abdomen: 29.0 vs 46.0). The scan length, CT dose index (CTDI) and dose-length product (DLP) were analysed. The estimated mean effective dose was calculated using normalized conversion factors. Student's t-test was used for statistics. Both the mean CTDI (mGy) (Scanner A: 53.8 ± 2.0, 10.3 ± 2.5, 14.4 ± 3.7; Scanner B: 48.7 ± 2.2, 7.1 ± 2.3, 9.1 ± 3.6; p < 0.001, respectively) and the mean DLP (mGy cm) (Scanner A: 1318.9 ± 167.8, 509.3 ± 134.7, 848.8 ± 254.0; Scanner B: 1190.6 ± 172.6, 354.6 ± 128.3, 561.0 ± 246.7; p < 0.001, respectively) for the head, thorax and abdomen were significantly reduced with Scanner B. There was no relevant difference in scan length. The total mean effective dose (mSv) was significantly decreased with Scanner B (24.4 ± 6.0, 17.2 ± 5.8; p < 0.001). The implementation of ASiR and a gemstone-based scintillator allows for significant dose savings in a clinical WBCT protocol. Recent technical developments can significantly reduce radiation dose of WBCT in multiple trauma. Dose reductions of 10-34% can be achieved.

Multivariate analysis of stripe rust assessment and reactions of barley in multi-location nurseries

USDA-ARS?s Scientific Manuscript database

A total of 1357 entries, mainly consisting of hulled two-row, hulled six-row and hulless barley, were evaluated in stripe rust nurseries at Toluca, Mexico during 2007, Quito, Ecuador during 2007 and 2008, and Pullman and Mt. Vernon, USA [Pacific Northwest (PNW)] during 2007_2009. Disease screening d...

Half-dose non-contrast CT in the investigation of urolithiasis: image quality improvement with third-generation integrated circuit CT detectors.

PubMed

Wang, Jun; Kang, Tony; Arepalli, Chesnal; Barrett, Sarah; O'Connell, Tim; Louis, Luck; Nicolaou, Savvakis; McLaughlin, Patrick

2015-06-01

The objective of this study is to establish the effect of third-generation integrated circuit (IC) CT detector on objective image quality in full- and half-dose non-contrast CT of the urinary tract. 51 consecutive patients with acute renal colic underwent non-contrast CT of the urinary tract using a 128-slice dual-source CT before (n = 24) and after (n = 27) the installation of third-generation IC detectors. Half-dose images were generated using projections from detector A using the dual-source RAW data. Objective image noise in the liver, spleen, right renal cortex, and right psoas muscle was compared between DC and IC cohorts for full-dose and half-dose images reconstructed with FBP and IR algorithms using 1 cm(2) regions of interest. Presence and size of obstructing ureteric calculi were also compared for full-dose and half-dose reconstructions using DC and IC detectors. No statistical difference in age and lateral body size was found between patients in the IC and DC cohorts. Radiation dose, as measured by size-specific dose estimates, did not differ significantly either between the two cohorts (10.02 ± 4.54 mGy IC vs. 12.28 ± 7.03 mGy DC). At full dose, objective image noise was not significantly lower in the IC cohort as compared to the DC cohort for the liver, spleen, and right psoas muscle. At half dose, objective image noise was lower in the IC cohort as compared to DC cohort at the liver (21.32 IC vs. 24.99 DC, 14.7% decrease, p < 0.001), spleen (19.33 IC vs. 20.83 DC, 7.20% decrease, p = 0.02), and right renal cortex (20.28 IC vs. 22.98 DC, 11.7% decrease, p = 0.005). Mean obstructing ureteric calculi size was not significantly different when comparison was made between full-dose and half-dose images, regardless of detector type (p > 0.05 for all comparisons). Third-generation IC detectors result in lower objective image noise at full- and half-radiation dose levels as compared with traditional DC detectors. The magnitude of noise reduction was greater at half-radiation dose indicating that the benefits of using novel IC detectors are greater in low and ultra-low-dose CT imaging.

High Information Capacity Quantum Imaging

DTIC Science & Technology

2014-09-19

single-pixel camera [41, 75]. An object is imaged onto a Digital Micromirror device ( DMD ), a 2D binary array of individually-addressable mirrors that...reflect light either to a single detector or a dump. Rows of the sensing matrix A consist of random, binary patterns placed sequentially on the DMD ...The single-pixel camera concept naturally adapts to imaging correlations by adding a second detector. Consider placing separate DMDs in the near-field

Highly-Integrated CMOS Interface Circuits for SiPM-Based PET Imaging Systems.

PubMed

Dey, Samrat; Lewellen, Thomas K; Miyaoka, Robert S; Rudell, Jacques C

2012-01-01

Recent developments in the area of Positron Emission Tomography (PET) detectors using Silicon Photomultipliers (SiPMs) have demonstrated the feasibility of higher resolution PET scanners due to a significant reduction in the detector form factor. The increased detector density requires a proportionally larger number of channels to interface the SiPM array with the backend digital signal processing necessary for eventual image reconstruction. This work presents a CMOS ASIC design for signal reducing readout electronics in support of an 8×8 silicon photomultiplier array. The row/column/diagonal summation circuit significantly reduces the number of required channels, reducing the cost of subsequent digitizing electronics. Current amplifiers are used with a single input from each SiPM cathode. This approach helps to reduce the detector loading, while generating all the necessary row, column and diagonal addressing information. In addition, the single current amplifier used in our Pulse-Positioning architecture facilitates the extraction of pulse timing information. Other components under design at present include a current-mode comparator which enables threshold detection for dark noise current reduction, a transimpedance amplifier and a variable output impedance I/O driver which adapts to a wide range of loading conditions between the ASIC and lines with the off-chip Analog-to-Digital Converters (ADCs).

Highly-Integrated CMOS Interface Circuits for SiPM-Based PET Imaging Systems

PubMed Central

Dey, Samrat; Lewellen, Thomas K.; Miyaoka, Robert S.; Rudell, Jacques C.

2013-01-01

Recent developments in the area of Positron Emission Tomography (PET) detectors using Silicon Photomultipliers (SiPMs) have demonstrated the feasibility of higher resolution PET scanners due to a significant reduction in the detector form factor. The increased detector density requires a proportionally larger number of channels to interface the SiPM array with the backend digital signal processing necessary for eventual image reconstruction. This work presents a CMOS ASIC design for signal reducing readout electronics in support of an 8×8 silicon photomultiplier array. The row/column/diagonal summation circuit significantly reduces the number of required channels, reducing the cost of subsequent digitizing electronics. Current amplifiers are used with a single input from each SiPM cathode. This approach helps to reduce the detector loading, while generating all the necessary row, column and diagonal addressing information. In addition, the single current amplifier used in our Pulse-Positioning architecture facilitates the extraction of pulse timing information. Other components under design at present include a current-mode comparator which enables threshold detection for dark noise current reduction, a transimpedance amplifier and a variable output impedance I/O driver which adapts to a wide range of loading conditions between the ASIC and lines with the off-chip Analog-to-Digital Converters (ADCs). PMID:24301987

[CT measurement and clinical application of double-row suture anchor reconstruction for the treatment of Tossy type III acromioclavicular joint dislocation].

PubMed

Zhang, Chuan-Kai; Liu, Chen; Han, Bing; Feng, Hui; Chen, Qi-Zhong; Sunx, Sun Yi-Yan

2017-04-25

To study feasibility and reliability of reconstruction of the acromioclavicular ligament with double-row suture anchor for the treatment of acromioclavicular joint dislocation through coracoid coronal CT measurement, and to provide a new operation method for treating acromioclavicular joint dislocation. Total 60 healthy people received CT examination of shoulder joint, including 30 males and 30 females, ranging in age from 18 to 50 years old. The coronal width, thickness and 20 degree camber angle in the medial part of the toot of coronal were measured using CT scan. The results were applied to clinical treatment for 12 patients with acromioclavicular joint dislocation of Tossy III type. The width in the medial part of the root of the coracoid was(17.65±1.82) mm(left side) and (17.67±1.80) mm(right side) in males; (16.55±1.78) mm(left side) and (16.52±1.74) mm (right side) in females. The vertical thickness of the roots of the coracoid: (13.11±2.11) mm(left side) and (13.16±2.09) mm(right side) in males;(12.79±2.21) mm(left side) and (12.76±2.19) mm (right side) in females. The thickness of 20 degrees camber angle of the coracoid roots: (16.32±1.74) mm (left side) and (16.30±1.69) mm(right side) in males; (15.68±1.44) mm(left side) and (15.67±1.43) mm(right side) in females. Total 12 patients were treated with anchor nail with extraversion 20 degrees. The postoperative X-ray films showed bone anchors were located in the coracoid process, no bone splitting. Double-row suture anchor of 5 mm diameter nails can be placed into coracoid with extraversion 20 degrees, which is safety.

Comparison of DWI and 18F-FDG PET/CT for assessing preoperative N-staging in gastric cancer: evidence from a meta-analysis.

PubMed

Luo, Mingxu; Song, Hongmei; Liu, Gang; Lin, Yikai; Luo, Lintao; Zhou, Xin; Chen, Bo

2017-10-13

The diagnostic values of diffusion weighted imaging (DWI) and 18 F-fluorodeoxyglucose positron emission tomography/computed tomography ( 18 F-FDG PET/CT) for N-staging of gastric cancer (GC) were identified and compared. After a systematic search to identify relevant articles, meta-analysis was used to summarize the sensitivities, specificities, and areas under curves (AUCs) for DWI and PET/CT. To better understand the diagnostic utility of DWI and PET/CT for N-staging, the performance of multi-detector computed tomography (MDCT) was used as a reference. Fifteen studies were analyzed. The pooled sensitivity, specificity, and AUC with 95% confidence intervals of DWI were 0.79 (0.73-0.85), 0.69 (0.61-0.77), and 0.81 (0.77-0.84), respectively. For PET/CT, the corresponding values were 0.52 (0.39-0.64), 0.88 (0.61-0.97), and 0.66 (0.62-0.70), respectively. Comparison of the two techniques revealed DWI had higher sensitivity and AUC, but no difference in specificity. DWI exhibited higher sensitivity but lower specificity than MDCT, and 18 F-FDG PET/CT had lower sensitivity and equivalent specificity. Overall, DWI performed better than 18 F-FDG PET/CT for preoperative N-staging in GC. When the efficacy of MDCT was taken as a reference, DWI represented a complementary imaging technique, while 18 F-FDG PET/CT had limited utility for preoperative N-staging.

Task III: Development of an Effective Computational Methodology for Body Force Representation of High-speed Rotor 37

NASA Technical Reports Server (NTRS)

Tan, Choon-Sooi; Suder, Kenneth (Technical Monitor)

2003-01-01

A framework for an effective computational methodology for characterizing the stability and the impact of distortion in high-speed multi-stage compressor is being developed. The methodology consists of using a few isolated-blade row Navier-Stokes solutions for each blade row to construct a body force database. The purpose of the body force database is to replace each blade row in a multi-stage compressor by a body force distribution to produce same pressure rise and flow turning. To do this, each body force database is generated in such a way that it can respond to the changes in local flow conditions. Once the database is generated, no hrther Navier-Stokes computations are necessary. The process is repeated for every blade row in the multi-stage compressor. The body forces are then embedded as source terms in an Euler solver. The method is developed to have the capability to compute the performance in a flow that has radial as well as circumferential non-uniformity with a length scale larger than a blade pitch; thus it can potentially be used to characterize the stability of a compressor under design. It is these two latter features as well as the accompanying procedure to obtain the body force representation that distinguish the present methodology from the streamline curvature method. The overall computational procedures have been developed. A dimensional analysis was carried out to determine the local flow conditions for parameterizing the magnitudes of the local body force representation of blade rows. An Euler solver was modified to embed the body forces as source terms. The results from the dimensional analysis show that the body forces can be parameterized in terms of the two relative flow angles, the relative Mach number, and the Reynolds number. For flow in a high-speed transonic blade row, they can be parameterized in terms of the local relative Mach number alone.

Evaluation of prosthetic valve obstruction on electrocardiographically gated multidetector-row computed tomography--identification of subprosthetic pannus in the aortic position.

PubMed

Ueda, Tomohiro; Teshima, Hideki; Fukunaga, Shuji; Aoyagi, Shigeaki; Tanaka, Hiroyuki

2013-01-01

This study was performed to evaluate the diagnostic role of electrocardiographically gated multidetector-row computed tomography (MDCT) for prosthetic valve obstruction (PVO) in the aortic position. Between 2002 and 2006, 9 patients were diagnosed with PVO of an aortic bileaflet mechanical valve based on echocardiographic and cineradiographic criteria. These 9 patients were examined using MDCT before replacement of the mechanical valve, and intraoperative findings were compared to morphologic periprosthetic abnormalities observed on MDCT. CT attenuation (Hounsfield units; HU) of the periprosthetic abnormalities was measured to investigate the underlying cause of the PVO. MDCT showed subprosthetic masses extending beyond the prosthetic ring into the orifice of the valve. At reoperation, presence of subprosthetic pannus was confirmed in all of the 9 patients, but no periprosthetic thrombus was found. The mean CT attenuation of the subprosthetic pannus was 170 HU, and it was significantly greater than that obtained from the interventricular septum (108 HU; P<0.0001). MDCT can be used to clearly visualize subprosthetic pannus causing PVO and the mean CT attenuation of subprosthetic pannus is significantly higher than that of the interventricular septum on MDCT.

Intravenous leiomyomatosis of the uterus with extension to the right heart

PubMed Central

2011-01-01

A 42-year-old woman admitted with debilitation and engorgement both lower extremities. Transthoracic two-dimensional echocardiography, abdominal ultrasound and computerized tomography revealed a lobulated pelvic mass, a mass within right internal iliac vein, both common iliac vein, as well as the inferior vena cava, extending into the right atrium. In addition, echocardiography and abdominal ultrasound showed the tumor of right atrium and inferior vena cave has no stalk and has well-demarcated borders with the wall of right atrium and inferior vena cave. Hence, the presumptive diagnosis of IVL was made by echocardiography and abdominal ultrasound and the presumptive diagnosis of sarcoma with invasion in right internal iliac vein, both common iliac vein, the inferior vena cava, as well as the right atrium was made by multi-detector-row computerized tomography. The patient underwent a one-stage combined multidisciplinary thoraco-abdominal operation under general anaesthetic. Subsequently the pathologic report confirmed IVL. PMID:21943238

A novel scatter separation method for multi-energy x-ray imaging

NASA Astrophysics Data System (ADS)

Sossin, A.; Rebuffel, V.; Tabary, J.; Létang, J. M.; Freud, N.; Verger, L.

2016-06-01

X-ray imaging coupled with recently emerged energy-resolved photon counting detectors provides the ability to differentiate material components and to estimate their respective thicknesses. However, such techniques require highly accurate images. The presence of scattered radiation leads to a loss of spatial contrast and, more importantly, a bias in radiographic material imaging and artefacts in computed tomography (CT). The aim of the present study was to introduce and evaluate a partial attenuation spectral scatter separation approach (PASSSA) adapted for multi-energy imaging. This evaluation was carried out with the aid of numerical simulations provided by an internal simulation tool, Sindbad-SFFD. A simplified numerical thorax phantom placed in a CT geometry was used. The attenuation images and CT slices obtained from corrected data showed a remarkable increase in local contrast and internal structure detectability when compared to uncorrected images. Scatter induced bias was also substantially decreased. In terms of quantitative performance, the developed approach proved to be quite accurate as well. The average normalized root-mean-square error between the uncorrected projections and the reference primary projections was around 23%. The application of PASSSA reduced this error to around 5%. Finally, in terms of voxel value accuracy, an increase by a factor  >10 was observed for most inspected volumes-of-interest, when comparing the corrected and uncorrected total volumes.

Volvulus of the ascending colon in a non-rotated midgut: Plain film and MDCT findings.

PubMed

Camera, Luigi; Calabrese, Milena; Mainenti, Pier Paolo; Masone, Stefania; Vecchio, Walter Del; Persico, Giovanni; Salvatore, Marco

2012-10-28

Colonic volvulus is a relatively uncommon cause of large bowel obstruction usually involving mobile, intra-peritoneal, colonic segments. Congenital or acquired anatomic variation may be associated with an increased risk of colonic volvulus which can occasionally involve retro-peritoneal segments. We report a case of 54-year-old female who presented to our Institution to perform a plain abdominal film series for acute onset of cramping abdominal pain. Both the upright and supine films showed signs of acute colonic obstruction which was thought to be due to an internal hernia of the transverse colon into the lesser sac. The patient was therefore submitted to a multi-detector contrast-enhanced computed tomography (CT). CT findings were initially thought to be consistent with the presumed diagnosis of internal hernia but further evaluation and coronal reformatting clearly depicted the presence of a colonic volvulus possibly resulting from a retro-gastric colon. At surgery, a volvulus of the ascending colon was found and a right hemi-colectomy had to be performed. However, a non rotated midgut with a right-sided duodeno-jejunal flexure and a left sided colon was also found at laparotomy and overlooked in the pre-operative CT. Retrospective evaluation of CT images was therefore performed and a number of CT signs of intestinal malrotation could be identified.

Photon Counting Energy Dispersive Detector Arrays for X-ray Imaging

PubMed Central

Iwanczyk, Jan S.; Nygård, Einar; Meirav, Oded; Arenson, Jerry; Barber, William C.; Hartsough, Neal E.; Malakhov, Nail; Wessel, Jan C.

2009-01-01

The development of an innovative detector technology for photon-counting in X-ray imaging is reported. This new generation of detectors, based on pixellated cadmium telluride (CdTe) and cadmium zinc telluride (CZT) detector arrays electrically connected to application specific integrated circuits (ASICs) for readout, will produce fast and highly efficient photon-counting and energy-dispersive X-ray imaging. There are a number of applications that can greatly benefit from these novel imagers including mammography, planar radiography, and computed tomography (CT). Systems based on this new detector technology can provide compositional analysis of tissue through spectroscopic X-ray imaging, significantly improve overall image quality, and may significantly reduce X-ray dose to the patient. A very high X-ray flux is utilized in many of these applications. For example, CT scanners can produce ~100 Mphotons/mm2/s in the unattenuated beam. High flux is required in order to collect sufficient photon statistics in the measurement of the transmitted flux (attenuated beam) during the very short time frame of a CT scan. This high count rate combined with a need for high detection efficiency requires the development of detector structures that can provide a response signal much faster than the transit time of carriers over the whole detector thickness. We have developed CdTe and CZT detector array structures which are 3 mm thick with 16×16 pixels and a 1 mm pixel pitch. These structures, in the two different implementations presented here, utilize either a small pixel effect or a drift phenomenon. An energy resolution of 4.75% at 122 keV has been obtained with a 30 ns peaking time using discrete electronics and a 57Co source. An output rate of 6×106 counts per second per individual pixel has been obtained with our ASIC readout electronics and a clinical CT X-ray tube. Additionally, the first clinical CT images, taken with several of our prototype photon-counting and energy-dispersive detector modules, are shown. PMID:19920884

Photon Counting Energy Dispersive Detector Arrays for X-ray Imaging.

PubMed

Iwanczyk, Jan S; Nygård, Einar; Meirav, Oded; Arenson, Jerry; Barber, William C; Hartsough, Neal E; Malakhov, Nail; Wessel, Jan C

2009-01-01

The development of an innovative detector technology for photon-counting in X-ray imaging is reported. This new generation of detectors, based on pixellated cadmium telluride (CdTe) and cadmium zinc telluride (CZT) detector arrays electrically connected to application specific integrated circuits (ASICs) for readout, will produce fast and highly efficient photon-counting and energy-dispersive X-ray imaging. There are a number of applications that can greatly benefit from these novel imagers including mammography, planar radiography, and computed tomography (CT). Systems based on this new detector technology can provide compositional analysis of tissue through spectroscopic X-ray imaging, significantly improve overall image quality, and may significantly reduce X-ray dose to the patient. A very high X-ray flux is utilized in many of these applications. For example, CT scanners can produce ~100 Mphotons/mm(2)/s in the unattenuated beam. High flux is required in order to collect sufficient photon statistics in the measurement of the transmitted flux (attenuated beam) during the very short time frame of a CT scan. This high count rate combined with a need for high detection efficiency requires the development of detector structures that can provide a response signal much faster than the transit time of carriers over the whole detector thickness. We have developed CdTe and CZT detector array structures which are 3 mm thick with 16×16 pixels and a 1 mm pixel pitch. These structures, in the two different implementations presented here, utilize either a small pixel effect or a drift phenomenon. An energy resolution of 4.75% at 122 keV has been obtained with a 30 ns peaking time using discrete electronics and a (57)Co source. An output rate of 6×10(6) counts per second per individual pixel has been obtained with our ASIC readout electronics and a clinical CT X-ray tube. Additionally, the first clinical CT images, taken with several of our prototype photon-counting and energy-dispersive detector modules, are shown.

NOTE: An innovative phantom for quantitative and qualitative investigation of advanced x-ray imaging technologies

NASA Astrophysics Data System (ADS)

Chiarot, C. B.; Siewerdsen, J. H.; Haycocks, T.; Moseley, D. J.; Jaffray, D. A.

2005-11-01

Development, characterization, and quality assurance of advanced x-ray imaging technologies require phantoms that are quantitative and well suited to such modalities. This note reports on the design, construction, and use of an innovative phantom developed for advanced imaging technologies (e.g., multi-detector CT and the numerous applications of flat-panel detectors in dual-energy imaging, tomosynthesis, and cone-beam CT) in diagnostic and image-guided procedures. The design addresses shortcomings of existing phantoms by incorporating criteria satisfied by no other single phantom: (1) inserts are fully 3D—spherically symmetric rather than cylindrical; (2) modules are quantitative, presenting objects of known size and contrast for quality assurance and image quality investigation; (3) features are incorporated in ideal and semi-realistic (anthropomorphic) contexts; and (4) the phantom allows devices to be inserted and manipulated in an accessible module (right lung). The phantom consists of five primary modules: (1) head, featuring contrast-detail spheres approximate to brain lesions; (2) left lung, featuring contrast-detail spheres approximate to lung modules; (3) right lung, an accessible hull in which devices may be placed and manipulated; (4) liver, featuring conrast-detail spheres approximate to metastases; and (5) abdomen/pelvis, featuring simulated kidneys, colon, rectum, bladder, and prostate. The phantom represents a two-fold evolution in design philosophy—from 2D (cylindrically symmetric) to fully 3D, and from exclusively qualitative or quantitative to a design accommodating quantitative study within an anatomical context. It has proven a valuable tool in investigations throughout our institution, including low-dose CT, dual-energy radiography, and cone-beam CT for image-guided radiation therapy and surgery.

Using the MDCT thick slab MinIP method for the follow-up of pulmonary emphysema.

PubMed

Lan, Hai; Nishitani, Hiromu; Nishihara, Sadamitsu; Ueno, Junji; Takao, Shoichiro; Iwamoto, Seiji; Kawanaka, Takashi; Mahmut, Mawlan; Qingge, Si

2011-08-01

The purpose of this study was to evaluate the usefulness of thick slab minimum intensity projection (MinIP) as a follow-up method in patients with pulmonary emphysema. This method was used to determine the presence or absence of changes over time in the lung field based on multi-detector-row CT (MDCT) data. Among patients diagnosed with pulmonary emphysema who underwent 16-MDCT (slice thickness, 1 mm) twice at an interval of 6 months or more, 12 patients without changes in the lung field and 14 with clear changes in the lung field were selected as subjects. An image interpretation experiment was performed by five image interpreters. Pulmonary emphysema was followed up using two types of thick slab MinIP (thick slab MinIP 1 and 2) and multi-planar reformation (MPR), and the results of image interpretation were evaluated by receiver operating characteristic (ROC) analysis. In addition, the time required for image interpretation was compared among the three follow-up methods. The area under the ROC curve (Az) was 0.794 for thick slab MinIP 1, 0.778 for the thick slab MinIP 2, and 0.759 for MPR, showing no significant differences among the three methods. Individual differences in each item were significantly more marked for MPR than for thick slab MinIP. The time required for image interpretation was around 18 seconds for thick slab MinIP 1, 11 seconds for thick slab MinIP 2, and approximately 127 seconds for MPR, showing significant differences among the three methods. There were no significant differences in the results of image interpretation regarding the presence or absence of changes in the lung fields between thick slab MinIP and MPR. However, thick slab MinIP showed a shorter image interpretation time and smaller individual differences in the results among image interpreters than MPR, suggesting the usefulness of this method for determining the presence or absence of changes with time in the lung fields of patients with pulmonary emphysema.

The Road to the Common PET/CT Detector

NASA Astrophysics Data System (ADS)

Nassalski, Antoni; Moszynski, Marek; Szczesniak, Tomasz; Wolski, Dariusz; Batsch, Tadeusz

2007-10-01

Growing interest in the development of dual modality positron emission/X-rays tomography (PET/CT) systems prompts researchers to face a new challenge: to acquire both the anatomical and functional information in the same measurement, simultaneously using the same detection system and electronics. The aim of this work was to study a detector consisting of LaBr3, LSO or LYSO pixel crystals coupled to an avalanche photodiode (APD). The measurements covered tests of the detectors in PET and CT modes, respectively. The measurements included the determination of light output, energy resolution, the non-proportionality of the light yield and the time resolution for 511 keV annihilation quanta; analysis also included characterizing the PET detector, and determining the dependence of counting rate versus mean current of the APD in the X-ray detection. In the present experiment, the use of counting and current modes in the CT detection increases the dynamic range of the measured dose of X-rays by a factor of 20, compared to the counting mode alone.

Comparison of multi-arm VRX CT scanners through computer models

NASA Astrophysics Data System (ADS)

Rendon, David A.; DiBianca, Frank A.; Keyes, Gary S.

2007-03-01

Variable Resolution X-ray (VRX) CT scanners allow imaging of different sized anatomy at the same level of detail using the same device. This is achieved by tilting the x-ray detectors so that the projected size of the detecting elements is varied producing reconstructions of smaller fields of view with higher spatial resolution.1 The detector can be divided in two or more separate segments, called arms, which can be placed at different angles, allowing some flexibility for the scanner design. In particular, several arms can be set at different angles creating a target region of considerably higher resolution that can be used to track the evolution of a previously diagnosed condition, while keeping the patient completely inside the field of view (FOV).2 This work presents newly-developed computer models of single-slice VRX scanners that allow us to study and compare different configurations (that is, various types of detectors arranged in any number of arms arranged in different geometries) in terms of spatial and contrast resolution. In particular, we are interested in comparing the performance of various geometric configurations that would otherwise be considered equivalent (using the same equipment, imaging FOVs of the same sizes, and having a similar overall scanner size). For this, a VRX simulator was developed, along with mathematical phantoms for spatial resolution and contrast analysis. These tools were used to compare scanner configurations that can be reproduced with materials presently available in our lab.

Potential of combining iterative reconstruction with noise efficient detector design: aggressive dose reduction in head CT

PubMed Central

Bender, B; Schabel, C; Fenchel, M; Ernemann, U; Korn, A

2015-01-01

Objective: With further increase of CT numbers and their dominant contribution to medical exposure, there is a recent quest for more effective dose control. While reintroduction of iterative reconstruction (IR) has proved its potential in many applications, a novel focus is placed on more noise efficient detectors. Our purpose was to assess the potential of IR in combination with an integrated circuit detector (ICD) for aggressive dose reduction in head CT. Methods: Non-contrast low-dose head CT [190 mAs; weighted volume CT dose index (CTDIvol), 33.2 mGy] was performed in 50 consecutive patients, using a new noise efficient detector and IR. Images were assessed in terms of quantitative and qualitative image quality and compared with standard dose acquisitions (320 mAs; CTDIvol, 59.7 mGy) using a conventional detector and filtered back projection. Results: By combining ICD and IR in low-dose examinations, the signal to noise was improved by about 13% above the baseline level in the standard-dose control group. Both, contrast-to-noise ratio (2.02 ± 0.6 vs 1.88 ± 0.4; p = 0.18) and objective measurements of image sharpness (695 ± 84 vs 705 ± 151 change in Hounsfield units per pixel; p = 0.79) were fully preserved in the low-dose group. Likewise, there was no significant difference in the grading of several subjective image quality parameters when both noise-reducing strategies were used in low-dose examinations. Conclusion: Combination of noise efficient detector with IR allows for meaningful dose reduction in head CT without compromise of standard image quality. Advances in knowledge: Our study demonstrates the feasibility of almost 50% dose reduction in head CT dose (1.1 mSv per scan) through combination of novel dose-reducing strategies. PMID:25827204

Usefulness of model-based iterative reconstruction in semi-automatic volumetry for ground-glass nodules at ultra-low-dose CT: a phantom study.

PubMed

Maruyama, Shuki; Fukushima, Yasuhiro; Miyamae, Yuta; Koizumi, Koji

2018-06-01

This study aimed to investigate the effects of parameter presets of the forward projected model-based iterative reconstruction solution (FIRST) on the accuracy of pulmonary nodule volume measurement. A torso phantom with simulated nodules [diameter: 5, 8, 10, and 12 mm; computed tomography (CT) density: - 630 HU] was scanned with a multi-detector CT at tube currents of 10 mA (ultra-low-dose: UL-dose) and 270 mA (standard-dose: Std-dose). Images were reconstructed with filtered back projection [FBP; standard (Std-FBP), ultra-low-dose (UL-FBP)], FIRST Lung (UL-Lung), and FIRST Body (UL-Body), and analyzed with a semi-automatic software. The error in the volume measurement was determined. The errors with UL-Lung and UL-Body were smaller than that with UL-FBP. The smallest error was 5.8% ± 0.3 for the 12-mm nodule with UL-Body (middle lung). Our results indicated that FIRST Body would be superior to FIRST Lung in terms of accuracy of nodule measurement with UL-dose CT.

Monte Carlo simulation of simultaneous radiation detection in the hybrid tomography system ClearPET-XPAD3/CT

NASA Astrophysics Data System (ADS)

Dávila, H. Olaya; Sevilla, A. C.; Castro, H. F.; Martínez, S. A.

2016-07-01

Using the Geant4 based simulation framework SciFW1, a detailed simulation was performed for a detector array in the hybrid tomography prototype for small animals called ClearPET / XPAD, which was built in the Centre de Physique des Particules de Marseille. The detector system consists of an array of phoswich scintillation detectors: LSO (Lutetium Oxy-ortosilicate doped with cerium Lu2SiO5:Ce) and LuYAP (Lutetium Ortoaluminate of Yttrium doped with cerium Lu0.7Y0.3AlO3:Ce) for Positron Emission Tomography (PET) and hybrid pixel detector XPAD for Computed Tomography (CT). Simultaneous acquisition of deposited energy and the corresponding time - position for each recorded event were analyzed, independently, for both detectors. interference between detection modules for PET and CT. Information about amount of radiation reaching each phoswich crystal and XPAD detector using a phantom in order to study the effectiveness by radiation attenuation and influence the positioning of the radioactive source 22Na was obtained. The simulation proposed will improve distribution of detectors rings and interference values will be taken into account in the new versions of detectors.

A Novel CMOS Multi-band THz Detector with Embedded Ring Antenna

NASA Astrophysics Data System (ADS)

Xu, Lei-jun; Guan, Jia-ning; Bai, Xue; Li, Qin; Mao, Han-ping

2017-10-01

To overcome the large chip area occupation for the traditional terahertz multi-frequency detector by using the antenna elements in a different frequency, a novel structure for a multi-frequency detector is proposed and studied. Based on the ring antenna detector, an embedded multi-ring antenna with multi-port is proposed for the multi-frequency detector. A single-ring and dual-ring detectors are analyzed and designed in 0.18 μ m CMOS. For the single-ring detector, the best responsivity and NEP is 701 V/W and 261 pW/Hz0.5 at the frequency of 290 GHz. For the dual-ring detector, the best responsivity is 367 V/W and 297 V/W, NEP is 578 pW/Hz0.5 and 713pW/Hz0.5, at the frequency of 600 GHz and 806 GHz, respectively. This embedded multi-ring detector has a simple structure which can be expanded easily in a compact size.

Cardiac Multi-detector CT Segmentation Based on Multiscale Directional Edge Detector and 3D Level Set.

PubMed

Antunes, Sofia; Esposito, Antonio; Palmisano, Anna; Colantoni, Caterina; Cerutti, Sergio; Rizzo, Giovanna

2016-05-01

Extraction of the cardiac surfaces of interest from multi-detector computed tomographic (MDCT) data is a pre-requisite step for cardiac analysis, as well as for image guidance procedures. Most of the existing methods need manual corrections, which is time-consuming. We present a fully automatic segmentation technique for the extraction of the right ventricle, left ventricular endocardium and epicardium from MDCT images. The method consists in a 3D level set surface evolution approach coupled to a new stopping function based on a multiscale directional second derivative Gaussian filter, which is able to stop propagation precisely on the real boundary of the structures of interest. We validated the segmentation method on 18 MDCT volumes from healthy and pathologic subjects using manual segmentation performed by a team of expert radiologists as gold standard. Segmentation errors were assessed for each structure resulting in a surface-to-surface mean error below 0.5 mm and a percentage of surface distance with errors less than 1 mm above 80%. Moreover, in comparison to other segmentation approaches, already proposed in previous work, our method presented an improved accuracy (with surface distance errors less than 1 mm increased of 8-20% for all structures). The obtained results suggest that our approach is accurate and effective for the segmentation of ventricular cavities and myocardium from MDCT images.

Objective image characterization of a spectral CT scanner with dual-layer detector

NASA Astrophysics Data System (ADS)

Ozguner, Orhan; Dhanantwari, Amar; Halliburton, Sandra; Wen, Gezheng; Utrup, Steven; Jordan, David

2018-01-01

This work evaluated the performance of a detector-based spectral CT system by obtaining objective reference data, evaluating attenuation response of iodine and accuracy of iodine quantification, and comparing conventional CT and virtual monoenergetic images in three common phantoms. Scanning was performed using the hospital’s clinical adult body protocol. Modulation transfer function (MTF) was calculated for a tungsten wire and visual line pair targets were evaluated. Image noise power spectrum (NPS) and pixel standard deviation were calculated. MTF for monoenergetic images agreed with conventional images within 0.05 lp cm-1. NPS curves indicated that noise texture of 70 keV monoenergetic images is similar to conventional images. Standard deviation measurements showed monoenergetic images have lower noise except at 40 keV. Mean CT number and CNR agreed with conventional images at 75 keV. Measured iodine concentration agreed with true concentration within 6% for inserts at the center of the phantom. Performance of monoenergetic images at detector based spectral CT is the same as, or better than, that of conventional images. Spectral acquisition and reconstruction with a detector based platform represents the physical behaviour of iodine as expected and accurately quantifies the material concentration.

Application of an oscillation-type linear cadmium telluride detector to enhanced gadolinium K-edge computed tomography

NASA Astrophysics Data System (ADS)

Matsukiyo, Hiroshi; Sato, Eiichi; Hagiwara, Osahiko; Abudurexiti, Abulajiang; Osawa, Akihiro; Enomoto, Toshiyuki; Watanabe, Manabu; Nagao, Jiro; Sato, Shigehiro; Ogawa, Akira; Onagawa, Jun

2011-03-01

A linear cadmium telluride (CdTe) detector is useful for carrying out energy-discrimination X-ray imaging, including computed tomography (CT). To perform enhanced gadolinium K-edge CT, we used an oscillation-type linear CdTe detector with an energy resolution of 1.2 keV. CT is performed by repeating the linear scan and the rotation of an object. Penetrating X-ray photons from the object are detected by the CdTe detector, and event signals of X-ray photons are produced using charge-sensitive and shaping amplifiers. Both the photon energy and the energy width are selected using a multichannel analyzer, and the number of photons is counted by a counter card. In energy-discrimination CT, tube voltage and current were 80 kV and 20 μA, respectively, and X-ray intensity was 1.55 μGy/s at 1.0 m from the source at a tube voltage of 80 kV. Demonstration of enhanced gadolinium K-edge X-ray CT was carried out by selecting photons with energies just beyond gadolinium K-edge energy of 50.3 keV.

User's Guide for MSAP2D: A Program for Unsteady Aerodynamic and Aeroelastic (Flutter and Forced Response) Analysis of Multistage Compressors and Turbines. 1.0

NASA Technical Reports Server (NTRS)

Reddy, T. S. R.; Srivastava, R.

1996-01-01

This guide describes the input data required for using MSAP2D (Multi Stage Aeroelastic analysis Program - Two Dimensional) computer code. MSAP2D can be used for steady, unsteady aerodynamic, and aeroelastic (flutter and forced response) analysis of bladed disks arranged in multiple blade rows such as those found in compressors, turbines, counter rotating propellers or propfans. The code can also be run for single blade row. MSAP2D code is an extension of the original NPHASE code for multiblade row aerodynamic and aeroelastic analysis. Euler equations are used to obtain aerodynamic forces. The structural dynamic equations are written for a rigid typical section undergoing pitching (torsion) and plunging (bending) motion. The aeroelastic equations are solved in time domain. For single blade row analysis, frequency domain analysis is also provided to obtain unsteady aerodynamic coefficients required in an eigen analysis for flutter. In this manual, sample input and output are provided for a single blade row example, two blade row example with equal and unequal number of blades in the blade rows.

Technical Note: Confirming the prescribed angle of CT localizer radiographs and c-arm projection acquisitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szczykutowicz, Timothy P., E-mail: tszczykutowicz@uwhealth.org; Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705; Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706

2016-02-15

Purpose: Accurate CT radiograph angle is not usually important in diagnostic CT. However, there are applications in radiation oncology and interventional radiology in which the orientation of the x-ray source and detector with respect to the patient is clinically important. The authors present a method for measuring the accuracy of the tube/detector assembly with respect to the prescribed tube/detector position for CT localizer, fluoroscopic, and general radiograph imaging using diagnostic, mobile, and c-arm based CT systems. Methods: A mathematical expression relating the x-ray projection of two metal BBs is related to gantry angle. Measurement of the BBs at a prescribedmore » gantry (i.e., c-arm) angle can be obtained and using this relation the prescribed versus actual gantry angle compared. No special service mode or proprietary information is required, only access to projection images is required. Projection images are available in CT via CT localizer radiographs and in the interventional setting via fluorography. Results: The technique was demonstrated on two systems, a mobile CT scanner and a diagnostic CT scanner. The results confirmed a known issue with the mobile scanner and accurately described the CT localizer angle of the diagnostic system tested. Conclusions: This method can be used to quantify gantry angle, which is important when projection images are used for procedure guidance, such as in brachytherapy and interventional radiology applications.« less

Missed rib fractures on evaluation of initial chest CT for trauma patients: pattern analysis and diagnostic value of coronal multiplanar reconstruction images with multidetector row CT

PubMed Central

Cho, S H; Sung, Y M; Kim, M S

2012-01-01

Objective The objective of this study was to review the prevalence and radiological features of rib fractures missed on initial chest CT evaluation, and to examine the diagnostic value of additional coronal images in a large series of trauma patients. Methods 130 patients who presented to an emergency room for blunt chest trauma underwent multidetector row CT of the thorax within the first hour during their stay, and had follow-up CT or bone scans as diagnostic gold standards. Images were evaluated on two separate occasions: once with axial images and once with both axial and coronal images. The detection rates of missed rib fractures were compared between readings using a non-parametric method of clustered data. In the cases of missed rib fractures, the shapes, locations and associated fractures were evaluated. Results 58 rib fractures were missed with axial images only and 52 were missed with both axial and coronal images (p=0.088). The most common shape of missed rib fractures was buckled (56.9%), and the anterior arc (55.2%) was most commonly involved. 21 (36.2%) missed rib fractures had combined fractures on the same ribs, and 38 (65.5%) were accompanied by fracture on neighbouring ribs. Conclusion Missed rib fractures are not uncommon, and radiologists should be familiar with buckle fractures, which are frequently missed. Additional coronal imagescan be helpful in the diagnosis of rib fractures that are not seen on axial images. PMID:22514102

Image quality and radiation reduction of 320-row area detector CT coronary angiography with optimal tube voltage selection and an automatic exposure control system: comparison with body mass index-adapted protocol.

PubMed

Lim, Jiyeon; Park, Eun-Ah; Lee, Whal; Shim, Hackjoon; Chung, Jin Wook

2015-06-01

To assess the image quality and radiation exposure of 320-row area detector computed tomography (320-ADCT) coronary angiography with optimal tube voltage selection with the guidance of an automatic exposure control system in comparison with a body mass index (BMI)-adapted protocol. Twenty-two patients (study group) underwent 320-ADCT coronary angiography using an automatic exposure control system with the target standard deviation value of 33 as the image quality index and the lowest possible tube voltage. For comparison, a sex- and BMI-matched group (control group, n = 22) using a BMI-adapted protocol was established. Images of both groups were reconstructed by an iterative reconstruction algorithm. For objective evaluation of the image quality, image noise, vessel density, signal to noise ratio (SNR), and contrast to noise ratio (CNR) were measured. Two blinded readers then subjectively graded the image quality using a four-point scale (1: nondiagnostic to 4: excellent). Radiation exposure was also measured. Although the study group tended to show higher image noise (14.1 ± 3.6 vs. 9.3 ± 2.2 HU, P = 0.111) and higher vessel density (665.5 ± 161 vs. 498 ± 143 HU, P = 0.430) than the control group, the differences were not significant. There was no significant difference between the two groups for SNR (52.5 ± 19.2 vs. 60.6 ± 21.8, P = 0.729), CNR (57.0 ± 19.8 vs. 67.8 ± 23.3, P = 0.531), or subjective image quality scores (3.47 ± 0.55 vs. 3.59 ± 0.56, P = 0.960). However, radiation exposure was significantly reduced by 42 % in the study group (1.9 ± 0.8 vs. 3.6 ± 0.4 mSv, P = 0.003). Optimal tube voltage selection with the guidance of an automatic exposure control system in 320-ADCT coronary angiography allows substantial radiation reduction without significant impairment of image quality, compared to the results obtained using a BMI-based protocol.

30 CFR 75.1714-7 - Multi-gas detectors.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Multi-gas detectors. 75.1714-7 Section 75.1714... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Miscellaneous § 75.1714-7 Multi-gas detectors. (a) Availability. A mine operator shall provide an MSHA-approved, handheld, multi-gas detector that...

30 CFR 75.1714-7 - Multi-gas detectors.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Multi-gas detectors. 75.1714-7 Section 75.1714... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Miscellaneous § 75.1714-7 Multi-gas detectors. (a) Availability. A mine operator shall provide an MSHA-approved, handheld, multi-gas detector that...

30 CFR 75.1714-7 - Multi-gas detectors.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Multi-gas detectors. 75.1714-7 Section 75.1714... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Miscellaneous § 75.1714-7 Multi-gas detectors. (a) Availability. A mine operator shall provide an MSHA-approved, handheld, multi-gas detector that...

30 CFR 75.1714-7 - Multi-gas detectors.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Multi-gas detectors. 75.1714-7 Section 75.1714... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Miscellaneous § 75.1714-7 Multi-gas detectors. (a) Availability. A mine operator shall provide an MSHA-approved, handheld, multi-gas detector that...

30 CFR 75.1714-7 - Multi-gas detectors.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Multi-gas detectors. 75.1714-7 Section 75.1714... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Miscellaneous § 75.1714-7 Multi-gas detectors. (a) Availability. A mine operator shall provide an MSHA-approved, handheld, multi-gas detector that...

Influence of different length of core suture purchase among suture row on the strength of 6-strand tendon repairs.

PubMed

Okubo, Hirotaka; Kusano, Nozomu; Kinjo, Masaki; Kanaya, Fuminori

2015-01-01

In multi-strand suture methods consisting of several suture rows, the different length of core suture purchase between each suture row may affect the strength of repairs. We evaluated the influence of the different length of core suture purchase between each suture row on the strength of 6-strand tendon repairs. Rabbit flexor tendons were repaired by using a triple-looped suture technique in which the suture purchase length in each suture row was modified. Group 1, all lengths are 8-mm. Group 2, all lengths are 10-mm. Group 3, two are 10-mm and one is 8-mm. Group 4, one is 10-mm and two are 8-mm. The repaired tendons were subjected to load-to-failure test. The gap strength was significantly greater in Group 1 and Group 2 than in Group 3 and Group 4. This study demonstrates that maintaining equal core suture purchase lengths of each suture row increases the gap resistance.

[Diagnostic values of bronchoscopy and multi-slice spiral CT for congenital dysplasia of the respiratory system in infants: a comparative study].

PubMed

Wang, Xing-Lu; Huang, Ying; Li, Qu-Bei; Dai, Ji-Hong

2013-09-01

To investigate and compare the diagnostic values of bronchoscopy and multi-slice spiral computed tomography (CT) for congenital dysplasia of the respiratory system in infants. Analysis was performed on the clinical data, bronchoscopic findings and multi-slice spiral CT findings of 319 infants (≤1 years old) who underwent bronchoscopy and/or multi-slice spiral CT and were diagnosed with congenital dysplasia of the respiratory system. A total of 476 cases of congenital dysplasia of the respiratory system were found in the 319 infants, including primary dysplasia of the respiratory system (392 cases) and compressive dysplasia of the respiratory system (84 cases). Of the 392 cases of primary dysplasia of the respiratory system, 225 (57.4%) were diagnosed by bronchoscopy versus 167 (42.6%) by multi-slice spiral CT. There were significant differences in etiological diagnosis between bronchoscopy and multi-slice spiral CT in infants with congenital dysplasia of the respiratory system (P<0.05). All 76 cases of primary dysplasia of the respiratory system caused by tracheobronchomalacia were diagnosed by bronchoscopy and all 17 cases of primary dysplasia of the respiratory system caused by lung tissue dysplasia were diagnosed by multi-slice spiral CT. Of the 84 cases of compressive dysplasia of the respiratory system, 74 cases were diagnosed by multi-slice spiral CT and only 10 cases were diagnosed by bronchoscopy. Compared with multi-slice spiral CT, bronchoscopy can detect primary dysplasia of the respiratory system more directly. Bronchoscopy is valuable in the confirmed diagnosis of tracheobronchomalacia. Multi-slice spiral CT has a higher diagnostic value for lung tissue dysplasia than bronchoscopy.

Project Report: Active Pipeline Encroachment Detector (Phase I)

DOT National Transportation Integrated Search

2008-06-10

Of the many pipeline accident causes that occur to oil and gas pipelines, approximately 40% of are caused by third-party excavating activities into the buried pipeline right of way (ROW). According to DOT statistics, excavation damage is the second l...

Pancreatitis-imaging approach

PubMed Central

Busireddy, Kiran K; AlObaidy, Mamdoh; Ramalho, Miguel; Kalubowila, Janaka; Baodong, Liu; Santagostino, Ilaria; Semelka, Richard C

2014-01-01

Pancreatitis is defined as the inflammation of the pancreas and considered the most common pancreatic disease in children and adults. Imaging plays a significant role in the diagnosis, severity assessment, recognition of complications and guiding therapeutic interventions. In the setting of pancreatitis, wider availability and good image quality make multi-detector contrast-enhanced computed tomography (MD-CECT) the most used imaging technique. However, magnetic resonance imaging (MRI) offers diagnostic capabilities similar to those of CT, with additional intrinsic advantages including lack of ionizing radiation and exquisite soft tissue characterization. This article reviews the proposed definitions of revised Atlanta classification for acute pancreatitis, illustrates a wide range of morphologic pancreatic parenchymal and associated peripancreatic changes for different types of acute pancreatitis. It also describes the spectrum of early and late chronic pancreatitis imaging findings and illustrates some of the less common types of chronic pancreatitis, with special emphasis on the role of CT and MRI. PMID:25133027

Image quality improvement in MDCT cardiac imaging via SMART-RECON method

NASA Astrophysics Data System (ADS)

Li, Yinsheng; Cao, Ximiao; Xing, Zhanfeng; Sun, Xuguang; Hsieh, Jiang; Chen, Guang-Hong

2017-03-01

Coronary CT angiography (CCTA) is a challenging imaging task currently limited by the achievable temporal resolution of modern Multi-Detector CT (MDCT) scanners. In this paper, the recently proposed SMARTRECON method has been applied in MDCT-based CCTA imaging to improve the image quality without any prior knowledge of cardiac motion. After the prospective ECG-gated data acquisition from a short-scan angular span, the acquired data were sorted into several sub-sectors of view angles; each corresponds to a 1/4th of the short-scan angular range. Information of the cardiac motion was thus encoded into the data in each view angle sub-sector. The SMART-RECON algorithm was then applied to jointly reconstruct several image volumes, each of which is temporally consistent with the data acquired in the corresponding view angle sub-sector. Extensive numerical simulations were performed to validate the proposed technique and investigate the performance dependence.

A variable resolution x-ray detector for computed tomography: II. Imaging theory and performance.

PubMed

DiBianca, F A; Zou, P; Jordan, L M; Laughter, J S; Zeman, H D; Sebes, J

2000-08-01

A computed tomography (CT) imaging technique called variable resolution x-ray (VRX) detection provides variable image resolution ranging from that of clinical body scanning (1 cy/mm) to that of microscopy (100 cy/mm). In this paper, an experimental VRX CT scanner based on a rotating subject table and an angulated storage phosphor screen detector is described and tested. The measured projection resolution of the scanner is > or = 20 lp/mm. Using this scanner, 4.8-s CT scans are made of specimens of human extremities and of in vivo hamsters. In addition, the system's projected spatial resolution is calculated to exceed 100 cy/mm for a future on-line CT scanner incorporating smaller focal spots (0.1 mm) than those currently used and a 1008-channel VRX detector with 0.6-mm cell spacing.

Image deblurring by motion estimation for remote sensing

NASA Astrophysics Data System (ADS)

Chen, Yueting; Wu, Jiagu; Xu, Zhihai; Li, Qi; Feng, Huajun

2010-08-01

The imagery resolution of imaging systems for remote sensing is often limited by image degradation resulting from unwanted motion disturbances of the platform during image exposures. Since the form of the platform vibration can be arbitrary, the lack of priori knowledge about the motion function (the PSF) suggests blind restoration approaches. A deblurring method which combines motion estimation and image deconvolution both for area-array and TDI remote sensing has been proposed in this paper. The image motion estimation is accomplished by an auxiliary high-speed detector and a sub-pixel correlation algorithm. The PSF is then reconstructed from estimated image motion vectors. Eventually, the clear image can be recovered by the Richardson-Lucy (RL) iterative deconvolution algorithm from the blurred image of the prime camera with the constructed PSF. The image deconvolution for the area-array detector is direct. While for the TDICCD detector, an integral distortion compensation step and a row-by-row deconvolution scheme are applied. Theoretical analyses and experimental results show that, the performance of the proposed concept is convincing. Blurred and distorted images can be properly recovered not only for visual observation, but also with significant objective evaluation increment.

Multi-energy spectral CT: adding value in emergency body imaging.

PubMed

Punjabi, Gopal V

2018-04-01

Most vendors offer scanners capable of dual- or multi-energy computed tomography (CT) imaging. Advantages of multi-energy CT scanning include superior tissue characterization, detection of subtle iodine uptake differences, and opportunities to reduce contrast dose. However, utilization of this technology in the emergency department (ED) remains low. The purpose of this pictorial essay is to illustrate the value of multi-energy CT scanning in emergency body imaging.

High-quality 3D correction of ring and radiant artifacts in flat panel detector-based cone beam volume CT imaging

NASA Astrophysics Data System (ADS)

Abu Anas, Emran Mohammad; Kim, Jae Gon; Lee, Soo Yeol; Kamrul Hasan, Md

2011-10-01

The use of an x-ray flat panel detector is increasingly becoming popular in 3D cone beam volume CT machines. Due to the deficient semiconductor array manufacturing process, the cone beam projection data are often corrupted by different types of abnormalities, which cause severe ring and radiant artifacts in a cone beam reconstruction image, and as a result, the diagnostic image quality is degraded. In this paper, a novel technique is presented for the correction of error in the 2D cone beam projections due to abnormalities often observed in 2D x-ray flat panel detectors. Template images are derived from the responses of the detector pixels using their statistical properties and then an effective non-causal derivative-based detection algorithm in 2D space is presented for the detection of defective and mis-calibrated detector elements separately. An image inpainting-based 3D correction scheme is proposed for the estimation of responses of defective detector elements, and the responses of the mis-calibrated detector elements are corrected using the normalization technique. For real-time implementation, a simplification of the proposed off-line method is also suggested. Finally, the proposed algorithms are tested using different real cone beam volume CT images and the experimental results demonstrate that the proposed methods can effectively remove ring and radiant artifacts from cone beam volume CT images compared to other reported techniques in the literature.

Design and Construction of Detector and Data Acquisition Elements for Proton Computed Tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fermi Research Alliance; Northern Illinois University

2015-07-15

Proton computed tomography (pCT) offers an alternative to x-ray imaging with potential for three-dimensional imaging, reduced radiation exposure, and in-situ imaging. Northern Illinois University (NIU) is developing a second-generation proton computed tomography system with a goal of demonstrating the feasibility of three-dimensional imaging within clinically realistic imaging times. The second-generation pCT system is comprised of a tracking system, a calorimeter, data acquisition, a computing farm, and software algorithms. The proton beam encounters the upstream tracking detectors, the patient or phantom, the downstream tracking detectors, and a calorimeter. The schematic layout of the PCT system is shown. The data acquisition sendsmore » the proton scattering information to an offline computing farm. Major innovations of the second generation pCT project involve an increased data acquisition rate ( MHz range) and development of three-dimensional imaging algorithms. The Fermilab Particle Physics Division and Northern Illinois Center for Accelerator and Detector Development at Northern Illinois University worked together to design and construct the tracking detectors, calorimeter, readout electronics and detector mounting system.« less

A hyperspectral X-ray computed tomography system for enhanced material identification

NASA Astrophysics Data System (ADS)

Wu, Xiaomei; Wang, Qian; Ma, Jinlei; Zhang, Wei; Li, Po; Fang, Zheng

2017-08-01

X-ray computed tomography (CT) can distinguish different materials according to their absorption characteristics. The hyperspectral X-ray CT (HXCT) system proposed in the present work reconstructs each voxel according to its X-ray absorption spectral characteristics. In contrast to a dual-energy or multi-energy CT system, HXCT employs cadmium telluride (CdTe) as the x-ray detector, which provides higher spectral resolution and separate spectral lines according to the material's photon-counter working principle. In this paper, a specimen containing ten different polymer materials randomly arranged was adopted for material identification by HXCT. The filtered back-projection algorithm was applied for image and spectral reconstruction. The first step was to sort the individual material components of the specimen according to their cross-sectional image intensity. The second step was to classify materials with similar intensities according to their reconstructed spectral characteristics. The results demonstrated the feasibility of the proposed material identification process and indicated that the proposed HXCT system has good prospects for a wide range of biomedical and industrial nondestructive testing applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruger, R.

The US National Lung Screening Trial (NLST) was a multi-center randomized, controlled trial comparing a low-dose CT (LDCT) to posterior-anterior (PA) chest x-ray (CXR) in screening older, current and former heavy smokers for early detection of lung cancer. Recruitment was launched in September 2002 and ended in April 2004 when 53,454 participants had been randomized at 33 screening sites in equal proportions. Funded by the National Cancer Institute this trial demonstrated that LDCT screening reduced lung cancer mortality. The US Preventive Services Task Force (USPSTF) cited NLST findings and conclusions in its deliberations and analysis of lung cancer screening. Undermore » the 2010 Patient Protection and Affordable Care Act, the USPSTF favorable recommendation regarding lung cancer CT screening assisted in obtaining third-party payers coverage for screening. The objective of this session is to provide an introduction to the NLST and the trial findings, in addition to a comprehensive review of the dosimetry investigations and assessments completed using individual NLST participant CT and CXR examinations. Session presentations will review and discuss the findings of two independent assessments, a CXR assessment and the findings of a CT investigation calculating individual organ dosimetry values. The CXR assessment reviewed a total of 73,733 chest x-ray exams that were performed on 92 chest imaging systems of which 66,157 participant examinations were used. The CT organ dosimetry investigation collected scan parameters from 23,773 CT examinations; a subset of the 75,133 CT examinations performed using 97 multi-detector CT scanners. Organ dose conversion coefficients were calculated using a Monte Carlo code. An experimentally-validated CT scanner simulation was coupled with 193 adult hybrid computational phantoms representing the height and weight of the current U.S. population. The dose to selected organs was calculated using the organ dose library and the abstracted scan parameters. This session will review the results and summarize the individualized doses to major organs and the mean effective dose and CTDIvol estimate for 66,157 PA chest and 23,773 CT examinations respectively, using size-dependent computational phantoms coupled with Monte Carlo calculations. Learning Objectives: Review and summarize relevant NLST findings and conclusions. Understand the scope and scale of the NLST specific to participant dosimetry. Provide a comprehensive review of NLST participant dosimetry assessments. Summarize the results of an investigation providing individualized organ dose estimates for NLST participant cohorts.« less

Multispectral x-ray CT: multivariate statistical analysis for efficient reconstruction

NASA Astrophysics Data System (ADS)

Kheirabadi, Mina; Mustafa, Wail; Lyksborg, Mark; Lund Olsen, Ulrik; Bjorholm Dahl, Anders

2017-10-01

Recent developments in multispectral X-ray detectors allow for an efficient identification of materials based on their chemical composition. This has a range of applications including security inspection, which is our motivation. In this paper, we analyze data from a tomographic setup employing the MultiX detector, that records projection data in 128 energy bins covering the range from 20 to 160 keV. Obtaining all information from this data requires reconstructing 128 tomograms, which is computationally expensive. Instead, we propose to reduce the dimensionality of projection data prior to reconstruction and reconstruct from the reduced data. We analyze three linear methods for dimensionality reduction using a dataset with 37 equally-spaced projection angles. Four bottles with different materials are recorded for which we are able to obtain similar discrimination of their content using a very reduced subset of tomograms compared to the 128 tomograms that would otherwise be needed without dimensionality reduction.

Solid-state Image Sensor with Focal-plane Digital Photon-counting Pixel Array

NASA Technical Reports Server (NTRS)

Fossum, Eric R.; Pain, Bedabrata

1997-01-01

A solid-state focal-plane imaging system comprises an NxN array of high gain. low-noise unit cells. each unit cell being connected to a different one of photovoltaic detector diodes, one for each unit cell, interspersed in the array for ultra low level image detection and a plurality of digital counters coupled to the outputs of the unit cell by a multiplexer(either a separate counter for each unit cell or a row of N of counters time shared with N rows of digital counters). Each unit cell includes two self-biasing cascode amplifiers in cascade for a high charge-to-voltage conversion gain (greater than 1mV/e(-)) and an electronic switch to reset input capacitance to a reference potential in order to be able to discriminate detection of an incident photon by the photoelectron (e(-))generated in the detector diode at the input of the first cascode amplifier in order to count incident photons individually in a digital counter connected to the output of the second cascade amplifier. Reseting the input capacitance and initiating self-biasing of the amplifiers occurs every clock cycle of an integratng period to enable ultralow light level image detection by the may of photovoltaic detector diodes under such ultralow light level conditions that the photon flux will statistically provide only a single photon at a time incident on anyone detector diode during any clock cycle.

Comparison of DWI and 18F-FDG PET/CT for assessing preoperative N-staging in gastric cancer: evidence from a meta-analysis

PubMed Central

Luo, Mingxu; Song, Hongmei; Liu, Gang; Lin, Yikai; Luo, Lintao; Zhou, Xin; Chen, Bo

2017-01-01

The diagnostic values of diffusion weighted imaging (DWI) and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) for N-staging of gastric cancer (GC) were identified and compared. After a systematic search to identify relevant articles, meta-analysis was used to summarize the sensitivities, specificities, and areas under curves (AUCs) for DWI and PET/CT. To better understand the diagnostic utility of DWI and PET/CT for N-staging, the performance of multi-detector computed tomography (MDCT) was used as a reference. Fifteen studies were analyzed. The pooled sensitivity, specificity, and AUC with 95% confidence intervals of DWI were 0.79 (0.73–0.85), 0.69 (0.61–0.77), and 0.81 (0.77–0.84), respectively. For PET/CT, the corresponding values were 0.52 (0.39–0.64), 0.88 (0.61–0.97), and 0.66 (0.62–0.70), respectively. Comparison of the two techniques revealed DWI had higher sensitivity and AUC, but no difference in specificity. DWI exhibited higher sensitivity but lower specificity than MDCT, and 18F-FDG PET/CT had lower sensitivity and equivalent specificity. Overall, DWI performed better than 18F-FDG PET/CT for preoperative N-staging in GC. When the efficacy of MDCT was taken as a reference, DWI represented a complementary imaging technique, while 18F-FDG PET/CT had limited utility for preoperative N-staging. PMID:29137440

Installation for the catalytic afterburning of exhaust gases of a multi-cylinder internal combustion engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lange, K.

1974-04-24

An installation for the catalytic afterburning of exhaust gases of a multi-cylinder internal combustion engine has two cylinder rows with two exhaust gas lines, each of which includes at least one catalyst. A temperature-responsive control is operable during engine start-up to conduct substantially the entire exhaust gas flow from the internal combustion engine during warmup for a predetermined time by way of only one of the two catalyst and then, after a short period of time, to conduct the exhaust gas flow from each row of cylinders by way of its associated gas line and catalyst.

A multi-channel photometric detector for multi-component analysis in flow injection analysis

PubMed Central

Tan, Aimin; Huang, Jialin; Geng, Liudi; Xu, Jinhua; Zhao, Xinna

1994-01-01

The detector, a multi-channel photometric detector, described in this paper was developed using multi-wavelength LEDs (light emitting diode) and phototransistors for absorbance measurement controlled by an Intel 8031 8-bit single chip microcomputer. Up to four flow cells can be attached to the detector. The LEDs and phototransistors are both inexpensive, and reliable. The results given by the detector for simultaneous determination of trace amounts of cobalt and cadmium in zinc sulphate electrolyte are reported. Because of the newly developed detector, this approach employs much less hardware apparatus than by employing conventional photometric detectors. PMID:18924688

A multi-channel photometric detector for multi-component analysis in flow injection analysis.

PubMed

Tan, A; Huang, J; Geng, L; Xu, J; Zhao, X

1994-01-01

The detector, a multi-channel photometric detector, described in this paper was developed using multi-wavelength LEDs (light emitting diode) and phototransistors for absorbance measurement controlled by an Intel 8031 8-bit single chip microcomputer. Up to four flow cells can be attached to the detector. The LEDs and phototransistors are both inexpensive, and reliable. The results given by the detector for simultaneous determination of trace amounts of cobalt and cadmium in zinc sulphate electrolyte are reported. Because of the newly developed detector, this approach employs much less hardware apparatus than by employing conventional photometric detectors.

CT-angiography protocol with low dose radiation and low volume contrast medium for non-cardiac chest pain

PubMed Central

Ozkurt, Huseyin; Tokgoz, Safiye; Karabay, Esra; Ucan, Berna; Akdogan, Melek Pala; Basak, Muzaffer

2014-01-01

Aim To evaluate the diagnostic quality of a new multiple detector-row computed tomography angiography (MDCT-A) protocol using low dose radiation and low volume contrast medium techniques for evaluation of non-cardiac chest pain. Methods Forty-five consecutive patients with clinically suspected noncardiac chest pain and requiring contrast-enhanced chest computed tomography (CT) were examined. The patients were assigned to the protocol, with 80 kilovolt (peak) (kV[p]) and 150 effective milliampere-second (eff mA-s). In our study group, 40 mL of low osmolar contrast material was administered at 3.0 mL/s. Results In the study group, four patients with pulmonary embolism, four with pleural effusion, two with ascending aortic aneurysm and eight patients with pneumonic consolidation were detected. The mean attenuation of the pulmonary truncus and ascendant aortic locations was considered 264±44 and 249±51 HU, respectively. The mean effective radiation dose was 0.83 mSv for MDCT-A. Conclusions Pulmonary artery and the aorta scanning simultaneously was significantly reduced radiation exposure with the mentioned dose saving technique. Additionally, injection of low volume (40 cc) contrast material may reduce the risk of contrast induced nephropathy, therefore, facilitate the diagnostic approach. This technique can be applied to all cases and particularly patients at high risk of contrast induced nephropathy due to its similar diagnostic quality with a low dose and high levels of arteriovenous enhancement simultaneously. PMID:25392818

Simultaneous acquisition of magnetic resonance spectroscopy (MRS) data and positron emission tomography (PET) images with a prototype MR-compatible, small animal PET imager

NASA Astrophysics Data System (ADS)

Raylman, Raymond R.; Majewski, Stan; Velan, S. Sendhil; Lemieux, Susan; Kross, Brian; Popov, Vladimir; Smith, Mark F.; Weisenberger, Andrew G.

2007-06-01

Multi-modality imaging (such as PET-CT) is rapidly becoming a valuable tool in the diagnosis of disease and in the development of new drugs. Functional images produced with PET, fused with anatomical images created by MRI, allow the correlation of form with function. Perhaps more exciting than the combination of anatomical MRI with PET, is the melding of PET with MR spectroscopy (MRS). Thus, two aspects of physiology could be combined in novel ways to produce new insights into the physiology of normal and pathological processes. Our team is developing a system to acquire MRI images and MRS spectra, and PET images contemporaneously. The prototype MR-compatible PET system consists of two opposed detector heads (appropriate in size for small animal imaging), operating in coincidence mode with an active field-of-view of ˜14 cm in diameter. Each detector consists of an array of LSO detector elements coupled through a 2-m long fiber optic light guide to a single position-sensitive photomultiplier tube. The use of light guides allows these magnetic field-sensitive elements of the PET imager to be positioned outside the strong magnetic field of our 3T MRI scanner. The PET scanner imager was integrated with a 12-cm diameter, 12-leg custom, birdcage coil. Simultaneous MRS spectra and PET images were successfully acquired from a multi-modality phantom consisting of a sphere filled with 17 brain relevant substances and a positron-emitting radionuclide. There were no significant changes in MRI or PET scanner performance when both were present in the MRI magnet bore. This successful initial test demonstrates the potential for using such a multi-modality to obtain complementary MRS and PET data.

Impact of reduced-radiation dual-energy protocols using 320-detector row computed tomography for analyzing urinary calculus components: initial in vitro evaluation.

PubMed

Cai, Xiangran; Zhou, Qingchun; Yu, Juan; Xian, Zhaohui; Feng, Youzhen; Yang, Wencai; Mo, Xukai

2014-10-01

To evaluate the impact of reduced-radiation dual-energy (DE) protocols using 320-detector row computed tomography on the differentiation of urinary calculus components. A total of 58 urinary calculi were placed into the same phantom and underwent DE scanning with 320-detector row computed tomography. Each calculus was scanned 4 times with the DE protocols using 135 kV and 80 kV tube voltage and different tube current combinations, including 100 mA and 570 mA (group A), 50 mA and 290 mA (group B), 30 mA and 170 mA (group C), and 10 mA and 60 mA (group D). The acquisition data of all 4 groups were then analyzed by stone DE analysis software, and the results were compared with x-ray diffraction analysis. Noise, contrast-to-noise ratio, and radiation dose were compared. Calculi were correctly identified in 56 of 58 stones (96.6%) using group A and B protocols. However, only 35 stones (60.3%) and 16 stones (27.6%) were correctly diagnosed using group C and D protocols, respectively. Mean noise increased significantly and mean contrast-to-noise ratio decreased significantly from groups A to D (P <.05). In addition, the effective dose decreased markedly from groups A to D at 3.78, 1.81, 1.07, and 0.37 mSv, respectively. Decreasing the DE tube currents from 100 mA and 570 mA to 50 mA and 290 mA resulted in 96.6% accuracy for urinary calculus component analysis while reducing patient radiation exposure to 1.81 mSv. Further reduction of tube currents may compromise diagnostic accuracy. Copyright © 2014 Elsevier Inc. All rights reserved.

Influence of Bony Defects on Preoperative Shoulder Function in Recurrent Anteroinferior Shoulder Instability.

PubMed

Wolke, Julia; Herrmann, Diem Anh; Krannich, Alexander; Scheibel, Markus

2016-05-01

Recurrent anteroinferior shoulder dislocations are often associated with bony glenoid and humeral defects. The influence of those bony lesions on the postoperative outcomes after arthroscopic shoulder stabilization procedures has been the subject of many studies. Little is known about the influence of those lesions on preoperative function. To evaluate the influence of glenoid and humeral bony defects on preoperative shoulder function in recurrent anteroinferior shoulder instability. Cross-sectional study; Level of evidence, 3. Included in the study were 90 patients (70 men, 20 women; mean age, 27.1 years; 24 patients with prior failed stabilization) with posttraumatic recurrent anteroinferior shoulder instability who underwent preoperative computed tomography (CT) of both shoulders. The glenoid index was used to measure glenoid defect on a 3-dimensional CT. Humeral head defect was measured on a 2-dimensional CT with evaluation of the Hill-Sachs quotient, product, sum, and difference. Preoperative evaluation also included the Rowe score, Constant score, Walch-Duplay score, Melbourne Instability Shoulder Score (MISS), Western Ontario Shoulder Instability Index (WOSI), and Subjective Shoulder Value (SSV). There was a weak but significant correlation of the Hill-Sachs quotient and the glenoid index with the Rowe score (P = .03, r = -0.22 and P = .03, r = 0.23, respectively). Furthermore, the Hill-Sachs product significantly correlated with the WOSI (P = .02); in particular, the physical symptoms subscore showed a significant correlation (P = .04). The glenoid index showed a significant correlation with the SSV (P < .01). No significant correlation was found between the Walch-Duplay score, Constant score, or MISS and bony defects. The results of this study show that objective and subjective scoring systems correlate significantly with the clinical condition of patients with recurrent shoulder instability and associated bony defects. It is recommended that clinicians use the Rowe score, WOSI, and SSV for the clinical evaluation of patients with recurrent anteroinferior shoulder instability and associated bony defects. These evaluation systems may provide an early clinical indication of bony defects. Furthermore, very poor results on these evaluations could underline the necessity of a CT scan for the diagnosis of bony defects in recurrent shoulder instability and might be helpful for decision making concerning the indication of a CT. © 2016 The Author(s).

Rectal cancer staging: Multidetector-row computed tomography diagnostic accuracy in assessment of mesorectal fascia invasion

PubMed Central

Ippolito, Davide; Drago, Silvia Girolama; Franzesi, Cammillo Talei; Fior, Davide; Sironi, Sandro

2016-01-01

AIM: To assess the diagnostic accuracy of multidetector-row computed tomography (MDCT) as compared with conventional magnetic resonance imaging (MRI), in identifying mesorectal fascia (MRF) invasion in rectal cancer patients. METHODS: Ninety-one patients with biopsy proven rectal adenocarcinoma referred for thoracic and abdominal CT staging were enrolled in this study. The contrast-enhanced MDCT scans were performed on a 256 row scanner (ICT, Philips) with the following acquisition parameters: tube voltage 120 KV, tube current 150-300 mAs. Imaging data were reviewed as axial and as multiplanar reconstructions (MPRs) images along the rectal tumor axis. MRI study, performed on 1.5 T with dedicated phased array multicoil, included multiplanar T2 and axial T1 sequences and diffusion weighted images (DWI). Axial and MPR CT images independently were compared to MRI and MRF involvement was determined. Diagnostic accuracy of both modalities was compared and statistically analyzed. RESULTS: According to MRI, the MRF was involved in 51 patients and not involved in 40 patients. DWI allowed to recognize the tumor as a focal mass with high signal intensity on high b-value images, compared with the signal of the normal adjacent rectal wall or with the lower tissue signal intensity background. The number of patients correctly staged by the native axial CT images was 71 out of 91 (41 with involved MRF; 30 with not involved MRF), while by using the MPR 80 patients were correctly staged (45 with involved MRF; 35 with not involved MRF). Local tumor staging suggested by MDCT agreed with those of MRI, obtaining for CT axial images sensitivity and specificity of 80.4% and 75%, positive predictive value (PPV) 80.4%, negative predictive value (NPV) 75% and accuracy 78%; while performing MPR the sensitivity and specificity increased to 88% and 87.5%, PPV was 90%, NPV 85.36% and accuracy 88%. MPR images showed higher diagnostic accuracy, in terms of MRF involvement, than native axial images, as compared to the reference magnetic resonance images. The difference in accuracy was statistically significant (P = 0.02). CONCLUSION: New generation CT scanner, using high resolution MPR images, represents a reliable diagnostic tool in assessment of loco-regional and whole body staging of advanced rectal cancer, especially in patients with MRI contraindications. PMID:27239115

Automatic tube current modulation technique for multidetector CT: is it effective with a 64-detector CT?

PubMed

Funama, Yoshinori; Awai, Kazuo; Hatemura, Masahiro; Shimamura, Masamitchi; Yanaga, Yumi; Oda, Seitaro; Yamashita, Yasuyuki

2008-01-01

To investigate whether it is possible to obtain adequate images at uniform image noise levels and reduced radiation exposure with our automatic tube current modulation (ATCM) technique for 64-detector CT. The study population consisted of 64 patients with known or suspected lung or abdominal disease. We used a 64-detector CT scanner (LightSpeed VCT, GE Healthcare, Waukesha, WI, USA) and a combined angular and longitudinal tube current modulation technique (Smart mA, GE Healthcare, Waukesha, WI, USA) to examine 34 patients. The scanning parameters were identical; the minimum and maximum tube current thresholds were 50 and 800 mA, respectively. For study of the constant tube current technique, 30 additional patients were examined at 350 mA. The CT number and image noise (SD of the CT number) were measured in the 64 patients at six levels, i.e., the center of the left ventricle, the liver dome, the porta hepatis, the center of the spleen and the right and left renal pelvis. When we used the ATCM technique, the mean image noise ranged from 8.40 at the center of the left ventricle to 11.31 at the porta hepatis; the mean tube current ranged from 105.9 mAs at the center of the left ventricle to 169.6 mAs at the center of the spleen. The mean dose reduction rate per constant tube current at 175 mAs ranged from 3.1 to 39.5%. By use of the ATCM technique, it is possible to maintain a constant image noise level with a 64-detector CT.

Detector response function of an energy-resolved CdTe single photon counting detector.

PubMed

Liu, Xin; Lee, Hyoung Koo

2014-01-01

While spectral CT using single photon counting detector has shown a number of advantages in diagnostic imaging, knowledge of the detector response function of an energy-resolved detector is needed to correct the signal bias and reconstruct the image more accurately. The objective of this paper is to study the photo counting detector response function using laboratory sources, and investigate the signal bias correction method. Our approach is to model the detector response function over the entire diagnostic energy range (20 keV

Evaluation of position-estimation methods applied to CZT-based photon-counting detectors for dedicated breast CT

PubMed Central

Makeev, Andrey; Clajus, Martin; Snyder, Scott; Wang, Xiaolang; Glick, Stephen J.

2015-01-01

Abstract. Semiconductor photon-counting detectors based on high atomic number, high density materials [cadmium zinc telluride (CZT)/cadmium telluride (CdTe)] for x-ray computed tomography (CT) provide advantages over conventional energy-integrating detectors, including reduced electronic and Swank noise, wider dynamic range, capability of spectral CT, and improved signal-to-noise ratio. Certain CT applications require high spatial resolution. In breast CT, for example, visualization of microcalcifications and assessment of tumor microvasculature after contrast enhancement require resolution on the order of 100  μm. A straightforward approach to increasing spatial resolution of pixellated CZT-based radiation detectors by merely decreasing the pixel size leads to two problems: (1) fabricating circuitry with small pixels becomes costly and (2) inter-pixel charge spreading can obviate any improvement in spatial resolution. We have used computer simulations to investigate position estimation algorithms that utilize charge sharing to achieve subpixel position resolution. To study these algorithms, we model a simple detector geometry with a 5×5 array of 200  μm pixels, and use a conditional probability function to model charge transport in CZT. We used COMSOL finite element method software to map the distribution of charge pulses and the Monte Carlo package PENELOPE for simulating fluorescent radiation. Performance of two x-ray interaction position estimation algorithms was evaluated: the method of maximum-likelihood estimation and a fast, practical algorithm that can be implemented in a readout application-specific integrated circuit and allows for identification of a quadrant of the pixel in which the interaction occurred. Both methods demonstrate good subpixel resolution; however, their actual efficiency is limited by the presence of fluorescent K-escape photons. Current experimental breast CT systems typically use detectors with a pixel size of 194  μm, with 2×2 binning during the acquisition giving an effective pixel size of 388  μm. Thus, it would be expected that the position estimate accuracy reported in this study would improve detection and visualization of microcalcifications as compared to that with conventional detectors. PMID:26158095

Evaluation of position-estimation methods applied to CZT-based photon-counting detectors for dedicated breast CT.

PubMed

Makeev, Andrey; Clajus, Martin; Snyder, Scott; Wang, Xiaolang; Glick, Stephen J

2015-04-01

Semiconductor photon-counting detectors based on high atomic number, high density materials [cadmium zinc telluride (CZT)/cadmium telluride (CdTe)] for x-ray computed tomography (CT) provide advantages over conventional energy-integrating detectors, including reduced electronic and Swank noise, wider dynamic range, capability of spectral CT, and improved signal-to-noise ratio. Certain CT applications require high spatial resolution. In breast CT, for example, visualization of microcalcifications and assessment of tumor microvasculature after contrast enhancement require resolution on the order of [Formula: see text]. A straightforward approach to increasing spatial resolution of pixellated CZT-based radiation detectors by merely decreasing the pixel size leads to two problems: (1) fabricating circuitry with small pixels becomes costly and (2) inter-pixel charge spreading can obviate any improvement in spatial resolution. We have used computer simulations to investigate position estimation algorithms that utilize charge sharing to achieve subpixel position resolution. To study these algorithms, we model a simple detector geometry with a [Formula: see text] array of [Formula: see text] pixels, and use a conditional probability function to model charge transport in CZT. We used COMSOL finite element method software to map the distribution of charge pulses and the Monte Carlo package PENELOPE for simulating fluorescent radiation. Performance of two x-ray interaction position estimation algorithms was evaluated: the method of maximum-likelihood estimation and a fast, practical algorithm that can be implemented in a readout application-specific integrated circuit and allows for identification of a quadrant of the pixel in which the interaction occurred. Both methods demonstrate good subpixel resolution; however, their actual efficiency is limited by the presence of fluorescent [Formula: see text]-escape photons. Current experimental breast CT systems typically use detectors with a pixel size of [Formula: see text], with [Formula: see text] binning during the acquisition giving an effective pixel size of [Formula: see text]. Thus, it would be expected that the position estimate accuracy reported in this study would improve detection and visualization of microcalcifications as compared to that with conventional detectors.

TU-EF-204-12: Quantitative Evaluation of Spectral Detector CT Using Virtual Monochromatic Images: Initial Results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, X; Guild, J; Arbique, G

2015-06-15

Purpose To evaluate the image quality and spectral information of a spectral detector CT (SDCT) scanner using virtual monochromatic (VM) energy images. Methods The SDCT scanner (Philips Healthcare) was equipped with a dual-layer detector and spectral iterative reconstruction (IR), which generates conventional 80–140 kV polychromatic energy (PE) CT images using both detector layers, PE images from the low-energy (upper) and high-energy (lower) detector layers and VM images. A solid water phantom with iodine (2.0–20.0 mg I/ml) and calcium (50.0–600.0 mg Ca/ml) rod inserts was used to evaluate effective energy estimate (EEE) and iodine contrast to noise ratio (CNR). The EEEmore » corresponding to an insert CT number in a PE image was calculated from a CT number fit to the VM image set. Since PE image is prone to beam-hardening artifact EEE may underestimate the actual energy separation from two layers of the detector. A 30-cm-diameter water phantom was used to evaluate noise power spectrum (NPS). The phantoms were scanned at 120 and 140 kV with the same CTDIvol. Results The CT number difference for contrast inserts in VM images (50–150 keV) was 1.3±6% between 120 and 140 kV scans. The difference of EEE calculated from low- and high-energy detector images was 11.5 and 16.7 keV for 120 and 140 kV scans, respectively. The differences calculated from 140 and 100 kV conventional PE images were 12.8, and 20.1 keV from 140 and 80 kV conventional PE images. The iodine CNR increased monotonically with decreased keV. Compared to conventional PE images, the peak of NPS curves from VM images were shifted to lower frequency. Conclusion The EEE results indicates that SDCT at 120 and 140 kV may have energy separation comparable to 100/140 kV and 80/140 kV dual-kV imaging. The effects of IR on CNR and NPS require further investigation for SDCT. Author YY and AD are Philips Healthcare employees.« less

Raw data normalization for a multi source inverse geometry CT system

PubMed Central

Baek, Jongduk; De Man, Bruno; Harrison, Daniel; Pelc, Norbert J.

2015-01-01

A multi-source inverse-geometry CT (MS-IGCT) system consists of a small 2D detector array and multiple x-ray sources. During data acquisition, each source is activated sequentially, and may have random source intensity fluctuations relative to their respective nominal intensity. While a conventional 3rd generation CT system uses a reference channel to monitor the source intensity fluctuation, the MS-IGCT system source illuminates a small portion of the entire field-of-view (FOV). Therefore, it is difficult for all sources to illuminate the reference channel and the projection data computed by standard normalization using flat field data of each source contains error and can cause significant artifacts. In this work, we present a raw data normalization algorithm to reduce the image artifacts caused by source intensity fluctuation. The proposed method was tested using computer simulations with a uniform water phantom and a Shepp-Logan phantom, and experimental data of an ice-filled PMMA phantom and a rabbit. The effect on image resolution and robustness of the noise were tested using MTF and standard deviation of the reconstructed noise image. With the intensity fluctuation and no correction, reconstructed images from simulation and experimental data show high frequency artifacts and ring artifacts which are removed effectively using the proposed method. It is also observed that the proposed method does not degrade the image resolution and is very robust to the presence of noise. PMID:25837090

WE-B-207-02: CT Lung Cancer Screening and the Medical Physicist: A Dosimetry Summary of CT Participants in the National Lung Cancer Screening Trial (NLST)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, C.

2015-06-15

The US National Lung Screening Trial (NLST) was a multi-center randomized, controlled trial comparing a low-dose CT (LDCT) to posterior-anterior (PA) chest x-ray (CXR) in screening older, current and former heavy smokers for early detection of lung cancer. Recruitment was launched in September 2002 and ended in April 2004 when 53,454 participants had been randomized at 33 screening sites in equal proportions. Funded by the National Cancer Institute this trial demonstrated that LDCT screening reduced lung cancer mortality. The US Preventive Services Task Force (USPSTF) cited NLST findings and conclusions in its deliberations and analysis of lung cancer screening. Undermore » the 2010 Patient Protection and Affordable Care Act, the USPSTF favorable recommendation regarding lung cancer CT screening assisted in obtaining third-party payers coverage for screening. The objective of this session is to provide an introduction to the NLST and the trial findings, in addition to a comprehensive review of the dosimetry investigations and assessments completed using individual NLST participant CT and CXR examinations. Session presentations will review and discuss the findings of two independent assessments, a CXR assessment and the findings of a CT investigation calculating individual organ dosimetry values. The CXR assessment reviewed a total of 73,733 chest x-ray exams that were performed on 92 chest imaging systems of which 66,157 participant examinations were used. The CT organ dosimetry investigation collected scan parameters from 23,773 CT examinations; a subset of the 75,133 CT examinations performed using 97 multi-detector CT scanners. Organ dose conversion coefficients were calculated using a Monte Carlo code. An experimentally-validated CT scanner simulation was coupled with 193 adult hybrid computational phantoms representing the height and weight of the current U.S. population. The dose to selected organs was calculated using the organ dose library and the abstracted scan parameters. This session will review the results and summarize the individualized doses to major organs and the mean effective dose and CTDIvol estimate for 66,157 PA chest and 23,773 CT examinations respectively, using size-dependent computational phantoms coupled with Monte Carlo calculations. Learning Objectives: Review and summarize relevant NLST findings and conclusions. Understand the scope and scale of the NLST specific to participant dosimetry. Provide a comprehensive review of NLST participant dosimetry assessments. Summarize the results of an investigation providing individualized organ dose estimates for NLST participant cohorts.« less

SU-E-T-458: Determining Threshold-Of-Failure for Dead Pixel Rows in EPID-Based Dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gersh, J; Wiant, D

Purpose: A pixel correction map is applied to all EPID-based applications on the TrueBeam (Varian Medical Systems, Palo Alto, CA). When dead pixels are detected, an interpolative smoothing algorithm is applied using neighboring-pixel information to supplement missing-pixel information. The vendor suggests that when the number of dead pixels exceeds 70,000, the panel should be replaced. It is common for entire detector rows to be dead, as well as their neighboring rows. Approximately 70 rows can be dead before the panel reaches this threshold. This study determines the number of neighboring dead-pixel rows that would create a large enough deviation inmore » measured fluence to cause failures in portal dosimetry (PD). Methods: Four clinical two-arc VMAT plans were generated using Eclipse's AXB algorithm and PD plans were created using the PDIP algorithm. These plans were chosen to represent those commonly encountered in the clinic: prostate, lung, abdomen, and neck treatments. During each iteration of this study, an increasing number of dead-pixel rows are artificially applied to the correction map and a fluence QA is performed using the EPID (corrected with this map). To provide a worst-case-scenario, the dead-pixel rows are chosen so that they present artifacts in the highfluence region of the field. Results: For all eight arc-fields deemed acceptable via a 3%/3mm gamma analysis (pass rate greater than 99%), VMAT QA yielded identical results with a 5 pixel-width dead zone. When 10 dead lines were present, half of the fields had pass rates below the 99% pass rate. With increasing dead rows, the pass rates were reduced substantially. Conclusion: While the vendor still suggests to request service at the point where 70,000 dead rows are measured (as recommended by the vendor), the authors suggest that service should be requested when there are greater than 5 consecutive dead rows.« less

A SiPM-based isotropic-3D PET detector X'tal cube with a three-dimensional array of 1 mm(3) crystals.

PubMed

Yamaya, Taiga; Mitsuhashi, Takayuki; Matsumoto, Takahiro; Inadama, Naoko; Nishikido, Fumihiko; Yoshida, Eiji; Murayama, Hideo; Kawai, Hideyuki; Suga, Mikio; Watanabe, Mitsuo

2011-11-07

We are developing a novel, general purpose isotropic-3D PET detector X'tal cube which has high spatial resolution in all three dimensions. The research challenge for this detector is implementing effective detection of scintillation photons by covering six faces of a segmented crystal block with silicon photomultipliers (SiPMs). In this paper, we developed the second prototype of the X'tal cube for a proof-of-concept. We aimed at realizing an ultimate detector with 1.0 mm(3) cubic crystals, in contrast to our previous development using 3.0 mm(3) cubic crystals. The crystal block was composed of a 16 × 16 × 16 array of lutetium gadolinium oxyorthosilicate (LGSO) crystals 0.993 × 0.993 × 0.993 mm(3) in size. The crystals were optically glued together without inserting any reflector inside and 96 multi-pixel photon counters (MPPCs, S10931-50P, i.e. six faces each with a 4 × 4 array of MPPCs), each having a sensitive area of 3.0 × 3.0 mm(2), were optically coupled to the surfaces of the crystal block. Almost all 4096 crystals were identified through Anger-type calculation due to the finely adjusted reflector sheets inserted between the crystal block and light guides. The reflector sheets, which formed a belt of 0.5 mm width, were placed to cover half of the crystals of the second rows from the edges in order to improve identification performance of the crystals near the edges. Energy resolution of 12.7% was obtained at 511 keV with almost uniform light output for all crystal segments thanks to the effective detection of the scintillation photons.

Patient-specific dose calculations for pediatric CT of the chest, abdomen and pelvis

PubMed Central

Fraser, Nicholas D.; Carver, Diana E.; Pickens, David R.; Price, Ronald R.; Hernanz-Schulman, Marta; Stabin, Michael G.

2015-01-01

Background Organ dose is essential for accurate estimates of patient dose from CT. Objective To determine organ doses from a broad range of pediatric patients undergoing diagnostic chest–abdomen–pelvis CT and investigate how these relate to patient size. Materials and methods We used a previously validated Monte Carlo simulation model of a Philips Brilliance 64 multi-detector CT scanner (Philips Healthcare, Best, The Netherlands) to calculate organ doses for 40 pediatric patients (M:F=21:19; range 0.6–17 years). Organ volumes and positions were determined from the images using standard segmentation techniques. Non-linear regression was performed to determine the relationship between volume CT dose index (CTDIvol)-normalized organ doses and abdominopelvic diameter. We then compared results with values obtained from independent studies. Results We found that CTDIvol-normalized organ dose correlated strongly with exponentially decreasing abdominopelvic diameter (R2>0.8 for most organs). A similar relationship was determined for effective dose when normalized by dose-length product (R2=0.95). Our results agreed with previous studies within 12% using similar scan parameters (i.e. bowtie filter size, beam collimation); however results varied up to 25% when compared to studies using different bowtie filters. Conclusion Our study determined that organ doses can be estimated from measurements of patient size, namely body diameter, and CTDIvol prior to CT examination. This information provides an improved method for patient dose estimation. PMID:26142256

Relevant incidental findings at abdominal multi-detector contrast-enhanced computed tomography: A collateral screening?

PubMed Central

Sconfienza, Luca Maria; Mauri, Giovanni; Muzzupappa, Claudia; Poloni, Alessandro; Bandirali, Michele; Esseridou, Anastassia; Tritella, Stefania; Secchi, Francesco; Di Leo, Giovanni; Sardanelli, Francesco

2015-01-01

AIM: To investigate the prevalence of relevant incidental findings (RIFs) detected during routine abdominal contrast-enhanced computed tomography (CeCT). METHODS: We retrospectively evaluated the reports of a consecutive series of abdominal CeCT studies performed between January and May 2013. For each report, patients’ age and sex, admission as inpatient or outpatient, clinical suspicion as indicated by the requesting physician, availability of a previous abdominal examination, and name of the reporting radiologist were recorded. Based on the clinical suspicion, the presence and features of any RIFs (if needing additional workup) was noted. RESULTS: One thousand forty abdominal CeCT were performed in 949 patients (528 males, mean age 66 ± 14 years). No significant difference was found between inpatients and outpatients age and sex distribution (P > 0.472). RIFs were found in 195/1040 (18.8%) CeCT [inpatients = 108/470 (23.0%); outpatients = 87/570 (15.2%); P = 0.002]. RIFs were found in 30/440 (6.8%) CeCT with a previous exam and in 165/600 (27.5%) without a previous exam (P < 0.001). Radiologists’ distribution between inpatients or outpatients was significantly different (P < 0.001). RIFs prevalence increased with aging, except for a peak in 40-49 year group. Most involved organs were kidneys, gallbladder, and lungs. CONCLUSION: A RIF is detected in 1/5 patients undergoing abdominal CeCT. Risk of overdiagnosis should be taken into account. PMID:26516432

An iterative reconstruction method for high-pitch helical luggage CT

NASA Astrophysics Data System (ADS)

Xue, Hui; Zhang, Li; Chen, Zhiqiang; Jin, Xin

2012-10-01

X-ray luggage CT is widely used in airports and railway stations for the purpose of detecting contrabands and dangerous goods that may be potential threaten to public safety, playing an important role in homeland security. An X-ray luggage CT is usually in a helical trajectory with a high pitch for achieving a high passing speed of the luggage. The disadvantage of high pitch is that conventional filtered back-projection (FBP) requires a very large slice thickness, leading to bad axial resolution and helical artifacts. Especially when severe data inconsistencies are present in the z-direction, like the ends of a scanning object, the partial volume effect leads to inaccuracy value and may cause a wrong identification. In this paper, an iterative reconstruction method is developed to improve the image quality and accuracy for a large-spacing multi-detector high-pitch helical luggage CT system. In this method, the slice thickness is set to be much smaller than the pitch. Each slice involves projection data collected in a rather small angular range, being an ill-conditioned limited-angle problem. Firstly a low-resolution reconstruction is employed to obtain images, which are used as prior images in the following process. Then iterative reconstruction is performed to obtain high-resolution images. This method enables a high volume coverage speed and a thin reconstruction slice for the helical luggage CT. We validate this method with data collected in a commercial X-ray luggage CT.

Quality of routine diagnostic abdominal images generated from a novel detector-based spectral CT scanner: a technical report on a phantom and clinical study.

PubMed

Hojjati, Mojgan; Van Hedent, Steven; Rassouli, Negin; Tatsuoka, Curtis; Jordan, David; Dhanantwari, Amar; Rajiah, Prabhakar

2017-11-01

To evaluate the image quality of routine diagnostic images generated from a novel detector-based spectral detector CT (SDCT) and compare it with CT images obtained from a conventional scanner with an energy-integrating detector (Brilliance iCT), Routine diagnostic (conventional/polyenergetic) images are non-material-specific images that resemble single-energy images obtained at the same radiation, METHODS: ACR guideline-based phantom evaluations were performed on both SDCT and iCT for CT adult body protocol. Retrospective analysis was performed on 50 abdominal CT scans from each scanner. Identical ROIs were placed at multiple locations in the abdomen and attenuation, noise, SNR, and CNR were measured. Subjective image quality analysis on a 5-point Likert scale was performed by 2 readers for enhancement, noise, and image quality. On phantom studies, SDCT images met the ACR requirements for CT number and deviation, CNR and effective radiation dose. In patients, the qualitative scores were significantly higher for the SDCT than the iCT, including enhancement (4.79 ± 0.38 vs. 4.60 ± 0.51, p = 0.005), noise (4.63 ± 0.42 vs. 4.29 ± 0.50, p = 0.000), and quality (4.85 ± 0.32, vs. 4.57 ± 0.50, p = 0.000). The SNR was higher in SDCT than iCT for liver (7.4 ± 4.2 vs. 7.2 ± 5.3, p = 0.662), spleen (8.6 ± 4.1 vs. 7.4 ± 3.5, p = 0.152), kidney (11.1 ± 6.3 vs. 8.7 ± 5.0, p = 0.033), pancreas (6.90 ± 3.45 vs 6.11 ± 2.64, p = 0.303), aorta (14.2 ± 6.2 vs. 11.0 ± 4.9, p = 0.007), but was slightly lower in lumbar-vertebra (7.7 ± 4.2 vs. 7.8 ± 4.5, p = 0.937). The CNR of the SDCT was also higher than iCT for all abdominal organs. Image quality of routine diagnostic images from the SDCT is comparable to images of a conventional CT scanner with energy-integrating detectors, making it suitable for diagnostic purposes.

High-definition computed tomography for coronary artery stents imaging compared with standard-definition 64-row multidectector computed tomography: an initial in vivo study.

PubMed

Yang, Wen Jie; Zhang, Huan; Xiao, Hua; Li, Jian Ying; Liu, Yan; Pan, Zi Lai; Chen, Ke Min

2012-01-01

The evaluation of coronary stents by computed tomography (CT) remains difficult. We assessed the imaging performance of a high-definition CT scanner (HDCT) by comparing with a conventional 64-row standard-definition CT (SDCT). One hundred thirty-eight consecutive stented patients underwent coronary CT angiography, among whom 66 patients were examined by HDCT, and 72 patients by SDCT (LightSpeed VCT XT; GE Healthcare, Waukesha, Wis). The image quality score, the inner stent diameter (ISD), and the radiation dose were analyzed. All data were statistically tested by SPSS 13.0 software (SPSS Inc, Chicago, Ill). In 72 patients examined using SDCT, 135 stents were detected; in 66 patients examined using HDCT, 119 stents were detected. The image quality score on HDCT was significantly better than that on SDCT (1.4 [SD, 0.7] vs 1.9 [SD, 0.8]). The ISD on HDCT was significantly higher than that on SDCT (1.8 [SD, 0.5] vs 1.6 [SD, 0.4]). There was no significant difference of either image quality score or ISD between the HDCT and SDCT groups in stents with 2.5-mm diameter. Images on HDCT showed significantly better image quality score and larger ISD than images on SDCT in 2.75-, 3-, and 3.5-mm stents. For patients examined by retrospective electrocardiogram-gated technique, the radiation dose on HDCT was significantly lower than that on SDCT (11.3 [SD, 2.9] vs 15.1 [SD, 3.8] mSv). High-definition CT scanner offered improved image quality and measurement accuracy for imaging coronary stents compared with conventional SDCT, providing higher spatial resolution and lower dose for evaluating coronary stents with 2.75- to 3.5-mm diameter.

JPRS Report, Science & Technology, China.

DTIC Science & Technology

1987-07-07

Detector Response , Projection Sampling on the Contrast of CT Reconstructed Images (Qu Jianxiong; ZHONGGUO KEXUE JISHU DAXUE XUEBAO, No 3, Sep 86) 5...Plan’ Update 92 Hunan Soft Sciences Research Association 92 Burgeoning Technology Market .92 Radioactive Waste Depots Set...DETECTOR RESPONSE , PROJECTION SAMPLING ON THE CONTRAST OF CT RECONSTRUCTED IMAGES Hefei ZHONGGUO KEXUE JISHU DAXUE XUEBAO [JOURNAL OF CHINA

Novel detector design for reducing intercell x-ray cross-talk in the variable resolution x-ray CT scanner: a Monte Carlo study.

PubMed

Arabi, Hosein; Asl, Ali Reza Kamali; Ay, Mohammad Reza; Zaidi, Habib

2011-03-01

The variable resolution x-ray (VRX) CT scanner provides substantial improvement in the spatial resolution by matching the scanner's field of view (FOV) to the size of the object being imaged. Intercell x-ray cross-talk is one of the most important factors limiting the spatial resolution of the VRX detector. In this work, a new cell arrangement in the VRX detector is suggested to decrease the intercell x-ray cross-talk. The idea is to orient the detector cells toward the opening end of the detector. Monte Carlo simulations were used for performance assessment of the oriented cell detector design. Previously published design parameters and simulation results of x-ray cross-talk for the VRX detector were used for model validation using the GATE Monte Carlo package. In the first step, the intercell x-ray cross-talk of the actual VRX detector model was calculated as a function of the FOV. The obtained results indicated an optimum cell orientation angle of 28 degrees to minimize the x-ray cross-talk in the VRX detector. Thereafter, the intercell x-ray cross-talk in the oriented cell detector was modeled and quantified. The intercell x-ray cross-talk in the actual detector model was considerably high, reaching up to 12% at FOVs from 24 to 38 cm. The x-ray cross-talk in the oriented cell detector was less than 5% for all possible FOVs, except 40 cm (maximum FOV). The oriented cell detector could provide considerable decrease in the intercell x-ray cross-talk for the VRX detector, thus leading to significant improvement in the spatial resolution and reduction in the spatial resolution nonuniformity across the detector length. The proposed oriented cell detector is the first dedicated detector design for the VRX CT scanners. Application of this concept to multislice and flat-panel VRX detectors would also result in higher spatial resolution.

Energy-resolved CT imaging with a photon-counting silicon-strip detector

NASA Astrophysics Data System (ADS)

Persson, Mats; Huber, Ben; Karlsson, Staffan; Liu, Xuejin; Chen, Han; Xu, Cheng; Yveborg, Moa; Bornefalk, Hans; Danielsson, Mats

2014-03-01

Photon-counting detectors are promising candidates for use in the next generation of x-ray CT scanners. Among the foreseen benefits are higher spatial resolution, better trade-off between noise and dose, and energy discriminating capabilities. Silicon is an attractive detector material because of its low cost, mature manufacturing process and high hole mobility. However, it is sometimes claimed to be unsuitable for use in computed tomography because of its low absorption efficiency and high fraction of Compton scatter. The purpose of this work is to demonstrate that high-quality energy-resolved CT images can nonetheless be acquired with clinically realistic exposure parameters using a photon-counting silicon-strip detector with eight energy thresholds developed in our group. We use a single detector module, consisting of a linear array of 50 0.5 × 0.4 mm detector elements, to image a phantom in a table-top lab setup. The phantom consists of a plastic cylinder with circular inserts containing water, fat and aqueous solutions of calcium, iodine and gadolinium, in different concentrations. We use basis material decomposition to obtain water, calcium, iodine and gadolinium basis images and demonstrate that these basis images can be used to separate the different materials in the inserts. We also show results showing that the detector has potential for quantitative measurements of substance concentrations.

CT liver volumetry using geodesic active contour segmentation with a level-set algorithm

NASA Astrophysics Data System (ADS)

Suzuki, Kenji; Epstein, Mark L.; Kohlbrenner, Ryan; Obajuluwa, Ademola; Xu, Jianwu; Hori, Masatoshi; Baron, Richard

2010-03-01

Automatic liver segmentation on CT images is challenging because the liver often abuts other organs of a similar density. Our purpose was to develop an accurate automated liver segmentation scheme for measuring liver volumes. We developed an automated volumetry scheme for the liver in CT based on a 5 step schema. First, an anisotropic smoothing filter was applied to portal-venous phase CT images to remove noise while preserving the liver structure, followed by an edge enhancer to enhance the liver boundary. By using the boundary-enhanced image as a speed function, a fastmarching algorithm generated an initial surface that roughly estimated the liver shape. A geodesic-active-contour segmentation algorithm coupled with level-set contour-evolution refined the initial surface so as to more precisely fit the liver boundary. The liver volume was calculated based on the refined liver surface. Hepatic CT scans of eighteen prospective liver donors were obtained under a liver transplant protocol with a multi-detector CT system. Automated liver volumes obtained were compared with those manually traced by a radiologist, used as "gold standard." The mean liver volume obtained with our scheme was 1,520 cc, whereas the mean manual volume was 1,486 cc, with the mean absolute difference of 104 cc (7.0%). CT liver volumetrics based on an automated scheme agreed excellently with "goldstandard" manual volumetrics (intra-class correlation coefficient was 0.95) with no statistically significant difference (p(F<=f)=0.32), and required substantially less completion time. Our automated scheme provides an efficient and accurate way of measuring liver volumes.

TH-CD-207B-06: Swank Factor of Segmented Scintillators in Multi-Slice CT Detectors: Pulse Height Spectra and Light Escape

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howansky, A; Peng, B; Lubinsky, A

Purpose: Pulse height spectra (PHS) have been used to determine the Swank factor of a scintillator by measuring fluctuations in its light output per x-ray interaction. The Swank factor and x-ray quantum efficiency of a scintillator define the upper limit to its imaging performance, i.e. DQE(0). The Swank factor below the K-edge is dominated by optical properties, i.e. variations in light escape efficiency from different depths of interaction, denoted e(z). These variations can be optimized to improve tradeoffs in x-ray absorption, light yield, and spatial resolution. This work develops a quantitative model for interpreting measured PHS, and estimating e(z) onmore » an absolute scale. The method is used to investigate segmented ceramic GOS scintillators used in multi-slice CT detectors. Methods: PHS of a ceramic GOS plate (1 mm thickness) and segmented GOS array (1.4 mm thick) were measured at 46 keV. Signal and noise propagation through x-ray conversion gain, light escape, detection by a photomultiplier tube and dynode amplification were modeled using a cascade of stochastic gain stages. PHS were calculated with these expressions and compared to measurements. Light escape parameters were varied until modeled PHS agreed with measurements. The resulting estimates of e(z) were used to calculate PHS without measurement noise to determine the inherent Swank factor. Results: The variation in e(z) was 67.2–89.7% in the plate and 40.2–70.8% in the segmented sample, corresponding to conversion gains of 28.6–38.1 keV{sup −1} and 17.1–30.1 keV{sup −1}, respectively. The inherent Swank factors of the plate and segmented sample were 0.99 and 0.95, respectively. Conclusion: The high light escape efficiency in the ceramic GOS samples yields high Swank factors and DQE(0) in CT applications. The PHS model allows the intrinsic optical properties of scintillators to be deduced from PHS measurements, thus it provides new insights for evaluating the imaging performance of segmented ceramic GOS scintillators.« less

WE-B-207-00: CT Lung Cancer Screening Part 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

2015-06-15

The US National Lung Screening Trial (NLST) was a multi-center randomized, controlled trial comparing a low-dose CT (LDCT) to posterior-anterior (PA) chest x-ray (CXR) in screening older, current and former heavy smokers for early detection of lung cancer. Recruitment was launched in September 2002 and ended in April 2004 when 53,454 participants had been randomized at 33 screening sites in equal proportions. Funded by the National Cancer Institute this trial demonstrated that LDCT screening reduced lung cancer mortality. The US Preventive Services Task Force (USPSTF) cited NLST findings and conclusions in its deliberations and analysis of lung cancer screening. Undermore » the 2010 Patient Protection and Affordable Care Act, the USPSTF favorable recommendation regarding lung cancer CT screening assisted in obtaining third-party payers coverage for screening. The objective of this session is to provide an introduction to the NLST and the trial findings, in addition to a comprehensive review of the dosimetry investigations and assessments completed using individual NLST participant CT and CXR examinations. Session presentations will review and discuss the findings of two independent assessments, a CXR assessment and the findings of a CT investigation calculating individual organ dosimetry values. The CXR assessment reviewed a total of 73,733 chest x-ray exams that were performed on 92 chest imaging systems of which 66,157 participant examinations were used. The CT organ dosimetry investigation collected scan parameters from 23,773 CT examinations; a subset of the 75,133 CT examinations performed using 97 multi-detector CT scanners. Organ dose conversion coefficients were calculated using a Monte Carlo code. An experimentally-validated CT scanner simulation was coupled with 193 adult hybrid computational phantoms representing the height and weight of the current U.S. population. The dose to selected organs was calculated using the organ dose library and the abstracted scan parameters. This session will review the results and summarize the individualized doses to major organs and the mean effective dose and CTDIvol estimate for 66,157 PA chest and 23,773 CT examinations respectively, using size-dependent computational phantoms coupled with Monte Carlo calculations. Learning Objectives: Review and summarize relevant NLST findings and conclusions. Understand the scope and scale of the NLST specific to participant dosimetry. Provide a comprehensive review of NLST participant dosimetry assessments. Summarize the results of an investigation providing individualized organ dose estimates for NLST participant cohorts.« less

Organ dose measurements from multiple-detector computed tomography using a commercial dosimetry system and tomographic, physical phantoms

NASA Astrophysics Data System (ADS)

Lavoie, Lindsey K.

The technology of computed tomography (CT) imaging has soared over the last decade with the use of multi-detector CT (MDCT) scanners that are capable of performing studies in a matter of seconds. While the diagnostic information obtained from MDCT imaging is extremely valuable, it is important to ensure that the radiation doses resulting from these studies are at acceptably safe levels. This research project focused on the measurement of organ doses resulting from modern MDCT scanners. A commercially-available dosimetry system was used to measure organ doses. Small dosimeters made of optically-stimulated luminescent (OSL) material were analyzed with a portable OSL reader. Detailed verification of this system was performed. Characteristics studied include energy, scatter, and angular responses; dose linearity, ability to erase the exposed dose and ability to reuse dosimeters multiple times. The results of this verification process were positive. While small correction factors needed to be applied to the dose reported by the OSL reader, these factors were small and expected. Physical, tomographic pediatric and adult phantoms were used to measure organ doses. These phantoms were developed from CT images and are composed of tissue-equivalent materials. Because the adult phantom is comprised of numerous segments, dosimeters were placed in the phantom at several organ locations, and doses to select organs were measured using three clinical protocols: pediatric craniosynostosis, adult brain perfusion and adult cardiac CT angiography (CTA). A wide-beam, 320-slice, volumetric CT scanner and a 64-slice, MDCT scanner were used for organ dose measurements. Doses ranged from 1 to 26 mGy for the pediatric protocol, 1 to 1241 mGy for the brain perfusion protocol, and 2-100 mGy for the cardiac protocol. In most cases, the doses measured on the 64-slice scanner were higher than those on the 320-slice scanner. A methodology to measure organ doses with OSL dosimeters received from CT imaging has been presented. These measurements are especially important in keeping with the ALARA (as low as reasonably achievable) principle. While diagnostic information from CT imaging is valuable and necessary, the dose to patients is always a consideration. This methodology aids in this important task. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)

CMOS Active Pixel Sensors as energy-range detectors for proton Computed Tomography.

PubMed

Esposito, M; Anaxagoras, T; Evans, P M; Green, S; Manolopoulos, S; Nieto-Camero, J; Parker, D J; Poludniowski, G; Price, T; Waltham, C; Allinson, N M

2015-06-03

Since the first proof of concept in the early 70s, a number of technologies has been proposed to perform proton CT (pCT), as a means of mapping tissue stopping power for accurate treatment planning in proton therapy. Previous prototypes of energy-range detectors for pCT have been mainly based on the use of scintillator-based calorimeters, to measure proton residual energy after passing through the patient. However, such an approach is limited by the need for only a single proton passing through the energy-range detector in a read-out cycle. A novel approach to this problem could be the use of pixelated detectors, where the independent read-out of each pixel allows to measure simultaneously the residual energy of a number of protons in the same read-out cycle, facilitating a faster and more efficient pCT scan. This paper investigates the suitability of CMOS Active Pixel Sensors (APSs) to track individual protons as they go through a number of CMOS layers, forming an energy-range telescope. Measurements performed at the iThemba Laboratories will be presented and analysed in terms of correlation, to confirm capability of proton tracking for CMOS APSs.

Case series of 64 slice computed tomography-computed tomographic angiography with 3D reconstruction to diagnose symptomatic cerebral aneurysms: new standard of care?

PubMed Central

Jehle, Dietrich; Chae, Floria; Wai, Jonathan; Cloud, Sam; Pierce, David; Meyer, Michael

2012-01-01

CT angiography (CTA) has improved significantly over the past few years such that the reconstructed images of the cerebral arteries may now be equivalent to conventional digital angiography. The new technology of 64 slice multi-detector CTA can reconstruct detailed images that can reliably identify small cerebral aneurysms, even those <3mm. In addition, it is estimated that CT followed by lumbar puncture (LP) misses up to 4% of symptomatic aneurysms. We present a series of cases that illustrates how CT followed by CTA may be replacing CT-LP as the standard of care in working up patients for symptomatic cerebral aneurysms and the importance of performing three dimensional (3D) reconstructions. A series of seven cases of symptomatic cerebral aneurysms were identified that illustrate the sensitivity of CT-CTA versus CT-LP and the importance of 3D reconstruction in identifying these aneurysms. Surgical treatment was recommended for 6 of the 7 patients with aneurysms and strict hypertension control was recommended for the seventh patient. Some of these patients demonstrated subarachnoid hemorrhage on presentation while others had negative LPs. A number of these patients with negative LPs were clearly symptomatic from their aneurysms. At least one of these cerebral aneurysms was not apparent on CTA without 3D reconstruction. 3D reconstruction of CTA is crucial to adequately identify cerebral aneurysms. This case series helps reinforce the importance of 3D reconstruction. There is some data to suggest that 64 slice CT-CTA may be equivalent or superior to CT-LP in the detection of symptomatic cerebral aneurysms. PMID:22593806

Soil aggregates and their associated carbon and nitrogen content in winter annual pastures using different tillage management options

USDA-ARS?s Scientific Manuscript database

Traditionally, winter annual pastures are established on grazing areas that are steeply sloping and not regarded as suitable for row-crop production. Using conventional (CT) tillage methods to prepare these fragile lands for winter annual pastures leads to increased erosion and rapid soil degradatio...

Gas scintillation glass GEM detector for high-resolution X-ray imaging and CT

NASA Astrophysics Data System (ADS)

Fujiwara, T.; Mitsuya, Y.; Fushie, T.; Murata, K.; Kawamura, A.; Koishikawa, A.; Toyokawa, H.; Takahashi, H.

2017-04-01

A high-spatial-resolution X-ray-imaging gaseous detector has been developed with a single high-gas-gain glass gas electron multiplier (G-GEM), scintillation gas, and optical camera. High-resolution X-ray imaging of soft elements is performed with a spatial resolution of 281 μm rms and an effective area of 100×100 mm. In addition, high-resolution X-ray 3D computed tomography (CT) is successfully demonstrated with the gaseous detector. It shows high sensitivity to low-energy X-rays, which results in high-contrast radiographs of objects containing elements with low atomic numbers. In addition, the high yield of scintillation light enables fast X-ray imaging, which is an advantage for constructing CT images with low-energy X-rays.

X-ray computed microtomography analysis of the influence of different agricultural treatments on the topsoil porosity of a Grey Brown Luvisol from Ontario

NASA Astrophysics Data System (ADS)

Taina, I. A.; Heck, R. J.; Scaiff, N. T.

2009-05-01

One of the most important applications of X-ray computed tomography (CT) for the study of soil is the characterization of the shape and spatial distribution of pores. Analysis of 3D X-ray CT image data, related to different pore categories, can provide insight to soil structural changes, which have implications in water infiltration and soil aeration, resulting from agricultural practices. The aim of this study was to evaluate changes in the spatial characteristics of voids, due to tillage practices, in the Ap horizon of an Orthic Grey- Brown Luvisol (located at the Elora Research Station of the University of Guelph). Undisturbed oriented soil samples were collected from ten plots representing different tillage treatments: spring moldboard plow, spring moldboard plow, cultivate and pack, fall moldboard plow, cultivate and pack, spring tandem disc, no cultivator, fall offset disc, fall offset disc, cultivate and pack, fall chisel plow, cultivate and pack, zero zone till (soys twin rows), zero tillage (long term), and zero tillage (corn residue removed in row, soys twin rows). Since the utilization of standardized classes, in the quantification of similar features, proved to be necessary in order to obtain comparable results, categories of pores, separated according to their size, circularity and orientation were considered in the interpretation of data. Total volume of pores and volume percentage of each class were calculated, revealing substantial differences among the analyzed soil samples.

Muscular performance and body composition changes following multi-joint versus combined multi- and single-joint exercises in aging adults.

PubMed

Bezerra, Ewertton de Souza; Moro, Antônio Renato Pereira; Orssatto, Lucas Bet da Rosa; da Silva, Mariane Eichendorf; Willardson, Jeffrey Michael; Simão, Roberto

2018-06-01

The aim of the present study was to compare muscular performance and body composition changes following low-volume resistance-training programs consisting of multi-joint (MJ) exercises (cable chest press and seated row) versus a combination of multi- and single-joint (MJ+SJ) exercises (cable chest press, seated row, biceps curl, and triceps extension). Thirty untrained healthy aging adults were randomly assigned to 3 groups: MJ (n = 11), MJ+SJ (n = 11), and control (n = 8). Twelve-repetition maximums (12-RMs) for the cable chest press and seated row, localized muscular endurance for the elbow flexors handgrip strength, and body composition were assessed before and after the 8-week training program. All comparisons were analyzed via a mixed-model analysis with repeated measures (group × time) and the Bonferroni post hoc test (p < 0.05). The MJ and MJ+SJ groups increased performance in the 12-RM cable chest press (MJ = 61.5% ± 24.6% and MJ+SJ = 71.1% ± 25.6%), 12-RM seated row (MJ = 46.4% ± 26.3% and MJ+SJ = 51.5% ± 21.0%), localized muscular endurance (MJ = 24.7% ± 16.7% and MJ+SJ = 37.0% ± 11.4%), and handgrip strength (MJ = 9.3% ± 10.4% and MJ+SJ = 16.6% ± 25.3%) after the intervention. Body composition (i.e., trunk and upper limb fat and lean mass) did not change for any groups. No significant differences were observed between the MJ versus the MJ+SJ protocols after the intervention for any variables. In conclusion, for aging adults, either MJ or MJ+SJ low-volume resistance training resulted in similar increases in 12-RM, localized muscular endurance, and handgrip strength, without changes in body composition after 8 weeks of training.

TU-E-217BCD-04: Spectral Breast CT: Effect of Adaptive Filtration on CT Numbers, CT Noise, and CNR.

PubMed

Silkwood, J; Matthews, K; Shikhaliev, P

2012-06-01

Photon counting spectral breast CT is feasible in part due to using an adaptive filter. An adaptive filter provides flat x-ray intensity profile and constant x-ray energy spectrum across detector surface, decreases required detector count rate, and eliminates beam hardening artifacts. However, the altered x-ray exposure profiles at the breast and detector surface may influence the distribution of CT noise, CT numbers, and contrast to noise ratio (CNR) across the CT images. The purpose of this work was to investigate these effects. Images of a CT phantom with and without adaptive filter were simulated at 60kVp, 90kVp, and 120kVp tube voltages and 660 mR total skin exposure. The CT phantom with water content had 14cm diameter, contrast elements representing adipose tissue and 2.5mg/cc iodine contrast located at 1cm, 3.5cm, and 6cm from center of the phantom. The CT numbers, CT noise, and CNR were measured at multiple locations for several filter/exposure combinations: (1)without adaptive filter for 660mR skin exposure; (2)with adaptive filter for 660mR skin exposure along central axis (mean skin exposure across the breast was <660mR); and (3)with adaptive filter for scaled exposure (mean skin exposure was 660mR). Beam hardening (cupping) artifacts had 47HU magnitude without adaptive filter but were eliminated with adaptive filter. CNR of contrast elements was comparable for (1) and (2) over central parts but was higher by 20-30% for (1) near the edge of the phantom. CNR was higher by 20-30% in (3) as compared to (2) over central parts and comparable near the edges. The adaptive filter provided: uniform distribution of CT noise, CNR, and CT numbers across CT images; comparable or better CNR with no dose penalty to the breast; and eliminated beam hardening artifacts. © 2012 American Association of Physicists in Medicine.

A novel technique for ventriculoperitoneal shunting by flat panel detector CT-guided real-time fluoroscopy

PubMed Central

Kobayashi, Shinya; Ishikawa, Tatsuya; Mutoh, Tatsushi; Hikichi, Kentaro; Suzuki, Akifumi

2012-01-01

Background: Surgical placement of a ventriculoperitoneal shunt (VPS) is the main strategy to manage hydrocephalus. However, the failure rate associated with placement of ventricular catheters remains high. Methods: A hybrid operating room, equipped with a flat-panel detector digital subtraction angiography system containing C-arm cone-beam computed tomography (CB-CT) imaging, has recently been developed and utilized to assist neurosurgical procedures. We have developed a novel technique using intraoperative fluoroscopy and a C-arm CB-CT system to facilitate accurate placement of a VPS. Results: Using this novel technique, 39 consecutive ventricular catheters were placed accurately, and no ventricular catheter failures were experienced during the follow-up period. Only two patients experienced obstruction of the VPS, both of which occurred in the extracranial portion of the shunt system. Conclusion: Surgical placement of a VPS assisted by flat panel detector CT-guided real-time fluoroscopy enabled accurate placement of ventricular catheters and was associated with a decreased need for shunt revision. PMID:23226605

Cervical range of motion, cervical and shoulder strength in senior versus age-grade Rugby Union International front-row forwards.

PubMed

Davies, Mark; Moore, Isabel S; Moran, Patrick; Mathema, Prabhat; Ranson, Craig A

2016-05-01

To provide normative values for cervical range of motion (CROM), isometric cervical and shoulder strength for; International Senior professional, and International Age-grade Rugby Union front-row forwards. Cross-sectional population study. All international level front-row players within a Rugby Union Tier 1 Nation. Nineteen Senior and 21 Age-grade front-row forwards underwent CROM, cervical and shoulder strength testing. CROM was measured using the CROM device and the Gatherer System was used to measure multi-directional isometric cervical and shoulder strength. The Age-grade players had significantly lower; cervical strength (26-57% deficits), cervical flexion to extension strength ratios (0.5 vs. 0.6), and shoulder strength (2-36% deficits) than the Senior players. However, there were no differences between front-row positions within each age group. Additionally, there were no differences between age groups or front-row positions in the CROM measurements. Senior Rugby Union front-row forwards have greater cervical and shoulder strength than Age-grade players, with the biggest differences being in cervical strength, highlighting the need for age specific normative values. Importantly, Age-grade players should be evaluated to ensure they have developed sufficient cervical strength prior to entering professional level Rugby Union. Copyright © 2015 Elsevier Ltd. All rights reserved.

Cutting blade dentitions in squaliform sharks form by modification of inherited alternate tooth ordering patterns

PubMed Central

Smith, Moya Meredith

2016-01-01

The squaliform sharks represent one of the most speciose shark clades. Many adult squaliforms have blade-like teeth, either on both jaws or restricted to the lower jaw, forming a continuous, serrated blade along the jaw margin. These teeth are replaced as a single unit and successor teeth lack the alternate arrangement present in other elasmobranchs. Micro-CT scans of embryos of squaliforms and a related outgroup (Pristiophoridae) revealed that the squaliform dentition pattern represents a highly modified version of tooth replacement seen in other clades. Teeth of Squalus embryos are arranged in an alternate pattern, with successive tooth rows containing additional teeth added proximally. Asynchronous timing of tooth production along the jaw and tooth loss prior to birth cause teeth to align in oblique sets containing teeth from subsequent rows; these become parallel to the jaw margin during ontogeny, so that adult Squalus has functional tooth rows comprising obliquely stacked teeth of consecutive developmental rows. In more strongly heterodont squaliforms, initial embryonic lower teeth develop into the oblique functional sets seen in adult Squalus, with no requirement to form, and subsequently lose, teeth arranged in an initial alternate pattern. PMID:28018617

Cutting blade dentitions in squaliform sharks form by modification of inherited alternate tooth ordering patterns

NASA Astrophysics Data System (ADS)

Underwood, Charlie; Johanson, Zerina; Smith, Moya Meredith

2016-11-01

The squaliform sharks represent one of the most speciose shark clades. Many adult squaliforms have blade-like teeth, either on both jaws or restricted to the lower jaw, forming a continuous, serrated blade along the jaw margin. These teeth are replaced as a single unit and successor teeth lack the alternate arrangement present in other elasmobranchs. Micro-CT scans of embryos of squaliforms and a related outgroup (Pristiophoridae) revealed that the squaliform dentition pattern represents a highly modified version of tooth replacement seen in other clades. Teeth of Squalus embryos are arranged in an alternate pattern, with successive tooth rows containing additional teeth added proximally. Asynchronous timing of tooth production along the jaw and tooth loss prior to birth cause teeth to align in oblique sets containing teeth from subsequent rows; these become parallel to the jaw margin during ontogeny, so that adult Squalus has functional tooth rows comprising obliquely stacked teeth of consecutive developmental rows. In more strongly heterodont squaliforms, initial embryonic lower teeth develop into the oblique functional sets seen in adult Squalus, with no requirement to form, and subsequently lose, teeth arranged in an initial alternate pattern.

X-ray imaging with sub-micron resolution using large-area photon counting detectors Timepix

NASA Astrophysics Data System (ADS)

Dudak, J.; Karch, J.; Holcova, K.; Zemlicka, J.

2017-12-01

As X-ray micro-CT became a popular tool for scientific purposes a number of commercially available CT systems have emerged on the market. Micro-CT systems have, therefore, become widely accessible and the number of research laboratories using them constantly increases. However, even when CT scans with spatial resolution of several micrometers can be performed routinely, data acquisition with sub-micron precision remains a complicated task. Issues come mostly from prolongation of the scan time inevitably connected with the use of nano-focus X-ray sources. Long exposure time increases the noise level in the CT projections. Furthermore, considering the sub-micron resolution even effects like source-spot drift, rotation stage wobble or thermal expansion become significant and can negatively affect the data. The use of dark-current free photon counting detectors as X-ray cameras for such applications can limit the issue of increased image noise in the data, however the mechanical stability of the whole system still remains a problem and has to be considered. In this work we evaluate the performance of a micro-CT system equipped with nano-focus X-ray tube and a large area photon counting detector Timepix for scans with effective pixel size bellow one micrometer.

Soil management practice in Croatian vineyard affect CO2 fluxes and soil degradation in trafficking zones. First results

NASA Astrophysics Data System (ADS)

Bogunovic, Igor; Bilandzija, Darija; Andabaka, Zeljko; Stupic, Domagoj; Cacic, Marija; Brezinscak, Luka; Maletic, Edi; Pereira, Paulo; Kisic, Ivica

2017-04-01

Vineyards represent one of the most degradation prone types of intensively managed land on Earth. Steep slopes encourage grape producers to adopt environmental friendly soil management like mulching or continuous no-tillage. In this context, producers have concerns about efficient fertilisation practices and water competitions between vine and grasses in continuous no-tillage inter rows. Vineyards in semi-humid areas like Continental Croatia mostly not suffer from water deficit during growth. Nevertheless, lack of research of different soil management practices open dilemma about soil compaction concerns in intensively trafficked soils in vineyard of semi-humid areas. Soil compaction, determined by bulk density (BD), soil water content (SWC) and CO2 fluxes from trafficked inter row positions were recorded in 2016 in an experiment in which four different soil management systems were compared in a vineyard raised on a silty clay loam soil, near Zagreb, Croatia: No-tillage (NT) system, continuous tillage (CT) and yearly inversed grass covered (INV-GC) and tillage managed (INV-T) inter rows are subjected to intensive traffic. Grape yield and must quality of grape variety Chardonnay was also monitored. Tractor traffic increased the soil BD at 0-10 and 10-20 cm, but especially at the 0-10 cm depth. CT treatment record lowest compaction at 0-10 cm because of tillage. Soil water content showed better conservation possibilities of INV-GC in drier period. In wet period SWC possibilities are similar between treatments. The results of soil compaction under different management indicate that vineyard soil differently response to traffic intensity and impact on microfauna activity and CO2 emissions. INV-GC and NT managed soils record lower CO2 fluxes from vineyard soil compared to CT and INV-T treatments. Management treatments did not statistically influenced on grape yields. Several years of investigation is needed to confirm the overall impact of different management treatments on the proportion of degradation process and their response to proportion of tractor circulation impacts.

Dose reduction and image quality optimizations in CT of pediatric and adult patients: phantom studies

NASA Astrophysics Data System (ADS)

Jeon, P.-H.; Lee, C.-L.; Kim, D.-H.; Lee, Y.-J.; Jeon, S.-S.; Kim, H.-J.

2014-03-01

Multi-detector computed tomography (MDCT) can be used to easily and rapidly perform numerous acquisitions, possibly leading to a marked increase in the radiation dose to individual patients. Technical options dedicated to automatically adjusting the acquisition parameters according to the patient's size are of specific interest in pediatric radiology. A constant tube potential reduction can be achieved for adults and children, while maintaining a constant detector energy fluence. To evaluate radiation dose, the weighted CT dose index (CTDIw) was calculated based on the CT dose index (CTDI) measured using an ion chamber, and image noise and image contrast were measured from a scanned image to evaluate image quality. The dose-weighted contrast-to-noise ratio (CNRD) was calculated from the radiation dose, image noise, and image contrast measured from a scanned image. The noise derivative (ND) is a quality index for dose efficiency. X-ray spectra with tube voltages ranging from 80 to 140 kVp were used to compute the average photon energy. Image contrast and the corresponding contrast-to-noise ratio (CNR) were determined for lesions of soft tissue, muscle, bone, and iodine relative to a uniform water background, as the iodine contrast increases at lower energy (i.e., k-edge of iodine is 33 keV closer to the beam energy) using mixed water-iodine contrast normalization (water 0, iodine 25, 100, 200, and 1000 HU, respectively). The proposed values correspond to high quality images and can be reduced if only high-contrast organs are assessed. The potential benefit of lowering the tube voltage is an improved CNRD, resulting in a lower radiation dose and optimization of image quality. Adjusting the tube potential in abdominal CT would be useful in current pediatric radiography, where the choice of X-ray techniques generally takes into account the size of the patient as well as the need to balance the conflicting requirements of diagnostic image quality and radiation dose optimization.

A high-resolution photon-counting breast CT system with tensor-framelet based iterative image reconstruction for radiation dose reduction

NASA Astrophysics Data System (ADS)

Ding, Huanjun; Gao, Hao; Zhao, Bo; Cho, Hyo-Min; Molloi, Sabee

2014-10-01

Both computer simulations and experimental phantom studies were carried out to investigate the radiation dose reduction with tensor framelet based iterative image reconstruction (TFIR) for a dedicated high-resolution spectral breast computed tomography (CT) based on a silicon strip photon-counting detector. The simulation was performed with a 10 cm-diameter water phantom including three contrast materials (polyethylene, 8 mg ml-1 iodine and B-100 bone-equivalent plastic). In the experimental study, the data were acquired with a 1.3 cm-diameter polymethylmethacrylate (PMMA) phantom containing iodine in three concentrations (8, 16 and 32 mg ml-1) at various radiation doses (1.2, 2.4 and 3.6 mGy) and then CT images were reconstructed using the filtered-back-projection (FBP) technique and the TFIR technique, respectively. The image quality between these two techniques was evaluated by the quantitative analysis on contrast-to-noise ratio (CNR) and spatial resolution that was evaluated using the task-based modulation transfer function (MTF). Both the simulation and experimental results indicated that the task-based MTF obtained from TFIR reconstruction with one-third of the radiation dose was comparable to that from the FBP reconstruction for low contrast target. For high contrast target, the TFIR was substantially superior to the FBP reconstruction in terms of spatial resolution. In addition, TFIR was able to achieve a factor of 1.6-1.8 increase in CNR, depending on the target contrast level. This study demonstrates that the TFIR can reduce the required radiation dose by a factor of two-thirds for a CT image reconstruction compared to the FBP technique. It achieves much better CNR and spatial resolution for high contrast target in addition to retaining similar spatial resolution for low contrast target. This TFIR technique has been implemented with a graphic processing unit system and it takes approximately 10 s to reconstruct a single-slice CT image, which can potentially be used in a future multi-slit multi-slice spiral CT system.

Comparative investigation of the detective quantum efficiency of direct and indirect conversion detector technologies in dedicated breast CT.

PubMed

Kuttig, Jan D; Steiding, Christian; Kolditz, Daniel; Hupfer, Martin; Karolczak, Marek; Kalender, Willi A

2015-06-01

To investigate the dose saving potential of direct-converting CdTe photon-counting detector technology for dedicated breast CT. We analyzed the modulation transfer function (MTF), the noise power spectrum (NPS) and the detective quantum efficiency (DQE) of two detector technologies, suitable for breast CT (BCT): a flat-panel energy-integrating detector with a 70 μm and a 208 μm thick gadolinium oxysulfide (GOS) and a 150 μm thick cesium iodide (CsI) scintillator and a photon-counting detector with a 1000 μm thick CdTe sensor. The measurements for GOS scintillator thicknesses of 70 μm and 208 μm delivered 10% pre-sampled MTF values of 6.6 mm(-1) and 3.2 mm(-1), and DQE(0) values of 23% and 61%. The 10% pre-sampled MTF value for the 150 μm thick CsI scintillator 6.9 mm(-1), and the DQE(0) value was 49%. The CdTe sensor reached a 10% pre-sampled MTF value of 8.5 mm(-1) and a DQE(0) value of 85%. The photon-counting CdTe detector technology allows for significant dose reduction compared to the energy-integrating scintillation detector technology used in BCT today. Our comparative evaluation indicates that a high potential dose saving may be possible for BCT by using CdTe detectors, without loss of spatial resolution. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Photon counting spectral breast CT: effect of adaptive filtration on CT numbers, noise, and contrast to noise ratio.

PubMed

Silkwood, Justin D; Matthews, Kenneth L; Shikhaliev, Polad M

2013-05-01

Photon counting spectral (PCS) computed tomography (CT) shows promise for breast imaging. An issue with current photon-counting detectors is low count rate capabilities, artifacts resulting from nonuniform count rate across the field of view, and suboptimal spectral information. These issues are addressed in part by using tissue-equivalent adaptive filtration of the x-ray beam. The purpose of the study was to investigate the effect of adaptive filtration on different aspects of PCS breast CT. The theoretical formulation for the filter shape was derived for different filter materials and evaluated by simulation and an experimental prototype of the filter was fabricated from a tissue-like material (acrylic). The PCS CT images of a glandular breast phantom with adipose and iodine contrast elements were simulated at 40, 60, 90, and 120 kVp tube voltages, with and without adaptive filter. The CT numbers, CT noise, and contrast-to-noise ratio (CNR) were compared for spectral CT images acquired with and without adaptive filters. Similar comparison was made for material-decomposed PCS CT images. The adaptive filter improved the uniformity of CT numbers, CT noise, and CNR in both ordinary and material decomposed PCS CT images. At the same tube output the average CT noise with adaptive filter, although uniform, was higher than the average noise without adaptive filter due to x-ray absorption by the filter. Increasing tube output, so that average skin exposure with the adaptive filter was same as without filter, made the noise with adaptive filter comparable to or lower than that without adaptive filter. Similar effects were observed when energy weighting was applied, and when material decompositions were performed using energy selective CT data. An adaptive filter decreases count rate requirements to the photon counting detectors which enables PCS breast CT based on commercially available detector technologies. Adaptive filter also improves image quality in PCS breast CT by decreasing beam hardening artifacts and by eliminating spatial nonuniformities of CT numbers, noise, and CNR.

Multi-wavelength access gate for WDM-formatted words in optical RAM row architectures

NASA Astrophysics Data System (ADS)

Fitsios, D.; Alexoudi, T.; Vagionas, C.; Miliou, A.; Kanellos, G. T.; Pleros, N.

2013-03-01

Optical RAM has emerged as a promising solution for overcoming the "Memory Wall" of electronics, indicating the use of light in RAM architectures as the approach towards enabling ps-regime memory access times. Taking a step further towards exploiting the unique wavelength properties of optical signals, we reveal new architectural perspectives in optical RAM structures by introducing WDM principles in the storage area. To this end, we demonstrate a novel SOAbased multi-wavelength Access Gate for utilization in a 4x4 WDM optical RAM bank architecture. The proposed multiwavelength Access Gate can simultaneously control random access to a 4-bit optical word, exploiting Cross-Gain-Modulation (XGM) to process 8 Bit and Bit channels encoded in 8 different wavelengths. It also suggests simpler optical RAM row architectures, allowing for the effective sharing of one multi-wavelength Access Gate for each row, substituting the eight AGs in the case of conventional optical RAM architectures. The scheme is shown to support 10Gbit/s operation for the incoming 4-bit data streams, with a power consumption of 15mW/Gbit/s. All 8 wavelength channels demonstrate error-free operation with a power penalty lower than 3 dB for all channels, compared to Back-to-Back measurements. The proposed optical RAM architecture reveals that exploiting the WDM capabilities of optical components can lead to RAM bank implementations with smarter column/row encoders/decoders, increased circuit simplicity, reduced number of active elements and associated power consumption. Moreover, exploitation of the wavelength entity can release significant potential towards reconfigurable optical cache mapping schemes when using the wavelength dimension for memory addressing.

Prevalence of ligamentum arteriosum calcification on multi-section spiral CT and digital radiography.

PubMed

Hong, Gil-Sun; Goo, Hyun Woo; Song, Jae-Woo

2012-06-01

To investigate the prevalence of ligamentum arteriosum calcification (LAC) on multi-section spiral CT and digital radiography. Five hundred and eight children and 232 adults who performed multi-section chest CT were included in this study and were divided into nine age groups: A (0-5 years), B (6-10 years), C (11-15 years), D (16-20 years), E (21-30 years), F (31-40 years), G (41-50 years), H (51-60 years), and I (61-70 years). Two radiologists assessed the presence of LAC on axial and coronal CT images, defined as focal calcific density on both or on one plane with attenuation >100 Hounsfield unit. The prevalence of LAC on CT was compared between children and adults, and between unenhanced and enhanced CT in children. The prevalence of LAC on digital radiography was evaluated in 476 children. The prevalence of definite LAC on unenhanced multi-section CT was significantly higher in children (37.8 %) than in adults (11.2 %) (P < 0.001), with prevalences in groups: A through I of 35.8, 48.7, 35.1, 28.6, 25.0, 10.2, 15.5, 7.8, and 5.6 %, respectively. The prevalences of indeterminate LAC in age groups A-I on unenhanced multi-section CT were 4.5, 12.8, 8.1, 19.0, 0.0, 0.0, 0.0, 2.0, and 1.9 %. In children, the prevalence of LAC was significantly higher on unenhanced than on enhanced CT (37.8 vs. 16.4 %, P < 0.001). The prevalence of LAC on digital radiography was 3.6 % in children. LAC is frequently observed in children and adults on multi-section spiral CT, more frequently than previously reported. Compared with that on multi-section spiral CT, the prevalence of LAC on digital radiography is substantially low.

Clustering header categories extracted from web tables

NASA Astrophysics Data System (ADS)

Nagy, George; Embley, David W.; Krishnamoorthy, Mukkai; Seth, Sharad

2015-01-01

Revealing related content among heterogeneous web tables is part of our long term objective of formulating queries over multiple sources of information. Two hundred HTML tables from institutional web sites are segmented and each table cell is classified according to the fundamental indexing property of row and column headers. The categories that correspond to the multi-dimensional data cube view of a table are extracted by factoring the (often multi-row/column) headers. To reveal commonalities between tables from diverse sources, the Jaccard distances between pairs of category headers (and also table titles) are computed. We show how about one third of our heterogeneous collection can be clustered into a dozen groups that exhibit table-title and header similarities that can be exploited for queries.

Timeliness of contact tracing among flight passengers for influenza A/H1N1 2009

PubMed Central

2011-01-01

Background During the initial containment phase of influenza A/H1N1 2009, close contacts of cases were traced to provide antiviral prophylaxis within 48 h after exposure and to alert them on signs of disease for early diagnosis and treatment. Passengers seated on the same row, two rows in front or behind a patient infectious for influenza, during a flight of ≥ 4 h were considered close contacts. This study evaluates the timeliness of flight-contact tracing (CT) as performed following national and international CT requests addressed to the Center of Infectious Disease Control (CIb/RIVM), and implemented by the Municipal Health Services of Schiphol Airport. Methods Elapsed days between date of flight arrival and the date passenger lists became available (contact details identified - CI) was used as proxy for timeliness of CT. In a retrospective study, dates of flight arrival, onset of illness, laboratory diagnosis, CT request and identification of contacts details through passenger lists, following CT requests to the RIVM for flights landed at Schiphol Airport were collected and analyzed. Results 24 requests for CT were identified. Three of these were declined as over 4 days had elapsed since flight arrival. In 17 out of 21 requests, contact details were obtained within 7 days after arrival (81%). The average delay between arrival and CI was 3,9 days (range 2-7), mainly caused by delay in diagnosis of the index patient after arrival (2,6 days). In four flights (19%), contacts were not identified or only after > 7 days. CI involving Dutch airlines was faster than non-Dutch airlines (P < 0,05). Passenger locator cards did not improve timeliness of CI. In only three flights contact details were identified within 2 days after arrival. Conclusion CT for influenza A/H1N1 2009 among flight passengers was not successful for timely provision of prophylaxis. CT had little additional value for alerting passengers for disease symptoms, as this information already was provided during and after the flight. Public health authorities should take into account patient delays in seeking medical advise and laboratory confirmation in relation to maximum time to provide postexposure prophylaxis when deciding to install contact tracing measures. International standardization of CT guidelines is recommended. PMID:22204494

SU-C-207-01: Four-Dimensional Inverse Geometry Computed Tomography: Concept and Its Validation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, K; Kim, D; Kim, T

2015-06-15

Purpose: In past few years, the inverse geometry computed tomography (IGCT) system has been developed to overcome shortcomings of a conventional computed tomography (CT) system such as scatter problem induced from large detector size and cone-beam artifact. In this study, we intend to present a concept of a four-dimensional (4D) IGCT system that has positive aspects above all with temporal resolution for dynamic studies and reduction of motion artifact. Methods: Contrary to conventional CT system, projection data at a certain angle in IGCT was a group of fractionated narrow cone-beam projection data, projection group (PG), acquired from multi-source array whichmore » have extremely short time gap of sequential operation between each of sources. At this, for 4D IGCT imaging, time-related data acquisition parameters were determined by combining multi-source scanning time for collecting one PG with conventional 4D CBCT data acquisition sequence. Over a gantry rotation, acquired PGs from multi-source array were tagged time and angle for 4D image reconstruction. Acquired PGs were sorted into 10 phase and image reconstructions were independently performed at each phase. Image reconstruction algorithm based upon filtered-backprojection was used in this study. Results: The 4D IGCT had uniform image without cone-beam artifact on the contrary to 4D CBCT image. In addition, the 4D IGCT images of each phase had no significant artifact induced from motion compared with 3D CT. Conclusion: The 4D IGCT image seems to give relatively accurate dynamic information of patient anatomy based on the results were more endurable than 3D CT about motion artifact. From this, it will be useful for dynamic study and respiratory-correlated radiation therapy. This work was supported by the Industrial R&D program of MOTIE/KEIT [10048997, Development of the core technology for integrated therapy devices based on real-time MRI guided tumor tracking] and the Mid-career Researcher Program (2014R1A2A1A10050270) through the National Research Foundation of Korea funded by the Ministry of Science, ICT&Future Planning.« less

Quantitative PET and SPECT performance characteristics of the Albira Trimodal pre-clinical tomograph

NASA Astrophysics Data System (ADS)

Spinks, T. J.; Karia, D.; Leach, M. O.; Flux, G.

2014-02-01

The Albira Trimodal pre-clinical scanner comprises PET, SPECT and CT sub-systems and thus provides a range of pre-clinical imaging options. The PET component consists of three rings of single-crystal LYSO detectors with axial/transverse fields-of-view (FOVs) of 148/80 mm. The SPECT component has two opposing CsI detectors (100 × 100 mm2) with single-pinhole (SPH) or multi(9)-pinhole (MPH) collimators; the detectors rotate in 6° increments and their spacing can be adjusted to provide different FOVs (25 to 120 mm). The CT sub-system provides ‘low’ (200 µA, 35 kVp) or ‘high’ (400 µA, 45 kVp) power x-rays onto a flat-panel CsI detector. This study examines the performance characteristics and quantitative accuracy of the PET and SPECT components. Using the NEMA NU 4-2008 specifications (22Na point source), the PET spatial resolution is 1.5 + 0.1 mm on axis and sensitivity 6.3% (axial centre) and 4.6% (central 70 mm). The usable activity range is ≤ 10 MBq (18F) over which good linearity (within 5%) is obtained for a uniform cylinder spanning the axial FOV; increasing deviation from linearity with activity is, however, observed for the NEMA (mouse) line source phantom. Image uniformity axially is within 5%. Spatial resolution (SPH/MPH) for the minimum SPECT FOV used for mouse imaging (50 mm) is 1.5/1.7 mm and point source sensitivity 69/750 cps MBq-1. Axial uniformity of SPECT images (%CV of regions-of-interest counts along the axis) is mostly within 8% although there is a range of 30-40% for the largest FOV. The variation is significantly smaller within the central 40 mm. Instances of count rate nonlinearity (PET) and axial non-uniformity (SPECT) were found to be reproducible and thus amenable to empirical correction.

Effect of Edge-Preserving Adaptive Image Filter on Low-Contrast Detectability in CT Systems: Application of ROC Analysis

PubMed Central

Okumura, Miwa; Ota, Takamasa; Kainuma, Kazuhisa; Sayre, James W.; McNitt-Gray, Michael; Katada, Kazuhiro

2008-01-01

Objective. For the multislice CT (MSCT) systems with a larger number of detector rows, it is essential to employ dose-reduction techniques. As reported in previous studies, edge-preserving adaptive image filters, which selectively eliminate only the noise elements that are increased when the radiation dose is reduced without affecting the sharpness of images, have been developed. In the present study, we employed receiver operating characteristic (ROC) analysis to assess the effects of the quantum denoising system (QDS), which is an edge-preserving adaptive filter that we have developed, on low-contrast resolution, and to evaluate to what degree the radiation dose can be reduced while maintaining acceptable low-contrast resolution. Materials and Methods. The low-contrast phantoms (Catphan 412) were scanned at various tube current settings, and ROC analysis was then performed for the groups of images obtained with/without the use of QDS at each tube current to determine whether or not a target could be identified. The tube current settings for which the area under the ROC curve (Az value) was approximately 0.7 were determined for both groups of images with/without the use of QDS. Then, the radiation dose reduction ratio when QDS was used was calculated by converting the determined tube current to the radiation dose. Results. The use of the QDS edge-preserving adaptive image filter allowed the radiation dose to be reduced by up to 38%. Conclusion. The QDS was found to be useful for reducing the radiation dose without affecting the low-contrast resolution in MSCT studies. PMID:19043565

Regularization design for high-quality cone-beam CT of intracranial hemorrhage using statistical reconstruction

NASA Astrophysics Data System (ADS)

Dang, H.; Stayman, J. W.; Xu, J.; Sisniega, A.; Zbijewski, W.; Wang, X.; Foos, D. H.; Aygun, N.; Koliatsos, V. E.; Siewerdsen, J. H.

2016-03-01

Intracranial hemorrhage (ICH) is associated with pathologies such as hemorrhagic stroke and traumatic brain injury. Multi-detector CT is the current front-line imaging modality for detecting ICH (fresh blood contrast 40-80 HU, down to 1 mm). Flat-panel detector (FPD) cone-beam CT (CBCT) offers a potential alternative with a smaller scanner footprint, greater portability, and lower cost potentially well suited to deployment at the point of care outside standard diagnostic radiology and emergency room settings. Previous studies have suggested reliable detection of ICH down to 3 mm in CBCT using high-fidelity artifact correction and penalized weighted least-squared (PWLS) image reconstruction with a post-artifact-correction noise model. However, ICH reconstructed by traditional image regularization exhibits nonuniform spatial resolution and noise due to interaction between the statistical weights and regularization, which potentially degrades the detectability of ICH. In this work, we propose three regularization methods designed to overcome these challenges. The first two compute spatially varying certainty for uniform spatial resolution and noise, respectively. The third computes spatially varying regularization strength to achieve uniform "detectability," combining both spatial resolution and noise in a manner analogous to a delta-function detection task. Experiments were conducted on a CBCT test-bench, and image quality was evaluated for simulated ICH in different regions of an anthropomorphic head. The first two methods improved the uniformity in spatial resolution and noise compared to traditional regularization. The third exhibited the highest uniformity in detectability among all methods and best overall image quality. The proposed regularization provides a valuable means to achieve uniform image quality in CBCT of ICH and is being incorporated in a CBCT prototype for ICH imaging.

Diagnostic performance and radiation dose of lower extremity CT angiography using a 128-slice dual source CT at 80 kVp and high pitch.

PubMed

Kim, Jin Woo; Choo, Ki Seok; Jeon, Ung Bae; Kim, Tae Un; Hwang, Jae Yeon; Yeom, Jeong A; Jeong, Hee Seok; Choi, Yoon Young; Nam, Kyung Jin; Kim, Chang Won; Jeong, Dong Wook; Lim, Soo Jin

2016-07-01

Multi-detector computed tomography (MDCT) angiography is now used for the diagnosing patients with peripheral arterial disease. The dose of radiation is related to variable factors, such as tube current, tube voltage, and helical pitch. To assess the diagnostic performance and radiation dose of lower extremity CT angiography (CTA) using a 128-slice dual source CT at 80 kVp and high pitch in patients with critical limb ischemia (CLI). Twenty-eight patients (mean, 64.1 years; range, 39-80 years) with CLI were enrolled in this retrospective study and underwent CTA using a 128-slice dual source CT at 80 kVp and high pitch and subsequent intra-arterial digital subtraction angiography (DSA), which was used as a reference standard for assessing diagnostic performance. For arterial segments with significant disease (>50% stenosis), overall sensitivity, specificity, and accuracy of lower extremity CTA were 94.8% (95% CI, 91.7-98.0%), 91.5% (95% CI, 87.7-95.2%), and 93.1% (95% CI, 90.6-95.6%), respectively, and its positive and negative predictive values were 91.0% (95% CI, 87.1-95.0%), and 95.1% (95% CI, 92.1-98.1%), respectively. Mean radiation dose delivered to lower extremities was 266.6 mGy.cm. Lower extremity CTA using a 128-slice dual source CT at 80 kVp and high pitch was found to have good diagnostic performance for the assessment of patients with CLI using an extremely low radiation dose. © The Foundation Acta Radiologica 2015.

Ossicles of lumbar articular facets: normal variant or spondylolytic variant?

PubMed

Kumar, Dalavaye S; Fotiadou, Anastasia; Lalam, Radhesh; Ginder, Laurence M; Eisenstein, Stephen M; Tins, Bernard J; Tyrrell, Prudencia N M; Delieu, John M; McCall, Iain W; Rees, Dai A; Cassar-Pullicino, Victor N

2012-12-01

The objective of this study was to establish the prevalence and significance of ossicles of lumbar articular facets (OLAF) in young athletes with backache diagnosed by multi-detector computed tomography (MDCT). The MDCT examinations of the lumbar spine carried out for suspected spondylolysis on 46 consecutive symptomatic young athletes presenting to a sports injury clinic over a 1-year period were retrospectively reviewed. OLAF study included detailed correlation with the structural and morphological stress features of the posterior neural arches. This was then compared with a control group composed of 39 patients. Twenty-three OLAF were identified in 15 patients. Eleven of the 15 patients with ossicles had posterior element stress changes (PEST)/pars defects. In the control group, two OLAF were identified in two patients, one demonstrating PEST changes. The high prevalence of OLAF in young symptomatic athletes compared with the asymptomatic control group is indicative of stress fractures. The non-united articular process fractures should be regarded as part of the spectrum of stress-induced changes in the posterior neural arch in the same way as spondylolysis. MDCT with volumetric acquisition and multi-planar reformation is the most reliable investigation in the diagnosis of OLAF. 1) This CT study supports a traumatic aetiology for lumbar articular facets ossicles. 2) OLAF represent part of a spectrum of stress-induced changes in the posterior neural arch. 3) OLAF are associated with typical spondylolysis. 4) OLAF can be overlooked on reverse gantry angle computed tomography (RG-CT). 5) OLAF may account for some of the discrepancy between radionuclide and RG-CT studies.

Unsteady flows in rotor-stator cascades

NASA Astrophysics Data System (ADS)

Lee, Yu-Tai; Bein, Thomas W.; Feng, Jin Z.; Merkle, Charles L.

1991-03-01

A time-accurate potential-flow calculation method has been developed for unsteady incompressible flows through two-dimensional multi-blade-row linear cascades. The method represents the boundary surfaces by distributing piecewise linear-vortex and constant-source singularities on discrete panels. A local coordinate is assigned to each independently moving object. Blade-shed vorticity is traced at each time step. The unsteady Kutta condition applied is nonlinear and requires zero blade trailing-edge loading at each time. Its influence on the solutions depends on the blade trailing-edge shapes. Steady biplane and cascade solutions are presented and compared to exact solutions and experimental data. Unsteady solutions are validated with the Wagner function for an airfoil moving impulsively from rest and the Theodorsen function for an oscillating airfoil. The shed vortex motion and its interaction with blades are calculated and compared to an analytic solution. For multi-blade-row cascade, the potential effect between blade rows is predicted using steady and quasi unsteady calculations. The accuracy of the predictions is demonstrated using experimental results for a one-stage turbine stator-rotor.

Bolted joints in graphite-epoxy composites

NASA Technical Reports Server (NTRS)

Hart-Smith, L. J.

1976-01-01

All-graphite/epoxy laminates and hybrid graphite-glass/epoxy laminates were tested. The tests encompassed a range of geometries for each laminate pattern to cover the three basic failure modes - net section tension failure through the bolt hole, bearing and shearout. Static tensile and compressive loads were applied. A constant bolt diameter of 6.35 mm (0.25 in.) was used in the tests. The interaction of stress concentrations associated with multi-row bolted joints was investigated by testing single- and double-row bolted joints and open-hole specimens in tension. For tension loading, linear interaction was found to exist between the bearing stress reacted at a given bolt hole and the remaining tension stress running by that hole to be reacted elsewhere. The interaction under compressive loading was found to be non-linear. Comparative tests were run using single-lap bolted joints and double-lap joints with pin connection. Both of these joint types exhibited lower strengths than were demonstrated by the corresponding double-lap joints. The analysis methods developed here for single bolt joints are shown to be capable of predicting the behavior of multi-row joints.

Photon-counting CT with silicon detectors: feasibility for pediatric imaging

NASA Astrophysics Data System (ADS)

Yveborg, Moa; Xu, Cheng; Fredenberg, Erik; Danielsson, Mats

2009-02-01

X-ray detectors made of crystalline silicon have several advantages including low dark currents, fast charge collection and high energy resolution. For high-energy x-rays, however, silicon suffers from its low atomic number, which might result in low detection efficiency, as well as low energy and spatial resolution due to Compton scattering. We have used a monte-carlo model to investigate the feasibility of a detector for pediatric CT with 30 to 40 mm of silicon using x-ray spectra ranging from 80 to 140 kVp. A detection efficiency of 0.74 was found at 80 kVp, provided the noise threshold could be set low. Scattered photons were efficiently blocked by a thin metal shielding between the detector units, and Compton scattering in the detector could be well separated from photo absorption at 80 kVp. Hence, the detector is feasible at low acceleration voltages, which is also suitable for pediatric imaging. We conclude that silicon detectors may be an alternative to other designs for this special case.

Inpainting approaches to fill in detector gaps in phase contrast computed tomography

NASA Astrophysics Data System (ADS)

Brun, F.; Delogu, P.; Longo, R.; Dreossi, D.; Rigon, L.

2018-01-01

Photon counting semiconductor detectors in radiation imaging present attractive properties, such as high efficiency, low noise, and energy sensitivity. The very complex electronics limits the sensitive area of current devices to a few square cm. This disadvantage is often compensated by tiling a larger matrix with an adequate number of detector units but this usually results in non-negligible insensitive gaps between two adjacent modules. When considering the case of Computed Tomography (CT), these gaps lead to degraded reconstructed images with severe streak and ring artifacts. This work presents two digital image processing solutions to fill in these gaps when considering the specific case of synchrotron radiation x-ray parallel beam phase contrast CT. While not discussed with experimental data, other CT modalities, such as spectral, cone beam and other geometries might benefit from the presented approaches.

Dynamic CT myocardial perfusion imaging: detection of ischemia in a porcine model with FFR verification

NASA Astrophysics Data System (ADS)

Fahmi, Rachid; Eck, Brendan L.; Vembar, Mani; Bezerra, Hiram G.; Wilson, David L.

2014-03-01

Dynamic cardiac CT perfusion (CTP) is a high resolution, non-invasive technique for assessing myocardial blood ow (MBF), which in concert with coronary CT angiography enable CT to provide a unique, comprehensive, fast analysis of both coronary anatomy and functional ow. We assessed perfusion in a porcine model with and without coronary occlusion. To induce occlusion, each animal underwent left anterior descending (LAD) stent implantation and angioplasty balloon insertion. Normal ow condition was obtained with balloon completely de ated. Partial occlusion was induced by balloon in ation against the stent with FFR used to assess the extent of occlusion. Prospective ECG-triggered partial scan images were acquired at end systole (45% R-R) using a multi-detector CT (MDCT) scanner. Images were reconstructed using FBP and a hybrid iterative reconstruction (iDose4, Philips Healthcare). Processing included: beam hardening (BH) correction, registration of image volumes using 3D cubic B-spline normalized mutual-information, and spatio-temporal bilateral ltering to reduce partial scan artifacts and noise variation. Absolute blood ow was calculated with a deconvolutionbased approach using singular value decomposition (SVD). Arterial input function was estimated from the left ventricle (LV) cavity. Regions of interest (ROIs) were identi ed in healthy and ischemic myocardium and compared in normal and occluded conditions. Under-perfusion was detected in the correct LAD territory and ow reduction agreed well with FFR measurements. Flow was reduced, on average, in LAD territories by 54%.

A retrospective comparison of smart prep and test bolus multi-detector CT pulmonary angiography protocols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suckling, Tara; Smith, Tony; Reed, Warren

2013-06-15

Optimal arterial opacification is crucial in imaging the pulmonary arteries using computed tomography (CT). This poses the challenge of precisely timing data acquisition to coincide with the transit of the contrast bolus through the pulmonary vasculature. The aim of this quality assurance exercise was to investigate if a change in CT pulmonary angiography (CTPA) scanning protocol resulted in improved opacification of the pulmonary arteries. Comparison was made between the smart prep protocol (SPP) and the test bolus protocol (TBP) for opacification in the pulmonary trunk. A total of 160 CTPA examinations (80 using each protocol) performed between January 2010 andmore » February 2011 were assessed retrospectively. CT attenuation coefficients were measured in Hounsfield Units (HU) using regions of interest at the level of the pulmonary trunk. The average pixel value, standard deviation (SD), maximum, and minimum were recorded. For each of these variables a mean value was then calculated and compared for these two CTPA protocols. Minimum opacification of 200 HU was achieved in 98% of the TBP sample but only 90% of the SPP sample. The average CT attenuation over the pulmonary trunk for the SPP was 329 (SD = ±21) HU, whereas for the TBP it was 396 (SD = ±22) HU (P = 0.0017). The TBP also recorded higher maximum (P = 0.0024) and minimum (P = 0.0039) levels of opacification. This study has found that a TBP resulted in significantly better opacification of the pulmonary trunk than the SPP.« less

Development of CT and 3D-CT Using Flat Panel Detector Based Real-Time Digital Radiography System

NASA Astrophysics Data System (ADS)

Ravindran, V. R.; Sreelakshmi, C.; Vibin, Vibin

2008-09-01

The application of Digital Radiography in the Nondestructive Evaluation (NDE) of space vehicle components is a recent development in India. A Real-time DR system based on amorphous silicon Flat Panel Detector has been developed for the NDE of solid rocket motors at Rocket Propellant Plant of VSSC in a few years back. The technique has been successfully established for the nondestructive evaluation of solid rocket motors. The DR images recorded for a few solid rocket specimens are presented in the paper. The Real-time DR system is capable of generating sufficient digital X-ray image data with object rotation for the CT image reconstruction. In this paper the indigenous development of CT imaging based on the Realtime DR system for solid rocket motor is presented. Studies are also carried out to generate 3D-CT image from a set of adjacent CT images of the rocket motor. The capability of revealing the spatial location and characterisation of defect is demonstrated by the CT and 3D-CT images generated.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melnyk, Roman; DiBianca, Frank A.

The detector presampling modulation transfer function (MTF) of a 576-channel variable resolution x-ray (VRX) computed tomography (CT) scanner was evaluated in this study. The scanner employs a VRX detector, which provides increased spatial resolution by matching the scanner's field of view (FOV) to the size of an object being imaged. Because spatial resolution is the parameter the scanner promises to improve, the evaluation of this resolution is important. The scanner's pre-reconstruction spatial resolution, represented by the detector presampling MTF, was evaluated using both modeling (Monte Carlo simulation) and measurement (the moving slit method). The theoretical results show the increase inmore » the cutoff frequency of the detector presampling MTF from 1.39 to 43.38 cycles/mm as the FOV of the VRX CT scanner decreases from 32 to 1 cm. The experimental results are in reasonable agreement with the theoretical data. Some discrepancies between the measured and the modeled detector presampling MTFs can be explained by the limitations of the model. At small FOVs (1-8 cm), the MTF measurements were limited by the size of the focal spot. The obtained results are important for further development of the VRX CT scanner.« less

High-resolution clustered pinhole (131)Iodine SPECT imaging in mice.

PubMed

van der Have, Frans; Ivashchenko, Oleksandra; Goorden, Marlies C; Ramakers, Ruud M; Beekman, Freek J

2016-08-01

High-resolution pre-clinical (131)I SPECT can facilitate development of new radioiodine therapies for cancer. To this end, it is important to limit resolution-degrading effects of pinhole edge penetration by the high-energy γ-photons of iodine. Here we introduce, optimize and validate (131)I SPECT performed with a dedicated high-energy clustered multi-pinhole collimator. A SPECT-CT system (VECTor/CT) with stationary gamma-detectors was equipped with a tungsten collimator with clustered pinholes. Images were reconstructed with pixel-based OSEM, using a dedicated (131)I system matrix that models the distance- and energy-dependent resolution and sensitivity of each pinhole, as well as the intrinsic detector blurring and variable depth of interaction in the detector. The system performance was characterized with phantoms and in vivo static and dynamic (131)I-NaI scans of mice. Reconstructed image resolution reached 0.6mm, while quantitative accuracy measured with a (131)I filled syringe reaches an accuracy of +3.6±3.5% of the gold standard value. In vivo mice scans illustrated a clear shape of the thyroid and biodistribution of (131)I within the animal. Pharmacokinetics of (131)I was assessed with 15-s time frames from the sequence of dynamic images and time-activity curves of (131)I-NaI. High-resolution quantitative and fast dynamic (131)I SPECT in mice is possible by means of a high-energy collimator and optimized system modeling. This enables analysis of (131)I uptake even within small organs in mice, which can be highly valuable for development and optimization of targeted cancer therapies. Copyright © 2016 Elsevier Inc. All rights reserved.

Image reconstruction and system modeling techniques for virtual-pinhole PET insert systems

PubMed Central

Keesing, Daniel B; Mathews, Aswin; Komarov, Sergey; Wu, Heyu; Song, Tae Yong; O'Sullivan, Joseph A; Tai, Yuan-Chuan

2012-01-01

Virtual-pinhole PET (VP-PET) imaging is a new technology in which one or more high-resolution detector modules are integrated into a conventional PET scanner with lower-resolution detectors. It can locally enhance the spatial resolution and contrast recovery near the add-on detectors, and depending on the configuration, may also increase the sensitivity of the system. This novel scanner geometry makes the reconstruction problem more challenging compared to the reconstruction of data from a standalone PET scanner, as new techniques are needed to model and account for the non-standard acquisition. In this paper, we present a general framework for fully 3D modeling of an arbitrary VP-PET insert system. The model components are incorporated into a statistical reconstruction algorithm to estimate an image from the multi-resolution data. For validation, we apply the proposed model and reconstruction approach to one of our custom-built VP-PET systems – a half-ring insert device integrated into a clinical PET/CT scanner. Details regarding the most important implementation issues are provided. We show that the proposed data model is consistent with the measured data, and that our approach can lead to reconstructions with improved spatial resolution and lesion detectability. PMID:22490983

Reduced exposure using asymmetric cone beam processing for wide area detector cardiac CT

PubMed Central

Bedayat, Arash; Kumamaru, Kanako; Powers, Sara L.; Signorelli, Jason; Steigner, Michael L.; Steveson, Chloe; Soga, Shigeyoshi; Adams, Kimberly; Mitsouras, Dimitrios; Clouse, Melvin; Mather, Richard T.

2011-01-01

The purpose of this study was to estimate dose reduction after implementation of asymmetrical cone beam processing using exposure differences measured in a water phantom and a small cohort of clinical coronary CTA patients. Two separate 320 × 0.5 mm detector row scans of a water phantom used identical cardiac acquisition parameters before and after software modifications from symmetric to asymmetric cone beam acquisition and processing. Exposure was measured at the phantom surface with Optically Stimulated Luminescence (OSL) dosimeters at 12 equally spaced angular locations. Mean HU and standard deviation (SD) for both approaches were compared using ROI measurements obtained at the center plus four peripheral locations in the water phantom. To assess image quality, mean HU and standard deviation (SD) for both approaches were compared using ROI measurements obtained at five points within the water phantom. Retrospective evaluation of 64 patients (37 symmetric; 27 asymmetric acquisition) included clinical data, scanning parameters, quantitative plus qualitative image assessment, and estimated radiation dose. In the water phantom, the asymmetric cone beam processing reduces exposure by approximately 20% with no change in image quality. The clinical coronary CTA patient groups had comparable demographics. The estimated dose reduction after implementation of the asymmetric approach was roughly 24% with no significant difference between the symmetric and asymmetric approach with respect to objective measures of image quality or subjective assessment using a four point scale. When compared to a symmetric approach, the decreased exposure, subsequent lower patient radiation dose, and similar image quality from asymmetric cone beam processing supports its routine clinical use. PMID:21336552

Reduced exposure using asymmetric cone beam processing for wide area detector cardiac CT.

PubMed

Bedayat, Arash; Rybicki, Frank J; Kumamaru, Kanako; Powers, Sara L; Signorelli, Jason; Steigner, Michael L; Steveson, Chloe; Soga, Shigeyoshi; Adams, Kimberly; Mitsouras, Dimitrios; Clouse, Melvin; Mather, Richard T

2012-02-01

The purpose of this study was to estimate dose reduction after implementation of asymmetrical cone beam processing using exposure differences measured in a water phantom and a small cohort of clinical coronary CTA patients. Two separate 320 × 0.5 mm detector row scans of a water phantom used identical cardiac acquisition parameters before and after software modifications from symmetric to asymmetric cone beam acquisition and processing. Exposure was measured at the phantom surface with Optically Stimulated Luminescence (OSL) dosimeters at 12 equally spaced angular locations. Mean HU and standard deviation (SD) for both approaches were compared using ROI measurements obtained at the center plus four peripheral locations in the water phantom. To assess image quality, mean HU and standard deviation (SD) for both approaches were compared using ROI measurements obtained at five points within the water phantom. Retrospective evaluation of 64 patients (37 symmetric; 27 asymmetric acquisition) included clinical data, scanning parameters, quantitative plus qualitative image assessment, and estimated radiation dose. In the water phantom, the asymmetric cone beam processing reduces exposure by approximately 20% with no change in image quality. The clinical coronary CTA patient groups had comparable demographics. The estimated dose reduction after implementation of the asymmetric approach was roughly 24% with no significant difference between the symmetric and asymmetric approach with respect to objective measures of image quality or subjective assessment using a four point scale. When compared to a symmetric approach, the decreased exposure, subsequent lower patient radiation dose, and similar image quality from asymmetric cone beam processing supports its routine clinical use.

Combined multi-kernel head computed tomography images optimized for depicting both brain parenchyma and bone.

PubMed

Takagi, Satoshi; Nagase, Hiroyuki; Hayashi, Tatsuya; Kita, Tamotsu; Hayashi, Katsumi; Sanada, Shigeru; Koike, Masayuki

2014-01-01

The hybrid convolution kernel technique for computed tomography (CT) is known to enable the depiction of an image set using different window settings. Our purpose was to decrease the number of artifacts in the hybrid convolution kernel technique for head CT and to determine whether our improved combined multi-kernel head CT images enabled diagnosis as a substitute for both brain (low-pass kernel-reconstructed) and bone (high-pass kernel-reconstructed) images. Forty-four patients with nondisplaced skull fractures were included. Our improved multi-kernel images were generated so that pixels of >100 Hounsfield unit in both brain and bone images were composed of CT values of bone images and other pixels were composed of CT values of brain images. Three radiologists compared the improved multi-kernel images with bone images. The improved multi-kernel images and brain images were identically displayed on the brain window settings. All three radiologists agreed that the improved multi-kernel images on the bone window settings were sufficient for diagnosing skull fractures in all patients. This improved multi-kernel technique has a simple algorithm and is practical for clinical use. Thus, simplified head CT examinations and fewer images that need to be stored can be expected.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnston, H; UT Southwestern Medical Center, Dallas, TX; Hilts, M

Purpose: To commission a multislice computed tomography (CT) scanner for fast and reliable readout of radiation therapy (RT) dose distributions using CT polymer gel dosimetry (PGD). Methods: Commissioning was performed for a 16-slice CT scanner using images acquired through a 1L cylinder filled with water. Additional images were collected using a single slice machine for comparison purposes. The variability in CT number associated with the anode heel effect was evaluated and used to define a new slice-by-slice background image subtraction technique. Image quality was assessed for the multislice system by comparing image noise and uniformity to that of the singlemore » slice machine. The consistency in CT number across slices acquired simultaneously using the multislice detector array was also evaluated. Finally, the variability in CT number due to increasing x-ray tube load was measured for the multislice scanner and compared to the tube load effects observed on the single slice machine. Results: Slice-by-slice background subtraction effectively removes the variability in CT number across images acquired simultaneously using the multislice scanner and is the recommended background subtraction method when using a multislice CT system. Image quality for the multislice machine was found to be comparable to that of the single slice scanner. Further study showed CT number was consistent across image slices acquired simultaneously using the multislice detector array for each detector configuration of the slice thickness examined. In addition, the multislice system was found to eliminate variations in CT number due to increasing x-ray tube load and reduce scanning time by a factor of 4 when compared to imaging a large volume using a single slice scanner. Conclusion: A multislice CT scanner has been commissioning for CT PGD, allowing images of an entire dose distribution to be acquired in a matter of minutes. Funding support provided by the Natural Sciences and Engineering Research Council of Canada (NSERC)« less

Technical Note: Quantitative accuracy evaluation for spectral images from a detector-based spectral CT scanner using an iodine phantom.

PubMed

Duan, Xinhui; Arbique, Gary; Guild, Jeffrey; Xi, Yin; Anderson, Jon

2018-05-01

The purpose of this study was to evaluate the quantitative accuracy of spectral images from a detector-based spectral CT scanner using a phantom with iodine-loaded inserts. A 40-cm long-body phantom with seven iodine inserts (2-20 mg/ml of iodine) was used in the study. The inserts could be placed at 5.5 or 10.5 cm from the phantom axis. The phantom was scanned five times for each insert configuration using 120 kVp tube voltage. A set of iodine, virtual noncontrast, effective atomic number, and virtual monoenergetic spectral CT images were generated and measurements were made for all the iodine rods. Measured values were compared with reference values calculated from the chemical composition information provided by the phantom manufacturer. Radiation dose from the spectral CT was compared to a conventional CT using a CTDI (32 cm) phantom. Good agreement between measurements and reference values was achieved for all types of spectral images. The differences ranged from -0.46 to 0.1 mg/ml for iodine concentration, -9.95 to 6.41 HU for virtual noncontrast images, 0.12 to 0.35 for effective Z images, and -17.7 to 55.7 HU for virtual monoenergetic images. For a similar CTDIvol, image noise from the conventional CT was 10% lower than the spectral CT. The detector-based spectral CT can achieve accurate spectral measurements on iodine concentration, virtual non-contrast images, effective atomic numbers, and virtual monoenergetic images. © 2018 American Association of Physicists in Medicine.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leng, Shuai; Yu, Lifeng; Wang, Jia

Purpose: Our purpose was to reduce image noise in spectral CT by exploiting data redundancies in the energy domain to allow flexible selection of the number, width, and location of the energy bins. Methods: Using a variety of spectral CT imaging methods, conventional filtered backprojection (FBP) reconstructions were performed and resulting images were compared to those processed using a Local HighlY constrained backPRojection Reconstruction (HYPR-LR) algorithm. The mean and standard deviation of CT numbers were measured within regions of interest (ROIs), and results were compared between FBP and HYPR-LR. For these comparisons, the following spectral CT imaging methods were used:(i)more » numerical simulations based on a photon-counting, detector-based CT system, (ii) a photon-counting, detector-based micro CT system using rubidium and potassium chloride solutions, (iii) a commercial CT system equipped with integrating detectors utilizing tube potentials of 80, 100, 120, and 140 kV, and (iv) a clinical dual-energy CT examination. The effects of tube energy and energy bin width were evaluated appropriate to each CT system. Results: The mean CT number in each ROI was unchanged between FBP and HYPR-LR images for each of the spectral CT imaging scenarios, irrespective of bin width or tube potential. However, image noise, as represented by the standard deviation of CT numbers in each ROI, was reduced by 36%-76%. In all scenarios, image noise after HYPR-LR algorithm was similar to that of composite images, which used all available photons. No difference in spatial resolution was observed between HYPR-LR processing and FBP. Dual energy patient data processed using HYPR-LR demonstrated reduced noise in the individual, low- and high-energy images, as well as in the material-specific basis images. Conclusions: Noise reduction can be accomplished for spectral CT by exploiting data redundancies in the energy domain. HYPR-LR is a robust method for reducing image noise in a variety of spectral CT imaging systems without losing spatial resolution or CT number accuracy. This method improves the flexibility to select energy bins in the manner that optimizes material identification and separation without paying the penalty of increased image noise or its corollary, increased patient dose.« less

Dual-Energy CT: New Horizon in Medical Imaging

PubMed Central

Goo, Jin Mo

2017-01-01

Dual-energy CT has remained underutilized over the past decade probably due to a cumbersome workflow issue and current technical limitations. Clinical radiologists should be made aware of the potential clinical benefits of dual-energy CT over single-energy CT. To accomplish this aim, the basic principle, current acquisition methods with advantages and disadvantages, and various material-specific imaging methods as clinical applications of dual-energy CT should be addressed in detail. Current dual-energy CT acquisition methods include dual tubes with or without beam filtration, rapid voltage switching, dual-layer detector, split filter technique, and sequential scanning. Dual-energy material-specific imaging methods include virtual monoenergetic or monochromatic imaging, effective atomic number map, virtual non-contrast or unenhanced imaging, virtual non-calcium imaging, iodine map, inhaled xenon map, uric acid imaging, automatic bone removal, and lung vessels analysis. In this review, we focus on dual-energy CT imaging including related issues of radiation exposure to patients, scanning and post-processing options, and potential clinical benefits mainly to improve the understanding of clinical radiologists and thus, expand the clinical use of dual-energy CT; in addition, we briefly describe the current technical limitations of dual-energy CT and the current developments of photon-counting detector. PMID:28670151

Automated characterization of normal and pathologic lung tissue by topological texture analysis of multidetector CT

NASA Astrophysics Data System (ADS)

Boehm, H. F.; Fink, C.; Becker, C.; Reiser, M.

2007-03-01

Reliable and accurate methods for objective quantitative assessment of parenchymal alterations in the lung are necessary for diagnosis, treatment and follow-up of pulmonary diseases. Two major types of alterations are pulmonary emphysema and fibrosis, emphysema being characterized by abnormal enlargement of the air spaces distal to the terminal, nonrespiratory bronchiole, accompanied by destructive changes of the alveolar walls. The main characteristic of fibrosis is coursening of the interstitial fibers and compaction of the pulmonary tissue. With the ability to display anatomy free from superimposing structures and greater visual clarity, Multi-Detector-CT has shown to be more sensitive than the chest radiograph in identifying alterations of lung parenchyma. In automated evaluation of pulmonary CT-scans, quantitative image processing techniques are applied for objective evaluation of the data. A number of methods have been proposed in the past, most of which utilize simple densitometric tissue features based on the mean X-ray attenuation coefficients expressed in terms of Hounsfield Units [HU]. Due to partial volume effects, most of the density-based methodologies tend to fail, namely in cases, where emphysema and fibrosis occur within narrow spatial limits. In this study, we propose a methodology based upon the topological assessment of graylevel distribution in the 3D image data of lung tissue which provides a way of improving quantitative CT evaluation. Results are compared to the more established density-based methods.

Clinical evaluation of new automatic coronary-specific best cardiac phase selection algorithm for single-beat coronary CT angiography.

PubMed

Wang, Hui; Xu, Lei; Fan, Zhanming; Liang, Junfu; Yan, Zixu; Sun, Zhonghua

2017-01-01

The aim of this study was to evaluate the workflow efficiency of a new automatic coronary-specific reconstruction technique (Smart Phase, GE Healthcare-SP) for selection of the best cardiac phase with least coronary motion when compared with expert manual selection (MS) of best phase in patients with high heart rate. A total of 46 patients with heart rates above 75 bpm who underwent single beat coronary computed tomography angiography (CCTA) were enrolled in this study. CCTA of all subjects were performed on a 256-detector row CT scanner (Revolution CT, GE Healthcare, Waukesha, Wisconsin, US). With the SP technique, the acquired phase range was automatically searched in 2% phase intervals during the reconstruction process to determine the optimal phase for coronary assessment, while for routine expert MS, reconstructions were performed at 5% intervals and a best phase was manually determined. The reconstruction and review times were recorded to measure the workflow efficiency for each method. Two reviewers subjectively assessed image quality for each coronary artery in the MS and SP reconstruction volumes using a 4-point grading scale. The average HR of the enrolled patients was 91.1±19.0bpm. A total of 204 vessels were assessed. The subjective image quality using SP was comparable to that of the MS, 1.45±0.85 vs 1.43±0.81 respectively (p = 0.88). The average time was 246 seconds for the manual best phase selection, and 98 seconds for the SP selection, resulting in average time saving of 148 seconds (60%) with use of the SP algorithm. The coronary specific automatic cardiac best phase selection technique (Smart Phase) improves clinical workflow in high heart rate patients and provides image quality comparable with manual cardiac best phase selection. Reconstruction of single-beat CCTA exams with SP can benefit the users with less experienced in CCTA image interpretation.

3D CT cerebral angiography technique using a 320-detector machine with a time-density curve and low contrast medium volume: comparison with fixed time delay technique.

PubMed

Das, K; Biswas, S; Roughley, S; Bhojak, M; Niven, S

2014-03-01

To describe a cerebral computed tomography angiography (CTA) technique using a 320-detector CT machine and a small contrast medium volume (35 ml, 15 ml for test bolus). Also, to compare the quality of these images with that of the images acquired using a larger contrast medium volume (90 or 120 ml) and a fixed time delay (FTD) of 18 s using a 16-detector CT machine. Cerebral CTA images were acquired using a 320-detector machine by synchronizing the scanning time with the time of peak enhancement as determined from the time-density curve (TDC) using a test bolus dose. The quality of CTA images acquired using this technique was compared with that obtained using a FTD of 18 s (by 16-detector CT), retrospectively. Average densities in four different intracranial arteries, overall opacification of arteries, and the degree of venous contamination were graded and compared. Thirty-eight patients were scanned using the TDC technique and 40 patients using the FTD technique. The arterial densities achieved by the TDC technique were higher (significant for supraclinoid and basilar arteries, p < 0.05). The proportion of images deemed as having "good" arterial opacification was 95% for TDC and 90% for FTD. The degree of venous contamination was significantly higher in images produced by the FTD technique (p < 0.001%). Good diagnostic quality CTA images with significant reduction of venous contamination can be achieved with a low contrast medium dose using a 320-detector machine by coupling the time of data acquisition with the time of peak enhancement. Copyright © 2013 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Percutaneous foot joint needle placement using a C-arm flat-panel detector CT.

PubMed

Wiewiorski, Martin; Takes, Martin Thanh Long; Valderrabano, Victor; Jacob, Augustinus Ludwig

2012-03-01

Image guidance is valuable for diagnostic injections in foot orthopaedics. Flat-detector computed tomography (FD-CT) was implemented using a C-arm, and the system was tested for needle guidance in foot joint injections. FD-CT-guided joint infiltration was performed in 6 patients referred from the orthopaedic department for diagnostic foot injections. All interventions were performed utilising a flat-panel fluoroscopy system utilising specialised image guidance and planning software. Successful infiltration was defined by localisation of contrast media depot in the targeted joint. The pre- and post-interventional numeric analogue scale (NAS) pain score was assessed. All injections were technically successful. Contrast media deposit was documented in all targeted joints. Significant relief of symptoms was noted by all 6 participants. FD-CT-guided joint infiltration is a feasible method for diagnostic infiltration of midfoot and hindfoot joints. The FD-CT approach may become an alternative to commonly used 2D-fluoroscopically guidance.

Improved motion compensation in 3D-CT using respiratory-correlated segment reconstruction: diagnostic and radiotherapy applications.

PubMed

Mori, S; Endo, M; Kohno, R; Minohara, S

2006-09-01

Conventional respiratory-gated CT and four-dimensional CT (4DCT) are disadvantaged by their low temporal resolution, which results in the inclusion of anatomic motion-induced artefacts. These represent a significant source of error both in radiotherapy treatment planning for the thorax and upper abdomen and in diagnostic procedures. In particular, temporal resolution and image quality are vitally important to accurate diagnosis and the minimization of planning target volume margin due to respiratory motion. To improve both temporal resolution and signal-to-noise ratio (SNR), we developed a respiratory-correlated segment reconstruction method (RS) and adapted it to the Feldkamp-Davis-Kress algorithm (FDK) with a 256 multidetector row CT (256MDCT). The 256MDCT scans approximately 100 mm in the craniocaudal direction with a 0.5 mm slice thickness in one rotation. Data acquisition for the RS-FDK relies on the assistance of a respiratory sensing system operating in cine scan mode (continuous axial scan with the table stationary). We evaluated the RS-FDK for volume accuracy and image noise in a phantom study with the 256MDCT and compared results with those for a full scan (FS-FDK), which is usually employed in conventional 4DCT and in half scan (HS-FDK). Results showed that the RS-FDK gave a more accurate volume than the others and had the same SNR as the FS-FDK. In a subsequent animal study, we demonstrated a practical sorting process for projection data which was unaffected by variations in respiratory period, and found that the RS-FDK gave the clearest visualization among the three algorithms of the margins of the liver and pulmonary vessels. In summary, the RS-FDK algorithm provides multi-phase images with higher temporal resolution and better SNR. This method should prove useful when combined with new radiotherapeutic and diagnostic techniques.

Research on radiation exposure from CT part of hybrid camera and diagnostic CT

NASA Astrophysics Data System (ADS)

Solný, Pavel; Zimák, Jaroslav

2014-11-01

Research on radiation exposure from CT part of hybrid camera in seven different Departments of Nuclear Medicine (DNM) was conducted. Processed data and effective dose (E) estimations led to the idea of phantom verification and comparison of absorbed doses and software estimation. Anonymous data from about 100 examinations from each DNM was gathered. Acquired data was processed and utilized by dose estimation programs (ExPACT, ImPACT, ImpactDose) with respect to the type of examination and examination procedures. Individual effective doses were calculated using enlisted programs. Preserving the same procedure in dose estimation process allows us to compare the resulting E. Some differences and disproportions during dose estimation led to the idea of estimated E verification. Consequently, two different sets of about 100 of TLD 100H detectors were calibrated for measurement inside the Aldersnon RANDO Anthropomorphic Phantom. Standard examination protocols were examined using a 2 Slice CT- part of hybrid SPECT/CT. Moreover, phantom exposure from body examining protocol for 32 Slice and 64 Slice diagnostic CT scanner was also verified. Absorbed dose (DT,R) measured using TLD detectors was compared with software estimation of equivalent dose HT values, computed by E estimation software. Though, only limited number of cavities for detectors enabled measurement within the regions of lung, liver, thyroid and spleen-pancreas region, some basic comparison is possible.

The development and test of ultra-large-format multi-anode microchannel array detector systems

NASA Technical Reports Server (NTRS)

Timothy, J. G.

1984-01-01

The specific tasks that were accomplished with each of the key elements of the multi-anode microchannel array detector system are described. The modes of operation of position-sensitive electronic readout systems for use with high-gain microchannel plates are described and their performance characteristics compared and contrasted. Multi-anode microchannel array detector systems with formats as large as 256 x 1024 pixels are currently under evaluation. Preliminary performance data for sealed ultraviolet and visible-light detector tubes show that the detector systems have unique characteristics which make them complementary to photoconductive array detectors, such as CCDs, and superior to alternative pulse-counting detector systems employing high-gain MCPs.

Safety of Landiolol Hydrochloride as a Premedication for Producing an Appropriate Heart Rate for Multidetector-Row Computed Tomography Coronary Angiography.

PubMed

Koyoshi, Rie; Shiga, Yuhei; Idemoto, Yoshiaki; Ueda, Yoko; Tashiro, Kohei; Kuwano, Takashi; Kitajima, Ken; Fujimi, Kanta; Kawamura, Akira; Ogawa, Masahiro; Miura, Shin-Ichiro

2018-01-01

We evaluated the safety of a bolus injection of landiolol hydrochloride, an ultrashort-acting β1-selective antagonist, as a premedication prior to multidetector-row computed tomography coronary angiography (CTA). The subjects consisted of 176 patients (M/F = 64:112, 67 ± 11 years) who had heart rate (HR) at rest ≥ 70 beats/min (bpm) and underwent CTA. Systolic/diastolic blood pressure (SBP/DBP) and HR were measured before and after the administration of landiolol. SBP/DBP and HR upon entry to the CT room were 136 ± 17/80 ± 11 mm Hg and 83 ± 10 bpm, respectively. HR was significantly reduced at the time of CTA scan (62 ± 7 bpm). Next, we divided the patients into three groups according to HR upon entry to the CT room: 70 - 79 bpm (n = 76), 80 - 89 bpm (n = 60) and ≥ 90 bpm (n = 40). HR at the time of CTA scan was significantly lower than that upon entry to the CT room in all three groups: 70 - 79 bpm (74 ± 3 bpm upon entry to the CT room to 61 ± 6 bpm at the time of CAT scan), 80 - 89 bpm (84 ± 3 to 63 ± 7 bpm) and ≥ 90 bpm (98 ± 6 to 65 ± 7 bpm). Although SBP/DBP was significantly decreased after the CTA scan (123 ± 18/72 ± 12 mm Hg), landiolol had no severe adverse events throughout CTA. In conclusion, a bolus injection of landiolol reduced HR by about 20 bpm without any severe adverse effects. Thus, a bolus injection of landiolol hydrochloride may be a suitable pretreatment for controlling HR in CTA.

Extended volume coverage in helical cone-beam CT by using PI-line based BPF algorithm

NASA Astrophysics Data System (ADS)

Cho, Seungryong; Pan, Xiaochuan

2007-03-01

We compared data requirements of filtered-backprojection (FBP) and backprojection-filtration (BPF) algorithms based on PI-lines in helical cone-beam CT. Since the filtration process in FBP algorithm needs all the projection data of PI-lines for each view, the required detector size should be bigger than the size that can cover Tam-Danielsson (T-D) window to avoid data truncation. BPF algorithm, however, requires the projection data only within the T-D window, which means smaller detector size can be used to reconstruct the same image than that in FBP. In other words, a longer helical pitch can be obtained by using BPF algorithm without any truncation artifacts when a fixed detector size is given. The purpose of the work is to demonstrate numerically that extended volume coverage in helical cone-beam CT by using PI-line-based BPF algorithm can be achieved.

Fetal shielding combined with state of the art CT dose reduction strategies during maternal chest CT.

PubMed

Chatterson, Leslie C; Leswick, David A; Fladeland, Derek A; Hunt, Megan M; Webster, Stephen; Lim, Hyun

2014-07-01

Custom bismuth-antimony shields were previously shown to reduce fetal dose by 53% on an 8DR (detector row) CT scanner without dynamic adaptive section collimation (DASC), automatic tube current modulation (ATCM) or adaptive statistical iterative reconstruction (ASiR). The purpose of this study is to compare the effective maternal and average fetal organ dose reduction both with and without bismuth-antimony shields on a 64DR CT scanner using DASC, ATCM and ASiR during maternal CTPA. A phantom with gravid prosthesis and a bismuth-antimony shield were used. Thermoluminescent dosimeters (TLDs) measured fetal radiation dose. The average fetal organ dose and effective maternal dose were determined using 100 kVp, scanning from the lung apices to the diaphragm utilizing DASC, ATCM and ASiR on a 64DR CT scanner with and without shielding in the first and third trimester. Isolated assessment of DASC was done via comparing a new 8DR scan without DASC to a similar scan on the 64DR with DASC. Average third trimester unshielded fetal dose was reduced from 0.22 mGy ± 0.02 on the 8DR to 0.13 mGy ± 0.03 with the conservative 64DR protocol that included 30% ASiR, DASC and ATCM (42% reduction, P<0.01). Use of a shield further reduced average third trimester fetal dose to 0.04 mGy ± 0.01 (69% reduction, P<0.01). The average fetal organ dose reduction attributable to DASC alone was modest (6% reduction from 0.17 mGy ± 0.02 to 0.16 mGy ± 0.02, P=0.014). First trimester fetal organ dose on the 8DR protocol was 0.07 mGy ± 0.03. This was reduced to 0.05 mGy ± 0.03 on the 64DR protocol without shielding (30% reduction, P=0.009). Shields further reduced this dose to below accurately detectable levels. Effective maternal dose was reduced from 4.0 mSv on the 8DR to 2.5 mSv on the 64DR scanner using the conservative protocol (38% dose reduction). ASiR, ATCM and DASC combined significantly reduce effective maternal and fetal organ dose during CTPA. Shields continue to be an effective means of fetal dose reduction. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

SU-E-I-42: Measurement of X-Ray Beam Width and Geometric Efficiency in MDCT Using Radiochromic Films.

PubMed

Liillau, T; Liebmann, M; von Boetticher, H; Poppe, B

2012-06-01

The purpose of this work was to measure the x-ray beam width and geometric efficiency (GE) of a multi detector computed tomography scanner (MDCT) for different beam collimations using radiochromic films. In MDCT, the primary beam width extends the nominal beam collimation to irradiate the active detector elements uniformly (called 'over-beaming') which contributes to increased radiation dose to the patient compared to single detector CT. Therefore, the precise determination of the primary beam width and GE is of value for any CT dose calculation using Monte Carlo or analytical methods. Single axial dose profiles free in air were measured for 6 different beam collimations nT for a Siemens SOMATOM Sensation 64 Scanner with Gafchromic XR-QA2 films. The films were calibrated relative to the measured charge of a PTW semiflex ionization chamber (type: 31010) for a single rotation in the CT scanner at the largest available beam collimation of 28.8 mm. The beam energy for all measurements in this work was set to 120 kVp. For every measured dose profile and beam collimation the GEin-air and the full-width-at-half- maximum value (FWHM) as a value for the x-ray beam width was determined. Over-beaming factors FWHM / nT were calculated accordingly. For MDCT beam collimations from 7.2 (12×0.6 mm) to 28.8 (24×1.2 mm) the geometric efficiency was between 58 and 85 %. The over- beaming factor ranged from 1.43 to 1.11. For beam collimations of 1×5 mm and 1×10 mm the GE was 77 % and 84 % respectively. The over-beaming factors were close to 1, as expected. This work has shown that radiochromic films can be used for accurate x-ray beam width and geometric efficiency measurements due to their high spatial resolution. The measured free-in-air geometric efficiency and the over-beaming factor depend strongly on beam collimation. © 2012 American Association of Physicists in Medicine.

SU-F-T-410: Investigation of Treatment Planning Accuracy with the Presence of Magnetic Injection Port (breast Tissue Expander)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, W; Wagar, M; Lyatskaya, Y

2016-06-15

Purpose: Mastectomy patients with breast reconstruction usually have a magnetic injection port inside the breast during radiation treatments. The magnet has a very high CT number and produces severe streaking artifact across the entire breast in CT images. Our routine strategy is to replace the artifact volumes with uniform water, and it is necessary to validate that the planned dose, with such an artifact correction, is sufficiently accurate. Methods: A phantom was made with a gelatine-filled container sitting on a Matrixx detector, and the magnetic port was inserted into gelatine with specific depths and orientations. The phantom was scanned onmore » a CT simulator and imported into Eclipse for treatment planning. The dose distribution at the Matrixx detector plane was calculated for raw CT images and artifact-corrected images. The treatment beams were then delivered to the phantom and the dose distributions were acquired by the Matrixx detector. Gamma index was calculated to compare the planned dose and the measurement. Results: Three field sizes (10×10, 15×15 and 20×20) and two depths (50mm and 20mm) were investigated. With the 2%/2mm or 3%/3mm criteria, several points (6–10) failed in the plan for raw CT images, and the number of failure was reduced close to zero for the corrected CT images. An assignment of 10,000 HU to the magnet further reduced the dose error directly under the magnet. Conclusion: It is validated that our routine strategy of artifact correction can effectively reduce the number of failures in the detector plane. It is also recommended to set the magnet with a CT number of 10,000HU, which could potentially improve the dose calculation at the points right behind the magnet.« less

Development of CT and 3D-CT Using Flat Panel Detector Based Real-Time Digital Radiography System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ravindran, V. R.; Sreelakshmi, C.; Vibin

2008-09-26

The application of Digital Radiography in the Nondestructive Evaluation (NDE) of space vehicle components is a recent development in India. A Real-time DR system based on amorphous silicon Flat Panel Detector has been developed for the NDE of solid rocket motors at Rocket Propellant Plant of VSSC in a few years back. The technique has been successfully established for the nondestructive evaluation of solid rocket motors. The DR images recorded for a few solid rocket specimens are presented in the paper. The Real-time DR system is capable of generating sufficient digital X-ray image data with object rotation for the CTmore » image reconstruction. In this paper the indigenous development of CT imaging based on the Realtime DR system for solid rocket motor is presented. Studies are also carried out to generate 3D-CT image from a set of adjacent CT images of the rocket motor. The capability of revealing the spatial location and characterisation of defect is demonstrated by the CT and 3D-CT images generated.« less

Reduced complexity of multi-track joint 2-D Viterbi detectors for bit-patterned media recording channel

NASA Astrophysics Data System (ADS)

Myint, L. M. M.; Warisarn, C.

2017-05-01

Two-dimensional (2-D) interference is one of the prominent challenges in ultra-high density recording system such as bit patterned media recording (BPMR). The multi-track joint 2-D detection technique with the help of the array-head reading can tackle this problem effectively by jointly processing the multiple readback signals from the adjacent tracks. Moreover, it can robustly alleviate the impairments due to track mis-registration (TMR) and media noise. However, the computational complexity of such detectors is normally too high and hard to implement in a reality, even for a few multiple tracks. Therefore, in this paper, we mainly focus on reducing the complexity of multi-track joint 2-D Viterbi detector without paying a large penalty in terms of the performance. We propose a simplified multi-track joint 2-D Viterbi detector with a manageable complexity level for the BPMR's multi-track multi-head (MTMH) system. In the proposed method, the complexity of detector's trellis is reduced with the help of the joint-track equalization method which employs 1-D equalizers and 2-D generalized partial response (GPR) target. Moreover, we also examine the performance of a full-fledged multi-track joint 2-D detector and the conventional 2-D detection. The results show that the simplified detector can perform close to the full-fledge detector, especially when the system faces high media noise, with the significant low complexity.

Radiation dose in 320-slice multidetector cardiac CT: a single center experience of evolving dose minimization.

PubMed

Tung, Matthew K; Cameron, James D; Casan, Joshua M; Crossett, Marcus; Troupis, John M; Meredith, Ian T; Seneviratne, Sujith K

2013-01-01

Minimization of radiation exposure remains an important subject that occurs in parallel with advances in scanner technology. We report our experience of evolving radiation dose and its determinants after the introduction of 320-multidetector row cardiac CT within a single tertiary cardiology referral service. Four cohorts of consecutive patients (total 525 scans), who underwent cardiac CT at defined time points as early as 2008, are described. These include a cohort just after scanner installation, after 2 upgrades of the operating system, and after introduction of an adaptive iterative image reconstruction algorithm. The proportions of nondiagnostic coronary artery segments and studies with nondiagnostic segments were compared between cohorts. Significant reductions were observed in median radiation doses in all cohorts compared with the initial cohort (P < .001). Median dose-length product fell from 944 mGy · cm (interquartile range [IQR], 567.3-1426.5 mGy · cm) to 156 mGy · cm (IQR, 99.2-265.0 mGy · cm). Although the proportion of prospectively triggered scans has increased, reductions in radiation dose have occurred independently of distribution of scan formats. In multiple regression that combined all groups, determinants of dose-length product were tube output, the number of cardiac cycles scanned, tube voltage, scan length, scan format, body mass index, phase width, and heart rate (adjusted R(2) = 0.85, P < .001). The proportion of nondiagnostic coronary artery segments was slightly increased in group 4 (2.9%; P < .01). While maintaining diagnostic quality in 320-multidetector row cardiac CT, the radiation dose has decreased substantially because of a combination of dose-reduction protocols and technical improvements. Continued minimization of radiation dose will increase the potential for cardiac CT to expand as a cardiac imaging modality. Copyright © 2013 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.

Risk factors of postoperative pancreatic fistula after distal pancreatectomy using a triple-row stapler.

PubMed

Kawaida, Hiromichi; Kono, Hiroshi; Watanabe, Mitsuaki; Hosomura, Naohiro; Amemiya, Hidetake; Fujii, Hideki

2018-01-01

Postoperative pancreatic fistula (POPF) is one of the major complications in patients who undergo distal pancreatectomy (DP). Recently, dividing the pancreas by stapler is a commonly performed technique, however, POPF still occurs. Therefore, the purpose of this study was to investigate the risk factors for POPF after DP using a triple-row stapler. A total of 75 patients underwent DP using a triple-row stapler (Endo GIA™ Reloads with Tri-Staple™ Technology 60 mm; COVIDIEN, North Haven, CT, USA) at Yamanashi University from December 2012 to December 2016. The clinical risk factors for POPF after DP using a triple-row stapler were identified based on univariate and multivariate analyses. Clinical POPF (ISGPF Grade B and C) was seen in 7 of 75 patients (9.3%). The body mass index (BMI) was significantly higher in the patients with POPF (26.8 ± 0.5 kg/m 2 ) compared with the patients without POPF (21.4 ± 0.4 kg/m 2 ; a cut-off value; 25.7 kg/m 2 ). In addition, the patients with POPF were significantly younger than the patients without POPF (56.4 ± 5.6 vs 67.0 ± 1.5; a cut-off value was 57.0 years old). BMI and age were found to be significant risk factors for POPF after DP using a triple-row stapler.

X-ray micro-CT and neutron CT as complementary imaging tools for non-destructive 3D imaging of rare silicified fossil plants

NASA Astrophysics Data System (ADS)

Karch, J.; Dudák, J.; Žemlička, J.; Vavřík, D.; Kumpová, I.; Kvaček, J.; Heřmanová, Z.; Šoltés, J.; Viererbl, L.; Morgano, M.; Kaestner, A.; Trtík, P.

2017-12-01

Computed tomography provides 3D information of inner structures of investigated objects. The obtained information is, however, strongly dependent on the used radiation type. It is known that as X-rays interact with electron cloud and neutrons with atomic nucleus, the obtained data often provide different contrast of sample structures. In this work we present a set of comparative radiographic and CT measurements of rare fossil plant samples using X-rays and thermal neutrons. The X-ray measurements were performed using large area photon counting detectors Timepix at IEAP CTU in Prague and Perkin Elmer flat-panel detector at Center of Excellence Telč. The neutron CT measurement was carried out at Paul Scherrer Institute using BOA beam-line. Furthermore, neutron radiography of fossil samples, provided by National Museum, were performed using a large-area Timepix detector with a neutron-sensitive converting 6LiF layer at Research Centre Rez, Czech Republic. The obtained results show different capabilities of both imaging approaches. While X-ray micro-CT provides very high resolution and enables visualization of fine cracks or small cavities in the samples neutron imaging provides high contrast of morphological structures of fossil plant samples, where X-ray imaging provides insufficient contrast.

Iodine X-ray fluorescence computed tomography system utilizing a cadmium telluride detector in conjunction with a cerium-target tube

NASA Astrophysics Data System (ADS)

Hagiwara, Osahiko; Watanabe, Manabu; Sato, Eiichi; Matsukiyo, Hiroshi; Osawa, Akihiro; Enomoto, Toshiyuki; Nagao, Jiro; Sato, Shigehiro; Ogawa, Akira; Onagawa, Jun

2011-06-01

An X-ray fluorescence computed tomography system (XRF-CT) is useful for determining the main atoms in objects. To detect iodine atoms without using a synchrotron, we developed an XRF-CT system utilizing a cadmium telluride (CdTe) detector and a cerium X-ray generator. CT is performed by repeated linear scans and rotations of an object. When cerium K-series characteristic X-rays are absorbed by iodine atoms in objects, iodine K fluorescence is produced from atoms and is detected by the CdTe detector. Next, event signals of X-ray photons are produced with the use of charge-sensitive and shaping amplifiers. Iodine Kα fluorescence is isolated using a multichannel analyzer, and the number of photons is counted using a counter card. In energy-dispersive XRF-CT, the tube voltage and tube current were 70 kV and 0.40 mA, respectively, and the X-ray intensity was 115.3 μGy/s at a distance of 1.0 m from the source. The demonstration of XRF-CT was carried out by the selection of photons in an energy range from 27.5 to 29.5 keV with a photon-energy resolution of 1.2 keV.

Overland flow connectivity in olive orchard plots with cover crops and conventional tillage, and under different rainfall scenarios

NASA Astrophysics Data System (ADS)

López-Vicente, Manuel; García-Ruiz, Roberto; Guzmán, Gema; Vicente-Vicente, José Luis; Gómez, José Alfonso

2016-04-01

The study of overland flow connectivity (QC) allows understanding the redistribution dynamics of runoff and soil components as an emergent property of the spatio-temporal interactions of hydrological and geomorphic processes. However, very few studies have dealt with runoff connectivity in olive orchards. In this study we simulated QC in four olive orchard plots, located on the Santa Marta farm (37° 20' 33.6" N, 6° 13' 44" W), in Seville province (Andalusia) in SW Spain. The olive plantation was established in 1985 with trees planted at 8 m x 6 m. Each bounded plot is 8 m wide (between 2 tree lines) and 60 m long (total area of 480 m2), laid out with the longest dimension parallel to the maximum slope and to the tree lines. The slope is uniform, with an average steepness of 11%. Two plots (P2 and P4) were devoted to conventional tillage (CT) consisting of regular chisel plow passes depending on weed growth. Another set of two plots had two types of cover crops (CC) in the inter tree rows (the area outside the vertical olive canopy projection): uniform CC of Lolium multiflorum (P3) and a mixture of L. rigidum and L. multiflorum together with other species (P5). The tree rows were treated with herbicide to keep bare soil. We selected the Index of runoff and sediment Connectivity (IC) of Borselli et al. (2008) to simulate three rainfall scenarios: i) low rainfall intensity (Sc-LowInt) and using the MD flow accumulation algorithm; ii) moderate rainfall intensity (Sc-ModInt) and using MD8; and iii) high rainfall intensity (Sc-HighInt) and using D8. After analysing the values of rainfall intensity during two hydrological years (Oct'09-Sep'10 and Oct'10-Sep'11) we associated the three scenarios with the followings months: Sc-LowInt during the period Jan-Mar, that summarizes 42% of all annual rainfall events; Sc-ModInt during Oct-Nov and Apr-May (32% of all events); and Sc-HighInt during the period Jun-Sep and in December (26% of all events). Instead of using the C-RUSLE factor as it is indicated in the original version of the IC model, we chosen the product between the C (cover-management) and P (support-practices) factors. Previous studies in olive orchards (Gómez et al., 2003) demonstrated that this product is advisable in soil erosion studies. We distinguished four areas within the plots: inter-row-CC, inter-row-CT, olive trees and bare soil under the tree line. Values of the C-RUSLE factor were obtained from previous studies (e.g. Moreira-Madueño, 1991 in Andalusia; Panagos et al., 2015 in Europe). The minimum, mean and maximum values of connectivity in the two plots with CC were lower (-8% on average) than the corresponding values in the two plots under CT. This trend remained by using any of the three algorithms. CC efficiently reduced overland flow connectivity. Areas with low connectivity (deposition-prone areas) appeared more frequently in inter-row-CC in comparison with CT. The assessment of the C-RUSLE factor for each month according to the phenology of the CC and the sowing practices will be explored in further research.

Added value of integrated circuit detector in head CT: objective and subjective image quality in comparison to conventional detector design.

PubMed

Korn, Andreas; Bender, Benjamin; Spira, Daniel; Schabel, Christoph; Bhadelia, Rafeeque; Claussen, Claus; Ernemann, Ulrike; Brodoefel, Harald

2014-12-01

A new computed tomography (CT) detector with integrated electric components and shorter conducting pathways has recently been introduced to decrease system inherent electronic noise. The purpose of this study was to assess the potential benefit of such integrated circuit detector (ICD) in head CT by comparing objective and subjective image quality in low-dose examinations with a conventional detector design. Using a conventional detector, reduced-dose noncontrast head CT (255 mAs; effective dose, 1.7 mSv) was performed in 25 consecutive patients. Following transition to ICD, 25 consecutive patients were scanned using identical imaging parameters. Images in both groups were reconstructed with iterative reconstruction (IR) and filtered back projection (FBP) and assessed in terms of quantitative and qualitative image quality. Acquisition of head CT using ICD increased signal-to-noise ratio of gray and white matter by 14% (10.0 ± 1.6 vs. 11.4 ± 2.5; P = .02) and 17% (8.2 ± 0.8 vs. 9.6 ± 1.5; P = .000). The associated improvement in contrast-to-noise ratio was 12% (2.0 ± 0.5 vs. 2.2 ± 0.6; P = .121). In addition, there was a 51% increase in objective image sharpness (582 ± 85 vs. 884.5 ± 191; change in HU/Pixel; P < .000). Compared to standard acquisitions, subjective grading of noise and overall image quality scores were significantly improved with ICD (2.1 ± 0.3 vs. 1.6 ± 0.3; P < .000; 2.0 ± 0.5 vs. 1.6 ± 0.3; P = .001). Moreover, streak artifacts in the posterior fossa were substantially reduced (2.3 ± 0.7 vs. 1.7 ± 0.5; P = .004). At the same radiation level, acquisition of head CT with ICD achieves superior objective and subjective image quality and provides potential for significant dose reduction. Copyright © 2014 AUR. Published by Elsevier Inc. All rights reserved.

The vascularized groin lymph node flap (VGLN): Anatomical study and flap planning using multi-detector CT scanner. The golden triangle for flap harvesting.

PubMed

Zeltzer, Assaf A; Anzarut, Alexander; Braeckmans, Delphine; Seidenstuecker, Katrin; Hendrickx, Benoit; Van Hedent, Eddy; Hamdi, Moustapha

2017-09-01

A growing number of surgeons perform lymph node transfers for the treatment of lymphedema. When harvesting a vascularized lymph node groin flap (VGLNF) one of the major concerns is the potential risk of iatrogenic lymphedema of the donor-site. This article helps understanding of the lymph node distribution of the groin in order to minimize this risk. Fifty consecutive patients undergoing abdominal mapping by multi-detector CT scanner were included and 100 groins analyzed. The groin was divided in three zones (of which zone II is the safe zone) and lymph nodes were counted and mapped with their distances to anatomic landmarks. Further node units were plotted and counted. The average age was 48 years. A mean number of nodes of 6.5/groin was found. In zone II, which is our zone of interest a mean of 3.1 nodes were counted with a mean size of 7.8 mm. In three patients no nodes were found in zone II. In five patients nodes were seen in zone II but were not sufficient in size or number to be considered a lymph node unit. On average the lymph node unit in zone II was found to be 48.3 mm from the pubic tubercle when projected on a line from the pubic tubercle to the anterior superior iliac spine, 16.0 mm caudal to this line, and 20.4 mm above the groin crease. On average the lymph node unit was a mean of 41.7 mm lateral to the SCIV-SIEV confluence. This study provides increased understanding of the lymphatic anatomy in zone II of the groin flap and suggests a refined technique for designing the VGLNF. As with any flap there is a degree of individual patient variability. However, having information on the most common anatomy and flap design is of great value. © 2017 Wiley Periodicals, Inc.

Implementation of material decomposition using an EMCCD and CMOS-based micro-CT system.

PubMed

Podgorsak, Alexander R; Nagesh, Sv Setlur; Bednarek, Daniel R; Rudin, Stephen; Ionita, Ciprian N

2017-02-11

This project assessed the effectiveness of using two different detectors to obtain dual-energy (DE) micro-CT data for the carrying out of material decomposition. A micro-CT coupled to either a complementary metal-oxide semiconductor (CMOS) or an electron multiplying CCD (EMCCD) detector was used to acquire image data of a 3D-printed phantom with channels filled with different materials. At any instance, materials such as iohexol contrast agent, water, and platinum were selected to make up the scanned object. DE micro-CT data was acquired, and slices of the scanned object were differentiated by material makeup. The success of the decomposition was assessed quantitatively through the computation of percentage normalized root-mean-square error (%NRMSE). Our results indicate a successful decomposition of iohexol for both detectors (%NRMSE values of 1.8 for EMCCD, 2.4 for CMOS), as well as platinum (%NRMSE value of 4.7). The CMOS detector performed material decomposition on air and water on average with 7 times more %NRMSE, possibly due to the decreased sensitivity of the CMOS system. Material decomposition showed the potential to differentiate between materials such as the iohexol and platinum, perhaps opening the door for its use in the neurovascular anatomical region. Work supported by Toshiba America Medical Systems, and partially supported by NIH grant 2R01EB002873.

Implementation of material decomposition using an EMCCD and CMOS-based micro-CT system

NASA Astrophysics Data System (ADS)

Podgorsak, Alexander R.; Nagesh, S. V. Setlur; Bednarek, Daniel R.; Rudin, Stephen; Ionita, Ciprian N.

2017-03-01

This project assessed the effectiveness of using two different detectors to obtain dual-energy (DE) micro-CT data for the carrying out of material decomposition. A micro-CT coupled to either a complementary metal-oxide semiconductor (CMOS) or an electron multiplying CCD (EMCCD) detector was used to acquire image data of a 3D-printed phantom with channels filled with different materials. At any instance, materials such as iohexol contrast agent, water, and platinum were selected to make up the scanned object. DE micro-CT data was acquired, and slices of the scanned object were differentiated by material makeup. The success of the decomposition was assessed quantitatively through the computation of percentage normalized root-mean-square error (%NRMSE). Our results indicate a successful decomposition of iohexol for both detectors (%NRMSE values of 1.8 for EMCCD, 2.4 for CMOS), as well as platinum (%NRMSE value of 4.7). The CMOS detector performed material decomposition on air and water on average with 7 times more %NRMSE, possibly due to the decreased sensitivity of the CMOS system. Material decomposition showed the potential to differentiate between materials such as the iohexol and platinum, perhaps opening the door for its use in the neurovascular anatomical region. Work supported by Toshiba America Medical Systems, and partially supported by NIH grant 2R01EB002873.

Noise reduction in spectral CT: reducing dose and breaking the trade-off between image noise and energy bin selection.

PubMed

Leng, Shuai; Yu, Lifeng; Wang, Jia; Fletcher, Joel G; Mistretta, Charles A; McCollough, Cynthia H

2011-09-01

Our purpose was to reduce image noise in spectral CT by exploiting data redundancies in the energy domain to allow flexible selection of the number, width, and location of the energy bins. Using a variety of spectral CT imaging methods, conventional filtered backprojection (FBP) reconstructions were performed and resulting images were compared to those processed using a Local HighlY constrained backPRojection Reconstruction (HYPR-LR) algorithm. The mean and standard deviation of CT numbers were measured within regions of interest (ROIs), and results were compared between FBP and HYPR-LR. For these comparisons, the following spectral CT imaging methods were used:(i) numerical simulations based on a photon-counting, detector-based CT system, (ii) a photon-counting, detector-based micro CT system using rubidium and potassium chloride solutions, (iii) a commercial CT system equipped with integrating detectors utilizing tube potentials of 80, 100, 120, and 140 kV, and (iv) a clinical dual-energy CT examination. The effects of tube energy and energy bin width were evaluated appropriate to each CT system. The mean CT number in each ROI was unchanged between FBP and HYPR-LR images for each of the spectral CT imaging scenarios, irrespective of bin width or tube potential. However, image noise, as represented by the standard deviation of CT numbers in each ROI, was reduced by 36%-76%. In all scenarios, image noise after HYPR-LR algorithm was similar to that of composite images, which used all available photons. No difference in spatial resolution was observed between HYPR-LR processing and FBP. Dual energy patient data processed using HYPR-LR demonstrated reduced noise in the individual, low- and high-energy images, as well as in the material-specific basis images. Noise reduction can be accomplished for spectral CT by exploiting data redundancies in the energy domain. HYPR-LR is a robust method for reducing image noise in a variety of spectral CT imaging systems without losing spatial resolution or CT number accuracy. This method improves the flexibility to select energy bins in the manner that optimizes material identification and separation without paying the penalty of increased image noise or its corollary, increased patient dose.

Experimental validation of a multi-energy x-ray adapted scatter separation method

NASA Astrophysics Data System (ADS)

Sossin, A.; Rebuffel, V.; Tabary, J.; Létang, J. M.; Freud, N.; Verger, L.

2016-12-01

Both in radiography and computed tomography (CT), recently emerged energy-resolved x-ray photon counting detectors enable the identification and quantification of individual materials comprising the inspected object. However, the approaches used for these operations require highly accurate x-ray images. The accuracy of the images is severely compromised by the presence of scattered radiation, which leads to a loss of spatial contrast and, more importantly, a bias in radiographic material imaging and artefacts in CT. The aim of the present study was to experimentally evaluate a recently introduced partial attenuation spectral scatter separation approach (PASSSA) adapted for multi-energy imaging. For this purpose, a prototype x-ray system was used. Several radiographic acquisitions of an anthropomorphic thorax phantom were performed. Reference primary images were obtained via the beam-stop (BS) approach. The attenuation images acquired from PASSSA-corrected data showed a substantial increase in local contrast and internal structure contour visibility when compared to uncorrected images. A substantial reduction of scatter induced bias was also achieved. Quantitatively, the developed method proved to be in relatively good agreement with the BS data. The application of the proposed scatter correction technique lowered the initial normalized root-mean-square error (NRMSE) of 45% between the uncorrected total and the reference primary spectral images by a factor of 9, thus reducing it to around 5%.

Material identification in x-ray microscopy and micro CT using multi-layer, multi-color scintillation detectors

PubMed Central

Modgil, Dimple; Rigie, David S.; Wang, Yuxin; Xiao, Xianghui; Vargas, Phillip A.; La Rivière, Patrick J.

2015-01-01

We demonstrate that a dual-layer, dual-color scintillator construct for microscopic CT, originally proposed to increase sensitivity in synchrotron imaging, can also be used to perform material quantification and classification when coupled with polychromatic illumination. We consider two different approaches to data handling: (1) a data-domain material decomposition whose estimation performance can be characterized by the Cramer-Rao Lower Bound formalism but which requires careful calibration and (2) an image-domain material classification approach that is more robust to calibration errors. The data-domain analysis indicates that useful levels of SNR (>5) could be achieved in one second or less at typical bending magnet fluxes for relatively large amounts of contrast (several mm path length, such as in a fluid flow experiment) and at typical undulator fluxes for small amount of contrast (tens of microns path length, such as an angiography experiment). The tools introduced could of course be used to study and optimize parameters for a wider range of potential applications. The image domain approach was analyzed in terms of its ability to distinguish different elemental stains by characterizing the angle between the lines traced out in a two-dimensional space of effective attenuation coefficient in the front and back layer images. This approach was implemented at a synchrotron and the results were consistent with simulation predictions. PMID:26422059

Material identification in x-ray microscopy and micro CT using multi-layer, multi-color scintillation detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Modgil, Dimple; Rigie, David S.; Wang, Yuxin

We demonstrate that a dual-layer, dual-color scintillator construct for microscopic CT, originally proposed to increase sensitivity in synchrotron imaging, can also be used to perform material quantification and classification when coupled with polychromatic illumination. We consider two different approaches to data handling: (1) a data-domain material decomposition whose estimation performance can be characterized by the Cramer-Rao lower bound formalism but which requires careful calibration and (2) an image-domain material classification approach that is more robust to calibration errors. The data-domain analysis indicates that useful levels of SNR (>5) could be achieved in one second or less at typical bending magnetmore » fluxes for relatively large amounts of contrast (several mm path length, such as in a fluid flow experiment) and at typical undulator fluxes for small amount of contrast (tens of microns path length, such as an angiography experiment). The tools introduced could of course be used to study and optimize parameters for a wider range of potential applications. The image domain approach was analyzed in terms of its ability to distinguish different elemental stains by characterizing the angle between the lines traced out in a two-dimensional space of effective attenuation coefficient in the front and back layer images. As a result, this approach was implemented at a synchrotron and the results were consistent with simulation predictions.« less

Material identification in x-ray microscopy and micro CT using multi-layer, multi-color scintillation detectors

DOE PAGES

Modgil, Dimple; Rigie, David S.; Wang, Yuxin; ...

2015-09-30

We demonstrate that a dual-layer, dual-color scintillator construct for microscopic CT, originally proposed to increase sensitivity in synchrotron imaging, can also be used to perform material quantification and classification when coupled with polychromatic illumination. We consider two different approaches to data handling: (1) a data-domain material decomposition whose estimation performance can be characterized by the Cramer-Rao lower bound formalism but which requires careful calibration and (2) an image-domain material classification approach that is more robust to calibration errors. The data-domain analysis indicates that useful levels of SNR (>5) could be achieved in one second or less at typical bending magnetmore » fluxes for relatively large amounts of contrast (several mm path length, such as in a fluid flow experiment) and at typical undulator fluxes for small amount of contrast (tens of microns path length, such as an angiography experiment). The tools introduced could of course be used to study and optimize parameters for a wider range of potential applications. The image domain approach was analyzed in terms of its ability to distinguish different elemental stains by characterizing the angle between the lines traced out in a two-dimensional space of effective attenuation coefficient in the front and back layer images. As a result, this approach was implemented at a synchrotron and the results were consistent with simulation predictions.« less

A Numerical Analysis on the Effects of Self-Excited Tip Flow Unsteadiness and Upstream Blade Row Interactions on the Performance Predictions of a Transonic Compressor

NASA Astrophysics Data System (ADS)

Heberling, Brian

Computational fluid dynamics (CFD) simulations can offer a detailed view of the complex flow fields within an axial compressor and greatly aid the design process. However, the desire for quick turnaround times raises the question of how exact the model must be. At design conditions, steady CFD simulating an isolated blade row can accurately predict the performance of a rotor. However, as a compressor is throttled and mass flow rate decreased, axial flow becomes weaker making the capturing of unsteadiness, wakes, or other flow features more important. The unsteadiness of the tip clearance flow and upstream blade wake can have a significant impact on a rotor. At off-design conditions, time-accurate simulations or modeling multiple blade rows can become necessary in order to receive accurate performance predictions. Unsteady and multi- bladerow simulations are computationally expensive, especially when used in conjunction. It is important to understand which features are important to model in order to accurately capture a compressor's performance. CFD simulations of a transonic axial compressor throttling from the design point to stall are presented. The importance of capturing the unsteadiness of the rotor tip clearance flow versus capturing upstream blade-row interactions is examined through steady and unsteady, single- and multi-bladerow computations. It is shown that there are significant differences at near stall conditions between the different types of simulations.

Effects of stream turbine array configuration on tidal current energy extraction near an island

NASA Astrophysics Data System (ADS)

Chen, Yaling; Lin, Binliang; Lin, Jie; Wang, Shujie

2015-04-01

Enhanced tidal currents around islands appear to present the potential for power extraction. In this research, a three-dimensional numerical model is applied to investigate the naturally occurring tidal dynamics and the extractable energy from turbines close to Zhaitang Island, located off the east coast of China. In the model, the effect of tidal turbine is represented by a horizontal thrust and added to the momentum equations. To determine a better configuration of turbine array, a detailed work has been undertaken to investigate the combined influences of the topographic features and array arrangement on the performance of power generation. First, three single row arrays are examined with lateral spacing being 2, 3 and 4 times rotor diameters. Then, corresponding to each lateral spacing, three multi-row arrays in a staggered manner with longitudinal spacing being 5, 10 and 15 times rotor diameters are developed. It has been found that single row arrays with higher local blockage outperform arrays with lower blockage. While for multi-row arrays, the performance of inside turbine is significantly experienced the wake influence of upstream turbines, which can be weakened with an increment of turbine spacing. And a remarkable improvement of turbine performance is observed as the longitudinal spacing increases to 10 times rotor diameters. However, the change pattern of power extraction is mainly dependent on that of naturally kinetic energy when the turbine density is further decreasing in the given region.

Multi-atlas-based CT synthesis from conventional MRI with patch-based refinement for MRI-based radiotherapy planning.

PubMed

Lee, Junghoon; Carass, Aaron; Jog, Amod; Zhao, Can; Prince, Jerry L

2017-02-01

Accurate CT synthesis, sometimes called electron density estimation, from MRI is crucial for successful MRI-based radiotherapy planning and dose computation. Existing CT synthesis methods are able to synthesize normal tissues but are unable to accurately synthesize abnormal tissues (i.e., tumor), thus providing a suboptimal solution. We propose a multi-atlas-based hybrid synthesis approach that combines multi-atlas registration and patch-based synthesis to accurately synthesize both normal and abnormal tissues. Multi-parametric atlas MR images are registered to the target MR images by multi-channel deformable registration, from which the atlas CT images are deformed and fused by locally-weighted averaging using a structural similarity measure (SSIM). Synthetic MR images are also computed from the registered atlas MRIs by using the same weights used for the CT synthesis; these are compared to the target patient MRIs allowing for the assessment of the CT synthesis fidelity. Poor synthesis regions are automatically detected based on the fidelity measure and refined by a patch-based synthesis. The proposed approach was tested on brain cancer patient data, and showed a noticeable improvement for the tumor region.

CT Colonography (Virtual Colonoscopy)

MedlinePlus

... Rotating around you, the x-ray tube and electronic x-ray detectors are located opposite each other ... numerous x-ray beams and a set of electronic x-ray detectors rotate around you, measuring the ...

Multi-Mounted X-Ray Computed Tomography.

PubMed

Fu, Jian; Liu, Zhenzhong; Wang, Jingzheng

2016-01-01

Most existing X-ray computed tomography (CT) techniques work in single-mounted mode and need to scan the inspected objects one by one. It is time-consuming and not acceptable for the inspection in a large scale. In this paper, we report a multi-mounted CT method and its first engineering implementation. It consists of a multi-mounted scanning geometry and the corresponding algebraic iterative reconstruction algorithm. This approach permits the CT rotation scanning of multiple objects simultaneously without the increase of penetration thickness and the signal crosstalk. Compared with the conventional single-mounted methods, it has the potential to improve the imaging efficiency and suppress the artifacts from the beam hardening and the scatter. This work comprises a numerical study of the method and its experimental verification using a dataset measured with a developed multi-mounted X-ray CT prototype system. We believe that this technique is of particular interest for pushing the engineering applications of X-ray CT.

High density associative memory

NASA Technical Reports Server (NTRS)

Moopenn, Alexander W. (Inventor); Thakoor, Anilkumar P. (Inventor); Daud, Taher (Inventor); Lambe, John J. (Inventor)

1989-01-01

A multi-layered, thin-film, digital memory having associative recall. There is a first memory matrix and a second memory matrix. Each memory matrix comprises, a first layer comprising a plurality of electrically separated row conductors; a second layer comprising a plurality of electrically separated column conductors intersecting but electrically separated from the row conductors; and, a plurality of resistance elements electrically connected between the row condutors and the column conductors at respective intersections of the row conductors and the column conductors, each resistance element comprising, in series, a first resistor of sufficiently high ohmage to conduct a sensible element current therethrough with virtually no heat-generating power consumption when a low voltage as employed in thin-film applications is applied thereacross and a second resistor of sufficiently high ohmage to conduct no sensible current therethrough when a low voltage as employed in thin-film applications is applied thereacross, the second resistor having the quality of breaking down to create a short therethrough upon the application of a breakdown level voltage across the first and second resistors.

A review of turbomachinery blade-row interaction research

NASA Technical Reports Server (NTRS)

Smith, Todd E.

1988-01-01

Analytical and experimental research in the area of unsteady aerodynamics of turbomachinery has conventionally been applied to blading which oscillates when placed in a uniformly flowing fluid. Comparatively less effort has been offered for the study of blading which is subjected to nonuniformities within the flow field. The fluid dynamic environment of a blade-row embedded within multi-stage turbomachines is dominated by such highly unsteady fluid flow conditions. The production of wakes and circumferential pressure variations from adjacent blade-rows causes large unsteady energy transfers between the fluid and the blades. Determination of the forced response of a blade requires the ability to predict the unsteady loads which are induced by these aerodynamic sources. A review of research publications was done to determine recent investigations of the response of turbomachinery blading subjected to aerodynamic excitations. Such excitations are a direct result of the blade-row aerodynamic interaction which occurs between adjacent cascades of blades. The reports and papers reviewed have been organized into areas emphasizing experimental or analytical efforts.

Analysis of Patients' X-ray Exposure in 146 Percutaneous Radiologic Gastrostomies.

PubMed

Petersen, Tim-Ole; Reinhardt, Martin; Fuchs, Jochen; Gosch, Dieter; Surov, Alexey; Stumpp, Patrick; Kahn, Thomas; Moche, Michael

2017-09-01

Purpose  Analysis of patient´s X-ray exposure during percutaneous radiologic gastrostomies (PRG) in a larger population. Materials and Methods  Data of primary successful PRG-procedures, performed between 2004 and 2015 in 146 patients, were analyzed regarding the exposition to X-ray. Dose-area-product (DAP), dose-length-product (DLP) respectively, and fluoroscopy time (FT) were correlated with the used x-ray systems (Flatpanel Detector (FD) vs. Image Itensifier (BV)) and the necessity for periprocedural placement of a nasogastric tube. Additionally, the effective X-ray dose for PRG placement using fluoroscopy (DL), computed tomography (CT), and cone beam CT (CBCT) was estimated using a conversion factor. Results  The median DFP of PRG-placements under fluoroscopy was 163 cGy*cm 2 (flat panel detector systems: 155 cGy*cm 2 ; X-ray image intensifier: 175 cGy*cm 2 ). The median DLZ was 2.2 min. Intraprocedural placement of a naso- or orogastric probe (n = 68) resulted in a significant prolongation of the median DLZ to 2.5 min versus 2 min in patients with an already existing probe. In addition, dose values were analyzed in smaller samples of patients in which the PRG was placed under CBCT (n = 7, median DFP = 2635 cGy*cm 2 ), or using CT (n = 4, median DLP = 657 mGy*cm). Estimates of the median DFP and DLP showed effective doses of 0.3 mSv for DL-assisted placements (flat panel detector 0.3 mSv, X-ray image converter 0.4 mSv), 7.9 mSv using a CBCT - flat detector, and 9.9 mSv using CT. This corresponds to a factor 26 of DL versus CBCT, or a factor 33 of DL versus CT. Conclusion  In order to minimize X-ray exposure during PRG-procedures for patients and staff, fluoroscopically-guided interventions should employ flat detector systems with short transmittance sequences in low dose mode and with slow image frequency. Series recordings can be dispensed with. The intraprocedural placement of a naso- or orogastric probe significantly extends FT, but has little effect on the overall dose of the intervention. Due to the significantly higher X-ray exposure, the use of a CBCT as well as PRG-placements using CT should be limited to clinically absolutely necessary exceptions with strict indication. Key Points   · Fluoroscopically-guided PRG placements are interventions with low X-ray exposure.. · X-ray exposure from fluoroscopy is lower using flat panel detector systems as compared to image intensifier systems.. · The concomitant placement of an oro- or nasogastric probe extends the fluoroscopy time.. · Gastric probe placement is worthwhile to prevent the premature use of the significantly radiation-intensive CT.. · The use of the C-arm CT or the CT increases the beam exposure by 26 or 33 times, respectively.. · The PRG placement using C-arm CT and CT should only be performed in exceptional cases.. Citation Format · Petersen TO, Reinhardt M, Fuchs J et al. Analysis of Patients' X-ray Exposure in 146 Percutaneous Radiologic Gastrostomies. Fortschr Röntgenstr 2017; 189: 820 - 827. © Georg Thieme Verlag KG Stuttgart · New York.

Multimode C-arm fluoroscopy, tomosynthesis, and cone-beam CT for image-guided interventions: from proof of principle to patient protocols

NASA Astrophysics Data System (ADS)

Siewerdsen, J. H.; Daly, M. J.; Bachar, G.; Moseley, D. J.; Bootsma, G.; Brock, K. K.; Ansell, S.; Wilson, G. A.; Chhabra, S.; Jaffray, D. A.; Irish, J. C.

2007-03-01

High-performance intraoperative imaging is essential to an ever-expanding scope of therapeutic procedures ranging from tumor surgery to interventional radiology. The need for precise visualization of bony and soft-tissue structures with minimal obstruction to the therapy setup presents challenges and opportunities in the development of novel imaging technologies specifically for image-guided procedures. Over the past ~5 years, a mobile C-arm has been modified in collaboration with Siemens Medical Solutions for 3D imaging. Based upon a Siemens PowerMobil, the device includes: a flat-panel detector (Varian PaxScan 4030CB); a motorized orbit; a system for geometric calibration; integration with real-time tracking and navigation (NDI Polaris); and a computer control system for multi-mode fluoroscopy, tomosynthesis, and cone-beam CT. Investigation of 3D imaging performance (noise-equivalent quanta), image quality (human observer studies), and image artifacts (scatter, truncation, and cone-beam artifacts) has driven the development of imaging techniques appropriate to a host of image-guided interventions. Multi-mode functionality presents a valuable spectrum of acquisition techniques: i.) fluoroscopy for real-time 2D guidance; ii.) limited-angle tomosynthesis for fast 3D imaging (e.g., ~10 sec acquisition of coronal slices containing the surgical target); and iii.) fully 3D cone-beam CT (e.g., ~30-60 sec acquisition providing bony and soft-tissue visualization across the field of view). Phantom and cadaver studies clearly indicate the potential for improved surgical performance - up to a factor of 2 increase in challenging surgical target excisions. The C-arm system is currently being deployed in patient protocols ranging from brachytherapy to chest, breast, spine, and head and neck surgery.

A novel digital image sensor with row wise gain compensation for Hyper Spectral Imager (HySI) application

NASA Astrophysics Data System (ADS)

Lin, Shengmin; Lin, Chi-Pin; Wang, Weng-Lyang; Hsiao, Feng-Ke; Sikora, Robert

2009-08-01

A 256x512 element digital image sensor has been developed which has a large pixel size, slow scan and low power consumption for Hyper Spectral Imager (HySI) applications. The device is a mixed mode, silicon on chip (SOC) IC. It combines analog circuitry, digital circuitry and optical sensor circuitry into a single chip. This chip integrates a 256x512 active pixel sensor array, a programming gain amplifier (PGA) for row wise gain setting, I2C interface, SRAM, 12 bit analog to digital convertor (ADC), voltage regulator, low voltage differential signal (LVDS) and timing generator. The device can be used for 256 pixels of spatial resolution and 512 bands of spectral resolution ranged from 400 nm to 950 nm in wavelength. In row wise gain readout mode, one can set a different gain on each row of the photo detector by storing the gain setting data on the SRAM thru the I2C interface. This unique row wise gain setting can be used to compensate the silicon spectral response non-uniformity problem. Due to this unique function, the device is suitable for hyper-spectral imager applications. The HySI camera located on-board the Chandrayaan-1 satellite, was successfully launched to the moon on Oct. 22, 2008. The device is currently mapping the moon and sending back excellent images of the moon surface. The device design and the moon image data will be presented in the paper.

Development of a multi-element microdosimetric detector based on a thick gas electron multiplier

NASA Astrophysics Data System (ADS)

Anjomani, Z.; Hanu, A. R.; Prestwich, W. V.; Byun, S. H.

2017-03-01

A prototype multi-element gaseous microdosimetric detector was developed using the Thick Gas Electron Multiplier (THGEM) technique. The detector aims at measuring neutron and gamma-ray dose rates for weak neutron-gamma radiation fields. The multi-element design was employed to increase the neutron detection efficiency. The prototype THGEM multi-element detector consists of three layers of tissue equivalent plastic hexagons and each layer houses a hexagonal array of seven cylindrical gas cavity elements with equal heights and diameters of 17 mm. The final detector structure incorporates 21 gaseous volumes. Owing to the absence of wire electrodes, the THGEM multi-element detector offers flexible and convenient fabrication. The detector responses to neutron and gamma-ray were investigated using the McMaster Tandetron 7Li(p,n) neutron source. The dosimetric performance of the detector is presented in contrast to the response of a commercial tissue equivalent proportional counter. Compared to the standard TEPC response, the detector gave a consistent microdosimetric response with an average discrepancy of 8 % in measured neutron absorbed dose. An improvement of a factor of 3.0 in neutron detection efficiency has been accomplished with only a small degradation in energy resolution. However, its low energy cut off is about 6 keV/μm, which is not sufficient to measure the gamma-ray dose. This problem will be addressed by increasing the electron multiplication gain using double THGEM layers.

Histogram-driven cupping correction (HDCC) in CT

NASA Astrophysics Data System (ADS)

Kyriakou, Y.; Meyer, M.; Lapp, R.; Kalender, W. A.

2010-04-01

Typical cupping correction methods are pre-processing methods which require either pre-calibration measurements or simulations of standard objects to approximate and correct for beam hardening and scatter. Some of them require the knowledge of spectra, detector characteristics, etc. The aim of this work was to develop a practical histogram-driven cupping correction (HDCC) method to post-process the reconstructed images. We use a polynomial representation of the raw-data generated by forward projection of the reconstructed images; forward and backprojection are performed on graphics processing units (GPU). The coefficients of the polynomial are optimized using a simplex minimization of the joint entropy of the CT image and its gradient. The algorithm was evaluated using simulations and measurements of homogeneous and inhomogeneous phantoms. For the measurements a C-arm flat-detector CT (FD-CT) system with a 30×40 cm2 detector, a kilovoltage on board imager (radiation therapy simulator) and a micro-CT system were used. The algorithm reduced cupping artifacts both in simulations and measurements using a fourth-order polynomial and was in good agreement to the reference. The minimization algorithm required less than 70 iterations to adjust the coefficients only performing a linear combination of basis images, thus executing without time consuming operations. HDCC reduced cupping artifacts without the necessity of pre-calibration or other scan information enabling a retrospective improvement of CT image homogeneity. However, the method can work with other cupping correction algorithms or in a calibration manner, as well.

Investigation on the Accuracy of Superposition Predictions of Film Cooling Effectiveness

NASA Astrophysics Data System (ADS)

Meng, Tong; Zhu, Hui-ren; Liu, Cun-liang; Wei, Jian-sheng

2018-05-01

Film cooling effectiveness on flat plates with double rows of holes has been studied experimentally and numerically in this paper. This configuration is widely used to simulate the multi-row film cooling on turbine vane. Film cooling effectiveness of double rows of holes and each single row was used to study the accuracy of superposition predictions. Method of stable infrared measurement technique was used to measure the surface temperature on the flat plate. This paper analyzed the factors that affect the film cooling effectiveness including hole shape, hole arrangement, row-to-row spacing and blowing ratio. Numerical simulations were performed to analyze the flow structure and film cooling mechanisms between each film cooling row. Results show that the blowing ratio within the range of 0.5 to 2 has a significant influence on the accuracy of superposition predictions. At low blowing ratios, results obtained by superposition method agree well with the experimental data. While at high blowing ratios, the accuracy of superposition prediction decreases. Another significant factor is hole arrangement. Results obtained by superposition prediction are nearly the same as experimental values of staggered arrangement structures. For in-line configurations, the superposition values of film cooling effectiveness are much higher than experimental data. For different hole shapes, the accuracy of superposition predictions on converging-expanding holes is better than cylinder holes and compound angle holes. For two different hole spacing structures in this paper, predictions show good agreement with the experiment results.

Value of tomosynthesis for lesion evaluation of small joints in osteoarthritic hands using the OARSI score.

PubMed

Martini, K; Becker, A S; Guggenberger, R; Andreisek, G; Frauenfelder, T

2016-07-01

To determine the diagnostic performance of tomosynthesis in depicting osteoarthritic lesions in comparison to conventional radiographs, with use of computed tomography (CT) as standard-of-reference. Imaging of 12 cadaveric hands was performed with tomosynthesis in dorso-palmar (dp) projection, conventional radiographs (dp) and multi-detector CT. Distal interphalangeal joint (DIP)II, DIPIII, proximal interphalangeal joint (PIP)II, PIPIII, first carpometacarpal (CMC) and scaphotrapezotrapezoidal joint (STT) were graded by two independent readers using the Osteoarthritis Research Society International (OARSI) score. The mean score for each feature was calculated for all modalities. Additional wrists were evaluated for presence of calcium pyrophosphate disease (CPPD). CT served as reference-standard. Inter-reader agreement (ICC) was calculated. Comparing tomosynthesis and conventional radiographs to CT, the sensitivity for the presence of osteophytes was 95,7% vs 65,2%; for joint space narrowing 95,8% vs 52,1%; for subchondral sclerosis 61,5% vs 51,3%; for lateral deformity 83.3% vs 83,3%; and for subchondral cysts 45,8% vs 29,2%. Erosions were not present. While tomosynthesis showed no significant difference in OARSI score grading to CT (mean OARSI-score CT: 16.8, SD = 10.6; mean OARSI-score Tomosynthesis: 16.3, SD = 9.6; P = 0.84), conventional radiographs had significant lower mean OARSI scores (mean OARSI-score X-ray: 11.1, SD = 8.3; P = 0.04). Inter-reader agreement for OARSI scoring was excellent (ICC = 0.99). CPPD calcifications present in CT, were also visible with tomosynthesis, but not with conventional radiography. In conclusion, tomosynthesis depicts more osteoarthritic changes in the small joints of the hand than conventional radiography using the OARSI scoring system and CT as the standard of reference. Copyright © 2016 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Development and calibration of a new gamma camera detector using large square Photomultiplier Tubes

NASA Astrophysics Data System (ADS)

Zeraatkar, N.; Sajedi, S.; Teimourian Fard, B.; Kaviani, S.; Akbarzadeh, A.; Farahani, M. H.; Sarkar, S.; Ay, M. R.

2017-09-01

Large area scintillation detectors applied in gamma cameras as well as Single Photon Computed Tomography (SPECT) systems, have a major role in in-vivo functional imaging. Most of the gamma detectors utilize hexagonal arrangement of Photomultiplier Tubes (PMTs). In this work we applied large square-shaped PMTs with row/column arrangement and positioning. The Use of large square PMTs reduces dead zones in the detector surface. However, the conventional center of gravity method for positioning may not introduce an acceptable result. Hence, the digital correlated signal enhancement (CSE) algorithm was optimized to obtain better linearity and spatial resolution in the developed detector. The performance of the developed detector was evaluated based on NEMA-NU1-2007 standard. The acquired images using this method showed acceptable uniformity and linearity comparing to three commercial gamma cameras. Also the intrinsic and extrinsic spatial resolutions with low-energy high-resolution (LEHR) collimator at 10 cm from surface of the detector were 3.7 mm and 7.5 mm, respectively. The energy resolution of the camera was measured 9.5%. The performance evaluation demonstrated that the developed detector maintains image quality with a reduced number of used PMTs relative to the detection area.

Cost-effectiveness of 64-slice CT angiography compared to conventional coronary angiography based on a coverage with evidence development study in Ontario.

PubMed

Goeree, Ron; Blackhouse, Gord; Bowen, James M; O'Reilly, Daria; Sutherland, Simone; Hopkins, Robert; Chow, Benjamin; Freeman, Michael; Provost, Yves; Dennie, Carole; Cohen, Eric; Marcuzzi, Dan; Iwanochko, Robert; Moody, Alan; Paul, Narinder; Parker, John D

2013-10-01

Conventional coronary angiography (CCA) is the standard diagnostic for coronary artery disease (CAD), but multi-detector computed tomography coronary angiography (CTCA) is a non-invasive alternative. A multi-center coverage with evidence development study was undertaken and combined with an economic model to estimate the cost-effectiveness of CTCA followed by CCA vs CCA alone. Alternative assumptions were tested in patient scenario and sensitivity analyses. CCA was found to dominate CTCA, however, CTCA was relatively more cost-effective in females, in advancing age, in patients with lower pre-test probabilities of CAD, the higher the sensitivity of CTCA and the lower the probability of undergoing a confirmatory CCA following a positive CTCA. RESULTS were very sensitive to alternative patient populations and modeling assumptions. Careful consideration of patient characteristics, procedures to improve the diagnostic yield of CTCA and selective use of CCA following CTCA will impact whether CTCA is cost-effective or dominates CCA.

Geometry-constraint-scan imaging for in-line phase contrast micro-CT.

PubMed

Fu, Jian; Yu, Guangyuan; Fan, Dekai

2014-01-01

X-ray phase contrast computed tomography (CT) uses the phase shift that x-rays undergo when passing through matter, rather than their attenuation, as the imaging signal and may provide better image quality in soft-tissue and biomedical materials with low atomic number. Here a geometry-constraint-scan imaging technique for in-line phase contrast micro-CT is reported. It consists of two circular-trajectory scans with x-ray detector at different positions, the phase projection extraction method with the Fresnel free-propagation theory and the filter back-projection reconstruction algorithm. This method removes the contact-detector scan and the pure phase object assumption in classical in-line phase contrast Micro-CT. Consequently it relaxes the experimental conditions and improves the image contrast. This work comprises a numerical study of this technique and its experimental verification using a biomedical composite dataset measured at an x-ray tube source Micro-CT setup. The numerical and experimental results demonstrate the validity of the presented method. It will be of interest for a wide range of in-line phase contrast Micro-CT applications in biology and medicine.

PHACES syndrome associated with carcinoid endobronchial tumor.

PubMed

Mama, Nadia; H'mida, Dorra; Lahmar, Imen; Yacoubi, Mohamed Tahar; Tlili-Graiess, Kalthoum

2014-05-01

PHACES syndrome consists of the constellation of manifestations including posterior fossa anomalies of the brain (most commonly Dandy-Walker malformations), hemangiomas of the face and scalp, arterial abnormalities, cardiac defects, eye anomalies and sternal defects. We present a case with a possible PHACES syndrome including sternal cleft and supraumbilical raphé, precordial skin tag, persistent left superior vena cava and subtle narrowing of the aorta with an endobronchial carcinoid tumor. All these anomalies were discovered on chest multi-detector CT. This is a unique case of PHACES syndrome associated with carcinoid tumor. Review of the literature revealed 3 cases of PHACES syndrome with glial tumor. The authors tried to find the relationship between PHACES syndrome and carcinoid tumors or gliomas, which all derive from the neural crest cells.

Nonlinear dynamic simulation of single- and multi-spool core engines

NASA Technical Reports Server (NTRS)

Schobeiri, T.; Lippke, C.; Abouelkheir, M.

1993-01-01

In this paper a new computational method for accurate simulation of the nonlinear dynamic behavior of single- and multi-spool core engines, turbofan engines, and power generation gas turbine engines is presented. In order to perform the simulation, a modularly structured computer code has been developed which includes individual mathematical modules representing various engine components. The generic structure of the code enables the dynamic simulation of arbitrary engine configurations ranging from single-spool thrust generation to multi-spool thrust/power generation engines under adverse dynamic operating conditions. For precise simulation of turbine and compressor components, row-by-row calculation procedures were implemented that account for the specific turbine and compressor cascade and blade geometry and characteristics. The dynamic behavior of the subject engine is calculated by solving a number of systems of partial differential equations, which describe the unsteady behavior of the individual components. In order to ensure the capability, accuracy, robustness, and reliability of the code, comprehensive critical performance assessment and validation tests were performed. As representatives, three different transient cases with single- and multi-spool thrust and power generation engines were simulated. The transient cases range from operating with a prescribed fuel schedule, to extreme load changes, to generator and turbine shut down.

A Quasiparticle Detector for Imaging Quantum Turbulence in Superfluid He-B

NASA Astrophysics Data System (ADS)

Ahlstrom, S. L.; Bradley, D. I.; Fisher, S. N.; Guénault, A. M.; Guise, E. A.; Haley, R. P.; Holt, S.; Kolosov, O.; McClintock, P. V. E.; Pickett, G. R.; Poole, M.; Schanen, R.; Tsepelin, V.; Woods, A. J.

2014-06-01

We describe the development of a two-dimensional quasiparticle detector for use in visualising quantum turbulence in superfluid He-B at ultra-low temperatures. The detector consists of a matrix of pixels, each a 1 mm diameter hole in a copper block containing a miniature quartz tuning fork. The damping on each fork provides a measure of the local quasiparticle flux. The detector is illuminated by a beam of ballistic quasiparticles generated from a nearby black-body radiator. A comparison of the damping on the different forks provides a measure of the cross-sectional profile of the beam. Further, we generate a tangle of vortices (quantum turbulence) in the path of the beam using a vibrating wire resonator. The vortices cast a shadow onto the face of the detector due to the Andreev reflection of quasiparticles in the beam. This allows us to image the vortices and to investigate their dynamics. Here we give details of the design and construction of the detector and show some preliminary results for one row of pixels which demonstrates its successful application to measuring quasiparticle beams and quantum turbulence.

Experimental study of boron-coated straws with a neutron source

NASA Astrophysics Data System (ADS)

Xie, Zhaoyang; Zhou, Jianrong; Song, Yushou; Lacy, Jeffrey L.; Sun, Liang; Sun, Zhijia; Hu, Bitao; Chen, Yuanbo

2018-04-01

Multiple types of high quality neutron detectors are proposed for the first phase of the China Spallation Neutron Source (CSNS), which will be commissioned in 2018. Considering the shortage of 3He supply, a detector module composed of 49 boron-coated straws (BCS) was developed by Proportional Technologies Inc. (PTI). Each straw has a length of 1000 mm and a diameter of 7.5 mm. Seven straws are tightly packed in a tube, and seven tubes are organized in a row to form a detector module. The charge division method is used for longitudinal positioning. A specific readout system was utilized to output the signal and simultaneously encode each straw. The performance of this detector module was studied using a moderated 252Cf source at the Institute of High Energy Physics (IHEP). The signal amplitude spectrum indicates its n-gamma discrimination capability. Despite the complex readout method, a longitudinal resolution of FWHM=6.1 ± 0.5 mm was obtained. The three-dimensional positioning ability qualifies this BCS detector module as a promising detector for small angle neutron scattering.

A new technique to characterize CT scanner bow-tie filter attenuation and applications in human cadaver dosimetry simulations

PubMed Central

Li, Xinhua; Shi, Jim Q.; Zhang, Da; Singh, Sarabjeet; Padole, Atul; Otrakji, Alexi; Kalra, Mannudeep K.; Xu, X. George; Liu, Bob

2015-01-01

Purpose: To present a noninvasive technique for directly measuring the CT bow-tie filter attenuation with a linear array x-ray detector. Methods: A scintillator based x-ray detector of 384 pixels, 307 mm active length, and fast data acquisition (model X-Scan 0.8c4-307, Detection Technology, FI-91100 Ii, Finland) was used to simultaneously detect radiation levels across a scan field-of-view. The sampling time was as short as 0.24 ms. To measure the body bow-tie attenuation on a GE Lightspeed Pro 16 CT scanner, the x-ray tube was parked at the 12 o’clock position, and the detector was centered in the scan field at the isocenter height. Two radiation exposures were made with and without the bow-tie in the beam path. Each readout signal was corrected for the detector background offset and signal-level related nonlinear gain, and the ratio of the two exposures gave the bow-tie attenuation. The results were used in the geant4 based simulations of the point doses measured using six thimble chambers placed in a human cadaver with abdomen/pelvis CT scans at 100 or 120 kV, helical pitch at 1.375, constant or variable tube current, and distinct x-ray tube starting angles. Results: Absolute attenuation was measured with the body bow-tie scanned at 80–140 kV. For 24 doses measured in six organs of the cadaver, the median or maximum difference between the simulation results and the measurements on the CT scanner was 8.9% or 25.9%, respectively. Conclusions: The described method allows fast and accurate bow-tie filter characterization. PMID:26520720

Saccular aortic aneurysm that resembled a mediastinal neoplasm

PubMed Central

Nose, Naohiro; Kataoka, Hiroumi; Hamada, Masakatsu; Kosako, Yukio; Matsuno, Yasuji; Ishii, Takahiro

2012-01-01

INTRODUCTION Saccular aortic arch aneurysms in unusual sites may be misdiagnosed as a neoplasm. We present the case of a rare saccular aortic arch aneurysm between trachea and esophagus that resembled a mediastinal neoplasm in the preoperative findings. PRESENTATION OF CASE A 63-year-old male with an abnormal mediastinal shadow on chest X-ray was referred to the hospital. An axial plain computed tomogram of the chest revealed mediastinal soft tissue next to the right side of the aortic arch resembling a neoplasm originating from the gap between the trachea and the esophagus. The coronal view constructed by enhanced 64-row multi detector computed tomography revealed the soft tissue was an aneurysm arising from the inner side of the aortic arch. An aortic arch replacement was performed via a median sternotomy. DISCUSSION A thoracic aortic aneurysm sometimes behaves like a mediastinal neoplasm. The multiple cross-sectional image from multidetector computed tomography was useful for the correct diagnosis of such an aneurysm. CONCLUSION The possibility of an aneurysm should be considered whenever a mass in contact with the aortic wall is identified. PMID:22995656

Characteristics and performance of a micro-MOSFET: an "imageable" dosimeter for image-guided radiotherapy.

PubMed

Rowbottoma, Carl G; Jaffray, David A

2004-03-01

The performance and characteristics of a miniature metal oxide semiconductor field effect transistor (micro-MOSFET) detector was investigated for its potential application to integral system tests for image-guided radiotherapy. In particular, the position of peak response to a slit of radiation was determined for the three principal axes to define the co-ordinates for the center of the active volume of the detector. This was compared to the radiographically determined center of the micro-MOSFET visible using cone-beam CT. Additionally, the angular sensitivity of the micro-MOSFET was measured. The micro-MOSFETs are clearly visible on the cone-beam CT images, and produce no artifacts. The center of the active volume of the micro-MOSFET aligned with the center of the visible micro-MOSFET on the cone-beam CT images for the x and y axes to within 0.20 mm and 0.15 mm, respectively. In z, the long axis of the detector, the peak response was found to be 0.79 mm from the tip of the visible micro-MOSFET. Repeat experiments verified that the position of the peak response of the micro-MOSFET was reproducible. The micro-MOSFET response for 360 degrees of rotation in the axial plane to the micro-MOSFET was +/-2%, consistent with values quoted by the manufacturer. The location of the active volume of the micro-MOSFETs under investigation can be determined from the centroid of the visible micro-MOSFET on cone-beam CT images. The CT centroid position corresponds closely to the center of the detector response to radiation. The ability to use the cone-beam CT to locate the active volume to within 0.20 mm allows their use in an integral system test for the imaging of and dose delivery to a phantom containing an array of micro-MOSFETs. The small angular sensitivity allows the investigation of noncoplanar beams.

TU-F-CAMPUS-I-05: Investigation of An EMCCD Detector with Variable Gain in a Micro-CT System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishnakumar, S Bysani; Ionita, C; Rudin, S

Purpose: To investigate the performance of a newly built Electron Multiplying Charged Coupled Device (EMCCD) based Micro-CT system, with variable detector gain, using a phantom containing contrast agent of different concentrations. Methods: We built a micro- CT system with an EMCCD having 8 microns pixels and on-chip variable gain. We tested the system using a phantom containing five tubes filled with different iodine contrast solutions (30% to 70%). First, we scanned the phantom using various x-ray exposures values at 40 kVp and constant detector gain. Next, for the same tube currents, the detector gain was increased to maintain the airmore » value of the projection image constant. A standard FDK algorithm was used to reconstruct the data. Performance was analyzed by comparing the signal-to-noise ratio (SNR) measurements for increased gain with those for the low constant gain at each exposure. Results: The high detector gain reconstructed data SNR was always greater than the low gain data SNR for all x-ray settings and for all iodine features. The largest increases were observed for low contrast features, 30% iodine concentration, where the SNR improvement approached 2. Conclusion: One of the first implementations of an EMCCD based micro- CT system was presented and used to image a phantom with various iodine solution concentrations. The analysis of the reconstructed volumes showed a significant improvement of the SNR especially for low contrast features. The unique on-chip gain feature is a substantial benefit allowing the use of the system at very low x-ray exposures per frame.Partial support: NIH grant R01EB002873 and Toshiba Medical Systems Corp. Partial support: NIH grant R01EB002873 and Toshiba Medical Systems Corp.« less

Simultaneous CT and SPECT tomography using CZT detectors

DOEpatents

Paulus, Michael J.; Sari-Sarraf, Hamed; Simpson, Michael L.; Britton, Jr., Charles L.

2002-01-01

A method for simultaneous transmission x-ray computed tomography (CT) and single photon emission tomography (SPECT) comprises the steps of: injecting a subject with a tracer compound tagged with a .gamma.-ray emitting nuclide; directing an x-ray source toward the subject; rotating the x-ray source around the subject; emitting x-rays during the rotating step; rotating a cadmium zinc telluride (CZT) two-sided detector on an opposite side of the subject from the source; simultaneously detecting the position and energy of each pulsed x-ray and each emitted .gamma.-ray captured by the CZT detector; recording data for each position and each energy of each the captured x-ray and .gamma.-ray; and, creating CT and SPECT images from the recorded data. The transmitted energy levels of the x-rays lower are biased lower than energy levels of the .gamma.-rays. The x-ray source is operated in a continuous mode. The method can be implemented at ambient temperatures.

Three-Dimensional Weighting in Cone Beam FBP Reconstruction and Its Transformation Over Geometries.

PubMed

Tang, Shaojie; Huang, Kuidong; Cheng, Yunyong; Niu, Tianye; Tang, Xiangyang

2018-06-01

With substantially increased number of detector rows in multidetector CT (MDCT), axial scan with projection data acquired along a circular source trajectory has become the method-of-choice in increasing clinical applications. Recognizing the practical relevance of image reconstruction directly from the projection data acquired in the native cone beam (CB) geometry, especially in scenarios wherein the most achievable in-plane resolution is desirable, we present a three-dimensional (3-D) weighted CB-FBP algorithm in such geometry in this paper. We start the algorithm's derivation in the cone-parallel geometry. Via changing of variables, taking the Jacobian into account and making heuristic and empirical assumptions, we arrive at the formulas for 3-D weighted image reconstruction in the native CB geometry. Using the projection data simulated by computer and acquired by an MDCT scanner, we evaluate and verify performance of the proposed algorithm for image reconstruction directly from projection data acquired in the native CB geometry. The preliminary data show that the proposed algorithm performs as well as the 3-D weighted CB-FBP algorithm in the cone-parallel geometry. The proposed algorithm is anticipated to find its utility in extensive clinical and preclinical applications wherein the reconstruction of images in the native CB geometry, i.e., the geometry for data acquisition, is of relevance.

In-vivo x-ray micro-imaging and micro-CT with the Medipix2 semiconductor detector at UniAndes

NASA Astrophysics Data System (ADS)

Caicedo, I.; Avila, C.; Gomez, B.; Bula, C.; Roa, C.; Sanabria, J.

2012-02-01

This poster contains the procedure to obtain micro-CTs and to image moving samples using the Medipix2 detector, with its corresponding results. The high granularity of the detector makes it suitable for micro-CT. We used commercial software (Octopus) to do the 3D reconstruction of the samples in the first place, and we worked on modifying free reconstruction software afterwards. Medipix has a very fast response ( ~ hundreds of nanoseconds) and high sensibility. These features allow obtaining nearly in-vivo high resolution (55m * 55m) images. We used an exposure time of 0.1 s for each frame, and the resulting images were animated. The High Energy Physics Group at UniAndes is a member of the Medipix3 collaboration. Its research activities are focused on developing set-ups for biomedical applications and particle tracking using the Medipix2 and Timepix detectors, and assessing the feasibility of the Medipix3 detector for future applications.

Automatic categorization of anatomical landmark-local appearances based on diffeomorphic demons and spectral clustering for constructing detector ensembles.

PubMed

Hanaoka, Shouhei; Masutani, Yoshitaka; Nemoto, Mitsutaka; Nomura, Yukihiro; Yoshikawa, Takeharu; Hayashi, Naoto; Ohtomo, Kuni

2012-01-01

A method for categorizing landmark-local appearances extracted from computed tomography (CT) datasets is presented. Anatomical landmarks in the human body inevitably have inter-individual variations that cause difficulty in automatic landmark detection processes. The goal of this study is to categorize subjects (i.e., training datasets) according to local shape variations of such a landmark so that each subgroup has less shape variation and thus the machine learning of each landmark detector is much easier. The similarity between each subject pair is measured based on the non-rigid registration result between them. These similarities are used by the spectral clustering process. After the clustering, all training datasets in each cluster, as well as synthesized intermediate images calculated from all subject-pairs in the cluster, are used to train the corresponding subgroup detector. All of these trained detectors compose a detector ensemble to detect the target landmark. Evaluation with clinical CT datasets showed great improvement in the detection performance.

Filtered-backprojection reconstruction for a cone-beam computed tomography scanner with independent source and detector rotations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rit, Simon, E-mail: simon.rit@creatis.insa-lyon.fr; Clackdoyle, Rolf; Keuschnigg, Peter

Purpose: A new cone-beam CT scanner for image-guided radiotherapy (IGRT) can independently rotate the source and the detector along circular trajectories. Existing reconstruction algorithms are not suitable for this scanning geometry. The authors propose and evaluate a three-dimensional (3D) filtered-backprojection reconstruction for this situation. Methods: The source and the detector trajectories are tuned to image a field-of-view (FOV) that is offset with respect to the center-of-rotation. The new reconstruction formula is derived from the Feldkamp algorithm and results in a similar three-step algorithm: projection weighting, ramp filtering, and weighted backprojection. Simulations of a Shepp Logan digital phantom were used tomore » evaluate the new algorithm with a 10 cm-offset FOV. A real cone-beam CT image with an 8.5 cm-offset FOV was also obtained from projections of an anthropomorphic head phantom. Results: The quality of the cone-beam CT images reconstructed using the new algorithm was similar to those using the Feldkamp algorithm which is used in conventional cone-beam CT. The real image of the head phantom exhibited comparable image quality to that of existing systems. Conclusions: The authors have proposed a 3D filtered-backprojection reconstruction for scanners with independent source and detector rotations that is practical and effective. This algorithm forms the basis for exploiting the scanner’s unique capabilities in IGRT protocols.« less

Multi-Grid detector for neutron spectroscopy: results obtained on time-of-flight spectrometer CNCS

NASA Astrophysics Data System (ADS)

Anastasopoulos, M.; Bebb, R.; Berry, K.; Birch, J.; Bryś, T.; Buffet, J.-C.; Clergeau, J.-F.; Deen, P. P.; Ehlers, G.; van Esch, P.; Everett, S. M.; Guerard, B.; Hall-Wilton, R.; Herwig, K.; Hultman, L.; Höglund, C.; Iruretagoiena, I.; Issa, F.; Jensen, J.; Khaplanov, A.; Kirstein, O.; Lopez Higuera, I.; Piscitelli, F.; Robinson, L.; Schmidt, S.; Stefanescu, I.

2017-04-01

The Multi-Grid detector technology has evolved from the proof-of-principle and characterisation stages. Here we report on the performance of the Multi-Grid detector, the MG.CNCS prototype, which has been installed and tested at the Cold Neutron Chopper Spectrometer, CNCS at SNS. This has allowed a side-by-side comparison to the performance of 3He detectors on an operational instrument. The demonstrator has an active area of 0.2 m2. It is specifically tailored to the specifications of CNCS. The detector was installed in June 2016 and has operated since then, collecting neutron scattering data in parallel to the He-3 detectors of CNCS. In this paper, we present a comprehensive analysis of this data, in particular on instrument energy resolution, rate capability, background and relative efficiency. Stability, gamma-ray and fast neutron sensitivity have also been investigated. The effect of scattering in the detector components has been measured and provides input to comparison for Monte Carlo simulations. All data is presented in comparison to that measured by the 3He detectors simultaneously, showing that all features recorded by one detector are also recorded by the other. The energy resolution matches closely. We find that the Multi-Grid is able to match the data collected by 3He, and see an indication of a considerable advantage in the count rate capability. Based on these results, we are confident that the Multi-Grid detector will be capable of producing high quality scientific data on chopper spectrometers utilising the unprecedented neutron flux of the ESS.

A multi-reader in vitro study using porcine kidneys to determine the impact of integrated circuit detectors and iterative reconstruction on the detection accuracy, size measurement, and radiation dose for small (<4 mm) renal stones.

PubMed

Wells, Michael L; Froemming, Adam T; Kawashima, Akira; Vrtiska, Terri J; Kim, Bohyun; Hartman, Robert P; Holmes, David R; Carter, Rickey E; Bartley, Adam C; Leng, Shuai; McCollough, Cynthia H; Fletcher, Joel G

2017-08-01

Background Detection of small renal calculi has benefitted from recent advances in computed tomography (CT) scanner design. Information regarding observer performance when using state-of-the-art CT scanners for this application is needed. Purpose To assess observer performance and the impact of radiation dose for detection and size measurement of <4 mm renal stones using CT with integrated circuit detectors and iterative reconstruction. Material and Methods Twenty-nine <4 mm calcium oxalate stones were randomly placed in 20 porcine kidneys in an anthropomorphic phantom. Four radiologists used a workstation to record each calculus detection and size. JAFROC Figure of Merit (FOM), sensitivity, false positive detections, and calculus size were calculated. Results Mean calculus size was 2.2 ± 0.7 mm. The CTDI vol values corresponding to the automatic exposure control settings of 160, 80, 40, 25, and 10 Quality Reference mAs (QRM) were 15.2, 7.9, 4.2, 2.7, and 1.3 mGy, respectively. JAFROC FOM was ≥ 0.97 at ≥ 80 QRM, ≥ 0.89 at ≥ 25 QRM, and was inferior to routine dose (160 QRM) at 10 QRM (0.72, P < 0.05). Per-calculus sensitivity remained ≥ 85% for every reader at ≥ 25 QRM. Mean total false positive detections per reader were ≤ 3 at ≥ 80 QRM, but increased substantially for two readers ( ≥ 12) at ≤ 40 QRM. Measured calculus size significantly decreased at ≤ 25 QRM ( P ≤ 0.01). Conclusion Using low dose renal CT with iterative reconstruction and ≥ 25 QRM results in high sensitivity, but false positive detections increase for some readers at very low dose levels (≤ 40 QRM). At very low doses with iterative reconstruction, measured calculus size will artifactually decrease.

Diagnostic performance of multi-slice CT angiography combined with enterography for small bowel obstruction and intestinal ischaemia.

PubMed

He, Bosheng; Gu, Jinhua; Huang, Sheng; Gao, Xuesong; Fan, Jinhe; Sheng, Meihong; Wang, Lin; Gong, Shenchu

2017-02-01

This study was performed to evaluate the diagnostic performance of multi-slice CT angiography combined with enterography in determining the cause and location of obstruction as well as intestinal ischaemia in patients with small bowel obstruction (SBO). This study retrospectively summarized the image data of 57 SBO patients who received both multi-slice CT angiography and enterography examination between December 2012 and May 2013. The CT diagnoses of SBO and intestinal ischaemia were correlated with the findings at surgery or digital subtraction angiography, which were set as standard references. Multi-slice CT angiography and enterography indicated that the cause of SBO in three patients was misjudged, suggesting a diagnostic accuracy of 94.7%. In one patient the level of obstruction was incorrect, demonstrating a diagnostic accuracy of 98.2%. Based on the results of the receiver operating characteristic (ROC) curve analysis, the diagnostic criterion for ischaemic SBO was at least two of the four CT signs (circumferential bowel wall thickening, reduced enhancement of the intestinal wall, mesenteric oedema and mesenteric vascular engorgement). The criterion yielded a sensitivity of 94.4%, a specificity of 92.3%, a positive predicted value of 85.0% and a negative predicted value of 97.3%, and the area under curve (AUC) was 0.92 (95% CI, 0.85-0.99). Multi-slice CT angiography and enterography have high diagnostic value in identifying the cause and site of SBO. In addition, the suggested diagnostic criterion using CT signs is helpful for diagnosing intestinal ischaemia in SBO patients. © 2016 The Royal Australian and New Zealand College of Radiologists.

Multi-Mounted X-Ray Computed Tomography

PubMed Central

Fu, Jian; Liu, Zhenzhong; Wang, Jingzheng

2016-01-01

Most existing X-ray computed tomography (CT) techniques work in single-mounted mode and need to scan the inspected objects one by one. It is time-consuming and not acceptable for the inspection in a large scale. In this paper, we report a multi-mounted CT method and its first engineering implementation. It consists of a multi-mounted scanning geometry and the corresponding algebraic iterative reconstruction algorithm. This approach permits the CT rotation scanning of multiple objects simultaneously without the increase of penetration thickness and the signal crosstalk. Compared with the conventional single-mounted methods, it has the potential to improve the imaging efficiency and suppress the artifacts from the beam hardening and the scatter. This work comprises a numerical study of the method and its experimental verification using a dataset measured with a developed multi-mounted X-ray CT prototype system. We believe that this technique is of particular interest for pushing the engineering applications of X-ray CT. PMID:27073911

Methods for radiation detection and characterization using a multiple detector probe

DOEpatents

Akers, Douglas William; Roybal, Lyle Gene

2014-11-04

Apparatuses, methods, and systems relating to radiological characterization of environments are disclosed. Multi-detector probes with a plurality of detectors in a common housing may be used to substantially concurrently detect a plurality of different radiation activities and types. Multiple multi-detector probes may be used in a down-hole environment to substantially concurrently detect radioactive activity and contents of a buried waste container. Software may process, analyze, and integrate the data from the different multi-detector probes and the different detector types therein to provide source location and integrated analysis as to the source types and activity in the measured environment. Further, the integrated data may be used to compensate for differential density effects and the effects of radiation shielding materials within the volume being measured.

Right heart on multidetector CT

PubMed Central

Gopalan, D

2011-01-01

Right ventricular function plays an integral role in the pathogenesis and outcome of many cardiovascular diseases. Imaging the right ventricle has long been a challenge because of its complex geometry. In recent years there has been a tremendous expansion in multidetector row CT (MDCT) and its cardiac applications. By judicious modification of contrast medium protocol, it is possible to achieve good opacification of the right-sided cardiac chambers, thereby paving the way for exploring the overshadowed right heart. This article will describe the key features of right heart anatomy, review MDCT acquisition techniques, elaborate the various morphological and functional information that can be obtained, and illustrate some important clinical conditions associated with an abnormal right heart. PMID:22723537

Computed tomography imaging and angiography - principles.

PubMed

Kamalian, Shervin; Lev, Michael H; Gupta, Rajiv

2016-01-01

The evaluation of patients with diverse neurologic disorders was forever changed in the summer of 1973, when the first commercial computed tomography (CT) scanners were introduced. Until then, the detection and characterization of intracranial or spinal lesions could only be inferred by limited spatial resolution radioisotope scans, or by the patterns of tissue and vascular displacement on invasive pneumoencaphalography and direct carotid puncture catheter arteriography. Even the earliest-generation CT scanners - which required tens of minutes for the acquisition and reconstruction of low-resolution images (128×128 matrix) - could, based on density, noninvasively distinguish infarct, hemorrhage, and other mass lesions with unprecedented accuracy. Iodinated, intravenous contrast added further sensitivity and specificity in regions of blood-brain barrier breakdown. The advent of rapid multidetector row CT scanning in the early 1990s created renewed enthusiasm for CT, with CT angiography largely replacing direct catheter angiography. More recently, iterative reconstruction postprocessing techniques have made possible high spatial resolution, reduced noise, very low radiation dose CT scanning. The speed, spatial resolution, contrast resolution, and low radiation dose capability of present-day scanners have also facilitated dual-energy imaging which, like magnetic resonance imaging, for the first time, has allowed tissue-specific CT imaging characterization of intracranial pathology. © 2016 Elsevier B.V. All rights reserved.

Multiple-image encryption via lifting wavelet transform and XOR operation based on compressive ghost imaging scheme

NASA Astrophysics Data System (ADS)

Li, Xianye; Meng, Xiangfeng; Yang, Xiulun; Wang, Yurong; Yin, Yongkai; Peng, Xiang; He, Wenqi; Dong, Guoyan; Chen, Hongyi

2018-03-01

A multiple-image encryption method via lifting wavelet transform (LWT) and XOR operation is proposed, which is based on a row scanning compressive ghost imaging scheme. In the encryption process, the scrambling operation is implemented for the sparse images transformed by LWT, then the XOR operation is performed on the scrambled images, and the resulting XOR images are compressed in the row scanning compressive ghost imaging, through which the ciphertext images can be detected by bucket detector arrays. During decryption, the participant who possesses his/her correct key-group, can successfully reconstruct the corresponding plaintext image by measurement key regeneration, compression algorithm reconstruction, XOR operation, sparse images recovery, and inverse LWT (iLWT). Theoretical analysis and numerical simulations validate the feasibility of the proposed method.

Software platform for simulation of a prototype proton CT scanner.

PubMed

Giacometti, Valentina; Bashkirov, Vladimir A; Piersimoni, Pierluigi; Guatelli, Susanna; Plautz, Tia E; Sadrozinski, Hartmut F-W; Johnson, Robert P; Zatserklyaniy, Andriy; Tessonnier, Thomas; Parodi, Katia; Rosenfeld, Anatoly B; Schulte, Reinhard W

2017-03-01

Proton computed tomography (pCT) is a promising imaging technique to substitute or at least complement x-ray CT for more accurate proton therapy treatment planning as it allows calculating directly proton relative stopping power from proton energy loss measurements. A proton CT scanner with a silicon-based particle tracking system and a five-stage scintillating energy detector has been completed. In parallel a modular software platform was developed to characterize the performance of the proposed pCT. The modular pCT software platform consists of (1) a Geant4-based simulation modeling the Loma Linda proton therapy beam line and the prototype proton CT scanner, (2) water equivalent path length (WEPL) calibration of the scintillating energy detector, and (3) image reconstruction algorithm for the reconstruction of the relative stopping power (RSP) of the scanned object. In this work, each component of the modular pCT software platform is described and validated with respect to experimental data and benchmarked against theoretical predictions. In particular, the RSP reconstruction was validated with both experimental scans, water column measurements, and theoretical calculations. The results show that the pCT software platform accurately reproduces the performance of the existing prototype pCT scanner with a RSP agreement between experimental and simulated values to better than 1.5%. The validated platform is a versatile tool for clinical proton CT performance and application studies in a virtual setting. The platform is flexible and can be modified to simulate not yet existing versions of pCT scanners and higher proton energies than those currently clinically available. © 2017 American Association of Physicists in Medicine.

Improved quantitation and reproducibility in multi-PET/CT lung studies by combining CT information.

PubMed

Holman, Beverley F; Cuplov, Vesna; Millner, Lynn; Endozo, Raymond; Maher, Toby M; Groves, Ashley M; Hutton, Brian F; Thielemans, Kris

2018-06-05

Matched attenuation maps are vital for obtaining accurate and reproducible kinetic and static parameter estimates from PET data. With increased interest in PET/CT imaging of diffuse lung diseases for assessing disease progression and treatment effectiveness, understanding the extent of the effect of respiratory motion and establishing methods for correction are becoming more important. In a previous study, we have shown that using the wrong attenuation map leads to large errors due to density mismatches in the lung, especially in dynamic PET scans. Here, we extend this work to the case where the study is sub-divided into several scans, e.g. for patient comfort, each with its own CT (cine-CT and 'snap shot' CT). A method to combine multi-CT information into a combined-CT has then been developed, which averages the CT information from each study section to produce composite CT images with the lung density more representative of that in the PET data. This combined-CT was applied to nine patients with idiopathic pulmonary fibrosis, imaged with dynamic 18 F-FDG PET/CT to determine the improvement in the precision of the parameter estimates. Using XCAT simulations, errors in the influx rate constant were found to be as high as 60% in multi-PET/CT studies. Analysis of patient data identified displacements between study sections in the time activity curves, which led to an average standard error in the estimates of the influx rate constant of 53% with conventional methods. This reduced to within 5% after use of combined-CTs for attenuation correction of the study sections. Use of combined-CTs to reconstruct the sections of a multi-PET/CT study, as opposed to using the individually acquired CTs at each study stage, produces more precise parameter estimates and may improve discrimination between diseased and normal lung.

Progressive transmission of road network

NASA Astrophysics Data System (ADS)

Ai, Bo; Ai, Tinghua; Tang, Xinming; Li, Zhen

2009-10-01

The progressive transmission of vector map data requires efficient multi-scale data model to process the data into hierarchical structure. This paper presents such a data structure of road network without redundancy of geometry for progressive transmission. For a given scale, the road network display has to settle two questions. One is which road objects to be represented and the other is what geometric details to be visualized for the selected roads. This paper combines the Töpfer law and the BLG-tree structure into a multi-scale representation matrix to answer simultaneously the above two questions. In the matrix, rows from top to bottom represent the roads in the sequence of descending classification of traffic and length, which can support the Töpfer law to retrieve the more important roads. In a row, columns record one road by a linear BLG-tree to provide good line graphics.

Does a bout of strength training affect 2,000 m rowing ergometer performance and rowing-specific maximal power 24 h later?

PubMed

Gee, Thomas I; French, Duncan N; Howatson, Glyn; Payton, Stephen J; Berger, Nicolas J; Thompson, Kevin G

2011-11-01

Rowers regularly undertake rowing training within 24 h of performing bouts of strength training; however, the effect of this practice has not been investigated. This study evaluated the impact of a bout of high-intensity strength training on 2,000 m rowing ergometer performance and rowing-specific maximal power. Eight highly trained male club rowers performed baseline measures of five separate, static squat jumps (SSJ) and countermovement jumps (CMJ), maximal rowing ergometer power strokes (PS) and a single 2,000 m rowing ergometer test (2,000 m). Subsequently, participants performed a high-intensity strength training session consisting of various multi-joint barbell exercises. The 2,000 m test was repeated at 24 and 48 h post-ST, in addition SSJ, CMJ and PS tests were performed at these time points and also at 2 h post-ST. Muscle soreness, serum creatine kinase (CK) and lactate dehydrogenase (LDH) were assessed pre-ST and 2, 24 and 48 h post-ST. Following the ST, there were significant elevations in muscle soreness (2 and 24 h, P < 0.01), CK (2, 24 and 48 h, P < 0.01), and LDH (2 h, P < 0.05) in comparison to baseline values. There were significant decrements across all time points for SSJ, CMJ and PS, which ranged between 3 and 10% (P < 0.05). However, 2,000 m performance and related measurements of heart rate and blood lactate were not significantly affected by ST. In summary, a bout of high-intensity strength training resulted in symptoms of muscle damage and decrements in rowing-specific maximal power, but this did not affect 2,000 m rowing ergometer performance in highly trained rowers.

Multi-GPU Acceleration of Branchless Distance Driven Projection and Backprojection for Clinical Helical CT.

PubMed

Mitra, Ayan; Politte, David G; Whiting, Bruce R; Williamson, Jeffrey F; O'Sullivan, Joseph A

2017-01-01

Model-based image reconstruction (MBIR) techniques have the potential to generate high quality images from noisy measurements and a small number of projections which can reduce the x-ray dose in patients. These MBIR techniques rely on projection and backprojection to refine an image estimate. One of the widely used projectors for these modern MBIR based technique is called branchless distance driven (DD) projection and backprojection. While this method produces superior quality images, the computational cost of iterative updates keeps it from being ubiquitous in clinical applications. In this paper, we provide several new parallelization ideas for concurrent execution of the DD projectors in multi-GPU systems using CUDA programming tools. We have introduced some novel schemes for dividing the projection data and image voxels over multiple GPUs to avoid runtime overhead and inter-device synchronization issues. We have also reduced the complexity of overlap calculation of the algorithm by eliminating the common projection plane and directly projecting the detector boundaries onto image voxel boundaries. To reduce the time required for calculating the overlap between the detector edges and image voxel boundaries, we have proposed a pre-accumulation technique to accumulate image intensities in perpendicular 2D image slabs (from a 3D image) before projection and after backprojection to ensure our DD kernels run faster in parallel GPU threads. For the implementation of our iterative MBIR technique we use a parallel multi-GPU version of the alternating minimization (AM) algorithm with penalized likelihood update. The time performance using our proposed reconstruction method with Siemens Sensation 16 patient scan data shows an average of 24 times speedup using a single TITAN X GPU and 74 times speedup using 3 TITAN X GPUs in parallel for combined projection and backprojection.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Persson, Mats, E-mail: mats.persson@mi.physics.kth

Purpose: The highest photon fluence rate that a computed tomography (CT) detector must be able to measure is an important parameter. The authors calculate the maximum transmitted fluence rate in a commercial CT scanner as a function of patient size for standard head, chest, and abdomen protocols. Methods: The authors scanned an anthropomorphic phantom (Kyoto Kagaku PBU-60) with the reference CT protocols provided by AAPM on a GE LightSpeed VCT scanner and noted the tube current applied with the tube current modulation (TCM) system. By rescaling this tube current using published measurements on the tube current modulation of a GEmore » scanner [N. Keat, “CT scanner automatic exposure control systems,” MHRA Evaluation Report 05016, ImPACT, London, UK, 2005], the authors could estimate the tube current that these protocols would have resulted in for other patient sizes. An ECG gated chest protocol was also simulated. Using measured dose rate profiles along the bowtie filters, the authors simulated imaging of anonymized patient images with a range of sizes on a GE VCT scanner and calculated the maximum transmitted fluence rate. In addition, the 99th and the 95th percentiles of the transmitted fluence rate distribution behind the patient are calculated and the effect of omitting projection lines passing just below the skin line is investigated. Results: The highest transmitted fluence rates on the detector for the AAPM reference protocols with centered patients are found for head images and for intermediate-sized chest images, both with a maximum of 3.4 ⋅ 10{sup 8} mm{sup −2} s{sup −1}, at 949 mm distance from the source. Miscentering the head by 50 mm downward increases the maximum transmitted fluence rate to 5.7 ⋅ 10{sup 8} mm{sup −2} s{sup −1}. The ECG gated chest protocol gives fluence rates up to 2.3 ⋅ 10{sup 8} − 3.6 ⋅ 10{sup 8} mm{sup −2} s{sup −1} depending on miscentering. Conclusions: The fluence rate on a CT detector reaches 3 ⋅ 10{sup 8} − 6 ⋅ 10{sup 8} mm{sup −2} s{sup −1} in standard imaging protocols, with the highest rates occurring for ECG gated chest and miscentered head scans. These results will be useful to developers of CT detectors, in particular photon counting detectors.« less

Multi-atlas-based CT synthesis from conventional MRI with patch-based refinement for MRI-based radiotherapy planning

NASA Astrophysics Data System (ADS)

Lee, Junghoon; Carass, Aaron; Jog, Amod; Zhao, Can; Prince, Jerry L.

2017-02-01

Accurate CT synthesis, sometimes called electron density estimation, from MRI is crucial for successful MRI-based radiotherapy planning and dose computation. Existing CT synthesis methods are able to synthesize normal tissues but are unable to accurately synthesize abnormal tissues (i.e., tumor), thus providing a suboptimal solution. We propose a multiatlas- based hybrid synthesis approach that combines multi-atlas registration and patch-based synthesis to accurately synthesize both normal and abnormal tissues. Multi-parametric atlas MR images are registered to the target MR images by multi-channel deformable registration, from which the atlas CT images are deformed and fused by locally-weighted averaging using a structural similarity measure (SSIM). Synthetic MR images are also computed from the registered atlas MRIs by using the same weights used for the CT synthesis; these are compared to the target patient MRIs allowing for the assessment of the CT synthesis fidelity. Poor synthesis regions are automatically detected based on the fidelity measure and refined by a patch-based synthesis. The proposed approach was tested on brain cancer patient data, and showed a noticeable improvement for the tumor region.

Feasibility of spectral CT imaging for the detection of liver lesions with gold-based contrast agents - A simulation study.

PubMed

Müllner, Marie; Schlattl, Helmut; Hoeschen, Christoph; Dietrich, Olaf

2015-12-01

To demonstrate the feasibility of gold-specific spectral CT imaging for the detection of liver lesions in humans at low concentrations of gold as targeted contrast agent. A Monte Carlo simulation study of spectral CT imaging with a photon-counting and energy-resolving detector (with 6 energy bins) was performed in a realistic phantom of the human abdomen. The detector energy thresholds were optimized for the detection of gold. The simulation results were reconstructed with the K-edge imaging algorithm; the reconstructed gold-specific images were filtered and evaluated with respect to signal-to-noise ratio and contrast-to-noise ratio (CNR). The simulations demonstrate the feasibility of spectral CT with CNRs of the specific gold signal between 2.7 and 4.8 after bilateral filtering. Using the optimized bin thresholds increases the CNRs of the lesions by up to 23% compared to bin thresholds described in former studies. Gold is a promising new CT contrast agent for spectral CT in humans; minimum tissue mass fractions of 0.2 wt% of gold are required for sufficient image contrast. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Monte Carlo modeling of a conventional X-ray computed tomography scanner for gel dosimetry purposes.

PubMed

Hayati, Homa; Mesbahi, Asghar; Nazarpoor, Mahmood

2016-01-01

Our purpose in the current study was to model an X-ray CT scanner with the Monte Carlo (MC) method for gel dosimetry. In this study, a conventional CT scanner with one array detector was modeled with use of the MCNPX MC code. The MC calculated photon fluence in detector arrays was used for image reconstruction of a simple water phantom as well as polyacrylamide polymer gel (PAG) used for radiation therapy. Image reconstruction was performed with the filtered back-projection method with a Hann filter and the Spline interpolation method. Using MC results, we obtained the dose-response curve for images of irradiated gel at different absorbed doses. A spatial resolution of about 2 mm was found for our simulated MC model. The MC-based CT images of the PAG gel showed a reliable increase in the CT number with increasing absorbed dose for the studied gel. Also, our results showed that the current MC model of a CT scanner can be used for further studies on the parameters that influence the usability and reliability of results, such as the photon energy spectra and exposure techniques in X-ray CT gel dosimetry.

The prevalence of lumbar spondylolysis in young children: a retrospective analysis using CT.

PubMed

Lemoine, Thibaut; Fournier, Joseph; Odent, Thierry; Sembély-Taveau, Catherine; Merenda, Pauline; Sirinelli, Dominique; Morel, Baptiste

2018-05-01

Although lumbar spondylolysis is encountered in general population with an incidence estimated to be 3-10%, limited information is available for children. The aim of the study is to determine the prevalence of spondylolysis according to associated vertebral bony malformation and spinopelvic parameters in children under eight requiring CT evaluation for unrelated lumbar conditions. Seven hundred and seventeen abdominal and pelvic multi-detector CT scans were obtained in patients under 8 years of age were reviewed. Two board certificated radiologists and two resident radiologists retrospectively evaluated CT scans for lumbar spondylolysis and associated malformations. Pelvic incidence and spondylolisthesis were reported. Our analysis included 717 CT scans in 532 children (259 girls and 273 boys). Twenty-five cases of spondylolysis were diagnosed (16 bilateral and 9 unilateral, 64 and 36%, respectively) in 14 boys (56%) and 11 girls (44%), associating with 12 grade I spondylolisthesis. The mean normal pelvic incidence was 45° (median 44°, SD 7°). The prevalence of spondylolysis was 1% in children under age 3 (n = 3 among 292 patients), 3.7% in children under age 6 (n = 17 among 454 patients) and 4.7% among the 532 patients. Unilateral spondylolysis was significantly associated with a spinal malformation (p = 0.04, Fisher's exact test), with normal pelvic incidence. Half of the patients with bilateral spondylolysis had high pelvic incidence. We observed a prevalence peak of unilateral spondylolysis in the context of a specific malformation in young infants under age 4 with normal pelvic incidence, and, then, a progressive increase in the prevalence of bilateral isolated spondylolysis.

Ultrasonography in the diagnosis of nasal bone fractures: a comparison with conventional radiography and computed tomography.

PubMed

Lee, In Sook; Lee, Jung-Hoon; Woo, Chang-Ki; Kim, Hak Jin; Sol, Yu Li; Song, Jong Woon; Cho, Kyu-Sup

2016-02-01

The purpose of this study was to evaluate and compare the diagnostic efficacy of ultrasonography (US) with radiography and multi-detector computed tomography (CT) for the detection of nasal bone fractures. Forty-one patients with a nasal bone fracture who underwent prospective US examinations were included. Plain radiographs and CT images were obtained on the day of trauma. For US examinations, radiologist used a linear array transducer (L17-5 MHz) in 24 patients and hockey-stick probe (L15-7 MHz) in 17. The bony component of the nose was divided into three parts (right and left lateral nasal walls, and midline of nasal bone). Fracture detection by three modalities was subjected to analysis. Furthermore, findings made by each modality were compared with intraoperative findings. Nasal bone fractures were located in the right lateral wall (n = 28), midline of nasal bone (n = 31), or left lateral wall (n = 31). For right and left lateral nasal walls, CT had greater sensitivity and specificity than US or radiography, and better agreed with intraoperative findings. However, for midline fractures of nasal bone, US had higher specificity, positive predictive value, and negative predictive value than CT. Although two US evaluations showed good agreements at all three sites, US findings obtained by the hockey-stick probe showed closer agreement with intraoperative findings for both lateral nasal wall and midline of nasal bone. Although CT showed higher sensitivity and specificity than US or radiography, US found to be helpful for evaluating the midline of nasal bone. Furthermore, for US examinations of the nasal bone, a smaller probe and higher frequency may be required.

Changes in entrance surface dose in relation to the location of shielding material in chest computed tomography

NASA Astrophysics Data System (ADS)

Kang, Y. M.; Cho, J. H.; Kim, S. C.

2015-07-01

This study examined the effects of entrance surface dose (ESD) on the abdomen and pelvis of the patient when undergoing chest computed tomography (CT) procedure, and evaluated the effects of ESD reduction depending on the location of radiation shield. For CT scanner, the 64-slice multi-detector computed tomography was used. The alderson radiation therapy phantom and optically stimulated luminescence dosimeter (OSLD), which enabled measurement from low to high dose, were also used. For measurement of radiation dose, the slice number from 9 to 21 of the phantom was set as the test range, which included apex up to both costophrenic angles. A total of 10 OSLD nanoDots were attached for measurement of the front and rear ESD. Cyclic tests were performed using the low-dose chest CT and high-resolution CT (HRCT) protocol on the following set-ups: without shielding; shielding only on the front side; shielding only on the rear side; and shielding for both front and rear sides. According to the test results, ESD for both front and rear sides was higher in HRCT than low-dose CT when radiation shielding was not used. It was also determined that, compared to the set-up that did not use the radiation shield, locating the radiation shield on the front side was effective in reducing front ESD, while locating the radiation shield on the rear side reduced rear ESD level. Shielding both the front and rear sides resulted in ESD reduction. In conclusion, it was confirmed that shielding the front and rear sides was the most effective method to reduce the ESD effect caused by scatter ray during radiography.

Image Reconstruction for Hybrid True-Color Micro-CT

PubMed Central

Xu, Qiong; Yu, Hengyong; Bennett, James; He, Peng; Zainon, Rafidah; Doesburg, Robert; Opie, Alex; Walsh, Mike; Shen, Haiou; Butler, Anthony; Butler, Phillip; Mou, Xuanqin; Wang, Ge

2013-01-01

X-ray micro-CT is an important imaging tool for biomedical researchers. Our group has recently proposed a hybrid “true-color” micro-CT system to improve contrast resolution with lower system cost and radiation dose. The system incorporates an energy-resolved photon-counting true-color detector into a conventional micro-CT configuration, and can be used for material decomposition. In this paper, we demonstrate an interior color-CT image reconstruction algorithm developed for this hybrid true-color micro-CT system. A compressive sensing-based statistical interior tomography method is employed to reconstruct each channel in the local spectral imaging chain, where the reconstructed global gray-scale image from the conventional imaging chain served as the initial guess. Principal component analysis was used to map the spectral reconstructions into the color space. The proposed algorithm was evaluated by numerical simulations, physical phantom experiments, and animal studies. The results confirm the merits of the proposed algorithm, and demonstrate the feasibility of the hybrid true-color micro-CT system. Additionally, a “color diffusion” phenomenon was observed whereby high-quality true-color images are produced not only inside the region of interest, but also in neighboring regions. It appears harnessing that this phenomenon could potentially reduce the color detector size for a given ROI, further reducing system cost and radiation dose. PMID:22481806

Reducing the Read Noise of HAWAII-2RG Detector Systems with Improved Reference Sampling and Subtraction (IRS2)

NASA Technical Reports Server (NTRS)

Rauscher, Bernard J.; Arendt, Richard G.; Fixsen, D. J.; Lander, Matthew; Lindler, Don; Loose, Markus; Moseley, S. H.; Wilson, Donna V.; Xenophontos, Christos

2012-01-01

IRS2 is a Wiener-optimal approach to using all of the reference information that Teledyne's HAWAII-2RG detector arrays provide. Using a new readout pattern, IRS2 regularly interleaves reference pixels with the normal pixels during readout. This differs from conventional clocking, in which the reference pixels are read out infrequently, and only in a few rows and columns around the outside edges of the detector array. During calibration, the data are processed in Fourier space, which is <;:lose to the noise's eigenspace. Using IRS2, we have reduced the read noise of the James Webb Space Telescope Near Infrared Spectrograph by 15% compared to conventional readout. We are attempting to achieve further gains by calibrating out recently recognized non-stationary noise that appears at the frame rate.

Optimization of an on-board imaging system for extremely rapid radiation therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherry Kemmerling, Erica M.; Wu, Meng, E-mail: mengwu@stanford.edu; Yang, He

2015-11-15

Purpose: Next-generation extremely rapid radiation therapy systems could mitigate the need for motion management, improve patient comfort during the treatment, and increase patient throughput for cost effectiveness. Such systems require an on-board imaging system that is competitively priced, fast, and of sufficiently high quality to allow good registration between the image taken on the day of treatment and the image taken the day of treatment planning. In this study, three different detectors for a custom on-board CT system were investigated to select the best design for integration with an extremely rapid radiation therapy system. Methods: Three different CT detectors aremore » proposed: low-resolution (all 4 × 4 mm pixels), medium-resolution (a combination of 4 × 4 mm pixels and 2 × 2 mm pixels), and high-resolution (all 1 × 1 mm pixels). An in-house program was used to generate projection images of a numerical anthropomorphic phantom and to reconstruct the projections into CT datasets, henceforth called “realistic” images. Scatter was calculated using a separate Monte Carlo simulation, and the model included an antiscatter grid and bowtie filter. Diagnostic-quality images of the phantom were generated to represent the patient scan at the time of treatment planning. Commercial deformable registration software was used to register the diagnostic-quality scan to images produced by the various on-board detector configurations. The deformation fields were compared against a “gold standard” deformation field generated by registering initial and deformed images of the numerical phantoms that were used to make the diagnostic and treatment-day images. Registrations of on-board imaging system data were judged by the amount their deformation fields differed from the corresponding gold standard deformation fields—the smaller the difference, the better the system. To evaluate the registrations, the pointwise distance between gold standard and realistic registration deformation fields was computed. Results: By most global metrics (e.g., mean, median, and maximum pointwise distance), the high-resolution detector had the best performance but the medium-resolution detector was comparable. For all medium- and high-resolution detector registrations, mean error between the realistic and gold standard deformation fields was less than 4 mm. By pointwise metrics (e.g., tracking a small lesion), the high- and medium-resolution detectors performed similarly. For these detectors, the smallest error between the realistic and gold standard registrations was 0.6 mm and the largest error was 3.6 mm. Conclusions: The medium-resolution CT detector was selected as the best for an extremely rapid radiation therapy system. In essentially all test cases, data from this detector produced a significantly better registration than data from the low-resolution detector and a comparable registration to data from the high-resolution detector. The medium-resolution detector provides an appropriate compromise between registration accuracy and system cost.« less

A new scanning device in CT with dose reduction potential

NASA Astrophysics Data System (ADS)

Tischenko, Oleg; Xu, Yuan; Hoeschen, Christoph

2006-03-01

The amount of x-ray radiation currently applied in CT practice is not utilized optimally. A portion of radiation traversing the patient is either not detected at all or is used ineffectively. The reason lies partly in the reconstruction algorithms and partly in the geometry of the CT scanners designed specifically for these algorithms. In fact, the reconstruction methods widely used in CT are intended to invert the data that correspond to ideal straight lines. However, the collection of such data is often not accurate due to likely movement of the source/detector system of the scanner in the time interval during which all the detectors are read. In this paper, a new design of the scanner geometry is proposed that is immune to the movement of the CT system and will collect all radiation traversing the patient. The proposed scanning design has a potential to reduce the patient dose by a factor of two. Furthermore, it can be used with the existing reconstruction algorithm and it is particularly suitable for OPED, a new robust reconstruction algorithm.