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Sample records for high ct numbers

  1. Bronchogenic cysts with high CT numbers

    SciTech Connect

    Mendelson, D.S.; Rose, J.S.; Efremidis, S.C.; Kirschner, P.A.; Cohen, B.A.

    1983-03-01

    Four patients with mediastinal masses are described. CT examinations demonstrated masses of high attenuation, and solid masses were suspected. At thoracotomy each patient had a cystic mass containing a brownish, turbid, mucoid material. The pathologic diagnosis in each case was a bronchogenic cyst. The possibility of such a cyst should not be excluded because of a high CT number, which reflects the turbid contents of the cyst.

  2. CT number definition

    NASA Astrophysics Data System (ADS)

    Bryant, J. A.; Drage, N. A.; Richmond, S.

    2012-04-01

    The accuracy of CT number plots has been found lacking in several medical applications. This is of concern since the ability to compare and evaluate results on a reproducible and standard basis is essential to long term development. Apart from the technical limitations arising from the CT scanner and the data treatment, there are fundamental issues with the definition of the Hounsfield number, namely the absence of a standard photon energy and the need to specify the attenuation mechanism for standard measurements. This paper presents calculations to demonstrate the shortcomings of the present definition with a brief discussion. The remedy is straightforward, but probably of long duration as it would require an international agreement.

  3. Ion Stopping Powers and CT Numbers

    SciTech Connect

    Moyers, Michael F.; Sardesai, Milind; Sun, Sean; Miller, Daniel W.

    2010-10-01

    One of the advantages of ion beam therapy is the steep dose gradient produced near the ion's range. Use of this advantage makes knowledge of the stopping powers for all materials through which the beam passes critical. Most treatment planning systems calculate dose distributions using depth dose data measured in water and an algorithm that converts the kilovoltage X-ray computed tomography (CT) number of a given material to its linear stopping power relative to water. Some materials present in kilovoltage scans of patients and simulation phantoms do not lie on the standard tissue conversion curve. The relative linear stopping powers (RLSPs) of 21 different tissue substitutes and positioning, registration, immobilization, and beamline materials were measured in beams of protons accelerated to energies of 155, 200, and 250 MeV; carbon ions accelerated to 290 MeV/n; and iron ions accelerated to 970 MeV/n. These same materials were scanned with both kilovoltage and megavoltage CT scanners to obtain their CT numbers. Measured RLSPs and CT numbers were compared with calculated and/or literature values. Relationships of RLSPs to physical densities, electronic densities, kilovoltage CT numbers, megavoltage CT numbers, and water equivalence values converted by a treatment planning system are given. Usage of CT numbers and substitution of measured values into treatment plans to provide accurate patient and phantom simulations are discussed.

  4. Energy Dependence of Measured CT Numbers on Substituted Materials Used for CT Number Calibration of Radiotherapy Treatment Planning Systems

    PubMed Central

    Mahmoudi, Reza; Jabbari, Nasrollah; aghdasi, Mehdi; Khalkhali, Hamid Reza

    2016-01-01

    Introduction For accurate dose calculations, it is necessary to provide a correct relationship between the CT numbers and electron density in radiotherapy treatment planning systems (TPSs). The purpose of this study was to investigate the energy dependence of measured CT numbers on substituted materials used for CT number calibration of radiotherapy TPSs and the resulting errors in the treatment planning calculation doses. Materials and Methods In this study, we designed a cylindrical water phantom with different materials used as tissue equivalent materials for the simulation of tissues and obtaining the related CT numbers. For evaluating the effect of CT number variations of substituted materials due to energy changing of scanner (kVp) on the dose calculation of TPS, the slices of the scanned phantom at three kVp's were imported into the desired TPSs (MIRS and CorePLAN). Dose calculations were performed on two TPSs. Results The mean absolute percentage differences between the CT numbers of CT scanner and two treatment planning systems for all the samples were 3.22%±2.57% for CorePLAN and 2.88%±2.11% for MIRS. It was also found that the maximum absolute percentage difference between all of the calculated doses from each photon beam of linac (6 and 15 MV) at three kVp's was less than 1.2%. Discussion The present study revealed that, for the materials with effective low atomic number, the mean CT number increased with increasing energy, which was opposite for the materials with an effective high atomic number. We concluded that the tissue substitute materials had a different behavior in the energy ranges from 80 to 130 kVp. So, it is necessary to consider the energy dependence of the substitute materials used for the measurement or calibration of CT number for radiotherapy treatment planning systems. PMID:27391672

  5. Fabrication and control of CT number through polymeric composites based on coronary plaque CT phantom applications

    PubMed Central

    Hoy, Carlton F. O.; Naguib, Hani E.; Paul, Narinder

    2016-01-01

    Abstract. Biomedical phantoms are commonly used for various medical imaging modalities to improve imaging quality and procedures. Current biomedical phantoms fabricated commercially are high in cost and limited in the specificity of human environments and structures that can be mimicked. This study aimed to control the measurable computed tomography (CT) number in Hounsfield units through polymeric biomedical phantom materials using controlled amounts of hydroxyapatite (hA). The purpose was to fabricate CT phantoms capable of mimicking various coronary plaque types while introducing a fabrication technique and basis for a numerical model to which the technique may be applied. The CT number is tunable based on the controlled material properties of electron density and atomic numbers. Three different polymeric matrices of polyethylene (PE), thermoplastic polyurethane (TPU), and polyvinylidene fluoride (PVDF) were selected due to their varied specific densities and ease of fabrication acting as integral properties for CT phantom fabrication. These polymers were processed together with additions of hA in mass percentages of 2.5, 5, 10, and 20% hA as well as a 0% hA as a control for each polymeric material. By adding hA to PE, TPU, and PVDF an increasing trend was exhibited between CT number and weight percent of hA. PMID:26958580

  6. Fabrication and control of CT number through polymeric composites based on coronary plaque CT phantom applications.

    PubMed

    Hoy, Carlton F O; Naguib, Hani E; Paul, Narinder

    2016-01-01

    Biomedical phantoms are commonly used for various medical imaging modalities to improve imaging quality and procedures. Current biomedical phantoms fabricated commercially are high in cost and limited in the specificity of human environments and structures that can be mimicked. This study aimed to control the measurable computed tomography (CT) number in Hounsfield units through polymeric biomedical phantom materials using controlled amounts of hydroxyapatite (hA). The purpose was to fabricate CT phantoms capable of mimicking various coronary plaque types while introducing a fabrication technique and basis for a numerical model to which the technique may be applied. The CT number is tunable based on the controlled material properties of electron density and atomic numbers. Three different polymeric matrices of polyethylene (PE), thermoplastic polyurethane (TPU), and polyvinylidene fluoride (PVDF) were selected due to their varied specific densities and ease of fabrication acting as integral properties for CT phantom fabrication. These polymers were processed together with additions of hA in mass percentages of 2.5, 5, 10, and 20% hA as well as a 0% hA as a control for each polymeric material. By adding hA to PE, TPU, and PVDF an increasing trend was exhibited between CT number and weight percent of hA.

  7. Diagnostic value of CT numbers in pelvocalyceal flling defects

    SciTech Connect

    Parienty, R.A.; Ducellier, R.; Pradel, J.; Lubrano, J.M.; Coquille, F.; Francois, R.

    1982-12-01

    Thirty-seven patients, found to have a nonopaque pelvocalyceal filling defect on excretory urograhy, were shown to have an intrapelvic mass on computed tomography (CT). There were 20 nonopaque stones, 14 cases of transitionalcell carcinoma, 1 benign papilloma, and 2 blood clots. All had a sufficiently specific range of CT numbers and differences in contrast enhancement to allow the correct diagnosis on plain CT scans, or, if necessary, a dynamic CT study following a rapid intravenous bolus of contrast medium.

  8. Dual source CT (DSCT) imaging of obese patients: evaluation of CT number accuracy, uniformity, and noise

    NASA Astrophysics Data System (ADS)

    Walz-Flannigan, A.; Schmidt, B.,; Apel, A.; Eusemann, C.; Yu, L.; McCollough, C. H.

    2009-02-01

    Obese patients present challenges in obtaining sufficient x-ray exposure over reasonable time periods for acceptable CT image quality. To overcome this limitation, the exposure can be divided between two x-ray sources using a dualsource (DS) CT system. However, cross-scatter issues in DS CT may also compromise image quality. We evaluated a DS CT system optimized for imaging obese patients, comparing the CT number accuracy and uniformity to the same images obtained with a single-source (SS) acquisition. The imaging modes were compared using both solid cylindrical PMMA phantoms and a semi-anthropomorphic thorax phantom fitted with extension rings to simulate different size patients. Clinical protocols were used and CTDIvol and kVp were held constant between SS and DS modes. Results demonstrated good agreement in CT number between SS and DS modes in CT number, with the DS mode showing better axial uniformity for the largest phantoms.

  9. Thyroid CT number and its relationship to iodine concentration

    SciTech Connect

    Iida, Y.; Konishi, J.; Harioka, T.; Misaki, T.; Endo, K.; Torizuka, K.

    1983-06-01

    Sixty-seven patients with thyroid disease and 24 normal controls were examined with computed tomography (CT). The mean CT number (Hounsfield units +/- SD) in the normal controls (118.1 +/- 12.2) was significantly higher (p < 0.001) than the mean CT number in patients with diseased thyroids, except for 2 cases of simple goiter (CT numbers 113, 132). The Graves disease (69.5 +/- 17.6) amd Hishimoto thyroiditis (61.4 +/- 9.1) were significaantly higher than those in patients with adenoma (41.7 +/- 10.6, p < 0.001), cyst (33.1 +/- 14.8, p < 0.001), or cancer (48.7 +/- 13, p < 0.01). In 14 patients studied, a significant correlation was observed between thyroid CT numbers and the iodine concentration of the tissue (r = 0.889; p < 0.001).

  10. 78 FR 7848 - Connecticut Disaster Number CT-00028

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-04

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Connecticut Disaster Number CT-00028 AGENCY: U.S. Small Business Administration. ACTION: Amendment...: U.S. Small Business Administration, Processing and Disbursement Center, 14925 Kingsport Road,...

  11. High Reynolds Number Research

    NASA Technical Reports Server (NTRS)

    Baals, D. D. (Editor)

    1977-01-01

    Fundamental aerodynamic questions for which high Reynolds number experimental capability is required are discussed. The operational characteristics and design features of the National Transonic Facility are reviewed.

  12. 76 FR 58329 - Connecticut Disaster Number CT-00024

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-20

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Connecticut Disaster Number CT-00024 AGENCY: U.S. Small Business Administration. ACTION: Amendment.... (Catalog of Federal Domestic Assistance Numbers 59002 and 59008) James E. Rivera, Associate Administrator...

  13. 76 FR 58559 - Connecticut Disaster Number CT-00023

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-21

    ... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Connecticut Disaster Number CT-00023 AGENCY: U.S. Small Business Administration. ACTION: Amendment... Assistance Numbers 59002 and 59008) James E. Rivera, Associate Administrator for Disaster Assistance. BILLING...

  14. Imaging properties of gold nanoparticles: CT number dependence study

    NASA Astrophysics Data System (ADS)

    Tu, Shu-Ju; Hsieh, Hui-Ling; Chao, Tsi-Chian

    2010-04-01

    In recent years, there has been a rapid research progress of molecular imaging technology. Many investigations in molecular imaging such as the nanoparticle applications in targeted drug delivery have been widely studied in several key small animal models. Various nanoparticles used as either the drug delivery carriers, imaging contrast mediums or target-specific therapeutic agents have established a novel research platform for biomedical related scientists and clinicians. Among these nanoparticles, gold nanoparticles have the unique non-toxic and stability properties. In this work, a commercially-available micro CT imaging system was used to specifically study the imaging properties for 15 nm spherical-shaped gold particles. Imaging properties were quantified by the CT numbers obtained from a series of photon energy levels in the micro CT scanner. We also compared the imaging results between gold nanoparticles and iodinated contrast medium to study the potential impact of gold nanoparticles served as the contrast agent.

  15. [Development of the QA/QC-tools for CT number calibration of the treatment planning CT-scanner.].

    PubMed

    Kusano, Yohsuke; Minohara, Shinichi; Ishii, Takayoshi; Fujimori, Kengo; Ikeda, Noritoshi; Kondo, Takanori; Tubuku, Hideo; Ito, Atsushi; Uchida, Hirohisa

    2006-01-01

    In order to support a routine QA of the CT number for treatment planning, we developed a phantom and a sample holder for easy handling. At most particle radiotherapy facilities in Japan, the CT number is calibrated by the poly-binary calibration method using liquid samples of 100% ethanol and 40% K(2)HPO(4) which are set in a cylindrical water phantom. However it is hard to remove air bubbles from the calibration liquid sample and maintain its stable concentration for a long time. So much time is needed for QA of the CT number. The new sample holder, which we developed, was able to keep a stable concentration of the liquid for more than 300 days. Consequently, the CT number of each sample, which was set in a water equivalent solid phantom, was the same as the CT number in a water phantom within 7 HU. In addition, we developed software which could measure the CT number of each sample semi-automatically and could calculate the calibration coefficients between the CT number and water equivalent length (WEL). Using this software, we could check the calibration result instantly at the time of CT data acquisition. These tools should be useful to carry out calibration of the CT-WEL routinely in a short time.

  16. High Reynolds Number Turbulence

    DTIC Science & Technology

    2007-03-27

    wall relation of McKeon et al. (2005), and the results for the smallest sandgrain roughness used by Nikuradse (1933). 3 57xI03 "eI : uhp - 2 8 1 6 8 x l 0...Reynolds Number Turbulent Pipe Flow," ASME International Mechanical Engineering Conference and Exposition, Washington, D.C., November 16-21, 2003... Engineering Sciences, Vol. 365 (1852) pp. 699-714, 2007. 14 ’Pipe flow roughness Allen, J.J., Shockling, M.A. and Smits, A.J. "Effects of a machined rough

  17. TU-F-18A-09: CT Number Stability Across Patient Sizes Using Virtual-Monoenergetic Dual-Energy CT

    SciTech Connect

    Michalak, G; Grimes, J; Fletcher, J; McCollough, C; Halaweish, A

    2014-06-15

    Purpose: Virtual-monoenergetic imaging uses dual-energy CT data to synthesize images corresponding to a single photon energy, thereby reducing beam-hardening artifacts. This work evaluated the ability of a commercial virtual-monoenergetic algorithm to achieve stable CT numbers across patient sizes. Methods: Test objects containing a range of iodine and calcium hydroxyapatite concentrations were placed inside 8 torso-shaped water phantoms, ranging in lateral width from 15 to 50 cm, and scanned on a dual-source CT system (Siemens Somatom Force). Single-energy scans were acquired from 70-150 kV in 10 kV increments; dual-energy scans were acquired using 4 energy pairs (low energy: 70, 80, 90, and 100 kV; high energy: 150 kV + 0.6 mm Sn). CTDIvol was matched for all single- and dual-energy scans for a given phantom size. All scans used 128×0.6 mm collimation and were reconstructed with 1-mm thickness at 0.8-mm increment and a medium smooth body kernel. Monoenergetic images were generated using commercial software (syngo Via Dual Energy, VA30). Iodine contrast was calculated as the difference in mean iodine and water CT numbers from respective regions-of-interest in 10 consecutive images. Results: CT numbers remained stable as phantom width varied from 15 to 50 cm for all dual-energy data sets (except for at 50 cm using 70/150Sn due to photon starvation effects). Relative to the 15 cm phantom, iodine contrast was within 5.2% of the 70 keV value for phantom sizes up to 45 cm. At 90/150Sn, photon starvation did not occur at 50 cm, and iodine contrast in the 50-cm phantom was within 1.4% of the 15-cm phantom. Conclusion: Monoenergetic imaging, as implemented in the evaluated commercial system, eliminated the variation in CT numbers due to patient size, and may provide more accurate data for quantitative tasks, including radiation therapy treatment planning. Siemens Healthcare.

  18. Patient specific respiratory motion modeling using a limited number of 3D lung CT images.

    PubMed

    Cui, Xueli; Gao, Xin; Xia, Wei; Liu, Yangchuan; Liang, Zhiyuan

    2014-01-01

    To build a patient specific respiratory motion model with a low dose, a novel method was proposed that uses a limited number of 3D lung CT volumes with an external respiratory signal. 4D lung CT volumes were acquired for patients with in vitro labeling on the upper abdominal surface. Meanwhile, 3D coordinates of in vitro labeling were measured as external respiratory signals. A sequential correspondence between the 4D lung CT and the external respiratory signal was built using the distance correlation method, and a 3D displacement for every registration control point in the CT volumes with respect to time can be obtained by the 4D lung CT deformable registration. A temporal fitting was performed for every registration control point displacements and an external respiratory signal in the anterior-posterior direction respectively to draw their fitting curves. Finally, a linear regression was used to fit the corresponding samples of the control point displacement fitting curves and the external respiratory signal fitting curve to finish the pulmonary respiration modeling. Compared to a B-spline-based method using the respiratory signal phase, the proposed method is highly advantageous as it offers comparable modeling accuracy and target modeling error (TME); while at the same time, the proposed method requires 70% less 3D lung CTs. When using a similar amount of 3D lung CT data, the mean of the proposed method's TME is smaller than the mean of the PCA (principle component analysis)-based methods' TMEs. The results indicate that the proposed method is successful in striking a balance between modeling accuracy and number of 3D lung CT volumes.

  19. High resolution extremity CT for biomechanics modeling

    SciTech Connect

    Ashby, A.E.; Brand, H.; Hollerbach, K.; Logan, C.M.; Martz, H.E.

    1995-09-23

    With the advent of ever more powerful computing and finite element analysis (FEA) capabilities, the bone and joint geometry detail available from either commercial surface definitions or from medical CT scans is inadequate. For dynamic FEA modeling of joints, precise articular contours are necessary to get appropriate contact definition. In this project, a fresh cadaver extremity was suspended in parafin in a lucite cylinder and then scanned with an industrial CT system to generate a high resolution data set for use in biomechanics modeling.

  20. Accuracies of the synthesized monochromatic CT numbers and effective atomic numbers obtained with a rapid kVp switching dual energy CT scanner

    SciTech Connect

    Goodsitt, Mitchell M.; Christodoulou, Emmanuel G.; Larson, Sandra C.

    2011-04-15

    Purpose: This study was performed to investigate the accuracies of the synthesized monochromatic images and effective atomic number maps obtained with the new GE Discovery CT750 HD CT scanner. Methods: A Gammex-RMI model 467 tissue characterization phantom and the CT number linearity section of a Phantom Laboratory Catphan 600 phantom were scanned using the dual energy (DE) feature on the GE CT750 HD scanner. Synthesized monochromatic images at various energies between 40 and 120 keV and effective atomic number (Z{sub eff}) maps were generated. Regions of interest were placed within these images/maps to measure the average monochromatic CT numbers and average Z{sub eff} of the materials within these phantoms. The true Z{sub eff} values were either supplied by the phantom manufacturer or computed using Mayneord's equation. The linear attenuation coefficients for the true CT numbers were computed using the NIST XCOM program with the input of manufacturer supplied elemental compositions and densities. The effects of small variations in the assumed true densities of the materials were also investigated. Finally, the effect of body size on the accuracies of the synthesized monochromatic CT numbers was investigated using a custom lumbar section phantom with and without an external fat-mimicking ring. Results: Other than the Z{sub eff} of the simulated lung inserts in the tissue characterization phantom, which could not be measured by DECT, the Z{sub eff} values of all of the other materials in the tissue characterization and Catphan phantoms were accurate to 15%. The accuracies of the synthesized monochromatic CT numbers of the materials in both phantoms varied with energy and material. For the 40-120 keV range, RMS errors between the measured and true CT numbers in the Catphan are 8-25 HU when the true CT numbers were computed using the nominal plastic densities. These RMS errors improve to 3-12 HU for assumed true densities within the nominal density {+-}0.02 g

  1. Technical Note: Improved CT number stability across patient size using dual-energy CT virtual monoenergetic imaging

    SciTech Connect

    Michalak, Gregory; Grimes, Joshua; Fletcher, Joel; Yu, Lifeng; Leng, Shuai; McCollough, Cynthia; Halaweish, Ahmed

    2016-01-15

    Purpose: The purpose of this study was to evaluate, over a wide range of phantom sizes, CT number stability achieved using two techniques for generating dual-energy computed tomography (DECT) virtual monoenergetic images. Methods: Water phantoms ranging in lateral diameter from 15 to 50 cm and containing a CT number test object were scanned on a DSCT scanner using both single-energy (SE) and dual-energy (DE) techniques. The SE tube potentials were 70, 80, 90, 100, 110, 120, 130, 140, and 150 kV; the DE tube potential pairs were 80/140, 70/150Sn, 80/150Sn, 90/150Sn, and 100/150Sn kV (Sn denotes that the 150 kV beam was filtered with a 0.6 mm tin filter). Virtual monoenergetic images at energies ranging from 40 to 140 keV were produced from the DECT data using two algorithms, monoenergetic (mono) and monoenergetic plus (mono+). Particularly in large phantoms, water CT number errors and/or artifacts were observed; thus, datasets with water CT numbers outside ±10 HU or with noticeable artifacts were excluded from the study. CT numbers were measured to determine CT number stability across all phantom sizes. Results: Data exclusions were generally limited to cases when a SE or DE technique with a tube potential of less than 90 kV was used to scan a phantom larger than 30 cm. The 90/150Sn DE technique provided the most accurate water background over the large range of phantom sizes evaluated. Mono and mono+ provided equally improved CT number stability as a function of phantom size compared to SE; the average deviation in CT number was only 1.4% using 40 keV and 1.8% using 70 keV, while SE had an average deviation of 11.8%. Conclusions: The authors’ report demonstrates, across all phantom sizes, the improvement in CT number stability achieved with mono and mono+ relative to SE.

  2. Influence of age and position on the CT number of adipose tissues in pigs.

    PubMed

    McEvoy, Fintan J; Madsen, Mads T; Svalastoga, Eiliv L

    2008-10-01

    The location of adipose tissue depots is important in determining their significance. Research into the physical and chemical differences between these depots is therefore of interest. Using image analysis, this paper examines the influence of location on the linear attenuation coefficient of adipose tissue for X-rays, in computed tomography (as indicated by CT number) at three time points. Nine pigs were CT scanned on three separate occasions approximately 1 month apart. The mean CT number was -78, -100, and -104 for visceral adipose tissue (VAT) from the first to the final scan, respectively. The corresponding CT numbers for subcutaneous adipose tissue (SAT) were -80, -101, and -106. There was a significant difference between the CT numbers at each location at each scan (P values from 0.025 to <0.001) and between the CT numbers for each location at different times (P < 0.05). In a separate analysis of the final scan session, the mean CT number of adipose tissue at increasing distances from a mathematically defined center of the animal was determined. Regression analysis showed that the CT number of adipose tissue decreases with increasing distance from the animal's center (y = -102.7 - 0.04 x, P < 0.001, where y is the predicted CT number for adipose tissue, from the animal center (x = 0) to the skin (x = 100)). It can thus be expected that the overall mean CT number for adipose tissue can be used as an indicator of the relative quantities of adipose tissue at each location if the mean for each is known.

  3. High Reynolds number research - 1980

    NASA Technical Reports Server (NTRS)

    Mckinney, L. W. (Editor); Baals, D. D. (Editor)

    1981-01-01

    The fundamental aerodynamic questions for which high Reynolds number experimental capability is required were examined. Potential experiments which maximize the research returns from the use of the National Transonic Facility (NTF) were outlined. Calibration plans were reviewed and the following topics were discussed: fluid dynamics; high lit; configuration aerodynamics; aeroelasticity and unsteady aerodynamics; wind tunnel/flight correlation; space vehicles; and theoretical aerodynamics

  4. Influence of anatomical location on CT numbers in cone beam computed tomography.

    PubMed

    Oliveira, Matheus L; Tosoni, Guilherme M; Lindsey, David H; Mendoza, Kristopher; Tetradis, Sotirios; Mallya, Sanjay M

    2013-04-01

    To assess the influence of anatomical location on computed tomography (CT) numbers in mid- and full field of view (FOV) cone beam computed tomography (CBCT) scans. Polypropylene tubes with varying concentrations of dipotassium hydrogen phosphate (K₂HPO₄) solutions (50-1200 mg/mL) were imaged within the incisor, premolar, and molar dental sockets of a human skull phantom. CBCT scans were acquired using the NewTom 3G and NewTom 5G units. The CT numbers of the K₂HPO₄ phantoms were measured, and the relationship between CT numbers and K₂HPO₄ concentration was examined. The measured CT numbers of the K₂HPO₄ phantoms were compared between anatomical sites. At all six anatomical locations, there was a strong linear relationship between CT numbers and K₂HPO₄ concentration (R(2)>0.93). However, the absolute CT numbers varied considerably with the anatomical location. The relationship between CT numbers and object density is not uniform through the dental arch on CBCT scans. Copyright © 2013 Elsevier Inc. All rights reserved.

  5. How to measure CT image quality: variations in CT-numbers, uniformity and low contrast resolution for a CT quality assurance phantom.

    PubMed

    Gulliksrud, Kristine; Stokke, Caroline; Martinsen, Anne Catrine Trægde

    2014-06-01

    Quality assurance (QA) phantoms for testing different image quality parameters in computed tomography (CT) are commercially available. Such phantoms are also used as reference for acceptance in the specifications of CT-scanners. The aim of this study was to analyze the characteristics of the most commonly used QA phantom in CT: Catphan 500/504/600. Nine different phantoms were scanned on the same day, on one CT-scanner with the same parameter settings. Interphantom variations in CT-number values, image uniformity and low contrast resolution were evaluated for the phantoms. Comparisons between manual image analysis and results obtained from the automatic evaluation software QAlite were performed. Some interphantom variations were observed in the low contrast resolution and the CT-number modules of the phantoms. Depending on the chosen regulatory framework, the variations in CT-numbers can be interpreted as substantial. The homogenous modules were found more invariable. However, the automatic image analysis software QAlite measures image uniformity differently than recommended in international standards, and will not necessarily give results in agreement with these standards. It is important to consider the interphantom variations in relation to ones framework, and to be aware of which phantom is used to study CT-numbers and low contrast resolution for a specific scanner. Comparisons with predicted values from manual and acceptance values should be performed with care and consideration. If automatic software-based evaluations are to be used, users should be aware that large differences can exist for the image uniformity testing. Copyright © 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  6. High resolution CT of Meckel's cave.

    PubMed

    Chui, M; Tucker, W; Hudson, A; Bayer, N

    1985-01-01

    High resolution CT of the parasellar region was carried out in 50 patients studied for suspected pituitary microadenoma, but who showed normal pituitary gland or microadenoma on CT. This control group of patients all showed an ellipsoid low-density area in the posterior parasellar region. Knowledge of the gross anatomy and correlation with metrizamide cisternography suggest that the low density region represents Meckel's cave, rather than just the trigeminal ganglion alone. Though there is considerable variation in the size of Meckel's cave in different patients as well as the two sides of the same patient, the rather constant ellipsoid configuration of the cave in normal subjects will aid in diagnosing small pathological lesions, thereby obviating more invasive cisternography via the transovale or lumbar route. Patients with "idiopathic" tic douloureux do not show a Meckel's cave significantly different from the control group.

  7. Detection of increased vasa vasorum in artery walls: improving CT number accuracy using image deconvolution

    NASA Astrophysics Data System (ADS)

    Rajendran, Kishore; Leng, Shuai; Jorgensen, Steven M.; Abdurakhimova, Dilbar; Ritman, Erik L.; McCollough, Cynthia H.

    2017-03-01

    Changes in arterial wall perfusion are an indicator of early atherosclerosis. This is characterized by an increased spatial density of vasa vasorum (VV), the micro-vessels that supply oxygen and nutrients to the arterial wall. Detection of increased VV during contrast-enhanced computed tomography (CT) imaging is limited due to contamination from blooming effect from the contrast-enhanced lumen. We report the application of an image deconvolution technique using a measured system point-spread function, on CT data obtained from a photon-counting CT system to reduce blooming and to improve the CT number accuracy of arterial wall, which enhances detection of increased VV. A phantom study was performed to assess the accuracy of the deconvolution technique. A porcine model was created with enhanced VV in one carotid artery; the other carotid artery served as a control. CT images at an energy range of 25-120 keV were reconstructed. CT numbers were measured for multiple locations in the carotid walls and for multiple time points, pre and post contrast injection. The mean CT number in the carotid wall was compared between the left (increased VV) and right (control) carotid arteries. Prior to deconvolution, results showed similar mean CT numbers in the left and right carotid wall due to the contamination from blooming effect, limiting the detection of increased VV in the left carotid artery. After deconvolution, the mean CT number difference between the left and right carotid arteries was substantially increased at all the time points, enabling detection of the increased VV in the artery wall.

  8. Quasiperpendicular High Mach Number Shocks

    NASA Astrophysics Data System (ADS)

    Sulaiman, A. H.; Masters, A.; Dougherty, M. K.; Burgess, D.; Fujimoto, M.; Hospodarsky, G. B.

    2015-09-01

    Shock waves exist throughout the Universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this Letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasiperpendicular shocks across 2 orders of magnitude in Alfvén Mach number (MA ) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted time scale of ˜0.3 τc , where τc is the ion gyroperiod. In addition, we experimentally reveal the relationship between reformation and MA and focus on the magnetic structure of such shocks to further show that for the same MA , a reforming shock exhibits stronger magnetic field amplification than a shock that is not reforming.

  9. Quasiperpendicular High Mach Number Shocks.

    PubMed

    Sulaiman, A H; Masters, A; Dougherty, M K; Burgess, D; Fujimoto, M; Hospodarsky, G B

    2015-09-18

    Shock waves exist throughout the Universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this Letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasiperpendicular shocks across 2 orders of magnitude in Alfvén Mach number (M_{A}) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted time scale of ~0.3τ_{c}, where τ_{c} is the ion gyroperiod. In addition, we experimentally reveal the relationship between reformation and M_{A} and focus on the magnetic structure of such shocks to further show that for the same M_{A}, a reforming shock exhibits stronger magnetic field amplification than a shock that is not reforming.

  10. Computation of CT-number and Z(eff) in teeth.

    PubMed

    Manjunatha, H C; Rudraswamy, B

    2011-05-01

    Computerized tomography (CT) number (it is a normalized value of the x ray absorption coefficient of a pixel in a computed tomogram) and the effective atomic number (Z(eff)) of teeth [enamel outer surface (EOS), enamel middle (EM), enamel dentin junction towards enamel (EDJE), enamel dentin junction towards dentin (EDJD), dentin middle (DM), and dentin inner surface (DIS)] have been calculated for photon interactions by a direct method in the energy range of 1 keV-100 GeV using the computer program, WinXCOM. The sum of the computed values are tabulated. The estimated CT numbers are tabulated. All of the selected materials show an almost constant Z(eff) value in the energy range 500 keV to 1.5 MeV. Also, it is expected that the computed CT numbers are useful in medical diagnosis. Dosimetric implication of mass attenuation coefficient in teeth has also been discussed.

  11. Turbulent Skin Friction at High Mach Numbers and Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Matting, Fred W.; Chapman, Dean R.

    1958-01-01

    For a number of years now, experimenters have been making measurements of skin friction. Formerly, the main interest was at low Mach numbers; later, measurements were made at supersonic Mach numbers. However, almost all of these measurements were over a limited range of Reynolds numbers. On the other hand, these measurements fairly well determined the effects of Mach number and heat transfer on skin friction. The purpose of this paper is to give the results of skin-friction measurements in turbulent boundary layers at high Mach numbers and high Reynolds numbers where data have not previously existed. The equipment used was expressly designed to provide these conditions. As is well known, it is difficult to obtain high Mach numbers and high Reynolds numbers simultaneously with air in a wind tunnel. In order to avoid condensation, it is necessary to heat the air, with a resulting loss in density and Reynolds number. It is desirable, then, to use a gas that does not condense at high Mach numbers. This suggested helium, which was used as a working fluid in some of the tests. At high Mach numbers in a given wind tunnel, higher Reynolds numbers can be obtained with helium than with air, principally because no heating of the helium is required. The different ratios of specific heats also contribute to the increase. In using helium as a working fluid, it is, of course, necessary to determine the equivalence of air and helium in the turbulent boundary layer.

  12. CT Hounsfield Numbers of Soft Tissues on Unenhanced Abdominal CT Scans: Variability Between Two Different Manufacturers’ MDCT Scanners

    PubMed Central

    Lamba, Ramit; McGahan, John P.; Corwin, Michael T.; Li, Chin-Shang; Tran, Tien; Seibert, J. Anthony; Boone, John M.

    2016-01-01

    OBJECTIVE The purpose of this study is to determine whether Hounsfield numbers of soft tissues on unenhanced abdominal CT of the same patient vary on repeat scans done on two different manufacturers’ MDCT scanners. MATERIALS AND METHODS A database search was performed to identify patients older than 18 years who underwent unenhanced CT of the abdomen and pelvis performed both on a Volume CT (GE Healthcare) and a Definition AS Plus (Siemens Healthcare) 64-MDCT scanner within 12 months of each other. After excluding those patients for whom Hounsfield unit measurements would be affected by mitigating factors, 48 patients (mean age, 58.8 years) were identified. Hounsfield unit measurements were obtained in nine different soft-tissue anatomic locations on each scan, and the location of these sites was kept identical on each scan pair. Data were analyzed to evaluate Hounsfield unit differences between these scanners. RESULTS In general, there was a low consistency in the Hounsfield unit measurements for each of these sites on scans obtained by the two scanners, with the subcutaneous fat in the left posterolateral flank showing the lowest correlation (intraclass correlation coefficient, 0.198). There were differences in the Hounsfield unit measurements obtained in all anatomic sites on scans obtained by both scanners. Mean Hounsfield unit measurements obtained on the Definition AS Plus scanner were lower than those obtained on the Volume CT scanner, with the intriguing exception of the anterior midline subcutaneous fat Hounsfield unit measurements, which were higher on the Definition AS Plus scanner. All differences were statistically significant (p < 0.05). CONCLUSION Hounsfield unit measurements for unenhanced abdominal soft tissues of the same patient vary between scanners of two common MDCT manufacturers. PMID:25341139

  13. CT Hounsfield numbers of soft tissues on unenhanced abdominal CT scans: variability between two different manufacturers' MDCT scanners.

    PubMed

    Lamba, Ramit; McGahan, John P; Corwin, Michael T; Li, Chin-Shang; Tran, Tien; Seibert, J Anthony; Boone, John M

    2014-11-01

    The purpose of this study is to determine whether Hounsfield numbers of soft tissues on unenhanced abdominal CT of the same patient vary on repeat scans done on two different manufacturers' MDCT scanners. A database search was performed to identify patients older than 18 years who underwent unenhanced CT of the abdomen and pelvis performed both on a Volume CT (GE Healthcare) and a Definition AS Plus (Siemens Healthcare) 64-MDCT scanner within 12 months of each other. After excluding those patients for whom Hounsfield unit measurements would be affected by mitigating factors, 48 patients (mean age, 58.8 years) were identified. Hounsfield unit measurements were obtained in nine different soft-tissue anatomic locations on each scan, and the location of these sites was kept identical on each scan pair. Data were analyzed to evaluate Hounsfield unit differences between these scanners. In general, there was a low consistency in the Hounsfield unit measurements for each of these sites on scans obtained by the two scanners, with the subcutaneous fat in the left posterolateral flank showing the lowest correlation (intraclass correlation coefficient, 0.198). There were differences in the Hounsfield unit measurements obtained in all anatomic sites on scans obtained by both scanners. Mean Hounsfield unit measurements obtained on the Definition AS Plus scanner were lower than those obtained on the Volume CT scanner, with the intriguing exception of the anterior midline subcutaneous fat Hounsfield unit measurements, which were higher on the Definition AS Plus scanner. All differences were statistically significant (p < 0.05). Hounsfield unit measurements for unenhanced abdominal soft tissues of the same patient vary between scanners of two common MDCT manufacturers.

  14. Dependence Of The Computerized Tomography (CT) Number - Electron Density Relationship On Patient Size And X-Ray Beam Filtration For Fan Beam CT Scanners

    NASA Astrophysics Data System (ADS)

    Masterson, M. E.; Thomason, C. L.; McGary, R.; Hunt, M. A.; Simpson, L. D.; Miller, D. W.; Laughlin, J. S.

    1981-07-01

    The applicability of quantitative information contained in CT scans to diagnostic radiology and to radiation therapy treatment planning and the heterogeneity problem has been recognized by members of the radiological community and by manufacturers. Determination of the relationship between electron density and CT number is important for these applications. As CT technology has evolved, CT number generation has changed. CT number variation was limited in the early water bag systems. However, later generation "air" scanners may exhibit variation in CT numbers across a reconstructed image which are re-lated to positioning within the scan circle and scan field size. Results of experimental investigations using tissue-equivalent phantoms of different cross-sectional shapes and areas on the Technicare Delta 2020 are presented. Investigations also cover the effect of "shaped" and "flat" x-ray beam filters. A variation in CT number is demonstrated on this fan beam geometry scanner for phantoms of different sizes and for different scan circle diameters. An explanation of these effects is given. Differences of as much as 20% in determination of tissue electron density relative to water under different experimental conditions are obtained and reported. A family of curves (electron density vs. CT number) is presented for different patient cross-sectional areas and different scanner settings.

  15. Growth-pattern classification of pulmonary nodules based on variation of CT number histogram and its potential usefulness in nodule differentiation

    NASA Astrophysics Data System (ADS)

    Kawata, Y.; Kawamata, A.; Niki, N.; Ohmatsu, H.; Kakinuma, R.; Eguchi, K.; Kaneko, M.; Moriyama, N.

    2009-02-01

    In recent years, high resolution CT has been developed. CAD system is indispensable for pulmonary cancer screening. In research and development of computer-aided differential diagnosis, there is now widespread interest in the use of nodule doubling time for measuring the volumetric changes of pulmonary nodule. The evolution pattern of each nodule might depend on the CT number distribution pattern inside nodule such as pure GGO, mixed GGO, or solid nodules. This paper presents a computerized approach to measure nodule CT number variation inside pulmonary nodule. The approach consists of four steps: (1) nodule segmentation, (2) computation of CT number histogram, (3) nodule categorization (α, β, γ, ɛ) based on CT number histogram, (4) computation of doubling time based on CT number histogram, and growth-pattern classification which consists of six categories such as decrease, gradual decrease, no change, slow increase, gradual increase, and increase, and (5) classification between benign and malignant cases. Using our dataset of follow-up scans for whom the final diagnosis was known (62 benign and 42 malignant cases), we evaluated growth-pattern of nodules and designed the classification strategy between benign and malignant cases. In order to compare the performance between the proposed features and volumetric doubling time, the classification result was analyzed by an area under the receiver operating characteristic curve. The preliminary experimental result demonstrated that our approach has a highly potential usefulness to assess the nodule evolution using 3-D thoracic CT images.

  16. Highly accurate fast lung CT registration

    NASA Astrophysics Data System (ADS)

    Rühaak, Jan; Heldmann, Stefan; Kipshagen, Till; Fischer, Bernd

    2013-03-01

    Lung registration in thoracic CT scans has received much attention in the medical imaging community. Possible applications range from follow-up analysis, motion correction for radiation therapy, monitoring of air flow and pulmonary function to lung elasticity analysis. In a clinical environment, runtime is always a critical issue, ruling out quite a few excellent registration approaches. In this paper, a highly efficient variational lung registration method based on minimizing the normalized gradient fields distance measure with curvature regularization is presented. The method ensures diffeomorphic deformations by an additional volume regularization. Supplemental user knowledge, like a segmentation of the lungs, may be incorporated as well. The accuracy of our method was evaluated on 40 test cases from clinical routine. In the EMPIRE10 lung registration challenge, our scheme ranks third, with respect to various validation criteria, out of 28 algorithms with an average landmark distance of 0.72 mm. The average runtime is about 1:50 min on a standard PC, making it by far the fastest approach of the top-ranking algorithms. Additionally, the ten publicly available DIR-Lab inhale-exhale scan pairs were registered to subvoxel accuracy at computation times of only 20 seconds. Our method thus combines very attractive runtimes with state-of-the-art accuracy in a unique way.

  17. SU-E-J-272: Auto-Segmentation of Regions with Differentiating CT Numbers for Treatment Response Assessment

    SciTech Connect

    Yang, C; Noid, G; Dalah, E; Paulson, E; Li, X; Gilat-Schmidt, T

    2015-06-15

    Purpose: It has been reported recently that the change of CT number (CTN) during and after radiation therapy (RT) may be used to assess RT response. The purpose of this work is to develop a tool to automatically segment the regions with differentiating CTN and/or with change of CTN in a series of CTs. Methods: A software tool was developed to identify regions with differentiating CTN using K-mean Cluster of CT numbers and to automatically delineate these regions using convex hull enclosing method. Pre- and Post-RT CT, PET, or MRI images acquired for sample lung and pancreatic cancer cases were used to test the software tool. K-mean cluster of CT numbers within the gross tumor volumes (GTVs) delineated based on PET SUV (standard uptake value of fludeoxyglucose) and/or MRI ADC (apparent diffusion coefficient) map was analyzed. The cluster centers with higher value were considered as active tumor volumes (ATV). The convex hull contours enclosing preset clusters were used to delineate these ATVs with color washed displays. The CTN defined ATVs were compared with the SUV- or ADC-defined ATVs. Results: CTN stability of the CT scanner used to acquire the CTs in this work is less than 1.5 Hounsfield Unit (HU) variation annually. K-mean cluster centers in the GTV have difference of ∼20 HU, much larger than variation due to CTN stability, for the lung cancer cases studied. The dice coefficient between the ATVs delineated based on convex hull enclosure of high CTN centers and the PET defined GTVs based on SUV cutoff value of 2.5 was 90(±5)%. Conclusion: A software tool was developed using K-mean cluster and convex hull contour to automatically segment high CTN regions which may not be identifiable using a simple threshold method. These CTN regions were reasonably overlapped with the PET or MRI defined GTVs.

  18. CT and Ultrasound Guided Stereotactic High Intensity Focused Ultrasound (HIFU)

    SciTech Connect

    Wood, Bradford J.; Frenkel, V.; Viswanathan, A.; Dromi, S.; Oh, K.; Kam, A.; Li, K. C. P.; Yanof, J.; Bauer, C.; Kruecker, J.; Seip, R.

    2006-05-08

    To demonstrate the feasibility of CT and B-mode Ultrasound (US) targeted HIFU, a prototype coaxial focused ultrasound transducer was registered and integrated to a CT scanner. CT and diagnostic ultrasound were used for HIFU targeting and monitoring, with the goals of both thermal ablation and non-thermal enhanced drug delivery. A 1 megahertz coaxial ultrasound transducer was custom fabricated and attached to a passive position-sensing arm and an active six degree-of-freedom robotic arm via a CT stereotactic frame. The outer therapeutic transducer with a 10 cm fixed focal zone was coaxially mounted to an inner diagnostic US transducer (2-4 megahertz, Philips Medical Systems). This coaxial US transducer was connected to a modified commercial focused ultrasound generator (Focus Surgery, Indianapolis, IN) with a maximum total acoustic power of 100 watts. This pre-clinical paradigm was tested for ability to heat tissue in phantoms with monitoring and navigation from CT and live US. The feasibility of navigation via image fusion of CT with other modalities such as PET and MRI was demonstrated. Heated water phantoms were tested for correlation between CT numbers and temperature (for ablation monitoring). The prototype transducer and integrated CT/US imaging system enabled simultaneous multimodality imaging and therapy. Pre-clinical phantom models validated the treatment paradigm and demonstrated integrated multimodality guidance and treatment monitoring. Temperature changes during phantom cooling corresponded to CT number changes. Contrast enhanced or non-enhanced CT numbers may potentially be used to monitor thermal ablation with HIFU. Integrated CT, diagnostic US, and therapeutic focused ultrasound bridges a gap between diagnosis and therapy. Preliminary results show that the multimodality system may represent a relatively inexpensive, accessible, and simple method of both targeting and monitoring HIFU effects. Small animal pre-clinical models may be translated to large

  19. Number Theory in the High School Classroom.

    ERIC Educational Resources Information Center

    Dence, Thomas

    1999-01-01

    Demonstrates some of the usefulness of number theory to students on the high school setting in four areas: Fibonacci numbers, Diophantine equations, continued fractions, and algorithms for computing pi. (ASK)

  20. Number Theory in the High School Classroom.

    ERIC Educational Resources Information Center

    Dence, Thomas

    1999-01-01

    Demonstrates some of the usefulness of number theory to students on the high school setting in four areas: Fibonacci numbers, Diophantine equations, continued fractions, and algorithms for computing pi. (ASK)

  1. Normal mediastinal lymph node size and number: CT and anatomic study

    SciTech Connect

    Genereux, G.P.; Howie, J.L.

    1984-06-01

    Normal lymph nodes were studied retrospectively by computed tomography (CT) in 39 patients and by dissection at autopsy in 12 cadavers. The mediastinum was divided arbitrarily into four zones relating to the left innominate vein (zone 1), pretracheal space (zone 2), precarinal/subcarinal compartment (zone 3), and aorticopulmonary window (zone 4). Of 225 lymph nodes from all zones in the CT study, 99% measured less than 16 mm in largest diameter. Using contiguous 10-mm CT scans, lymph nodes were detected in 65%-95% of patients, depending on the zone studies. The mean number of lymph nodes on a representative section was 1.1. There was a significant size difference between lymph nodes residing in the superior mediastinum compared with those in the middle mediastinum contiguous to the carina. Thus, only 7% of lymph nodes in zone 1 were larger than 5 mm, whereas 90% and 67% of lymph nodes in zones 3 and 4, respectively, were larger, in the 6-10 mm range.

  2. Optical Colonoscopy and Virtual Colonoscopy Numbers after Initiation of a CT Colonography Program: Long Term Data

    PubMed Central

    Benson, Mark; Pier, Jeff; Kraft, Sally; Kim, David; Pickhardt, Perry; Weiss, Jennifer; Gopal, Deepak; Reichelderfer, Mark; Pfau, Patrick

    2015-01-01

    Background & Aims The effect of CT colonography (CTC) screening on colonoscopy is unknown. The objective of this study is to determine the effect of a CTC screening program on the number of screening, therapeutic and total colonoscopies performed. Methods We compared the quarterly mean numbers of colonoscopic examinations performed for 50-79 year olds undergoing colorectal cancer screening in 2003, before initiation of a CTC program, to 2011, seven years after the CTC program began at our academic tertiary care facility. Results The CTC program began in 2004 with a peak number of 387 CTC examinations performed in the 3rd quarter of 2005 and 275 examinations in the final quarter of 2011. Screening colonoscopies increased from 555 mean/quarter in 2003 to 1460 in 2011 (P < 0.001). The mean/quarter number of total colonoscopies performed increased from 1104 in 2003 to 2382 in 2011 (P < 0.001). The number of overall colon cancer screening examinations (Colonoscopy + CTC) increased from 555/quarter in 2003 to 1736 in 2011 (P < 0.001). Conclusions Since the initiation of CTC screening at our institution, the overall number of total colorectal cancer screening examinations (CTC + colonoscopy) has greatly increased. The initiation of a CTC screening program did not lead to a reduction in the number of colonoscopic examinations performed. Conversely, a significant increase in the number of screening and total colonoscopies completed was observed. PMID:23256122

  3. Extracting atomic numbers and electron densities from a dual source dual energy CT scanner: experiments and a simulation model.

    PubMed

    Landry, Guillaume; Reniers, Brigitte; Granton, Patrick Vincent; van Rooijen, Bart; Beaulieu, Luc; Wildberger, Joachim E; Verhaegen, Frank

    2011-09-01

    Dual energy CT (DECT) imaging can provide both the electron density ρ(e) and effective atomic number Z(eff), thus facilitating tissue type identification. This paper investigates the accuracy of a dual source DECT scanner by means of measurements and simulations. Previous simulation work suggested improved Monte Carlo dose calculation accuracy when compared to single energy CT for low energy photon brachytherapy, but lacked validation. As such, we aim to validate our DECT simulation model in this work. A cylindrical phantom containing tissue mimicking inserts was scanned with a second generation dual source scanner (SOMATOM Definition FLASH) to obtain Z(eff) and ρ(e). A model of the scanner was designed in ImaSim, a CT simulation program, and was used to simulate the experiment. Accuracy of measured Z(eff) (labelled Z) was found to vary from -10% to 10% from low to high Z tissue substitutes while the accuracy on ρ(e) from DECT was about 2.5%. Our simulation reproduced the experiments within ±5% for both Z and ρ(e). A clinical DECT scanner was able to extract Z and ρ(e) of tissue substitutes. Our simulation tool replicates the experiments within a reasonable accuracy. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  4. Metrology, applications and methods with high energy CT systems

    SciTech Connect

    Uhlmann, N.; Voland, V.; Salamon, M.; Hebele, S.; Boehnel, M.; Reims, N.; Schmitt, M.; Kasperl, S.

    2014-02-18

    The increase of Computed Tomography (CT) as an applicable metrology and Non Destructive Testing (NDT) method raises interest on developing the application fields to larger objects, which were rarely used in the past due to their requirements on the imaging system. Especially the classical X-ray generation techniques based on standard equipment restricted the applications of CT to typical material penetration lengths of only a few cm of steel. Even with accelerator technology that offers a suitable way to overcome these restrictions just the 2D radioscopy technique found a widespread application. Beside the production and detection of photons in the MeV range itself, the achievable image quality is limited using standard detectors due to the dominating absorption effect of Compton Scattering at high energies. Especially for CT reconstruction purposes these effects have to be considered on the development path from 2D to 3D imaging. Most High Energy CT applications are therefore based on line detectors shielding scattered radiation to a maximum with an increase in imaging quality but with time consuming large volume scan capabilities. In this contribution we present the High-Energy X-ray Imaging project at the Fraunhofer Development Centre for X-ray Technology with the characterization and the potential of the CT-system according to metrological and other application capabilities.

  5. X-ray CT high-density artefact suppression in the presence of bones

    NASA Astrophysics Data System (ADS)

    Wei, Jikun; Chen, Laigao; Sandison, George A.; Liang, Yun; Xu, Lisa X.

    2004-12-01

    This paper presents a novel method of reducing x-ray CT high-density artefacts generated by metal objects when abundant bone structures are present in the region of interest. This method has an advantage over previously proposed methods since it heavily suppresses the metal artefacts without introducing extra bone artefacts. The method of suppression requires that bone pixels are isolated and segmented by thresholding. Then artificial CT numbers are assigned to the bone pixels so that their projection profiles are smooth and thus can be properly simulated by a polynomial interpolation. The projection profile of the metal object is then removed to fully suppress the artefacts. The resulting processed profile is fed to a reconstruction routine and the previously preserved bone pixels added back. The new method utilizes two important features of the CT image with metal artefacts: (a) metal and bone pixels are not severely affected by the high-density artefacts and (b) the high-density artefacts can be located in specific projection channels in the profile domain, although they are spread out in the image domain. This suppression method solves the problem of CT image artefacts arising from metal objects in the body. It has the potential to greatly improve diagnostic CT imaging in the presence of these objects and treatment planning that utilizes CT for patients with metal applicators (e.g., brachytherapy for cervix cancer and prostate cryotherapy).

  6. Effective atomic number accuracy for kidney stone characterization using spectral CT

    NASA Astrophysics Data System (ADS)

    Joshi, M.; Langan, D. A.; Sahani, D. S.; Kambadakone, A.; Aluri, S.; Procknow, K.; Wu, X.; Bhotika, R.; Okerlund, D.; Kulkarni, N.; Xu, D.

    2010-04-01

    The clinical application of Gemstone Spectral ImagingTM, a fast kV switching dual energy acquisition, is explored in the context of noninvasive kidney stone characterization. Utilizing projection-based material decomposition, effective atomic number and monochromatic images are generated for kidney stone characterization. Analytical and experimental measurements are reported and contrasted. Phantoms were constructed using stone specimens extracted from patients. This allowed for imaging of the different stone types under similar conditions. The stone specimens comprised of Uric Acid, Cystine, Struvite and Calcium-based compositions. Collectively, these stone types span an effective atomic number range of approximately 7 to 14. While Uric Acid and Calcium based stones are generally distinguishable in conventional CT, stone compositions like Cystine and Struvite are difficult to distinguish resulting in treatment uncertainty. Experimental phantom measurements, made under increasingly complex imaging conditions, illustrate the impact of various factors on measurement accuracy. Preliminary clinical studies are reported.

  7. Effects of Hounsfield number conversion on CT based proton Monte Carlo dose calculations

    SciTech Connect

    Jiang Hongyu; Seco, Joao; Paganetti, Harald

    2007-04-15

    The Monte Carlo method provides the most accurate dose calculations on a patient computed tomography (CT) geometry. The increase in accuracy is, at least in part, due to the fact that instead of treating human tissues as water of various densities as in analytical algorithms, the Monte Carlo method allows human tissues to be characterized by elemental composition and mass density, and hence allows the accurate consideration of all relevant electromagnetic and nuclear interactions. On the other hand, the algorithm to convert CT Hounsfield numbers to tissue materials for Monte Carlo dose calculation introduces uncertainties. There is not a simple one to one correspondence between Hounsfield numbers and tissue materials. To investigate the effects of Hounsfield number conversion for proton Monte Carlo dose calculations, clinical proton treatment plans were simulated using the Geant4 Monte Carlo code. Three Hounsfield number to material conversion methods were studied. The results were compared in forms of dose volume histograms of gross tumor volume and clinical target volume. The differences found are generally small but can be dosimetrically significant. Further, different methods may cause deviations in the predicted proton beam range in particular for deep proton fields. Typically, slight discrepancies in mass density assignments play only a minor role in the target region, whereas more significant effects are caused by different assignments in elemental compositions. In the presence of large tissue inhomogeneities, for head and neck treatments, treatment planning decisions could be affected by these differences because of deviations in the predicted tumor coverage. Outside the target area, differences in elemental composition and mass density assignments both may play a role. This can lead to pronounced effects for organs at risk, in particular in the spread-out Bragg peak penumbra or distal regions. In addition, the significance of the elemental composition

  8. Effects of Hounsfield number conversion on CT based proton Monte Carlo dose calculations

    PubMed Central

    Jiang, Hongyu; Seco, Joao; Paganetti, Harald

    2008-01-01

    The Monte Carlo method provides the most accurate dose calculations on a patient computed tomography (CT) geometry. The increase in accuracy is, at least in part, due to the fact that instead of treating human tissues as water of various densities as in analytical algorithms, the Monte Carlo method allows human tissues to be characterized by elemental composition and mass density, and hence allows the accurate consideration of all relevant electromagnetic and nuclear interactions. On the other hand, the algorithm to convert CT Hounsfield numbers to tissue materials for Monte Carlo dose calculation introduces uncertainties. There is not a simple one to one correspondence between Hounsfield numbers and tissue materials. To investigate the effects of Hounsfield number conversion for proton Monte Carlo dose calculations, clinical proton treatment plans were simulated using the Geant4 Monte Carlo code. Three Hounsfield number to material conversion methods were studied. The results were compared in forms of dose volume histograms of gross tumor volume and clinical target volume. The differences found are generally small but can be dosimetrically significant. Further, different methods may cause deviations in the predicted proton beam range in particular for deep proton fields. Typically, slight discrepancies in mass density assignments play only a minor role in the target region, whereas more significant effects are caused by different assignments in elemental compositions. In the presence of large tissue inhomogeneities, for head and neck treatments, treatment planning decisions could be affected by these differences because of deviations in the predicted tumor coverage. Outside the target area, differences in elemental composition and mass density assignments both may play a role. This can lead to pronounced effects for organs at risk, in particular in the spread-out Bragg peak penumbra or distal regions. In addition, the significance of the elemental composition

  9. Effects of Hounsfield number conversion on CT based proton Monte Carlo dose calculations.

    PubMed

    Jiang, Hongyu; Seco, Joao; Paganetti, Harald

    2007-04-01

    The Monte Carlo method provides the most accurate dose calculations on a patient computed tomography (CT) geometry. The increase in accuracy is, at least in part, due to the fact that instead of treating human tissues as water of various densities as in analytical algorithms, the Monte Carlo method allows human tissues to be characterized by elemental composition and mass density, and hence allows the accurate consideration of all relevant electromagnetic and nuclear interactions. On the other hand, the algorithm to convert CT Hounsfield numbers to tissue materials for Monte Carlo dose calculation introduces uncertainties. There is not a simple one to one correspondence between Hounsfield numbers and tissue materials. To investigate the effects of Hounsfield number conversion for proton Monte Carlo dose calculations, clinical proton treatment plans were simulated using the Geant4 Monte Carlo code. Three Hounsfield number to material conversion methods were studied. The results were compared in forms of dose volume histograms of gross tumor volume and clinical target volume. The differences found are generally small but can be dosimetrically significant. Further, different methods may cause deviations in the predicted proton beam range in particular for deep proton fields. Typically, slight discrepancies in mass density assignments play only a minor role in the target region, whereas more significant effects are caused by different assignments in elemental compositions. In the presence of large tissue inhomogeneities, for head and neck treatments, treatment planning decisions could be affected by these differences because of deviations in the predicted tumor coverage. Outside the target area, differences in elemental composition and mass density assignments both may play a role. This can lead to pronounced effects for organs at risk, in particular in the spread-out Bragg peak penumbra or distal regions. In addition, the significance of the elemental composition

  10. Comparison of CT-Number and Gray Scale Value of Different Dental Materials and Hard Tissues in CT and CBCT

    PubMed Central

    Emadi, Naghmeh; Safi, Yaser; Akbarzadeh Bagheban, Alireza; Asgary, Saeed

    2014-01-01

    Introduction: Computed tomography (CT) and cone-beam CT (CBCT) are valuable diagnostic aids for many clinical applications. This study was designed to compare the gray scale value (GSV) and Hounsfield unit (HU) of selected dental materials and various hard tissues using CT or CBCT. Methods and Materials: Three samples of all test materials including amalgam (AM), composite resin (CR), glass ionomer (GI), zinc-oxide eugenol (ZOE), calcium-enriched mixture (CEM) cement, AH-26 root canal sealer (AH-26), gutta-percha (GP), Coltosol (Col), Dycal (DL), mineral trioxide aggregate (MTA), zinc phosphate (ZP), and polycarbonate cement (PC) were prepared and scanned together with samples of bone, dentin and enamel using two CBCT devices, Scanora 3D (S3D) and NewTom VGi (NTV) and a spiral CT (SCT) scanner (Somatom Emotion 16 multislice spiral CT);. Subsequently, the HU and GSV values were determined and evaluated. The data were analyzed by the Kruskal-Wallis and Mann-Whitney U tests. The level of significance was determined at 0.05. Results: There were significant differences among the three different scanners (P<0.05). The differences between HU/GSV values of 12 selected dental materials using NTV was significant (P<0.05) and for S3D and SCT was insignificant (P>0.05). All tested materials showed maximum values in S3D and SCT (3094 and 3071, respectively); however, bone and dentin showed low/medium values (P<0.05). In contrast, the tested materials and tissues showed a range of values in NTV (366 to15383; P<0.05). Conclusion: Scanner system can influence the obtained HU/GSV of dental materials. NTV can discriminate various dental materials, in contrast to S3D/SCT scanners. NTV may be a more useful diagnostic aid for clinical practice. PMID:25386210

  11. Determination of CT number and density profile of binderless, pre-treated and tannin-based Rhizophora spp. particleboards using computed tomography imaging and electron density phantom

    NASA Astrophysics Data System (ADS)

    Yusof, Mohd Fahmi Mohd; Hamid, Puteri Nor Khatijah Abdul; Bauk, Sabar; Hashim, Rokiah; Tajuddin, Abdul Aziz

    2015-04-01

    Plug density phantoms were constructed in accordance to CT density phantom model 062M CIRS using binderless, pre-treated and tannin-based Rhizophora Spp. particleboards. The Rhizophora Spp. plug phantoms were scanned along with the CT density phantom using Siemens Somatom Definition AS CT scanner at three CT energies of 80, 120 and 140 kVp. 15 slices of images with 1.0 mm thickness each were taken from the central axis of CT density phantom for CT number and CT density profile analysis. The values were compared to water substitute plug phantom from the CT density phantom. The tannin-based Rhizophora Spp. gave the nearest value of CT number to water substitute at 80 and 120 kVp CT energies with χ2 value of 0.011 and 0.014 respectively while the binderless Rhizphora Spp. gave the nearest CT number to water substitute at 140 kVp CT energy with χ2 value of 0.023. The tannin-based Rhizophora Spp. gave the nearest CT density profile to water substitute at all CT energies. This study indicated the suitability of Rhizophora Spp. particleboard as phantom material for the use in CT imaging studies.

  12. Determination of CT number and density profile of binderless, pre-treated and tannin-based Rhizophora spp. particleboards using computed tomography imaging and electron density phantom

    SciTech Connect

    Yusof, Mohd Fahmi Mohd Hamid, Puteri Nor Khatijah Abdul; Tajuddin, Abdul Aziz; Bauk, Sabar; Hashim, Rokiah

    2015-04-29

    Plug density phantoms were constructed in accordance to CT density phantom model 062M CIRS using binderless, pre-treated and tannin-based Rhizophora Spp. particleboards. The Rhizophora Spp. plug phantoms were scanned along with the CT density phantom using Siemens Somatom Definition AS CT scanner at three CT energies of 80, 120 and 140 kVp. 15 slices of images with 1.0 mm thickness each were taken from the central axis of CT density phantom for CT number and CT density profile analysis. The values were compared to water substitute plug phantom from the CT density phantom. The tannin-based Rhizophora Spp. gave the nearest value of CT number to water substitute at 80 and 120 kVp CT energies with χ{sup 2} value of 0.011 and 0.014 respectively while the binderless Rhizphora Spp. gave the nearest CT number to water substitute at 140 kVp CT energy with χ{sup 2} value of 0.023. The tannin-based Rhizophora Spp. gave the nearest CT density profile to water substitute at all CT energies. This study indicated the suitability of Rhizophora Spp. particleboard as phantom material for the use in CT imaging studies.

  13. Intrinsic dependencies of CT radiomic features on voxel size and number of gray levels.

    PubMed

    Shafiq-Ul-Hassan, Muhammad; Zhang, Geoffrey G; Latifi, Kujtim; Ullah, Ghanim; Hunt, Dylan C; Balagurunathan, Yoganand; Abdalah, Mahmoud Abrahem; Schabath, Matthew B; Goldgof, Dmitry G; Mackin, Dennis; Court, Laurence Edward; Gillies, Robert James; Moros, Eduardo Gerardo

    2017-03-01

    moderate variation (%COV <50%) and were negligibly affected by resampling. Group 2 features were further studied by modifying feature definitions to include voxel size. Original and voxel-size normalized features were used for interscanner comparisons. A subsequent analysis investigated feature dependency on gray-level discretization by extracting 51 texture features from ROIs from each of the 10 different phantom cartridges using 16, 32, 64, 128, and 256 gray levels. Out of the 213 features extracted, 150 were reproducible across voxel sizes, 42 improved significantly (%COV <30, Group 2) after resampling, and 21 had large variations before and after resampling (Group 1). Ten features improved significantly after definition modification effectively removed their voxel-size dependency. Interscanner comparison indicated that feature variability among scanners nearly vanished for 8 of these 10 features. Furthermore, 17 out of 51 texture features were found to be dependent on the number of gray levels. These features were redefined to include the number of gray levels which greatly reduced this dependency. Voxel-size resampling is an appropriate pre-processing step for image datasets acquired with variable voxel sizes to obtain more reproducible CT features. We found that some of the radiomics features were voxel size and gray-level discretization-dependent. The introduction of normalizing factors in their definitions greatly reduced or removed these dependencies. © 2017 American Association of Physicists in Medicine.

  14. Chaotic behaviour of high Mach number flows

    NASA Technical Reports Server (NTRS)

    Varvoglis, H.; Ghosh, S.

    1985-01-01

    The stability of the super-Alfvenic flow of a two-fluid plasma model with respect to the Mach number and the angle between the flow direction and the magnetic field is investigated. It is found that, in general, a large scale chaotic region develops around the initial equilibrium of the laminar flow when the Mach number exceeds a certain threshold value. After reaching a maximum the size of this region begins shrinking and goes to zero as the Mach number tends to infinity. As a result high Mach number flows in time independent astrophysical plasmas may lead to the formation of 'quasi-shocks' in the presence of little or no dissipation.

  15. Chaotic behaviour of high Mach number flows

    NASA Technical Reports Server (NTRS)

    Varvoglis, H.; Ghosh, S.

    1985-01-01

    The stability of the super-Alfvenic flow of a two-fluid plasma model with respect to the Mach number and the angle between the flow direction and the magnetic field is investigated. It is found that, in general, a large scale chaotic region develops around the initial equilibrium of the laminar flow when the Mach number exceeds a certain threshold value. After reaching a maximum the size of this region begins shrinking and goes to zero as the Mach number tends to infinity. As a result high Mach number flows in time independent astrophysical plasmas may lead to the formation of 'quasi-shocks' in the presence of little or no dissipation.

  16. High Reynolds Number Thermal Stability Experiments

    NASA Technical Reports Server (NTRS)

    Emens, Jessica M.; Brown, Sarah P.; Frederick Robert A., Jr.; Wood, A. John

    2004-01-01

    This work represents preliminary thermal stability results for liquid hydrocarbon fuels. High Reynolds Number Thermal Stability experiments with Jet A and RP-1 resulted in a quantitative measurement of the thermal stability. Each fuel flowed through a heated capillary tube that held the outlet temperature at 290 C. An optical pyrometer measured the surface temperature of the tube at 12 locations as a function of time. The High Reynolds Number Thermal Stability number was then determined using standards published by the American Society for Testing and Materials. The results for Jet A showed lower thermal stability than similar tests conducted at another facility. The RP-1 results are the first reported using this technique. Because the temperature rise on the capillary tube during testing for the RP-1 fuels was not significant, a new standard for the testing conditions should be developed for these types of fuels.

  17. 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.

  18. CTC-ask: a new algorithm for conversion of CT numbers to tissue parameters for Monte Carlo dose calculations applying DICOM RS knowledge.

    PubMed

    Ottosson, Rickard O; Behrens, Claus F

    2011-11-21

    One of the building blocks in Monte Carlo (MC) treatment planning is to convert patient CT data to MC compatible phantoms, consisting of density and media matrices. The resulting dose distribution is highly influenced by the accuracy of the conversion. Two major contributing factors are precise conversion of CT number to density and proper differentiation between air and lung. Existing tools do not address this issue specifically. Moreover, their density conversion may depend on the number of media used. Differentiation between air and lung is an important task in MC treatment planning and misassignment may lead to local dose errors on the order of 10%. A novel algorithm, CTC-ask, is presented in this study. It enables locally confined constraints for the media assignment and is independent of the number of media used for the conversion of CT number to density. MC compatible phantoms were generated for two clinical cases using a CT-conversion scheme implemented in both CTC-ask and the DICOM-RT toolbox. Full MC dose calculation was subsequently conducted and the resulting dose distributions were compared. The DICOM-RT toolbox inaccurately assigned lung in 9.9% and 12.2% of the voxels located outside of the lungs for the two cases studied, respectively. This was completely avoided by CTC-ask. CTC-ask is able to reduce anatomically irrational media assignment. The CTC-ask source code can be made available upon request to the authors.

  19. CTC-ask: a new algorithm for conversion of CT numbers to tissue parameters for Monte Carlo dose calculations applying DICOM RS knowledge

    NASA Astrophysics Data System (ADS)

    Ottosson, Rickard O.; Behrens, Claus F.

    2011-11-01

    One of the building blocks in Monte Carlo (MC) treatment planning is to convert patient CT data to MC compatible phantoms, consisting of density and media matrices. The resulting dose distribution is highly influenced by the accuracy of the conversion. Two major contributing factors are precise conversion of CT number to density and proper differentiation between air and lung. Existing tools do not address this issue specifically. Moreover, their density conversion may depend on the number of media used. Differentiation between air and lung is an important task in MC treatment planning and misassignment may lead to local dose errors on the order of 10%. A novel algorithm, CTC-ask, is presented in this study. It enables locally confined constraints for the media assignment and is independent of the number of media used for the conversion of CT number to density. MC compatible phantoms were generated for two clinical cases using a CT-conversion scheme implemented in both CTC-ask and the DICOM-RT toolbox. Full MC dose calculation was subsequently conducted and the resulting dose distributions were compared. The DICOM-RT toolbox inaccurately assigned lung in 9.9% and 12.2% of the voxels located outside of the lungs for the two cases studied, respectively. This was completely avoided by CTC-ask. CTC-ask is able to reduce anatomically irrational media assignment. The CTC-ask source code can be made available upon request to the authors.

  20. Noise suppression with high Mach number inlets

    NASA Technical Reports Server (NTRS)

    Lumsdaine, E.; Cherng, J. G.; Tag, I.

    1976-01-01

    Experimental results were obtained for two types of high Mach number inlets, one with a translating centerbody and a fixed geometry inlet (collapsing cowl) with no centerbody. The aerodynamic and acoustic performance of these inlets was examined. The effects of area ratio, length/diameter ratio, and lip geometry were among several parameters investigated. The translating centerbody type inlet was found to be superior to the collapsing cowl both acoustically and aerodynamically, particularly for area ratios greater than 1.5. Comparison of length/diameter ratio and area ratio effects on performance near choked flow showed the latter to be more significant. Also, greater high frequency noise attenuation was achieved by increasing Mach number from low to high subsonic values.

  1. Generating high Reynolds-number flows.

    NASA Technical Reports Server (NTRS)

    Russell, D. A.

    1972-01-01

    Present test facilities are seriously limited regarding investigations involving high Reynolds numbers due to financial considerations. Quasi-steady testing facilities offer a practical immediate solution to the problem of high-Re testing. A familiar example is the blowdown wind tunnel, but even more flexibility and economy may be provided by using shock-tube devices. The Ludwieg tube is the shock-tube device most often proposed as a means of generating high-Re flows. Two-stage nozzles may be used with a Ludwieg tube. Quasi-steady facilities will be useful only if the available test time exceeds that required to establish steady flow.

  2. Prolactin-secreting pituitary microadenomas: inaccuracy of high-resolution CT imaging

    SciTech Connect

    Davis, P.C.; Hoffman, J.C. Jr.; Tindall, G.T.; Braun, I.F.

    1985-01-01

    Computed tomographic (CT) and surgical findings were correlated retrospectively in 51 patients with preoperative diagnoses of prolactin-secreting pituitary microadenomas. Thirty-nine had microadenomas at surgery. Twenty-three had identifiable discrete lesions. Of these, 21 had microadenomas and two did not; these two groups could not be distinguished reliably. Six patients with proven microadenomas had normal CT scans. Focal hypodense lesions, sellar floor erosion, infundibulum displacement, gland height greater than 8 mm, and an abnormal diaphragma sellae configuration are neither sensitive nor specific findings or microadenoma. A significant number of patients with proven microadenomas has few or none of these abnormalities. Thus, recognition of prolactin microadenoma may not be possible by CT alone, even with high-resolution direct coronal imaging.

  3. A fast method based on NESTA to accurately reconstruct CT image from highly undersampled projection measurements.

    PubMed

    He, Zhijie; Qiao, Quanbang; Li, Jun; Huang, Meiping; Zhu, Shouping; Huang, Liyu

    2016-11-22

    The CT image reconstruction algorithm based compressed sensing (CS) can be formulated as an optimization problem that minimizes the total-variation (TV) term constrained by the data fidelity and image nonnegativity. There are a lot of solutions to this problem, but the computational efficiency and reconstructed image quality of these methods still need to be improved. To investigate a faster and more accurate mathematical algorithm to settle TV term minimization problem of CT image reconstruction. A Nesterov's algorithm (NESTA) is a fast and accurate algorithm for solving TV minimization problem, which can be ascribed to the use of most notably Nesterov's smoothing technique and a subtle averaging of sequences of iterates, which has been shown to improve the convergence properties of standard gradient-descent algorithms. In order to demonstrate the superior performance of NESTA on computational efficiency and image quality, a comparison with Simultaneous Algebraic Reconstruction Technique-TV (SART-TV) and Split-Bregman (SpBr) algorithm is made using a digital phantom study and two physical phantom studies from highly undersampled projection measurements. With only 25% of conventional full-scan dose and, NESTA method reduces the average CT number error from 51.76HU to 9.98HU on Shepp-Logan phantom and reduces the average CT number error from 50.13HU to 0.32HU on Catphan 600 phantom. On an anthropomorphic head phantom, the average CT number error is reduced from 84.21HU to 1.01HU in the central uniform area. To the best of our knowledge this is the first work that apply the NESTA method into CT reconstruction based CS. Research shows that this method is of great potential, further studies and optimization are necessary.

  4. Application of offset-CT scanning to the inspection of high power feeder lines and connections

    NASA Astrophysics Data System (ADS)

    Schneberk, Daniel; Maziuk, Robert; Soyfer, Boris; Shashishekhar, N.; Alreja, Rahul

    2016-02-01

    VJT is developing techniques and scanning methods for the in-situ Radiographic and Computed Tomographic inspection of underground high-power feeder cables. The goals for the inspection are to measure the 3D state of the cables and the cable-connections. Recent in-situ Digital Radiographic inspections performed by VJT have demonstrated the value of NDE inspection information for buried power lines. These NDE data have raised further questions as to the exact state of the cables and connections and pointed to the need for more 3D information of the type provided by volumetric CT scanning. VJT is pursuing a three phased approach to address the many issues involved in this type of inspection: 1) develop a high-power feeder-cable test-bed CT scanner, 2) acquire scans on underground feeder pipes that have been removed from service, and 3) from the work in 1) and 2) develop limited-angle CT scanning methods for extending in-situ Digital Radiography to volumetric CT measurements. To this end, VJT has developed and fielded a high-energy test-bed Gantry-type CT scanner (the source and detector move around the object) with a number of important properties. First, the geometry of the gantry-scans can be configured to match the techniques used in the in-situ radiographic inspection. The same X-ray source is employed as in portable Radiographic inspections, a 7.5 MeV Betatron coupled to a Perkin-Elmer Amorphous Silicon detector. Offset-CT scanning is employed as the high-power feeder line assembly is larger than the detector. A description of this scanner and the scan geometry will be presented showing the connection to in-situ radiography. Results from the CT scans of high-power feeder-cable specimens removed from service will be presented with a focus on the inspection potential of volumetric CT data on these assemblies. An evaluation of the scan performance properties of these data compared to the spectrum of life-cycle inspection issues will be presented. Continuing and

  5. Turbulent Convection at Very High Rayleigh Numbers

    NASA Astrophysics Data System (ADS)

    Sreenivasan, K. R..

    1999-11-01

    This talk will describe experimental work on turbulent convection at very high Rayleigh numbers. The work was done in collaboration with J. J. Niemela, L. Skrbek and R.J. Donnelly at the University of Oregon. Turbulent convection was set up in a large cylindrical cell 1 m in height and 0.5 m in diameter, using cryogenic helium gas as the working fluid. The experiments measured heat flux at the boundary as well as internal temperature and velocity fluctuations, the latter inferred by correlating signals from two closely-spaced temperature probes. The Nusselt number, Nu, was obtained over eleven orders of magnitude of the Rayleigh number, Ra, ranging between 10^6 and 10^17. This is the largest dynamic range of Ra ever attained in a single experiment; the upper end of the Rayleigh number is also the highest ever attained. We find that Nu = 0.124 Ra^0.309 ± 0.0043 over the entire range of Ra. Possible logarithmic corrections to this power-law and Prandtl number effects will be summarized. Comparisons with various theories will be attempted. Probability density functions and power spectra of temperature fluctuations will be described.

  6. High Atom Number in Microsized Atom Traps

    DTIC Science & Technology

    2015-12-14

    2012 conference of the Division of Atomic , Molecular, and Optical Physics (DAMOP) of the American Physical Society (APS). We have reconfigured the...Final Performance Report on ONR Grant N00014-12-1-0608 High atom number in microsized atom traps for the period 15 May 2012 through 14 September...2015 J. M. Grossman Department of Physics St. Mary’s College of Maryland 18952 E. Fisher Road St. Mary’s City, MD 20686 jmgrossman @smcm. edu

  7. Coronary calcium screening with dual-source CT: reliability of ungated, high-pitch chest CT in comparison with dedicated calcium-scoring CT.

    PubMed

    Hutt, Antoine; Duhamel, Alain; Deken, Valérie; Faivre, Jean-Baptiste; Molinari, Francesco; Remy, Jacques; Remy-Jardin, Martine

    2016-06-01

    To investigate the reliability of ungated, high-pitch dual-source CT for coronary artery calcium (CAC) screening. One hundred and eighty-five smokers underwent a dual-source CT examination with acquisition of two sets of images during the same session: (a) ungated, high-pitch and high-temporal resolution acquisition over the entire thorax (i.e., chest CT); (b) prospectively ECG-triggered acquisition over the cardiac cavities (i.e., cardiac CT). Sensitivity and specificity of chest CT for detecting positive CAC scores were 96.4 % and 100 %, respectively. There was excellent inter-technique agreement for determining the quantitative CAC score (ICC = 0.986). The mean difference between the two techniques was 11.27, representing 1.81 % of the average of the two techniques. The inter-technique agreement for categorizing patients into the four ranks of severity was excellent (weighted kappa = 0.95; 95 % CI 0.93-0.98). The inter-technique differences for quantitative CAC scores did not correlate with BMI (r = 0.05, p = 0.575) or heart rate (r = -0.06, p = 0.95); 87.2 % of them were explained by differences at the level of the right coronary artery (RCA: 0.8718; LAD: 0.1008; LCx: 0.0139; LM: 0.0136). Ungated, high-pitch dual-source CT is a reliable imaging mode for CAC screening in the conditions of routine chest CT examinations. • CAC is an independent risk factor for major cardiac events. • ECG-gated techniques are the reference standard for calcium scoring. • Great interest is directed toward calcium scoring on non-gated chest CT examinations. • Reliable calcium scoring can be obtained with dual-source CT in a high-pitch mode.

  8. Prediction of positron emission tomography/computed tomography (PET/CT) positivity in patients with high-risk primary melanoma.

    PubMed

    Danielsen, Maria; Kjaer, Andreas; Wu, Max; Martineau, Lea; Nosrati, Mehdi; Leong, Stanley Pl; Sagebiel, Richard W; Iii, James R Miller; Kashani-Sabet, Mohammed

    2016-01-01

    Positron emission tomography/computed tomography (PET/CT) is an important tool to identify occult melanoma metastasis. To date, it is controversial which patients with primary cutaneous melanoma should have staging PET/CT. In this retrospective analysis of more than 800 consecutive patients with cutaneous melanoma, we sought to identify factors predictive of PET/CT positivity in the setting of newly-diagnosed high-risk primary melanoma to determine those patients most appropriate to undergo a PET/CT scan as part of their diagnostic work up. 167 patients with newly-diagnosed high-risk primary cutaneous melanoma underwent a PET/CT scan performed as part of their initial staging. Clinical and histologic factors were evaluated as possible predictors of melanoma metastasis identified on PET/CT scanning using both univariate and multivariate logistic regression. In all, 32 patients (19.2%) had a positive PET/CT finding of metastatic melanoma. In more than half of these patients (56.3%), PET/CT scanning identified disease that was not detectable on clinical examination. Mitotic rate, tumor thickness, lymphadenopathy, and bleeding were significantly predictive of PET/CT positivity. A combinatorial index constructed from these factors revealed a significant association between number of high-risk factors observed and prevalence of PET/CT positivity, which increased from 5.8% (with the presence of 0-2 factors) to 100.0%, when all four factors were present. These results indicate that combining clinical and histologic prognostic factors enables the identification of patients with a higher likelihood of a positive PET/CT scan.

  9. Prediction of positron emission tomography/computed tomography (PET/CT) positivity in patients with high-risk primary melanoma

    PubMed Central

    Danielsen, Maria; Kjaer, Andreas; Wu, Max; Martineau, Lea; Nosrati, Mehdi; Leong, Stanley PL; Sagebiel, Richard W; III, James R Miller; Kashani-Sabet, Mohammed

    2016-01-01

    Positron emission tomography/computed tomography (PET/CT) is an important tool to identify occult melanoma metastasis. To date, it is controversial which patients with primary cutaneous melanoma should have staging PET/CT. In this retrospective analysis of more than 800 consecutive patients with cutaneous melanoma, we sought to identify factors predictive of PET/CT positivity in the setting of newly-diagnosed high-risk primary melanoma to determine those patients most appropriate to undergo a PET/CT scan as part of their diagnostic work up. 167 patients with newly-diagnosed high-risk primary cutaneous melanoma underwent a PET/CT scan performed as part of their initial staging. Clinical and histologic factors were evaluated as possible predictors of melanoma metastasis identified on PET/CT scanning using both univariate and multivariate logistic regression. In all, 32 patients (19.2%) had a positive PET/CT finding of metastatic melanoma. In more than half of these patients (56.3%), PET/CT scanning identified disease that was not detectable on clinical examination. Mitotic rate, tumor thickness, lymphadenopathy, and bleeding were significantly predictive of PET/CT positivity. A combinatorial index constructed from these factors revealed a significant association between number of high-risk factors observed and prevalence of PET/CT positivity, which increased from 5.8% (with the presence of 0-2 factors) to 100.0%, when all four factors were present. These results indicate that combining clinical and histologic prognostic factors enables the identification of patients with a higher likelihood of a positive PET/CT scan. PMID:27766186

  10. High Reynolds number oscillating contact lines

    NASA Astrophysics Data System (ADS)

    Liu, Ziyuan; Schultz, William W.; Perlin, Marc

    1999-11-01

    Stainless steel, instead of Ting and Perlin's (1995) glass, is used in vertically oscillating plate experiments for a large range of Reynolds numbers. We used the non-wetting stainless steel to minimize the static meniscus that we ignore in our analysis. Except for the different static contact angle serving as an initial condition, the dynamic features in both cases are similar. In low Reynolds number oscillation, a pinned-edge condition can appropriately describe the contact line motion. In high Reynolds number oscillation, contact-line behavior becomes nonlinear and very complicated. The periodic, non-sinusoidal motion exhibits three types of motion: stick (associated with contact angle hysteresis), partial stick, and total slip. Increasing the Reynolds number, reduces the hysteresis phenomenon that still cannot be ignored. An edge condition allowing both the static range and dynamic interface behavior uses a slip coefficient mode that varies with time, stroke amplitude and frequency by introducing additional harmonic modes. Using this edge condition, we calculate the dynamic contact angle and the contact-line position for both stick and slip motion and compare them to our experimental data. Results show that the inviscid, linearized boundary-value problem combined with our slip coefficient model provides an improved prediction of the contact-line behavior.

  11. Turbulent convection at very high Rayleigh numbers

    PubMed

    Niemela; Skrbek; Sreenivasan; Donnelly

    2000-04-20

    Turbulent convection occurs when the Rayleigh number (Ra)--which quantifies the relative magnitude of thermal driving to dissipative forces in the fluid motion--becomes sufficiently high. Although many theoretical and experimental studies of turbulent convection exist, the basic properties of heat transport remain unclear. One important question concerns the existence of an asymptotic regime that is supposed to occur at very high Ra. Theory predicts that in such a state the Nusselt number (Nu), representing the global heat transport, should scale as Nu proportional to Ra(beta) with beta = 1/2. Here we investigate thermal transport over eleven orders of magnitude of the Rayleigh number (10(6) < or = Ra < or = 10(7)), using cryogenic helium gas as the working fluid. Our data, over the entire range of Ra, can be described to the lowest order by a single power-law with scaling exponent beta close to 0.31. In particular, we find no evidence for a transition to the Ra(1/2) regime. We also study the variation of internal temperature fluctuations with Ra, and probe velocity statistics indirectly.

  12. Accurate Coregistration between Ultra-High-Resolution Micro-SPECT and Circular Cone-Beam Micro-CT Scanners.

    PubMed

    Ji, Changguo; van der Have, Frans; Gratama van Andel, Hugo; Ramakers, Ruud; Beekman, Freek

    2010-01-01

    Introduction. Spatially registering SPECT with CT makes it possible to anatomically localize SPECT tracers. In this study, an accurate method for the coregistration of ultra-high-resolution SPECT volumes and multiple cone-beam CT volumes is developed and validated, which does not require markers during animal scanning. Methods. Transferable animal beds were developed with an accurate mounting interface. Simple calibration phantoms make it possible to obtain both the spatial transformation matrix for stitching multiple CT scans of different parts of the animal and to register SPECT and CT. The spatial transformation for image coregistration is calculated once using Horn's matching algorithm. Animal images can then be coregistered without using markers. Results. For mouse-sized objects, average coregistration errors between SPECT and CT in X, Y, and Z directions are within 0.04 mm, 0.10 mm, and 0.19 mm, respectively. For rat-sized objects, these numbers are 0.22 mm, 0.14 mm, and 0.28 mm. Average 3D coregistration errors were within 0.24 mm and 0.42 mm for mouse and rat imaging, respectively. Conclusion. Extending the field-of-view of cone-beam CT by stitching is improved by prior registration of the CT volumes. The accuracy of registration between SPECT and CT is typically better than the image resolution of current ultra-high-resolution SPECT.

  13. Confined microbubbles at high capillary numbers

    NASA Astrophysics Data System (ADS)

    Sauzade, Martin; Cubaud, Thomas

    2014-11-01

    We experimentally investigate the flow behavior of bubbles in highly viscous silicone oils within various microgeometries. A square focusing section is used to examine the bubble generation process at large capillary numbers. We notably vary the continuous phase viscosity from 1 to 10,000 cS and study the dynamics of interfacial cusps during bubble pinch-off. The resulting segmented flows are then scrutinized in straight microchannels for both dissolving and non-dissolving bubbles. Finally, we examine the motion of bubbles in periodically constricted microchannels over a wide range of flow conditions. Our findings highlight the possibility to control and exploit the interplay between capillary and mass transfer phenomena with highly viscous fluids in microsystems. This work is supported by NSF (CBET-1150389).

  14. How can a massive training artificial neural network (MTANN) be trained with a small number of cases in the distinction between nodules and vessels in thoracic CT?

    PubMed

    Suzuki, Kenji; Doi, Kunio

    2005-10-01

    To demonstrate that a massive training artificial neural network (MTANN) can be adequately trained with a small number of cases in the distinction between nodules and vessels (non-nodules) in thoracic computed tomography (CT) images. An MTANN is a trainable, highly nonlinear filter consisting of a linear-output multilayer artificial neural network model. For enhancement of nodules and suppression of vessels, we used 10 nodules and 10 non-nodule images as training cases for MTANNs. The MTANN is trained with a large number of input subregions selected from the training cases and the corresponding pixels in teaching images that contain Gaussian distributions for nodules and zero for non-nodules. We trained three MTANNs with different numbers (1, 9, and 361) of training samples (pairs of the subregion and the teaching pixel) selected from the training cases. In order to investigate the basic characteristics of the trained MTANNs, we applied the MTANNs to simulated CT images containing various-sized model nodules (spheres) with different contrasts and various-sized model vessels (cylinders) with different orientations. In addition, we applied the trained MTANNs to nontraining actual clinical cases with 59 nodules and 1,726 non-nodules. In the output images for the simulated CT images by use of the MTANNs trained with small numbers (one and nine) of subregions, model vessels were clearly visible and were not removed; thus, the MTANNs were not trained properly. However, in the output image of the MTANN trained with a large number of subregions, various-sized model nodules with different contrasts were represented by light nodular distributions, whereas various-sized model vessels with different orientations were dark and thus were almost removed. This result indicates that the MTANN was able to learn, from a very small number of actual nodule and non-nodule cases, the distinction between nodules (spherelike objects) and vessels (cylinder-like objects). In nontraining

  15. Preston Probe Calibrations at High Reynolds Number

    NASA Technical Reports Server (NTRS)

    Smits, Alexander J.

    1998-01-01

    The overall goal of the research effort is to study the performance of two Preston probes designed by NASA Langley Research Center across an unprecedented range of Reynolds number (based on friction velocity and probe diameter), and perform an accurate calibration over the same Reynolds number range. Using the Superpipe facility in Princeton, two rounds of experiments were performed. In each round of experiments for each Reynolds number, the pressure gradient, static pressure from the Preston probes and the total pressure from the Preston probes were measured. In the first round, 3 Preston probes having outer diameters of 0.058 inches, 0.083 inches and 0.203 inches were tested over a large range of pipe Reynolds numbers. Two data reduction methods were employed: first, the static pressure measured on the Preston probe was used to calculate P (modified Preston probe configuration), and secondly, the static pressure measured at the reference pressure tap was used to calculate P (un-modified Preston probe configuration). For both methods, the static pressure was adjusted to correspond with the static pressure at the Preston probe tip using the pressure gradient. The measurements for Preston probes with diameters of 0.058 inches, and 0.083 inches respectively were performed in the test pipe before it was polished a second time. Therefore, the measurements at high pipe Reynolds numbers may have been affected by roughness. In the second round of experiments the 0.058 inches and 0.083 inches diameter, un-modified probes were tested after the pipe was polished and prepared to ensure that the surface was smooth. The average velocity was estimated by assuming that the connection between the centerline velocity and the average velocity was known, and by using a Pitot tube to measure the centerline velocity. A preliminary error estimate suggests that it is possible to introduce a 1% to 2% error in estimating the average velocity using this approach. The evidence on the errors

  16. SU-E-J-268: Change of CT Number During the Course of Chemoradiation Therapy for Pancreatic Cancer

    SciTech Connect

    Chen, X; Dalah, E; Liu, F; Li, X; Zhang, J

    2015-06-15

    Purpose: It has been observed radiation can induce changes in CT number (CTN) inside tumor during the course of radiation therapy (RT) for several tumor sites including lung and head and neck, suggesting that the CTN change may be potentially used to assess RT response. In this study, we investigate the CTN changes inside tumor during the course of chemoradiation therapy (CRT) for pancreatic cancer. Methods: Daily diagnostic-quality CT data acquired during IGRT for 17 pancreatic head cancer patients using an in-room CT (CTVision, Siemens) were analyzed. All patients were treated with a radiation dose of 50.4 in 1.8 Gy per fraction. On each daily CT set, The contour of the pancreatic head, included in the treatment target, was generated by populating the pancreatic head contour from the planning CT or MRI using an auto-segmentation tool based on deformable registration (ABAS, Elekta) with manual editing if necessary. The CTN at each voxel in the pancreatic head contour was extracted and the 3D distribution of the CTNs was processed using MATLAB. The mean value of CTN distribution was used to quantify the daily CTN change in the pancreatic head. Results: Reduction of CTN in pancreatic head was observed during the CRT delivery in 14 out the 17 (82%) patients studied. Although the average reduction is only 3.5 Houncefield Unit (HU), this change is significant (p<0.01). Among them, there are 7 patients who had a CTN drop larger than 5 HU, ranging from 6.0 to 11.8 HU. In contrast to this trend, CTN was increased in 3 patients. Conclusion: Measurable changes in the CT number in tumor target were observed during the course of chemoradiation therapy for the pancreas cancer patients, indicating this radiation-induced CTN change may be used to assess treatment response.

  17. Binary droplet collision at high Weber number

    NASA Astrophysics Data System (ADS)

    Pan, Kuo-Long; Chou, Ping-Chung; Tseng, Yu-Jen

    2009-09-01

    By using the techniques developed for generating high-speed droplets, we have systematically investigated binary droplet collision when the Weber number (We) was increased from the range usually tested in previous studies on the order of 10 to a much larger value of about 5100 for water (a droplet at 23 m/s with a diameter of 0.7 mm). Various liquids were also used to explore the effects of viscosity and surface tension. Specifically, beyond the well-known regimes at moderate We’s, which exhibited coalescence, separation, and separation followed by satellite droplets, we found different behaviors showing a fingering lamella, separation after fingering, breakup of outer fingers, and prompt splattering into multiple secondary droplets as We was increased. The critical Weber numbers that mark the boundaries between these impact regimes are identified. The specific impact behaviors, such as fingering and prompt splattering or splashing, share essential similarity with those also observed in droplet-surface impacts, whereas substantial variations in the transition boundaries may result from the disparity of the boundary conditions at impacts. To compare the outcomes of both types of collisions, a simple model based on energy conservation was carried out to predict the maximum diameter of an expanding liquid disk for a binary droplet collision. The results oppose the dominance of viscous drag, as proposed by previous studies, as the main deceleration force to effect a Rayleigh-Taylor instability and ensuing periphery fingers, which may further lead to the formations of satellite droplets.

  18. Absolute measurement of the effective atomic number and the electron density by using dual-energy CT images

    NASA Astrophysics Data System (ADS)

    Kim, Dae-Hong; Lee, Won-Hyung; Jeon, Sung-Soo; Kim, Hee-Joung

    2012-12-01

    Material decomposition using dual-energy and material-selective techniques was performed using computed-tomography (CT)-generated reconstructed images. Previous work using the dual-energy method focused on extracting the effective atomic number and the electron density of materials to confirm the dosimetric accuracy in radiation therapy. Dual-energy methods mostly depend on the device generating the X-rays, such as a synchrotron, and on dose verification for radiation treatment planning. Information obtained from CT imaging is important both in diagnosis and in planning radiation therapy. In a clinical setting, CT images are usually displayed as Houndsfield units (HU), which are extracted from the attenuation coefficient of a material. The attenuation coefficient is calculated using the effective atomic number and the electron density of a material; thus, information expressed in HU can be converted into the effective atomic number and the electron density by using the dual-energy equation. This study was performed using realistic Xray spectra to differentiate between the contrast media and plaque in vascular images. Our results suggest that the effective atomic number and electron density are useful in distinguishing between two adjacent materials with similar HUs.

  19. Mixing in High Schmidt Number Turbulent Jets.

    NASA Astrophysics Data System (ADS)

    Miller, Paul Lewis

    This thesis is an experimental investigation of the passive scalar (species concentration) field in the far-field of round, axisymmetric, high Schmidt number (liquid phase), turbulent jets issuing into a quiescent reservoir, by means of a quantitative laser-induced fluorescence technique. Single -point concentration measurements are made on the jet centerline, at axial locations from 100 to 305 nozzle diameters downstream, and Reynolds numbers of 3,000 to 102,000, yielding data with a resolved temporal dynamic range up to 2.5 times 10^5, and capturing as many as 504 large-scale structure passages. Long-time statistics of the jet concentration are found to converge slowly. Between 100 and 300 large-scale structure passages are required to reduce the uncertainty in the mean to 1%, or so. The behavior of the jet varies with Reynolds number. The centerline concentration pdf's become taller and narrower with increasing Re, and the normalized concentration variances correspondingly decrease with Re. The concentration power spectra also evolve with Re. The behavior of the spectral slopes is examined. No constant -1 (Batchelor) spectral slope range is present. Rather, in the viscous region, the power spectra exhibit log-normal behavior, over a range of scales exceeding a factor of 40, in some cases. The frequency of the beginning of this log-normal range scales like Re^{3/4} (Kolmogorov scaling). Mixing in the far-field is found to be susceptible to initial conditions. Disturbances in the jet plenum fluid and near the nozzle exit strongly influence the scalar variance, with larger disturbances causing larger variances, i.e., less homogeneous mixing. The plenum/nozzle geometry also influences the variance. These effects of initial conditions persist for hundreds of diameters from the nozzle exit, over hundreds of large scales. Mixing in these jets differs from gas-phase, order unity Sc, jet mixing. At low to moderate Re, the higher Sc jet is less well mixed. The difference

  20. Noise, sampling, and the number of projections in cone-beam CT with a flat-panel detector

    SciTech Connect

    Zhao, Z.; Gang, G. J.; Siewerdsen, J. H.

    2014-06-15

    Purpose: To investigate the effect of the number of projection views on image noise in cone-beam CT (CBCT) with a flat-panel detector. Methods: This fairly fundamental consideration in CBCT system design and operation was addressed experimentally (using a phantom presenting a uniform medium as well as statistically motivated “clutter”) and theoretically (using a cascaded systems model describing CBCT noise) to elucidate the contributing factors of quantum noise (σ{sub Q}), electronic noise (σ{sub E}), and view aliasing (σ{sub view}). Analysis included investigation of the noise, noise-power spectrum, and modulation transfer function as a function of the number of projections (N{sub proj}), dose (D{sub tot}), and voxel size (b{sub vox}). Results: The results reveal a nonmonotonic relationship between image noise andN{sub proj} at fixed total dose: for the CBCT system considered, noise decreased with increasing N{sub proj} due to reduction of view sampling effects in the regime N{sub proj} <∼200, above which noise increased with N{sub proj} due to increased electronic noise. View sampling effects were shown to depend on the heterogeneity of the object in a direct analytical relationship to power-law anatomical clutter of the form κ/f {sup β}—and a general model of individual noise components (σ{sub Q}, σ{sub E}, and σ{sub view}) demonstrated agreement with measurements over a broad range in N{sub proj}, D{sub tot}, and b{sub vox}. Conclusions: The work elucidates fairly basic elements of CBCT noise in a manner that demonstrates the role of distinct noise components (viz., quantum, electronic, and view sampling noise). For configurations fairly typical of CBCT with a flat-panel detector (FPD), the analysis reveals a “sweet spot” (i.e., minimum noise) in the rangeN{sub proj} ∼ 250–350, nearly an order of magnitude lower in N{sub proj} than typical of multidetector CT, owing to the relatively high electronic noise in FPDs. The analysis

  1. High resolution X-ray CT for advanced electronics packaging

    NASA Astrophysics Data System (ADS)

    Oppermann, M.; Zerna, T.

    2017-02-01

    Advanced electronics packaging is a challenge for non-destructive Testing (NDT). More, smaller and mostly hidden interconnects dominate modern electronics components and systems. To solve the demands of customers to get products with a high functionality by low volume, weight and price (e.g. mobile phones, personal medical monitoring systems) often the designers use System-in-Package solutions (SiP). The non-destructive testing of such devices is a big challenge. So our paper will impart fundamentals and applications for non-destructive evaluation of inner structures of electronics packaging for quality assurance and reliability investigations with a focus on X-ray methods, especially on high resolution X-ray computed tomography (CT).

  2. High speed optical quantum random number generation.

    PubMed

    Fürst, Martin; Weier, Henning; Nauerth, Sebastian; Marangon, Davide G; Kurtsiefer, Christian; Weinfurter, Harald

    2010-06-07

    We present a fully integrated, ready-for-use quantum random number generator (QRNG) whose stochastic model is based on the randomness of detecting single photons in attenuated light. We show that often annoying deadtime effects associated with photomultiplier tubes (PMT) can be utilized to avoid postprocessing for bias or correlations. The random numbers directly delivered to a PC, generated at a rate of up to 50 Mbit/s, clearly pass all tests relevant for (physical) random number generators.

  3. High Rayleigh number convection numerical experiments

    NASA Astrophysics Data System (ADS)

    Verzicco, Roberto

    2002-03-01

    temperature variance dissipations. The achieved results seem to support the idea that the observed transitional behaviors have to be attributed to the change in the topology of the mean flow rather than to a transition from a laminar to a turbulent state of the viscous boundary layers. Other issues accomplished by the simulation concern the study of the scaling properties of the turbulent quantities and length scales in terms of Ra. Finally, further details on the turbulence dynamics are obtained by the analysis of the power spectra and low order structure functions of both the temperature and the velocity components, computed from the numerical probes both within the bulk region and close to the walls. References Roche, PE; Castaing, B; Chabaud, B; Hebral, B. ``Observation of the 1/2 power law in Rayleigh-Benard convection'' Phys. Rev. E, 2001, 6304(4), p. 5303. Niemela, J.J.; Skrbek, L.; Sreenivasan, K.R. and Donnelly, R.J. ``Turbulent convection at very high Rayleigh numbers'' Nature, 405, 243-253 (11 May 2000). Verzicco, R. and Camussi, R. ``Prandtl number effects in convective turbulence'' J. of Fluid Mech., 383, (1999), 55-73.

  4. Viscous thermocapillary convection at high Marangoni number

    NASA Technical Reports Server (NTRS)

    Cowley, S. J.; Davis, S. H.

    1983-01-01

    A liquid, contained in a quarter plane, undergoes steady motion due to thermocapillary forcing on its upper boundary, a free surface separating the liquid from a passive gas. The rigid vertical sidewall has a strip whose temperature is elevated compared with the liquid at infinity. A boudnary-layer analysis is performed that is valid for large Marangoni numbers M and Prandtl numbers P. It is found that the Nusselt number N for the horizontal heat transport satisfies N proportional to min (M to the 1 2/7/power, M to the 1 1/5/power, M to the 1 1/10/power) Generalizations are discussed.

  5. Random Number Generation for High Performance Computing

    DTIC Science & Technology

    2015-01-01

    SECURITY CLASSIFICATION OF: The primary objectives of the Phase II of the project are: (a) implement the context-aware parallel random number...Report Title The primary objectives of the Phase II of the project are: (a) implement the context-aware parallel random number generator (CPRNG...standard Unix/Linux systems, and a parallel RNG based on cryptographic operations from the family of generators proposed by D.E. Shaw Group [12], and a

  6. Proton tracking in a high-granularity Digital Tracking Calorimeter for proton CT purposes

    NASA Astrophysics Data System (ADS)

    Pettersen, H. E. S.; Alme, J.; Biegun, A.; van den Brink, A.; Chaar, M.; Fehlker, D.; Meric, I.; Odland, O. H.; Peitzmann, T.; Rocco, E.; Ullaland, K.; Wang, H.; Yang, S.; Zhang, C.; Röhrich, D.

    2017-07-01

    Radiation therapy with protons as of today utilizes information from x-ray CT in order to estimate the proton stopping power of the traversed tissue in a patient. The conversion from x-ray attenuation to proton stopping power in tissue introduces range uncertainties of the order of 2-3% of the range, uncertainties that are contributing to an increase of the necessary planning margins added to the target volume in a patient. Imaging methods and modalities, such as Dual Energy CT and proton CT, have come into consideration in the pursuit of obtaining an as good as possible estimate of the proton stopping power. In this study, a Digital Tracking Calorimeter is benchmarked for proof-of-concept for proton CT purposes. The Digital Tracking Calorimeter was originally designed for the reconstruction of high-energy electromagnetic showers for the ALICE-FoCal project. The presented prototype forms the basis for a proton CT system using a single technology for tracking and calorimetry. This advantage simplifies the setup and reduces the cost of a proton CT system assembly, and it is a unique feature of the Digital Tracking Calorimeter concept. Data from the AGORFIRM beamline at KVI-CART in Groningen in the Netherlands and Monte Carlo simulation results are used to in order to develop a tracking algorithm for the estimation of the residual ranges of a high number of concurrent proton tracks. High energy protons traversing the detector leave a track through the sensor layers. These tracks are spread out through charge diffusion processes. A charge diffusion model is applied for acquisition of estimates of the deposited energy of the protons in each sensor layer by using the size of the charge diffused area. A model fit of the Bragg Curve is applied to each reconstructed track and through this, estimating the residual range of each proton. The range of the individual protons can at present be estimated with a resolution of 4%. The readout system for this prototype is able to

  7. A new method to measure electron density and effective atomic number using dual-energy CT images

    NASA Astrophysics Data System (ADS)

    Ramos Garcia, Luis Isaac; Pérez Azorin, José Fernando; Almansa, Julio F.

    2016-01-01

    The purpose of this work is to present a new method to extract the electron density ({ρ\\text{e}} ) and the effective atomic number (Z eff) from dual-energy CT images, based on a Karhunen-Loeve expansion (KLE) of the atomic cross section per electron. This method was used to calibrate a Siemens Definition CT using the CIRS phantom. The predicted electron density and effective atomic number using 80 kVp and 140 kVp were compared with a calibration phantom and an independent set of samples. The mean absolute deviations between the theoretical and calculated values for all the samples were 1.7 %  ±  0.1 % for {ρ\\text{e}} and 4.1 %  ±  0.3 % for Z eff. Finally, these results were compared with other stoichiometric method. The application of the KLE to represent the atomic cross section per electron is a promising method for calculating {ρ\\text{e}} and Z eff using dual-energy CT images.

  8. A new method to measure electron density and effective atomic number using dual-energy CT images.

    PubMed

    Garcia, Luis Isaac Ramos; Azorin, José Fernando Pérez; Almansa, Julio F

    2016-01-07

    The purpose of this work is to present a new method to extract the electron density ([Formula: see text]) and the effective atomic number (Z eff) from dual-energy CT images, based on a Karhunen-Loeve expansion (KLE) of the atomic cross section per electron. This method was used to calibrate a Siemens Definition CT using the CIRS phantom. The predicted electron density and effective atomic number using 80 kVp and 140 kVp were compared with a calibration phantom and an independent set of samples. The mean absolute deviations between the theoretical and calculated values for all the samples were 1.7 %  ±  0.1 % for [Formula: see text] and 4.1 %  ±  0.3 % for Z eff. Finally, these results were compared with other stoichiometric method. The application of the KLE to represent the atomic cross section per electron is a promising method for calculating [Formula: see text] and Z eff using dual-energy CT images.

  9. EDITORIAL: Special issue on High Reynolds Number Experiments Special issue on High Reynolds Number Experiments

    NASA Astrophysics Data System (ADS)

    Tsuji, Yoshiyuki

    2009-04-01

    Why do we need high Reynolds number experiments? This is a question I sometimes ask myself. You may have your own answer to this question, but those people who are doing numerical simulation, theorists and experimentalists should each have their own answer. In this special issue, the leading experts present their new ideas or original experiments in response to this question. Personally, I think that high Reynolds number experiments are necessary to seek novel physics in turbulence. For instance, we do not have much information about the Lagrangian quantities. You can understand this point by reading the article 'Why we need experiments at high Reynolds numbers' by Warhaft. High Reynolds number experiments are also indispensable to reveal the universality of turbulence. One famous example is Kolmogorov's similarity hypothesis; another is the logarithmic velocity profile derived by von Kármán. They become clearly satisfied as Reynolds number increases. But there have been many arguments over these problems even in this century, thus we still have to make an effort to reveal the nature of turbulence. Kolmogorov's idea is based on small scale physics; in this sense, Mouri and Hori's paper 'Vortex tubes in turbulence velocity fields at high Reynolds numbers' is a contribution to understanding how eddy size is defined and scaled. In contrast to the universality in the small scale limit, the large scale anisotropy effect is a key factor in considering the local isotropic condition even in grid turbulence. This point is discussed by Kurian and Fransson in 'Grid generated turbulence revisited'. The mean velocity profile over a flat plate in a zero-pressure gradient boundary layer is discussed with the help of a composite profile in 'Criteria for assessing experiments in zero pressure gradient boundary layers' by Chauhan et al. Related important physical quantities are computed, and how they are scaled against Reynolds number is discussed, analyzing the vast experimental

  10. Number theory meets high energy physics

    NASA Astrophysics Data System (ADS)

    Todorov, Ivan

    2017-03-01

    Feynman amplitudes in perturbative quantum field theory are being expressed in terms of an algebra of functions, extending the familiar logarithms, and associated numbers— periods. The study of these functions (including hyperlogarithms) and numbers (like the multiple zeta values), that dates back to Leibniz and Euler, has attracted anew the interest of algebraic geometers and number theorists during the last decades. The two originally independent developments are recently coming together in an unlikely collaboration between particle physics and what were regarded as the most abstruse branches of mathematics.

  11. Analysis of CT Numbers and Relative Proton Stopping Powers for Real Tissue Samples

    SciTech Connect

    Ryazantsev, Oleg; Karpunin, Vladimir; Haibullin, Vadim; Matusova, Tatiana

    2010-01-05

    The accuracy of computer planning of clinical proton dose distribution is partly determined by the precision of the conversion of CT Hounsfield Units to relative proton stopping powers. The calibration curves from three different sources were compared. We have found about 5% differences between proton stopping power values in the range from -700 HU to 0 HU. Calibration data for several soft tissues and phantom materials were also experimentally measured. The data for the tissues are in a good agreement with the calibration curves however data for phantom materials have significant deviations.

  12. High-resolution and high-speed CT in industry and research

    NASA Astrophysics Data System (ADS)

    Zabler, S.; Fella, C.; Dietrich, A.; Nachtrab, F.; Salamon, Michael; Voland, V.; Ebensperger, T.; Oeckl, S.; Hanke, R.; Uhlmann, N.

    2012-10-01

    The application of industrial CT covers many orders of magnitude of object sizes, ranging from freight containers (few meters) down to liquid foams (i.e. for food industry) or even parts of insects which are only several hundreds of micrometers in size. Similarly, the specifications for acquisition speed extend over some orders of magnitude, from hours to sub-second CT. We present the current technology in terms of X-ray sources and detectors, along with numerous applications from industry and materials research: e.g. industrial high-speed CT of car pistons, in situ micro-CT of milk foam decay at micrometer spatial resolution and 8 s scan time, as well as ex situ scans of tensile tested Nickel-alloys. The Fraunhofer Development Center X-ray Technology (Fürth, Germany) and the Chair of X-ray Microscopy (University Würzburg, Germany) are currently working on extending the technological limits, demonstrated, e,g. by the development of advanced X-ray detectors or a new inhouse CT system which comprises a high-brilliance liquid metal jet anode.

  13. Calibration of megavoltage cone-beam CT for radiotherapy dose calculations: Correction of cupping artifacts and conversion of CT numbers to electron density

    SciTech Connect

    Petit, Steven F.; Elmpt, Wouter J. C. van; Nijsten, Sebastiaan M. J. J. G.; Lambin, Philippe; Dekker, Andre L. A. J.

    2008-03-15

    Megavoltage cone-beam CT (MV CBCT) is used for three-dimensional imaging of the patient anatomy on the treatment table prior to or just after radiotherapy treatment. To use MV CBCT images for radiotherapy dose calculation purposes, reliable electron density (ED) distributions are needed. Patient scatter, beam hardening and softening effects result in cupping artifacts in MV CBCT images and distort the CT number to ED conversion. A method based on transmission images is presented to correct for these effects without using prior knowledge of the object's geometry. The scatter distribution originating from the patient is calculated with pencil beam scatter kernels that are fitted based on transmission measurements. The radiological thickness is extracted from the scatter subtracted transmission images and is then converted to the primary transmission used in the cone-beam reconstruction. These corrections are performed in an iterative manner, without using prior knowledge regarding the geometry and composition of the object. The method was tested using various homogeneous and inhomogeneous phantoms with varying shapes and compositions, including a phantom with different electron density inserts, phantoms with large density variations, and an anthropomorphic head phantom. For all phantoms, the cupping artifact was substantially removed from the images and a linear relation between the CT number and electron density was found. After correction the deviations in reconstructed ED from the true values were reduced from up to 0.30 ED units to 0.03 for the majority of the phantoms; the residual difference is equal to the amount of noise in the images. The ED distributions were evaluated in terms of absolute dose calculation accuracy for homogeneous cylinders of different size; errors decreased from 7% to below 1% in the center of the objects for the uncorrected and corrected images, respectively, and maximum differences were reduced from 17% to 2%, respectively. The

  14. Unresectable colorectal liver metastases: percutaneous ablation using CT-guided high-dose-rate brachytherapy (CT-HDBRT).

    PubMed

    Collettini, F; Lutter, A; Schnapauff, D; Hildebrandt, B; Puhl, G; Denecke, T; Wust, P; Gebauer, B

    2014-06-01

    To evaluate the clinical outcome of CT-guided high-dose-rate brachytherapy (CT-HDRBT) of unresectable colorectal liver metastases (CRLMs). Retrospective analysis of all consecutive patients with unresectable CRLMs treated with CT-HDRBT between January 2008 and November 2012. Treatment was performed by CT-guided catheter placement and high-dose-rate brachytherapy with an iridium-192 source. MRI follow-up was performed after 6 weeks and then every 3 months post-intervention. The primary endpoint was local tumor control (LTC); secondary endpoints included time to progression (TTP) and overall survival (OS). 80 heavily pretreated patients with 179 metastases were available for MRI evaluation for a mean follow-up time of 16.9 months. The mean tumor diameter was 28.5 mm (range: 8 - 107 mm). No major complications were observed. A total of 23 (12.9 %) local tumor progressions were observed. Lesions ≥ 4 cm in diameter showed significantly more local progression than smaller lesions (< 4 cm). 50 patients (62.5 %) experienced systemic tumor progression. The median TTP was 6 months. 28 (43 %) patients died during the follow-up period. The median OS after ablation was 18 months. CT-HDRBT is an effective technique for the treatment of unresectable CRLMs and warrants promising LTC rates compared to thermal ablative techniques. A combination with other local and systemic therapies should be evaluated in patients with lesions > 4 cm in diameter, in which higher progression rates are expected. • CT-HDRBT enables a highly cytotoxic irradiation of colorectal liver metastases with simultaneous conservation of important neighboring structures (eg liver parenchyma, bile ducts and bowel)• The local tumor control rates obtained by CT-HDRBT in patients with colorectal liver metastases are promising, also compared to the local tumor control rates after RFA• Metastases with a diameter of 4 cm or abow, display a higher local progression rate after CT

  15. Efficacy of high-pitch CT protocols for radiation dose reduction.

    PubMed

    Guberina, N; Lechel, U; Forsting, M; Ringelstein, A

    2016-12-01

    Various strategies have been developed to reduce radiation exposure of patients in CT examinations. The aim of this study was to evaluate the efficacy of high pitch in representative CT protocols examining lung embolism. We performed thermoluminescence measurements with an anthropomorphic phantom exposing it to CT algorithms for lung embolism in a 128-multislice, dual-source CT scanner: a standard CT protocol (sCT) and a CT protocol with a high pitch (+ F). Radiation doses for both CT algorithms were compared and the dose reduction potential of high pitch for individual organs was evaluated. As expected, the  +F mode reduced the effective dose and organ doses in the primary beam of radiation (namely, lung, bone marrow, heart, breast, skin and skeleton) compared with sCT by up to 52% for an equivalent image quality. On the contrary, for organs at the margin of the primary beam (thymus, thyroid, liver, pancreas, kidneys, colon and small intestine), the  +F mode reduced effective radiation doses by only 0-30%, compared with sCT. The dose reduction potential of the  +F mode greatly depends on the position of the organ in the scan field. While for organs in the primary beam  + F leads to a considerable dose reduction, it is less effective for tissues at the margin of the scanned area.

  16. Dripping dynamics at high Bond numbers

    NASA Astrophysics Data System (ADS)

    Rubio-Rubio, Mariano; Taconet, Paloma; Sevilla, Alejandro

    2014-11-01

    When dispensing liquid from a vertically oriented injector under gravity, drops grow at the outlet until the surface tension forces can no longer balance their weight, and the pinch-off occurs. This dripping regime no longer exists above a critical flow rate, at which an abrupt transition to jetting takes place. These phenomena are governed by the liquid properties, the injector size and the injection flow rate, or non-dimensionally, by the Bond, Bo , Weber, We , and Kapitza, Γ, numbers. Detailed accounts of the rich dynamics of the dripping regime and the transition leading to jetting can be found in the literature (e.g. Phys. Rev. Lett. vol. 93, 2004, and Phys. Fluids vol. 18, 2006), but only for two different values of Bo . Therefore, we present new experiments on the dripping dynamics and jetting transition for a wide range of both the liquid viscosity and the size of the injector, reaching values of Bo up to one order-of-magnitude larger than those present in the literature. Our results reveal the existence of new dynamics in the dripping regime not observed at small Bond numbers. In addition, we quantify the hysteresis present in the dripping-jetting transition, previously measured only for the inviscid case. Supported by Spanish MINECO under Project DPI 2011-28356-C03-02.

  17. Impact of number of repeated scans on model observer performance for a low-contrast detection task in CT

    NASA Astrophysics Data System (ADS)

    Ma, Chi; Yu, Lifeng; Chen, Baiyu; Vrieze, Thomas; Favazza, Christopher; Leng, Shuai; McCollough, Cynthia

    2015-03-01

    In previous investigations on CT image quality, channelized Hotelling observer (CHO) models have been shown to well represent human observer performance in several phantom-based detection/discrimination tasks. In these studies, a large number of independent images was necessary to estimate the expectation images and covariance matrices for each test condition. The purpose of this study is to investigate how the number of repeated scans affects the precision and accuracy of the CHO's performance in a signal-known-exactly detection task. A phantom containing 21 low-contrast objects (3 contrast levels and 7 sizes) was scanned with a 128-slice CT scanner at three dose levels. For each dose level, 100 independent images were acquired for each test condition. All images were reconstructed using filtered-backprojection (FBP) and a commercial iterative reconstruction algorithm. For each combination of dose level and reconstruction method, the low-contrast detectability, quantified with the area under receiver operating characteristic curve (Az), was calculated using a previously validated CHO model. To determine the dependency of CHO performance on the number of repeated scans, the Az value was calculated for different number of channel filters, for each object size and contrast, and for different dose/reconstruction settings using all 100 repeated scans. The Az values were also calculated using randomly selected subsets of the scans (from 10 to 90 scans with an increment of 10 scans). Using the Az from the 100 scans as the reference, the accuracy of Az values calculated from a fewer number of scans was determined and the minimal number of scans was subsequently derived. For the studied signal-known-exactly detection task, results demonstrated that, the minimal number of scans depends on dose level, object size and contrast level, and channel filters.

  18. A comprehensive study on decreasing the kilovoltage cone-beam CT dose by reducing the projection number.

    PubMed

    Lu, Bo; Lu, Haibin; Palta, Jatinder

    2010-05-12

    The objective of this study was to evaluate the effect of kilovoltage cone-beam computed tomography (CBCT) on registration accuracy and image qualities with a reduced number of planar projections used in volumetric imaging reconstruction. The ultimate goal is to evaluate the possibility of reducing the patient dose while maintaining registration accuracy under different projection-number schemes for various clinical sites. An Elekta Synergy Linear accelerator with an onboard CBCT system was used in this study. The quality of the Elekta XVI cone-beam three-dimensional volumetric images reconstructed with a decreasing number of projections was quantitatively evaluated by a Catphan phantom. Subsequently, we tested the registration accuracy of imaging data sets on three rigid anthropomorphic phantoms and three real patient sites under the reduced projection-number (as low as 1/6th) reconstruction of CBCT data with different rectilinear shifts and rota-tions. CBCT scan results of the Catphan phantom indicated the CBCT images got noisier when the number of projections was reduced, but their spatial resolution and uniformity were hardly affected. The maximum registration errors under the small amount transformation of the reference CT images were found to be within 0.7 mm translation and 0.3 masculine rotation. However, when the projection number was lower than one-fourth of the full set with a large amount of transformation of reference CT images, the registration could easily be trapped into local minima solutions for a nonrigid anatomy. We concluded, by using projection-number reduction strategy under conscientious care, imaging-guided localization procedure could achieve a lower patient dose without losing the registration accuracy for various clinical sites and situations. A faster scanning time is the main advantage compared to the mA decrease-based, dose-reduction method.

  19. High Reynolds number turbulent pipe flow

    NASA Astrophysics Data System (ADS)

    Zhao, Rongrong

    Fully developed turbulent pipe is studied in this thesis. Streamwise and wall-normal turbulence components are measured using a crossed hot-wire probe. In the process, a new calibration method for the crossed hot-wire probe is developed, and the binormal cooling error for hot-wire measurement, which is caused by cooling in the direction normal to the hot-wire measurement plane, is studied and found to be the major error contributor for both mean velocity and turbulence intensity measurements using a crossed-wire probe. The new calibration scheme utilizes the fact that the total stress in a fully developed turbulent pipe flow is defined by the streamwise pressure gradient, so directional sensibility calibration could be done by recording the crossed hot-wire signals against a known shear stress distribution. This information, when combined with mean velocity calibration against a Pitot tube measurement, provide a full calibration for crossed hot-wire probes. The new calibration method is especially convenient for pipe and channel flow measurements. For other measurements, the calibration could be done by using a simple pipe apparatus as the calibration device. Streamwise and wall-normal turbulence components are measured over a Reynolds number range from 1.1 x 105 to 9.8 x 10 6. Similarity arguments are studied for turbulence intensity and spectra. The most relevant physical assumption for the 'similarity' is Townsend's distinction between 'active' and 'inactive' motions. Perry's attached eddy hypothesis, which is based on Townsend's work, offers a more detailed physical model and provides extensive quantitative prediction, is also reviewed and discussed in the context of these new measurements. For the wall-normal turbulence intensity, a constant region in u'rms is found for the region 200 ≤ y+ ≤ 0.1R+ in inner and outer scaling for Reynolds numbers up to 1.0 x 106. An increase in u'rms is observed closer to the wall at about y + ˜ 100, and is suggestive of

  20. The High/Scope Report. Number Four.

    ERIC Educational Resources Information Center

    Silverman, Charles, Ed.

    This report provides articles on several topics related to the education of young children. In the introduction High/Scope President David P. Weikart suggests that public investment in preschool education is a wise and economically sound social policy. New studies of the long term effects of preschool are demonstrating the staying power of early…

  1. Effects of High Power Lasers, Number 4

    DTIC Science & Technology

    1974-10-31

    the R\\S dynamic structures of the resultant stationary plasmatron . New theoretical results are obtained relating to t-mperaturts and pressures in...the erosion of specimens, depended on their thermal processing history . Thus the high erosion of hardened specimens in comparison to the erosion...Investigations were done using two methods: 1. Optical diagnostics. A single-stage PIM-3 electron-optical converter was used for scanning plasma

  2. SU-F-R-50: Radiation-Induced Changes in CT Number Histogram During Chemoradiation Therapy for Pancreatic Cancer

    SciTech Connect

    Chen, X; Schott, D; Song, Y; Li, D; Hall, W; Erickson, B; Li, X

    2016-06-15

    Purpose: In an effort of early assessment of treatment response, we investigate radiation induced changes in CT number histogram of GTV during the delivery of chemoradiation therapy (CRT) for pancreatic cancer. Methods: Diagnostic-quality CT data acquired daily during routine CT-guided CRT using a CT-on-rails for 20 pancreatic head cancer patients were analyzed. All patients were treated with a radiation dose of 50.4 in 28 fractions. On each daily CT set, the contours of the pancreatic head and the spinal cord were delineated. The Hounsfiled Units (HU) histogram in these contourswere extracted and processed using MATLAB. Eight parameters of the histogram including the mean HU over all the voxels, peak position, volume, standard deviation (SD), skewness, kurtosis, energy, and entropy were calculated for each fraction. The significances were inspected using paired two-tailed t-test and the correlations were analyzed using Spearman rank correlation tests. Results: In general, HU histogram in pancreatic head (but not in spinal cord) changed during the CRT delivery. Changes from the first to the last fraction in mean HU in pancreatic head ranged from −13.4 to 3.7 HU with an average of −4.4 HU, which was significant (P<0.001). Among other quantities, the volume decreased, the skewness increased (less skewed), and the kurtosis decreased (less sharp) during the CRT delivery. The changes of mean HU, volume, skewness, and kurtosis became significant after two weeks of treatment. Patient pathological response status is associated with the changes of SD (ΔSD), i.e., ΔSD= 1.85 (average of 7 patients) for good reponse, −0.08 (average of 6 patients) for moderate and poor response. Conclusion: Significant changes in HU histogram and the histogram-based metrics (e.g., meam HU, skewness, and kurtosis) in tumor were observed during the course of chemoradiation therapy for pancreas cancer. These changes may be potentially used for early assessment of treatment response.

  3. High-quality four-dimensional cone-beam CT by deforming prior images

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Gu, Xuejun

    2013-01-01

    Due to a limited number of projections at each phase, severe view aliasing artifacts are present in four-dimensional cone beam computed tomography (4D-CBCT) when reconstruction is performed using conventional algorithms. In this work, we aim to obtain high-quality 4D-CBCT of lung cancer patients in radiation therapy by deforming the planning CT. The deformation vector fields (DVF) to deform the planning CT are estimated through matching the forward projection of the deformed prior image and measured on-treatment CBCT projection. The estimation of the DVF is formulated as an unconstrained optimization problem, where the objective function to be minimized is the sum of the squared difference between the forward projection of the deformed planning CT and the measured 4D-CBCT projection. A nonlinear conjugate gradient method is used to solve the DVF. As the number of the variables in the DVF is much greater than the number of measurements, the solution to such a highly ill-posed problem is very sensitive to the initials during the optimization process. To improve the estimation accuracy of DVF, we proposed a new strategy to obtain better initials for the optimization. In this strategy, 4D-CBCT is first reconstructed by total variation minimization. Demons deformable registration is performed to register the planning CT and the 4D-CBCT reconstructed by total variation minimization. The resulted DVF from demons registration is then used as the initial parameters in the optimization process. A 4D nonuniform rotational B-spline-based cardiac-torso (NCAT) phantom and a patient 4D-CBCT are used to evaluate the algorithm. Image quality of 4D-CBCT is substantially improved by using the proposed strategy in both NCAT phantom and patient studies. The proposed method has the potential to improve the temporal resolution of 4D-CBCT. Improved 4D-CBCT can better characterize the motion of lung tumors and will be a valuable tool for image-guided adaptive radiation therapy.

  4. High-quality four-dimensional cone-beam CT by deforming prior images.

    PubMed

    Wang, Jing; Gu, Xuejun

    2013-01-21

    Due to a limited number of projections at each phase, severe view aliasing artifacts are present in four-dimensional cone beam computed tomography (4D-CBCT) when reconstruction is performed using conventional algorithms. In this work, we aim to obtain high-quality 4D-CBCT of lung cancer patients in radiation therapy by deforming the planning CT. The deformation vector fields (DVF) to deform the planning CT are estimated through matching the forward projection of the deformed prior image and measured on-treatment CBCT projection. The estimation of the DVF is formulated as an unconstrained optimization problem, where the objective function to be minimized is the sum of the squared difference between the forward projection of the deformed planning CT and the measured 4D-CBCT projection. A nonlinear conjugate gradient method is used to solve the DVF. As the number of the variables in the DVF is much greater than the number of measurements, the solution to such a highly ill-posed problem is very sensitive to the initials during the optimization process. To improve the estimation accuracy of DVF, we proposed a new strategy to obtain better initials for the optimization. In this strategy, 4D-CBCT is first reconstructed by total variation minimization. Demons deformable registration is performed to register the planning CT and the 4D-CBCT reconstructed by total variation minimization. The resulted DVF from demons registration is then used as the initial parameters in the optimization process. A 4D nonuniform rotational B-spline-based cardiac-torso (NCAT) phantom and a patient 4D-CBCT are used to evaluate the algorithm. Image quality of 4D-CBCT is substantially improved by using the proposed strategy in both NCAT phantom and patient studies. The proposed method has the potential to improve the temporal resolution of 4D-CBCT. Improved 4D-CBCT can better characterize the motion of lung tumors and will be a valuable tool for image-guided adaptive radiation therapy.

  5. Radiation dose reduction in time-resolved CT angiography using highly constrained back projection reconstruction

    PubMed Central

    Supanich, Mark; Tao, Yinghua; Nett, Brian; Pulfer, Kari; Hsieh, Jiang; Turski, Patrick; Mistretta, Charles; Rowley, Howard; Chen, Guang-Hong

    2010-01-01

    Recently dynamic, time-resolved three-dimensional computed tomography angiography (CTA) has been introduced to the neurological imaging community. However, the radiation dose delivered to patients in time-resolved CTA protocol is a high and potential risk associated with the ionizing radiation dose. Thus, minimizing the radiation dose is highly desirable for time-resolved CTA. In order to reduce the radiation dose delivered during dynamic, contrast-enhanced CT applications, we introduce here the CT formulation of HighlY constrained back PRojection (HYPR) imaging. We explore the radiation dose reduction approaches of both acquiring a reduced number of projections for each image and lowering the tube current used during acquisition. We then apply HYPR image reconstruction to produce image sets at a reduced patient dose and with low image noise. Numerical phantom experiments and retrospective analysis of in vivo canine studies are used to assess the accuracy and quality of HYPR reduced dose image sets and validate our approach. Experimental results demonstrated that a factor of 6–8 times radiation dose reduction is possible when the HYPR algorithm is applied to time-resolved CTA exams. PMID:19567941

  6. Initial implementation of the conversion from the energy-subtracted CT number to electron density in tissue inhomogeneity corrections: An anthropomorphic phantom study of radiotherapy treatment planning

    SciTech Connect

    Tsukihara, Masayoshi; Noto, Yoshiyuki; Sasamoto, Ryuta; Hayakawa, Takahide; Saito, Masatoshi

    2015-03-15

    Purpose: To achieve accurate tissue inhomogeneity corrections in radiotherapy treatment planning, the authors had previously proposed a novel conversion of the energy-subtracted computed tomography (CT) number to an electron density (ΔHU–ρ{sub e} conversion), which provides a single linear relationship between ΔHU and ρ{sub e} over a wide range of ρ{sub e}. The purpose of this study is to present an initial implementation of the ΔHU–ρ{sub e} conversion method for a treatment planning system (TPS). In this paper, two example radiotherapy plans are used to evaluate the reliability of dose calculations in the ΔHU–ρ{sub e} conversion method. Methods: CT images were acquired using a clinical dual-source CT (DSCT) scanner operated in the dual-energy mode with two tube potential pairs and an additional tin (Sn) filter for the high-kV tube (80–140 kV/Sn and 100–140 kV/Sn). Single-energy CT using the same DSCT scanner was also performed at 120 kV to compare the ΔHU–ρ{sub e} conversion method with a conventional conversion from a CT number to ρ{sub e} (Hounsfield units, HU–ρ{sub e} conversion). Lookup tables for ρ{sub e} calibration were obtained from the CT image acquisitions for tissue substitutes in an electron density phantom (EDP). To investigate the beam-hardening effect on dosimetric uncertainties, two EDPs with different sizes (a body EDP and a head EDP) were used for the ρ{sub e} calibration. Each acquired lookup table was applied to two radiotherapy plans designed using the XiO TPS with the superposition algorithm for an anthropomorphic phantom. The first radiotherapy plan was for an oral cavity tumor and the second was for a lung tumor. Results: In both treatment plans, the performance of the ΔHU–ρ{sub e} conversion was superior to that of the conventional HU–ρ{sub e} conversion in terms of the reliability of dose calculations. Especially, for the oral tumor plan, which dealt with dentition and bony structures, treatment

  7. TU-EF-304-06: A Comparison of CT Number to Relative Linear Stopping Power Conversion Curves Used by Proton Therapy Centers

    SciTech Connect

    Taylor, P; Lowenstein, J; Kry, S; Ibbott, G; Followill, D

    2015-06-15

    Purpose: To compare the CT Number (CTN) to Relative Linear Stopping Power (RLSP) conversion curves used by 14 proton institutions in their dose calculations. Methods: The proton institution’s CTN to RLSP conversion curves were collected by the Imaging and Radiation Oncology Core (IROC) Houston QA Center during its on-site dosimetry review audits. The CTN values were converted to scaled CT Numbers. The scaling assigns a CTN of 0 to air and 1000 to water to allow intercomparison. The conversion curves were compared and the mean curve was calculated based on institutions’ predicted RLSP values for air (CTN 0), lung (CTN 250), fat (CTN 950), water (1000), liver (CTN 1050), and bone (CTN 2000) points. Results: One institution’s curve was found to have a unique curve shape between the scaled CTN of 1025 to 1225. This institution modified its curve based on the findings. Another institution had higher RLSP values than expected for both low and high CTNs. This institution recalibrated their two CT scanners and the new data placed their curve closer to the mean of all institutions. After corrections were made to several conversion curves, four institutions still fall outside 2 standard deviations at very low CTNs (100–200), and two institutions fall outside between CTN 850–900. The largest percent difference in RLSP values between institutions for the specific tissues reviewed was 22% for the lung point. Conclusion: The review and comparison of CTN to RLSP conversion curves allows IROC Houston to identify any outliers and make recommendations for improvement. Several institutions improved their clinical dose calculation accuracy as a Result of this review. There is still area for improvement, particularly in the lung area of the curve. The IROC Houston QA Center is supported by NCI grant CA180803.

  8. High Prandtl number effect on Rayleigh-Bénard convection heat transfer at high Rayleigh number

    NASA Astrophysics Data System (ADS)

    Ma, Li; Li, Jing; Ji, Shui; Chang, Huajian

    2017-02-01

    This paper represents results of the Rayleigh-Bénard convection heat transfer in silicon oil confined by two horizontal plates, heated from below, and cooled from above. The Prandtl numbers considered as 100-10,000 corresponding to three types of silicon oil. The experiments covered a range of Rayleigh numbers from 2.14·109 to 2.27·1013. The data points that the Nusselt number dependents on the Rayleigh number, which is asymptotic to a 0.248 power. Furthermore, the experiment results can fit the data in low Rayleigh number well.

  9. Hepatic contrast agents for computed tomography: high atomic number particulate material.

    PubMed

    Seltzer, S E; Adams, D F; Davis, M A; Hessel, S J; Havron, A; Judy, P F; Paskins-Hurlburt, A J; Hollenberg, N K

    1981-06-01

    We used a stepwise approach to identify, design, synthesize, and test new high atomic number particulate contrast agents that would be especially well suited for use with computed tomography (CT). Our goal was to produce extremely radiopaque compounds with highly selective biodistribution to the normal liver. In this way, dose requirements could be lessened and toxicity minimized. Suspensions of cerium, gadolinium, and dysprosium oxide particles and silver iodide colloid were tested and compared with standard agents. All four experimental agents were selectively concentrated in the reticuloendothelial systems of rats and rabbits. These compounds produced greater and longer opacification of normal livers and larger liver-to-tumor differences in rabbits with hepatic tumors than did equivalent amounts of standard, iodinated agents. Lesions as small as 5 mm were visible with CT. These experimental materials have favorable characteristics as hepatic contrast agents, but their toxicity and long term retention may limit clinical use.

  10. Hepatic contrast agents for computed tomography: high atomic number particulate material

    SciTech Connect

    Seltzer, S.E.; Adams, D.F.; Davis, M.A.; Hessel, S.J.; Havron, A.; Judy, P.F.; Paskins-Hurlburt, A.J.; Hollenberg, N.K.

    1981-06-01

    We used a stepwise approach to identify, design, synthesize, and test new high atomic number particulate contrast agents that would be especially well suited for use with computed tomography (CT). Our goal was to produce extremely radiopaque compounds with highly selective biodistribution to the normal liver. In this way, dose requirements could be lessened and toxicity minimized. Suspensions of cerium, gadolinium, and dysprosium oxide particles and silver iodide colloid were tested and compared with standard agents. All four experimental agents were selectively concentrated in the reticuloendothelial systems of rats and rabbits. These compounds produced greater and longer opacification of normal livers and larger liver-to-tumor differences in rabbits with hepatic tumors than did equivalent amounts of standard, iodinated agents. Lesions as small as 5 mm were visible with CT. These experimental materials have favorable characteristics as hepatic contrast agents, but their toxicity and long term retention may limit clinical use.

  11. A Simple Low-dose X-ray CT Simulation from High-dose Scan.

    PubMed

    Zeng, Dong; Huang, Jing; Bian, Zhaoying; Niu, Shanzhou; Zhang, Hua; Feng, Qianjin; Liang, Zhengrong; Ma, Jianhua

    2015-10-01

    Low-dose X-ray computed tomography (CT) simulation from high-dose scan is required in optimizing radiation dose to patients. In this study, we propose a simple low-dose CT simulation strategy in sinogram domain using the raw data from high-dose scan. Specially, a relationship between the incident fluxes of low- and high- dose scans is first determined according to the repeated projection measurements and analysis. Second, the incident flux level of the simulated low-dose scan is generated by properly scaling the incident flux level of high-dose scan via the determined relationship in the first step. Third, the low-dose CT transmission data by energy integrating detection is simulated by adding a statistically independent Poisson noise distribution plus a statistically independent Gaussian noise distribution. Finally, a filtered back-projection (FBP) algorithm is implemented to reconstruct the resultant low-dose CT images. The present low-dose simulation strategy is verified on the simulations and real scans by comparing it with the existing low-dose CT simulation tool. Experimental results demonstrated that the present low-dose CT simulation strategy can generate accurate low-dose CT sinogram data from high-dose scan in terms of qualitative and quantitative measurements.

  12. High-density renal cysts in autosomal dominant polycystic kidney disease demonstrated by CT

    SciTech Connect

    Levine, E.; Grantham, J.J.

    1985-02-01

    Unenhanced abdominal CT scans of 35 patients with autosomal dominant polycystic kidney disease (ADPKD) showed multiple high-density (58-84 HU) renal cysts in 42.9% of patients, occasional high-density cysts in 25.7%, and no high-density cysts in 31.4%. These high-density cysts were usually subcapsular and were more frequent in patients with markedly enlarged kidneys and flank pain at the time of CT. Follow-up CT often showed a reduction in cyst densities, although some cysts developed mural calcification and calcification of their contents. Renal carcinomas occur rarely in ADPKD and may occasionally be hyperdense. However, high-density cysts may usually be distinguished from carcinomas on CT by their smooth contours, sharp interfaces with renal parenchyma, homogeneity, and lack of contrast enhancement.

  13. User Friendly Processing of Sediment CT Data: Software and Application in High Resolution Non-Destructive Sediment Core Data Sets

    NASA Astrophysics Data System (ADS)

    Reilly, B. T.; Stoner, J. S.; Wiest, J.; Abbott, M. B.; Francus, P.; Lapointe, F.

    2015-12-01

    Computed Tomography (CT) of sediment cores allow for high resolution images, three dimensional volumes, and down core profiles, generated through the attenuation of X-rays as a function of density and atomic number. When using a medical CT-Scanner, these quantitative data are stored in pixels using the Hounsfield scale, which are relative to the attenuation of X-rays in water and air at standard temperature and pressure. Here we present MATLAB based software specifically designed for sedimentary applications with a user friendly graphical interface to process DICOM files and stitch overlapping CT scans. For visualization, the software allows easy generation of core slice images with grayscale and false color relative to a user defined Hounsfield number range. For comparison to other high resolution non-destructive methods, down core Hounsfield number profiles are extracted using a method robust to coring imperfections, like deformation, bowing, gaps, and gas expansion. We demonstrate the usefulness of this technique with lacustrine sediment cores from the Western United States and Canadian High Arctic, including Fish Lake, Oregon, and Sawtooth Lake, Ellesmere Island. These sites represent two different depositional environments and provide examples for a variety of common coring defects and lithologies. The Hounsfield profiles and images can be used in combination with other high resolution data sets, including sediment magnetic parameters, XRF core scans and many other types of data, to provide unique insights into how lithology influences paleoenvironmental and paleomagnetic records and their interpretations.

  14. Mineral volume and morphology in carotid plaque specimens using high-resolution MRI and CT.

    PubMed

    Wolf, Ronald L; Wehrli, Suzanne L; Popescu, Andra M; Woo, John H; Song, Hee Kwon; Wright, Alexander C; Mohler, Emile R; Harding, John D; Zager, Eric L; Fairman, Ronald M; Golden, Michael A; Velazquez, Omaida C; Carpenter, Jeffrey P; Wehrli, Felix W

    2005-08-01

    High-resolution MRI methods have been used to evaluate carotid artery atherosclerotic plaque content. The purpose of this study was to assess the performance of high-resolution MRI in evaluation of the quantity and pattern of mineral deposition in carotid endarterectomy (CEA) specimens, with quantitative micro-CT as the gold standard. High-resolution MRI and CT were compared in 20 CEA specimens. Linear regression comparing mineral volumes generated from CT (VCT) and MRI (VMRI) data demonstrated good correlation using simple thresholding (VMRI=-0.01+0.98VCT; R2=0.90; threshold=4xnoise) and k-means clustering methods (VMRI=-0.005+1.38VCT; R2=0.93). Bone mineral density (BMD) and bone mineral content (BMC [mineral mass]) were calculated for CT data and BMC verified with ash weight. Patterns of mineralization like particles, granules, and sheets were more clearly depicted on CT. Mineral volumes generated from MRI or CT data were highly correlated. CT provided a more detailed depiction of mineralization patterns and provided BMD and BMC in addition to mineral volume. The extent of mineralization as well as the morphology may ultimately be useful in assessing plaque stability.

  15. High Resolution X-Ray Micro-CT of Ultra-Thin Wall Space Components

    NASA Technical Reports Server (NTRS)

    Roth, Don J.; Rauser, R. W.; Bowman, Randy R.; Bonacuse, Peter; Martin, Richard E.; Locci, I. E.; Kelley, M.

    2012-01-01

    A high resolution micro-CT system has been assembled and is being used to provide optimal characterization for ultra-thin wall space components. The Glenn Research Center NDE Sciences Team, using this CT system, has assumed the role of inspection vendor for the Advanced Stirling Convertor (ASC) project at NASA. This article will discuss many aspects of the development of the CT scanning for this type of component, including CT system overview; inspection requirements; process development, software utilized and developed to visualize, process, and analyze results; calibration sample development; results on actual samples; correlation with optical/SEM characterization; CT modeling; and development of automatic flaw recognition software. Keywords: Nondestructive Evaluation, NDE, Computed Tomography, Imaging, X-ray, Metallic Components, Thin Wall Inspection

  16. Neuroendocrine Cell Hyperplasia of Infancy: Diagnosis With High-Resolution CT

    PubMed Central

    Brody, Alan S.; Guillerman, R. Paul; Hay, Thomas C.; Wagner, Brandie D.; Young, Lisa R.; Deutsch, Gail H.; Fan, Leland L.; Deterding, Robin R.

    2013-01-01

    OBJECTIVE Neuroendocrine cell hyperplasia of infancy is a form of childhood interstitial lung disease originally reported as persistent tachypnea of infancy. Reports of small series of cases and anecdotal experience have suggested that this disorder may have a consistent CT pattern. The purpose of this study was to review the CT findings in children with neuroendocrine cell hyperplasia of infancy to determine the findings at high-resolution CT, the diagnostic accuracy of CT compared with biopsy, and interrater reliability. MATERIALS AND METHODS Images from 23 CT examinations of children with biopsy-proven neuroendocrine cell hyperplasia of infancy and six CT examinations of children with other childhood interstitial lung diseases were reviewed by two pediatric radiologists with special expertise in thoracic imaging. Identifying digital data were removed, and images were reviewed without clinical data. A CT assessment form was completed for each patient. RESULTS Ground-glass opacification was the most common finding in patients with neuroendocrine cell hyperplasia of infancy. The right middle lobe and lingula were most commonly involved. Air trapping with a mosaic pattern was the second most common finding. Interrater reliability was very good with a kappa value of 0.93. The sensitivity and specificity of CT in the diagnosis of neuroendocrine cell hyperplasia of infancy were at least 78% and 100%. CONCLUSION Neuroendocrine cell hyperplasia of infancy can have a characteristic appearance on high-resolution CT scans, the imaging findings being useful in differentiating neuroendocrine cell hyperplasia of infancy from other types of childhood interstitial lung disease. The appearance aids radiologists in suggesting a specific diagnosis but does not exclude this diagnosis; in 17–22% of cases, the readers in this study did not suggest the diagnosis of neuroendocrine cell hyperplasia of infancy when it was present. PMID:20028928

  17. NOTE: Suppression of high-density artefacts in x-ray CT images using temporal digital subtraction with application to cryotherapy

    NASA Astrophysics Data System (ADS)

    Baissalov, R.; Sandison, G. A.; Donnelly, B. J.; Saliken, J. C.; McKinnon, J. G.; Muldrew, K.; Rewcastle, J. C.

    2000-05-01

    Image guidance in cryotherapy is usually performed using ultrasound. Although not currently in routine clinical use, x-ray CT imaging is an alternative means of guidance that can display the full 3D structure of the iceball, including frozen and unfrozen regions. However, the quality of x-ray CT images is compromised by the presence of high-density streak artefacts. To suppress these artefacts we applied temporal digital subtraction (TDS). This TDS method has the added advantage of improving the grey-scale contrast between frozen and unfrozen tissue in the CT images. Two sets of CT images were taken of a phantom material, cryoprobes and a urethral warmer (UW) before and during the cryoprobe freeze cycle. The high-density artefacts persisted in both image sets. TDS was performed on these two image sets using the corresponding mask image of unfrozen material and the same geometrical configuration of the cryoprobes and the UW. The resultant difference image had a significantly reduced artefact content. Thus TDS can be used to significantly suppress or eliminate high-density CT streak artefacts without reducing the metallic content of the cryoprobes. In vivo study needs to be conducted to establish the utility of this TDS procedure for CT assisted prostate or liver cryotherapy. Applying TDS in x-ray CT guided cryotherapy will facilitate estimation of the number and location of all frozen and unfrozen regions, potentially making cryotherapy safer and less operator dependent.

  18. Response of osteosarcoma to preoperative intravenous high-dose methotrexate chemotherapy: CT evaluation

    SciTech Connect

    Mail, J.T.; Cohen, M.D.; Mirkin, L.D.; Provisor, A.J.

    1985-01-01

    The histologic response of an osteosarcoma to preamputation high-dose methotrexate therapy can be used to determine the optimum maintenance chemotherapy regimen to be administered after amputation. This study evaluates computed tomography (CT) as a method of assessing the response of the tumor to the methotrexate therapy. Nine patients with nonmetastatic osteosarcoma of an extremity had a CT scan of the tumor at initial presentation. This was compared with a second CT scan after four courses of high-dose intravenous methotrexate. Each set of scans was evaluated for changes in bony destruction, soft-tissue mass, pattern of calcification, and extent of tumor involvement of the marrow cavity. These findings were correlated with the histologic response of the tumor as measured by the degree of tumor necrosis. The changes seen on CT correlated well with the degree of the histologic response in seven of the nine patients.

  19. High resolution 3D dosimetry for microbeam radiation therapy using optical CT

    NASA Astrophysics Data System (ADS)

    McErlean, C.; Bräuer-Krisch, E.; Adamovics, J.; Leach, M. O.; Doran, S. J.

    2015-01-01

    Optical Computed Tomography (CT) is a promising technique for dosimetry of Microbeam Radiation Therapy (MRT), providing high resolution 3D dose maps. Here different MRT irradiation geometries are visualised showing the potential of Optical CT as a tool for future MRT trials. The Peak-to-Valley dose ratio (PVDR) is calculated to be 7 at a depth of 3mm in the radiochromic dosimeter PRESAGE®. This is significantly lower than predicted values and possible reasons for this are discussed.

  20. Feasibility of dual-source cardiac CT angiography with high-pitch scan protocols.

    PubMed

    Hausleiter, Jörg; Bischoff, Bernhard; Hein, Franziska; Meyer, Tanja; Hadamitzky, Martin; Thierfelder, Carsten; Allmendinger, Thomas; Flohr, Thomas G; Schömig, Albert; Martinoff, Stefan

    2009-01-01

    Cardiac CT angiography (CCTA) has become a frequently used diagnostic tool in clinical practice, but concern remains about the radiation exposure. Because of the second x-ray acquisition system, dual-source CT systems might allow for high-pitch CT data acquisition and thus for examination of the whole heart during a single heart beat, with the potential for radiation dose reduction. We assessed the feasibility of a high-pitch scan mode with a dual-source CT system. High-pitch modes were used in patients undergoing CCTA with a dual-source CT system. Diagnostic image quality for cardiac structures and coronary arteries was assessed. Radiation dose was estimated from the scanner-generated dose-length product (DLP). CCTA was performed in 14 patients during a single heart beat applying a pitch value of 3.4. Mean heart rate during examination was 56.4+/-8.1 beats/min. Diagnostic image quality for the assessment of larger cardiac structures was obtained in all patients, whereas diagnostic image quality could be achieved in 82% of all coronary segments. With a mean DLP of 145+/-47 mGy x cm, the resulting estimated radiation dose was 2.0+/-0.7 mSv. This proof-of-concept study shows the ability of dual-source CT scanners to scan the whole heart during one single heart beat at low radiation dose.

  1. High energy x-ray phase contrast CT using glancing-angle grating interferometers

    SciTech Connect

    Sarapata, A.; Stayman, J. W.; Siewerdsen, J. H.; Finkenthal, M.; Stutman, D.; Pfeiffer, F.

    2014-02-15

    Purpose: The authors present initial progress toward a clinically compatible x-ray phase contrast CT system, using glancing-angle x-ray grating interferometry to provide high contrast soft tissue images at estimated by computer simulation dose levels comparable to conventional absorption based CT. Methods: DPC-CT scans of a joint phantom and of soft tissues were performed in order to answer several important questions from a clinical setup point of view. A comparison between high and low fringe visibility systems is presented. The standard phase stepping method was compared with sliding window interlaced scanning. Using estimated dose values obtained with a Monte-Carlo code the authors studied the dependence of the phase image contrast on exposure time and dose. Results: Using a glancing angle interferometer at high x-ray energy (∼45 keV mean value) in combination with a conventional x-ray tube the authors achieved fringe visibility values of nearly 50%, never reported before. High fringe visibility is shown to be an indispensable parameter for a potential clinical scanner. Sliding window interlaced scanning proved to have higher SNRs and CNRs in a region of interest and to also be a crucial part of a low dose CT system. DPC-CT images of a soft tissue phantom at exposures in the range typical for absorption based CT of musculoskeletal extremities were obtained. Assuming a human knee as the CT target, good soft tissue phase contrast could be obtained at an estimated absorbed dose level around 8 mGy, similar to conventional CT. Conclusions: DPC-CT with glancing-angle interferometers provides improved soft tissue contrast over absorption CT even at clinically compatible dose levels (estimated by a Monte-Carlo computer simulation). Further steps in image processing, data reconstruction, and spectral matching could make the technique fully clinically compatible. Nevertheless, due to its increased scan time and complexity the technique should be thought of not as

  2. High energy x-ray phase contrast CT using glancing-angle grating interferometers.

    PubMed

    Sarapata, A; Stayman, J W; Finkenthal, M; Siewerdsen, J H; Pfeiffer, F; Stutman, D

    2014-02-01

    The authors present initial progress toward a clinically compatible x-ray phase contrast CT system, using glancing-angle x-ray grating interferometry to provide high contrast soft tissue images at estimated by computer simulation dose levels comparable to conventional absorption based CT. DPC-CT scans of a joint phantom and of soft tissues were performed in order to answer several important questions from a clinical setup point of view. A comparison between high and low fringe visibility systems is presented. The standard phase stepping method was compared with sliding window interlaced scanning. Using estimated dose values obtained with a Monte-Carlo code the authors studied the dependence of the phase image contrast on exposure time and dose. Using a glancing angle interferometer at high x-ray energy (∼ 45 keV mean value) in combination with a conventional x-ray tube the authors achieved fringe visibility values of nearly 50%, never reported before. High fringe visibility is shown to be an indispensable parameter for a potential clinical scanner. Sliding window interlaced scanning proved to have higher SNRs and CNRs in a region of interest and to also be a crucial part of a low dose CT system. DPC-CT images of a soft tissue phantom at exposures in the range typical for absorption based CT of musculoskeletal extremities were obtained. Assuming a human knee as the CT target, good soft tissue phase contrast could be obtained at an estimated absorbed dose level around 8 mGy, similar to conventional CT. DPC-CT with glancing-angle interferometers provides improved soft tissue contrast over absorption CT even at clinically compatible dose levels (estimated by a Monte-Carlo computer simulation). Further steps in image processing, data reconstruction, and spectral matching could make the technique fully clinically compatible. Nevertheless, due to its increased scan time and complexity the technique should be thought of not as replacing, but as complimentary to

  3. Performance of turbo high-pitch dual-source CT for coronary CT angiography: first ex vivo and patient experience.

    PubMed

    Morsbach, Fabian; Gordic, Sonja; Desbiolles, Lotus; Husarik, Daniela; Frauenfelder, Thomas; Schmidt, Bernhard; Allmendinger, Thomas; Wildermuth, Simon; Alkadhi, Hatem; Leschka, Sebastian

    2014-08-01

    To evaluate image quality, maximal heart rate allowing for diagnostic imaging, and radiation dose of turbo high-pitch dual-source coronary computed tomographic angiography (CCTA). First, a cardiac motion phantom simulating heart rates (HRs) from 60-90 bpm in 5-bpm steps was examined on a third-generation dual-source 192-slice CT (prospective ECG-triggering, pitch 3.2; rotation time, 250 ms). Subjective image quality regarding the presence of motion artefacts was interpreted by two readers on a four-point scale (1, excellent; 4, non-diagnostic). Objective image quality was assessed by calculating distortion vectors. Thereafter, 20 consecutive patients (median, 50 years) undergoing clinically indicated CCTA were included. In the phantom study, image quality was rated diagnostic up to the HR75 bpm, with object distortion being 1 mm or less. Distortion increased above 1 mm at HR of 80-90 bpm. Patients had a mean HR of 66 bpm (47-78 bpm). Coronary segments were of diagnostic image quality for all patients with HR up to 73 bpm. Average effective radiation dose in patients was 0.6 ± 0.3 mSv. Our combined phantom and patient study indicates that CCTA with turbo high-pitch third-generation dual-source 192-slice CT can be performed at HR up to 75 bpm while maintaining diagnostic image quality, being associated with an average radiation dose of 0.6 mSv. • CCTA is feasible with the turbo high-pitch mode. • Turbo high-pitch CCTA provides diagnostic image quality up to 73 bpm. • The radiation dose of high-pitch CCTA is 0.6 mSv on average.

  4. SU-E-J-190: Characterization of Radiation Induced CT Number Changes in Tumor and Normal Lung During Radiation Therapy for Lung Cancer

    SciTech Connect

    Yang, C; Liu, F; Tai, A; Gore, E; Johnstone, C; Li, X

    2014-06-01

    Purpose: To measure CT number (CTN) changes in tumor and normal lung as a function of radiation therapy (RT) dose during the course of RT delivery for lung cancer using daily IGRT CT images and single respiration phase CT images. Methods: 4D CT acquired during planning simulation and daily 3D CT acquired during daily IGRT for 10 lung cancer cases randomly selected in terms of age, caner type and stage, were analyzed using an in-house developed software tool. All patients were treated in 2 Gy fractions to primary tumors and involved nodal regions. Regions enclosed by a series of isodose surfaces in normal lung were delineated. The obtained contours along with target contours (GTVs) were populated to each singlephase planning CT and daily CT. CTN in term of Hounsfield Unit (HU) of each voxel in these delineated regions were collectively analyzed using histogram, mean, mode and linear correlation. Results: Respiration induced normal lung CTN change, as analyzed from single-phase planning CTs, ranged from 9 to 23 (±2) HU for the patients studied. Normal lung CTN change was as large as 50 (±12) HU over the entire treatment course, was dose and patient dependent and was measurable with dose changes as low as 1.5 Gy. For patients with obvious tumor volume regression, CTN within the GTV drops monotonically as much as 10 (±1) HU during the early fractions with a total dose of 20 Gy delivered. The GTV and CTN reductions are significantly correlated with correlation coefficient >0.95. Conclusion: Significant RT dose induced CTN changes in lung tissue and tumor region can be observed during even the early phase of RT delivery, and may potentially be used for early prediction of radiation response. Single respiration phase CT images have dramatically reduced statistical noise in ROIs, making daily dose response evaluation possible.

  5. Automatic high-resolution infarct detection using volumetric multiphase dual-energy CT.

    PubMed

    Sandfort, Veit; Kwan, Alan C; Elumogo, Comfort; Vigneault, Davis M; Symons, Rolf; Pourmorteza, Amir; Rice, Kelly; Davies-Venn, Cynthia; Ahlman, Mark A; Liu, Chia-Ying; Zimmerman, Stefan L; Bluemke, David A

    Late contrast enhancement CT (LCE-CT) visualizes the presence of myocardial infarcts. Differentiation of the contrast-enhanced infarct from blood pool is challenging. We developed a novel method using data from first pass CT angiography (CTA) imaging to enable automatic infarct detection. A canine model of myocardial infarction was produced in 11 animals. Two months later, first pass CTA (90 kVp) and LCE-CT (dual energy 90 kVp/150 kVp tin filtered) were performed. Late gadolinium enhancement MRI was used as reference standard. The CTA and LCE-CT were co-registered using a fully automatic non-rigid method based on curved B-splines. The method allowed for limited elastic deformation and the considerable differences in attenuation between first-pass and delayed image. The blood pool was easily identified on the CTA image by high attenuation. Because CTA and LCE-CT were registered, the blood pool segmentation can be directly transferred to the LCE-CT - thereby solving the key problem of infarct/blood pool differentiation. The remaining segmentation of infarcted vs. noninfarcted myocardium was performed using a threshold. Automatic and MRI-guided expert segmentations of LCE-CT infarcts were compared to each other on volume and area basis (intraclass correlation coefficient, ICC) and on voxel basis (dice similarity coefficient, DSC between automatic and expert CT segmentation). CT infarct volumes were compared with the reference standard MRI. The infarcts were mainly subendocardial (81%) and relatively small (median MRI infarct mass 7.4 g). The automatic segmentation showed excellent agreement with expert segmentation on volume and area measurements (ICC = 0.96 and 0.87, respectively). DSC showed moderately good agreement (DSC = 0.47). Compared to MRI there was modest agreement (ICC = 0.62) and excellent correlation (R = 0.9). Manual interaction was less than 1 min per exam. We propose an automatic method for infarct segmentation on LCE-CT using multiphase CT

  6. SU-E-J-271: Correlation of CT Number Change with Radiation Treatment Response for Pancreatic Cancer

    SciTech Connect

    Dalah, E; Tai, A; Oshima, K; Hall, W; Knechtges, P; Erickson, B; Li, X

    2015-06-15

    Purpose: It has been reported recently that radiation can induce CT number (CTN) change during radiation therapy (RT) delivery. In the effort to explore whether CTN can be used to assess RT response, we analyze the relationship between the pathological treatment response (PTR) and the changes of CTN, MRI, and PET before and after the neoadjuvant chemoradiation (nCR) for pancreatic adenocarcinoma. Methods: The preand post-nCR CT, MRI, and PET data for a total of 8 patients with resectable, or borderline resectable pancreatic head adenocarcinoma treated with nCR were retrospectively analyzed. Radiographic characteristics were correlated to PTR data. The histograms, means and standard derivations (SD) of the CTNs in pancreatic head (CTNPH), the GTV defined by ADC (CTNGTV), and the rest of pancreatic head (CTNPH-CTNGTV) were compared. Changes before and after nCR were correlated with the corresponding changes of ADC, lean body mass normalized SUV (SUVlb), and PTR using Pearson’ s correlation coefficient test. Results: The average mean and SD in CTPH for all the patients analyzed were higher in post-nCR (53.17 ± 31.05 HU) compared to those at pre-nCR (28.09 ± 4.253 HU). The CTNGTV were generally higher than CTNPH and CTNPH-CTNGTV, though the differences were not significant. The post-nCR changes of mean CTN, ADC, and SUVlb values in pancreatic head were correlated with PTR (R=0.3273/P=0.5357, R=−0.5455/P<0.0001, and R=0.7638/P=0.0357, respectively). The mean difference in the maximum tumor dimension measured from CTN, ADC, and SUVlb as compared with pathological measurements was −2.1, −0.5, and 0.22 cm, respectively. Conclusion: The radiation-induced change of CTN in pancreas head after chemoradiation therapy of pancreatic cancer was observed, which may be related to treatment responses as assessed by biological imaging and pathology. More data are needed to determine whether the CTN can be used as a quantitative biomarker for response to neoadjuvant therapy.

  7. 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.

  8. Reversed halo sign on high-resolution CT of cryptogenic organizing pneumonia: diagnostic implications.

    PubMed

    Kim, Sang Jin; Lee, Kyung Soo; Ryu, Young Hoon; Yoon, Young Cheol; Choe, Kyu Ok; Kim, Tae Sung; Sung, Ki Jun

    2003-05-01

    The aim of our study was to evaluate the usefulness of the reversed halo sign on high-resolution CT in the diagnosis of cryptogenic organizing pneumonia. Between 1996 and 2001, we saw 31 patients with biopsy-proven cryptogenic organizing pneumonia. During the same period, we also saw 30 patients with non-cryptogenic organizing pneumonia diseases, from which cryptogenic organizing pneumonia should be differentiated: Wegener's granulomatosis (n = 14), diffuse bronchioloalveolar carcinoma (n = 10), chronic eosinophilic pneumonia (n = 5), and Churg-Strauss syndrome (n = 1). Two independent observers analyzed CT findings and recorded how frequently the so-called reversed halo sign (central ground-glass opacity and surrounding air-space consolidation of crescentic and ring shape) was seen on high-resolution CT. The most common patterns of parenchymal abnormalities of cryptogenic organizing pneumonia were ground-glass opacity (28/31 patients, 90%) and consolidation (27/31, 87%). The ground-glass opacity pattern showed random distribution, and the consolidation pattern showed subpleural or peribronchovascular (20/27 patients, 74%) distribution with predominance in the middle or lower lung zone. The reversed CT halo sign was seen in six (19%) of 31 patients with cryptogenic organizing pneumonia and in none of the patients with the diseases that needed to be differentiated from cryptogenic organizing pneumonia on CT. The reversed halo sign, although seen only in one fifth of patients with the disease, appears relatively specific to make a diagnosis of cryptogenic organizing pneumonia on CT.

  9. A new high-resolution computed tomography (CT) segmentation method for trabecular bone architectural analysis.

    PubMed

    Scherf, Heike; Tilgner, Rico

    2009-09-01

    In the last decade, high-resolution computed tomography (CT) and microcomputed tomography (micro-CT) have been increasingly used in anthropological studies and as a complement to traditional histological techniques. This is due in large part to the ability of CT techniques to nondestructively extract three-dimensional representations of bone structures. Despite prior studies employing CT techniques, no completely reliable method of bone segmentation has been established. Accurate preprocessing of digital data is crucial for measurement accuracy, especially when subtle structures such as trabecular bone are investigated. The research presented here is a new, reproducible, accurate, and fully automated computerized segmentation method for high-resolution CT datasets of fossil and recent cancellous bone: the Ray Casting Algorithm (RCA). We compare this technique with commonly used methods of image thresholding (i.e., the half-maximum height protocol and the automatic, adaptive iterative thresholding procedure). While the quality of the input images is crucial for conventional image segmentation, the RCA method is robust regarding the signal to noise ratio, beam hardening, ring artifacts, and blurriness. Tests with data of extant and fossil material demonstrate the superior quality of RCA compared with conventional thresholding procedures, and emphasize the need for careful consideration of optimal CT scanning parameters.

  10. Impact of high mathematics education on the number sense.

    PubMed

    Castronovo, Julie; Göbel, Silke M

    2012-01-01

    In adult number processing two mechanisms are commonly used: approximate estimation of quantity and exact calculation. While the former relies on the approximate number sense (ANS) which we share with animals and preverbal infants, the latter has been proposed to rely on an exact number system (ENS) which develops later in life following the acquisition of symbolic number knowledge. The current study investigated the influence of high level math education on the ANS and the ENS. Our results showed that the precision of non-symbolic quantity representation was not significantly altered by high level math education. However, performance in a symbolic number comparison task as well as the ability to map accurately between symbolic and non-symbolic quantities was significantly better the higher mathematics achievement. Our findings suggest that high level math education in adults shows little influence on their ANS, but it seems to be associated with a better anchored ENS and better mapping abilities between ENS and ANS.

  11. Iterative reconstruction optimisations for high angle cone-beam micro-CT

    NASA Astrophysics Data System (ADS)

    Recur, B.; Fauconneau, M.; Kingston, A.; Myers, G.; Sheppard, A.

    2014-09-01

    We address several acquisition questions that have arisen for the high cone-angle helical-scanning micro-CT facility developed at the Australian National University. These challenges are generally known in medical and industrial cone-beam scanners but can be neglected in these systems. For our large datasets, with more than 20483 voxels, minimising the number of operations (or iterations) is crucial. Large cone-angles enable high signal-to-noise ratio imaging and a large helical pitch to be used. This introduces two challenges: (i) non-uniform resolution throughout the reconstruction, (ii) over-scan beyond the region-of-interest significantly increases re- quired reconstructed volume size. Challenge (i) can be addressed by using a double-helix or lower pitch helix but both solutions slow down iterations. Challenge (ii) can also be improved by using a lower pitch helix but results in more projections slowing down iterations. This may be overcome using less projections per revolution but leads to more iterations required. Here we assume a given total time for acquisition and a given reconstruction technique (SART) and seek to identify the optimal trajectory and number of projections per revolution in order to produce the best tomogram, minimise reconstruction time required, and minimise memory requirements.

  12. Towards a high-speed quantum random number generator

    NASA Astrophysics Data System (ADS)

    Stucki, Damien; Burri, Samuel; Charbon, Edoardo; Chunnilall, Christopher; Meneghetti, Alessio; Regazzoni, Francesco

    2013-10-01

    Randomness is of fundamental importance in various fields, such as cryptography, numerical simulations, or the gaming industry. Quantum physics, which is fundamentally probabilistic, is the best option for a physical random number generator. In this article, we will present the work carried out in various projects in the context of the development of a commercial and certified high speed random number generator.

  13. Microphysics of a multidimensional high beta low Mach number shock

    NASA Astrophysics Data System (ADS)

    Matsukiyo, S.; Matsumoto, Y.

    2014-12-01

    It is generally thought that a high beta shock is weak so that its structre is relatively laminar and stationary. Such low Mach number shocks have not been paid much attention in terms of particle acceleration. However, Voyager spacecraft revealed that the fluxes of not only the non-thermal ions, which are called as the termination shock particles, but also of the non-thermal electrons are enhanced at the crossings of the termination shock. The heliospheric termination shock has a high effective beta due to the presence of pickup ions which are the component having rather high thermal energy. Radio synchrotron emissions from relics of galaxy cluster mergers imply the presence of relativistic electrons accelerated in merger shocks. A plasma beta of such a merger shock is also thought to be rather high so that the merger shocks are usually assumed to have low Mach numbers. These observational facts imply that even a low Mach number shock can be a good accelerator of non-thermal particles. Here, we perform two-dimensional full particle-in-cell simulation to study microstructure of a high beta low Mach number shock and the associated electron acceleration process. Although the effective magnotosonic Mach number is rather low, ~2.6, the structure of the transition region is highly complex. Ion and electron scale structures coexist. Furthermore, some electrons are accelerated to high energy. We will discuss the mechanisms of producing those two-dimensional microstructures and high energy electrons.

  14. Three-rooted premolar analyzed by high-resolution and cone beam CT.

    PubMed

    Marca, Caroline; Dummer, Paul M H; Bryant, Susan; Vier-Pelisser, Fabiana Vieira; Só, Marcus Vinicius Reis; Fontanella, Vania; Dutra, Vinicius D'avila; de Figueiredo, José Antonio Poli

    2013-07-01

    The aim of this study was to analyze the variations in canal and root cross-sectional area in three-rooted maxillary premolars between high-resolution computed tomography (μCT) and cone beam computed tomography (CBCT). Sixteen extracted maxillary premolars with three distinct roots and fully formed apices were scanned using μCT and CBCT. Photoshop CS software was used to measure root and canal cross-sectional areas at the most cervical and the most apical points of each root third in images obtained using the two tomographic computed (CT) techniques, and at 30 root sections equidistant from both root ends using μCT images. Canal and root areas were compared between each method using the Student t test for paired samples and 95 % confidence intervals. Images using μCT were sharper than those obtained using CBCT. There were statistically significant differences in mean area measurements of roots and canals between the μCT and CBCT techniques (P < 0.05). Root and canal areas had similar variations in cross-sectional μCT images and became proportionally smaller in a cervical to apical direction as the cementodentinal junction was approached, from where the area then increased apically. Although variation was similar in the roots and canals under study, CBCT produced poorer image details than μCT. Although CBCT is a strong diagnosis tool, it still needs improvement to provide accuracy in details of the root canal system, especially in cases with anatomical variations, such as the three-rooted maxillary premolars.

  15. Promoting Number Theory in High Schools or Birthday Problem and Number Theory

    ERIC Educational Resources Information Center

    Srinivasan, V. K.

    2010-01-01

    The author introduces the birthday problem in this article. This can amuse willing members of any birthday party. This problem can also be used as the motivational first day lecture in number theory for the gifted students in high schools or in community colleges or in undergraduate classes in colleges.

  16. Promoting number theory in high schools or birthday problem and number theory

    NASA Astrophysics Data System (ADS)

    Srinivasan, V. K.

    2010-04-01

    The author introduces the birthday problem in this article. This can amuse willing members of any birthday party. This problem can also be used as the motivational first day lecture in number theory for the gifted students in high schools or in community colleges or in undergraduate classes in colleges.

  17. Promoting Number Theory in High Schools or Birthday Problem and Number Theory

    ERIC Educational Resources Information Center

    Srinivasan, V. K.

    2010-01-01

    The author introduces the birthday problem in this article. This can amuse willing members of any birthday party. This problem can also be used as the motivational first day lecture in number theory for the gifted students in high schools or in community colleges or in undergraduate classes in colleges.

  18. Noncontrast perfusion single-photon emission CT/CT scanning: a new test for the expedited, high-accuracy diagnosis of acute pulmonary embolism.

    PubMed

    Lu, Yang; Lorenzoni, Alice; Fox, Josef J; Rademaker, Jürgen; Vander Els, Nicholas; Grewal, Ravinder K; Strauss, H William; Schöder, Heiko

    2014-05-01

    Standard ventilation and perfusion (V˙/Q˙) scintigraphy uses planar images for the diagnosis of pulmonary embolism (PE). To evaluate whether tomographic imaging improves the diagnostic accuracy of the procedure, we compared noncontrast perfusion single-photon emission CT (Q˙-SPECT)/CT scans with planar V˙/Q˙scans in patients at high risk for PE. Between 2006 and 2010, most patients referred for diagnosis of PE underwent both Q˙-SPECT/CT scan and planar V˙/Q˙scintigraphy. All scans were reviewed retrospectively by four observers; planar scans were read with modified Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) II and Prospective Investigative Study of Pulmonary Embolism Diagnosis (PISA-PED) criteria. On Q˙-SPECT/CT scan, any wedge-shaped peripheral perfusion defect occupying > 50% of a segment without corresponding pulmonary parenchymal or pleural disease was considered to show PE. The final diagnosis was established with a composite reference standard that included ECG, ultrasound of lower-extremity veins, D-dimer levels, CT pulmonary angiography (when available), and clinical follow-up for at least 3 months. One hundred six patients with cancer and mean Wells score of 4.4 had sufficient follow-up; 22 patients were given a final diagnosis of PE, and 84 patients were given a final diagnosis of no PE. According to PIOPED II, 13 studies were graded as intermediate probability. Sensitivity and specificity for PE were 50% and 98%, respectively, based on PIOPED II criteria; 86% and 93%, respectively, based on PISA-PED criteria; and 91% and 94%, respectively, based on Q˙-SPECT/CT scan. Seventy-six patients had additional relevant findings on the CT image of the Q˙-SPECT/CT scan. Noncontrast Q˙-SPECT/CT imaging has a higher accuracy than planar V˙/Q˙imaging based on PIOPED II criteria in patients with cancer and a high risk for PE.

  19. An experimental investigation of turbulent boundary layers at high Mach number and Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Holden, M. S.

    1972-01-01

    Skin friction, heat transfer and pressure measurements were obtained in laminar, transitional and turbulent boundary layers on flat plates at Mach numbers from 7 to 13 at wall-to-free stream stagnation temperature ratios from 0.1 to 0.3. Measurements in laminar flows were in excellent agreement with the theory of Cheng. Correlations of the transition measurements with measurements on flight vehicles and in ballistic ranges show good agreement. Our transition measurements do not correlate well with those of Pate and Schueler. Comparisons have been made between the skin friction and heat transfer measurements and the theories of Van Driest, Eckert and Spalding and Chi. These comparisons reveal in general that at the high end of our Mach number range (10-13) the theory of Van Driest is in best agreement with the data, whereas at lower Mach numbers (6.5-10) the Spalding Chi theory is in better agreement with the measurements.

  20. A Curve Fitting Approach Using ANN for Converting CT Number to Linear Attenuation Coefficient for CT-based PET Attenuation Correction

    NASA Astrophysics Data System (ADS)

    Lai, Chia-Lin; Lee, Jhih-Shian; Chen, Jyh-Cheng

    2015-02-01

    Energy-mapping, the conversion of linear attenuation coefficients (μ) calculated at the effective computed tomography (CT) energy to those corresponding to 511 keV, is an important step in CT-based attenuation correction (CTAC) for positron emission tomography (PET) quantification. The aim of this study was to implement energy-mapping step by using curve fitting ability of artificial neural network (ANN). Eleven digital phantoms simulated by Geant4 application for tomographic emission (GATE) and 12 physical phantoms composed of various volume concentrations of iodine contrast were used in this study to generate energy-mapping curves by acquiring average CT values and linear attenuation coefficients at 511 keV of these phantoms. The curves were built with ANN toolbox in MATLAB. To evaluate the effectiveness of the proposed method, another two digital phantoms (liver and spine-bone) and three physical phantoms (volume concentrations of 3%, 10% and 20%) were used to compare the energy-mapping curves built by ANN and bilinear transformation, and a semi-quantitative analysis was proceeded by injecting 0.5 mCi FDG into a SD rat for micro-PET scanning. The results showed that the percentage relative difference (PRD) values of digital liver and spine-bone phantom are 5.46% and 1.28% based on ANN, and 19.21% and 1.87% based on bilinear transformation. For 3%, 10% and 20% physical phantoms, the PRD values of ANN curve are 0.91%, 0.70% and 3.70%, and the PRD values of bilinear transformation are 3.80%, 1.44% and 4.30%, respectively. Both digital and physical phantoms indicated that the ANN curve can achieve better performance than bilinear transformation. The semi-quantitative analysis of rat PET images showed that the ANN curve can reduce the inaccuracy caused by attenuation effect from 13.75% to 4.43% in brain tissue, and 23.26% to 9.41% in heart tissue. On the other hand, the inaccuracy remained 6.47% and 11.51% in brain and heart tissue when the bilinear transformation

  1. Transitional boundary layer in low-Prandtl-number convection at high Rayleigh number

    NASA Astrophysics Data System (ADS)

    Schumacher, Joerg; Bandaru, Vinodh; Pandey, Ambrish; Scheel, Janet

    2016-11-01

    The boundary layer structure of the velocity and temperature fields in turbulent Rayleigh-Bénard flows in closed cylindrical cells of unit aspect ratio is revisited from a transitional and turbulent viscous boundary layer perspective. When the Rayleigh number is large enough the boundary layer dynamics at the bottom and top plates can be separated into an impact region of downwelling plumes, an ejection region of upwelling plumes and an interior region (away from side walls) that is dominated by a shear flow of varying orientation. This interior plate region is compared here to classical wall-bounded shear flows. The working fluid is liquid mercury or liquid gallium at a Prandtl number of Pr = 0 . 021 for a range of Rayleigh numbers of 3 ×105 <= Ra <= 4 ×108 . The momentum transfer response to these system parameters generates a fluid flow in the closed cell with a macroscopic flow Reynolds number that takes values in the range of 1 . 8 ×103 <= Re <= 4 . 6 ×104 . It is shown that particularly the viscous boundary layers for the largest Ra are highly transitional and obey some properties that are directly comparable to transitional channel flows at friction Reynolds numbers below 100. This work is supported by the Deutsche Forschungsgemeinschaft.

  2. Wave phenomena in a high Reynolds number compressible boundary layer

    NASA Technical Reports Server (NTRS)

    Bayliss, A.; Maestrello, L.; Parikh, P.; Turkel, E.

    1985-01-01

    Growth of unstable disturbances in a high Reynolds number compressible boundary layer is numerically simulated. Localized periodic surface heating and cooling as a means of active control of these disturbances is studied. It is shown that compressibility in itself stabilizes the flow but at a lower Mach number, significant nonlinear distortions are produced. Phase cancellation is shown to be an effective mechanism for active boundary layer control.

  3. Heliospheric shocks: From low- to high-Mach numbers

    NASA Astrophysics Data System (ADS)

    Gedalin, Michael

    Collisionless shocks have been studied for more than five decades. From time to time it seems that most of the questions are answered and the shock physics is essentially understood. Each time this impression is broken due to the progress in observations and numerical simulations, which brings about the necessity to update our views and develop theory. Recent advances posed a number of new questions related to the transition from the low- to high-Mach number regime. These include the deviation of the shock front from planar shape (rippling), non-stationarity, and effects of high energy particles. The three issues are inter-connected and have a potential to change our understanding of how high-Mach number shocks work.

  4. High pitch CT in triple rule-out studies: Radiation dose and image quality compared to multidetector CT.

    PubMed

    Fernández del Valle, A; Delgado Sánchez-Gracián, C; Oca Pernas, R; Grande Astorquiza, A; Bustos Fiore, A; Trinidad López, C; Tardáguila de la Fuente, G

    2015-01-01

    To compare the image quality and radiation dose from high pitch dual source CT (128-DSCT) versus those from retrospective acquisition with 64-row multidetector CT (64-MDCT) in triple rule-out studies. We retrospectively studied 60 patients with acute chest pain: 30 with a retrospective EKG acquisition with 64-MDCT and 30 with high pitch 128-DSCT. We quantitatively analyzed the image quality by calculating the vascular density, muscular density (DM), noise, vascular density/noise ratio (VDNR), and contrast/noise ratio (CNR). We qualitatively evaluated the artifacts in the vena cava, aorta, and coronary arteries. We estimated the effective dose (ED) of radiation by means of the dose-length product. There were no significant differences between 128-DSCT and 64-MDCT in the vascular density. The VDNR and CNR were higher on 128-DSCT than on 64-MDCT in the aorta (VDNR: 28.9 ± 11.7 vs. 20 ± 5.5; CNR: 24.4 ± 10.9 vs. 16.8 ± 5.4; P<.01), in the pulmonary arteries (VDNR: 25.5 ± 10 vs. 20.6 ± 6.5; CNR: 24.5 ± 5.4 vs. 17.4 ± 6.4; P<.01), and in the coronary arteries (VDNR: 25.9 ± 8.2 vs. 18.9 ± 4.9; CNR: 24.9 ± 8.2 vs. 15.6 ± 4.6; P<.01). There were fewer artifacts in the coronary arteries on 128-DSCT than on 64-MDCT (3 vs. 34 nondiagnostic segments; P<.001), and the ED in 128-DSCT was lower than in 64-MDCT (13.77 ± 4 vs. 2.77 ± 0.6 mSv; P<.001). In triple rule-out studies, high pitch 128-DSCT delivers a lower dose of radiation and provides better image quality than retrospective acquisition with 64-MDCT. Copyright © 2014 SERAM. Published by Elsevier España, S.L.U. All rights reserved.

  5. Target delineation for radiosurgery of a small brain arteriovenous malformation using high-resolution contrast-enhanced cone beam CT.

    PubMed

    van der Bom, Imramsjah M J; Gounis, Matthew J; Ding, Linda; Kühn, Anna Luisa; Goff, David; Puri, Ajit S; Wakhloo, Ajay K

    2014-06-01

    Three years following endovascular embolization of a 3 mm ruptured arteriovenous malformation (AVM) of the left superior colliculus in a 42-year-old man, digital subtraction angiography showed continuous regrowth of the lesion. Thin-slice MRI acquired for treatment planning did not show the AVM nidus. The patient was brought back to the angiography suite for high-resolution contrast-enhanced cone beam CT (VasoCT) acquired using an angiographic c-arm system. The lesion and nidus were visualized with VasoCT. MRI, CT and VasoCT data were transferred to radiation planning software and mutually co-registered. The nidus was annotated for radiation on VasoCT data by an experienced neurointerventional radiologist and a dose/treatment plan was completed. Due to image registration, the treatment area could be directly adopted into the MRI and CT data. The AVM was completely obliterated 10 months following completion of the radiosurgery treatment.

  6. Target delineation for radiosurgery of a small brain arteriovenous malformation using high-resolution contrast-enhanced cone beam CT.

    PubMed

    van der Bom, Imramsjah M J; Gounis, Matthew J; Ding, Linda; Kühn, Anna Luisa; Goff, David; Puri, Ajit S; Wakhloo, Ajay K

    2013-08-14

    Three years following endovascular embolization of a 3 mm ruptured arteriovenous malformation (AVM) of the left superior colliculus in a 42-year-old man, digital subtraction angiography showed continuous regrowth of the lesion. Thin-slice MRI acquired for treatment planning did not show the AVM nidus. The patient was brought back to the angiography suite for high-resolution contrast-enhanced cone beam CT (VasoCT) acquired using an angiographic c-arm system. The lesion and nidus were visualized with VasoCT. MRI, CT and VasoCT data were transferred to radiation planning software and mutually co-registered. The nidus was annotated for radiation on VasoCT data by an experienced neurointerventional radiologist and a dose/treatment plan was completed. Due to image registration, the treatment area could be directly adopted into the MRI and CT data. The AVM was completely obliterated 10 months following completion of the radiosurgery treatment.

  7. Enthalpy damping for high Mach number Euler solutions

    NASA Technical Reports Server (NTRS)

    Moitra, Anutosh

    1990-01-01

    An improvement on the enthalpy damping procedure currently in use in solving supersonic flow fields is described. A correction based on entropy values is shown to produce a very efficient scheme for simulation of high Mach number three-dimensional flows. Substantial improvements in convergence rates have been achieved by incorporating this enthalpy damping scheme in a finite-volume Runge-Kutta method for solving the Euler equations. Results obtained for blended wing-body geometries at very high Mach numbers are presented.

  8. Impact of High Mathematics Education on the Number Sense

    PubMed Central

    Castronovo, Julie; Göbel, Silke M.

    2012-01-01

    In adult number processing two mechanisms are commonly used: approximate estimation of quantity and exact calculation. While the former relies on the approximate number sense (ANS) which we share with animals and preverbal infants, the latter has been proposed to rely on an exact number system (ENS) which develops later in life following the acquisition of symbolic number knowledge. The current study investigated the influence of high level math education on the ANS and the ENS. Our results showed that the precision of non-symbolic quantity representation was not significantly altered by high level math education. However, performance in a symbolic number comparison task as well as the ability to map accurately between symbolic and non-symbolic quantities was significantly better the higher mathematics achievement. Our findings suggest that high level math education in adults shows little influence on their ANS, but it seems to be associated with a better anchored ENS and better mapping abilities between ENS and ANS. PMID:22558077

  9. High-resolution CT assessment of the pediatric airways: structure and function

    NASA Astrophysics Data System (ADS)

    Kramer, Sandra S.; Hoffman, Eric A.; Amirav, Israel

    1994-05-01

    The airway has always been a central focus for respiratory pathology in infants and children. Imaging of the larynx, trachea, and the central bronchi can be readily accomplished by radiographic or conventional CT techniques. Newer high resolution CT (HRCT) techniques have extended our view of the bronchi peripherally to the limits of scanner resolution, i.e., to bronchial generations 7 - 9, and rapid volumetric CT data acquisitions have made it possible to follow the same lung anatomic level through the rapidly occurring changes in a series of experimental protocols. These techniques together with a custom designed computer software program for image display and analysis have enabled us to objectively study changes in airway caliber and lung density that occurred in an animal mode of airway reactivity and thereby relate structure with function in the airways.

  10. LES Studies of Scalar Fluctuations at High Convective Mach Numbers

    DTIC Science & Technology

    2001-08-01

    the compilation report: ADP013620 thru ADP013707 UNCLASSIFIED LES STUDIES OF SCALAR FLUCTUATIONS AT HIGH CONVECTIVE MACH NUMBERS WILLIAM H. CALHOON , JR...modeling [3] and for PDF-based turbulent combustion modeling [4]. 715 716 W. H. CALHOON , Jr., C. KANNEPALLI, AND S. M. DASH For supersonic flows with high...in this flow regime makes the calibration and application of RANS scalar fluctuation models difficult. Recently, Calhoon [4] found that a RANS scalar

  11. Probability density distribution of velocity differences at high Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Praskovsky, Alexander A.

    1993-01-01

    Recent understanding of fine-scale turbulence structure in high Reynolds number flows is mostly based on Kolmogorov's original and revised models. The main finding of these models is that intrinsic characteristics of fine-scale fluctuations are universal ones at high Reynolds numbers, i.e., the functional behavior of any small-scale parameter is the same in all flows if the Reynolds number is high enough. The only large-scale quantity that directly affects small-scale fluctuations is the energy flux through a cascade. In dynamical equilibrium between large- and small-scale motions, this flux is equal to the mean rate of energy dissipation epsilon. The pdd of velocity difference is a very important characteristic for both the basic understanding of fully developed turbulence and engineering problems. Hence, it is important to test the findings: (1) the functional behavior of the tails of the probability density distribution (pdd) represented by P(delta(u)) is proportional to exp(-b(r) absolute value of delta(u)/sigma(sub delta(u))) and (2) the logarithmic decrement b(r) scales as b(r) is proportional to r(sup 0.15) when separation r lies in the inertial subrange in high Reynolds number laboratory shear flows.

  12. CT imaging of the internal human ear: Test of a high resolution scanner

    NASA Astrophysics Data System (ADS)

    Bettuzzi, M.; Brancaccio, R.; Morigi, M. P.; Gallo, A.; Strolin, S.; Casali, F.; Lamanna, Ernesto; Ariù, Marilù

    2011-08-01

    During the course of 2009, in the framework of a project supported by the National Institute of Nuclear Physics, a number of tests were carried out at the Department of Physics of the University of Bologna in order to achieve a good quality CT scan of the internal human ear. The work was carried out in collaboration with the local “S. Orsola” Hospital in Bologna and a company (CEFLA) already involved in the production and commercialization of a CT scanner dedicated to dentistry. A laboratory scanner with a simple concept detector (CCD camera-lens-mirror-scintillator) was used to see to what extent it was possible to enhance the quality of a conventional CT scanner when examining the internal human ear. To test the system, some conventional measurements were made, such as the spatial resolution calculation with the MTF and dynamic range evaluation. Different scintillators were compared to select the most suitable for the purpose. With 0.5 mm thick structured cesium iodide and a field of view of 120×120 mm2, a spatial resolution of 6.5l p/mm at 5% MTF was obtained. The CT of a pair of human head phantoms was performed at an energy of 120 kVp. The first phantom was a rough representation of the human head shape, with soft tissue made of coarse slabs of Lucite. Some inserts, like small aluminum cylinders and cubes, with 1 mm diameter drilled holes, were used to simulate the channels that one finds inside the human inner ear. The second phantom is a plastic PVC fused head with a real human cranium inside. The bones in the cranium are well conserved and the inner ear features, such as the cochlea and semicircular channels, are clearly detectable. After a number of CT tests we obtained good results as far as structural representation and channel detection are concerned. Some images of the 3D rendering of the CT volume are shown below. The doctors of the local hospital who followed our experimentation expressed their satisfaction. The CT was compared to a virtual

  13. High-accuracy registration of intraoperative CT imaging

    NASA Astrophysics Data System (ADS)

    Oentoro, A.; Ellis, R. E.

    2010-02-01

    Image-guided interventions using intraoperative 3D imaging can be less cumbersome than systems dependent on preoperative images, especially by needing neither potentially invasive image-to-patient registration nor a lengthy process of segmenting and generating a 3D surface model. In this study, a method for computer-assisted surgery using direct navigation on intraoperative imaging is presented. In this system the registration step of a navigated procedure was divided into two stages: preoperative calibration of images to a ceiling-mounted optical tracking system, and intraoperative tracking during acquisition of the 3D medical image volume. The preoperative stage used a custom-made multi-modal calibrator that could be optically tracked and also contained fiducial spheres for radiological detection; a robust registration algorithm was used to compensate for the very high false-detection rate that was due to the high physical density of the optical light-emitting diodes. Intraoperatively, a tracking device was attached to plastic bone models that were also instrumented with radio-opaque spheres; A calibrated pointer was used to contact the latter spheres as a validation of the registration. Experiments showed that the fiducial registration error of the preoperative calibration stage was approximately 0.1 mm. The target registration error in the validation stage was approximately 1.2 mm. This study suggests that direct registration, coupled with procedure-specific graphical rendering, is potentially a highly accurate means of performing image-guided interventions in a fast, simple manner.

  14. "High-precision, reconstructed 3D model" of skull scanned by conebeam CT: Reproducibility verified using CAD/CAM data.

    PubMed

    Katsumura, Seiko; Sato, Keita; Ikawa, Tomoko; Yamamura, Keiko; Ando, Eriko; Shigeta, Yuko; Ogawa, Takumi

    2016-01-01

    Computed tomography (CT) scanning has recently been introduced into forensic medicine and dentistry. However, the presence of metal restorations in the dentition can adversely affect the quality of three-dimensional reconstruction from CT scans. In this study, we aimed to evaluate the reproducibility of a "high-precision, reconstructed 3D model" obtained from a conebeam CT scan of dentition, a method that might be particularly helpful in forensic medicine. We took conebeam CT and helical CT images of three dry skulls marked with 47 measuring points; reconstructed three-dimensional images; and measured the distances between the points in the 3D images with a computer-aided design/computer-aided manufacturing (CAD/CAM) marker. We found that in comparison with the helical CT, conebeam CT is capable of reproducing measurements closer to those obtained from the actual samples. In conclusion, our study indicated that the image-reproduction from a conebeam CT scan was more accurate than that from a helical CT scan. Furthermore, the "high-precision reconstructed 3D model" facilitates reliable visualization of full-sized oral and maxillofacial regions in both helical and conebeam CT scans.

  15. Vorticity isotropy in high Karlovitz number premixed flames

    NASA Astrophysics Data System (ADS)

    Bobbitt, Brock; Blanquart, Guillaume

    2016-10-01

    The isotropy of the smallest turbulent scales is investigated in premixed turbulent combustion by analyzing the vorticity vector in a series of high Karlovitz number premixed flame direct numerical simulations. It is found that increasing the Karlovitz number and the ratio of the integral length scale to the flame thickness both reduce the level of anisotropy. By analyzing the vorticity transport equation, it is determined that the vortex stretching term is primarily responsible for the development of any anisotropy. The local dynamics of the vortex stretching term and vorticity resemble that of homogeneous isotropic turbulence to a greater extent at higher Karlovitz numbers. This results in small scale isotropy at sufficiently high Karlovitz numbers and supports a fundamental similarity of the behavior of the smallest turbulent scales throughout the flame and in homogeneous isotropic turbulence. At lower Karlovitz numbers, the vortex stretching term and the vorticity alignment in the strain-rate tensor eigenframe are altered by the flame. The integral length scale has minimal impact on these local dynamics but promotes the effects of the flame to be equal in all directions. The resulting isotropy in vorticity does not reflect a fundamental similarity between the smallest turbulent scales in the flame and in homogeneous isotropic turbulence.

  16. Low-dose high-resolution CT of lung parenchyma

    SciTech Connect

    Zwirewich, C.V.; Mayo, J.R.; Mueller, N.L. )

    1991-08-01

    To evaluate the efficacy of low-dose high-resolution computed tomography (HRCT) in the assessment of lung parenchyma, three observers reviewed the scans of 31 patients. The 1.5-mm-collimation, 2-second, 120-kVp scans were obtained at 20 and 200 mA at selected identical levels in the chest. The observers evaluated the visualization of normal pulmonary anatomy, various parenchymal abnormalities and their distribution, and artifacts. The low-dose and conventional scans were equivalent in the evaluation of vessels, lobar and segmental bronchi, and anatomy of secondary pulmonary lobules, and in characterizing the extent and distribution of reticulation, honeycomb cysts, and thickened interlobular septa. The low-dose technique failed to demonstrate ground-glass opacity in two of 10 cases (20%) and emphysema in one of nine cases (11%), in which they were evident but subtle on the high-dose scans. These differences were not statistically significant. Linear streak artifact was more prominent on images acquired with the low-dose technique, but the two techniques were judged equally diagnostic in 97% of cases. The authors conclude that HRCT images acquired at 20 mA yield anatomic information equivalent to that obtained with 200-mA scans in the majority of patients, without significant loss of spatial resolution or image degradation due to linear streak artifact.

  17. Predictive Role of the Number of 18F-FDG-Positive Lymph Nodes Detected by PET/CT for Pre-Treatment Evaluation of Locally Advanced Gastric Cancer

    PubMed Central

    Wang, Xin; Wei, Yuzhe; Xue, Yingwei; Lu, Peiou; Yu, Lijuan; Shen, Baozhong

    2016-01-01

    Objectives The aim of this study was to investigate the predictive value of the numbers of metabolically positive lymph nodes (MPLN) detected by 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) in patients with locally advanced gastric cancer (LAGC). Methods We retrospectively analyzed the records of 50 patients with LAGC (stage T2-T4) who had undergone pre-operative PET/CT examination and laparotomy (total gastrectomy, n = 11; subtotal gastrectomy, n = 13; distal gastrectomy, n = 22; and bypass with gastrojejunstomy, n = 4). The numbers of MPLN were determined by combining visual observations with semi-quantitative measurements of the maximized standardized uptake value (SUVmax). Performance was investigated in terms of predicting post-surgical overall survival (OS). Results The median post-surgical OS was 32.57 months (range 3.0-94 months). The numbers of MPLN were moderately correlated with the numbers of histological positive LN (r = 0.694, p = 0.001). In univariate analyses, the numbers of MPLN (≤ 2 vs. ≥3), PET/CT LN (positivity vs. negativity), SUVmax of LN (< 2.8 vs. ≥ 2.8), TNM stage (I, II vs. III, IV), and surgery type (R0 vs. non-R0) were significantly associated with OS. In multivariate analysis, surgery type (R0 vs. non-R0) and numbers of MPLN (≤ 2 vs. ≥ 3) were both independent factors for poor OS. Conclusions This explored study indicates that the number of MPLN could provide additional information for LAGC prognosis. Patients with MPLNs ≥ 3 may be at the risk of the more bad outcomes, and the further clinical trials are needed. PMID:27936109

  18. Cryptogenic organizing pneumonia: serial high-resolution CT findings in 22 patients.

    PubMed

    Lee, Ju Won; Lee, Kyung Soo; Lee, Ho Yun; Chung, Man Pyo; Yi, Chin A; Kim, Tae Sung; Chung, Myung Jin

    2010-10-01

    We conducted a review of serial high-resolution CT (HRCT) findings of cryptogenic organizing pneumonia (COP). Over the course of 14 years, we saw 32 patients with biopsy-confirmed COP. Serial HRCT scans were available for only 22 patients (seven men and 15 women; mean age, 52 years; median follow-up period, 8 months; range, 5-135 months). Serial CT scans were evaluated by two chest radiologists who reached a conclusion by consensus. Overall changes in disease extent were classified as cured, improved (i.e., ≥ 10% decrease in extent), not changed, or progressed (i.e., ≥ 10% increase in extent). When there were remaining abnormalities, the final follow-up CT images were analyzed to express observers' ideas regarding what type of interstitial lung disease the images most likely suggested. The two most common patterns of lung abnormality on initial scans were ground-glass opacification (86% of patients [19/22]) and consolidation (77% of patients [17/22]), distributed along the bronchovascular bundles or subpleural lungs in 13 patients (59%). In six patients (27%), the disease disappeared completely; in 15 patients (68%), the disease was decreased in extent; and in one patient (5%), no change in extent was detected on follow-up CT. When lesions remained, the final follow-up CT findings were reminiscent of fibrotic nonspecific interstitial pneumonia in 10 of 16 patients (63%). Although COP is a disease with a generally good prognosis, most patients (73%) with COP have some remaining disease seen on follow-up CT scans, and, in such cases, the lesions generally resemble a fibrotic nonspecific interstitial pneumonia pattern.

  19. High-resolution imaging of murine myocardial infarction with delayed-enhancement cine micro-CT.

    PubMed

    Nahrendorf, Matthias; Badea, Cristian; Hedlund, Laurence W; Figueiredo, Jose-Luiz; Sosnovik, David E; Johnson, G Allan; Weissleder, Ralph

    2007-06-01

    The objective of this study was to determine the feasibility of delayed-enhancement micro-computed tomography (microCT) imaging to quantify myocardial infarct size in experimental mouse models. A total of 20 mice were imaged 5 or 35 days after surgical ligation of the left coronary artery or sham surgery (n=6 or 7 per group). We utilized a prototype microCT that covers a three-dimensional (3D) volume with an isotropic spatial resolution of 100 microm. A series of image acquisitions were started after a 200 microl bolus of a high-molecular-weight blood pool CT agent to outline the ventricles. CT imaging was continuously performed over 60 min, while an intravenous constant infusion with iopamidol 370 was started at a dosage of 1 ml/h. Thirty minutes after the initiation of this infusion, signal intensity in Hounsfield units was significantly higher in the infarct than in the remote, uninjured myocardium. Cardiac morphology and motion were visualized with excellent contrast and in fine detail. In vivo CT determination of infarct size at the midventricular level was in good agreement with ex vivo staining with triphenyltetrazolium chloride [5 days post-myocardial infarction (MI): r(2)=0.86, P<0.01; 35 days post-MI: r(2)=0.92, P<0.01]. In addition, we detected significant left ventricular remodeling consisting of left ventricular dilation and decreased ejection fraction. 3D cine microCT reliably and rapidly quantifies infarct size and assesses murine anatomy and physiology after coronary ligation, despite the small size and fast movement of the mouse heart. This efficient imaging tool is a valuable addition to the current phenotyping armamentarium and will allow rapid testing of novel drugs and cell-based interventions in murine models.

  20. High Resolution Imaging of Murine Myocardial Infarction With Delayed Enhancement and Cine Micro-CT

    PubMed Central

    Nahrendorf, Matthias; Badea, Cristian; Hedlund, Laurence W; Figueiredo, Jose-Luiz; Sosnovik, David E.; Johnson, G Allan; Weissleder, Ralph

    2009-01-01

    Objective To determine the feasibility of delayed enhancement µCT imaging to quantify myocardial infarct size in experimental mouse models. Methods and Results A total of 20 mice were imaged 5 or 35 days after surgical ligation of the left coronary artery, or sham surgery (n=6–7 per group). We utilized a prototype εCT which covers a 3D volume with an isotropic spatial resolution of 100 µm. A series of image acquisitions were started after a 200 µL bolus of a high molecular weight blood pool CT agent to outline the ventricles. CT imaging was continuously performed over 60 minutes, while an intravenous constant infusion with iopamidol 370 was started at a dosage of 1 mL/h. Thirty minutes after the initiation of this infusion, signal intensity in Hounsfild Units was significantly higher in the infarct than in the remote, uninjured myocardium. Cardiac morphology and motion was visualized with excellent contrast and in fine detail. In vivo CT determination of infarct extension and transmurality was in good agreement with ex vivo staining with triphenyltetrazolium chloride (5 days post MI: r2= 0.86, p < 0.01; 35 days post MI r2=0.92, p < 0.01). In addition, we detected significant left ventricular remodeling consisting of left ventricular dilation and decreased ejection fraction. Conclusion 3D cine µCT reliably and rapidly quantifies infarct size and assesses murine anatomy and physiology after coronary ligation, despite the small size and the fast movement of the mouse heart. This efficient imaging tool is a valuable addition to the current phenotyping armamentarium and will allow rapid testing of novel drugs and cell based interventions in murine models. PMID:17322414

  1. CT Scan Screening for Lung Cancer: Risk Factors for Nodules and Malignancy in a High-Risk Urban Cohort

    PubMed Central

    Greenberg, Alissa K.; Lu, Feng; Goldberg, Judith D.; Eylers, Ellen; Tsay, Jun-Chieh; Yie, Ting-An; Naidich, David; McGuinness, Georgeann; Pass, Harvey; Tchou-Wong, Kam-Meng; Addrizzo-Harris, Doreen; Chachoua, Abraham; Crawford, Bernard; Rom, William N.

    2012-01-01

    Background Low-dose computed tomography (CT) for lung cancer screening can reduce lung cancer mortality. The National Lung Screening Trial reported a 20% reduction in lung cancer mortality in high-risk smokers. However, CT scanning is extremely sensitive and detects non-calcified nodules (NCNs) in 24–50% of subjects, suggesting an unacceptably high false-positive rate. We hypothesized that by reviewing demographic, clinical and nodule characteristics, we could identify risk factors associated with the presence of nodules on screening CT, and with the probability that a NCN was malignant. Methods We performed a longitudinal lung cancer biomarker discovery trial (NYU LCBC) that included low-dose CT-screening of high-risk individuals over 50 years of age, with more than 20 pack-year smoking histories, living in an urban setting, and with a potential for asbestos exposure. We used case-control studies to identify risk factors associated with the presence of nodules (n = 625) versus no nodules (n = 557), and lung cancer patients (n = 30) versus benign nodules (n = 128). Results The NYU LCBC followed 1182 study subjects prospectively over a 10-year period. We found 52% to have NCNs >4 mm on their baseline screen. Most of the nodules were stable, and 9.7% of solid and 26.2% of sub-solid nodules resolved. We diagnosed 30 lung cancers, 26 stage I. Three patients had synchronous primary lung cancers or multifocal disease. Thus, there were 33 lung cancers: 10 incident, and 23 prevalent. A sub-group of the prevalent group were stable for a prolonged period prior to diagnosis. These were all stage I at diagnosis and 12/13 were adenocarcinomas. Conclusions NCNs are common among CT-screened high-risk subjects and can often be managed conservatively. Risk factors for malignancy included increasing age, size and number of nodules, reduced FEV1 and FVC, and increased pack-years smoking. A sub-group of screen-detected cancers are slow-growing and may contribute to

  2. Aeroacoustic data for high Reynolds number supersonic axisymmetric jets

    NASA Astrophysics Data System (ADS)

    Seiner, J. M.; Ponton, M. K.

    1985-01-01

    Both aerodynamic and near field acoustic behavior of several unheated axisymmetric shock free and shock containing high speed jet plumes are reported. The exit Mach number range for these data is from 0.9 to 2.5. The aerodynamic measurements include both mean and turbulence quantities for a shock free jet plume produced by a convergent divergent nozzle designed to have an exit Mach number of 2. The near field acoustic measurements presented include narrow band spectra, directivity and contour plots of select one third octave band data, and near field microphone correlations from a linear array. Shock noise results are also included as obtained by operating an underexpanded convergent nozzle at the design point of two supersonic exist Mach number convergent divergent nozzles.

  3. Very high Mach number shocks - Theory. [in space plasmas

    NASA Technical Reports Server (NTRS)

    Quest, Kevin B.

    1986-01-01

    The theory and simulation of collisionless perpendicular supercritical shock structure is reviewed, with major emphasis on recent research results. The primary tool of investigation is the hybrid simulation method, in which the Newtonian orbits of a large number of ion macroparticles are followed numerically, and in which the electrons are treated as a charge neutralizing fluid. The principal results include the following: (1) electron resistivity is not required to explain the observed quasi-stationarity of the earth's bow shock, (2) the structure of the perpendicular shock at very high Mach numbers depends sensitively on the upstream value of beta (the ratio of the thermal to magnetic pressure) and electron resistivity, (3) two-dimensional turbulence will become increasingly important as the Mach number is increased, and (4) nonadiabatic bulk electron heating will result when a thermal electron cannot complete a gyrorbit while transiting the shock.

  4. Magnetic resonance imaging assessed cortical porosity is highly correlated with μCT porosity.

    PubMed

    Bae, Won C; Patil, Shantanu; Biswas, Reni; Li, Shihong; Chang, Eric Y; Statum, Sheronda; D'Lima, Darryl D; Chung, Christine B; Du, Jiang

    2014-09-01

    Cortical bone is typically regarded as "MR invisible" with conventional clinical magnetic resonance imaging (MRI) pulse sequences. However, recent studies have demonstrated that free water in the microscopic pores of cortical bone has a short T2* but a relatively long T2, and may be detectable with conventional clinical spin echo (SE) or fast spin echo (FSE) sequences. In this study we describe the use of a conventional two-dimensional (2D) FSE sequence to assess cortical bone microstructure and measure cortical porosity using a clinical 3T scanner. Twelve cadaveric human cortical bone samples were studied with MRI and microcomputed tomography (μCT) (downsampled to the same spatial resolution). Preliminary results show that FSE-determined porosity is highly correlated (R(2)=0.83; P<0.0001) with μCT porosity. Bland-Altman analysis suggested a good agreement between FSE and μCT with tight limit of agreement at around 3%. There is also a small bias of -2% for the FSE data, which suggested that the FSE approach slightly underestimated μCT porosity. The results demonstrate that cortical porosity can be directly assessed using conventional clinical FSE sequences. The clinical feasibility of this approach was also demonstrated on six healthy volunteers using 2D FSE sequences as well as 2D ultrashort echo time (UTE) sequences with a minimal echo time (TE) of 8μs, which provide high contrast imaging of cortical bone in vivo.

  5. NOTE: X-ray CT high-density artefact suppression in cryosurgery

    NASA Astrophysics Data System (ADS)

    Wei, Jikun; Sandison, George A.; Chen, Laigao; Liang, Yun; Xu, Lisa X.

    2002-12-01

    Advantages of x-ray CT for imaging guidance of cryosurgery include 3D visualization of frozen and unfrozen tissue and calibration of temperature in the tissue water-ice interface (0-10 °C) to Hounsfield units. However, use of x-ray CT images and their thermal calibration can be compromised by the cryoprobes generating high-density streak artefacts. A new subtraction technique for artefact suppression is proposed and tested in prostate cryosurgery simulations. By subtracting the measured CT x-ray projection profile without cryoprobes from the profile with cryoprobes plus iceballs, one obtains the combined profile of the cryoprobes and a low value background. Polynomial interpolation to obtain the background profile allows its addition to the original profile without probes. The result may then be fed to a conventional filtered back-projection routine to reconstruct the probe-free image. Finally the cryoprobe pixels in the originally constructed image with probes and iceballs are added back to the probe-free image to get the final artefact-suppressed image. The major advantage of this subtraction technique is that it can successfully suppress the high-density artefacts in bone-abundant body regions such as the pelvis. X-ray CT images of cryoprobe arrays in a homogeneous gelatin phantom and the pelvic region of an anthropomorphic Rando phantom containing a human skeleton were generated. After suppression, cryoprobe metal artefact streaks are reduced and visualization of the positions and dimensions of the cryoprobes are well preserved.

  6. High-resolution CT findings of patients with pulmonary nocardiosis

    PubMed Central

    Tsujimoto, Naoki; Saraya, Takeshi; Kikuchi, Ken; Takata, Saori; Kurihara, Yasuyuki; Hiraoka, Sayuki; Makino, Hiroshi; Yonetani, Shota; Araki, Koji; Ishii, Haruyuki; Takizawa, Hajime

    2012-01-01

    Background Opportunistic pulmonary infection with Nocardia species is rare in humans, and only a few studies have radiologically analyzed patients with pulmonary nocardiosis using high-resolution computed tomography (HRCT). Methods We retrospectively reviewed the medical records of patients with pulmonary nocardiosis at our hospital between April 2006 and December 2011 to assess HRCT and clinical findings. We also searched the medical literature for pulmonary nocardiosis reported in Japan between 2002 and 2011 for comparison. Results We identified seven patients at our institution and 33 reported infections in Japan. Four of our patients were immunocompetent, whereas the other three had impaired cellular immunity due to type 2 diabetes mellitus or having been inappropriately treated with steroid. Thoracic HRCT revealed no zonal predominance, but tropism for distribution from the middle to the peripheral area, and radiological findings of nodules, cavitation, mass, consolidations, bronchial wall thickening, septal line thickening and ground glass opacity (GGO) were evident. The main HRCT finding in our study comprised nodules (n=5, 71.4%) <30 mm and four patients had multiple nodules as described in other reports. Furthermore, we discovered a crazy paving appearance (CPA) around nodules, cavities, masses or consolidations in five patients (71.4%). Conclusions Multiple nodules distributed from the middle to the peripheral area on HRCT might reflect pulmonary nocardiosis, and CPA seemed to be a worth paying attention to the diagnosis. PMID:23205281

  7. Inhalational pulmonary talcosis: high-resolution CT findings in 3 patients.

    PubMed

    Marchiori, Edson; Souza Júnior, Arthur Soares; Müller, Nestor L

    2004-01-01

    We describe the high-resolution CT findings in 3 patients with pulmonary talcosis acquired by the inhalation of talc. The predominant abnormalities consisted of small centrilobular and subpleural nodules and conglomerated masses containing focal areas of high attenuation consistent with talc deposition. All patients also had focal ground glass opacities. The abnormalities were diffuse but were most severe in the upper and middle lung zones with relative sparing of the lung bases.

  8. Exploring crystallization kinetics in natural rhyolitic melts using high resolution CT imagery of spherulites

    NASA Astrophysics Data System (ADS)

    Clow, T. W.; Befus, K. S.; Gardner, J. E.

    2014-12-01

    Little of our understanding of crystallization kinetics has been directly derived from studies of natural samples. We examine crystallization of rhyolitic melts by quantifying spherulite sizes and number densities in obsidian collected from Yellowstone caldera using high-resolution x-ray computed tomography (CT) imagery. Spherulites are spherical to ellipsoidal masses of intergrown alkali feldspar and quartz in a radiating, fibrous structure. They are thought to form in response to relatively rapid crystallization of melt in response to large amounts of undercooling. Recent research using compositional gradients that form outside of spherulites has suggested that they nucleate at 700 to 500 ˚C and their growth slows exponentially until it eventually ceases at ~400 ˚C. By quantifying spherulite textures, and using those temperature constraints, we derive new kinetic information regarding crystallization in natural rhyolitic systems. We find that spherulites range from 0.2 to 12.3 mm in diameter, and are 0.004 to 49.5 mm3 in volume. Such values generate number densities of 70 to 185 spherulites cm-3. Histograms of size display positively skewed distributions indicating small spherulites are far more abundant than larger ones. Those distributions imply nucleation rates change as a function of temperature. At higher temperatures where the melt is undercooled by 400-500 ˚C, nucleation is rare and growth is favored. With decreasing temperature, nucleation rates increase rapidly until cold enough temperatures are reached that diffusion limits crystallization and causes it to cease (undercoolings of ~650 ˚C). Assuming a cooling rate for the host obsidian of 10-5 ˚C s-1, then overall spherulite nucleation rates are 0.01 to 0.03 spherulites cm-3 hour-1.

  9. Characterization of Incidental Renal Mass With Dual-Energy CT: Diagnostic Accuracy of Effective Atomic Number Maps for Discriminating Nonenhancing Cysts From Enhancing Masses.

    PubMed

    Mileto, Achille; Allen, Brian C; Pietryga, Jason A; Farjat, Alfredo E; Zarzour, Jessica G; Bellini, Davide; Ebner, Lukas; Morgan, Desiree E

    2017-10-01

    The purpose of this study was to assess the diagnostic accuracy of effective atomic number maps reconstructed from dual-energy contrast-enhanced data for discriminating between nonenhancing renal cysts and enhancing masses. Two hundred six patients (128 men, 78 women; mean age, 64 years) underwent a CT renal mass protocol (single-energy unenhanced and dual-energy contrast-enhanced nephrographic imaging) at two different hospitals. For each set of patients, two blinded, independent observers performed measurements on effective atomic number maps from contrast-enhanced dual-energy data. Renal mass assessment on unenhanced and nephrographic images, corroborated by imaging and medical records, was the reference standard. The diagnostic accuracy of effective atomic number maps was assessed with ROC analysis. Significant differences in mean effective atomic numbers (Zeff) were observed between nonenhancing and enhancing masses (set A, 8.19 vs 9.59 Zeff; set B, 8.05 vs 9.19 Zeff; sets combined, 8.13 vs 9.37 Zeff) (p < 0.0001). An effective atomic number value of 8.36 Zeff was the optimal threshold, rendering an AUC of 0.92 (95% CI, 0.89-0.94), sensitivity of 90.8% (158/174 [95% CI, 85.5-94.7%]), specificity of 85.2% (445/522 [95% CI, 81.9-88.2%]), and overall diagnostic accuracy of 86.6% (603/696 [95% CI, 83.9-89.1%]). Nonenhancing renal cysts, including hyperattenuating cysts, can be discriminated from enhancing masses on effective atomic number maps generated from dual-energy contrast-enhanced CT data. This technique may be of clinical usefulness when a CT protocol for comprehensive assessment of renal masses is not available.

  10. High Reynolds Number Transition Experiments in ETW (TELFONA project)

    NASA Astrophysics Data System (ADS)

    Perraud, J.; Archambaud, J.-P.; Schrauf, G.; Donelli, R. S.; Hanifi, A.; Quest, J.; Hein, S.; Streit, T.; Fey, U.; Egami, Y.

    A wind-tunnel experiment on laminar-turbulent transition has been performed in ETW (the European Transonic Wind Tunnel in Koln) at high Reynolds number and cryogenic conditions. The studied geometry is a sting mounted full model in swept-wing configuration. The transition location was determined by means of Temperature Sensitive Paint (CryoTSP). The experimental observations were further analysed using different transition prediction tools, based on linear stability theory.

  11. Number-ratio fluctuations in high-energy particle production

    SciTech Connect

    Christiansen, P.; Haslum, E.; Stenlund, E.

    2009-09-15

    In this article we will discuss the previously proposed quantity {nu}{sub dyn}[C. Pruneau, S. Gavin, and S. Voloshin, Phys. Rev. C 66, 044904 (2002)], as a measure of the number-ratio fluctuations in high-energy particle production. We will show that {nu}{sub dyn} has pleasing mathematical properties making it ideal for the purpose. We will demonstrate its relation to two-particle correlations and how this measure can be generalized to higher-order correlations.

  12. Very High Mach Number Quasi-Perpendicular Collisionless Shocks

    NASA Astrophysics Data System (ADS)

    Scholer, M.; Comisel, H.

    2011-12-01

    A high Mach number quasi-perpendicular collisionless shock is studied with one-dimensional (1-D) full particle simulations. The Alfven Mach number is M_A=22, the shock normal-magnetic field angle is Θ=85 and the ion and electron beta (particle to magnetic pressure) is 0.5. We have used in the simulations a large value for the ratio of the electron plasma frequency to the gyrofrequency of ω_pe/Ω_ce=20, and a high value of the ion to electron mass ratio, (m_i/m_e=1500). The shock is highly non-stationary but does not exhibit the reformation pattern seen in previous simulations of lower Mach number perpendicular or quasi-perpendicular shocks. The magnetic field profiles flattens and steepens with a time period of 1.4-1.5 inverse ion gyrofrequencies while the ions are specular reflected from the steepened ramp and finally return downstream just at the subsequent steepening of the ramp. The scale of the ramp varies between ~ 10 to ~ 20 electron inertial lengths corresponding to the changes from a steep to a flat profile. By tracing all trajectories of the reflected ions in the simulation box we have determined the absolute reflection rate as well as an average energy gain related to the non-stationarity of the shock ramp. The reflection rate varies between almost zero percent during flat profiles and ~ 100 percent during steep profiles.

  13. Microinstabilities associated with a high Mach number, perpendicular bow shock

    NASA Technical Reports Server (NTRS)

    Wu, C. S.; Winske, D.; Tanaka, M.; Papadopoulos, K.; Akimoto, K.; Goodrich, C. C.; Zhou, Y. M.; Tsai, S. T.; Rodriguez, P.; Lin, C. S.

    1984-01-01

    Instability analyses incorporating insights gained through ISEE observations and hybrid simulations are used in an examination of the instabilities associated with a high Mach number perpendicular shock akin to the earth's bow shock. In the regions in front of, and at, the shock transition the cross-field instabilities are subdivided into the ion-ion streaming, kinetic cross-field streaming, and drift lower hybrid instability low frequency modes, as well as the electron cyclotron drift, ion sound, and electron whisker instability high frequency modes. Further downstream, ion ring-like and anisotropy-driven instabilities are considered. The implications of these results for wave signatures, plasma heating and acceleration are noted.

  14. High-resolution CT scan findings in patients with symptomatic scleroderma-related interstitial lung disease.

    PubMed

    Goldin, Jonathan G; Lynch, David A; Strollo, Diane C; Suh, Robert D; Schraufnagel, Dean E; Clements, Philip J; Elashoff, Robert M; Furst, Daniel E; Vasunilashorn, Sarinnapha; McNitt-Gray, Michael F; Brown, Mathew S; Roth, Michael D; Tashkin, Donald P

    2008-08-01

    Lung disease has become the leading cause of mortality and morbidity in scleroderma (SSc) patients. The frequency, nature, and progression of interstitial lung disease seen on high-resolution CT (HRCT) scans in patients with diffuse SSc (dcSSc) compared with those with limited SSc (lcSSc) has not been well characterized. Baseline HRCT scan images of 162 participants randomized into a National Institutes of Health-funded clinical trial were compared to clinical features, pulmonary function test measures, and BAL fluid cellularity. The extent and distribution of interstitial lung disease HRCT findings, including pure ground-glass opacity (pGGO), pulmonary fibrosis (PF), and honeycomb cysts (HCs), were recorded in the upper, middle, and lower lung zones on baseline and follow-up CT scan studies. HRCT scan findings included 92.9% PF, 49.4% pGGO, and 37.2% HCs. There was a significantly higher incidence of HCs in the three zones in lcSSc patients compared to dcSSc patients (p = 0.034, p = 0.048, and p = 0.0007, respectively). The extent of PF seen on HRCT scans was significantly negatively correlated with FVC (r = - 0.22), diffusing capacity of the lung for carbon monoxide (r = - 0.44), and total lung capacity (r = - 0.36). A positive correlation was found between pGGO and the increased number of acute inflammatory cells found in BAL fluid (r = 0.28). In the placebo group, disease progression was assessed as 30% in the upper and middle lung zones, and 45% in the lower lung zones. No difference in the progression rate was seen between lcSSc and dcSSc patients. PF and GGO were the most common HRCT scan findings in symptomatic SSc patients. HCs were seen in more than one third of cases, being more common in lcSSc vs dcSSc. There was no relationship between progression and baseline PF extent or lcSSc vs dcSSc. Clinicaltrials.gov Identifier: NCT00004563.

  15. Yttrium-90 internal pair production imaging using first generation PET/CT provides high-resolution images for qualitative diagnostic purposes

    PubMed Central

    Kao, Y H; Tan, E H; Lim, K Y; Ng, C E; Goh, S W

    2012-01-01

    Yttrium-90 (90Y) internal pair production can be imaged by positron emission tomography (PET)/CT and is superior to bremsstrahlung single-photon emission CT/CT for evaluating hepatic 90Y microsphere biodistribution. We illustrate a case of 90Y imaging using first generation PET/CT technology, producing high-quality images for qualitative diagnostic purposes. PMID:21976634

  16. A wire scanning based method for geometric calibration of high resolution CT system

    NASA Astrophysics Data System (ADS)

    Jiang, Ruijie; Li, Guang; Gu, Ning; Chen, Gong; Luo, Shouhua

    2015-03-01

    This paper is about geometric calibration of the high resolution CT (Computed Tomography) system. Geometric calibration refers to the estimation of a set of parameters that describe the geometry of the CT system. Such parameters are so important that a little error of them will degrade the reconstruction images seriously, so more accurate geometric parameters are needed in the higher-resolution CT systems. But conventional calibration methods are not accurate enough for the current high resolution CT system whose resolution can reach sub-micrometer or even tens of nanometers. In this paper, we propose a new calibration method which has higher accuracy and it is based on the optimization theory. The superiority of this method is that we build a new cost function which sets up a relationship between the geometrical parameters and the binary reconstruction image of a thin wire. When the geometrical parameters are accurate, the cost function reaches its maximum value. In the experiment, we scanned a thin wire as the calibration data and a thin bamboo stick as the validation data to verify the correctness of the proposed method. Comparing with the image reconstructed with the geometric parameters calculated by using the conventional calibration method, the image reconstructed with the parameters calculated by our method has less geometric artifacts, so it can verify that our method can get more accurate geometric calibration parameters. Although we calculated only one geometric parameter in this paper, the geometric artifacts are still eliminated significantly. And this method can be easily generalized to all the geometrical parameters calibration in fan-beam or cone-beam CT systems.

  17. Numerical Simulation of a High Mach Number Jet Flow

    NASA Technical Reports Server (NTRS)

    Hayder, M. Ehtesham; Turkel, Eli; Mankbadi, Reda R.

    1993-01-01

    The recent efforts to develop accurate numerical schemes for transition and turbulent flows are motivated, among other factors, by the need for accurate prediction of flow noise. The success of developing high speed civil transport plane (HSCT) is contingent upon our understanding and suppression of the jet exhaust noise. The radiated sound can be directly obtained by solving the full (time-dependent) compressible Navier-Stokes equations. However, this requires computational storage that is beyond currently available machines. This difficulty can be overcome by limiting the solution domain to the near field where the jet is nonlinear and then use acoustic analogy (e.g., Lighthill) to relate the far-field noise to the near-field sources. The later requires obtaining the time-dependent flow field. The other difficulty in aeroacoustics computations is that at high Reynolds numbers the turbulent flow has a large range of scales. Direct numerical simulations (DNS) cannot obtain all the scales of motion at high Reynolds number of technological interest. However, it is believed that the large scale structure is more efficient than the small-scale structure in radiating noise. Thus, one can model the small scales and calculate the acoustically active scales. The large scale structure in the noise-producing initial region of the jet can be viewed as a wavelike nature, the net radiated sound is the net cancellation after integration over space. As such, aeroacoustics computations are highly sensitive to errors in computing the sound sources. It is therefore essential to use a high-order numerical scheme to predict the flow field. The present paper presents the first step in a ongoing effort to predict jet noise. The emphasis here is in accurate prediction of the unsteady flow field. We solve the full time-dependent Navier-Stokes equations by a high order finite difference method. Time accurate spatial simulations of both plane and axisymmetric jet are presented. Jet Mach

  18. Cassini Observations of Saturn's High-Mach Number Bow Shock

    NASA Astrophysics Data System (ADS)

    Masters, A.; Sulaiman, A.; Sergis, N.; Stawarz, L.; Fujimoto, M.; Coates, A. J.; Dougherty, M. K.

    2016-12-01

    The leading explanation for the origin of galactic cosmic rays is particle acceleration at the shocks surrounding young supernova remnants (SNRs), although crucial aspects of the acceleration process are unclear. The similar collisionless plasma shocks frequently encountered by spacecraft in the solar wind are generally far weaker (lower Mach number) than these SNR shocks. However, the Cassini spacecraft has shown that the shock standing in the solar wind sunward of Saturn (Saturn's bow shock) can occasionally reach this high-Mach number astrophysical regime. In this regime Cassini has provided the first in situ evidence for electron acceleration under quasi-parallel upstream magnetic conditions. Here we review the most recent published work based on Cassini data taken at Saturn's bow shock. We then present an interpretation and discussion of the sum of the Cassini findings to date, with emphasis on the implications for shock-acceleration of charged particles. Future directions for work in this area are outlined.

  19. Improving spatial-resolution in high cone-angle micro-CT by source deblurring

    NASA Astrophysics Data System (ADS)

    Li, Heyang; Kingston, Andrew; Myers, Glenn; Recur, Benoit; Turner, Michael; Sheppard, Andrian

    2014-09-01

    Micro scale computed tomography (CT) can resolve many features in cellular structures, bone formations, minerals properties and composite materials not seen at lower spatial-resolution. Those features enable us to build a more comprehensive model for the object of interest. CT resolution is limited by a fundamental trade off between source size and signal-to-noise ratio (SNR) for a given acquisition time. There is a limit on the X-ray flux that can be emitted from a certain source size, and fewer photons cause a lower SNR. A large source size creates penumbral blurring in the radiograph, limiting the effective spatial-resolution in the reconstruction. High cone-angle CT improves SNR by increasing the X-ray solid angle that passes through the sample. In the high cone-angle regime current source deblurring methods break down due to incomplete modelling of the physical process. This paper presents high cone-angle source de-blurring models. We implement these models using a novel multi-slice Richardson-Lucy (M-RL) and 3D Conjugate Gradient deconvolution on experimental high cone-angle data to improve the spatial-resolution of the reconstructed volume. In M-RL, we slice the back projection volume into subsets which can be considered to have a relative uniform convolution kernel. We compare these results to those obtained from standard reconstruction techniques and current source deblurring methods (i.e. 2D Richardson-Lucy in the radiograph and the volume respectively).

  20. PET/CT and High Resolution CT as potential imaging biomarkers associated with treatment outcomes in MDR-TB

    PubMed Central

    Chen, Ray Y.; Dodd, Lori E.; Lee, Myungsun; Paripati, Praveen; Hammoud, Dima A.; Mountz, James M.; Jeon, Doosoo; Zia, Nadeem; Zahiri, Homeira; Coleman, M. Teresa; Carroll, Matthew W.; Lee, Jong Doo; Jeong, Yeon Joo; Herscovitch, Peter; Lahouar, Saher; Tartakovsky, Michael; Rosenthal, Alexander; Somaiyya, Sandeep; Lee, Soyoung; Goldfeder, Lisa C.; Cai, Ying; Via, Laura E.; Park, Seung-Kyu; Cho, Sang-Nae; Barry, Clifton E.

    2017-01-01

    Definitive clinical trials of new chemotherapies for tuberculosis (TB) treatment require following subjects until at least six months after treatment discontinuation to assess for durable cure, making these trials expensive and lengthy. Surrogate endpoints relating to treatment failure and relapse are currently limited to sputum microbiology, which has limited sensitivity and specificity. In this study we prospectively assessed radiographic changes using 2-deoxy-2-[18F]-fluoro-D-glucose (FDG) positron emission tomography/computed tomography (PET/CT) at two months and six months (CT only) in a cohort of subjects with multidrug-resistant (MDR) TB who were treated with second-line TB therapy for two years and then followed for an additional six months. CT scans were read semi-quantitatively by radiologists and computationally evaluated using custom software to provide volumetric assessment of TB-associated abnormalities. CT scans at six months assessed by readers were predictive of outcomes but not two months and changes in computed abnormal volumes were predictive at both time points. Quantitative changes in FDG uptake two months after starting treatment were associated with long-term outcomes. In this cohort, some radiologic markers were more sensitive than conventional sputum microbiology in distinguishing successful from unsuccessful treatment. These results support the potential of imaging biomarkers as possible surrogate endpoints in clinical trials of new TB drug regimens. Larger cohorts confirming these results are needed. PMID:25473034

  1. DSMC Simulation of High Mach Number Taylor-Couette Flow

    NASA Astrophysics Data System (ADS)

    Pradhan, Sahadev, , Dr.

    2017-01-01

    The main focus of this work is to characterise the Taylor-Couette flow of an ideal gas between two coaxial cylinders at Mach number Ma = (U_w /√{ kbT_w / m }) in the range 0.01 < Ma < 10, and Knudsen number Kn = (1 / (√{ 2 } πd2 n_d (r _ 2 - r _ 1))) in the range 0.001 number density of the gas molecules, m and d are the molecular mass and diameter, and kb is the Boltzmann constant. The cylindrical surfaces are specified as being diffusely reflecting with the thermal accommodation coefficient equal to one. In the present analysis of high Mach number compressible Taylor-Couette flow using DSMC method, wall slip in the temperature and the velocities are found to be significant. Slip occurs because the temperature/velocity of the molecules incident on the wall could be very different from that of the wall, even though the temperature/velocity of the reflected molecules is equal to that of the wall. Due to the high surface speed of the inner cylinder, significant heating of the gas is taking place. The gas temperature increases until the heat transfer to the surface equals the work done in moving the surface. The highest temperature is obtained near the moving surface of the inner cylinder at a radius of about (1.26 r_1).

  2. CT Image Contrast of High-Z Elements: Phantom Imaging Studies and Clinical Implications

    PubMed Central

    Colborn, Robert E.; Edic, Peter M.; Lambert, Jack W.; Torres, Andrew S.; Bonitatibus, Peter J.; Yeh, Benjamin M.

    2016-01-01

    Purpose To quantify the computed tomographic (CT) image contrast produced by potentially useful contrast material elements in clinically relevant imaging conditions. Materials and Methods Equal mass concentrations (grams of active element per milliliter of solution) of seven radiodense elements, including iodine, barium, gadolinium, tantalum, ytterbium, gold, and bismuth, were formulated as compounds in aqueous solutions. The compounds were chosen such that the active element dominated the x-ray attenuation of the solution. The solutions were imaged within a modified 32-cm CT dose index phantom at 80, 100, 120, and 140 kVp at CT. To simulate larger body sizes, 0.2-, 0.5-, and 1.0-mm-thick copper filters were applied. CT image contrast was measured and corrected for measured concentrations and presence of chlorine in some compounds. Results Each element tested provided higher image contrast than iodine at some tube potential levels. Over the range of tube potentials that are clinically practical for average-sized and larger adults—that is, 100 kVp and higher—barium, gadolinium, ytterbium, and tantalum provided consistently increased image contrast compared with iodine, respectively demonstrating 39%, 56%, 34%, and 24% increases at 100 kVp; 39%, 66%, 53%, and 46% increases at 120 kVp; and 40%, 72%, 65%, and 60% increases at 140 kVp, with no added x-ray filter. Conclusion The consistently high image contrast produced with 100–140 kVp by tantalum compared with bismuth and iodine at equal mass concentration suggests that tantalum could potentially be favorable for use as a clinical CT contrast agent. © RSNA, 2015 Online supplemental material is available for this article. PMID:26356064

  3. CT-guided high-dose-rate brachytherapy of unresectable hepatocellular carcinoma.

    PubMed

    Collettini, Federico; Schreiber, Nadja; Schnapauff, Dirk; Denecke, Timm; Wust, Peter; Schott, Eckart; Hamm, Bernd; Gebauer, Bernhard

    2015-05-01

    The purpose of the present study was to evaluate the clinical outcome of CT-guided high-dose-rate brachytherapy (CT-HDRBT) in patients with unresectable hepatocellular carcinoma (HCC). Over a 6-year period, 98 patients with 212 unresectable HCC underwent CT-HDRBT applying a (192)Ir source at our institution. Magnetic resonance imaging (MRI) follow-up was performed 6 weeks after the intervention and then every 3 months. The primary endpoint was local tumor control (LTC); secondary endpoints included progression-free survival (PFS) and overall survival (OS). Patients were available for MRI evaluation for a mean follow-up of 23.1 months (range 4-64 months; median 20 months). Mean tumor diameter was 5 cm (range 1.8-12 cm). Eighteen of 212 (8.5 %) tumors showed local progression after a mean LTC of 21.1 months. In all, 67 patients (68.4 %) experienced distant tumor progression. The mean PFS was 15.2 months. Forty-six patients died during the follow-up period. Median OS was 29.2 months. Actuarial 1-, 2-, and 3-year OS rates were 80, 62, and 46 %, respectively. CT-HDRBT is an effective therapy to attain local tumor control in patients with unresectable HCC. Prospective randomized studies comparing CT-HDRBT with the standard treatments like Radiofrequency ablation (RFA) and chemoembolization (TACE) are mandatory.

  4. 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.

  5. CT of multiple sclerosis: reassessment of delayed scanning with high doses of contrast material

    SciTech Connect

    Spiegel, S.M.; Vinuela, F.; Fox, A.J.; Pelz, D.M.

    1985-09-01

    A prospective study involving 87 patients was carried out to evaluate the necessity for a high dose of contrast material in addition to delayed computed tomographic (CT) scanning for optimal detection of the lesions of multiple sclerosis in the brain. In patients with either clinically definite multiple sclerosis or laboratory-supported definite multiple sclerosis, CT scans were obtained with a uniform protocol. Lesions consistent with multiple sclerosis were demonstrated on the second scan in 54 patients. In 36 of these 54 patients, the high-dose delayed scan added information. These results are quite similar to those of a previous study from this institution using different patients, in whom the second scan was obtained immediately after the bolus injection of contrast material containing 40 g of organically bound iodine. The lack of real difference in the results of the two studies indicate that the increased dose, not just the delay in scanning, is necessary for a proper study.

  6. Design of a high-resolution small-animal SPECT-CT system sharing a CdTe semiconductor detector

    NASA Astrophysics Data System (ADS)

    Ryu, Hyun-Ju; Lee, Young-Jin; Lee, Seung-Wan; Cho, Hyo-Min; Choi, Yu-Na; Kim, Hee-Joung

    2012-07-01

    A single photon emission computed tomography (SPECT) system with a co-registered X-y computed tomography (CT) system allows the convergence of functional information and morphologic information. The localization of radiopharmaceuticals on a SPECT can be enhanced by combining the SPECT with an anatomical modality, such as X-ray CT. Gamma-ray imaging for nuclear medicine devices and X-ray imaging systems for diagnostics has recently been developed based on semiconductor detectors, and semiconductor detector materials such as cadmium telluride (CdTe) or cadmium zinc telluride (CZT) are available for both X-ray and gamma-ray systems for small-animal imaging. CdTe or CZT detectors provide strong absorption and high detection efficiency of high energy X-ray and gamma-ray photons because of their large atomic numbers. In this study, a pinhole collimator SPECT system sharing a cadmium telluride (CdTe) detector with a CT was designed. The GEANT4 application for tomographic emission (GATE) v.6.1 was used for the simulation. The pinhole collimator was designed to obtain a high spatial resolution of the SPECT system. The acquisition time for each projection was 40 seconds, and 60 projections were obtained for tomographic image acquisition. The reconstruction was performed using ordered subset expectation maximization (OS-EM) algorithms. The sensitivity and the spatial resolution were measured on the GATE simulation to evaluate the system characteristics. The spatial resolution of the system calculated from the FWHM of Gaussian fitted PSF curve was 0.69 mm, and the sensitivity of the system was measured to be 0.354 cps/kBq by using a Tc-99m point source of 1 MBq for 800 seconds. A phantom study was performed to verify the design of the dual imaging modality system. The system will be built as designed, and it can be applied as a pre-clinical imaging system.

  7. Wall-bounded turbulence at high Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Vallikivi, Margit

    Measurements are reported that give new insight into the behavior of turbulent wall-bounded flows at high Reynolds number. Turbulent pipe and boundary layer flows are examined experimentally over a wide range of Reynolds numbers -- up to Retau=100,000 (Re D=6x106) in pipe flow, and up to Re tau=73,000 (ReD=235x103) in a flat plate zero pressure gradient boundary layer. A Nano-Scale Thermal Anemometry Probe (NSTAP) was developed for very high spatial and temporal resolution measurements. Sensors with wire lengths 30 and 60 mum were fabricated, tested and validated in known flows, and then used to obtain single-point measurements at high Reynolds numbers in pipe and boundary layers. The mean velocity data together with data from previous studies and extensive error analysis showed that the von Karman's constant in the log-law is kappa=0.40+/-0.02. It was shown that the streamwise Reynolds stress exhibits a logarithmic behavior in the inertial sublayer for Retau≥20,000, in both pipes and boundary layers. Variances as well as higher order even moments were compared for pipes and boundary layers and it was shown that all even moments have a logarithmic behavior in the inertial sublayer, suggesting a true scale separation. Streamwise turbulent spectra showed a clear k --5/3 region for up to two decades in wavenumber. No k--1 region was found to be present in any of the cases in the pipe or the boundary layer. The location of the outer spectral peak, associated with very large scale motions, was found to have only a weak dependence on Reynolds number. The loci of these peak occur at the same wall-normal distance where the streamwise stresses establish a logarithmic behavior and where the amplitude modulation coefficient has a zero value. This suggests that with Reynolds number increasing to infinity most of the energy is contained within a diminishing wall-layer in physical coordinates.

  8. Reynolds Number Effects at High Angles of Attack

    NASA Technical Reports Server (NTRS)

    Fisher, David F.; Cobleigh, Brent R.; Banks, Daniel W.; Hall, Robert M.; Wahls, Richard A.

    1998-01-01

    Lessons learned from comparisons between ground-based tests and flight measurements for the high-angle-of-attack programs on the F-18 High Alpha Research Vehicle (HARV), the X-29 forward-swept wing aircraft, and the X-31 enhanced fighter maneuverability aircraft are presented. On all three vehicles, Reynolds number effects were evident on the forebodies at high angles of attack. The correlation between flight and wind tunnel forebody pressure distributions for the F-18 HARV were improved by using twin longitudinal grit strips on the forebody of the wind-tunnel model. Pressure distributions obtained on the X-29 wind-tunnel model at flight Reynolds numbers showed excellent correlation with the flight data up to alpha = 50 deg. Above (alpha = 50 deg. the pressure distributions for both flight and wind tunnel became asymmetric and showed poorer agreement, possibly because of the different surface finish of the model and aircraft. The detrimental effect of a very sharp nose apex was demonstrated on the X-31 aircraft. Grit strips on the forebody of the X-31 reduced the randomness but increased the magnitude of the asymmetry. Nose strakes were required to reduce the forebody yawing moment asymmetries and the grit strips on the flight test noseboom improved the aircraft handling qualities.

  9. High Order Difference Method for Low Mach Number Aeroacoustics

    NASA Technical Reports Server (NTRS)

    Mueller, B.; Yee, H. C.; Mansour, Nagi (Technical Monitor)

    2001-01-01

    A high order finite difference method with improved accuracy and stability properties for computational aeroacoustics (CAA) at low Mach numbers is proposed. The Euler equations are split into a conservative and a symmetric non- conservative portion to allow the derivation of a generalized energy estimate. Since the symmetrization is based on entropy variables, that splitting of the flux derivatives is referred to as entropy splitting. Its discretization by high order central differences was found to need less numerical dissipation than conventional conservative schemes. Owing to the large disparity of acoustic and stagnation quantities in low Mach number aeroacoustics, the split Euler equations are formulated in perturbation form. The unknowns are the small changes of the conservative variables with respect to their large stagnation values. All nonlinearities and the conservation form of the conservative portion of the split flux derivatives can be retained, while cancellation errors are avoided with its discretization opposed to the conventional conservative form. The finite difference method is third-order accurate at the boundary and the conventional central sixth-order accurate stencil in the interior. The difference operator satisfies the summation by parts property analogous to the integration by parts in the continuous energy estimate. Thus, strict stability of the difference method follows automatically. Spurious high frequency oscillations are suppressed by a characteristic-based filter similar to but without limiter. The time derivative is approximated by a 4-stage low-storage second-order explicit Runge-Kutta method. The method has been applied to simulate vortex sound at low Mach numbers. We consider the Kirchhoff vortex, which is an elliptical patch of constant vorticity rotating with constant angular frequency in irrotational flow. The acoustic pressure generated by the Kirchhoff vortex is governed by the 2D Helmholtz equation, which can be solved

  10. High Order Difference Method for Low Mach Number Aeroacoustics

    NASA Technical Reports Server (NTRS)

    Mueller, B.; Yee, H. C.; Mansour, Nagi (Technical Monitor)

    2001-01-01

    A high order finite difference method with improved accuracy and stability properties for computational aeroacoustics (CAA) at low Mach numbers is proposed. The Euler equations are split into a conservative and a symmetric non- conservative portion to allow the derivation of a generalized energy estimate. Since the symmetrization is based on entropy variables, that splitting of the flux derivatives is referred to as entropy splitting. Its discretization by high order central differences was found to need less numerical dissipation than conventional conservative schemes. Owing to the large disparity of acoustic and stagnation quantities in low Mach number aeroacoustics, the split Euler equations are formulated in perturbation form. The unknowns are the small changes of the conservative variables with respect to their large stagnation values. All nonlinearities and the conservation form of the conservative portion of the split flux derivatives can be retained, while cancellation errors are avoided with its discretization opposed to the conventional conservative form. The finite difference method is third-order accurate at the boundary and the conventional central sixth-order accurate stencil in the interior. The difference operator satisfies the summation by parts property analogous to the integration by parts in the continuous energy estimate. Thus, strict stability of the difference method follows automatically. Spurious high frequency oscillations are suppressed by a characteristic-based filter similar to but without limiter. The time derivative is approximated by a 4-stage low-storage second-order explicit Runge-Kutta method. The method has been applied to simulate vortex sound at low Mach numbers. We consider the Kirchhoff vortex, which is an elliptical patch of constant vorticity rotating with constant angular frequency in irrotational flow. The acoustic pressure generated by the Kirchhoff vortex is governed by the 2D Helmholtz equation, which can be solved

  11. A moving frame algorithm for high Mach number hydrodynamics

    NASA Astrophysics Data System (ADS)

    Trac, Hy; Pen, Ue-Li

    2004-07-01

    We present a new approach to Eulerian computational fluid dynamics that is designed to work at high Mach numbers encountered in astrophysical hydrodynamic simulations. Standard Eulerian schemes that strictly conserve total energy suffer from the high Mach number problem and proposed solutions to additionally solve the entropy or thermal energy still have their limitations. In our approach, the Eulerian conservation equations are solved in an adaptive frame moving with the fluid where Mach numbers are minimized. The moving frame approach uses a velocity decomposition technique to define local kinetic variables while storing the bulk kinetic components in a smoothed background velocity field that is associated with the grid velocity. Gravitationally induced accelerations are added to the grid, thereby minimizing the spurious heating problem encountered in cold gas flows. Separately tracking local and bulk flow components allows thermodynamic variables to be accurately calculated in both subsonic and supersonic regions. A main feature of the algorithm, that is not possible in previous Eulerian implementations, is the ability to resolve shocks and prevent spurious heating where both the pre-shock and post-shock fluid are supersonic. The hybrid algorithm combines the high-resolution shock capturing ability of the second-order accurate Eulerian TVD scheme with a low-diffusion Lagrangian advection scheme. We have implemented a cosmological code where the hydrodynamic evolution of the baryons is captured using the moving frame algorithm while the gravitational evolution of the collisionless dark matter is tracked using a particle-mesh N-body algorithm. Hydrodynamic and cosmological tests are described and results presented. The current code is fast, memory-friendly, and parallelized for shared-memory machines.

  12. Axisymmetric bubble pinch-off at high Reynolds numbers.

    PubMed

    Gordillo, J M; Sevilla, A; Rodríguez-Rodríguez, J; Martínez-Bazán, C

    2005-11-04

    Analytical considerations and potential-flow numerical simulations of the pinch-off of bubbles at high Reynolds numbers reveal that the bubble minimum radius, rn, decreases as tau proportional to r2n sqrt[1lnr2n], where tau is the time to break up, when the local shape of the bubble near the singularity is symmetric. However, if the gas convective terms in the momentum equation become of the order of those of the liquid, the bubble shape is no longer symmetric and the evolution of the neck changes to a rn proportional to tau1/3 power law. These findings are verified experimentally.

  13. Computation of high Reynolds number internal/external flows

    NASA Technical Reports Server (NTRS)

    Cline, M. C.; Wilmoth, R. G.

    1981-01-01

    A general, user oriented computer program, called VNAP2, was developed to calculate high Reynolds number, internal/ external flows. The VNAP2 program solves the two dimensional, time dependent Navier-Stokes equations. The turbulence is modeled with either a mixing-length, a one transport equation, or a two transport equation model. Interior grid points are computed using the explicit MacCormack Scheme with special procedures to speed up the calculation in the fine grid. All boundary conditions are calculated using a reference plane characteristic scheme with the viscous terms treated as source terms. Several internal, external, and internal/external flow calculations are presented.

  14. Wave phenomena in a high Reynolds number compressible boundary layer

    NASA Technical Reports Server (NTRS)

    Bayliss, A.; Maestrello, L.; Parikh, P.; Turkel, E.

    1987-01-01

    The behavior of spatially unstable waves in a high Reynolds number compressible laminar boundary layer is investigated by solution of the laminar two-dimensional compressible Navier-Stokes equations (solved to fourth-order accuracy) over a flat plate with a fluctuating disturbance generated at the inflow. A significant nonlinear distortion is produced, in qualitative agreement with experimental data. It is shown that increasing compressibility can significantly stabilize the flow over a flat plate, and that the mechanism of phase cancellation is a viable mechanism for the control of growing disturbances.

  15. Computation of high Reynolds number internal/external flows

    NASA Technical Reports Server (NTRS)

    Cline, M. C.; Wilmoth, R. G.

    1981-01-01

    A general, user oriented computer program, called VNAF2, developed to calculate high Reynolds number internal/external flows is described. The program solves the two dimensional, time dependent Navier-Stokes equations. Turbulence is modeled with either a mixing length, a one transport equation, or a two transport equation model. Interior grid points are computed using the explicit MacCormack scheme with special procedures to speed up the calculation in the fine grid. All boundary conditions are calculated using a reference plane characteristic scheme with the viscous terms treated as source terms. Several internal, external, and internal/external flow calculations are presented.

  16. Anisotropic Structure of Rotating Homogeneous Turbulence at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Cambon, Claude; Mansour, Nagi N.; Squires, Kyle D.; Rai, Man Mohan (Technical Monitor)

    1995-01-01

    Large eddy simulation is used to investigate the development of anisotropies and the evolution towards a quasi two-dimensional state in rotating homogeneous turbulence at high Reynolds number. The present study demonstrates the existence of two transitions in the development of anisotropy. The first transition marks the onset of anisotropy and occurs when a macro-Rossby number (based on a longitudinal integral lengthscale) has decreased to near unity while the second transition occurs when a micro-Rossby number (defined in this work as the ratio of the rms fluctuating vorticity to background vorticity) has decreased to unity. The anisotropy marked by the first transition corresponds to a reduction in dimensionality while the second transition corresponds to a polarization of the flow, i.e., relative dominance of the velocity components in the plane normal to the rotation axis. Polarization is reflected by emergence of anisotropy measures based on the two-dimensional component of the turbulence. Investigation of the vorticity structure shows that the second transition is also characterized by an increasing tendency for alignment between the fluctuating vorticity vector and the background angular velocity vector with a preference for corrotative vorticity.

  17. Anisotropic Structure of Rotating Homogeneous Turbulence at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Cambon, Claude; Mansour, Nagi N.; Squires, Kyle D.; Rai, Man Mohan (Technical Monitor)

    1995-01-01

    Large eddy simulation is used to investigate the development of anisotropies and the evolution towards a quasi two-dimensional state in rotating homogeneous turbulence at high Reynolds number. The present study demonstrates the existence of two transitions in the development of anisotropy. The first transition marks the onset of anisotropy and occurs when a macro-Rossby number (based on a longitudinal integral lengthscale) has decreased to near unity while the second transition occurs when a micro-Rossby number (defined in this work as the ratio of the rms fluctuating vorticity to background vorticity) has decreased to unity. The anisotropy marked by the first transition corresponds to a reduction in dimensionality while the second transition corresponds to a polarization of the flow, i.e., relative dominance of the velocity components in the plane normal to the rotation axis. Polarization is reflected by emergence of anisotropy measures based on the two-dimensional component of the turbulence. Investigation of the vorticity structure shows that the second transition is also characterized by an increasing tendency for alignment between the fluctuating vorticity vector and the background angular velocity vector with a preference for corrotative vorticity.

  18. High Reynolds number pump facility for cavitation research

    NASA Astrophysics Data System (ADS)

    Farrell, K. J.; McBride, M. W.; Billet, M. L.

    1987-09-01

    A High Reynolds Number Pump Facility (HIREP) designed for cavitation studies in the bladetip/endwall region of an axial flow pump is described. The facility consists of a 1.07-m diameter pump state driven by a 1.22-m diameter downstream turbine. An incompressible Reynolds Number of 6,000,000 at the rotor tip is achievable. The two units rotate on a common shaft and operate in the 1.22-m diameter test section of the Garfield Thomas Water Tunnel of the Applied Research Laboratory at Penn State. The facility was designed to accommodate laser velocimeter (LV) measurements in the pump stage, radially traversing five-hole probes in every stage, and a number of transducers in the rotating frame of reference: steady and unsteady pressure transducers force and torque cells, and accelerometers. The latter capability is provided by a slip-ring unit and hollow blade passage ways for conductors from the instrumentation in rotor-tip region. An optical quality window for LV measurements and other windows and ports are available for visual observation and instrumentation access.

  19. Experiments on horizontal convection at high Rayleigh and Prandtl numbers

    NASA Astrophysics Data System (ADS)

    Passaggia, Pierre-Yves; Scotti, Alberto; White, Brian

    2016-11-01

    Horizontal convection is a flow driven by a differential buoyancy forcing across a horizontal surface. It has been considered as a simple model to study the influence of heating, cooling and fresh water fluxes at the ocean surface on the meridional overturning circulation. In order to investigate the flow properties and energetics of horizontal convection at high Prandtl numbers, the flow is driven by the diffusion of salt in water across membranes localized at the surface. The resulting experiments are examined for a Prandtl number Pr 500 and Rayleigh numbers up to Ra 1016 . Time resolved particle image velocimetry is performed together with with planar laser induced fluorescence. To quantify the salt concentration and therefore the density of the fluid, sodium bisulfate is added to the salt water to decrease its pH of and thereby reduce the emission rate of the fluorescein dye. Rhodamine WT, insensitive to pH variations, is also introduced to correct for the spatial nonuniformity of the intensity of the laser sheet, a technique also known as ratiometric PLIF (Coppeta & Rogers, 1998). The local turbulent energetics are finally investigated using the local approach to available potential energy of Scotti & White (2014). The authors acknowledge the support by the National Science Foundation Grant No OCE-1155558.

  20. Resistance of plates and pipes at high Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Schiller, L; Hermann, R

    1931-01-01

    It was learned that the law of resistance for high R values does not follow the simple powers, and that the powers, which can be obtained approximately for the velocity distribution, gradually change. Since, moreover, very important investigations have recently been made on the resistance of plates at very high R values, it seemed of interest to apply the above line of reasoning to the new general law of resistance. For this purpose, the resistance and velocity distribution along the plate must always be equal to the values of the pipe flow at the corresponding Reynolds number. We made two kinds of calculations, of which the one given here is the simpler and more practical and also agrees better with the experimental results.

  1. Vortex shedding from a hydrofoil at high Reynolds number

    NASA Astrophysics Data System (ADS)

    Bourgoyne, Dwayne A.; Ceccio, Steven L.; Dowling, David R.

    2005-05-01

    High Reynolds number (Re) wall-bounded turbulent flows occur in many hydro- and aerodynamic applications. However, the limited amount of high-Re experimental data has hampered the development and validation of scaling laws and modelling techniques applicable to such flows. This paper presents measurements of the turbulent flow near the trailing edge of a two-dimensional lifting surface at chord-based Reynolds numbers, Re_{C}, typical of heavy-lift aircraft wings and full-scale ship propellers. The experiments were conducted in the William B. Morgan Large Cavitation Channel at flow speeds from 0.50 to 18.3ms(-1) with a cambered hydrofoil having a 3.05m span and a 2.13m chord that generated 60 metric tons of lift at the highest flow speed, Re_{C}{≈}50{×}10(6) . Flow-field measurements concentrated on the foil's near wake and include results from trailing edges having terminating bevel angles of 44(°) and 56(°) . Although generic turbulent boundary layer and wake characteristics were found at any fixed Re_{C} in the trailing-edge region, the variable strength of near-wake vortex shedding caused the flow-field fluctuations to be Reynolds-number and trailing-edge-geometry dependent. In the current experiments, vortex-shedding strength peaked at Re_{C}{=}4{×}10(6) with the 56(°) bevel-angle trailing edge. A dimensionless scaling for this phenomenon constructed from the free-stream speed, the wake thickness, and an average suction-side shear-layer vorticity at the trailing edge collapses the vortex-shedding strength measurements for 1.4{×}10(6}{≤) Re_{C}{≤}50{×}10(6) from both trailing edges and from prior measurements on two-dimensional struts at Re_{C}{˜}2{×}10(6) with asymmetrical trailing edges.

  2. High-throughput multiple-mouse imaging with micro-PET/CT for whole-skeleton assessment.

    PubMed

    Yagi, Masashi; Arentsen, Luke; Shanley, Ryan M; Hui, Susanta K

    2014-11-01

    Recent studies have proven that skeleton-wide functional assessment is essential to comprehensively understand physiological aspects of the skeletal system. Therefore, in contrast to regional imaging studies utilizing a multiple-animal holder (mouse hotel), we attempted to develop and characterize a multiple-mouse imaging system with micro-PET/CT for high-throughput whole-skeleton assessment. Using items found in a laboratory, a simple mouse hotel that houses four mice linked with gas anesthesia was constructed. A mouse-simulating phantom was used to measure uniformity in a cross sectional area and flatness (Amax/Amin*100) along the axial, radial and tangential directions, where Amax and Amin are maximum and minimum activity concentration in the profile, respectively. Fourteen mice were used for single- or multiple-micro-PET/CT scans. NaF uptake was measured at eight skeletal sites (skull to tibia). Skeletal (18)F activities measured with mice in the mouse hotel were within 1.6 ± 4% (mean ± standard deviation) of those measured with mice in the single-mouse holder. Single-holder scanning yields slightly better uniformity and flatness over the hotel. Compared to use of the single-mouse holder, scanning with the mouse hotel reduced study time (by 65%), decreased the number of scans (four-fold), reduced cost, required less computer storage space (40%), and maximized (18)F usage. The mouse hotel allows high-throughput, quantitatively equivalent scanning compared to the single-mouse holder for micro-PET/CT imaging for whole-skeleton assessment of mice.

  3. High-throughput multiple-mouse imaging with micro-PET/CT for whole-skeleton assessment

    PubMed Central

    Yagi, Masashi; Arentsen, Luke; Shanley, Ryan M; Hui, Susanta K

    2014-01-01

    Recent studies have proven that skeleton-wide functional assessment is essential to comprehensively understand physiological aspects of the skeletal system. Therefore, in contrast to regional imaging studies utilizing a multiple-animal holder (mouse hotel), we attempted to develop and characterize a multiple-mouse imaging system with micro-PET/CT for high-throughput whole-skeleton assessment. Using items found in a laboratory, a simple mouse hotel that houses four mice linked with gas anesthesia was constructed. A mouse-simulating phantom was used to measure uniformity in a cross sectional area and flatness (Amax/Amin*100) along the axial, radial and tangential directions, where Amax and Amin are maximum and minimum activity concentration in the profile, respectively. Fourteen mice were used for single- or multiple-micro-PET/CT scans. NaF uptake was measured at eight skeletal sites (skull to tibia). Skeletal 18F activities measured with mice in the mouse hotel were within 1.6±4% (mean±standard deviation) of those measured with mice in the single-mouse holder. Single-holder scanning yields slightly better uniformity and flatness over the hotel. Compared to use of the single-mouse holder, scanning with the mouse hotel reduced study time (by 65%), decreased the number of scans (four-fold), reduced cost, required less computer storage space (40%), and maximized 18F usage. The mouse hotel allows high-throughput, quantitatively equivalent scanning compared to the single-mouse holder for micro-PET/CT imaging for whole-skeleton assessment of mice. PMID:24998335

  4. Precise 3D dimensional metrology using high-resolution x-ray computed tomography (μCT)

    NASA Astrophysics Data System (ADS)

    Brunke, Oliver; Santillan, Javier; Suppes, Alexander

    2010-09-01

    Over the past decade computed tomography (CT) with conventional x-ray sources has evolved from an imaging method in medicine to a well established technology for industrial applications in fields such as material science, light metals and plastics processing, microelectronics and geology. By using modern microfocus and nanofocus X-ray tubes, parts can be scanned with sub-micrometer resolutions. Currently, micro-CT is a technology increasingly used for metrology applications in the automotive industry. CT offers big advantages compared with conventional tactile or optical coordinate measuring machines (CMMs). This is of greater importance if complex parts with hidden or difficult accessible surfaces have to be measured. In these cases, CT offers the advantage of a high density of measurement points and a non-destructive and fast capturing of the sample's complete geometry. When using this growing technology the question arises how precise a μCT based CMM can measure as compared to conventional and established methods for coordinate measurements. For characterizing the metrological capabilities of a tactile or optical CMM, internationally standardized parameters like length measurement error and probing error are defined and used. To increase the acceptance of CT as a metrological method, our work seeks to clarify the definition and usage of parameters used in the field of metrology as these apply to CT. In this paper, an overview of the process chain in CT based metrology will be given and metrological characteristics will be described. For the potential user of CT as 3D metrology tool it is important to show the measurement accuracy and repeatability on realistic samples. Following a discussion of CT metrology techniques, two samples are discussed. The first compares a measured CT Data set to CAD data using CMM data as a standard for comparison of results. The second data second realistic data set will compare the results of applying both the CMM method of

  5. Ultra-high resolution flat-panel volume CT: fundamental principles, design architecture, and system characterization.

    PubMed

    Gupta, Rajiv; Grasruck, Michael; Suess, Christoph; Bartling, Soenke H; Schmidt, Bernhard; Stierstorfer, Karl; Popescu, Stefan; Brady, Tom; Flohr, Thomas

    2006-06-01

    Digital flat-panel-based volume CT (VCT) represents a unique design capable of ultra-high spatial resolution, direct volumetric imaging, and dynamic CT scanning. This innovation, when fully developed, has the promise of opening a unique window on human anatomy and physiology. For example, the volumetric coverage offered by this technology enables us to observe the perfusion of an entire organ, such as the brain, liver, or kidney, tomographically (e.g., after a transplant or ischemic event). By virtue of its higher resolution, one can directly visualize the trabecular structure of bone. This paper describes the basic design architecture of VCT. Three key technical challenges, viz., scatter correction, dynamic range extension, and temporal resolution improvement, must be addressed for successful implementation of a VCT scanner. How these issues are solved in a VCT prototype and the modifications necessary to enable ultra-high resolution volumetric scanning are described. The fundamental principles of scatter correction and dose reduction are illustrated with the help of an actual prototype. The image quality metrics of this prototype are characterized and compared with a multi-detector CT (MDCT).

  6. High-resolution CT findings of primary lung cancer with cavitation: a comparison between adenocarcinoma and squamous cell carcinoma.

    PubMed

    Kunihiro, Y; Kobayashi, T; Tanaka, N; Matsumoto, T; Okada, M; Kamiya, M; Ueda, K; Kawano, H; Matsunaga, N

    2016-11-01

    To evaluate the high-resolution computed tomography (CT) findings of primary lung cancer with cavitation and compare the findings in adenocarcinoma and squamous cell carcinoma. The high-resolution CT findings of tumours with cavitation were retrospectively evaluated in 60 patients. Forty-seven of the lesions were diagnosed as adenocarcinomas; 13 were diagnosed as squamous cell carcinomas. The diameters of the tumour and cavity, the maximum thickness of the cavity wall, shape of the cavity wall, the number of cavities, and the presence of ground-glass opacity, bronchial obstruction, intratumoural bronchiectasis, emphysema, and honeycombing were evaluated. The mechanisms of cavity formation were examined according to the pathological features. The maximum thickness of the cavity wall was significantly greater in squamous cell carcinomas than in adenocarcinomas (p=0.002). Ground-glass opacity and intratumoural bronchiectasis were significantly more common in adenocarcinomas than in squamous cell carcinomas (p<0.001 and p=0.040, respectively). Regarding the pathological findings, intratumoural bronchiectasis with or without alveolar wall destruction contributed to a significant difference between adenocarcinoma and squamous cell carcinoma (p<0.001; odds ratio [OR], 20.35; 95% confidence interval [CI], 3.87-107.10). The cavity wall tends to be thicker in squamous cell carcinomas than in adenocarcinomas. The presence of ground-glass opacity and intratumoural bronchiectasis is strongly suggestive of adenocarcinoma. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

  7. Development of a high-speed CT imaging system using EMCCD camera

    NASA Astrophysics Data System (ADS)

    Thacker, Samta C.; Yang, Kai; Packard, Nathan; Gaysinskiy, Valeriy; Burkett, George; Miller, Stuart; Boone, John M.; Nagarkar, Vivek

    2009-02-01

    The limitations of current CCD-based microCT X-ray imaging systems arise from two important factors. First, readout speeds are curtailed in order to minimize system read noise, which increases significantly with increasing readout rates. Second, the afterglow associated with commercial scintillator films can introduce image lag, leading to substantial artifacts in reconstructed images, especially when the detector is operated at several hundred frames/second (fps). For high speed imaging systems, high-speed readout electronics and fast scintillator films are required. This paper presents an approach to developing a high-speed CT detector based on a novel, back-thinned electron-multiplying CCD (EMCCD) coupled to various bright, high resolution, low afterglow films. The EMCCD camera, when operated in its binned mode, is capable of acquiring data at up to 300 fps with reduced imaging area. CsI:Tl,Eu and ZnSe:Te films, recently fabricated at RMD, apart from being bright, showed very good afterglow properties, favorable for high-speed imaging. Since ZnSe:Te films were brighter than CsI:Tl,Eu films, for preliminary experiments a ZnSe:Te film was coupled to an EMCCD camera at UC Davis Medical Center. A high-throughput tungsten anode X-ray generator was used, as the X-ray fluence from a mini- or micro-focus source would be insufficient to achieve high-speed imaging. A euthanized mouse held in a glass tube was rotated 360 degrees in less than 3 seconds, while radiographic images were recorded at various readout rates (up to 300 fps); images were reconstructed using a conventional Feldkamp cone-beam reconstruction algorithm. We have found that this system allows volumetric CT imaging of small animals in approximately two seconds at ~110 to 190 μm resolution, compared to several minutes at 160 μm resolution needed for the best current systems.

  8. Radiology reports for incidental thyroid nodules on CT and MRI: high variability across subspecialties.

    PubMed

    Grady, A T; Sosa, J A; Tanpitukpongse, T P; Choudhury, K R; Gupta, R T; Hoang, J K

    2015-02-01

    practices for incidental thyroid nodules detected on CT and MR imaging are predominantly influenced by nodule size and the radiologist's subspecialty. Reporting was highly variable for nodules measuring 10-19 mm; this finding can be partially attributed to different reporting styles among radiology subspecialty divisions. The variability demonstrated in this study further underscores the need to develop CT and MR imaging practice guidelines with the goal of standardizing reporting of incidental thyroid nodules and thereby potentially improving the consistency and quality of patient care. © 2015 by American Journal of Neuroradiology.

  9. Magnetic Reconnection in high-Lundquist-number plasmas

    NASA Astrophysics Data System (ADS)

    Loureiro, Nuno

    2011-10-01

    Magnetic reconnection is the driver of explosive phenomena in both laboratory and astrophysical contexts. Sawtooth crashes in fusion experiments and solar flares are prominent examples of fascinating events where reconnection plays a key role. Over the past few years, the basic understanding of this fundamental process has undergone profound changes. The validity of the most basic, and widely accepted, reconnection paradigm - the famous Sweet-Parker (SP) model, which predicts that, in MHD, reconnection is extremely slow, its rate scaling as S - 1 / 2, where S is the Lundquist number of the system - has been called into question as it was analytically demonstrated that, for S >> 1 , SP-like current sheets are violently unstable to the formation of a large number of secondary islands, or plasmoids. Subsequent numerical work has confirmed the validity of the linear theory, and shown that plasmoids quickly grow to become wider than the thickness of the original SP current sheet, thus effectively changing the underlying reconnection geometry. Ensuing numerical work has revealed that the process of plasmoid formation, coalescence and ejection from the sheet drastically modifies the steady state picture assumed by Sweet and Parker, and leads to the unexpected result that MHD reconnection is actually fast (i.e., independent of S). In this talk, we review these recent developments and present a novel theoretical model of MHD reconnection in high Lundquist number plasmas. The results of a detailed numerical study are presented, validating the main predictions of this theory, which we thus suggest as valid replacement of the SP paradigm. In particular, we discuss the formation of so-called monster plasmoids (whose widths are 10% of the system size, and thus not only detectable but also potentially disruptive), predicted by the theory and observed in our simulations.

  10. High Reynolds number magnetohydrodynamic turbulence using a Lagrangian model.

    PubMed

    Graham, J Pietarila; Mininni, P D; Pouquet, A

    2011-07-01

    With the help of a model of magnetohydrodynamic (MHD) turbulence tested previously, we explore high Reynolds number regimes up to equivalent resolutions of 6000(3) grid points in the absence of forcing and with no imposed uniform magnetic field. For the given initial condition chosen here, with equal kinetic and magnetic energy, the flow ends up being dominated by the magnetic field, and the dynamics leads to an isotropic Iroshnikov-Kraichnan energy spectrum. However, the locally anisotropic magnetic field fluctuations perpendicular to the local mean field follow a Kolmogorov law. We find that the ratio of the eddy turnover time to the Alfvén time increases with wave number, contrary to the so-called critical balance hypothesis. Residual energy and helicity spectra are also considered; the role played by the conservation of magnetic helicity is studied, and scaling laws are found for the magnetic helicity and residual helicity spectra. We put these results in the context of the dynamics of a globally isotropic MHD flow that is locally anisotropic because of the influence of the strong large-scale magnetic field, leading to a partial equilibration between kinetic and magnetic modes for the energy and the helicity.

  11. Two phosphonium ionic liquids with high Li(+) transport number.

    PubMed

    Martins, Vitor L; Sanchez-Ramirez, Nédher; Ribeiro, Mauro C C; Torresi, Roberto M

    2015-09-21

    This work presents the physicochemical characterization of two ionic liquids (ILs) with small phosphonium cations, triethylpenthylphosphonium bis(trifluoromethanesulfonyl)imide ([P2225][Tf2N]) and (2-methoxyethyl)trimethylphosphonium bis(trifluoromethanesulfonyl)imide ([P222(201)][Tf2N]), and their mixtures with Li(+). Properties such as the electrochemical window, density, viscosity and ionic conductivity are presented. The diffusion coefficient was obtained using two different techniques, PGSE-NMR and Li electrodeposition with microelectrodes. In addition, the Li(+) transport number was calculated using the PGSE-NMR technique and an electrochemical approach. The use of these three techniques showed that the PGSE-NMR technique underestimates the diffusion coefficient for charged species. The Li(+) transport number was found to be as high as 0.54. Raman spectroscopy and molecular dynamics simulations were used to evaluate the short-range structure of the liquids. These experiments suggested that the interaction between the Li(+) and the Tf2N(-) anion is similar to that seen with other ILs containing the same anion. However, the MD simulations also showed that the Li(+) ions interact differently with the cation containing an alkyl ether chain. The results found in this work suggest that these Li(+) mixtures have promising potential to be applied as electrolytes in batteries.

  12. Experimental investigations of He II flows at high Reynolds number

    NASA Technical Reports Server (NTRS)

    Van Sciver, Steve W.

    1991-01-01

    Fluid dynamics studies of He II at high Reynolds number (Re(d) greater than 10 exp 6) reveal characteristics which are best interpreted in terms of classical scaling relationships. In particular, the smooth tube friction factor is seen to correlate with the Von Karman-Nikuradse formulation. Also, the performance of a centrifugal pump is unchanged whether being used with He I or He II. These effects are expected to result provided the He II possesses a viscous sublayer and that the drag is determined by laminar flow within this layer. On the other hand, heat transfer in He II is substantially different from that of He I because of the unique internal convection mechanism present in this quantum fluid. These experiments are performed in the University of Wisconsin liquid helium flow facility which has unique capabilities of He II temperature, pressure and flow.

  13. A High Altitude-Low Reynolds Number Aerodynamic Flight Experiment

    NASA Technical Reports Server (NTRS)

    Greer, Don; Krake, Keith; Hamory, Phil; Drela, Mark; Lee, Seunghee (Technical Monitor)

    1999-01-01

    A sailplane is currently being developed at NASA's Dryden Flight Research Center to support a high altitude flight experiment. The purpose of the experiment is to measure the performance characteristics of an airfoil at altitudes between 100,000 and 70,000 feet at Mach numbers between 0.65 and 0.5. The airfoil lift and drag are measured from pilot and static pressures. The location of the separation bubble and vortex shedding are measured from a hot film strip. The details of the flight experiment are presented. A comparison of several estimates of the airfoil performance is also presented. The airfoil, APEX-16, was designed by Drela (MIT) with his MSES code. A two dimensional Navier-Stokes analysis has been performed by Tatineni and Zhong (UCLA) and another at the Dryden Flight Research Center. The role these analysis served to define the experiment is discussed.

  14. Ultra-high resolution optical CT dosimetry for the visualisation of synchrotron microbeam therapy doses

    NASA Astrophysics Data System (ADS)

    Doran, S. J.; Rahman, A. T. Abdul; Bräuer-Krisch, E.; Brochard, T.; Adamovics, J.

    2013-06-01

    Optical CT is a method that can potentially provide both accurate dosimetry at high spatial resolution and 3-D visualisation over a large field-of-view in a single dataset. The major factors limiting spatial resolution in previous studies are analysed here and it is shown that improvements in equipment specification can overcome many of these. The need for ultra-high spatial resolution in the verification of microbeam radiation therapy verification is demonstrated and example images of a PRESAGE® sample are presented.

  15. High-resolution three-dimensional visualization of the rat spinal cord microvasculature by synchrotron radiation micro-CT

    SciTech Connect

    Hu, Jianzhong; Cao, Yong; Wu, Tianding; Li, Dongzhe; Lu, Hongbin

    2014-10-15

    Purpose: Understanding the three-dimensional (3D) morphology of the spinal cord microvasculature has been limited by the lack of an effective high-resolution imaging technique. In this study, synchrotron radiation microcomputed tomography (SRµCT), a novel imaging technique based on absorption imaging, was evaluated with regard to the detection of the 3D morphology of the rat spinal cord microvasculature. Methods: Ten Sprague-Dawley rats were used in this ex vivo study. After contrast agent perfusion, their spinal cords were isolated and scanned using conventional x-rays, conventional micro-CT (CµCT), and SRµCT. Results: Based on contrast agent perfusion, the microvasculature of the rat spinal cord was clearly visualized for the first time ex vivo in 3D by means of SRµCT scanning. Compared to conventional imaging techniques, SRµCT achieved higher resolution 3D vascular imaging, with the smallest vessel that could be distinguished approximately 7.4 μm in diameter. Additionally, a 3D pseudocolored image of the spinal cord microvasculature was generated in a single session of SRµCT imaging, which was conducive to detailed observation of the vessel morphology. Conclusions: The results of this study indicated that SRµCT scanning could provide higher resolution images of the vascular network of the spinal cord. This modality also has the potential to serve as a powerful imaging tool for the investigation of morphology changes in the 3D angioarchitecture of the neurovasculature in preclinical research.

  16. The SPECT/CT Evaluation of Compartmental Changes after Open Wedge High Tibial Osteotomy

    PubMed Central

    Kim, Tae Won; Kim, Byung Kag; Kim, Dong Whan; Sim, Jae Ang; Lee, Beom Koo; Lee, Yong Seuk

    2016-01-01

    Purpose The purpose of this study was to evaluate compartmental changes using combined single-photon emission computerized tomography and conventional computerized tomography (SPECT/CT) after open wedge high tibial osteotomy (OWHTO) for providing clinical guidance for proper correction. Materials and Methods Analysis was performed using SPECT/CT from around 1 year after surgery on 22 patients who underwent OWHTO. Postoperative mechanical axis was measured and classified into 3 groups: group I (varus), group II (0°–3° valgus), and group III (>3° valgus). Patella location was evaluated using Blackburne-Peel (BP) ratio. On SPECT/CT, the knee joint was divided into medial, lateral, and patellofemoral compartments and the brighter signal was marked as a positive signal. Results Increased signal activity in the medial compartment was observed in 12 cases. No correlation was observed between postoperative mechanical axis and medial signal increase. Lateral increased signal activity was observed in 3 cases, and as valgus degree increased, lateral compartment’s signal activity increased. Increased signal activity of the patellofemoral joint was observed in 7 cases, and significant correlation was observed between changes in BP ratio and increased signal activity. Conclusions For the treatment of medial osteoarthritis, OWHTO requires overcorrection that does not exceed 3 valgus. In addition, the possibility of a patellofemoral joint problem after OWHTO should be kept in mind. PMID:27894172

  17. Spectral deblurring: an algorithm for high-resolution, hybrid spectral CT

    NASA Astrophysics Data System (ADS)

    Clark, D. P.; Badea, C. T.

    2015-03-01

    We are developing a hybrid, dual-source micro-CT system based on the combined use of an energy integrating (EID) x-ray detector and a photon counting x-ray detector (PCXD). Due to their superior spectral resolving power, PCXDs have the potential to reduce radiation dose and to enable functional and molecular imaging with CT. In most current PCXDs, however, spatial resolution and field of view are limited by hardware development and charge sharing effects. To address these problems, we propose spectral deblurring—a relatively simple algorithm for increasing the spatial resolution of hybrid, spectral CT data. At the heart of the algorithm is the assumption that the underlying CT data is piecewise constant, enabling robust recovery in the presence of noise and spatial blur by enforcing gradient sparsity. After describing the proposed algorithm, we summarize simulation experiments which assess the trade-offs between spatial resolution, contrast, and material decomposition accuracy given realistic levels of noise. When the spatial resolution between imaging chains has a ratio of 5:1, spectral deblurring results in a 52% increase in the material decomposition accuracy of iodine, gadolinium, barium, and water vs. linear interpolation. For a ratio of 10:1, a realistic representation of our hybrid imaging system, a 52% improvement was also seen. Overall, we conclude that the performance breaks down around high frequency and low contrast structures. Following the simulation experiments, we apply the algorithm to ex vivo data acquired in a mouse injected with an iodinated contrast agent and surrounded by vials of iodine, gadolinium, barium, and water.

  18. Asbestosis and other pulmonary fibrosis in asbestos-exposed workers: high-resolution CT features with pathological correlations.

    PubMed

    Arakawa, Hiroaki; Kishimoto, Takumi; Ashizawa, Kazuto; Kato, Katsuya; Okamoto, Kenzo; Honma, Koichi; Hayashi, Seiji; Akira, Masanori

    2016-05-01

    The purpose was to identify distinguishing CT features of pathologically diagnosed asbestosis, and correlate diagnostic confidence with asbestos body burden. Thirty-three workers (mean age at CT: 73 years) with clinical diagnoses of asbestosis, who were autopsied (n = 30) or underwent lobectomy (n = 3), were collected. Two radiologists independently scored high-resolution CT images for various CT findings and the likelihood of asbestosis was scored. Two pathologists reviewed the pathology specimens and scored the confidence of their diagnoses. Asbestos body count was correlated with CT and pathology scores. Pathologically, 15 cases were diagnosed as asbestosis and 18 cases with various lung fibroses other than asbestosis. On CT, only the score of the subpleural curvilinear lines was significantly higher in asbestosis (p = 0.03). Accuracy of CT diagnosis of asbestosis with a high confidence ranged from 0.73 to 0.79. Asbestos body count positively correlated with CT likelihood of asbestosis (r = 0.503, p = 0.003), and with the confidence level of pathological diagnosis (r = 0.637, p < 0.001). Subpleural curvilinear lines were the only clue for the diagnosis of asbestosis. However, this was complicated by other lung fibrosis, especially at low asbestos body burden. • Various patterns of pulmonary fibrosis occurred in asbestos-exposed workers. • The fibre burden in lungs paralleled confident CT diagnosis of asbestosis. • The fibre burden in lungs paralleled confident pathological diagnosis of asbestosis. • Subpleural curvilinear lines were an important CT finding favouring asbestosis.

  19. Turbomachinery for Low-to-High Mach Number Flight

    NASA Technical Reports Server (NTRS)

    Tan, Choon S.; Shah, Parthiv N.

    2004-01-01

    The thrust capability of turbojet cycles is reduced at high flight Mach number (3+) by the increase in inlet stagnation temperature. The 'hot section' temperature limit imposed by materials technology sets the maximum heat addition and, hence, sets the maximum flight Mach number of the operating envelope. Compressor pre-cooling, either via a heat exchanger or mass-injection, has been suggested as a means to reduce compressor inlet temperature and increase mass flow capability, thereby increasing thrust. To date, however, no research has looked at compressor cooling (i.e., using a compressor both to perform work on the gas path air and extract heat from it simultaneously). We wish to assess the feasibility of this novel concept for use in low-to-high Mach number flight. The results to-date show that an axial compressor with cooling: (1) relieves choking in rear stages (hence opening up operability), (2) yields higher-pressure ratio and (3) yields higher efficiency for a given corrected speed and mass flow. The performance benefit is driven: (i) at the blade passage level, by a decrease in the total pressure reduction coefficient and an increase in the flow turning; and (ii) by the reduction in temperature that results in less work required for a given pressure ratio. The latter is a thermodynamic effect. As an example, calculations were performed for an eight-stage compressor with an adiabatic design pressure ratio of 5. By defining non-dimensional cooling as the percentage of compressor inlet stagnation enthalpy removed by a heat sink, the model shows that a non-dimensional cooling of percent in each blade row of the first two stages can increase the compressor pressure ratio by as much as 10-20 percent. Maximum corrected mass flow at a given corrected speed may increase by as much as 5 percent. In addition, efficiency may increase by as much as 5 points. A framework for characterizing and generating the performance map for a cooled compressor has been developed

  20. Unseen Progenitors of Luminous High-z Quasars in the R h  = ct Universe

    NASA Astrophysics Data System (ADS)

    Fatuzzo, Marco; Melia, Fulvio

    2017-09-01

    Quasars at high redshift provide direct information on the mass growth of supermassive black holes (SMBHs) and, in turn, yield important clues about how the universe evolved since the first (Pop III) stars started forming. Yet even basic questions regarding the seeds of these objects and their growth mechanism remain unanswered. The anticipated launch of eROSITA and ATHENA is expected to facilitate observations of high-redshift quasars needed to resolve these issues. In this paper, we compare accretion-based SMBH growth in the concordance ΛCDM model with that in the alternative Friedmann–Robertson–Walker cosmology known as the R h = ct universe. Previous work has shown that the timeline predicted by the latter can account for the origin and growth of the ≳109 M ⊙ highest redshift quasars better than that of the standard model. Here, we significantly advance this comparison by determining the soft X-ray flux that would be observed for Eddington-limited accretion growth as a function of redshift in both cosmologies. Our results indicate that a clear difference emerges between the two in terms of the number of detectable quasars at redshift z ≳ 7, raising the expectation that the next decade will provide the observational data needed to discriminate between these two models based on the number of detected high-redshift quasar progenitors. For example, while the upcoming ATHENA mission is expected to detect ∼0.16 (i.e., essentially zero) quasars at z ∼ 7 in R h = ct, it should detect ∼160 in ΛCDM—a quantitatively compelling difference.

  1. Suppression of high-density artifacts in x-ray CT images using temporal digital subtraction with application to cryotherapy

    NASA Astrophysics Data System (ADS)

    Baissalov, Roustem; Sandison, George A.; Donnelly, Bryan J.; Saliken, John C.; Muldrew, Ken; Rewcastle, John C.

    2000-06-01

    Image guidance of cryotherapy is usually performed using ultrasound or x-ray CT. Despite the ability of CT to display the full 3D structure of the iceball, including frozen and unfrozen regions, the quality of the images is compromised by the presence of high density streak artifacts. To suppress these artifacts we applied Temporal Digital Subtraction (TDS). This TDS method has the added advantage of improving the gray scale contrast between frozen and unfrozen tissue in the CT images. Two sets of CT images were taken of a phantom material, cryoprobes and a urethral warmer (UW) before and during the cryoprobe freeze cycle. The high density artifacts persisted in both image sets. TDS was performed on these two image sets using the corresponding mask image of unfrozen material and the same geometrical configuration of the cryoprobes and the UW. The resultant difference image had a significantly reduced content of the artifacts. This TDS can be used in x-ray CT assisted cryotherapy to significantly suppress or eliminate high density x-ray CT streak artifacts by digitally processing x-ray CT images. Applying TDS in cryotherapy will facilitate estimation of the amount and location of all frozen and unfrozen regions, potentially making cryotherapy safer and less operator dependent.

  2. High amplitude surging and plunging motions at low Reynolds number

    NASA Astrophysics Data System (ADS)

    Choi, Jeesoon; Colonius, Tim; Williams, David; Caltech Collaboration; IIT Collaboration

    2014-11-01

    Aerodynamic forces and flow structures associated with high amplitude oscillations of an airfoil in the streamwise (surging) and transverse (plunging) direction are investigated in two-dimensional simulations at low Reynolds number (Re = 102 ~ 103). While the unsteady aerodynamic forces for low-amplitude motions were mainly affected by the leading-edge vortex (LEV) acting in- or out-of phase with the quasi-component of velocity, large-amplitude motions involve complex vortex interactions of LEVs and trailing-edge vortices (TEVs) with the moving body. For high-amplitude surging, the TEV, instead of the LEV, induces low-pressure regions above the airfoil during the retreating portion of the cycle near the reduced frequency, k = 0.5, and enhances the time-average forces. The time required for the LEV to convect along the chord becomes an intrinsic time scale, and for plunging motions, there is a sudden change of flow structure when the period of the motion is not long enough for the LEV to convect through the whole chord.

  3. Extension of sonic anemometry to high subsonic Mach number flows

    NASA Astrophysics Data System (ADS)

    Otero, R.; Lowe, K. T.; Ng, W. F.

    2017-03-01

    In the literature, the application of sonic anemometry has been limited to low subsonic Mach number, near-incompressible flow conditions. To the best of the authors’ knowledge, this paper represents the first time a sonic anemometry approach has been used to characterize flow velocity beyond Mach 0.3. Using a high speed jet, flow velocity was measured using a modified sonic anemometry technique in flow conditions up to Mach 0.83. A numerical study was conducted to identify the effects of microphone placement on the accuracy of the measured velocity. Based on estimated error strictly due to uncertainty in time-of-acoustic flight, a random error of +/- 4 m s‑1 was identified for the configuration used in this experiment. Comparison with measurements from a Pitot probe indicated a velocity RMS error of +/- 9 m s‑1. The discrepancy in error is attributed to a systematic error which may be calibrated out in future work. Overall, the experimental results from this preliminary study support the use of acoustics for high subsonic flow characterization.

  4. Onset of turbulence in accelerated high-Reynolds-number flow.

    PubMed

    Zhou, Ye; Robey, Harry F; Buckingham, Alfred C

    2003-05-01

    A new criterion, flow drive time, is identified here as a necessary condition for transition to turbulence in accelerated, unsteady flows. Compressible, high-Reynolds-number flows initiated, for example, in shock tubes, supersonic wind tunnels with practical limitations on dimensions or reservoir capacity, and high energy density pulsed laser target vaporization experimental facilities may not provide flow duration adequate for turbulence development. In addition, for critical periods of the overall flow development, the driving background flow is often unsteady in the experiments as well as in the physical flow situations they are designed to mimic. In these situations transition to fully developed turbulence may not be realized despite achievement of flow Reynolds numbers associated with or exceeding stationary flow transitional criteria. Basically our transitional criterion and prediction procedure extends to accelerated, unsteady background flow situations the remarkably universal mixing transition criterion proposed by Dimotakis [P. E. Dimotakis, J. Fluid Mech. 409, 69 (2000)] for stationary flows. This provides a basis for the requisite space and time scaling. The emphasis here is placed on variable density flow instabilities initiated by constant acceleration Rayleigh-Taylor instability (RTI) or impulsive (shock) acceleration Richtmyer-Meshkov instability (RMI) or combinations of both. The significant influences of compressibility on these developing transitional flows are discussed with their implications on the procedural model development. A fresh perspective for predictive modeling and design of experiments for the instability growth and turbulent mixing transitional interval is provided using an analogy between the well-established buoyancy-drag model with applications of a hierarchy of single point turbulent transport closure models. Experimental comparisons with the procedural results are presented where use is made of three distinctly different types

  5. Predicting the Mortality Benefit of CT Screening for Second Lung Cancer in a High-Risk Population

    PubMed Central

    Kinsey, C. Matthew; Hamlington, Katharine L.; O’Toole, Jacqueline; Stapleton, Renee; Bates, Jason H. T.

    2016-01-01

    Patients who survive an index lung cancer (ILC) after surgical resection continue to be at significant risk for a metachronous lung cancer (MLC). Indeed, this risk is much higher than the risk of developing an ILC in heavy smokers. There is currently little evidence upon which to base guidelines for screening at-risk patients for MLC, and the risk-reward tradeoffs for screening this patient population are unknown. The goal of this investigation was to estimate the maximum mortality benefit of CT screening for MLC. We developed a computational model to estimate the maximum rates of CT detection of MLC and surgical resection to be expected in a given population as a function of time after resection of an ILC. Applying the model to a hypothetical high-risk population suggests that screening for MLC within 5 years after resection of an ILC may identify only a very small number of treatable cancers. The risk of death from a potentially resectable MLC increases dramatically past this point, however, suggesting that screening after 5 years is imperative. The model also predicts a substantial detection gap for MLC that demonstrates the benefit to be gained as more sensitive screening methods are developed. PMID:27806080

  6. High temporal resolution cardiac cone-beam CT using a slowly rotating C-arm gantry

    NASA Astrophysics Data System (ADS)

    Chen, Guang-Hong; Tang, Jie; Nett, Brian; Leng, Shuai; Zambelli, Joseph; Qi, Zhihua; Bevins, Nick; Reeder, Scott; Rowley, Howard

    2009-02-01

    Purpose: To achieve three dimensional isotropic dynamic cardiac CT imaging with high temporal resolution for evaluation of cardiac function with a slowly rotating C-arm system. Method and Materials: A recently introduced extension to compressed sensing, viz. Prior Image Constrained Compressed Sensing (PICCS), in which a prior image is used as a constraint in the reconstruction has enabled this application. An in-vivo animal experiment (e.g. a beagle model) was conducted using an interventional C-arm system. The imaging protocol was as follows: contrast was injected, the contrast equilibrated, breathing was suspended for ~14 seconds during which time 420 equally spaced projections were acquired. This data set was used to reconstruct a fully sampled blurred image volume using the conventional FDK algorithm (e.g. the prior image). Then the data set was retrospectively gated into 19 phases according to the recorded ECG signal (heart rate ~ 95bpm) and images were reconstructed with the PICCS algorithm. Results: Cardiac MR was used as the gold standard due to its high temporal resolution. The same short-axis slice was selected from the PICCS-CT data set and the MR data set. Manual contouring on the peak systolic and peak diastolic frames was performed to assess the ejection fraction contribution from this single plane. The calculated ejection fractions with PICCS-CT agreed well with the MR results. Conclusion: We have demonstrated the ability to use a slowly rotating interventional C-arm system in order to make measurements of cardiac function. The new technique provides high isotropic spatial resolution (~0.5 mm) along with high temporal resolution (~ 33 ms). The evaluation of cardiac function demonstrated a great agreement with single slice cardiac MR.

  7. Lumley decomposition of turbulent boundary layer at high Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Tutkun, Murat; George, William K.

    2017-02-01

    The decomposition proposed by Lumley in 1966 is applied to a high Reynolds number turbulent boundary layer. The experimental database was created by a hot-wire rake of 143 probes in the Laboratoire de Mécanique de Lille wind tunnel. The Reynolds numbers based on momentum thickness (Reθ) are 9800 and 19 100. Three-dimensional decomposition is performed, namely, proper orthogonal decomposition (POD) in the inhomogeneous and bounded wall-normal direction, Fourier decomposition in the homogeneous spanwise direction, and Fourier decomposition in time. The first POD modes in both cases carry nearly 50% of turbulence kinetic energy when the energy is integrated over Fourier dimensions. The eigenspectra always peak near zero frequency and most of the large scale, energy carrying features are found at the low end of the spectra. The spanwise Fourier mode which has the largest amount of energy is the first spanwise mode and its symmetrical pair. Pre-multiplied eigenspectra have only one distinct peak and it matches the secondary peak observed in the log-layer of pre-multiplied velocity spectra. Energy carrying modes obtained from the POD scale with outer scaling parameters. Full or partial reconstruction of turbulent velocity signal based only on energetic modes or non-energetic modes revealed the behaviour of urms in distinct regions across the boundary layer. When urms is based on energetic reconstruction, there exists (a) an exponential decay from near wall to log-layer, (b) a constant layer through the log-layer, and (c) another exponential decay in the outer region. The non-energetic reconstruction reveals that urms has (a) an exponential decay from the near-wall to the end of log-layer and (b) a constant layer in the outer region. Scaling of urms using the outer parameters is best when both energetic and non-energetic profiles are combined.

  8. Numerical study of high frequency oscillatory air flow and convective mixing in a CT-based human airway model

    PubMed Central

    Choi, Jiwoong; Xia, Guohua; Tawhai, Merryn H.; Hoffman, Eric A.; Lin, Ching-Long

    2011-01-01

    High frequency oscillatory ventilation (HFOV) is considered an efficient and safe respiratory technique to ventilate neonates and patients with acute respiratory distress syndrome. HFOV has very different characteristics from normal breathing physiology, with a much smaller tidal volume and a higher breathing frequency. In this work, the high frequency oscillatory flow is studied using a computational fluid dynamics (CFD) analysis in three different geometrical models with increasing complexity: a straight tube, a single-bifurcation tube model, and a computed-tomography (CT)-based human airway model of up to seven generations. We aim to understand the counter-flow phenomenon at flow reversal and its role in convective mixing in these models using sinusoidal waveforms of different frequencies and Reynolds numbers. Mixing is quantified by the stretch rate analysis. In the straight-tube model, coaxial counter flow with opposing fluid streams is formed around flow reversal, agreeing with an analytical Womersley solution. However, counter flow yields no net convective mixing at end cycle. In the single-bifurcation model, counter flow at high Re is intervened with secondary vortices in the parent (child) branch at end expiration (inspiration), resulting in an irreversible mixing process. For the CT-based airway model three cases are considered, consisting of the normal breathing case, the high-frequency-normal-Re case, and the HFOV case. The counter-flow structure is more evident in the high-frequency-normal-Re case than the HFOV case. The instantaneous and time-averaged stretch rates at the end of two breathing cycles and in the vicinity of flow reversal are computed. It is found that counter flow contributes about 20% to mixing in HFOV. PMID:20614248

  9. Myocardial ischemia detection with single-phase CT perfusion in symptomatic patients using high-pitch helical image acquisition technique.

    PubMed

    Bischoff, Bernhard; Deseive, Simon; Rampp, Martin; Todica, Andrei; Wermke, Marc; Martinoff, Stefan; Massberg, Steffen; Reiser, Maximilian F; Becker, Hans-Christoph; Hausleiter, Jörg

    2017-04-01

    Coronary CT angiography (CCTA) suffers from a reduced diagnostic accuracy in patients with heavily calcified coronary arteries or prior myocardial revascularisation due to artefacts caused by calcifications and stent material. CT myocardial perfusion imaging (CTMPI) yields high potential for the detection of myocardial ischemia and might help to overcome the above mentioned limitations. We analysed CT single-phase perfusion using high-pitch helical image acquisition technique in patients with prior myocardial revascularisation. Thirty-six patients with an indication for invasive coronary angiography (28 with coronary stents, 2 with coronary artery bypass grafts and 6 with both) were included in this prospective study at two study sites. All patients were examined on a 2nd generation dual-source CT system. Stress CT images were obtained using a prospectively ECG-triggered single-phase high-pitch helical image acquisition technique. During stress the tracer for myocardial perfusion (MP) SPECT imaging was administered. Rest CT images were acquired using prospectively ECG-triggered sequential CT. MP-SPECT imaging and invasive coronary angiography served as standard of reference. In this heavily diseased patient cohort CCTA alone showed a low overall diagnostic accuracy for detection of hemodynamically relevant coronary artery stenosis of only 31% on a per-patient base and 60% on a per-vessel base. Combining CCTA and CTMPI allowed for a significantly higher overall diagnostic accuracy of 78% on a per-patient base and 92% on a per-vessel base (p < 0.001). Mean radiation dose for stress CT scans was 0.9 mSv, mean radiation dose for rest CT scans was 5.0 mSv. In symptomatic patients with known coronary artery disease and prior myocardial revascularization combining CCTA and CTMPI showed significantly higher diagnostic accuracy in detection of hemodynamically significant coronary artery stenosis when compared to CCTA alone.

  10. High density resolution synchrotron radiation based x-ray microtomography (SR μCT) for quantitative 3D-morphometrics in zoological sciences

    NASA Astrophysics Data System (ADS)

    Nickel, Michael; Hammel, Jörg U.; Herzen, Julia; Bullinger, Eric; Beckmann, Felix

    2008-08-01

    Zoological sciences widely rely on morphological data to reconstruct and understand body structures of animals. The best suitable methods like tomography allow for a direct representation of 3D-structures. In recent years, synchrotron radiation based x-ray microtomography (SR μCT) placed high resolutions to the disposal of morphologists. With the development of highly brilliant and collimated third generation synchrotron sources, phase contrast SR μCT became widely available. A number of scientific contributions stressed the superiority of phase contrast over absorption contrast. However, here we demonstrate the power of high density resolution methods based on absorption-contrast SRμCT for quantitative 3D-measurements of tissues and other delicate bio-structures in zoological sciences. We used beamline BW2 at DORIS III (DESY, Hamburg, Germany) to perform microtomography on tissue and mineral skeletons of marine sponges (Porifera) which were shock frozen and/or fixed in a glutamate osmium tetroxide solution, followed by critical point drying. High density resolution tomographic reconstructions allowed running quantitative 3D-image analyses in Matlab and ImageJ. By applying contrast and shape rule based algorithms we semi-automatically extracted and measured sponge body structures like mineral spicules, elements of the canal system or tissue structures. This lead to a better understanding of sponge biology: from skeleton functional morphology and internal water flow regimes to body contractility. Our high density resolution based quantitative approach can be applied to a wide variety of biological structures. However, two prerequisites apply: (1) maximum density resolution is necessary; (2) edge effects as seen for example in phase outline contrast SR μCT must not be present. As a consequence, to allow biological sciences to fully exploit the power of SR μCT further increase of density resolution in absorption contrast methods is desirable.

  11. Efficient Data Archive And Rapid Image Analysis For High Speed CT

    NASA Astrophysics Data System (ADS)

    Ackelsberg, Sholom M.; Napel, Sandy; Gould, Robert G.; Boyd, Douglas P.

    1986-06-01

    The Imatron C-100 Cine-CT TM scanner is a multi-slice high speed Computed Tomography (CT) scanner that produces a pair of anatomically contiguous slices in 50 milliseconds. The scanner operates in several modes. In flow mode, the scanner images up to 8 anatomically contiguous slices in 224 milliseconds without moving the patient. In cine mode, the scanner acquires data at a rate of 34 images/second. In both of these modes, a typical run generates 80 images in just a few seconds. Most patient studies involve one or more cine runs and one or more flow runs. Thus, the C-100 often produces an order of magnitude more images per patient than any other CT scanner. The large amount of data involved in each study requires rapid, easy to use analysis software and efficient data archiving. The C-100 achieves fast scan times by eliminating all moving parts. It generates a moving x-ray fan by scanning a highly focused electron beam along semi-circular tungsten targets that partially surround the patient. The scanner acquires data with a solid-state detector system, converts it to digital form, and sends it via fiber optic cables to a 32 Mbyte dual-ported high speed bulk memory. An array processor and back-projector reconstruct the images, which are stored on a dual-ported 1.37 Gbyte hard disk system. The scanner incorporates two workstations, each containing its own graphic display system. The work-stations communicate with each other through the dual-ported disks. The system stores images for long-term archive on magnetic tape, multi-format film, videotape, or removable optical disks. The C-100 provides interactive image analysis software that includes cine display, func-tional imaging, time-density analysis for flow measurements, off-axis reformatting, cardiac wall motion analysis, and image subtraction. Data management software includes file selection, merging, deletion, archiving, and retrieval.

  12. High-resolution CT findings of Mycobacterium avium-intracellulare complex pulmonary disease: correlation with pulmonary function test results.

    PubMed

    Song, Jong Woon; Koh, Won-Jung; Lee, Kyung Soo; Lee, Ji Young; Chung, Myung Jin; Kim, Tae Sung; Kwon, O Jung

    2008-10-01

    The purpose of our study was to analyze the high-resolution CT findings of the nodular bronchiectatic form of Mycobacterium avium-intracellulare complex (MAC) pulmonary disease and to correlate the extent of high-resolution CT findings with pulmonary function test (PFT) results. From January 2005 through December 2005, we identified 47 patients (mean age, 58 +/- 13 years; age range, 24-72 years; male-female ratio, 11:36) with the nodular bronchiectatic form of MAC pulmonary disease who underwent both high-resolution CT and PFTs. High-resolution CT findings were reviewed retrospectively in terms of the presence and extent of bronchiectasis, cellular or inflammatory bronchiolitis (centrilobular small nodules and tree-in-bud signs), cavity, nodule, and other findings. The extent of the abnormalities seen on high-resolution CT was scored by modifying the cystic fibrosis scoring system proposed by Helbich and coworkers. The scores were correlated with PFT results using Spearman's correlation coefficient. On high-resolution CT, the three most frequently observed patterns of parenchymal abnormalities were, in decreasing order of frequency, cellular bronchiolitis (n = 47, 100%), bronchiectasis (n = 46, 98%), and consolidation (n = 27, 57%). The total CT score showed a significant correlation with the residual volume-total lung capacity (RV/TLC) ratio (r = 0.572, p < 0.001), forced expiratory volume in 1 second (FEV(1)) value (r = -0.426, p = 0.003), forced vital capacity (FVC) value (r = -0.360, p = 0.013), peak expiratory flow value (r = -0.352, p = 0.015), and peak expiratory flow between 25% and 75% of the forced vital capacity (FEF(25-75%)) (r = -0.289, p = 0.049). CT scoring of pulmonary abnormalities correlates with measures of functional impairment in patients with MAC pulmonary disease.

  13. Opportunities for new CT contrast agents to maximize the diagnostic potential of emerging spectral CT technologies.

    PubMed

    Yeh, Benjamin M; FitzGerald, Paul F; Edic, Peter M; Lambert, Jack W; Colborn, Robert E; Marino, Michael E; Evans, Paul M; Roberts, Jeannette C; Wang, Zhen J; Wong, Margaret J; Bonitatibus, Peter J

    2016-09-09

    The introduction of spectral CT imaging in the form of fast clinical dual-energy CT enabled contrast material to be differentiated from other radiodense materials, improved lesion detection in contrast-enhanced scans, and changed the way that existing iodine and barium contrast materials are used in clinical practice. More profoundly, spectral CT can differentiate between individual contrast materials that have different reporter elements such that high-resolution CT imaging of multiple contrast agents can be obtained in a single pass of the CT scanner. These spectral CT capabilities would be even more impactful with the development of contrast materials designed to complement the existing clinical iodine- and barium-based agents. New biocompatible high-atomic number contrast materials with different biodistribution and X-ray attenuation properties than existing agents will expand the diagnostic power of spectral CT imaging without penalties in radiation dose or scan time.

  14. KENNEDY SPACE CENTER, FLA. - Inside the cab of crawler-transporter (CT) number 2, driver Sam Dove, with United Space Alliance, operates the vehicle on a test run to the launch pad. The CT recently underwent modifications to the cab. The CT is transporting a Mobile Launch Platform (MLP). The CT moves Space Shuttle vehicles, situated on the MLP, between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds. Seen on top of the MLP are two tail service masts that support the fluid, gas and electrical requirements of the orbiter’s liquid oxygen and liquid hydrogen aft umbilicals.

    NASA Image and Video Library

    2003-08-18

    KENNEDY SPACE CENTER, FLA. - Inside the cab of crawler-transporter (CT) number 2, driver Sam Dove, with United Space Alliance, operates the vehicle on a test run to the launch pad. The CT recently underwent modifications to the cab. The CT is transporting a Mobile Launch Platform (MLP). The CT moves Space Shuttle vehicles, situated on the MLP, between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds. Seen on top of the MLP are two tail service masts that support the fluid, gas and electrical requirements of the orbiter’s liquid oxygen and liquid hydrogen aft umbilicals.

  15. KENNEDY SPACE CENTER, FLA. - A closeup of crawler-transportation (CT) number 2 shows the new muffler system on the vehicle. The CT also recently underwent modifications to the cab. The CT is transporting a Mobile Launch Platform (MLP). The CT moves Space Shuttle vehicles, situated on the MLP, between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds. Seen on top of the MLP are two tail service masts that support the fluid, gas and electrical requirements of the orbiter’s liquid oxygen and liquid hydrogen aft umbilicals.

    NASA Image and Video Library

    2003-08-18

    KENNEDY SPACE CENTER, FLA. - A closeup of crawler-transportation (CT) number 2 shows the new muffler system on the vehicle. The CT also recently underwent modifications to the cab. The CT is transporting a Mobile Launch Platform (MLP). The CT moves Space Shuttle vehicles, situated on the MLP, between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds. Seen on top of the MLP are two tail service masts that support the fluid, gas and electrical requirements of the orbiter’s liquid oxygen and liquid hydrogen aft umbilicals.

  16. Dynamics of Active Separation Control at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Pack, LaTunia G.; Seifert, Avi

    2000-01-01

    A series of active flow control experiments were recently conducted at high Reynolds numbers on a generic separated configuration. The model simulates the upper surface of a 20% thick Glauert-Goldschmied type airfoil at zero angle of attack. The flow is fully turbulent since the tunnel sidewall boundary layer flows over the model. The main motivation for the experiments is to generate a comprehensive data base for validation of unsteady numerical simulation as a first step in the development of a CFD design tool, without which it would not be possible to effectively utilize the great potential of unsteady flow control. This paper focuses on the dynamics of several key features of the baseline as well as the controlled flow. It was found that the thickness of the upstream boundary layer has a negligible effect on the flow dynamics. It is speculated that separation is caused mainly by the highly convex surface while viscous effects are less important. The two-dimensional separated flow contains unsteady waves centered on a reduced frequency of 0.8, while in the three dimensional separated flow, frequencies around a reduced frequency of 0.3 and 1 are active. Several scenarios of resonant wave interaction take place at the separated shear-layer and in the pressure recovery region. The unstable reduced frequency bands for periodic excitation are centered on 1.5 and 5, but these reduced frequencies are based on the length of the baseline bubble that shortens due to the excitation. The conventional swept wing-scaling works well for the coherent wave features. Reproduction of these dynamic effects by a numerical simulation would provide benchmark validation.

  17. Interaction of upstream flow distortions with high Mach number cascades

    NASA Technical Reports Server (NTRS)

    Englert, G. W.

    1981-01-01

    Features of the interaction of flow distortions, such as gusts and wakes with blade rows of advance type fans and compressors having high tip Mach numbers are modeled. A typical disturbance was assumed to have harmonic time dependence and was described, at a far upstream location, in three orthogonal spatial coordinates by a double Fourier series. It was convected at supersonic relative to a linear cascade described as an unrolled annulus. Conditions were selected so that the component of this velocity parallel to the axis of the turbomachine was subsonic, permitting interaction between blades through the upstream as well as downstream flow media. A strong, nearly normal shock was considered in the blade passages which was allowed curvature and displacement. The flows before and after the shock were linearized relative to uniform mean velocities in their respective regions. Solution of the descriptive equations was by adaption of the Wiener-Hopf technique, enabling a determination of distortion patterns through and downstream of the cascade as well as pressure distributions on the blade and surfaces. Details of interaction of the disturbance with the in-passage shock were discussed. Infuences of amplitude, wave length, and phase of the disturbance on lifts and moments of cascade configurations are presented. Numerical results are clarified by reference to an especially orderly pattern of upstream vertical motion in relation to the cascade parameters.

  18. Interaction of two high Reynolds number axisymmetric turbulent wakes

    NASA Astrophysics Data System (ADS)

    Obligado, M.; Klein, S.; Vassilicos, J. C.

    2015-11-01

    With the recent discovery of non-equilibrium high Reynolds number scalings in the wake of axisymmetric plates (Nedic et al., PRL, 2013), it has become of importance to develop an experimental technique that permits to easily discriminate between different wake scalings. We propose an experimental setup that tests the presence of non-equilibrium turbulence using the streamwise variation of velocity fluctuations between two bluff bodies facing a flow. We have studied two different sets of plates (one with regular and another with irregular peripheries) with Hot-Wire Anemometry in a wind tunnel. By acquiring streamwise profiles for different plate separations and identifying the wake interaction length for each separation it is possible to estimate the streamwise evolution of the single wake width. From this evolution it is also possible to deduce the turbulence dissipation scalings. This work generalizes previous studies on the interaction of plane wakes (see Gomes-Fernandes et al., JFM, 2012) to include axisymmetric wakes. We find that the wake interaction length proposed in this cited work and a constant anisotropy assumption can be used to collapse the streamwise developments of the first three moments.

  19. Efficient simulation of detached flows at high Reynolds number

    NASA Astrophysics Data System (ADS)

    Vega, Jose M.; Asensio, Victor; Herrero, Raul; Varas, Fernando

    2014-11-01

    A method is presented for the computationally efficient simulation of quasi-periodic detached flows in multi-parameter problems at very large Reynolds numbers, keeping in mind a variety of applications, including helicopter flight simulators, control and certification of unmanned aerial vehicles, control of wind turbines, conceptual design in aeronautics, and civil aerodynamics. In many of these applications, the large scale flows (ignoring the smaller turbulent scales) are at most quasi-periodic, namely the Fourier transform exhibits a finite set of concentrated peaks resulting from the nonlinear passive interaction of periodic wakes. The method consists in an offline preprocess and the online operation. In the preprocess, a standard CFD solver (such as URANS) is used in combination with several ingredients such as an iterative combination proper orthogonal decomposition and fast Fourier transform. The online operation is made with a combination of high order singular value decomposition and interpolation. The performance of the method is tested considering the ow over a fairly complex urban topography, for various free stream intensities and orientations, seeking real time online simulations.

  20. Statistics of High Atwood Number Turbulent Mixing Layers

    NASA Astrophysics Data System (ADS)

    Baltzer, Jon; Livescu, Daniel

    2015-11-01

    The statistical properties of incompressible shear-driven planar mixing layers between two miscible streams of fluids with different densities are investigated by means of Direct Numerical Simulations. The simulations begin from a thin interface perturbed by a thin broadband random disturbance, and the mixing layers are allowed to develop to self-similar states. The temporal simulations are performed in unprecedented domain sizes, with grid sizes up to 6144 x 2048 x 1536, which allows turbulent structures to grow and merge naturally. This allows the flow to reach states far-removed from the initial disturbances, thereby enabling high-quality statistics to be obtained for higher moments, pdfs, and other quantities critical to developing closure models. A wide range of Atwood numbers are explored, ranging from nearly constant density to At=0.87. The consequences of increasing the density contrast are investigated for global quantities, such as growth rates, and asymmetries that form in statistical profiles. Additional simulations in smaller domains are performed to study the effects of domain size.

  1. Development of high-resolution x-ray CT system using parallel beam geometry

    SciTech Connect

    Yoneyama, Akio Baba, Rika; Hyodo, Kazuyuki; Takeda, Tohoru; Nakano, Haruhisa; Maki, Koutaro; Sumitani, Kazushi; Hirai, Yasuharu

    2016-01-28

    For fine three-dimensional observations of large biomedical and organic material samples, we developed a high-resolution X-ray CT system. The system consists of a sample positioner, a 5-μm scintillator, microscopy lenses, and a water-cooled sCMOS detector. Parallel beam geometry was adopted to attain a field of view of a few mm square. A fine three-dimensional image of birch branch was obtained using a 9-keV X-ray at BL16XU of SPring-8 in Japan. The spatial resolution estimated from the line profile of a sectional image was about 3 μm.

  2. Development of high-resolution x-ray CT system using parallel beam geometry

    NASA Astrophysics Data System (ADS)

    Yoneyama, Akio; Baba, Rika; Hyodo, Kazuyuki; Takeda, Tohoru; Nakano, Haruhisa; Maki, Koutaro; Sumitani, Kazushi; Hirai, Yasuharu

    2016-01-01

    For fine three-dimensional observations of large biomedical and organic material samples, we developed a high-resolution X-ray CT system. The system consists of a sample positioner, a 5-μm scintillator, microscopy lenses, and a water-cooled sCMOS detector. Parallel beam geometry was adopted to attain a field of view of a few mm square. A fine three-dimensional image of birch branch was obtained using a 9-keV X-ray at BL16XU of SPring-8 in Japan. The spatial resolution estimated from the line profile of a sectional image was about 3 μm.

  3. The reconstruction algorithm used for [(68)Ga]PSMA-HBED-CC PET/CT reconstruction significantly influences the number of detected lymph node metastases and coeliac ganglia.

    PubMed

    Krohn, Thomas; Birmes, Anita; Winz, Oliver H; Drude, Natascha I; Mottaghy, Felix M; Behrendt, Florian F; Verburg, Frederik A

    2017-04-01

    To investigate whether the numbers of lymph node metastases and coeliac ganglia delineated on [(68)Ga]PSMA-HBED-CC PET/CT scans differ among datasets generated using different reconstruction algorithms. Data were constructed using the BLOB-OS-TF, BLOB-OS and 3D-RAMLA algorithms. All reconstructions were assessed by two nuclear medicine physicians for the number of pelvic/paraaortal lymph node metastases as well the number of coeliac ganglia. Standardized uptake values (SUV) were also calculated in different regions. At least one [(68)Ga]PSMA-HBED-CC PET/CT-positive pelvic or paraaortal lymph node metastasis was found in 49 and 35 patients using the BLOB-OS-TF algorithm, in 42 and 33 patients using the BLOB-OS algorithm, and in 41 and 31 patients using the 3D-RAMLA algorithm, respectively, and a positive ganglion was found in 92, 59 and 24 of 100 patients using the three algorithms, respectively. Quantitatively, the SUVmean and SUVmax were significantly higher with the BLOB-OS algorithm than with either the BLOB-OS-TF or the 3D-RAMLA algorithm in all measured regions (p < 0.001 for all comparisons). The differences between the SUVs with the BLOB-OS-TF- and 3D-RAMLA algorithms were not significant in the aorta (SUVmean, p = 0.93; SUVmax, p = 0.97) but were significant in all other regions (p < 0.001 in all cases). The SUVmean ganglion/gluteus ratio was significantly higher with the BLOB-OS-TF algorithm than with either the BLOB-OS or the 3D-RAMLA algorithm and was significantly higher with the BLOB-OS than with the 3D-RAMLA algorithm (p < 0.001 in all cases). The results of [(68)Ga]PSMA-HBED-CC PET/CT are affected by the reconstruction algorithm used. The highest number of lesions and physiological structures will be visualized using a modern algorithm employing time-of-flight information.

  4. Toward Immersed Boundary Simulation of High Reynolds Number Flows

    NASA Technical Reports Server (NTRS)

    Kalitzin, Georgi; Iaccarino, Gianluca

    2003-01-01

    of high Reynolds number wall bounded flows is particularly challenging as it requires the consideration of thin turbulent boundary layers, i.e. near wall regions with large gradients of the flow field variables. For such flows, the representation of the wall boundary has a large impact on the accuracy of the computation. It is also critical for the robustness and convergence of the flow solver.

  5. The accuracy of (68)Ga-PSMA PET/CT in primary lymph node staging in high-risk prostate cancer.

    PubMed

    Öbek, Can; Doğanca, Tünkut; Demirci, Emre; Ocak, Meltem; Kural, Ali Rıza; Yıldırım, Asıf; Yücetaş, Uğur; Demirdağ, Çetin; Erdoğan, Sarper M; Kabasakal, Levent

    2017-06-18

    To assess the diagnostic accuracy of (68)Ga-PSMA PET in predicting lymph node (LN) metastases in primary N staging in high-risk and very high-risk nonmetastatic prostate cancer in comparison with morphological imaging. This was a multicentre trial of the Society of Urologic Oncology in Turkey in conjunction with the Nuclear Medicine Department of Cerrahpasa School of Medicine, Istanbul University. Patients were accrued from eight centres. Patients with high-risk and very high-risk disease scheduled to undergo surgical treatment with extended LN dissection between July 2014 and October 2015 were included. Either MRI or CT was used for morphological imaging. PSMA PET/CT was performed and evaluated at a single centre. Sensitivity, specificity and accuracy were calculated for the detection of lymphatic metastases by PSMA PET/CT and morphological imaging. Kappa values were calculated to evaluate the correlation between the numbers of LN metastases detected by PSMA PET/CT and by histopathology. Data on 51 eligible patients are presented. The sensitivity, specificity and accuracy of PSMA PET in detecting LN metastases in the primary setting were 53%, 86% and 76%, and increased to 67%, 88% and 81% in the subgroup with of patients with ≥15 LN removed. Kappa values for the correlation between imaging and pathology were 0.41 for PSMA PET and 0.18 for morphological imaging. PSMA PET/CT is superior to morphological imaging for the detection of metastatic LNs in patients with primary prostate cancer. Surgical dissection remains the gold standard for precise lymphatic staging.

  6. Compton Scattering in Clinical PET/CT With High Resolution Half Ring PET Insert Device

    PubMed Central

    Komarov, Sergey A.; Wu, Heyu; Keesing, Daniel B.; O'Sullivan, Joseph A.; Tai, Yuan-Chuan

    2011-01-01

    The integration of a high resolution PET insert into a conventional PET system can significantly improve the resolution and the contrast of its images within a reduced imaging field of view. For the rest of the scanner imaging field of view, the insert is a highly attenuating and scattering media. In order to use all available coincidence events (including coincidences between 2 detectors in the original scanner, namely the scanner-scanner coincidences), appropriate scatter and attenuation corrections have to be implemented. In this work, we conducted a series of Monte Carlo simulations to estimate the composition of the scattering background and the importance of the scatter correction. We implemented and tested the Single Scatter Simulation (SSS) algorithm for a hypothetical system and show good agreement between the estimated scatter using SSS and Monte Carlo simulated scatter contribution. We further applied the SSS to estimate scatter contribution from an existing prototype PET insert for a clinical PET/CT scanner. The results demonstrated the applicability of SSS to estimate the scatter contribution within a clinical PET/CT system even when there is a high resolution half ring PET insert device in its imaging field of view. PMID:21552470

  7. Helicon waves in uniform plasmas. II. High m numbers

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.; Urrutia, J. M.

    2015-09-01

    Helicons are whistler modes with azimuthal wave numbers. They have been studied in solids and plasmas where boundaries play a role. The present work shows that very similar modes exist in unbounded gaseous plasmas. Instead of boundaries, the antenna properties determine the topology of the wave packets. The simplest antenna is a magnetic loop which excites m = 0 or m = 1 helicons depending on whether the dipole moment is aligned parallel or perpendicular to the ambient background magnetic field B0. While these low order helicons have been described by J. M. Urrutia and R. L. Stenzel ["Helicon modes in uniform plasmas. I. Low m modes," Phys. Plasmas 22, 092111 (2015)], the present work focuses on high order modes up to m = 8. These are excited by antenna arrays forming magnetic multipoles. Their wave magnetic field has been measured in space and time in a large and uniform laboratory plasma free of boundary effects. The observed wave topology exhibits m pairs of unique field line spirals which may have inspired the name "helicon" to this mode. All field lines converge into these nested spirals which propagate like corkscrews along B0. The field lines near the axis of helicons are perpendicular to B0 and circularly polarized as in parallel whistlers. Helical antennas couple to these transverse fields but not to the spiral fields of helicons. Using a circular antenna array of phased m = 0 loops, right or left rotating or non-rotating multipole antenna fields are generated. They excite m < 0 and m > 0 modes, showing that the plasma supports both modes equally well. The poor excitation of m < 0 modes is a characteristic of loops with dipole moment across B0. The radiation efficiency of multipole antennas has been found to decrease with m.

  8. Helicon waves in uniform plasmas. II. High m numbers

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.

    2015-09-15

    Helicons are whistler modes with azimuthal wave numbers. They have been studied in solids and plasmas where boundaries play a role. The present work shows that very similar modes exist in unbounded gaseous plasmas. Instead of boundaries, the antenna properties determine the topology of the wave packets. The simplest antenna is a magnetic loop which excites m = 0 or m = 1 helicons depending on whether the dipole moment is aligned parallel or perpendicular to the ambient background magnetic field B{sub 0}. While these low order helicons have been described by J. M. Urrutia and R. L. Stenzel [“Helicon modes in uniform plasmas. I. Low m modes,” Phys. Plasmas 22, 092111 (2015)], the present work focuses on high order modes up to m = 8. These are excited by antenna arrays forming magnetic multipoles. Their wave magnetic field has been measured in space and time in a large and uniform laboratory plasma free of boundary effects. The observed wave topology exhibits m pairs of unique field line spirals which may have inspired the name “helicon” to this mode. All field lines converge into these nested spirals which propagate like corkscrews along B{sub 0}. The field lines near the axis of helicons are perpendicular to B{sub 0} and circularly polarized as in parallel whistlers. Helical antennas couple to these transverse fields but not to the spiral fields of helicons. Using a circular antenna array of phased m = 0 loops, right or left rotating or non-rotating multipole antenna fields are generated. They excite m < 0 and m > 0 modes, showing that the plasma supports both modes equally well. The poor excitation of m < 0 modes is a characteristic of loops with dipole moment across B{sub 0}. The radiation efficiency of multipole antennas has been found to decrease with m.

  9. High (18)F-FDG uptake in urinary calculi on PET/CT: An unrecognized non-malignant accumulation.

    PubMed

    Fu, Zhanli; Li, Ziao; Huang, Jia; Zhang, Jin; Liu, Meng; Li, Qian; Li, Yi

    2016-08-01

    To assess the high (18)F-fluorodeoxyglucose ((18)F-FDG) uptake in urinary calculi on positron-emission tomography/computed tomography (PET/CT). In this study, (18)F-FDG PET/CT examinations were retrospectively reviewed from November 2013 to February 2016 in a single center, and patients with high (18)F-FDG uptake in urinary calculi were identified. The following data were collected from each patient, including age, sex, primary disease, method to verify the urinary calculus, and imaging characteristics of the calculus. A total of 2758 PET/CT studies (2567 patients) were reviewed, and 52 patients with urinary calculi were identified, in which 6 (11.5%, 6/52) patients (5 males, 1 female, age 34-73 years, median age 60.5 years) demonstrated high (18)F-FDG uptake in the urinary calculi. Among the 6 patients, 3 patients had bladder calculi, 2 patients had renal calculi, and 1 patient had both bladder and renal calculi. The size of the urinary calculi varied from sandy to 19mm on CT. The maximal Hounsfield units of the calculi ranged from 153 to 1078. The SUVmax of the calculi on the routine PET/CT scan ranged from 11.7 to 143.0. Delayed PET/CT scans were performed on 4 patients, which showed the calculi SUVmax increasing in 2 patients, while decreasing in the other 2 patients. One patient with bladder calculus underwent a follow-up PET/CT, which showed enlargement of the calculus as well as the increased SUVmax. This study shows an uncommon high (18)F-FDG uptake in urinary calculi. Recognition of this non-malignant accumulation in urinary calculi is essential for correct interpretation of PET/CT findings. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  10. In-vivo Comparison of 18F-FLT uptake, CT Number, Tumor Volume in Evaluation of Repopulation during Radiotherapy for Lung cancer

    PubMed Central

    Zhang, Xiaoli; Yu, Jinming; Li, Chengming; Sun, Xindong; Meng, Xue

    2017-01-01

    Accelerated repopulation has been observed in various tumors. This study was aimed to evaluate the potential of 3′-deoxy-3′-18F-fluorothymidine (18F-FLT) uptake and Computed Tomography Number (CTN) in monitoring tumor responses to radiotherapy compared with tumor volume (TV) changes. Tumor bearing nude mice were assigned to either irradiated daily or every second day group and then randomized to 6 sub-groups to receive 0Gy, 6Gy, 12Gy, 18Gy, 24Gy, 36Gy irradiation, respectively. TV was measured every 3 days. 18F-FLT micro-PET/CT scans were performed after irradiation being completed. Tumor sections were stained to calculate the immunohistochemical (Ki-67) labeling index (LI). Comparison analysis between FLT uptake parameters, CTNs, VTs and Ki-67 LI results were conducted to determine the correlation. Ki-67 LI increased significantly after 6 times of irradiation at irradiated daily group and after 3 times at irradiated every second day group, suggesting accelerated repopulation. No shrinkage of TV was noticed at two groups during irradiation delivery. Both 18F-FLT uptake and CTN increased significantly after irradiation of 12Gy/6f/6d and 6Gy/3f/6d. Comparison analysis found a significant relationship between Ki-67 LI and 18F-FLT uptake parameters as well as CTN. Both 18F-FLT PET and CT have the potential to reflect the tumor proliferative response during radiation delivery. PMID:28387306

  11. A sparsity-based iterative algorithm for reconstruction of micro-CT images from highly undersampled projection datasets obtained with a synchrotron X-ray source

    NASA Astrophysics Data System (ADS)

    Melli, S. Ali; Wahid, Khan A.; Babyn, Paul; Cooper, David M. L.; Gopi, Varun P.

    2016-12-01

    Synchrotron X-ray Micro Computed Tomography (Micro-CT) is an imaging technique which is increasingly used for non-invasive in vivo preclinical imaging. However, it often requires a large number of projections from many different angles to reconstruct high-quality images leading to significantly high radiation doses and long scan times. To utilize this imaging technique further for in vivo imaging, we need to design reconstruction algorithms that reduce the radiation dose and scan time without reduction of reconstructed image quality. This research is focused on using a combination of gradient-based Douglas-Rachford splitting and discrete wavelet packet shrinkage image denoising methods to design an algorithm for reconstruction of large-scale reduced-view synchrotron Micro-CT images with acceptable quality metrics. These quality metrics are computed by comparing the reconstructed images with a high-dose reference image reconstructed from 1800 equally spaced projections spanning 180°. Visual and quantitative-based performance assessment of a synthetic head phantom and a femoral cortical bone sample imaged in the biomedical imaging and therapy bending magnet beamline at the Canadian Light Source demonstrates that the proposed algorithm is superior to the existing reconstruction algorithms. Using the proposed reconstruction algorithm to reduce the number of projections in synchrotron Micro-CT is an effective way to reduce the overall radiation dose and scan time which improves in vivo imaging protocols.

  12. Fast kVp-switching dual energy contrast-enhanced thorax and cardiac CT: A phantom study on the accuracy of iodine concentration and effective atomic number measurement.

    PubMed

    Papadakis, Antonios E; Damilakis, John

    2017-09-01

    To assess the effect of vessel diameter and exposure parameters on the estimation accuracy of concentration and effective atomic number (Zeff ) of iodine (I) in contrast-enhanced thorax and cardiac dual-energy CT using a modern fast kVp-switching CT scanner. A standard semi-anthropomorphic cardiac CT phantom devised to simulate the human chest at three different body habitus i.e., medium-sized, large-sized, and obese, was scanned using a fast kVp-switching Revolution-GSI GE CT scanner. Five cylindrical, 10 mm diameter, vials were filled with solutions prepared by diluting I contrast at five concentrations (2.5, 5, 10, 15, and 20 mg I/ml). To simulate small vessels, pipette tips with a diameter ranging from 5 mm to 0.5 mm were employed. The vials and pipette tips were accommodated within the semi-anthropomorphic phantom. CT acquisitions were performed in the fast kVp-switching dual-energy mode at six different CTDIw values. Acquisitions were also performed at 80, 100, 120, and 140 kVp. Images were acquired at 64 × 0.625 mm beam collimation and reconstructed at 2.5 mm using all available reconstruction filter kernels. Virtual monochromatic spectral (VMS) images, iodine concentration (IMeas ), and Zeff maps were reconstructed. Hounsfield unit as a function of energy (HUkeV ) in VMS and single-kVp (HUkVp ), IMeas and Zeff were measured at each CTDIw . The effect of vessel diameter on IMeas and Zeff was investigated. Measured HUkeV and Zeff were compared to theoretically estimated values and IMeas were compared to nominal (INom ) values. In 10 mm diameter vessels, HUkeV values were accurate to 18% for the medium-sized, 22% for the large-sized and 39% for the obese phantoms. IMeas was underestimated by up to 10% for the medium-sized, 26% for the large-sized and 33% for the obese phantom. IMeas error decreased with increasing CTDIw from ±0.799 mg/ml at 8.61 mGy to ±0.082 mg/ml at 32.01 mGy. The percentage difference between measured and theoretically estimated Zeff

  13. Promising electron mobility and high thermal conductivity in Sc2CT2 (T = F, OH) MXenes.

    PubMed

    Zha, Xian-Hu; Zhou, Jie; Zhou, Yuhong; Huang, Qing; He, Jian; Francisco, Joseph S; Luo, Kan; Du, Shiyu

    2016-03-21

    MXenes, the new 2D transition metal carbides and nitrides, have recently attracted extensive attention due to their diverse applications and excellent performances. However, the thermal and electrical properties of most MXene materials are yet to be studied. In this work, we investigate the electrical and thermal properties of semiconducting Sc2CT2 (T = F, OH) MXenes using first-principles calculations. Both of the Sc2CT2 (T = F, OH) MXenes are determined to show excellent carrier mobilities. The electron mobility in the Sc2CF2 MXene is found to be strongly anisotropic at room temperature, with values of 5.03 × 10(3) and 1.07 × 10(3) cm(2) V(-1) s(-1) in the zigzag and armchair directions, respectively. The predicted electron mobility in the zigzag direction of the Sc2CF2 is nearly four-fold that in the armchair direction of the promising semiconductor phosphorene. In contrast to Sc2CF2, Sc2C(OH)2 presents approximately isotropic electron mobility. The values at room temperature in the zigzag and armchair directions are calculated as 2.06 × 10(3) cm(2) V(-1) s(-1) and 2.19 × 10(3) cm(2) V(-1) s(-1), respectively. In regard to the thermal properties, the thermal conductivities of the Sc2CT2 (T = F, OH) MXenes have been determined. The predicted values are higher than those of most metals and semiconducting low-dimensional materials, such as monolayer MoS2 and phosphorene. In particular, the room-temperature thermal conductivity along the Sc2CF2 armchair direction has been determined to be as high as 472 W m(-1) K(-1) based on a flake length of 5 μm, which is even higher than that of the best traditional conductor silver. The corresponding value in the zigzag direction of Sc2CF2 is calculated to be 178 W m(-1) K(-1). The thermal conductivity in Sc2C(OH)2 is less anisotropic and lower compared to that in Sc2CF2. The room-temperature value in the armchair (zigzag) direction is determined to be 173 W m(-1) K(-1) (107 W m(-1) K(-1)). Based on their excellent

  14. Promising electron mobility and high thermal conductivity in Sc2CT2 (T = F, OH) MXenes

    NASA Astrophysics Data System (ADS)

    Zha, Xian-Hu; Zhou, Jie; Zhou, Yuhong; Huang, Qing; He, Jian; Francisco, Joseph S.; Luo, Kan; Du, Shiyu

    2016-03-01

    MXenes, the new 2D transition metal carbides and nitrides, have recently attracted extensive attention due to their diverse applications and excellent performances. However, the thermal and electrical properties of most MXene materials are yet to be studied. In this work, we investigate the electrical and thermal properties of semiconducting Sc2CT2 (T = F, OH) MXenes using first-principles calculations. Both of the Sc2CT2 (T = F, OH) MXenes are determined to show excellent carrier mobilities. The electron mobility in the Sc2CF2 MXene is found to be strongly anisotropic at room temperature, with values of 5.03 × 103 and 1.07 × 103 cm2 V-1 s-1 in the zigzag and armchair directions, respectively. The predicted electron mobility in the zigzag direction of the Sc2CF2 is nearly four-fold that in the armchair direction of the promising semiconductor phosphorene. In contrast to Sc2CF2, Sc2C(OH)2 presents approximately isotropic electron mobility. The values at room temperature in the zigzag and armchair directions are calculated as 2.06 × 103 cm2 V-1 s-1 and 2.19 × 103 cm2 V-1 s-1, respectively. In regard to the thermal properties, the thermal conductivities of the Sc2CT2 (T = F, OH) MXenes have been determined. The predicted values are higher than those of most metals and semiconducting low-dimensional materials, such as monolayer MoS2 and phosphorene. In particular, the room-temperature thermal conductivity along the Sc2CF2 armchair direction has been determined to be as high as 472 W m-1 K-1 based on a flake length of 5 μm, which is even higher than that of the best traditional conductor silver. The corresponding value in the zigzag direction of Sc2CF2 is calculated to be 178 W m-1 K-1. The thermal conductivity in Sc2C(OH)2 is less anisotropic and lower compared to that in Sc2CF2. The room-temperature value in the armchair (zigzag) direction is determined to be 173 W m-1 K-1 (107 W m-1 K-1). Based on their excellent electron mobilities and high thermal

  15. The cryogenic wind tunnel concept for high Reynolds number testing

    NASA Technical Reports Server (NTRS)

    Kilgore, R. A.; Goodyer, M. J.; Adcock, J. B.; Davenport, E. E.

    1974-01-01

    Theoretical considerations indicate that cooling the wind-tunnel test gas to cryogenic temperatures will provide a large increase in Reynolds number with no increase in dynamic pressure while reducing the tunnel drive-power requirements. Studies were made to determine the expected variations of Reynolds number and other parameters over wide ranges of Mach number, pressure, and temperature, with due regard to avoiding liquefaction. Practical operational procedures were developed in a low-speed cryogenic tunnel. Aerodynamic experiments in the facility demonstrated the theoretically predicted variations in Reynolds number and drive power. The continuous-flow-fan-driven tunnel is shown to be particularly well suited to take full advantage of operating at cryogenic temperatures.

  16. Renal stone characterization using high resolution imaging mode on a photon counting detector CT system

    NASA Astrophysics Data System (ADS)

    Ferrero, A.; Gutjahr, R.; Henning, A.; Kappler, S.; Halaweish, A.; Abdurakhimova, D.; Peterson, Z.; Montoya, J.; Leng, S.; McCollough, C.

    2017-03-01

    In addition to the standard-resolution (SR) acquisition mode, a high-resolution (HR) mode is available on a research photon-counting-detector (PCD) whole-body CT system. In the HR mode each detector consists of a 2x2 array of 0.225 mm x 0.225 mm subpixel elements. This is in contrast to the SR mode that consists of a 4x4 array of the same subelements, and results in 0.25 mm isotropic resolution at iso-center for the HR mode. In this study, we quantified ex vivo the capabilities of the HR mode to characterize renal stones in terms of morphology and mineral composition. Forty pure stones - 10 uric acid (UA), 10 cystine (CYS), 10 calcium oxalate monohydrate (COM) and 10 apatite (APA) - and 14 mixed stones were placed in a 20 cm water phantom and scanned in HR mode, at radiation dose matched to that of routine dual-energy stone exams. Data from micro CT provided a reference for the quantification of morphology and mineral composition of the mixed stones. The area under the ROC curve was 1.0 for discriminating UA from CYS, 0.89 for CYS vs COM and 0.84 for COM vs APA. The root mean square error (RMSE) of the percent UA in mixed stones was 11.0% with a medium-sharp kernel and 15.6% with the sharpest kernel. The HR showed qualitatively accurate characterization of stone morphology relative to micro CT.

  17. Validation of the 4D NCAT simulation tools for use in high-resolution x-ray CT research

    NASA Astrophysics Data System (ADS)

    Segars, W. P.; Mahesh, Mahadevappa; Beck, T.; Frey, E. C.; Tsui, B. M. W.

    2005-04-01

    We validate the computer-based simulation tools developed in our laboratory for use in high-resolution CT research. The 4D NURBS-based cardiac-torso (NCAT) phantom was developed to provide a realistic and flexible model of the human anatomy and physiology. Unlike current phantoms in CT, the 4D NCAT has the advantage, due to its design, that its organ shapes can be changed to realistically model anatomical variations and patient motion. To efficiently simulate high-resolution CT images, we developed a unique analytic projection algorithm (including scatter and quantum noise) to accurately calculate projections directly from the surface definition of the phantom given parameters defining the CT scanner and geometry. The projection data are reconstructed into CT images using algorithms developed in our laboratory. The 4D NCAT phantom contains a level of detail that is close to impossible to produce in a physical test object. We, therefore, validate our CT simulation tools and methods through a series of direct comparisons with data obtained experimentally using existing, simple physical phantoms at different doses and using different x-ray energy spectra. In each case, the first-order simulations were found to produce comparable results (<12%). We reason that since the simulations produced equivalent results using simple test objects, they should be able to do the same in more anatomically realistic conditions. We conclude that, with the ability to provide realistic simulated CT image data close to that from actual patients, the simulation tools developed in this work will have applications in a broad range of CT imaging research.

  18. Optimizing synchrotron microCT for high-throughput phenotyping of zebrafish

    NASA Astrophysics Data System (ADS)

    La Rivière, Patrick J.; Clark, Darin; Rojek, Alexandra; Vargas, Phillip; Xiao, Xianghui; DeCarlo, Francesco; Kindlmann, Gordon; Cheng, Keith

    2010-09-01

    We are creating a state-of-the-art 2D and 3D imaging atlas of zebrafish development. The atlas employs both 2D histology slides and 3D benchtop and synchrotron micro CT results. Through this atlas, we expect to document normal and abnormal organogenesis, to reveal new levels of structural detail, and to advance image informatics as a form of systems biology. The zebrafish has become a widely used model organism in biological and biomedical research for studies of vertebrate development and gene function. In this work, we will report on efforts to optimize synchrotron microCT imaging parameters for zebrafish at crucial developmental stages. The aim of these studies is to establish protocols for high-throughput phenotyping of normal, mutant and diseased zebrafish. We have developed staining and embedding protocols using different heavy metal stains (osmium tetroxide and uranyl acetate) and different embedding media (Embed 812 and glycol methacrylate). We have explored the use of edge subtraction and multi-energy techniques for contrast enhancement and we have examined the use of different sample-detector distances with unstained samples to explore and optimize phase-contrast enhancement effects. We will report principally on our efforts to optimize energy choice for single- and multi-energy studies as well as our efforts to optimize the degree of phase contrast enhancement.

  19. Nonlinear histogram binning for quantitative analysis of lung tissue fibrosis in high-resolution CT data

    NASA Astrophysics Data System (ADS)

    Zavaletta, Vanessa A.; Bartholmai, Brian J.; Robb, Richard A.

    2007-03-01

    Diffuse lung diseases, such as idiopathic pulmonary fibrosis (IPF), can be characterized and quantified by analysis of volumetric high resolution CT scans of the lungs. These data sets typically have dimensions of 512 x 512 x 400. It is too subjective and labor intensive for a radiologist to analyze each slice and quantify regional abnormalities manually. Thus, computer aided techniques are necessary, particularly texture analysis techniques which classify various lung tissue types. Second and higher order statistics which relate the spatial variation of the intensity values are good discriminatory features for various textures. The intensity values in lung CT scans range between [-1024, 1024]. Calculation of second order statistics on this range is too computationally intensive so the data is typically binned between 16 or 32 gray levels. There are more effective ways of binning the gray level range to improve classification. An optimal and very efficient way to nonlinearly bin the histogram is to use a dynamic programming algorithm. The objective of this paper is to show that nonlinear binning using dynamic programming is computationally efficient and improves the discriminatory power of the second and higher order statistics for more accurate quantification of diffuse lung disease.

  20. Fractal analysis of high-resolution CT images as a tool for quantification of lung diseases

    SciTech Connect

    Uppaluri, R.; Mitsa, T.; Galvin, J.R.

    1995-12-31

    Fractal geometry is increasingly being used to model complex naturally occurring phenomena. There are two types of fractals in nature-geometric fractals and stochastic fractals. The pulmonary branching structure is a geometric fractal and the intensity of its grey scale image is a stochastic fractal. In this paper, the authors attempt to quantify the texture of CT lung images using properties of both types of fractals. A simple algorithm for detecting of abnormality in human lungs, based on 2-D and 3-D fractal dimensions, is presented. This method involves calculating the local fractal dimensions, based on intensities, in the 2-D slice to air edge enhancement. Following this, grey level thresholding is performed and a global fractal dimension, based on structure, for the entire data is estimated in 2-D and 3-D. High Resolution CT images of normal and abnormal lungs were analyzed. Preliminary results showed that classification of normal and abnormal images could be obtained based on the differences between their global fractal dimensions.

  1. High speed imaging of dynamic processes with a switched source x-ray CT system

    NASA Astrophysics Data System (ADS)

    Thompson, William M.; Lionheart, William R. B.; Morton, Edward J.; Cunningham, Mike; Luggar, Russell D.

    2015-05-01

    Conventional x-ray computed tomography (CT) scanners are limited in their scanning speed by the mechanical constraints of their rotating gantries and as such do not provide the necessary temporal resolution for imaging of fast-moving dynamic processes, such as moving fluid flows. The Real Time Tomography (RTT) system is a family of fast cone beam CT scanners which instead use multiple fixed discrete sources and complete rings of detectors in an offset geometry. We demonstrate the potential of this system for use in the imaging of such high speed dynamic processes and give results using simulated and real experimental data. The unusual scanning geometry results in some challenges in image reconstruction, which are overcome using algebraic iterative reconstruction techniques and explicit regularisation. Through the use of a simple temporal regularisation term and by optimising the source firing pattern, we show that temporal resolution of the system may be increased at the expense of spatial resolution, which may be advantageous in some situations. Results are given showing temporal resolution of approximately 500 µs with simulated data and 3 ms with real experimental data.

  2. Evaluating differential nuclear DNA yield rates and osteocyte numbers among human bone tissue types: A synchrotron radiation micro-CT approach.

    PubMed

    Andronowski, Janna M; Mundorff, Amy Z; Pratt, Isaac V; Davoren, Jon M; Cooper, David M L

    2017-05-01

    Molecular human identification has conventionally focused on DNA sampling from dense, weight-bearing cortical bone tissue, typically from femora or tibiae. A comparison of skeletal elements from three contemporary individuals demonstrated that elements with high quantities of cancellous bone yielded nuclear DNA at the highest rates, suggesting that preferentially sampling cortical bone may be suboptimal (Mundorff & Davoren, 2014). Despite these findings, the reason for the differential DNA yields between cortical and cancellous bone tissues remains unknown. The primary goal of this work is to ascertain whether differences in bone microstructure can be used to explain differential nuclear DNA yield among bone tissue types observed by Mundorff and Davoren (2014), with a focus on osteocytes and the three-dimensional (3D) quantification of their associated lacunae. Osteocytes and other bone cells are recognized to house DNA in bone tissue, thus examining the density of their lacunae may explain why nuclear DNA yield rates differ among bone tissue types. Lacunae were visualized and quantified using synchrotron radiation-based micro-Computed Tomographic imaging (SR micro-CT). Volumes of interest (VOIs) from cortical and cancellous bone tissues (n=129) were comparatively analyzed from the three skeletons sampled for Mundorff and Davoren's (2014) study. Analyses tested the primary hypothesis that the abundance and density of osteocytes (inferred from their lacunar spaces) vary between cortical and cancellous bone tissue types. Results demonstrated that osteocyte lacunar abundance and density vary between cortical and cancellous bone tissue types, with cortical bone VOIs containing a higher lacunar abundance and density. We found that the osteocyte lacunar density values are independent of nuclear DNA yield, suggesting an alternative explanation for the higher nuclear DNA yields from bones with greater quantities of cancellous bone tissue. The use of SR micro-CT allowed for

  3. Evaluation of four-dimensional computed tomography (4D-CT)-based pulmonary ventilation: The high correlation between 4D-CT ventilation and (81m)Kr-planar images was found.

    PubMed

    Kanai, Takayuki; Kadoya, Noriyuki; Ito, Kengo; Kishi, Kazuma; Dobashi, Suguru; Yamamoto, Takaya; Umezawa, Rei; Matsushita, Haruo; Takeda, Ken; Jingu, Keiichi

    2016-06-01

    To evaluate four-dimensional computed tomography (4D-CT)-derived pulmonary ventilation by comparing with (81m)Kr-gas ventilation (VRI). We also proposed two methods to improve the functional accuracy of 4D-CT ventilation images and evaluated these methods. Eleven lung cancer patients with 4D-CT and VRI were analyzed. Hounsfield unit-based (VHU) and a Jacobian-based (VJac) 4D-CT ventilation images were calculated. They were evaluated by voxel-by-voxel spearman's rank correlation coefficient (r) between 4D-CT ventilation and VRI images. After applying an averaging ventilation method and a slope calculating method, correlations were also calculated. 4D-CT ventilation showed the high correlation to VRI (r=0.875 with VHU). An averaging method brought significantly higher (p=0.012) correlations to nuclear medicine images with VHU. The improvement was not significant (p=0.619) with VJac. Slope calculating method improved the correlation with VHU and slightly worsened the correlation with VJac. The averaging method we proposed might be useful to improve 4D-CT ventilation images. We found good agreement between 4D-CT ventilation and nuclear medicine ventilation, indicating the high physiologic accuracy of 4D-CT ventilation. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  4. Prediction of Very High Reynolds Number Compressible Skin Friction

    NASA Technical Reports Server (NTRS)

    Carlson, John R.

    1998-01-01

    Flat plate skin friction calculations over a range of Mach numbers from 0.4 to 3.5 at Reynolds numbers from 16 million to 492 million using a Navier Stokes method with advanced turbulence modeling are compared with incompressible skin friction coefficient correlations. The semi-empirical correlation theories of van Driest; Cope; Winkler and Cha; and Sommer and Short T' are used to transform the predicted skin friction coefficients of solutions using two algebraic Reynolds stress turbulence models in the Navier-Stokes method PAB3D. In general, the predicted skin friction coefficients scaled well with each reference temperature theory though, overall the theory by Sommer and Short appeared to best collapse the predicted coefficients. At the lower Reynolds number 3 to 30 million, both the Girimaji and Shih, Zhu and Lumley turbulence models predicted skin-friction coefficients within 2% of the semi-empirical correlation skin friction coefficients. At the higher Reynolds numbers of 100 to 500 million, the turbulence models by Shih, Zhu and Lumley and Girimaji predicted coefficients that were 6% less and 10% greater, respectively, than the semi-empirical coefficients.

  5. High Reynolds number effects on a localized stratified turbulent flow

    NASA Astrophysics Data System (ADS)

    Zhou, Qi; Diamessis, Peter

    2015-11-01

    We report large-eddy simulations (LES) of the turbulent flow behind a sphere of diameter D translating at speed U in a linearly stratified Boussinesq fluid with buoyancy frequency N. These simulations are performed using a spectral-multidomain-penalty incompressible Navier-Stokes solver, at Reynolds numbers Re ≡ UD / ν ∈ { 5 ×103 , 105 , 4 ×105 } and Froude numbers Fr ≡ 2 U / (ND) ∈ { 4 , 16 , 64 } . An increasingly richer turbulent fine-structure is observed within the larger-scale quasi-horizontal vortices at later times. Turbulent transport of momentum is examined during the non-equilibrium (NEQ) regime of the turbulent life cycle, with an emphasis on the vertical transport that occurs after the establishment of local buoyancy control. The turbulent viscosities in both horizontal and vertical directions are estimated through the LES data; possible parameterization of the vertical turbulent viscosity with the buoyancy Reynolds number Reb = ɛ / (νN2) (or its easy-to-obtain surrogates) is discussed. The dynamical role of the buoyancy Reynolds number in choosing the vertical turbulence length scales is also investigated. ONR grant N00014-13-1-0665 (managed by Dr. R. Joslin); HPCMP Frontier Project FP-CFD-FY14-007 (P.I.: Dr. S. de Bruyn Kops).

  6. Numerical simulations of thermal convection at high Prandtl numbers

    NASA Astrophysics Data System (ADS)

    Silano, Gabriella

    2008-11-01

    Direct numerical simulations of thermal convection are conducted for a cylindrical cell of aspect ratio .5ex1-.1em/ -.15em.25ex2 . The Prandtl number (Pr) varies from 10^0 to 10^4 and the Rayleigh numbers (Ra) are moderate (10^5 < Ra < 10^9). This study is motivated by the fact that the role of the Prandtl number in convective heat transport is not yet fully understood. The three-dimensional behaviors of the temperature and velocity fields, of the viscous and thermal dissipation fields, and of the diffusive and convective heat fluxes are explored. In the ranges of Pr and Ra considered, we find steady, periodic and chaotic regimes, and large-scale structures which are more complex than the single recirculation cell filling the whole volume. Multiple flow structures are found to be associated with a given set of conditions. The multiple solutions seem to be more probable at higher Pr numbers and could explain the scatter in some data trends. In collaboration with Katepalli Raju Sreenivasan, The Abdus Salam International Centre for Theoretical Physics - Trieste, and Roberto Verzicco, DIM, Universitàdegli Studi di Roma Tor Vergata - Roma.

  7. High performance lung nodule detection schemes in CT using local and global information

    PubMed Central

    Guo, Wei; Li, Qiang

    2012-01-01

    Purpose: A key issue in current computer-aided diagnostic (CAD) schemes for nodule detection in CT is the large number of false positives, because current schemes use only global three-dimensional (3D) information to detect nodules and discard useful local two-dimensional (2D) information. Thus, the authors integrated local and global information to markedly improve the performance levels of CAD schemes. Methods: Our database was obtained from the standard CT lung nodule database created by the Lung Image Database Consortium (LIDC). It consisted of 85 CT scans with 111 nodules of 3 mm or larger in diameter. The 111 nodules were confirmed by at least two of the four radiologists participated in the LIDC. Twenty-six nodules were missed by two of the four radiologists and were thus very difficult to detect. The authors developed five CAD schemes for nodule detection in CT using global 3D information (3D scheme), local 2D information (2D scheme), and both local and global information (2D + 3D scheme, 2D − 3D scheme, and 3D − 2D scheme). The 3D scheme, which was developed previously, used only global 3D information and discarded local 2D information, as other CAD schemes did. The 2D scheme used a uniform viewpoint reformation technique to decompose a 3D nodule candidate into a set of 2D reformatted images generated from representative viewpoints, and selected and used “effective” 2D reformatted images to remove false positives. The 2D + 3D scheme, 2D − 3D scheme, and 3D − 2D scheme used complementary local and global information in different ways to further improve the performance of lung nodule detection. The authors employed a leave-one-scan-out testing method for evaluation of the performance levels of the five CAD schemes. Results: At the sensitivities of 85%, 80%, and 75%, the existing 3D scheme reported 17.3, 7.4, and 2.8 false positives per scan, respectively; the 2D scheme improved the detection performance and reduced the numbers of false positives

  8. High-Resolution SPECT-CT/MR Molecular Imaging of Angiogenesis in the Vx2 Model

    PubMed Central

    Lijowski, Michal; Caruthers, Shelton; Hu, Grace; Zhang, Huiying; Scott, Michael J.; Williams, Todd; Erpelding, Todd; Schmieder, Anne H.; Kiefer, Garry; Gulyas, Gyongyi; Athey, Phillip S.; Gaffney, Patrick J.; Wickline, Samuel A.; Lanza, Gregory M.

    2009-01-01

    Background The use of antiangiogenic therapy in conjunction with traditional chemotherapy is becoming increasingly in cancer management, but the optimal benefit of these targeted pharmaceuticals has been limited to a subset of the population treated. Improved imaging probes that permit sensitive detection and high-resolution characterization of tumor angiogenesis could improve patient risk-benefit stratification. Objectives The overarching objective of these experiments was to develop a dual modality αvβ3-targeted nanoparticle molecular imaging agent that affords sensitive nuclear detection in conjunction with high-resolution MR characterization of tumor angiogenesis. Materials and Methods In part 1, New Zealand white rabbits (n = 21) bearing 14d Vx2 tumor received either αvβ3-targeted 99mTc nanoparticles at doses of 11, 22, or 44 MBq/kg, nontargeted 99mTc nanoparticles at 22 MBq/kg, or αvβ3-targeted 99mTc nanoparticles (22 MBq/kg) competitively inhibited with unlabeled αvβ3-nanoparticles. All animals were imaged dynamically over 2 hours with a planar camera using a pinhole collimator. In part 2, the effectiveness of αvβ3-targeted 99mTc nanoparticles in the Vx2 rabbit model was demonstrated using clinical SPECT-CT imaging techniques. Next, MR functionality was incorporated into αvβ3-targeted 99mTc nanoparticles by inclusion of lipophilic gadolinium chelates into the outer phospholipid layer, and the concept of high sensitivity – high-resolution detection and characterization of tumor angiogenesis was shown using sequential SPECT-CT and MR molecular imaging with 3D neovascular mapping. Results αvβ3-Targeted 99mTc nanoparticles at 22 MBq/kg produced the highest tumor-to-muscle contrast ratio (8.56 ± 0.13, TMR) versus the 11MBq/kg (7.32 ± 0.12) and 44 MBq/kg (6.55 ± 0.07) doses, (P < 0.05). TMR of nontargeted particles at 22.2 MBq/kg (5.48 ± 0.09) was less (P < 0.05) than the equivalent dosage of αvβ3-targeted 99mTc nanoparticles. Competitively

  9. Multiplier less high-speed squaring circuit for binary numbers

    NASA Astrophysics Data System (ADS)

    Sethi, Kabiraj; Panda, Rutuparna

    2015-03-01

    The squaring operation is important in many applications in signal processing, cryptography etc. In general, squaring circuits reported in the literature use fast multipliers. A novel idea of a squaring circuit without using multipliers is proposed in this paper. Ancient Indian method used for squaring decimal numbers is extended here for binary numbers. The key to our success is that no multiplier is used. Instead, one squaring circuit is used. The hardware architecture of the proposed squaring circuit is presented. The design is coded in VHDL and synthesised and simulated in Xilinx ISE Design Suite 10.1 (Xilinx Inc., San Jose, CA, USA). It is implemented in Xilinx Vertex 4vls15sf363-12 device (Xilinx Inc.). The results in terms of time delay and area is compared with both modified Booth's algorithm and squaring circuit using Vedic multipliers. Our proposed squaring circuit seems to have better performance in terms of both speed and area.

  10. Quasi-static magnetohydrodynamic turbulence at high Reynolds number

    NASA Astrophysics Data System (ADS)

    Delache, A.; Favier, B.; Godeferd, F. S.; Cambon, C.; Bos, W. J. T.

    2011-12-01

    We analyse the anisotropy of turbulence in an electrically conducting fluid submitted to a uniform magnetic field, for low magnetic Reynolds number, using the quasi-static approximation. In the linear limit, the kinetic energy of velocity components normal to the magnetic field decays faster than the kinetic energy of the component along the magnetic field (Moffatt, 1967). However, numerous numerical studies predict a different behaviour, wherein the final state is characterised by dominant horizontal energy. We investigate the corresponding nonlinear phenomenon using Direct Numerical Simulations (DNS) and spectral closures based on Eddy Damping Quasi-Normal Markovian (EDQNM) models. The initial temporal evolution of the decaying flow indicates that the turbulence is very similar to the so-called "two-and-a-half-dimensional" flow (Montgomery & Turner, 1982) which explains the observations in numerical studies. EDQNM models confirm this statement at higher Reynolds number.

  11. Vorticity spectra in high Reynolds number anisotropic turbulence

    NASA Astrophysics Data System (ADS)

    Morris, Scott C.; Foss, John F.

    2005-08-01

    Assuming a turbulent flow to be homogeneous and isotropic allows for significant theoretical simplification in the description of its motions. The validity of these assumptions, first put forth by Kolmogorov [A. N. Kolmogorov, "The local structure of turbulence in incompressible viscous fluids for very large Reynolds numbers," C. R. Acad. Sci. URSS 30, 301 (1941)], has been the subject of considerable analytical development and extensive research as they are applied to actual flows. The present investigation describes the one-dimensional vorticity spectra of two flow fields: a single stream shear layer and the near surface region of an atmospheric boundary layer. Both flow fields exhibit a power-law region with a slope of -1 in the one-dimensional spectra of the spanwise component of vorticity in the same wave-number range for which the velocity spectra indicated the isotropic behavior. This is in strong disagreement with the isotropic prediction, which does not exhibit a power-law behavior.

  12. The riddle of high-energy baryon number violation

    SciTech Connect

    Mattis, M.P.

    1991-09-01

    The exciting possibility that anomalous baryon and lepton number violation might be observable at the next generation of supercolliders is suggested by an instanton calculation due to Ringwald and Espinosa. In these Lectures, the current controversial status of these claims is discussed, and several new technologies designed to analyze this question are reviewed. These technologies should contribute more generally to our understanding of weakly- coupled field theories in the nonperturbative regime where both energies and multiplicities are very large. 61 refs., 35 figs.

  13. Local anisotropy in strained turbulence at high Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Durbin, P. A.; Speziale, C. G.

    1991-01-01

    It is shown that the hypothesis of local isotropy is implausible in the presence of significant mean rates of strain. In fact, it appears that in uniform shear flow near equilibrium, local isotropy can never constitute a systematic approximation, even in the limit of infinite Reynolds number. An estimate of the level of mean strain rate for which local isotropy is formally a good approximation is provided.

  14. Early postoperative 18F-FDG PET/CT in high-risk stage III colorectal cancer.

    PubMed

    Wasserberg, Nir; Purim, Ofer; Bard, Vyacheslav; Kundel, Yulia; Gordon, Noa; Groshar, David; Goldberg, Natalia; Kashtan, Hanoch; Sulkes, Aaron; Brenner, Baruch

    2015-04-01

    PET/CT may contribute to staging modification in different phases of colorectal cancer (CRC) management. However, it is not routinely indicated for stage III CRC. This study sought to determine the role of early postoperative PET/CT in patients with high-risk stage III CRC. The tumor registry of a tertiary medical center was searched (2004-2011) for all patients with stage III CRC who underwent early postoperative PET/CT because of the presence of high-risk factors for systemic disease. Demographic and clinicopathological characteristics were compared between patients found/not found to have metastatic disease. The cohort included 91 patients with a median age of 67 years (range, 29-90 years). Pathological FDG uptake was observed in 38 (41%). Of these, 14 (15% of the whole cohort) were upstaged with alteration of their treatment protocol, 10 (11%) had local postoperative changes, and 14 (15%) had false-positive findings. The sensitivity and specificity of PET/CT for detecting metastatic disease were 100% and 69%, respectively. Elevated postoperative carcinoembryonic antigen and CA-19.9 levels correlated with a positive PET/CT (P = 0.05 and P = 0.03, respectively). The median follow-up time was 34 months (range, 4-85 months). The estimated 5-year survival rate was significantly higher in patients with a negative than a positive scan (70% vs 42%, P < 0.0006). Findings on early postoperative PET/CT may influence staging and treatment in 15% of selected patients with high-risk stage III CRC. Postoperative levels of carcinoembryonic antigen and CA-19.9 may serve as indications for PET/CT scanning in this setting. Prospective validation is warranted.

  15. Cardiac imaging with a high-speed Cine-CT Scanner: preliminary results

    SciTech Connect

    Lipton, M.J.; Higgins, C.B.; Farmer, D.; Boyd, D.P.

    1984-09-01

    CT scans were obtained with a Cine-CT Scanner that uses a rapidly moving focused electron beam. The 50-msec CT scans were obtained at two transverse levels simultaneously through the hearts of a series of four normal dogs and six patients, four with coronary artery disease and two with hypertrophic cardiomyopathy. Two scanning mode options were chosen. Myocardial wall thickening and motion were studied by obtaining ten 50-msec CT exposures during one heartbeat within less than one second (Cine-CT mode). Regional myocardial blood flow was assessed by obtaining approximately 20 scans at the same level of the left ventricle. These initial studies show the feasibility of defining regional and global myocardial contraction using the Cine-CT mode, and the considerable potential for measuring regional myocardial perfusion using the flow (dynamic) mode.

  16. Automated method for relating regional pulmonary structure and function: integration of dynamic multislice CT and thin-slice high-resolution CT

    NASA Astrophysics Data System (ADS)

    Tajik, Jehangir K.; Kugelmass, Steven D.; Hoffman, Eric A.

    1993-07-01

    We have developed a method utilizing x-ray CT for relating pulmonary perfusion to global and regional anatomy, allowing for detailed study of structure to function relationships. A thick slice, high temporal resolution mode is used to follow a bolus contrast agent for blood flow evaluation and is fused with a high spatial resolution, thin slice mode to obtain structure- function detail. To aid analysis of blood flow, we have developed a software module, for our image analysis package (VIDA), to produce the combined structure-function image. Color coded images representing blood flow, mean transit time, regional tissue content, regional blood volume, regional air content, etc. are generated and imbedded in the high resolution volume image. A text file containing these values along with a voxel's 3-D coordinates is also generated. User input can be minimized to identifying the location of the pulmonary artery from which the input function to a blood flow model is derived. Any flow model utilizing one input and one output function can be easily added to a user selectable list. We present examples from our physiologic based research findings to demonstrate the strengths of combining dynamic CT and HRCT relative to other scanning modalities to uniquely characterize pulmonary normal and pathophysiology.

  17. U.S. Opioid Prescriptions Fall, But Numbers Still High

    MedlinePlus

    ... many people being provided lengthy prescriptions of the narcotics at high doses. "We're still seeing too ... Human Services. More Health News on Health Disparities Opioid Abuse and Addiction Recent Health News Related MedlinePlus Health Topics Health ...

  18. Detecting metastasis of gastric carcinoma using high-resolution micro-CT system: in vivo small animal study

    NASA Astrophysics Data System (ADS)

    Liu, Junting; Tian, Jie; Liang, Jimin; Li, Xiangsi; Yang, Xiang; Chen, Xiaofeng; Chen, Yi; Zhou, Yuanfang; Wang, Xiaorui

    2011-03-01

    Immunocytochemical and immunofluorescence staining are used for identifying the characteristics of metastasis in traditional ways. Micro-computed tomography (micro-CT) is a useful tool for monitoring and longitudinal imaging of tumor in small animal in vivo. In present study, we evaluated the feasibility of the detection for metastasis of gastric carcinoma by high-resolution micro-CT system with omnipaque accumulative enhancement method in the organs. Firstly, a high-resolution micro-CT ZKKS-MCT-sharp micro-CT was developed by our research group and Guangzhou Zhongke Kaisheng Medical Technology Co., Ltd. Secondly, several gastric carcinoma models were established through inoculating 2x106 BGC-823 gastric carcinoma cells subcutaneously. Thirdly, micro-CT scanning was performed after accumulative enhancement method of intraperitoneal injection of omnipaque contrast agent containing 360 mg iodine with a concentration of 350 mg I/ml. Finally, we obtained high-resolution anatomical information of the metastasis in vivo in a BALB/c NuNu nude mouse, the 3D tumor architecture is revealed in exquisite detail at about 35 μm spatial resolution. In addition, the accurate shape and volume of the micrometastasis as small as 0.78 mm3 can be calculated with our software. Overall, our data suggest that this imaging approach and system could be used to enhance the understanding of tumor proliferation, metastasis and could be the basis for evaluating anti-tumor therapies.

  19. Turbulent Boundary Layer in High Rayleigh Number Convection in Air

    NASA Astrophysics Data System (ADS)

    du Puits, Ronald; Li, Ling; Resagk, Christian; Thess, André; Willert, Christian

    2014-03-01

    Flow visualizations and particle image velocimetry measurements in the boundary layer of a Rayleigh-Bénard experiment are presented for the Rayleigh number Ra =1.4×1010. Our visualizations indicate that the appearance of the flow structures is similar to ordinary (isothermal) turbulent boundary layers. Our particle image velocimetry measurements show that vorticity with both positive and negative sign is generated and that the smallest flow structures are 1 order of magnitude smaller than the boundary layer thickness. Additional local measurements using laser Doppler velocimetry yield turbulence intensities up to I=0.4 as in turbulent atmospheric boundary layers. From our observations, we conclude that the convective boundary layer becomes turbulent locally and temporarily although its Reynolds number Re ≈200 is considerably smaller than the value 420 underlying existing phenomenological theories. We think that, in turbulent Rayleigh-Bénard convection, the transition of the boundary layer towards turbulence depends on subtle details of the flow field and is therefore not universal.

  20. High-Reynolds Number Taylor-Couette Turbulence

    NASA Astrophysics Data System (ADS)

    Grossmann, Siegfried; Lohse, Detlef; Sun, Chao

    2016-01-01

    Taylor-Couette flow, the flow between two coaxial co- or counter-rotating cylinders, is one of the paradigmatic systems in the physics of fluids. The (dimensionless) control parameters are the Reynolds numbers of the inner and outer cylinders, the ratio of the cylinder radii, and the aspect ratio. One key response of the system is the torque required to retain constant angular velocities, which can be connected to the angular velocity transport through the gap. Whereas the low-Reynolds number regime was well explored in the 1980s and 1990s of the past century, in the fully turbulent regime major research activity developed only in the past decade. In this article, we review this recent progress in our understanding of fully developed Taylor-Couette turbulence from the experimental, numerical, and theoretical points of view. We focus on the parameter dependence of the global torque and on the local flow organization, including velocity profiles and boundary layers. Next, we discuss transitions between different (turbulent) flow states. We also elaborate on the relevance of this system for astrophysical disks (quasi-Keplerian flows). The review ends with a list of challenges for future research on turbulent Taylor-Couette flow.

  1. Design of a High-Reynolds Number Recirculating Water Tunnel

    NASA Astrophysics Data System (ADS)

    Daniel, Libin; Elbing, Brian

    2014-11-01

    An experimental fluid mechanics laboratory focused on turbulent boundary layers, drag reduction techniques, multiphase flows and fluid-structure interactions has recently been established at Oklahoma State University. This laboratory has three primary components; (1) a recirculating water tunnel, (2) a multiphase pipe flow loop, and (3) a multi-scale flow visualization system. The design of the water tunnel is the focus of this talk. The criteria used for the water tunnel design was that it had to produce a momentum-thickness based Reynolds number in excess of 104, negligible flow acceleration due to boundary layer growth, maximize optical access for use of the flow visualization system, and minimize inlet flow non-uniformity. This Reynolds number was targeted to bridge the gap between typical university/commercial water tunnels (103) and the world's largest water tunnel facilities (105) . These objectives were achieved with a 152 mm (6-inch) square test section that is 1 m long and has a maximum flow speed of 10 m/s. The flow non-uniformity was mitigated with the use of a tandem honeycomb configuration, a settling chamber and an 8.5:1 contraction. The design process that produced this final design will be presented along with its current status.

  2. Turbulent boundary layer in high Rayleigh number convection in air.

    PubMed

    du Puits, Ronald; Li, Ling; Resagk, Christian; Thess, André; Willert, Christian

    2014-03-28

    Flow visualizations and particle image velocimetry measurements in the boundary layer of a Rayleigh-Bénard experiment are presented for the Rayleigh number Ra=1.4×1010. Our visualizations indicate that the appearance of the flow structures is similar to ordinary (isothermal) turbulent boundary layers. Our particle image velocimetry measurements show that vorticity with both positive and negative sign is generated and that the smallest flow structures are 1 order of magnitude smaller than the boundary layer thickness. Additional local measurements using laser Doppler velocimetry yield turbulence intensities up to I=0.4 as in turbulent atmospheric boundary layers. From our observations, we conclude that the convective boundary layer becomes turbulent locally and temporarily although its Reynolds number Re≈200 is considerably smaller than the value 420 underlying existing phenomenological theories. We think that, in turbulent Rayleigh-Bénard convection, the transition of the boundary layer towards turbulence depends on subtle details of the flow field and is therefore not universal.

  3. High Reynolds number rough-wall turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    Squire, Dougal; Morrill-Winter, Caleb; Schultz, Michael; Hutchins, Nicholas; Klewicki, Joseph; Marusic, Ivan

    2015-11-01

    In his review of turbulent flows over rough-walls, Jimenez (2004) concludes that there are gaps in the current database of relevant experiments. The author calls for measurements in which δ / k and k+ are both large--low blockage, fully-rough flow--and where δ / k is large and k+ is small--low blockage, transitionally-rough flow--to help clarify ongoing questions regarding the physics of rough-wall-bounded flows. The present contribution details results from a large set of measurements carried out above sandpaper in the Melbourne Wind Tunnel. The campaign spans 45 rough-wall measurements using single and multiple-wire hot-wire anemometry sensors and particle image velocimetry. A floating element drag balance is employed to obtain the rough-wall skin friction force. The data span 20 number range of 2800 < Reτ < 30000 , targeting areas in the parameter space identified by Jimenez (2004) as being sparsely populated by pre-existing data. Smooth-wall data are also obtained across a similar Reynolds number range to enable comparison of smooth- and rough-wall structural features. Generally, the data indicate similarity in the outer-layer of smooth- and fully-rough wall-bounded flows.

  4. Direct microCT imaging of non-mineralized connective tissues at high resolution.

    PubMed

    Naveh, Gili R S; Brumfeld, Vlad; Dean, Mason; Shahar, Ron; Weiner, Steve

    2014-01-01

    The 3D imaging of soft tissues in their native state is challenging, especially when high resolution is required. An X-ray-based microCT is, to date, the best choice for high resolution 3D imaging of soft tissues. However, since X-ray attenuation of soft tissues is very low, contrasting enhancement using different staining materials is needed. The staining procedure, which also usually involves tissue fixation, causes unwanted and to some extent unknown tissue alterations. Here, we demonstrate that a method that enables 3D imaging of soft tissues without fixing and staining using an X-ray-based bench-top microCT can be applied to a variety of different tissues. With the sample mounted in a custom-made loading device inside a humidity chamber, we obtained soft tissue contrast and generated 3D images of fresh, soft tissues with a resolution of 1 micron voxel size. We identified three critical conditions which make it possible to image soft tissues: humidified environment, mechanical stabilization of the sample and phase enhancement. We demonstrate the capability of the technique using different specimens: an intervertebral disc, the non-mineralized growth plate, stingray tessellated radials (calcified cartilage) and the collagenous network of the periodontal ligament. Since the scanned specimen is fresh an interesting advantage of this technique is the ability to scan a specimen under load and track the changes of the different structures. This method offers a unique opportunity for obtaining valuable insights into 3D structure-function relationships of soft tissues.

  5. Aeroacoustic Data for a High Reynolds Number Axisymmetric Subsonic Jet

    NASA Technical Reports Server (NTRS)

    Ponton, Michael K.; Ukeiley, Lawrence S.; Lee, Sang W.

    1999-01-01

    The near field fluctuating pressure and aerodynamic mean flow characteristics of a cold subsonic jet issuing from a contoured convergent nozzle are presented. The data are presented for nozzle exit Mach numbers of 0.30, 0.60, and 0.85 at a constant jet stagnation temperature of 104 F. The fluctuating pressure measurements were acquired via linear and semi-circular microphone arrays and the presented results include plots of narrowband spectra, contour maps, streamwise/azimuthal spatial correlations for zero time delay, and cross-spectra of the azimuthal correlations. A pitot probe was used to characterize the mean flow velocity by assuming the subsonic flow to be pressure-balanced with the ambient field into which it exhausts. Presented are mean flow profiles and the momentum thickness of the free shear layer as a function of streamwise position.

  6. Convection in an ideal gas at high Rayleigh numbers.

    PubMed

    Tilgner, A

    2011-08-01

    Numerical simulations of convection in a layer filled with ideal gas are presented. The control parameters are chosen such that there is a significant variation of density of the gas in going from the bottom to the top of the layer. The relations between the Rayleigh, Peclet, and Nusselt numbers depend on the density stratification. It is proposed to use a data reduction which accounts for the variable density by introducing into the scaling laws an effective density. The relevant density is the geometric mean of the maximum and minimum densities in the layer. A good fit to the data is then obtained with power laws with the same exponent as for fluids in the Boussinesq limit. Two relations connect the top and bottom boundary layers: The kinetic energy densities computed from free fall velocities are equal at the top and bottom, and the products of free fall velocities and maximum horizontal velocities are equal for both boundaries.

  7. Binary tree models of high-Reynolds-number turbulence

    NASA Astrophysics Data System (ADS)

    Aurell, Erik; Dormy, Emmanuel; Frick, Peter

    1997-08-01

    We consider hierarchical models for turbulence, that are simple generalizations of the standard Gledzer-Ohkitani-Yamada shell models (E. B. Gledzer, Dokl, Akad. Nauk SSSR 209, 5 (1973) [Sov. Phys. Dokl. 18, 216 (1973)]; M. Yamada and K. Ohkitani, J. Phys. Soc. Jpn. 56, 4210 (1987)). The density of degrees of freedom is constant in wave-number space. Looking only at this behavior and at the quadratic invariants in the inviscid unforced limit, the models can be thought of as systems living naturally in one spatial dimension, but being qualitatively similar to hydrodynamics in two (2D) and three dimensions. We investigated cascade phenomena and intermittency in the different cases. We observed and studied a forward cascade of enstrophy in the 2D case.

  8. Numerical simulation of high Reynolds number bubble motion

    SciTech Connect

    McLaughlin, J.B.

    1995-12-31

    This paper presents the results of numerical simulations of bubble motion. All the results are for single bubbles in unbounded fluids. The liquid phase is quiescent except for the motion created by the bubble, which is axisymmetric. The main focus of the paper is on bubbles that are of order 1 mm in diameter in water. Of particular interest is the effect of surfactant molecules on bubble motion. Results for the {open_quotes}insoluble surfactant{close_quotes} model will be presented. These results extend research by other investigators to finite Reynolds numbers. The results indicate that, by assuming complete coverage of the bubble surface, one obtains good agreement with experimental observations of bubble motion in tap water. The effect of surfactant concentration on the separation angle is discussed.

  9. Comparison of the effects of salmon calcitonin (sCT) and calcitonin gene-related peptide (CGRP) in a number of in vivo and in vitro tests

    SciTech Connect

    Welch, S.P.; Brase, D.; Cooper, C.; Dewey, W.L.

    1986-03-05

    sCT and CGRP have been shown previously to have multiple activities in the central nervous system (CNS). Recent work has shown that CGRP (15 ..mu..g) intraventricularly (IVT) produces a naloxone reversible 37% inhibition in the p-phenylquinone test (PPQ) accompanied by severe diarrhea. The ED50 of sCT in the PPQ test is 362 ng and this effect is not reversed totally by naloxone. The onset of CGRP is more rapid than that of sCT. sCT and CGRP (10/sup -6/M) both produce naloxone reversible inhibition of the electrically stimulated guinea pig ileum (GPI) (25% and 50% respectively). Both sCT and CGRP (10/sup -6/ M) produce contracture (15% and 40% respectively) of the non-stimulated GPI that is not blocked by atropine. Both sCT and CGRP block the naloxone-induced contracture of the morphine (MS04) dependent ilea (29% and 68% respectively). Both sCT and CGRP produce biphasic shifts in the MS04 acetylcholine dose-effect curves in the stimulated and nonstimulated GPI, respectively. Neither sCT nor CGRP (10/sup -9/ to 10/sup -4/ M) displaces /sup 3/H-naloxone binding to mouse brain membranes. Both sCT and CGRP may produce their effects by modulation of CA/sup +2/ fluxes in the CNS and GPI.

  10. Treatment response evaluation with (18)F-FDG PET/CT and (18)F-NaF PET/CT in multiple myeloma patients undergoing high-dose chemotherapy and autologous stem cell transplantation.

    PubMed

    Sachpekidis, Christos; Hillengass, J; Goldschmidt, H; Wagner, B; Haberkorn, U; Kopka, K; Dimitrakopoulou-Strauss, A

    2017-01-01

    The aim of this study was to assess the combined use of the radiotracers (18)F-FDG and (18)F-NaF in treatment response evaluation of a group of multiple myeloma (MM) patients undergoing high-dose chemotherapy (HDT) followed by autologous stem cell transplantation (ASCT) by means of static (whole-body) and dynamic PET/CT (dPET/CT). Thirty-four patients with primary, previously untreated MM scheduled for treatment with HDT followed by ASCT were enrolled in the study. All patients underwent PET/CT scanning with (18)F-FDG and (18)F-NaF before and after therapy. Treatment response by means of PET/CT was assessed according to the European Organization for Research and Treatment of Cancer (EORTC) 1999 criteria. The evaluation of dPET/CT studies was based on qualitative evaluation, semi-quantitative (SUV) calculation, and quantitative analysis based on two-tissue compartment modelling and a non-compartmental approach leading to the extraction of fractal dimension (FD). An analysis was possible in 29 patients: three with clinical complete response (CR) and 26 with non-CR (13 patients near complete response-nCR, four patients very good partial response-VGPR, nine patients partial response-PR). After treatment, (18)F-FDG PET/CT was negative in 14/29 patients and positive in 15/29 patients, showing a sensitivity of 57.5 % and a specificity of 100 %. According to the EORTC 1999 criteria, (18)F-FDG PET/CT-based treatment response revealed CR in 14 patients ((18)F-FDG PET/CT CR), PR in 11 patients ((18)F-FDG PET/CT PR) and progressive disease in four patients ((18)F-FDG PET/CT PD). In terms of (18)F-NaF PET/CT, 4/29 patients (13.8 %) had a negative baseline scan, thus failed to depict MM. Regarding the patients for which a direct lesion-to-lesion comparison was feasible, (18)F-NaF PET/CT depicted 56 of the 129 (18)F-FDG positive lesions (43 %). Follow-up (18)F-NaF PET/CT showed persistence of 81.5 % of the baseline (18)F-NaF positive MM lesions after treatment, despite the

  11. High-fidelity artifact correction for cone-beam CT imaging of the brain

    NASA Astrophysics Data System (ADS)

    Sisniega, A.; Zbijewski, W.; Xu, J.; Dang, H.; Stayman, J. W.; Yorkston, J.; Aygun, N.; Koliatsos, V.; Siewerdsen, J. H.

    2015-02-01

    CT is the frontline imaging modality for diagnosis of acute traumatic brain injury (TBI), involving the detection of fresh blood in the brain (contrast of 30-50 HU, detail size down to 1 mm) in a non-contrast-enhanced exam. A dedicated point-of-care imaging system based on cone-beam CT (CBCT) could benefit early detection of TBI and improve direction to appropriate therapy. However, flat-panel detector (FPD) CBCT is challenged by artifacts that degrade contrast resolution and limit application in soft-tissue imaging. We present and evaluate a fairly comprehensive framework for artifact correction to enable soft-tissue brain imaging with FPD CBCT. The framework includes a fast Monte Carlo (MC)-based scatter estimation method complemented by corrections for detector lag, veiling glare, and beam hardening. The fast MC scatter estimation combines GPU acceleration, variance reduction, and simulation with a low number of photon histories and reduced number of projection angles (sparse MC) augmented by kernel de-noising to yield a runtime of ~4 min per scan. Scatter correction is combined with two-pass beam hardening correction. Detector lag correction is based on temporal deconvolution of the measured lag response function. The effects of detector veiling glare are reduced by deconvolution of the glare response function representing the long range tails of the detector point-spread function. The performance of the correction framework is quantified in experiments using a realistic head phantom on a testbench for FPD CBCT. Uncorrected reconstructions were non-diagnostic for soft-tissue imaging tasks in the brain. After processing with the artifact correction framework, image uniformity was substantially improved, and artifacts were reduced to a level that enabled visualization of ~3 mm simulated bleeds throughout the brain. Non-uniformity (cupping) was reduced by a factor of 5, and contrast of simulated bleeds was improved from ~7 to 49.7 HU, in good agreement

  12. High Rayleigh Number 3d Spherical Mantle Convection Models

    NASA Astrophysics Data System (ADS)

    Davies, J. H.

    2003-04-01

    features. The convection model was then advanced to a circulation model by driving the upper surface by a plate velocity model for the past 119Myr. At this Rayleigh number the Farallon and Tethys fast seismic anomalies are not as well fit by cold anomalies as they were by lower Rayleigh number calculations of Bunge et al. (Phil. Trans. R. Soc. London, 360, 2545-2567, 2002). Other cases with phase changes and increased bottom heating will also be reported. Future work needs to involve temperature dependent viscosity and tracking of composition. The limited results to date give us encouragement to continue pursuing this class of model.

  13. Laboratory Experiments of High Mach Number Raditaive Jets

    NASA Astrophysics Data System (ADS)

    Frank, A.; Gardiner, T.; Blackman, E.; Lebedev, S.; Chittenden, J.; Beg, S.; Bland, S.; Ciardi, A.; Ampleford, D.; Hughes, S.; Haines, M. G.

    2001-05-01

    We present astrophysically relevent experiments on the generation of a highly supersonic plasma jet by a convergent plasma flow. The flow is produced by electrodynamic acceleration of plasma in a conical array of fine metallic wires (a modification of the wire array Z-pinch). Stagnation of the plasma flow on the axis of symmetry forms a standing conical shock, which effectively collimates the flow in the axial direction. This scenario is essentially similar to that discussed by Cantó et al 1988 as a possible, purely hydrodynamic mechanism of jet formation in young stellar objects. Experiments using different materials (Al, Fe and W) show that a highly supersonic (M 20) and a well-collimated jet is generated when the radiative cooling rate of the plasma is significant. The interaction of this jet with a plasma target could be used for scaled laboratory astrophysical experiments on hydrodynamic instabilities in decelerated plasma flow.

  14. 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.

  15. Automated Classification of Usual Interstitial Pneumonia using Regional Volumetric Texture Analysis in High-Resolution CT

    PubMed Central

    Depeursinge, Adrien; Chin, Anne S.; Leung, Ann N.; Terrone, Donato; Bristow, Michael; Rosen, Glenn; Rubin, Daniel L.

    2014-01-01

    Objectives We propose a novel computational approach for the automated classification of classic versus atypical usual interstitial pneumonia (UIP). Materials and Methods 33 patients with UIP were enrolled in this study. They were classified as classic versus atypical UIP by a consensus of two thoracic radiologists with more than 15 years of experience using the American Thoracic Society evidence–based guidelines for CT diagnosis of UIP. Two cardiothoracic fellows with one year of subspecialty training provided independent readings. The system is based on regional characterization of the morphological tissue properties of lung using volumetric texture analysis of multiple detector CT images. A simple digital atlas with 36 lung subregions is used to locate texture properties, from which the responses of multi-directional Riesz wavelets are obtained. Machine learning is used to aggregate and to map the regional texture attributes to a simple score that can be used to stratify patients with UIP into classic and atypical subtypes. Results We compared the predictions based on regional volumetric texture analysis with the ground truth established by expert consensus. The area under the receiver operating characteristic curve of the proposed score was estimated to be 0.81 using a leave-one-patient-out cross-validation, with high specificity for classic UIP. The performance of our automated method was found to be similar to that of the two fellows and to the agreement between experienced chest radiologists reported in the literature. However, the errors of our method and the fellows occurred on different cases, which suggests that combining human and computerized evaluations may be synergistic. Conclusions Our results are encouraging and suggest that an automated system may be useful in routine clinical practice as a diagnostic aid for identifying patients with complex lung disease such as classic UIP, obviating the need for invasive surgical lung biopsy and its

  16. A complete CAD system for pulmonary nodule detection in high resolution CT images

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangwei; McLennan, Geoffrey; Hoffman, Eric A.; Sonka, Milan

    2005-04-01

    The purpose of this study is to develop a computer-aided diagnosis (CAD) system to detect small-sized (from 2mm to 10mm) pulmonary nodules in high resolution helical CT scans. A new CAD system is proposed to locate both juxtapleural nodules and non-pleural nodules. Isotropic resampling and lung segmentation are performed as preprocessing steps. Morphological closing was utilized to smooth the lung contours to include the indented possible juxtapleural locations, thresholding and 3D component analysis were used to obtain 3D volumetric nodule candidates; furthermore, gray level and geometric features were extracted, and analyzed using linear discriminant analysis (LDA) classifier. Leave one case out method was used to evaluate the LDA. To deal with non-pleural nodules, a discrete-time cellular neural network (DTCNN) based on local shape features was developed. This scheme employed the local shape property to perform voxel classification. The shape index feature successfully captured the local shape difference between nodules and non-nodules, especially vessels. To tailor it for lung nodule detection, this DTCNN was trained using genetic algorithms (GAs) to derive the shape index variation pattern of nodules. Nonoverlapping training and testing sets were utilized in the non-pleural nodule detection. 19 clinical thoracic CT cases involving a total of 4838 sectional images were used in this work. The juxtapleural nodule detection method was able to obtain sensitivity 81.25% with an average of 8.29 FPs per case. The non-pleural nodule finding scheme attained sensitivity of 83.9% with an average 3.47 FPs/case. Combining the two subsystems together, an overall performance of 82.98% sensitivity with 11.76 FPs/case can be obtained.

  17. High-resolution CT of the sternoclavicular joint and first costochondral synchondrosis in asymptomatic individuals.

    PubMed

    De Maeseneer, Michel; Lenchik, Leon; Buls, Nico; Boulet, Cedric; Döring, Seema; de Mey, Johan; Willekens, Inneke

    2016-09-01

    To assess CT features of the sternoclavicular joint (SCJ) and first costochondral junction in asymptomatic patients. In 66 patients transverse and coronal oblique high-resolution multiple detector CT images of the SCJ and first costochondral junction were obtained. Images were reviewed by consensus of two radiologists. Joint space width was measured at three levels, and osteophytes, geodes, and erosions were evaluated. Variants and degree of ossification were noted. Statistical analysis consisted of Shapiro-Wilk test, Pearson's test, and paired sample t test. There were 34 men and 32 women with a mean age of 60 years (age range, 17-98 years). The width of the joint spaces showed a normal distribution. There was no significant difference between the left and right sides. On coronal images the joint space was wider superiorly and on transverse images posteriorly. There was a trend toward decreasing joint space with age, although it did not reach significance (p > 0.05). Clavicular osteophytes were seen in 16 out of 66 patients (24 %) and sternal osteophytes in 16 out of 66 patients. Clavicular geodes were seen in 10 out of 66 patients (15 %) and sternal geodes in 14 out of 66 patients (14 %). No erosions were seen. Clefts of the first costochondral junction were seen in 31 out of 66 patients (47 %). In asymptomatic patients, there is no significant asymmetry of the SCJ. The joint spaces did not significantly decrease with age, although such a trend could be observed. Pronounced joint space narrowing with large geodes and osteophytes was not seen. Clefts of the first costochondral junction are common and not significant.

  18. A simple formulation for deriving effective atomic numbers via electron density calibration from dual-energy CT data in the human body.

    PubMed

    Saito, Masatoshi; Sagara, Shota

    2017-06-01

    The main objective of this study is to propose a simple formulation (which we called DEEDZ) for deriving effective atomic numbers (Zeff ) via electron density (ρe ) calibration from dual-energy (DE) CT data. We carried out numerical analysis of this DEEDZ method for a large variety of materials with known elemental compositions and mass densities using an available photon cross sections database. The new conversion approach was also applied to previously published experimental DECT data to validate its practical feasibility. We performed numerical analysis of the DEEDZ conversion method for tissue surrogates that have the same chemical compositions and mass densities as a commercial tissue-characterization phantom in order to determine the parameters necessary for the ρe and Zeff calibrations in the DEEDZ conversion. These parameters were then applied to the human-body-equivalent tissues of ICRU Report 46 as objects of interest with unknown ρe and Zeff . The attenuation coefficients of these materials were calculated using the XCOM photon cross sections database. We also applied the DEEDZ conversion to experimental DECT data available in the literature, which was measured for two commercial phantoms of different shapes and sizes using a dual-source CT scanner at 80 kV and 140 kV/Sn. The simulated Zeff 's were in excellent agreement with the reference values for almost all of the ICRU-46 human tissues over the Zeff range from 5.83 (gallstones-cholesterol) to 16.11 (bone mineral-hydroxyapatite). The relative deviations from the reference Zeff were within ± 0.3% for all materials, except for one outlier that presented a -3.1% deviation, namely, the thyroid. The reason for this discrepancy is that the thyroid contains a small amount of iodine, an element with a large atomic number (Z = 53). In the experimental case, we confirmed that the simple formulation with less fit parameters enable to calibrate Zeff as accurately as the existing calibration procedure

  19. CT enterography.

    PubMed

    Zamboni, Giulia A; Raptopoulos, Vassilios

    2010-04-01

    Conventional radiologic and endoscopic evaluations of the small bowel are often limited by the length, caliber, and motility of the small bowel loops. The development of new multidetector-row CT scanners, with faster scan times and isotropic spatial resolution, allows high-resolution multiphasic and multiplanar assessment of the bowel, bowel wall, and lumen. CT Enterography (CTE) is a variant of routine abdominal scanning, geared toward more sustained bowel filling with oral contrast material, and the use of multiplanar images, that can enhance gastrointestinal (GI) tract imaging. This article examines the techniques and clinical applications of CTE in comparison with CT enteroclysis, focusing on Crohn disease, obscure GI bleeding, GI tumors, acute abdominal pain, and bowel obstruction. Copyright 2010 Elsevier Inc. All rights reserved.

  20. Onset of Chaotic Motion in High Prandtl Number Liquid

    NASA Astrophysics Data System (ADS)

    Melnikov, D. E.; Shevtsova, V. M.

    2002-01-01

    Floating zone method is a very attractive containerless technique for commercial growing the purest large- volume crystals. Liquid bridge is a configuration where a model liquid is held between two coaxial circular disks kept at different temperatures. Due to temperature-dependence of surface tension, convective flow appears. When the temperature difference between the disks exceeds the critical value, T>Tcr, the two- dimensional toroidal flow undergoes a transition to time-dependent three-dimensional one. For liquids with Pr>0.1, the resulting oscillatory flow is two hydrothermal waves, propagating azimuthaly in opposite directions. Depending on ratio of amplitudes of the two counter propagating waves, traveling or standing resulting waves are observed. A great number of numerical and experimental studies have been devoted to the oscillatory instabilities that occur at critical temperature difference between the two disks. But the real crystal growth processes deal with far-supercritical temperature differences T. At large temperature difference secondary instabilities leading to chaos take place. Actually, what route to chaos the system chooses depends on the many factors such as physical parameters of the liquid bridge, initial state of the system in phase-plane etc. Little information has been published regarding the temperature and flow fields in liquid bridge with increase T further to far-supercritical area up to chaotic regime. A real ground-based experiment with silicone oil of 1cSt (Pr18.76 at T=-20°C) is simulated in taking the real temperature-dependence of viscosity into consideration. As in the modeled experiment, the temperature of the cold disk is kept at T=-20°C. The transition process (also called the route) that leads the oscillatory thermoconvective flow in liquid bridge from a periodic behavior to chaos is under investigation. The simulations are done using finite volume method for solving the 3-D, time-dependent Navier-Stokes equations in

  1. Ultra-high-resolution dual-source CT for forensic dental visualization-discrimination of ceramic and composite fillings.

    PubMed

    Jackowski, C; Wyss, M; Persson, A; Classens, M; Thali, M J; Lussi, A

    2008-07-01

    Dental identification is the most valuable method to identify human remains in single cases with major postmortem alterations as well as in mass casualties because of its practicability and demanding reliability. Computed tomography (CT) has been investigated as a supportive tool for forensic identification and has proven to be valuable. It can also scan the dentition of a deceased within minutes. In the present study, we investigated currently used restorative materials using ultra-high-resolution dual-source CT and the extended CT scale for the purpose of a color-encoded, in scale, and artifact-free visualization in 3D volume rendering. In 122 human molars, 220 cavities with 2-, 3-, 4- and 5-mm diameter were prepared. With presently used filling materials (different composites, temporary filling materials, ceramic, and liner), these cavities were restored in six teeth for each material and cavity size (exception amalgam n = 1). The teeth were CT scanned and images reconstructed using an extended CT scale. Filling materials were analyzed in terms of resulting Hounsfield units (HU) and filling size representation within the images. Varying restorative materials showed distinctively differing radiopacities allowing for CT-data-based discrimination. Particularly, ceramic and composite fillings could be differentiated. The HU values were used to generate an updated volume-rendering preset for postmortem extended CT scale data of the dentition to easily visualize the position of restorations, the shape (in scale), and the material used which is color encoded in 3D. The results provide the scientific background for the application of 3D volume rendering to visualize the human dentition for forensic identification purposes.

  2. High-resolution copy number arrays in cancer and the problem of normal genome copy number variation.

    PubMed

    Gorringe, Kylie L; Campbell, Ian G

    2008-11-01

    High-resolution techniques for analysis of genome copy number (CN) enable the analysis of complex cancer somatic genetics. However, the analysis of these data is difficult, and failure to consider a number of issues in depth may result in false leads or unnecessary rejection of true positives. First, segmental duplications may falsely generate CN breakpoints in aneuploid samples. Second, even when tumor data were each normalized to matching lymphocyte DNA, we still observed copy number polymorphisms masquerading as somatic alterations due to allelic imbalance. We investigated a number of different solutions and determined that evaluating matching normal DNA, or at least using locally derived normal baseline data, were preferable to relying on current online databases because of poor cross-platform compatibility and the likelihood of excluding genuine small somatic alterations.

  3. HIGH-z QUASARS IN THE R {sub h} = ct UNIVERSE

    SciTech Connect

    Melia, Fulvio

    2013-02-10

    One cannot understand the early appearance of 10{sup 9} M {sub Sun} supermassive black holes without invoking anomalously high accretion rates or the creation of exotically massive seeds, neither of which is seen in the local universe. Recent observations have compounded this problem by demonstrating that most, if not all, of the high-z quasars appear to be accreting at the Eddington limit. In the context of {Lambda}CDM, the only viable alternative now appears to be the assemblage of supermassive black holes via mergers, as long as the seeds started forming at redshifts >40, but ceased being created by z {approx} 20-30. In this paper, we show that, whereas the high-z quasars may be difficult to explain within the framework of the standard model, they can instead be interpreted much more sensibly in the context of the R {sub h} = ct universe. In this cosmology, 5-20 M {sub Sun} seeds produced after the onset of re-ionization (at z {approx}< 15) could have easily grown to M {approx}> 10{sup 9} M {sub Sun} by z {approx}> 6, merely by accreting at the standard Eddington rate.

  4. High level cross of the esophagus with the descending aorta in scoliosis: CT study

    SciTech Connect

    Takahashi, Koji; Kikuno, Motoyuki; Hyodoh, Hideki

    1996-05-01

    The esophagus occasionally crosses the descending aorta at an unusually high level (3-5 cm inferior to the carina) in right-sided scoliosis. The purpose of this study was to analyze the mechanism of this finding. We prospectively evaluated thoracic CT scans in 30 patients with right-sided scoliosis. We assessed the alterations in the positions of the esophagus and the descending aorta by the thoracic deformity. The descending aorta followed the scoliotic curve of the spine in 26 (87%) patients. The esophagus followed the scoliotic curve of the spine in 14 (47%) patients and did not in 16 (53%). The anteroposterior diameter of the thorax in the former group was significantly smaller than that in the latter (p < 0.01). High level cross of both structures was identified in 14 (47%) patients, and all of them belonged to the group in which the esophagus did not follow the scoliotic curve of the spine. The unusual high level cross of the esophagus with the descending aorta occasionally seen in scoliosis is due to a difference in the positional alterations of the two structures resulting from the scoliosis. 6 refs., 3 figs.

  5. Optimization of a retrospective technique for respiratory-gated high speed micro-CT of free-breathing rodents

    NASA Astrophysics Data System (ADS)

    Ford, Nancy L.; Wheatley, Andrew R.; Holdsworth, David W.; Drangova, Maria

    2007-09-01

    The objective of this study was to develop a technique for dynamic respiratory imaging using retrospectively gated high-speed micro-CT imaging of free-breathing mice. Free-breathing C57Bl6 mice were scanned using a dynamic micro-CT scanner, comprising a flat-panel detector mounted on a slip-ring gantry. Projection images were acquired over ten complete gantry rotations in 50 s, while monitoring the respiratory motion in synchrony with projection-image acquisition. Projection images belonging to a selected respiratory phase were retrospectively identified and used for 3D reconstruction. The effect of using fewer gantry rotations—which influences both image quality and the ability to quantify respiratory function—was evaluated. Images reconstructed using unique projections from six or more gantry rotations produced acceptable images for quantitative analysis of lung volume, CT density, functional residual capacity and tidal volume. The functional residual capacity (0.15 ± 0.03 mL) and tidal volumes (0.08 ± 0.03 mL) measured in this study agree with previously reported measurements made using prospectively gated micro-CT and at higher resolution (150 µm versus 90 µm voxel spacing). Retrospectively gated micro-CT imaging of free-breathing mice enables quantitative dynamic measurement of morphological and functional parameters in the mouse models of respiratory disease, with scan times as short as 30 s, based on the acquisition of projection images over six gantry rotations.

  6. High-resolution dynamic imaging and quantitative analysis of lung cancer xenografts in nude mice using clinical PET/CT

    PubMed Central

    Wang, Ying Yi; Wang, Kai; Xu, Zuo Yu; Song, Yan; Wang, Chu Nan; Zhang, Chong Qing; Sun, Xi Lin; Shen, Bao Zhong

    2017-01-01

    Considering the general application of dedicated small-animal positron emission tomography/computed tomography is limited, an acceptable alternative in many situations might be clinical PET/CT. To estimate the feasibility of using clinical PET/CT with [F-18]-fluoro-2-deoxy-D-glucose for high-resolution dynamic imaging and quantitative analysis of cancer xenografts in nude mice. Dynamic clinical PET/CT scans were performed on xenografts for 60 min after injection with [F-18]-fluoro-2-deoxy-D-glucose. Scans were reconstructed with or without SharpIR method in two phases. And mice were sacrificed to extracting major organs and tumors, using ex vivo γ-counting as a reference. Strikingly, we observed that the image quality and the correlation between the all quantitive data from clinical PET/CT and the ex vivo counting was better with the SharpIR reconstructions than without. Our data demonstrate that clinical PET/CT scanner with SharpIR reconstruction is a valuable tool for imaging small animals in preclinical cancer research, offering dynamic imaging parameters, good image quality and accurate data quatification. PMID:28881772

  7. High-resolution dynamic imaging and quantitative analysis of lung cancer xenografts in nude mice using clinical PET/CT.

    PubMed

    Wang, Ying Yi; Wang, Kai; Xu, Zuo Yu; Song, Yan; Wang, Chu Nan; Zhang, Chong Qing; Sun, Xi Lin; Shen, Bao Zhong

    2017-08-08

    Considering the general application of dedicated small-animal positron emission tomography/computed tomography is limited, an acceptable alternative in many situations might be clinical PET/CT. To estimate the feasibility of using clinical PET/CT with [F-18]-fluoro-2-deoxy-D-glucose for high-resolution dynamic imaging and quantitative analysis of cancer xenografts in nude mice. Dynamic clinical PET/CT scans were performed on xenografts for 60 min after injection with [F-18]-fluoro-2-deoxy-D-glucose. Scans were reconstructed with or without SharpIR method in two phases. And mice were sacrificed to extracting major organs and tumors, using ex vivo γ-counting as a reference. Strikingly, we observed that the image quality and the correlation between the all quantitive data from clinical PET/CT and the ex vivo counting was better with the SharpIR reconstructions than without. Our data demonstrate that clinical PET/CT scanner with SharpIR reconstruction is a valuable tool for imaging small animals in preclinical cancer research, offering dynamic imaging parameters, good image quality and accurate data quatification.

  8. Preliminary experience with CT-guided high-dose rate brachytherapy as an alternative treatment for hepatic recurrence of cholangiocarcinoma

    PubMed Central

    Kamphues, Carsten; Seehofer, Daniel; Collettini, Federico; Bahra, Marcus; Neuhaus, Peter; Wust, Peter; Denecke, Timm; Gebauer, Bernhard; Schnapauff, Dirk

    2012-01-01

    Background Intrahepatic recurrence after resection of intrahepatic or hilar cholangiocarcinoma represents a main reason for the poor prognosis of bile duct cancer. As no standard treatment has been established so far, the aim of this study was to analyse the safety and efficacy of computed tomography-guided high-dose rate brachytherapy (CT-HDRBT) as an alternative treatment in those patients. Methods The outcomes of 10 patients, who had been treated at least once for recurrent cholangiocarcinoma by CT-HDRBT, were retrospectively analysed. Results The median survival of all patients after primary liver resection was 85 months [95% confidence interval (CI) 68.129-101.871] with overall 1- and 5-year survival rates of 100% and 78.7%, respectively. After the occurrence of intrahepatic tumour recurrence, a total of 15 CT-HDRBT procedures were performed, alone or combined with other recurrence treatments, without any major complications according to the Society of Interventional Radiology classification. The 1-year and 5-year survival rates after recurrence treatment were 77.1% and 51.4%, respectively. Conclusions CT-HDRBT represents a safe treatment option for patients with recurrent bile duct cancer. As a part of a multimodal concept, CT-HDRBT might lead to a prolongation of survival in selected patients but further studies are urgently needed to prove this concept. PMID:23134179

  9. Optimization of a retrospective technique for respiratory-gated high speed micro-CT of free-breathing rodents.

    PubMed

    Ford, Nancy L; Wheatley, Andrew R; Holdsworth, David W; Drangova, Maria

    2007-10-07

    The objective of this study was to develop a technique for dynamic respiratory imaging using retrospectively gated high-speed micro-CT imaging of free-breathing mice. Free-breathing C57Bl6 mice were scanned using a dynamic micro-CT scanner, comprising a flat-panel detector mounted on a slip-ring gantry. Projection images were acquired over ten complete gantry rotations in 50 s, while monitoring the respiratory motion in synchrony with projection-image acquisition. Projection images belonging to a selected respiratory phase were retrospectively identified and used for 3D reconstruction. The effect of using fewer gantry rotations--which influences both image quality and the ability to quantify respiratory function--was evaluated. Images reconstructed using unique projections from six or more gantry rotations produced acceptable images for quantitative analysis of lung volume, CT density, functional residual capacity and tidal volume. The functional residual capacity (0.15 +/- 0.03 mL) and tidal volumes (0.08 +/- 0.03 mL) measured in this study agree with previously reported measurements made using prospectively gated micro-CT and at higher resolution (150 microm versus 90 microm voxel spacing). Retrospectively gated micro-CT imaging of free-breathing mice enables quantitative dynamic measurement of morphological and functional parameters in the mouse models of respiratory disease, with scan times as short as 30 s, based on the acquisition of projection images over six gantry rotations.

  10. Plasmoid instability in high-Lundquist-number magnetic reconnection

    SciTech Connect

    Huang, Yi-Min; Bhattacharjee, A.

    2013-05-15

    Our understanding of magnetic reconnection in resistive magnetohydrodynamics has gone through a fundamental change in recent years. The conventional wisdom is that magnetic reconnection mediated by resistivity is slow in laminar high Lundquist (S) plasmas, constrained by the scaling of the reconnection rate predicted by Sweet-Parker theory. However, recent studies have shown that when S exceeds a critical value ∼10{sup 4}, the Sweet-Parker current sheet is unstable to a super-Alfvénic plasmoid instability, with a linear growth rate that scales as S{sup 1/4}. In the fully developed statistical steady state of two-dimensional resistive magnetohydrodynamic simulations, the normalized average reconnection rate is approximately 0.01, nearly independent of S, and the distribution function f(ψ) of plasmoid magnetic flux ψ follows a power law f(ψ)∼ψ{sup −1}. When Hall effects are included, the plasmoid instability may trigger onset of Hall reconnection even when the conventional criterion for onset is not satisfied. The rich variety of possible reconnection dynamics is organized in the framework of a phase diagram.

  11. Rayleigh Taylor instability of viscoelastic drops at high Weber numbers

    NASA Astrophysics Data System (ADS)

    Joseph, D. D.; Beavers, G. S.; Funada, T.

    2002-02-01

    Movies of the breakup of viscous and viscoelastic drops in the high-speed airstream behind a shock wave in a shock tube have been reported by Joseph, Belanger & Beavers (1999). They performed a Rayleigh Taylor stability analysis for the initial breakup of a drop of Newtonian liquid and found that the most unstable Rayleigh Taylor wave fits nearly perfectly with waves measured on enhanced images of drops from the movies, but the effects of viscosity cannot be neglected. Here we construct a Rayleigh Taylor stability analysis for an Oldroyd-B fluid using measured data for acceleration, density, viscosity and relaxation time [lambda]1. The most unstable wave is a sensitive function of the retardation time [lambda]2 which fits experiments when [lambda]2/[lambda]1 = O(10-3). The growth rates for the most unstable wave are much larger than for the comparable viscous drop, which agrees with the surprising fact that the breakup times for viscoelastic drops are shorter. We construct an approximate analysis of Rayleigh Taylor instability based on viscoelastic potential flow which gives rise to nearly the same dispersion relation as the unapproximated analysis.

  12. Plasmoid instability in high-Lundquist-number magnetic reconnectiona)

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Min; Bhattacharjee, A.

    2013-05-01

    Our understanding of magnetic reconnection in resistive magnetohydrodynamics has gone through a fundamental change in recent years. The conventional wisdom is that magnetic reconnection mediated by resistivity is slow in laminar high Lundquist (S) plasmas, constrained by the scaling of the reconnection rate predicted by Sweet-Parker theory. However, recent studies have shown that when S exceeds a critical value ˜104, the Sweet-Parker current sheet is unstable to a super-Alfvénic plasmoid instability, with a linear growth rate that scales as S1/4. In the fully developed statistical steady state of two-dimensional resistive magnetohydrodynamic simulations, the normalized average reconnection rate is approximately 0.01, nearly independent of S, and the distribution function f(ψ) of plasmoid magnetic flux ψ follows a power law f(ψ)˜ψ-1. When Hall effects are included, the plasmoid instability may trigger onset of Hall reconnection even when the conventional criterion for onset is not satisfied. The rich variety of possible reconnection dynamics is organized in the framework of a phase diagram.

  13. Extracting material parameters from x-ray attenuation: a CT feasibility study using kilovoltage synchrotron x-rays incident upon low atomic number absorbers.

    PubMed

    Kirby, B J; Davis, J R; Grant, J A; Morgan, M J

    2003-10-21

    The work reported here is a feasibility study of the extraction of material parameters from measurements of the linear x-ray attenuation coefficient of low atomic number absorbers. Computed tomography (CT) scans of small samples containing several liquids and solids were carried out with synchrotron radiation at the Australian National Beamline Facility (BL 20B) in Japan. Average values of the x-ray linear attenuation coefficient were extracted for each material for x-ray energies ranging from 11 keV to 20.5 keV. The electron density was estimated by applying results derived from a parametrization of the x-ray linear attenuation coefficient first developed by Jackson and Hawkes and extended for this work. Average estimates for the electron density of triethanolamine and acetic acid were made to within +5.3% of the actual value. Other materials examined included furfuraldehyde, perspex and teflon, for which average estimates of the electron density were less than 10% in excess of the calculated value.

  14. Pushing the boundaries of diagnostic CT systems for high spatial resolution imaging tasks

    NASA Astrophysics Data System (ADS)

    Cruz-Bastida, Juan P.; Gomez-Cardona, Daniel; Garrett, John W.; Szczykutowicz, Timothy P.; Chen, Guang-Hong; Li, Ke

    2017-03-01

    In a previous work [Cruz-Bastida et al Med. Phys. 43, 2399 (2016)], the spatial resolution performance of a new High-Resolution (Hi-Res) multi-detector row CT (MDCT) scan mode and the associated High Definition (HD) reconstruction kernels was systematically characterized. The purpose of the present work was to study the noise properties of the Hi-Res scan mode and the joint impact of spatial resolution and noise characteristics on high contrast and high spatial resolution imaging tasks. Using a physical phantom and a diagnostic MDCT system, equipped with both Hi-Res and conventional scan modes, noise power spectrum (NPS) measurements were performed at 8 off-centered positions (0 to 14 cm with an increment of 2 cm) for 8 non-HD kernels and 7 HD kernels. An in vivo rabbit experiment was then performed to demonstrate the potential clinical value of the Hi-Res scan mode. Without the HD kernels, the Hi-Res scan mode preserved the shape of the NPS and slightly increased noise magnitude across all object positions. The combined use of the Hi-Res scan mode and HD kernels led to a greater noise increase and pushed the NPS towards higher frequencies, particularly for those edge-preserving or edge-enhancing HD kernels. Results of the in vivo rabbit study demonstrate important trade-offs between spatial resolution and noise characteristics. Overall, for a given high contrast and high spatial resolution imaging task (bronchi imaging), the benefit of spatial resolution improvement introduced by the Hi-Res scan mode outweighs the potential noise amplification, leading to better overall imaging performance for both centered and off-centered positions.

  15. Value of Combined PET/CT for Radiation Planning in CT-Guided Percutaneous Interstitial High-Dose-Rate Single-Fraction Brachytherapy for Colorectal Liver Metastases

    SciTech Connect

    Steffen, Ingo G.; Wust, Peter; Ruehl, Ricarda

    2010-07-15

    Purpose: To determine the additional value of fluorodeoxyglucose-positron emission tomography (PET) for clinical target volume definition in the planning of computed tomography (CT)-guided interstitial brachytherapy for liver metastases. Patients and Methods: A total of 19 patients with liver metastases from colorectal cancer treated in 25 sessions were included in the present study. All patients had undergone fluorodeoxyglucose-PET for patient evaluation before interstitial CT-guided brachytherapy. A contrast-enhanced CT scan of the upper abdomen was obtained for radiation planning. The clinical target volume (CTV) was defined by a radiation oncologist and radiologist. After registration of the CT scan with the PET data set, the target volume was defined again using the fusion images. Results: PET revealed one additional liver lesion that was not visible on CT. The median CT-CTV (defined using CT and magnetic resonance imaging) was 68 cm{sup 3} (range 4-260). The PET/CT-CTV (median, 78 cm{sup 3}; range, 4-273) was significantly larger, with a median gain of 24.5% (interquartile range, 2.1-71.5%; p = .022). An increased CTV was observed in 15 cases and a decrease in 6; in 4 cases, the CT-CTV and PET/CT-CTV were equal. Incomplete dose coverage of PET/CT-CTVs was indicative of early local progression (p = .004); however, CT-based radiation plans did not show significant differences in the local control rates when stratified by dose coverage. Conclusion: Retrospective implementation of fluorodeoxyglucose-PET for CTV specification for CT-guided brachytherapy for colorectal liver metastases revealed a significant change in the CTVs. Additional PET-positive tumor regions with incomplete dose coverage could explain unexpected early local progression.

  16. [11C]Choline PET/CT in therapy response assessment of a neoadjuvant therapy in locally advanced and high risk prostate cancer before radical prostatectomy

    PubMed Central

    Schwarzenböck, Sarah M.; Knieling, Anna; Souvatzoglou, Michael; Kurth, Jens; Steiger, Katja; Eiber, Matthias; Esposito, Irene; Retz, Margitta; Kübler, Hubert; Gschwend, Jürgen E.; Schwaiger, Markus; Krause, Bernd J.; Thalgott, Mark

    2016-01-01

    Purpose Recent studies have shown promising results of neoadjuvant therapy in prostate cancer (PC). The aim of this study was to evaluate the potential of [11C]Choline PET/CT in therapy response monitoring after combined neoadjuvant docetaxel chemotherapy and complete androgen blockade in locally advanced and high risk PC patients. Results In [11C]Choline PET/CT there was a significant decrease of SUVmax and SUVmean (p = 0.004, each), prostate volume (p = 0.005) and PSA value (p = 0.003) after combined neoadjuvant therapy. MRI showed a significant prostate and tumor volume reduction (p = 0.003 and 0.005, respectively). Number of apoptotic cells was significantly higher in prostatectomy specimens of the therapy group compared to pretherapeutic biopsies and the control group (p = 0.02 and 0.003, respectively). Methods 11 patients received two [11C]Choline PET/CT and MRI scans before and after combined neoadjuvant therapy followed by radical prostatectomy and pelvic lymph node dissection. [11C]Choline uptake, prostate and tumor volume, PSA value (before/after neoadjuvant therapy) and apoptosis (of pretherapeutic biopsy/posttherapeutic prostatectomy specimens of the therapy group and prostatectomy specimens of a matched control group without neoadjuvant therapy) were assessed and tested for differences and correlation using SPSS. Conclusions The results showing a decrease in choline uptake after combined neoadjuvant therapy (paralleled by regressive and apoptotic changes in histopathology) confirm the potential of [11C]Choline PET/CT to monitor effects of neoadjuvant therapy in locally advanced and high risk PC patients. Further studies are recommended to evaluate its use during the course of neoadjuvant therapy for early response assessment. PMID:27572317

  17. A CT-analogous method for high-resolution fluorescence molecular tomography

    NASA Astrophysics Data System (ADS)

    Li, Jiao; Gao, Feng; Zhu, Qingzhen; Li, Fenghui; Wang, Xin; Zhang, Limin; Zhao, Huijuan

    2012-03-01

    In vivo biomedical imaging using near-infrared light must overcome the effects of highly light scattering, which limit the spatial resolution and affect image quality. The high-resolution, sensitive and quantitative fluorescence imaging tool is an urgent need for the applications in small-animal imaging and clinical cancer research. A CT-analogous method for fluorescence molecular tomography (FMT) on small-animal-sized models is presented to improve the spatial resolution of FMT to a limit of several millimeters, depending on the size of the tissue region to be imaged. The method combines FMT physics with the filtered back-projection scheme for image reconstruction of the fan-beam computed tomography, based on the early-photon detection of time-resolved optical signals, and is suitable for two-dimensional (2D) imaging of small size biological models. By use of a normalized Born formulation for the inversion, the algorithm is validated using full time-resolved simulated data for 2D phantom that are generated from a hybrid finite-element and finite-time-difference photon diffusion modeling, and its superiority in the improvement of the spatial resolution is demonstrated by imaging different target-to-background contrast ratios.

  18. Flow and Noise Control in High Speed and High Reynolds Number Jets Using Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Samimy, M.; Kastner, J.; Kim, J.-H.; Utkin, Y.; Adamovich, I.; Brown, C. A.

    2006-01-01

    The idea of manipulating flow to change its characteristics is over a century old. Manipulating instabilities of a jet to increase its mixing and to reduce its radiated noise started in the 1970s. While the effort has been successful in low-speed and low Reynolds number jets, available actuators capabilities in terms of their amplitude, bandwidth, and phasing have fallen short in control of high-speed and high Reynolds number jets of practical interest. Localized arc filament plasma actuators have recently been developed and extensively used at Gas Dynamics and Turbulence Laboratory (GDTL) for control of highspeed and high Reynolds number jets. While the technique has been quite successful and is very promising, all the work up to this point had been carried out using small high subsonic and low supersonic jets from a 2.54 cm diameter nozzle exit with a Reynolds number of about a million. The preliminary work reported in this paper is a first attempt to evaluate the scalability of the technique. The power supply/plasma generator was designed and built in-house at GDTL to operate 8 actuators simultaneously over a large frequency range (0 to 200 kHz) with independent control over phase and duty cycle of each actuator. This allowed forcing the small jet at GDTL with azimuthal modes m = 0, 1, 2, 3, plus or minus 1, plus or minus 2, and plus or minus 4 over a large range of frequencies. This power supply was taken to and used, with minor modifications, at the NASA Nozzle Acoustic Test Rig (NATR). At NATR, 32 actuators were distributed around the 7.5 in. nozzle (a linear increase with nozzle exit diameter would require 60 actuators). With this arrangement only 8 actuators could operate simultaneously, thus limiting the forcing of the jet at NATR to only three azimuthal modes m = plus or minus 1, 4, and 8. Very preliminary results at NATR indicate that the trends observed in the larger NASA facility in terms of the effects of actuation frequency and azimuthal modes are

  19. A computer simulation method for low-dose CT images by use of real high-dose images: a phantom study.

    PubMed

    Takenaga, Tomomi; Katsuragawa, Shigehiko; Goto, Makoto; Hatemura, Masahiro; Uchiyama, Yoshikazu; Shiraishi, Junji

    2016-01-01

    Practical simulations of low-dose CT images have a possibility of being helpful means for optimization of the CT exposure dose. Because current methods reported by several researchers are limited to specific vendor platforms and generally rely on raw sinogram data that are difficult to access, we have developed a new computerized scheme for producing simulated low-dose CT images from real high-dose images without use of raw sinogram data or of a particular phantom. Our computerized scheme for low-dose CT simulation was based on the addition of a simulated noise image to a real high-dose CT image reconstructed by the filtered back-projection algorithm. First, a sinogram was generated from the forward projection of a high-dose CT image. Then, an additional noise sinogram resulting from use of a reduced exposure dose was estimated from a predetermined noise model. Finally, a noise CT image was reconstructed with a predetermined filter and was added to the real high-dose CT image to create a simulated low-dose CT image. The noise power spectrum and modulation transfer function of the simulated low-dose images were very close to those of the real low-dose images. In order to confirm the feasibility of our method, we applied this method to clinical cases which were examined with the high dose initially and then followed with a low-dose CT. In conclusion, our proposed method could simulate the low-dose CT images from their real high-dose images with sufficient accuracy and could be used for determining the optimal dose setting for various clinical CT examinations.

  20. Dual-energy CT angiography of abdomen with routine concentration contrast agent in comparison with conventional single-energy CT with high concentration contrast agent.

    PubMed

    He, Jingzhen; Wang, Qing; Ma, Xiangxing; Sun, Zhiyuan

    2015-02-01

    To compare the quantitative and subjective image quality in abdominal angiography between dual-energy CT (DECT) at the routine concentration of iodinated contrast agent (300mg/mL) and conventional 120-kVp single-energy CT (SECT) at the high concentration of contrast agent (370mg/mL). Abdominal computed tomography angiography (CTA) was performed in 104 patients, including 56 with conventional 120-kVp SECT at the high concentration of contrast agent and 48 with DECT at the routine concentration of contrast agent. The monochromatic images at the optimal kiloelectron-voltage (keV) of DECT that demonstrated the best contrast-to-noise ratio were reconstructed. The signal intensity and noise in abdominal arteries were comparatively analyzed between DECT and SECT. The image quality and visibility of the branch orders of superior mesenteric artery and renal arteries were further assessed. The radiation doses were recorded. Compared with SECT, DECT demonstrated higher signal intensity, signal-to-noise ratio, and contrast-to-noise ratio (all P<0.01) with moderately increased noise (40%, P<0.01) in all abdominal arteries. The image quality of DECT was superior to that of SECT (P<0.01) as evaluated with a subjective five-point scale system. Visualization of the branches of superior mesenteric artery and renal arteries was also better by DECT (P<0.01) than SECT. The radiation dose of DECT was slight higher than that of SECT (P<0.0001). DECT with image reconstruction at the optimal keV provides a high-quality angiographic technique, which allows use of a lower concentration of contrast agent compared with conventional 120-kVp SECT. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  1. Optimizing radiation dose by using advanced modelled iterative reconstruction in high-pitch coronary CT angiography.

    PubMed

    Gordic, Sonja; Desbiolles, Lotus; Sedlmair, Martin; Manka, Robert; Plass, André; Schmidt, Bernhard; Husarik, Daniela B; Maisano, Francesco; Wildermuth, Simon; Alkadhi, Hatem; Leschka, Sebastian

    2016-02-01

    To evaluate the potential of advanced modeled iterative reconstruction (ADMIRE) for optimizing radiation dose of high-pitch coronary CT angiography (CCTA). High-pitch 192-slice dual-source CCTA was performed in 25 patients (group 1) according to standard settings (ref. 100 kVp, ref. 270 mAs/rot). Images were reconstructed with filtered back projection (FBP) and ADMIRE (strength levels 1-5). In another 25 patients (group 2), high-pitch CCTA protocol parameters were adapted according to results from group 1 (ref. 160 mAs/rot), and images were reconstructed with ADMIRE level 4. In ten patients of group 1, vessel sharpness using full width at half maximum (FWHM) analysis was determined. Image quality was assessed by two independent, blinded readers. Interobserver agreements for attenuation and noise were excellent (r = 0.88/0.85, p < 0.01). In group 1, ADMIRE level 4 images were most often selected (84%, 21/25) as preferred data set; at this level noise reduction was 40% compared to FBP. Vessel borders showed increasing sharpness (FWHM) at increasing ADMIRE levels (p < 0.05). Image quality in group 2 was similar to that of group 1 at ADMIRE levels 2-3. Radiation dose in group 2 (0.3 ± 0.1 mSv) was significantly lower than in group 1 (0.5 ± 0.3 mSv; p < 0.05). In a selected population, ADMIRE can be used for optimizing high-pitch CCTA to an effective dose of 0.3 mSv. • Advanced modeled IR (ADMIRE) reduces image noise up to 50% as compared to FBP. • Coronary artery vessel borders show an increasing sharpness at higher ADMIRE levels. • High-pitch CCTA with ADMIRE is possible at a radiation dose of 0.3 mSv.

  2. Contrast media volume optimization in high-pitch dual-source CT coronary angiography: feasibility study.

    PubMed

    Yang, Wen Jie; Chen, Ke Min; Liu, Bo; Pang, Li Fang; Zhang, Huan; Pan, Zi Lai; Yan, Fu Hua

    2013-01-01

    To investigate the feasibility of contrast media (CM) volume reduction in dual-source coronary computed tomography angiography high-pitch mode without affecting coronary artery enhancement. Eighty patients were involved in a preliminary experiment with a default injection protocol (60 ml of CM). The age, BMI, test bolus (TB) enhancement peak and the CT values of coronary artery for each patient were recorded and the key factors for determining coronary artery enhancement were investigated. Based on the results of the preliminary experiment, 120 patients were involved in the main experiment with a new injection protocol. For each patient, the CT values and noise of left coronary sinus (LCS), and the distal segment of right coronary artery were measured. In the preliminary experiment, the peak enhancement of TB correlated most strongly with the HU values of coronary artery. Consequently, the new injection protocol was devised to catalog patients into four groups (30, 40, 50 and 60 ml) of CM based on their TB peak enhancement. In the main experiment, the 30 ml CM injection group whose peak attenuation of TB were the highest (30 vs. 40,50,60 ml: 323.0 ± 27.5 vs. 264.2 ± 11.9, 242.1 ± 8.8, 206.2 ± 18.2 HU, p < 0.05), obtained the highest attenuation of LCS (30 vs. 40,50,60 ml: 365.0 ± 41.2 vs. 341.8 ± 40.0, 326.9 ± 34.7, 312.5 ± 38.2 HU p < 0.05). Contrast optimization is feasible in high-pitch DSCT coronary angiography. Certain patients may receive 30 ml of CM without affecting vessel enhancement.

  3. 21 CFR 1020.33 - Computed tomography (CT) equipment.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... change in linear attenuation coefficient per CT number relative to water; that is: EC01AP93.000 where: μw=Linear attenuation coefficient of water. μx=Linear attenuation coefficient of material of interest. (CT)w=CT number of water. (CT)x=CT number of material of interest. (3) CT conditions of operation means...

  4. 21 CFR 1020.33 - Computed tomography (CT) equipment.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... change in linear attenuation coefficient per CT number relative to water; that is: EC01AP93.000 where: μw=Linear attenuation coefficient of water. μx=Linear attenuation coefficient of material of interest. (CT)w=CT number of water. (CT)x=CT number of material of interest. (3) CT conditions of operation means...

  5. High Atomic Number Contrast Media Offer Potential for Radiation Dose Reduction in Contrast-Enhanced Computed Tomography.

    PubMed

    Roessler, Ann-Christin; Hupfer, Martin; Kolditz, Daniel; Jost, Gregor; Pietsch, Hubertus; Kalender, Willi A

    2016-04-01

    Spectral optimization of x-ray computed tomography (CT) has led to substantial radiation dose reduction in contrast-enhanced CT studies using standard iodinated contrast media. The purpose of this study was to analyze the potential for further dose reduction using high-atomic-number elements such as hafnium and tungsten. As in previous studies, spectra were determined for which the patient dose necessary to provide a given contrast-to-noise ratio (CNR) is minimized. We used 2 different quasi-anthropomorphic phantoms representing the liver cross-section of a normal adult and an obese adult patient with the lateral widths of 360 and 460 mm and anterior-posterior heights of 200 and 300 mm, respectively. We simulated and measured on 2 different scanners with x-ray spectra from 80 to 140 kV and from 70 to 150 kV, respectively. We determined the contrast for iodine-, hafnium-, and tungsten-based contrast media, the noise, and 3-dimensional dose distributions at all available tube voltages by measurements and by simulations. The dose-weighted CNR was determined as optimization parameter. Simulations and measurements were in good agreement regarding their dependence on energy for all parameters investigated. Hafnium provided the best performance for normal and for obese patient phantoms, indicating a dose reduction potential of 30% for normal and 50% for obese patients at 120 kV compared with iodine; this advantage increased further with higher kV values. Dose-weighted CNR values for tungsten were always slightly below the hafnium results. Iodine proved to be the superior choice at voltage values of 80 kV and below. Hafnium and tungsten both seem to be candidates for contrast-medium-enhanced CT of normal and obese adult patients with strongly reduced radiation dose at unimpaired image quality. Computed tomography examinations of obese patients will decrease in dose for higher kV values.

  6. Development of 36M-pixel x-ray detector for large field of view and high-resolution micro-CT

    NASA Astrophysics Data System (ADS)

    Umetani, Keiji; Kawata, Yoshiki; Niki, Noboru

    2016-10-01

    A high-resolution and large field-of-view micro-CT system is indispensable for the visualization of fine threedimensional (3-D) structures of a large specimen. Such a system drastically increases the overall number of effective sensor pixels. At SPring-8 over a decade ago, a micro-CT system based on a 10M-pixel CCD camera was developed for 3-D specimen imaging of centimeter-sized objects with approximately 7 μm spatial resolution. Subsequently, more recent studies have required systems with higher spatial resolution and a wider field-of-view. Detectors with spatial resolution of around 5 μm can visualize capillaries. However, such detectors make it extremely expensive to develop a new x-ray detector with several tens of megapixels in a conventional manner. Fortunately, dizzying advances in image sensor technology for consumer appliances have enabled the development of x-ray detectors with spatial resolution of around 5 μm using a commercial digital single-lens reflex camera fitted with a 36M-pixel CMOS image sensor for the visualization of fine 3-D structures of large human lung specimens. This paper describes a comparison of the performance offered by the new 36M-pixel micro-CT system and the 10M-pixel system.

  7. A survey of the three-dimensional high Reynolds number transonic wind tunnel

    NASA Technical Reports Server (NTRS)

    Takashima, K.; Sawada, H.; Aoki, T.

    1982-01-01

    The facilities for aerodynamic testing of airplane models at transonic speeds and high Reynolds numbers are surveyed. The need for high Reynolds number testing is reviewed, using some experimental results. Some approaches to high Reynolds number testing such as the cryogenic wind tunnel, the induction driven wind tunnel, the Ludwieg tube, the Evans clean tunnel and the hydraulic driven wind tunnel are described. The level of development of high Reynolds number testing facilities in Japan is discussed.

  8. ESTIMATION OF GIARDIA CT VALUES AT HIGH PH FOR THE SURFACE WATER TREATMENT RULE

    EPA Science Inventory

    The U.S. Environmental Protection Agency currently recommends Ct (disinfectant concentration multiplied by the exposure time) values to achieve required levels of inactivation of Giardia lamblia cysts by different disinfectants including free chlorine. Current guidance covers ina...

  9. ESTIMATION OF GIARDIA CT VALUES AT HIGH PH FOR THE SURFACE WATER TREATMENT RULE

    EPA Science Inventory

    The U.S. Environmental Protection Agency currently recommends Ct (disinfectant concentration multiplied by the exposure time) values to achieve required levels of inactivation of Giardia lamblia cysts by different disinfectants including free chlorine. Current guidance covers ina...

  10. High spatial range velocity measurements in a high Reynolds number turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    de Silva, C. M.; Gnanamanickam, E. P.; Atkinson, C.; Buchmann, N. A.; Hutchins, N.; Soria, J.; Marusic, I.

    2014-02-01

    Here, we detail and analyse a multi-resolution particle image velocity measurement that resolves the wide range of scales prevalent in a zero pressure gradient turbulent boundary layer at high Reynolds numbers (up to Reτ ≈ 20 000). A unique configuration is utilised, where an array of eight high resolution cameras at two magnification levels are used simultaneously to obtain a large field of view, while still resolving the smaller scales prevalent in the flow. Additionally, a highly magnified field of view targeted at the near wall region is employed to capture the viscous sublayer and logarithmic region, with a spatial resolution of a few viscous length scales. Flow statistics from these measurements show good agreement with prior, well resolved hot-wire anemometry measurements. Analysis shows that the instantaneous wall shear stress can be reliably computed, which is historically known to be challenging in boundary layers. A statistical assessment of the wall shear stress shows good agreement with existing correlations, prior experimental and direct numerical simulation data, extending this view to much higher Reynolds numbers. Furthermore, conditional analysis using multiple magnification levels is detailed, to study near-wall events associated with high skin friction fluctuations and their associated overlaying structures in the log region. Results definitively show that the passage of very large-scale positive (or negative) velocity fluctuations are associated with increased (or reduced) small-scale variance in wall shear stress fluctuations.

  11. Stereotactic CT-Guided Percutaneous Microwave Ablation of Liver Tumors With the Use of High-Frequency Jet Ventilation: An Accuracy and Procedural Safety Study.

    PubMed

    Engstrand, Jennie; Toporek, Grzegorz; Harbut, Piotr; Jonas, Eduard; Nilsson, Henrik; Freedman, Jacob

    2017-01-01

    The purpose of the present study is to evaluate the accuracy and safety of antenna placement performed with the use of a CT-guided stereotactic navigation system for percutaneous ablation of liver tumors and to assess the safety of high-frequency jet ventilation for target motion control. Twenty consecutive patients with malignant liver lesions for which surgical resection was contraindicated or that were not readily visible on ultrasound or not accessible by ultrasound guidance were included in the study. Patients were treated with percutaneous microwave ablation performed using a CT-guided stereotactic navigation system. High-frequency jet ventilation was used to reduce liver motion during all interventions. The accuracy of antenna placement, the number of needle readjustments required, overall safety, and the radiation doses were assessed. Microwave ablation was completed for 20 patients (28 lesions). Performance data could be evaluated for 17 patients with 25 lesions (mean [± SD] lesion diameter, 14.9 ± 5.9 mm; mean lesion location depth, 87.5 ± 27.3 mm). The antennae were placed with a mean lateral error of 4.0 ± 2.5 mm, a depth error of 3.4 ± 3.2 mm, and a total error of 5.8 ± 3.2 mm in relation to the intended target. The median number of antenna readjustments required was zero (range, 0-1 adjustment). No major complications were related to either the procedure or the use of high-frequency jet ventilation. The mean total patient radiation dose was 957.5 ± 556.5 mGy × cm, but medical personnel were not exposed to irradiation. Percutaneous microwave ablation performed with CT-guided stereotactic navigation provides sufficient accuracy and requires almost no repositioning of the needle. Therefore, it is technically feasible and applicable for safe treatments.

  12. Quantification of CT images for the classification of high- and low-risk pancreatic cysts

    NASA Astrophysics Data System (ADS)

    Gazit, Lior; Chakraborty, Jayasree; Attiyeh, Marc; Langdon-Embry, Liana; Allen, Peter J.; Do, Richard K. G.; Simpson, Amber L.

    2017-03-01

    Pancreatic cancer is the most lethal cancer with an overall 5-year survival rate of 7%1 due to the late stage at diagnosis and the ineffectiveness of current therapeutic strategies. Given the poor prognosis, early detection at a pre-cancerous stage is the best tool for preventing this disease. Intraductal papillary mucinous neoplasms (IPMN), cystic tumors of the pancreas, represent the only radiographically identifiable precursor lesion of pancreatic cancer and are known to evolve stepwise from low-to-high-grade dysplasia before progressing into an invasive carcinoma. Observation is usually recommended for low-risk (low- and intermediate-grade dysplasia) patients, while high-risk (high-grade dysplasia and invasive carcinoma) patients undergo resection; hence, patient selection is critically important in the management of pancreatic cysts.2 Radiologists use standard criteria such as main pancreatic duct size, cyst size, or presence of a solid enhancing component in the cyst to optimally select patients for surgery.3 However, these findings are subject to a radiologist's interpretation and have been shown to be inconsistent with regards to the presence of a mural nodule or solid component.4 We propose objective classification of risk groups based on quantitative imaging features extracted from CT scans. We apply new features that represent the solid component (i.e. areas of high intensity) within the cyst and extract standard texture features. An adaptive boost classifier5 achieves the best performance with area under receiver operating characteristic curve (AUC) of 0.73 and accuracy of 77.3% for texture features. The random forest classifier achieves the best performance with AUC of 0.71 and accuracy of 70.8% with the solid component features.

  13. Comparison of CT and MRI findings for cervical spine clearance in obtunded patients without high impact trauma.

    PubMed

    Tan, Lee A; Kasliwal, Manish K; Traynelis, Vincent C

    2014-05-01

    Cervical spinal injuries occur in 2.0-6.6% of patients after blunt trauma and can have devastating neurological sequelae if left unrecognized. Although there is high quality evidence addressing cervical clearance in asymptomatic and symptomatic awake patients, cervical spine clearance in patients with altered level of alertness (i.e., obtunded patients with Glasgow coma scale (GCS) of 14 or less) following blunt trauma has been a matter of great controversy. Furthermore, there are no data on cervical spine clearance in obtunded patients without high impact trauma and these patients are often treated based on evidence from similar patients with high impact trauma. This retrospective study was conducted on this specific subgroup of patients who were admitted to a neurointensive care unit (NICU) with primary diagnoses of intracranial hemorrhage with history of minor trauma; the objective being to evaluate and compare cervical spinal computed tomography (CT) and magnetic resonance imaging (MRI) findings in this particular group of patients. Patients with GCS of 14 or less admitted to neruointensive care unit (NICU) at RUSH University Medical Center from 2008 to 2010 with diagnoses of intracranial hemorrhage (surgical or non-surgical) who had reported or presumed fall (i.e., "found down") were queried from the computer data registry. A group of these patients had cervical spine CT and subsequently MRI for clearing the cervical spine and removal of the cervical collar. Medical records of these patients were reviewed for demographics, GCS score and injury specific data and presence or absence of cervical spine injury. Eighty-three patients were identified from the computer database. Twenty-eight of these patients had positive findings on both CT and MRI (33.73% - Group I); four patients had a negative CT but had positive findings on follow-up MRI (4.82% - Group II); fifty-one patients had both negative CT and MRI (61.44% - Group III). All patients in Group I required

  14. Photon-Counting CT: High-Resolution Imaging of Coronary Stents.

    PubMed

    Mannil, Manoj; Hickethier, Tilman; von Spiczak, Jochen; Baer, Matthias; Henning, André; Hertel, Madeleine; Schmidt, Bernhard; Flohr, Thomas; Maintz, David; Alkadhi, Hatem

    2017-09-23

    The aim of this study was to investigate computed tomography (CT) imaging characteristics of coronary stents using a novel photon-counting detector (PCD) in comparison with a conventional energy-integrating detector (EID). In this in vitro study, 18 different coronary stents were expanded in plastic tubes of 3 mm diameter, were filled with contrast agent (diluted to an attenuation of 250 Hounsfield units [HU] at 120 kVp), and were sealed. Stents were placed in an oil-filled custom phantom calibrated to an attenuation of -100 HU at 120 kVp for resembling pericardial fat. The phantom was positioned in the gantry at 2 different angles at 0 degree and 90 degrees relative to the z axis, and was imaged in a research dual-source PCD-CT scanner. Detector subsystem "A" used a standard 64-row EID, while detector subsystem "B" used a PCD, allowing high-resolution scanning (detector pixel-size 0.250 × 0.250 mm in the isocenter). Images were obtained from both detector systems at identical tube voltage (100 kVp) and tube current-time product (100 mA), and were both reconstructed using a typical convolution kernel for stent imaging (B46f) and using the same reconstruction parameters. Two independent, blinded readers evaluated in-stent visibility and measured noise, intraluminal stent diameter, and in-stent attenuation for each detector subsystem. Differences in noise, intraluminal stent diameter, and in-stent attenuation where tested using a paired t test; differences in subjective in-stent visibility were evaluated using a Wilcoxon signed-rank test. Best results for in-stent visibility, noise, intraluminal stent diameter, and in-stent attenuation in EID and PCD were observed at 0-degree phantom position along the z axis, suggesting higher in-plane compared with through-plane resolution. Subjective in-stent visibility was superior in coronary stent images obtained from PCD compared with EID (P < 0.001). Mean in-stent diameter was 28.8% and 8.4% greater in PCD (0.85 ± 0.24 mm

  15. High-resolution in-vivo micro-CT scanner for small animals

    NASA Astrophysics Data System (ADS)

    Sasov, Alexander

    2001-06-01

    Small laboratory animals (mice and rats) are widely used in development of drags and treatments. To recognize the internal changes in the very early stage inside the animal body, Skyscan starts development on high-resolution micro-CT scanner for in-vivo 3D-imaging. Initial changes in the bone structure can be found as features in the size range of 10 microns. By this reason a voxel size for reconstructed cross sections has been chosen as < 10 microns. Because of full animal may be up to 8 cm in diameter the reconstructed cross section format selected as 8000 X 8000-pixels (float- point). A 2D detection system with new multi-beam geometry produce dataset for reconstruction of hundreds cross- sections after one scan. Object illuminated by microfocus sealed X-ray source with 5 microns spot size. Continuously variable energy in the range of 20 - 100 kV and energy filters allows estimate material composition like in DEXA systems. Direct streaming of the projection data to the disk reduce irradiation dose to the animal under scanning. Software package can create realistic 3D-images from the set of reconstructed cross sections and calculate internal morphological parameters.

  16. High-resolution in-vivo micro-CT scanner for small animals

    NASA Astrophysics Data System (ADS)

    Sasov, Alexander; Dewaele, Daniel

    2002-01-01

    Small laboratory animals (mice and rats) are widely used in development of drugs and treatments. To recognize the internal changes in the very early stage inside the body of alive animal, high-resolution micro-CT scanner has been developed. Initial changes in the bone structure can be found as features in the size range of 10 microns. By this reason a voxel size for reconstructed cross sections has been chosen as small as 10 microns. Full animal body may be up to 80 mm in diameter and up to 200 mm in length. By this reason the reconstructed cross section format selected as 8000 x 8000 pixels (float-point). A new 2D detection system with multibeam geometry produces dataset for reconstruction of hundreds of cross sections after one scan. Object illuminated by microfocus sealed x-ray source with 5 microns spot size. Continuously variable energy in the range of 20- 100 kV and energy filters allows estimate material composition like in DEXA systems. Direct streaming of the projection data to the disk reduce irradiation dose to the animal under scanning. Software package can create realistic 3D images from the set of reconstructed cross sections and calculate internal morphological parameters.

  17. Phase-contrast tomography of neuronal tissues: from laboratory- to high resolution synchrotron CT

    NASA Astrophysics Data System (ADS)

    Töpperwien, Mareike; Krenkel, Martin; Müller, Kristin; Salditt, Tim

    2016-10-01

    Assessing the three-dimensional architecture of neuronal tissues with sub-cellular resolution presents a significant analytical challenge. Overcoming the limitations associated with serial slicing, phase-contrast x-ray tomography has the potential to contribute to this goal. Even compact laboratory CT at an optimized liquid-metal jet micro- focus source combined with suitable phase-retrieval algorithms and preparation protocols can yield renderings with single cell sensitivity in millimeter sized brain areas of mouse. Here, we show the capabilities of the setup by imaging a Golgi-Cox impregnated mouse brain. Towards higher resolution we extend these studies at our recently upgraded waveguide-based cone-beam holo-tomography instrument GINIX at DESY. This setup allows high resolution recordings with adjustable field of view and resolution, down to the voxel sizes in the range of a few ten nanometers. The recent results make us confident that important issues of neuronal connectivity can be addressed by these methods, and that 3D (virtual) histology with nanoscale resolution will become an attractive modality for neuroscience research.

  18. Automated volumetric segmentation method for growth consistency of nonsolid pulmonary nodules in high-resolution CT

    NASA Astrophysics Data System (ADS)

    Browder, William A.; Reeves, Anthony P.; Apananosovich, Tatiyana V.; Cham, Matthew D.; Yankelevitz, David F.; Henschke, Claudia I.

    2007-03-01

    There is widespread clinical interest in the study of pulmonary nodules for early diagnosis of lung cancer. These nodules can be broadly classified into one of three types, solid, nonsolid and part-solid. Solid nodules have been extensively studied, while little research has focused on the characterization of nonsolid and part-solid nodules. Nonsolid nodules have an appearance in high-resolution CT consisting of voxels only slightly more dense than that of the surrounding lung parenchyma. For the solid nodule, robust techniques are available to estimate growth rate and this is commonly used to distinguish benign from malignant. For the nonsolid types, these techniques are less well developed. In this research, we propose an automated volumetric segmentation method for nonsolid nodules that accurately determines a nonsolid nodule's growth rate. Our method starts with an initial noise-filtering stage in the parenchyma region. Each voxel is then classified into one of three tissue types; lung parenchyma, nonsolid and solid. Removal of vessel attachments to the lesion is achieved with the use of a filter that focuses on vessel characteristics. Our results indicate that the automated method is more consistent than the radiologist with a median growth consistency of 1.87 compared to 3.12 for the radiologist on a database of 25 cases.

  19. [Chest high resolution CT features of extrinsic allergic alveolitis and its diagnostic value].

    PubMed

    Ban, Cheng-jun; Dai, Hua-ping; Zhang, Shu; Zhang, Lei; Ye, Qiao; Zhu, Min

    2010-04-27

    To summarize the chest high-resolution CT (HRCT) features of the patients with extrinsic allergic alveolitis (EAA). We analyzed the images of chest HRCT of 34 patients diagnosed as EAA at our hospital from February 2001 to August 2009. All patients had a history of environmental exposure. The duration of intermittent or continuous antigen exposure was from 3 months to 13 years. Two patients showed acute clinical manifestations. There were 22 sub-acute and 10 chronic cases. Acute EAA was characterized by ground-glass opacities, air trapping and/or mosaic sign on HRCT. The HRCT features of subacute EAA included patchy ground-glass opacities with mosaic sign (n = 11, 50.0%) and diffusely distributed centrilobular nodules (n = 7, 31.8%) with mosaic sign (n = 4, 18.2%). All patients with chronic EAA had reticular and honeycombing lesions on HRCT. There were 3 cases with ground-glass opacities, 3 with mosaic sign, and 3 with centrilobular nodules. The typical findings of chest HRCT are helpful for making a diagnosis and differential diagnosis of EAA.

  20. PET/CT in giant cell arteritis: High (18)F-FDG uptake in the temporal, occipital and vertebral arteries.

    PubMed

    Rehak, Z; Vasina, J; Ptacek, J; Kazda, T; Fojtik, Z; Nemec, P

    (18)F-FDG PET/CT imaging is useful in patients with fever of unknown origin and can detect giant cell arteritis in extracranial large arteries. However, it is usually assumed that temporal arteries cannot be visualized with a PET/CT scanner due to their small diameter. Three patients with clinical symptoms of temporal arteritis were examined using a standard whole body PET/CT protocol (skull base - mid thighs) followed by a head PET/CT scan using the brain protocol. High (18)F-FDG uptake in the aorta and some arterial branches were detected in all 3 patients with the whole body protocol. Using the brain protocol, head imaging led to detection of high (18)F-FDG uptake in temporal arteries as well as in their branches (3 patients), in occipital arteries (2 patients) and also in vertebral arteries (3 patients). Copyright © 2016 Elsevier España, S.L.U. y SEMNIM. All rights reserved.

  1. KENNEDY SPACE CENTER, FLA. -Crawler-transporter (CT) number 2, moves away from the Vehicle Assembly Building, with a Mobile Launcher Platform on top, on a test run to the launch pad. The CT recently underwent modifications to the cab. The CT moves Space Shuttle vehicles between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds.

    NASA Image and Video Library

    2003-08-18

    KENNEDY SPACE CENTER, FLA. -Crawler-transporter (CT) number 2, moves away from the Vehicle Assembly Building, with a Mobile Launcher Platform on top, on a test run to the launch pad. The CT recently underwent modifications to the cab. The CT moves Space Shuttle vehicles between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds.

  2. KENNEDY SPACE CENTER, FLA. - Crawler-transporter (CT) number 2 nears the launch pad with a Mobile Launcher Platform (MLP) on top. After recent modifications to the cab and muffler system, the CT was taken on a test run. The CT moves Space Shuttle vehicles, situated on the MLP, between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds. Seen on top of the MLP are two tail service masts that support the fluid, gas and electrical requirements of the orbiter’s liquid oxygen and liquid hydrogen aft umbilicals.

    NASA Image and Video Library

    2003-08-19

    KENNEDY SPACE CENTER, FLA. - Crawler-transporter (CT) number 2 nears the launch pad with a Mobile Launcher Platform (MLP) on top. After recent modifications to the cab and muffler system, the CT was taken on a test run. The CT moves Space Shuttle vehicles, situated on the MLP, between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds. Seen on top of the MLP are two tail service masts that support the fluid, gas and electrical requirements of the orbiter’s liquid oxygen and liquid hydrogen aft umbilicals.

  3. KENNEDY SPACE CENTER, FLA. - Crawler-transporter (CT) number 2, moves away from the Vehicle Assembly Building with a Mobile Launcher Platform (MLP) on top on a test run to the launch pad. The CT recently underwent modifications to the cab. The CT moves Space Shuttle vehicles, situated on the MLP, between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds. Seen on top of the MLP are two tail service masts that support the fluid, gas and electrical requirements of the orbiter’s liquid oxygen and liquid hydrogen aft umbilicals.

    NASA Image and Video Library

    2003-08-18

    KENNEDY SPACE CENTER, FLA. - Crawler-transporter (CT) number 2, moves away from the Vehicle Assembly Building with a Mobile Launcher Platform (MLP) on top on a test run to the launch pad. The CT recently underwent modifications to the cab. The CT moves Space Shuttle vehicles, situated on the MLP, between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds. Seen on top of the MLP are two tail service masts that support the fluid, gas and electrical requirements of the orbiter’s liquid oxygen and liquid hydrogen aft umbilicals.

  4. KENNEDY SPACE CENTER, FLA. - A closeup of crawler-transporter (CT) number 2 shows the cab, at left, that recently underwent modifications. The CT is transporting a Mobile Launch Platform (MLP) on a test run to the pad. The CT moves Space Shuttle vehicles, situated on the MLP, between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds. Seen on top of the MLP are two tail service masts that support the fluid, gas and electrical requirements of the orbiter’s liquid oxygen and liquid hydrogen aft umbilicals.

    NASA Image and Video Library

    2003-08-18

    KENNEDY SPACE CENTER, FLA. - A closeup of crawler-transporter (CT) number 2 shows the cab, at left, that recently underwent modifications. The CT is transporting a Mobile Launch Platform (MLP) on a test run to the pad. The CT moves Space Shuttle vehicles, situated on the MLP, between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds. Seen on top of the MLP are two tail service masts that support the fluid, gas and electrical requirements of the orbiter’s liquid oxygen and liquid hydrogen aft umbilicals.

  5. KENNEDY SPACE CENTER, FLA. - A closeup of crawler-transporter (CT) number 2 shows the cab (left, above the tracks) that recently underwent modifications. The CT is transporting a Mobile Launch Platform (MLP) on a test run to the pad. The CT moves Space Shuttle vehicles, situated on the MLP, between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds. Seen on top of the MLP are two tail service masts that support the fluid, gas and electrical requirements of the orbiter’s liquid oxygen and liquid hydrogen aft umbilicals.

    NASA Image and Video Library

    2003-08-18

    KENNEDY SPACE CENTER, FLA. - A closeup of crawler-transporter (CT) number 2 shows the cab (left, above the tracks) that recently underwent modifications. The CT is transporting a Mobile Launch Platform (MLP) on a test run to the pad. The CT moves Space Shuttle vehicles, situated on the MLP, between the VAB and launch pad. Moving on four double-tracked crawlers, the CT uses a laser guidance system and a leveling system for the journey that keeps the top of a Space Shuttle vertical within plus- or minus-10 minutes of arc. The system enables the CT-MLP-Shuttle to negotiate the ramp leading to the launch pads and keep the load level. Unloaded, the CT weighs 6 million pounds. Seen on top of the MLP are two tail service masts that support the fluid, gas and electrical requirements of the orbiter’s liquid oxygen and liquid hydrogen aft umbilicals.

  6. Ultra-High Spatial Resolution, Multi-Energy CT using Photon Counting Detector Technology.

    PubMed

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

    2017-02-11

    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.

  7. Image-Based Motion Compensation for High-Resolution Extremities Cone-Beam CT

    PubMed Central

    Sisniega, A.; Stayman, J. W.; Cao, Q.; Yorkston, J.; Siewerdsen, J. H.; Zbijewski, W.

    2016-01-01

    Purpose Cone-beam CT (CBCT) of the extremities provides high spatial resolution, but its quantitative accuracy may be challenged by involuntary sub-mm patient motion that cannot be eliminated with simple means of external immobilization. We investigate a two-step iterative motion compensation based on a multi-component metric of image sharpness. Methods Motion is considered with respect to locally rigid motion within a particular region of interest, and the method supports application to multiple locally rigid regions. Motion is estimated by maximizing a cost function with three components: a gradient metric encouraging image sharpness, an entropy term that favors high contrast and penalizes streaks, and a penalty term encouraging smooth motion. Motion compensation involved initial coarse estimation of gross motion followed by estimation of fine-scale displacements using high resolution reconstructions. The method was evaluated in simulations with synthetic motion (1–4 mm) applied to a wrist volume obtained on a CMOS-based CBCT testbench. Structural similarity index (SSIM) quantified the agreement between motion-compensated and static data. The algorithm was also tested on a motion contaminated patient scan from dedicated extremities CBCT. Results Excellent correction was achieved for the investigated range of displacements, indicated by good visual agreement with the static data. 10–15% improvement in SSIM was attained for 2–4 mm motions. The compensation was robust against increasing motion (4% decrease in SSIM across the investigated range, compared to 14% with no compensation). Consistent performance was achieved across a range of noise levels. Significant mitigation of artifacts was shown in patient data. Conclusion The results indicate feasibility of image-based motion correction in extremities CBCT without the need for a priori motion models, external trackers, or fiducials. PMID:27346909

  8. 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.

  9. Image-based motion compensation for high-resolution extremities cone-beam CT

    NASA Astrophysics Data System (ADS)

    Sisniega, A.; Stayman, J. W.; Cao, Q.; Yorkston, J.; Siewerdsen, J. H.; Zbijewski, W.

    2016-03-01

    Purpose: Cone-beam CT (CBCT) of the extremities provides high spatial resolution, but its quantitative accuracy may be challenged by involuntary sub-mm patient motion that cannot be eliminated with simple means of external immobilization. We investigate a two-step iterative motion compensation based on a multi-component metric of image sharpness. Methods: Motion is considered with respect to locally rigid motion within a particular region of interest, and the method supports application to multiple locally rigid regions. Motion is estimated by maximizing a cost function with three components: a gradient metric encouraging image sharpness, an entropy term that favors high contrast and penalizes streaks, and a penalty term encouraging smooth motion. Motion compensation involved initial coarse estimation of gross motion followed by estimation of fine-scale displacements using high resolution reconstructions. The method was evaluated in simulations with synthetic motion (1-4 mm) applied to a wrist volume obtained on a CMOS-based CBCT testbench. Structural similarity index (SSIM) quantified the agreement between motion-compensated and static data. The algorithm was also tested on a motion contaminated patient scan from dedicated extremities CBCT. Results: Excellent correction was achieved for the investigated range of displacements, indicated by good visual agreement with the static data. 10-15% improvement in SSIM was attained for 2-4 mm motions. The compensation was robust against increasing motion (4% decrease in SSIM across the investigated range, compared to 14% with no compensation). Consistent performance was achieved across a range of noise levels. Significant mitigation of artifacts was shown in patient data. Conclusion: The results indicate feasibility of image-based motion correction in extremities CBCT without the need for a priori motion models, external trackers, or fiducials.

  10. Ultra-High Spatial Resolution, Multi-Energy CT using Photon Counting Detector Technology

    PubMed Central

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

    2017-01-01

    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. PMID:28392615

  11. High-risk carotid plaques identified by CT-angiogram can predict acute myocardial infarction.

    PubMed

    Mosleh, Wassim; Adib, Keenan; Natdanai, Punnanithinont; Carmona-Rubio, Andres; Karki, Roshan; Paily, Jacienta; Ahmed, Mohamed Abdel-Aal; Vakkalanka, Sujit; Madam, Narasa; Gudleski, Gregory D; Chung, Charles; Sharma, Umesh C

    2017-04-01

    Prior studies identified the incremental value of non-invasive imaging by CT-angiogram (CTA) to detect high-risk coronary atherosclerotic plaques. Due to their superficial locations, larger calibers and motion-free imaging, the carotid arteries provide the best anatomic access for the non-invasive characterization of atherosclerotic plaques. We aim to assess the ability of predicting obstructive coronary artery disease (CAD) or acute myocardial infarction (MI) based on high-risk carotid plaque features identified by CTA. We retrospectively examined carotid CTAs of 492 patients that presented with acute stroke to characterize the atherosclerotic plaques of the carotid arteries and examined development of acute MI and obstructive CAD within 12-months. Carotid lesions were defined in terms of calcifications (large or speckled), presence of low-attenuation plaques, positive remodeling, and presence of napkin ring sign. Adjusted relative risks were calculated for each plaque features. Patients with speckled (<3 mm) calcifications and/or larger calcifications on CTA had a higher risk of developing an MI and/or obstructive CAD within 1 year compared to patients without (adjusted RR of 7.51, 95%CI 1.26-73.42, P = 0.001). Patients with low-attenuation plaques on CTA had a higher risk of developing an MI and/or obstructive CAD within 1 year than patients without (adjusted RR of 2.73, 95%CI 1.19-8.50, P = 0.021). Presence of carotid calcifications and low-attenuation plaques also portended higher sensitivity (100 and 79.17%, respectively) for the development of acute MI. Presence of carotid calcifications and low-attenuation plaques can predict the risk of developing acute MI and/or obstructive CAD within 12-months. Given their high sensitivity, their absence can reliably exclude 12-month events.

  12. Coronary CT angiography in patients with high calcium score: evaluation of plaque characteristics and diagnostic accuracy.

    PubMed

    Park, Mi Jung; Jung, Jung Im; Choi, Yun-Seok; Ann, Soe Hee; Youn, Ho-Joong; Jeon, Gyeong Nyeo; Choi, Ho Cheol

    2011-12-01

    Our aim was to evaluate the plaque characteristics of coronary arteries related to significant stenosis with coronary CT angiography (CCTA) and to discuss the diagnostic accuracy of CCTA in patients with high calcium scores. After institutional review board approval, 110 patients (63 men; mean age: 67.1 ± 7.9 years) with Agatston scores >400 were retrospectively reviewed. Patients underwent Agatston calcium scoring and 64-slice CCTA, in addition to invasive coronary angiography (CAG). The composition (calcified, mixed, and non-calcified) and configuration (concentric, eccentric) of coronary artery plaques were analyzed on a per-segment basis by CCTA. We analyzed the differences in plaque composition and configuration between significant (≥ 50%) and non-significant (<50%) stenosis. Additionally, the diagnostic accuracy of stenosis according to plaque composition was evaluated by CCTA, using CAG as a reference method. Significant differences in plaque composition and configurations were observed between the two groups. In cases of significant stenosis, the proportions of concentric, mixed, and non-calcified plaques were significantly higher than those of eccentric and calcified plaques (P < 0.001). The sensitivity and positive predictive value of mixed (97.4, 87.6%) and non-calcified plaques (97.8, 95.7%) were significantly higher than those of calcified plaques (87.6, 67.2%). Although CCTA has limited value due to low diagnostic accuracy of calcified plaques, knowledge about the high frequencies of mixed and non-calcified plaques in significant stenosis help to make an accurate assessment of CAD with CCTA in patients with high calcium scores.

  13. High prevalence of abnormalities on CT and MR imaging in children with unilateral sensorineural hearing loss irrespective of age or degree of hearing loss.

    PubMed

    van Beeck Calkoen, E A; Sanchez Aliaga, E; Merkus, P; Smit, C F; van de Kamp, J M; Mulder, M F; Goverts, S T; Hensen, E F

    2017-06-01

    Evaluation of causal abnormalities identified on CT and MR imaging in children with unilateral sensorineural hearing loss (USNHL), and the association with age and severity of hearing loss. Retrospective cohort study. Tertiary referral otology/audiology center. 102 children diagnosed with USNHL between 2006 and 2016 were included. They underwent CT and/or MR imaging for the evaluation of the etiology of their hearing loss. Radiologic abnormalities of the inner ear and brain associated with USNHL. Using CT and/or MR imaging, causal abnormalities were identified in 49%, which is higher than previously reported (25-40%). The most frequently affected site was the labyrinth (29%), followed by the cochlear nerve (9%) and brain (7%). No significant difference in the number or type of abnormalities was found for the degree of hearing loss or age categories. Imaging is essential in the etiologic analysis of USNHL because of the high prevalence of causative abnormalities that can be identified with radiology, irrespective of the patients' age or degree of hearing loss. CT and MR imaging are complementary imaging options. The ideal imaging algorithm is controversial. Based on our findings, we conclude that there is limited additional diagnostic value of simultaneous dual modality imaging over sequential diagnostics. We therefore perform a stepwise radiological workup in order to maximize the diagnostic yield while minimizing impact and costs. If the primary imaging modality does not identify a cause for USNHL, performing the alternative imaging modality should be considered. Retrospective cohort study 2b. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Comparison of quantitative myocardial perfusion imaging CT to fluorescent microsphere-based flow from high-resolution cryo-images

    NASA Astrophysics Data System (ADS)

    Eck, Brendan L.; Fahmi, Rachid; Levi, Jacob; Fares, Anas; Wu, Hao; Li, Yuemeng; Vembar, Mani; Dhanantwari, Amar; Bezerra, Hiram G.; Wilson, David L.

    2016-03-01

    Myocardial perfusion imaging using CT (MPI-CT) has the potential to provide quantitative measures of myocardial blood flow (MBF) which can aid the diagnosis of coronary artery disease. We evaluated the quantitative accuracy of MPI-CT in a porcine model of balloon-induced LAD coronary artery ischemia guided by fractional flow reserve (FFR). We quantified MBF at baseline (FFR=1.0) and under moderate ischemia (FFR=0.7) using MPI-CT and compared to fluorescent microsphere-based MBF from high-resolution cryo-images. Dynamic, contrast-enhanced CT images were obtained using a spectral detector CT (Philips Healthcare). Projection-based mono-energetic images were reconstructed and processed to obtain MBF. Three MBF quantification approaches were evaluated: singular value decomposition (SVD) with fixed Tikhonov regularization (ThSVD), SVD with regularization determined by the L-Curve criterion (LSVD), and Johnson-Wilson parameter estimation (JW). The three approaches over-estimated MBF compared to cryo-images. JW produced the most accurate MBF, with average error 33.3+/-19.2mL/min/100g, whereas LSVD and ThSVD had greater over-estimation, 59.5+/-28.3mL/min/100g and 78.3+/-25.6 mL/min/100g, respectively. Relative blood flow as assessed by a flow ratio of LAD-to-remote myocardium was strongly correlated between JW and cryo-imaging, with R2=0.97, compared to R2=0.88 and 0.78 for LSVD and ThSVD, respectively. We assessed tissue impulse response functions (IRFs) from each approach for sources of error. While JW was constrained to physiologic solutions, both LSVD and ThSVD produced IRFs with non-physiologic properties due to noise. The L-curve provided noise-adaptive regularization but did not eliminate non-physiologic IRF properties or optimize for MBF accuracy. These findings suggest that model-based MPI-CT approaches may be more appropriate for quantitative MBF estimation and that cryo-imaging can support the development of MPI-CT by providing spatial distributions of MBF.

  15. C-arm cone beam CT guidance of sinus and skull base surgery: quantitative surgical performance evaluation and development of a novel high-fidelity phantom

    NASA Astrophysics Data System (ADS)

    Vescan, A. D.; Chan, H.; Daly, M. J.; Witterick, I.; Irish, J. C.; Siewerdsen, J. H.

    2009-02-01

    Surgical simulation has become a critical component of surgical practice and training in the era of high-precision image-guided surgery. While the ability to simulate surgery of the paranasal sinuses and skull base has been conventionally limited to 3D digital simulation or cadaveric dissection, we have developed novel methods employing rapid prototyping technology and 3D printing to create high-fidelity models from real patient images (CT or MR). Such advances allow creation of patient-specific models for preparation, simulation, and training before embarking on the actual surgery. A major challenge included the development of novel material formulations compatible with the rapid prototyping process while presenting anatomically realistic flexibility, cut-ability, drilling purchase, and density (CT number). Initial studies have yielded realistic models of the paranasal sinuses and skull base for simulation and training in image-guided surgery. The process of model development and material selection is reviewed along with the application of the phantoms in studies of high-precision surgery guided by C-arm cone-beam CT (CBCT). Surgical performance is quantitatively evaluated under CBCT guidance, with the high-fidelity phantoms providing an excellent test-bed for reproducible studies across a broad spectrum of challenging surgical tasks. Future work will broaden the atlas of models to include normal anatomical variations as well as a broad spectrum of benign and malignant disease. The role of high-fidelity models produced by rapid prototyping is discussed in the context of patient-specific case simulation, novel technology development (specifically CBCT guidance), and training of future generations of sinus and skull base surgeons.

  16. Is there still a role for cardiac CT in the emergency department in the era of highly-sensitive troponins?

    PubMed

    Dedic, Admir; Nieman, Koen; Hoffmann, Udo; Ferencik, Maros

    2017-06-01

    Physicians practicing cardiovascular medicine are every day confronted with patients presenting with symptoms suggestive of an acute coronary syndrome (ACS). Over the years, there have been substantial technical advances, such as the introduction of new non-invasive imaging techniques and the introduction of new highly sensitive cardiac biomarkers. Physicians have adopted these new assets and have become more experienced with them thus improving medical care. Nevertheless, the search for an efficient, yet safe diagnostic work-up for patients presenting with symptoms suggestive of ACS is ongoing. A large proportion of patients will require some form of non-invasive testing and the choice for the diagnostic modality as well as its timing are important steps in this process. Cardiac computed tomography (CT), a non-invasive imaging technique that rapidly provides visualization of the coronary artery tree, is an attractive option, with its unparalleled negative predictive value for obstructive coronary artery disease (CAD). With the introduction of highly-sensitive troponins (hsTn), the role of non-invasive testing, including cardiac CT, has changed. This review will provide an oversight on what is known about cardiac CT in acute chest presentations. Furthermore, we will discuss the changing role of cardiac CT in the era of hsTn and the possibility of their combined use in the work-up of suspected ACS patients. hsTn is currently an established tool for the diagnosis and triage of patients with suspected ACS. The role of cardiac CT has shifted now to a secondary, comprehensive rule-out test in patients with inconclusive biomarker status, providing information on stenosis severity, plaque burden, high-risk features and the presence of other serious conditions that can also give rise to hsTn.

  17. Use of computed tomography (CT) for urolithiasis in pediatric patients.

    PubMed

    Gupta, Angela; Castellan, Miguel

    2015-01-01

    Numbers of annual CT examinations have been increasing incrementally each year during the last 10-20 years. Use of unenhanced CT has been increasingly used for evaluation of urolithiasis, and concerned had been raised about the risks of increased radiation exposure in pediatric patients. Sensitivities and specificity for ureteral stones on conventional CT have been reported up to 98-100%, respectively. Low dose protocols have been developed with the goal of reducing radiation dose with adequate image quality. Although the sensitivity and the specificity of CT is the highest, many can be diagnosed with combination of KUB and ultrasound. CT can be utilized in equivocal cases. Low-dose radiation CT protocols have been reported with high sensitivity and specificity and should be used in pediatric patients when a CT scan is needed.

  18. Use of computed tomography (CT) for urolithiasis in pediatric patients

    PubMed Central

    Gupta, Angela

    2015-01-01

    Numbers of annual CT examinations have been increasing incrementally each year during the last 10-20 years. Use of unenhanced CT has been increasingly used for evaluation of urolithiasis, and concerned had been raised about the risks of increased radiation exposure in pediatric patients. Sensitivities and specificity for ureteral stones on conventional CT have been reported up to 98-100%, respectively. Low dose protocols have been developed with the goal of reducing radiation dose with adequate image quality. Although the sensitivity and the specificity of CT is the highest, many can be diagnosed with combination of KUB and ultrasound. CT can be utilized in equivocal cases. Low-dose radiation CT protocols have been reported with high sensitivity and specificity and should be used in pediatric patients when a CT scan is needed. PMID:26835357

  19. High Fidelity System Modeling for High Quality Image Reconstruction in Clinical CT

    PubMed Central

    Do, Synho; Karl, William Clem; Singh, Sarabjeet; Kalra, Mannudeep; Brady, Tom; Shin, Ellie; Pien, Homer

    2014-01-01

    Today, while many researchers focus on the improvement of the regularization term in IR algorithms, they pay less concern to the improvement of the fidelity term. In this paper, we hypothesize that improving the fidelity term will further improve IR image quality in low-dose scanning, which typically causes more noise. The purpose of this paper is to systematically test and examine the role of high-fidelity system models using raw data in the performance of iterative image reconstruction approach minimizing energy functional. We first isolated the fidelity term and analyzed the importance of using focal spot area modeling, flying focal spot location modeling, and active detector area modeling as opposed to just flying focal spot motion. We then compared images using different permutations of all three factors. Next, we tested the ability of the fidelity terms to retain signals upon application of the regularization term with all three factors. We then compared the differences between images generated by the proposed method and Filtered-Back-Projection. Lastly, we compared images of low-dose in vivo data using Filtered-Back-Projection, Iterative Reconstruction in Image Space, and the proposed method using raw data. The initial comparison of difference maps of images constructed showed that the focal spot area model and the active detector area model also have significant impacts on the quality of images produced. Upon application of the regularization term, images generated using all three factors were able to substantially decrease model mismatch error, artifacts, and noise. When the images generated by the proposed method were tested, conspicuity greatly increased, noise standard deviation decreased by 90% in homogeneous regions, and resolution also greatly improved. In conclusion, the improvement of the fidelity term to model clinical scanners is essential to generating higher quality images in low-dose imaging. PMID:25390888

  20. A high-energy-density, high-Mach number single jet experiment

    SciTech Connect

    Hansen, J. F.; Dittrich, T. R.; Elliott, J. B.; Glendinning, S. G.; Cotrell, D. L.

    2011-08-15

    A high-energy-density, x-ray-driven, high-Mach number (M{>=} 17) single jet experiment shows constant propagation speeds of the jet and its bowshock into the late time regime. The jet assumes a characteristic mushroom shape with a stalk and a head. The width of the head and the bowshock also grow linearly in time. The width of the stalk decreases exponentially toward an asymptotic value. In late time images, the stalk kinks and develops a filamentary nature, which is similar to experiments with applied magnetic fields. Numerical simulations match the experiment reasonably well, but ''exterior'' details of the laser target must be included to obtain a match at late times.

  1. Multiresolution iterative reconstruction in high-resolution extremity cone-beam CT

    NASA Astrophysics Data System (ADS)

    Cao, Qian; Zbijewski, Wojciech; Sisniega, Alejandro; Yorkston, John; Siewerdsen, Jeffrey H.; Webster Stayman, J.

    2016-10-01

    Application of model-based iterative reconstruction (MBIR) to high resolution cone-beam CT (CBCT) is computationally challenging because of the very fine discretization (voxel size  <100 µm) of the reconstructed volume. Moreover, standard MBIR techniques require that the complete transaxial support for the acquired projections is reconstructed, thus precluding acceleration by restricting the reconstruction to a region-of-interest. To reduce the computational burden of high resolution MBIR, we propose a multiresolution penalized-weighted least squares (PWLS) algorithm, where the volume is parameterized as a union of fine and coarse voxel grids as well as selective binning of detector pixels. We introduce a penalty function designed to regularize across the boundaries between the two grids. The algorithm was evaluated in simulation studies emulating an extremity CBCT system and in a physical study on a test-bench. Artifacts arising from the mismatched discretization of the fine and coarse sub-volumes were investigated. The fine grid region was parameterized using 0.15 mm voxels and the voxel size in the coarse grid region was varied by changing a downsampling factor. No significant artifacts were found in either of the regions for downsampling factors of up to 4×. For a typical extremities CBCT volume size, this downsampling corresponds to an acceleration of the reconstruction that is more than five times faster than a brute force solution that applies fine voxel parameterization to the entire volume. For certain configurations of the coarse and fine grid regions, in particular when the boundary between the regions does not cross high attenuation gradients, downsampling factors as high as 10×  can be used without introducing artifacts, yielding a ~50×  speedup in PWLS. The proposed multiresolution algorithm significantly reduces the computational burden of high resolution iterative CBCT reconstruction and can be extended to other applications of

  2. Is CT angiography of the pulmonary arteries indicated in patients with high clinical probability of pulmonary embolism?

    PubMed

    Martínez Montesinos, L; Plasencia Martínez, J M; García Santos, J M

    2017-06-30

    When a diagnostic test confirms clinical suspicion, the indicated treatment can be administered. A problem arises when the diagnostic test does not confirm the initially suspected diagnosis; when the suspicion is grounded in clinically validated predictive rules and is high, the problem is even worse. This situation arises in up to 40% of patients with high suspicion for acute pulmonary embolism, raising the question of whether CT angiography of the pulmonary arteries should be done systematically. This paper reviews the literature about this issue and lays out the best evidence about the relevant recommendations for patients with high clinical suspicion of acute pulmonary embolism and negative findings on CT angiography. It also explains the probabilistic concepts derived from Bayes' theorem that can be useful for ascertaining the most appropriate approach in these patients. Copyright © 2017 SERAM. Publicado por Elsevier España, S.L.U. All rights reserved.

  3. Seventh-generation CT

    NASA Astrophysics Data System (ADS)

    Besson, G. M.

    2016-03-01

    A new dual-drum CT system architecture has been recently introduced with the potential to achieve significantly higher temporal resolution than is currently possible in medical imaging CT. The concept relies only on known technologies; in particular rotation speeds several times higher than what is possible today could be achieved leveraging typical x-ray tube designs and capabilities. However, the architecture lends itself to the development of a new arrangement of x-ray sources in a toroidal vacuum envelope containing a rotating cathode ring and a (optionally rotating) shared anode ring to potentially obtain increased individual beam power as well as increase total exposure per rotation. The new x-ray source sub-system design builds on previously described concepts and could make the provision of multiple conventional high-power cathodes in a CT system practical by distributing the anode target between the cathodes. In particular, relying on known magnetic-levitation technologies, it is in principle possible to more than double the relative speed of the electron-beam with respect to the target, thus potentially leading to significant individual beam power increases as compared to today's state-of-the-art. In one embodiment, the proposed design can be naturally leveraged by the dual-drum CT concept previously described to alleviate the problem of arranging a number of conventional rotating anode-stem x-ray tubes and power conditioners on the limited space of a CT gantry. In another embodiment, a system with three cathodes is suggested leveraging the architecture previously proposed by Franke.

  4. Journal Club: the Alvarado score as a method for reducing the number of CT studies when appendiceal ultrasound fails to visualize the appendix in adults.

    PubMed

    Jones, Robert P; Jeffrey, R Brooke; Shah, Bhavya R; Desser, Terry S; Rosenberg, Jarrett; Olcott, Eric W

    2015-03-01

    OBJECTIVE. The purpose of this article is to evaluate the hypothesis that Alvarado scores of 3 or lower identify adult patients who are unlikely to benefit from CT after appendiceal ultrasound fails to show the appendix and is otherwise normal. MATERIALS AND METHODS. We identified 119 consecutive adults for whom the appendix was not seen on otherwise normal appendiceal sonography performed as the first imaging study for suspected appendicitis, who subsequently underwent CT within 48 hours, and whose data permitted retrospective calculation of admission Alvarado scores. Specific benefits of CT were defined as diagnoses of appendicitis or significant alternative findings, and specific benefits were compared between patients with Alvarado scores of 3 or less and 4 or higher. Significant alternative findings on CT were findings other than appendicitis that were treated with medical or surgical therapy during the admission or that were to be addressed during follow-up care. Diagnostic reference standards were discharge diagnoses, pathologic examinations, and clinical follow-up. RESULTS. No patients (0.0%, 0/49) with Alvarado scores 3 or lower had appendicitis, compared with 17.1% (12/70) of patients with Alvarado scores 4 or higher (p = 0.001), and CT showed neither appendicitis nor significant alternative findings in 85.7% (42/49) versus 58.6% (41/70) of these patients, respectively (p = 0.002). The rates of perforated appendicitis, as well as significant alternative CT findings, did not differ significantly. CONCLUSION. Adults with Alvarado scores 3 or lower who have nonvisualized appendixes and otherwise normal appendiceal sonography are at very low risk for appendicitis or significant alternative findings and therefore are not likely to benefit from CT.

  5. High-pitch low-dose abdominopelvic CT with tin-filtration technique for detecting urinary stones.

    PubMed

    Zhang, Gu-Mu-Yang; Shi, Bing; Sun, Hao; Xue, Hua-Dan; Wang, Yun; Liang, Ji-Xiang; Xu, Kai; Wang, Ming; Wang, Man; Xu, Min; Jin, Zheng-Yu

    2017-08-01

    To evaluate urinary stone detection, radiation exposure, image quality, breathing-motion artifacts, and scanning time with high-pitch tin filter-based abdominopelvic CT. Sixty-three consecutive patients with urolithiasis underwent non-enhanced abdominopelvic CT with both regular (120 kV, pitch 0.6) and low-dose (Sn150kV, pitch 3.0) protocols on a third-generation dual-source CT. Stone characteristics, image noise (SD), signal-to-noise ratio (SNR), subjective image quality on a 5-point likert scale breathing-motion artifacts, and scanning time were evaluated. Volume CT dose index (CTDIvol), dose-length product (DLP), effective dose (ED) were compared. A total of 157 urinary stones were detected by regular protocol; 154 were correctly identified by low-dose protocol with an overall detection rate of 98.1%. No significant differences were observed in SD, SNR, or subjective image quality between two protocols (P > 0.05). Compared to regular protocol, CTDIvol and ED were 56.6% (7.19 vs. 3.12 mGy, P < 0.001) and 55.6% (5.25 vs. 2.33 mSv, P < 0.001) lower; scanning time was 89.5% (7.9 vs. 0.83, P < 0.001) shorter; and breathing-motion artifacts were fewer (8 vs. 0 patients) with low-dose protocol. High-pitch abdominopelvic CT with Sn150kV substantially reduced radiation exposure and scanning time, while maintained stone detection and image quality and prevented breathing-motion artifacts.

  6. Investigation of a Dedicated, High Resolution PET/CT Scanner for Staging and Treatment Planning of Head and Neck Cancer

    NASA Astrophysics Data System (ADS)

    Raylman, Raymond R.; Stolin, Alexander V.; Sompalli, Prashanth; Randall, Nicole Bunda; Martone, Peter F.; Clinthorne, Neal H.

    2015-10-01

    Staging of head and neck cancer (HNC) is often hindered by the limited resolution of standard whole body PET scanners, which can make it challenging to detect small areas of metastatic disease in regional lymph nodes and accurately delineate tumor boundaries. In this investigation, the performance of a proposed high resolution PET/CT scanner designed specifically for imaging of the head and neck region was explored. The goal is to create a dedicated PET/CT system that will enhance the staging and treatment of HNCs. Its performance was assessed by simulating the scanning of a three-dimensional Rose-Burger contrast phantom. To extend the results from the simulation studies, an existing scanner with a similar geometry to the dedicated system and a whole body, clinical PET/CT scanner were used to image a Rose-Burger contrast phantom and a phantom simulating the neck of an HNC patient (out-of-field-of-view sources of activity were not included). Images of the contrast detail phantom acquired with Breast-PET/CT and simulated head and neck scanner both produced object contrasts larger than the images created by the clinical scanner. Images of a neck phantom acquired with the Breast-PET/CT scanner permitted the identification of all of the simulated metastases, while it was not possible to identify any of the simulated metastasis with the clinical scanner. The initial results from this study demonstrate the potential benefits of high-resolution PET systems for improving the diagnosis and treatment of HNC.

  7. Profiles of US and CT imaging features with a high probability of appendicitis

    PubMed Central

    Laméris, W.; van Es, H. W.; ten Hove, W.; Bouma, W. H.; van Leeuwen, M. S.; van Keulen, E. M.; van der Hulst, V. P. M.; Henneman, O. D.; Bossuyt, P. M.; Boermeester, M. A.; Stoker, J.

    2010-01-01

    Objectives To identify and evaluate profiles of US and CT features associated with acute appendicitis. Methods Consecutive patients presenting with acute abdominal pain at the emergency department were invited to participate in this study. All patients underwent US and CT. Imaging features known to be associated with appendicitis, and an imaging diagnosis were prospectively recorded by two independent radiologists. A final diagnosis was assigned after 6 months. Associations between appendiceal imaging features and a final diagnosis of appendicitis were evaluated with logistic regression analysis. Results Appendicitis was assigned to 284 of 942 evaluated patients (30%). All evaluated features were associated with appendicitis. Imaging profiles were created after multivariable logistic regression analysis. Of 147 patients with a thickened appendix, local transducer tenderness and peri-appendiceal fat infiltration on US, 139 (95%) had appendicitis. On CT, 119 patients in whom the appendix was completely visualised, thickened, with peri-appendiceal fat infiltration and appendiceal enhancement, 114 had a final diagnosis of appendicitis (96%). When at least two of these essential features were present on US or CT, sensitivity was 92% (95% CI 89–96%) and 96% (95% CI 93–98%), respectively. Conclusion Most patients with appendicitis can be categorised within a few imaging profiles on US and CT. When two of the essential features are present the diagnosis of appendicitis can be made accurately. PMID:20119730

  8. High-Performance Hybrid Bismuth-Carbon Nanotube Based Contrast Agent for X-ray CT Imaging.

    PubMed

    Hernández-Rivera, Mayra; Kumar, Ish; Cho, Stephen Y; Cheong, Benjamin Y; Pulikkathara, Merlyn X; Moghaddam, Sakineh E; Whitmire, Kenton H; Wilson, Lon J

    2017-02-22

    Carbon nanotubes (CNTs) have been used for a plethora of biomedical applications, including their use as delivery vehicles for drugs, imaging agents, proteins, DNA, and other materials. Here, we describe the synthesis and characterization of a new CNT-based contrast agent (CA) for X-ray computed tomography (CT) imaging. The CA is a hybrid material derived from ultrashort single-walled carbon nanotubes (20-80 nm long, US-tubes) and Bi(III) oxo-salicylate clusters with four Bi(III) ions per cluster (Bi4C). The element bismuth was chosen over iodine, which is the conventional element used for CT CAs in the clinic today due to its high X-ray attenuation capability and its low toxicity, which makes bismuth a more-promising element for new CT CA design. The new CA contains 20% by weight bismuth with no detectable release of bismuth after a 48 h challenge by various biological media at 37 °C, demonstrating the presence of a strong interaction between the two components of the hybrid material. The performance of the new Bi4C@US-tubes solid material as a CT CA has been assessed using a clinical scanner and found to possess an X-ray attenuation ability of >2000 Hounsfield units (HU).

  9. High-resolution CT analysis of facial struts in trauma: 2. Osseous and soft-tissue complications.

    PubMed

    Gentry, L R; Manor, W F; Turski, P A; Strother, C M

    1983-03-01

    In six cadavers, high-resolution thin-section computed tomography (CT) was used to evaluate the sequelae of experimentally produced facial trauma. As confirmed by pluridirectional tomography, CT was an effective imaging method for the detection and classification of facial fractures. The ability of CT to simultaneously depict both osseous and soft-tissue structures expands the role that diagnostic radiology can play in the evaluation of the traumatized face. A method of evaluation is presented in which the face is geometrically conceptualized as a series of triplanar (horizontal, sagittal, and coronal) osseous struts. Sequential, systematic assessment of each strut for fracture and its adjacent soft tissue for injury can facilitate evaluation of the traumatized face. Using this approach the osseous and soft-tissue complications arising from experimentally produced trauma are reviewed and illustrated with CT. Examples of potential soft-tissue complications that may occur with fractures of the horizontal group of struts include disruption of the dura matter at the cribiform plate, involvement of the structures of the anterior cranial fossa, injury to the optic nerve, and involvement of the superior and inferior groups of extraocular muscles. Injury to the nasolacrimal duct, maxillary sinus ostium, medial and lateral rectus muscles, or the soft-tissue structures in the superior and inferior orbital fissures may arise from disruption of the sagittal struts. Fractures of the coronal struts may involve the frontal sinus, anterior cranial fossa, lacrimal gland, nasofrontal duct, lacrimal sac, or the soft tissues of the pterygopalatine fossa.

  10. Fully automatic segmentation of femurs with medullary canal definition in high and in low resolution CT scans.

    PubMed

    Almeida, Diogo F; Ruben, Rui B; Folgado, João; Fernandes, Paulo R; Audenaert, Emmanuel; Verhegghe, Benedict; De Beule, Matthieu

    2016-12-01

    Femur segmentation can be an important tool in orthopedic surgical planning. However, in order to overcome the need of an experienced user with extensive knowledge on the techniques, segmentation should be fully automatic. In this paper a new fully automatic femur segmentation method for CT images is presented. This method is also able to define automatically the medullary canal and performs well even in low resolution CT scans. Fully automatic femoral segmentation was performed adapting a template mesh of the femoral volume to medical images. In order to achieve this, an adaptation of the active shape model (ASM) technique based on the statistical shape model (SSM) and local appearance model (LAM) of the femur with a novel initialization method was used, to drive the template mesh deformation in order to fit the in-image femoral shape in a time effective approach. With the proposed method a 98% convergence rate was achieved. For high resolution CT images group the average error is less than 1mm. For the low resolution image group the results are also accurate and the average error is less than 1.5mm. The proposed segmentation pipeline is accurate, robust and completely user free. The method is robust to patient orientation, image artifacts and poorly defined edges. The results excelled even in CT images with a significant slice thickness, i.e., above 5mm. Medullary canal segmentation increases the geometric information that can be used in orthopedic surgical planning or in finite element analysis.

  11. Breast CT.

    PubMed

    Glick, Stephen J

    2007-01-01

    Breast cancer is a serious disease that accounts for approximately 40,000 deaths per year in the United States. Unfortunately, there is no known cause of breast cancer, and therefore the best way to prevent mortality is early detection. In the past 15 years, breast cancer mortality has been reduced significantly, which is in part due to screening with film-screen mammography. Nonetheless, conventional mammography lacks sensitivity, especially for certain subgroups of women such as those with dense breast tissue, those under 50 years old, and pre- or perimenopausal women. In addition, mammography has a very poor positive predictive value for biopsy, with 70%-90% of biopsies performed turning out negative. By improving visualization of breast tissue, X-ray computerized tomography (CT) of the breast can potentially provide improvements in diagnostic accuracy over conventional mammography. Owing to recent technological developments in digital detector technology, flat-panel CT imagers dedicated to imaging of the breast are now feasible. A number of academic groups are currently researching dedicated breast CT and prototype systems are currently being evaluated in the clinical setting.

  12. High prevalence of brain pathology in violent prisoners: a qualitative CT and MRI scan study.

    PubMed

    Schiltz, Kolja; Witzel, Joachim G; Bausch-Hölterhoff, Josef; Bogerts, Bernhard

    2013-10-01

    The aim of this study was to determine the frequency and extent of brain anomalies in a large sample of incarcerated violent offenders not previously considered neuropsychiatrically ill, in comparison with non-violent offenders and non-offending controls. MRI and CT brain scans from 287 male prison inmates (162 violent and 125 non-violent) not diagnosed as mentally ill before that were obtained due to headache, vertigo or psychological complaints during imprisonment were assessed and compared to 52 non-criminal controls. Brain scans were rated qualitatively with respect to evidence of structural brain damage. Each case received a semiquantitative rating of "normal" (=0), "questionably abnormal" (=1) or "definitely abnormal" (=2) for the lateral ventricles, frontal/parietal cortex and medial temporal structures bilaterally as well as third ventricle. Overall, offenders displayed a significantly higher rate of morphological abnormality, with the violent offenders scoring significantly higher than non-violent offenders and controls. This difference was statistically detectable for frontal/parietal cortex, medial temporal structures, third ventricle and the left but not the right lateral ventricle. The remarkable prevalence of brain pathology in convicted violent prisoners detectable by neuroradiological routine assessment not only highlights the importance of frontal and temporal structures in the control of social, and specifically of violent behaviour, but also raises questions on the legal culpability of violent offenders with brain abnormalities. The high proportion of undetected presence of structural brain damage emphasizes the need that in violent criminals, the comprehensive routine neuropsychiatric assessment usually performed in routine forensic psychiatric expertises should be complemented with brain imaging.

  13. Preliminary application of high-definition CT Gemstone Spectral Imaging in hand and foot tendons.

    PubMed

    Deng, Kai; Zhang, Cheng-Qi; Li, Wei; Wang, Jun-Jun; Wang, Xin-Yi; Pang, Tao; Wang, Guang-Li; Liu, Cheng

    2012-01-01

    To assess the feasibility of visualizing hand and foot tendon anatomy and disorders by Gemstone Spectral Imaging (GSI) high-definition CT (HDCT). Thirty-five patients who suffered from hand or foot pain were scanned with GSI mode HDCT and MRI. Spectrum analysis was used to select the monochromatic images that provide the optimal contrast-to-noise ratio (CNR) for tendons. The image quality at the best selected monochromatic level and the conventional polychromatic images were compared. Tendon anatomy and disease were also analyzed at GSI and MRI. The monochromatic images at about 65 keV (mean 65.09 ± 2.98) provided the optimal CNR for hand and foot tendons. The image quality at the optimal selected monochromatic level was superior to conventional polychromatic images (p = 0.005, p < 0.05). GSI was useful in visualizing hand and foot tendon anatomy and disorders. There were no statistical differences between GSI and MRI with regard to tendon thickening (χ(2) = 0, p > 0.05), compression (χ(2) = 0.5, p > 0.05), absence (χ(2) = 0, p > 0.05) and rupture (χ(2) = 0, p > 0.05). GSI was significantly less sensitive than MRI in displaying tendon adhesion (χ(2) = 4.17, p < 0.05), degeneration (χ(2) = 4.17, p < 0.05), and tendinous sheath disease (χ(2) = 10.08, p < 0.05). GSI with monochromatic images at 65 keV displays clearly the most hand and foot tendon anatomy and disorders with image quality improved, as compared with conventional polychromatic images. It may be used solely or combined with MRI in clinical work, depending on individual patient disease condition.

  14. Automatic identification of colonic polyp in high-resolution CT images

    NASA Astrophysics Data System (ADS)

    Dehmeshki, Jamshid; Amin, Hamdan; Wong, Wing; Ebadian Dehkordi, Mandana; Kamangari, Nahid; Roddie, Mary; Costello, John

    2004-05-01

    Automatic polyp detection is a challenging task as polyps come in different sizes and shape. The detection generally consists of colon segmentation, identification of suspected polyps and classification. Classification involves discriminating polyps from among many suspected regions based on a number of features extracted from the detected regions. This paper presents the work on the first two stages of the detection. For the colon segmentation, the fuzzy connectivity region growing technique is used while for the identification of suspected polyps concave region searching is applied. A rule-based filtering based on 3D volumetric features is used to reduce a large number of non-polyp structures (false positives). The method is fast, robust and validated with a number of high-resolution colon datasets.

  15. [Study of low radiation exposure dose and low contrast medium dose in coronary CT angiography with High-pitch spiral acquisition mode of dual source CT].

    PubMed

    Dai, Yingyu; Guo, Liang; Dai, Qichun; Liu, Yonghao; Ma, Xinxing

    2014-08-05

    To evaluate the feasibility of low radiation exposure and low contrast medium volume for coronary CT angiography with High- pitch spiral acquisition mode of dual source CT. 135 patients whose BMI <23 kg/m² and heart rates <65 bpm selected from 291 patients diagnosed of suspected CHD at our institution from September 2013 to February 2014 were randomly divided into 3 groups before CCTA, and there were 45 patients in each group. 80 kV , Iodixanol (320 mgI/ml) and sinogram affirmed iterative reconstruction (SAFIRE) were used in A group. 80 kV , Iopamidol (370 mgI/ml) and SAFIRE were used in B group. 100 kV, Iodixanol and filtered back projection (FBP) were used in C group. Two radiologists assessed image quality with 5-piont scale subjectively and double-blind. Independent-Sample Test was used to analyze statistical significance of image quality including signal to noise ratio(SNR) and contrast to noise ratio (CNR) between A and B group or between A and C group. At the same time, Contrast medium dose statistical significance between A and B group and mean effective Radiation dose (ED)statistical significance between A and C were analyzed by the same way. There were no significant difference of image quality including SNR and CNR of aortic root (AO), left main coronary artery (LM), left anterior descending artery (LAD), circumflex coronary artery (CX) and right coronary artery (RCA) Between A and B group (P = non-significant for all comparison), whereas Iodine in taken of A group decreased 14% (17 600 mg vs 20 350 mg). There were no significant difference of image quality including SNR and CNR of AO, LM, LAD, CX and RCA Between A and C group (P = non-significant for all comparison), whereas mean ED of A group decreased 50% (0.41 ± 0.05 mSv vs 0.79 ± 0.15 mSv). The double low dose application which use High-pitch spiral mode, 80 kV, SAFIRE, and Iodixanol (320 mgI/ml) can be used in those patients whose BMI <23 kg/m² and heart rates <65 bpm to reduce the burden of

  16. Intramammary Findings on CT of the Chest – a Review of Normal Anatomy and Possible Findings

    PubMed Central

    Gossner, Johannes

    2016-01-01

    Summary Computed tomography (CT) is a frequently performed examination in women of all ages. In all thoracic CT examinations of the chest at least parts of the breasts are included. Therefore incidental breast pathology may be observed. It has been suggested that one out of 250 women undergoing chest CT will show a malignant incidental breast lesion. Given the high number of performed chest CT examinations, this contributes to a significant number of malignancies. In this review, after a brief discussion of the value of computed tomography in breast imaging, normal and pathologic findings are discussed to create awareness of this potential “black box” on chest CT. PMID:28058068

  17. Monte Carlo simulations of a high-resolution X-ray CT system for industrial applications

    NASA Astrophysics Data System (ADS)

    Miceli, A.; Thierry, R.; Flisch, A.; Sennhauser, U.; Casali, F.; Simon, M.

    2007-12-01

    An X-ray computed tomography (CT) model based on the GEANT4 Monte Carlo code was developed for simulation of a cone-beam CT system for industrial applications. The full simulation of the X-ray tube, object, and area detector was considered. The model was validated through comparison with experimental measurements of different test objects. There is good agreement between the simulated and measured projections. To validate the model we reduced the beam aperture of the X-ray tube, using a source-collimator, to decrease the scattered radiation from the CT system structure and from the walls of the X-ray shielding room. The degradation of the image contrast using larger beam apertures is also shown. Thereafter, the CT model was used to calculate the spatial distribution and the magnitude of the scattered radiation from different objects. It has been assessed that the scatter-to-primary ratio (SPR) is below 5% for small aluminum objects (approx. 5 cm path length), and in the case of large aluminum objects (approx. 20 cm path length) it can reach up to a factor of 3 in the region corresponding to the maximum path length. Therefore, the scatter from the object significantly affects quantitative accuracy. The model was also used to evaluate the degradation of the image contrast due to the detector box.

  18. A maximum likelihood method for high resolution proton radiography/proton CT.

    PubMed

    Collins-Fekete, Charles-Antoine; Brousmiche, Sébastien; Portillo, Stephen K N; Beaulieu, Luc; Seco, Joao

    2016-12-07

    Multiple Coulomb scattering (MCS) is the largest contributor to blurring in proton imaging. In this work, we developed a maximum likelihood least squares estimator that improves proton radiography's spatial resolution. The water equivalent thickness (WET) through projections defined from the source to the detector pixels were estimated such that they maximizes the likelihood of the energy loss of every proton crossing the volume. The length spent in each projection was calculated through the optimized cubic spline path estimate. The proton radiographies were produced using Geant4 simulations. Three phantoms were studied here: a slanted cube in a tank of water to measure 2D spatial resolution, a voxelized head phantom for clinical performance evaluation as well as a parametric Catphan phantom (CTP528) for 3D spatial resolution. Two proton beam configurations were used: a parallel and a conical beam. Proton beams of 200 and 330 MeV were simulated to acquire the radiography. Spatial resolution is increased from 2.44 lp cm(-1) to 4.53 lp cm(-1) in the 200 MeV beam and from 3.49 lp cm(-1) to 5.76 lp cm(-1) in the 330 MeV beam. Beam configurations do not affect the reconstructed spatial resolution as investigated between a radiography acquired with the parallel (3.49 lp cm(-1) to 5.76 lp cm(-1)) or conical beam (from 3.49 lp cm(-1) to 5.56 lp cm(-1)). The improved images were then used as input in a photon tomography algorithm. The proton CT reconstruction of the Catphan phantom shows high spatial resolution (from 2.79 to 5.55 lp cm(-1) for the parallel beam and from 3.03 to 5.15 lp cm(-1) for the conical beam) and the reconstruction of the head phantom, although qualitative, shows high contrast in the gradient region. The proposed formulation of the optimization demonstrates serious potential to increase the spatial resolution (up by 65[Formula: see text]) in proton radiography and greatly accelerate proton computed tomography reconstruction.

  19. A maximum likelihood method for high resolution proton radiography/proton CT

    NASA Astrophysics Data System (ADS)

    Collins-Fekete, Charles-Antoine; Brousmiche, Sébastien; Portillo, Stephen K. N.; Beaulieu, Luc; Seco, Joao

    2016-12-01

    Multiple Coulomb scattering (MCS) is the largest contributor to blurring in proton imaging. In this work, we developed a maximum likelihood least squares estimator that improves proton radiography’s spatial resolution. The water equivalent thickness (WET) through projections defined from the source to the detector pixels were estimated such that they maximizes the likelihood of the energy loss of every proton crossing the volume. The length spent in each projection was calculated through the optimized cubic spline path estimate. The proton radiographies were produced using Geant4 simulations. Three phantoms were studied here: a slanted cube in a tank of water to measure 2D spatial resolution, a voxelized head phantom for clinical performance evaluation as well as a parametric Catphan phantom (CTP528) for 3D spatial resolution. Two proton beam configurations were used: a parallel and a conical beam. Proton beams of 200 and 330 MeV were simulated to acquire the radiography. Spatial resolution is increased from 2.44 lp cm-1 to 4.53 lp cm-1 in the 200 MeV beam and from 3.49 lp cm-1 to 5.76 lp cm-1 in the 330 MeV beam. Beam configurations do not affect the reconstructed spatial resolution as investigated between a radiography acquired with the parallel (3.49 lp cm-1 to 5.76 lp cm-1) or conical beam (from 3.49 lp cm-1 to 5.56 lp cm-1). The improved images were then used as input in a photon tomography algorithm. The proton CT reconstruction of the Catphan phantom shows high spatial resolution (from 2.79 to 5.55 lp cm-1 for the parallel beam and from 3.03 to 5.15 lp cm-1 for the conical beam) and the reconstruction of the head phantom, although qualitative, shows high contrast in the gradient region. The proposed formulation of the optimization demonstrates serious potential to increase the spatial resolution (up by 65 % ) in proton radiography and greatly accelerate proton computed tomography reconstruction.

  20. CT-guided high-dose-rate brachytherapy in the interdisciplinary treatment of patients with liver metastases of pancreatic cancer.

    PubMed

    Wieners, Gero; Schippers, Alexander Christian; Collettini, Federico; Schnapauff, Dirk; Hamm, Bernd; Wust, Peter; Riess, Hanno; Gebauer, Bernhard

    2015-10-01

    CT-guided high-dose-rate brachytherapy (CT-HDRBT) is an interventional radiologic technique for local ablation of primary and secondary malignomas applying a radiation source through a brachycatheter percutaneously into the targeted lesion. The aim of this study was to assess local tumor control, safety and efficacy of CT-HDRBT in the treatment of liver metastases of pancreatic cancer. Twenty consecutive patients with 49 unresectable liver metastases of pancreatic cancer were included in this retrospective trial and treated with CT-HDRBT, applied as a single fraction high-dose irradiation (15-20 Gy) using a 192Ir-source. Primary endpoint was local tumor control and secondary endpoints were complications, progression-free survival and overall survival. The mean tumor diameter was 29 mm (range 10-73). The mean irradiation time was 20 minutes (range 7-42). The mean coverage of the clinical target volume was 98% (range 88%-100%). The mean D100 was 18.1 Gy and the median D100 was 19.78 Gy. Three major complications occurred with post-interventional abscesses, three of which were seen in 15 patients with biliodigestive anastomosis (20%) and overall 15%. The mean follow-up time was 13.7 months (range 1.4-55.0). The median progression-free survival was 4.9 months (range 1.4-42.9, mean 9.4). Local recurrence occurred in 5 (10%) of 49 metastases treated. The median overall survival after CT-HDRBT was 8.6 months (range 1.5-55.3). Eleven patients received chemotherapy after ablation with a median progression-free survival of 4.9 months (mean 12.9). Nine patients did not receive chemotherapy after intervention with a median progression-free survival of 3.2 months (mean 5.0). The rate of local tumor control was 91% in both groups after 12 months. CT-HDRBT was safe and effective for the treatment of liver metastases of pancreatic cancer.

  1. Unexpected High Digestion Rate of Cooked Starch by the Ct-Maltase-Glucoamylase Small Intestine Mucosal α-Glucosidase Subunit

    PubMed Central

    Lin, Amy Hui-Mei; Nichols, Buford L.; Quezada-Calvillo, Roberto; Avery, Stephen E.; Sim, Lyann; Rose, David R.; Naim, Hassan Y.; Hamaker, Bruce R.

    2012-01-01

    For starch digestion to glucose, two luminal α-amylases and four gut mucosal α-glucosidase subunits are employed. The aim of this research was to investigate, for the first time, direct digestion capability of individual mucosal α-glucosidases on cooked (gelatinized) starch. Gelatinized normal maize starch was digested with N- and C-terminal subunits of recombinant mammalian maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI) of varying amounts and digestion periods. Without the aid of α-amylase, Ct-MGAM demonstrated an unexpected rapid and high digestion degree near 80%, while other subunits showed 20 to 30% digestion. These findings suggest that Ct-MGAM assists α-amylase in digesting starch molecules and potentially may compensate for developmental or pathological amylase deficiencies. PMID:22563462

  2. Micro-CT scan reveals an unexpected high-volume and interconnected pore network in a Cretaceous Sanagasta dinosaur eggshell.

    PubMed

    Hechenleitner, E Martín; Grellet-Tinner, Gerald; Foley, Matthew; Fiorelli, Lucas E; Thompson, Michael B

    2016-03-01

    The Cretaceous Sanagasta neosauropod nesting site (La Rioja, Argentina) was the first confirmed instance of extinct dinosaurs using geothermal-generated heat to incubate their eggs. The nesting strategy and hydrothermal activities at this site led to the conclusion that the surprisingly 7 mm thick-shelled eggs were adapted to harsh hydrothermal microenvironments. We used micro-CT scans in this study to obtain the first three-dimensional microcharacterization of these eggshells. Micro-CT-based analyses provide a robust assessment of gas conductance in fossil dinosaur eggshells with complex pore canal systems, allowing calculation, for the first time, of the shell conductance through its thickness. This novel approach suggests that the shell conductance could have risen during incubation to seven times more than previously estimated as the eggshell erodes. In addition, micro-CT observations reveal that the constant widening and branching of pore canals form a complex funnel-like pore canal system. Furthermore, the high density of pore canals and the presence of a lateral canal network in the shell reduce the risks of pore obstruction during the extended incubation of these eggs in a relatively highly humid and muddy nesting environment.

  3. Micro-CT scan reveals an unexpected high-volume and interconnected pore network in a Cretaceous Sanagasta dinosaur eggshell

    PubMed Central

    Grellet-Tinner, Gerald; Foley, Matthew; Thompson, Michael B.

    2016-01-01

    The Cretaceous Sanagasta neosauropod nesting site (La Rioja, Argentina) was the first confirmed instance of extinct dinosaurs using geothermal-generated heat to incubate their eggs. The nesting strategy and hydrothermal activities at this site led to the conclusion that the surprisingly 7 mm thick-shelled eggs were adapted to harsh hydrothermal microenvironments. We used micro-CT scans in this study to obtain the first three-dimensional microcharacterization of these eggshells. Micro-CT-based analyses provide a robust assessment of gas conductance in fossil dinosaur eggshells with complex pore canal systems, allowing calculation, for the first time, of the shell conductance through its thickness. This novel approach suggests that the shell conductance could have risen during incubation to seven times more than previously estimated as the eggshell erodes. In addition, micro-CT observations reveal that the constant widening and branching of pore canals form a complex funnel-like pore canal system. Furthermore, the high density of pore canals and the presence of a lateral canal network in the shell reduce the risks of pore obstruction during the extended incubation of these eggs in a relatively highly humid and muddy nesting environment. PMID:27009182

  4. Syntheses and characterization of lisinopril-coated gold nanoparticles as highly stable targeted CT contrast agents in cardiovascular diseases.

    PubMed

    Ghann, William E; Aras, Omer; Fleiter, Thorsten; Daniel, Marie-Christine

    2012-07-17

    Lisinopril was used as the targeting moiety to prepare gold nanoparticle-based functional CT contrast agents. Pure lisinopril, thioctic acid-lisinopril conjugate, and reduced thioctic acid-lisinopril conjugate were used to obtain GNP-Lis, GNP-TA-Lis, and GNP-RTA-Lis, respectively, via ligand exchange reaction on citrate-coated gold nanoparticles (GNPs). These lisinopril-decorated GNPs were fully characterized, and their chemical stabilities in biological relevant media and in high salt concentration were compared. Their relative stabilities toward lyophilization and against cyanide-induced decomposition were also investigated. Because of their higher stability, GNP-TA-Lis were used to assess the targeting of angiotensin converting enzyme (ACE) using X-ray computed tomography (CT). The images obtained displayed high contrast in the region of the lungs and heart, clearly indicating the targeting of ACE, whose overexpression is associated with development of cardiac and pulmonary fibrosis. Thus, the new nanoprobes prepared here will serve as very useful tools for the monitoring of cardiovascular pathophysiologies using CT imaging.

  5. Dual-source CT in blunt trauma patients: elimination of diaphragmatic motion using high-pitch spiral technique.

    PubMed

    Liang, Teresa; McLaughlin, Patrick; Arepalli, Chesnal D; Louis, Luck J; Bilawich, Ana-Maria; Mayo, John; Nicolaou, Savvas

    2016-04-01

    The purpose of this study was to compare diaphragmatic motion on dual-source high-pitch (DS-HP) and conventional single-source (SS) CT scans in trauma patients. Seventy-five consecutive trauma patients who presented to a level one trauma center over a 6-month period were scanned with a standardized whole body trauma CT protocol including both DS-HP chest (pitch = 2.1-2.5) and SS abdominal CT scans. Subjective analysis of diaphragmatic motion was performed by two readers using a four-point motion scale in seven regions of the diaphragm on coronal and axial slices. An overall confidence score to exclude a diaphragmatic tear was determined (1 to 10, 10: completely confident and 1: impossible to exclude). Wilcoxon rank sum tests were used for statistical analysis, and p < 0.05 was considered significant. Mean confidence score of 9.85 for DS-HP was significantly better than the mean score of 7.66 for SS images (p < 0.0001). Diaphragmatic motion scores and subjective diaphragmatic motion artifact on coronal and axial images were significantly better for DS-HP images in all areas when compared individually (p < 0.0001) and overall (p < 0.0001). Regions of DS-HP (99.2 %) were diagnostic, whereas only 87.0 % % regions on SS were. Complete agreement of motion scores was present in 92 % of cases, with moderate overall agreement for confidence to exclude a diaphragmatic tear (κ = 0.45). Dual-source high-pitch CT scanning is advantageous as it allows for significantly better evaluation of diaphragmatic structures by minimizing motion artifacts on images of freely breathing trauma patients.

  6. Computed-tomography-guided high-dose-rate brachytherapy (CT-HDRBT) ablation of metastases adjacent to the liver hilum.

    PubMed

    Collettini, Federico; Singh, Anju; Schnapauff, Dirk; Powerski, Maciej Janusz; Denecke, Timm; Wust, Peter; Hamm, Bernd; Gebauer, Bernhard

    2013-10-01

    To evaluate technical feasibility and clinical outcome of computed tomography-guided high-dose-rate-brachytherapy (CT-HDRBT) ablation of metastases adjacent to the liver hilum. Between November 2007 and May 2012, 32 consecutive patients with 34 metastases adjacent to the liver hilum (common bile duct or hepatic bifurcation ≤5 mm distance) were treated with CT-HDRBT. Treatment was performed by CT-guided applicator placement and high-dose-rate brachytherapy with an iridium-192 source. MRI follow-up was performed 6 weeks and every 3 months post intervention. The primary endpoint was local tumor control (LTC); secondary endpoints included time to progression (TTP) and overall survival (OS). Patients were available for MRI evaluation for a mean follow-up time of 18.75 months (range: 3-56 months). Mean tumor diameter was 4.3 cm (range: 1.3-10.7 cm). One major complication was observed. Four (11.8%) local recurrences were observed after a local tumor control of 5, 8, 9 and 10 months, respectively. Twenty-two patients (68.75%) experienced a systemic tumor progression during the follow up period. Mean TTP was 12.9 months (range: 2-56 months). Nine patients died during the follow-up period. Median OS was 20.24 months. Minimally invasive CT-HDRBT is a safe and effective option also for unresectable liver metastases adjacent to the liver hilum that would have been untreatable by thermal ablation. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  7. Genetic evidence suggests that homosporous ferns with high chromosome numbers are diploid.

    PubMed

    Haufler, C H; Soltis, D E

    1986-06-01

    Homosporous ferns have usually been considered highly polyploid because they have high chromosome numbers (average n = 57.05). In angiosperms, species with chromosome numbers higher than n = 14 generally have more isozymes than those with lower numbers, consistent with their polyploidy. By extrapolation, homosporous ferns would be expected to have many isozymes. However, ongoing surveys indicate that within fern genera, species having the lowest chromosome numbers have the number of isozymes considered typical of diploid seed plants. Only species above these lowest numbers have additional isozymes. Therefore, homosporous ferns either have gone through repeated cycles of polyploidy and gene silencing or were initiated with relatively high chromosome numbers. The latter possibility represents a radical departure from currently advocated hypotheses of fern evolution and suggests that there may be fundamental differences between the genomes of homosporous ferns and those of higher plants. These hypotheses can be tested by genetic, karyological, and molecular techniques.

  8. Photon counting spectral CT versus conventional CT: comparative evaluation for breast imaging application

    NASA Astrophysics Data System (ADS)

    Shikhaliev, Polad M.; Fritz, Shannon G.

    2011-04-01

    Spectral CT systems with photon counting detectors have more advantages compared to conventional CT systems. However, clinical applications have been hampered for a long time due to the high demands of clinical systems and limitations of spectroscopic x-ray detectors. Photon counting detector technology has gained considerable improvements in the past decade, and spectral CT has become a hot topic. Several experimental spectral CT systems are under investigation. The purpose of this work was to perform the first direct, side-by-side comparison of existing spectral CT technology with a mature clinical CT system based on a conventional energy integrating detector. We have built an experimental spectral CT system whose main parameters are similar to the parameters of a clinical CT system. The system uses a spectroscopic cadmium zinc telluride (CZT) detector. The detector includes two rows of CZT pixels with 256 pixels in each row. The pixel size is 1 × 1 mm2, and the maximum count rate is 2 Mcounts/pixel/s. The spectral CT system has a magnification factor of 1.62 and the source to detector and source to image distances of 85 and 53 cm, respectively. The above parameters are similar to those of the clinical CT system, Siemens Sensation 16, used for comparison. The two systems were compared by imaging spatial resolution and contrast resolution phantoms made from acrylic cylinders with 14 cm diameters. The resolution phantom included Al wires with 0.3, 0.6, and 1 mm diameters, and 0.25 g cc-1 CaCO3 contrast. The contrast phantom included contrast elements with 1.7, 5, and 15 mg cc-1 iodine, and 1.1, 3.3, and 10 mg cc-1 gadolinium. The phantoms were imaged with the two systems using 120 kVp tube voltage and 470 mR total skin exposure. The spectral CT showed CT numbers, image noise, and spatial and contrast resolutions to be similar within 10% compared to the Siemens 16 system, and provided an average of 10% higher CNR. However, the spectral CT system had a major

  9. Photon counting spectral CT versus conventional CT: comparative evaluation for breast imaging application.

    PubMed

    Shikhaliev, Polad M; Fritz, Shannon G

    2011-04-07

    Spectral CT systems with photon counting detectors have more advantages compared to conventional CT systems. However, clinical applications have been hampered for a long time due to the high demands of clinical systems and limitations of spectroscopic x-ray detectors. Photon counting detector technology has gained considerable improvements in the past decade, and spectral CT has become a hot topic. Several experimental spectral CT systems are under investigation. The purpose of this work was to perform the first direct, side-by-side comparison of existing spectral CT technology with a mature clinical CT system based on a conventional energy integrating detector. We have built an experimental spectral CT system whose main parameters are similar to the parameters of a clinical CT system. The system uses a spectroscopic cadmium zinc telluride (CZT) detector. The detector includes two rows of CZT pixels with 256 pixels in each row. The pixel size is 1 × 1 mm(2), and the maximum count rate is 2 Mcounts/pixel/s. The spectral CT system has a magnification factor of 1.62 and the source to detector and source to image distances of 85 and 53 cm, respectively. The above parameters are similar to those of the clinical CT system, Siemens Sensation 16, used for comparison. The two systems were compared by imaging spatial resolution and contrast resolution phantoms made from acrylic cylinders with 14 cm diameters. The resolution phantom included Al wires with 0.3, 0.6, and 1 mm diameters, and 0.25 g cc(-1) CaCO(3) contrast. The contrast phantom included contrast elements with 1.7, 5, and 15 mg cc(-1) iodine, and 1.1, 3.3, and 10 mg cc(-1) gadolinium. The phantoms were imaged with the two systems using 120 kVp tube voltage and 470 mR total skin exposure. The spectral CT showed CT numbers, image noise, and spatial and contrast resolutions to be similar within 10% compared to the Siemens 16 system, and provided an average of 10% higher CNR. However, the spectral CT system had a

  10. Imaging of pore networks and related interfaces in soil systems by using high resolution X-ray micro-CT

    NASA Astrophysics Data System (ADS)

    Zacher, Gerhard; Eickhorst, Thilo; Schmidt, Hannes; Halisch, Matthias

    2016-04-01

    Today's high-resolution X-ray CT with its powerful tubes and great detail detectability lends itself naturally to geological and pedological applications. Those include the non-destructive interior examination and textural analysis of rock and soil samples and their permeability and porosity - to name only a few. Especially spatial distribution and geometry of pores, mineral phases and fractures are important for the evaluation of hydrologic and aeration properties in soils as well as for root development in the soil matrix. The possibility to visualize a whole soil aggregate or root tissue in a non-destructive way is undoubtedly the most valuable feature of this type of analysis and is a new area for routine application of high resolution X-ray micro-CT. The paper outlines recent developments in hard- and software requirements for high resolution CT. It highlights several pedological applications which were performed with the phoenix nanotom m, the first 180 kV nanofocus CT system tailored specifically for extremely high-resolution scans of variable sized samples with voxel-resolutions down to < 300 nm. In addition very good contrast resolution can be obtained as well which is necessary to distinguish biogenic material in soil aggregates amongst others. We will address visualization and quantification of porous networks in 3D in different environmental samples ranging from clastic sedimentary rock to soil cores and individual soil aggregates. As several processes and habitat functions are related to various pore sizes imaging of the intact soil matrix will be presented on different scales of interest - from the mm-scale representing the connectivity of macro-pores down to the micro-scale representing the space of microbial habitats. Therefore, soils were impregnated with resin and scanned via X-ray CT. Scans at higher resolution were obtained from sub-volumes cut from the entire resin impregnated block and from crop roots surrounded by rhizosphere soil. Within the

  11. High Rayleigh number heat transfer in a horizontal cylinder with adiabatic wall

    NASA Technical Reports Server (NTRS)

    Schiroky, G. H.; Rosenberger, F.

    1984-01-01

    The present investigation is concerned with an experimentally guided approach to the estimation of Nusselt numbers (Nu) at high Rayleigh numbers (Ra) for a cylinder with an adiabatic side wall. The Rayleigh number dependence of the Nusselt number for a horizontal cylinder with an adiabatic wall is presented in a graph. The obtained data are compared with results reported by Shih (1981). Shih has extended a three-term expansion for velocity and temperature distributions reported by Bejan and Tien (1978).

  12. The effect of iodine uptake on radiation dose absorbed by patient tissues in contrast enhanced CT imaging: Implications for CT dosimetry.

    PubMed

    Perisinakis, Kostas; Tzedakis, Antonis; Spanakis, Kostas; Papadakis, Antonios E; Hatzidakis, Adam; Damilakis, John

    2017-07-14

    To investigate the effect of iodine uptake on tissue/organ absorbed doses from CT exposure and its implications in CT dosimetry. The contrast-induced CT number increase of several radiosensitive tissues was retrospectively determined in 120 CT examinations involving both non-enhanced and contrast-enhanced CT imaging. CT images of a phantom containing aqueous solutions of varying iodine concentration were obtained. Plots of the CT number increase against iodine concentration were produced. The clinically occurring iodine tissue uptake was quantified by attributing recorded CT number increase to a certain concentration of aqueous iodine solution. Clinically occurring iodine uptake was represented in mathematical anthropomorphic phantoms. Standard 120 kV CT exposures were simulated using Monte Carlo methods and resulting organ doses were derived for non-enhanced and iodine contrast-enhanced CT imaging. The mean iodine uptake range during contrast-enhanced CT imaging was found to be 0.02-0.46% w/w for the investigated tissues, while the maximum value recorded was 0.82% w/w. For the same CT exposure, iodinated tissues were found to receive higher radiation dose than non-iodinated tissues, with dose increase exceeding 100% for tissues with high iodine uptake. Administration of iodinated contrast medium considerably increases radiation dose to tissues from CT exposure. • Radiation absorption ability of organs/tissues is considerably affected by iodine uptake • Iodinated organ/tissues may absorb up to 100 % higher radiation dose • Compared to non-enhanced, contrast-enhanced CT may deliver higher dose to patient tissues • CT dosimetry of contrast-enhanced CT imaging should encounter tissue iodine uptake.

  13. High-order numerical simulations of the flow around wings at moderately high Reynolds number

    NASA Astrophysics Data System (ADS)

    Vinuesa, Ricardo; Negi, Prabal; Hosseini, Seyed M.; Hanifi, Ardeshir; Henningson, Dan S.; Schlatter, Philipp

    2016-11-01

    The results of a DNS of the flow around a wing section represented by a NACA4412 profile, with Rec = 400 , 000 and 5° angle of attack, are presented in this study. The high-order spectral-element code Nek5000 was used for the computations. The Clauser pressure-gradient parameter β ranges from = 0 to 85 on the suction side, and the maximum Reθ and Reτ values are around 2 , 800 and 373, respectively. The adversre pressure gradient (APG) on the suction side of the wing leads to a progressively increasing value of the inner peak in the tangential velocity fluctuations, as well as the development of an outer peak, which is also observed in the other components of the Reynolds-stress tensor. Close to the trailing edge, i.e., at x / c = 0 . 9 , the outer peak in the inner-scaled tangential velocity profile is larger than the inner peak. These effects are connected to the fact that the large-scale motions of the flow become energized due to the APG, as apparent from spanwise-premultiplied power spectral density plots. Preliminary comparisons between DNS and well-resolved LES data, based on a relaxation-term filtering approach, are also presented with the aim of further extending the Reynolds number to Rec = 1 , 000 , 000 . Funded by the Swedish Research Council (VR) and the Knut and Alice Wallenberg Foundation.

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

    PubMed

    Torres Espallardo, I

    2017-01-12

    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

  15. Implications of CT noise and artifacts for quantitative {sup 99m}Tc SPECT/CT imaging

    SciTech Connect

    Hulme, K. W.; Kappadath, S. C.

    2014-04-15

    Purpose: This paper evaluates the effects of computed tomography (CT) image noise and artifacts on quantitative single-photon emission computed-tomography (SPECT) imaging, with the aim of establishing an appropriate range of CT acquisition parameters for low-dose protocols with respect to accurate SPECT attenuation correction (AC). Methods: SPECT images of two geometric and one anthropomorphic phantom were reconstructed iteratively using CT scans acquired at a range of dose levels (CTDI{sub vol} = 0.4 to 46 mGy). Resultant SPECT image quality was evaluated by comparing mean signal, background noise, and artifacts to SPECT images reconstructed using the highest dose CT for AC. Noise injection was performed on linear-attenuation (μ) maps to determine the CT noise threshold for accurate AC. Results: High levels of CT noise (σ ∼ 200–400 HU) resulted in low μ-maps noise (σ ∼ 1%–3%). Noise levels greater than ∼10% in 140 keV μ-maps were required to produce visibly perceptible increases of ∼15% in {sup 99m}Tc SPECT images. These noise levels would be achieved at low CT dose levels (CTDI{sub vol} = 4 μGy) that are over 2 orders of magnitude lower than the minimum dose for diagnostic CT scanners. CT noise could also lower (bias) the expected μ values. The relative error in reconstructed SPECT signal trended linearly with the relative shift in μ. SPECT signal was, on average, underestimated in regions corresponding with beam-hardening artifacts in CT images. Any process that has the potential to change the CT number of a region by ∼100 HU (e.g., misregistration between CT images and SPECT images due to motion, the presence of contrast in CT images) could introduce errors in μ{sub 140} {sub keV} on the order of 10%, that in turn, could introduce errors on the order of ∼10% into the reconstructed {sup 99m}Tc SPECT image. Conclusions: The impact of CT noise on SPECT noise was demonstrated to be negligible for clinically achievable CT parameters. Because

  16. Helical CT of abdominal trauma.

    PubMed

    Novelline, R A; Rhea, J T; Bell, T

    1999-05-01

    CT has revolutionized the diagnostic work-up of trauma patients with suspected abdominal injuries. A wide range of intraperitoneal and retroperitoneal organ injuries can be quickly and accurately diagnosed with CT. Today, helical CT technology permits even faster examinations, with improved intravenous contrast opacification of parenchymal organs and vascular structures and reduced CT artifacts caused by patient motion, respiration, and arterial pulsation. Severely injured and potentially unstable patients, who might not have been able to tolerate the long CT examinations of the past, may be quickly evaluated today with helical CT. Accurate diagnosis requires high quality CT examinations that are performed with optimum CT protocols. This article reviews the currently recommended helical CT protocols for evaluating patients with suspected abdominal injuries, and the CT findings when injuries are present.

  17. N-231 High Reynolds Number Channel I is a blowdown Facility that utilizes interchangeable test

    NASA Technical Reports Server (NTRS)

    1980-01-01

    N-231 High Reynolds Number Channel I is a blowdown Facility that utilizes interchangeable test sections and nozzles. The facility provides experimental support for the fluid mechanics research, including experimental verification of aerodynamic computer codes and boundary-layer and airfoil studies that require high Reynolds number simulation. (Tunnel 1)

  18. N-231 High Reynolds Number Channel I is a blowdown Facility that utilizes interchangeable test

    NASA Technical Reports Server (NTRS)

    1980-01-01

    N-231 High Reynolds Number Channel I is a blowdown Facility that utilizes interchangeable test sections and nozzles. The facility provides experimental support for the fluid mechanics research, including experimental verification of aerodynamic computer codes and boundary-layer and airfoil studies that require high Reynolds number simulation. (Tunnel 1)

  19. High Resolution Multi-Detector CT Aided Tissue Analysis and Quantification of Lung Fibrosis

    PubMed Central

    Zavaletta, Vanessa A.; Bartholmai, Brian J.; Robb, Richard A

    2009-01-01

    Rational and Objectives Volumetric high-resolution scans can be acquired of the lungs with multi-detector CT (MDCT). Such scans have potential to facilitate useful visualization, characterization, and quantification of the extent of diffuse lung diseases, such as Usual Interstitial Pneumonitis or Idiopathic Pulmonary Fibrosis (UIP/IPF). There is a need to objectify, standardize and improve the accuracy and repeatability of pulmonary disease characterization and quantification from such scans. This paper presents a novel texture analysis approach toward classification and quantification of various pathologies present in lungs with UIP/IPF. The approach integrates a texture matching method with histogram feature analysis. Materials and Methods Patients with moderate UIP/IPF were scanned on a Lightspeed 8-detector GE CT scanner (140kVp, 250mAs). Images were reconstructed with 1.25mm slice thickness in a high-frequency sparing algorithm (BONE) with 50% overlap and a 512 × 512 axial matrix, (0.625 mm3 voxels). Eighteen scans were used in this study. Each dataset is pre-processed which includes segmentation of the lungs and the broncho-vascular trees. Two types of analysis were performed, first an analysis of independent volume of interests (VOIs) and second an analysis of whole lung datasets. 1.) Fourteen of the eighteen scans were used to create a database of independent 15×15×15 cubic voxel VOIs. The VOIs were selected by experts as having greater than 70% of the defined class. The database was composed of the following: Honeycombing (# of VOIs 337), Reticular (130), Ground glass (148), Normal (240), and Emphysema (54). This database was used to develop our algorithm. Three progressively challenging classification experiments were designed to test our algorithm. All three experiments were performed using a 10-fold cross validation method for error estimation. Experiment 1 consisted of a two class discrimination: Normal and Abnormal. Experiment 2 consisted of a four

  20. Cardiac CT Scan

    MedlinePlus

    ... rate. Before the test, a contrast dye, often iodine, may be injected into a vein in your ... should not receive more CT scans than the number that clinical guidelines recommend. Another risk is that ...

  1. X-ray microtomography (micro-CT): a reference technology for high-resolution quantification of xylem embolism in trees.

    PubMed

    Cochard, H; Delzon, S; Badel, E

    2015-01-01

    As current methods for measuring xylem embolism in trees are indirect and prone to artefacts, there is an ongoing controversy over the capacity of trees to resist or recover from embolism. The debate will not end until we get direct visualization of the vessel content. Here, we propose desktop X-ray microtomography (micro-CT) as a reference direct technique to quantify xylem embolism and thus validate more widespread measurements based upon either hydraulic or acoustic methods. We used desktop micro-CT to measure embolism levels in dehydrated or centrifuged shoots of laurel - a long-vesseled species thought to display daily cycles of embolism formation and refilling. Our direct observations demonstrate that this Mediterranean species is highly resistant to embolism and is not vulnerable to drought-induced embolism in a normal range of xylem tensions. We therefore recommend that embolism studies in long-vesseled species should be validated by direct methods such as micro-CT to clear up any misunderstandings on their physiology.

  2. Identification of predictive CT angiographic factors in the development of high-risk type 2 endoleaks after endovascular aneurysm repair in patients with infrarenal aortic aneurysms.

    PubMed

    Löwenthal, D; Herzog, L; Rogits, B; Bulla, K; Weston, S; Meyer, F; Halloul, Z; Pech, M; Ricke, J; Dudeck, O

    2015-01-01

    An extensive analysis of the value of computed tomography (CT) parameters as potential predictors of the clinical outcome of type 2 endoleaks after endovascular aortic aneurysm repair (EVAR). Initial CT scans of 130 patients with abdominal aortic aneurysms (AAAs) were retrospectively reviewed. On the basis of postoperative CT scans and angiographies, patients were stratified into a low-risk group (LRG; without or transient type 2 endoleak; n = 80) and a high-risk group (HRG, persistent type 2 endoleak or need for reintervention; n = 50). Statistical analysis comprised a univariate and multivariate analysis. Anatomical, thrombus-specific, as well as aortic side branch parameters were assessed on the initial CT scan. Of all anatomical parameters, the diameter of the immediate infrarenal aorta was significantly different in the univariate analysis (LRG 22.4 ± 3.8 mm; HRG 23.6 ± 2.5 mm; p = 0.03). The investigation of the thrombus-specific parameters showed a trend towards statistical significance for the relative thrombus load (LRG 31.7 ± 18.0%; HRG 25.3 ± 17.5%; p = 0.09). Assessment of aortic side branches revealed only for the univariate analysis significant differences in the patency of the inferior mesenteric artery (LRG 71.3%; HRG 92.0%; p = 0.003) and their diameter (LRG 3.3 ± 0.7 mm; HRG 3.8 ± 0.9 mm; p = 0.004). In contrast, the number of lumbar arteries (LAs; LRG 2.7 ± 1.4; HRG 3.6 ± 1.2; univariate: p = 0.01; multivariate: p = 0.006) as well as their diameter (LRG 2.1 ± 0.4 mm; HRG 2.4 ± 0.4 mm; univariate: p < 0.001; multivariate: p = 0.006) were highly significantly associated with the development of type 2 endoleaks of the HRG. The most important predictive factors for the development of high-risk type 2 endoleaks were mainly the number and the diameter of the LAs which perfused the AAA. • This study is a very detailed and comprehensive analysis of the

  3. CT-guided fine-needle biopsy of focal lung lesions as the method for reducing the number of invasive diagnostic procedures

    PubMed Central

    Chodorowska, Anna; Rzechonek, Adam; Dyła, Tomasz; Muszczyńska-Bernhard, Beata; Adamek, Jarosław

    2010-01-01

    Summary Background: CT-guided fine-needle biopsy (FNB) of focal lung lesions is one of the possibilities of obtaining histopathological diagnosis in pulmonary diseases. Its place in the algorithm is determined by the invasiveness. In case of no diagnosis after bronchoscopy or endobronchial ultrasonography (EBUS) guided biopsy, CT-guided FNB can become an alternative for more invasive procedures, such as open lung biopsy – thoracotomy. Material/Methods: Since January 2009 until February 2010, we performed 37 CT-guided FNB in 34 patients aged 31 to 76 (mean age 60.9). Among them, there were 16 women and 18 men. All patients underwent a standard chest CT with contrast medium injection. They were diagnosed with focal lesions and they were rejected from surgery as the primary method of treatment. During biopsy, the patient was positioned prone or supine, depending on the location of lesions. After performing a scout image and initial slices, we marked the level of biopsy, using a metal marker. Next, the biopsy needle was introduced under local anesthesia. When the obtained position of the needle in the lesion was correct, the specimen was taken. After needle removal, the patient was controlled for the presence of complications (i.e. pneumothorax). Biopsy time ranged from 10 to 50 minutes. Results: In 94.6% of biopsies, the specimens for histopathological and cytological examinations were obtained. In 22 (64.7%) patients, histopathological diagnoses (in 14 cases this was the non-small cell cancer and in 8, inflammatory lesions) were established which allowed us to resign from invasive thoracotomy and to introduce an appropriate treatment. In the remaining 12 patients, no diagnosis was established. Complications in the form of a minor pneumothorax occurred in 2 patients. Conclusions: Fine-needle biopsy of the focal lung lesions is an affective and a relatively safe method, which can replace the more invasive diagnostic thoracotomy in the majority of patients. PMID

  4. Validation study of ultrasound-based high-dose-rate prostate brachytherapy planning compared with CT-based planning.

    PubMed

    Batchelar, Deidre; Gaztañaga, Miren; Schmid, Matt; Araujo, Cynthia; Bachand, François; Crook, Juanita

    2014-01-01

    The use of transrectal ultrasound (TRUS) to both guide and plan high-dose-rate (HDR) brachytherapy (BT) for prostate is increasing. Studies using prostate phantoms have demonstrated the accuracy of ultrasound (US) needle tip reconstruction compared with CT imaging standard. We have assessed the in vivo accuracy of needle tip localization by TRUS using cone-beam CT (CBCT) as our reference standard. Needle positions from 37 implants have been analyzed. A median of 16 needles (range, 16-18) per implant were inserted, advanced to the prostate base, and their tips identified using live TRUS images and real-time planning BT software. Needle protrusion length from the template was recorded to allow for reverification before capturing images for planning. The needles remained locked in the template, which was fixed to the stepper, while a set of three-dimensional TRUS images was acquired for needle path reconstruction and HDR-BT treatment planning. Following treatment, CBCT images were acquired for subsequent needle reconstruction using a BT Treatment Planning System. The coordinates of each needle tip were recorded from the Treatment Planning System for CT and US and compared. A total of 574 needle tip positions have been compared between TRUS and CBCT. Of these, 59% agreed within 1 mm, 27% within 1-2 mm, and 11% agreed within 2-3 mm. The discrepancy between tip positions in the two modalities was greater than 3 mm for only 20 needles (3%). The US needle tip identification in vivo is at least as accurate as CT identification, while providing all the advantages of a one-step procedure. Copyright © 2014 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

  5. Risk stratification in the investigation of pulmonary nodules in a high risk cohort - PET/CT outperforms clinical risk prediction algorithms.

    PubMed

    Gibson, Glenna; Ravi Kumar, Aravind; Steinke, Karin; Bashirzadeh, Farzad; Roach, Rebecca; Windsor, Morgan; Ware, Robert; Fielding, David

    2017-08-07

    Clinical prediction models and 18F-FDG-PET/CT are used for assessment of solitary pulmonary nodules (SPNs) however biopsy is still required before treatment which carries risk. To determine combined predictive benefit of one such model combined with modern PET/CT data to improve decision making about biopsy prior to treatment and possibly reduce costs. Patients with a SPN undergoing 18F-FDG-PET/CT from January 2011-December 2012 were retrospectively identified. 143 patients met inclusion criteria. PET/CT studies were rated (5-point visual scale), and CT characteristics were determined. Tissue was obtained by EBUS-GS, CT-guided biopsy and/or surgery. EBUS-TBNA was used instead of nodule biopsy if there were PET-positive subcentimeter lymph nodes. The prediction model yielded an AUC-ROC curve of 64% (95% CI 0.55-0.75). PET/CT increased this to 75% (95% CI 0.65-0.84). The 11% improvement is statistically significant. PET/CT score was the best single predictor for malignancy. A PET score of 1-2 had a specificity of 100% (CI 0.73-1.0) whereas a score of 4-5 had a sensitivity of only 76% (CI 0.68-0.84). No significant difference in clinical prediction scores between groups was noted. PET/CT showed greatest benefit in true negatives and in detecting small mediastinal lymph nodes to allow EBUS-TBNA with higher diagnostic rate. Cost analysis didn't support a policy of resection-without-tissue-diagnosis. PET/CT improves clinical prediction of SPNs, but its greatest use is in proving benignity. High PET scores had high false positive rates and didn't add to clinical prediction. PET should be incorporated early in decision making to allow more effective biopsy strategies. This article is protected by copyright. All rights reserved.

  6. High-resolution secondary reconstructions with the use of flat panel CT in the clinical assessment of patients with cochlear implants.

    PubMed

    Pearl, M S; Roy, A; Limb, C J

    2014-06-01

    Radiologic assessment of cochlear implants can be limited because of metallic streak artifacts and the high attenuation of the temporal bones. We report on 14 patients with 18 cochlear implants (17 Med-El standard 31.5-mm arrays, 1 Med-El medium 24-mm array) who underwent flat panel CT with the use of high-resolution secondary reconstruction techniques. Flat panel CT depicted the insertion site, cochlear implant course, and all 216 individual electrode contacts. The calculated mean angular insertion depth for standard arrays was 591.9° (SD = 70.9; range, 280°). High-resolution secondary reconstructions of the initial flat panel CT dataset, by use of a manually generated field of view, Hounsfield unit kernel type, and sharp image characteristics, provided high-quality images with improved spatial resolution. Flat panel CT is a promising imaging tool for the postoperative evaluation of cochlear implant placement.

  7. Synthetic Hounsfield units from spectral CT data

    NASA Astrophysics Data System (ADS)

    Bornefalk, Hans

    2012-04-01

    Beam-hardening-free synthetic images with absolute CT numbers that radiologists are used to can be constructed from spectral CT data by forming ‘dichromatic’ images after basis decomposition. The CT numbers are accurate for all tissues and the method does not require additional reconstruction. This method prevents radiologists from having to relearn new rules-of-thumb regarding absolute CT numbers for various organs and conditions as conventional CT is replaced by spectral CT. Displaying the synthetic Hounsfield unit images side-by-side with images reconstructed for optimal detectability for a certain task can ease the transition from conventional to spectral CT.

  8. Synthetic Hounsfield units from spectral CT data.

    PubMed

    Bornefalk, Hans

    2012-04-07

    Beam-hardening-free synthetic images with absolute CT numbers that radiologists are used to can be constructed from spectral CT data by forming 'dichromatic" images after basis decomposition. The CT numbers are accurate for all tissues and the method does not require additional reconstruction. This method prevents radiologists from having to relearn new rules-of-thumb regarding absolute CT numbers for various organs and conditions as conventional CT is replaced by spectral CT. Displaying the synthetic Hounsfield unit images side-by-side with images reconstructed for optimal detectability for a certain task can ease the transition from conventional to spectral CT.

  9. The role of early 18F-FDG PET/CT in therapeutic management and ongoing risk stratification of high/intermediate-risk thyroid carcinoma.

    PubMed

    Triviño Ibáñez, E M; Muros, M A; Torres Vela, E; Llamas Elvira, J M

    2016-03-01

    Little is known about the role in ongoing risk stratification of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) performed early after radioactive iodine (RAI) ablation in differentiated thyroid carcinoma (DTC). The aim of the study is to investigate whether 18F-FDG PET/CT performed early after RAI ablation is useful to detect disease and to influence therapy and ongoing risk stratification. Patients with high/intermediate risk of recurrent DTC were included. 18F-FDG PET/CT scan was performed within 6 months after RAI ablation. We confirmed results with other imaging techniques, pathology reports, or follow-up. We classified the patient response as excellent, acceptable, or incomplete. Modified Hicks criteria were used to evaluate clinical impact. We included 81 patients with high/intermediate risk of recurrent DTC. Forty-one (50.6%) had positive uptake in 18F-FDG PET/CT, with negative (131)I whole-body scan ((131)I WBS). Sensitivity, specificity, and diagnostic accuracy of 18F-FDG PET/CT were 92.5, 90.2, and 91.4%, respectively. 18F-FDG PET/CT results had an impact on therapy in 38.3% of patients. One year after initial therapy, 45.7% showed excellent response, 8.6% acceptable response, and 45.7% incomplete response. A statistically significant relationship was found between negative 18F-FDG PET/CT and excellent response (80 vs. 12.2%, p < 0.001; OR 52.8). 18F-FDG PET/CT scan performed early in surveillance of patients with high/intermediate-risk thyroid carcinoma provides important additional information not available with conventional follow-up methods and had a high impact on therapy. A negative 18F-FDG PET/CT predicts an excellent response to therapy in the new ongoing risk stratification.

  10. Effect of a small number of training cases on the performance of massive training artificial neural network (MTANN) for reduction of false positives in computerized detection of lung nodules in low-dose CT

    NASA Astrophysics Data System (ADS)

    Suzuki, Kenji; Armato, Samuel G., III; Li, Feng; Sone, Shusuke; Doi, Kunio

    2003-05-01

    In this study, we investigated a pattern-classification technique which can be trained with a small number of cases with a massive training artificial neural network (MTANN) for reduction of false positives in computerized detection of lung nodules in low-dose CT (LDCT). The MTANN consists of a modified multilayer artificial neural network (ANN), which is capable of operating on image data directly. The MTANN is trained by use of a large number of sub-regions extracted from input images together with the teacher images containing the distribution for the "likelihood of being a nodule." The output image is obtained by scanning of an input image with the MTANN. In the MTANN, the distinction between nodules and non-nodules is treated as an image-processing task, in other words, as a highly nonlinear filter that performs both nodule enhancement and non-nodule suppression. This allows us to train the MTANN not on a case basis, but on a sub-region basis. Therefore, the MTANN can be trained with a very small number of cases. Our database consisted of 101 LDCT scans acquired from 71 patients in a lung cancer screening program. The scans consisted of 2,822 sections, and contained 121 nodules including 104 nodules representing confirmed primary cancers. With our current CAD scheme, a sensitivity of 81.0% (98/121 nodules) with 0.99 false positives per section (2,804/2,822) was achieved. By use of the MTANN trained with a small number of training cases (n=10), i.e., five pairs of nodules and non-nodules, we were able to remove 55.8% of false positives without a reduction in the number of true positives, i.e., a classification sensitivity of 100%. Thus, the false-positive rate of our current CAD scheme was reduced from 0.99 to 0.44 false positive per section, while the current sensitivity (81.0%) was maintained.

  11. Heat-flux measurement in high-Prandtl-number turbulent Rayleigh-Bénard convection.

    PubMed

    Xia, Ke-Qing; Lam, Siu; Zhou, Sheng-Qi

    2002-02-11

    We report Nusselt number measurements from high Prandtl number turbulent thermal convection experiments. The experiments are conducted in four fluids with the Prandtl number Pr varying from 4 to 1350 and the Rayleigh number Ra from 2x10(7) to 3x10(10), all in a single convection cell of unity aspect ratio. We find that the measured Nusselt number decreased about 20% over the range of Pr spanned in the experiment. The measure data are also found in good agreement with the prediction of a recent theory over the extended range of Pr covered in the experiment.

  12. Renal cortical retention of contrast medium on delayed CT and nephropathy following transcatheter arterial chemoembolisation in patients with high serum creatinine level.

    PubMed

    Yamazaki, H; Oi, H; Matshushita, M; Inoue, T; Nakamura, H; Inoue, T

    2002-11-01

    The aim of this study was to investigate the prevalence of renal cortical retention (RCR) of contrast media seen on delayed CT, and nephropathy following transarterial chemoembolisation (TACE) in high-risk patients. The findings of 18 patients with abnormally high serum creatinine levels who underwent TACE were reviewed. Nephropathy was defined as an increase in serum creatinine level of more than 44 micromol l(-1), or more than 25%, on day 1, 3, 7 or 14. RCR was defined as mild (CT value >50) or severe (CT value >100). RCR was seen in 16 cases (89%) and in seven cases (39%) of post-TACE nephropathy. Patients without severe RCR did not develop nephropathy post-TACE, whereas 50% of those with such retention did (p=0.19). Delayed CT appears to have the potential as an early detector of nephropathy post-TACE in high-risk patients.

  13. SU-E-I-04: Improving CT Quality for Radiation Therapy of Patients with High Body Mass Index Using Iterative Reconstruction Algorithms

    SciTech Connect

    Noid, G; Tai, A; Li, X

    2015-06-15

    Purpose: Iterative reconstruction (IR) algorithms are developed to improve CT image quality (IQ) by reducing noise without diminishing spatial resolution or contrast. The CT IQ for patients with a high Body Mass Index (BMI) can suffer from increased noise due to photon starvation. The purpose of this study is to investigate and to quantify the IQ enhancement for high BMI patients through the application of IR algorithms. Methods: CT raw data collected for 6 radiotherapy (RT) patients with BMI, greater than or equal to 30 were retrospectively analyzed. All CT data were acquired using a CT scanner (Somaton Definition AS Open, Siemens) installed in a linac room (CT-on-rails) using standard imaging protocols. The CT data were reconstructed using the Sinogram Affirmed Iterative Reconstruction (SAFIRE) and Filtered Back Projection (FBP) methods. IQ metrics of the obtained CTs were compared and correlated with patient depth and BMI. The patient depth was defined as the largest distance from anterior to posterior along the bilateral symmetry axis. Results: IR techniques are demonstrated to preserve contrast and reduce noise in comparison to traditional FBP. Driven by the reduction in noise, the contrast to noise ratio is roughly doubled by adopting the highest SAFIRE strength. A significant correlation was observed between patient depth and IR noise reduction through Pearson’s correlation test (R = 0.9429/P = 0.0167). The mean patient depth was 30.4 cm and the average relative noise reduction for the strongest iterative reconstruction was 55%. Conclusion: The IR techniques produce a measureable enhancement to CT IQ by reducing the noise. Dramatic noise reduction is evident for the high BMI patients. The improved CT IQ enables more accurate delineation of tumors and organs at risk and more accuarte dose calculations for RT planning and delivery guidance. Supported by Siemens.

  14. Flat-Panel Computed Tomography (DYNA-CT) in Neuroradiology. From High-Resolution Imaging of Implants to One-Stop-Shopping for Acute Stroke.

    PubMed

    Doerfler, A; Gölitz, P; Engelhorn, T; Kloska, S; Struffert, T

    2015-10-01

    Originally aimed at improving standard radiography by providing higher absorption efficiency and a wider dynamic range, flat-panel detector technology has meanwhile got widely accepted in the neuroradiological community. Especially flat-panel detector computed tomography (FD-CT) using rotational C-arm mounted flat-panel detector technology is capable of volumetric imaging with a high spatial resolution. By providing CT-like images of the brain within the angio suite, FD-CT is able to rapidly visualize hemorrhage and may thus improve complication management without the need of patient transfer. As "Angiographic CT" FD-CT may be helpful during many diagnostic and neurointerventional procedures and for noninvasive monitoring and follow-up. In addition, spinal interventions and high-resolution imaging of the temporal bone might also benefit from FD-CT. Finally, using novel dynamic perfusion and angiographic protocols, FD-CT may provide functional information on brain perfusion and vasculature with the potential to replace standard imaging in selected acute stroke patients.

  15. CT Scans

    MedlinePlus

    ... cross-sectional pictures of your body. Doctors use CT scans to look for Broken bones Cancers Blood clots Signs of heart disease Internal bleeding During a CT scan, you lie still on a table. The table ...

  16. Calculation of the vacuum Green's function valid for high toroidal mode number in tokamaks.

    NASA Astrophysics Data System (ADS)

    Chance, Morrell; Turnbull, Alan

    2005-10-01

    The present evaluation of the Green's function used for the magmetic scalar potential in vacuum calculations for axisymmetric geometry in the vacuum segments of gato, pest and other mhd stability codes has been found to be deficient for moderately high toroidal mode numbers. This was due to the loss of numerical precision arising from the upward recursion relation used for generating the functions to high mode numbers. The recursion is initiated from the complete elliptic integrals of the first and second kinds. To ameliorate this, a direct integration of the integral representation of the function was crafted to achieve the necessary high accuracy for moderately high mode numbers. At very high mode numbers the loss of numerical precision due to the oscillatory behavior of the integrand is further avoided by judiciously deforming the integration contour in the complex plane. Machine precision, roughly 14 -- 16 digits, accuracy can be achieved by using a combination of both these techniques.

  17. High precision localization of intracerebral hemorrhage based on 3D MPR on head CT images

    NASA Astrophysics Data System (ADS)

    Sun, Jianyong; Hou, Xiaoshuai; Sun, Shujie; Zhang, Jianguo

    2017-03-01

    The key step for minimally invasive intracerebral hemorrhage surgery is precisely positioning the hematoma location in the brain before and during the hematoma surgery, which can significantly improves the success rate of puncture hematoma. We designed a 3D computerized surgical plan (CSP) workstation precisely to locate brain hematoma based on Multi-Planar Reconstruction (MPR) visualization technique. We used ten patients' CT/MR studies to verify our designed CSP intracerebral hemorrhage localization method. With the doctor's assessment and comparing with the results of manual measurements, the output of CSP WS for hematoma surgery is more precise and reliable than manual procedure.

  18. High EGFR gene copy number predicts poor outcome in triple-negative breast cancer.

    PubMed

    Park, Heae Surng; Jang, Min Hye; Kim, Eun Joo; Kim, Hyun Jeong; Lee, Hee Jin; Kim, Yu Jung; Kim, Jee Hyun; Kang, Eunyoung; Kim, Sung-Won; Kim, In Ah; Park, So Yeon

    2014-09-01

    Epidermal growth factor receptor (EGFR) is frequently overexpressed in triple-negative breast cancer and is emerging as a therapeutic target. EGFR gene copy number alteration and mutation are highly variable and scientists have been challenged to define their prognostic significance in triple-negative breast cancer. We examined EGFR protein expression, EGFR gene copy number alteration and mutation of exon 18 to 21 in 151 cases of triple-negative breast cancer and correlated these findings with clinical outcomes. In addition, intratumoral agreement of EGFR protein overexpression and gene copy number alteration was evaluated. EGFR overexpression was found in 97 of 151 cases (64%) and high EGFR gene copy number was detected in 50 cases (33%), including 3 gene amplification (2%) and 47 high polysomy (31%). Five EGFR mutations were detected in 4 of 151 cases (3%) and included G719A in exon 18 (n=1), V786M in exon 20 (n=1), and L858R in exon 21 (n=3). One case had two mutations (G719A and L858R). High EGFR copy number, but not EGFR mutation, correlated with EGFR protein overexpression. Intratumoral heterogeneity of EGFR protein overexpression and EGFR copy number alteration was not significant. In survival analyses, high EGFR copy number was found to be an independent prognostic factor for poor disease-free survival in patients with triple-negative breast cancer. Our findings showed that EGFR mutation was a rare event, but high EGFR copy number was relatively frequent and correlated with EGFR overexpression in triple-negative breast cancer. Moreover, high EGFR copy number was associated with poor clinical outcome in triple-negative breast cancer, suggesting that evaluation of EGFR copy number may be useful for predicting outcomes in patients with triple-negative breast cancer and for selecting patients for anti-EGFR-targeted therapy.

  19. 18F-FDG PET/CT in Detecting Metastatic Infection in Children.

    PubMed

    Kouijzer, Ilse J E; Blokhuis, Gijsbert J; Draaisma, Jos M T; Oyen, Wim J G; de Geus-Oei, Lioe-Fee; Bleeker-Rovers, Chantal P

    2016-04-01

    Metastatic infection is a severe complication of bacteremia with high morbidity and mortality. The aim of this study was to investigate the diagnostic value of 18F-FDG PET combined with CT (FDG PET/CT) in children suspected of having metastatic infection. The results of FDG PET/CT scans performed in children because of suspected metastatic infection from September 2003 to June 2013 were analyzed retrospectively. The results were compared with the final clinical diagnosis. FDG PET/CT was performed in 13 children with suspected metastatic infection. Of the total number of FDG PET/CT scans, 38% were clinically helpful. Positive predictive value of FDG PET/CT was 71%, and negative predictive value was 100%. FDG PET/CT appears to be a valuable diagnostic technique in children with suspected metastatic infection. Prospective studies of FDG PET/CT as part of a structured diagnostic protocol are needed to assess the exact additional diagnostic value.

  20. High Reynolds numbers scaling of the turbulent/non-turbulent interface

    NASA Astrophysics Data System (ADS)

    Bettencourt da Silva, Carlos; Silva, Tiago S.; Idmec Team

    2016-11-01

    The scaling of the turbulent/non-turbulent interface (TNTI) at high Reynolds numbers is assessed using new direct numerical simulations (DNS) of turbulent planar jets (PJET) and shear free turbulence (SFT) with Reynolds numbers ranging from 142 <= Reλ <= 300 . The thickness of the turbulent sublayer (TSL), where the enstrophy production dominates over enstrophy diffusion, is of the order of the Taylor micro-scale, and is roughly one order of magnitude larger than the Kolmogorov micro-scale for these Reynolds numbers, however it clearly scales with the Kolmogorov micro-scale, at sufficiently high Reynolds numbers. It is argued the same scaling should be observed in TNTI from mixing layers, wakes and boundary layers, provided the Reynolds number is sufficiently high.

  1. Simulated flight effects on noise characteristics of a fan inlet with high throat Mach number

    NASA Technical Reports Server (NTRS)

    Wesoky, H. L.; Dietrich, D. A.; Abbott, J. M.

    1978-01-01

    An anechoic wind tunnel experiment was conducted to determine the effects of simulated flight on the noise characteristics of a high throat Mach number fan inlet. Comparisons were made with the performance of a conventional low throat Mach number inlet with the same 50.8 cm fan noise source. Simulated forward velocity of 41 m/sec reduced perceived noise levels for both inlets, the largest effect being more than 3 db for the high throat Mach number inlet. The high throat Mach number inlet was as much as 7.5 db quieter than the low throat Mach number inlet with tunnel airflow and about 6 db quieter without tunnel airflow. Effects of inlet flow angles up to 30 deg were seemingly irregular and difficult to characterize because of the complex flow fields and generally small noise variations. Some modifications of tones and directivity at blade passage harmonics resulting from inlet flow angle variation were noted.

  2. Viscous dissipation effects on heat transfer from turbulent flow with high Prandtl number fluids

    NASA Astrophysics Data System (ADS)

    Chung, B. T. F.; Pang, Y.; Thomas, L. C.

    A comprehensive surface renewal type model, namely, the surface rejuvenation model, is employed to determine the viscous dissipation effect on heat transfer from turbulent flow with high Prandtl number fluids. In this work, the probability distributions for the stochastic variables which include the approach distance, the contact time, the residence time, and the initial temperature profile of the incoming eddies near the wall region are utilized. The Nusselt number, recovery factor, and temperature profile are obtained in integral forms which are then solved numerically. The ratio of Nusselt numbers in the presence of viscous effect to that in the absence of dissipation is presented in terms of Brinkman number, Prandtl number and Reynolds number for both cases of wall heating and cooling. Comparisons of the predicted recovery factor for turbulent pipe flow are also made based on the present model, previous eddy diffusivity models and the elementary surface renewal model for a wide range of Prandtl number.

  3. The Effects of Number Theory Study on High School Students' Metacognition and Mathematics Attitudes

    ERIC Educational Resources Information Center

    Miele, Anthony M.

    2014-01-01

    The purpose of this study was to determine how the study of number theory might affect high school students' metacognitive functioning, mathematical curiosity, and/or attitudes towards mathematics. The study utilized questionnaire and/or interview responses of seven high school students from New York City and 33 high school students from Dalian,…

  4. The Effects of Number Theory Study on High School Students' Metacognition and Mathematics Attitudes

    ERIC Educational Resources Information Center

    Miele, Anthony M.

    2014-01-01

    The purpose of this study was to determine how the study of number theory might affect high school students' metacognitive functioning, mathematical curiosity, and/or attitudes towards mathematics. The study utilized questionnaire and/or interview responses of seven high school students from New York City and 33 high school students from Dalian,…

  5. Object-constrained meshless deformable algorithm for high speed 3D nonrigid registration between CT and CBCT

    SciTech Connect

    Chen Ting; Kim, Sung; Goyal, Sharad; Jabbour, Salma; Zhou Jinghao; Rajagopal, Gunaretnum; Haffty, Bruce; Yue Ning

    2010-01-15

    Purpose: High-speed nonrigid registration between the planning CT and the treatment CBCT data is critical for real time image guided radiotherapy (IGRT) to improve the dose distribution and to reduce the toxicity to adjacent organs. The authors propose a new fully automatic 3D registration framework that integrates object-based global and seed constraints with the grayscale-based ''demons'' algorithm. Methods: Clinical objects were segmented on the planning CT images and were utilized as meshless deformable models during the nonrigid registration process. The meshless models reinforced a global constraint in addition to the grayscale difference between CT and CBCT in order to maintain the shape and the volume of geometrically complex 3D objects during the registration. To expedite the registration process, the framework was stratified into hierarchies, and the authors used a frequency domain formulation to diffuse the displacement between the reference and the target in each hierarchy. Also during the registration of pelvis images, they replaced the air region inside the rectum with estimated pixel values from the surrounding rectal wall and introduced an additional seed constraint to robustly track and match the seeds implanted into the prostate. The proposed registration framework and algorithm were evaluated on 15 real prostate cancer patients. For each patient, prostate gland, seminal vesicle, bladder, and rectum were first segmented by a radiation oncologist on planning CT images for radiotherapy planning purpose. The same radiation oncologist also manually delineated the tumor volumes and critical anatomical structures in the corresponding CBCT images acquired at treatment. These delineated structures on the CBCT were only used as the ground truth for the quantitative validation, while structures on the planning CT were used both as the input to the registration method and the ground truth in validation. By registering the planning CT to the CBCT, a

  6. Reynolds Number Effects on a Supersonic Transport at Subsonic High-Lift Conditions (Invited)

    NASA Technical Reports Server (NTRS)

    Owens, L.R.; Wahls, R. A.

    2001-01-01

    A High Speed Civil Transport configuration was tested in the National Transonic Facility at the NASA Langley Research Center as part of NASA's High Speed Research Program. The primary purposes of the tests were to assess Reynolds number scale effects and high Reynolds number aerodynamic characteristics of a realistic, second generation supersonic transport while providing data for the assessment of computational methods. The tests included longitudinal and lateral/directional studies at transonic and low-speed, high-lift conditions across a range of Reynolds numbers from that available in conventional wind tunnels to near flight conditions. Results are presented which focus on Reynolds number and static aeroelastic sensitivities of longitudinal characteristics at Mach 0.30 for a configuration without an empennage. A fundamental change in flow-state occurred between Reynolds numbers of 30 to 40 million, which is characterized by significantly earlier inboard leading-edge separation at the high Reynolds numbers. Force and moment levels change but Reynolds number trends are consistent between the two states.

  7. Use of CT in detection of internal damage and repair and determination of authenticity in high-quality bowed stringed instruments.

    PubMed

    Sirr, S A; Waddle, J R

    1999-01-01

    Computed tomography (CT) was used to evaluate 17 high-quality violins and cellos crafted between 1633 and 1872 by master craftsmen such as Guarneri, Amati, and Stradivari. Multiple high-resolution CT scans were obtained in each instrument, and additional scans were obtained when defects or repair was detected. Varying degrees of internal damage (eg, wormholes, air gaps, plastic deformities of wood) or repair (eg, glue lines, filler material, wooden cleats and patches) not seen at visual inspection were detected in all 17 instruments. In addition, CT allowed noninvasive identification of the internal wood grain pattern unique to each instrument, thereby facilitating verification of authenticity to help protect against loss, theft, or forgery. The information provided by CT analysis of valuable bowed stringed instruments may prove useful to prospective buyers or to insurance companies that specialize in insuring such instruments against accidental loss or damage.

  8. CT based three dimensional dose-volume evaluations for high-dose rate intracavitary brachytherapy for cervical cancer

    PubMed Central

    2014-01-01

    Background In this study, high risk clinical target volumes (HR-CTVs) according to GEC-ESTRO guideline were contoured retrospectively based on CT images taken at the time of high-dose rate intracavitary brachytherapy (HDR-ICBT) and correlation between clinical outcome and dose of HR-CTV were analyzed. Methods Our study population consists of 51 patients with cervical cancer (Stages IB-IVA) treated with 50 Gy external beam radiotherapy (EBRT) using central shield combined with 2–5 times of 6 Gy HDR-ICBT with or without weekly cisplatin. Dose calculation was based on Manchester system and prescribed dose of 6 Gy were delivered for point A. CT images taken at the time of each HDR-ICBT were reviewed and HR-CTVs were contoured. Doses were converted to the equivalent dose in 2 Gy (EQD2) by applying the linear quadratic model (α/β = 10 Gy). Results Three-year overall survival, Progression-free survival, and local control rate was 82.4%, 85.3% and 91.7%, respectively. Median cumulative dose of HR-CTV D90 was 65.0 Gy (52.7-101.7 Gy). Median length from tandem to the most lateral edge of HR-CTV at the first ICBT was 29.2 mm (range, 18.0-51.9 mm). On univariate analysis, both LCR and PFS was significantly favorable in those patients D90 for HR-CTV was 60 Gy or greater (p = 0.001 and 0.03, respectively). PFS was significantly favorable in those patients maximum length from tandem to edge of HR-CTV at first ICBT was shorter than 3.5 cm (p = 0.042). Conclusion Volume-dose showed a relationship to the clinical outcome in CT based brachytherapy for cervical carcinoma. PMID:24938757

  9. Recurrent thyroid cancer diagnosis: ROC study of the effect of a high-resolution head and neck 18F-FDG PET/CT scan.

    PubMed

    Chatziioannou, Sofia N; Georgakopoulos, Alexandros T; Pianou, Nikoletta K; Kafiri, Georgia Th; Pavlou, Spyros N; Kallergi, Maria

    2014-01-01

    (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) has demonstrated significant value in the evaluation of patients with indication of recurrent thyroid cancer with negative conventional workup. The hypothesis of this study was that the addition of a dedicated, high-resolution head and neck scan (HNS) to the standard whole-body scan (WBS) improves the accuracy of the detection and diagnosis of recurrent thyroid cancer. Forty-three consecutive patients suspected for recurrent thyroid cancer, as indicated by increased tumor markers, prospectively underwent a WBS and a HNS with (18)F-FDG PET/CT. The patients were followed up to establish ground truth. A receiver operator characteristic (ROC) study with two observers was conducted to evaluate the impact of the additional HNS on the detection and diagnosis of recurrent thyroid cancer. Indices of performance included the area under the ROC curve (AUC), the number of detected abnormal foci, and the size of the detected foci without and with the HNS images. ROC results showed that the addition of the HNS to the standard WBS increased the average AUC index of performance from 0.69 to 0.96, a statistically significant difference with a confidence interval (CI) of -0.33 to -0.19. Diagnosis was also improved with the average AUC increasing from 0.79 to 0.87 but differences were not statistically significant (CI, -0.19 to 0.04). Interreader agreement was "good" in the detection task and "excellent" in the diagnostic task. The addition of the HNS increased the number of detected foci in the positive patients by an average of 37%, whereas false-positive detections in the negative patients increased by an average of 10%. Reported average maximum lesion size also increased with the HNS addition by an average of 11%. The addition of a high-resolution HNS to the standard whole-body PET/CT imaging improves readers' performance in the detection and diagnosis of recurrent thyroid cancer and

  10. An investigation of small scales of turbulence in a boundary layer at high Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Wallace, James M.; Ong, L.; Balint, J.-L.

    1993-01-01

    The assumption that turbulence at large wave-numbers is isotropic and has universal spectral characteristics which are independent of the flow geometry, at least for high Reynolds numbers, has been a cornerstone of closure theories as well as of the most promising recent development in the effort to predict turbulent flows, viz. large eddy simulations. This hypothesis was first advanced by Kolmogorov based on the supposition that turbulent kinetic energy cascades down the scales (up the wave-numbers) of turbulence and that, if the number of these cascade steps is sufficiently large (i.e. the wave-number range is large), then the effects of anisotropies at the large scales are lost in the energy transfer process. Experimental attempts were repeatedly made to verify this fundamental assumption. However, Van Atta has recently suggested that an examination of the scalar and velocity gradient fields is necessary to definitively verify this hypothesis or prove it to be unfounded. Of course, this must be carried out in a flow with a sufficiently high Reynolds number to provide the necessary separation of scales in order unambiguously to provide the possibility of local isotropy at large wave-numbers. An opportunity to use our 12-sensor hot-wire probe to address this issue directly was made available at the 80'x120' wind tunnel at the NASA Ames Research Center, which is normally used for full-scale aircraft tests. An initial report on this high Reynolds number experiment and progress toward its evaluation is presented.

  11. High Reynolds number and turbulence effects on aerodynamics and heat transfer in a turbine cascade

    NASA Technical Reports Server (NTRS)

    Yeh, Frederick C.; Hippensteele, Steven A.; Vanfossen, G. James; Poinsatte, Philip E.; Ameri, Ali

    1993-01-01

    Experimental data on pressure distribution and heat transfer on a turbine airfoil were obtained over a range of Reynolds numbers from 0.75 to 7.5 x 10 exp 6 and a range of turbulence intensities from 1.8 to about 15 percent. The purpose of this study was to obtain fundamental heat transfer and pressure distribution data over a wide range of high Reynolds numbers and to extend the heat transfer data base to include the range of Reynolds numbers encountered in the Space Shuttle main engine (SSME) turbopump turbines. Specifically, the study aimed to determine (1) the effect of Reynolds number on heat transfer, (2) the effect of upstream turbulence on heat transfer and pressure distribution, and (3) the relationship between heat transfer at high Reynolds numbers and the current data base. The results of this study indicated that Reynolds number and turbulence intensity have a large effect on both the transition from laminar to turbulent flow and the resulting heat transfer. For a given turbulence intensity, heat transfer for all Reynolds numbers at the leading edge can be correlated with the Frossling number developed for lower Reynolds numbers. For a given turbulence intensity, heat transfer for the airfoil surfaces downstream of the leading edge can be approximately correlated with a dimensionless parameter. Comparison of the experimental results were also made with a numerical solution from a two-dimensional Navier-Stokes code.

  12. DSMC simulations of leading edge flat-plate boundary layer flows at high Mach number

    NASA Astrophysics Data System (ADS)

    Pradhan, Sahadev, , Dr.

    2017-01-01

    The flow over a 2D leading-edge flat plate is studied at Mach number Ma = (Uinf /√{kBTinf / m }) in the range number number Re = (LTUinfrhoinf) /muinf equal to 10 using two-dimensional (2D) direct simulation Monte Carlo (DSMC) simulations to understand the flow phenomena of the leading-edge flat plate boundary layer at high Mach number. Here, LT is the characteristic dimension, Uinf and Tinf are the free stream velocity and temperature, rhoinf is the free stream density, m is the molecular mass, muinf is the molecular viscosity based on the free stream temperature Tinf , and kB is the Boltzmann constant. The variation of streamwise velocity, temperature, number-density, and mean free path along the wall normal direction away from the plate surface is studied. The qualitative nature of the streamwise velocity at high Mach number is similar to those in the incompressible limit (parabolic profile). However, there are important differences. The amplitudes of the streamwise velocity increase as the Mach number increases and turned into a more flatter profile near the wall. There is significant velocity and temperature slip at the surface of the plate, and the slip increases as the Mach number is increased. It is interesting to note that for the highest Mach numbers considered here, the streamwise velocity at the wall exceeds the sound speed, and the flow is supersonic throughout the flow domain.

  13. DSMC simulations of leading edge flat-plate boundary layer flows at high Mach number

    NASA Astrophysics Data System (ADS)

    Pradhan, Sahadev

    2016-10-01

    The flow over a 2D leading-edge flat plate is studied at Mach number Ma = (Uinf / {kBTinf /m}) in the range number number Re = (LTUinf rhoinf)/muinf equal to 10 using two-dimensional (2D) direct simulation Monte Carlo (DSMC) simulations to understand the flow phenomena of the leading-edge flat plate boundary layer at high Mach number. Here, LT is the characteristic dimension, Uinf and Tinf are the free stream velocity and temperature, rhoinf is the free stream density, m is the molecular mass, muinf is the molecular viscosity based on the free stream temperature Tinf , and kB is the Boltzmann constant. The variation of streamwise velocity, temperature, number-density, and mean free path along the wall normal direction away from the plate surface is studied. The qualitative nature of the streamwise velocity at high Mach number is similar to those in the incompressible limit (parabolic profile). However, there are important differences. The amplitudes of the streamwise velocity increase as the Mach number increases and turned into a more flatter profile near the wall. There is significant velocity and temperature slip at the surface of the plate, and the slip increases as the Mach number is increased. It is interesting to note that for the highest Mach numbers considered here, the streamwise velocity at the wall exceeds the sound speed, and the flow is supersonic throughout the flow domain.

  14. DSMC simulations of leading edge flat-plate boundary layer flows at high Mach number

    NASA Astrophysics Data System (ADS)

    Pradhan, Sahadev, , Dr.

    2016-11-01

    The flow over a 2D leading-edge flat plate is studied at Mach number Ma = (Uinf /√{kBTinf / m }) in the range number number Re = (LTUinfρinf) / muinf equal to 104 using two-dimensional (2D) direct simulation Monte Carlo (DSMC) simulations to understand the flow phenomena of the leading-edge flat plate boundary layer at high Mach number. Here, LT is the characteristic dimension, Uinf and Tinf are the free stream velocity and temperature, ρinf is the free stream density, mis the molecular mass, μinf is the molecular viscosity based on the free stream temperature Tinf, and kB is the Boltzmann constant. The variation of streamwise velocity, temperature, number-density, and mean free path along the wall normal direction away from the plate surface is studied. The qualitative nature of the streamwise velocity at high Mach number is similar to those in the incompressible limit (parabolic profile). However, there are important differences. The amplitudes of the streamwise velocity increase as the Mach number increases and turned into a more flatter profile near the wall. There is significant velocity and temperature slip at the surface of the plate, and the slip increases as the Mach number is increased. It is interesting to note that for the highest Mach numbers considered here, the streamwise velocity at the wall exceeds the sound speed, and the flow is supersonic throughout the flow domain.

  15. Low-Grade and High-Grade Mucoepidermoid Carcinoma of the Lung: CT Findings and Clinical Features of 17 Cases.

    PubMed

    Wang, Yiqi Q; Mo, Yunxian X; Li, Sheng; Luo, Rongzhen Z; Mao, Siyue Y; Shen, Jingxian X

    2015-12-01

    The objective of our study was to characterize the CT features and clinical findings of low-grade and high-grade mucoepidermoid carcinoma (MEC) of the lung. The CT findings and clinical information of 17 consecutive patients with primary low-grade (n = 11) or high-grade (n = 6) MEC were analyzed retrospectively. We assessed tumor location, size, contour, margin, density, calcification, obstructive changes, presence of metastasis, and enhancement. In patients with low-grade MEC, tumor location was central in 10 and peripheral in one. In contrast, one and five tumors in patients with high-grade MEC were central and peripheral, respectively. There was a significant difference between central and peripheral locations among tumor grades (p = 0.005). In low-grade MECs, tumor contour was smoothly oval (n = 3) or spheric (n = 4); four were lobular. In five patients with low-grade MEC, tumors had well-defined margins; margins in the other six were poorly defined. Tumor density was homogeneous and heterogeneous in eight and three low-grade tumors, respectively. All six high-grade tumors had heterogeneous density, lobular contours, and poorly defined margins. Enhancement in both low-grade and high-grade tumors was greater than that of chest wall muscles, and low-grade tumors showed greater enhancement (46.90 ± 20.44 HU) than did high-grade tumors (22.50 ± 8.38 HU) (p = 0.015). A markedly enhanced homogeneous central bronchial nodule or mass may suggest low-grade MEC. High-grade MEC tends to be peripheral, to have poorly defined margins, and to be lobular, heterogeneous nodules or masses with less enhancement.

  16. Performance Limiting Flow Processes in High-State Loading High-Mach Number Compressors

    DTIC Science & Technology

    2008-03-13

    the Doctoral Thesis Committee of the doctoral student. 3 3.0 Technical Background A strong incentive exists to reduce airfoil count in aircraft engine ...Advanced Turbine Engine ). A basic constraint on blade reduction is seen from the Euler turbine equation, which shows that, although a design can be carried...on the vane to rotor blade ratio of 8:11). Within the MSU Turbo code, specifying a small number of time steps requires more iteration at each time

  17. High-performance C-arm cone-beam CT guidance of thoracic surgery

    NASA Astrophysics Data System (ADS)

    Schafer, Sebastian; Otake, Yoshito; Uneri, Ali; Mirota, Daniel J.; Nithiananthan, Sajendra; Stayman, J. W.; Zbijewski, Wojciech; Kleinszig, Gerhard; Graumann, Rainer; Sussman, Marc; Siewerdsen, Jeffrey H.

    2012-02-01

    Localizing sub-palpable nodules in minimally invasive video-assisted thoracic surgery (VATS) presents a significant challenge. To overcome inherent problems of preoperative nodule tagging using CT fluoroscopic guidance, an intraoperative C-arm cone-beam CT (CBCT) image-guidance system has been developed for direct localization of subpalpable tumors in the OR, including real-time tracking of surgical tools (including thoracoscope), and video-CBCT registration for augmentation of the thoracoscopic scene. Acquisition protocols for nodule visibility in the inflated and deflated lung were delineated in phantom and animal/cadaver studies. Motion compensated reconstruction was implemented to account for motion induced by the ventilated contralateral lung. Experience in CBCT-guided targeting of simulated lung nodules included phantoms, porcine models, and cadavers. Phantom studies defined low-dose acquisition protocols providing contrast-to-noise ratio sufficient for lung nodule visualization, confirmed in porcine specimens with simulated nodules (3-6mm diameter PE spheres, ~100-150HU contrast, 2.1mGy). Nodule visibility in CBCT of the collapsed lung, with reduced contrast according to air volume retention, was more challenging, but initial studies confirmed visibility using scan protocols at slightly increased dose (~4.6-11.1mGy). Motion compensated reconstruction employing a 4D deformation map in the backprojection process reduced artifacts associated with motion blur. Augmentation of thoracoscopic video with renderings of the target and critical structures (e.g., pulmonary artery) showed geometric accuracy consistent with camera calibration and the tracking system (2.4mm registration error). Initial results suggest a potentially valuable role for CBCT guidance in VATS, improving precision in minimally invasive, lungconserving surgeries, avoid critical structures, obviate the burdens of preoperative localization, and improve patient safety.

  18. Denoising and artefact reduction in dynamic flat detector CT perfusion imaging using high speed acquisition: first experimental and clinical results

    NASA Astrophysics Data System (ADS)

    Manhart, Michael T.; Aichert, André; Struffert, Tobias; Deuerling-Zheng, Yu; Kowarschik, Markus; Maier, Andreas K.; Hornegger, Joachim; Doerfler, Arnd

    2014-08-01

    Flat detector CT perfusion (FD-CTP) is a novel technique using C-arm angiography systems for interventional dynamic tissue perfusion measurement with high potential benefits for catheter-guided treatment of stroke. However, FD-CTP is challenging since C-arms rotate slower than conventional CT systems. Furthermore, noise and artefacts affect the measurement of contrast agent flow in tissue. Recent robotic C-arms are able to use high speed protocols (HSP), which allow sampling of the contrast agent flow with improved temporal resolution. However, low angular sampling of projection images leads to streak artefacts, which are translated to the perfusion maps. We recently introduced the FDK-JBF denoising technique based on Feldkamp (FDK) reconstruction followed by joint bilateral filtering (JBF). As this edge-preserving noise reduction preserves streak artefacts, an empirical streak reduction (SR) technique is presented in this work. The SR method exploits spatial and temporal information in the form of total variation and time-curve analysis to detect and remove streaks. The novel approach is evaluated in a numerical brain phantom and a patient study. An improved noise and artefact reduction compared to existing post-processing methods and faster computation speed compared to an algebraic reconstruction method are achieved.

  19. Denoising and artefact reduction in dynamic flat detector CT perfusion imaging using high speed acquisition: first experimental and clinical results.

    PubMed

    Manhart, Michael T; Aichert, André; Struffert, Tobias; Deuerling-Zheng, Yu; Kowarschik, Markus; Maier, Andreas K; Hornegger, Joachim; Doerfler, Arnd

    2014-08-21

    Flat detector CT perfusion (FD-CTP) is a novel technique using C-arm angiography systems for interventional dynamic tissue perfusion measurement with high potential benefits for catheter-guided treatment of stroke. However, FD-CTP is challenging since C-arms rotate slower than conventional CT systems. Furthermore, noise and artefacts affect the measurement of contrast agent flow in tissue. Recent robotic C-arms are able to use high speed protocols (HSP), which allow sampling of the contrast agent flow with improved temporal resolution. However, low angular sampling of projection images leads to streak artefacts, which are translated to the perfusion maps. We recently introduced the FDK-JBF denoising technique based on Feldkamp (FDK) reconstruction followed by joint bilateral filtering (JBF). As this edge-preserving noise reduction preserves streak artefacts, an empirical streak reduction (SR) technique is presented in this work. The SR method exploits spatial and temporal information in the form of total variation and time-curve analysis to detect and remove streaks. The novel approach is evaluated in a numerical brain phantom and a patient study. An improved noise and artefact reduction compared to existing post-processing methods and faster computation speed compared to an algebraic reconstruction method are achieved.

  20. Multiscale structures of resistive magnetic reconnection at high magnetic Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Miyoshi, Takahiro; Kusano, Kanya

    Magnetic reconnection is the most important process of explosive phenomena in space plasmas. The magnetic Reynolds number for the space plasmas are extremely high in general since those plasmas are thought to be collisionless or semi-collisional. However, magnetic reconnection rate becomes low as magnetic Reynolds number increases within the framework of a stationary resistive MHD model. Thus, modern models of magnetic reconnection often include kinetic effects such as the Hall effect to explain realistic explosive magnetic reconnection. It is thought, on the other hand, that the MHD approximation is valid for the plasmas within a very wide range of scales since the scale gap between the macro-and micro-scale is quite large, e.g., in the solar corona, the ratio of the macro to micro will be more than 107 . Such multiscale structures of MHD with wide range of scales, however, have not been clarified so far. Therefore, in this paper, resistive magnetic reconnection at high magnetic Reynolds numbers are investigated using very high-resolution MHD simulations. Simulation results show that the magnetic energy at high magnetic Reynolds numbers is explosively released, while that at not-so-high magnetic Reynolds numbers is steadily dissipated. In the case of high magnetic Reynolds numbers, multiple small scale plasmoids are intermittently created and ejected via secondary tearing modes in a nonlinearly developed thin current sheet. It is revealed that a secondary plasmoid is not only accelerated up to a local magnetosonic speed toward the down-stream region but also perturbs the up-stream region. Thus, complicated multiscale structures appear around the magnetic field reversal layer. Perspective for the high-resolution simulation of extremely high magnetic Reynolds numbers will be also discussed.

  1. Comparison of 68Ga-PSMA PET/CT and multiparametric MRI for staging of high-risk prostate cancer68Ga-PSMA PET and MRI in prostate cancer.

    PubMed

    Tulsyan, Shruti; Das, Chandan J; Tripathi, Madhavi; Seth, Amlesh; Kumar, Rajeev; Bal, Chandrasekhar

    2017-09-27

    We carried out this study to compare Glu-NH-CO-NH-Lys-(Ahx) [Ga(HBED-CC)] [Ga prostate-specific membrane antigen-11 (PSMA-11)] PET with multiparametric MRI (mpMRI) for the staging of high-risk prostate cancer. This was a prospective study in which 36 patients with high-risk prostate cancer were included. The criteria for inclusion were biopsy-proven prostate cancer with a serum prostate specific antigen of at least 20 and/or Gleason's score of at least 8. Each patient then underwent both gallium-68 (Ga)-PSMA PET/computed tomography (CT) and mpMRI including diffusion-weighted whole-body imaging with background body signal suppression within an interval of 1 week and both modalities were compared for staging of primary disease, lymph node, and distant metastasis. The median age of the 36 patients included was 65 years (range: 44-80 years) and the median prostate specific antigen was 94.3 ng/ml (range: 20-19005  ng/ml). Concordance for localization of primary on Ga-PSMA PET/CT and MRI was observed in 19/36 (52.7%) patients. Concurrence for T staging on Ga-PSMA and MRI was observed in 58.3% of patients. Ga-PSMA PET/CT detected higher numbers of patients with regional (29) and nonregional (15) lymph nodes in comparison with MRI (20 and 5, respectively). Concurrence for regional and nonregional lymph node staging was observed in 72.2% of patients. Additional sites of metastatic disease reported on Ga-PSMA PET/CT were to the skeleton in one patient, the lung in two patients, and the liver in one patient. This study suggests that Ga-PSMA PET/CT is useful for lymph node and metastases staging in high-risk prostate cancers, whereas its utility for staging of disease in the prostate is limited.

  2. Pulmonary fibrosis: tissue characterization using late-enhanced MRI compared with unenhanced anatomic high-resolution CT

    PubMed Central

    Lavelle, Lisa P.; Brady, Darragh; McEvoy, Sinead; Murphy, David; Gibney, Brian; Gallagher, Annika; Butler, Marcus; Shortt, Fionnula; McMullen, Marie; Fabre, Aurelie; Lynch, David A.; Keane, Michael P.; Dodd, Jonathan D.

    2017-01-01

    PURPOSE We aimed to prospectively evaluate anatomic chest computed tomography (CT) with tissue characterization late gadolinium-enhanced magnetic resonance imaging (MRI) in the evaluation of pulmonary fibrosis (PF). METHODS Twenty patients with idiopathic pulmonary fibrosis (IPF) and twelve control patients underwent late-enhanced MRI and high-resolution CT. Tissue characterization of PF was depicted using a segmented inversion-recovery turbo low-angle shot MRI sequence. Pulmonary arterial blood pool nulling was achieved by nulling main pulmonary artery signal. Images were read in random order by a blinded reader for presence and extent of overall PF (reticulation and honeycombing) at five anatomic levels. Overall extent of IPF was estimated to the nearest 5% as well as an evaluation of the ratios of IPF made up of reticulation and honeycombing. Overall grade of severity was dependent on the extent of reticulation and honeycombing. RESULTS No control patient exhibited contrast enhancement on lung late-enhanced MRI. All IPF patients were identified with late-enhanced MRI. Mean signal intensity of the late-enhanced fibrotic lung was 31.8±10.6 vs. 10.5±1.6 for normal lung regions, P < 0.001, resulting in a percent elevation in signal intensity from PF of 204.8%±90.6 compared with the signal intensity of normal lung. The mean contrast-to-noise ratio was 22.8±10.7. Late-enhanced MRI correlated significantly with chest CT for the extent of PF (R=0.78, P = 0.001) but not for reticulation, honeycombing, or coarseness of reticulation or honeycombing. CONCLUSION Tissue characterization of IPF is possible using inversion recovery sequence thoracic MRI. PMID:28067202

  3. 3D printing for orthopedic applications: from high resolution cone beam CT images to life size physical models

    NASA Astrophysics Data System (ADS)

    Jackson, Amiee; Ray, Lawrence A.; Dangi, Shusil; Ben-Zikri, Yehuda K.; Linte, Cristian A.

    2017-03-01

    With increasing resolution in image acquisition, the project explores capabilities of printing toward faithfully reflecting detail and features depicted in medical images. To improve safety and efficiency of orthopedic surgery and spatial conceptualization in training and education, this project focused on generating virtual models of orthopedic anatomy from clinical quality computed tomography (CT) image datasets and manufacturing life-size physical models of the anatomy using 3D printing tools. Beginning with raw micro CT data, several image segmentation techniques including thresholding, edge recognition, and region-growing algorithms available in packages such as ITK-SNAP, MITK, or Mimics, were utilized to separate bone from surrounding soft tissue. After converting the resulting data to a standard 3D printing format, stereolithography (STL), the STL file was edited using Meshlab, Netfabb, and Meshmixer. The editing process was necessary to ensure a fully connected surface (no loose elements), positive volume with manifold geometry (geometry possible in the 3D physical world), and a single, closed shell. The resulting surface was then imported into a "slicing" software to scale and orient for printing on a Flashforge Creator Pro. In printing, relationships between orientation, print bed volume, model quality, material use and cost, and print time were considered. We generated anatomical models of the hand, elbow, knee, ankle, and foot from both low-dose high-resolution cone-beam CT images acquired using the soon to be released scanner developed by Carestream, as well as scaled models of the skeletal anatomy of the arm and leg, together with life-size models of the hand and foot.

  4. CT Scan Findings of Probable Usual Interstitial Pneumonitis Have a High Predictive Value for Histologic Usual Interstitial Pneumonitis

    PubMed Central

    Chawla, Ashish; Peljto, Anna L.; Cool, Carlyne D.; Groshong, Steve D.; Talbert, Janet L.; McKean, David F.; Brown, Kevin K.; Fingerlin, Tasha E.; Schwarz, Marvin I.; Schwartz, David A.; Lynch, David A.

    2015-01-01

    BACKGROUND: The current usual interstitial pneumonitis (UIP)/idiopathic pulmonary fibrosis CT scan classification system excludes probable UIP as a diagnostic category. We sought to determine the predictive effect of probable UIP on CT scan on histology and the effect of the promoter polymorphism in MUC5B (rs35705950) on histologic and CT scan UIP diagnosis. METHODS: The cohort included 201 subjects with pulmonary fibrosis who had lung tissue samples obtained within 1 year of chest CT scan. UIP diagnosis on CT scan was categorized as inconsistent with, indeterminate, probable, or definite UIP by two to three pulmonary radiologists. Tissue slides were scored by two expert pulmonary pathologists. All subjects with available DNA (N = 200) were genotyped for rs35705950. RESULTS: The proportion of CT scan diagnoses were as follows: inconsistent with (69 of 201, 34.3%), indeterminate (72 of 201, 35.8%), probable (34 of 201, 16.9%), and definite (26 of 201, 12.9%) UIP. Subjects with probable UIP on CT scan were more likely to have histologic probable/definite UIP than subjects with indeterminate UIP on CT scan (82.4% [28 of 34] vs 54.2% [39 of 72]; P = .01). CT scan and microscopic honeycombing were not associated with each other (P = .76). The minor (T) allele of the MUC5B polymorphism was associated with concordant CT scan and histologic UIP diagnosis (P = .03). CONCLUSIONS: Probable UIP on CT scan is associated with a higher rate of histologic UIP than indeterminate UIP on CT scan suggesting that they are distinct groups and should not be combined into a single CT scan category as currently recommended by guidelines. CT scan and microscopic honeycombing may be dissimilar entities. The T allele at rs35705950 predicts a UIP diagnosis by both chest CT scan and histology. PMID:25317858

  5. National Program for Inspection of Non-Federal Dams. Bristol Reservoir Number 5 Dam (CT 00366), Farmington River Basin, Harwinton, Connecticut. Phase I Inspection Report.

    DTIC Science & Technology

    1980-07-01

    6.0 FT. D-33 BY .... A TE..DT f. 𔄂q... R 0 A L D H A ES TAD, I N C. SHEET NO.....3..... OF .3.7 .... .0 CONSULTING ENGINEERS CKD BY . J ...S-. DATE...HARWINTO’N, CONNECTICUT r sreou RESEhIVOIR NO.5DA I! C CT 003664 j ! avwa PHAS-E -,I 14N8PEO-T-4ONa--RfiPOR-T e~ NATIONAL D’AMiNSPEtO 7PROGG RA M - MOr 60...CONTRACT OR GRANT NUMU[R( J ) U.S. ARMY CORPS OF ENGINEERS NEW ENGLAND DIVISION 9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT

  6. ChromAIX2: A large area, high count-rate energy-resolving photon counting ASIC for a Spectral CT Prototype

    NASA Astrophysics Data System (ADS)

    Steadman, Roger; Herrmann, Christoph; Livne, Amir

    2017-08-01

    Spectral CT based on energy-resolving photon counting detectors is expected to deliver additional diagnostic value at a lower dose than current state-of-the-art CT [1]. The capability of simultaneously providing a number of spectrally distinct measurements not only allows distinguishing between photo-electric and Compton interactions but also discriminating contrast agents that exhibit a K-edge discontinuity in the absorption spectrum, referred to as K-edge Imaging [2]. Such detectors are based on direct converting sensors (e.g. CdTe or CdZnTe) and high-rate photon counting electronics. To support the development of Spectral CT and show the feasibility of obtaining rates exceeding 10 Mcps/pixel (Poissonian observed count-rate), the ChromAIX ASIC has been previously reported showing 13.5 Mcps/pixel (150 Mcps/mm2 incident) [3]. The ChromAIX has been improved to offer the possibility of a large area coverage detector, and increased overall performance. The new ASIC is called ChromAIX2, and delivers count-rates exceeding 15 Mcps/pixel with an rms-noise performance of approximately 260 e-. It has an isotropic pixel pitch of 500 μm in an array of 22×32 pixels and is tile-able on three of its sides. The pixel topology consists of a two stage amplifier (CSA and Shaper) and a number of test features allowing to thoroughly characterize the ASIC without a sensor. A total of 5 independent thresholds are also available within each pixel, allowing to acquire 5 spectrally distinct measurements simultaneously. The ASIC also incorporates a baseline restorer to eliminate excess currents induced by the sensor (e.g. dark current and low frequency drifts) which would otherwise cause an energy estimation error. In this paper we report on the inherent electrical performance of the ChromAXI2 as well as measurements obtained with CZT (CdZnTe)/CdTe sensors and X-rays and radioactive sources.

  7. Multigrid solution of the convection-diffusion equation with high-Reynolds number

    SciTech Connect

    Zhang, Jun

    1996-12-31

    A fourth-order compact finite difference scheme is employed with the multigrid technique to solve the variable coefficient convection-diffusion equation with high-Reynolds number. Scaled inter-grid transfer operators and potential on vectorization and parallelization are discussed. The high-order multigrid method is unconditionally stable and produces solution of 4th-order accuracy. Numerical experiments are included.

  8. pMHC Multiplexing Strategy to Detect High Numbers of T Cell Responses in Parallel.

    PubMed

    Philips, Daisy; van den Braber, Marlous; Schumacher, Ton N; Kvistborg, Pia

    2017-01-01

    The development of peptide loaded major histocompatibility complexes (MHC) conjugated to fluorochromes by Davis and colleagues 20 years ago provided a highly useful tool to identify and characterize antigen-specific T cells. In this chapter we describe a multiplexing strategy that allows detection of high numbers of T cell responses in parallel.

  9. Roughness Effects on Compressor Outlet Guide Vanes at High Reynolds Number and High Turning Angle.

    DTIC Science & Technology

    1982-11-01

    controlled environment was necessary to reduce the effects of ambient temperture fluctuations on the resistance of the bridoe circuit of the anemormeter...RD-Ai24 688 ROUGHNESS EFFECTS ON COMPRESSOR OUTLET GUIDE YANES AT I HIGH REYNOLDS NUMBE..(U) AR FORCE INST OF TECH IRIGHT-PRTTERSONRRFB OH SCHOOL OF...RESOLUTION TEST CHART ~.~~-NAONAL BUREAU OF STAMDOARDS-1963-A AF....ED , . - . . . .Genovese ili t~t.V ROUGHESS EFFECTS ON COMP RROTT .AND HIGH

  10. Technical Note: Skin thickness measurements using high-resolution flat-panel cone-beam dedicated breast CT

    SciTech Connect

    Shi Linxi; Vedantham, Srinivasan; Karellas, Andrew; O'Connell, Avice M.

    2013-03-15

    Purpose: To determine the mean and range of location-averaged breast skin thickness using high-resolution dedicated breast CT for use in Monte Carlo-based estimation of normalized glandular dose coefficients. Methods: This study retrospectively analyzed image data from a clinical study investigating dedicated breast CT. An algorithm similar to that described by Huang et al.['The effect of skin thickness determined using breast CT on mammographic dosimetry,' Med. Phys. 35(4), 1199-1206 (2008)] was used to determine the skin thickness in 137 dedicated breast CT volumes from 136 women. The location-averaged mean breast skin thickness for each breast was estimated and the study population mean and range were determined. Pathology results were available for 132 women, and were used to investigate if the distribution of location-averaged mean breast skin thickness varied with pathology. The effect of surface fitting to account for breast curvature was also studied. Results: The study mean ({+-} interbreast SD) for breast skin thickness was 1.44 {+-} 0.25 mm (range: 0.87-2.34 mm), which was in excellent agreement with Huang et al. Based on pathology, pair-wise statistical analysis (Mann-Whitney test) indicated that at the 0.05 significance level, there were no significant difference in the location-averaged mean breast skin thickness distributions between the groups: benign vs malignant (p= 0.223), benign vs hyperplasia (p= 0.651), hyperplasia vs malignant (p= 0.229), and malignant vs nonmalignant (p= 0.172). Conclusions: Considering this study used a different clinical prototype system, and the study participants were from a different geographical location, the observed agreement between the two studies suggests that the choice of 1.45 mm thick skin layer comprising the epidermis and the dermis for breast dosimetry is appropriate. While some benign and malignant conditions could cause skin thickening, in this study cohort the location-averaged mean breast skin thickness

  11. Technical note: Skin thickness measurements using high-resolution flat-panel cone-beam dedicated breast CT.

    PubMed

    Shi, Linxi; Vedantham, Srinivasan; Karellas, Andrew; O'Connell, Avice M

    2013-03-01

    To determine the mean and range of location-averaged breast skin thickness using high-resolution dedicated breast CT for use in Monte Carlo-based estimation of normalized glandular dose coefficients. This study retrospectively analyzed image data from a clinical study investigating dedicated breast CT. An algorithm similar to that described by Huang et al. ["The effect of skin thickness determined using breast CT on mammographic dosimetry," Med. Phys. 35(4), 1199-1206 (2008)] was used to determine the skin thickness in 137 dedicated breast CT volumes from 136 women. The location-averaged mean breast skin thickness for each breast was estimated and the study population mean and range were determined. Pathology results were available for 132 women, and were used to investigate if the distribution of location-averaged mean breast skin thickness varied with pathology. The effect of surface fitting to account for breast curvature was also studied. The study mean (± interbreast SD) for breast skin thickness was 1.44 ± 0.25 mm (range: 0.87-2.34 mm), which was in excellent agreement with Huang et al. Based on pathology, pair-wise statistical analysis (Mann-Whitney test) indicated that at the 0.05 significance level, there were no significant difference in the location-averaged mean breast skin thickness distributions between the groups: benign vs malignant (p = 0.223), benign vs hyperplasia (p = 0.651), hyperplasia vs malignant (p = 0.229), and malignant vs nonmalignant (p = 0.172). Considering this study used a different clinical prototype system, and the study participants were from a different geographical location, the observed agreement between the two studies suggests that the choice of 1.45 mm thick skin layer comprising the epidermis and the dermis for breast dosimetry is appropriate. While some benign and malignant conditions could cause skin thickening, in this study cohort the location-averaged mean breast skin thickness distributions did not differ

  12. SU-C-207A-01: A Novel Maximum Likelihood Method for High-Resolution Proton Radiography/proton CT

    SciTech Connect

    Collins-Fekete, C; Schulte, R; Beaulieu, L; Seco, J

    2016-06-15

    Purpose: Multiple Coulomb scattering is the largest contributor to blurring in proton imaging. Here we tested a maximum likelihood least squares estimator (MLLSE) to improve the spatial resolution of proton radiography (pRad) and proton computed tomography (pCT). Methods: The object is discretized into voxels and the average relative stopping power through voxel columns defined from the source to the detector pixels is optimized such that it maximizes the likelihood of the proton energy loss. The length spent by individual protons in each column is calculated through an optimized cubic spline estimate. pRad images were first produced using Geant4 simulations. An anthropomorphic head phantom and the Catphan line-pair module for 3-D spatial resolution were studied and resulting images were analyzed. Both parallel and conical beam have been investigated for simulated pRad acquisition. Then, experimental data of a pediatric head phantom (CIRS) were acquired using a recently completed experimental pCT scanner. Specific filters were applied on proton angle and energy loss data to remove proton histories that underwent nuclear interactions. The MTF10% (lp/mm) was used to evaluate and compare spatial resolution. Results: Numerical simulations showed improvement in the pRad spatial resolution for the parallel (2.75 to 6.71 lp/cm) and conical beam (3.08 to 5.83 lp/cm) reconstructed with the MLLSE compared to averaging detector pixel signals. For full tomographic reconstruction, the improved pRad were used as input into a simultaneous algebraic reconstruction algorithm. The Catphan pCT reconstruction based on the MLLSE-enhanced projection showed spatial resolution improvement for the parallel (2.83 to 5.86 lp/cm) and conical beam (3.03 to 5.15 lp/cm). The anthropomorphic head pCT displayed important contrast gains in high-gradient regions. Experimental results also demonstrated significant improvement in spatial resolution of the pediatric head radiography. Conclusion: The

  13. Detection of coronary artery stenoses by low-dose, prospectively ECG-triggered, high-pitch spiral coronary CT angiography.

    PubMed

    Achenbach, Stephan; Goroll, Tobias; Seltmann, Martin; Pflederer, Tobias; Anders, Katharina; Ropers, Dieter; Daniel, Werner G; Uder, Michael; Lell, Michael; Marwan, Mohamed

    2011-04-01

    We sought to evaluate the diagnostic accuracy of a new prospectively electrocardiogram (ECG)-triggered high-pitch scan mode for coronary computed tomography angiography (CTA), which allows an effective dose of less than 1 mSv. Coronary CTA provides increasingly reliable image quality, but the associated radiation exposure can be high. Seventy-five patients with suspected coronary artery disease and in sinus rhythm were screened for participation. After exclusion of 25 patients for body weight >100 kg or failure to lower heart rate to ≤ 60 beats/min, 50 patients were studied by prospectively ECG-triggered high-pitch spiral computed tomography (CT). Coronary CTA was performed using a dual-source CT system with 2 × 128 × 0.6-mm collimation, 0.28-s rotation time, a pitch of 3.4, 100-kVp tube voltage, and current of 320 mA. Data acquisition was prospectively triggered at 60% of the R-R interval and completed within 1 cardiac cycle. Diagnostic accuracy for detection of coronary artery stenoses ≥ 50% diameter stenosis was determined by comparison to invasive coronary angiography. Per-patient diagnostic performance was the primary form of analysis. In all 50 patients (34 males, 59 ± 12 years of age), imaging was successful. For the detection of 16 patients with at least 1 coronary artery stenosis, CT demonstrated a sensitivity of 100% (95% confidence interval [CI]: 79% to 100%) and specificity of 82% (95% CI: 65% to 93%). The positive predictive value was 72% (95% CI: 49% to 89%) and the negative predictive value was 100% (95% CI: 87% to 100%). Sensitivity was 100% (95% CI: 88% to 100%) and specificity was 94% (95% CI: 89% to 97%) on a per-vessel basis. Per-segment sensitivity was 92% (95% CI: 80% to 97%), and specificity was 98% (95% CI: 96% to 98%). Mean dose-length product for coronary CTA was 54 ± 6 mGy · cm, the effective dose was 0.76 ± 0.08 mSv (0.64 to 0.95 mSv). In nonobese patients with a low and stable heart rate, prospectively ECG-triggered high

  14. Prospectively ECG-triggered high-pitch spiral acquisition for cardiac CT angiography in routine clinical practice: initial results.

    PubMed

    Kröpil, Patric; Rojas, Carlos A; Ghoshhajra, Brian; Lanzman, Rotem S; Miese, Falk R; Scherer, Axel; Kalra, Mannudeep; Abbara, Suhny

    2012-05-01

    This study was conducted to evaluate the mode of application, image quality (IQ), and radiation exposure resulting from introduction of a prospectively electrocardiogram-triggered high-pitch cardiac computed tomography angiography (CTA) acquisition mode into routine clinical practice. A total of 42 prospectively triggered cardiac CTAs were conducted on 34 patients (11 female, 23 male; mean age 56 ± 15 y) using a high-pitch mode (pitch 3.4) on a dual-source CT. In 8 of these patients with higher heart rates or occasional premature ventricular contractions, 2 immediately subsequent CTAs were performed ("double flash protocol"). Subjective IQ was assessed for coronary arteries using a 4-point scale (1=unevaluable to 4=excellent). Contrast-to-noise ratio (CNR) was measured in 9 locations. CT Dose Index and dose-length product were obtained, and the patients' effective dose was calculated. Mean effective doses were 2.6 ± 1.4 mSv (range: 1.1 to 6.4) for the entire cardiac examination and 1.4 ± 0.7 mSv (0.4 to 3.1) for individual high-pitch cardiac CTA. z-coverage ranged from 9.9 cm in a native coronary CTA to 31.4 cm in a bypass graft case. The overall subjective IQ was good to excellent (mean score: 3.5), with 1.5% unevaluable coronary segments. The "double flash protocol" resulted in a fully diagnostic CT study in all cases just after taking both scans into consideration. The mean CNR of all locations was 19.7 ± 2.6. Prospectively electrocardiograph-triggered high-pitch-mode cardiac CTA is a feasible and promising technique in clinical routine, allowing for evaluation of coronaries at good-to-excellent IQ and providing high CNR and minimal radiation doses. The "double flash protocol" might become a more robust tool in patients with elevated heart rates or premature ventricular contractions.

  15. A high-resolution algorithm for wave number estimation using holographic array processing

    NASA Astrophysics Data System (ADS)

    Roux, Philippe; Cassereau, Didier; Roux, André

    2004-03-01

    This paper presents an original way to perform wave number inversion from simulated data obtained in a noisy shallow-water environment. In the studied configuration an acoustic source is horizontally towed with respect to a vertical hydrophone array. The inversion is achieved from the combination of three ingre