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Sample records for intraprocedural diffusion-weighted propeller

  1. A comparative quantitative analysis of magnetic susceptibility artifacts in echo planar and PROPELLER diffusion-weighted images

    NASA Astrophysics Data System (ADS)

    Cho, Jae-Hwan; Lee, Hae-Kag; Yang, Han-Joon; Lee, Gui-Won; Park, Yong-Soon; Chung, Woon-Kwan

    2013-01-01

    In this study, the authors investigated whether periodically-rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) diffusion-weighted imaging (DWI) can remove magnetic susceptibility artifacts and compared apparent diffusion coefficient (ADC) values for PROPELLER DWI and the common echo planar (EP) DWI. Twenty patients that underwent brain MRI with a metal dental implant were selected. A 3.0T MR scanner was then used to obtain EP DWI, PROPELLER DWI, and corresponding apparent diffusion coefficient (ADC) maps for a b-value of 0 and 1,000 s/mm2. The frequencies of magnetic susceptibility artifacts in four parts of the brain (bilateral temporal lobes, pons, and orbit) were selected. In the ADC maps, we measured the ADC values of both sides of the temporal lobe and the pons. According to the study results, the frequency of magnetic susceptibility artifacts in PROPELLER DW images was lower than it was in EP DW images. In ADC maps, the ADC values of the bilateral temporal lobes and the pons were all higher in PROPELLER ADC maps than in EP ADC maps. Our findings show that when a high-field MRI machine is used, magnetic susceptibility artifacts can distort anatomical structures and produce high-intensity signals. Furthermore, our findings suggest that in many cases, PROPELLER DWI would be helpful in terms of achieving a correct diagnosis.

  2. Diffusion weighted vertical gradient and spin echo.

    PubMed

    Engström, Mathias; Bammer, Roland; Skare, Stefan

    2012-12-01

    In this work, diffusion weighting and parallel imaging is combined with a vertical gradient and spin echo data readout. This sequence was implemented and evaluated on healthy volunteers using a 1.5 and a 3 T whole-body MR system. As the vertical gradient and spin echo trajectory enables a higher k-space velocity in the phase-encoding direction than single-shot echo planar imaging, the geometrical distortions are reduced. When combined with parallel imaging such as generalized autocalibrating partially parallel acquisition, the geometric distortions are reduced even further, while also keeping the minimum echo time reasonably low. However, this combination of a diffusion preparation and multiple refocusing pulses during the vertical gradient and spin echo readout, generally violates the Carr-Purcell-Meiboom-Gill condition, which leads to interferences between echo pathways. To suppress the stimulated echo pathway, refocusing pulses with a sharper slice profiles and an odd/even crusher variation scheme were implemented and evaluated. Being a single-shot acquisition technique, the reconstructed images are robust to rigid-body head motion and spatially varying brain motion, both of which are common sources of artifacts in diffusion MRI.

  3. Diffusion weighted imaging: Technique and applications

    PubMed Central

    Baliyan, Vinit; Das, Chandan J; Sharma, Raju; Gupta, Arun Kumar

    2016-01-01

    Diffusion weighted imaging (DWI) is a method of signal contrast generation based on the differences in Brownian motion. DWI is a method to evaluate the molecular function and micro-architecture of the human body. DWI signal contrast can be quantified by apparent diffusion coefficient maps and it acts as a tool for treatment response evaluation and assessment of disease progression. Ability to detect and quantify the anisotropy of diffusion leads to a new paradigm called diffusion tensor imaging (DTI). DTI is a tool for assessment of the organs with highly organised fibre structure. DWI forms an integral part of modern state-of-art magnetic resonance imaging and is indispensable in neuroimaging and oncology. DWI is a field that has been undergoing rapid technical evolution and its applications are increasing every day. This review article provides insights in to the evolution of DWI as a new imaging paradigm and provides a summary of current role of DWI in various disease processes. PMID:27721941

  4. Interpolation of diffusion weighted imaging datasets.

    PubMed

    Dyrby, Tim B; Lundell, Henrik; Burke, Mark W; Reislev, Nina L; Paulson, Olaf B; Ptito, Maurice; Siebner, Hartwig R

    2014-12-01

    Diffusion weighted imaging (DWI) is used to study white-matter fibre organisation, orientation and structural connectivity by means of fibre reconstruction algorithms and tractography. For clinical settings, limited scan time compromises the possibilities to achieve high image resolution for finer anatomical details and signal-to-noise-ratio for reliable fibre reconstruction. We assessed the potential benefits of interpolating DWI datasets to a higher image resolution before fibre reconstruction using a diffusion tensor model. Simulations of straight and curved crossing tracts smaller than or equal to the voxel size showed that conventional higher-order interpolation methods improved the geometrical representation of white-matter tracts with reduced partial-volume-effect (PVE), except at tract boundaries. Simulations and interpolation of ex-vivo monkey brain DWI datasets revealed that conventional interpolation methods fail to disentangle fine anatomical details if PVE is too pronounced in the original data. As for validation we used ex-vivo DWI datasets acquired at various image resolutions as well as Nissl-stained sections. Increasing the image resolution by a factor of eight yielded finer geometrical resolution and more anatomical details in complex regions such as tract boundaries and cortical layers, which are normally only visualized at higher image resolutions. Similar results were found with typical clinical human DWI dataset. However, a possible bias in quantitative values imposed by the interpolation method used should be considered. The results indicate that conventional interpolation methods can be successfully applied to DWI datasets for mining anatomical details that are normally seen only at higher resolutions, which will aid in tractography and microstructural mapping of tissue compartments.

  5. Isotropic anomalous filtering in Diffusion-Weighted Magnetic Resonance Imaging.

    PubMed

    da S Senra Filho, Antonio Carlos; Jinzenji Duque, Juliano; Murta Junior, Luiz Otávio

    2013-01-01

    Noise is inherent to Diffusion-Weighted Magnetic Resonance Imaging (DWI) and noise reduction methods are necessary. Although process based on classical diffusion is one of the most used approaches for digital image, anomalous diffusion has the potential for image enhancement and it has not been tested for DWI noise reduction. This study evaluates Anomalous Diffusion (AD) filter as DWI enhancement method. The proposed method was applied to magnetic resonance diffusion weighted images (DW-MRI) with different noise levels. Results show better performance for anomalous diffusion when compared to classical diffusion approach. The proposed method has shown potential in DWI enhancement and can be an important process to improve quality in DWI for neuroimage-based diagnosis.

  6. Comparative analysis of isotropic diffusion weighted imaging sequences

    NASA Astrophysics Data System (ADS)

    Vellmer, Sebastian; Stirnberg, Rüdiger; Edelhoff, Daniel; Suter, Dieter; Stöcker, Tony; Maximov, Ivan I.

    2017-02-01

    Visualisation of living tissue structure and function is a challenging problem of modern imaging techniques. Diffusion MRI allows one to probe in vivo structures on a micrometer scale. However, conventional diffusion measurements are time-consuming procedures, because they require several measurements with different gradient directions. Considerable time savings are therefore possible by measurement schemes that generate an isotropic diffusion weighting in a single shot. Multiple approaches for generating isotropic diffusion weighting are known and have become very popular as useful tools in clinical research. Thus, there is a strong need for a comprehensive comparison of different isotropic weighting approaches. In the present work we introduce two new sequences based on simple (co)sine modulations and compare their performance to established q-space magic-angle spinning sequences and conventional DTI, using a diffusion phantom assembled from microcapillaries and in vivo experiments at 7 T. The advantages and disadvantages of all compared schemes are demonstrated and discussed.

  7. Diffusion Weighted Image Denoising Using Overcomplete Local PCA

    PubMed Central

    Manjón, José V.; Coupé, Pierrick; Concha, Luis; Buades, Antonio; Collins, D. Louis; Robles, Montserrat

    2013-01-01

    Diffusion Weighted Images (DWI) normally shows a low Signal to Noise Ratio (SNR) due to the presence of noise from the measurement process that complicates and biases the estimation of quantitative diffusion parameters. In this paper, a new denoising methodology is proposed that takes into consideration the multicomponent nature of multi-directional DWI datasets such as those employed in diffusion imaging. This new filter reduces random noise in multicomponent DWI by locally shrinking less significant Principal Components using an overcomplete approach. The proposed method is compared with state-of-the-art methods using synthetic and real clinical MR images, showing improved performance in terms of denoising quality and estimation of diffusion parameters. PMID:24019889

  8. Diffusion-Weighted Images Superresolution Using High-Order SVD.

    PubMed

    Wu, Xi; Yang, Zhipeng; Hu, Jinrong; Peng, Jing; He, Peiyu; Zhou, Jiliu

    2016-01-01

    The spatial resolution of diffusion-weighted imaging (DWI) is limited by several physical and clinical considerations, such as practical scanning times. Interpolation methods, which are widely used to enhance resolution, often result in blurred edges. Advanced superresolution scanning acquires images with specific protocols and long acquisition times. In this paper, we propose a novel single image superresolution (SR) method which introduces high-order SVD (HOSVD) to regularize the patch-based SR framework on DWI datasets. The proposed method was implemented on an adaptive basis which ensured a more accurate reconstruction of high-resolution DWI datasets. Meanwhile, the intrinsic dimensional decreasing property of HOSVD is also beneficial for reducing the computational burden. Experimental results from both synthetic and real DWI datasets demonstrate that the proposed method enhances the details in reconstructed high-resolution DWI datasets and outperforms conventional techniques such as interpolation methods and nonlocal upsampling.

  9. Diffusion-Weighted Images Superresolution Using High-Order SVD

    PubMed Central

    Yang, Zhipeng; Hu, Jinrong; Peng, Jing; He, Peiyu

    2016-01-01

    The spatial resolution of diffusion-weighted imaging (DWI) is limited by several physical and clinical considerations, such as practical scanning times. Interpolation methods, which are widely used to enhance resolution, often result in blurred edges. Advanced superresolution scanning acquires images with specific protocols and long acquisition times. In this paper, we propose a novel single image superresolution (SR) method which introduces high-order SVD (HOSVD) to regularize the patch-based SR framework on DWI datasets. The proposed method was implemented on an adaptive basis which ensured a more accurate reconstruction of high-resolution DWI datasets. Meanwhile, the intrinsic dimensional decreasing property of HOSVD is also beneficial for reducing the computational burden. Experimental results from both synthetic and real DWI datasets demonstrate that the proposed method enhances the details in reconstructed high-resolution DWI datasets and outperforms conventional techniques such as interpolation methods and nonlocal upsampling. PMID:27635150

  10. Diffusion-weighted imaging of the liver: Current applications

    PubMed Central

    Saito, Kazuhiro; Tajima, Yu; Harada, Taiyo L

    2016-01-01

    Diffusion-weighted imaging (DWI) of the liver can be performed using most commercially available machines and is currently accepted in routine sequence. This sequence has some potential as an imaging biomarker for fibrosis, tumor detection/characterization, and following/predicting therapy. To improve reliability including accuracy and reproducibility, researchers have validated this new technique in terms of image acquisition, data sampling, and analysis. The added value of DWI in contrast-enhanced magnetic resonance imaging was established in the detection of malignant liver lesions. However, some limitations remain in terms of lesion characterization and fibrosis detection. Furthermore, the methodologies of image acquisition and data analysis have been inconsistent. Therefore, researchers should make every effort to not only improve accuracy and reproducibility but also standardize imaging parameters. PMID:27928467

  11. Diffusion-weighted MRI in neuro-oncology.

    PubMed

    Baehring, Joachim M; Fulbright, Robert K

    2012-11-01

    Diffusion-weighted MRI (DW-MRI) provides image contrast dependent on the molecular movement of water. It has been most widely used in the diagnosis of cytotoxic edema secondary to acute cerebral ischemia, but has also proven useful in assessing tumor cellularity and grade, abscess formation, cysts and various forms of white matter disorders. Furthermore, DW-MRI is used to generate maps of subcortical white matter tracts and their relationship to structural brain lesions that may serve for preoperative planning and intraoperative guidance. We provide a comprehensive review of current practical applications of DW-MRI in the diagnosis and treatment of primary brain tumors, metastases and nonmetastatic neurologic complications of cancer. A detailed description of diffusion tensor imaging is beyond the scope of this review. We performed a comprehensive search of the PubMed database of the USA National Library of Medicine with use of various combinations of the following search terms: diffusion-weighted imaging, apparent diffusion coefficient, diffusion tensor imaging, diffusion tensor, brain, tumor, glioblastoma, lymphoma, primary CNS lymphoma, stroke, cancer, abscess, leukoencephalopathy, methotrexate, fluorouracil, capecitabine. We identified original articles and well-documented case reports of DW-MRI applications in patients with primary brain neoplasms, metastases and nonmetastatic neurologic complications that we judged to be of high impact on the field. We largely selected publications from the past 10 years, but did not exclude commonly referenced and highly regarded older publications. We also searched the reference lists of articles identified by this search strategy and selected those we judged relevant. Review articles are cited to provide readers with more details and more references than can be covered here.

  12. Diffusion-weighted MR imaging in musculoskeletal diseases: current concepts.

    PubMed

    Dallaudière, B; Lecouvet, F; Vande Berg, B; Omoumi, P; Perlepe, V; Cerny, M; Malghem, J; Larbi, A

    2015-04-01

    MR imaging is currently regarded as a pivotal technique for the assessment of a variety of musculoskeletal conditions. Diffusion-weighted MR imaging (DWI) is a relatively recent sequence that provides information on the degree of cellularity of lesions. Apparent diffusion coefficient (ADC) value provides information on the movement of water molecules outside the cells. The literature contains many studies that have evaluated the role of DWI in musculoskeletal diseases. However, to date they yielded conflicting results on the use and the diagnostic capabilities of DWI in the area of musculoskeletal diseases. However, many of them have showed that DWI is a useful technique for the evaluation of the extent of the disease in a subset of musculoskeletal cancers. In terms of tissue characterization, DWI may be an adjunct to the more conventional MR imaging techniques but should be interpreted along with the signal of the lesion as observed on conventional sequences, especially in musculoskeletal cancers. Regarding the monitoring of response to therapy in cancer or inflammatory disease, the use of ADC value may represent a more reliable additional tool but must be compared to the initial ADC value of the lesions along with the knowledge of the actual therapy.

  13. Diffusion-weighted magnetic resonance imaging in cystic renal masses

    PubMed Central

    Balyemez, Fikret; Aslan, Ahmet; Inan, Ibrahim; Ayaz, Ercan; Karagöz, Vildan; Özkanli, Sıdıka Şeyma; Acar, Murat

    2017-01-01

    Introduction: We aimed to introduce the diagnostic value of diffusion-weighted (DWI) magnetic resonance imaging (MRI) for distinguishing benign and malignant renal cystic masses. Methods: Abdominal DWI-MRIs of patients with Bosniak categories 2F, 3, and 4 cystic renal masses were evaluated retrospectively. Cystic masses were assigned as benign or malignant according to histopathological or followup MRI findings and compared with apparent diffusion coefficient (ADC) values. Results: There were 30 patients (18 males and 12 females, mean age was 59.23 ± 12.08 years [range 38–83 years]) with cystic renal masses (eight Bosniak category 2F, 12 Bosniak category 3, 10 Bosniak category 4). Among them, 14 cysts were diagnosed as benign and 16 as malignant by followup imaging or histopathological findings. For the malignant lesions, the mean ADC values were lower than for benign lesions (p=0.001). An ADC value of ≤2.28 ×10−6 mm2/s or less had a sensitivity of 75% and a specificity of 92.86% for detecting malignancy. Conclusions: ADC can improve the diagnostic performance of MRI in the evaluation of complex renal cysts when used together with conventional MRI sequences. PMID:28163806

  14. Enhanced Diffusion Weighting Generated by Selective Adiabatic Pulse Trains

    PubMed Central

    Sun, Ziqi; Bartha, Robert

    2007-01-01

    A theoretical description and experimental validation of the enhanced diffusion weighting generated by selective adiabatic full passage (AFP) pulse trains is provided. Six phantoms (Ph-1 to Ph-6) were studied on a 4T Varian/Siemens whole body MRI system. Phantoms consisted of 2.8 cm diameter plastic tubes containing a mixture of 10 μm ORGASOL polymer beads and 2 mM Gd-DTPA dissolved in 5% agar (Ph-1) or nickel(II) ammonium sulphate hexahydrate doped (56.3 mM – 0.8 mM) water solutions (Ph-2 to Ph-6). A customized localization by adiabatic selective refocusing (LASER) sequence containing slice selective AFP pulse trains and pulsed diffusion gradients applied in the phase encoding direction was used to measure 1H2O diffusion. The b-value associated with the LASER sequence was derived using the Bloch-Torrey equation. The apparent diffusion coefficients measured by LASER were comparable to those measured by a conventional pulsed gradient spin-echo (PGSE) sequence for all phantoms. Image signal intensity increased in Ph-1 and decreased in Ph-2 – Ph-6 as AFP pulse train length increased while maintaining a constant echo-time. These experimental results suggest that such AFP pulse trains can enhance contrast between regions containing microscopic magnetic susceptibility variations and homogeneous regions in which dynamic dephasing relaxation mechanisms are dominant. PMID:17600741

  15. Liver diffusion-weighted MR imaging: the tower of Babel?

    PubMed

    Guiu, Boris; Cercueil, Jean-Pierre

    2011-03-01

    There is a growing amount of literature regarding diffusion-weighted imaging (DWI) of the liver. The apparent diffusion coefficient (ADC) was introduced in 1986 and is used extensively in studies. However, methods for calculating ADC vary considerably and the value of the ADC strongly depends on the b values chosen for its calculation. Indeed, the ADC incorporates the effects of both diffusion and perfusion, which can vary independently. Since signal attenuation as a function of b follows a bi-exponential pattern, other diffusion/perfusion coefficients can be calculated using DWI, and these may provide more meaningful measurements than the ADC. The absence of standardization for both the terminology and the methodology in DWI of the liver makes it difficult for readers to understand the technique used and strongly limits comparisons between studies. Here, we review the main principles of DWI of the liver, the limits of the ADC, and the exciting capabilities of multi-parametric DWI. We also insisted on the need for a common language for DWI of the liver.

  16. Diffusion-Weighted Imaging and Diagnosis of Transient Ischemic Attack

    PubMed Central

    Brazzelli, Miriam; Chappell, Francesca M; Miranda, Hector; Shuler, Kirsten; Dennis, Martin; Sandercock, Peter A G; Muir, Keith; Wardlaw, Joanna M

    2014-01-01

    Objective Magnetic resonance (MR) diffusion-weighted imaging (DWI) is sensitive to small acute ischemic lesions and might help diagnose transient ischemic attack (TIA). Reclassification of patients with TIA and a DWI lesion as “stroke” is under consideration. We assessed DWI positivity in TIA and implications for reclassification as stroke. Methods We searched multiple sources, without language restriction, from January 1995 to July 2012. We used PRISMA guidelines, and included studies that provided data on patients presenting with suspected TIA who underwent MR DWI and reported the proportion with an acute DWI lesion. We performed univariate random effects meta-analysis to determine DWI positive rates and influencing factors. Results We included 47 papers and 9,078 patients (range = 18–1,693). Diagnosis was by a stroke specialist in 26 of 47 studies (55%); all studies excluded TIA mimics. The pooled proportion of TIA patients with an acute DWI lesion was 34.3% (95% confidence interval [CI] = 30.5–38.4, range = 9–67%; I2 = 89.3%). Larger studies (n > 200) had lower DWI-positive rates (29%; 95% CI = 23.2–34.6) than smaller (n < 50) studies (40.1%; 95% CI = 33.5–46.6%; p = 0.035), but no other testable factors, including clinician speciality and time to scanning, reduced or explained the 7-fold DWI-positive variation. Interpretation The commonest DWI finding in patients with definite TIA is a negative scan. Available data do not explain why ⅔ of patients with definite specialist-confirmed TIA have negative DWI findings. Until these factors are better understood, reclassifying DWI-positive TIAs as strokes is likely to increase variance in estimates of global stroke and TIA burden of disease. ANN NEUROL 2014;75:67–76 PMID:24085376

  17. Prognostic Value of Brain Diffusion Weighted Imaging After Cardiac Arrest

    PubMed Central

    Wijman, Christine A.C.; Mlynash, Michael; Caulfield, Anna Finley; Hsia, Amie W.; Eyngorn, Irina; Bammer, Roland; Fischbein, Nancy; Albers, Gregory W.; Moseley, Michael

    2009-01-01

    Objective Outcome prediction is challenging in comatose post-cardiac arrest survivors. We assessed the feasibility and prognostic utility of brain diffusion-weighted MRI (DWI) during the first week. Methods Consecutive comatose post-cardiac arrest patients were prospectively enrolled. MRI data of patients who met predefined specific prognostic criteria were used to determine distinguishing ADC thresholds. Group 1: death at 6 months and absent motor response or absent pupillary reflexes or bilateral absent cortical responses at 72 hours, or vegetative at 1 month. Group 2A: Glasgow outcome scale (GOS) score of 4 or 5 at 6 months. Group 2B: GOS of 3 at 6 months. The percentage of voxels below different apparent diffusion coefficient (ADC) thresholds was calculated at 50 × 10−6 mm2/sec intervals. Results Overall, 86% of patients underwent MR imaging. Fifty-one patients with 62 brain MRIs were included in the analyses. Forty patients met the specific prognostic criteria. The percentage of brain volume with an ADC value below 650–700 × 10−6 mm2/sec best differentiated between group 1 and groups 2A and 2B combined (p<0.001), while the 400–450 × 10−6 mm2/sec threshold best differentiated between groups 2A and 2B (p=0.003). The ideal time window for prognostication using DWI was between 49 to 108 hours after the arrest. When comparing MRI in this time window with the 72 hour neurological examination MRI improved the sensitivity for predicting poor outcome by 38% while maintaining 100% specificity (p=0.021). Interpretation Quantitative DWI in comatose post-cardiac arrest survivors holds great promise as a prognostic adjunct. PMID:19399889

  18. Evaluating the utility of 3D TRUS image information in guiding intra-procedure registration for motion compensation

    NASA Astrophysics Data System (ADS)

    De Silva, Tharindu; Cool, Derek W.; Romagnoli, Cesare; Fenster, Aaron; Ward, Aaron D.

    2014-03-01

    In targeted 3D transrectal ultrasound (TRUS)-guided biopsy, patient and prostate movement during the procedure can cause target misalignments that hinder accurate sampling of pre-planned suspicious tissue locations. Multiple solutions have been proposed for motion compensation via registration of intra-procedural TRUS images to a baseline 3D TRUS image acquired at the beginning of the biopsy procedure. While 2D TRUS images are widely used for intra-procedural guidance, some solutions utilize richer intra-procedural images such as bi- or multi-planar TRUS or 3D TRUS, acquired by specialized probes. In this work, we measured the impact of such richer intra-procedural imaging on motion compensation accuracy, to evaluate the tradeoff between cost and complexity of intra-procedural imaging versus improved motion compensation. We acquired baseline and intra-procedural 3D TRUS images from 29 patients at standard sextant-template biopsy locations. We used the planes extracted from the 3D intra-procedural scans to simulate 2D and 3D information available in different clinically relevant scenarios for registration. The registration accuracy was evaluated by calculating the target registration error (TRE) using manually identified homologous fiducial markers (micro-calcifications). Our results indicate that TRE improves gradually when the number of intra-procedural imaging planes used in registration is increased. Full 3D TRUS information helps the registration algorithm to robustly converge to more accurate solutions. These results can also inform the design of a fail-safe workflow during motion compensation in a system using a tracked 2D TRUS probe, by prescribing rotational acquisitions that can be performed quickly and easily by the physician immediately prior to needle targeting.

  19. Magnetic resonance diffusion-weighted imaging: extraneurological applications.

    PubMed

    Colagrande, S; Carbone, S F; Carusi, L M; Cova, M; Villari, N

    2006-04-01

    Diffusion-weighted (Dw) imaging has for a number of years been a diagnostic tool in the field of neuroradiology, yet only since the end of the 1990s, with the introduction of echoplanar imaging (EPI) and the use of sequences capable of performing diffusion studies during a single breath hold, has it found diagnostic applications at the level of the abdomen. The inherent sensitivity to motion and the magnetic susceptibility of Dw sequences nonetheless still create problems in the study of the abdomen due to artefacts caused by the heartbeat and intestinal peristalsis, as well as the presence of various parenchymal-gas interfaces. With regard to focal liver lesions, a review of the literature reveals that Dw imaging is able to differentiate lesions with high water content (cysts and angiomas) from solid lesions. With regard to the latter, although there are differences between benign forms [focal nodular hyperplasia (FNH), adenoma] and malignant forms [metastasis, hepatocellular carcinoma (HCC)] in their apparent diffusion coefficient (ADC) in the average values for histological type, there is a significant overlap in values when lesions are assessed individually, with the consequent problem of their correct identification. One promising aspect is the possibility of quantifying the degree of fibrosis in patients with chronic liver disease and cirrhosis given that the deposit of collagen fibres "restricts" the motion of water molecules and therefore reduces ADC values. However, even in this field, studies can only be considered preliminary and far from real clinical applications. The retroperitoneum is less affected by motion artefacts and similarly deserves the attention of Dw imaging. Here it is possible to differentiate mucin-producing tumours of the pancreas from pseudocystic forms on the basis of ADC values even though the limited spatial resolution of Dw imaging does not enable the identification of small lesions. Dw imaging may be applied to the study of the

  20. Diffusion-weighted MR imaging of solid and cystic lesions of the pancreas.

    PubMed

    Wang, Yi; Miller, Frank H; Chen, Zongming E; Merrick, Laura; Mortele, Koenraad J; Hoff, Frederick L; Hammond, Nancy A; Yaghmai, Vahid; Vahid, Yaghmai; Nikolaidis, Paul

    2011-01-01

    Diffusion-weighted magnetic resonance (MR) imaging is increasingly used in the detection and characterization of pancreatic lesions. Diffusion-weighted imaging may provide additional information to radiologists evaluating patients who have cystic or solid neoplasms of the pancreas. Because of greater freedom of motion of water molecules in fluid-rich environments, simple cysts in the pancreas have higher signal intensity on diffusion-weighted images with a b value of 0 sec/mm2 and lower signal intensity on high-b-value images. High apparent diffusion coefficient (ADC) values can be obtained on ADC maps because of the T2 “shine-through” effect. In contrast, solid neoplasms of the pancreas show increased signal intensity relative to the pancreas on diffusion-weighted images with a b value of 0 sec/mm2 and relatively high signal intensity on high-b-value images. Diffusion-weighted imaging can help detect solid pancreatic neoplasms with extremely dense cellularity or extracellular fibrosis by demonstrating significantly low ADC values, and these neoplasms may be better detected on diffusion-weighted MR images because of better contrast, although the resolution is generally worse. However, diffusion-weighted imaging may not be capable of helping definitively characterize solid lesions as inflammatory or neoplastic because of an overlap in ADC values between the two types. For example, it is difficult to distinguish poorly differentiated pancreatic adenocarcinoma from mass-forming pancreatitis at diffusion-weighted imaging because of similarly low ADC values attributed to dense fibrosis.

  1. Diffusion-Weighted Imaging of Traumatic Optic Neuropathy: Diagnosis and Predicting the Prognosis

    DTIC Science & Technology

    2014-01-01

    AFRL-SA-WP-SR-2014-0004 Diffusion-Weighted Imaging of Traumatic Optic Neuropathy : Diagnosis and Predicting the Prognosis...Diffusion-Weighted Imaging of Traumatic Optic Neuropathy : Diagnosis and Predicting the Prognosis 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...Number: 88ABW-2014-1607, 11 Apr 2014 13. SUPPLEMENTARY NOTES 14. ABSTRACT Traumatic optic neuropathy is an axonal injury of the optic nerve

  2. Rocky Mountain spotted fever: 'starry sky' appearance with diffusion-weighted imaging in a child.

    PubMed

    Crapp, Seth; Harrar, Dana; Strother, Megan; Wushensky, Curtis; Pruthi, Sumit

    2012-04-01

    We present a case of Rocky Mountain spotted fever encephalitis in a child imaged utilizing diffusion-weighted MRI. Although the imaging and clinical manifestations of this entity have been previously described, a review of the literature did not reveal any such cases reported in children utilizing diffusion-weighted imaging. The imaging findings and clinical history are presented as well as a brief review of this disease.

  3. Intra-procedural Path-insensitve Grams (I-GRAMS) and Disassembly Based Features for Packer Tool Classification and Detection

    DTIC Science & Technology

    2012-06-14

    Captain, USAF AFIT/ GCE /ENG/12-07 DEPARTMENT OF THE AIR FORCE AIR UNIVERSITY AIR FORCE INSTITUTE OF TECHNOLOGY Wright-Patterson Air Force Base, Ohio...Government and is not subject to copyright protection in the United States AFIT/ GCE /ENG/12-07 INTRA-PROCEDURAL PATH-INSENSITIVE GRAMS (I-GRAMS) AND...PUBLIC RELEASE; DISTRIBUTION UNLIMITED AFIT/ GCE /ENG/12-07 INTRA-PROCEDURAL PATH-INSENSITIVE GRAMS (I-GRAMS) AND DISASSEMBLY BASED FEATURES FOR PACKER

  4. Design and Implementation of a Numerical Technique to Inform Anisotropic Hyperelastic Finite Element Models using Diffusion-Weighted Imaging

    DTIC Science & Technology

    2011-10-01

    Design and Implementation of a Numerical Technique to Inform Anisotropic Hyperelastic Finite Element Models using Diffusion-Weighted Imaging by...Implementation of a Numerical Technique to Inform Anisotropic Hyperelastic Finite Element Models using Diffusion-Weighted Imaging Reuben H. Kraft and Amy M. Dagro...Implementation of a Numerical Technique to Inform Anisotropic Hyperelastic Finite Element Models using Diffusion-Weighted Imaging AH80Reuben H. Kraft and

  5. Diagnosis of pericardial cysts using diffusion weighted magnetic resonance imaging: A case series

    PubMed Central

    2011-01-01

    Introduction Congenital pericardial cysts are benign lesions that arise from the pericardium during embryonic development. The diagnosis is based on typical imaging features, but atypical locations and signal magnetic resonance imaging sequences make it difficult to exclude other lesions. Diffusion-weighted magnetic resonance imaging is a novel method that can be used to differentiate tissues based on their restriction to proton diffusion. Its use in differentiating pericardial cysts from other pericardial lesions has not yet been described. Case presentation We present three cases (a 51-year-old Caucasian woman, a 66-year-old Caucasian woman and a 77-year-old Caucasian woman) with pericardial cysts evaluated with diffusion-weighted imaging using cardiac magnetic resonance imaging. Each lesion demonstrated a high apparent diffusion coefficient similar to that of free water. Conclusion This case series is the first attempt to investigate the utility of diffusion-weighted magnetic resonance imaging in the assessment of pericardial cysts. Diffusion-weighted imaging may be a useful noninvasive diagnostic tool for pericardial cysts when conventional imaging findings are inconclusive. PMID:21943086

  6. Clear Depiction of Inflammatory Abdominal Aortic Aneurysm with Diffusion-Weighted Magnetic Resonance Imaging

    SciTech Connect

    Orta Kilickesmez, Kadriye; Kilickesmez, Ozgur

    2010-04-15

    We report the case of an inflammatory abdominal aortic aneurysm incidentally detected clearly with diffusion-weighted magnetic resonance imaging (DW-MRI) during the examination of a patient with myelofibrosis with myeloid metaplasia that later converted to acute myeloid leukemia. DW-MRI revealed a hyperintense halo surrounding the abdominal aorta with aneurysmatic dilatation, establishing the diagnosis.

  7. Tensor Based Representation and Analysis of Diffusion-Weighted Magnetic Resonance Images

    ERIC Educational Resources Information Center

    Barmpoutis, Angelos

    2009-01-01

    Cartesian tensor bases have been widely used to model spherical functions. In medical imaging, tensors of various orders can approximate the diffusivity function at each voxel of a diffusion-weighted MRI data set. This approximation produces tensor-valued datasets that contain information about the underlying local structure of the scanned tissue.…

  8. 3-D residual eddy current field characterisation: applied to diffusion weighted magnetic resonance imaging.

    PubMed

    O'Brien, Kieran; Daducci, Alessandro; Kickler, Nils; Lazeyras, Francois; Gruetter, Rolf; Feiweier, Thorsten; Krueger, Gunnar

    2013-08-01

    Clinical use of the Stejskal-Tanner diffusion weighted images is hampered by the geometric distortions that result from the large residual 3-D eddy current field induced. In this work, we aimed to predict, using linear response theory, the residual 3-D eddy current field required for geometric distortion correction based on phantom eddy current field measurements. The predicted 3-D eddy current field induced by the diffusion-weighting gradients was able to reduce the root mean square error of the residual eddy current field to ~1 Hz. The model's performance was tested on diffusion weighted images of four normal volunteers, following distortion correction, the quality of the Stejskal-Tanner diffusion-weighted images was found to have comparable quality to image registration based corrections (FSL) at low b-values. Unlike registration techniques the correction was not hindered by low SNR at high b-values, and results in improved image quality relative to FSL. Characterization of the 3-D eddy current field with linear response theory enables the prediction of the 3-D eddy current field required to correct eddy current induced geometric distortions for a wide range of clinical and high b-value protocols.

  9. Conductivity tensor imaging of the brain using diffusion-weighted magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Sekino, Masaki; Yamaguchi, Kikuo; Iriguchi, Norio; Ueno, Shoogo

    2003-05-01

    Conductivity tensor images of the rat brain were obtained by a method based on diffusion-weighted magnetic resonance imaging (MRI). Diffusion-weighted images were acquired by a 4.7 T MRI system with motion probing gradients (MPGs) applied in three directions. Conductivities in each MPG direction were calculated from the fast component of the apparent diffusion coefficient and the fraction of the fast component, and two-dimensional conductivity tensor was estimated. Regions of interest (ROIs) were selected in the cortex and the corpus callosum. The mean conductivities in each ROI were 0.014 S/m and 0.018 S/m, respectively. The corpus callosum exhibited higher conductivity anisotropy resulting from anisotropic tissue structures such as axons and dendrites.

  10. Separation of extra- and intracellular metabolites using hyperpolarized 13C diffusion weighted MR

    NASA Astrophysics Data System (ADS)

    Koelsch, Bertram L.; Sriram, Renuka; Keshari, Kayvan R.; Leon Swisher, Christine; Van Criekinge, Mark; Sukumar, Subramaniam; Vigneron, Daniel B.; Wang, Zhen J.; Larson, Peder E. Z.; Kurhanewicz, John

    2016-09-01

    This work demonstrates the separation of extra- and intracellular components of glycolytic metabolites with diffusion weighted hyperpolarized 13C magnetic resonance spectroscopy. Using b-values of up to 15,000 s mm-2, a multi-exponential signal response was measured for hyperpolarized [1-13C] pyruvate and lactate. By fitting the fast and slow asymptotes of these curves, their extra- and intracellular weighted diffusion coefficients were determined in cells perfused in a MR compatible bioreactor. In addition to measuring intracellular weighted diffusion, extra- and intracellular weighted hyperpolarized 13C metabolites pools are assessed in real-time, including their modulation with inhibition of monocarboxylate transporters. These studies demonstrate the ability to simultaneously assess membrane transport in addition to enzymatic activity with the use of diffusion weighted hyperpolarized 13C MR. This technique could be an indispensible tool to evaluate the impact of microenvironment on the presence, aggressiveness and metastatic potential of a variety of cancers.

  11. Diffusion-weighted imaging to assess treatment response in a child with trilateral retinoblastoma.

    PubMed

    Bonci, Gregory A; Rosenblum, Marc K; Gilheeney, Stephen W; Dunkel, Ira J; Holodny, Andrei I

    2013-09-01

    Trilateral retinoblastoma (TRb) is a rare condition in which children with bilateral retinoblastoma develop primary midline intracranial neuroblastic tumors. The intracranial lesions are difficult to follow after treatment due to residual mass-like enhancement that may represent persistent tumor or treated disease. We highlight a case where close evaluation of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) characteristics accurately depicted the extent of treated disease versus residual tumor after chemotherapy.

  12. Differentiating Sensitivity of Post-Stimulus Undershoot under Diffusion Weighting: Implication of Vascular and Neuronal Hierarchy

    PubMed Central

    Harshbarger, Todd B.; Song, Allen W.

    2008-01-01

    The widely used blood oxygenation level dependent (BOLD) signal during brain activation, as measured in typical fMRI methods, is composed of several distinct phases, the last of which, and perhaps the least understood, is the post-stimulus undershoot. Although this undershoot has been consistently observed, its hemodynamic and metabolic sources are still under debate, as evidences for sustained blood volume increases and metabolic activities have been presented. In order to help differentiate the origins of the undershoot from vascular and neuronal perspectives, we applied progressing diffusion weighting gradients to investigate the BOLD signals during visual stimulation. Three distinct regions were established and found to have fundamentally different properties in post-stimulus signal undershoot. The first region, with a small but focal spatial extent, shows a clear undershoot with decreasing magnitude under increasing diffusion weighting, which is inferred to represent intravascular signal from larger vessels with large apparent diffusion coefficients (ADC), or high mobility. The second region, with a large continuous spatial extent in which some surrounds the first region while some spreads beyond, also shows a clear undershoot but no change in undershoot amplitude with progressing diffusion weighting. This would indicate a source based on extravascular and small vessel signal with smaller ADC, or lower mobility. The third region shows no significant undershoot, and is largely confined to higher order visual areas. Given their intermediate ADC, it would likely include both large and small vessels. Thus the consistent observation of this third region would argue against a vascular origin but support a metabolic basis for the post-stimulus undershoot, and would appear to indicate a lack of sustained metabolic rate likely due to a lower oxygen metabolism in these higher visual areas. Our results are the first, to our knowledge, to suggest that the post

  13. The Efficiency of Diffusion Weighted MRI and MR Spectroscopy On Breast MR Imaging

    PubMed Central

    Altay, Canan; Balcı, Pınar

    2014-01-01

    The main purpose of breast magnetic resonance imaging (MRI) in radiologically routine is to establish an imaging protocol that will create high quality images with a short period of time. Fort this purpose, an imaging protocol should include a conventional breast MRI and contrast enhanced sequences. Proton MR spectroscopy (MRS) and diffusion weighted imaging (DWI) are important MR techniques for evaluation to complicated breast lesions. In this article, we will evaluate that technical properties of the MRS and DWI as additional MR imaging.

  14. Diffeomorphic susceptibility artifact correction of diffusion-weighted magnetic resonance images

    NASA Astrophysics Data System (ADS)

    Ruthotto, L.; Kugel, H.; Olesch, J.; Fischer, B.; Modersitzki, J.; Burger, M.; Wolters, C. H.

    2012-09-01

    Diffusion-weighted magnetic resonance imaging is a key investigation technique in modern neuroscience. In clinical settings, diffusion-weighted imaging and its extension to diffusion tensor imaging (DTI) are usually performed applying the technique of echo-planar imaging (EPI). EPI is the commonly available ultrafast acquisition technique for single-shot acquisition with spatial encoding in a Cartesian system. A drawback of these sequences is their high sensitivity against small perturbations of the magnetic field, caused, e.g., by differences in magnetic susceptibility of soft tissue, bone and air. The resulting magnetic field inhomogeneities thus cause geometrical distortions and intensity modulations in diffusion-weighted images. This complicates the fusion with anatomical T1- or T2-weighted MR images obtained with conventional spin- or gradient-echo images and negligible distortion. In order to limit the degradation of diffusion-weighted MR data, we present here a variational approach based on a reference scan pair with reversed polarity of the phase- and frequency-encoding gradients and hence reversed distortion. The key novelty is a tailored nonlinear regularization functional to obtain smooth and diffeomorphic transformations. We incorporate the physical distortion model into a variational image registration framework and derive an accurate and fast correction algorithm. We evaluate the applicability of our approach to distorted DTI brain scans of six healthy volunteers. For all datasets, the automatic correction algorithm considerably reduced the image degradation. We show that, after correction, fusion with T1- or T2-weighted images can be obtained by a simple rigid registration. Furthermore, we demonstrate the improvement due to the novel regularization scheme. Most importantly, we show that it provides meaningful, i.e. diffeomorphic, geometric transformations, independent of the actual choice of the regularization parameters.

  15. Noise estimation from averaged diffusion weighted images: Can unbiased quantitative decay parameters assist cancer evaluation?

    PubMed Central

    Dikaios, Nikolaos; Punwani, Shonit; Hamy, Valentin; Purpura, Pierpaolo; Rice, Scott; Forster, Martin; Mendes, Ruheena; Taylor, Stuart; Atkinson, David

    2014-01-01

    Purpose Multiexponential decay parameters are estimated from diffusion-weighted-imaging that generally have inherently low signal-to-noise ratio and non-normal noise distributions, especially at high b-values. Conventional nonlinear regression algorithms assume normally distributed noise, introducing bias into the calculated decay parameters and potentially affecting their ability to classify tumors. This study aims to accurately estimate noise of averaged diffusion-weighted-imaging, to correct the noise induced bias, and to assess the effect upon cancer classification. Methods A new adaptation of the median-absolute-deviation technique in the wavelet-domain, using a closed form approximation of convolved probability-distribution-functions, is proposed to estimate noise. Nonlinear regression algorithms that account for the underlying noise (maximum probability) fit the biexponential/stretched exponential decay models to the diffusion-weighted signal. A logistic-regression model was built from the decay parameters to discriminate benign from metastatic neck lymph nodes in 40 patients. Results The adapted median-absolute-deviation method accurately predicted the noise of simulated (R2 = 0.96) and neck diffusion-weighted-imaging (averaged once or four times). Maximum probability recovers the true apparent-diffusion-coefficient of the simulated data better than nonlinear regression (up to 40%), whereas no apparent differences were found for the other decay parameters. Conclusions Perfusion-related parameters were best at cancer classification. Noise-corrected decay parameters did not significantly improve classification for the clinical data set though simulations show benefit for lower signal-to-noise ratio acquisitions. PMID:23913479

  16. Real Diffusion-Weighted MRI Enabling True Signal Averaging and Increased Diffusion Contrast

    PubMed Central

    Eichner, Cornelius; Cauley, Stephen F; Cohen-Adad, Julien; Möller, Harald E; Turner, Robert; Setsompop, Kawin; Wald, Lawrence L

    2015-01-01

    This project aims to characterize the impact of underlying noise distributions on diffusion-weighted imaging. The noise floor is a well-known problem for traditional magnitude-based diffusion-weighted MRI (dMRI) data, leading to biased diffusion model fits and inaccurate signal averaging. Here, we introduce a total-variation-based algorithm to eliminate shot-to-shot phase variations of complex-valued diffusion data with the intention to extract real-valued dMRI datasets. The obtained real-valued diffusion data are no longer superimposed by a noise floor but instead by a zero-mean Gaussian noise distribution, yielding dMRI data without signal bias. We acquired high-resolution dMRI data with strong diffusion weighting and, thus, low signal-to-noise ratio. Both the extracted real-valued and traditional magnitude data were compared regarding signal averaging, diffusion model fitting and accuracy in resolving crossing fibers. Our results clearly indicate that real-valued diffusion data enables idealized conditions for signal averaging. Furthermore, the proposed method enables unbiased use of widely employed linear least squares estimators for model fitting and demonstrates an increased sensitivity to detect secondary fiber directions with reduced angular error. The use of phase-corrected, real-valued data for dMRI will therefore help to clear the way for more detailed and accurate studies of white matter microstructure and structural connectivity on a fine scale. PMID:26241680

  17. An intravoxel oriented flow model for diffusion-weighted imaging of the kidney.

    PubMed

    Hilbert, Fabian; Bock, Maximilian; Neubauer, Henning; Veldhoen, Simon; Wech, Tobias; Bley, Thorsten Alexander; Köstler, Herbert

    2016-10-01

    By combining intravoxel incoherent motion (IVIM) and diffusion tensor imaging (DTI) we introduce a new diffusion model called intravoxel oriented flow (IVOF) that accounts for anisotropy of diffusion and the flow-related signal. An IVOF model using a simplified apparent flow fraction tensor (IVOFf ) is applied to diffusion-weighted imaging of human kidneys. The kidneys of 13 healthy volunteers were examined on a 3 T scanner. Diffusion-weighted images were acquired with six b values between 0 and 800 s/mm(2) and 30 diffusion directions. Diffusivity and flow fraction were calculated for different diffusion models. The Akaike information criterion was used to compare the model fit of the proposed IVOFf model to IVIM and DTI. In the majority of voxels the proposed IVOFf model with a simplified apparent flow fraction tensor performs better than IVIM and DTI. Mean diffusivity is significantly higher in DTI compared with models that account for the flow-related signal. The fractional anisotropy of diffusion is significantly reduced when flow fraction is considered to be anisotropic. Anisotropy of the apparent flow fraction tensor is significantly higher in the renal medulla than in the cortex region. The IVOFf model describes diffusion-weighted data in the human kidney more accurately than IVIM or DTI. The apparent flow fraction in the kidney proved to be anisotropic.

  18. Clinically silent choroid plexus cyst: evaluation by diffusion-weighted MRI.

    PubMed

    Kinoshita, Toshibumi; Moritani, Toshio; Hiwatashi, Akio; Numaguchi, Yuji; Wang, Henry Z; Westesson, Per-Lennart A; Sugihara, Shuji; Matsusue, Eiji; Fujii, Shinya; Ohama, Eisaku; Ogawa, Toshihide

    2005-04-01

    We retrospectively reviewed diffusion-weighted magnetic resonance images of 57 patients with a choroid plexus cyst diagnosed by contrast-enhanced T1-weighted imaging. All the cysts appeared to represent incidental findings. Thirty-eight of 57 patients had bilateral cysts and 19 had unilateral ones. On diffusion-weighted images, 78 of 95 cysts showed homogeneously high signal intensity, 12 showed focal high signal areas, and 5 had no portion with a high signal. The apparent diffusion coefficient of the high signal areas in the cysts was (1.46+/-0.14) x10(-3) mm(2)/s, intermediate between the apparent diffusion coefficients of cerebrospinal fluid and cerebral white matter, (3.15+/-0.67) x10(-3) and (0.79+/-0.22) x10(-3) mm(2)/s, respectively. Pathological correlation was available in one case, showing high signal intensity areas in the glomera of the choroid plexuses in the lateral ventricles on diffusion-weighted images corresponding to gelatinous cysts with highly proteinaceous content.

  19. Real diffusion-weighted MRI enabling true signal averaging and increased diffusion contrast.

    PubMed

    Eichner, Cornelius; Cauley, Stephen F; Cohen-Adad, Julien; Möller, Harald E; Turner, Robert; Setsompop, Kawin; Wald, Lawrence L

    2015-11-15

    This project aims to characterize the impact of underlying noise distributions on diffusion-weighted imaging. The noise floor is a well-known problem for traditional magnitude-based diffusion-weighted MRI (dMRI) data, leading to biased diffusion model fits and inaccurate signal averaging. Here, we introduce a total-variation-based algorithm to eliminate shot-to-shot phase variations of complex-valued diffusion data with the intention to extract real-valued dMRI datasets. The obtained real-valued diffusion data are no longer superimposed by a noise floor but instead by a zero-mean Gaussian noise distribution, yielding dMRI data without signal bias. We acquired high-resolution dMRI data with strong diffusion weighting and, thus, low signal-to-noise ratio. Both the extracted real-valued and traditional magnitude data were compared regarding signal averaging, diffusion model fitting and accuracy in resolving crossing fibers. Our results clearly indicate that real-valued diffusion data enables idealized conditions for signal averaging. Furthermore, the proposed method enables unbiased use of widely employed linear least squares estimators for model fitting and demonstrates an increased sensitivity to detect secondary fiber directions with reduced angular error. The use of phase-corrected, real-valued data for dMRI will therefore help to clear the way for more detailed and accurate studies of white matter microstructure and structural connectivity on a fine scale.

  20. Diffusion Weighted MRI by Spatiotemporal Encoding: Analytical Description and In Vivo Validations

    PubMed Central

    Solomon, Eddy; Shemesh, Noam; Frydman, Lucio

    2016-01-01

    Diffusion-Weighted (DW) MRI is a powerful modality for studying microstructure in normal and pathological tissues. DW MRI, however, is of limited use in regions suffering from large magnetic field or chemical shift heterogeneities. Spatio-temporal encoding (SPEN) is a single-scan imaging technique that can deliver its information with a remarkable insensitivity to field inhomogeneities; this study explores the use of diffusion-weighted SPEN (dSPEN) MRI as an alternative for acquiring this kind of information. Owing to SPEN’s combined use of gradients and radiofrequency-swept pulses, spatially-dependent diffusion weightings arise in these sequences that are not present in conventional k-space DW MRI. In order to account for these phenomena an analytical formalism is presented that extends Stejskal & Tanner’s and Karlicek & Lowe’s work, to derive the b-values arising upon taking into account the effects of adiabatic pulses, of imaging as well as diffusion gradients, and of cross-terms between them. Excellent agreement is found between the new features predicted by these analytical and numerical derivations, and SPEN diffusion experiments in phantoms and in anisotropic ex vivo systems. Examinations of apparent diffusion coefficients in human breast volunteers also verify the advantages of the new methods in vivo, which exhibit substantial robustness vis-à-vis comparable DW echo planar imaging. PMID:23562003

  1. Extension of the double-wave-vector diffusion-weighting experiment to multiple concatenations.

    PubMed

    Finsterbusch, Jürgen

    2009-06-01

    Experiments involving two diffusion-weightings in a single acquisition, so-called double- or two-wave-vector experiments, have recently been applied to measure the microscopic anisotropy in macroscopically isotropic samples or to estimate pore or compartment sizes. These informations are derived from the signal modulation observed when varying the wave vectors' orientations. However, the modulation amplitude can be small and, for short mixing times between the two diffusion-weightings, decays with increased gradient pulse lengths which hampers its detectability on whole-body MR systems. Here, an approach is investigated that involves multiple concatenations of the two diffusion-weightings in a single experiment. The theoretical framework for double-wave-vector experiments of fully restricted diffusion is adapted and the corresponding tensor approach recently presented for short mixing times extended and compared to numerical simulations. It is shown that for short mixing times (i) the extended tensor approach well describes the signal behavior observed for multiple concatenations and (ii) the relative amplitude of the signal modulation increases with the number of concatenations. Thus, the presented extension of the double-wave-vector experiment may help to improve the detectability of the signal modulations observed for short mixing times, in particular on whole-body MR systems with their limited gradient amplitudes.

  2. Continuous saturation EPI with diffusion weighting at 3.0 T.

    PubMed

    Francis, S T; Gowland, P A; Bowtell, R W

    1999-11-01

    This paper presents a steady-state method of arterial spin labelling using continuous saturation in conjunction with echo-planar imaging (EPI), which has been implemented at 3 T. The continuous saturation technique has the advantage of having high sensitivity compared to transient labelling techniques, when long repetition times are used. It is also easy to implement and requires minimal data to be acquired for quantitation. Like other arterial spin labelling techniques, continuous saturation is potentially prone to overestimation of perfusion rates due to the effect of tagged blood in vessels within the image slice. Using a simple model of the vasculature, the degree of diffusion weighting required to suppress the arterial signal has been determined, with the results indicating that a value of 2 s/mm2 is adequate. Histogram analysis of the experimental data has been used to evaluate the effect of diffusion weighting. Using a b-value of 2 s/mm2, the mean perfusion-related signal change in grey matter on continuous saturation was found to be 1.5 +/- 0.2%, yielding a mean perfusion rate of 87 +/- 9 ml/100 g/min. Brain activation studies using the diffusion weighted continuous saturation technique gave a mean increase in perfusion of 36 +/- 12% in activated motor cortex.

  3. [The clinical application of diffusion weighted magnetic resonance imaging to acute cerebrovascular disorders].

    PubMed

    Chu, B C; Miyasaka, K

    1998-09-01

    Diffusion is a measure of motion freedom and is a sensitive parameter to characterize the tissue at the microscopic level. The methods of measuring in vivo diffusion by magnetic resonance imaging (MRI) have been based mainly on the addition of two motion-probing gradients (MPG) to the spin echo sequence to produce signal attenuation for the spins moving at random. The resultant MR images reflect the intravoxel incoherent motions (IVIM), which contain both water molecule diffusion and perfusion in the capillary network, and can be quantified by an apparent diffusion coefficient (ADC). Diffusion weighted MRI, acquired from IVIM MR imaging by the addition of the very strong MPG predicate water diffusion and anisotropy. High signal or reduced ADC can be observed in case of the slower diffusion. The anisotropy depends upon the orientation of the subjects and the gradients. Greater signal attenuation (faster diffusion) can be observed when the relative orientation of white matter tracts to the MPG is parallel as compared to that obtained with a perpendicular alignment. This anisotropy may preclude the detection or delineation of an ischemic lesion. Diffusion tensor trace has been designated to eliminate this anisotropy effect. In ischemic animal models, low signal (fast diffusion) and high signal (slow diffusion) have been noted in the vasogenic edema and cytotoxic edema, respectively. High signal appears only in case of cerebral blood flow below 15-20 ml/100 g per minute, a value identical to the threshold of tissue at high energetic metabolism and ion homeostasis. ADC value decreases following the cerebral vessel occlusion, or remains unchanged when collateral circulation develops. It has been speculated that reduction in ADC reflects the water shift from extracellular space to intracellular space due to the membrane permeability and/or intracellular osmolality increase. These results suggest that diffusion weighted MRI correlates well with the cell metabolism, and

  4. Effects of equilibrium exchange on diffusion-weighted NMR signals: the diffusigraphic "shutter-speed".

    PubMed

    Lee, Jing-Huei; Springer, Charles S

    2003-03-01

    A general picture is presented of the implications for diffusion-weighted NMR signals of the parsimonious two-site-exchange (2SX) paradigm. In particular, it is shown that the diffusigraphic "shutter-speed," tau(-1) identical with |q(2)(D(A) - D(B))|, is a useful concept. The "wave-number" q has its standard definition (given in the text), and D(A) and D(B) are the apparent diffusion coefficients (ADCs) of molecules in the two "sites," A and B, if there is no exchange between them. At low gradient strengths (center of q-space), tau(-1) is less than rate constants for intercompartmental water molecule exchange in most tissue cases. Thus, the exchange reaction appears fast. However, q is increased during the course of most experiments and, as it is, the shutter-speed becomes "faster" and the exchange reaction, the kinetics of which do not change, appears to slow down. This causes a multiexponential behavior in the diffusion-weighting dimension, b, which also has its standard definition. This picture is found to be in substantial agreement with a number of different experimental observations. It is applied here to literature (1)H(2)O data from a yeast cell suspension and from the human and the rat brain. Since the equilibrium transcytolemmal water exchange reaction appears to be in the fast-exchange-limit at small b, the initial slope represents the weighted-average of the ADCs of intra- and extracellular water. Of course, in tissue the former is in the significant majority. Furthermore, a consideration of reasonable values for the other 2SX parameters suggests that, for resting brain tissue, the intracellular water ADC may be larger than the extracellular water ADC. There are some independent inferences of this, which would have ramifications for many applications of diffusion-weighted MRI.

  5. Assessment of Activity of Crohn Disease by Diffusion-Weighted Magnetic Resonance Imaging.

    PubMed

    Li, Xue-Hua; Sun, Can-Hui; Mao, Ren; Zhang, Zhong-Wei; Jiang, Xiao-Song; Pui, Margaret H; Chen, Min-Hu; Li, Zi-Ping

    2015-10-01

    To assess the diagnostic efficacy of diffusion-weighted MR imaging (DWI) for evaluating inflammatory activity in patients with Crohn's disease (CD). A total of 47 CD patients underwent MR enterography (MRE) and DWI using 3 b values of 50, 400, and 800 s/mm. Apparent diffusion coefficients (ADCs) of inflamed and normal bowel wall were calculated. The conventional MRE findings and DWI signal intensities were qualitatively scored from 0 to 3. The correlation between Crohn disease activity index (CDAI) and both ADCs and magnetic resonance imaging scores was analyzed. Receiver-operating characteristic curve analysis was used to determine the diagnostic accuracy of CD activity. Of the 47 patients, 25 were active CD (CDAI≥150) and 22 were inactive (CDAI<150). Diffusion-weighted MR imaging and MRE + DWI scores of active CD were significantly higher than that of inactive CD (both P < 0.001). Apparent diffusion coefficients in inflamed segments of active CD were lower than that of inactive CD (P < 0.001). The DWI scores (r = 0.74, P < 0.001), ADCs (r = -0.71, P < 0.001), MRE scores (r = 0.54, P < 0.001), and MRE + DWI scores (r = 0.66, P < 0.001) were all correlated with CDAI. The areas under the receiver-operating characteristics curves for ADCs, DWI scores, MRE scores, and MRE + DWI scores ranged from 0.83 to 0.98. The threshold ADC value of 1.17 × 10 mm/s allowed differentiation of active from inactive CD with 100% sensitivity and 88% specificity. Diffusion-weighted MR imaging and ADC correlated with CD activity, and had excellent diagnostic accuracy for differentiating active from inactive CD.

  6. Measuring Restriction Sizes Using Diffusion Weighted Magnetic Resonance Imaging: A Review

    PubMed Central

    Martin, Melanie

    2013-01-01

    This article reviews a new concept in magnetic resonance as applied to cellular and biological systems. Diffusion weighted magnetic resonance imaging can be used to infer information about restriction sizes of samples being measured. The measurements rely on the apparent diffusion coefficient changing with diffusion times as measurements move from restricted to free diffusion regimes. Pulsed gradient spin echo (PGSE) measurements are limited in the ability to shorten diffusion times and thus are limited in restriction sizes which can be probed. Oscillating gradient spin echo (OGSE) measurements could provide shorter diffusion times so smaller restriction sizes could be probed. PMID:25114548

  7. Diffusion-Weighted Imaging Outside the Brain: Consensus Statement From an ISMRM-Sponsored Workshop

    PubMed Central

    Taouli, Bachir; Beer, Ambros J.; Chenevert, Thomas; Collins, David; Lehman, Constance; Matos, Celso; Padhani, Anwar R.; Rosenkrantz, Andrew B.; Shukla-Dave, Amita; Sigmund, Eric; Tanenbaum, Lawrence; Thoeny, Harriet; Thomassin-Naggara, Isabelle; Barbieri, Sebastiano; Corcuera-Solano, Idoia; Orton, Matthew; Partridge, Savannah C.; Koh, Dow-Mu

    2016-01-01

    The significant advances in magnetic resonance imaging (MRI) hardware and software, sequence design, and postprocessing methods have made diffusion-weighted imaging (DWI) an important part of body MRI protocols and have fueled extensive research on quantitative diffusion outside the brain, particularly in the oncologic setting. In this review, we summarize the most up-to-date information on DWI acquisition and clinical applications outside the brain, as discussed in an ISMRM-sponsored symposium held in April 2015. We first introduce recent advances in acquisition, processing, and quality control; then review scientific evidence in major organ systems; and finally describe future directions. PMID:26892827

  8. The use of diffusion weighted imaging to evaluate pathology outside the brain parenchyma in neuroimaging studies.

    PubMed

    Benjamin, Philip; Khan, Faraan; MacKinnon, Andrew D

    2017-04-01

    Diffusion-weighted imaging (DWI) has transformed the radiological assessment of a variety of cerebral pathologies, in particular acute stroke. In neuroimaging studies, DWI can also be used to evaluate pathology outside the brain parenchyma, although it is sometimes underutilized for this purpose. In this pictorial review, the principles of DWI are outlined, and 13 cases of abnormal diffusion outside the brain parenchyma are illustrated in order to show DWI as a useful sequence for the evaluation of the following recommended review areas: the dural venous sinuses, internal carotid arteries, meninges, ventricles, cavernous sinus and orbits, skull base and lymph nodes.

  9. Interdisciplinary treatment of unruptured intracranial aneurysms: impact of intraprocedural rupture and ischemia in 563 aneurysms.

    PubMed

    Kunz, Mathias; Bakhshai, Yasmin; Zausinger, Stefan; Fesl, Gunther; Janssen, Hendrik; Brückmann, Hartmut; Tonn, Jörg Christian; Schichor, Christian

    2013-05-01

    This study was conducted to determine the risk factors and the clinical impact of intraprocedural aneurysm rupture (IAR) and periprocedural ischemia in the treatment of symptomatic and asymptomatic unruptured intracranial aneurysms (UIAs). A single-center retrospective data analysis of 563 UIAs treated between 2000 and 2010 was conducted. Treatment assignment was made on the basis of individual aneurysmal criteria in an interdisciplinary neurovascular conference with attending neurosurgeons, neuroradiologists and neurologists. In 363 microsurgical and 200 endovascular procedures, the permanent morbidity rate was 4.9 and 6 %. The overall mortality rate was 0.7 %-no procedure-related death occurred in microsurgery, and four patients had fatal outcomes after endovascular treatment. IAR occurred in 34 (9.4 %) microsurgical and 8 (4 %) endovascular procedures (p = 0.03). Risk factors for IAR were age, aneurysm diameter, symptomatic aneurysms, hypertension and smoking in microsurgery. IAR was associated with significantly worse outcome at discharge after microsurgical and at discharge and follow-up after endovascular procedures and was followed by fatal outcome in four endovascular cases. Periprocedural ischemia (12.1 vs. 9 %) resulted in significantly worse outcome in both groups. Risk factors for periprocedural ischemia were IAR during microsurgery, aneurysm diameter, symptomatic aneurysms and smoking in either group. Treatment of UIAs can be conducted with an equivalent low rate of permanent morbidity for clipping and coiling-treatment of symptomatic aneurysms elevates the procedural risk. IAR was less frequent during coiling, but was associated with relevant mortality. IAR and periprocedural ischemia represent significant treatment-associated risks, which should be taken into account in interdisciplinary treatment planning and patient counseling.

  10. Registering preprocedure volumetric images with intraprocedure 3-D ultrasound using an ultrasound imaging model.

    PubMed

    King, A P; Rhode, K S; Ma, Y; Yao, C; Jansen, C; Razavi, R; Penney, G P

    2010-03-01

    For many image-guided interventions there exists a need to compute the registration between preprocedure image(s) and the physical space of the intervention. Real-time intraprocedure imaging such as ultrasound (US) can be used to image the region of interest directly and provide valuable anatomical information for computing this registration. Unfortunately, real-time US images often have poor signal-to-noise ratio and suffer from imaging artefacts. Therefore, registration using US images can be challenging and significant preprocessing is often required to make the registrations robust. In this paper we present a novel technique for computing the image-to-physical registration for minimally invasive cardiac interventions using 3-D US. Our technique uses knowledge of the physics of the US imaging process to reduce the amount of preprocessing required on the 3-D US images. To account for the fact that clinical US images normally undergo significant image processing before being exported from the US machine our optimization scheme allows the parameters of the US imaging model to vary. We validated our technique by computing rigid registrations for 12 cardiac US/magnetic resonance imaging (MRI) datasets acquired from six volunteers and two patients. The technique had mean registration errors of 2.1-4.4 mm, and 75% capture ranges of 5-30 mm. We also demonstrate how the same approach can be used for respiratory motion correction: on 15 datasets acquired from five volunteers the registration errors due to respiratory motion were reduced by 45%-92%.

  11. [Effect of vibration caused by time-varying magnetic fields on diffusion-weighted MRI].

    PubMed

    Ogura, Akio; Maeda, Fumie; Miyai, Akira; Hayashi, Kohji; Hongoh, Takaharu

    2006-04-20

    Diffusion-weighted images (DWIs) with high b-factor in the body are often used to detect and diagnose cancer at MRI. The echo planar imaging (EPI) sequence and high motion probing gradient pulse are used at diffusion weighted imaging, causing high table vibration. The purpose of this study was to assess whether the diffusion signal and apparent diffusion coefficient (ADC) values are influenced by this vibration because of time-varying magnetic fields. Two DWIs were compared. In one, phantoms were fixed on the MRI unit's table transmitting the vibration. In the other, phantoms were supported in air, in the absence of vibration. The phantoms called "solution phantoms" were made from agarose of a particular density. The phantoms called "jelly phantoms" were made from agarose that was heated. The diffusion signal and ADC value of each image were compared. The results showed that the signal of DWI units using the solution phantom was not affected by vibration. However, the signal of DWI and ADC were increased in the low-density jelly phantom as a result of vibration, causing the jelly phantom to vibrate. The DWIs of vibrating regions such as the breast maybe be subject to error. A countermeasure seems to be to support the region adequately.

  12. Diffusion-Weighted Magnetic Resonance Imaging to Evaluate Major Salivary Gland Function Before and After Radiotherapy

    SciTech Connect

    Dirix, Piet Keyzer, Frederik de; Vandecaveye, Vincent; Stroobants, Sigrid; Hermans, Robert; Nuyts, Sandra

    2008-08-01

    Purpose: To evaluate diffusion-weighted (DW)-MRI as a noninvasive tool to investigate major salivary gland function before and after radiotherapy (RT) for head and neck cancer (HNC). Methods and Materials: DW-MRI was performed in 8 HNC patients before and after parotid-sparing RT (mean dose to the contralateral parotid gland <26 Gy). A DW sequence was performed once at rest and then repeated continuously during salivary stimulation. Apparent diffusion coefficient (ADC) maps for both parotid and submandibular glands were calculated. Findings were compared with salivary gland scintigraphy. Results: Before RT, the mean ADC value at rest was significantly lower in the parotid than in the submandibular glands. During the first 5 min of stimulation, the ADC value of the salivary glands showed a decrease, followed by a steady increase until a peak ADC, significantly higher than the baseline value, was reached after a median of 17 min. The baseline ADC value at rest was significantly higher after RT than before RT in the nonspared salivary glands but not in the spared parotid glands. In the contralateral parotid glands, the same response was seen as before RT. This pattern was completely lost in the nonspared glands. These results corresponded with remaining or loss of salivary function, respectively, as confirmed by salivary gland scintigraphy. Conclusions: Diffusion-weighted-MRI allows noninvasive evaluation of functional changes in the major salivary glands after RT and is a promising tool for investigating radiation-induced xerostomia.

  13. Segmentation of Hyperacute Cerebral Infarcts Based on Sparse Representation of Diffusion Weighted Imaging

    PubMed Central

    Zhang, Xiaodong; Jing, Shasha; Gao, Peiyi; Xue, Jing; Su, Lu; Li, Weiping; Ren, Lijie

    2016-01-01

    Segmentation of infarcts at hyperacute stage is challenging as they exhibit substantial variability which may even be hard for experts to delineate manually. In this paper, a sparse representation based classification method is explored. For each patient, four volumetric data items including three volumes of diffusion weighted imaging and a computed asymmetry map are employed to extract patch features which are then fed to dictionary learning and classification based on sparse representation. Elastic net is adopted to replace the traditional L0-norm/L1-norm constraints on sparse representation to stabilize sparse code. To decrease computation cost and to reduce false positives, regions-of-interest are determined to confine candidate infarct voxels. The proposed method has been validated on 98 consecutive patients recruited within 6 hours from onset. It is shown that the proposed method could handle well infarcts with intensity variability and ill-defined edges to yield significantly higher Dice coefficient (0.755 ± 0.118) than the other two methods and their enhanced versions by confining their segmentations within the regions-of-interest (average Dice coefficient less than 0.610). The proposed method could provide a potential tool to quantify infarcts from diffusion weighted imaging at hyperacute stage with accuracy and speed to assist the decision making especially for thrombolytic therapy. PMID:27746825

  14. A Fast Algorithm for Denoising Magnitude Diffusion-Weighted Images with Rank and Edge Constraints

    PubMed Central

    Lam, Fan; Liu, Ding; Song, Zhuang; Schuff, Norbert; Liang, Zhi-Pei

    2015-01-01

    Purpose To accelerate denoising of magnitude diffusion-weighted images subject to joint rank and edge constraints. Methods We extend a previously proposed majorize-minimize (MM) method for statistical estimation that involves noncentral χ distributions and joint rank and edge constraints. A new algorithm is derived which decomposes the constrained noncentral χ denoising problem into a series of constrained Gaussian denoising problems each of which is then solved using an efficient alternating minimization scheme. Results The performance of the proposed algorithm has been evaluated using both simulated and experimental data. Results from simulations based on ex vivo data show that the new algorithm achieves about a factor of 10 speed up over the original Quasi-Newton based algorithm. This improvement in computational efficiency enabled denoising of large data sets containing many diffusion-encoding directions. The denoising performance of the new efficient algorithm is found to be comparable to or even better than that of the original slow algorithm. For an in vivo high-resolution Q-ball acquisition, comparison of fiber tracking results around hippocampus region before and after denoising will also be shown to demonstrate the denoising effects of the new algorithm. Conclusion The optimization problem associated with denoising noncentral χ distributed diffusion-weighted images subject to joint rank and edge constraints can be solved efficiently using an MM-based algorithm. PMID:25733066

  15. Intravoxel incoherent motion diffusion-weighted MR imaging in assessing and characterizing solitary pulmonary lesions

    PubMed Central

    Wan, Qi; Deng, Ying-Shi; Zhou, Jia-Xuan; Yu, Yu-Dong; Bao, Ying-Ying; Lei, Qiang; Chen, Hou-Jin; Peng, Ya-Hui; Mei, Ying-Jie; Zeng, Qing-Si; Li, Xin-Chun

    2017-01-01

    This study aimed to investigate the potential of intravoxel incoherent motion (IVIM) diffusion-weighted MR imaging in assessing solitary pulmonary lesions (SPLs). Sixty-two patients with pathologically confirmed SPLs, including 51 and 11 cases of malignant and benign lesions, respectively, were assessed. Diffusion weighted imaging (DWI) with 13 b values was used to derive apparent diffusion coefficient (ADC) and IVIM parameters, including true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (f). Our results showed that, there was an excellent inter-observer agreement on the measurements of D and ADC between observers (inter-class correlation coefficient, ICC = 0.902 and 0.884, respectively). Meanwhile, f and D* showed good and substantial reproducibility (ICC = 0.787 and 0.623, respectively). D and ADC of malignant lesions were significantly lower than those of benign lesions (both P ≤ 0.001), while similar values were obtained in both groups for D* and f (both P > 0.05). In receiver operating characteristic (ROC) analysis, D showed the highest area under curve (AUC) for distinguishing malignant from benign lesions, followed by ADC. Accompanying signs of SPLs have specific features on IVIM maps. In conclusion, IVIM provides functional information in characterizing SPLs which is helpful to differential diagnosis. D and ADC have a significantly higher diagnostic value than f and D*. PMID:28225064

  16. Motion Compensated Abdominal Diffusion Weighted MRI by Simultaneous Image Registration and Model Estimation (SIR-ME).

    PubMed

    Kurugol, Sila; Freiman, Moti; Afacan, Onur; Domachevsky, Liran; Perez-Rossello, Jeannette M; Callahan, Michael J; Warfield, Simon K

    2015-01-01

    Non-invasive characterization of water molecule's mobility variations by quantitative analysis of diffusion-weighted MRI (DW-MRI) signal decay in the abdomen has the potential to serve as a biomarker in gastrointestinal and oncological applications. Accurate and reproducible estimation of the signal decay model parameters is challenging due to the presence of respiratory, cardiac, and peristalsis motion. Independent registration of each b-value image to the b-value=0 s/mm(2) image prior to parameter estimation might be sub-optimal because of the low SNR and contrast difference between images of varying b-value. In this work, we introduce a motion-compensated parameter estimation framework that simultaneously solves image registration and model estimation (SIR-ME) problems by utilizing the interdependence of acquired volumes along the diffusion weighting dimension. We evaluated the improvement in model parameters estimation accuracy using 16 in-vivo DW-MRI data sets of Crohn's disease patients by comparing parameter estimates obtained using the SIR-ME model to the parameter estimates obtained by fitting the signal decay model to the acquired DW-MRI images. The proposed SIR-ME model reduced the average root-mean-square error between the observed signal and the fitted model by more than 50%. Moreover, the SIR-ME model estimates discriminate between normal and abnormal bowel loops better than the standard parameter estimates.

  17. Preliminary study of diffusion-weighted imaging and magnetic resonance spectroscopy imaging in Kimura disease.

    PubMed

    Wang, Jie; Tang, Zuohua; Feng, Xiaoyuan; Zeng, Wenjiao; Tang, Weijun; Wu, Lingjie; Jin, Lixin

    2014-11-01

    In this study, we evaluated the value of diffusion-weighted imaging (DWI) and magnetic resonance (MR) spectroscopy imaging (MRSI) combined with computed tomography (CT) and conventional MR imaging (MRI) in the diagnosis of Kimura disease (KD). The clinical data and CT and MRI findings of 5 patients with KD proven by histopathologic examination were retrospectively reviewed. Diffusion-weighted imaging and MRSI were performed at 1.5 T in 3 patients with KD. Apparent diffusion coefficient (ADC) values and the choline/creatine ratio of the lesions were compared with those of the contralateral normal parotid glands. All imaging results were compared with histopathologic findings. The typical features of KD were subcutaneous lesions, continuously infiltrative parotid lesions with or without intraparotid lymphadenopathies, and reactive cervical lymphadenopathies on CT and conventional MRI. On DWI, the ADC values of all subcutaneous and infiltrative parotid lesions were higher compared to those of normal parotid glands, and the ADC values of reactive lymphadenopathies were lower compared to both. The choline/creatine levels of subcutaneous and infiltrative parotid lesions were slightly higher than those of normal parotid glands. In conclusion, DWI and MRSI offer valuable information that may be characteristic of KD, which can highly suggest the diagnosis of KD when combined with morphological imaging.

  18. Non-local means variants for denoising of diffusion-weighted and diffusion tensor MRI.

    PubMed

    Wiest-Daesslé, Nicolas; Prima, Sylvain; Coupé, Pierrick; Morrissey, Sean Patrick; Barillot, Christian

    2007-01-01

    Diffusion tensor imaging (DT-MRI) is very sensitive to corrupting noise due to the non linear relationship between the diffusion-weighted image intensities (DW-MRI) and the resulting diffusion tensor. Denoising is a crucial step to increase the quality of the estimated tensor field. This enhanced quality allows for a better quantification and a better image interpretation. The methods proposed in this paper are based on the Non-Local (NL) means algorithm. This approach uses the natural redundancy of information in images to remove the noise. We introduce three variations of the NL-means algorithms adapted to DW-MRI and to DT-MRI. Experiments were carried out on a set of 12 diffusion-weighted images (DW-MRI) of the same subject. The results show that the intensity based NL-means approaches give better results in the context of DT-MRI than other classical denoising methods, such as Gaussian Smoothing, Anisotropic Diffusion and Total Variation.

  19. Controversies of diffusion weighted imaging in the diagnosis of brain death.

    PubMed

    Luchtmann, Michael; Bernarding, Johannes; Beuing, Oliver; Kohl, Jana; Bondar, Imre; Skalej, Martin; Firsching, Raimund

    2013-10-01

    Imaging techniques as confirmatory tests may add safety to the diagnosis of brain death, but are partly not accepted either because they are too invasive, such as conventional arterial angiography, or because there is still lack of evidence of its reliability, such as magnetic resonance angiography. In this study the reliability of diffusion weighted imaging for the diagnosis of brain death was evaluated according in terms of its sensitivity and specificity. The apparent diffusion coefficients (ADC) of 18 brain dead patients were registered from 14 distinct brain areas. The mean ADC values of the brain dead patients were compared with normal controls of physiological ADC values of unaffected brain tissue. Despite a highly significant decrease of the mean ADC value in 16 patients, two patients showed mean ADC values that were within normal physiological range. An explanation may be the pseudonormalization of ADC values seen in stroke patients that depends on the time of the onset of the brain damage. We conclude, diffusion-weighted imaging may provide additional information on damage of the brain tissue but is not a practicable confirmatory test for the reliable diagnosis of brain death.

  20. Diffusion-Weighted Magnetic Resonance Imaging in Monitoring Rectal Cancer Response to Neoadjuvant Chemoradiotherapy

    SciTech Connect

    Barbaro, Brunella; Vitale, Renata; Valentini, Vincenzo; Illuminati, Sonia; Vecchio, Fabio M.; Rizzo, Gianluca; Gambacorta, Maria Antonietta; Coco, Claudio; Crucitti, Antonio; Persiani, Roberto; Sofo, Luigi; Bonomo, Lorenzo

    2012-06-01

    Purpose: To prospectively monitor the response in patients with locally advanced nonmucinous rectal cancer after chemoradiotherapy (CRT) using diffusion-weighted magnetic resonance imaging. The histopathologic finding was the reference standard. Methods and Materials: The institutional review board approved the present study. A total of 62 patients (43 men and 19 women; mean age, 64 years; range, 28-83) provided informed consent. T{sub 2}- and diffusion-weighted magnetic resonance imaging scans (b value, 0 and 1,000 mm{sup 2}/s) were acquired before, during (mean 12 days), and 6-8 weeks after CRT. We compared the median apparent diffusion coefficients (ADCs) between responders and nonresponders and examined the associations with the Mandard tumor regression grade (TRG). The postoperative nodal status (ypN) was evaluated. The Mann-Whitney/Wilcoxon two-sample test was used to evaluate the relationships among the pretherapy ADCs, extramural vascular invasion, early percentage of increases in ADCs, and preoperative ADCs. Results: Low pretreatment ADCs (<1.0 Multiplication-Sign 10{sup -3}mm{sup 2}/s) were correlated with TRG 4 scores (p = .0011) and associated to extramural vascular invasion with ypN+ (85.7% positive predictive value for ypN+). During treatment, the mean percentage of increase in tumor ADC was significantly greater in the responders than in the nonresponders (p < .0001) and a >23% ADC increase had a 96.3% negative predictive value for TRG 4. In 9 of 16 complete responders, CRT-related tumor downsizing prevented ADC evaluations. The preoperative ADCs were significantly different (p = .0012) between the patients with and without downstaging (preoperative ADC {>=}1.4 Multiplication-Sign 10{sup -3}mm{sup 2}/s showed a positive and negative predictive value of 78.9% and 61.8%, respectively, for response assessment). The TRG 1 and TRG 2-4 groups were not significantly different. Conclusion: Diffusion-weighted magnetic resonance imaging seems to be a promising

  1. Limitations and Prospects for Diffusion-Weighted MRI of the Prostate

    PubMed Central

    Bourne, Roger; Panagiotaki, Eleftheria

    2016-01-01

    Diffusion-weighted imaging (DWI) is the most effective component of the modern multi-parametric magnetic resonance imaging (mpMRI) scan for prostate pathology. DWI provides the strongest prediction of cancer volume, and the apparent diffusion coefficient (ADC) correlates moderately with Gleason grade. Notwithstanding the demonstrated cancer assessment value of DWI, the standard measurement and signal analysis methods are based on a model of water diffusion dynamics that is well known to be invalid in human tissue. This review describes the biophysical limitations of the DWI component of the current standard mpMRI protocol and the potential for significantly improved cancer assessment performance based on more sophisticated measurement and signal modeling techniques. PMID:27240408

  2. [The effect of the surroundings to the apparent diffusion coefficient on diffusion weighted imaging].

    PubMed

    Yamatani, Yuya; Doi, Tsukasa; Shimizu, Kozo; Nogi, Akihiro

    2010-10-20

    Diffusion weighted imaging (DWI) is now widely used in magnetic resonance (MR) imaging of the head and body. Moreover, the Apparent diffusion coefficient (ADC) value is often used for the differential diagnosis of the tumor. However, the effect of the surroundings on the ADC value has not been reported. In this study, we used the phantom completely sealed up to measure the change in the ADC value depending on the surroundings material. The results showed that the ADC value decreased according to the density of superparamagnetic iron oxide (SPIO) in the surroundings. Clinically, hemorrhage or iron deposit around the tumor may affect the ADC value of the tumor and result in under-estimation.

  3. Methanol-induced toxic optic neuropathy with diffusion weighted MRI findings.

    PubMed

    Tanrivermis Sayit, Asli; Aslan, Kerim; Elmali, Muzaffer; Gungor, Inci

    2016-12-01

    We report a 52-year-old man with methanol intoxication who showed optic nerve damage as assessed by magnetic resonance imaging (MRI). He was admitted to the hospital with blurred vision after the consumption of alcohol (600-700 ml of cologne). He was treated with intravenous ethanol, NaHCO3 and hemodialysis. On admission, a brain and orbital MRI was performed. Bilateral mild contrast enhancement was detected on the contrast-enhanced images in the retrobulbar segment of the optic nerves (RBONs). Also, diffusion-weighted images showed restricted diffusion in the RBONs. Diagnosis was considered as methanol-induced optic neuropathy based on the MRI findings of the optic nerves.

  4. Asymptomatic choroid plexus cysts in the lateral ventricles: an incidental finding on diffusion-weighted MRI.

    PubMed

    Cakir, B; Karakas, H M; Unlu, E; Tuncbilek, N

    2002-10-01

    We assessed the role of diffusion-weighted imaging (DWI) in the detection of choroid plexus cysts. We reviewed more than 1000 patients who had undergone MRI in a 1-year period. We reviewed echo-planar DWI with b=1000 s/mm(2), acquired at 1.0 tesla, for any difference in signal intensity which might indicate choroid plexus cysts. On conventional images, all cystic lesions were isointense with cerebrospinal fluid, and 72 cysts could not be identified. On DWI, 90 rounded high-signal foci were detected in 58 patients; 64 cysts were bilateral. Focal ventricular expansion due to large cysts was observed in nine cases. DWI were found to show choroid plexus cysts undetected within the cerebrospinal fluid on conventional images.

  5. Diffusion-weighted and diffusion-tensor imaging of normal and diseased uterus

    PubMed Central

    Kara Bozkurt, Duygu; Bozkurt, Murat; Nazli, Mehmet Ali; Mutlu, Ilhan Nahit; Kilickesmez, Ozgur

    2015-01-01

    Owing to technical advances and improvement of the software, diffusion weighted imaging and diffusion tensor imaging (DWI and DTI) greatly improved the diagnostic value of magnetic resonance imaging (MRI) of the pelvic region. These imaging sequences can exhibit important tissue contrast on the basis of random diffusion (Brownian motion) of water molecules in tissues. Quantitative measurements can be done with DWI and DTI by apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values respectively. ADC and FA values may be changed by various physiological and pathological conditions providing additional information to conventional MRI. The quantitative DWI assists significantly in the differentiation of benign and malignant lesions. It can demonstrate the microstructural architecture and celluler density of the normal and diseased uterine zones. On the other hand, DWI and DTI are useful for monitoring the treatment outcome of the uterine lesions. In this review, we discussed advantages of DWI and DTI of the normal and diseased uterus. PMID:26217454

  6. Comparison of stroke infarction between CT perfusion and diffusion weighted imaging: preliminary results

    NASA Astrophysics Data System (ADS)

    Abd. Rahni, Ashrani Aizzuddin; Arka, Israna Hossain; Chellappan, Kalaivani; Mukari, Shahizon Azura; Law, Zhe Kang; Sahathevan, Ramesh

    2016-03-01

    In this paper we present preliminary results of comparison of automatic segmentations of the infarct core, between that obtained from CT perfusion (based on time to peak parameter) and diffusion weighted imaging (DWI). For each patient, the two imaging volumes were automatically co-registered to a common frame of reference based on an acquired CT angiography image. The accuracy of image registration is measured by the overlap of the segmented brain from both images (CT perfusion and DWI), measured within their common field of view. Due to the limitations of the study, DWI was acquired as a follow up scan up to a week after initial CT based imaging. However, we found significant overlap of the segmented brain (Jaccard indices of approximately 0.8) and the percentage of infarcted brain tissue from the two modalities were still fairly highly correlated (correlation coefficient of approximately 0.9). The results are promising with more data needed in future for clinical inference.

  7. Sensitivity of Diffusion-Weighted STEAM MRI and EPI-DWI to Infratentorial Ischemic Stroke

    PubMed Central

    Hohenhaus, Marc; Kunze, Claudia; Schmidt, Wolf; Brunecker, Peter; Villringer, Kersten; Merboldt, Klaus-Dietmar; Frahm, Jens; Fiebach, Jochen B.

    2016-01-01

    Objectives To assess the sensitivity of stimulated echo acquisition mode diffusion weighted imaging (STEAM-DWI) to ischemic stroke in comparison to echo-planar imaging diffusion weighted imaging (EPI-DWI) in the infratentorial compartment. Methods Fifty-seven patients presenting with clinical features of infratentorial stroke underwent STEAM-DWI, high-resolution EPI-DWI (HR-DWI, 2.5 mm slice thickness) and low-resolution EPI-DWI (LR-DWI, 5 mm slice thickness). Four readers assessed the presence of ischemic lesions and artifacts. Agreement between sequences and interobserver agreement on the presence of ischemia were calculated. The sensitivities of the DWI sequences were calculated in 45 patients with a confirmed diagnosis of infratentorial stroke. Results Median time from symptom onset to imaging was 24 hours. STEAM-DWI agreed with LR-DWI in 89.5% of cases (kappa = 0.72, p<0.0001) and with HR-DWI in 89.5% of cases (kappa = 0.68, p<0.0001). STEAM-DWI showed fewer intraparenchymal artifacts (1/57) than HR-DWI (44/57) and LR-DWI (41/57). Ischemia was visible in 87% of cases for LR-DWI, 93% of cases for HR-DWI, and 89% of cases for STEAM-DWI. Interobserver agreement was good for STEAM-DWI (kappa = 0.62, p<0.0001). Conclusions Compared to the best currently available MR sequence for detecting ischemia (HR-DWI), STEAM-DWI shows fewer artifacts and a similar sensitivity to infratentorial stroke. PMID:27529697

  8. Whole-Body Diffusion-Weighted Imaging in Chronic Recurrent Multifocal Osteomyelitis in Children

    PubMed Central

    Leclair, Nadine; Thörmer, Gregor; Sorge, Ina; Ritter, Lutz; Schuster, Volker; Hirsch, Franz Wolfgang

    2016-01-01

    Objective Chronic recurrent multifocal osteomyelitis/ chronic non-bacterial osteomyelitis (CRMO/ CNO) is a rare auto-inflammatory disease and typically manifests in terms of musculoskeletal pain. Because of a high frequency of musculoskeletal disorders in children/ adolescents, it can be quite challenging to distinguish CRMO/ CNO from nonspecific musculosketetal pain or from malignancies. The purpose of this study was to evaluate the visibility of CRMO lesions in a whole-body diffusion-weighted imaging (WB-DWI) technique and its potential clinical value to better characterize MR-visible lesions. Material and Methods Whole-body imaging at 3T was performed in 16 patients (average: 13 years) with confirmed CRMO. The protocol included 2D Short Tau Inversion Recovery (STIR) imaging in coronal and axial orientation as well as diffusion-weighted imaging in axial orientation. Visibility of lesions in DWI and STIR was evaluated by two readers in consensus. The apparent diffusion coefficient (ADC) was measured for every lesion and corresponding reference locations. Results A total of 33 lesions (on average 2 per patient) visible in STIR and DWI images (b = 800 s/mm2 and ADC maps) were included, predominantly located in the long bones. With a mean value of 1283 mm2/s in lesions, the ADC was significantly higher than in corresponding reference regions (782 mm2/s). By calculating the ratio (lesion to reference), 82% of all lesions showed a relative signal increase of 10% or higher and 76% (25 lesions) showed a signal increase of more than 15%. The median relative signal increase was 69%. Conclusion This study shows that WB-DWI can be reliably performed in children at 3T and predominantly, the ADC values were substantially elevated in CRMO lesions. WB-DWI in conjunction with clinical data is seen as a promising technique to distinguish benign inflammatory processes (in terms of increased ADC values) from particular malignancies. PMID:26799970

  9. Correlation of diffusion-weighted MRI with whole mount radical prostatectomy specimens.

    PubMed

    Van As, N; Charles-Edwards, E; Jackson, A; Jhavar, S; Reinsberg, S; Desouza, N; Dearnaley, D; Bailey, M; Thompson, A; Christmas, T; Fisher, C; Corbishley, C; Sohaib, S

    2008-06-01

    The purpose of this study was to compare the apparent diffusion coefficient (ADC) of benign central gland (bCG), benign peripheral zone (bPZ) and cancer using diffusion-weighted MRI and whole mount specimens. 11 patients with biopsy-proven prostate cancer underwent diffusion-weighted MRI prior to radical prostatectomy. A single-shot echo planar image technique was used with b-values of 0 s mm(-2), 300 s mm(-2), 500 s mm(-2) and 800 s mm(-2). Whole mount specimens were compared with ADC maps. Areas of cancer, bCG and bPZ were identified, and regions of interest were drawn on ADC maps. Mean ADC values were recorded for all regions of interest, and paired t-tests were performed to compare mean values. Cancer was outlined in nine patients. In two patients, the tumours were too small to correlate with images; bCG was identified in 11 patients and bPZ was identified in 10 patients. Mean ADC values for bCG, bPZ and cancer were, 1.5 x 10(-3) mm(2) s(-1) (standard error (SE) = 0.04), 1.7 x 10(-3) mm(2) s(-1) (SE = 0.1), and 1.3 x 10(-3) mm(2) s(-1) (SE = 0.09), respectively. The most significant difference between benign tissue and cancer existed at b-values of 0-300 s mm(-2) (bCG vs cancer: mean difference = 0. 29, p = 0.001, 95% confidence interval (CI) = 0.17-0.41; bPZ vs cancer: mean difference = 0.34, p = 0.003, 95% CI = 0.18-0.61). In conclusion, we have confirmed, using whole mount verification, a significant difference in the ADC between benign tissue and cancer.

  10. Detection of targeted perfluorocarbon nanoparticle binding using 19F diffusion weighted MR spectroscopy.

    PubMed

    Waters, Emily A; Chen, Junjie; Yang, Xiaoxia; Zhang, Huiying; Neumann, Robert; Santeford, Andrea; Arbeit, Jeffrey; Lanza, Gregory M; Wickline, Samuel A

    2008-11-01

    Real-time detection of targeted contrast agent binding is challenging due to background signal from unbound agent. (19)F diffusion weighted MR spectroscopy (DWS) could selectively detect binding of angiogenesis-targeted perfluorocarbon nanoparticles in vivo. Transgenic K14-HPV16 mice with epidermal squamous carcinomas exhibiting up-regulated neovasculature were used, with nontransgenic littermates as controls. Mice were treated with alpha(v)beta(3)-integrin targeted perfluorocarbon nanoparticles. (19)F DWS (b-values from 0 to 16,000 s/mm(2)) was performed on mouse ears in vivo at 11.74 Tesla. Progressive decay of (19)F signal with increased diffusion weighting at low b-values (< 1500 s/mm(2)) was observed in ears of both K14-HPV16 and control mice, demonstrating suppression of background (19)F signal from unbound nanoparticles in the blood. Much of the (19)F signal from ears of K14-HPV16 mice persisted at high b-values, indicating a stationary signal source, reflecting abundant nanoparticle binding to angiogenesis. (19)F signal in controls decayed completely at high b-values (> 1500 s/mm(2)), reflecting a moving signal source due to absence of angiogenesis (no binding sites). Estimated ADCs of nanoparticles in K14-HPV16 and control mice were 33.1 +/- 12.9 microm(2)/s and 19563 +/- 5858 microm(2)/s (p < 0.01). In vivo (19)F DWS can be used for specific detection of bound perfluorocarbon nanoparticles by selectively suppressing background (19)F signal from nanoparticles flowing in blood.

  11. Evaluation of Angiographic and Technical Aspects of Carotid Stenting with Diffusion-Weighted Magnetic Resonance Imaging

    SciTech Connect

    Blasel, Stella Hattingen, Elke; Berkefeld, Joachim; Kurre, Wiebke; Morawe, Gerald; Zanella, Friedhelm; Rochemont, Richard Du Mesnil de

    2009-07-15

    The detection of clinically silent ischemic lesions on postprocedural diffusion-weighted magnetic resonance images has become a preferred method for the description of embolic risks. The purpose of this single-center study was to evaluate whether diffusion-weighted imaging (DWI) could determine material related or technical risk factors of filter-protected carotid stenting. Eighty-four patients with symptomatic severe ({>=}60%) carotid artery stenoses received filter-protected carotid stenting. Standard DWI (b = 1000) was performed within 48 h before and after carotid stenting. The occurrence and load of new postinterventional DWI lesions were assessed. Multivariate analysis was performed to determine risk factors associated with DWI lesions, with emphasis on technical factors such as use of different access devices (guiding catheter method vs. long carotid sheath method), type of stent (open-cell nitinol stent vs. closed-cell Wallstent), and protective device (filters with 80-{mu}m vs. 110-120-{mu}m pore size). Markers for generalized atherosclerosis and for degree and site of stenosis were assessed to allow comparison of adequate risk profiles. Access, protective device, and stent type were not significantly associated with new embolic DWI lesions when we compared patients with equivalent risk profiles (long carotid sheath method 48% [11 of 23] vs. guiding catheter method 44% [27 of 61], Wallstent 47% [15 of 32] vs. nitinol stent 44% [23 of 52], and small pore size filter 61% [11 of 18] vs. large pore size filter 41% [27 of 66]). Single-center DWI studies with a moderate number of cases are inadequate for proper assessment of the embolic risk of technical- or material-related risk factors in carotid stenting. Larger multicenter studies with more cases are needed.

  12. Cardiac angiosarcoma diagnosed by transvenous endomyocardial biopsy with the aid of transesophageal echocardiography and intra-procedural consultation.

    PubMed

    Hosokawa, Yusuke; Kodani, Eitaro; Kusama, Yoshiki; Kamiya, Masataka; Yoshikawa, Masatomo; Hirasawa, Yasuhiro; Nakagomi, Akihiro; Atarashi, Hirotsugu; Maeda, Shotaro; Mizuno, Kyoichi

    2010-01-01

    We report a case who had confirmed tumor cells in the biopsy specimens by transvenous endomyocardial biopsy with intra-procedural consultation and fast smear cytology. A 57-year-old female was admitted to our hospital because of shortness of breath and left back pain. Transthoracic echocardiography (TTE) and contrast-enhanced computed tomography (CT) scans demonstrated a large mass in the right atrium and multiple liver tumors thought to be due to spread of the disease. Coronary angiography showed the right coronary artery was involved in the mass. In order to confirm the histological diagnosis, we attempted transvenous endomyocardial tumor biopsy under fluoroscopic guidance. However, we failed to obtain adequate tissue material. Due to several risks associated with a surgical procedure such as an open surgical biopsy, transvenous endomyocardial tumor biopsy was again attempted with the aid of transesophageal echocardiography (TEE). Intra-procedural consultation and fast smear cytology enabled us to finish the procedure. Hematoxylin-eosin stained sections demonstrated spindle-shaped cells. Immunohistochemical stains of these cells were positive for anti-factor VIII antigen, CD31, and CD34. These findings indicated a definite diagnosis of angiosarcoma. Since there was no surgical indication for this tumor, the patient underwent chemotherapy with docetaxel and radiotherapy. Three months later, CT scans showed a reduction in the size of the cardiac tumor.

  13. Diffusion-weighted imaging and the skeletal system: a literature review.

    PubMed

    Yao, K; Troupis, J M

    2016-11-01

    Diffusion-weighted imaging (DWI) is a magnetic resonance imaging (MRI) sequence that has a well-established role in neuroimaging, and is increasingly being utilised in other clinical contexts, including the assessment of various skeletal disorders. It utilises the variability of Brownian motion of water molecules; the differing patterns of water molecular diffusion in various biological tissues help determine the contrast obtained in DWI. Although early research on the clinical role of DWI focused mainly on the field of neuroimaging, there are now more studies demonstrating the promising role DWI has in the diagnosis and monitoring of various osseous diseases. DWI has been shown to be useful in assessing a patient's skeletal tumour burden, monitoring the post-chemotherapy response of various bony malignancies, detecting hip ischaemia in patients with Legg-Calvé-Perthes disease, as well as determining the quality of repaired articular cartilage. Despite its relative successes, DWI has several limitations, including its limited clinical value in differentiating chondrosarcomas from benign bone lesions, as well as osteoporotic vertebral compression fractures from compression fractures due to malignancy. This literature review aims to provide an overview of the recent developments in the use of DWI in imaging the skeletal system, and to clarify the role of DWI in assessing various osseous diseases.

  14. Detection of peritoneal dissemination in gynecological malignancy: evaluation by diffusion-weighted MR imaging.

    PubMed

    Fujii, Shinya; Matsusue, Eiji; Kanasaki, Yoshiko; Kanamori, Yasunobu; Nakanishi, Junko; Sugihara, Shuji; Kigawa, Junzo; Terakawa, Naoki; Ogawa, Toshihide

    2008-01-01

    The aim of this study is to evaluate the usefulness of diffusion-weighted (DW) magnetic resonance (MR) imaging in detecting peritoneal dissemination in cases of gynecological malignancy. We retrospectively analyzed MR images obtained from 26 consecutive patients with gynecological malignancy. Peritoneal dissemination was histologically diagnosed in 15 of the 26 patients after surgery. We obtained DW images and half-Fourier single-shot turbo-spin-echo images in the abdomen and pelvis, and then generated fusion images. Coronal maximum-intensity-projection images were reconstructed from the axial source images. Reader interpretations were compared with the laparotomy findings in the surgical records. Receiver-operating characteristic (ROC) curves were used to represent the presence of peritoneal dissemination. In addition, the sensitivity and specificity were calculated. DW imaging depicted the tumors in 14 of 15 patients with peritoneal dissemination as abnormal signal intensity. ROC analysis yielded Az values of 0.974 and 0.932 for the two reviewers. The mean sensitivity and specificity were 90 and 95.5%. DW imaging plays an important role in the diagnosis and therapeutic management of patients with gynecological malignancy.

  15. An adaptive diffusion-weighted whole-body magnetic resonance imaging scheme using the multistation approach

    NASA Astrophysics Data System (ADS)

    Han, Yeji

    2016-02-01

    Whole-body diffusion-weighted imaging (DWI) is a useful tool in oncology, which enables fast screening of disseminated tumors, lymph nodes or abscesses in the body. Multistation magnetic resonance imaging (MRI) or continuously moving table (CMT) MRI can be performed to overcome the limited field of view (FOV) of the magnet bore in whole-body DWI. Although CMT-MRI is regarded as a more advanced form of whole-body MRI, it cannot be widely used because most of the available MR systems are not equipped with the required hardware/software to perform CMT. Thus, optimizing the multistation approach for whole-body DWI, which is more widely available and easier to perform with the existing MR systems, is worthwhile. To improve the quality of DW images acquired with the multistation approach, we used different combinations of the built-in body RF coil and the phased-array surface RF coils for reception of the signals in whole-body DWI in this work. If different coils are selectively used in the extended FOV and appropriate reconstruction algorithms are exploited, the screening ability of whole-body DWI can be improved while minimizing the patient's discomfort and the artifacts due to physiological motions.

  16. Support Vector Machine Classification of Major Depressive Disorder Using Diffusion-Weighted Neuroimaging and Graph Theory

    PubMed Central

    Sacchet, Matthew D.; Prasad, Gautam; Foland-Ross, Lara C.; Thompson, Paul M.; Gotlib, Ian H.

    2015-01-01

    Recently, there has been considerable interest in understanding brain networks in major depressive disorder (MDD). Neural pathways can be tracked in the living brain using diffusion-weighted imaging (DWI); graph theory can then be used to study properties of the resulting fiber networks. To date, global abnormalities have not been reported in tractography-based graph metrics in MDD, so we used a machine learning approach based on “support vector machines” to differentiate depressed from healthy individuals based on multiple brain network properties. We also assessed how important specific graph metrics were for this differentiation. Finally, we conducted a local graph analysis to identify abnormal connectivity at specific nodes of the network. We were able to classify depression using whole-brain graph metrics. Small-worldness was the most useful graph metric for classification. The right pars orbitalis, right inferior parietal cortex, and left rostral anterior cingulate all showed abnormal network connectivity in MDD. This is the first use of structural global graph metrics to classify depressed individuals. These findings highlight the importance of future research to understand network properties in depression across imaging modalities, improve classification results, and relate network alterations to psychiatric symptoms, medication, and comorbidities. PMID:25762941

  17. Investigation of Vibration Induced Artifact in Clinical Diffusion-Weighted Imaging of Pediatric Subjects

    PubMed Central

    Berl, Madison M.; Walker, Lindsay; Modi, Pooja; Irfanoglu, M. Okan; Sarlls, Joelle; Nayak, Amritha; Pierpaoli, Carlo

    2015-01-01

    It has been reported that mechanical vibrations of the MRI scanner could produce spurious signal dropouts in diffusion-weighted images resulting in artifactual anisotropy in certain regions of the brain with red appearance in the Directionally Encoded Color maps. We performed a review of the frequency of this artifact across pediatric studies, noting differences by scanner manufacturer, acquisition protocol, as well as weight and position of the subject. We also evaluated the ability of automated and quantitative methods to detect this artifact. We found that the artifact may be present in over 50% of data in certain protocols and is not limited to one scanner manufacturer. While a specific scanner had the highest incidence, low body weight and positioning were also associated with appearance of the artifact for both scanner types evaluated, making children potentially more susceptible than adults. Visual inspection remains the best method for artifact identification. Software for automated detection showed very low sensitivity (10%). The artifact may present inconsistently in longitudinal studies. We discuss a published case report that has been widely cited and used as evidence to set policy about diagnostic criteria for determining vegetative state. That report attributed longitudinal changes in anisotropy to white matter plasticity without considering the possibility that the changes were caused by this artifact. Our study underscores the need to check for the presence of this artifact in clinical studies, analyzes circumstances for when it may be more likely to occur, and suggests simple strategies to identify and potentially avoid its effects. PMID:26350492

  18. Anomalous diffusion of brain metabolites evidenced by diffusion-weighted magnetic resonance spectroscopy in vivo

    PubMed Central

    Marchadour, Charlotte; Brouillet, Emmanuel; Hantraye, Philippe; Lebon, Vincent; Valette, Julien

    2012-01-01

    Translational displacement of molecules within cells is a key process in cellular biology. Molecular motion potentially depends on many factors, including active transport, cytosol viscosity and molecular crowding, tortuosity resulting from cytoskeleton and organelles, and restriction barriers. However, the relative contribution of these factors to molecular motion in the cytoplasm remains poorly understood. In this work, we designed an original diffusion-weighted magnetic resonance spectroscopy strategy to probe molecular motion at subcellular scales in vivo. This led to the first observation of anomalous diffusion, that is, dependence of the apparent diffusion coefficient (ADC) on the diffusion time, for endogenous intracellular metabolites in the brain. The observed increase of the ADC at short diffusion time yields evidence that metabolite motion is characteristic of hindered random diffusion rather than active transport, for time scales up to the dozen milliseconds. Armed with this knowledge, data modeling based on geometrically constrained diffusion was performed. Results suggest that metabolite diffusion occurs in a low-viscosity cytosol hindered by ∼2-μm structures, which is consistent with known intracellular organization. PMID:22929443

  19. Usefulness of Diffusion-Weighted Imaging in the Localization of Prostate Cancer

    SciTech Connect

    Kajihara, Hiroo; Hayashida, Yoshiko; Murakami, Ryuji Katahira, Kazuhiro; Nishimura, Ryuichi; Hamada, Yasuyuki; Kitani, Kousuke; Kitaoka, Mitsuhiko; Suzuki, Yasuko; Kitajima, Mika; Hirai, Toshinori; Morishita, Shoji; Awai, Kazuo; Yamashita, Yasuyuki

    2009-06-01

    Purpose: Advances in high-precision radiation therapy techniques for patients with prostate cancer permit selective escalation of the radiation dose delivered to the dominant intraprostatic lesion and improve the therapeutic ratio. We evaluated the value of diffusion-weighted imaging (DWI) for dominant intraprostatic lesion assessment. Methods and Materials: The study population consisted of 23 patients with early prostate cancer. Before undergoing total prostatectomy, they were evaluated by means of magnetic resonance imaging, including DWI. T2-weighted imaging (T2WI) with and without DWI were retrospectively assessed by six independent observers. Imaging findings were compared with pathologic results from whole prostate specimens on a lesion-by-lesion basis. Results: Pathologic study identified 43 lesions in 23 patients. On magnetic resonance imaging, the six observers correctly identified 11-22 of 43 lesions (sensitivity, 26-51%) on T2WI alone and 20-31 (sensitivity, 47-72%) on T2WI plus DWI. Positive predictive values were 42-73% on T2WI alone and 58-80% on T2WI plus DWI. For all observers, detection was higher on combined T2WI and DWI than on T2WI alone. Conclusion: Because the addition of DWI to T2WI improves the detectability of prostate cancer, DWI may offer a promising new approach for radiation therapy planning.

  20. Whole body MRI: Improved Lesion Detection and Characterization With Diffusion Weighted Techniques

    PubMed Central

    Attariwala, Rajpaul; Picker, Wayne

    2013-01-01

    Diffusion-weighted imaging (DWI) is an established functional imaging technique that interrogates the delicate balance of water movement at the cellular level. Technological advances enable this technique to be applied to whole-body MRI. Theory, b-value selection, common artifacts and target to background for optimized viewing will be reviewed for applications in the neck, chest, abdomen, and pelvis. Whole-body imaging with DWI allows novel applications of MRI to aid in evaluation of conditions such as multiple myeloma, lymphoma, and skeletal metastases, while the quantitative nature of this technique permits evaluation of response to therapy. Persisting signal at high b-values from restricted hypercellular tissue and viscous fluid also permits applications of DWI beyond oncologic imaging. DWI, when used in conjunction with routine imaging, can assist in detecting hemorrhagic degradation products, infection/abscess, and inflammation in colitis, while aiding with discrimination of free fluid and empyema, while limiting the need for intravenous contrast. DWI in conjunction with routine anatomic images provides a platform to improve lesion detection and characterization with findings rivaling other combined anatomic and functional imaging techniques, with the added benefit of no ionizing radiation. PMID:23960006

  1. Investigation of vibration-induced artifact in clinical diffusion-weighted imaging of pediatric subjects.

    PubMed

    Berl, Madison M; Walker, Lindsay; Modi, Pooja; Irfanoglu, M Okan; Sarlls, Joelle E; Nayak, Amritha; Pierpaoli, Carlo

    2015-12-01

    It has been reported that mechanical vibrations of the magnetic resonance imaging scanner could produce spurious signal dropouts in diffusion-weighted images resulting in artifactual anisotropy in certain regions of the brain with red appearance in the Directionally Encoded Color maps. We performed a review of the frequency of this artifact across pediatric studies, noting differences by scanner manufacturer, acquisition protocol, as well as weight and position of the subject. We also evaluated the ability of automated and quantitative methods to detect this artifact. We found that the artifact may be present in over 50% of data in certain protocols and is not limited to one scanner manufacturer. While a specific scanner had the highest incidence, low body weight and positioning were also associated with appearance of the artifact for both scanner types evaluated, making children potentially more susceptible than adults. Visual inspection remains the best method for artifact identification. Software for automated detection showed very low sensitivity (10%). The artifact may present inconsistently in longitudinal studies. We discuss a published case report that has been widely cited and used as evidence to set policy about diagnostic criteria for determining vegetative state. That report attributed longitudinal changes in anisotropy to white matter plasticity without considering the possibility that the changes were caused by this artifact. Our study underscores the need to check for the presence of this artifact in clinical studies, analyzes circumstances for when it may be more likely to occur, and suggests simple strategies to identify and potentially avoid its effects.

  2. Support vector machine classification of major depressive disorder using diffusion-weighted neuroimaging and graph theory.

    PubMed

    Sacchet, Matthew D; Prasad, Gautam; Foland-Ross, Lara C; Thompson, Paul M; Gotlib, Ian H

    2015-01-01

    Recently, there has been considerable interest in understanding brain networks in major depressive disorder (MDD). Neural pathways can be tracked in the living brain using diffusion-weighted imaging (DWI); graph theory can then be used to study properties of the resulting fiber networks. To date, global abnormalities have not been reported in tractography-based graph metrics in MDD, so we used a machine learning approach based on "support vector machines" to differentiate depressed from healthy individuals based on multiple brain network properties. We also assessed how important specific graph metrics were for this differentiation. Finally, we conducted a local graph analysis to identify abnormal connectivity at specific nodes of the network. We were able to classify depression using whole-brain graph metrics. Small-worldness was the most useful graph metric for classification. The right pars orbitalis, right inferior parietal cortex, and left rostral anterior cingulate all showed abnormal network connectivity in MDD. This is the first use of structural global graph metrics to classify depressed individuals. These findings highlight the importance of future research to understand network properties in depression across imaging modalities, improve classification results, and relate network alterations to psychiatric symptoms, medication, and comorbidities.

  3. Gradient preemphasis calibration in diffusion-weighted echo-planar imaging.

    PubMed

    Papadakis, N G; Martin, K M; Pickard, J D; Hall, L D; Carpenter, T A; Huang, C L

    2000-10-01

    This article describes a method which enables fast and objective pulse-sequence-specific preemphasis calibration, using standard pulse sequences and system hardware. The method is based on a k-space measurement technique, and has been applied to single-shot, diffusion-weighted, spin-echo, echo-planar imaging (DW-SE-EPI), which is particularly sensitive to eddy-current-induced image distortions. The efficiency of the technique was demonstrated not only by the reduction of eddy-current fields to a negligible level using full preemphasis compensation, but also by the fact that adjustment of the slow time-base alone sufficed for the practical elimination of image distortions in the DW-SE-EPI images and the subsequent diffusion tensor maps (in a phantom and a human brain). By seeking to eliminate directly the effect of eddy-current-induced phase shifts during the EPI data collection, the method is free of the complications and restrictions associated with other eddy-current correction techniques for DW-SE-EPI (such as acquisition of additional calibration scans, intense postprocessing, extensive pulse-sequence modifications), making their use redundant.

  4. PCLR: Phase-Constrained Low-Rank Model for Compressive Diffusion-Weighted MRI

    PubMed Central

    Zhang, Kai; Zhou, Weifeng; Hu, Xiaoping

    2015-01-01

    Purpose This work develops a compressive sensing approach for diffusion-weighted (DW) MRI. Methods A phase-constrained low-rank (PCLR) approach was developed using the image coherence across the DW directions for efficient compressive DW MRI, while accounting for drastic phase changes across the DW directions, possibly as a result of eddy current, and rigid and non-rigid motions. In PCLR, a low-resolution phase estimation was used for removing phase inconsistency between DW directions. In our implementation, GRAPPA was incorporated for better phase estimation while allowing higher undersampling factor. An efficient and easy-to-implement image reconstruction algorithm, consisting mainly of partial Fourier update and singular value decomposition, was developed for solving PCLR. Results The error measures based on diffusion-tensor-derived metrics and tractography indicated that PCLR, with its joint reconstruction of all DW images using the image coherence, outperformed the frame-independent reconstruction through zero-padding FFT. Furthermore, using GRAPPA for phase estimation, PCLR readily achieved a 4-fold undersampling. Conclusion The PCLR is developed and demonstrated for compressive DW MRI. A 4-fold reduction in k-space sampling could be readily achieved without substantial degradation of reconstructed images and diffusion tensor measures, making it possible to significantly reduce the data acquisition in DW MRI and/or improve spatial and angular resolutions. PMID:24327553

  5. Advantage of Adding Diffusion Weighted Imaging to Routine MRI Examinations in the Diagnostics of Scrotal Lesions

    PubMed Central

    Algebally, Ahmed Mohamed; Tantawy, Hazim Ibrahim; Yousef, Reda Ramadan Hussein; Szmigielski, Wojciech; Darweesh, Adham

    2015-01-01

    Summary Background The purpose of the study is to identify the diagnostic value of adding diffusion weighted images (DWI) to routine MRI examinations of the scrotum. Material/Methods The study included 100 testes of 50 patients with a unilateral testicular disease. Fifty normal contralateral testes were used as a control group. All patients underwent conventional MRI and DWI examinations of the scrotum. The results of MRI and DWI of the group of patients treated surgically were correlated with histopathological findings. The MRI and DWI results of non-surgical cases were correlated with the results of clinical, laboratory and other imaging studies. Comparison of the ADC value of normal and pathological tissues was carried out followed by a statistical analysis. Results There was a significant difference between ADC values of malignant testicular lesions and normal testicular tissues as well as benign testicular lesions (P=0.000). At a cut-off ADC value of ≤0.99, it had a sensitivity of 93.3%, specificity of 90%, positive predictive value of 87.5%, and negative predictive value of 94.7% in the characterization of intratesticular masses. Conclusions Inclusion of DWI to routine MRI has a substantial value in improving diagnosis in patients with scrotal lesions and consequently can reduce unnecessary radical surgical procedures in these patients. PMID:26491491

  6. Layer-specific diffusion weighted imaging in human primary visual cortex in vitro.

    PubMed

    Kleinnijenhuis, Michiel; Zerbi, Valerio; Küsters, Benno; Slump, Cornelis H; Barth, Markus; van Cappellen van Walsum, Anne-Marie

    2013-10-01

    One of the most prominent characteristics of the human neocortex is its laminated structure. The first person to observe this was Francesco Gennari in the second half the 18th century: in the middle of the depth of primary visual cortex, myelinated fibres are so abundant that he could observe them with bare eyes as a white line. Because of its saliency, the stria of Gennari has a rich history in cyto- and myeloarchitectural research as well as in magnetic resonance (MR) microscopy. In the present paper we show for the first time the layered structure of the human neocortex with ex vivo diffusion weighted imaging (DWI). To achieve the necessary spatial and angular resolution, primary visual cortex samples were scanned on an 11.7 T small-animal MR system to characterize the diffusion properties of the cortical laminae and the stria of Gennari in particular. The results demonstrated that fractional anisotropy varied over cortical depth, showing reduced anisotropy in the stria of Gennari, the inner band of Baillarger and the deepest layer of the cortex. Orientation density functions showed multiple components in the stria of Gennari and deeper layers of the cortex. Potential applications of layer-specific diffusion imaging include characterization of clinical abnormalities, cortical mapping and (intra)cortical tractography. We conclude that future high-resolution in vivo cortical DWI investigations should take into account the layer-specificity of the diffusion properties.

  7. A novel tensor distribution model for the diffusion-weighted MR signal✩

    PubMed Central

    Jian, Bing; Vemuri, Baba C.; Özarslan, Evren; Carney, Paul R.; Mareci, Thomas H.

    2008-01-01

    Diffusion MRI is a non-invasive imaging technique that allows the measurement of water molecule diffusion through tissue in vivo. The directional features of water diffusion allow one to infer the connectivity patterns prevalent in tissue and possibly track changes in this connectivity over time for various clinical applications. In this paper, we present a novel statistical model for diffusion-weighted MR signal attenuation which postulates that the water molecule diffusion can be characterized by a continuous mixture of diffusion tensors. An interesting observation is that this continuous mixture and the MR signal attenuation are related through the Laplace transform of a probability distribution over symmetric positive definite matrices. We then show that when the mixing distribution is a Wishart distribution, the resulting closed form of the Laplace transform leads to a Rigaut-type asymptotic fractal expression, which has been phenomenologically used in the past to explain the MR signal decay but never with a rigorous mathematical justification until now. Our model not only includes the traditional diffusion tensor model as a special instance in the limiting case, but also can be adjusted to describe complex tissue structure involving multiple fiber populations. Using this new model in conjunction with a spherical deconvolution approach, we present an efficient scheme for estimating the water molecule displacement probability functions on a voxel-by-voxel basis. Experimental results on both simulations and real data are presented to demonstrate the robustness and accuracy of the proposed algorithms. PMID:17570683

  8. Robust optimal design of diffusion-weighted magnetic resonance experiments for skin microcirculation

    NASA Astrophysics Data System (ADS)

    Choi, J.; Raguin, L. G.

    2010-10-01

    Skin microcirculation plays an important role in several diseases including chronic venous insufficiency and diabetes. Magnetic resonance (MR) has the potential to provide quantitative information and a better penetration depth compared with other non-invasive methods such as laser Doppler flowmetry or optical coherence tomography. The continuous progress in hardware resulting in higher sensitivity must be coupled with advances in data acquisition schemes. In this article, we first introduce a physical model for quantifying skin microcirculation using diffusion-weighted MR (DWMR) based on an effective dispersion model for skin leading to a q-space model of the DWMR complex signal, and then design the corresponding robust optimal experiments. The resulting robust optimal DWMR protocols improve the worst-case quality of parameter estimates using nonlinear least squares optimization by exploiting available a priori knowledge of model parameters. Hence, our approach optimizes the gradient strengths and directions used in DWMR experiments to robustly minimize the size of the parameter estimation error with respect to model parameter uncertainty. Numerical evaluations are presented to demonstrate the effectiveness of our approach as compared to conventional DWMR protocols.

  9. Evaluation of three inverse problem models to quantify skin microcirculation using diffusion-weighted MRI

    NASA Astrophysics Data System (ADS)

    Cordier, G.; Choi, J.; Raguin, L. G.

    2008-11-01

    Skin microcirculation plays an important role in diseases such as chronic venous insufficiency and diabetes. Magnetic resonance imaging (MRI) can provide quantitative information with a better penetration depth than other noninvasive methods, such as laser Doppler flowmetry or optical coherence tomography. Moreover, successful MRI skin studies have recently been reported. In this article, we investigate three potential inverse models to quantify skin microcirculation using diffusion-weighted MRI (DWI), also known as q-space MRI. The model parameters are estimated based on nonlinear least-squares (NLS). For each of the three models, an optimal DWI sampling scheme is proposed based on D-optimality in order to minimize the size of the confidence region of the NLS estimates and thus the effect of the experimental noise inherent to DWI. The resulting covariance matrices of the NLS estimates are predicted by asymptotic normality and compared to the ones computed by Monte-Carlo simulations. Our numerical results demonstrate the effectiveness of the proposed models and corresponding DWI sampling schemes as compared to conventional approaches.

  10. Diffusion Weighted MRI and MRS to Differentiate Radiation Necrosis and Recurrent Disease in Gliomas

    NASA Astrophysics Data System (ADS)

    Ewell, Lars

    2006-03-01

    A difficulty encountered in the diagnosis of patients with gliomas is the differentiation between recurrent disease and Radiation Induced Necrosis (RIN). Both can appear as ‘enhancing lesions’ on a typical T2 weighted MRI scan. Magnetic Resonance Spectroscopy (MRS) and Diffusion Weighted MRI (DWMRI) have the potential to be helpful regarding this differentiation. MRS has the ability to measure the concentration of brain metabolites, such as Choline, Creatin and N- Acetyl Aspartate, the ratios of which have been shown to discriminate between RIN and recurrent disease. DWMRI has been linked via a rise in the Apparent Diffusion Coefficient (ADC) to successful treatment of disease. Using both of these complimentary non-invasive imaging modalities, we intend to initiate an imaging protocol whereby we will study how best to combine metabolite ratios and ADC values to obtain the most useful information in the least amount of scan time. We will look for correlations over time between ADC values, and MRS, among different sized voxels.

  11. On the least-square estimation of parameters for statistical diffusion weighted imaging model.

    PubMed

    Yuan, Jing; Zhang, Qinwei

    2013-01-01

    Statistical model for diffusion-weighted imaging (DWI) has been proposed for better tissue characterization by introducing a distribution function for apparent diffusion coefficients (ADC) to account for the restrictions and hindrances to water diffusion in biological tissues. This paper studies the precision and uncertainty in the estimation of parameters for statistical DWI model with Gaussian distribution, i.e. the position of distribution maxima (Dm) and the distribution width (σ), by using non-linear least-square (NLLS) fitting. Numerical simulation shows that precise parameter estimation, particularly for σ, imposes critical requirements on the extremely high signal-to-noise ratio (SNR) of DWI signal when NLLS fitting is used. Unfortunately, such extremely high SNR may be difficult to achieve for the normal setting of clinical DWI scan. For Dm and σ parameter mapping of in vivo human brain, multiple local minima are found and result in large uncertainties in the estimation of distribution width σ. The estimation error by using NLLS fitting originates primarily from the insensitivity of DWI signal intensity to distribution width σ, as given in the function form of the Gaussian-type statistical DWI model.

  12. New paradigm to assess brain cell morphology by diffusion-weighted MR spectroscopy in vivo

    PubMed Central

    Palombo, Marco; Ligneul, Clémence; Najac, Chloé; Le Douce, Juliette; Flament, Julien; Escartin, Carole; Hantraye, Philippe; Brouillet, Emmanuel; Bonvento, Gilles; Valette, Julien

    2016-01-01

    The brain is one of the most complex organs, and tools are lacking to assess its cellular morphology in vivo. Here we combine original diffusion-weighted magnetic resonance (MR) spectroscopy acquisition and novel modeling strategies to explore the possibility of quantifying brain cell morphology noninvasively. First, the diffusion of cell-specific metabolites is measured at ultra-long diffusion times in the rodent and primate brain in vivo to observe how cell long-range morphology constrains metabolite diffusion. Massive simulations of particles diffusing in synthetic cells parameterized by morphometric statistics are then iterated to fit experimental data. This method yields synthetic cells (tentatively neurons and astrocytes) that exhibit striking qualitative and quantitative similarities with histology (e.g., using Sholl analysis). With our approach, we measure major interspecies difference regarding astrocytes, whereas dendritic organization appears better conserved throughout species. This work suggests that the time dependence of metabolite diffusion coefficient allows distinguishing and quantitatively characterizing brain cell morphologies noninvasively. PMID:27226303

  13. Robust nonparametric segmentation of infarct lesion from diffusion-weighted MR images.

    PubMed

    Hevia-Montiel, Nidiyare; Jiménez-Alaniz, Juan Ramón; Medina-Bañuelos, Verónica; Yáñez-Suárez, Oscar; Rosso, Charlotte; Samson, Yves; Baillet, Sylvain

    2007-01-01

    Magnetic Resonance Imaging (MRI) is increasingly used for the diagnosis and monitoring of neurological disorders. In particular Diffusion-Weighted MRI (DWI) is highly sensitive in detecting early cerebral ischemic changes in acute stroke. Cerebral infarction lesion segmentation from DWI is accomplished in this work by applying nonparametric density estimation. The quality of the class boundaries is improved by including an edge confidence map, that is the confidence of truly being in the presence of a border between adjacent regions. The adjacency graph, that is constructed with the label regions, is analyzed and pruned to merge adjacent regions. The method was applied to real images, keeping all parameters constant throughout the process for each data set. The combination of region segmentation and edge detection proved to be a robust automatic technique of segmentation from DWI images of cerebral infarction regions in acute ischemic stroke. In a comparison with the reference infarct lesions segmentation, the automatic segmentation presented a significant correlation (r=0.935), and an average Tanimoto index of 0.538.

  14. Diffusion weighted magnetic resonance imaging in the diagnosis of parotid masses. Preliminary results

    PubMed Central

    Yologlu, Zeynel; Aydin, Hasan; Alp, Nalan A.; Aribas, Bilgin K.; Kizilgoz, Volkan; Arda, Kemal

    2016-01-01

    Objective To demonstrate the diagnostic potentials of MRI, diffusion weighted imaging (DWI), and apparent diffusion coefficient (ADC) mapping in the detection of parotid masses correlated to the histopathological results. Methods Study design was retrospective. Fifteen patients with parotid gland masses were included as the study group and contralateral normal parotis glands of same patients were taken as the control group. Patients with bilateral parotid gland tumors were excluded, 7 right-sided and 8 left-sided parotid masses were included in the research. The study took place at the Department of Radiology, Ankara, Turkey, between May 2012 and September 2014. Results Apparent diffusion coefficient measurements of 15 parotis tumors in 1000 and 750 sec/mm2 b-values with comparison to the contralateral normal gland parenchyma were demonstrated. Neurofibromas was predicted as the highest, and lipomas as the lowest ADC values. Pleomorphic adenomas, Warthin’s tumor, and normal parotid parenchyma indicate significant statistical differences from each other on the basis of mean ADC values (p<0.05). Conclusion The DWI and ADC mapping of parotis gland could aid in the differential diagnosis of benign and malignant masses. PMID:27874161

  15. Characterizing the distribution of anisotropic micro-structural environments with diffusion-weighted imaging (DIAMOND).

    PubMed

    Scherrer, Benoit; Schwartzman, Armin; Taquet, Maxime; Prabhu, Sanjay P; Sahin, Mustafa; Akhondi-Asl, Alireza; Warfield, Simon K

    2013-01-01

    Diffusion-weighted imaging (DWI) enables investigation of the brain microstructure by probing natural barriers to diffusion in tissues. In this work, we propose a novel generative model of the DW signal based on considerations of the tissue microstructure that gives rise to the diffusion attenuation. We consider that the DW signal can be described as the sum of a large number of individual homogeneous spin packets, each of them undergoing local 3-D Gaussian diffusion represented by a diffusion tensor. We consider that each voxel contains a number of large scale microstructural environments and describe each of them via a matrix-variate Gamma distribution of spin packets. Our novel model of DIstribution of Anisotropic MicrOstructural eNvironments in DWI (DIAMOND) is derived from first principles. It enables characterization of the extra-cellular space, of each individual white matter fascicle in each voxel and provides a novel measure of the microstructure heterogeneity. We determine the number of fascicles at each voxel with a novel model selection framework based upon the minimization of the generalization error. We evaluate our approach with numerous in-vivo experiments, with cross-testing and with pathological DW-MRI. We show that DIAMOND may provide novel biomarkers that captures the tissue integrity.

  16. Fast and accurate simulations of diffusion-weighted MRI signals for the evaluation of acquisition sequences

    NASA Astrophysics Data System (ADS)

    Rensonnet, Gaëtan; Jacobs, Damien; Macq, Benoît.; Taquet, Maxime

    2016-03-01

    Diffusion-weighted magnetic resonance imaging (DW-MRI) is a powerful tool to probe the diffusion of water through tissues. Through the application of magnetic gradients of appropriate direction, intensity and duration constituting the acquisition parameters, information can be retrieved about the underlying microstructural organization of the brain. In this context, an important and open question is to determine an optimal sequence of such acquisition parameters for a specific purpose. The use of simulated DW-MRI data for a given microstructural configuration provides a convenient and efficient way to address this problem. We first present a novel hybrid method for the synthetic simulation of DW-MRI signals that combines analytic expressions in simple geometries such as spheres and cylinders and Monte Carlo (MC) simulations elsewhere. Our hybrid method remains valid for any acquisition parameters and provides identical levels of accuracy with a computational time that is 90% shorter than that required by MC simulations for commonly-encountered microstructural configurations. We apply our novel simulation technique to estimate the radius of axons under various noise levels with different acquisition protocols commonly used in the literature. The results of our comparison suggest that protocols favoring a large number of gradient intensities such as a Cube and Sphere (CUSP) imaging provide more accurate radius estimation than conventional single-shell HARDI acquisitions for an identical acquisition time.

  17. [Application of brain diffusion-weighted imaging performed using readout segmentation of long variable echo trains].

    PubMed

    Ishida, Go; Oishi, Makoto; Morii, Ken; Hasegawa, Kenji; Saito, Akihiko; Sato, Mitsuya; Takizawa, Osamu; Murata, Katsutoshi; Porter, D A; Matsuzawa, Hitoshi; Fujii, Yukihiko

    2015-01-01

    We report the preliminary use of the readout segmentation of long variable echo trains(RESOLVE)sequence, a novel magnetic resonance(MR)scanning technique based on a readout segmented echo planar imaging(EPI)strategy. RESOLVE enables high-resolution diffusion-weighted imaging(DWI)by minimizing susceptibility distortions and T2* blurring. The software for this sequence was provided by Siemens AG, Germany. Previously, we determined appropriate sequence parameters to obtain sufficiently high-resolution images through phantom studies. Then, we applied the sequence to some clinical cases with neurological disorders and analyzed the RESOLVE-DWI data with diffusion tensor imaging(DTI)techniques. In this article, we report clinical application of the RESOLVE sequence in two cases, one with cerebellar infarction and one with an intracranial epidermoid cyst. In both cases, RESOLVE-DWI clearly exposed structures that were obscured or severely distorted by artifacts on usual single-shot EPI-DWI. DTI analyses for RESOLVE-DWI data provided detailed information about fiber tracts and cranial nerves.

  18. High angular resolution diffusion-weighted imaging in mild traumatic brain injury.

    PubMed

    Mohammadian, Mehrbod; Roine, Timo; Hirvonen, Jussi; Kurki, Timo; Ala-Seppälä, Henna; Frantzén, Janek; Katila, Ari; Kyllönen, Anna; Maanpää, Henna-Riikka; Posti, Jussi; Takala, Riikka; Tallus, Jussi; Tenovuo, Olli

    2017-01-01

    We sought to investigate white matter abnormalities in mild traumatic brain injury (mTBI) using diffusion-weighted magnetic resonance imaging (DW-MRI). We applied a global approach based on tract-based spatial statistics skeleton as well as constrained spherical deconvolution tractography. DW-MRI was performed on 102 patients with mTBI within two months post-injury and 30 control subjects. A robust global approach considering only the voxels with a single-fiber configuration was used in addition to global analysis of the tract skeleton and probabilistic whole-brain tractography. In addition, we assessed whether the microstructural parameters correlated with age, time from injury, patient's outcome and white matter MRI hyperintensities. We found that whole-brain global approach restricted to single-fiber voxels showed significantly decreased fractional anisotropy (FA) (p = 0.002) and increased radial diffusivity (p = 0.011) in patients with mTBI compared with controls. The results restricted to single-fiber voxels were more significant and reproducible than those with the complete tract skeleton or the whole-brain tractography. FA correlated with patient outcomes, white matter hyperintensities and age. No correlation was observed between FA and time of scan post-injury. In conclusion, the global approach could be a promising imaging biomarker to detect white matter abnormalities following traumatic brain injury.

  19. Assessment of allograft function using diffusion-weighted magnetic resonance imaging in kidney transplant patients.

    PubMed

    Kaul, Anupma; Sharma, Raj Kumar; Gupta, Rakesh Kumar; Lal, Hira; Yadav, Abhishek; Bhadhuria, Dharmendra; Prasad, Narayan; Gupta, Amit

    2014-11-01

    Developing a non-invasive method such as diffusion-weighted magnetic resonance imaging (DWMRI) could be used as a feasible and reproducible modality in the differential diagnosis of allograft dysfunction. We assessed the functional status of the renal allograft by DWMRI and its applicability in assessment of graft dysfunction on all end-stage renal transplant patients who attained normal renal function on the 7th day post-transplantation. Follow-up imaging of the recipient allograft was performed at the end of 90 and 180 days and in case of graft dysfunction. Kidney biopsies were performed to correlate with the corresponding MRI. The apparent diffusion coefficient (ADC) maps of the cortex and medulla were obtained by studying the DWMRI. The ADC values were significantly lower in the medulla compared with the cortex in normal donor kidneys and normally functioning transplanted kidneys, while they decreased significantly when rejection occurred. The reduction in ADC values occurred both in the cortex and in the medulla, and correlated with the degree of rejection on the kidney biopsies. The ADC values increased significantly during the recovery from rejection. We conclude that DWMRI can be beneficial in the diagnosis and follow-up of transplant patients during acute rejection.

  20. Integrative Diffusion-Weighted Imaging and Radiogenomic Network Analysis of Glioblastoma multiforme

    PubMed Central

    Heiland, Dieter Henrik; Simon-Gabriel, Carl Philipp; Demerath, Theo; Haaker, Gerrit; Pfeifer, Dietmar; Kellner, Elias; Kiselev, Valerij G.; Staszewski, Ori; Urbach, Horst; Weyerbrock, Astrid; Mader, Irina

    2017-01-01

    In the past, changes of the Apparent Diffusion Coefficient in glioblastoma multiforme have been shown to be related to specific genes and described as being associated with survival. The purpose of this study was to investigate diffusion imaging parameters in combination with genome-wide expression data in order to obtain a comprehensive characterisation of the transcriptomic changes indicated by diffusion imaging parameters. Diffusion-weighted imaging, molecular and clinical data were collected prospectively in 21 patients. Before surgery, MRI diffusion metrics such as axial (AD), radial (RD), mean diffusivity (MD) and fractional anisotropy (FA) were assessed from the contrast enhancing tumour regions. Intraoperatively, tissue was sampled from the same areas using neuronavigation. Transcriptional data of the tissue samples was analysed by Weighted Gene Co-Expression Network Analysis (WGCNA) thus classifying genes into modules based on their network-based affiliations. Subsequent Gene Set Enrichment Analysis (GSEA) identified biological functions or pathways of the expression modules. Network analysis showed a strong association between FA and epithelial-to-mesenchymal-transition (EMT) pathway activation. Also, patients with high FA had a worse clinical outcome. MD correlated with neural function related genes and patients with high MD values had longer overall survival. In conclusion, FA and MD are associated with distinct molecular patterns and opposed clinical outcomes. PMID:28266556

  1. Intravoxel incoherent motion diffusion-weighted MR imaging of gliomas: efficacy in preoperative grading.

    PubMed

    Hu, Yu-Chuan; Yan, Lin-Feng; Wu, Lang; Du, Pang; Chen, Bao-Ying; Wang, Liang; Wang, Shu-Mei; Han, Yu; Tian, Qiang; Yu, Ying; Xu, Tian-Yong; Wang, Wen; Cui, Guang-Bin

    2014-12-01

    The preoperative grading of gliomas, which is critical for guiding therapeutic strategies, remains unsatisfactory. We aimed to retrospectively assess the efficacy of intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) in the grading of gliomas. Forty-two newly diagnosed glioma patients underwent conventional MR imaging, DWI, and contrast-enhanced MR imaging. Parameters of apparent diffusion coefficient (ADC), slow diffusion coefficient (D), fast diffusion coefficient (D*), and fraction of fast ADC (f) were generated. They were tested for differences between low- and high-grade gliomas based on one-way ANOVA. Receiver-operating characteristic (ROC) analyses were conducted to determine the optimal thresholds as well as the sensitivity and specificity for grading. ADC, D, and f were higher in the low-grade gliomas, whereas D* tended to be lower (all P<0.05). The AUC, sensitivity, specificity and the cutoff value, respectively, for differentiating low- from high-grade gliomas for ADC, D and f, and differentiating high- from low-grade gliomas for D* were as follows: ADC, 0.926, 100%, 82.8%, and 0.7 × 10(-3) mm(2)/sec; D, 0.942, 92.3%, 86.2%, and 0.623 × 10(-3) mm(2)/sec; f, 0.902, 92.3%, 86.2%, and 35.3%; D*, 0.798, 79.3%, 84.6%, and 0.303 × 10(-3) mm(2)/sec. The IVIM DWI demonstrates efficacy in differentiating the low- from high-grade gliomas.

  2. Diffusion-Weighted MRI of Malignant versus Benign Portal Vein Thrombosis

    PubMed Central

    Ahn, Jhii-Hyun; Cho, Eun-Suk; Chung, Jae-Joon; Kim, Joo Hee; Kim, Ki Whang

    2016-01-01

    Objective To validate the diffusion-weighted MRI (DWI) for differentiation of benign from malignant portal vein thrombosis. Materials and Methods The Institutional Review Board approved this retrospective study and waived informed consent. A total of 59 consecutive patients (52 men and 7 women, aged 40–85 years) with grossly defined portal vein thrombus (PVT) on hepatic MRI were retrospectively analyzed. Among them, liver cirrhosis was found in 45 patients, and hepatocellular carcinoma in 47 patients. DWI was performed using b values of 50 and 800 sec/mm2 at 1.5-T unit. A thrombus was considered malignant if it enhanced on dynamic CT or MRI; otherwise, it was considered bland. There were 18 bland thrombi and 49 malignant thrombi in 59 patients, including 8 patients with simultaneous benign and malignant PVT. Mean apparent diffusion coefficients (ADCs) of benign and malignant PVTs were compared by using Mann-Whitney U test. Diagnostic accuracy was evaluated using receiver operating characteristic (ROC) curve analysis. Results The mean ADC ± standard deviation of bland and malignant PVT were 1.00 ± 0.39 × 10-3 mm2/sec and 0.92 ± 0.25 × 10-3 mm2/sec, respectively; without significant difference (p = 0.799). The area under ROC curve for ADC was 0.520. An ADC value of > 1.35 × 10-3 mm2/sec predicted bland PVT with a specificity of 94.6% (95% confidence interval [CI]: 84.9–98.9%) and a sensitivity of 22.2% (95% CI: 6.4–47.6%), respectively. Conclusion Due to the wide range and considerable overlap of the ADCs, DWI cannot differentiate the benign from malignant thrombi efficiently. PMID:27390544

  3. Supratentorial and infratentorial damage in spinocerebellar ataxia 2: a diffusion-weighted MRI study.

    PubMed

    Salvatore, Elena; Tedeschi, Enrico; Mollica, Carmine; Vicidomini, Caterina; Varrone, Andrea; Coda, Anna Rita Daniela; Brunetti, Arturo; Salvatore, Marco; De Michele, Giuseppe; Filla, Alessandro; Pappatà, Sabina

    2014-05-01

    Spinocerebellar ataxia type 2 (SCA2) is an autosomal-dominant degenerative disorder that is neuropathologically characterized primarily by infratentorial damage, although less severe supratentorial involvement may contribute to the clinical manifestation. Diffusion-weighted imaging (DWI)-Magnetic Resonance Imaging (MRI) studies of SCA2 have enabled in vivo quantification of neurodegeneration in infratentorial regions, whereas supratentorial regions have been explored less thoroughly. We measured microstructural changes in both infratentorial and supratentorial regions in 13 SCA2 patients (9 men, 4 women; mean age, 50 ± 12 years) and 15 controls (10 men, 5 women; mean age, 49 ± 14 years) using DWI-MRI and correlated the DWI changes with disease severity and duration. Disease severity was evaluated using the International Cooperative Ataxia Rating Scale and the Inherited Ataxia Clinical Rating Scale. Cerebral diffusion trace ( D¯) values were generated, and regions of interest (ROIs) and voxel-based analysis with Statistical Parametric Mapping (SPM) were used for data analysis. In SCA2 patients, ROI analysis and SPM confirmed significant increases in D¯ values in the pons, cerebellar white matter (CWM) and middle cerebellar peduncles. Moreover, SPM analysis revealed increased D¯ values in the right thalamus, bilateral temporal cortex/white matter, and motor cortex/pyramidal tract regions. Increased diffusivity in the frontal white matter (FWM) and the CWM was significantly correlated with ataxia severity. DWI-MRI revealed that both infratentorial and supratentorial microstructural changes may characterize SCA2 patients in the course of the disease and might contribute to the severity of the symptoms.

  4. Utility of diffusion-weighted imaging to assess hepatocellular carcinoma viability following transarterial chemoembolization.

    PubMed

    Yuan, Zheng; Li, Wen-Tao; Ye, Xiao-Dan; Peng, Wei-Jun; Xiao, Xiang-Sheng

    2014-08-01

    The purpose of the present study was to evaluate whether diffusion-weighted imaging (DWI) can be used to assess hepatocellular carcinoma (HCC) viability following transarterial chemoembolization (TACE). A total of 41 consecutive patients were treated according to chemoembolization protocols. The follow-up was performed between six and eight weeks post-chemoembolization by multidetector computed tomography [or enhanced magnetic resonance imaging (MRI)] and DW-MRI on the same day. The presence of any residual tumor and the extent of tumor necrosis were evaluated according to the European Association for the Study of the Liver. The apparent diffusion coefficient (ADC) values of the entire area of the treated mass and the vital and necrotic tumor tissues were recorded. Correlation coefficients were also calculated to compare the percentage of necrosis with ADC values. The mean ADC values of the necrotic and vital tumor tissues were 2.22±0.31×10(-3) mm(2)/sec and 1.42±0.25×10(-3) mm(2)/sec, respectively (Mann-Whitney U test, P<0.001). The results from the receiver operating characteristic analysis showed that the threshold ADC value was 1.84×10(-3) mm(2)/sec with 92.3% sensitivity and 100% specificity for identifying the necrotic tumor tissues. A significant linear regression correlation was identified between the ADC value of the entire area of the treated mass and the extent of tumor necrosis (r=0.58; P<0.001). In conclusion, DWI can be used to assess HCC viability following TACE.

  5. 3T diffusion-weighted MRI of the thyroid gland with reduced distortion: preliminary results

    PubMed Central

    Nagala, S; Priest, A N; McLean, M A; Jani, P; Graves, M J

    2013-01-01

    Objective: Single-shot diffusion-weighted (DW) echo planar imaging (EPI), which is commonly used for imaging the thyroid, is characterised by severe blurring and distortion. The objectives of this work were: 1, to show that a reduced-field of view (r-FOV) DW EPI technique can improve image quality; and 2, to investigate the effect of different reconstruction strategies on the resulting apparent diffusion coefficients (ADCs). Methods: We implemented a single-shot, r-FOV DW EPI technique with a two-dimensional radiofrequency excitation pulse for DW imaging of the thyroid at 3T. Images were reconstructed using root sum of squares (SOS) and an optimal-B1 reconstruction (OBR). Phantom and in vivo experiments were performed to compare r-FOV and conventional full-FOV DW EPI with root SOS and OBR. Results: r-FOV with OBR substantially improved image quality at 3T. In phantoms, r-FOV gave more accurate ADCs than full-FOV. In vivo r-FOV always gave lower ADC values with respect to the full-FOV technique irrespective of the reconstruction used and whether only two or multiple b-values were used to compute the ADCs. Conclusion: r-FOV DW EPI can reduce image blurring and distortion at the expense of a low signal-to-noise ratio. OBR is a promising reconstruction technique for accurate ADC measurements in lower signal-to-noise ratio regimes, although further studies are needed to characterise its performance. Advances in knowledge: DW imaging of the thyroid at 3T could potentially benefit from r-FOV acquisition strategies, such as the r-FOV DW EPI technique proposed in this paper. PMID:23770539

  6. Diffusion-weighted imaging in cancer: Physical foundations and applications of Restriction Spectrum Imaging

    PubMed Central

    White, Nathan S.; McDonald, Carrie; Farid, Niky; Kuperman, Josh; Karow, David; Schenker-Ahmed, Natalie M.; Bartsch, Hauke; Rakow-Penner, Rebecca; Holland, Dominic; Shabaik, Ahmed; Bjørnerud, Atle; Hope, Tuva; Hattangadi-Gluth, Jona; Liss, Michael; Parsons, J. Kellogg; Chen, Clark C.; Raman, Steve; Margolis, Daniel; Reiter, Robert E.; Marks, Leonard; Kesari, Santosh; Mundt, Arno J.; Kane, Chris J.; Carter, Bob S.; Bradley, William G.; Dale, Anders M.

    2014-01-01

    Diffusion weighted imaging (DWI) has been at the forefront of cancer imaging since the early 2000’s. Prior to its application in clinical oncology, this powerful technique had already achieved widespread recognition due to its utility in the diagnosis of cerebral infarction. Following this initial success, the ability of DWI to detect inherent tissue contrast began to be exploited in the field of oncology. Although the initial oncologic applications for tumor detection and characterization, assessing treatment response, and predicting survival were primarily in the field of neuro-oncology, the scope of DWI has since broadened to include oncologic imaging of the prostate gland, breast, and liver. Despite its growing success and application, misconceptions as to the underlying physical basis of the DWI signal exist among researchers and clinicians alike. In this review, we provide a detailed explanation of the biophysical basis of diffusion contrast, emphasizing the difference between hindered and restricted diffusion, and elucidating how diffusion parameters in tissue are derived from the measurements via the diffusion model. We describe one advanced DWI modeling technique, called Restriction Spectrum Imaging (RSI). This technique offers a more direct in vivo measure of tumor cells, due to its ability to distinguish separable pools of water within tissue based on their intrinsic diffusion characteristics. Using RSI as an example, we then highlight the ability of advanced DWI techniques to address key clinical challenges in neuro-oncology, including improved tumor conspicuity, distinguishing actual response to therapy from pseudoresponse, and delineation of white matter tracts in regions of peritumoral edema. We also discuss how RSI, combined with new methods for correction of spatial distortions inherent diffusion MRI scans, may enable more precise spatial targeting of lesions, with implications for radiation oncology, and surgical planning. PMID:25183788

  7. Pure monoparesis of the leg due to cerebral infarctions: a diffusion-weighted imaging study.

    PubMed

    Hiraga, Akiyuki; Uzawa, Akiyuki; Tanaka, Saiko; Ogawara, Kazue; Kamitsukasa, Ikuo

    2009-11-01

    Pure monoparesis of the leg due to cerebral infarction is rare compared to that of the hand. The anterior cerebral artery (ACA) territory is the most common lesion site in leg monoparesis, but diffusion-weighted (DW) MRI has not commonly been used for lesion detection. The purpose of this study was to use DW MRI to evaluate the radiological correlation with lesion location in patients presenting with pure leg monoparesis. We retrospectively studied six cerebral infarct patients with pure leg monoparesis who had undergone DW MRI. Patients were scanned within 3 days of symptom onset. DW MRI identified lesions in the posterior limb of the internal capsule (PLIC) in two patients, in the corona radiata (two patients), in the subcortical white matter of the posterior frontal lobe (one patient), and in the frontal and parietal cortex, including the paracentral lobule and precuneus (one patient). The two patients with PLIC infarctions had characteristic linear infarction abnormalities along the long axis of the internal capsule. Corona radiata infarction were located posteriorly, and the two subcortical and cortical infarction were thought to be in the territory of the ACA. We thus concluded that in leg monoparesis due to infarctions, lesions may be located in the PLIC, corona radiata, or in the ACA territory. Recently, magnetic resonance tractography has shown that foot fibres of the corticospinal tract in the PLIC somatotopically may be posteromedial to hand fibres along the short axis of the internal capsule, rather than posterolateral along the long axis as has been thought. Thus, damage along the long axis of the PLIC by linear infarctions can cause pure monoparesis of the leg.

  8. Diffusion-weighted imaging of the abdomen: Impact of b-values on texture analysis features.

    PubMed

    Becker, Anton S; Wagner, Matthias W; Wurnig, Moritz C; Boss, Andreas

    2017-01-01

    The purpose of this work was to systematically assess the impact of the b-value on texture analysis in MR diffusion-weighted imaging (DWI) of the abdomen. In eight healthy male volunteers, echo-planar DWI sequences at 16 b-values ranging between 0 and 1000 s/mm(2) were acquired at 3 T. Three different apparent diffusion coefficient (ADC) maps were computed (0, 750/100, 390, 750 s/mm(2) /all b-values). Texture analysis of rectangular regions of interest in the liver, kidney, spleen, pancreas, paraspinal muscle and subcutaneous fat was performed on DW images and the ADC maps, applying 19 features computed from the histogram, grey-level co-occurrence matrix (GLCM) and grey-level run-length matrix (GLRLM). Correlations between b-values and texture features were tested with a linear and an exponential model; the best fit was determined by the smallest sum of squared residuals. Differences between the ADC maps were assessed with an analysis of variance. A Bonferroni-corrected p-value less than 0.008 (=0.05/6) was considered statistically significant. Most GLCM and GLRLM-derived texture features (12-18 per organ) showed significant correlations with the b-value. Four texture features correlated significantly with changing b-values in all organs (p < 0.008). Correlation coefficients varied between 0.7 and 1.0. The best fit varied across different structures, with fat exhibiting mostly exponential (17 features), muscle mostly linear (12 features) and the parenchymatous organs mixed feature alterations. Two GLCM features showed significant variability in the different ADC maps. Several texture features vary systematically in healthy tissues at different b-values, which needs to be taken into account if DWI data with different b-values are analyzed. Histogram and GLRLM-derived texture features are stable on ADC maps computed from different b-values.

  9. Cerebral Effects of Targeted Temperature Management Methods Assessed by Diffusion-Weighted Magnetic Resonance Imaging.

    PubMed

    Grejs, Anders Morten; Gjedsted, Jakob; Pedersen, Michael; Birke-Sørensen, Hanne; Rauff-Mortensen, Andreas; Andersen, Kristian Kjær; Kirkegaard, Hans

    2016-12-01

    The aim of this randomized porcine study was to compare surface targeted temperature management (TTM) to endovascular TTM evaluated by cerebral diffusion-weighted magnetic resonance imaging (MRI): apparent diffusion coefficient (ADC), and by intracerebral/intramuscular microdialysis. It is well known that alteration in the temperature affects ADC, but the relationship between cerebral ADC values and the cooling method per se has not been established. Eighteen anesthetized 60-kg female swine were hemodynamically and intracerebrally monitored and subsequently subjected to a baseline MRI. The animals were then randomized into three groups: (1) surface cooling (n = 6) at 33.5°C using EMCOOLSpad(®), (2) endovascular cooling (n = 6) at 33.5°C using an Icy(®) cooling catheter with the CoolGard 3000(®), or (3) control (n = 6) at 38.5°C using a Bair Hugger™. The swine were treated with TTM for 6 hours followed by a second MRI examination, including ADC. Blood and microdialysate were sampled regularly throughout the experiment, and glucose, lactate, pyruvate, glycerol, and the lactate/pyruvate ratio did not differ among groups, neither intracerebrally nor intramuscularly. Surface cooling yielded a significantly lower median ADC than endovascular cooling: 714 (634; 804) × 10(-6) mm(2)/s versus 866 (828; 927) × 10(-6) mm(2)/s, (p < 0.05). The surface cooling ADC was lowered to a range usually attributed to cytotoxic edema and these low values could not be explained solely by the temperature effect per se. To what extent the ADC is fully reversible at rewarming is unknown and the clinical implications should be further investigated in clinical studies.

  10. Diffusion weighted imaging for the differential diagnosis of benign vs. malignant ovarian neoplasms.

    PubMed

    Meng, Xiang-Fu; Zhu, Shi-Cai; Sun, Shao-Juan; Guo, Ji-Cai; Wang, Xue

    2016-06-01

    In order to assess the diagnostic accuracy of diffusion weighted imaging (DWI) in differentiating between benign and malignant ovarian neoplasms, a systemic meta-analysis was conducted. Relevant studies were retrieved from scientific literature databases, including the PubMed, Wiley, EBSCO, Ovid, Web of Science, Wanfang, China National Knowledge Infrastructure and VIP databases. Following a multi-step screening and study selection process, the relevant data was extracted for use in the present study. Statistical analyses were performed using Meta-disc software version 1.4 and STATA statistical software version 12.0. A total of 285 articles were retrieved from the database searches. Following a careful screening process, 10 case-control studies were selected for the present meta-analysis. The 10 studies investigated the efficacy of DWI in diagnosing ovarian neoplasms, and included a combined total of 1,159 subjects, of which 559 patients had malignant lesions and 600 had benign lesions. The results showed that the pooled sensitivity, pooled specificity, pooled positive likelihood ratio, pooled negative likelihood ratio, pooled diagnostic odds ratio (DOR) and area under the curve of the summary receiver operating characteristics curve of DWI for differentiating between benign and malignant ovarian neoplasms were 0.93, 0.89, 7.58, 0.10, 85.33 and 0.95, respectively. A subgroup analysis based on ethnicity revealed no significant difference between Asians and Caucasians. Another subgroup analysis by magnetic resonance imaging (MRI) type showed that the DORs for GE Healthcare Life Sciences and Siemens AG machines were 100.76 [95% confidence interval (CI), 65.28-155.53] and 30.85 (95% CI, 10.40-91.53), respectively; this indicates that the diagnostic efficiency of the GE Healthcare Life Sciences MRI is superior compared with the Siemens AG MRI. The DWI demonstrated an excellent diagnostic performance in discriminating between benign and malignant ovarian neoplasms, and

  11. Diffusion-weighted imaging improves outcome prediction in pediatric traumatic brain injury.

    PubMed

    Galloway, Nicholas R; Tong, Karen A; Ashwal, Stephen; Oyoyo, Udochukwu; Obenaus, André

    2008-10-01

    Diffusion-weighted imaging (DWI) and consequent apparent diffusion coefficient (ADC) maps have been used for lesion detection and as a predictor of outcome in adults with traumatic brain injury (TBI), but few studies have been reported in children. We evaluated the role of DWI and ADC for outcome prediction after pediatric TBI (n=37 TBI; n=10 controls). Fifteen regions of interest (ROIs) were manually drawn on ADC maps that were grouped for analysis into peripheral gray matter, peripheral white matter, deep gray and white matter, and posterior fossa. All ROIs excluded areas that appeared abnormal on T2-weighted images (T2WI). Acute injury severity was measured using the Glasgow Coma Scale (GCS) score, and 6-12-month outcomes were assessed using the Pediatric Cerebral Performance Category Scale (PCPCS) score. Patients were categorized into five groups: (1) controls; (2) all TBI patients; (3) mild/moderate TBI with good outcomes; (4) severe TBI with good outcomes; and (5) severe TBI with poor outcomes. ADC values in the peripheral white matter were significantly reduced in children with severe TBI with poor outcomes (72.8+/-14.4x10(-3) mm2/sec) compared to those with severe TBI and good outcomes (82.5+/-3.8x10(-3) mm2/sec; p<0.05). We also found that the average total brain ADC value alone had the greatest ability to predict outcome and could correctly predict outcome in 84% of cases. Assessment of DWI and ADC values in pediatric TBI is useful in evaluating injury, particularly in brain regions that appear normal on conventional imaging. Early identification of children at high risk for poor outcome may assist in aggressive clinical management of pediatric TBI patients.

  12. Temporal and spatial profile of brain diffusion-weighted MRI after cardiac arrest

    PubMed Central

    Mlynash, M.; Campbell, D.M.; Leproust, E.M.; Fischbein, N.J.; Bammer, R.; Eyngorn, I.; Hsia, A.W.; Moseley, M.; Wijman, C.A.C.

    2010-01-01

    Background and Purpose Diffusion-weighted MRI (DWI) of the brain is a promising technique to help predict functional outcome in comatose survivors of cardiac arrest. We aimed to evaluate prospectively the temporal-spatial profile of brain apparent diffusion coefficient (ADC) changes in comatose survivors during the first 8 days after cardiac arrest. Methods ADC values were measured by two independent and blinded investigators in predefined brain regions in 18 good and 15 poor outcome patients with 38 brain MRIs, and compared with 14 normal controls. The same brain regions were also assessed qualitatively by two other independent and blinded investigators. Results In poor outcome patients, cortical structures, in particular the occipital and temporal lobes, and the putamen exhibited the most profound ADC reductions, which were noted as early as 1.5 days and reached nadir between 3 to 5 days after the arrest. Conversely, when compared to normal controls, good outcome patients exhibited increased diffusivity, in particular in the hippocampus, temporal and occipital lobes, and corona radiata. By the qualitative MRI readings, one or more cortical gray matter structures were read as moderately-to-severely abnormal in all poor outcome patients imaged beyond 54 hours after the arrest, but not in the three patients imaged earlier. Conclusions Brain DWI changes in comatose post-cardiac arrest survivors in the first week after the arrest are region- and time-dependent and differ between good and poor outcome patients. With the increasing use of MRI in this context, it is important to be aware of these relationships. PMID:20595666

  13. Diffusion-weighted imaging in extracranial head and neck schwannomas: A distinctive appearance

    PubMed Central

    Das, Abanti; Bhalla, Ashu S; Sharma, Raju; Kumar, Atin; Thakar, Alok; Goyal, Ankur

    2016-01-01

    Purpose: To evaluate the diffusion weighted (DW) magnetic resonance imaging (MRI) features of the extracranial schwannomas of head and neck. Materials and Methods: The MRI (including DWI) of 12 patients with pathologically proven head and neck schwannomas (4 men, 8 women, with mean age of 32.6 years; age range 16–50 years) were retrospectively evaluated. Images were analyzed for signal intensity and morphology on conventional sequences followed by the qualitative evaluation of DW images (DWI) and measurement of apparent diffusion coefficient (ADC) values. Results: Majority of the tumors were located in the parapharyngeal space (8/12). All but one showed heterogeneous appearance, with 10 tumors showing scattered areas of hemorrhage. Eight out of 12 tumors showed intensely hyperintense core surrounded by intermediate signal intensity peripheral rim (reverse target sign) on T2-weighted (T2W) images. On DWI, these eight tumors showed a distinctive appearance, resembling target sign on trace DWI and reverse target on ADC map. Out of the remaining four tumors, one showed uniformly restricted diffusion whereas three showed free diffusion. Mean ADC value in the central area of free diffusion was 2.277 × 10−3 mm2/s (range of 1.790 × 10 −3 to 2.605 × 10−3 mm2/s) whereas in the peripheral area was 1.117 × 10−3 mm2/s (range of 0.656 × 10−3 to 1.701 × 10−3 mm2/s). Rest of the schwannomas showing free diffusion had a mean ADC value of 1.971 × 10−3 mm2/s. Conclusion: Majority of the head and neck schwannomas showed a characteristic appearance of free diffusion in the centre and restricted diffusion in the periphery of the mass. PMID:27413271

  14. Diffusion-Weighted MR Imaging of Hepatocellular Carcinoma: Current Value in Clinical Evaluation of Tumor Response to Locoregional Treatment.

    PubMed

    Yuan, Zheng; Zhang, Jian; Yang, Huan; Ye, Xiao-Dan; Xu, Li-Chao; Li, Wen-Tao

    2016-01-01

    The established size-based image biomarkers for tumor burden measurement continue to be applied to solid tumors, as size measurement can easily be used in clinical practice. However, in the setting of novel targeted therapies and liver-directed locoregional treatments for hepatocellular carcinoma (HCC), simple tumor anatomic changes can be less informative and usually appear later than biologic changes. Functional magnetic resonance (MR) imaging has the potential to be a promising technique for assessment of HCC response to therapy. Diffusion-weighted MR imaging is now widely used as a standard imaging modality to evaluate the liver. This review discusses the current clinical value of diffusion-weighted MR imaging in the evaluation of tumor response after nonsurgical locoregional treatment of HCC.

  15. Hypercellularity Components of Glioblastoma Identified by High b-Value Diffusion-Weighted Imaging

    SciTech Connect

    Pramanik, Priyanka P.; Parmar, Hemant A.; Mammoser, Aaron G.; Junck, Larry R.; Kim, Michelle M.; Tsien, Christina I.; Lawrence, Theodore S.; Cao, Yue

    2015-07-15

    Purpose: Use of conventional magnetic resonance imaging (MRI) for target definition may expose glioblastomas (GB) to inadequate radiation dose coverage of the nonenhanced hypercellular subvolume. This study aimed to develop a technique to identify the hypercellular components of GB by using high b-value diffusion-weighted imaging (DWI) and to investigate its relationship with the prescribed 95% isodose volume (PDV) and progression-free survival (PFS). Methods and Materials: Twenty-one patients with GB underwent chemoradiation therapy post-resection and biopsy. Radiation therapy (RT) treatment planning was based upon conventional MRI. Pre-RT DWIs were acquired in 3 orthogonal directions with b-values of 0, 1000, and 3000 s/mm{sup 2}. Hypercellularity volume (HCV) was defined on the high b-value (3000 s/mm{sup 2}) DWI by a threshold method. Nonenhanced signified regions not covered by the Gd-enhanced gross tumor volume (GTV-Gd) on T1-weighted images. The PDV was used to evaluate spatial coverage of the HCV by the dose plan. Association between HCV and PFS or other clinical covariates were assessed using univariate proportional hazards regression models. Results: HCVs and nonenhanced HCVs varied from 0.58 to 67 cm{sup 3} (median: 9.8 cm{sup 3}) and 0.15 to 60 cm{sup 3} (median: 2.5 cm{sup 3}), respectively. Fourteen patients had incomplete dose coverage of the HCV, 6 of whom had >1 cm{sup 3} HCV missed by the 95% PDV (range: 1.01-25.4 cm{sup 3}). Of the 15 patients who progressed, 5 progressed earlier, within 6 months post-RT, and 10 patients afterward. Pre-RT HCVs within recurrent GTVs-Gd were 78% (range: 65%-89%) for the 5 earliest progressions but lower, 53% (range: 0%-85%), for the later progressions. HCV and nonenhanced HCV were significant negative prognostic indicators for PFS (P<.002 and P<.01, respectively). The hypercellularity subvolume not covered by the 95% PDV was a significant negative predictor for PFS (P<.05). Conclusions: High b-value DWI

  16. Role of diffusion-weighted magnetic resonance imaging in differentiating malignancies from benign ovarian tumors

    PubMed Central

    Fan, Xinhua; Zhang, Hongbin; Meng, Shuang; Zhang, Jing; Zhang, Chuge

    2015-01-01

    Objective: We conducted a case-control study to evaluate the diagnostic values of computed tomography (CT) and diffusion-weighted magnetic resonance imaging (DW-MRI) in differentiating malignancies from benign ovarian tumors and a meta-analysis to further confirm our results on DW-MRI. Methods: Totally 64 patients pathologically confirmed as ovarian cancer were included in this study. CT scan and DWI-MRI were performed and analyzed to get compared with pathological results, thereby assessing their accuracy, sensitivity and specificity. Meta-analysis was conducted by database searching and strict eligibility criteria, using STATA 12.0 (Stata Corp, College Station, TX, USA) software. Results: The accuracy, sensitivity, specificity, positive predictive value and negative predictive value for diagnosis of ovarian cancer in CT were 81.82%, 84.48%, 76.67%, 87.50% and 71.88%, respectively; those in DW-MRI were 89.77%, 93.10%, 83.33%, 91.53% and 86.21%, respectively. The Kappa coefficient of DW-MRI (K = 0.771) compared with pathological results was higher than CT (K = 0.602). The average apparent diffusion coefficient values of DW-MRI in diagnosis of benign and malignant ovarian tumors suggested statistically significant difference (1.325 ± 0.269×10-3 mm2/s vs. 0.878 ± 0.246×10-3 mm2/s, P < 0.001). Meta-analysis results showed that the combined sensitivity, specificity, positive likelihood ratio, negative likelihood ratio and diagnostic odds ratio of DW-MRI in discriminating benign versus malignant ovarian tumors were 0.93, 0.88, 7.70, 0.08 and 101.24, respectively. The area under the summary receiver operating characteristic curve was 0.95. Conclusions: Both CT and DW-MRI were of great diagnostic value in differentiating malignancies from benign ovarian tumors, while DW-MRI was superior to CT with higher accuracy, sensitivity and specificity. PMID:26884905

  17. Diffusion weighted imaging and diffusion tensor imaging in the evaluation of transplanted kidneys

    PubMed Central

    Palmucci, Stefano; Cappello, Giuseppina; Attinà, Giancarlo; Foti, Pietro Valerio; Siverino, Rita Olivia Anna; Roccasalva, Federica; Piccoli, Marina; Sinagra, Nunziata; Milone, Pietro; Veroux, Massimiliano; Ettorre, Giovanni Carlo

    2015-01-01

    Objective The aim of this study is to investigate the relation between renal indexes and functional MRI in a population of kidney transplant recipients who underwent MR with diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) of the transplanted graft. Method Study population included 40 patients with single kidney transplant. The patients were divided into 3 groups, on the basis of creatinine clearance (CrCl) values calculated using Cockcroft-Gault formula: group A, including patients with normal renal function (CrCl ≥ 60 mL/min); group B, which refers to patients with moderate renal impairment (CrCl > 30 but <60 mL/min); and, finally, group C, which means severe renal deterioration (CrCl ≤ 30 mL/min). All patients were investigated with a 1.5 Tesla MRI scanner, acquiring DWI and DTI sequences. A Mann–Whitney U test was adopted to compare apparent diffusion coefficients (ADCs) and fractional anisotropy (FA) measurements between groups. Receiver operating characteristic (ROC) curves were created for prediction of normal renal function (group A) and renal failure (group C). Pearson correlation was performed between renal clearance and functional imaging parameter (ADC and FA), obtained for cortical and medullar regions. Results Mann–Whitney U test revealed a highly significant difference (p < 0.01) between patients with low CrCl (group C) and normal CrCl (group A) considering both medullar ADC and FA and cortical ADC. Regarding contiguous groups, the difference between group B and C was highly significant (p < 0.01) for medullar ADC and significant (p < 0.05) for cortical ADC and medullar FA. No difference between these groups was found considering cortical FA. Analyzing groups A and B, we found a significant difference (p < 0.05) for medullar both ADC and FA, while no difference was found for cortical ADC and FA. Strongest Pearson correlation was found between CrCl and medullar ADC (r = 0.65). For predicting normal renal

  18. Modeling diffusion-weighted MRI as a spatially variant Gaussian mixture: Application to image denoising

    PubMed Central

    Gonzalez, Juan Eugenio Iglesias; Thompson, Paul M.; Zhao, Aishan; Tu, Zhuowen

    2011-01-01

    classification tasks. Conclusions: The presented spatially variant mixture model for diffusion MRI provides excellent denoising results at low signal-to-noise ratios. This makes it possible to restore data acquired with a fast (i.e., noisy) pulse sequence to acceptable noise levels. This is the case in diffusion MRI, where a large number of diffusion-weighted volumes have to be acquired under clinical time constraints. PMID:21859036

  19. Diffusion Weighted Magnetic Resonance Imaging Assessment of Blood Flow in the Microvasculature of Abdominal Organs

    NASA Astrophysics Data System (ADS)

    Truica, Loredana Sorina

    In this thesis, water diffusion in human liver and placenta is studied using diffusion weighted magnetic resonance imaging. For short, randomly oriented vascular segments, intravascular water motion is diffusion-like. For tissues with large vascular compartments the diffusion decay is bi-exponential with one component corresponding to diffusing water and the other to water in the microvasculature. This model, known as the intravoxel incoherent motion (IVIM) model, is seldom used with abdominal organs because of motion artifacts. This limitation was overcome for the experiments reported here by introducing: 1) parallel imaging, 2) navigator echo respiratory triggering (NRT), 3) a double echo diffusion sequence that inherently compensates for eddy current effects, 4) SPAIR fat suppression and 5) a superior approach to image analysis. In particular, the use of NRT allowed us to use a free breathing protocol instead of the previously required breath hold protocol. The resulting DWI images were of high quality and motion artifact free. Diffusion decays were measured over a larger portion of the decay than had previously been reported and the results are considerably better than those previously reported. For both studies, reliable measurements of the diffusion coefficient (D), pseudo-diffusion coefficient (D) and perfusion fraction (f), were obtained using a region of interest analysis as well as a pixel-by-pixel approach. To within experimental error, all patients had the same values of D (1.10 mum 2/ms +/- 0.16 mum2/ms), D* (46 mum2/ms +/- 17 mum2/ms) and f (44.0% +/- 6.9%) in liver and D (1.8 mum 2/ms +/- 0.2 mum2/ms), D* (30 mum 2/ms +/- 12 mmu2/ms), and f (40% +/- 6%) in the placenta. No dependence on gestational age was found for the placental study. Parametric maps of f and D* were consistent with blood flow patterns in both systems. The model worked well for both investigated organs even though their anatomical structures are quite different. A method for

  20. Diagnostic Performance of Diffusion-weighted Magnetic Resonance Imaging in Bone Malignancy

    PubMed Central

    Liu, Li-Peng; Cui, Long-Biao; Zhang, Xin-Xin; Cao, Jing; Chang, Ning; Tang, Xing; Qi, Shun; Zhang, Xiao-Liang; Yin, Hong; Zhang, Jian

    2015-01-01

    Abstract Current state-of-the-art nuclear medicine imaging methods (such as PET/CT or bone scintigraphy) may have insufficient sensitivity for predicting bone tumor, and substantial exposure to ionizing radiation is associated with the risk of secondary cancer development. Diffusion-weighted MRI (DW-MRI) is radiation free and requires no intravenous contrast media, and hence is more suitable for population groups that are vulnerable to ionizing radiation and/or impaired renal functions. This meta-analysis was conducted to investigate whether whole-body DW-MRI is a viable means in differentiating bone malignancy. Medline and Embase databases were searched from their inception to May 2015 without language restriction for studies evaluating DW-MRI for detection of bone lesions. Methodological quality was assessed by the quality assessment of diagnostic studies (QUADAS-2) instrument. Sensitivities, specificities, diagnostic odds ratio (DOR), and areas under the curve (AUC) were used as measures of the diagnostic accuracy. We combined the effects by using the random-effects mode. Potential threshold effects and publication bias were investigated. We included data from 32 studies with 1507 patients. The pooled sensitivity, specificity, and AUC were 0.95 (95% CI, 0.90–0.97), 0.92 (95% CI, 0.88–0.95), and 0.98 on a per-patient basis, and they were 0.91 (95% CI, 0.87–0.94), 0.94 (95% CI, 0.90–0.96), and 0.97 on a per-lesion basis. In subgroup analysis, there is no statistical significance found in the sensitivity and specificity of using DWI only and DWI combined with other morphological or functional imaging sequence in both basis (P > 0.05). A b value of 750 to 1000 s/mm2 enables higher AUC and DOR for whole-body imaging purpose when compared with other values in both basis either (P < 0.01). The ROC space did not show a curvilinear trend of points and a threshold effect was not observed. According to the Deek's plots, there was no publication bias on

  1. Diffusion weighted imaging for the differential diagnosis of benign vs. malignant ovarian neoplasms

    PubMed Central

    MENG, XIANG-FU; ZHU, SHI-CAI; SUN, SHAO-JUAN; GUO, JI-CAI; WANG, XUE

    2016-01-01

    In order to assess the diagnostic accuracy of diffusion weighted imaging (DWI) in differentiating between benign and malignant ovarian neoplasms, a systemic meta-analysis was conducted. Relevant studies were retrieved from scientific literature databases, including the PubMed, Wiley, EBSCO, Ovid, Web of Science, Wanfang, China National Knowledge Infrastructure and VIP databases. Following a multi-step screening and study selection process, the relevant data was extracted for use in the present study. Statistical analyses were performed using Meta-disc software version 1.4 and STATA statistical software version 12.0. A total of 285 articles were retrieved from the database searches. Following a careful screening process, 10 case-control studies were selected for the present meta-analysis. The 10 studies investigated the efficacy of DWI in diagnosing ovarian neoplasms, and included a combined total of 1,159 subjects, of which 559 patients had malignant lesions and 600 had benign lesions. The results showed that the pooled sensitivity, pooled specificity, pooled positive likelihood ratio, pooled negative likelihood ratio, pooled diagnostic odds ratio (DOR) and area under the curve of the summary receiver operating characteristics curve of DWI for differentiating between benign and malignant ovarian neoplasms were 0.93, 0.89, 7.58, 0.10, 85.33 and 0.95, respectively. A subgroup analysis based on ethnicity revealed no significant difference between Asians and Caucasians. Another subgroup analysis by magnetic resonance imaging (MRI) type showed that the DORs for GE Healthcare Life Sciences and Siemens AG machines were 100.76 [95% confidence interval (CI), 65.28–155.53] and 30.85 (95% CI, 10.40–91.53), respectively; this indicates that the diagnostic efficiency of the GE Healthcare Life Sciences MRI is superior compared with the Siemens AG MRI. The DWI demonstrated an excellent diagnostic performance in discriminating between benign and malignant ovarian neoplasms

  2. Complete Separation of Intracellular and Extracellular Information in NMR Spectra of Perfused Cells by Diffusion-Weighted Spectroscopy

    NASA Astrophysics Data System (ADS)

    van Zijl, Peter C. M.; Moonen, Chrit T. W.; Faustino, Patrick; Pekar, James; Kaplan, Ofer; Cohen, Jack S.

    1991-04-01

    A method is outlined that completely separates intracellular and extracellular information in NMR spectra of perfused cells. The technique uses diffusion weighting to exploit differences in motional properties between intra- and extracellular constituents. This allows monitoring of intracellular metabolism, and of transport of small drugs and nutrients through the cell membrane, under controlled physiological conditions. As a first example, proton spectra of drug-resistant MCF-7 human breast cancer cells are studied, and uptake of phenylalanine is monitored.

  3. A Framework for Linear and Non-Linear Registration of Diffusion-Weighted MRIs Using Angular Interpolation

    PubMed Central

    Duarte-Carvajalino, Julio M.; Sapiro, Guillermo; Harel, Noam; Lenglet, Christophe

    2013-01-01

    Registration of diffusion-weighted magnetic resonance images (DW-MRIs) is a key step for population studies, or construction of brain atlases, among other important tasks. Given the high dimensionality of the data, registration is usually performed by relying on scalar representative images, such as the fractional anisotropy (FA) and non-diffusion-weighted (b0) images, thereby ignoring much of the directional information conveyed by DW-MR datasets itself. Alternatively, model-based registration algorithms have been proposed to exploit information on the preferred fiber orientation(s) at each voxel. Models such as the diffusion tensor or orientation distribution function (ODF) have been used for this purpose. Tensor-based registration methods rely on a model that does not completely capture the information contained in DW-MRIs, and largely depends on the accurate estimation of tensors. ODF-based approaches are more recent and computationally challenging, but also better describe complex fiber configurations thereby potentially improving the accuracy of DW-MRI registration. A new algorithm based on angular interpolation of the diffusion-weighted volumes was proposed for affine registration, and does not rely on any specific local diffusion model. In this work, we first extensively compare the performance of registration algorithms based on (i) angular interpolation, (ii) non-diffusion-weighted scalar volume (b0), and (iii) diffusion tensor image (DTI). Moreover, we generalize the concept of angular interpolation (AI) to non-linear image registration, and implement it in the FMRIB Software Library (FSL). We demonstrate that AI registration of DW-MRIs is a powerful alternative to volume and tensor-based approaches. In particular, we show that AI improves the registration accuracy in many cases over existing state-of-the-art algorithms, while providing registered raw DW-MRI data, which can be used for any subsequent analysis. PMID:23596381

  4. Propeller aeroacoustic methodologies

    NASA Technical Reports Server (NTRS)

    Korkan, K. D.; Gregorek, G. M.

    1980-01-01

    The aspects related to propeller performance by means of a review of propeller methodologies are addressed. Preliminary wind tunnel propeller performance data are presented and the predominent limitations of existing propeller performance methodologies are discussed. Airfoil developments appropriate for propeller applications are also reviewed.

  5. Diffusional anisotropy of the human brain assessed with diffusion-weighted MR: Relation with normal brain development and aging

    SciTech Connect

    Nomura, Toshiyuki; Sakuma, Hajime; Takeda, Kan; Tagami, Tomoyasu; Okuda, Yasuyuki; Nakagawa, Tsuyoshi )

    1994-02-01

    To analyze diffusional anisotropy in frontal and occipital white matter of human brain quantitatively as a function of age by using diffusion-weighted MR imaging. Ten neonates (<1 month), 13 infants (1-10 months), 9 children (1-11 years), and 16 adults (20-79 years) were examined. After taking axial spin-echo images of the brain, diffusion-sensitive gradients were added parallel or perpendicular to the orientation of nerve fibers. The apparent diffusion coefficient parallel to the nerve fibers (0) and that perpendicular to the fibers (90) were computed. The anisotropic ratio (90/0) was calculated as a function of age. Anisotropic ratios of frontal white matter were significantly larger in neonates as compared with infants, children, or adults. The ratios showed rapid decrease until 6 months and thereafter were identical in all subjects. In the occipital lobe, the ratios were also greater in neonates, but the differences from other age groups were not so prominent as in the frontal lobe. Comparing anisotropic ratios between frontal and occipital lobes, a significant difference was observed only in neonates. Diffusion-weighted images demonstrated that the myelination process starts earlier in the occipital lobe than in the frontal lobe. The changes of diffusional anisotropy in white matter are completed within 6 months after birth. Diffusion-weighted imaging provides earlier detection of brain myelination compared with the conventional T1- and T2-weighted images. 18 refs., 6 figs., 1 tab.

  6. Variable pitch propeller

    NASA Technical Reports Server (NTRS)

    Pistolesi, Enrico

    1923-01-01

    The advantages of variable pitch propellers over constant pitch propellers is presented along with different methods of varying the pitch. The technique of varying the shape of the propeller is presented as the most efficient one.

  7. Evaluation of Psoas Major and Quadratus Lumborum Recruitment Using Diffusion-Weighted Imaging Before and After 5 Trunk Exercises.

    PubMed

    Imai, Atsushi; Okubo, Yu; Kaneoka, Koji

    2017-02-01

    Study Design Controlled laboratory study, with a pretest-posttest design. Background Diffusion-weighted imaging is a noninvasive magnetic resonance imaging technique that can be used to assess the recruitment of the psoas major (PM) and quadratus lumborum (QL). The recruitment of these muscles during trunk exercises has not been evaluated. Objective To evaluate the diffusion of water movement in several trunk muscles using diffusion-weighted imaging before and after specific trunk exercises and thereby to understand the level of recruitment of each muscle during each exercise. Methods Nine healthy male participants performed the right side bridge, knee raise, and 3 front bridges, including the hand-knee, elbow-knee, and elbow-toe bridges. Diffusion-weighted imaging was performed before and after each exercise. After scanning, the apparent diffusion coefficient (ADC) map was constructed, and ADC values of the rectus abdominis, lateral abdominal muscles, QL, PM, and back muscles were calculated. Results The right PM following the elbow-toe bridge demonstrated the largest increase in ADC values, a change significantly greater than that demonstrated by the hand-knee bridge (P<.001) and side bridge (P = .002) exercises. The ADC change in the right QL following the side bridge exercise was significantly larger than that of other exercises (P<.008). Conclusion Of the 5 exercises investigated, the elbow-toe bridge and side bridge exercises elicit the greatest recruitment of the PM and QL, respectively. J Orthop Sports Phys Ther 2017;47(2):108-114. Epub 5 Nov 2016. doi:10.2519/jospt.2017.6730.

  8. Distinction Between Recurrent Glioma and Radiation Injury Using Magnetic Resonance Spectroscopy in Combination With Diffusion-Weighted Imaging

    SciTech Connect

    Zeng, Q.-S. . E-mail: nanwushan@yahoo.com; Li, C.-F.; Liu Hong; Zhen, J.-H.; Feng, D.-C.

    2007-05-01

    Purpose: The aim of this study was to explore the diagnostic effectiveness of magnetic resonance (MR) spectroscopy with diffusion-weighted imaging on the evaluation of the recurrent contrast-enhancing areas at the site of treated gliomas. Methods and Materials: In 55 patients who had new contrast-enhancing lesions in the vicinity of the previously resected and irradiated high-grade gliomas, two-dimensional MR spectroscopy and diffusion-weighted imaging were performed. Spectral data for N-acetylaspartate (NAA), choline (Cho), creatine (Cr), lipid (Lip), and lactate (Lac) were analyzed in conjunction with the apparent diffusion coefficient (ADC) in all patients. Diagnosis of these lesions was assigned by means of follow-up or histopathology. Results: The Cho/NAA and Cho/Cr ratios were significantly higher in recurrent tumor than in regions of radiation injury (p < 0.01). The ADC value and ADC ratios (ADC of contrast-enhancing lesion to matching structure in the contralateral hemisphere) were significantly higher in radiation injury regions than in recurrent tumor (p < 0.01). With MR spectroscopic data, two variables (Cho/NAA and Cho/Cr ratios) were shown to differentiate recurrent glioma from radiation injury, and 85.5% of total subjects were correctly classified into groups. However, with discriminant analysis of MR spectroscopy imaging plus diffusion-weighted imaging, three variables (Cho/NAA, Cho/Cr, and ADC ratio) were identified and 96.4% of total subjects were correctly classified. There was a significant difference between the diagnostic accuracy of the two discriminant analyses (Chi-square = 3.96, p = 0.046). Conclusion: Using discriminant analysis, this study found that MR spectroscopy in combination with ADC ratio, rather than ADC value, can improve the ability to differentiate recurrent glioma and radiation injury.

  9. Intravoxel incoherent motion diffusion-weighted imaging for monitoring chemotherapeutic efficacy in gastric cancer

    PubMed Central

    Song, Xiao-Li; Kang, Heoung Keun; Jeong, Gwang Woo; Ahn, Kyu Youn; Jeong, Yong Yeon; Kang, Yang Joon; Cho, Hye Jung; Moon, Chung Man

    2016-01-01

    AIM: To assess intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) for monitoring early efficacy of chemotherapy in a human gastric cancer mouse model. METHODS: IVIM-DWI was performed with 12 b-values (0-800 s/mm2) in 25 human gastric cancer-bearing nude mice at baseline (day 0), and then they were randomly divided into control and 1-, 3-, 5- and 7-d treatment groups (n = 5 per group). The control group underwent longitudinal MRI scans at days 1, 3, 5 and 7, and the treatment groups underwent subsequent MRI scans after a specified 5-fluorouracil/calcium folinate treatment. Together with tumor volumes (TV), the apparent diffusion coefficient (ADC) and IVIM parameters [true water molecular diffusion coefficient (D), perfusion fraction (f) and pseudo-related diffusion coefficient (D*)] were measured. The differences in those parameters from baseline to each measurement (ΔTV%, ΔADC%, ΔD%, Δf% and ΔD*%) were calculated. After image acquisition, tumor necrosis, microvessel density (MVD) and cellular apoptosis were evaluated by hematoxylin-eosin (HE), CD31 and terminal-deoxynucleotidyl transferase mediated nick end labeling (TUNEL) staining respectively, to confirm the imaging findings. Mann-Whitney test and Spearman's correlation coefficient analysis were performed. RESULTS: The observed relative volume increase (ΔTV%) in the treatment group were significantly smaller than those in the control group at day 5 (ΔTVtreatment% = 19.63% ± 3.01% and ΔTVcontrol% = 83.60% ± 14.87%, P = 0.008) and day 7 (ΔTVtreatment% = 29.07% ± 10.01% and ΔTVcontrol% = 177.06% ± 63.00%, P = 0.008). The difference in ΔTV% between the treatment and the control groups was not significant at days 1 and 3 after a short duration of treatment. Increases in ADC in the treatment group (ΔADC%treatment, median, 30.10% ± 18.32%, 36.11% ± 21.82%, 45.22% ± 24.36%) were significantly higher compared with the control group (ΔADC%control, median, 4.98% ± 3.39%, 6.26% ± 3

  10. Diffusion-Weighted Imaging with Two Different b-Values in Detection of Solid Focal Liver Lesions.

    PubMed

    Yang, Da-wei; Wang, Ke-yang; Yao, Xun; Ye, Hui-yi; Jiang, Tao; Liu, Yuan; Gao, Jia-yin; Chen, Min; Zhou, Cheng; Yang, Zheng-han

    2016-01-01

    One hundred and eighty-two consecutive patients with suspected liver disease were recruited to receive diffusion-weighted imaging (DWI) with two different b-values, in comparison with T2-weighted imaging (T2WI). The detection rate of three MR sequences in solid focal liver lesions (FLLs) and subgroup analyses were performed. Our prospective study found that DWI600 was equivalent to DWI100 and T2WI for the detection of solid FLLs overall but was significantly more accurate in the detection of malignant solid FLLs and lesions larger than 10 mm.

  11. Role of diffusion weighted imaging in diagnosis of post transplant lymphoproliferative disorders: Case reports and review of literature

    PubMed Central

    Singh, A.; Das, C. J.; Gupta, A. K.; Bagchi, S.

    2016-01-01

    Post transplant lymphoproliferative disorder include a spectrum of conditions occurring in immunosuppressed post transplant recipients, lymphoma being the most ominous. 18F-fludeoxyglucose positron emission tomography with computed tomography CT) is the current imaging gold standard for lymphoma imaging as it allows both morphological and functional assessment. CT and/or conventional magnetic resonance imaging (MRI) are used for morphological evaluation in transplant recipients. Integrating diffusion weighted imaging with apparent diffusion coefficient analysis in MRI protocol enhances its sensitivity and may prove invaluable in response assessment in transplant recipients. PMID:27194838

  12. Detection of Low-Signal Pulvinar Areas Using Diffusion-Weighted Imaging in Patients with Dementia Experiencing Visual Hallucinations

    PubMed Central

    Sugiura, Mayuko; Satoh, Masayuki; Tabei, Ken-ichi; Saito, Tomoki; Mori, Mutsuki; Abe, Makiko; Kida, Hirotaka; Maeda, Masayuki; Sakuma, Hajime; Tomimoto, Hidekazu

    2016-01-01

    Background Little research has been conducted regarding the role of pulvinar nuclei in the pathogenesis of visual hallucinations due to the difficulty of assessing abnormalities in this region using conventional magnetic resonance imaging (MRI). The present study aimed to retrospectively investigate the relative abilities of diffusion-weighted imaging (DWI), fluid-attenuated inversion recovery (FLAIR), and susceptibility-weighted imaging (SWI) to visualize the pulvinar and to ascertain the relationship between pulvinar visualization and visual hallucinations. Methods A retrospective analysis of 3T MRIs from 73 patients (31 males, 42 females; mean age 73.5 ± 12.7 years) of the Memory Clinic of Mie University Hospital was conducted. Correlations between pulvinar visualization and the following were analyzed: age, sex, education, hypertension, hyperlipidemia, diabetes mellitus, Mini-Mental State Examination score, Evans index, and visual hallucinations. Results DWI detected low-signal pulvinar areas in approximately half of the patients (52.1%). Participants with pulvinar visualization were significantly older, and the pulvinar was more frequently visualized in patients who had experienced visual hallucinations compared to those who had not. No significant association was observed between whole brain atrophy and pulvinar visualization. Conclusions The results of the present study indicate that diffusion-weighted 3T MRI is the most suitable method for the detection of pulvinar nuclei in patients with dementia experiencing visual hallucinations. PMID:27790244

  13. Aircraft propeller control

    NASA Technical Reports Server (NTRS)

    Day, Stanley G. (Inventor)

    1990-01-01

    In the invention, the speeds of both propellers in a counterrotating aircraft propeller pair are measured. Each speed is compared, using a feedback loop, with a demanded speed and, if actual speed does not equal demanded speed for either propeller, pitch of the proper propeller is changed in order to attain the demanded speed. A proportional/integral controller is used in the feedback loop. Further, phase of the propellers is measured and, if the phase does not equal a demanded phase, the speed of one propeller is changed, by changing pitch, until the proper phase is attained.

  14. Investigations on the efficiency of cardiac-gated methods for the acquisition of diffusion-weighted images

    NASA Astrophysics Data System (ADS)

    Nunes, Rita G.; Jezzard, Peter; Clare, Stuart

    2005-11-01

    Diffusion-weighted images are inherently very sensitive to motion. Pulsatile motion of the brain can give rise to artifactual signal attenuation leading to over-estimation of the apparent diffusion coefficients, even with snapshot echo planar imaging. Such miscalculations can result in erroneous estimates of the principal diffusion directions. Cardiac gating can be performed to confine acquisition to the quiet portion of the cycle. Although effective, this approach leads to significantly longer acquisition times. On the other hand, it has been demonstrated that pulsatile motion is not significant in regions above the corpus callosum. To reduce acquisition times and improve the efficiency of whole brain cardiac-gated acquisitions, the upper slices of the brain can be imaged during systole, reserving diastole for those slices most affected by pulsatile motion. The merits and disadvantages of this optimized approach are investigated here, in comparison to a more standard gating method and to the non-gated approach.

  15. Whole-body diffusion-weighted magnetic resonance imaging: current evidence in oncology and potential role in colorectal cancer staging.

    PubMed

    Lambregts, Doenja M J; Maas, Monique; Cappendijk, Vincent C; Prompers, Leonne M; Mottaghy, Felix M; Beets, Geerard L; Beets-Tan, Regina G H

    2011-09-01

    Tumour staging in cancer patients generally entails a multimodality imaging approach. Whole-body (WB) imaging techniques may, however, be more time- and cost-effective than a multimodality approach. 2-fluorine-18-fluoro-2-deoxy-D-glucose positron emission tomography (18FDG-PET), computed tomography (CT) and hybrid positron emission tomography and computed tomography (PET/CT) are the most established WB modalities, although new techniques, amongst which diffusion-weighted magnetic resonance imaging (DWI), are emerging. This review aims to evaluate the current evidence for WB-DWI in oncology, to discuss its potential for the WB staging of (colo)rectal cancer and to relate it to the established WB techniques.

  16. A case of mass-forming splenic tuberculosis: MRI findings with emphasis of diffusion-weighted imaging characteristics.

    PubMed

    Lim, Jihe; Yu, Jeong-Sik; Hong, Soon Won; Chung, Jae-Joon; Kim, Joo Hee; Kim, Ki Whang

    2011-03-01

    Tuberculosis remains one of the most prevalent and fatal infectious diseases in spite of considerable improvements in medical science. The diagnosis and treatment of extrapulmonary tuberculosis involving the abdomen is still complicated owing to vague or non-specific clinical features. Although rare, isolated splenic involvement is one of the important manifestations of extrapulmonary tuberculosis, and imaging suspicion of the disease is essential. We report a case of surgically confirmed mass-forming splenic tuberculosis showing a layered pattern consisting of caseous necrosis with profound restriction of water molecules surrounded by an irregular rind of granulation tissue with less diffusion restriction on diffusion-weighted magnetic resonance imaging (DWI). In the differential diagnosis of neoplastic or non-neoplastic mass-forming lesions involving the spleen, this unique DWI feature could be helpful in characterizing splenic tuberculosis. The patient has been in clinically disease free status for nearly 20 months after splenectomy.

  17. The effect of a performance-based intra-procedural checklist on a simulated emergency laparoscopic task in novice surgeons.

    PubMed

    El Boghdady, Michael; Tang, Benjie; Alijani, Afshin

    2016-09-01

    Surgical checklists are in use as means to reduce errors. Checklists are infrequently applied during emergency situations in surgery. We aimed to study the effect of a simple self-administered performance-based checklist on the laparoscopic task when applied during an emergency-simulated scenario. The aviation checklist for unexpected situations is commonly used for simulated training of pilots to handle emergency during flights. This checklist was adopted for use as a standardised-performance-based checklist during emergency surgical tasks. Thirty consented laparoscopic novices were exposed unexpectedly to a bleeding vessel in a laparoscopic virtual reality simulator as an emergency scenario. The task consisted of using laparoscopic clips to achieve haemostasis. Subjects were randomly allocated into two equal groups; those using the checklist that was applied once every 20 s (checklist group) and those without (control group). The checklist group performed significantly better in 5 out of 7 technical factors when compared to the control group: right instrument path length (m), median (IQR) 1.44 [1.22] versus 2.06 [1.70] (p = 0.029), right instrument angular path (degree) 312.10 (269.44 versus 541.80 [455.16] (p = 0.014), left instrument path length (m) 1.20 [0.60] versus 2.08 [2.02] (p = 0.004), and left instrument angular path (degree) 277.62 [132.11] versus 385.88 [428.42] (p = 0.017). The checklist group committed significantly fewer number of errors in the application of haemostatic clips, 3 versus 28 (p = 0.006). Although statistically not significant, total blood loss (lit) decreased in the checklist group from 0.83 [1.23] to 0.78 [0.28] (p = 0.724) and total time (sec) from 186.51 [145.69] to 125.14 [101.46] (p = 0.165). The performance-based intra-procedural checklist significantly enhanced the surgical task performance of novices in an emergency-simulated scenario.

  18. Relationship between pretreatment FDG-PET and diffusion-weighted MRI biomarkers in diffuse large B-cell lymphoma

    PubMed Central

    de Jong, Antoinette; Kwee, Thomas C; de Klerk, John MH; Adam, Judit A; de Keizer, Bart; Fijnheer, Rob; Kersten, Marie José; Ludwig, Inge; Jauw, Yvonne WS; Zijlstra, Josée M; den Bos, Indra C Pieters - Van; Stoker, Jaap; Hoekstra, Otto S; Nievelstein, Rutger AJ

    2014-01-01

    The purpose of this study was to determine the correlation between the 18F-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) standardized uptake value (SUV) and the diffusion-weighted magnetic resonance imaging (MRI) apparent diffusion coefficient (ADC) in newly diagnosed diffuse large B-cell lymphoma (DLBCL). Pretreatment FDG-PET and diffusion-weighted MRI of 21 patients with histologically proven DLBCL were prospectively analyzed. In each patient, maximum, mean and peak standardized uptake value (SUV) was measured in the lesion with visually highest FDG uptake and in the largest lesion. Mean ADC (ADCmean, calculated with b-values of 0 and 1000 s/mm2) was measured in the same lesions. Correlations between FDG-PET metrics (SUVmax, SUVmean, SUVpeak) and ADCmean were assessed using Pearson’s correlation coefficients. In the lesions with visually highest FDG uptake, no significant correlations were found between the SUVmax, SUVmean, SUVpeak and the ADCmean (P=0.498, P=0.609 and P=0.595, respectively). In the largest lesions, there were no significant correlations either between the SUVmax, SUVmean, SUVpeak and the ADCmean (P=0.992, P=0.843 and P=0.894, respectively). The results of this study indicate that the glycolytic rate as measured by FDG-PET and changes in water compartmentalization and water diffusion as measured by the ADC are independent biological phenomena in newly diagnosed DLBCL. Further studies are warranted to assess the complementary roles of these different imaging biomarkers in the evaluation and follow-up of DLBCL. PMID:24795837

  19. Spatially constrained incoherent motion method improves diffusion-weighted MRI signal decay analysis in the liver and spleen

    PubMed Central

    Taimouri, Vahid; Afacan, Onur; Perez-Rossello, Jeannette M.; Callahan, Michael J.; Mulkern, Robert V.; Warfield, Simon K.; Freiman, Moti

    2015-01-01

    Purpose: To evaluate the effect of the spatially constrained incoherent motion (SCIM) method on improving the precision and robustness of fast and slow diffusion parameter estimates from diffusion-weighted MRI in liver and spleen in comparison to the independent voxel-wise intravoxel incoherent motion (IVIM) model. Methods: We collected diffusion-weighted MRI (DW-MRI) data of 29 subjects (5 healthy subjects and 24 patients with Crohn’s disease in the ileum). We evaluated parameters estimates’ robustness against different combinations of b-values (i.e., 4 b-values and 7 b-values) by comparing the variance of the estimates obtained with the SCIM and the independent voxel-wise IVIM model. We also evaluated the improvement in the precision of parameter estimates by comparing the coefficient of variation (CV) of the SCIM parameter estimates to that of the IVIM. Results: The SCIM method was more robust compared to IVIM (up to 70% in liver and spleen) for different combinations of b-values. Also, the CV values of the parameter estimations using the SCIM method were significantly lower compared to repeated acquisition and signal averaging estimated using IVIM, especially for the fast diffusion parameter in liver (CVIV IM = 46.61 ± 11.22, CVSCIM = 16.85 ± 2.160, p < 0.001) and spleen (CVIV IM = 95.15 ± 19.82, CVSCIM = 52.55 ± 1.91, p < 0.001). Conclusions: The SCIM method characterizes fast and slow diffusion more precisely compared to the independent voxel-wise IVIM model fitting in the liver and spleen. PMID:25832079

  20. Efficient and precise calculation of the b-matrix elements in diffusion-weighted imaging pulse sequences

    NASA Astrophysics Data System (ADS)

    Zubkov, Mikhail; Stait-Gardner, Timothy; Price, William S.

    2014-06-01

    Precise NMR diffusion measurements require detailed knowledge of the cumulative dephasing effect caused by the numerous gradient pulses present in most NMR pulse sequences. This effect, which ultimately manifests itself as the diffusion-related NMR signal attenuation, is usually described by the b-value or the b-matrix in the case of multidirectional diffusion weighting, the latter being common in diffusion-weighted NMR imaging. Neglecting some of the gradient pulses introduces an error in the calculated diffusion coefficient reaching in some cases 100% of the expected value. Therefore, ensuring the b-matrix calculation includes all the known gradient pulses leads to significant error reduction. Calculation of the b-matrix for simple gradient waveforms is rather straightforward, yet it grows cumbersome when complexly shaped and/or numerous gradient pulses are introduced. Making three broad assumptions about the gradient pulse arrangement in a sequence results in an efficient framework for calculation of b-matrices as well providing some insight into optimal gradient pulse placement. The framework allows accounting for the diffusion-sensitising effect of complexly shaped gradient waveforms with modest computational time and power. This is achieved by using the b-matrix elements of the simple unmodified pulse sequence and minimising the integration of the complexly shaped gradient waveform in the modified sequence. Such re-evaluation of the b-matrix elements retains all the analytical relevance of the straightforward approach, yet at least halves the amount of symbolic integration required. The application of the framework is demonstrated with the evaluation of the expression describing the diffusion-sensitizing effect, caused by different bipolar gradient pulse modules.

  1. Efficient and precise calculation of the b-matrix elements in diffusion-weighted imaging pulse sequences.

    PubMed

    Zubkov, Mikhail; Stait-Gardner, Timothy; Price, William S

    2014-06-01

    Precise NMR diffusion measurements require detailed knowledge of the cumulative dephasing effect caused by the numerous gradient pulses present in most NMR pulse sequences. This effect, which ultimately manifests itself as the diffusion-related NMR signal attenuation, is usually described by the b-value or the b-matrix in the case of multidirectional diffusion weighting, the latter being common in diffusion-weighted NMR imaging. Neglecting some of the gradient pulses introduces an error in the calculated diffusion coefficient reaching in some cases 100% of the expected value. Therefore, ensuring the b-matrix calculation includes all the known gradient pulses leads to significant error reduction. Calculation of the b-matrix for simple gradient waveforms is rather straightforward, yet it grows cumbersome when complexly shaped and/or numerous gradient pulses are introduced. Making three broad assumptions about the gradient pulse arrangement in a sequence results in an efficient framework for calculation of b-matrices as well providing some insight into optimal gradient pulse placement. The framework allows accounting for the diffusion-sensitising effect of complexly shaped gradient waveforms with modest computational time and power. This is achieved by using the b-matrix elements of the simple unmodified pulse sequence and minimising the integration of the complexly shaped gradient waveform in the modified sequence. Such re-evaluation of the b-matrix elements retains all the analytical relevance of the straightforward approach, yet at least halves the amount of symbolic integration required. The application of the framework is demonstrated with the evaluation of the expression describing the diffusion-sensitizing effect, caused by different bipolar gradient pulse modules.

  2. Diffusion-Weighted Imaging with Dual-Echo Echo-Planar Imaging for Better Sensitivity to Acute Stroke

    PubMed Central

    Holdsworth, S.J.; Yeom, K.W.; Antonucci, M.U.; Andre, J.B.; Rosenberg, J.; Aksoy, M.; Straka, M.; Fischbein, N.J.; Bammer, R.; Moseley, M.E.; Zaharchuk, G.; Skare, S.

    2015-01-01

    BACKGROUND AND PURPOSE Parallel imaging facilitates the acquisition of echo-planar images with a reduced TE, enabling the incorporation of an additional image at a later TE. Here we investigated the use of a parallel imaging–enhanced dual-echo EPI sequence to improve lesion conspicuity in diffusion-weighted imaging. MATERIALS AND METHODS Parallel imaging–enhanced dual-echo DWI data were acquired in 50 consecutive patients suspected of stroke at 1.5T. The dual-echo acquisition included 2 EPI for 1 diffusion-preparation period (echo 1 [TE = 48 ms] and echo 2 [TE = 105 ms]). Three neuroradiologists independently reviewed the 2 echoes by using the routine DWI of our institution as a reference. Images were graded on lesion conspicuity, diagnostic confidence, and image quality. The apparent diffusion coefficient map from echo 1 was used to validate the presence of acute infarction. Relaxivity maps calculated from the 2 echoes were evaluated for potential complementary information. RESULTS Echo 1 and 2 DWIs were rated as better than the reference DWI. While echo 1 had better image quality overall, echo 2 was unanimously favored over both echo 1 and the reference DWI for its high sensitivity in detecting acute infarcts. CONCLUSIONS Parallel imaging–enhanced dual-echo diffusion-weighted EPI is a useful method for evaluating lesions with reduced diffusivity. The long TE of echo 2 produced DWIs that exhibited superior lesion conspicuity compared with images acquired at a shorter TE. Echo 1 provided higher SNR ADC maps for specificity to acute infarction. The relaxivity maps may serve to complement information regarding blood products and mineralization. PMID:24763417

  3. Aluminum Hydride Propellant Shelflife

    DTIC Science & Technology

    1974-11-01

    PODE propellants, namely a model PCDE propellant processed at LPC using di-n-butylphthalate -: a chemically inert plasticizer, and a ballistically...prepolymer. The propellant processed at LPC used PCDE prepared by the Shell Development Company, while the Aerojet propellant was processed with PCDE...failures after 180 days storage at 40 and 60 0 C, nor was there any noticeable deformation of the elliptical tubes to suggest internal gas pressure

  4. Settled Cryogenic Propellant Transfer

    NASA Technical Reports Server (NTRS)

    Kutter, Bernard F.; Zegler, Frank; Sakla, Steve; Wall, John; Hopkins, Josh; Saks, Greg; Duffey, Jack; Chato, David J.

    2006-01-01

    Cryogenic propellant transfer can significantly benefit NASA s space exploration initiative. LMSSC parametric studies indicate that "Topping off" the Earth Departure Stage (EDS) in LEO with approx.20 mT of additional propellant using cryogenic propellant transfer increases the lunar delivered payload by 5 mT. Filling the EDS to capacity in LEO with 78 mT of propellants increases the delivered payload by 20 mT. Cryogenic propellant transfer is directly extensible to Mars exploration in that it provides propellant for the Mars Earth Departure stage and in-situ propellant utilization at Mars. To enable the significant performance increase provided by cryogenic propellant transfer, the reliability and robustness of the transfer process must be guaranteed. By utilizing low vehicle acceleration during the cryogenic transfer the operation is significantly simplified and enables the maximum use of existing, reliable, mature upper stage cryogenic-fluid-management (CFM) techniques. Due to settling, large-scale propellant transfer becomes an engineering effort, and not the technology development endeavor required with zero-gravity propellant transfer. The following key CFM technologies are all currently implemented by settling on both the Centaur and Delta IV upper stages: propellant acquisition, hardware chilldown, pressure control, and mass gauging. The key remaining technology, autonomous rendezvous and docking, is already in use by the Russians, and must be perfected for NASA whether the use of propellant transfer is utilized or not.

  5. Therapeutic effect of nerve growth factor on cerebral infarction in dogs using the hemisphere anomalous volume ratio of diffusion-weighted magnetic resonance imaging.

    PubMed

    Wang, Yong; Zhang, Hui; Wang, Zhe; Geng, Zuojun; Liu, Huaijun; Yang, Haiqing; Song, Peng; Liu, Qing

    2012-08-25

    A model of focal cerebral ischemic infarction was established in dogs through middle cerebral artery occlusion of the right side. Thirty minutes after occlusion, models were injected with nerve growth factor adjacent to the infarct locus. The therapeutic effect of nerve growth factor against cerebral infarction was assessed using the hemisphere anomalous volume ratio, a quantitative index of diffusion-weighted MRI. At 6 hours, 24 hours, 7 days and 3 months after modeling, the hemisphere anomalous volume ratio was significantly reduced after treatment with nerve growth factor. Hematoxylin-eosin staining, immunohistochemistry, electron microscopy and neurological function scores showed that infarct defects were slightly reduced and neurological function significantly improved after nerve growth factor treatment. This result was consistent with diffusion-weighted MRI measurements. Experimental findings indicate that nerve growth factor can protect against cerebral infarction, and that the hemisphere anomalous volume ratio of diffusion-weighted MRI can be used to evaluate the therapeutic effect.

  6. Therapeutic effect of nerve growth factor on cerebral infarction in dogs using the hemisphere anomalous volume ratio of diffusion-weighted magnetic resonance imaging★

    PubMed Central

    Wang, Yong; Zhang, Hui; Wang, Zhe; Geng, Zuojun; Liu, Huaijun; Yang, Haiqing; Song, Peng; Liu, Qing

    2012-01-01

    A model of focal cerebral ischemic infarction was established in dogs through middle cerebral artery occlusion of the right side. Thirty minutes after occlusion, models were injected with nerve growth factor adjacent to the infarct locus. The therapeutic effect of nerve growth factor against cerebral infarction was assessed using the hemisphere anomalous volume ratio, a quantitative index of diffusion-weighted MRI. At 6 hours, 24 hours, 7 days and 3 months after modeling, the hemisphere anomalous volume ratio was significantly reduced after treatment with nerve growth factor. Hematoxylin-eosin staining, immunohistochemistry, electron microscopy and neurological function scores showed that infarct defects were slightly reduced and neurological function significantly improved after nerve growth factor treatment. This result was consistent with diffusion-weighted MRI measurements. Experimental findings indicate that nerve growth factor can protect against cerebral infarction, and that the hemisphere anomalous volume ratio of diffusion-weighted MRI can be used to evaluate the therapeutic effect. PMID:25624813

  7. Propeller/wing interaction

    NASA Technical Reports Server (NTRS)

    Witkowski, David P.; Johnston, Robert T.; Sullivan, John P.

    1989-01-01

    The present experimental investigation of the steady-state and unsteady-state effects due to the interaction between a tractor propeller's wake and a wing employs, in the steady case, wind tunnel measurements at low subsonic speed; results are obtained which demonstrate wing performance response to variations in configuration geometry. Other steady-state results involve the propeller-hub lift and side-force due to the wing's influence on the propeller. The unsteady effects of interaction were studied through flow visualization of propeller-tip vortex distortion over a wing, again using a tractor-propeller configuration.

  8. Counter-propeller

    NASA Technical Reports Server (NTRS)

    De Caria, Ugo

    1931-01-01

    A counter-propeller is a fixed propeller smaller than the main propeller, mounted either fore or aft of the latter and performing the function of changing the direction of motion of the fluid filaments, which naturally tend to adopt a helicoidal form. This paper presents a consideration of the real advantage of counter-propellers on aircraft and the best shape of the blades. First, the author determines the possible energy absorption by the tangential increments. This process will be facilitated by the examination of the polygons of the relative velocities fore and aft of the generic section, of radius r, of one of the blades of the propeller.

  9. Liquid propellant rockets.

    NASA Technical Reports Server (NTRS)

    Dipprey, D. F.

    1972-01-01

    A brief overview of the state of knowledge in liquid rocket technology is presented and examples are provided of instances where some fundamental principles of chemistry, fluid mechanics, and mathematics can be applied. A liquid propellant rocket classification is discussed together with rocket system performance, applications for liquid propellants, the effective exhaust velocity, aspects of simplified nozzle expansion, questions about theoretical propellant performance, the effect of chamber pressure on equilibrium performance, and the kinetic recombination in nozzles. Details of propellant combustion are examined, giving attention to propellant injection, evaporation-controlled combustion, combustion instability, and monopropellant decomposition.

  10. Solid propellant motor

    NASA Technical Reports Server (NTRS)

    Shafer, J. I.; Marsh, H. E., Jr. (Inventor)

    1978-01-01

    A case bonded end burning solid propellant rocket motor is described. A propellant with sufficiently low modulus to avoid chamber buckling on cooling from cure and sufficiently high elongation to sustain the stresses induced without cracking is used. The propellant is zone cured within the motor case at high pressures equal to or approaching the pressure at which the motor will operate during combustion. A solid propellant motor with a burning time long enough that its spacecraft would be limited to a maximum acceleration of less than 1 g is provided by one version of the case bonded end burning solid propellant motor of the invention.

  11. Tandem Air Propellers

    NASA Technical Reports Server (NTRS)

    Lesley, E.P.

    1937-01-01

    Tests of 2-blade, adjustable-pitch, counterrotating tandem model propellers, adjusted to absorb equal power at maximum efficiency, were made at Stanford University. The characteristics, for 15 degrees, 25 degrees, 35 degrees, and 45 degrees pitch settings at 0.75 R of the forward propeller and for 8 1/2%, 15% and 30% diameter spacings, were compared with those of 2-blade and 4-blade propellers of the same blade form. The tests showed that the efficiency of the tandem propellers was from 0.5% to 4% greater than that of a 4-blade propeller and, at the high pitch settings, not appreciable inferior to that of a 2-blade propeller. It was found that the rear tandem propeller should be set at a pitch angle slightly less than that of the forward propeller to realize the condition of equal power at maximum efficiency. Under this condition the total power absorbed by the tandem propellers was from 3% to 9% more than that absorbed by the 4-blade propeller and about twice that absorbed by a 2-blade propeller.

  12. Anisotropic diffusion of metabolites in peripheral nerve using diffusion weighted magnetic resonance spectroscopy at ultra-high field

    NASA Astrophysics Data System (ADS)

    Ellegood, Jacob; McKay, Ryan T.; Hanstock, Chris C.; Beaulieu, Christian

    2007-01-01

    Although the diffusivity and anisotropy of water has been investigated thoroughly in ordered axonal systems (i.e., nervous tissue), there have been very few studies on the directional dependence of diffusion of metabolites. In this study, the mean apparent diffusion coefficient (Trace/3 ADC) and fractional anisotropy (FA) values of the intracellular metabolites N-acetyl aspartate (NAA), creatine and phosphocreatine (tCr), choline (Cho), taurine (Tau), and glutamate and glutamine (Glx) were measured parallel and perpendicular to the length of excised frog sciatic nerve using a water suppressed, diffusion-weighted, spin-echo pulse sequence at 18.8 T. The degree of anisotropy (FA) of NAA (0.41 ± 0.09) was determined to be less than tCr (0.59 ± 0.07) and Cho (0.61 ± 0.11), which is consistent with previously reported human studies of white matter. In contrast, Glx diffusion was found to be almost isotropic with an FA value of 0.20 ± 0.06. The differences of FA between the metabolites is most likely due to their differing micro-environments and could be beneficial as an indicator of compartment specific changes with disease, information not readily available with water diffusion.

  13. Super-Resolution Reconstruction of Diffusion-Weighted Images using 4D Low-Rank and Total Variation

    PubMed Central

    Shi, Feng; Cheng, Jian; Wang, Li; Yap, Pew-Thian; Shen, Dinggang

    2016-01-01

    Diffusion-weighted imaging (DWI) provides invaluable information in white matter microstructure and is widely applied in neurological applications. However, DWI is largely limited by its relatively low spatial resolution. In this paper, we propose an image post-processing method, referred to as super-resolution reconstruction, to estimate a high spatial resolution DWI from the input low-resolution DWI, e.g., at a factor of 2. Instead of requiring specially designed DWI acquisition of multiple shifted or orthogonal scans, our method needs only a single DWI scan. To do that, we propose to model both the blurring and downsampling effects in the image degradation process where the low-resolution image is observed from the latent high-resolution image, and recover the latent high-resolution image with the help of two regularizations. The first regularization is 4-dimensional (4D) low-rank, proposed to gather self-similarity information from both the spatial domain and the diffusion domain of 4D DWI. The second regularization is total variation, proposed to depress noise and preserve local structures such as edges in the image recovery process. Extensive experiments were performed on 20 subjects, and results show that the proposed method is able to recover the fine details of white matter structures, and outperform other approaches such as interpolation methods, non-local means based upsampling, and total variation based upsampling. PMID:27845833

  14. Estimation of pore size in a microstructure phantom using the optimised gradient waveform diffusion weighted NMR sequence.

    PubMed

    Siow, Bernard; Drobnjak, Ivana; Chatterjee, Aritrick; Lythgoe, Mark F; Alexander, Daniel C

    2012-01-01

    There has been increasing interest in nuclear magnetic resonance (NMR) techniques that are sensitive to diffusion of molecules containing NMR visible nuclei for the estimation of microstructure parameters. A microstructure parameter of particular interest is pore radius distribution. A recent in silico study optimised the shape of the gradient waveform in diffusion weighted spin-echo experiments for estimating pore size. The study demonstrated that optimised gradient waveform (GEN) protocols improve pore radius estimates compared to optimised pulse gradient spin-echo (PGSE) protocols, particularly at shorter length scales. This study assesses the feasibility of implementing GEN protocols on a small bore 9.4 T scanner and verifies their additional sensitivity to pore radius. We implement GEN and PGSE protocols optimised for pore radii of 1, 2.5, 5, 7.5, 10 μm and constrained to maximum gradient strengths of 40, 80, 200 mT m(-1). We construct microstructure phantoms, which have a single pore radius for each phantom, using microcapillary fibres. The measured signal shows good agreement with simulated signal, strongly indicating that the GEN waveforms can be implemented on a 9.4 T system. We also demonstrate that GEN protocols provide improved sensitivity to the smaller pore radii when compared to optimised PGSE protocols, particularly at the lower gradient amplitudes investigated in this study. Our results suggest that this improved sensitivity of GEN protocols would be reflected in clinical scenarios.

  15. Applicable apparent diffusion coefficient of an orthotopic mouse model of gastric cancer by improved clinical MRI diffusion weighted imaging

    PubMed Central

    Sun, Jia; Zhang, Xiao-Peng; Li, Xiao-Ting; Tang, Lei; Cui, Yong; Zhang, Xiao-Yan; Sun, Ying-Shi

    2014-01-01

    In vivo imaging studies in animal models are hindered by variables that contribute to poor image quality and measurement reliability. As such we sought to improve the diffusion coefficient (ADC) of an orthotopic mouse model of gastric cancer in diffusion-weighted images (DWI) using alginate moulding and Ultrasonic coupling medium. BGC-823 human gastric cancer cells were subcutaneously injected into the abdomen of nude mice and 1 mm3 primary tumour was orthotopically transplanted. Alginate and coupling medium were applied to the mice and MRI (T2 and DWI) was performed for 6 weeks. Regions of interest (ROI) were drawn and liver and tumour ADC were evaluated. Using alginate moulding, the mean quality total score of DW imaging was 8.53; however, in control animals this value was 5.20 (p < 0.001). The coefficient of variation of ADC of liver in experimental and control groups were 0.071 and 0.270 (p < 0.001), respectively, suggesting this method may be helpful for DWI studies of important human diseases such as gastric cancer. PMID:25123166

  16. Bidirectional iterative parcellation of diffusion weighted imaging data: separating cortical regions connected by the arcuate fasciculus and extreme capsule.

    PubMed

    Patterson, Dianne K; Van Petten, Cyma; Beeson, Pélagie M; Rapcsak, Steven Z; Plante, Elena

    2014-11-15

    This paper introduces a Bidirectional Iterative Parcellation (BIP) procedure designed to identify the location and size of connected cortical regions (parcellations) at both ends of a white matter tract in diffusion weighted images. The procedure applies the FSL option "probabilistic tracking with classification targets" in a bidirectional and iterative manner. To assess the utility of BIP, we applied the procedure to the problem of parcellating a limited set of well-established gray matter seed regions associated with the dorsal (arcuate fasciculus/superior longitudinal fasciculus) and ventral (extreme capsule fiber system) white matter tracts in the language networks of 97 participants. These left hemisphere seed regions and the two white matter tracts, along with their right hemisphere homologues, provided an excellent test case for BIP because the resulting parcellations overlap and their connectivity via the arcuate fasciculi and extreme capsule fiber systems are well studied. The procedure yielded both confirmatory and novel findings. Specifically, BIP confirmed that each tract connects within the seed regions in unique, but expected ways. Novel findings included increasingly left-lateralized parcellations associated with the arcuate fasciculus/superior longitudinal fasciculus as a function of age and education. These results demonstrate that BIP is an easily implemented technique that successfully confirmed cortical connectivity patterns predicted in the literature, and has the potential to provide new insights regarding the architecture of the brain.

  17. Role of diffusion-weighted imaging for detecting bone marrow infiltration in skull in children with acute lymphoblastic leukemia

    PubMed Central

    Cao, Weiguo; Liang, Changhong; Gen, Yungan; Wang, Chen; Zhao, Cailei; Sun, Longwei

    2016-01-01

    PURPOSE We aimed to determine whether diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) measurement can detect skull bone marrow infiltration in newly diagnosed acute lymphoblastic leukemia (ALL) children before therapy and normalization in complete remission after treatment. METHODS Fifty-one newly diagnosed acute lymphoblastic leukemia (ALL) patients and 30 healthy age-matched subjects were included. Cranial magnetic resonance imaging (MRI) scans were reviewed, and skull marrow ADC values were compared before treatment and in complete remission after therapy. RESULTS Skull marrow infiltration, manifested with abnormal DWI signals, was present in 37 patients (72.5%) before treatment. Of these, 23 (62.2%) showed scattered signal abnormalities and 14 (37.8%) showed a uniform abnormal signal pattern. Compared with the control group, ADC was significantly decreased in patients with ALL. DWI signal intensity and ADC normalized in patients with complete remission. CONCLUSION DWI is a useful and noninvasive tool for detecting skull infiltration in ALL children before treatment and normalization at complete remission after therapy, and it is superior to conventional MRI in terms of conspicuity of these lesions. DWI could be used as an MRI biomarker for evaluation of treatment in ALL children. PMID:27763327

  18. Can diffusion-weighted imaging be used as a tool to predict seizures in patients with PLEDS?

    PubMed

    Narayanan, Jaishree

    2016-12-01

    It is unclear which patients with PLEDs will have associated seizures and therefore will need to be treated aggressively with antiepileptic medications. We present a prospective observational study of ten consecutive non-anoxic patients with PLEDs based on continuous 24-hour EEG monitoring. According to the EEG, five of the patients had seizures associated with PLEDs and five had PLEDs but no seizures. The aetiology included: neoplasm (n=1), cortical dysplasia (n=1), acute head trauma (n=1), encephalomalacia related to healed abscess (n=1), intra-parenchymal haemorrhage (n=1), and no structural lesion (n=5). All patients underwent brain MRI using diffusion-weighted imaging (DWI). We found that the five patients who had seizures with PLEDs on continuous EEG had restricted diffusion on DWI. In contrast, the five patients who had PLEDs but no seizures on continuous EEG did not show a restricted diffusion pattern on DWI. We will continue to prospectively assess DWI findings in this group of patients and encourage other centres to also review similar data. If our observation is replicated, this would indicate that restricted diffusion on brain MRI may be a useful marker to identify patients with PLEDs on their EEG who are likely to have associated seizures.

  19. Diffusion-weighted imaging-based probabilistic segmentation of high- and low-proliferative areas in high-grade gliomas

    PubMed Central

    Fritzsche, Klaus H.; Thieke, Christian; Klein, Jan; Parzer, Peter; Weber, Marc-André; Stieltjes, Bram

    2012-01-01

    Abstract The apparent diffusion coefficient (ADC) derived from diffusion-weighted imaging (DWI) correlates inversely with tumor proliferation rates. High-grade gliomas are typically heterogeneous and the delineation of areas of high and low proliferation is impeded by partial volume effects and blurred borders. Commonly used manual delineation is further impeded by potential overlap with cerebrospinal fluid and necrosis. Here we present an algorithm to reproducibly delineate and probabilistically quantify the ADC in areas of high and low proliferation in heterogeneous gliomas, resulting in a reproducible quantification in regions of tissue inhomogeneity. We used an expectation maximization (EM) clustering algorithm, applied on a Gaussian mixture model, consisting of pure superpositions of Gaussian distributions. Soundness and reproducibility of this approach were evaluated in 10 patients with glioma. High- and low-proliferating areas found using the clustering correspond well with conservative regions of interest drawn using all available imaging data. Systematic placement of model initialization seeds shows good reproducibility of the method. Moreover, we illustrate an automatic initialization approach that completely removes user-induced variability. In conclusion, we present a rapid, reproducible and automatic method to separate and quantify heterogeneous regions in gliomas. PMID:22487677

  20. Task-based evaluation of segmentation algorithms for diffusion-weighted MRI without using a gold standard.

    PubMed

    Jha, Abhinav K; Kupinski, Matthew A; Rodríguez, Jeffrey J; Stephen, Renu M; Stopeck, Alison T

    2012-07-07

    In many studies, the estimation of the apparent diffusion coefficient (ADC) of lesions in visceral organs in diffusion-weighted (DW) magnetic resonance images requires an accurate lesion-segmentation algorithm. To evaluate these lesion-segmentation algorithms, region-overlap measures are used currently. However, the end task from the DW images is accurate ADC estimation, and the region-overlap measures do not evaluate the segmentation algorithms on this task. Moreover, these measures rely on the existence of gold-standard segmentation of the lesion, which is typically unavailable. In this paper, we study the problem of task-based evaluation of segmentation algorithms in DW imaging in the absence of a gold standard. We first show that using manual segmentations instead of gold-standard segmentations for this task-based evaluation is unreliable. We then propose a method to compare the segmentation algorithms that does not require gold-standard or manual segmentation results. The no-gold-standard method estimates the bias and the variance of the error between the true ADC values and the ADC values estimated using the automated segmentation algorithm. The method can be used to rank the segmentation algorithms on the basis of both the ensemble mean square error and precision. We also propose consistency checks for this evaluation technique.

  1. Intraventricular temperature measured by diffusion-weighted imaging compared with brain parenchymal temperature measured by MRS in vivo.

    PubMed

    Sumida, Kaoru; Sato, Noriko; Ota, Miho; Sakai, Koji; Sone, Daichi; Yokoyama, Kota; Kimura, Yukio; Maikusa, Norihide; Imabayashi, Etsuko; Matsuda, Hiroshi; Kunimatsu, Akira; Ohtomo, Kuni

    2016-07-01

    We examined and compared the temperatures of the intraventricular cerebrospinal fluid (Tv ) and the brain parenchyma (Tp ) using MRI, with reference to the tympanic membrane temperature (Tt ) in healthy subjects. We estimated Tv and Tp values from data gathered simultaneously by MR diffusion-weighted imaging (DWI) and MRS, respectively, in 35 healthy volunteers (17 males, 18 females; age 25-78 years). We also obtained Tt values just before each MR examination to evaluate the relationships among the three temperatures. There were significant positive correlations between Tv and Tp (R = 0.611, p < 0.001). The correlation was also significant after correction for Tt (R = 0.642, p < 0.001). There was no significant correlation between Tv and Tt or between Tp and Tt in the men or the women. Negative correlations were found between Tv and age and between Tp and age in the males but not females. DWI thermometry seems to reflect the intracranial environment as accurately as MRS thermometry. An age-dependent decline in temperature was evident in our male subjects by both DWI and MRS thermometry, probably due to the decrease in cerebral metabolism with age. Copyright © 2016 John Wiley & Sons, Ltd.

  2. Quantitative Evaluation of Growth Plates around the Knees of Adolescent Soccer Players by Diffusion-Weighted Magnetic Resonance Imaging

    PubMed Central

    Krajnc, Zmago; Rupreht, Mitja; Drobnič, Matej

    2015-01-01

    Purpose. To quantitatively evaluate growth plates around the knees in adolescent soccer players utilizing the diffusion-weighted MR imaging (DWI). Methods. The knees and adjacent growth plates of eleven 14-year-old male soccer players were evaluated by MRI before (end of season's summer break) and after two months of intense soccer training. MRI evaluation was conducted in coronal plane by PD-FSE and DWI. All images were screened for any major pathological changes. Later, central growth plate surface area (CGPSA) was measured and the apparent diffusion coefficient (ADC) values were calculated in two most central coronal slices divided into four regions: distal femur medial (DFM), distal femur lateral (DFL), proximal tibia medial (PTM), and proximal tibia lateral (PTL). Results. No gross pathology was diagnosed on MRI. CGPSA was not significantly reduced: DFM 278 versus 272, DFL 265 versus 261, PTM 193 versus 192, and PTL 214 versus 210. ADC decrease was statistically significant only for PTM: DFM 1.27 versus 1.22, DFL 1.37 versus 1.34, PTM 1.13 versus 1.03 (p = 0.003), and PTL 1.28 versus 1.22. Conclusions. DWI measurements indicate increased cellularity in growth plates around knees in footballers most prominent in PTM after intense training. No detectable differences on a standard PD-FSE sequence were observed. PMID:26693482

  3. Case Report of False-Negative Diffusion-Weighted Image of Brain Magnetic Resonance Imaging (MRI) in Acute Ischemic Stroke

    PubMed Central

    Chang, Wei-Lun; Lai, Ji-Ching; Chen, Rong-Fu; Hu, Han-Hwa; Pan, Chau-Shiung

    2017-01-01

    Patient: Male, 75 Final Diagnosis: Acute ischemic stroke Symptoms: Dizziness • unsteady gait Medication: — Clinical Procedure: None Specialty: Radiology Objective: Challenging differential diagnosis Background: Acute ischemic stroke is a major cause of mortality and morbidity in Taiwan. Diffusion-weighted image (DWI) is a sensitive and common strategy used for imaging acute ischemic stroke. Case report: We present a case of a negative DWI MRI for detecting acute ischemic stroke in a clinical setting. A 75-year-old male had a DWI performed after onset of symptoms suggesting acute ischemic stroke. The initial DWI result was negative at 72 hours of presentation. The neurological symptoms of the patient persisted and DWI was repeated. After 14 days, the DWI data confirmed and demonstrated an acute ischemic stroke. The delay in DWI confirmation, from symptom onset until DWI diagnosis, was 336 hours. Conclusions: DWI may not have 100% sensitivity and accuracy in early stages of acute ischemic stroke. The time course to the development of abnormalities detected by DWI may be longer than anticipated. PMID:28111452

  4. Multivariate General Linear Models (MGLM) on Riemannian Manifolds with Applications to Statistical Analysis of Diffusion Weighted Images

    PubMed Central

    Kim, Hyunwoo J.; Adluru, Nagesh; Collins, Maxwell D.; Chung, Moo K.; Bendlin, Barbara B.; Johnson, Sterling C.; Davidson, Richard J.; Singh, Vikas

    2014-01-01

    Linear regression is a parametric model which is ubiquitous in scientific analysis. The classical setup where the observations and responses, i.e., (xi, yi) pairs, are Euclidean is well studied. The setting where yi is manifold valued is a topic of much interest, motivated by applications in shape analysis, topic modeling, and medical imaging. Recent work gives strategies for max-margin classifiers, principal components analysis, and dictionary learning on certain types of manifolds. For parametric regression specifically, results within the last year provide mechanisms to regress one real-valued parameter, xi ∈ R, against a manifold-valued variable, yi ∈ . We seek to substantially extend the operating range of such methods by deriving schemes for multivariate multiple linear regression —a manifold-valued dependent variable against multiple independent variables, i.e., f : Rn → . Our variational algorithm efficiently solves for multiple geodesic bases on the manifold concurrently via gradient updates. This allows us to answer questions such as: what is the relationship of the measurement at voxel y to disease when conditioned on age and gender. We show applications to statistical analysis of diffusion weighted images, which give rise to regression tasks on the manifold GL(n)/O(n) for diffusion tensor images (DTI) and the Hilbert unit sphere for orientation distribution functions (ODF) from high angular resolution acquisition. The companion open-source code is available on nitrc.org/projects/riem_mglm. PMID:25580070

  5. [Examination of upper abdominal region in high spatial resolution diffusion-weighted imaging using 3-Tesla MRI].

    PubMed

    Terada, Masaki; Matsushita, Hiroki; Oosugi, Masanori; Inoue, Kazuyasu; Yaegashi, Taku; Anma, Takeshi

    2009-03-20

    The advantage of the higher signal-to-noise ratio (SNR) of 3-Tesla magnetic resonance imaging (3-Tesla) has the possibility of contributing to the improvement of high spatial resolution without causing image deterioration. In this study, we compared SNR and the apparent diffusion coefficient (ADC) value with 3-Tesla as the condition in the diffusion-weighted image (DWI) parameter of the 1.5-Tesla magnetic resonance imaging (1.5-Tesla) and we examined the high spatial resolution images in the imaging method [respiratory-triggering (RT) method and breath free (BF) method] and artifact (motion and zebra) in the upper abdominal region of DWI at 3-Tesla. We have optimized scan parameters based on phantom and in vivo study. As a result, 3-Tesla was able to obtain about 1.5 times SNR in comparison with the 1.5-Tesla, ADC value had few differences. Moreover, the RT method was effective in correcting the influence of respiratory movement in comparison with the BF method, and image improvement by the effective acquisition of SNR and reduction of the artifact were provided. Thus, DWI of upper abdominal region was a useful sequence for the high spatial resolution in 3-Tesla.

  6. Diffusion-weighted and PET/MR Imaging after Radiation Therapy for Malignant Head and Neck Tumors.

    PubMed

    Varoquaux, Arthur; Rager, Olivier; Dulguerov, Pavel; Burkhardt, Karim; Ailianou, Angeliki; Becker, Minerva

    2015-01-01

    Interpreting imaging studies of the irradiated neck constitutes a challenge because of radiation therapy-induced tissue alterations, the variable appearances of recurrent tumors, and functional and metabolic phenomena that mimic disease. Therefore, morphologic magnetic resonance (MR) imaging, diffusion-weighted (DW) imaging, positron emission tomography with computed tomography (PET/CT), and software fusion of PET and MR imaging data sets are increasingly used to facilitate diagnosis in clinical practice. Because MR imaging and PET often yield complementary information, PET/MR imaging holds promise to facilitate differentiation of tumor recurrence from radiation therapy-induced changes and complications. This review focuses on clinical applications of DW and PET/MR imaging in the irradiated neck and discusses the added value of multiparametric imaging to solve diagnostic dilemmas. Radiologists should understand key features of radiation therapy-induced tissue alterations and potential complications seen at DW and PET/MR imaging, including edema, fibrosis, scar tissue, soft-tissue necrosis, bone and cartilage necrosis, cranial nerve palsy, and radiation therapy-induced arteriosclerosis, brain necrosis, and thyroid disorders. DW and PET/MR imaging also play a complementary role in detection of residual and recurrent disease. Interpretation pitfalls due to technical, functional, and metabolic phenomena should be recognized and avoided. Familiarity with DW and PET/MR imaging features of expected findings, potential complications, and treatment failure after radiation therapy increases diagnostic confidence when interpreting images of the irradiated neck. Online supplemental material is available for this article.

  7. Intravoxel Incoherent Motion Diffusion Weighted Magnetic Resonance Imaging for Differentiation Between Nasopharyngeal Carcinoma and Lymphoma at the Primary Site

    PubMed Central

    Yu, Xiao-Ping; Hou, Jing; Li, Fei-Ping; Wang, Hui; Hu, Ping-Sheng; Bi, Feng; Wang, Wei

    2016-01-01

    Objective The aim of the study was to investigate the utility of intravoxel incoherent motion (IVIM) diffusion-weighted magnetic resonance imaging (DWI) for differentiating nasopharyngeal carcinoma (NPC) from lymphoma. Methods Intravoxel incoherent motion–based parameters including the apparent diffusion coefficient (ADC), pure diffusion coefficient (D), pseudodiffusion coefficient (D*), perfusion fraction (f), and fD* (the product of D* and f) were retrospectively compared between 102 patients (82 with NPC, 20 with lymphoma) who received pretreatment IVIM DWI. Results Compared with lymphoma, NPC exhibited higher ADC, D, D*, fD* values (P < 0.001) and f value (P = 0.047). The optimal cutoff values (area under the curve, sensitivity, and specificity, respectively) for distinguishing the 2 tumors were as follows: ADC value of 0.761 × 10−3 mm2/s (0.781, 93.90%, 55.00%); D, 0.66 × 10−3 mm2/s (0.802, 54.88%, 100.00%); D*, 7.89 × 10−3 mm2/s (0.898, 82.93%, 85.00%); f, 0.29 (0.644, 41.46%, 95.00%); and fD*, 1.99 × 10−3 mm2/s (0.960, 85.37%, 100.00%). Conclusions Nasopharyngeal carcinoma exhibits different IVIM-based imaging features from lymphoma. Intravoxel incoherent motion DWI is useful for differentiating lymphoma from NPC. PMID:26953769

  8. Evaluation of Fat Suppression of Diffusion-weighted Imaging Using Section Select Gradient Reversal Technique on 3 T Breast MRI.

    PubMed

    Takemori, Daichi; Kimura, Daisuke; Yamada, Eiji; Higashida, Mitsuji

    2016-07-01

    This study evaluates fat suppression of diffusion-weighted imaging (DWI) using section select gradient reversal (SSGR) technique in clinical images on 3 T breast MRI. A total of 20 patients with breast cancer were examined at a Philips Ingenia 3 T MRI. We acquired DWI with SPAIR, SSGR-SPAIR, STIR, and SSGR-STIR. We evaluated contrast between the fat region and lesion, the coefficient of variance (CV) of the fat region and the apparent diffusion coefficient (ADC) of normal breast tissue and lesion. The contrast between the fat region and lesion was improved with SSGR technique. The CV of the fattest region did not have any significant difference in SPAIR technique (p>0.05), but it was significantly decreased in the STIR technique using SSGR technique (p<0.05). Positive correlation was observed in ADC value between SPAIR and other fat suppression techniques (SSGR-SPAIR, STIR, SSGR-STIR). DWI using SSGR technique was suggested to be effective on 3 T breast MRI.

  9. Characterization of spinal cord white matter by suppressing signal from hindered space. A Monte Carlo simulation and an ex vivo ultrahigh-b diffusion-weighted imaging study.

    PubMed

    Sapkota, Nabraj; Yoon, Sook; Thapa, Bijaya; Lee, YouJung; Bisson, Erica F; Bowman, Beth M; Miller, Scott C; Shah, Lubdha M; Rose, John W; Jeong, Eun-Kee

    2016-11-01

    Signal measured from white matter in diffusion-weighted imaging is difficult to interpret because of the heterogeneous structure of white matter. Characterization of the white matter will be straightforward if the signal contributed from the hindered space is suppressed and purely restricted signal is analyzed. In this study, a Monte Carlo simulation (MCS) of water diffusion in white matter was performed to understand the behavior of the diffusion-weighted signal in white matter. The signal originating from the hindered space of an excised pig cervical spinal cord white matter was suppressed using the ultrahigh-b radial diffusion-weighted imaging. A light microscopy image of a section of white matter was obtained from the excised pig cervical spinal cord for the MCS. The radial diffusion-weighted signals originating from each of the intra-axonal, extra-axonal, and total spaces were studied using the MCS. The MCS predicted that the radial diffusion-weighted signal remains almost constant in the intra-axonal space and decreases gradually to about 2% of its initial value in the extra-axonal space when the b-value is increased to 30,000s/mm(2). The MCS also revealed that the diffusion-weighted signal for a b-value greater than 20,000s/mm(2) is mostly from the intra-axonal space. The decaying behavior of the signal-b curve obtained from ultrahigh-b diffusion-weighted imaging (bmax∼30,000s/mm(2)) of the excised pig cord was very similar to the decaying behavior of the total signal-b curve synthesized in the MCS. A mono-exponential plus constant fitting of the signal-b curve obtained from a white matter pixel estimated the values of constant fraction and apparent diffusion coefficient of decaying fraction as 0.32±0.05 and (0.16±0.01)×10(-3)mm(2)/s, respectively, which agreed well with the results of the MCS. The signal measured in the ultrahigh-b region (b>20,000s/mm(2)) is mostly from the restricted (intra-axonal) space. Integrity and intactness of the axons can be

  10. Characterization of spinal cord white matter by suppressing signal from hindered space. A Monte Carlo simulation and an ex vivo ultrahigh-b diffusion-weighted imaging study

    NASA Astrophysics Data System (ADS)

    Sapkota, Nabraj; Yoon, Sook; Thapa, Bijaya; Lee, YouJung; Bisson, Erica F.; Bowman, Beth M.; Miller, Scott C.; Shah, Lubdha M.; Rose, John W.; Jeong, Eun-Kee

    2016-11-01

    Signal measured from white matter in diffusion-weighted imaging is difficult to interpret because of the heterogeneous structure of white matter. Characterization of the white matter will be straightforward if the signal contributed from the hindered space is suppressed and purely restricted signal is analyzed. In this study, a Monte Carlo simulation (MCS) of water diffusion in white matter was performed to understand the behavior of the diffusion-weighted signal in white matter. The signal originating from the hindered space of an excised pig cervical spinal cord white matter was suppressed using the ultrahigh-b radial diffusion-weighted imaging. A light microscopy image of a section of white matter was obtained from the excised pig cervical spinal cord for the MCS. The radial diffusion-weighted signals originating from each of the intra-axonal, extra-axonal, and total spaces were studied using the MCS. The MCS predicted that the radial diffusion-weighted signal remains almost constant in the intra-axonal space and decreases gradually to about 2% of its initial value in the extra-axonal space when the b-value is increased to 30,000 s /mm2 . The MCS also revealed that the diffusion-weighted signal for a b-value greater than 20,000 s /mm2 is mostly from the intra-axonal space. The decaying behavior of the signal-b curve obtained from ultrahigh-b diffusion-weighted imaging (bmax ∼ 30,000 s /mm2) of the excised pig cord was very similar to the decaying behavior of the total signal-b curve synthesized in the MCS. A mono-exponential plus constant fitting of the signal-b curve obtained from a white matter pixel estimated the values of constant fraction and apparent diffusion coefficient of decaying fraction as 0.32 ± 0.05 and (0.16 ± 0.01) × 10-3 mm2/s, respectively, which agreed well with the results of the MCS. The signal measured in the ultrahigh-b region (b > 20,000 s/mm2) is mostly from the restricted (intra-axonal) space. Integrity and intactness of the axons

  11. Considerations on propeller efficiency

    NASA Technical Reports Server (NTRS)

    Betz, A

    1928-01-01

    The propeller cannot be considered alone, but the mutual interference between propeller and airplane must be considered. These difficulties are so great when the joint action of propeller and airplane is considered, that the aerodynamic laboratory at Gottingen originally abandoned the idea of applying the efficiency conception of the test results. These difficulties and the methods by which they are overcome are outlined in this report.

  12. Vortice-propeller interaction

    NASA Astrophysics Data System (ADS)

    Hemon, Alain; Huberson, Serge

    1989-08-01

    The interactions between a ship's propeller blades and the boundary layer created by the ship are investigated. A finite element calculation method based on Navier-Stokes equation is developed. The application of an k-epsilon turbulence model for improving the analysis is considered. The flow azimuthal homogenization hypothesis is applied and leads to an accurate evaluation of the propeller performances. The unsteady effects generated by the interaction between the propeller blades and the vortices are analyzed.

  13. New Propellant Formulation Development

    DTIC Science & Technology

    2013-01-30

    initiators, JA2 19-Perf Hex propellants and Hagedorn-Plastic manufactured Nitrocellulose with Alkohol - German manufacturer. STAR-ATO goal is to develop... propellants in the U.S. Army’s small, medium and large caliber munitions are all nitrocellulose -based. As the Army drives continuous improvement in both...understanding the influence of nitrocellulose properties on propellant performance. Projectiles are getting heavier, ammunition is being exposed to

  14. Cryogenic Propellant Densification Study

    NASA Technical Reports Server (NTRS)

    Ewart, R. O.; Dergance, R. H.

    1978-01-01

    Ground and vehicle system requirements are evaluated for the use of densified cryogenic propellants in advanced space transportation systems. Propellants studied were slush and triple point liquid hydrogen, triple point liquid oxygen, and slush and triple point liquid methane. Areas of study included propellant production, storage, transfer, vehicle loading and system requirements definition. A savings of approximately 8.2 x 100,000 Kg can be achieved in single stage to orbit gross liftoff weight for a payload of 29,484 Kg by utilizing densified cryogens in place of normal boiling point propellants.

  15. Evaluation of Treatment Associated Inflammatory Response on Diffusion Weighted-MRI and FDG-PET Imaging Biomarkers

    PubMed Central

    Galbán, Craig J.; Bhojani, Mahaveer S; Lee, Kuei C.; Meyer, Charles R.; Van Dort, Marcian; Kuszpit, Kyle; Koeppe, Robert A.; Ranga, Rajesh; Moffat, Bradford A.; Johnson, Timothy D.; Chenevert, Thomas L.; Rehemtulla, Alnawaz; Ross, Brian D.

    2010-01-01

    Purpose Functional imaging biomarkers of cancer treatment response offer the potential for early determination of outcome through assessment of biochemical, physiological, and micro-environmental readouts. Cell death may result in an immunological response thus complicating interpretation of biomarker readouts. This study evaluated the temporal impact of treatment-associated inflammatory activity on diffusion-MRI and FDG-PET imaging biomarkers to delineate the effects of the inflammatory response on imaging readouts. Experimental Design Rats with intracerebral 9L gliosarcomas were separated into four groups consisting of control, an immunosuppressive agent dexamethasone (Dex), 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), and BCNU+Dex (BCNU+Dex). Animals were imaged using diffusion-weighted MRI and FDG-PET at 0, 3 and 7 days post-treatment. Results In the BCNU and BCNU+Dex treated animal groups, diffusion values increased progressively over the 7 day study period to about 23% over baseline. FDG %SUV decreased at day 3 (−30.9%) but increased over baseline levels at day 7 (+20.1%). FDG-PET of BCNU+Dex treated animals were found to have %SUV reductions of −31.4% and −24.7% at days 3 and 7, respectively following treatment. Activated macrophages were observed on day 7 in the BCNU treatment group with much fewer found in the BCNU+Dex group. Conclusions Results revealed treatment-associated inflammatory response following tumor therapy resulted in accentuation of tumor diffusion response along with a corresponding increase in tumor FDG uptake due to the presence of glucose-consuming activated macrophages. The dynamics and magnitude of potential inflammatory response should be considered when interpreting imaging biomarker results. PMID:20160061

  16. Diffusion-Weighted Magnetic Resonance Imaging for Therapy Response Monitoring and Early Treatment Prediction of Photothermal Therapy.

    PubMed

    Fu, Guifeng; Zhu, Lei; Yang, Kai; Zhuang, Rongqiang; Xie, Jin; Zhang, Fan

    2016-03-02

    Photothermal therapy (PTT) as a relatively new cancer treatment method has attracted worldwide attention. Previous research on PTT has focused on its therapy efficiency and selectivity. The early prognosis of PTT, which is pivotal for the assessment of the treatment and the therapy stratification, however, has been rarely studied. In the present study, we investigated diffusion-weighted magnetic resonance imaging (DW-MRI) as a tool for therapy monitoring and early prognosis of PTT. To this end, we injected PEGylated graphene oxide (GO-PEG) or iron oxide deposited graphene oxide (GO-IONP-PEG) to 4T1 tumor models and irradiated the tumors at different drug-light intervals to induce PTT. For GO-IONP-PEG injected animals, we also included therapy arms where an external magnetic field was applied to the tumors to improve the delivery of the nanoparticle transducers. DW-MRI was performed at different time points after PTT and the tumor apparent diffusion coefficients (ADCs) were analyzed and compared. Our studies show that photothermal agents, magnetic guidance, and drug-light intervals can all affect PTT treatment efficacy. Impressively, ADC value changes at early time points after PTT (less than 48 h) were found to be well-correlated with tumor growth suppression that was apparent days or weeks later. The changes were most sensitive to conditions that can extend the survival for more than 4 weeks, in which cases the 48 h ADC values were increased by more than 80%. These studies demonstrate for the first time that DW-MRI can be an accurate prognosis tool for PTT, suggesting an important role it can play in the future PTT evaluation and clinical translation of the modality.

  17. The Role of White Matter Damage in the Risk of Periprocedural Diffusion-Weighted Lesions after Carotid Artery Stenting

    PubMed Central

    Maggio, Paola; Altamura, Claudia; Lupoi, Domenico; Paolucci, Matteo; Altavilla, Riccardo; Tibuzzi, Francesco; Passarelli, Francesco; Arpesani, Roberto; Di Giambattista, Guido; Grasso, Rosario Francesco; Luppi, Giacomo; Fiacco, Fabrizio; Silvestrini, Mauro; Pasqualetti, Patrizio; Vernieri, Fabrizio

    2017-01-01

    Background White matter hyperintensities (WMH) are a common finding in aged individuals affected by carotid artery disease and are a risk factor for first-ever and recurrent stroke. We investigated if white matter damage increases the risk of brain microembolism during carotid artery stenting (CAS), as evaluated by the appearance of new areas of restricted diffusion on diffusion-weighted images (DWI). Methods We evaluated 47 patients with severe internal carotid artery (ICA) stenosis undergoing CAS, comparing preprocedural clinical, ultrasound and radiological characteristics. WMH volume was computed on FLAIR images before CAS. After CAS, the DWI scan was looked over for areas of restricted diffusion (DWI lesions). A first univariate analysis was adopted to compare groups according to the occurrence of DWI lesions. Then, the variable DWI lesion was modelled by means of a logistic regression model. Results Seventeen patients developed at least 1 DWI lesion after CAS. Compared with non-DWI, DWI patients were more commonly treated in the left ICA (p = 0.007) and had a more severe WMH damage (p = 0.027). Indeed, the risk of a DWI lesion was higher in left versus right stenosis (OR = 9.0, 95% CI 1.9-42.7, p = 0.005) and increased for each log-unit of WMH lesion load (OR = 7.05, 95% CI 1.07-46.49, p = 0.042). A WMH lesion load of at least 5.25 cm3 had a 50% probability of occurrence of a new DWI lesion. Conclusions Treated side and preexisting white matter damage are risk conditions for brain microembolism during CAS. This should be taken into account to optimize severe carotid artery disease management. PMID:28125807

  18. Immunochemotherapy with Intensive Consolidation for Primary CNS Lymphoma: A Pilot Study and Prognostic Assessment by Diffusion-Weighted MRI

    PubMed Central

    Wieduwilt, Matthew J.; Valles, Francisco; Issa, Samar; Behler, Caroline M.; Hwang, James; McDermott, Michael; Treseler, Patrick; O’Brien, Joan; Shuman, Marc A.; Cha, Soonmee; Damon, Lloyd E.; Rubenstein, James L.

    2012-01-01

    Purpose We evaluated a novel therapy for primary central nervous system (CNS) lymphoma (PCNSL) using induction immunochemotherapy with high-dose methotrexate, temozolomide and rituximab (MT-R) followed by intensive consolidation with infusional etoposide and high-dose cytarabine (EA). In addition, we evaluated the prognostic value of the minimum apparent diffusion coefficient (ADCmin) derived from diffusion-weighted magnetic resonance imaging (DW-MRI) in patients treated with this regimen. Experimental Design Thirty-one patients (median age, 61; median KPS, 60) received induction with methotrexate every 14 days for 8 planned cycles. Rituximab was administered the first 6 cycles and temozolomide administered on odd-numbered cycles. Patients with responsive or stable CNS disease received EA consolidation. Pretreatment DW-MRI was used to calculate the ADCmin of contrast-enhancing lesions. Results The complete response rate for MT-R induction was 52%. At a median follow-up of 79 months, the 2-year progression-free and overall survival were 45% and 58%, respectively. For patients receiving EA consolidation, the 2-year progression-free and overall survival were 78% and 93%, respectively. EA consolidation was also effective in an additional 3 patients who presented with synchronous CNS and systemic lymphoma. Tumor ADCmin <384 × 10−6 mm2/s was significantly associated with shorter progression-free and overall survival. Conclusions MT-R induction was effective and well-tolerated. MT-R followed by EA consolidation yielded progression-free and overall survival outcomes comparable to regimens using chemotherapy followed by whole-brain radiotherapy consolidation but without evidence of neurotoxicity. Tumor ADCmin derived from DW-MRI provided better prognostic information for PCNSL patients treated with the MTR-EA regimen than established clinical risk scores. PMID:22228634

  19. Application of 18F-FDG PET and diffusion weighted imaging (DWI) in multiple myeloma: comparison of functional imaging modalities

    PubMed Central

    Sachpekidis, Christos; Mosebach, Jennifer; Freitag, Martin T; Wilhelm, Thomas; Mai, Elias K; Goldschmidt, Hartmut; Haberkorn, Uwe; Schlemmer, Heinz-Peter; Delorme, Stefan; Dimitrakopoulou-Strauss, Antonia

    2015-01-01

    Aim of this prospective study was to assess the sensitivity of positron emission tomography (PET) and diffusion-weighted imaging (DWI) in detecting multiple myeloma (MM) lesions, using the well-established morphologic modalities magnetic resonance imaging (MRI) and computed tomography (CT) as the standard of reference (RS). The study included 24 MM patients (15 newly diagnosed, 9 pre-treated). All underwent 18F-FDG PET/CT and wholebody DWI. The findings in PET and DWI were compared to matching imaging findings in combined non-enhanced T1w, fat-saturated T2w (TIRM)- MRI, and low-dose CT. Patient-based analysis revealed that 15/24 patients (10 primary MM, 5 pre-treated) had myeloma lesions according to our RS. PET was positive in 13/24 patients (11 primary MM, 2 pre-treated) and DWI in 18/24 patients (12 primary MM, 6 pre-treated). Lesion-based analysis demonstrated 128 MM lesions, of which PET depicted 60/128 lesions (sensitivity 47%), while DWI depicted 99/128 lesions (sensitivity 77%). Further analysis including only the 15 untreated MM patients revealed a sensitivity of 90% for both PET and DWI and an overall concordance of PET and DWI of 72%. In conclusion, DWI was more sensitive than 18F-FDG PET in detecting myeloma lesions in a mixed population of primary and pre-treated MM patients. However, 18F-FDG PET and DWI demonstrated equivalent sensitivities in the sub-population of primary, untreated MM patients. This higher sensitivity of DWI in pre-treated patients may be due to the fact that 18F-FDG PET becomes negative earlier in the course of treatment in contrary to MRI, in which already treated lesions can remain visible. PMID:26550539

  20. Intraoperative diffusion-weighted imaging for visualization of the pyramidal tracts. Part II: clinical study of usefulness and efficacy.

    PubMed

    Ozawa, N; Muragaki, Y; Nakamura, R; Lseki, H

    2008-04-01

    Precise identification and preservation of the pyramidal tract during surgery for parenchymal brain tumors is of crucial importance for the avoidance of postoperative deterioration of the motor function. The technique of intraoperative diffusion-weighted imaging (iDWI) using an intraoperative MR scanner of low magnetic field strength (0.3 Tesla) has been developed. Its clinical usefulness and efficacy were evaluated in 10 surgically treated patients with gliomas (5 men and 5 women, mean age: 41.2+/-13.9 years). iDWI permitted visualization of the pyramidal tract on the non-affected side in all 10 cases, and on the affected side in 8 cases. Motion artifacts were observed in four patients, but were not an obstacle to identification of the pyramidal tract. Good correspondence of the anatomical landmarks localization on iDWI and T (1)-weighted imaging was found. All participating neurosurgeons agreed that, in the majority of cases, iDWI was very useful for localization of the pyramidal tract and for clarification of its spatial relationships with the tumor. In conclusion, image quality and accuracy of the iDWI obtained with an MR scanner of low magnetic field strength (0.3 Tesla) are sufficient for possible incorporation into an intraoperative neuronavigation system. The use of iDWI in addition to structural iMRl and subcortical functional mapping with electrical stimulation can potentially result in a reduction of the postoperative morbidity after aggressive surgical removal of lesions located in the vicinity to the motor white matter tracts.

  1. Super-resolution reconstruction to increase the spatial resolution of diffusion weighted images from orthogonal anisotropic acquisitions

    PubMed Central

    Scherrer, Benoit; Gholipour, Ali; Warfield, Simon K.

    2012-01-01

    Diffusion-weighted imaging (DWI) enables non-invasive investigation and characterization of the white matter but suffers from a relatively poor spatial resolution. Increasing the spatial resolution in DWI is challenging with a single-shot EPI acquisition due to the decreased signal-to-noise ratio and T2* relaxation effect amplified with increased echo time. In this work we propose a super-resolution reconstruction (SRR) technique based on the acquisition of multiple anisotropic orthogonal DWI scans. DWI scans acquired in different planes are not typically closely aligned due to the geometric distortion introduced by magnetic susceptibility differences in each phase-encoding direction. We compensate each scan for geometric distortion by acquisition of a dual echo gradient echo field map, providing an estimate of the field inhomogeneity. We address the problem of patient motion by aligning the volumes in both space and q-space. The SRR is formulated as a maximum a posteriori problem. It relies on a volume acquisition model which describes how the acquired scans are observations of an unknown high-resolution image which we aim to recover. Our model enables the introduction of image priors that exploit spatial homogeneity and enables regularized solutions. We detail our SRR optimization procedure and report experiments including numerical simulations, synthetic SRR and real world SRR. In particular, we demonstrate that combining distortion compensation and SRR provides better results than acquisition of a single isotropic scan for the same acquisition duration time. Importantly, SRR enables DWI with resolution beyond the scanner hardware limitations. This work provides the first evidence that SRR, which employs conventional single shot EPI techniques, enables resolution enhancement in DWI, and may dramatically impact the role of DWI in both neuroscience and clinical applications. PMID:22770597

  2. Automated prostate cancer detection using T2-weighted and high-b-value diffusion-weighted magnetic resonance imaging

    PubMed Central

    Kwak, Jin Tae; Xu, Sheng; Wood, Bradford J.; Turkbey, Baris; Choyke, Peter L.; Pinto, Peter A.; Wang, Shijun; Summers, Ronald M.

    2015-01-01

    Purpose: The authors propose a computer-aided diagnosis (CAD) system for prostate cancer to aid in improving the accuracy, reproducibility, and standardization of multiparametric magnetic resonance imaging (MRI). Methods: The proposed system utilizes two MRI sequences [T2-weighted MRI and high-b-value (b = 2000 s/mm2) diffusion-weighted imaging (DWI)] and texture features based on local binary patterns. A three-stage feature selection method is employed to provide the most discriminative features. The authors included a total of 244 patients. Training the CAD system on 108 patients (78 MR-positive prostate cancers and 105 benign MR-positive lesions), two validation studies were retrospectively performed on 136 patients (68 MR-positive prostate cancers, 111 benign MR-positive lesions, and 117 MR-negative benign lesions). Results: In distinguishing cancer from MR-positive benign lesions, an area under receiver operating characteristic curve (AUC) of 0.83 [95% confidence interval (CI): 0.76–0.89] was achieved. For cancer vs MR-positive or MR-negative benign lesions, the authors obtained an AUC of 0.89 AUC (95% CI: 0.84–0.93). The performance of the CAD system was not dependent on the specific regions of the prostate, e.g., a peripheral zone or transition zone. Moreover, the CAD system outperformed other combinations of MRI sequences: T2W MRI, high-b-value DWI, and the standard apparent diffusion coefficient (ADC) map of DWI. Conclusions: The novel CAD system is able to detect the discriminative texture features for cancer detection and localization and is a promising tool for improving the quality and efficiency of prostate cancer diagnosis. PMID:25979032

  3. QIN DAWG Validation of Gradient Nonlinearity Bias Correction Workflow for Quantitative Diffusion-Weighted Imaging in Multicenter Trials

    PubMed Central

    Malyarenko, Dariya I.; Wilmes, Lisa J.; Arlinghaus, Lori R.; Jacobs, Michael A.; Huang, Wei; Helmer, Karl G.; Taouli, Bachir; Yankeelov, Thomas E.; Newitt, David; Chenevert, Thomas L.

    2017-01-01

    Previous research has shown that system-dependent gradient nonlinearity (GNL) introduces a significant spatial bias (nonuniformity) in apparent diffusion coefficient (ADC) maps. Here, the feasibility of centralized retrospective system-specific correction of GNL bias for quantitative diffusion-weighted imaging (DWI) in multisite clinical trials is demonstrated across diverse scanners independent of the scanned object. Using corrector maps generated from system characterization by ice-water phantom measurement completed in the previous project phase, GNL bias correction was performed for test ADC measurements from an independent DWI phantom (room temperature agar) at two offset locations in the bore. The precomputed three-dimensional GNL correctors were retrospectively applied to test DWI scans by the central analysis site. The correction was blinded to reference DWI of the agar phantom at magnet isocenter where the GNL bias is negligible. The performance was evaluated from changes in ADC region of interest histogram statistics before and after correction with respect to the unbiased reference ADC values provided by sites. Both absolute error and nonuniformity of the ADC map induced by GNL (median, 12%; range, −35% to +10%) were substantially reduced by correction (7-fold in median and 3-fold in range). The residual ADC nonuniformity errors were attributed to measurement noise and other non-GNL sources. Correction of systematic GNL bias resulted in a 2-fold decrease in technical variability across scanners (down to site temperature range). The described validation of GNL bias correction marks progress toward implementation of this technology in multicenter trials that utilize quantitative DWI. PMID:28105469

  4. Differentiation between Graves' disease and painless thyroiditis by diffusion-weighted imaging, thyroid iodine uptake, thyroid scintigraphy and serum parameters.

    PubMed

    Meng, Zhaowei; Zhang, Guizhi; Sun, Haoran; Tan, Jian; Yu, Chunshun; Tian, Weijun; Li, Weidong; Yang, Zhiqiang; Zhu, Mei; He, Qing; Zhang, Yujie; Han, Shugao

    2015-06-01

    The aim of the present study was to assess the apparent diffusion coefficient (ADC) in diffusion-weighted imaging (DWI), thyroid radioactive iodine uptake (RAIU), thyroid scintigraphy and thyrotropin receptor antibody (TRAb) levels in the differential diagnosis between Graves' disease (GD) and painless thyroiditis (PT). A total of 102 patients with GD and 37 patients with PT were enrolled in the study. DWI was obtained with a 3.0-T magnetic resonance scanner, and ADC values were calculated. RAIU and thyroid scintigraphy were performed. Tissue samples were obtained from patients with GD (6 cases) following thyroidectomy, and from patients with PT (2 cases) following biopsy. Receiver operating characteristic (ROC) curves were drawn, optimal cut-off values were selected, and the sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were assessed. It was found that the ADC, TRAb and RAIU were significantly higher in GD than in PT (P<0.05). ROC curves showed areas under the curves for RAIU, ADC and TRAb that were >0.900. RAIU was the reference method. Sensitivity, specificity, accuracy, PPV and NPV were 96.078, 91.892, 95.000, 97.059 and 89.474% for ADC, and 88.235, 75.676, 84.892, 90.909 and 70.000% for TRAb, after the optimal thresholds of 1.837×10(-3) mm(2)/sec and 1.350 IU/ml were determined respectively. Histopathology showed that tissue cellularity in PT was much higher than in GD due to massive lymphocytic infiltration. The results of the present study indicate that RAIU, ADC and TRAb are of diagnostic value for differentiating between GD and PT. DWI has great potential for thyroid pathophysiological imaging because it reflects differences in tissue cellularity between GD and PT.

  5. Evaluation of efficacy of transcatheter arterial chemoembolization for hepatocellular carcinoma using magnetic resonance diffusion-weighted imaging

    PubMed Central

    Wu, Xiao-Ming; Wang, Jun-Feng; Ji, Jian-Song; Chen, Ming-Gao; Song, Jian-Gang

    2017-01-01

    Although the efficacy of transcatheter arterial chemoembolization (TACE) has been recommended as first-line therapy for nonsurgical patients with hepatocellular carcinoma (HCC), it is difficult to accurately predict the efficacy of TACE. Therefore, this study evaluated the efficacy of TACE for HCC using magnetic resonance (MR) diffusion-weighted imaging (DWI). A total of 84 HCC patients who received initial TACE were selected and assigned to the stable group (n=39) and the progressive group (n=45). Before TACE treatment, a contrast-enhanced MR scan and DWI (b=300, 600, and 800 s/mm2) were performed on all patients. The modified response evaluation criteria in solid tumors were used for evaluation of tumor response. Receiver operating characteristic curve was employed to predict the value of apparent diffusion coefficient (ADC) for TACE efficacy. The ADC values of HCC patients in the progressive group were higher than those in the stable group at different b-values (b=300, 600, and 800 s/mm2) before TACE treatment. The area under the curve of ADC values with b-values of 300, 600, and 800 s/mm2 were 0.693, 0.724, and 0.746; the threshold values were 1.94×10−3 mm2/s, 1.28×10−3 mm2/s, and 1.20×10−3 mm2/s; the sensitivity values were 55.6%, 77.8%, and 73.3%; and the specificity values were 82.1%, 61.5%, and 71.8%, respectively. Our findings indicate that the ADC values of MR-DWI may accurately predict the efficacy of TACE in the treatment of HCC patients. PMID:28352195

  6. Detecting Acute Myocardial Infarction by Diffusion-Weighted versus T2-Weighted Imaging and Myocardial Necrosis Markers.

    PubMed

    Jin, Jiyang; Chen, Min; Li, Yongjun; Wang, YaLing; Zhang, Shijun; Wang, Zhen; Wang, Lin; Ju, Shenghong

    2016-10-01

    We used a porcine model of acute myocardial infarction to study the signal evolution of ischemic myocardium on diffusion-weighted magnetic resonance images (DWI). Eight Chinese miniature pigs underwent percutaneous left anterior descending or left circumflex coronary artery occlusion for 90 minutes followed by reperfusion, which induced acute myocardial infarction. We used DWI preprocedurally and hourly for 4 hours postprocedurally. We acquired turbo inversion recovery magnitude T2-weighted images (TIRM T2WI) and late gadolinium enhancement images from the DWI slices. We measured the serum myocardial necrosis markers myoglobin, creatine kinase-MB isoenzyme, and cardiac troponin I at the same time points as the magnetic resonance scanning. We used histochemical staining to confirm injury. All images were analyzed qualitatively. Contrast-to-noise ratio (the contrast between infarcted and healthy myocardium) and relative signal index were used in quantitative image analysis. We found that DWI identified myocardial signal abnormity early (<4 hr) after acute myocardial infarction and identified the infarct-related high signal more often than did TIRM T2WI: 7 of 8 pigs (87.5%) versus 3 of 8 (37.5%) (P=0.046). Quantitative image analysis yielded a significant difference in contrast-to-noise ratio and relative signal index between infarcted and normal myocardium on DWI. However, within 4 hours after infarction, the serologic myocardial injury markers were not significantly positive. We conclude that DWI can be used to detect myocardial signal abnormalities early after acute myocardial infarction-identifying the infarction earlier than TIRM T2WI and widely used clinical serologic biomarkers.

  7. Diffusion-Weighted MRI for Nodal Staging of Head and Neck Squamous Cell Carcinoma: Impact on Radiotherapy Planning

    SciTech Connect

    Dirix, Piet; Vandecaveye, Vincent; De Keyzer, Frederik; Op de beeck, Katya; Poorten, Vincent Vander; Delaere, Pierre; Verbeken, Eric; Hermans, Robert; Nuyts, Sandra

    2010-03-01

    Purpose: To evaluate the use of diffusion-weighted magnetic resonance imaging (DW-MRI) for nodal staging and its impact on radiotherapy (RT) planning. Methods and Materials: Twenty-two patients with locally advanced head and neck squamous cell carcinoma underwent contrast-enhanced computed tomography (CT), as well as MRI (with routine and DW sequences) prior to neck dissection. After topographic correlation, lymph nodes were evaluated microscopically with prekeratin immunostaining. Pathology results were correlated with imaging findings and an RT planning study was performed for these surgically treated patients. One set of target volumes was based on conventional imaging only, and another set was based on the corresponding DW-MRI images. A third reference set was contoured based solely on pathology results. Results: A sensitivity of 89% and a specificity of 97% per lymph node were found for DW-MRI. Nodal staging agreement between imaging and pathology was significantly stronger for DW-MRI (kappa = 0.97; 95% confidence interval [CI], 0.84-1.00) than for conventional imaging (kappa = 0.56; 95% CI, 0.16-0.96; p = 0.019, by McNemar's test). For both imaging modalities, the absolute differences between RT volumes and those obtained by pathology were calculated. Using an exact paired Wilcoxon test, the observed difference was significantly larger for conventional imaging than for DW-MRI for nodal gross tumor volume (p = 0.0013), as well as for nodal clinical target volume (p = 0.0415) delineation. Conclusions: These results suggest that DW-MRI is superior to conventional imaging for preradiotherapy nodal staging of head and neck squamous cell carcinoma, and provides a potential impact on organsparing and tumor control.

  8. Quantification of inflammatory activity in patients with Crohn's disease using diffusion weighted imaging (DWI) in MR enteroclysis and MR enterography.

    PubMed

    Stanescu-Siegmund, Nora; Nimsch, Yessica; Wunderlich, Arthur P; Wagner, Martin; Meier, Reinhard; Juchems, Markus S; Beer, Meinrad; Schmidt, Stefan A

    2017-03-01

    Background Individual studies have demonstrated the potential of diffusion-weighted magnetic resonance imaging (DWI-MRI) for identifying inflamed bowel segments. However, these studies were conducted with rather small patient cohorts and in most cases by means of MR enterography only. Purpose To demonstrate the feasibility of detecting inflamed bowel segments in a large collective of patients with Crohn's disease using DWI in MR enteroclysis and MR enterography and to compare the results of both techniques, also considering clinical parameters by means of the Harvey-Bradshaw Index (HBI). Material and Methods Ninety-six patients underwent MRI enteroclysis and 35 patients MR enterography, both with additional DWI. The HBI as well as apparent diffusion coefficients (ADC) in areas of inflamed and normal bowel wall were determined. Thus resulting in 208 bowel segments that were visualized and subsequently statistically analyzed. Results There were no significant differences in ADC values in MR enteroclysis and MR enterography ( P = 0.383 in inflammation, P = 0.223 in normal wall). Areas of inflammation showed statistically highly significant lower ADC values than areas of normal bowel wall ( P < 0.001). An ADC threshold of 1.56 × 10(-3 )mm(2)/s can distinguish between normal and inflamed bowel segments with a sensitivity of 97.4% and a specificity of 99.2%. A highly significant correlation could be shown between ADC and HBI values ( P = 0.001). Conclusion DWI-MRI facilitates recognition of inflamed bowel segments in patients with Crohn's disease and the ADC values show an excellent correlation to the HBI. There were no significant differences in ADC values in MR enteroclysis and MR enterography. An ADC threshold of 1.56 × 10(-3 )mm(2)/s differentiates between normal and inflamed bowel wall.

  9. Short-term reproducibility of apparent diffusion coefficient estimated from diffusion-weighted MRI of the prostate

    PubMed Central

    Sadinski, Meredith; Medved, Milica; Karademir, Ibrahim; Wang, Shiyang; Peng, Yahui; Jiang, Yulei; Sammet, Steffen; Karczmar, Gregory; Oto, Aytekin

    2015-01-01

    Purpose The purpose of the study is to determine short-term reproducibility of apparent diffusion coefficient (ADC) estimated from diffusion-weighted magnetic resonance (DW-MR) imaging of the prostate. Methods Fourteen patients with biopsy-proven prostate cancer were studied under an Institutional Review Board-approved protocol. Each patient underwent two, consecutive and identical DW-MR scans on a 3T system. ADC values were calculated from each scan and a deformable registration was performed to align corresponding images. The prostate and cancerous regions of interest (ROIs) were independently analyzed by two radiologists. The prostate volume was analyzed by sextant. Per-voxel absolute and relative percentage variations in ADC were compared between sextants. Per-voxel and per-ROI variations in ADC were calculated for cancerous ROIs. Results Per-voxel absolute difference in ADC in the prostate ranged from 0 to 1.60 × 10−3 mm2/s (per-voxel relative difference 0% to 200%, mean 10.5%). Variation in ADC was largest in the posterior apex (0% to 200%, mean 11.6%). Difference in ADC variation between sextants was not statistically significant. Cancer ROIs’ per-voxel variation in ADC ranged from 0.001 × 10−3 to 0.841 × 10−3 mm2/s (0% to 67.4%, mean 11.2%) and per-ROI variation ranged from 0 to 0.463 × 10−3 mm2/s (mean 0.122 × 10−3 mm2/s). Conclusions Variation in ADC within the human prostate is reasonably small, and is on the order of 10%. PMID:25805558

  10. Interrelations of muscle functional MRI, diffusion-weighted MRI and (31) P-MRS in exercised lower back muscles.

    PubMed

    Hiepe, Patrick; Gussew, Alexander; Rzanny, Reinhard; Anders, Christoph; Walther, Mario; Scholle, Hans-Christoph; Reichenbach, Jürgen R

    2014-08-01

    Exercise-induced changes of transverse proton relaxation time (T2 ), tissue perfusion and metabolic turnover were investigated in the lower back muscles of volunteers by applying muscle functional MRI (mfMRI) and diffusion-weighted imaging (DWI) before and after as well as dynamic (31) P-MRS during the exercise. Inner (M. multifidus, MF) and outer lower back muscles (M. erector spinae, ES) were examined in 14 healthy young men performing a sustained isometric trunk-extension. Significant phosphocreatine (PCr) depletions ranging from 30% (ES) to 34% (MF) and Pi accumulations between 95% (left ES) and 120%-140% (MF muscles and right ES) were observed during the exercise, which were accompanied by significantly decreased pH values in all muscles (∆pH ≈ -0.05). Baseline T2 values were similar across all investigated muscles (approximately 27 ms at 3 T), but revealed right-left asymmetric increases (T2 ,inc ) after the exercise (right ES/MF: T2 ,inc  = 11.8/9.7%; left ES/MF: T2 ,inc  = 4.6/8.9%). Analyzed muscles also showed load-induced increases in molecular diffusion D (p = .007) and perfusion fraction f (p = .002). The latter parameter was significantly higher in the MF than in the ES muscles both at rest and post exercise. Changes in PCr (p = .03), diffusion (p < .01) and perfusion (p = .03) were strongly associated with T2,inc , and linear mixed model analysis revealed that changes in PCr and perfusion both affect T2,inc (p < .001). These findings support previous assumptions that T2 changes are not only an intra-cellular phenomenon resulting from metabolic stress but are also affected by increased perfusion in loaded muscles.

  11. Feasibility study of reduced field of view diffusion-weighted magnetic resonance imaging in head and neck tumors.

    PubMed

    Vidiri, Antonello; Minosse, Silvia; Piludu, Francesca; Curione, Davide; Pichi, Barbara; Spriano, Giuseppe; Marzi, Simona

    2017-03-01

    Background Reduced field of view (rFOV) imaging may be used to improve the quality of diffusion-weighted imaging (DWI) in the head and neck (HN) region. Purpose To evaluate the feasibility of rFOV-DWI in patients affected by HN tumors, through a comparison with conventional full FOV (fFOV) DWI. Material and Methods Twenty-two patients with histologically-proven malignant or benign tumors of the head and neck were included in a retrospective study. All patients underwent pre-treatment magnetic resonance imaging (MRI) studies including rFOV-DWI and fFOV-DWI. The apparent diffusion coefficient (ADC) value distributions inside tumor and muscle were derived and the mean, standard deviation (SD), and kurtosis were calculated. Image distortion was quantitatively and qualitatively evaluated, as well as the capability of lesion identification. The Wilcoxon test was used to compare all variables. Agreements between the ADC estimations were assessed by Bland-Altman plots. Results Image distortion and lesion identification scores were both higher for rFOV-DWI compared to fFOV-DWI. A reduction in ADC values with rFOV-DWI emerged for both lesion and muscle, with a mean percentage difference in ADC of 6.2% in the lesions and 24.9% in the muscle. The difference in SD of ADC was statistically significant in the lesions, indicating a higher ADC homogeneity for rFOV DWI ( P = 0.005). Conclusion The application of rFOV DWI in patients affected by HN tumors is feasible and promising, based on both qualitative and quantitative analyses. This technique has potential for improving the diagnostic accuracy of fFOV-DWI for the study of specific tumoral areas.

  12. Detecting Acute Myocardial Infarction by Diffusion-Weighted versus T2-Weighted Imaging and Myocardial Necrosis Markers

    PubMed Central

    Chen, Min; Li, Yongjun; Wang, YaLing; Zhang, Shijun; Wang, Zhen; Wang, Lin; Ju, Shenghong

    2016-01-01

    We used a porcine model of acute myocardial infarction to study the signal evolution of ischemic myocardium on diffusion-weighted magnetic resonance images (DWI). Eight Chinese miniature pigs underwent percutaneous left anterior descending or left circumflex coronary artery occlusion for 90 minutes followed by reperfusion, which induced acute myocardial infarction. We used DWI preprocedurally and hourly for 4 hours postprocedurally. We acquired turbo inversion recovery magnitude T2-weighted images (TIRM T2WI) and late gadolinium enhancement images from the DWI slices. We measured the serum myocardial necrosis markers myoglobin, creatine kinase-MB isoenzyme, and cardiac troponin I at the same time points as the magnetic resonance scanning. We used histochemical staining to confirm injury. All images were analyzed qualitatively. Contrast-to-noise ratio (the contrast between infarcted and healthy myocardium) and relative signal index were used in quantitative image analysis. We found that DWI identified myocardial signal abnormity early (<4 hr) after acute myocardial infarction and identified the infarct-related high signal more often than did TIRM T2WI: 7 of 8 pigs (87.5%) versus 3 of 8 (37.5%) (P=0.046). Quantitative image analysis yielded a significant difference in contrast-to-noise ratio and relative signal index between infarcted and normal myocardium on DWI. However, within 4 hours after infarction, the serologic myocardial injury markers were not significantly positive. We conclude that DWI can be used to detect myocardial signal abnormalities early after acute myocardial infarction—identifying the infarction earlier than TIRM T2WI and widely used clinical serologic biomarkers. PMID:27777517

  13. Diffusion-weighted MR imaging for assessing synovitis of wrist and hand in patients with rheumatoid arthritis: a feasibility study.

    PubMed

    Li, Xubin; Liu, Xia; Du, Xiangke; Ye, Zhaoxiang

    2014-05-01

    The purpose of this study was to investigate the feasibility of diffusion-weighted imaging (DWI) in detecting synovitis of wrist and hand in patients with rheumatoid arthritis (RA) and evaluate its sensitivity, specificity and accuracy as compared to T2-weighted imaging (T2WI) with short tau inversion recovery (STIR) with the reference standard contrast-enhanced magnetic resonance imaging (CE-MRI). Twenty-five patients with RA underwent MR examinations including DWI, T2WI with STIR and CE-MRI. MR images were reviewed for the presence and location of synovitis of wrist and hand. The sensitivity, specificity and accuracy of DWI and T2WI with STIR were calculated respectively and then compared. All patients included in this study completed MR examinations and yielded diagnostic image quality of DWI. For individual joint, there was good to excellent inter-observer agreement (k=0.62-0.83) using DWI images, T2WI with STIR images and CE-MR images, respectively. There was a significance between DWI and T2WI with STIR in analyzing proximal interphalangeal joints II-V, respectively (P<0.05). The k-values for the detection of synovitis indicated excellent overall inter-observer agreements using DWI images (k=0.86), T2WI with STIR images (k=0.85) and CE-MR images (k=0.91), respectively. Overall, DWI demonstrated a sensitivity, specificity and accuracy of 75.6%, 89.3% and 84.6%, respectively, for detection of synovitis, while 43.0%, 95.7% and 77.6% for T2WI with STIR, respectively. DWI showed positive lesions much better and more than T2WI with STIR. Our results indicate that DWI presents a novel non-invasive approach to contrast-free imaging of synovitis. It may play a role as an addition to standard protocols.

  14. Longitudinal development in the preterm thalamus and posterior white matter: MRI correlations between diffusion weighted imaging and T2 relaxometry

    PubMed Central

    Eaton‐Rosen, Zach; Orasanu, Eliza; Price, David; Bainbridge, Alan; Cardoso, M. Jorge; Kendall, Giles S.; Robertson, Nicola J.; Marlow, Neil; Ourselin, Sebastien

    2016-01-01

    Abstract Infants born prematurely are at increased risk of adverse neurodevelopmental outcome. The measurement of white matter tissue composition and structure can help predict functional performance. Specifically, measurements of myelination and indicators of myelination status in the preterm brain could be predictive of later neurological outcome. Quantitative imaging of myelin could thus serve to develop biomarkers for prognosis or therapeutic intervention; however, accurate estimation of myelin content is difficult. This work combines diffusion MRI and multi‐component T2 relaxation measurements in a group of 37 infants born very preterm and scanned between 27 and 58 weeks equivalent gestational age. Seven infants have longitudinal data at two time points that we analyze in detail. Our aim is to show that measurement of the myelin water fraction is achievable using widely available pulse sequences and state‐of‐the‐art algorithmic modeling of the MR imaging procedure and that a multi‐component fitting routine to multi‐shell diffusion weighted data can show differences in neurite density and local spatial arrangement in grey and white matter. Inference on the myelin water fraction allows us to demonstrate that the change in diffusion properties of the preterm thalamus is not solely due to myelination (that increase in myelin content accounts for about a third of the observed changes) whilst the decrease in the posterior white matter T2 has no significant component that is due to myelin water content. This work applies multi‐modal advanced quantitative neuroimaging to investigate changing tissue properties in the longitudinal setting. Hum Brain Mapp 37:2479–2492, 2016. © The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.. PMID:26996400

  15. Comparison of Diffuse Weighted Imaging and Fluid Attenuation Inversion Recovery Sequences of MRI in Brain Multiple Sclerosis Plaques Detection

    PubMed Central

    NAFISI-MOGHADAM, Reza; RAHIMDEL, Abolghasem; SHANBEHZADEH, Tahereh; FALLAH, Razieh

    2017-01-01

    Objective Suitable magnetic resonance imaging (MRI) techniques from conventional to new devices can help physicians in diagnosis and follow up of Multiple Sclerosis (MS) patients. The aim of present research was to compare effectiveness of Fluid Attenuation Inversion Recovery (FLAIR) sequence of conventional MRI and Diffuse Weighted Imaging (DWI) sequence as a new technique in detection of brain MS plaques. Materials & Methods In this analytic cross sectional study, sample size was assessed as 40 people to detect any significant difference between two sequences with a level of 0.05. DWI and FLAIR sequences of without contrast brain MRI of consecutive MS patients referred to MRI center of Shahid Sadoughi Hospital, Yazd, Iran from January to May 2012, were evaluated. Results Thirty-two females and 8 males with mean age of 35.20±9.80 yr (range = 11-66 yr) were evaluated and finally 340 plaques including 127(37.2%) in T2WI, 127(37.2%) in FLAIR, 63(18.5%) in DWI and 24(7.1%) in T1WI were detected. FLAIR sequence was more efficient than DWI in detection of brain MS plaques, oval, round, amorphous plaque shapes, frontal and occipital lobes, periventricular, intracapsular, corpus callosum, centrum semiovale, subcortical, basal ganglia plaques and diameter of detected MS plaques in DWI sequence was smaller than in FLAIR. Conclusion Old lesion can be detected by conventional MRI and new techniques might be more useful in early inflammatory phase of MS and assessment of experimental treatments. PMID:28277551

  16. Mobile propeller dynamometer validation

    NASA Astrophysics Data System (ADS)

    Morris, Mason Wade

    With growing interest in UAVs and OSU's interest in propeller performance and manufacturing, evaluating UAV propeller and propulsion system performance has become essential. In attempts to evaluate these propellers a mobile propeller dynamometer has been designed, built, and tested. The mobile dyno has been designed to be cost effective through the ability to load it into the back of a test vehicle to create simulated forward flight characteristics. This allows much larger propellers to be dynamically tested without the use of large and expensive wind tunnels. While evaluating the accuracy of the dyno, several improvements had to be made to get accurate results. The decisions made to design and improve the mobile propeller dyno will be discussed along with attempts to validate the dyno by comparing its results against known sources. Another large part of assuring the accuracy of the mobile dyno is determining if the test vehicle will influence the flow going into the propellers being tested. The flow into the propeller needs to be as smooth and uniform as possible. This is determined by characterizing the boundary layer and accelerated flow over the vehicle. This evaluation was accomplished with extensive vehicle aerodynamic measurements with the use of full-scale tests using a pitot-rake and the actual test vehicle. Additional tests were conducted in Oklahoma State University's low speed wind tunnel with a 1/8-scale model using qualitative flow visualization with smoke. Continuing research on the mobile dyno will be discussed, along with other potential uses for the dyno.

  17. Liquid propellant densification

    NASA Technical Reports Server (NTRS)

    Lak, Tibor I. (Inventor); Petrilla, Steve P. (Inventor); Lozano, Martin E. (Inventor)

    1997-01-01

    Super cooling the cryogenic liquid propellant in a vehicle propellant tank densities the propellant allowing the vehicle propellant tank to carry more fuel in the same volume tank while lowering the vapor pressure and thus the tank operating pressure. Lowering the tank operating pressure reduces the stress and therefore allows the walls of the tank to be thinner. Both the smaller tank volume and thinner tank wall results in an overall smaller and lighter vehicle with increased payload capability. The cryogenic propellant can be supercooled well below the normal boiling point temperature level by transporting the liquid propellant from the vehicle tanks to a ground based cooling unit which utilizes a combination of heat exchanger and compressor. The compressor lowers the coolant fluid bath pressure resulting in a low temperature boiling liquid which is subsequently used to cool the recirculating liquid. The cooled propellant is then returned to the vehicle propellant tank. In addition to reducing the vehicle size and weight the invention also allows location of the vent valve on the ground, elimination of on-board recirculation pumps or bleed systems, smaller and lighter engine pumps and valves, lighter and more stable ullage gas, and significant reduction in tank fill operation. All of these mentioned attributes provide lower vehicle weight and cost.

  18. Return of the propeller

    SciTech Connect

    Not Available

    1987-05-01

    Resurrecting the propeller-driven airplane could help save fuel if there is another oil crisis like in the 1970s. This article discusses the new propeller engine, propfans, which are being developed for commercial airplanes. It discusses the three types of propfan engines and the advantages and disadvantages of each. It also tells about the propfan airplanes several companies are developing.

  19. Experiments on propeller noise

    NASA Astrophysics Data System (ADS)

    Grosche, F. R.; Stiewitt, H.

    Propeller sound generation was investigated. Tests were performed at flow velocities up to 58 m/sec on 90 cm dia. four bladed propellers driven by an electric motor enclosed in a streamlined nacelle. Five models with different blade geometries were tested at helical tip Mach numbers up to 0.69. Nearfield blade tip measurements were made at 0.14 dia. by an in-flow microphone. The acoustic far field was measured by four microphones outside the wind tunnel flow 2.7 m from the propeller axis. An acoustic mirror telescope with three microphones was used to investigate sound generation from the upper, central and lower parts of the propeller. The spectrum in the propeller plane is dominated by the tonal components at the blade passing frequency and its harmonics. Tonal component amplitude is greatly reduced downstream. The blades radiate high frequency noise mainly in motion direction.

  20. Propellant-remaining modeling

    NASA Technical Reports Server (NTRS)

    Torgovitsky, S.

    1991-01-01

    A successful satellite mission is predicted upon the proper maintenance of the spacecraft's orbit and attitude. One requirement for planning and predicting the orbit and attitude is the accurate estimation of the propellant remaining onboard the spacecraft. Focuss is on the three methods that were developed for calculating the propellant budget: the errors associated with each method and the uncertainties in the variables required to determine the propellant remaining that contribute to these errors. Based on these findings, a strategy is developed for improved propellant-remaining estimation. The first method is based on Boyle's law, which related the values of pressure, volume, and temperature (PVT) of an ideal gas. The PVT method is used for the monopropellant and the bipropellant engines. The second method is based on the engine performance tests, which provide data that relate thrust and specific impulse associated with a propellant tank to that tank's pressure. Two curves representing thrust and specific impulse as functions of pressure are then generated using a polynomial fit on the engine performance data. The third method involves a computer simulation of the propellant system. The propellant flow is modeled by creating a conceptual model of the propulsion system configuration, taking into account such factors as the propellant and pressurant tank characteristics, thruster functionality, and piping layout. Finally, a thrust calibration technique is presented that uses differential correction with the computer simulation method of propellant-remaining modeling. Thrust calibration provides a better assessment of thruster performance and therefore enables a more accurate estimation of propellant consumed during a given maneuver.

  1. Nonenhancing peritumoral hyperintense lesion on diffusion-weighted imaging in glioblastoma: a novel diagnostic and specific prognostic indicator.

    PubMed

    Kolakshyapati, Manish; Adhikari, Rupendra B; Karlowee, Vega; Takayasu, Takeshi; Nosaka, Ryo; Amatya, Vishwa J; Takeshima, Yukio; Akiyama, Yuji; Sugiyama, Kazuhiko; Kurisu, Kaoru; Yamasaki, Fumiyuki

    2017-03-31

    OBJECTIVE Glioblastoma differentials include intracranial tumors, like malignant lymphomas and metastatic brain tumors with indiscernible radiological characteristics. The purpose of this study was to identify a distinct radiological feature for the preoperative differentiation of glioblastoma from its differentials, which include malignant lymphomas and metastatic brain tumors. METHODS Preoperative MR images, including diffusion-weighted imaging (DWI) studies (b = 1000 and 4000 sec/mm(2)), obtained in patients with newly diagnosed malignant tumor, were analyzed retrospectively after receiving approval from the institutional review board. Sixty-four patients with histologically confirmed glioblastoma, 32 patients with malignant lymphoma, and 46 patients with brain metastases were included. The presence of a nonenhancing peritumoral DWI high lesion (NePDHL, i.e., hyperintense lesion in a nonenhancing peritumoral area on DWI) was confirmed in both DWI sequences. Gray matter lesions were excluded. Lesions were termed "definite" if present within 3 cm of the hyperintense tumor border with a signal intensity ratio ≥ 30% when compared with the contralateral normal white matter in both sequences. Discriminant analysis between the histological diagnosis and the presence of Definite-NePDHL was performed, as well as Kaplan-Meier survival analysis incorporating the existence of Definite-NePDHL. RESULTS In 25% of glioblastoma patients, Definite-NePDHL was present, while it was conspicuously absent in patients with malignant lymphoma and metastatic brain tumors. The specificity and positive predictive value were 100%. In the glioblastoma subset, a higher preoperative Karnofsky Performance Scale score (p = 0.0028), high recursive partitioning analysis class (p = 0.0006), and total surgical removal (p = 0.0012) were associated with better median overall survival. Patients with Definite-NePDHL had significantly early local (p = 0.0467) and distant/dissemination recurrence (p < 0

  2. Contribution of diffusion weighted MRI to diagnosis and staging in gastric tumors and comparison with multi-detector computed tomography

    PubMed Central

    Fatih Özbay, Mehmet; Çallı, İskan; Doğan, Erkan; Çelik, Sebahattin; Batur, Abdussamet; Bora, Aydın; Yavuz, Alpaslan; Bulut, Mehmet Deniz; Özgökçe, Mesut; Çetin Kotan, Mehmet

    2017-01-01

    Abstract Background Diagnostic performance of Diffusion-Weighted magnetic resonance Imaging (DWI) and Multi-Detector Computed Tomography (MDCT) for TNM (Tumor, Lymph node, Metastasis) staging of gastric cancer was compared. Patients and methods We used axial T2-weighted images and DWI (b-0,400 and b-800 s/mm2) protocol on 51 pre-operative patients who had been diagnosed with gastric cancer. We also conducted MDCT examinations on them. We looked for a signal increase in the series of DWI images. The depth of tumor invasion in the stomach wall (tumor (T) staging), the involvement of lymph nodes (nodal (N) staging), and the presence or absence of metastases (metastatic staging) in DWI and CT images according to the TNM staging system were evaluated. In each diagnosis of the tumors, sensitivity, specificity, positive and negative accuracy rates of DWI and MDCT examinations were found through a comparison with the results of the surgical pathology, which is the gold standard method. In addition to the compatibilities of each examination with surgical pathology, kappa statistics were used. Results Sensitivity and specificity of DWI and MDCT in lymph node staging were as follows: N1: DWI: 75.0%, 84.6%; MDCT: 66.7%, 82%;N2: DWI: 79.3%, 77.3%; MDCT: 69.0%, 68.2%; N3: DWI: 60.0%, 97.6%; MDCT: 50.0%, 90.2%. The diagnostic tool DWI seemed more compatible with the gold standard method (surgical pathology), especially in the staging of lymph node, when compared to MDCT. On the other hand, in T staging, the results of DWI and MDCT were better than the gold standard when the T stage increased. However, DWI did not demonstrate superiority to MDCT. The sensitivity and specificity of both imaging techniques for detecting distant metastasis were 100%. Conclusions The diagnostic accuracy of DWI for TNM staging in gastric cancer before surgery is at a comparable level with MDCT and adding DWI to routine protocol of evaluating lymph nodes metastasis might increase diagnostic accuracy

  3. Chemotherapy response evaluation in a mouse model of gastric cancer using intravoxel incoherent motion diffusion-weighted MRI and histopathology

    PubMed Central

    Cheng, Jin; Wang, Yi; Zhang, Chun-Fang; Wang, He; Wu, Wei-Zhen; Pan, Feng; Hong, Nan; Deng, Jie

    2017-01-01

    AIM To determine the role of intravoxel incoherent motion (IVIM) diffusion-weighted (DW) magnetic resonance imaging (MRI) using a bi-exponential model in chemotherapy response evaluation in a gastric cancer mouse model. METHODS Mice bearing MKN-45 human gastric adenocarcinoma xenografts were divided into four treated groups (TG1, 2, 3 and 4, n = 5 in each group) which received Fluorouracil and Calcium Folinate and a control group (CG, n = 7). DW-MRI scans with 14 b-values (0-1500 s/mm2) were performed before and after treatment on days 3, 7, 14 and 21. Fast diffusion component (presumably pseudo-perfusion) parameters including the fast diffusion coefficient (D*) and fraction volume (fp), slow diffusion coefficient (D) and the conventional apparent diffusion coefficients (ADC) were calculated by fitting the IVIM model to the measured DW signals. The median changes from the baseline to each post-treatment time point for each measurement (ΔADC, ΔD* and Δfp) were calculated. The differences in the median changes between the two groups were compared using the mixed linear regression model by the restricted maximum likelihood method shown as z values. Histopathological analyses including Ki-67, CD31, TUNEL and H&E were conducted in conjunction with the MRI scans. The median percentage changes were compared with the histopathological analyses between the pre- and post-treatment for each measurement. RESULTS Compared with the control group, D* in the treated group decreased significantly (ΔD*treated% = -30%, -34% and -20%, with z = -5.40, -4.18 and -1.95. P = 0.0001, 0.0001 and 0.0244) and fp increased significantly (Δfptreated% = 93%, 113% and 181%, with z = 4.63, 5.52, and 2.12, P = 0.001, 0.0001 and 0.0336) on day 3, 7 and 14, respectively. Increases in ADC in the treated group were higher than those in the control group on days 3 and 14 (z = 2.44 and 2.40, P = 0.0147 and P = 0.0164). CONCLUSION Fast diffusion measurements derived from the bi-exponential IVIM model

  4. Quantification of fibrosis in infarcted swine hearts by ex vivo late gadolinium-enhancement and diffusion-weighted MRI methods

    NASA Astrophysics Data System (ADS)

    Pop, Mihaela; Ghugre, Nilesh R.; Ramanan, Venkat; Morikawa, Lily; Stanisz, Greg; Dick, Alexander J.; Wright, Graham A.

    2013-08-01

    Many have speculated that MRI signal characteristics can be used to identify regions of heterogeneous infarct associated with an arrhythmogenic substrate; however, direct evidence of this relationship is limited. The aim of this study was to demonstrate the remodelling characteristics of fibrosis by means of histology and high-resolution MR imaging. For this purpose, we performed whole-mount histology in heart samples (n = 9) collected from five swine at six weeks post-infarction and compared the extent of fibrosis in the infarcted areas delineated in these histological images with that obtained ex vivo by MRI using late gadolinium-enhancement (LGE) and diffusion-weighted imaging (DWI) methods. All MR images were obtained at a submillimetre resolution (i.e., voxel size of 0.6×0.6×1.2 mm3). Specifically, in the histology images, we differentiated moderate fibrosis (consisting of a mixture of viable and non-viable myocytes, known as border zone, BZ) from severe fibrosis (i.e., the dense scar). Correspondingly, tissue heterogeneities in the MR images were categorized by a Gaussian mixture model into healthy, BZ and scar. Our results showed that (a) both MRI methods were capable of qualitatively distinguishing sharp edges between dense scar and healthy tissue from regions of heterogeneous BZ; (b) the BZ and dense scar areas had intermediate-to-high increased values of signal intensity in the LGE images and of apparent diffusion coefficient in the DWI, respectively. In addition, as demonstrated by the Picrosirius Red and immunohistochemistry stains, the viable bundles in the BZ were clearly separated by thin collagen strands and had reduced expression of Cx43, whereas the core scar was composed of dense fibrosis. A quantitative analysis demonstrated that the comparison between BZ/scar extent in LGE and DWI to the corresponding areas identified in histology yielded very good correlations (i.e., for the scar identified by LGE, R2 was 0.96 compared to R2 = 0.93 for the

  5. Diffusion-Weighted MR Enterography to Monitor Bowel Inflammation after Medical Therapy in Crohn's Disease: A Prospective Longitudinal Study

    PubMed Central

    Huh, Jimi; Kim, Kyung Jo; Park, So Hyun; Yang, Suk-Kyun; Ye, Byong Duk; Park, Sang Hyoung; Han, Kyunghwa; Kim, Ah Young

    2017-01-01

    Objective To prospectively evaluate the performance of diffusion-weighted imaging (DWI) to monitor bowel inflammation after medical therapy for Crohn's disease (CD). Materials and Methods Before and following 1–2 years of medical therapy, between October 2012 and May 2015, 18 randomly selected adult CD patients (male:female, 13:5; mean age ± SD, 25.8 ± 7.9 years at the time of enrollment) prospectively underwent MR enterography (MRE) including DWI (b = 900 s/mm2) and ileocolonoscopy. Thirty-seven prospectively defined index lesions (one contiguous endoscopy-confirmed inflamed area chosen from each inflamed anatomical bowel segment; 1–4 index lesions per patient; median, 2 lesions) were assessed on pre- and post-treatment MRE and endoscopy. Visual assessment of treatment responses on DWI in 4 categories including complete remission and reduced, unchanged or increased inflammation, and measurements of changes in apparent diffusion coefficient (ΔADC), i.e., pre-treatment–post-treatment, were performed by 2 independent readers. Endoscopic findings and CD MRI activity index (CDMI) obtained using conventional MRE served as reference standards. Results ΔADC significantly differed between improved (i.e., complete remission and reduced inflammation) and unimproved (i.e., unchanged or increased inflammation) lesions: mean ± SD (× 10-3 mm2/s) of -0.65 ± 0.58 vs. 0.06 ± 0.15 for reader 1 (p = 0.022) and -0.68 ± 0.56 vs. 0.10 ± 0.26 for reader 2 (p = 0.025). DWI accuracy for diagnosing complete remission or improved inflammation ranged from 76% (28/37) to 84% (31/37). A significant negative correlation was noted between ΔADC and ΔCDMI for both readers with correlation coefficients of -0.438 and -0.461, respectively (p < 0.05). Conclusion DWI is potentially a feasible tool to monitor quantitatively and qualitatively bowel inflammation of CD after medical treatment. PMID:28096726

  6. Diffusion-weighted magnetic resonance imaging in cancer: Reported apparent diffusion coefficients, in-vitro and in-vivo reproducibility

    PubMed Central

    Jafar, Maysam M; Parsai, Arman; Miquel, Marc E

    2016-01-01

    There is considerable disparity in the published apparent diffusion coefficient (ADC) values across different anatomies. Institutions are increasingly assessing repeatability and reproducibility of the derived ADC to determine its variation, which could potentially be used as an indicator in determining tumour aggressiveness or assessing tumour response. In this manuscript, a review of selected articles published to date in healthy extra-cranial body diffusion-weighted magnetic resonance imaging is presented, detailing reported ADC values and discussing their variation across different studies. In total 115 studies were selected including 28 for liver parenchyma, 15 for kidney (renal parenchyma), 14 for spleen, 13 for pancreatic body, 6 for gallbladder, 13 for prostate, 13 for uterus (endometrium, myometrium, cervix) and 13 for fibroglandular breast tissue. Median ADC values in selected studies were found to be 1.28 × 10-3 mm2/s in liver, 1.94 × 10-3 mm2/s in kidney, 1.60 × 10-3 mm2/s in pancreatic body, 0.85 × 10-3 mm2/s in spleen, 2.73 × 10-3 mm2/s in gallbladder, 1.64 × 10-3 mm2/s and 1.31 × 10-3 mm2/s in prostate peripheral zone and central gland respectively (combined median value of 1.54×10-3 mm2/s), 1.44 × 10-3 mm2/s in endometrium, 1.53 × 10-3 mm2/s in myometrium, 1.71 × 10-3 mm2/s in cervix and 1.92 × 10-3 mm2/s in breast. In addition, six phantom studies and thirteen in vivo studies were summarized to compare repeatability and reproducibility of the measured ADC. All selected phantom studies demonstrated lower intra-scanner and inter-scanner variation compared to in vivo studies. Based on the findings of this manuscript, it is recommended that protocols need to be optimised for the body part studied and that system-induced variability must be established using a standardized phantom in any clinical study. Reproducibility of the measured ADC must also be assessed in a volunteer population, as variations are far more significant in vivo compared

  7. Early Changes in Apparent Diffusion Coefficient From Diffusion-Weighted MR Imaging During Radiotherapy for Prostate Cancer

    SciTech Connect

    Park, Sung Yoon; Kim, Chan Kyo; Park, Byung Kwan; Park, Won; Park, Hee Chul; Han, Deok Hyun; Kim, Bohyun

    2012-06-01

    Purpose: To investigate the feasibility of diffusion-weighted MRI (DWI) as an early and reproducible change indicator in patients receiving radiotherapy for prostate cancer (PC). Methods and Materials: Eight consecutive patients with biopsy-proven PC underwent DWI at 3T. All patients who received external-beam radiotherapy had four serial MR scans, as follows: before therapy (PreTx); after 1 week of therapy (PostT1); after 3 weeks of therapy (PostT2); and 1 month after the completion of therapy (PostT3). At each time, the apparent diffusion coefficient (ADC) was measured in tumors and normal tissues. For reproducibility of the ADC measurement, five patients also had two separate pretreatment DWI scans at an interval of <2 weeks. Serum prostate-specific antigen (PSA) levels were evaluated at the same time as MR scans. Results: Thirteen tumors (peripheral zone = 10; transition zone = 3) were found. The mean ADC values for the tumors from PreTx to PostT3 were 0.86, 1.03, 1.15, and 1.26 Multiplication-Sign 10{sup -3} mm{sup 2}/s in sequence, respectively. Compared with PreTx, PostT1 (p = 0.005), PostT2 (p = 0.003), and PostT3 (p < 0.001) showed a significant increase in ADC values. The mean ADC values of the benign tissues from PreTx to PostT3 were 1.60, 1.58, 1.47, and 1.46 Multiplication-Sign 10{sup -3} mm{sup 2}/s in sequence, respectively. Reproducibility of ADC measurements was confirmed with a mean difference in ADC of -0.04 in peripheral zone and -0.017 in transition zone between two separate pretreatment MR scans. The mean PSA levels from PreTx to PostT3 were 9.05, 9.18, 9.25, and 4.11 ng/mL in sequence, respectively. Conclusions: DWI, as a reproducible biomarker, has the potential to evaluate the early therapeutic changes of PC to radiotherapy.

  8. Role of Diffusion-Weighted Magnetic Resonance Imaging in Predicting Sensitivity to Chemoradiotherapy in Muscle-Invasive Bladder Cancer

    SciTech Connect

    Yoshida, Soichiro; Koga, Fumitaka; Kobayashi, Shuichiro; Ishii, Chikako; Tanaka, Hiroshi; Tanaka, Hajime; Komai, Yoshinobu; Saito, Kazutaka; Masuda, Hitoshi; Fujii, Yasuhisa; Kawakami, Satoru; Kihara, Kazunori

    2012-05-01

    Purpose: In chemoradiation (CRT)-based bladder-sparing approaches for muscle invasive bladder cancer (MIBC), patients who respond favorably to induction CRT enjoy the benefits of bladder preservation, whereas nonresponders do not. Thus, accurate prediction of CRT sensitivity would optimize patient selection for bladder-sparing protocols. Diffusion-weighted MRI (DW-MRI) is a functional imaging technique that quantifies the diffusion of water molecules in a noninvasive manner. We investigated whether DW-MRI predicts CRT sensitivity of MIBC. Methods and Materials: The study cohort consisted of 23 MIBC patients (cT2/T3 = 7/16) who underwent induction CRT consisting of radiotherapy to the small pelvis (40 Gy) with two cycles of cisplatin (20 mg/day for 5 days), followed by partial or radical cystectomy. All patients underwent DW-MRI before the initiation of treatment. Associations of apparent diffusion coefficient (ADC) values with CRT sensitivity were analyzed. The proliferative potential of MIBC was also assessed by analyzing the Ki-67 labeling index (LI) in pretherapeutic biopsy specimens. Results: Thirteen patients (57%) achieved pathologic complete response (pCR) to CRT. These CRT-sensitive MIBCs showed significantly lower ADC values (median, 0.63 Multiplication-Sign 10{sup -3} mm{sup 2}/s; range, 0.43-0.77) than CRT-resistant (no pCR) MIBCs (median, 0.84 Multiplication-Sign 10{sup -3} mm{sup 2}/s; range, 0.69-1.09; p = 0.0003). Multivariate analysis identified ADC value as the only significant and independent predictor of CRT sensitivity (p < 0.0001; odds ratio per 0.001 Multiplication-Sign 10{sup -3} mm{sup 2}/s increase, 1.03; 95% confidence interval, 1.01-1.08). With a cutoff ADC value at 0.74 Multiplication-Sign 10{sup -3} mm{sup 2}/s, sensitivity/specificity/accuracy in predicting CRT sensitivity was 92/90/91%. Ki-67 LI was significantly higher in CRT-sensitive MIBCs (p = 0.0005) and significantly and inversely correlated with ADC values ({rho} = -0.67, p = 0

  9. Microgravity liquid propellant management

    NASA Technical Reports Server (NTRS)

    Hung, R. J.

    1990-01-01

    The requirement to settle or to position liquid fluid over the outlet end of a spacecraft propellant tank prior to main engine restart, poses a microgravity fluid behavior problem. Resettlement or reorientation of liquid propellant can be accomplished by providing optimal acceleration to the spacecraft such that the propellant is reoriented over the tank outlet without any vapor entrainment, any excessive geysering, or any other undersirable fluid motion for the space fluid management under microgravity environment. The most efficient technique is studied for propellant resettling through the minimization of propellant usage and weight penalties. Both full scale and subscale liquid propellant tank of Space Transfer Vehicle were used to simulate flow profiles for liquid hydrogen reorientation over the tank outlet. In subscale simulation, both constant and impulsive resettling acceleration were used to simulate the liquid flow reorientation. Comparisons between the constant reverse gravity acceleration and impulsive reverse gravity acceleration to be used for activation of propellant resettlement shows that impulsive reverse gravity thrust is superior to constant reverse gravity thrust.

  10. Nitramine smokeless propellant research

    NASA Technical Reports Server (NTRS)

    Cohen, N. S.; Strand, L. P.

    1977-01-01

    A transient ballistics and combustion model is derived to represent the closed vessel experiment that is widely used to characterize propellants. A computer program is developed to solve the time-dependent equations, and is applied to explain aspects of closed vessel behavior. In the case of nitramine propellants the cratering of the burning surface associated with combustion above break-point pressures augments the effective burning rate as deduced from the closed vessel experiment. Low pressure combustion is significantly affected by the ignition process and, in the case of nitramine propellants, by the developing and changing surface structure. Thus, burning rates deduced from the closed vessel experiment may or may not agree with those measured in the equilibrium strand burner. Series of T burner experiments are performed to compare the combustion instability characteristics of nitramine (HMX) containing propellants and ammonium perchlorate (AP)propellants. Although ash produced by more fuel rich propellants could have provided mechanical suppression, results from clean-burning propellants permit the conclusion that HMX reduces the acoustic driving.

  11. The parallel-antiparallel signal difference in double-wave-vector diffusion-weighted MR at short mixing times: A phase evolution perspective

    NASA Astrophysics Data System (ADS)

    Finsterbusch, Jürgen

    2011-01-01

    Experiments with two diffusion weightings applied in direct succession in a single acquisition, so-called double- or two-wave-vector diffusion-weighting (DWV) experiments at short mixing times, have been shown to be a promising tool to estimate cell or compartment sizes, e.g. in living tissue. The basic theory for such experiments predicts that the signal decays for parallel and antiparallel wave vector orientations differ by a factor of three for small wave vectors. This seems to be surprising because in standard, single-wave-vector experiments the polarity of the diffusion weighting has no influence on the signal attenuation. Thus, the question how this difference can be understood more pictorially is often raised. In this rather educational manuscript, the phase evolution during a DWV experiment for simple geometries, e.g. diffusion between parallel, impermeable planes oriented perpendicular to the wave vectors, is considered step-by-step and demonstrates how the signal difference develops. Considering the populations of the phase distributions obtained, the factor of three between the signal decays which is predicted by the theory can be reproduced. Furthermore, the intermediate signal decay for orthogonal wave vector orientations can be derived when investigating diffusion in a box. Thus, the presented “phase gymnastics” approach may help to understand the signal modulation observed in DWV experiments at short mixing times.

  12. Chemical shift and diffusion-weighted magnetic resonance imaging of the anterior mediastinum in oncology: Current clinical applications in qualitative and quantitative assessment.

    PubMed

    Priola, Adriano Massimiliano; Gned, Dario; Veltri, Andrea; Priola, Sandro Massimo

    2016-02-01

    Recently, the use of magnetic resonance (MR) in clinical practice for the evaluation of the anterior mediastinum has considerably increased due to technological improvements and standardization of thoracic protocols. Currently, MR imaging is increasingly seen as a useful problem-solving modality, especially in equivocal cases at computed tomography, with the advantage of a higher contrast resolution and no radiation exposure. Chemical shift and diffusion-weighted MR are helpful in tissue characterization and present advantages over conventional MR imaging, first in providing quantitative data, without the need for the administration of contrast medium. By detecting microscopic fat in tissue, chemical shift imaging is useful for differentiating normal thymus and rebound hyperplasia from cancer tissue at diagnosis and after chemotherapy in oncologic patients, and for distinguishing lymphoid hyperplasia from thymoma in autoimmune diseases such as myasthenia gravis. Diffusion-weighted MR reflects diffusivity of water molecules within tissue and is increasingly used as a cancer biomarker, even in the thorax, for the detection and characterization of tumors, for their differentiation from benign conditions, and for monitoring treatment response. In this review, based on the current literature, technical considerations about image acquisition and data analysis of chemical shift and diffusion-weighted MR are discussed along with clinical applications in the field of benign and malignant disease of the anterior mediastinum.

  13. Real-Time Correction of Rigid-Body-Motion-Induced Phase Errors for Diffusion-Weighted Steady State Free Precession Imaging

    PubMed Central

    O’Halloran, R; Aksoy, M; Aboussouan, E; Peterson, E; Van, A; Bammer, R

    2014-01-01

    Purpose Diffusion contrast in diffusion-weighted steady state free precession MRI is generated through the constructive addition of signal from many coherence pathways. Motion-induced phase causes destructive interference which results in loss of signal magnitude and diffusion contrast. In this work, a 3D navigator-based real-time correction of the rigid-body-motion-induced phase errors is developed for diffusion-weighted steady state free precession MRI. Methods The efficacy of the real-time prospective correction method in preserving phase coherence of the steady-state is tested in 3D phantom experiments and 3D scans of healthy human subjects. Results In nearly all experiments, the signal magnitude in images obtained with proposed prospective correction was higher than the signal magnitude in images obtained with no correction. In the human subjects the mean magnitude signal in the data was up to 30 percent higher with prospective motion correction than without. Prospective correction never resulted in a decrease in mean signal magnitude in either the data or in the images. Conclusions The proposed prospective motion correction method is shown to preserve the phase coherence of the steady state in diffusion-weighted steady state free precession MRI, thus mitigating signal magnitude losses that would confound the desired diffusion contrast. PMID:24715414

  14. Hydrodynamics of Ship Propellers

    NASA Astrophysics Data System (ADS)

    Breslin, John P.; Andersen, Poul

    1996-11-01

    This book deals with flows over propellers operating behind ships, and the hydrodynamic forces and movements that the propeller generates on the shaft and on the ship hull. The first part of the book is devoted to fundamentals of the flow about hydrofoil sections and wings, and to propellers in uniform flow, with guidance for design and pragmatic analysis of performance. The second part covers the development of unsteady forces arising from operation in nonuniform hull wakes. A final chapter discusses the optimization of efficiency of compound propulsors. Researchers in ocean technology and naval architecture will find this book appealing.

  15. Propeller tone bursts

    NASA Technical Reports Server (NTRS)

    Succi, G. P.; Munro, D. H.; Ingard, K. U.

    1983-01-01

    Intense high frequency (25-38 kHz) tone bursts have been observed in acoustic tests of a scale model of a general aviation propeller. The amplitude of the tone burst is approximately equal to the amplitude of the propeller noise signature. The conditions necessary for the production of these tone bursts are described. The experiments indicate that the origin of these bursts is a periodic flow oscillation on the suction surface of the propeller blade tips which may be due to the interaction between an oscillating shock wave and a laminar boundary layer.

  16. Automated Propellant Blending

    NASA Technical Reports Server (NTRS)

    Hohmann, Carl W. (Inventor); Harrington, Douglas W. (Inventor); Dutton, Maureen L. (Inventor); Tipton, Billy Charles, Jr. (Inventor); Bacak, James W. (Inventor); Salazar, Frank (Inventor)

    2000-01-01

    An automated propellant blending apparatus and method that uses closely metered addition of countersolvent to a binder solution with propellant particles dispersed therein to precisely control binder precipitation and particle aggregation is discussed. A profile of binder precipitation versus countersolvent-solvent ratio is established empirically and used in a computer algorithm to establish countersolvent addition parameters near the cloud point for controlling the transition of properties of the binder during agglomeration and finishing of the propellant composition particles. The system is remotely operated by computer for safety, reliability and improved product properties, and also increases product output.

  17. Automated Propellant Blending

    NASA Technical Reports Server (NTRS)

    Hohmann, Carl W. (Inventor); Harrington, Douglas W. (Inventor); Dutton, Maureen L. (Inventor); Tipton, Billy Charles, Jr. (Inventor); Bacak, James W. (Inventor); Salazar, Frank (Inventor)

    1999-01-01

    An automated propellant blending apparatus and method uses closely metered addition of countersolvent to a binder solution with propellant particles dispersed therein to precisely control binder precipitation and particle aggregation. A profile of binder precipitation versus countersolvent-solvent ratio is established empirically and used in a computer algorithm to establish countersolvent addition parameters near the cloud point for controlling the transition of properties of the binder during agglomeration and finishing of the propellant composition particles. The system is remotely operated by computer for safety, reliability and improved product properties, and also increases product output.

  18. Nitramine smokeless propellant research

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A transient ballistics and combustion model was derived to represent the closed vessel experiment that is widely used to characterize propellants. The model incorporates the nitramine combustion mechanisms. A computer program was developed to solve the time dependent equations, and was applied to explain aspects of closed vessel behavior. It is found that the rate of pressurization in the closed vessel is insufficient at pressures of interest to augment the burning rate by time dependent processes. Series of T-burner experiments were performed to compare the combustion instability characteristics of nitramine (HMX) containing propellants and ammonium perchlorate (AP) propellants. It is found that the inclusion of HMX consistently renders the propellant more stable.

  19. Propellant variability assessment

    NASA Technical Reports Server (NTRS)

    Tytula, Thomas P.; Schad, Kristin

    1991-01-01

    Efforts to determine whether rocket propellant density and modulus can be reliably measured using non-destructive ultrasonic techniques are reported. The objective was not achieved, primarily due to the approach taken.

  20. PROPELLANT STORABILITY IN SPACE

    DTIC Science & Technology

    other, thermal interactions between a cryogenic and an earth storable propellant combination will be studied. A final series of tests will be conducted...The design of the test tankage, meteorite shields, and support system was initiated.

  1. Solid Propellant Reclamation Study

    DTIC Science & Technology

    1982-11-01

    and Ethanol Amine (EA) NHC Recovery Process Flow Diagram Explosive Booster Process Flow’ Sheet Sol-Gel Extraction from Solid Propellant Chemical...Naval Weapons Center, China Lake, California, 1973-1975. e Leake, E. E., Recovery of HMX From Scrap PEX -9404 High Explosive. Silas Mason...ntly degraded by reacting ethanol - amlne (EA) with the urethane linkages In the binder MtwOrkt The propellent he studied was a polyurethane

  2. Liquid Propellant Guns

    DTIC Science & Technology

    1987-10-01

    GROUP SUB- GROUP 19. ABSTRAJ (Continue on reverse if necessary and identify by block number) Liquid propellants have been the focus of periodic...The ignition system of the BLG , more so than in a solid propellant gun, is key to safe ballistic operation. The coupling (temporal and spatial) of...based monopropellant.’i’ This approach offers advantages for mechanical simplification during loading. Satisfactory performance in a five round group

  3. Can Dynamic Contrast-Enhanced MRI (DCE-MRI) and Diffusion-Weighted MRI (DW-MRI) Evaluate Inflammation Disease

    PubMed Central

    Zhu, Jianguo; Zhang, Faming; Luan, Yun; Cao, Peng; Liu, Fei; He, Wenwen; Wang, Dehang

    2016-01-01

    Abstract The aim of the study was to investigate diagnosis efficacy of dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted MRI (DW-MRI) in Crohn's disease (CD). To find out the correlations between functional MRI parameters including Ktrans, Kep, Ve, Vp, and apparent diffusion coefficient (ADC) with a serologic biomarker. The relationships between pharmacokinetic parameters and ADC were also studied. Thirty-two patients with CD (22 men, 10 women; mean age: 30.5 years) and 18 healthy volunteers without any inflammatory disease (10 men, 8 women; mean age, 34.11 years) were enrolled into this approved prospective study. Pearson analysis was used to evaluate the correlation between Ktrans, Kep, Ve, Vp, and C-reactive protein (CRP), ADC, and CRP respectively. The diagnostic efficacy of the functional MRI parameters in terms of sensitivity and specificity were analyzed by receiver operating characteristic (ROC) curve analyses. Optimal cut-off values of each functional MRI parameters for differentiation of inflammatory from normal bowel were determined according to the Youden criterion. Mean value of Ktrans in the CD group was significantly higher than that of normal control group. Similar results were observed for Kep and Ve. On the contrary, the ADC value was lower in the CD group than that in the control group. Ktrans and Ve were shown to be correlated with CRP (r = 0.725, P < 0.001; r = 0.533, P = 0.002), meanwhile ADC showed negative correlation with CRP (r = −0.630, P < 0.001). There were negative correlations between the pharmacokinetic parameters and ADC, such as Ktrans to ADC (r = −0.856, P < 0.001), and Ve to ADC (r = −0.451, P = 0.01). The area under the curve (AUC) was 0.994 for Ktrans (P < 0.001), 0.905 for ADC (P < 0.001), 0.806 for Ve (P < 0.001), and 0.764 for Kep (P = 0.002). The cut-off point of the Ktrans was found to be 0.931 min–1. This value provided the best trade-off between

  4. Advanced propeller research

    NASA Technical Reports Server (NTRS)

    Groeneweg, John F.; Bober, Lawrence J.

    1987-01-01

    Resent results of aerodynamic and acoustic research on both single and counter-rotation propellers are reviewed. Data and analytical results are presented for three propellers: SR-7A, the single rotation design used in the NASA Propfan Test Assessment (PTA); and F7-A7, the 8+8 counterrotating design used in the proof-of-concept Unducted Fan (UDF) engine. In addition to propeller efficiencies, cruise and takeoff noise, and blade pressure data, off-design phenomena involving formation of leading edge vortices are described. Aerodynamic and acoustic computational results derived from three-dimensional Euler and acoustic radiation codes are presented. Research on unsteady flows, which are particularly important for understanding counterrotation interaction noise, unsteady loading effects on acoustics, and flutter or forced response is described. The first results of three-dimensional unsteady Euler solutions are illustrated for a single rotation propeller at an angle of attack and for a counterrotation propeller. Basic experimental and theoretical results from studies of the unsteady aerodynamics of oscillating cascades are outlined. Finally, advanced concepts involving swirl recovery vanes and ultra bypass ducted propellers are discussed.

  5. Propellant Readiness Level: A Methodological Approach to Propellant Characterization

    NASA Technical Reports Server (NTRS)

    Bossard, John A.; Rhys, Noah O.

    2010-01-01

    A methodological approach to defining propellant characterization is presented. The method is based on the well-established Technology Readiness Level nomenclature. This approach establishes the Propellant Readiness Level as a metric for ascertaining the readiness of a propellant or a propellant combination by evaluating the following set of propellant characteristics: thermodynamic data, toxicity, applications, combustion data, heat transfer data, material compatibility, analytical prediction modeling, injector/chamber geometry, pressurization, ignition, combustion stability, system storability, qualification testing, and flight capability. The methodology is meant to be applicable to all propellants or propellant combinations; liquid, solid, and gaseous propellants as well as monopropellants and propellant combinations are equally served. The functionality of the proposed approach is tested through the evaluation and comparison of an example set of hydrocarbon fuels.

  6. Propellers in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Sremcevic, M.; Stewart, G. R.; Albers, N.; Esposito, L. W.

    2013-12-01

    Theoretical studies and simulations have demonstrated the effects caused by objects embedded in planetary rings. Even if the objects are too small to be directly observed, each creates a much larger gravitational imprint on the surrounding ring material. These strongly depend on the mass of the object and range from "S" like propeller-shaped structures for about 100m-sized icy bodies to the opening of circumferential gaps as in the case of the embedded moons Pan and Daphnis and their corresponding Encke and Keeler Gaps. Since the beginning of the Cassini mission many of these smaller objects (~<500m in size) have been indirectly identified in Saturn's A ring through their propeller signature in the images. Furthermore, recent Cassini observations indicate the possible existence of objects embedded even in Saturn's B and C ring. In this paper we present evidence for the existence of propellers in Saturn's B ring by combining data from Cassini Ultraviolet Imaging Spectrograph (UVIS) and Imaging Science Subsystem (ISS) experiments. We show evidence that B ring seems to harbor two distinct populations of propellers: "big" propellers covering tens of degrees in azimuth situated in the densest part of B ring, and "small" propellers in less dense inner B ring that are similar in size and shape to known A ring propellers. The population of "big" propellers is exemplified with a single object which is observed for 5 years of Cassini data. The object is seen as a very elongated bright stripe (40 degrees wide) in unlit Cassini images, and dark stripe in lit geometries. In total we report observing the feature in images at 18 different epochs between 2005 and 2010. In UVIS occultations we observe this feature as an optical depth depletion in 14 out of 93 occultation cuts at corrotating longitudes compatible with imaging data. Combining the available Cassini data we infer that the object is a partial gap located at r=112,921km embedded in the high optical depth region of the B

  7. A longitudinal study of patients with cirrhosis treated with L-ornithine L-aspartate, examined with magnetization transfer, diffusion-weighted imaging and magnetic resonance spectroscopy.

    PubMed

    Grover, Vijay P B; McPhail, Mark J W; Wylezinska-Arridge, Marzena; Crossey, Mary M E; Fitzpatrick, Julie A; Southern, Louise; Saxby, Brian K; Cook, Nicola A; Cox, I Jane; Waldman, Adam D; Dhanjal, Novraj S; Bak-Bol, Aluel; Williams, Roger; Morgan, Marsha Y; Taylor-Robinson, Simon D

    2017-02-01

    The presence of overt hepatic encephalopathy (HE) is associated with structural, metabolic and functional changes in the brain discernible by use of a variety of magnetic resonance (MR) techniques. The changes in patients with minimal HE are less well documented. Twenty-two patients with well-compensated cirrhosis, seven of whom had minimal HE, were examined with cerebral 3 Tesla MR techniques, including T1- and T2-weighted, magnetization transfer and diffusion-weighted imaging and proton magnetic resonance spectroscopy sequences. Studies were repeated after a 4-week course of oral L-ornithine L-aspartate (LOLA). Results were compared with data obtained from 22 aged-matched healthy controls. There was no difference in mean total brain volume between patients and controls at baseline. Mean cerebral magnetization transfer ratios were significantly reduced in the globus pallidus and thalamus in the patients with cirrhosis irrespective of neuropsychiatric status; the mean ratio was significantly reduced in the frontal white matter in patients with minimal HE compared with healthy controls but not when compared with their unimpaired counterparts. There were no significant differences in either the median apparent diffusion coefficients or the mean fractional anisotropy, calculated from the diffusion-weighted imaging, or in the mean basal ganglia metabolite ratios between patients and controls. Psychometric performance improved in 50 % of patients with minimal HE following LOLA, but no significant changes were observed in brain volumes, cerebral magnetization transfer ratios, the diffusion weighted imaging variables or the cerebral metabolite ratios. MR variables, as applied in this study, do not identify patients with minimal HE, nor do they reflect changes in psychometric performance following LOLA.

  8. Propellers in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Sremcevic, M.; Stewart, G. R.; Albers, N.; Esposito, L. W.

    2014-04-01

    Theoretical studies and simulations have demonstrated the effects caused by objects embedded in planetary rings [5, 8]. Even if the objects are too small to be directly observed, each creates a much larger gravitational imprint on the surrounding ring material. These strongly depend on the mass of the object and range from "S" like propeller-shaped structures for about 100m-sized icy bodies to the opening of circumferential gaps as in the case of the embedded moons Pan and Daphnis and their corresponding Encke and Keeler Gaps. Since the beginning of the Cassini mission many of these smaller objects (~ 100m in size) have been identified in Saturn's A ring through their propeller signature in the images [10, 7, 9, 11]. Furthermore, recent Cassini observations indicate the possible existence of objects embedded even in Saturn's B and C ring [6, 2]. In this paper we present our new results about by now classical A ring propellers and more enigmatic B ring population. Due to the presence of self-gravity wakes the analysis of propeller brightness in ISS images always bears some ambiguity [7, 9] and consequently the exact morphology of propellers is not a settled issue. In 2008 we obtained a fortunate Cassini Ultraviolet Imaging Spectrograph (UVIS) occultation of the largest A ring propeller Bleriot. Utilizing Cassini ISS images we obtain Bleriot orbit and demonstrate that UVIS Persei Rev42 occultation did cut across Bleriot about 100km downstream from the center. The occultation itself shows a prominent partial gap and higher density outer flanking wakes, while their orientation is consistent with a downstream cut. While in the UVIS occultation the partial gap is more prominent than the flanking wakes, the features mostly seen in Bleriot images are actually flanking wakes. One of the most interesting aspects of the A ring propellers are their wanderings, or longitudinal deviations from a pure circular orbit [11]. We numerically investigated the possibility of simple moon

  9. Advanced propeller research

    NASA Technical Reports Server (NTRS)

    Groeneweg, John F.; Bober, Lawrence J.

    1990-01-01

    Recent results of aerodynamic and acoustic research on both single rotation and counterrotation propellers are reviewed. Data and analytical results are presented for three propellers: SR-7A, the single rotation design used in the NASA Propfan Test Assessment (PTA) flight program; CRP-X1, the initial 5+5 Hamilton Standard counterrotating design; and F7-A7, the 8+8 counterrotating G.E. design used in the proof of concept Unducted Fan (UDF) engine. In addition to propeller efficiencies, cruise and takeoff noise, and blade pressure data, off-design phenomena involving formation of leading edge vortexes are described. Aerodynamic and acoustic computational results derived from 3-D Euler and acoustic radiation codes are presented. Research on unsteady flows which are particularly important for understanding counterrotation interaction noise, unsteady loading effects on acoustics, and flutter or forced response is described. The first results of 3-D unsteady Euler solutions are illustrated for a single rotation propeller at angle of attack and for a counterrotation propeller. Basic experimental and theoretical results from studies on the unsteady aerodynamics of oscillating cascades are outlined.

  10. Aeroacoustics of advanced propellers

    NASA Technical Reports Server (NTRS)

    Groeneweg, John F.

    1990-01-01

    The aeroacoustics of advanced, high speed propellers (propfans) are reviewed from the perspective of NASA research conducted in support of the Advanced Turboprop Program. Aerodynamic and acoustic components of prediction methods for near and far field noise are summarized for both single and counterrotation propellers in uninstalled and configurations. Experimental results from tests at both takeoff/approach and cruise conditions are reviewed with emphasis on: (1) single and counterrotation model tests in the NASA Lewis 9 by 15 (low speed) and 8 by 6 (high speed) wind tunnels, and (2) full scale flight tests of a 9 ft (2.74 m) diameter single rotation wing mounted tractor and a 11.7 ft (3.57 m) diameter counterrotation aft mounted pusher propeller. Comparisons of model data projected to flight with full scale flight data show good agreement validating the scale model wind tunnel approach. Likewise, comparisons of measured and predicted noise level show excellent agreement for both single and counterrotation propellers. Progress in describing angle of attack and installation effects is also summarized. Finally, the aeroacoustic issues associated with ducted propellers (very high bypass fans) are discussed.

  11. In Vivo Magnetization Transfer and Diffusion-Weighted Magnetic Resonance Imaging Detects Thrombus Composition in a Mouse Model of Deep Vein Thrombosis

    PubMed Central

    Saha, Prakash; Modarai, Bijan; Smith, Alberto; Botnar, René M.

    2014-01-01

    Background Deep vein thrombosis remains a major health problem necessitating accurate diagnosis. Thrombolysis is associated with significant morbidity and is effective only for the treatment of unorganized thrombus. We tested the feasibility of in vivo magnetization transfer (MT) and diffusion-weighted magnetic resonance imaging to detect thrombus organization in a murine model of deep vein thrombosis. Methods and Results Deep vein thrombosis was induced in the inferior vena cava of male BALB/C mice. Magnetic resonance imaging was performed at days 1, 7, 14, 21, and 28 after thrombus induction using MT, diffusion-weighted, inversion-recovery, and T1-mapping protocols. Delayed enhancement and T1 mapping were repeated 2 hours after injection of a fibrin contrast agent. Finally, excised thrombi were used for histology. We found that MT and diffusion-weighted imaging can detect histological changes associated with thrombus aging. MT rate (MTR) maps and percentage of MT rate (%MTR) allowed visualization and quantification of the thrombus protein content, respectively. The %MTR increased with thrombus organization and was significantly higher at days 14, 21, and 28 after thrombus induction (days 1, 7, 14, 21, 28: %MTR=2483±451, 2079±1210, 7029±2490, 10 295±4356, 32 994±25 449; Panova<0.05). There was a significant positive correlation between the %MTR and the histological protein content of the thrombus (r=0.70; P<0.05). The apparent diffusion coefficient was lower in erythrocyte-rich and collagen-rich thrombus (0.72±0.10 and 0.69±0.05 [×10−3 mm2/s]). Thrombus at days 7 and 14 had the highest apparent diffusion coefficient values (0.95±0.09 and 1.10±0.18 [×10−3 mm2/s]). Conclusions MT and diffusion-weighted magnetic resonance imaging sequences are promising for the staging of thrombus composition and could be useful in guiding medical intervention. PMID:23564561

  12. Propeller pitch change mechanism

    SciTech Connect

    Hora, P.

    1992-10-13

    This patent describes an aircraft propulsion system. It comprises: a first turbine carrying a first set of propeller blades; a second turbine carrying a second set of propeller blades; a gear system carried by the first turbine for changing pitch of the first set of propeller blades, which includes a pair of ring gears, both coaxial with the first turbine; a first set of planet gears which engage both ring gears and which induce pitch change when the planet gears rotate; a sun gear which drives the planet gears; a second set of planet gears which are carried by a planet gear carrier affixed to the second turbine and which drive the sun gear in order to change pitch by causing relative motion between the sung ear and the first turbine; and means for preventing a change in speed of the planet gear carrier from causing a change in pitch.

  13. Self-propelled droplets

    NASA Astrophysics Data System (ADS)

    Seemann, Ralf; Fleury, Jean-Baptiste; Maass, Corinna C.

    2016-11-01

    Self-propelled droplets are a special kind of self-propelled matter that are easily fabricated by standard microfluidic tools and locomote for a certain time without external sources of energy. The typical driving mechanism is a Marangoni flow due to gradients in the interfacial energy on the droplet interface. In this article we review the hydrodynamic prerequisites for self-sustained locomotion and present two examples to realize those conditions for emulsion droplets, i.e. droplets stabilized by a surfactant layer in a surrounding immiscible liquid. One possibility to achieve self-propelled motion relies on chemical reactions affecting the surface active properties of the surfactant molecules. The other relies on micellar solubilization of the droplet phase into the surrounding liquid phase. Remarkable cruising ranges can be achieved in both cases and the relative insensitivity to their own `exhausts' allows to additionally study collective phenomena.

  14. Propellers in yaw

    NASA Technical Reports Server (NTRS)

    Ribner, Herbert S

    1945-01-01

    It was realized as early as 1909 that a propeller in yaw develops a side force like that of a fin. In 1917, R. G. Harris expressed this force in terms of the torque coefficient for the unyawed propeller. Of several attempts to express the side force directly in terms of the shape of the blades, however, none has been completely satisfactory. An analysis that incorporates induction effects not adequately covered in previous work and that gives good agreement with experiment over a wide range of operating conditions is presented. The present analysis shows that the fin analogy may be extended to the form of the side-force expression and that the effective fin area may be taken as the projected side area of the propeller.

  15. 78 FR 45052 - Airworthiness Directives; Hartzell Propeller, Inc. Propellers

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-26

    ... failures of the propeller hydraulic bladder diaphragm and resulting engine oil leak. This AD requires replacement of the propeller hydraulic bladder diaphragm. We are issuing this AD to prevent propeller hydraulic bladder diaphragm rupture, loss of engine oil, damage to the engine, and loss of the...

  16. 78 FR 18255 - Airworthiness Directives; Hartzell Propeller, Inc. Propellers

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-26

    .... This proposed AD was prompted by failures of the propeller hydraulic bladder diaphragm and resulting engine oil leak. This proposed AD would require replacement of the propeller hydraulic bladder diaphragm. We are proposing this AD to prevent propeller hydraulic bladder diaphragm rupture, loss of engine...

  17. 78 FR 9005 - Airworthiness Directives; Dowty Propellers Propellers

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-07

    ... Propellers R408/6-123-F/17 model propellers. The existing AD currently requires initial applications of...), and repetitive applications of sealant on all R408/6-123-F/17 model propellers. Since we issued that... procedures found in 14 CFR 11.43 and 11.45, by any of the following methods: Federal eRulemaking Portal:...

  18. Notes on propeller design III

    NASA Technical Reports Server (NTRS)

    Munk, Max M

    1922-01-01

    The air flow and the air force created by all elements of the propeller blades lying in a ring located between two concentric circles around the propeller axis are independent of what happens in other rings.

  19. Cryogenic Propellant Scavenging

    NASA Technical Reports Server (NTRS)

    Louie, B.; Kemp, N. J.; Daney, D. E.

    1985-01-01

    A detailed description of a computer model that has been developed for assessing the feasibility of low g cryogen propellant scavenging from the space shuttle External Tank (ET) is given. Either pump-assisted or pressure-induced propellant transfer may be selected. The program will accept a wide range of input variables, including the fuel to be transferred (LOX or LH2), heat leaks, tank temperatures, and piping and equipment specifications. The model has been parametrically analyzed to determine initial design specification for the system.

  20. Quantifying the effect of tissue deformation on diffusion-weighted MRI: a mathematical model and an efficient simulation framework applied to cardiac diffusion imaging

    NASA Astrophysics Data System (ADS)

    Mekkaoui, Imen; Moulin, Kevin; Croisille, Pierre; Pousin, Jerome; Viallon, Magalie

    2016-08-01

    Cardiac motion presents a major challenge in diffusion weighted MRI, often leading to large signal losses that necessitate repeated measurements. The diffusion process in the myocardium is difficult to investigate because of the unqualified sensitivity of diffusion measurements to cardiac motion. A rigorous mathematical formalism is introduced to quantify the effect of tissue motion in diffusion imaging. The presented mathematical model, based on the Bloch-Torrey equations, takes into account deformations according to the laws of continuum mechanics. Approximating this mathematical model by using finite elements method, numerical simulations can predict the sensitivity of the diffusion signal to cardiac motion. Different diffusion encoding schemes are considered and the diffusion weighted MR signals, computed numerically, are compared to available results in literature. Our numerical model can identify the existence of two time points in the cardiac cycle, at which the diffusion is unaffected by myocardial strain and cardiac motion. Of course, these time points depend on the type of diffusion encoding scheme. Our numerical results also show that the motion sensitivity of the diffusion sequence can be reduced by using either spin echo technique with acceleration motion compensation diffusion gradients or stimulated echo acquisition mode with unipolar and bipolar diffusion gradients.

  1. Diffusion-weighted imaging of normal fibroglandular breast tissue: influence of microperfusion and fat suppression technique on the apparent diffusion coefficient.

    PubMed

    Baron, Paul; Dorrius, Monique D; Kappert, Peter; Oudkerk, Matthijs; Sijens, Paul E

    2010-05-01

    The influence of microperfusion and fat suppression technique on the apparent diffusion coefficient (ADC) values obtained with diffusion weighted imaging (DWI) of normal fibroglandular breast tissue was investigated. Seven volunteers (14 breasts) were scanned using diffusion weighting factors (b values) up to 1600 s/mm(2) and the four different fat suppression techniques: STIR, fat saturation, SPAIR, and Water Excitation. The relationship between the logarithmic DW attenuation curves and b was linear for b values up to 600 s/mm(2) (R(2) > 0.999). Small differences were noted between the ADC values obtained with the various fat suppression methods, especially at the higher b values. Water Excitation had the highest mean SNR, exceeding STIR (p = 0.03) though not significantly different from fat saturation and SPAIR. In conclusion, the ADC of fibroglandular breast tissue is not influenced by microperfusion and Water Excitation is recommended because it yielded the best SNR values. These factors may be crucial in the differentiation between benign and malignant lesions.

  2. Quantifying the effect of tissue deformation on diffusion-weighted MRI: a mathematical model and an efficient simulation framework applied to cardiac diffusion imaging.

    PubMed

    Mekkaoui, Imen; Moulin, Kevin; Croisille, Pierre; Pousin, Jerome; Viallon, Magalie

    2016-08-07

    Cardiac motion presents a major challenge in diffusion weighted MRI, often leading to large signal losses that necessitate repeated measurements. The diffusion process in the myocardium is difficult to investigate because of the unqualified sensitivity of diffusion measurements to cardiac motion. A rigorous mathematical formalism is introduced to quantify the effect of tissue motion in diffusion imaging. The presented mathematical model, based on the Bloch-Torrey equations, takes into account deformations according to the laws of continuum mechanics. Approximating this mathematical model by using finite elements method, numerical simulations can predict the sensitivity of the diffusion signal to cardiac motion. Different diffusion encoding schemes are considered and the diffusion weighted MR signals, computed numerically, are compared to available results in literature. Our numerical model can identify the existence of two time points in the cardiac cycle, at which the diffusion is unaffected by myocardial strain and cardiac motion. Of course, these time points depend on the type of diffusion encoding scheme. Our numerical results also show that the motion sensitivity of the diffusion sequence can be reduced by using either spin echo technique with acceleration motion compensation diffusion gradients or stimulated echo acquisition mode with unipolar and bipolar diffusion gradients.

  3. Propeller torque load and propeller shaft torque response correlation during ice-propeller interaction

    NASA Astrophysics Data System (ADS)

    Polić, Dražen; Ehlers, Sören; Æsøy, Vilmar

    2017-01-01

    Ships use propulsion machinery systems to create directional thrust. Sailing in ice-covered waters involves the breaking of ice pieces and their submergence as the ship hull advances. Sometimes, submerged ice pieces interact with the propeller and cause irregular fluctuations of the torque load. As a result, the propeller and engine dynamics become imbalanced, and energy propagates through the propulsion machinery system until equilibrium is reached. In such imbalanced situations, the measured propeller shaft torque response is not equal to the propeller torque. Therefore, in this work, the overall system response is simulated under the ice-related torque load using the Bond graph model. The energy difference between the propeller and propeller shaft is estimated and related to their corresponding mechanical energy. Additionally, the mechanical energy is distributed among modes. Based on the distribution, kinetic and potential energy are important for the correlation between propeller torque and propeller shaft response.

  4. Propeller torque load and propeller shaft torque response correlation during ice-propeller interaction

    NASA Astrophysics Data System (ADS)

    Polić, Dražen; Ehlers, Sören; Æsøy, Vilmar

    2017-03-01

    Ships use propulsion machinery systems to create directional thrust. Sailing in ice-covered waters involves the breaking of ice pieces and their submergence as the ship hull advances. Sometimes, submerged ice pieces interact with the propeller and cause irregular fluctuations of the torque load. As a result, the propeller and engine dynamics become imbalanced, and energy propagates through the propulsion machinery system until equilibrium is reached. In such imbalanced situations, the measured propeller shaft torque response is not equal to the propeller torque. Therefore, in this work, the overall system response is simulated under the ice-related torque load using the Bond graph model. The energy difference between the propeller and propeller shaft is estimated and related to their corresponding mechanical energy. Additionally, the mechanical energy is distributed among modes. Based on the distribution, kinetic and potential energy are important for the correlation between propeller torque and propeller shaft response.

  5. Solid Propellant Flame Spectroscopy

    DTIC Science & Technology

    1988-08-01

    Flame, Vol. 44, pp. 27-34, 1982. 49. Stufflebeam , J. H., Shirley, J. A., CARS Diagnostics of High Pressure Combustion- II, Report on Contract DAAG 29...83-C-0001, United Technologies Research Center, Hartford, CT, 1985. 50. Stufflebeam , J. H., Progress of CARS Applications to Solid Propellant

  6. Hypergolic Propellant Safety Course

    NASA Technical Reports Server (NTRS)

    Rathgeber, Kurt A.; Hornung, Stephen D.; Baker, David L.; Fries, Joseph (Technical Monitor)

    2000-01-01

    Under the sponsorship of the NASA Safety Training Center at the Johnson Space Center, a hypergolic propellant safety course has been developed. This is a 2-day course on guidelines for hypergolic propellant system design, materials selection, operations, storage, and transportation. Recognizing that numerous fuels and oxidizers can be hypergolic, this course is specific to the hydrazine family of fuels and nitrogen tetroxide and its variants. The objectives of the course are to enable the student to identify and evaluate the hazards of hypergolic propellants, and to understand the methods for controlling those hazards and responding to emergencies. The course covers properties and hazards of the hydrazines and oxidizers; design and operations in hypergolic facilities; materials selection for use in hypergol systems; storage vessels, piping, and component considerations; hypergol detection; fire fighting practices; operating and transportation principles and procedures; and emergency practices and considerations. A hazards analysis methodology is presented. Numerous references are provided and the applicability of certain regulatory documents is discussed. A brief overview of other propellants, including hydrogen peroxide, is given at the end of the course.

  7. Navy LOVA propellant development

    NASA Technical Reports Server (NTRS)

    Vreatt, W. H.; Mitchell, S. E.

    1980-01-01

    The progress realized on evaluation of inert binder, nitramine formulations is considered with respect to their development for use as low vulnerability ammunition (LOVA) propellants. Burning rate, plasticizers, crosslink agents, physical property and vulnerability studies are discussed and some preliminary conclusions presented.

  8. Disposal of Liquid Propellants

    DTIC Science & Technology

    1990-03-13

    concentrate (formaldehydestrongly catalyzes the formation of nitrosamines from nitrite and secondary amines ). I ° Minimize concentrations of catalytically ...components, as interest in these compounds is relatively new. Therefore, methods for disposing of similar compounds such as triethanol- amine ...appears to have the greatest potential for accomplishing degradation of HAN- based liquid propellant residues in an economical, environmentally safe manner

  9. Propeller tests on airplanes

    NASA Technical Reports Server (NTRS)

    Senouque, A

    1922-01-01

    In order to determine the efficiency of a propeller as accurately as possible, its revolution speed, thrust and power absorbed must be measured during flight. Unfortunately, these measurements can only be made with very complicated equipment. To surmount this problem the testers contented themselves with approximate results obtainable in two or three hours of flight.

  10. The influence of gender on 'tissue at risk' in acute stroke: A diffusion-weighted magnetic resonance imaging study in a rat model of focal cerebral ischaemia.

    PubMed

    Baskerville, Tracey A; Macrae, I Mhairi; Holmes, William M; McCabe, Christopher

    2016-02-01

    This is the first study to assess the influence of sex on the evolution of ischaemic injury and penumbra. Permanent middle cerebral artery occlusion was induced in male (n = 9) and female (n = 10) Sprague-Dawley rats. Diffusion-weighted imaging was acquired over 4 h and infarct determined from T2 images at 24 h post-permanent middle cerebral artery occlusion. Penumbra was determined retrospectively from serial apparent diffusion coefficient lesions and T2-defined infarct. Apparent diffusion coefficient lesion volume was significantly smaller in females from 0.5 to 4 h post permanent middle cerebral artery occlusion as was infarct volume. Penumbral volume, and its loss over time, was not significantly different despite the sex difference in acute and final lesion volumes.

  11. Propellant thermal stratification

    NASA Technical Reports Server (NTRS)

    Winstead, T. W.

    1971-01-01

    The term thermal stratification is used to express nonuniform heat distribution within the bulk propellant. The nonuniform distribution of heat results in significant temperature variations in booster propulsion propellants and causes an undesirable increase in the self-pressurization rate of cryogen storage systems. A semiempirical prediction method has been developed for high gravity environments and is adequate for design purposes; model accuracy is somewhat limited to similarity in tank geometries, and additional work is needed to extend the correlation range. Several low gravity environment models that cover a broad range of predicted results have been developed. There are no applicable data by which any of these models may be selected in preference over the others.

  12. Detection of head and neck squamous cell carcinoma with diffusion weighted MRI after (chemo)radiotherapy: Correlation between radiologic and histopathologic findings

    SciTech Connect

    Vandecaveye, Vincent; Keyzer, Frederik de; Nuyts, Sandra; Deraedt, Karen; Dirix, Piet; Hamaekers, Pascal; Vander Poorten, Vincent; Delaere, Pierre; Hermans, Robert . E-mail: Robert.Hermans@uzleuven.be

    2007-03-15

    Purpose: To investigate the value of diffusion weighted magnetic resonance imaging (DW-MRI) in differentiating persistent or recurrent head and neck squamous cell carcinoma (HNSCC) from nontumoral postradiotherapeutic alterations. Methods and Materials: In 26 patients with suspicion of persistent or recurrent HNSCC, MRI of the head and neck was performed, including routine turbo spin-echo (TSE) sequences and an additional echo-planar DW-MRI sequence, using a large range of b-values (0-1000 s/mm{sup 2}). Apparent diffusion coefficient (ADC) maps were calculated. In the suspect areas at the primary site and in the suspect lymph nodes, signal intensity was measured on the native b0 and b1000 images and ADC values were calculated for these tissues. The same was done for surrounding irradiated normal tissue. Imaging results were correlated to histopathology. Results: Signal intensity on native b0 images was significantly lower for HNSCC than for nontumoral postradiotherapeutic tissue (p < 0.0001), resulting in a sensitivity of 66.2%, specificity of 60.8%, and accuracy of 62.4%. Signal intensity on native b1000 images was significantly higher for HNSCC than for nontumoral tissue (p < 0.0001), resulting in a sensitivity of 71.6%, specificity of 71.3%, and accuracy of 71.4%. ADC values were significantly lower for HNSCC than for nontumoral tissue (p < 0.0001), resulting in a sensitivity of 94.6%, specificity of 95.9%, and accuracy of 95.5%. When compared with computed tomography, TSE-MRI and fluorodeoxyglucose-positron emission tomography, DW-MRI yielded fewer false-positive results in persistent primary site abnormalities and in persistent adenopathies, and aided in the detection of subcentimetric nodal metastases. Conclusions: Diffusion weighted-MRI accurately differentiates persistent or recurrent HNSCC from nontumoral tissue changes after (chemo)radiotherapy.

  13. Demonstration of Non-Gaussian Restricted Diffusion in Tumor Cells Using Diffusion Time-Dependent Diffusion-Weighted Magnetic Resonance Imaging Contrast

    PubMed Central

    Hope, Tuva R.; White, Nathan S.; Kuperman, Joshua; Chao, Ying; Yamin, Ghiam; Bartch, Hauke; Schenker-Ahmed, Natalie M.; Rakow-Penner, Rebecca; Bussell, Robert; Nomura, Natsuko; Kesari, Santosh; Bjørnerud, Atle; Dale, Anders M.

    2016-01-01

    The diffusion-weighted magnetic resonance imaging (DWI) technique enables quantification of water mobility for probing microstructural properties of biological tissue and has become an effective tool for collecting information about the underlying pathology of cancerous tissue. Measurements using multiple b-values have indicated biexponential signal attenuation, ascribed to “fast” (high ADC) and “slow” (low ADC) diffusion components. In this empirical study, we investigate the properties of the diffusion time (Δ)-dependent components of the diffusion-weighted (DW) signal in a constant b-value experiment. A xenograft gliobastoma mouse was imaged using Δ = 11 ms, 20 ms, 40 ms, 60 ms, and b = 500–4000 s/mm2 in intervals of 500 s/mm2. Data were corrected for EPI distortions, and the Δ-dependence on the DW-signal was measured within three regions of interest [intermediate- and high-density tumor regions and normal-appearing brain (NAB) tissue regions]. In this study, we verify the assumption that the slow decaying component of the DW-signal is non-Gaussian and dependent on Δ, consistent with restricted diffusion of the intracellular space. As the DW-signal is a function of Δ and is specific to restricted diffusion, manipulating Δ at constant b-value (cb) provides a complementary and direct approach for separating the restricted from the hindered diffusion component. We found that Δ-dependence is specific to the tumor tissue signal. Based on an extended biexponential model, we verified the interpretation of the diffusion time-dependent contrast and successfully estimated the intracellular restricted ADC, signal volume fraction, and cell size within each ROI. PMID:27532028

  14. Nitramine Propellant Erosivity - III.

    DTIC Science & Technology

    1980-12-01

    a semi-log plot of wear vs rt,tre or c: M-e for M30 , IP, M.1, and MS propellants where one sees 15 al o falls 1,)1’ 1IP consistently. it is uncertain...Aerospace lnginecring! ATTN: I. Krier l)i rector Urbana II, 61803 Lawrence L, ivermore Laboratory .V ’N : I . Kury Livermore, CA 94551) Aberdeen Proving

  15. Comparative efficacy of new interfaces for intra-procedural imaging review: the Microsoft Kinect, Hillcrest Labs Loop Pointer, and the Apple iPad.

    PubMed

    Chao, Cherng; Tan, Justin; Castillo, Edward M; Zawaideh, Mazen; Roberts, Anne C; Kinney, Thomas B

    2014-08-01

    We adapted and evaluated the Microsoft Kinect (touchless interface), Hillcrest Labs Loop Pointer (gyroscopic mouse), and the Apple iPad (multi-touch tablet) for intra-procedural imaging review efficacy in a simulation using MIM Software DICOM viewers. Using each device, 29 radiologists executed five basic interactions to complete the overall task of measuring an 8.1-cm hepatic lesion: scroll, window, zoom, pan, and measure. For each interaction, participants assessed the devices on a 3-point subjective scale (3 = highest usability score). The five individual scores were summed to calculate a subjective composite usability score (max 15 points). Overall task time to completion was recorded. Each user also assessed each device for its potential to jeopardize a sterile field. The composite usability scores were as follows: Kinect 9.9 (out of 15.0; SD = 2.8), Loop Pointer 12.9 (SD = 13.5), and iPad 13.5 (SD = 1.8). Mean task completion times were as follows: Kinect 156.7 s (SD = 86.5), Loop Pointer 51.5 s (SD = 30.6), and iPad 41.1 s (SD = 25.3). The mean hepatic lesion measurements were as follows: Kinect was 7.3 cm (SD = 0.9), Loop Pointer 7.8 cm (SD = 1.1), and iPad 8.2 cm (SD = 1.2). The mean deviations from true hepatic lesion measurement were as follows: Kinect 1.0 cm and for both the Loop Pointer and iPad, 0.9 cm (SD = 0.7). The Kinect had the least and iPad had the most subjective concern for compromising the sterile field. A new intra-operative imaging review interface may be near. Most surveyed foresee these devices as useful in procedures, and most do not anticipate problems with a sterile field. An ideal device would combine iPad's usability and accuracy with the Kinect's touchless aspect.

  16. NASA Advanced Propeller Research

    NASA Technical Reports Server (NTRS)

    Groeneweg, John F.; Bober, Lawrence J.

    1988-01-01

    Acoustic and aerodynamic research at NASA Lewis Research Center on advanced propellers is reviewed including analytical and experimental results on both single and counterrotation. Computational tools used to calculate the detailed flow and acoustic i e l d s a r e described along with wind tunnel tests to obtain data for code verification . Results from two kinds of experiments are reviewed: ( 1 ) performance and near field noise at cruise conditions as measured in the NASA Lewis 8-by 6-Foot Wind Tunnel and ( 2 ) farfield noise and performance for takeoff/approach conditions as measured in the NASA Lewis 9-by 15-Font Anechoic Wind Tunnel. Detailed measurements of steady blade surface pressures are described along with vortex flow phenomena at off design conditions . Near field noise at cruise is shown to level out or decrease as tip relative Mach number is increased beyond 1.15. Counterrotation interaction noise is shown to be a dominant source at take off but a secondary source at cruise. Effects of unequal rotor diameters and rotor-to-rotor spacing on interaction noise a real so illustrated. Comparisons of wind tunnel acoustic measurements to flight results are made. Finally, some future directions in advanced propeller research such as swirl recovery vanes, higher sweep, forward sweep, and ducted propellers are discussed.

  17. NASA advanced propeller research

    NASA Technical Reports Server (NTRS)

    Groeneweg, John F.; Bober, Lawrence J.

    1988-01-01

    Acoustic and aerodynamic research at NASA Lewis Research Center on advanced propellers is reviewed including analytical and experimental results on both single and counterrotation. Computational tools used to calculate the detailed flow and acoustic fields are described along with wind tunnel tests to obtain data for code verification. Results from two kinds of experiments are reviewed: (1) performance and near field noise at cruise conditions as measured in the NASA Lewis 8- by 6-foot Wind Tunnel; and (2) far field noise and performance for takeoff/approach conditions as measured in the NASA Lewis 9- by 15-foot Anechoic Wind Tunnel. Detailed measurements of steady blade surface pressures are described along with vortex flow phenomena at off-design conditions. Near field noise at cruise is shown to level out or decrease as tip relative Mach number is increased beyond 1.15. Counterrotation interaction noise is shown to be a dominant source at takeoff but a secondary source at cruise. Effects of unequal rotor diameters and rotor-to-rotor spacing on interaction noise are also illustrated. Comparisons of wind tunnel acoustic measurements to flight results are made. Finally, some future directions in advanced propeller research such as swirl recovery vanes, higher sweep, forward sweep, and ducted propellers are discussed.

  18. Study of the supersonic propeller

    NASA Technical Reports Server (NTRS)

    Fabri, Jean; Siestrunck, Raymond

    1953-01-01

    In this paper a propeller having all sections operating at supersonic speeds is designated a supersonic propeller regardless of flight speed. Analyses assume subsonic flight speeds but very high rotational speeds. A very elementary analysis of the efficiency of a jet-propeller system is presented. A propeller analysis based on conventional vortex blade element theory is presented and reduced to a single point method which leads to an expression for optimum advance ratio in terms of hub-tip diameter ratio and airfoil fineness ratio. An expression for propeller efficiency in terms of advance ratio, hub-tip diameter ratio, and airfoil thickness ratio is also presented. Use is made of theoretical airfoil characteristics at supersonic speeds. A study of blade section interference, blade shock and expansion fields, at supersonic section speeds is presented. An example taken indicates that an efficiency of seventy percent can be obtained with a propeller having a tip Mach number of 2.3.

  19. Helium Saturation of Liquid Propellants

    NASA Technical Reports Server (NTRS)

    Yavrouian, A. H.; Moran, Clifford M.

    1990-01-01

    The research is in three areas which are: (1) techniques were devised for achieving the required levels of helium (He) saturation in liquid propellants (limited to monomethylhydrazine (MMH) and nitrogen tetroxide (NTO)); (2) the values were evaluated for equilibrium solubilities of He in liquid propellants as currently used in the industry; and (3) the He dissolved in liquid propellants were accurately measured. Conclusions drawn from these studies include: (1) Techniques for dissolving He in liquid propellants depending upon the capabilities of the testing facility (Verification of the quantity of gas dissolved is essential); (2) Until greater accuracy is obtained, the equilibrium solubility values of He in MMH and NTO as cited in the Air Force Propellant Handbooks should be accepted as standard (There are still enough uncertainties in the He saturation values to warrant further basic experimental studies); and (3) The manometric measurement of gas volume from a frozen sample of propellant should be the accepted method for gas analysis.

  20. Modeling of pulsed propellant reorientation

    NASA Technical Reports Server (NTRS)

    Patag, A. E.; Hochstein, J. I.; Chato, D. J.

    1989-01-01

    Optimization of the propellant reorientation process can provide increased payload capability and extend the service life of spacecraft. The use of pulsed propellant reorientation to optimize the reorientation process is proposed. The ECLIPSE code was validated for modeling the reorientation process and is used to study pulsed reorientation in small-scale and full-scale propellant tanks. A dimensional analysis of the process is performed and the resulting dimensionless groups are used to present and correlate the computational predictions for reorientation performance.

  1. 75 FR 51656 - Airworthiness Directives; Dowty Propellers R408/6-123-F/17 Model Propellers

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-23

    ...-11] RIN 2120-AA64 Airworthiness Directives; Dowty Propellers R408/6-123-F/17 Model Propellers AGENCY... Propellers R408/6-123-F/17 model propellers. These propellers are installed on, but not limited to... actions. (1) For R408/6-123-F/17 model propellers with a hub, actuator, and backplate assembly...

  2. Propeller Analysis from Experimental Data

    NASA Technical Reports Server (NTRS)

    Stickle, George W; Crigler, John L

    1941-01-01

    The operation of the propeller is analyzed by the use of the distribution of forces along the radius, combined with theoretical equations. The data were obtained in the NACA 20-foot wind tunnel on a 4-foot-diameter, two-blade propeller, operating in front of four body shapes, ranging from a small shaft to support the propeller to conventional NACA cowling. A method of estimating the axial and the rotational energy in the wake as a fractional part of the propeller power is given. A knowledge of the total thrust and torque is necessary for the estimation.

  3. Propeller blade retention system

    NASA Technical Reports Server (NTRS)

    Elston, III, Sidney B. (Inventor); Simon, III, Victor H. (Inventor); Tseng, Wu-Yang (Inventor); Butler, Lawrence (Inventor)

    1993-01-01

    The invention concerns the mounting of propeller blades to a ring-shaped rotor. The blades are of the variable pitch type, and the shank of each blade extends through a respective hole in the rotor. Each hole contains an annular shelf which is fastened to the wall of the hole and surrounds each shank. Each shank bears a pair of bearing races which sandwich the annular shelf in order to connect the blade to the rotor. Bearing rollers are positioned between the annular shelf and the bearing races.

  4. Monitoring of the tumor response to nano-graphene oxide-mediated photothermal/photodynamic therapy by diffusion-weighted and BOLD MRI.

    PubMed

    Cao, Jianbo; An, Hengqing; Huang, Xinglu; Fu, Guifeng; Zhuang, Rongqiang; Zhu, Lei; Xie, Jin; Zhang, Fan

    2016-05-21

    Photothermal therapy (PTT) and photodynamic therapy (PDT) are promising cancer treatment modalities. Because each modality has its own set of advantages and limitations, there has been interest in developing methods that can co-deliver the two regimens for enhanced tumor treatment. Among the efforts, nano-graphene oxide-mediated phototherapies have recently attracted much attention. Nano-graphene oxide has a broad absorbance spectrum and can be loaded with photosensitizers, such as chlorin e6, with high efficiency. Chlorin e6-loaded and PEGylated nano-graphene (GO-PEG-Ce6) can be excited at 660 nm, 808 nm, or both, to induce PDT, PTT, or PDT/PTT combination. Despite the potential of the treatments, there is a lack of a diagnostic tool which can monitor their therapeutic response in a non-invasive and prognostic manner; such an ability is urgently needed for the transformation and translation of the technologies. In this study, we performed diffusion-weighted and blood oxygenation level dependent (BOLD) magnetic resonance imaging (MRI) after GO-PEG-Ce6-mediated PTT, PDT, or PTT/PDT. We found that after efficient PTT, there is a significant increase of the tumor apparent diffusion coefficient (ADC) value in diffusion-weighted imaging (DWI) maps; meanwhile, an efficient PDT led to an increase of in BOLD images. In both the cases, the amplitude of the increase was correlated with the treatment outcomes. More interestingly, a synergistic treatment efficacy was observed when the PTT/PDT combination was applied, and the combination was associated with a greater ADC and increase than when either modality was used alone. In particular, the PTT/PDT condition that induced the most dramatic short-term increase of the ADC value (>70%) caused the most effective tumor control in the long-run, with 60% of the treated animals being tumor-free after 60 days. These results suggest the great promise of the combination of DWI and BOLD MRI as a tool for accurate monitoring and prognosis

  5. Differentiation of Low- and High-Grade Pediatric Brain Tumors with High b-Value Diffusion-weighted MR Imaging and a Fractional Order Calculus Model

    PubMed Central

    Sui, Yi; Wang, He; Liu, Guanzhong; Damen, Frederick W.; Wanamaker, Christian; Li, Yuhua

    2015-01-01

    Purpose To demonstrate that a new set of parameters (D, β, and μ) from a fractional order calculus (FROC) diffusion model can be used to improve the accuracy of MR imaging for differentiating among low- and high-grade pediatric brain tumors. Materials and Methods The institutional review board of the performing hospital approved this study, and written informed consent was obtained from the legal guardians of pediatric patients. Multi-b-value diffusion-weighted magnetic resonance (MR) imaging was performed in 67 pediatric patients with brain tumors. Diffusion coefficient D, fractional order parameter β (which correlates with tissue heterogeneity), and a microstructural quantity μ were calculated by fitting the multi-b-value diffusion-weighted images to an FROC model. D, β, and μ values were measured in solid tumor regions, as well as in normal-appearing gray matter as a control. These values were compared between the low- and high-grade tumor groups by using the Mann-Whitney U test. The performance of FROC parameters for differentiating among patient groups was evaluated with receiver operating characteristic (ROC) analysis. Results None of the FROC parameters exhibited significant differences in normal-appearing gray matter (P ≥ .24), but all showed a significant difference (P < .002) between low- (D, 1.53 μm2/msec ± 0.47; β, 0.87 ± 0.06; μ, 8.67 μm ± 0.95) and high-grade (D, 0.86 μm2/msec ± 0.23; β, 0.73 ± 0.06; μ, 7.8 μm ± 0.70) brain tumor groups. The combination of D and β produced the largest area under the ROC curve (0.962) in the ROC analysis compared with individual parameters (β, 0.943; D,0.910; and μ, 0.763), indicating an improved performance for tumor differentiation. Conclusion The FROC parameters can be used to differentiate between low- and high-grade pediatric brain tumor groups. The combination of FROC parameters or individual parameters may serve as in vivo, noninvasive, and quantitative imaging markers for classifying

  6. Monitoring of the tumor response to nano-graphene oxide-mediated photothermal/photodynamic therapy by diffusion-weighted and BOLD MRI

    NASA Astrophysics Data System (ADS)

    Cao, Jianbo; An, Hengqing; Huang, Xinglu; Fu, Guifeng; Zhuang, Rongqiang; Zhu, Lei; Xie, Jin; Zhang, Fan

    2016-05-01

    Photothermal therapy (PTT) and photodynamic therapy (PDT) are promising cancer treatment modalities. Because each modality has its own set of advantages and limitations, there has been interest in developing methods that can co-deliver the two regimens for enhanced tumor treatment. Among the efforts, nano-graphene oxide-mediated phototherapies have recently attracted much attention. Nano-graphene oxide has a broad absorbance spectrum and can be loaded with photosensitizers, such as chlorin e6, with high efficiency. Chlorin e6-loaded and PEGylated nano-graphene (GO-PEG-Ce6) can be excited at 660 nm, 808 nm, or both, to induce PDT, PTT, or PDT/PTT combination. Despite the potential of the treatments, there is a lack of a diagnostic tool which can monitor their therapeutic response in a non-invasive and prognostic manner; such an ability is urgently needed for the transformation and translation of the technologies. In this study, we performed diffusion-weighted and blood oxygenation level dependent (BOLD) magnetic resonance imaging (MRI) after GO-PEG-Ce6-mediated PTT, PDT, or PTT/PDT. We found that after efficient PTT, there is a significant increase of the tumor apparent diffusion coefficient (ADC) value in diffusion-weighted imaging (DWI) maps; meanwhile, an efficient PDT led to an increase of in BOLD images. In both the cases, the amplitude of the increase was correlated with the treatment outcomes. More interestingly, a synergistic treatment efficacy was observed when the PTT/PDT combination was applied, and the combination was associated with a greater ADC and increase than when either modality was used alone. In particular, the PTT/PDT condition that induced the most dramatic short-term increase of the ADC value (>70%) caused the most effective tumor control in the long-run, with 60% of the treated animals being tumor-free after 60 days. These results suggest the great promise of the combination of DWI and BOLD MRI as a tool for accurate monitoring and prognosis

  7. Low acid producing solid propellants

    NASA Technical Reports Server (NTRS)

    Bennett, Robert R.

    1995-01-01

    The potential environmental effects of the exhaust products of conventional rocket propellants have been assessed by various groups. Areas of concern have included stratospheric ozone, acid rain, toxicity, air quality and global warming. Some of the studies which have been performed on this subject have concluded that while the impacts of rocket use are extremely small, there are propellant development options which have the potential to reduce those impacts even further. This paper discusses the various solid propellant options which have been proposed as being more environmentally benign than current systems by reducing HCI emissions. These options include acid neutralized, acid scavenged, and nonchlorine propellants. An assessment of the acid reducing potential and the viability of each of these options is made, based on current information. Such an assessment is needed in order to judge whether the potential improvements justify the expenditures of developing the new propellant systems.

  8. Nocardia abscess during treatment of brain toxoplasmosis in a patient with aids, utility of proton MR spectroscopy and diffusion-weighted imaging in diagnosis.

    PubMed

    Soto-Hernández, José Luis; Moreno-Andrade, Talía; Góngora-Rivera, Fernando; Ramírez-Crescencio, María Antonieta

    2006-07-01

    We report the case of a 30-year-old man with known HIV-positive status who developed, 4 months prior to admission, recurrent left partial motor seizures followed by left hemiparesis. At another hospital, contrasted CT scan of the head revealed right frontal hypodense lesion with mass effect and focal contrast enhancement. A small left occipital lesion was also present. HIV-associated brain toxoplasmosis was considered and phenytoin, pyrimethamine, clindamycin and antiretrovirals were administered. Hemiparesis improved but, 3 weeks prior to admission, he developed progressive headache and bilateral visual defects. Upon admission to our center, he was found with left homonymous hemianopsia, right hemiparesis and a large hypodense left occipital lesion on a head CT scan. Proton MR spectroscopy showed lactate at 1.3ppm, amino acids at 0.9ppm, and diffusion-weighted imaging (DWI) revealed hyperintensity at the lesion, suggesting a pyogenic abscess. Aspiration yielded purulent material and Nocardia asteroides grew in culture. The patient was treated with trimethoprim-sulfametoxazole and recovered with a mild visual field residual defect.

  9. Staging of Primary Abdominal Lymphomas: Comparison of Whole-Body MRI with Diffusion-Weighted Imaging and 18F-FDG-PET/CT

    PubMed Central

    Stecco, Alessandro; Buemi, Francesco; Quagliozzi, Martina; Lombardi, Mariangela; Santagostino, Alberto; Sacchetti, Gian Mauro; Carriero, Alessandro

    2015-01-01

    Background. The purpose of this study was to compare the accuracy of whole-body MRI with diffusion-weighted sequences (WB-DW-MRI) with that of 18F-FDG-PET/CT in the staging of patients with primary gastrointestinal lymphoma. Methods. This retrospective study involved 17 untreated patients with primary abdominal gastrointestinal lymphoma. All patients underwent 18F-FDG-PET/CT and WB-DW-MRI. Histopathology findings or at least 6 months of clinical and radiological follow-up was the gold standard. The Musshoff-modified Ann Arbor system was used for staging, and diagnostic accuracy was evaluated on a per-node basis. Results. WB-DW-MRI exhibited 100% sensitivity, 96.3% specificity, and 96.1% and 100% positive and negative predictive values (PPV and NPV), respectively. The sensitivity, specificity, and PPV and NPV of PET/CT were 95.9%, 100%, and 100% and 96.4%, respectively. There were no statistically significant differences between the two techniques (p = 0.05). The weighted kappa agreement statistics with a 95% confidence interval were 0.97 (0.95–0.99) between the two MRI readers and 0.87 (0.82–0.92) between the two methods. Conclusions. WB-DW-MRI appears to have a comparable diagnostic value to 18F-FDG-PET/CT in staging patients with gastrointestinal lymphoma. PMID:26798331

  10. Separation of small metabolites and lipids in spectra from biopsies by diffusion-weighted HR-MAS NMR: a feasibility study.

    PubMed

    Diserens, G; Vermathen, M; Precht, C; Broskey, N T; Boesch, C; Amati, F; Dufour, J-F; Vermathen, P

    2015-01-07

    High Resolution Magic Angle Spinning (HR-MAS) NMR allows metabolic characterization of biopsies. HR-MAS spectra from tissues of most organs show strong lipid contributions that are overlapping metabolite regions, which hamper metabolite estimation. Metabolite quantification and analysis would benefit from a separation of lipids and small metabolites. Generally, a relaxation filter is used to reduce lipid contributions. However, the strong relaxation filter required to eliminate most of the lipids also reduces the signals for small metabolites. The aim of our study was therefore to investigate different diffusion editing techniques in order to employ diffusion differences for separating lipid and small metabolite contributions in the spectra from different organs for unbiased metabonomic analysis. Thus, 1D and 2D diffusion measurements were performed, and pure lipid spectra that were obtained at strong diffusion weighting (DW) were subtracted from those obtained at low DW, which include both small metabolites and lipids. This subtraction yielded almost lipid free small metabolite spectra from muscle tissue. Further improved separation was obtained by combining a 1D diffusion sequence with a T2-filter, with the subtraction method eliminating residual lipids from the spectra. Similar results obtained for biopsies of different organs suggest that this method is applicable in various tissue types. The elimination of lipids from HR-MAS spectra and the resulting less biased assessment of small metabolites have potential to remove ambiguities in the interpretation of metabonomic results. This is demonstrated in a reproducibility study on biopsies from human muscle.

  11. Comparison of non-Gaussian and Gaussian diffusion models of diffusion weighted imaging of rectal cancer at 3.0 T MRI

    PubMed Central

    Zhang, Guangwen; Wang, Shuangshuang; Wen, Didi; Zhang, Jing; Wei, Xiaocheng; Ma, Wanling; Zhao, Weiwei; Wang, Mian; Wu, Guosheng; Zhang, Jinsong

    2016-01-01

    Water molecular diffusion in vivo tissue is much more complicated. We aimed to compare non-Gaussian diffusion models of diffusion-weighted imaging (DWI) including intra-voxel incoherent motion (IVIM), stretched-exponential model (SEM) and Gaussian diffusion model at 3.0 T MRI in patients with rectal cancer, and to determine the optimal model for investigating the water diffusion properties and characterization of rectal carcinoma. Fifty-nine consecutive patients with pathologically confirmed rectal adenocarcinoma underwent DWI with 16 b-values at a 3.0 T MRI system. DWI signals were fitted to the mono-exponential and non-Gaussian diffusion models (IVIM-mono, IVIM-bi and SEM) on primary tumor and adjacent normal rectal tissue. Parameters of standard apparent diffusion coefficient (ADC), slow- and fast-ADC, fraction of fast ADC (f), α value and distributed diffusion coefficient (DDC) were generated and compared between the tumor and normal tissues. The SEM exhibited the best fitting results of actual DWI signal in rectal cancer and the normal rectal wall (R2 = 0.998, 0.999 respectively). The DDC achieved relatively high area under the curve (AUC = 0.980) in differentiating tumor from normal rectal wall. Non-Gaussian diffusion models could assess tissue properties more accurately than the ADC derived Gaussian diffusion model. SEM may be used as a potential optimal model for characterization of rectal cancer. PMID:27934928

  12. Evaluation of Free Breathing Versus Breath Hold Diffusion Weighted Imaging in Terms Apparent Diffusion Coefficient (ADC) and Signal-to-Noise Ratio (SNR) Values for Solid Abdominal Organs

    PubMed Central

    Herek, Duygu; Karabulut, Nevzat; Kocyıgıt, Ali; Yagcı, Ahmet Baki

    2016-01-01

    Summary Background Our aim was to compare the apparent diffusion coefficient (ADC) values of normal abdominal parenchymal organs and signal-to-noise ratio (SNR) measurements in the same patients with breath hold (BH) and free breathing (FB) diffusion weighted imaging (DWI). Material/Methods Forty-eight patients underwent both BH and FB DWI. Spherical region of interest (ROI) was placed on the right hepatic lobe, spleen, pancreas, and renal cortices. ADC values were calculated for each organ on each sequence using an automated software. Image noise, defined as the standard deviation (SD) of the signal intensities in the most artifact-free area of the image background was measured by placing the largest possible ROI on either the left or the right side of the body outside the object in the recorded field of view. SNR was calculated using the formula: SNR=signal intensity (SI)(organ)/standard deviation (SD)(noise). Results There were no statistically significant differences in ADC values of the abdominal organs between BH and FB DWI sequences (p>0.05). There were statistically significant differences between SNR values of organs on BH and FB DWIs. SNRs were found to be better on FB DWI than BH DWI (p<0.001). Conclusions Free breathing DWI technique reduces image noise and increases SNR for abdominal examinations. Free breathing technique is therefore preferable to BH DWI in the evaluation of abdominal organs by DWI. PMID:27822326

  13. Three-Tesla magnetic resonance elastography for hepatic fibrosis: Comparison with diffusion-weighted imaging and gadoxetic acid-enhanced magnetic resonance imaging

    PubMed Central

    Park, Hee Sun; Kim, Young Jun; Yu, Mi Hye; Choe, Won Hyeok; Jung, Sung Il; Jeon, Hae Jeong

    2014-01-01

    AIM: To evaluate the feasibility of 3-Tesla magnetic resonance elastography (MRE) for hepatic fibrosis and to compare that with diffusion-weighted imaging (DWI) and gadoxetic acid-enhanced magnetic resonance (MR) imaging. METHODS: Forty-two patients were included in the study. On MRE, mean stiffness values were measured on the elastograms in kilopascals. The apparent diffusion coefficient (ADC) of the liver was measured using DWI. On gadoxetic acid enhanced MR, the contrast enhancement index (CEI) was calculated as signal intensity (SI)post/SIpre, where SIpost is liver-to-muscle SI ratio on hepatobiliary phase images and SIpre is that on nonenhanced images. Correlation between aspartate aminotransferase to the platelet ratio index (APRI) and three MR parameters was assessed. Each MR parameter was compared between a hepatic fibrosis (HF) group and non-hepatic fibrosis (nHF) group. RESULTS: Liver stiffness showed strong positive correlation with APRI [Spearman correlation coeffiecient (r) = 0.773, P < 0.0001], while ADC and CEI showed weak or prominent negative correlation (r = -0.28 and -0.321, respectively). In the HF group, only liver stiffness showed strong correlation with APRI (r = 0.731, P < 0.0001). Liver stiffness, ADC, and APRI were significantly different between the HF group and nHF group. CONCLUSION: MRE at 3-Tesla could be a feasible method for the assessment of hepatic fibrosis. PMID:25516671

  14. Is quantitative diffusion-weighted MRI a valuable technique for the detection of changes in kidneys after extracorporeal shock wave lithotripsy?

    PubMed Central

    Hocaoglu, Elif; Inci, Ercan; Aydin, Sibel; Cesme, Dilek Hacer; Kalfazade, Nadir

    2015-01-01

    Objective The aim of this study was to evaluate the capability and the reliability of diffusion-weighted imaging (DWI) in the changes of kidneys occurring after extracorporeal shock wave lithotripsy (ESWL) treatment for renal stones. Materials and Methods A total of 32 patients who underwent ESWL treatment for renal stone disease between June and December 2011 were enrolled in this prospective study. Color Doppler ultrasonography (CDUS) and DWI were performed before and within 24 hours after ESWL. DWI was obtained with b factors of 0, 500 and 1000 s/mm2 at 1.5 T MRI. Each of Resistive index (RI) and ADC values were calculated from the three regions of renal upper, middle and lower zones for both of the affected and contralateral kidneys. Paired sample t test was used for statistical analyses. Results After ESWL, the treated kidneys had statistically significant lower ADC values in all different regions compared with previous renal images. The best discriminative parameter was signal intensity with a b value of 1000 s/mm2. The changes of DWI after ESWL were noteworthy in the middle of the treated kidney (p<0.01). There were no significant difference between RI values in all regions of treated and contralateral kidneys before and after treatment with ESWL (p>0.05). Conclusion DWI is a valuable technique enables the detection of changes in DWI after ESWL treatment that may provide useful information in prediction of renal damage by shock waves, even CDUS is normal. PMID:25928520

  15. High-resolution DTI of a localized volume using 3D single-shot diffusion-weighted STimulated echo-planar imaging (3D ss-DWSTEPI).

    PubMed

    Jeong, Eun-Kee; Kim, Seong-Eun; Kholmovski, Eugene G; Parker, Dennis L

    2006-12-01

    Diffusion tensor MRI (DTI) using conventional single-shot (SS) 2D diffusion-weighted (DW)-EPI is subject to severe susceptibility artifacts. Multishot DW imaging (DWI) techniques can reduce these distortions, but they generally suffer from artifacts caused by motion-induced phase errors. Parallel imaging can also reduce the distortions if the sensitivity profiles of the receiver coils allow a sufficiently high reduction factor for the desired field of view (FOV). A novel 3D DTI technique, termed 3D single-shot STimulated EPI (3D ss-STEPI), was developed to acquire high-resolution DW images of a localized region. The new technique completes k-space acquisition of a limited 3D volume after a single diffusion preparation. Because the DW magnetization is stored in the longitudinal direction until readout, it undergoes T(1) rather than T(2) decay. Inner volume imaging (IVI) is used to limit the imaging volume. This reduces the time required for EPI readout of each complete k(x)-k(y) plane, and hence reduces T(2)(*) decay during the readout and T(1) decay between the readout of each k(z). 3D ss-STEPI images appear to be free of severe susceptibility and motion artifacts. 3D ss-STEPI allows high-resolution DTI of limited volumes of interest, such as localized brain regions, cervical spinal cord, optic nerve, and other extracranial organs.

  16. Assessment of non-Gaussian diffusion with singly and doubly stretched biexponential models of diffusion-weighted MRI (DWI) signal attenuation in prostate tissue.

    PubMed

    Hall, Matt G; Bongers, Andre; Sved, Paul; Watson, Geoffrey; Bourne, Roger M

    2015-04-01

    Non-Gaussian diffusion dynamics was investigated in the two distinct water populations identified by a biexponential model of diffusion in prostate tissue. Diffusion-weighted MRI (DWI) signal attenuation was measured ex vivo in two formalin-fixed prostates at 9.4 T with diffusion times Δ = 10, 20 and 40 ms, and b values in the range 0.017-8.2 ms/µm(2) . A conventional biexponential model was compared with models in which either the lower diffusivity component or both of the components of the biexponential were stretched. Models were compared using Akaike's Information Criterion (AIC) and a leave-one-out (LOO) test of model prediction accuracy. The doubly stretched (SS) model had the highest LOO prediction accuracy and lowest AIC (highest information content) in the majority of voxels at Δ = 10 and 20 ms. The lower diffusivity stretching factor (α2 ) of the SS model was consistently lower (range ~0.3-0.9) than the higher diffusivity stretching factor (α1 , range ~0.7-1.1), indicating a high degree of diffusion heterogeneity in the lower diffusivity environment, and nearly Gaussian diffusion in the higher diffusivity environment. Stretched biexponential models demonstrate that, in prostate tissue, the two distinct water populations identified by the simple biexponential model individually exhibit non-Gaussian diffusion dynamics.

  17. A robust multi-shot scan strategy for high-resolution diffusion weighted MRI enabled by multiplexed sensitivity-encoding (MUSE).

    PubMed

    Chen, Nan-Kuei; Guidon, Arnaud; Chang, Hing-Chiu; Song, Allen W

    2013-05-15

    Diffusion weighted magnetic resonance imaging (DWI) data have been mostly acquired with single-shot echo-planar imaging (EPI) to minimize motion induced artifacts. The spatial resolution, however, is inherently limited in single-shot EPI, even when the parallel imaging (usually at an acceleration factor of 2) is incorporated. Multi-shot acquisition strategies could potentially achieve higher spatial resolution and fidelity, but they are generally susceptible to motion-induced phase errors among excitations that are exacerbated by diffusion sensitizing gradients, rendering the reconstructed images unusable. It has been shown that shot-to-shot phase variations may be corrected using navigator echoes, but at the cost of imaging throughput. To address these challenges, a novel and robust multi-shot DWI technique, termed multiplexed sensitivity-encoding (MUSE), is developed here to reliably and inherently correct nonlinear shot-to-shot phase variations without the use of navigator echoes. The performance of the MUSE technique is confirmed experimentally in healthy adult volunteers on 3Tesla MRI systems. This newly developed technique should prove highly valuable for mapping brain structures and connectivities at high spatial resolution for neuroscience studies.

  18. A robust multi-shot scan strategy for high-resolution diffusion weighted MRI enabled by multiplexed sensitivity-encoding (MUSE)

    PubMed Central

    Chen, Nan-kuei; Guidon, Arnaud; Chang, Hing-Chiu; Song, Allen W.

    2013-01-01

    Diffusion weighted magnetic resonance imaging (DWI) data have been mostly acquired with single-shot echo-planar imaging (EPI) to minimize motion induced artifacts. The spatial resolution, however, is inherently limited in single-shot EPI, even when the parallel imaging (usually at an acceleration factor of 2) is incorporated. Multi-shot acquisition strategies could potentially achieve higher spatial resolution and fidelity, but they are generally susceptible to motion-induced phase errors among excitations that are exacerbated by diffusion sensitizing gradients, rendering the reconstructed images unusable. It has been shown that shot-to-shot phase variations may be corrected using navigator echoes, but at the cost of imaging throughput. To address these challenges, a novel and robust multi-shot DWI technique, termed multiplexed sensitivity-encoding (MUSE), is developed here to reliably and inherently correct nonlinear shot-to-shot phase variations without the use of navigator echoes. The performance of the MUSE technique is confirmed experimentally in healthy adult volunteers on 3 Tesla MRI systems. This newly developed technique should prove highly valuable for mapping brain structures and connectivities at high spatial resolution for neuroscience studies. PMID:23370063

  19. Whole-body MRI including diffusion-weighted MRI compared with 5-HTP PET/CT in the detection of neuroendocrine tumors

    PubMed Central

    Carlbom, Lina; Caballero-Corbalán, José; Granberg, Dan; Sörensen, Jens; Eriksson, Barbro; Ahlström, Håkan

    2017-01-01

    Aim We wanted to explore if whole-body magnetic resonance imaging (MRI) including diffusion-weighted (DW) and liver-specific contrast agent-enhanced imaging could be valuable in lesion detection of neuroendocrine tumors (NET). [11C]-5-Hydroxytryptophan positron emission tomography/computed tomography (5-HTP PET/CT) was used for comparison. Materials and methods Twenty-one patients with NET were investigated with whole-body MRI, including DW imaging (DWI) and contrast-enhanced imaging of the liver, and whole-body 5-HTP PET/CT. Seven additional patients underwent upper abdomen MRI including DWI, liver-specific contrast agent-enhanced imaging, and 5-HTP PET/CT. Results There was a patient-based concordance of 61% and a lesion-based concordance of 53% between the modalities. MRI showed good concordance with PET in detecting bone metastases but was less sensitive in detecting metastases in mediastinal lymph nodes. MRI detected more liver metastases than 5-HTP PET/CT. Conclusion Whole-body MRI with DWI did not detect all NET lesions found with whole-body 5-HTP PET/CT. Our findings indicate that MRI of the liver including liver-specific contrast agent-enhanced imaging and DWI could be a useful complement to whole-body 5-HTP PET/CT. PMID:27894208

  20. Diffusion-weighted imaging in the prostate: an apparent diffusion coefficient comparison of half-Fourier acquisition single-shot turbo spin-echo and echo planar imaging.

    PubMed

    Babourina-Brooks, Ben; Cowin, Gary J; Wang, Deming

    2012-02-01

    Prostate cancer detection using diffusion-weighted imaging is highly affected by the accuracy of the apparent diffusion coefficient (ADC) values in an image. Echo planar imaging (EPI) is a fast sequence commonly used for diffusion imaging but has inherent magnetic susceptibility and chemical shift artefacts associated. A diffusion sequence that is less affected by these artefacts is therefore advantageous. The half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence was chosen. The diffusion sequences were compared in image quality, repeatability of the ADC value and the effect on the ADC value with varied b values. Eight volunteers underwent three scans of each sequence, on a 1.5-T Siemens system, using b values of 0, 150, 300, 450, 600, 750, 900 and 1000 s/mm(2). ADC maps were created to address the reproducibility of the ADC value when using two b values compared to eight b values. The ADC value using all b values with the HASTE sequence gave the best performance in all tested categories. Both sequences gave significantly different ADC mean values for two b values compared to when using eight b values (P<.05) suggesting larger error is present when using two b values. HASTE was shown to be an improvement over EPI in terms of repeatability, signal variation within a region of interest and standard deviation over the volunteer set. The improved accuracy of the ADC value in the HASTE sequence makes it potentially a more sensitive tumor detection technique.

  1. Adaptive smoothing of high angular resolution diffusion-weighted imaging data by generalized cross-validation improves Q-ball orientation distribution function reconstruction.

    PubMed

    Metwalli, Nader S; Hu, Xiaoping P; Carew, John D

    2010-09-01

    Q-ball imaging (QBI) is a high angular resolution diffusion-weighted imaging (HARDI) technique for reconstructing the orientation distribution function (ODF). Some form of smoothing or regularization is typically required in the ODF reconstruction from low signal-to-noise ratio HARDI data. The amount of smoothing or regularization is usually set a priori at the discretion of the investigator. In this article, we apply an adaptive and objective means of smoothing the raw HARDI data using the smoothing splines on the sphere method with generalized cross-validation (GCV) to estimate the diffusivity profile in each voxel. Subsequently, we reconstruct the ODF, from the smoothed data, based on the Funk-Radon transform (FRT) used in QBI. The spline method was applied to both simulated data and in vivo human brain data. Simulated data show that the smoothing splines on the sphere method with GCV smoothing reduces the mean squared error in estimates of the ODF as compared with the standard analytical QBI approach. The human data demonstrate the utility of the method for estimating smooth ODFs.

  2. [Depiction of the cranial nerves around the cavernous sinus by 3D reversed FISP with diffusion weighted imaging (3D PSIF-DWI)].

    PubMed

    Ishida, Go; Oishi, Makoto; Jinguji, Shinya; Yoneoka, Yuichiro; Sato, Mitsuya; Fujii, Yukihiko

    2011-10-01

    To evaluate the anatomy of cranial nerves running in and around the cavernous sinus, we employed three-dimensional reversed fast imaging with steady-state precession (FISP) with diffusion weighted imaging (3D PSIF-DWI) on 3-T magnetic resonance (MR) system. After determining the proper parameters to obtain sufficient resolution of 3D PSIF-DWI, we collected imaging data of 20-side cavernous regions in 10 normal subjects. 3D PSIF-DWI provided high contrast between the cranial nerves and other soft tissues, fluid, and blood in all subjects. We also created volume-rendered images of 3D PSIF-DWI and anatomically evaluated the reliability of visualizing optic, oculomotor, trochlear, trigeminal, and abducens nerves on 3D PSIF-DWI. All 20 sets of cranial nerves were visualized and 12 trochlear nerves and 6 abducens nerves were partially identified. We also presented preliminary clinical experiences in two cases with pituitary adenomas. The anatomical relationship between the tumor and cranial nerves running in and around the cavernous sinus could be three-dimensionally comprehended by 3D PSIF-DWI and the volume-rendered images. In conclusion, 3D PSIF-DWI has great potential to provide high resolution "cranial nerve imaging", which visualizes the whole length of the cranial nerves including the parts in the blood flow as in the cavernous sinus region.

  3. A quantitative evaluation of diffusion-weighted MR imaging of focal hepatic lesions by using an optimal b-value for differentiation of malignant and benign tumors

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Seung; Im, In-Chul; Kang, Su-Man; Goo, Eun-Hoe; Kim, Kwang

    2013-12-01

    In this study, we aimed to determine an optimized b-value for the characterization of focal hepatic lesions (malignant and benign tumors) and to perform a quantitative analysis of the results. To achieve this, we obtained diffusion-weighted images (DWIs) from 30 focal hepatic disease patients (liver metastasis: 20 patients, and liver hemangioma: 10 patients) by using a 1.5 T MR system and varying the b-value from 0 through 200. The experimental results revealed that at a b-value of 50, the DWIs of the lesions showed high signal-to-noise ratios (SNRs; SN R liver_meta . = 229.83 ± 19.08, SNR liver_hema . = 241.66 ± 29.02), high contrast-to-noise ratios (CNRs; CN R liver_meta . = 39.66 ± 3.87, C N R liver_hema . = 142.55 ± 12.97) and low signal intensities of the apparent diffusion coefficients (ADCs; ADC liver_meta . = 1.40 × 10-3 ± 0.29, ADC liver_hema . = 2.55 × 10-3 ± 0.92). The focal hepatic lesions were clearly depicted, with DW images and ADC maps corresponding well. Thus, we could present an optimized b-value ( b = 50) for the characterization of focal hepatic lesions. Additionally, the ADC values of liver lesions were found to be useful in differentiating benign from malignant tumors.

  4. Reduced Integration and Differentiation of the Imitation Network in Autism: A Combined Functional Connectivity Magnetic Resonance Imaging and Diffusion-Weighted Imaging Study

    PubMed Central

    Fishman, Inna; Datko, Michael; Cabrera, Yuliana; Carper, Ruth A.; Müller, Ralph-Axel

    2016-01-01

    Objective Converging evidence indicates that brain abnormalities in autism spectrum disorder (ASD) involve atypical network connectivity, but few studies have integrated functional with structural connectivity measures. This multimodal investigation examined functional and structural connectivity of the imitation network in children and adolescents with ASD, and its links with clinical symptoms. Methods Resting state functional magnetic resonance imaging and diffusion-weighted imaging were performed in 35 participants with ASD and 35 typically developing controls, aged 8 to 17 years, matched for age, gender, intelligence quotient, and head motion. Results Within-network analyses revealed overall reduced functional connectivity (FC) between distributed imitation regions in the ASD group. Whole brain analyses showed that underconnectivity in ASD occurred exclusively in regions belonging to the imitation network, whereas overconnectivity was observed between imitation nodes and extraneous regions. Structurally, reduced fractional anisotropy and increased mean diffusivity were found in white matter tracts directly connecting key imitation regions with atypical FC in ASD. These differences in microstructural organization of white matter correlated with weaker FC and greater ASD symptomatology. Interpretation Findings demonstrate atypical connectivity of the brain network supporting imitation in ASD, characterized by a highly specific pattern. This pattern of underconnectivity within, but overconnectivity outside the functional network is in contrast with typical development and suggests reduced network integration and differentiation in ASD. Our findings also indicate that atypical connectivity of the imitation network may contribute to ASD clinical symptoms, highlighting the role of this fundamental social cognition ability in the pathophysiology of ASD. PMID:26418284

  5. The Predictive Value of Early Assessment After 1 Cycle of Induction Chemotherapy with 18F-FDG PET/CT and Diffusion-Weighted MRI for Response to Radical Chemoradiotherapy in Head and Neck Squamous Cell Carcinoma.

    PubMed

    Wong, Kee H; Panek, Rafal; Welsh, Liam; Mcquaid, Dualta; Dunlop, Alex; Riddell, Angela; Murray, Iain; Du, Yong; Chua, Sue; Koh, Dow-Mu; Bhide, Shreerang; Nutting, Chris; Oyen, Wim J G; Harrington, Kevin; Newbold, Kate L

    2016-12-01

    The objective of this study was to assess the predictive value of early assessment (after 1 cycle of induction chemotherapy [IC]) with (18)F-FDG PET/CT and diffusion-weighted (DW) MRI for subsequent response to radical chemoradiotherapy in locally advanced head and neck squamous cell carcinoma (HNSCC).

  6. Environmentally compatible solid rocket propellants

    NASA Technical Reports Server (NTRS)

    Jacox, James L.; Bradford, Daniel J.

    1995-01-01

    Hercules' clean propellant development research is exploring three major types of clean propellant: (1) chloride-free formulations (no chlorine containing ingredients), being developed on the Clean Propellant Development and Demonstration (CPDD) contract sponsored by Phillips Laboratory, Edwards Air Force Base, CA; (2) low HCl scavenged formulations (HCl-scavenger added to propellant oxidized with ammonium perchlorate (AP)); and (3) low HCl formulations oxidized with a combination of AN and AP (with or without an HCl scavenger) to provide a significant reduction (relative to current solid rocket boosters) in exhaust HCl. These propellants provide performance approaching that of current systems, with less than 2 percent HCl in the exhaust, a significant reduction (greater than or equal to 70 percent) in exhaust HCl levels. Excellent processing, safety, and mechanical properties were achieved using only readily available, low cost ingredients. Two formulations, a sodium nitrate (NaNO3) scavenged HTPB and a chloride-free hydroxy terminated polyether (HTPE) propellant, were characterized for ballistic, mechanical, and rheological properties. In addition, the hazards properties were demonstrated to provide two families of class 1.3, 'zero-card' propellants. Further characterization is planned which includes demonstration of ballistic tailorability in subscale (one to 70 pound) motors over the range of burn rates required for retrofit into current Hercules space booster designs (Titan 4 SRMU and Delta 2 GEM).

  7. Cars Spectroscopy of Propellant Flames

    DTIC Science & Technology

    1983-11-01

    Bele,:1t )"(vaiaable Copy AD AD-E4OI 102 TECMNICA._ REPORT ;RLCD-TR-83047 CARS SPECTROSCOPY Of PROPELLANT FLAMES L. E. HARRIS DTIC ii IELECTE0 "" NOV...4. TITLE (mid Subtitle) 5. TYPE OF REPORT & PERIOD COVERED CARS SPECTROSCOPY OF PROPELLANT FLAMES Final Ś. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(a...ea•abo. Broadband CARS CARS spectra Spectroscopy Propellant *0AUINIACT (0w o roemtae 401 N uueedswr Mu $000tit? b7 61"k Auhee) Obtaining useful

  8. Space storable propellant acquisition system

    NASA Technical Reports Server (NTRS)

    Tegart, J. R.; Uney, P. E.; Anderson, J. E.; Fester, D. A.

    1972-01-01

    Surface tension propellant acquisition concepts for an advanced spacecraft propulsion system having a 10-year mission capability were investigated. Surface tension systems were specified because they were shown to be the best propellant acquisition technique for various interplanetery spacecraft in a prior study. A variety of surface tension concepts for accomplishing propellant acquisition were formulated for the baseline space storable propulsion module and Jupiter Orbiter mission. Analyses and evaluations were then conducted on each candidate concept to assess fabricability, performance capability, and spacecraft compatibility. A comparative evaluation of the results showed the Fruhof-class of low-g surface tension systems to be preferred for these interplanetary applications.

  9. Design of Propellers for Motorsoarers

    NASA Technical Reports Server (NTRS)

    Larrabee, E. E.

    1979-01-01

    A method was developed for the design of propellers of minimum induced loss matched to an arbitrary operating point characterized by disc loading (thrust or power), air density, shaft speed, flight speed, and number of blades. A consistent procedure is outlined to predict the performance of these propellers under off design conditions, or to predict the performance of propellers of general geometry. The examples discussed include a man powered airplane, a hang glider with a 7.5 kW (10 hp) 8,000 rpm engine, and an airplane-like motorsoarer.

  10. Casting propellant in rocket engine

    NASA Technical Reports Server (NTRS)

    Roach, J. E.; Froehling, S. C. (Inventor)

    1976-01-01

    A method is described for casting a solid propellant in the casing of a rocket engine having a continuous wall with a single opening which is formed by leaves of a material which melt at a temperature of the propellant and with curved edges concentric to the curvature of the spherical casing. The leaves are inserted into the spherical casing through the opening forming a core having a greater width than the width of the single opening and with curved peripheral edges. The cast propellant forms a solid mass and then heated to melt the leaves and provide a central opening with radial projecting flutes.

  11. Influence of fuselage on propeller design

    NASA Technical Reports Server (NTRS)

    Troller, Theodor

    1928-01-01

    In the present paper I shall not consider the problem of the best arrangement of airplane and propeller, but only a simple method for designing a propeller for a given arrangement of airplane parts. The inflow to the propeller and hence the efficiency of the propeller is affected most by the fuselage.

  12. Application of theory to propeller design

    NASA Technical Reports Server (NTRS)

    Cox, G. G.; Morgan, W. B.

    1974-01-01

    The various theories concerning propeller design are discussed. The use of digital computers to obtain specific blade shapes to meet appropriate flow conditions is emphasized. The development of lifting-line and lifting surface configurations is analyzed. Ship propulsive performance and basic propeller design considerations are investigated. The characteristics of supercavitating propellers are compared with those of subcavitating propellers.

  13. The value of intravoxel incoherent motion model-based diffusion-weighted imaging for outcome prediction in resin-based radioembolization of breast cancer liver metastases

    PubMed Central

    Pieper, Claus Christian; Meyer, Carsten; Sprinkart, Alois Martin; Block, Wolfgang; Ahmadzadehfar, Hojjat; Schild, Hans Heinz; Mürtz, Petra; Kukuk, Guido Matthias

    2016-01-01

    Purpose To evaluate prognostic values of clinical and diffusion-weighted magnetic resonance imaging-derived intravoxel incoherent motion (IVIM) parameters in patients undergoing primary radioembolization for metastatic breast cancer liver metastases. Subjects and methods A total of 21 females (mean age 54 years, range 43–72 years) with liver-dominant metastatic breast cancer underwent standard liver magnetic resonance imaging (1.5 T, diffusion-weighted imaging with b-values of 0, 50, and 800 s/mm2) before and 4–6 weeks after radioembolization. The IVIM model-derived estimated diffusion coefficient D’ and the perfusion fraction f’ were evaluated by averaging the values of the two largest treated metastases in each patient. Kaplan–Meier and Cox regression analyses for overall survival (OS) were performed. Investigated parameters were changes in f’- and D’-values after therapy, age, sex, Eastern Cooperative Oncology Group (ECOG) status, grading of primary tumor, hepatic tumor burden, presence of extrahepatic disease, baseline bilirubin, previous bevacizumab therapy, early stasis during radioembolization, chemotherapy after radioembolization, repeated radioembolization and Response Evaluation Criteria in Solid Tumors (RECIST) response at 6-week follow-up. Results Median OS after radioembolization was 6 (range 1.5–54.9) months. In patients with therapy-induced decreasing or stable f’-values, median OS was significantly longer than in those with increased f’-values (7.6 [range 2.6–54.9] vs 2.6 [range 1.5–17.4] months, P<0.0001). Longer median OS was also seen in patients with increased D’-values (6 [range 1.6–54.9] vs 2.8 [range 1.5–17.4] months, P=0.008). Patients with remission or stable disease (responders) according to RECIST survived longer than nonresponders (7.2 [range 2.6–54.9] vs 2.6 [range 1.5–17.4] months, P<0.0001). An ECOG status ≤1 resulted in longer median OS than >1 (7.6 [range 2.6–54.9] vs 1.7 [range 1.5–4

  14. MR diffusion-weighted imaging-based subcutaneous tumour volumetry in a xenografted nude mouse model using 3D Slicer: an accurate and repeatable method

    PubMed Central

    Ma, Zelan; Chen, Xin; Huang, Yanqi; He, Lan; Liang, Cuishan; Liang, Changhong; Liu, Zaiyi

    2015-01-01

    Accurate and repeatable measurement of the gross tumour volume(GTV) of subcutaneous xenografts is crucial in the evaluation of anti-tumour therapy. Formula and image-based manual segmentation methods are commonly used for GTV measurement but are hindered by low accuracy and reproducibility. 3D Slicer is open-source software that provides semiautomatic segmentation for GTV measurements. In our study, subcutaneous GTVs from nude mouse xenografts were measured by semiautomatic segmentation with 3D Slicer based on morphological magnetic resonance imaging(mMRI) or diffusion-weighted imaging(DWI)(b = 0,20,800 s/mm2) . These GTVs were then compared with those obtained via the formula and image-based manual segmentation methods with ITK software using the true tumour volume as the standard reference. The effects of tumour size and shape on GTVs measurements were also investigated. Our results showed that, when compared with the true tumour volume, segmentation for DWI(P = 0.060–0.671) resulted in better accuracy than that mMRI(P < 0.001) and the formula method(P < 0.001). Furthermore, semiautomatic segmentation for DWI(intraclass correlation coefficient, ICC = 0.9999) resulted in higher reliability than manual segmentation(ICC = 0.9996–0.9998). Tumour size and shape had no effects on GTV measurement across all methods. Therefore, DWI-based semiautomatic segmentation, which is accurate and reproducible and also provides biological information, is the optimal GTV measurement method in the assessment of anti-tumour treatments. PMID:26489359

  15. A Simplified Approach to Measure the Effect of the Microvasculature in Diffusion-weighted MR Imaging Applied to Breast Tumors: Preliminary Results.

    PubMed

    Teruel, Jose R; Goa, Pål E; Sjøbakk, Torill E; Østlie, Agnes; Fjøsne, Hans E; Bathen, Tone F

    2016-11-01

    Purpose To evaluate the relative change of the apparent diffusion coefficient (ADC) at low- and medium-b-value regimens as a surrogate marker of microcirculation, to study its correlation with dynamic contrast agent-enhanced (DCE) magnetic resonance (MR) imaging-derived parameters, and to assess its potential for differentiation between malignant and benign breast tumors. Materials and Methods Ethics approval and informed consent were obtained. From May 2013 to June 2015, 61 patients diagnosed with either malignant or benign breast tumors were prospectively recruited. All patients were scanned with a 3-T MR imager, including diffusion-weighted imaging (DWI) and DCE MR imaging. Parametric analysis of DWI and DCE MR imaging was performed, including a proposed marker, relative enhanced diffusivity (RED). Spearman correlation was calculated between DCE MR imaging and DWI parameters, and the potential of the different DWI-derived parameters for differentiation between malignant and benign breast tumors was analyzed by dividing the sample into equally sized training and test sets. Optimal cut-off values were determined with receiver operating characteristic curve analysis in the training set, which were then used to evaluate the independent test set. Results RED had a Spearman rank correlation of 0.61 with the initial area under the curve calculated from DCE MR imaging. Furthermore, RED differentiated cancers from benign tumors with an overall accuracy of 90% (27 of 30) on the test set with 88.2% (15 of 17) sensitivity and 92.3% (12 of 13) specificity. Conclusion This study presents promising results introducing a simplified approach to assess results from a DWI protocol sensitive to the intravoxel incoherent motion effect by using only three b values. This approach could potentially aid in the differentiation, characterization, and monitoring of breast pathologies. (©) RSNA, 2016 Online supplemental material is available for this article.

  16. Intravoxel Incoherent Motion Diffusion Weighted MR Imaging at 3.0 T: Assessment of Steatohepatitis and Fibrosis Compared with Liver Biopsy in Type 2 Diabetic Patients

    PubMed Central

    Parente, Daniella Braz; Paiva, Fernando Fernandes; Oliveira Neto, Jaime Araújo; Machado-Silva, Lilian; Figueiredo, Fatima Aparecida Ferreira; Lanzoni, Valeria; Campos, Carlos Frederico Ferreira; do Brasil, Pedro Emmanuel Alvarenga Americano; Gomes, Marilia de Brito; Perez, Renata de Mello; Rodrigues, Rosana Souza

    2015-01-01

    Objective To evaluate the capability of intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) to assess steatohepatitis and fibrosis determined by histopathology in type 2 diabetic patients. Methods Fifty-nine type 2 diabetic patients (49 women, 10 men; mean age, 54 ± 9 years) were submitted to liver biopsy for the evaluation of non-alcoholic fatty liver disease (NAFLD) and underwent DWI on a 3.0T MR system using 10 b values. Institutional approval and patient consent were obtained. Pure molecular-based (D), perfusion-related (D*), and vascular fraction (f) were calculated using a double exponential model and least squares curve fitting. D, D*, and f were compared between patients with and without steatohepatitis and between patients with and without fibrosis. The variables were compared by using the Ranksum test and Student t-test. Results Steatohepatitis was observed in 22 patients and fibrosis in 16 patients. A lower D median (0.70 s/mm2 vs. 0.83 s/mm2, p<0.05) and a lower D* median (34.39 s/mm2 vs. 45.23 s/mm2, p<0.05) were observed among those with steatohepatitis. A lower D median (0.70 s/mm2 vs. 0.82 s/mm2, p<0.05) and a lower D* median (35.01 s/mm2 vs. 44.76 s/mm2, p=0.05) were also observed among those with fibrosis. Conclusion IVIM-DWI has the potential to aid in the characterization of steatohepatitis and fibrosis. PMID:25961735

  17. Early Detection of Therapeutic Response to Hepatic Arterial Infusion Chemotherapy of Liver Metastases from Colorectal Cancer Using Diffusion-Weighted MR Imaging

    SciTech Connect

    Marugami, Nagaaki; Tanaka, Toshihiro Kitano, Satoru; Hirohashi, Shinji; Nishiofuku, Hideyuki; Takahashi, Aki; Sakaguchi, Hiroshi; Matsuoka, Masaki; Otsuji, Toshio; Takahama, Junko; Higashiura, Wataru; Kichikawa, Kimihiko

    2009-07-15

    The purpose of this study was to investigate whether diffusion-weighted magnetic resonance imaging (DWI) is useful for early detection of the response of hepatic colorectal metastases to hepatic arterial infusion chemotherapy (HAIC) with 5-fluorouracil (5-FU). The subjects were 12 patients with hepatic colorectal metastases. The indwelling catheter for HAIC was placed in the hepatic artery, and 1000 mg/m{sup 2} 5-FU was given repeatedly once a week. DWI was performed before and 9 days after HAIC. The minimum and mean apparent diffusion coefficient (ADC) values (minADC and meanADC) were measured. The relative change in ADC values (%ADC) and the relative change in tumor size on follow-up CT after 3 months (reduction ratio) were determined. Liver metastases were divided into two groups, responder and nonresponder. The correlation between %ADC and reduction ratio was determined, and %ADC was compared between the two groups. Eleven patients successfully completed HAIC over the 3-month period; 48 metastatic lesions were evaluated. Positive correlations were observed for relative change between %minADC and reduction ratio (r = 0.709) and between %meanADC and reduction ratio (r = 0.536). Both %minADC and %meanADC were significantly greater in the responder group than in the nonresponder group. With the threshold determined as < 3.5%, the receiver-operating curve analysis showed higher sensitivity and specificity values for %minADC (100% and 92.6%, respectively) than for %meanADC (66.7% and 74.1%, respectively). In conclusion, the relative change in minimum ADC values on DWI may be useful for early detection of the response of liver metastases to HAIC with 5-FU.

  18. Cerebral edema induced in mice by a convulsive dose of soman. Evaluation through diffusion-weighted magnetic resonance imaging and histology

    SciTech Connect

    Testylier, Guy . E-mail: guytestylier@crssa.net; Lahrech, Hana; Montigon, Olivier; Foquin, Annie; Delacour, Claire; Bernabe, Denis; Segebarth, Christoph; Dorandeu, Frederic; Carpentier, Pierre

    2007-04-15

    Purpose: In the present study, diffusion-weighted magnetic resonance imaging (DW-MRI) and histology were used to assess cerebral edema and lesions in mice intoxicated by a convulsive dose of soman, an organophosphate compound acting as an irreversible cholinesterase inhibitor. Methods: Three hours and 24 h after the intoxication with soman (172 {mu}g/kg), the mice were anesthetized with an isoflurane/N{sub 2}O mixture and their brain examined with DW-MRI. After the imaging sessions, the mice were sacrificed for histological analysis of their brain. Results: A decrease in the apparent diffusion coefficient (ADC) was detected as soon as 3 h after the intoxication and was found strongly enhanced at 24 h. A correlation was obtained between the ADC change and the severity of the overall brain damage (edema and cellular degeneration): the more severe the damage, the stronger the ADC drop. Anesthesia was shown to interrupt soman-induced seizures and to attenuate edema and cell change in certain sensitive brain areas. Finally, brain water content was assessed using the traditional dry/wet weight method. A significant increase of brain water was observed following the intoxication. Conclusions: The ADC decrease observed in the present study suggests that brain edema in soman poisoning is mainly intracellular and cytotoxic. Since entry of water into Brain was also evidenced, this type of edema is certainly mixed with others (vasogenic, hydrostatic, osmotic). The present study confirms the potential of DW-MRI as a non-invasive tool for monitoring the acute neuropathological consequences (edema and neurodegeneration) of soman-induced seizures.

  19. Combined diffusion-weighted and functional magnetic resonance imaging reveals a temporal-occipital network involved in auditory-visual object processing

    PubMed Central

    Beer, Anton L.; Plank, Tina; Meyer, Georg; Greenlee, Mark W.

    2013-01-01

    Functional magnetic resonance imaging (MRI) showed that the superior temporal and occipital cortex are involved in multisensory integration. Probabilistic fiber tracking based on diffusion-weighted MRI suggests that multisensory processing is supported by white matter connections between auditory cortex and the temporal and occipital lobe. Here, we present a combined functional MRI and probabilistic fiber tracking study that reveals multisensory processing mechanisms that remained undetected by either technique alone. Ten healthy participants passively observed visually presented lip or body movements, heard speech or body action sounds, or were exposed to a combination of both. Bimodal stimulation engaged a temporal-occipital brain network including the multisensory superior temporal sulcus (msSTS), the lateral superior temporal gyrus (lSTG), and the extrastriate body area (EBA). A region-of-interest (ROI) analysis showed multisensory interactions (e.g., subadditive responses to bimodal compared to unimodal stimuli) in the msSTS, the lSTG, and the EBA region. Moreover, sounds elicited responses in the medial occipital cortex. Probabilistic tracking revealed white matter tracts between the auditory cortex and the medial occipital cortex, the inferior occipital cortex (IOC), and the superior temporal sulcus (STS). However, STS terminations of auditory cortex tracts showed limited overlap with the msSTS region. Instead, msSTS was connected to primary sensory regions via intermediate nodes in the temporal and occipital cortex. Similarly, the lSTG and EBA regions showed limited direct white matter connections but instead were connected via intermediate nodes. Our results suggest that multisensory processing in the STS is mediated by separate brain areas that form a distinct network in the lateral temporal and inferior occipital cortex. PMID:23407860

  20. The Therapeutic Response of Gastrointestinal Stromal Tumors to Imatinib Treatment Assessed by Intravoxel Incoherent Motion Diffusion-Weighted Magnetic Resonance Imaging with Histopathological Correlation

    PubMed Central

    Zhang, Chunfang; Wang, He; Cheng, Jin; Wu, Weizhen; Hong, Nan; Wang, Yi

    2016-01-01

    Purpose To exploit the intravoxel incoherent motion (IVIM) diffusion-weighted (DW) MRI when evaluating the therapeutic response of gastrointestinal stromal tumors (GIST) to Imatinib in a mouse model. Materials and Methods Mice with xenografts bearing cells from the GIST-T1 cell line were randomly divided into a treated group receiving Imatinib and a control group. DWMRI scans with 14 b-values (0–1500 s/mm2) were performed before and after treatment (days 1, 3 and 7). IVIM related parameters perfusion fractions (fp) and perfusion-related diffusion coefficients (D*) and the conventional apparent diffusion coefficients (ADC) were calculated by fitting the DWMRI signal decay. The mean changes from baseline to each post-treatment time point for each measurement (ΔADC, Δfp and ΔD*) were calculated. The differences of mean changes between the two groups were tested for statistical significance. Histopathological analyses including Ki-67, CD31, TUNEL and H&E were conducted in conjunction with the MRI scans. Results Increases in ADC of the treated group were higher than those of the control group after treatment, whereas statistical significances were not observed. Compared to the control group, D* in the treated group decreased significantly (ΔD*treated = -41%, -49%, and -49% with P = 0.0001, 0.0001 and 0.0001), and fp increased significantly (Δfptreated = 79%, 82% and 110%, with P = 0.001, 0.0001 and P = 0.0007) on days 1, 3 and 7 after treatment. Histopathological analyses demonstrated different tumor tissue characteristics between the treated and control groups. Conclusion IVIM measurements may serve as more sensitive imaging biomarkers than ADC when assessing GIST response to Imatinib as early as one day after treatment. PMID:27911930

  1. Functional Independence following Endovascular Treatment for Basilar Artery Occlusion despite Extensive Bilateral Pontine Infarcts on Diffusion-Weighted Imaging: Refuting a Self-Fulfilling Prophecy

    PubMed Central

    Haussen, Diogo C.; Oliveira, Renato A.C.; Patel, Vikas; Nogueira, Raul G.

    2016-01-01

    Background and Purpose Extensive brainstem diffusion-weighted imaging (DWI) hyperintensity has been associated with poor outcomes. We aim at documenting a series of patients with extensive DWI pontine lesions who achieved independence following endovascular therapy and aggressive medical therapy in the setting of posterior circulation basilar artery occlusion (BAO). Methods This is a retrospective endovascular database review of a single-operator experience over a 9-year period for patients with (1) complete BAO, (2) extensive bilateral pontine DWI changes and (3) 90-day modified Rankin scale 0–2. Results Three out of a total of 40 patients met the inclusion criteria. Case 1 was an 18-year-old male with National Institutes of Health Stroke Scale (NIHSS) 32 on admission, treated 25 h after symptom onset. Case 2 was a 56-year-old male with NIHSS 19, treated 10 h after onset. Case 3 was a 73-year-old male with NIHSS 29, treated 6 h after onset. Full endovascular reperfusion was achieved in all 3 patients. A literature review identified 9 additional cases of extensive pontine DWI changes and good outcome. These patients were young (32 ± 22 years), mostly males (69%), presented with a relatively low posterior circulation Acute Stroke Prognosis Early CT Score (6 ± 1), were treated relatively late from last known normal (13 ± 10 h) and were mostly (84%) treated with endovascular intervention. Conclusion Extensive bilateral pontine DWI lesions among patients with BAO are not an unequivocal indicator of poor prognosis. We advise strong caution when considering these findings in the treatment decision algorithm. PMID:27781047

  2. Comparison of [{sup 11}C]choline Positron Emission Tomography With T2- and Diffusion-Weighted Magnetic Resonance Imaging for Delineating Malignant Intraprostatic Lesions

    SciTech Connect

    Chang, Joe H.; Lim Joon, Daryl; Davis, Ian D.; Lee, Sze Ting; Hiew, Chee-Yan; Esler, Stephen; Gong, Sylvia J.; Wada, Morikatsu; Clouston, David; O'Sullivan, Richard; Goh, Yin P.; Bolton, Damien; Scott, Andrew M.; Khoo, Vincent

    2015-06-01

    Purpose: The purpose of this study was to compare the accuracy of [{sup 11}C]choline positron emission tomography (CHOL-PET) with that of the combination of T2-weighted and diffusion-weighted (T2W/DW) magnetic resonance imaging (MRI) for delineating malignant intraprostatic lesions (IPLs) for guiding focal therapies and to investigate factors predicting the accuracy of CHOL-PET. Methods and Materials: This study included 21 patients who underwent CHOL-PET and T2W/DW MRI prior to radical prostatectomy. Two observers manually delineated IPL contours for each scan, and automatic IPL contours were generated on CHOL-PET based on varying proportions of the maximum standardized uptake value (SUV). IPLs identified on prostatectomy specimens defined reference standard contours. The imaging-based contours were compared with the reference standard contours using Dice similarity coefficient (DSC), and sensitivity and specificity values. Factors that could potentially predict the DSC of the best contouring method were analyzed using linear models. Results: The best automatic contouring method, 60% of the maximum SUV (SUV{sub 60}) , had similar correlations (DSC: 0.59) with the manual PET contours (DSC: 0.52, P=.127) and significantly better correlations than the manual MRI contours (DSC: 0.37, P<.001). The sensitivity and specificity values were 72% and 71% for SUV{sub 60}; 53% and 86% for PET manual contouring; and 28% and 92% for MRI manual contouring. The tumor volume and transition zone pattern could independently predict the accuracy of CHOL-PET. Conclusions: CHOL-PET is superior to the combination of T2W/DW MRI for delineating IPLs. The accuracy of CHOL-PET is insufficient for gland-sparing focal therapies but may be accurate enough for focal boost therapies. The transition zone pattern is a new classification that may predict how well CHOL-PET delineates IPLs.

  3. Differentiation of pancreatic carcinoma and mass-forming focal pancreatitis: qualitative and quantitative assessment by dynamic contrast-enhanced MRI combined with diffusion-weighted imaging

    PubMed Central

    Zhang, Ting-Ting; Wang, Li; Liu, Huan-huan; Zhang, Cai-yuan; Li, Xiao-ming; Lu, Jian-ping; Wang, Deng-bin

    2017-01-01

    Differentiation between pancreatic carcinoma (PC) and mass-forming focal pancreatitis (FP) is invariably difficult. For the differential diagnosis, we qualitatively and quantitatively assessed the value of dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted imaging (DWI) in PC and FP in the present study. This study included 32 PC and 18 FP patients with histological confirmation who underwent DCE-MRI and DWI. The time-signal intensity curve (TIC) of PC and FP were classified into 5 types according to the time of reaching the peak, namely, type I, II, III, IV, and V, respectively, and two subtypes, namely, subtype-a (washout type) and subtype-b (plateau type) according to the part of the TIC profile after the peak. Moreover, the mean and relative apparent diffusion coefficient (ADC) value between PC and FP on DWI were compared. The type V TIC was only recognized in PC group (P < 0.01). Type IV b were more frequently observed in PC (P = 0.036), while type- IIa (P < 0.01), type- Ia (P = 0.037) in FP. We also found a significant difference in the mean and relative ADC value between PC and FP. The combined image set of DCE-MRI and DWI yielded an excellent sensitivity, specificity, and diagnostic accuracy (96.9%, 94.4%, and 96.0%). The TIC of DCE-MRI and ADC value of DWI for pancreatic mass were found to provide reliable information in differentiating PC from FP, and the combination of DCE-MRI and DWI can achieve a higher sensitivity, specificity, and diagnostic accuracy. PMID:27661003

  4. Intravoxel incoherent motion model–based analysis of diffusion-weighted magnetic resonance imaging with 3 b-values for response assessment in locoregional therapy of hepatocellular carcinoma

    PubMed Central

    Mürtz, Petra; Penner, Arndt-Hendrik; Pfeiffer, Anne-Kristina; Sprinkart, Alois M; Pieper, Claus C; König, Roy; Block, Wolfgang; Schild, Hans H; Willinek, Winfried A; Kukuk, Guido M

    2016-01-01

    Purpose The aim of this study was to evaluate an intravoxel incoherent motion (IVIM) model–based analysis of diffusion-weighted imaging (DWI) for assessing the response of hepatocellular carcinoma (HCC) to locoregional therapy. Patients and methods Respiratory-gated DWI (b=0, 50, and 800 s/mm2) was retrospectively analyzed in 25 patients who underwent magnetic resonance imaging at 1.5 T before and 6 weeks following the first cycle of transarterial chemoembolization therapy, transarterial ethanol-lipiodol embolization therapy, and transarterial radioembolization therapy. In addition to the determination of apparent diffusion coefficient, ADC(0,800), an estimation of the diffusion coefficient, D′, and the perfusion fraction, f′, was performed by using a simplified IVIM approach. Parameters were analyzed voxel-wise. Tumor response was assessed in a central slice by using a region of interest (ROI) covering the whole tumor. HCCs were categorized into two groups, responders and nonresponders, according to tumor size changes on first and second follow ups (if available) and changes of contrast-enhanced region on the first follow up. Results In total, 31 HCCs were analyzed: 17 lesions were assigned to responders and 14 were to nonresponders. In responders, ADC(0,800) and D′ were increased after therapy by ~30% (P=0.00004) and ~42% (P=0.00001), respectively, whereas f′ was decreased by ~37% (P=0.00094). No significant changes were found in nonresponders. Responders and nonresponders were better differentiated by changes in D′ than by changes in ADC(0,800) (area under the curve =0.878 vs 0.819 or 0.714, respectively). Conclusion In patients with HCCs undergoing embolization therapy, diffusion changes were better reflected by D′ than by conventional ADC(0,800), which is influenced by counteracting perfusion changes as assessed by f′. PMID:27799790

  5. Diffusion-weighted whole-body imaging with background body signal suppression/T2 image fusion for the diagnosis of colorectal polyp and cancer

    PubMed Central

    Tomizawa, Minoru; Shinozaki, Fuminobu; Uchida, Yoshitaka; Uchiyama, Katsuhiro; Fugo, Kazunori; Sunaoshi, Takafumi; Ozaki, Aika; Sugiyama, Eriko; Baba, Akira; Kano, Daisuke; Shite, Misaki; Haga, Ryota; Fukamizu, Yoshiya; Kagayama, Satoshi; Hasegawa, Rumiko; Shirai, Yoshinori; Motoyoshi, Yasufumi; Sugiyama, Takao; Yamamoto, Shigenori; Kishimoto, Takashi; Ishige, Naoki

    2017-01-01

    Diffusion-weighted whole-body imaging with background body signal suppression/T2 image fusion (DWIBS/T2) is useful for the diagnosis of cancer as it presents a clear contrast between cancerous and non-cancerous tissue. The present study investigated the limitations and advantages of DWIBS/T2 with regards to the diagnosis of colorectal polyp (CP) or cancer (CRC). The current study included patients diagnosed with CP or CRC following colonoscopy, who were subjected to DWIBS/T2 between July 2012 and March 2015. Patient records were analyzed retrospectively. Patients were subjected to DWIBS/T2 when they presented with abdominal cancers or inflammation. Colonoscopy was performed as part of screening, or if patients had suspected colon cancer or inflammatory bowel disease. A total of 8 male and 7 female patients were enrolled in the present study. All patients, with the exception of one who had been diagnosed with CRC following colonoscopy, had positive results and all patients diagnosed with CP following a colonoscopy, with the exception of one, had negative results on DWIBS/T2. Thus, CRC was detected by DWIBS/T2, while CP was not (P=0.0028). The diameter of CRC lesions was significantly larger than that of CP (P<0.0001) and that of lesions positive on DWIBS/T2 was significantly larger than that of negative lesions (P=0.0004). The depth of invasion tended to be greater for lesions positive on DWIBS/T2 compared with that of negative ones. This indicated that DWIBS/T2 may be suitable for the detection of CRC but not for detection of CP. The results of DWIBS/T2 may also be affected by lesion diameter and depth of invasion. PMID:28352344

  6. Magnetic resonance imaging of blood-brain barrier permeability in ischemic stroke using diffusion-weighted arterial spin labeling in rats.

    PubMed

    Tiwari, Yash V; Lu, Jianfei; Shen, Qiang; Cerqueira, Bianca; Duong, Timothy Q

    2016-01-01

    Diffusion-weighted arterial spin labeling magnetic resonance imaging has recently been proposed to quantify the rate of water exchange (Kw) across the blood-brain barrier in humans. This study aimed to evaluate the blood-brain barrier disruption in transient (60 min) ischemic stroke using Kw magnetic resonance imaging with cross-validation by dynamic contrast-enhanced magnetic resonance imaging and Evans blue histology in the same rats. The major findings were: (i) at 90 min after stroke (30 min after reperfusion), group Kw magnetic resonance imaging data showed no significant blood-brain barrier permeability changes, although a few animals showed slightly abnormal Kw. Dynamic contrast-enhanced magnetic resonance imaging confirmed this finding in the same animals. (ii) At two days after stroke, Kw magnetic resonance imaging revealed significant blood-brain barrier disruption. Regions with abnormal Kw showed substantial overlap with regions of hyperintense T2 (vasogenic edema) and hyperperfusion. Dynamic contrast-enhanced magnetic resonance imaging and Evans blue histology confirmed these findings in the same animals. The Kw values in the normal contralesional hemisphere and the ipsilesional ischemic core two days after stroke were: 363 ± 17 and 261 ± 18 min(-1), respectively (P < 0.05, n = 9). Kw magnetic resonance imaging is sensitive to blood-brain barrier permeability changes in stroke, consistent with dynamic contrast-enhanced magnetic resonance imaging and Evans blue extravasation. Kw magnetic resonance imaging offers advantages over existing techniques because contrast agent is not needed and repeated measurements can be made for longitudinal monitoring or averaging.

  7. Joint correction of Nyquist artifact and minuscule motion-induced aliasing artifact in interleaved diffusion weighted EPI data using a composite two-dimensional phase correction procedure.

    PubMed

    Chang, Hing-Chiu; Chen, Nan-Kuei

    2016-09-01

    Diffusion-weighted imaging (DWI) obtained with interleaved echo-planar imaging (EPI) pulse sequence has great potential of characterizing brain tissue properties at high spatial-resolution. However, interleaved EPI based DWI data may be corrupted by various types of aliasing artifacts. First, inconsistencies in k-space data obtained with opposite readout gradient polarities result in Nyquist artifact, which is usually reduced with 1D phase correction in post-processing. When there exist eddy current cross terms (e.g., in oblique-plane EPI), 2D phase correction is needed to effectively reduce Nyquist artifact. Second, minuscule motion induced phase inconsistencies in interleaved DWI scans result in image-domain aliasing artifact, which can be removed with reconstruction procedures that take shot-to-shot phase variations into consideration. In existing interleaved DWI reconstruction procedures, Nyquist artifact and minuscule motion-induced aliasing artifact are typically removed subsequently in two stages. Although the two-stage phase correction generally performs well for non-oblique plane EPI data obtained from well-calibrated system, the residual artifacts may still be pronounced in oblique-plane EPI data or when there exist eddy current cross terms. To address this challenge, here we report a new composite 2D phase correction procedure, which effective removes Nyquist artifact and minuscule motion induced aliasing artifact jointly in a single step. Our experimental results demonstrate that the new 2D phase correction method can much more effectively reduce artifacts in interleaved EPI based DWI data as compared with the existing two-stage artifact correction procedures. The new method robustly enables high-resolution DWI, and should prove highly valuable for clinical uses and research studies of DWI.

  8. The Role of Diffusion-Weighted Magnetic Resonance Imaging in the Treatment Response Evaluation of Hepatocellular Carcinoma Patients Treated With Radiation Therapy

    SciTech Connect

    Yu, Jeong Il; Park, Hee Chul; Lim, Do Hoon; Choi, Yunseon; Jung, Sang Hoon; Paik, Seung Woon; Kim, Seong Hyun; Jeong, Woo Kyoung; Kim, Young Kon

    2014-07-15

    Purpose: We investigated the role of diffusion-weighted magnetic resonance imaging (DW MRI) as a response evaluation indicator for hepatocellular carcinoma (HCC) treated with radiation therapy (RT). Methods and Materials: Inclusion criteria of this retrospective study were DW MRI acquisition within 1 month before and 3 to 5 months after RT. In total, 48 patients were enrolled. Two radiation oncologists measured the apparent diffusion coefficient (ADC). Possible predictive factors, including alteration of the ADC value before and 3 to 5 month after RT, in relation to local progression-free survival (LPFS) were analyzed and compared. Results: Three months after RT, 6 patients (12.5%) showed a complete response, and 27 patients (56.3%) showed a partial response when evaluated using the modified response evaluation criteria in solid tumors (mRECIST). The average ADC ± SD values were 1.21 ± 0.27 ( × 10{sup −3} mm{sup 2}/s) before and 1.41 ± 0.36 ( × 10{sup −3} mm{sup 2}/s) after RT (P<.001). The most significant prognostic factor related to LPFS was mRECIST (P<.001). The increment of ADC value (≥20%) was also a significant factor (P=.02), but RECIST (version 1.1; P=.11) was not. When RECIST was combined with the increment of ADC value (≥20%), the LPFS rates were significantly different between the groups (P=.004), and the area under the curve value (0.745) was comparable with that of mRECIST (0.765). Conclusions: ADC value change before and after RT in HCC was closely related to LPFS. ADC value and RECIST may substitute for mRECIST in patients who cannot receive contrast agents.

  9. Prognostic Value of Diffusion-Weighted Imaging (DWI) Apparent Diffusion Coefficient (ADC) in Patients with Hyperacute Cerebral Infarction Receiving rt-PA Intravenous Thrombolytic Therapy

    PubMed Central

    Sui, Hai-Jing; Yan, Cheng-Gong; Zhao, Zhen-Guo; Bai, Qing-Ke

    2016-01-01

    Background The aim of this study was to investigate the potential value of apparent diffusion coefficient (ADC) of diffusion-weighted imaging (DWI) in the prognosis of patients with hyperacute cerebral infarction (HCI) receiving intravenous thrombolytic therapy with recombinant tissue plasminogen activator (rt-PA). Material/Methods From June 2012 to June 2015, 58 cases of HCI (<6 h) undergoing rt-PA intravenous thrombolytic therapy (thrombolysis group) and 70 cases of HCI (<6 h) undergoing conventional antiplatelet and anticoagulant therapy (control group) in the same period were collected. DWI was conducted on all the subjects, and ADC maps were generated with Functool software to quantify ADC value. The clinical outcomes of HCI patients were observed for 3 months, and prognostic factors were analyzed. Results Before thrombolysis treatment, the lesion area presented high signal intensity on DWI map and low signal intensity on ADC map, and gradually weakened signal intensity on DWI map and gradually enhanced signal intensity on ADC map were observed after thrombolysis. The ADC values of the thrombolysis group were significantly higher than those of the control group after treatment (24 h, 7 d, 30 d, and 90 d) (all P<0.05), and the ADC and rADC values in the thrombolysis group gradually increased over time (all P<0.05). Multiple logistic regression analysis showed that baseline National Institutes of Health Stroke Scale (NIHSS) score, baseline rADC value, and stroke history were the independent factors for the prognosis of HIC patients with thrombolysis (all P<0.05). Conclusions The values of ADC and rADC may provide guidance in the prognosis of HCI patients receiving rt-PA, and the baseline rADC value is the protective factor for the prognosis of HCI patients receiving rt-PA. PMID:27864581

  10. Critical Care Needs in Patients with Diffusion-Weighted Imaging Negative MRI after tPA - Does One Size Fit All?

    PubMed Central

    Faigle, Roland; Marsh, Elisabeth B.; Llinas, Rafael H.; Urrutia, Victor C.

    2015-01-01

    Background and Purpose Patients who receive intravenous (IV) tissue plasminogen activator (tPA) for ischemic stroke are currently monitored in an intensive care unit (ICU) or a comparable stroke unit for at least 24 hours due to the high frequency of neurological exams and vital sign checks. The present study evaluates ICU needs in patients with diffusion-weighted imaging (DWI) negative MRI after IV tPA. Methods A retrospective chart review was performed for 209 patients who received IV tPA for acute stroke. Data on stroke risk factors, physiologic parameters, stroke severity, MRI characteristics, and final diagnosis were collected. The timing and nature of ICU interventions, if needed, was recorded. Multivariable logistic regression was used to determine factors associated with subsequent ICU needs. Results Patients with cerebral infarct on MRI after tPA had over 9 times higher odds of requiring ICU care compared to patients with DWI negative MRI (OR 9.2, 95% CI 2.49–34.15). All DWI negative patients requiring ICU care did so by the end of tPA infusion (p = 0.006). Among patients with DWI negative MRI, need for ICU interventions was associated with higher NIH Stroke Scale (NIHSS) scores (p<0.001), uncontrolled hypertension (p<0.001), seizure at onset (p = 0.002), and reduced estimated glomerular filtration rate (eGFR) (p = 0.010). Conclusions Only a small number of DWI negative patients required ICU care. In patients without critical care needs by the end of thrombolysis, post-tPA MRI may be considered for triaging DWI negative patients to a less resource intense monitoring environment. PMID:26517543

  11. Diffusion-Weighted Magnetic Resonance Imaging Early After Chemoradiotherapy to Monitor Treatment Response in Head-and-Neck Squamous Cell Carcinoma

    SciTech Connect

    Vandecaveye, Vincent; Dirix, Piet; De Keyzer, Frederik; Op de Beeck, Katya; Vander Poorten, Vincent; Hauben, Esther; Lambrecht, Maarten; Nuyts, Sandra; Hermans, Robert

    2012-03-01

    Purpose: To evaluate diffusion-weighted imaging (DWI) for assessment of treatment response in head and neck squamous cell carcinoma (HNSCC) three weeks after the end of chemoradiotherapy (CRT). Methods and Materials: Twenty-nine patients with HNSCC underwent magnetic resonance imaging (MRI) prior to and 3 weeks after CRT, including T{sub 2}-weighted and pre- and postcontrast T{sub 1}-weighted sequences and an echo-planar DWI sequence with six b values (0 to 1,000 s/mm{sup 2}), from which the apparent diffusion coefficient (ADC) was calculated. ADC changes 3 weeks posttreatment compared to baseline ( Increment ADC) between responding and nonresponding primary lesions and adenopathies were correlated with 2 years locoregional control and compared with a Mann-Whitney test. In a blinded manner, the Increment ADC was compared to conventional MRI 3 weeks post-CRT and the routinely implemented CT, on average 3 months post-CRT, which used size-related and morphological criteria. Positive and negative predictive values (PPV and NPV, respectively) were compared between the Increment ADC and anatomical imaging. Results: The Increment ADC of lesions with later tumor recurrence was significantly lower than lesions with complete remission for both primary lesions (-2.3% {+-} 0.3% vs. 80% {+-} 41%; p < 0.0001) and adenopathies (19.9% {+-} 32% vs. 63% {+-} 36%; p = 0.003). The Increment ADC showed a PPV of 89% and an NPV of 100% for primary lesions and a PPV of 70% and an NPV of 96% for adenopathies per neck side. DWI improved PPV and NPV compared to anatomical imaging. Conclusion: DWI with the Increment ADC 3 weeks after concluding CRT for HNSCC allows for early assessment of treatment response.

  12. Multicentre multiobserver study of diffusion-weighted and fluid-attenuated inversion recovery MRI for the diagnosis of sporadic Creutzfeldt-Jakob disease: a reliability and agreement study.

    PubMed

    Fujita, Koji; Harada, Masafumi; Sasaki, Makoto; Yuasa, Tatsuhiko; Sakai, Kenji; Hamaguchi, Tsuyoshi; Sanjo, Nobuo; Shiga, Yusei; Satoh, Katsuya; Atarashi, Ryuichiro; Shirabe, Susumu; Nagata, Ken; Maeda, Tetsuya; Murayama, Shigeo; Izumi, Yuishin; Kaji, Ryuji; Yamada, Masahito; Mizusawa, Hidehiro

    2012-01-01

    Objectives To assess the utility of the display standardisation of diffusion-weighted MRI (DWI) and to compare the effectiveness of DWI and fluid-attenuated inversion recovery (FLAIR) MRI for the diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD). Design A reliability and agreement study. Setting Thirteen MRI observers comprising eight neurologists and five radiologists at two universities in Japan. Participants Data of 1.5-Tesla DWI and FLAIR were obtained from 29 patients with sCJD and 13 controls. Outcome measures Standardisation of DWI display was performed utilising b0 imaging. The observers participated in standardised DWI, variable DWI (the display adjustment was observer dependent) and FLAIR sessions. The observers independently assessed each MRI for CJD-related lesions, that is, hyperintensity in the cerebral cortex or striatum, using a continuous rating scale. Performance was evaluated by the area under the receiver operating characteristics curve (AUC). Results The mean AUC values were 0.84 (95% CI 0.81 to 0.87) for standardised DWI, 0.85 (95% CI 0.82 to 0.88) for variable DWI and 0.68 (95% CI 0.63 to 0.72) for FLAIR, demonstrating the superiority of DWI (p<0.05). There was a trend for higher intraclass correlations of standardised DWI (0.74, 95% CI 0.66 to 0.83) and variable DWI (0.72, 95% CI 0.62 to 0.81) than that of FLAIR (0.63, 95% CI 0.53 to 0.74), although the differences were not statistically significant. Conclusions Standardised DWI is as reliable as variable DWI, and the two DWI displays are superior to FLAIR for the diagnosis of sCJD. The authors propose that hyperintensity in the cerebral cortex or striatum on 1.5-Tesla DWI but not FLAIR can be a reliable diagnostic marker for sCJD.

  13. Diffusion-weighted 19F-MRI of lung periphery: Influence of pressure and air-SF6 composition on apparent diffusion coefficients.

    PubMed

    Ruiz-Cabello, Jesús; Pérez-Sánchez, José Manuel; Pérez de Alejo, Rigoberto; Rodríguez, Ignacio; González-Mangado, Nicolás; Peces-Barba, Germán; Cortijo, Manuel

    2005-08-25

    Lung functional magnetic resonance imaging (MRI) has become a reality using different inert hyperpolarized gases, such as 3He and 129Xe, which have provided an extraordinary boost in lung imaging and has also attracted interest to other chemically inert gaseous contrast agents. In this context, we have recently demonstrated the first diffusion-weighted images using thermally polarized inhaled sulfur hexafluoride (SF6) in small animals. The aim of this study was to evaluate whether or not the diffusion coefficient of this fluorinated gas is sensitive to pulmonary structure, gas concentration and air pressure in the airways. Diffusion coefficients of SF6 (both pure and in air mixtures) measured in vitro at different pressures and 20 degrees C showed an excellent agreement with theoretical values. Measurements of diffusion coefficients were also performed in vivo and post-mortem on healthy rats, achieving satisfactory signal-to-noise ratios (SNRs), and SF6 gas was found to be in an almost completely restricted diffusion regime in the lung, i.e., the transport by molecular diffusion is delayed by collisions with barriers such as the alveolar septa. This observed low diffusivity means that this gas will be less sensitive to structural changes in the lungs than other magnetic resonance sensitive gas such as 3He, particularly at human scale. However, it is still possible that SF6 plays a role since it opens a new structural window. Thus, the interest of researchers in delimiting the important limiting technical factors that makes this process very challenging is obvious. Among them, T2 relaxation is very fast, so gradient systems with very fast switching rate and probably large radiofrequency (RF) power and high field systems will be needed for hexafluoride to be used in human studies.

  14. The Minimum Energy Loss Propeller

    NASA Technical Reports Server (NTRS)

    Poliakhov, N.

    1945-01-01

    Various cases are presented of the solution of the problem ot the most efficient propeller, more general cases being considered than the one by Betz in 1919: namely, that of a propeller under a limiting light load, The problem is solved directly and also with the aid of the Ritz method which became readily applicable after the author proposed a method for the solution of the propeller problem, in general, with the aid of trigonometric series. The design of a propeller with the aid of this method is given and an analysis is made of the effect of the fuselage and of the viscosity coefficient mu on the character of the solution of the variational problem.

  15. Ion-thruster propellant utilization

    NASA Technical Reports Server (NTRS)

    Kaufman, H. R.

    1971-01-01

    The evaluation and understanding of maximum propellant utilization, with mercury used as the propellant are presented. The primary-electron region in the ion chamber of a bombardment thruster is analyzed at maximum utilization. The results of this analysis, as well as experimental data from a range of ion-chamber configurations, show a nearly constant loss rate for unionized propellant at maximum utilization over a wide range of total propellant flow rate. The discharge loss level of 1000 eV/ion was used as a definition of maximum utilization, but the exact level of this definition has no effect on the qualitative results and little effect on the quantitative results. There are obvious design applications for the results of this investigation, but the results are particularly significant whenever efficient throttled operation is required.

  16. Computational prediction of propellant reorientation

    NASA Technical Reports Server (NTRS)

    Hochstein, John I.

    1987-01-01

    Viewgraphs from a presentation on computational prediction of propellant reorientation are given. Information is given on code verification, test conditions, predictions for a one-quarter scale cryogenic tank, pulsed settling, and preliminary results.

  17. Propeller speed and phase sensor

    NASA Technical Reports Server (NTRS)

    Collopy, Paul D. (Inventor); Bennett, George W. (Inventor)

    1992-01-01

    A speed and phase sensor counterrotates aircraft propellers. A toothed wheel is attached to each propeller, and the teeth trigger a sensor as they pass, producing a sequence of signals. From the sequence of signals, rotational speed of each propeller is computer based on time intervals between successive signals. The speed can be computed several times during one revolution, thus giving speed information which is highly up-to-date. Given that spacing between teeth may not be uniform, the signals produced may be nonuniform in time. Error coefficients are derived to correct for nonuniformities in the resulting signals, thus allowing accurate speed to be computed despite the spacing nonuniformities. Phase can be viewed as the relative rotational position of one propeller with respect to the other, but measured at a fixed time. Phase is computed from the signals.

  18. Propeller aircraft interior noise model

    NASA Technical Reports Server (NTRS)

    Pope, L. D.; Wilby, E. G.; Wilby, J. F.

    1984-01-01

    An analytical model was developed to predict the interior noise of propeller-driven aircraft. The fuselage model is that of a cylinder with a structurally-integral floor. The cabin sidewall is stiffened by stringers and ring frames, and the floor by longitudinal beams. The cabin interior is covered with a sidewall treatments consisting of layers of porous material and an impervious trim septum. Representation of the propeller pressure field is utilized as input data in the form of the propeller noise signature at a series of locations on a grid over the fuselage structure. Results obtained from the analytical model are compared with test data measured by NASA in a scale model cylindrical fuselage excited by a model propeller.

  19. Lead-Free Propellant for Propellant Actuated Devices

    NASA Technical Reports Server (NTRS)

    Goodwin, John L.

    2000-01-01

    Naval Surface Warfare Center, Indian Head Division's CAD/PAD Department has been working to remove toxic compounds from our products for about a decade. In 1992, we embarked on an effort to develop a lead-free double base propellant to replace that of a foreign sole source. At the time there were availability concerns. In 1995, the department developed a strategic proposal to include a wider range of products. Efforts included such efforts as removing lead sheathing from linear explosives and replacing lead azide and lead styphnate compounds. This paper will discuss efforts specifically related to developing non-leaded double base propellant for use in various Propellant Actuated Devices (PADs) for aircrew escape systems. The propellants can replace their leaded counterparts, mitigating lead handling, processing, or toxic exposure to the environment and personnel. This work eliminates the use of leaded compounds, replacing them with a more environmentally benign metal-organic salt. Historically double-base propellants have held an advantage over other families of energetic materials through their relative insensitivity of the burning rate to changes in temperature and pressure. This desirable ballistic effect has been obtained with the use of a lead-organic salt alone or in a physical mixture with a copper-organic salt, or more recently with a lead-copper complex. These ballistic modifiers are typically added to the double-base 'paste' prior to gelatinization on heated calendars or one type or another. The effect of constant burning rate over a pressure range is called a 'plateau' while an even more beneficial effect of decreasing burning rate with increasing pressure is termed a 'mesa.' The latter effect results in very low temperature sensitivity of the propellant burning rate. Propellants with such effects are ideal tactical rocket motor propellants. The use of lead compounds poses a concern for the environment and personnel safety due to the metal's toxic

  20. 75 FR 67613 - Airworthiness Directives; McCauley Propeller Systems Five-Blade Propeller Assemblies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-03

    ... could cause failure of the propeller hub, blade separation, and loss of control of the airplane. DATES... propeller hubs, which could cause failure of the propeller hub, blade separation, and loss of control of...

  1. Aircraft Propeller Hub Repair

    SciTech Connect

    Muth, Thomas R.; Peter, William H.

    2015-02-13

    The team performed a literature review, conducted residual stress measurements, performed failure analysis, and demonstrated a solid state additive manufacturing repair technique on samples removed from a scrapped propeller hub. The team evaluated multiple options for hub repair that included existing metal buildup technologies that the Federal Aviation Administration (FAA) has already embraced, such as cold spray, high velocity oxy-fuel deposition (HVOF), and plasma spray. In addition the team helped Piedmont Propulsion Systems, LLC (PPS) evaluate three potential solutions that could be deployed at different stages in the life cycle of aluminum alloy hubs, in addition to the conventional spray coating method for repair. For new hubs, a machining practice to prevent fretting with the steel drive shaft was recommended. For hubs that were refurbished with some material remaining above the minimal material condition (MMC), a silver interface applied by an electromagnetic pulse additive manufacturing method was recommended. For hubs that were at or below the MMC, a solid state additive manufacturing technique using ultrasonic welding (UW) of thin layers of 7075 aluminum to the hub interface was recommended. A cladding demonstration using the UW technique achieved mechanical bonding of the layers showing promise as a viable repair method.

  2. Satellite Propellant Pump Research

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.; Veres, Joseph P.; Hah, Chunill; Nerone, Anthony L.; Cunningham, Cameron C.; Kraft, Thomas G.; Tavernelli, Paul F.; Fraser, Bryan

    2005-01-01

    NASA Glenn initiated a satellite propellant pump technology demonstration program. The goal was to demonstrate the technologies for a 60 percent efficient pump at 1 gpm flow rate and 500 psia pressure rise. The pump design and analysis used the in-house developed computer codes named PUMPA and HPUMP3D. The requirements lead to a 4-stage impeller type pump design with a tip diameter of 0.54 inches and a rotational speed of 57,000 rpm. Analyses indicated that flow cavitation was not a problem in the design. Since the flow was incompressible, the stages were identical. Only the 2-stage pump was designed, fabricated, assembled, and tested for demonstration. Water was selected as the surrogate fluid for hydrazine in this program. Complete mechanical design including stress and dynamic analyses were conducted. The pump was driven by an electric motor directly coupled to the impellers. Runs up to 57,000 rpm were conducted, where a pressure rise of 200 psia at a flow rate of 0.8 gpm was measured to validate the design effort.

  3. Experimental Performance of a Novel Trochoidal Propeller

    NASA Astrophysics Data System (ADS)

    Roesler, Bernard; Epps, Brenden

    2015-11-01

    In the quest for energy efficiency in marine transportation, a promising marine propulsor concept is the trochoidal propeller. We have designed and tested a novel trochoidal propeller using a sinusoidal blade pitch function. The main results presented are measurements of thrust and torque, as well as the calculated efficiency, for a range of advance coefficients. The experimental data show narrow 95% confidence bounds, demonstrating high accuracy and repeatability in the experimental methods. We compare our sinusoidal-pitch trochoidal propeller with prior cross-flow propellers, as well as a representative screw propeller. While the efficiency of our propeller exceeds that of the cycloidal-pitch trochoidal propeller, it is slightly lower than the efficiencies of the other propellers considered. We also present a theoretical model that can be used to further explore and optimize such trochoidal propellers, leading to new avenues for improvements in marine propulsion systems.

  4. Diffusion-Weighted Imaging in 3.0 Tesla Breast MRI: Diagnostic Performance and Tumor Characterization Using Small Subregions vs. Whole Tumor Regions of Interest

    PubMed Central

    Arponent, Otso; Sudah, Mazen; Masarwah, Amro; Taina, Mikko; Rautiainen, Suvi; Könönen, Mervi; Sironen, Reijo; Kosma, Veli-Matti; Sutela, Anna; Hakumäki, Juhana; Vanninen, Ritva

    2015-01-01

    small ROI could be advocated in diffusion-weighted imaging. PMID:26458106

  5. The Impact of Diffusion-Weighted MRI on the Definition of Gross Tumor Volume in Radiotherapy of Non-Small-Cell Lung Cancer

    PubMed Central

    Fleckenstein, Jochen; Jelden, Michael; Kremp, Stephanie; Jagoda, Philippe; Stroeder, Jonas; Khreish, Fadi; Ezziddin, Samer; Buecker, Arno; Rübe, Christian; Schneider, Guenther K.

    2016-01-01

    Objective The study was designed to evaluate diffusion-weighted magnetic resonance imaging (DWI) vs. PET-CT of the thorax in the determination of gross tumor volume (GTV) in radiotherapy planning of non-small-cell lung cancer (NSCLC). Materials and Methods Eligible patients with NSCLC who were supposed to receive definitive radio(chemo)therapy were prospectively recruited. For MRI, a respiratory gated T2-weighted sequence in axial orientation and non-gated DWI (b = 0, 800, 1,400 and apparent diffusion coefficient map [ADC]) were acquired on a 1.5 Tesla scanner. Primary tumors were delineated on FDG-PET/CT (stGTV) and DWI images (dwGTV). The definition of stGTV was based on the CT and visually adapted to the FDG-PET component if indicated (e.g., in atelectasis). For DWI, dwGTV was visually determined and adjusted for anatomical plausibility on T2w sequences. Beside a statistical comparison of stGTV and dwGTB, spatial agreement was determined with the “Hausdorff-Distance” (HD) and the “Dice Similarity Coefficient” (DSC). Results Fifteen patients (one patient with two synchronous NSCLC) were evaluated. For 16 primary tumors with UICC stages I (n = 4), II (n = 3), IIIA (n = 2) and IIIB (n = 7) mean values for dwGTV were significantly larger than those of stGTV (76.6 ± 84.5 ml vs. 66.6 ± 75.2 ml, p<0.01). The correlation of stGTV and dwGTV was highly significant (r = 0.995, p<0.001). Yet, some considerable volume deviations between these two methods were observed (median 27.5%, range 0.4–52.1%). An acceptable agreement between dwGTV and stGTV regarding the spatial extent of primary tumors was found (average HD: 2.25 ± 0.7 mm; DC 0.68 ± 0.09). Conclusion The overall level of agreement between PET-CT and MRI based GTV definition is acceptable. Tumor volumes may differ considerably in single cases. DWI-derived GTVs are significantly, yet modestly, larger than their PET-CT based counterparts. Prospective studies to assess the safety and efficacy of DWI

  6. Value of Diffusion-Weighted Magnetic Resonance Imaging for Prediction and Early Assessment of Response to Neoadjuvant Radiochemotherapy in Rectal Cancer: Preliminary Results

    SciTech Connect

    Lambrecht, Maarten; Vandecaveye, Vincent; De Keyzer, Frederik; Roels, Sarah; Penninckx, Freddy; Van Cutsem, Eric; Filip, Claus; Haustermans, Karin

    2012-02-01

    Purpose: To evaluate diffusion-weighted magnetic resonance imaging (DWI) for response prediction before and response assessment during and early after preoperative radiochemotherapy (RCT) for locally advanced rectal cancer (LARC). Methods and Materials: Twenty patients receiving RCT for LARC underwent MRI including DWI before RCT, after 10-15 fractions and 1 to 2 weeks before surgery. Tumor volume and apparent diffusion coefficient (ADC; b-values: 0-1000 s/mm{sup 2}) were determined at all time points. Pretreatment tumor ADC and volume, tumor ADC change ( Increment ADC), and volume change ( Increment V) between pretreatment and follow-up examinations were compared with histopathologic findings after total mesorectal excision (pathologic complete response [pCR] vs. no pCR, ypT0-2 vs. ypT3-4, T-downstaging or not). The discriminatory capability of pretreatment tumor ADC and volume, Increment ADC, and Increment V for the detection of pCR was compared with receiver operating characteristics analysis. Results: Pretreatment ADC was significantly lower in patients with pCR compared with patients without (in mm{sup 2}/s: 0.94 {+-} 0.12 Multiplication-Sign 10{sup -3} vs. 1.19 {+-} 0.22 Multiplication-Sign 10{sup -3}, p = 0.003), yielding a sensitivity of 100% and specificity of 86% for detection of pCR. The volume reduction during and after RCT was significantly higher in patients with pCR compared with patients without (in %: {Delta}V{sub during}: -62 {+-} 16 vs. -33 {+-} 16, respectively, p = 0.015; and {Delta}V{sub post}: -86 {+-} 12 vs. -60 {+-} 21, p = 0.012), yielding a sensitivity of 83% and specificity of 71% for the {Delta}V{sub during} and, respectively, 83% and 86% for the {Delta}V{sub post}. The Increment ADC during ({Delta}ADC{sub during}) and after RCT ({Delta}ADC{sub post}) showed a significantly higher value in patients with pCR compared with patients without (in %: {Delta}ADC{sub during}: 72 {+-} 14 vs. 16 {+-} 12, p = 0.0006; and {Delta}ADC{sub post}: 88

  7. Predictive values of diffusion-weighted imaging and perfusion-weighted imaging in evaluating the efficacy of transcatheter arterial chemoembolization for hepatocellular carcinoma

    PubMed Central

    Lin, Min; Tian, Man-Man; Zhang, Wei-Ping; Xu, Li; Jin, Ping

    2016-01-01

    This study explored the predictive values of diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) in evaluating the efficacy of transcatheter arterial chemoembolization (TACE) for patients with hepatocellular carcinoma (HCC). A total of 118 HCC patients treated with TACE were selected from April 2013 to November 2015. T1-weighted imaging (T1WI)/T2-weighted imaging (T2WI), DWI, and PWI were performed on all patients before and after TACE. Efficacy was evaluated according to modified Response Evaluation Criteria in Solid Tumors 1.1. Receiver operating characteristic curve was used to evaluate the diagnostic power of quantitative DWI and PWI parameters in evaluating the efficacy of TACE for HCC patients. Among the 118 HCC patients, there were 17 cases (14.4%) with complete response, 50 cases (42.4%) with partial response, 28 cases (23.7%) with stable disease, and 23 cases (19.5%) with progressive disease. There were 67 patients in the effective group (complete response + partial response) and 51 patients in the ineffective group (stable disease + progressive disease). Before TACE, there were significant differences in maximum tumor diameter (MTD), apparent diffusion coefficient (ADC), slow ADC (Dslow), fast ADC (Dfast), transfer constant of vessel at the maximum level (Ktrans), and rate constant of backflux (Kep) between the effective and ineffective groups (all P<0.05). After TACE, the effective group exhibited lower MTD, Dfast, and Kep and higher ADC and Dslow than the ineffective group (all P<0.05). Tumor regression rate negatively correlated with MTD, Ktrans, Kep, and Dfast but positively correlated with ADC and Dslow. Receiver operating characteristic curve analysis suggested that the area under the curve of ADC, Dslow, Dfast, Ktrans, and Kep were 0.869, 0.833, 0.812, 0.802, and 0.809, respectively. In conclusion, these results suggest that quantitative DWI and PWI parameters might be useful in evaluating the efficacy of TACE in the treatment of

  8. IVIM diffusion-weighted imaging of the liver at 3.0 T: Comparison with 1.5 T

    PubMed Central

    Cui, Yong; Dyvorne, Hadrien; Besa, Cecilia; Cooper, Nancy; Taouli, Bachir

    2015-01-01

    Purpose To compare intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) of the liver between 1.5 T and 3.0 T in terms of parameter quantification and inter-platform reproducibility. Materials and methods In this IRB approved prospective study, 19 subjects (17 patients with chronic liver disease and 2 healthy volunteers) underwent two repeat scans at 1.5 T and 3.0 T. Each scan included IVIM DWI using 16 b values from 0 to 800 s/mm2. A single observer measured IVIM parameters for each platform and estimated signal to noise ratio (eSNR) at b0, 200, 400 and 800 s/mm2. Wilcoxon paired tests were used to compare liver eSNR and IVIM parameters. Inter-platform reproducibility was assessed by calculating within-subject coefficient of variation (CV) and Bland–Altman limits of agreement. An ice water phantom was used to test ADC variability between the two MRI systems. Results The mean invitro difference in ADC between the two platforms was 6.8%. eSNR was significantly higher at 3.0T for all selected b values (p = 0.006–0.020), except for b0 (p = 0.239). Liver IVIM parameters were significantly different between 1.5 T and 3.0 T (p = 0.005–0.044), except for ADC (p = 0.748). The inter-platform reproducibility of true diffusion coefficient (D) and ADC were good, with mean CV of 10.9% and 11.1%, respectively. Perfusion fraction (PF) and pseudodiffusion coefficient (D*) showed more limited inter-platform reproducibility (mean CV of 22.6% for PF and 46.9% for D*). Conclusion Liver D and ADC values showed good reproducibility between 1.5 T and 3.0 T platforms; while there was more variability in PF, and large variability in D* parameters between the two platforms. These findings may have implications for drug trials assessing the role of IVIM DWI in tumor response and liver fibrosis. PMID:26393236

  9. Extended T2-IVIM model for correction of TE dependence of pseudo-diffusion volume fraction in clinical diffusion-weighted magnetic resonance imaging.

    PubMed

    Jerome, N P; d'Arcy, J A; Feiweier, T; Koh, D-M; Leach, M O; Collins, D J; Orton, M R

    2016-12-21

    The bi-exponential intravoxel-incoherent-motion (IVIM) model for diffusion-weighted MRI (DWI) fails to account for differential T 2 s in the model compartments, resulting in overestimation of pseudodiffusion fraction f. An extended model, T2-IVIM, allows removal of the confounding echo-time (TE) dependence of f, and provides direct compartment T 2 estimates. Two consented healthy volunteer cohorts (n  =  5, 6) underwent DWI comprising multiple TE/b-value combinations (Protocol 1: TE  =  62-102 ms, b  =  0-250 mm(-2)s, 30 combinations. Protocol 2: 8 b-values 0-800 mm(-2)s at TE  =  62 ms, with 3 additional b-values 0-50 mm(-2)s at TE  =  80, 100 ms; scanned twice). Data from liver ROIs were fitted with IVIM at individual TEs, and with the T2-IVIM model using all data. Repeat-measures coefficients of variation were assessed for Protocol 2. Conventional IVIM modelling at individual TEs (Protocol 1) demonstrated apparent f increasing with longer TE: 22.4  ±  7% (TE  =  62 ms) to 30.7  ±  11% (TE  =  102 ms); T2-IVIM model fitting accounted for all data variation. Fitting of Protocol 2 data using T2-IVIM yielded reduced f estimates (IVIM: 27.9  ±  6%, T2-IVIM: 18.3  ±  7%), as well as T 2  =  42.1  ±  7 ms, 77.6  ±  30 ms for true and pseudodiffusion compartments, respectively. A reduced Protocol 2 dataset yielded comparable results in a clinical time frame (11 min). The confounding dependence of IVIM f on TE can be accounted for using additional b/TE images and the extended T2-IVIM model.

  10. WE-G-18C-09: Separating Perfusion and Diffusion Components From Diffusion Weighted MRI of Rectum Tumors Based On Intravoxel Incoherent Motion (IVIM) Analysis

    SciTech Connect

    Tyagi, N; Wengler, K; Mazaheri, Y; Hunt, M; Deasy, J; Gollub, M

    2014-06-15

    Purpose: Pseudodiffusion arises from the microcirculation of blood in the randomly oriented capillary network and contributes to the signal decay acquired using a multi-b value diffusion weighted (DW)-MRI sequence. This effect is more significant at low b-values and should be properly accounted for in apparent diffusion coefficient (ADC) calculations. The purpose of this study was to separate perfusion and diffusion component based on a biexponential and a segmented monoexponential model using IVIM analysis Methods. The signal attenuation is modeled as S(b) = S0[(1−f)exp(−bD) + fexp(−bD*)]. Fitting the biexponetial decay leads to the quantification of D, the true diffusion coefficient, D*, the pseudodiffusion coefficient, and f, the perfusion fraction. A nonlinear least squares fit and two segmented monoexponential models were used to derive the values for D, D*,‘and f. In the segmented approach b = 200 s/mm{sup 2} was used as the cut-off value for calculation of D. DW-MRI's of a rectum cancer patient were acquired before chemotherapy, before radiation therapy (RT), and 4 weeks into RT and were investigated as an example case. Results: Mean ADC for the tumor drawn on the DWI cases was 0.93, 1.0 and 1.13 10{sup −3}×mm{sup 2}/s before chemotherapy, before RT and 4 weeks into RT. The mean (D.10{sup −3} × mm{sup 2}/s, D* 10{sup −3} × mm{sup 2}/s, and f %) based on biexponential fit was (0.67, 18.6, and 27.2%), (0.72, 17.7, and 28.9%) and (0.83,15.1, and 30.7%) at these time points. The mean (D, D* f) based on segmented fit was (0.72, 10.5, and 12.1%), (0.72, 8.2, and 17.4%) and (.82, 8.1, 16.5%) Conclusion: ADC values are typically higher than true diffusion coefficients. For tumors with significant perfusion effect, ADC should be analyzed at higher b-values or separated from the perfusion component. Biexponential fit overestimates the perfusion fraction because of increased sensitivity to noise at low b-values.

  11. Radiologic-Pathologic Analysis of Contrast-enhanced and Diffusion-weighted MR Imaging in Patients with HCC after TACE: Diagnostic Accuracy of 3D Quantitative Image Analysis

    PubMed Central

    Chapiro, Julius; Wood, Laura D.; Lin, MingDe; Duran, Rafael; Cornish, Toby; Lesage, David; Charu, Vivek; Schernthaner, Rüdiger; Wang, Zhijun; Tacher, Vania; Savic, Lynn Jeanette; Kamel, Ihab R.

    2014-01-01

    Purpose To evaluate the diagnostic performance of three-dimensional (3Dthree-dimensional) quantitative enhancement-based and diffusion-weighted volumetric magnetic resonance (MR) imaging assessment of hepatocellular carcinoma (HCChepatocellular carcinoma) lesions in determining the extent of pathologic tumor necrosis after transarterial chemoembolization (TACEtransarterial chemoembolization). Materials and Methods This institutional review board–approved retrospective study included 17 patients with HCChepatocellular carcinoma who underwent TACEtransarterial chemoembolization before surgery. Semiautomatic 3Dthree-dimensional volumetric segmentation of target lesions was performed at the last MR examination before orthotopic liver transplantation or surgical resection. The amount of necrotic tumor tissue on contrast material–enhanced arterial phase MR images and the amount of diffusion-restricted tumor tissue on apparent diffusion coefficient (ADCapparent diffusion coefficient) maps were expressed as a percentage of the total tumor volume. Visual assessment of the extent of tumor necrosis and tumor response according to European Association for the Study of the Liver (EASLEuropean Association for the Study of the Liver) criteria was performed. Pathologic tumor necrosis was quantified by using slide-by-slide segmentation. Correlation analysis was performed to evaluate the predictive values of the radiologic techniques. Results At histopathologic examination, the mean percentage of tumor necrosis was 70% (range, 10%–100%). Both 3Dthree-dimensional quantitative techniques demonstrated a strong correlation with tumor necrosis at pathologic examination (R2 = 0.9657 and R2 = 0.9662 for quantitative EASLEuropean Association for the Study of the Liver and quantitative ADCapparent diffusion coefficient, respectively) and a strong intermethod agreement (R2 = 0.9585). Both methods showed a significantly lower discrepancy with pathologically measured necrosis (residual

  12. TU-C-12A-05: Repeatability Study of Reduced Field-Of-View Diffusion-Weighted MRI On Human Thyroid Gland

    SciTech Connect

    Shukla-Dave, A; Lu, Y; Hatzoglou, V; Stambuk, H; Mazaheri, Y; Banerjee, S; Shankaranarayanan, A; Deasy, J

    2014-06-15

    Purpose: To investigate the repeatability of reduced field-of-view diffusion-weighted imaging (rFOV DWI) in quantifying apparent diffusion coefficients (ADCs) for human thyroid glands in a clinical setting. Methods: Nine healthy human volunteers were enrolled and underwent 3T MRI exams. For each volunteer, 3 longitudinal exams (2 weeks apart) with 2 repetitive sessions within each exam, including rFOV and conventional full field-of-view (fFOV) DWI scans, were performed. In the acquired DWI images, a fixed-size region of interest (ROI; diameter=8mm) was placed on thyroid glands to calculate ADC. ADC was calculated using a monoexponential function with a noise correction scheme. The repeatability of ADC was assessed by using coefficient variation (CV) across sessions or exams, which was defined to be: r = 1-CV, 0 < r < 1, where CV=STD/m, STD is the standard deviation of ADC, and m is the average of ADC across sessions or exams. An experienced radiologist assessed and scored rFOV and fFOV DW images based on image characteristics (1, nondiagnostic; 2, poor; 3, satisfactory; 4, good; and 5, excellent).Analysis of variance (ANOVA) was performed to compare ADC values, CV of ADC, repeatability of ADC across sessions and exams, and radiologic scores between rFOV and fFOV DWI techniques. Results: There was no significant difference in ADC values across sessions and exams either in rFOV or fFOV DWI. The average CVs of both rFOV and fFOV DWI were less than 13%. The repeatability of ADC measurement between rFOV and fFOV DWI was not significantly different. The overall image quality was significantly higher with rFOV DWI than with fFOV DWI. Conclusion: This study suggested that ADCs from both rFOV and fFOV DWI were repeatable, but rFOV DWI had superior imaging quality for human thyroid glands in a clinical setting.

  13. Extended T2-IVIM model for correction of TE dependence of pseudo-diffusion volume fraction in clinical diffusion-weighted magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Jerome, N. P.; d'Arcy, J. A.; Feiweier, T.; Koh, D.-M.; Leach, M. O.; Collins, D. J.; Orton, M. R.

    2016-12-01

    The bi-exponential intravoxel-incoherent-motion (IVIM) model for diffusion-weighted MRI (DWI) fails to account for differential T 2 s in the model compartments, resulting in overestimation of pseudodiffusion fraction f. An extended model, T2-IVIM, allows removal of the confounding echo-time (TE) dependence of f, and provides direct compartment T 2 estimates. Two consented healthy volunteer cohorts (n  =  5, 6) underwent DWI comprising multiple TE/b-value combinations (Protocol 1: TE  =  62-102 ms, b  =  0-250 mm-2s, 30 combinations. Protocol 2: 8 b-values 0-800 mm-2s at TE  =  62 ms, with 3 additional b-values 0-50 mm-2s at TE  =  80, 100 ms scanned twice). Data from liver ROIs were fitted with IVIM at individual TEs, and with the T2-IVIM model using all data. Repeat-measures coefficients of variation were assessed for Protocol 2. Conventional IVIM modelling at individual TEs (Protocol 1) demonstrated apparent f increasing with longer TE: 22.4  ±  7% (TE  =  62 ms) to 30.7  ±  11% (TE  =  102 ms) T2-IVIM model fitting accounted for all data variation. Fitting of Protocol 2 data using T2-IVIM yielded reduced f estimates (IVIM: 27.9  ±  6%, T2-IVIM: 18.3  ±  7%), as well as T 2  =  42.1  ±  7 ms, 77.6  ±  30 ms for true and pseudodiffusion compartments, respectively. A reduced Protocol 2 dataset yielded comparable results in a clinical time frame (11 min). The confounding dependence of IVIM f on TE can be accounted for using additional b/TE images and the extended T2-IVIM model.

  14. Magnetic resonance imaging, magnetisation transfer imaging, and diffusion weighted imaging correlates of optic nerve, brain, and cervical cord damage in Leber's hereditary optic neuropathy

    PubMed Central

    Inglese, M; Rovaris, M; Bianchi, S; Mantia, L; Mancardi, G; Ghezzi, A; Montagna, P; Salvi, F; Filippi, M

    2001-01-01

    OBJECTIVES—Leber's hereditary optic neuropathy (LHON) is a mitochondrial disease leading to bilateral loss of central vision and severe optic nerve atrophy. A subtype of LHON presents additional clinical and MRI aspects indistinguishable from those of multiple sclerosis (MS) (LHON-MS). In patients with LHON or LHON-MS, an assessment was made of (a) the severity of optic nerve damage, using MRI and magnetisation transfer imaging (MTI), and (b) the presence and extent of macroscopic and microscopic pathology in the brain and cervical cord, using MRI and MT ratio (MTR) and mean diffusivity (&Dmacr;) histogram analysis.
METHODS—Ten patients with LHON, four with LHON-MS, and 20 age and sex matched healthy controls were studied. For the optic nerve and the brain, dual-echo turbo spin echo (TSE), T1 weighted spin echo, and MT images were obtained. For the brain, fast fluid attenuated inversion recovery (fast FLAIR) and diffusion weighted images were also obtained. For the cervical cord, fast short tau inversion recovery (STIR) and MT images were obtained. The volume and the average MTR value of both the optic nerves were measured. MTR and &Dmacr; histograms of the normal appearing brain tissue (NABT) and MTR histograms of the whole cervical cord tissue were created.
RESULTS—The mean values of optic nerve volumes and MTR were significantly lower in patients with LHON than in healthy controls. Mean NABT-MTR histogram peak height was significantly lower in patients with LHON than in controls, whereas no significant difference was found for any of the cervical cord MTR histogram derived measures. Average diffusivity (&Dmacr;) was higher in patients with LHON than in controls. Optic nerve volume and MTR value and mean NABT-MTR were lower in patients with LHON-MS than in those with LHON.
CONCLUSIONS—The severity of optic nerve pathology in LHON is measurable in vivo using MRI and MTI. MTR and &Dmacr; histogram analysis suggests that microscopic brain damage occurs

  15. Tubo-Ovarian Abscess (with/without Pseudotumor Area) Mimicking Ovarian Malignancy: Role of Diffusion-Weighted MR Imaging with Apparent Diffusion Coefficient Values

    PubMed Central

    Wang, Tingting; Li, Wenhua; Wu, Xiangru; Yin, Bing; Chu, Caiting; Ding, Ming; Cui, Yanfen

    2016-01-01

    Objective To assess the added value of diffusion-weighted magnetic resonance imaging (DWI) with apparent diffusion coefficient (ADC) values compared to MRI, for characterizing the tubo-ovarian abscesses (TOA) mimicking ovarian malignancy. Materials and Methods Patients with TOA (or ovarian abscess alone; n = 34) or ovarian malignancy (n = 35) who underwent DWI and MRI were retrospectively reviewed. The signal intensity of cystic and solid component of TOAs and ovarian malignant tumors on DWI and the corresponding ADC values were evaluated, as well as clinical characteristics, morphological features, MRI findings were comparatively analyzed. Receiver operating characteristic (ROC) curve analysis based on logistic regression was applied to identify different imaging characteristics between the two patient groups and assess the predictive value of combination diagnosis with area under the curve (AUC) analysis. Results The mean ADC value of the cystic component in TOA was significantly lower than in malignant tumors (1.04 ± 0 .41 × 10−3 mm2/s vs. 2.42 ± 0.38 × 10−3 mm2/s; p < 0.001). The mean ADC value of the enhanced solid component in 26 TOAs was 1.43 ± 0.16×10−3mm2/s, and 46.2% (12 TOAs; pseudotumor areas) showed significantly higher signal intensity on DW-MRI than in ovarian malignancy (mean ADC value 1.44 ± 0.20×10−3 mm2/s vs.1.18 ± 0.36 × 10−3 mm2/s; p = 0.043). The combination diagnosis of ADC value and dilated tubal structure achieved the best AUC of 0.996. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of MRI vs. DWI with ADC values for predicting TOA were 47.1%, 91.4%, 84.2%, 64%, and 69.6% vs. 100%, 97.1%, 97.1%, 100%, and 98.6%, respectively. Conclusions DW-MRI is superior to MRI in the assessment of TOA mimicking ovarian malignancy, and the ADC values aid in discriminating the pseudotumor area of TOA from the solid portion of ovarian malignancy. PMID:26894926

  16. Self-propelled vehicle

    SciTech Connect

    Morrison, R.D.

    1986-03-04

    A self-propelled vehicle is described which includes a body and a set of four internal-force generating devices, each device having a central axis about which internal portions thereof rotate, the four devices being configured as two opposed pairs, the two devices of one pair having parallel axes, but turning in opposite directions, the two devices of the other pair also having parallel axes but turning in opposite directions the axes of the one pair being at right angles to the axes of the other pair. Each device consists of: stationary frame means, a stationary sun gear on the frame means, the sun gear being coaxial with the central axis of its respective device, a rotor pivoted about the axis of the sun gear, three crankshafts carried by the rotor at substantially 120/sup 0/ intervals, each having an eccentric portion, for each crankshaft a cylinder in the rotor, a piston mounted for riciprocation in each cylinder, and a connecting rod from the piston to the eccentric portion of the crankshaft, each crankshaft being fixed to rotate with a respective planetary gear, all planetary gears meshing with the sun gear and having the same pitch diameter as the sun gear, whereby any point on the pitch circle of a planetary gear describes a cardioid as the planetary gear rotates around the sun gear once, the crankshaft eccentricity being substantially 1/3 of the pitch radius of a planetary gear, fuel metering means for providing a combustible mixture for the cylinder, ignition means to ignite the combustible mixture in each cylinder, and valve means for admitting the combustible mixture to, and exhausting combustion gases from, each cylinder.

  17. Assay of potentially contaminated propellant

    SciTech Connect

    Koster, J.E.; Williams, H.E. III; Scott, W.S.

    1995-02-01

    One of the decontamination and decommissioning projects within DOD is demilitarization of an aging stockpile of munitions. A large portion of the stockpile contains depleted uranium (DU) as an armor piercing core and so these munitions must be assayed for the presence of uranium in other components. The assay method must be fast and preferably easy to implement. Presence of DU is indicated by its alpha decay. The alpha particles in turn produce ions in the ambient air. If a significant fraction of these ions can escape the quantity of propellant, the ions can be detected instead of the alpha particles. As a test of the feasibility of detecting alpha emissions from DU somewhere within a cartridge of propellant, the transmission of ions through layers of real propellant was measured. The propellant is in the form of graphite-coated cylindrical pellets. A 105nun cartridge was modified for use as a pellet chamber. A check source served as an ion source. The ion detector consisted of a grid held at 300V coupled to an ammeter. Results confirm that this is a promising technique for testing the propellant for the presence of DU quickly yet with sensitivity.

  18. Marine propellers: the latest topics.

    PubMed

    Kubo, H

    1996-02-01

    The impeller of the axial flow blood pump in an artificial heart is essentially based on the same principle as a marine propeller. Impellers designed for artificial hearts and marine propellers have a number of points in common. Decreased cavitation and relieved fluctuation load are only representative of them. As for a distinct concept of pressure distribution, the inverse method could be very useful. Skew may led to a more mild and natural character in the blood. Highly skewed blades and super elastic blades have the potential to decrease the burden on the entire circulatory system. This paper will address the main points and latest issues in propeller design concluding with a discussion of the implications of these issues for blood pump impellers.

  19. Wave energy propelling marine ship

    SciTech Connect

    Kitabayashi, S.

    1982-06-29

    A wave energy propelling marine ship comprises a cylindrical ship body having a hollow space therein for transporting fluid material therewithin, a ship body disposed in or on the sea; a propeller attached to the ship body for the purpose of propelling the marine ship for sailing; a rudder for controlling the moving direction of the marine ship; at least one rotary device which includes a plurality of compartments which are each partitioned into a plurality of water chambers by a plurality of radial plates, and a plurality of water charge and/or discharge ports, wherein wave energy is converted into mechanical energy; and device for adjusting buoyancy of the marine ship so that the rotary device is positioned advantageously on the sea surface.

  20. Combustion chemistry of solid propellants

    NASA Technical Reports Server (NTRS)

    Baer, A. D.; Ryan, N. W.

    1974-01-01

    Several studies are described of the chemistry of solid propellant combustion which employed a fast-scanning optical spectrometer. Expanded abstracts are presented for four of the studies which were previously reported. One study of the ignition of composite propellants yielded data which suggested early ammonium perchlorate decomposition and reaction. The results of a study of the spatial distribution of molecular species in flames from uncatalyzed and copper or lead catalyzed double-based propellants support previously published conclusions concerning the site of action of these metal catalysts. A study of the ammonium-perchlorate-polymeric-fuel-binder reaction in thin films, made by use of infrared absorption spectrometry, yielded a characterization of a rapid condensed-phase reaction which is likely important during the ignition transient and the burning process.

  1. Suppressants for lowering propellant binder burning rate

    NASA Technical Reports Server (NTRS)

    Thompson, W. W.

    1972-01-01

    Addition of boron compound to lower burning rate of solid propellant binder is reported. Chemical reactions involved in propellant binder modification are described. Advantages of method for lowering burning rate are analyzed.

  2. Characteristics of Five Propellers in Flight

    NASA Technical Reports Server (NTRS)

    Crowley, J W , Jr; Mixson, R E

    1928-01-01

    This investigation was made for the purpose of determining the characteristics of five full-scale propellers in flight. The equipment consisted of five propellers in conjunction with a VE-7 airplane and a Wright E-2 engine. The propellers were of the same diameter and aspect ratio. Four of them differed uniformly in thickness and pitch and the fifth propeller was identical with one of the other four with exception of a change of the airfoil section. The propeller efficiencies measured in flight are found to be consistently lower than those obtained in model tests. It is probable that this is mainly a result of the higher tip speeds used in the full-scale tests. The results show also that because of differences in propeller deflections it is difficult to obtain accurate comparisons of propeller characteristics. From this it is concluded that for accurate comparisons it is necessary to know the propeller pitch angles under actual operating conditions. (author)

  3. Orbiting propellant depot safety. Volume 3: Appendices

    NASA Technical Reports Server (NTRS)

    1971-01-01

    Appendices to support the findings of the Orbiting Propellant Depot Safety study are presented. The subjects discussed are ullage control subsystems, evaluation of methods, propellant transfer, and baseline subsystem selection.

  4. Modeling of impulsive propellant reorientation

    NASA Technical Reports Server (NTRS)

    Hochstein, John I.; Patag, Alfredo E.; Chato, David J.

    1988-01-01

    The impulsive propellant reorientation process is modeled using the (Energy Calculations for Liquid Propellants in a Space Environment (ECLIPSE) code. A brief description of the process and the computational model is presented. Code validation is documented via comparison to experimentally derived data for small scale tanks. Predictions of reorientation performance are presented for two tanks designed for use in flight experiments and for a proposed full scale OTV tank. A new dimensionless parameter is developed to correlate reorientation performance in geometrically similar tanks. Its success is demonstrated.

  5. Intra-procedural imaging of the left atrium and pulmonary veins with rotational angiography: a comparison of anatomy obtained by pre-procedural cardiac computed tomography and trans-thoracic echocardiography.

    PubMed

    Park, Yae Min; Kim, Mi Na; Choi, Jong-Il; Lim, Hong Euy; Park, Seong-Mi; Park, Sang Weon; Shim, Wan Joo; Kim, Young-Hoon

    2013-10-01

    This study evaluated the feasibility and accuracy of three-dimensional rotational angiography (3DRA) to determine the anatomy of the left atrium (LA) and pulmonary veins (PVs) compared with cardiac computed tomography (CCT) and trans-thoracic echocardiography (TTE). One hundred two patients (56.1 ± 9.9 years, 86 males) with an indication for atrial fibrillation ablation were prospectively enrolled. Intra-procedural 3DRA was performed with power injected contrast medium (20 cc/s for 4 s, 240°) in the LA. 3DRA images of the LA and PVs were assessed qualitatively and then compared quantitatively. LA volume measured by 3DRA, CCT and TTE were compared. The majority of 3DRA acquisitions were optimal in delineating the right-side LA-PV (95 % for right superior PV and 96 % for right inferior PV) and left inferior PV anatomy (91 %), whereas it was optimal in only 63 % of left superior PV and 73 % of the LA appendage. The circumferences of PV ostia identified by 3DRA and CCT were correlated in four PVs (r = 0.57 for right superior PV, r = 0.67 for right inferior PV, r = 0.60 for left superior PV, and r = 0.52 for left inferior PV, p < 0.001). The mean LA volume measured by 3DRA (120 ± 32 mL) was greater than that found by CCT (109 ± 35 mL) or TTE (64 ± 23 mL), but the 3DRA LA volume measurements correlated well with those of CCT (r = 0.83, p < 0.001) and TTE (r = 0.69, p < 0.001). Intra-procedural 3DRA provided anatomical accuracy of LA and PVs comparable to those of CCT. However, optimal delineation of the left superior PV and LA appendage was limited. The LA volume determined by 3DRA was well correlated with those of CCT and TTE, despite different absolute values of each.

  6. Note on the Effects of First-Order Aerodynamic Loads on Propeller Shaft Loads with Emphasis on Counterrotating Propellers

    NASA Technical Reports Server (NTRS)

    Rogallo, Vernon L.; McCloud, John L., III; Yaggy, Paul F.

    1954-01-01

    An investigation of the 1XP excitation of inclined single-rotation propellers has indicated a new concept for determining propeller shaft forces and moments of an inclined propeller. This report presents preliminary results, in particular to the counterrotating propeller.

  7. 14 CFR 35.23 - Propeller control system.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... hazardous propeller effect. (3) The loss of normal propeller pitch control does not cause a hazardous... shared across propellers does not cause a hazardous propeller effect. (c) Electronic propeller control... effect. (2) Failures or malfunctions directly affecting the propeller control system in a...

  8. SU-F-303-13: Initial Evaluation of Four Dimensional Diffusion- Weighted MRI (4D-DWI) and Its Effect On Apparent Diffusion Coefficient (ADC) Measurement

    SciTech Connect

    Liu, Y; Yin, F; Czito, B; Bashir, M; Palta, M; Cai, J; Zhong, X; Dale, B

    2015-06-15

    Purpose: Diffusion-weighted imaging(DWI) has been shown to have superior tumor-to-tissue contrast for cancer detection.This study aims at developing and evaluating a four dimensional DWI(4D-DWI) technique using retrospective sorting method for imaging respiratory motion for radiotherapy planning,and evaluate its effect on Apparent Diffusion Coefficient(ADC) measurement. Materials/Methods: Image acquisition was performed by repeatedly imaging a volume of interest using a multi-slice single-shot 2D-DWI sequence in the axial planes and cine MRI(served as reference) using FIESTA sequence.Each 2D-DWI image were acquired in xyz-diffusion-directions with a high b-value(b=500s/mm2).The respiratory motion was simultaneously recorded using bellows.Retrospective sorting was applied in each direction to reconstruct 4D-DWI.The technique was evaluated using a computer simulated 4D-digital human phantom(XCAT),a motion phantom and a healthy volunteer under an IRB-approved study.Motion trajectories of regions-of-interests(ROI) were extracted from 4D-DWI and compared with reference.The mean motion trajectory amplitude differences(D) between the two was calculated.To quantitatively analyze the motion artifacts,XCAT were controlled to simulate regular motion and the motions of 10 liver cancer patients.4D-DWI,free-breathing DWI(FB- DWI) were reconstructed.Tumor volume difference(VD) of each phase of 4D-DWI and FB-DWI from the input static tumor were calculated.Furthermore, ADC was measured for each phase of 4D-DWI and FB-DWI data,and mean tumor ADC values(M-ADC) were calculated.Mean M-ADC over all 4D-DWI phases was compared with M-ADC calculated from FB-DWI. Results: 4D-DWI of XCAT,the motion phantom and the healthy volunteer demonstrated the respiratory motion clearly.ROI D values were 1.9mm,1.7mm and 2.0mm,respectively.For motion artifacts analysis,XCAT 4D-DWI images show much less motion artifacts compare to FB-DWI.Mean VD for 4D-WDI and FB-DWI were 8.5±1.4% and 108±15

  9. [Correlation between the mRNA expression of tissue inhibitor of metalloproteinase-1 and apparent diffusion coefficient on diffusion-weighted imaging in rats' liver fibrosis].

    PubMed

    Zhan, Yuefu; Liang, Xianwen; Han, Xiangjun; Chen, Jianqiang; Zhang, Shufang; Tan, Shun; Li, Qun; Wang, Xiong; Liu, Fan

    2017-02-28

    目的:探讨大鼠肝纤维化不同分期肝表观扩散系数(apparent diffusion coefficient,ADC)与基质金属蛋白酶抑制剂-1(tissue inhibitor of metalloproteinase-1,TIMP-1) mRNA表达的相关性。方法:采用猪血清腹腔注射联合高脂饮食建立肝纤维化大鼠模型。给药4周后开始,取实验组大鼠48只和对照组大鼠12只行磁共振弥散加权成像(diffusion weighted imaging,DWI)检查,计算b值=800 s/mm2时的ADC值。DWI检查后快速处死大鼠,行病理检查,采用RT-PCR检测TIMP-1 mRNA表达。成模大鼠按肝纤维化病理分期结果又分为S0期组(n=4)、S1期组(n=11)、S2期组(n=12)、S3期组(n=10)和S4期组(n=9),比较肝纤维化各组ADC值及TIMP-1 mRNA的表达,并分析两者的相关性。结果:对照组、肝纤维化S1~4期组大鼠肝ADC值及TIMP-1 mRNA表达差异有统计学意义(分别F=46.54和53.87,均P<0.05),ADC值除对照组与肝纤维化S1期组、S1期组与S2期组、S2期组与S3期组比较差异无统计学意义(均P>0.05)外,其余各组间比较均有统计学意义(均P<0.05);各组TIMP-1 mRNA除肝纤维化S1期组与S2期组、S3期组与S4期组比较差异无统计学意义(均P>0.05)外,其余各组间差异均有统计学意义(均P<0.05)。秩相关分析显示肝ADC值与TIMP-1 mRNA表达的变化呈负相关(r=–0.76,P<0.01)。结论:随大鼠肝纤维化进程不断加深,ADC值逐渐减低,TIMP-1 mRNA表达逐渐升高,二者呈负相关。.

  10. In Acute Stroke, Can CT Perfusion-Derived Cerebral Blood Volume Maps Substitute for Diffusion-Weighted Imaging in Identifying the Ischemic Core?

    PubMed Central

    Copen, William A.; Morais, Livia T.; Wu, Ona; Schwamm, Lee H.; Schaefer, Pamela W.; González, R. Gilberto; Yoo, Albert J.

    2015-01-01

    Background and Purpose In the treatment of patients with suspected acute ischemic stroke, increasing evidence suggests the importance of measuring the volume of the irreversibly injured “ischemic core.” The gold standard method for doing this in the clinical setting is diffusion-weighted magnetic resonance imaging (DWI), but many authors suggest that maps of regional cerebral blood volume (CBV) derived from computed tomography perfusion imaging (CTP) can substitute for DWI. We sought to determine whether DWI and CTP-derived CBV maps are equivalent in measuring core volume. Methods 58 patients with suspected stroke underwent CTP and DWI within 6 hours of symptom onset. We measured low-CBV lesion volumes using three methods: “objective absolute,” i.e. the volume of tissue with CBV below each of six published absolute thresholds (0.9–2.5 mL/100 g), “objective relative,” whose six thresholds (51%-60%) were fractions of mean contralateral CBV, and “subjective,” in which two radiologists (R1, R2) outlined lesions subjectively. We assessed the sensitivity and specificity of each method, threshold, and radiologist in detecting infarction, and the degree to which each over- or underestimated the DWI core volume. Additionally, in the subset of 32 patients for whom follow-up CT or MRI was available, we measured the proportion of CBV- or DWI-defined core lesions that exceeded the follow-up infarct volume, and the maximum amount by which this occurred. Results DWI was positive in 72% (42/58) of patients. CBV maps’ sensitivity/specificity in identifying DWI-positive patients were 100%/0% for both objective methods with all thresholds, 43%/94% for R1, and 83%/44% for R2. Mean core overestimation was 156–699 mL for objective absolute thresholds, and 127–200 mL for objective relative thresholds. For R1 and R2, respectively, mean±SD subjective overestimation were -11±26 mL and -11±23 mL, but subjective volumes differed from DWI volumes by up to 117 and 124

  11. Equations for Composite-Propellant Burning

    NASA Technical Reports Server (NTRS)

    Strand, L. D.; Cohen, N. S.

    1983-01-01

    Reported study of composite-propellant burning summarizes recent advances in understanding behavior of propellant formulations based on ammonium perchlorate (AOP), binder, and aluminum in various proportions and particle size distributions. Approach presented incorporates adapted version of earlier model for monopropellant AP. Objective is to predict burning-rate characteristics of composite propellants at high pressure.

  12. 14 CFR 25.905 - Propellers.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... for which the propeller is certificated. (c) The propeller blade pitch control system must meet the requirements of §§ 35.21, 35.23, 35.42 and 35.43 of this chapter. (d) Design precautions must be taken to minimize the hazards to the airplane in the event a propeller blade fails or is released by a hub...

  13. 14 CFR 25.905 - Propellers.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... for which the propeller is certificated. (c) The propeller blade pitch control system must meet the requirements of §§ 35.21, 35.23, 35.42 and 35.43 of this chapter. (d) Design precautions must be taken to minimize the hazards to the airplane in the event a propeller blade fails or is released by a hub...

  14. 14 CFR 23.925 - Propeller clearance.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ..., an airplane with an aft mounted propeller must be designed such that the propeller will not contact...) Structural clearance. There must be— (1) At least one inch radial clearance between the blade tips and the... least one-half inch longitudinal clearance between the propeller blades or cuffs and stationary parts...

  15. 14 CFR 25.905 - Propellers.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... for which the propeller is certificated. (c) The propeller blade pitch control system must meet the requirements of §§ 35.21, 35.23, 35.42 and 35.43 of this chapter. (d) Design precautions must be taken to minimize the hazards to the airplane in the event a propeller blade fails or is released by a hub...

  16. 14 CFR 23.925 - Propeller clearance.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ..., an airplane with an aft mounted propeller must be designed such that the propeller will not contact...) Structural clearance. There must be— (1) At least one inch radial clearance between the blade tips and the... least one-half inch longitudinal clearance between the propeller blades or cuffs and stationary parts...

  17. 14 CFR 23.925 - Propeller clearance.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ..., an airplane with an aft mounted propeller must be designed such that the propeller will not contact...) Structural clearance. There must be— (1) At least one inch radial clearance between the blade tips and the... least one-half inch longitudinal clearance between the propeller blades or cuffs and stationary parts...

  18. 14 CFR 25.905 - Propellers.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... for which the propeller is certificated. (c) The propeller blade pitch control system must meet the requirements of §§ 35.21, 35.23, 35.42 and 35.43 of this chapter. (d) Design precautions must be taken to minimize the hazards to the airplane in the event a propeller blade fails or is released by a hub...

  19. 14 CFR 23.925 - Propeller clearance.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ..., an airplane with an aft mounted propeller must be designed such that the propeller will not contact...) Structural clearance. There must be— (1) At least one inch radial clearance between the blade tips and the... least one-half inch longitudinal clearance between the propeller blades or cuffs and stationary parts...

  20. 14 CFR 25.905 - Propellers.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... for which the propeller is certificated. (c) The propeller blade pitch control system must meet the requirements of §§ 35.21, 35.23, 35.42 and 35.43 of this chapter. (d) Design precautions must be taken to minimize the hazards to the airplane in the event a propeller blade fails or is released by a hub...

  1. Explosive laser light initiation of propellants

    DOEpatents

    Piltch, M.S.

    1993-05-18

    A improved initiator for artillery shell using an explosively generated laser light to uniformly initiate the propellent. A small quantity of a high explosive, when detonated, creates a high pressure and temperature, causing the surrounding noble gas to fluoresce. This fluorescence is directed into a lasing material, which lases, and directs laser light into a cavity in the propellant, uniformly initiating the propellant.

  2. Explosive laser light initiation of propellants

    DOEpatents

    Piltch, Martin S.

    1993-01-01

    A improved initiator for artillery shell using an explosively generated laser light to uniformly initiate the propellent. A small quantity of a high explosive, when detonated, creates a high pressure and temperature, causing the surrounding noble gas to fluoresce. This fluorescence is directed into a lasing material, which lases, and directs laser light into a cavity in the propellant, uniformly initiating the propellant.

  3. 21 CFR 189.191 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Chlorofluorocarbon propellants. 189.191 Section... Generally Prohibited From Direct Addition or Use as Human Food § 189.191 Chlorofluorocarbon propellants. The use of chlorofluorocarbons in human food as propellants in self-pressurized containers is...

  4. 21 CFR 189.191 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Chlorofluorocarbon propellants. 189.191 Section... Generally Prohibited From Direct Addition or Use as Human Food § 189.191 Chlorofluorocarbon propellants. The use of chlorofluorocarbons in human food as propellants in self-pressurized containers is...

  5. 21 CFR 300.100 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 5 2012-04-01 2012-04-01 false Chlorofluorocarbon propellants. 300.100 Section 300.100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... Chlorofluorocarbon propellants. The use of chlorofluorocarbons in human drugs as propellants in...

  6. 21 CFR 801.417 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Chlorofluorocarbon propellants. 801.417 Section... (CONTINUED) MEDICAL DEVICES LABELING Special Requirements for Specific Devices § 801.417 Chlorofluorocarbon propellants. The use of chlorofluorocarbon in devices as propellants in self-pressurized containers...

  7. 21 CFR 300.100 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 5 2011-04-01 2011-04-01 false Chlorofluorocarbon propellants. 300.100 Section 300.100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... Chlorofluorocarbon propellants. The use of chlorofluorocarbons in human drugs as propellants in...

  8. 21 CFR 189.191 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Chlorofluorocarbon propellants. 189.191 Section 189... Generally Prohibited From Direct Addition or Use as Human Food § 189.191 Chlorofluorocarbon propellants. The use of chlorofluorocarbons in human food as propellants in self-pressurized containers is...

  9. 21 CFR 801.417 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Chlorofluorocarbon propellants. 801.417 Section... (CONTINUED) MEDICAL DEVICES LABELING Special Requirements for Specific Devices § 801.417 Chlorofluorocarbon propellants. The use of chlorofluorocarbon in devices as propellants in self-pressurized containers...

  10. 21 CFR 700.23 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 7 2011-04-01 2010-04-01 true Chlorofluorocarbon propellants. 700.23 Section 700...) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.23 Chlorofluorocarbon propellants. The use of chlorofluorocarbons in cosmetics as propellants in self-pressurized containers is prohibited...

  11. 21 CFR 700.23 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 7 2013-04-01 2013-04-01 false Chlorofluorocarbon propellants. 700.23 Section 700...) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.23 Chlorofluorocarbon propellants. The use of chlorofluorocarbons in cosmetics as propellants in self-pressurized containers is prohibited...

  12. 21 CFR 700.23 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 7 2010-04-01 2010-04-01 false Chlorofluorocarbon propellants. 700.23 Section 700...) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.23 Chlorofluorocarbon propellants. The use of chlorofluorocarbons in cosmetics as propellants in self-pressurized containers is prohibited...

  13. 21 CFR 300.100 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 5 2013-04-01 2013-04-01 false Chlorofluorocarbon propellants. 300.100 Section 300.100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... Chlorofluorocarbon propellants. The use of chlorofluorocarbons in human drugs as propellants in...

  14. 21 CFR 189.191 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Chlorofluorocarbon propellants. 189.191 Section... Generally Prohibited From Direct Addition or Use as Human Food § 189.191 Chlorofluorocarbon propellants. The use of chlorofluorocarbons in human food as propellants in self-pressurized containers is...

  15. 21 CFR 700.23 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 7 2012-04-01 2012-04-01 false Chlorofluorocarbon propellants. 700.23 Section 700...) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.23 Chlorofluorocarbon propellants. The use of chlorofluorocarbons in cosmetics as propellants in self-pressurized containers is prohibited...

  16. 21 CFR 300.100 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 5 2014-04-01 2014-04-01 false Chlorofluorocarbon propellants. 300.100 Section 300.100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... Chlorofluorocarbon propellants. The use of chlorofluorocarbons in human drugs as propellants in...

  17. 21 CFR 801.417 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Chlorofluorocarbon propellants. 801.417 Section... (CONTINUED) MEDICAL DEVICES LABELING Special Requirements for Specific Devices § 801.417 Chlorofluorocarbon propellants. The use of chlorofluorocarbon in devices as propellants in self-pressurized containers...

  18. 21 CFR 300.100 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 5 2010-04-01 2010-04-01 false Chlorofluorocarbon propellants. 300.100 Section 300.100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... Chlorofluorocarbon propellants. The use of chlorofluorocarbons in human drugs as propellants in...

  19. 21 CFR 700.23 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 7 2014-04-01 2014-04-01 false Chlorofluorocarbon propellants. 700.23 Section 700...) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.23 Chlorofluorocarbon propellants. The use of chlorofluorocarbons in cosmetics as propellants in self-pressurized containers is prohibited...

  20. 21 CFR 801.417 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Chlorofluorocarbon propellants. 801.417 Section... (CONTINUED) MEDICAL DEVICES LABELING Special Requirements for Specific Devices § 801.417 Chlorofluorocarbon propellants. The use of chlorofluorocarbon in devices as propellants in self-pressurized containers...

  1. 21 CFR 801.417 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Chlorofluorocarbon propellants. 801.417 Section... (CONTINUED) MEDICAL DEVICES LABELING Special Requirements for Specific Devices § 801.417 Chlorofluorocarbon propellants. The use of chlorofluorocarbon in devices as propellants in self-pressurized containers...

  2. 14 CFR 35.2 - Propeller configuration.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Propeller configuration. 35.2 Section 35.2 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: PROPELLERS General § 35.2 Propeller configuration. The applicant must provide a list of all...

  3. Micarta Propellers II : Method of Construction

    NASA Technical Reports Server (NTRS)

    Caldwell, F W; Clay, N S

    1924-01-01

    The methods used in manufacturing Micarta propellers differ considerably from those employed with wood propellers on account of the hardness of the materials. The propellers must be formed accurately to size in a mold and afterwards balanced without the customary trimming of the material from the tips. Described here are the pressing and molding processes, filing, boring, balancing, and curing.

  4. Pressure Oscillations in a Liquid Propellant Gun - Possible Dependence on Propellant Burning Rate

    DTIC Science & Technology

    1992-06-01

    associated with a fundamental property of the combustion of the propellants used. The HAN-based propellants, in general, are aqueous, homogeneous mixtures...gun propellants. A number of physical and chemical properties must be considered in selecting propellant components (Klein 1988) and HAN is easily the...ions in HAN strongly influences the physical properties of the propellant mixture and primarily involves the hydrogen of the OH group (Klein and Wong

  5. Liquid propellant rocket combustion instability

    NASA Technical Reports Server (NTRS)

    Harrje, D. T.

    1972-01-01

    The solution of problems of combustion instability for more effective communication between the various workers in this field is considered. The extent of combustion instability problems in liquid propellant rocket engines and recommendations for their solution are discussed. The most significant developments, both theoretical and experimental, are presented, with emphasis on fundamental principles and relationships between alternative approaches.

  6. Analysis of propellant feedline dynamics

    NASA Technical Reports Server (NTRS)

    Astleford, W. J.; Holster, J. L.; Gerlach, C. R.

    1972-01-01

    An analytical model and computer program were developed for studying the disturbances of liquid propellants in engine feedline systems. It was found that the predominant effect of turbulence is to increase the spatial attenuation at low frequencies; at high frequencies the laminar and turbulent frequencies coincide. Recommendations for future work are included.

  7. The Propeller and the Frog

    NASA Astrophysics Data System (ADS)

    Pan, Margaret; Chiang, Eugene

    2010-10-01

    "Propellers" in planetary rings are disturbances in ring material excited by moonlets that open only partial gaps. We describe a new type of co-orbital resonance that can explain the observed non-Keplerian motions of propellers. The resonance is between the moonlet underlying the propeller and co-orbiting ring particles downstream of the moonlet where the gap closes. The moonlet librates within the gap about an equilibrium point established by co-orbiting material and stabilized by the Coriolis force. In the limit of small libration amplitude, the libration period scales linearly with the gap azimuthal width and inversely as the square root of the co-orbital mass. The new resonance recalls but is distinct from conventional horseshoe and tadpole orbits; we call it the "frog" resonance, after the relevant term in equine hoof anatomy. For a ring surface density and gap geometry appropriate for the propeller Blériot in Saturn's A ring, our theory predicts a libration period of ~4 years, similar to the ~3.7 year period over which Blériot's orbital longitude is observed to vary. These librations should be subtracted from the longitude data before any inferences about moonlet migration are made.

  8. SSME propellant path leak detection

    NASA Technical Reports Server (NTRS)

    Crawford, Roger; Shohadaee, Ahmad Ali

    1989-01-01

    The complicated high-pressure cycle of the space shuttle main engine (SSME) propellant path provides many opportunities for external propellant path leaks while the engine is running. This mode of engine failure may be detected and analyzed with sufficient speed to save critical engine test hardware from destruction. The leaks indicate hardware failures which will damage or destroy an engine if undetected; therefore, detection of both cryogenic and hot gas leaks is the objective of this investigation. The primary objective of this phase of the investigation is the experimental validation of techniques for detecting and analyzing propellant path external leaks which have a high probability of occurring on the SSME. The selection of candidate detection methods requires a good analytic model for leak plumes which would develop from external leaks and an understanding of radiation transfer through the leak plume. One advanced propellant path leak detection technique is obtained by using state-of-the-art technology infrared (IR) thermal imaging systems combined with computer, digital image processing, and expert systems for the engine protection. The feasibility of IR leak plume detection is evaluated on subscale simulated laboratory plumes to determine sensitivity, signal to noise, and general suitability for the application.

  9. THE PROPELLER AND THE FROG

    SciTech Connect

    Pan, Margaret; Chiang, Eugene

    2010-10-20

    'Propellers' in planetary rings are disturbances in ring material excited by moonlets that open only partial gaps. We describe a new type of co-orbital resonance that can explain the observed non-Keplerian motions of propellers. The resonance is between the moonlet underlying the propeller and co-orbiting ring particles downstream of the moonlet where the gap closes. The moonlet librates within the gap about an equilibrium point established by co-orbiting material and stabilized by the Coriolis force. In the limit of small libration amplitude, the libration period scales linearly with the gap azimuthal width and inversely as the square root of the co-orbital mass. The new resonance recalls but is distinct from conventional horseshoe and tadpole orbits; we call it the 'frog' resonance, after the relevant term in equine hoof anatomy. For a ring surface density and gap geometry appropriate for the propeller Bleriot in Saturn's A ring, our theory predicts a libration period of {approx}4 years, similar to the {approx}3.7 year period over which Bleriot's orbital longitude is observed to vary. These librations should be subtracted from the longitude data before any inferences about moonlet migration are made.

  10. Liquid Bismuth Propellant Flow Sensor

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Stanojev, B. J.; Korman, V.

    2007-01-01

    Quantifying the propellant mass flow rate in liquid bismuth-fed electric propulsion systems has two challenging facets. First, the flow sensors must be capable of providing a resolvable measurement at propellant mass flow rates on the order of 10 mg/see with and uncertainty of less that 5%. The second challenge has to do with the fact that the materials from which the flow sensors are fabricated must be capable of resisting any of the corrosive effects associated with the high-temperature propellant. The measurement itself is necessary in order to properly assess the performance (thrust efficiency, Isp) of thruster systems in the laboratory environment. The hotspot sensor[I] has been designed to provide the bismuth propellant mass flow rate measurement. In the hotspot sensor, a pulse of thermal energy (derived from a current pulse and associated joule heating) is applied near the inlet of the sensor. The flow is "tagged" with a thermal feature that is convected downstream by the flowing liquid metal. Downstream, a temperature measurement is performed to detect a "ripple" in the local temperature associated with the passing "hotspot" in the propellant. By measuring the time between the upstream generation and downstream detection of the thermal feature, the flow speed can be calculated using a "time of flight" analysis. In addition, the system can be calibrated by measuring the accumulated mass exiting the system as a-function of time and correlating this with the time it takes the hotspot to convect through the sensor. The primary advantage of this technique is that it doesn't depend on an absolute measurement of temperature but, instead, relies on the observation of thermal features. This makes the technique insensitive to other externally generated thermal fluctuations. In this paper, we describe experiments performed using the hotspot flow sensor aimed at quantifying the resolution of the sensor technology. Propellant is expelled onto an electronic scale to

  11. High-Speed Propeller for Aircraft

    NASA Technical Reports Server (NTRS)

    Sagerser, D. A.; Gatzen, B. S.

    1986-01-01

    Engine efficiency increased. Propeller blades required to be quite thin and highly swept to minimize compressibility losses and propeller noise during high-speed cruise. Use of 8 or 10 blades with highpropeller-power loading allows overall propeller diameter to be kept relatively small. Area-ruled spinner and integrated nacelle shape reduce compressibility losses in propeller hub region. Finally, large modern turboshaft engine and gearbox provide power to advanced propeller. Fuel savings of 30 to 50 percent over present systems anticipated. Propfan system adaptable to number of applications, such as highspeed (subsonic) business and general-aviation aircraft, and military aircraft including V/STOL.

  12. Diagnostic Value of Diffusion-weighted Imaging and Apparent Diffusion Coefficient Values in the Differentiation of Breast Lesions, Histpathologic Subgroups and Correlatıon with Prognostıc Factors using 3.0 Tesla MR

    PubMed Central

    Akın, Yasin; Uğurlu, M. Ümit; Kaya, Handan; Arıbal, Erkin

    2016-01-01

    Objective The aim of this study was to evaluate the effect of the apparent diffusion coefficient (ADC) and diffusion-weighted imaging in differentiating benign from malignant breast lesions, histopathologic subtypes of breast tumors, and to find a correlation with prognostic factors using 3T MR. Materials and Methods A total of 165 patients aged between 16 and 78 years with 181 histopathologically-verifed breast lesions were enrolled in this study. A 3T MR system and bilateral phased array breast coil was used. Diffusion-weighted imaging was performed with spin echo “echo planar” with “b” values: 50, 400, and 800 seconds/mm2. ADC values were calculated for normal fibroglandular tissue and breast lesions. ADC values of independent groups were compared using Student’s t-test. ROC analysis was used to find a threshold ADC value in the differentiation of lesions. Results The mean ADC values were 1.35±0.16 × 10−3 mm2/s for normal fibroglandular tissue, 1.41±0.24 × 10−3 mm2/s for benign breast lesions and 0.83±0.19 × 10−3 mm2/s for malignant breast lesions. The AUC with ROC analysis was 0.945 and the threshold for ADC was 1.08 × 10−3 mm2/s with a sensitivity and specificity of 92% and 92%, respectively. The threshold value for ADC ratio was 0.9 with 96% sensitivity and 89% specificity. The mean ADC of malignant breast lesions was statistically lower for benign lesions (p<0.01). We found no correlation between the mean ADC values and ER-PR receptor, Her2, and Ki-67 values. Conclusion Diffusion-weighted imaging has high diagnostic value with high sensitivity and specificity in differentiating malignant and benign breast lesions.

  13. Brain intracellular metabolites are freely diffusing along cell fibers in grey and white matter, as measured by diffusion-weighted MR spectroscopy in the human brain at 7 T.

    PubMed

    Najac, Chloé; Branzoli, Francesca; Ronen, Itamar; Valette, Julien

    2016-04-01

    Due to the specific compartmentation of brain metabolites, diffusion-weighted magnetic resonance spectroscopy opens unique insight into neuronal and astrocytic microstructures. The apparent diffusion coefficient (ADC) of brain metabolites depends on various intracellular parameters including cytosol viscosity and molecular crowding. When diffusion time (t d) is long enough, the size and geometry of the compartment in which the metabolites diffuse strongly influence metabolites ADC. In a previous study, performed in the macaque brain, we measured neuronal and astrocytic metabolites ADC at long t d (from 86 to 1,011 ms) in a large voxel enclosing an equal proportion of white and grey matter. We showed that metabolites apparently diffuse freely along the axis of dendrites, axons and astrocytic processes. To assess potential differences between these two tissue types, here we measured for the first time in the Human brain the t d-dependency of metabolites trace/3 ADC at 7 teslas using a localized diffusion-weighted STEAM sequence, in parietal and occipital voxels, respectively, containing mainly white and grey matter. We show that, in both tissues and over the observed timescale (t d varying from 92 to 712 ms) metabolite ADC reaches a non-zero plateau, suggesting that metabolites are not confined inside subcellular regions such as cell bodies, or inside subcellular compartments such as organelles, but are rather free to diffuse in the whole fiber-like structure of neurons and astrocytes. Beyond the fundamental insights into intracellular compartmentation of metabolites, this work also provides a new framework for interpreting results of neuroimaging techniques based on molecular diffusion, such as diffusion-weighted magnetic resonance spectroscopy and imaging.

  14. Brain intracellular metabolites are freely diffusing along cell fibers in grey and white matter, as measured by diffusion-weighted MR spectroscopy in the human brain at 7 T

    PubMed Central

    Najac, Chloé; Branzoli, Francesca; Ronen, Itamar; Valette, Julien

    2016-01-01

    Due to the specific compartmentation of brain metabolites, diffusion-weighted magnetic resonance spectroscopy opens unique insight into neuronal and astrocytic microstructures. The apparent diffusion coefficient (ADC) of brain metabolites depends on various intracellular parameters including cytosol viscosity and molecular crowding. When diffusion time (td) is long enough, the size and geometry of the compartment in which the metabolites diffuse strongly influence metabolites ADC. In a previous study, performed in the macaque brain, we measured neuronal and astrocytic metabolites ADC at long td (from 86 ms to 1011 ms) in a large voxel enclosing an equal proportion of white and grey matter. We showed that metabolites apparently diffuse freely along the axis of dendrites, axons and astrocytic processes. To assess potential differences between these two tissue types, here we measured for the first time in the Human brain the td-dependency of metabolites trace/3 ADC at 7 teslas using a localized diffusion-weighted STEAM sequence, in parietal and occipital voxels respectively containing mainly white and grey matter. We show that, in both tissues and over the observed timescale (td varying from 92 to 712 ms) metabolite ADC reaches a non-zero plateau, suggesting that metabolites are not confined inside subcellular regions such as cell bodies, or inside subcellular compartments such as organelles, but are rather free to diffuse in the whole fiber-like structure of neurons and astrocytes. Beyond the fundamental insights into intracellular compartmentation of metabolites, this work also provides a new framework for interpreting results of neuroimaging techniques based on molecular diffusion, such as diffusion-weighted magnetic resonance spectroscopy and imaging. PMID:25520054

  15. Diffusion-prepared stimulated-echo turbo spin echo (DPsti-TSE): An eddy current-insensitive sequence for three-dimensional high-resolution and undistorted diffusion-weighted imaging.

    PubMed

    Zhang, Qinwei; Coolen, Bram F; Versluis, Maarten J; Strijkers, Gustav J; Nederveen, Aart J

    2017-03-13

    In this study, we present a new three-dimensional (3D), diffusion-prepared turbo spin echo sequence based on a stimulated-echo read-out (DPsti-TSE) enabling high-resolution and undistorted diffusion-weighted imaging (DWI). A dephasing gradient in the diffusion preparation module and rephasing gradients in the turbo spin echo module create stimulated echoes, which prevent signal loss caused by eddy currents. Near to perfect agreement of apparent diffusion coefficient (ADC) values between DPsti-TSE and diffusion-weighted echo planar imaging (DW-EPI) was demonstrated in both phantom transient signal experiments and phantom imaging experiments. High-resolution and undistorted DPsti-TSE was demonstrated in vivo in prostate and carotid vessel wall. 3D whole-prostate DWI was achieved with four b values in only 6 min. Undistorted ADC maps of the prostate peripheral zone were obtained at low and high imaging resolutions with no change in mean ADC values [(1.60 ± 0.10) × 10(-3) versus (1.60 ± 0.02) × 10(-3)  mm(2) /s]. High-resolution 3D DWI of the carotid vessel wall was achieved in 12 min, with consistent ADC values [(1.40 ± 0.23) × 10(-3)  mm(2) /s] across different subjects, as well as slice locations through the imaging volume. This study shows that DPsti-TSE can serve as a robust 3D diffusion-weighted sequence and is an attractive alternative to the traditional two-dimensional DW-EPI approaches.

  16. Propeller Study. Part 2: the Design of Propellers for Minimum Noise

    NASA Technical Reports Server (NTRS)

    Ormsbee, A. I.; Woan, C. J.

    1977-01-01

    The design of propellers which are efficient and yet produce minimum noise requires accurate determinations of both the flow over the propeller. Topics discussed in relating aerodynamic propeller design and propeller acoustics include the necessary approximations and assumptions involved, the coordinate systems and their transformations, the geometry of the propeller blade, and the problem formulations including the induced velocity, required in the determination of mean lines of blade sections, and the optimization of propeller noise. The numerical formulation for the lifting-line model are given. Some applications and numerical results are included.

  17. Experimental research on air propellers

    NASA Technical Reports Server (NTRS)

    Durand, William F

    1918-01-01

    The purposes of the experimental investigation on the performance of air propellers described in this report are as follows: (1) the development of a series of design factors and coefficients drawn from model forms distributed with some regularity over the field of air-propeller design and intended to furnish a basis of check with similar work done in other aerodynamic laboratories, and as a point of departure for the further study of special or individual types and forms; (2) the establishment of a series of experimental values derived from models and intended for later use as a basis for comparison with similar results drawn from certain selected full-sized forms and tested in free flight.

  18. Electromechanical propellant control system actuator

    NASA Technical Reports Server (NTRS)

    Myers, W. Neill; Weir, Rae Ann

    1990-01-01

    New control mechanism technologies are currently being sought to provide alternatives to hydraulic actuation systems. The Propulsion Laboratory at Marshall Space Flight Center (MSFC) is involved in the development of electromechanical actuators (EMA's) for this purpose. Through this effort, an in-house designed electromechanical propellant valve actuator has been assembled and is presently being evaluated. This evaluation will allow performance comparisons between EMA and hydraulics systems. The in-house design consists of the following hardware: a three-phase brushless motor, a harmonic drive, and an output spline which will mate with current Space Shuttle Main Engine (SSME) propellant control valves. A resolver and associated electronics supply position feedback for the EMA. System control is provided by a solid-state electronic controller and power supply. Frequency response testing has been performed with further testing planned as hardware and test facilities become available.

  19. Multi-propeller drive system

    NASA Astrophysics Data System (ADS)

    Belenger, Robert V.

    1995-05-01

    A multipropeller drive system having a single input shaft for connection to an engine system, a differential gear assembly for dividing the driving force from the input drive shaft between a pair of output shafts, and a pair of laterally spaced propellers driven by the output shafts of the differential gear assembly is disclosed. The differential gear assembly operates in a manner wherein one output shaft, if required, is permitted to revolve at a different rate than the other output shaft. A pair of brake mechanisms acting on the output shafts of the differential gear assembly enable an operator to control the rotational speed of the respective propellers without modifying the engine speed or transmission settings.

  20. High performance ammonium nitrate propellant

    NASA Technical Reports Server (NTRS)

    Anderson, F. A. (Inventor)

    1979-01-01

    A high performance propellant having greatly reduced hydrogen chloride emission is presented. It is comprised of: (1) a minor amount of hydrocarbon binder (10-15%), (2) at least 85% solids including ammonium nitrate as the primary oxidizer (about 40% to 70%), (3) a significant amount (5-25%) powdered metal fuel, such as aluminum, (4) a small amount (5-25%) of ammonium perchlorate as a supplementary oxidizer, and (5) optionally a small amount (0-20%) of a nitramine.

  1. Alternate propellant program, phase 1

    NASA Technical Reports Server (NTRS)

    Anderson, F. A.; West, W. R.

    1979-01-01

    Candidate propellant systems for the shuttle booster solid rocket motor (SRM), which would eliminate, or greatly reduce, the amount of HCl produced in the exhaust of the shuttle SRM were investigated. Ammonium nitrate was selected for consideration as the main oxidizer, with ammonium perchlorate and the nitramine, cyclo-tetramethylene-tetranitramine as secondary oxidizers. The amount of ammonium perchlorate used was limited to an amount which would produce an exhaust containing no more than 3% HCl.

  2. Subsonic and transonic propeller noise

    NASA Astrophysics Data System (ADS)

    Lewy, S.; Gounet, H.

    Models for the noise levels from propellers are discussed, with results compared to in-flight measurements. Methods originally applied to noise from light aircraft are modified and extended to high speed passenger aircraft. Noise emitted from propellers has three components: a monopolar emission due to the air displaced by a blade; a bipolar form from average and fluctuating forces exerted by the blades; and a quadripolar component produced by deformation of the streamlines around the blade profile and defined by the Lighthill tensor. The latter is not a factor in the subsonic regime and can be neglected. Attention is given to a formalism which accounts for the sound level along each band, the frequency harmonics at each blade passage, the number of blades, and the rotation rate. The measured directivities of the two components are described. It is found that the radiated noise levels can be reduced in slow aircraft by lowering the peripheral velocity while keeping the same power with more blades. Calculations including the quadripolar term are necessary for modeling noise levels in transonic propellers.

  3. Aeroacoustic wind tunnel measurements on propeller noise

    NASA Astrophysics Data System (ADS)

    Grosche, F. R.; Stiewitt, H.

    1985-02-01

    Model tests were conducted in a low speed wind tunnel to determine the sound radiation of 5 propellers with different blade designs including variations of thickness ratios, blade profiles, blade planforms and blade tip configurations. The diameter of the propellers was 0.9 m, the propeller speed was kept constant. The tip Mach number was M sub I = 0.66 and the helical tip Mach number varied between 0.66 and 0.69. The main objectives were to investigate the effects of blade geometry on near field and far field noise and to locate the dominant sound sources in the propeller plane, radiating to the observer, by means of a highly directional microphone system. The results include: (1) comparisons of noise spectra of different propeller configurations; (2) near field sound pressures as function of axial distance from the propeller plane; and (3) directivity of sound radiation from the moving blades.

  4. Soviet chemical propellant research and development

    SciTech Connect

    deButts, E.H.; Baum, K.; Beckstead, M.W.; Christe, K.O.; Hartman, K.O.; Jeffrey, W.A.

    1991-12-01

    In the second half of the 1980s, the Soviet Union had a strong and continuing research effort devoted to understanding the behavior of chemical propellants suitable to support development of advanced propellants for practical applications. Recent Soviet work concentrated on solid propellants, though liquid propellants powered the largest and most advanced deployed Soviet rockets. This assessment summarizes the Soviet state of the art in chemical propellants in the late 1980s and projects the trends of that period into the next decade. It is based on a broad and deep review of Soviet literature published in 1985--1991 and is presented in an unclassified report. Speculation about or prediction of the effects of recent political and social events on chemical propellant research and development in the old Soviet Union is outside the scope of this assessment, though the effects are likely to be profound.

  5. Crack Propagation in Double-Base Propellants

    DTIC Science & Technology

    1976-01-01

    propagation tests were conducted on a composite modified double- base ( CMDB ) propellant with the use of center-cracked strip biaxial specimens...double-base ( CMDB ) propellant. He performed a stress analysis of small, precracked, subscale STV motors formulated in terms of stress intensity factors...assumed for Solithane 113. The present program was aimed at evaluating the Schapery theory when it was applied to a CMDB propellant under similar loading

  6. Catalytic ignitor for regenerative propellant gun

    NASA Technical Reports Server (NTRS)

    Voecks, Gerald E. (Inventor); Ferraro, Ned W. (Inventor)

    1994-01-01

    An ignitor initiates combustion of liquid propellant in a gun by utilizing a heated catalyst onto which the liquid propellant is sprayed in a manner which mitigates the occurrence of undesirable combustion chamber oscillations. The heater heats the catalyst sufficiently to provide the activation necessary to initiate combustion of the liquid propellant sprayed thereonto. Two embodiments of the ignitor and three alternative mountings thereof within the combustion chamber are disclosed. The ignitor may also be utilized to dispose of contaminated, excess, or waste liquid propellant in a safe, controlled, simple, and reliable manner.

  7. Catalytic Ignitor for Regenerative Propellant Gun

    NASA Technical Reports Server (NTRS)

    Voecks, Gerald E. (Inventor); Ferraro, Ned W. (Inventor)

    1997-01-01

    An ignitor initiates combustion of liquid propellant in a gun by utilizing a heated catalyst onto which the liquid propellant is sprayed in a manner which mitigates the occurrence of undesirable combustion chamber oscillations. The heater heats the catalyst sufficiently to provide the activation necessary to initiate combustion of the liquid propellant sprayed thereonto. Two embodiments of the igniter and three alternative mountings thereof within the combustion chamber are disclosed. The ignitor may also be utilized to dispose of contaminated, excess, or waste liquid propellant in a safe, controlled, simple, and reliable manner.

  8. Low speed propellers: Impact of advanced technologies

    NASA Technical Reports Server (NTRS)

    Keiter, I. D.

    1980-01-01

    Sensitivity studies performed to evaluate the potential of several advanced technological elements on propeller performance, noise, weight, and cost for general aviation aircraft are discussed. Studies indicate that the application of advanced technologies to general aviation propellers can reduce fuel consumption in future aircraft an average of ten percent, meeting current regulatory noise limits. Through the use of composite blade construction, up to 25 percent propeller weight reduction can be achieved. This weight reduction in addition to seven percent propeller efficiency improvements through application of advanced technologies result in four percent reduction in direct operating costs, ten percent reduction in aircraft acquisition cost, and seven percent lower gross weight for general aviation aircraft.

  9. Application of Theodorsen's Theory to Propeller Design

    NASA Technical Reports Server (NTRS)

    Crigler, John L

    1948-01-01

    A theoretical analysis is presented for obtaining by use of Theodorsen's propeller theory the load distribution along a propeller radius to give the optimum propeller efficiency for any design condition.The efficiencies realized by designing for the optimum load distribution are given in graphs, and the optimum efficiency for any design condition may be read directly from the graph without any laborious calculations. Examples are included to illustrate the method of obtaining the optimum load distributions for both single-rotating and dual-rotating propellers.

  10. Application of Theodorsen's theory to propeller design

    NASA Technical Reports Server (NTRS)

    Crigler, John L

    1949-01-01

    A theoretical analysis is presented for obtaining, by use of Theodorsen's propeller theory, the load distribution along a propeller radius to give the optimum propeller efficiency for any design condition. The efficiencies realized by designing for the optimum load distribution are given in graphs, and the optimum efficiency for any design condition may be read directly from the graph without any laborious calculations. Examples are included to illustrate the method of obtaining the optimum load distributions for both single-rotating and dual-rotating propellers.

  11. Combustion of Gas-Permeable Gun Propellants

    NASA Astrophysics Data System (ADS)

    Li, Yuxiang; Yang, Weitao; Ying, Sanjiu; Peng, Jinhua

    2015-07-01

    Foamed propellants prepared by supercritical fluid foaming show considerably high burning rates due to their porous structures. To further investigate combustion of foamed propellants, quenched combustion experiments and closed-vessel experiments were carried out, Scanning electron microscopy (SEM) was also used to observe their porous morphology. The SEM images show that foamed propellant grains exhibit a porous core and compact skin. The research results show that the porous core is first burned out and the compact skin is burned out at the later burning stage. The results also demonstrate that pore size exerts an important effect on the burning behaviors of foamed propellants.

  12. Deflection of Propeller Blades While Running

    NASA Technical Reports Server (NTRS)

    Katzmayr, R

    1922-01-01

    The forces acting on the blades of a propeller proceed from the mass of the propeller and the resistance of the surrounding medium. The magnitude, direction and point of application of the resultant to the propeller blade is of prime importance for the strength calculation. Since it was obviously impracticable to bring any kind of testing device near the revolving propeller, not so much on account of the element of danger as on account of the resulting considerable disturbance of the air flow, the deflection in both cases was photographically recorded and subsequently measured at leisure.

  13. Injection dynamics of gelled propellants

    NASA Astrophysics Data System (ADS)

    Yoon, Changjin

    Gel propellants have been recognized as attractive candidates for future propulsion systems due to the reduced tendency to spill and the energy advantages over solid propellants. One of strong benefits emphasized in gel propellant applications is a throttling capability, but the accurate flow control is more complicated and difficult than with conventional Newtonian propellants because of the unique rheological behaviors of gels. This study is a computational effort directed to enhance understanding of the injector internal flow characteristics for gel propellants under rocket injection conditions. In simulations, the emphasized rheology is a shear-thinning which represents a viscosity decrease with increasing a shear rate. It is described by a generalized Newtonian fluid constitutive equation and Carreau-Yasuda model. Using this rheological model, two injection schemes are considered in the present study: axially-fed and cross-fed injection for single-element and multi-element impinging injectors, respectively. An axisymmetric model is developed to describe the axially-fed injector flows and fully three-dimensional model is utilized to simulate cross-fed injector flows. Under axially-fed injection conditions investigated, three distinct modes, an unsteady, steady, and hydraulic flip mode, are observed and mapped in terms of Reynolds number and orifice design. In an unsteady mode, quasi-periodic oscillations occur near the inlet lip leading mass pulsations and viscosity fluctuations at the orifice exit. This dynamic behavior is characterized using a time-averaged discharge coefficient, oscillation magnitude and frequency by a parametric study with respect to an orifice design, Reynolds number and rheology. As a result, orifice exit flows for gel propellants appear to be significantly influenced by a viscous damping and flow resistance due to a shear thinning behavior and these are observed in each factors considered. Under conditions driven by a manifold crossflow

  14. 78 FR 45052 - Critical Parts for Airplane Propellers; Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-26

    ... TRANSPORTATION Federal Aviation Administration 14 CFR Part 35 RIN 2120-AJ88 Critical Parts for Airplane... analysis to identify a propeller critical part. Manufacturers would identify propeller critical parts, and establish engineering, manufacturing, and maintenance processes for propeller critical parts....

  15. High-Temperature Solid Propellant

    DTIC Science & Technology

    1965-08-24

    aluminum matrix are 0.1 ta 0.25 in./sec, depending upon the compaction pressure with the polymer in a finely ground state (pass 230-mesh sieve). SThis...ptessure was reached, constant pressure was maintained for 1 min before the pressure was released. The " compacted pellet was removed from the mold...closed vessel can be written 2 .2 P (V + + C = C T (1) 0 M. where P is the partial pressure of the propellant , • • •gases V is the initial volume

  16. Low-g propellant gaging

    NASA Technical Reports Server (NTRS)

    Orton, George

    1987-01-01

    A program to develop and demonstrate technology for low gravity propellant gaging on future geostationary satellites is described. Evaluations were performed to select four gaging concepts for ground tests and low gravity tests in the NASA KC-135 aircraft. The selected concepts were: (1) an ultrasonic point sensor system, (2) a nucleonic gaging system, (3) an ultrasonic torsional wave guide, and (4) an ultrasonic flowmeter. As a result of successful ground and KC-135 tests, two concepts (the ultrasonic point sensor and the nucleonic systems) were selected for orbital test in a shuttle Get-Away-Special experiment.

  17. Analysis of propellant feedline dynamics

    NASA Technical Reports Server (NTRS)

    Holster, J. L.; Astleford, W. J.; Gerlach, C. R.

    1973-01-01

    An analytical model and corresponding computer program for studying disturbances of liquid propellants in typical engine feedline systems were developed. The model includes the effects of steady turbulent mean flow, the influence of distributed compliances, the effects of local compliances, and various factors causing structural-hydraulic coupling. The computer program was set up such that the amplitude and phase of the terminal pressure/input excitation is calculated over any desired frequency range for an arbitrary assembly of various feedline components. A user's manual is included.

  18. Light metal explosives and propellants

    DOEpatents

    Wood, Lowell L.; Ishikawa, Muriel Y.; Nuckolls, John H.; Pagoria, Phillip F.; Viecelli, James A.

    2005-04-05

    Disclosed herein are light metal explosives, pyrotechnics and propellants (LME&Ps) comprising a light metal component such as Li, B, Be or their hydrides or intermetallic compounds and alloys containing them and an oxidizer component containing a classic explosive, such as CL-20, or a non-explosive oxidizer, such as lithium perchlorate, or combinations thereof. LME&P formulations may have light metal particles and oxidizer particles ranging in size from 0.01 .mu.m to 1000 .mu.m.

  19. Fluorinated Desensitizing Ingredients for Propellants

    DTIC Science & Technology

    1980-05-24

    Entered) 19. KEY WORDS (Continued) 20 ABSTRACT (Continued) Compound Structure 3-Fluoro-1,2- propanediol dinitrate FCH2CH(ONO2 )CH2ONO2 FDNP 3,3,3...Trifluoro-1,2- propanediol dinitrate F3 CCH(ONO2 )CH2ONO2 TFDNP 4,4,4-Trifluoro-l,2,3-butanetriol F3CCH(ONO 2 )CH(ONO2)CH2ONO 2 Trinitrate TFBTTN Preliminary...are potentially useful propellant ingredients. When compared with 1,2- propanediol dinitrate (DNP), which is currently used in Otto Fuel II, FDNP has a

  20. Effects of propellant composition variables on acceleration-induced burning-rate augmentation of solid propellants

    NASA Technical Reports Server (NTRS)

    Northam, G. B.

    1972-01-01

    This work was conducted to define further the effects of propellant composition variables on the acceleration-induced burning rate augmentation of solid propellants. The rate augmentation at a given acceleration was found to be a nonlinear inverse function of the reference burning rate and not controlled by binder or catalyst type at a given reference rate. A nonaluminized propellant and a low rate double-base propellant exhibited strong transient rate augmentation due to surface pitting resulting from the retention of hot particles on the propellant surface.

  1. Preventing Growth Of Barnacles On Propellers

    NASA Technical Reports Server (NTRS)

    Parrish, Kemp L.

    1993-01-01

    Possible to prevent barnacles and other marine life from obtaining firm bonds on propellers and other metal parts by coating parts with NEDOX (or equivalent) cavitation-resistant material. Available in several forms; one that works best is mold-release coating. Also provides improved surface hardness, protection against electrolysis, better resistance to abrasion, and less friction between propellers and water.

  2. Cryogenic propellant prestart conditioning for NLS

    NASA Technical Reports Server (NTRS)

    Gaynor, T. L.; Merlin, M. V.; Gautney, T. T.

    1992-01-01

    An overview is presented of a candidate National Launch System (NLS) passive cryogenic propellant prestart conditioning system that offers a stable propellant thermal environment and minimum system complexity. A 2D, multinode model utilizing real fluid properties was developed. This model predicts flow recirculation due to thermal gradients by assuming vertical cold and warm opposing flow streams produced by density differential.

  3. Propeller Study. Part 1: Introduction and Overview

    NASA Technical Reports Server (NTRS)

    Ormsbee, A. I.

    1977-01-01

    A general aerodynamic-acoustic theory was developed for determining the acoustical design of propellers used on general aviation aircraft. Data from the theoretical investigation were applied in the design of a propeller whose thrust and torque were measured during a series of YO-3A aircraft flight tests.

  4. Recovery of aluminum from composite propellants

    NASA Technical Reports Server (NTRS)

    Shaw, G. C. (Inventor)

    1980-01-01

    Aluminum was recovered from solid rocket propellant containing a small amount of oxidizer by depolymerizing and dissolving propellant binders (containing functional or hydrolyzable groups in a solution of sodium methoxide) in an alcohol solvent optionally containing an aliphatic or aromatic hydrocarbon co-solvent. The solution was filtered to recover substantially all the aluminum in active form.

  5. 21 CFR 189.191 - Chlorofluorocarbon propellants.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Chlorofluorocarbon propellants. 189.191 Section 189.191 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... or Use as Human Food § 189.191 Chlorofluorocarbon propellants. The use of chlorofluorocarbons...

  6. 14 CFR 21.129 - Tests: propellers.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Tests: propellers. 21.129 Section 21.129... PROCEDURES FOR PRODUCTS AND PARTS Production Under Type Certificate Only § 21.129 Tests: propellers. Each... acceptable functional test to determine if it operates properly throughout the normal range of operation....

  7. 14 CFR 21.129 - Tests: propellers.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Tests: propellers. 21.129 Section 21.129... PROCEDURES FOR PRODUCTS AND PARTS Production Under Type Certificate § 21.129 Tests: propellers. Each person... functional test to determine if it operates properly throughout the normal range of operation....

  8. 14 CFR 21.129 - Tests: propellers.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Tests: propellers. 21.129 Section 21.129... PROCEDURES FOR PRODUCTS AND PARTS Production Under Type Certificate § 21.129 Tests: propellers. Each person... functional test to determine if it operates properly throughout the normal range of operation....

  9. Composite Solid Propellant Predictability and Quality Assurance

    NASA Technical Reports Server (NTRS)

    Ramohalli, Kumar

    1989-01-01

    Reports are presented at the meeting at the University of Arizona on the study of predictable and reliable solid rocket motors. The following subject areas were covered: present state and trends in the research of solid propellants; the University of Arizona program in solid propellants, particularly in mixing (experimental and analytical results are presented).

  10. Materials characterization of propellants using ultrasonics

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.; Jones, David

    1993-01-01

    Propellant characteristics for solid rocket motors were not completely determined for its use as a processing variable in today's production facilities. A major effort to determine propellant characteristics obtainable through ultrasonic measurement techniques was performed in this task. The information obtained was then used to determine the uniformity of manufacturing methods and/or the ability to determine non-uniformity in processes.

  11. 14 CFR 25.929 - Propeller deicing.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Propeller deicing. 25.929 Section 25.929 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Powerplant General § 25.929 Propeller deicing. (a) For...

  12. 14 CFR 25.929 - Propeller deicing.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Propeller deicing. 25.929 Section 25.929 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Powerplant General § 25.929 Propeller deicing. (a) For...

  13. 14 CFR 25.929 - Propeller deicing.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Propeller deicing. 25.929 Section 25.929 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Powerplant General § 25.929 Propeller deicing. (a) For...

  14. 14 CFR 25.929 - Propeller deicing.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Propeller deicing. 25.929 Section 25.929 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Powerplant General § 25.929 Propeller deicing. (a) For...

  15. 14 CFR 25.929 - Propeller deicing.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Propeller deicing. 25.929 Section 25.929 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Powerplant General § 25.929 Propeller deicing. (a) For...

  16. ISRU Propellant Selection for Space Exploration Vehicles

    NASA Technical Reports Server (NTRS)

    Chen, Timothy T.

    2013-01-01

    Chemical propulsion remains the only viable solution as technically matured technology for the near term human space transportation to Lunar and Mars. Current mode of space travel requires us to "take everything we will need", including propellant for the return trip. Forcing the mission designers to carry propellant for the return trip limits payload mass available for mission operations and results in a large and costly (and often unaffordable) design. Producing propellant via In-Situ Resource Utilization (ISRU) will enable missions with chemical propulsion by the "refueling" of return-trip propellant. It will reduce vehicle propellant mass carrying requirement by over 50%. This mass reduction can translates into increased payload to enhance greater mission capability, reduces vehicle size, weight and cost. It will also reduce size of launch vehicle fairing size as well as number of launches for a given space mission and enables exploration missions with existing chemical propulsion. Mars remains the ultimate destination for Human Space Exploration within the Solar System. The Mars atmospheric consist of 95% carbon dioxide (CO2) and the presence of Ice (water) was detected on Mars surfaces. This presents a basic chemical building block for the ISRU propellant manufacturing. However, the rationale for the right propellant to produce via ISRU appears to be limited to the perception of "what we can produce" as oppose to "what is the right propellant". Methane (CH4) is often quoted as a logical choice for Mars ISRU propellant, however; it is believed that there are better alternatives available that can result in a better space transportation architecture. A system analysis is needed to determine on what is the right propellant choice for the exploration vehicle. This paper examines the propellant selection for production via ISRU method on Mars surfaces. It will examine propellant trades for the exploration vehicle with resulting impact on vehicle performance, size

  17. MAST Propellant and Delivery System Design Methods

    NASA Technical Reports Server (NTRS)

    Nadeem, Uzair; Mc Cleskey, Carey M.

    2015-01-01

    A Mars Aerospace Taxi (MAST) concept and propellant storage and delivery case study is undergoing investigation by NASA's Element Design and Architectural Impact (EDAI) design and analysis forum. The MAST lander concept envisions landing with its ascent propellant storage tanks empty and supplying these reusable Mars landers with propellant that is generated and transferred while on the Mars surface. The report provides an overview of the data derived from modeling between different methods of propellant line routing (or "lining") and differentiate the resulting design and operations complexity of fluid and gaseous paths based on a given set of fluid sources and destinations. The EDAI team desires a rough-order-magnitude algorithm for estimating the lining characteristics (i.e., the plumbing mass and complexity) associated different numbers of vehicle propellant sources and destinations. This paper explored the feasibility of preparing a mathematically sound algorithm for this purpose, and offers a method for the EDAI team to implement.

  18. The theory of the screw propeller

    NASA Technical Reports Server (NTRS)

    Betz, A

    1922-01-01

    Given here is a brief review of the fundamental principles of the propeller slip-stream theory and its further development through later researches, which demonstrate the connection between the propeller slip-stream theory and Frounde's so-called 'propeller blade theory.' The propeller slip-stream theory, especially in its improved form, now gives us the basis for determining the mutual influence of the parts of the blade, so that, in calculating the shape of the blade, we can get along with certain section characteristics, which have been determined once and for all. It is argued that new theories present the possibility of investigating the phenomena in the vicinity of the propeller, allowing us to calculate its action on the basis of fewer experimental values.

  19. Annoyance caused by propeller airplane flyover noise

    NASA Technical Reports Server (NTRS)

    Mccurdy, D. A.; Powell, C. A.

    1984-01-01

    Laboratory experiments were conducted to provide information on quantifying the annoyance response of people to propeller airplane noise. The items of interest were current noise metrics, tone corrections, duration corrections, critical band corrections, and the effects of engine type, operation type, maximum takeoff weight, blade passage frequency, and blade tip speed. In each experiment, 64 subjects judged the annoyance of recordings of propeller and jet airplane operations presented at d-weighted sound pressure levels of 70, 80, and 90 dB in a testing room which simulates the outdoor acoustic environment. The first experiment examined 11 propeller airplanes with maximum takeoff weights greater than or equal to 5700 kg. The second experiment examined 14 propeller airplanes weighting 5700 kg or less. Five jet airplanes were included in each experiment. For both the heavy and light propeller airplanes, perceived noise level and perceived level (Stevens Mark VII procedure) predicted annoyance better than other current noise metrics.

  20. AP reclamation and reuse in RSRM propellant

    NASA Technical Reports Server (NTRS)

    Miks, Kathryn F.; Harris, Stacey A.

    1995-01-01

    A solid propellant ingredient reclamation pilot plant has been evaluated at the Strategic Operations of Thiokol Corporation, located in Brigham City, Utah. The plant produces AP wet cake (95 percent AP, 5 percent water) for recycling at AP vendors. AP has been obtained from two standard propellant binder systems (PBAN and HTPB). Analytical work conducted at Thiokol indicates that the vendor-recrystallized AP meets Space Shuttle propellant specification requirements. Thiokol has processed 1-, 5-, and 600-gallon propellant mixes with the recrystallized AP. Processing, cast, cure, ballistic, mechanical, and safety properties have been evaluated. Phillips Laboratory static-test-fired 70-pound and 800-pound BATES motors. The data indicate that propellant processed with reclaimed AP has nominal properties.

  1. Handbook on Hypergolic Propellant Discharges and Disposal

    NASA Technical Reports Server (NTRS)

    Bowman, T. E.; Sivik, H. E.; Thomas, J. J.

    1977-01-01

    The efficiency of all treatment methods formerly or currently used in treating chemical wastes is assessed with emphasis on the disposal of hypergolic propellants. Maximum focus is on the space shuttle propellants MMH and N2O4. Except for hydrogen peroxide oxidizers, all the propellants are nitrogen based and can be potentially reduced to valuable plant nutrients. In theory, all the propellants can be reduced to carbon, hydrogen, nitrogen, and oxygen, except of fuming nitric acid which contains a small amount of fluorine. Appendices cover: (1) a general design criteria for disposal ponds; (2) thermal aspects of reaction in dilute solution; (3) gas bubble growth, detachment, and rise (4) absorption scrubber fundamentals and descriptions; (5) separation of a propellant vapor from a helium stream by permeation; and (6) atmospheric emission limits.

  2. Interaction Between Air Propellers and Airplane Structures

    NASA Technical Reports Server (NTRS)

    Durand, W F

    1927-01-01

    The purpose of this investigation was the determination of the character and amount of interaction between air propellers as usually mounted on airplanes and the adjacent parts of the airplane structure - or, more specifically, those parts of the airplane structure within the wash of the propeller, and capable of producing any significant effect on propeller performance. In report no. 177 such interaction between air propellers and certain simple geometrical forms was made the subject of investigation and report. The present investigation aims to carry this general study one stage further by substituting actual airplane structures for the simple geometrical forms. From the point of view of the present investigation, the airplane structures, viewed as an obstruction in the wake of the propeller, must also be viewed as a necessary part of the airplane and not as an appendage which might be installed or removed at will. (author)

  3. The influence of gender on ‘tissue at risk’ in acute stroke: A diffusion-weighted magnetic resonance imaging study in a rat model of focal cerebral ischaemia

    PubMed Central

    Baskerville, Tracey A; Holmes, William M; McCabe, Christopher

    2015-01-01

    This is the first study to assess the influence of sex on the evolution of ischaemic injury and penumbra. Permanent middle cerebral artery occlusion was induced in male (n = 9) and female (n = 10) Sprague-Dawley rats. Diffusion-weighted imaging was acquired over 4 h and infarct determined from T2 images at 24 h post-permanent middle cerebral artery occlusion. Penumbra was determined retrospectively from serial apparent diffusion coefficient lesions and T2-defined infarct. Apparent diffusion coefficient lesion volume was significantly smaller in females from 0.5 to 4 h post permanent middle cerebral artery occlusion as was infarct volume. Penumbral volume, and its loss over time, was not significantly different despite the sex difference in acute and final lesion volumes. PMID:26661149

  4. Computational modeling of magnetically actuated propellant orientation

    NASA Technical Reports Server (NTRS)

    Hochstein, John I.

    1996-01-01

    Unlike terrestrial applications where gravity positions liquid at the 'bottom' of the tank, the location of liquid propellant in spacecraft tanks is uncertain unless specific actions are taken or special features are built into the tank. Some mission events require knowledge of liquid position prior to a particular action: liquid must be positioned over the tank outlet prior to starting the main engines and must be moved away from the tank vent before vapor can be released overboard to reduce pressure. It may also be desirable to positively position liquid to improve propulsion system performance: moving liquid away from the tank walls will dramatically decrease the rate of heat transfer to the propellant, suppressing the boil-off rate, thereby reducing overall mission propellant requirements. The process of moving propellant to a desired position is referred to as propellant orientation or reorientation. Several techniques have been developed to positively position propellant in spacecraft tanks and each technique imposes additional requirements on vehicle design. Propulsive reorientation relies on small auxiliary thrusters to accelerate the tank. The inertia of the liquid causes it to collect in the aft-end of the tank if the acceleration is forward. This technique requires that additional thrusters be added to the vehicle, that additional propellant be carried in the vehicle, and that an additional operational maneuver be executed. Another technique uses Liquid Acquisition Devices (LAD's) to positively position propellants. These devices rely on surface tension to hold the liquid within special geometries (i.e. vanes, wire-mesh channels, start-baskets). While avoiding some of the penalties of propulsive orientation, this technique requires the addition of complicated hardware inside the propellant tank and performance for long duration missions is uncertain. The subject of the present research is an alternate technique for positively positioning liquid within

  5. Application of an optimization method to high performance propeller designs

    NASA Technical Reports Server (NTRS)

    Li, K. C.; Stefko, G. L.

    1984-01-01

    The application of an optimization method to determine the propeller blade twist distribution which maximizes propeller efficiency is presented. The optimization employs a previously developed method which has been improved to include the effects of blade drag, camber and thickness. Before the optimization portion of the computer code is used, comparisons of calculated propeller efficiencies and power coefficients are made with experimental data for one NACA propeller at Mach numbers in the range of 0.24 to 0.50 and another NACA propeller at a Mach number of 0.71 to validate the propeller aerodynamic analysis portion of the computer code. Then comparisons of calculated propeller efficiencies for the optimized and the original propellers show the benefits of the optimization method in improving propeller performance. This method can be applied to the aerodynamic design of propellers having straight, swept, or nonplanar propeller blades.

  6. Runtime and Pressurization Analyses of Propellant Tanks

    NASA Technical Reports Server (NTRS)

    Field, Robert E.; Ryan, Harry M.; Ahuja, Vineet; Hosangadi, Ashvin; Lee, Chung P.

    2007-01-01

    Multi-element unstructured CFD has been utilized at NASA SSC to carry out analyses of propellant tank systems in different modes of operation. The three regimes of interest at SSC include (a) tank chill down (b) tank pressurization and (c) runtime propellant draw-down and purge. While tank chill down is an important event that is best addressed with long time-scale heat transfer calculations, CFD can play a critical role in the tank pressurization and runtime modes of operation. In these situations, problems with contamination of the propellant by inclusion of the pressurant gas from the ullage causes a deterioration of the quality of the propellant delivered to the test article. CFD can be used to help quantify the mixing and propellant degradation. During tank pressurization under some circumstances, rapid mixing of relatively warm pressurant gas with cryogenic propellant can lead to rapid densification of the gas and loss of pressure in the tank. This phenomenon can cause serious problems during testing because of the resulting decrease in propellant flow rate. With proper physical models implemented, CFD can model the coupling between the propellant and pressurant including heat transfer and phase change effects and accurately capture the complex physics in the evolving flowfields. This holds the promise of allowing the specification of operational conditions and procedures that could minimize the undesirable mixing and heat transfer inherent in propellant tank operation. It should be noted that traditional CFD modeling is inadequate for such simulations because the fluids in the tank are in a range of different sub-critical and supercritical states and elaborate phase change and mixing rules have to be developed to accurately model the interaction between the ullage gas and the propellant. We show a typical run-time simulation of a spherical propellant tank, containing RP-1 in this case, being pressurized with room-temperature nitrogen at 540 R. Nitrogen

  7. Propellant isolation shutoff valve program

    NASA Technical Reports Server (NTRS)

    Merritt, F. L.

    1973-01-01

    An analysis and design effort directed to advancing the state-of-the-art of space storable isolation valves for control of flow of the propellants liquid fluorine/hydrazine and Flox/monomethylhydrazine is discussed. Emphasis is on achieving zero liquid leakage and capability of withstanding missions up to 10 years in interplanetary space. Included is a study of all-metal poppet sealing theory, an evaluation of candidate seal configurations, a valve actuator trade-off study and design description of a pneumo-thermally actuated soft metal poppet seal valve. The concepts and analysis leading to the soft seal approach are documented. A theoretical evaluation of seal leakage versus seal loading, related finishes and yield strengths of various materials is provided. Application of a confined soft aluminum seal loaded to 2 to 3 times yield strength is recommended. Use of either an electro-mechanical or pneumatic actuator appears to be feasible for the application.

  8. Propellant Chemistry for CFD Applications

    NASA Technical Reports Server (NTRS)

    Farmer, R. C.; Anderson, P. G.; Cheng, Gary C.

    1996-01-01

    Current concepts for reusable launch vehicle design have created renewed interest in the use of RP-1 fuels for high pressure and tri-propellant propulsion systems. Such designs require the use of an analytical technology that accurately accounts for the effects of real fluid properties, combustion of large hydrocarbon fuel modules, and the possibility of soot formation. These effects are inadequately treated in current computational fluid dynamic (CFD) codes used for propulsion system analyses. The objective of this investigation is to provide an accurate analytical description of hydrocarbon combustion thermodynamics and kinetics that is sufficiently computationally efficient to be a practical design tool when used with CFD codes such as the FDNS code. A rigorous description of real fluid properties for RP-1 and its combustion products will be derived from the literature and from experiments conducted in this investigation. Upon the establishment of such a description, the fluid description will be simplified by using the minimum of empiricism necessary to maintain accurate combustion analyses and including such empirical models into an appropriate CFD code. An additional benefit of this approach is that the real fluid properties analysis simplifies the introduction of the effects of droplet sprays into the combustion model. Typical species compositions of RP-1 have been identified, surrogate fuels have been established for analyses, and combustion and sooting reaction kinetics models have been developed. Methods for predicting the necessary real fluid properties have been developed and essential experiments have been designed. Verification studies are in progress, and preliminary results from these studies will be presented. The approach has been determined to be feasible, and upon its completion the required methodology for accurate performance and heat transfer CFD analyses for high pressure, tri-propellant propulsion systems will be available.

  9. New delivery systems and propellants.

    PubMed

    Dolovich, M

    1999-01-01

    The removal of chlorofluorocarbon (CFC) propellants from industrial and household products has been agreed to by over 165 countries of which more than 135 are developing countries. The timetable for this process is outlined in the Montreal Protocol on Substances that Deplete the Ozone Layer document and in several subsequent amendments. Pressured metered dose inhalers (pMDIs) for medical use have been granted temporary exemptions until replacement formulations, providing the same medication via the same route, and with the same efficacy and safety profiles, are approved for human use. Hydrofluoroalkanes (HFAs) are the alternative propellants for CFCs-12 and -114. Their potential for damage to the ozone layer is nonexistent, and while they are greenhouse gases, their global warming potential is a fraction (one-tenth) of that of CFCs. Replacement formulations for almost all inhalant respiratory medications have been or are being produced and tested; in Canada, it is anticipated that the transition to these HFA or CFC-free pMDIs will be complete by the year 2005. Initially, an HFA pMDI was to be equivalent to the CFC pMDI being replaced, in terms of aerosol properties and effective clinical dose. However, this will not necessarily be the situation, particularly for some corticosteroid products. Currently, only one CFC-free formulation is available in Canada - Airomir, a HFA salbutamol pMDI. This paper discusses the in vitro aerosol characteristics, in vivo deposition and clinical data for several HFA pMDIs for which there are data available in the literature. Alternative delivery systems to the pMDI, namely, dry powder inhalers and nebulizers, are briefly reviewed.

  10. Cryogenic Propellant Management Device: Conceptual Design Study

    NASA Technical Reports Server (NTRS)

    Wollen, Mark; Merino, Fred; Schuster, John; Newton, Christopher

    2010-01-01

    Concepts of Propellant Management Devices (PMDs) were designed for lunar descent stage reaction control system (RCS) and lunar ascent stage (main and RCS propulsion) missions using liquid oxygen (LO2) and liquid methane (LCH4). Study ground rules set a maximum of 19 days from launch to lunar touchdown, and an additional 210 days on the lunar surface before liftoff. Two PMDs were conceptually designed for each of the descent stage RCS propellant tanks, and two designs for each of the ascent stage main propellant tanks. One of the two PMD types is a traditional partial four-screen channel device. The other type is a novel, expanding volume device which uses a stretched, flexing screen. It was found that several unique design features simplified the PMD designs. These features are (1) high propellant tank operating pressures, (2) aluminum tanks for propellant storage, and (3) stringent insulation requirements. Consequently, it was possible to treat LO2 and LCH4 as if they were equivalent to Earth-storable propellants because they would remain substantially subcooled during the lunar mission. In fact, prelaunch procedures are simplified with cryogens, because any trapped vapor will condense once the propellant tanks are pressurized in space.

  11. Advances in Green Cryogenic Solid Propellant Propulsion

    NASA Astrophysics Data System (ADS)

    Lo, R. E.; Adirim, H.; Poller, S.; Glaeser, S.; Schoeyer, H.; Caramelli, F.

    2004-10-01

    The combustion of hydrocarbons with hydrogen peroxide or oxygen based oxidizers is known as the best possible realization of green bipropellants in the realm of conventional propellants. By the nature of these constituents, corresponding rocket motors are either hybrids or bi-liquids. This is advantageous in all applications requiring the merits of these categories, such as variations of the thrust - time profile (throttle-ability up to shut down and restart), or variable propellant loading and mixture ratio variation in liquid bipropellants. However, when it comes to thriving on the simplicity and reliability of solid propellant technology, it takes cryogenic solid propulsion (CSP) as enabling technology to make these normally liquid propellants available for many solid propellant applications, in particular for high thrust Earth-to-orbit boosting. It is obvious that proper CSP propellant selection yields solids that are as "green" as any chemical propellant combination can be. The paper describes recent advances in CSP technology related investigations sponsored by the German Aerospace Centre DLR and the European Space Agency ESA at AI/ICT.

  12. Launch vehicle performance using metallized propellants

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan A.; Powell, Richard

    1991-01-01

    Metallized propellant propulsion systems are considered as replacements for the solid rocket boosters and liquid sustainer stages on the current launch vehicles: both the Space Transportation System (STS) and the Titan 4. Liquid rocket boosters for the STS were analyzed as replacements for current solid rocket boosters. These boosters can provide a liquid propulsion system within the volume constraints of a solid rocket booster. A replacement for the Space Shuttle Main Engines using metallized O2/H2/Al was studied. The liquid stages of the Titan 4 were also investigated; the Aerozine-50 (A-50) fuel was replaced with metallized storable A-50/Al. A metallized propellant is similar to a traditional liquid propellant. However, it has metal particles, such as aluminum, that are suspended in a gelled fuel, such as hydrogen, RP-1, A-50 or monomethyl hydrazine (MMH). The fuels then undergo combustion with liquid oxygen or nitrogen tetroxide (NTO). These propellants provide options for increasing the performance of existing launch vehicle chemical propulsion systems by increasing fuel density or specific impulse or both. These increases in density and specific impulse can significantly reduce the propulsion system liftoff weight and allow a liquid rocket booster to fit into the same volume as an existing solid rocket booster. Also, because gelled fuels are akin to liquid propellants, metallized systems can provide enhanced controllability over solid propulsion systems. Gelling of the propellant also reduces the sensitivity to impacts and consequently reduces the propellant explosion hazard.

  13. Analytic Modeling of Pressurization and Cryogenic Propellant

    NASA Technical Reports Server (NTRS)

    Corpening, Jeremy H.

    2010-01-01

    An analytic model for pressurization and cryogenic propellant conditions during all mission phases of any liquid rocket based vehicle has been developed and validated. The model assumes the propellant tanks to be divided into five nodes and also implements an empirical correlation for liquid stratification if desired. The five nodes include a tank wall node exposed to ullage gas, an ullage gas node, a saturated propellant vapor node at the liquid-vapor interface, a liquid node, and a tank wall node exposed to liquid. The conservation equations of mass and energy are then applied across all the node boundaries and, with the use of perfect gas assumptions, explicit solutions for ullage and liquid conditions are derived. All fluid properties are updated real time using NIST Refprop.1 Further, mass transfer at the liquid-vapor interface is included in the form of evaporation, bulk boiling of liquid propellant, and condensation given the appropriate conditions for each. Model validation has proven highly successful against previous analytic models and various Saturn era test data and reasonably successful against more recent LH2 tank self pressurization ground test data. Finally, this model has been applied to numerous design iterations for the Altair Lunar Lander, Ares V Core Stage, and Ares V Earth Departure Stage in order to characterize Helium and autogenous pressurant requirements, propellant lost to evaporation and thermodynamic venting to maintain propellant conditions, and non-uniform tank draining in configurations utilizing multiple LH2 or LO2 propellant tanks. In conclusion, this model provides an accurate and efficient means of analyzing multiple design configurations for any cryogenic propellant tank in launch, low-acceleration coast, or in-space maneuvering and supplies the user with pressurization requirements, unusable propellants from evaporation and liquid stratification, and general ullage gas, liquid, and tank wall conditions as functions of time.

  14. Neurosurgical uses for intraprocedural magnetic resonance imaging.

    PubMed

    Mutchnick, Ian S; Moriarty, Thomas M

    2005-10-01

    Neurosurgical procedures demand precision, and efforts to create accurate neurosurgical navigation have been central to the profession through its history. Magnetic resonance image (MRI)-guided navigation offers the possibility of real-time, image-based stereotactic information for the neurosurgeon, which makes possible a number of diagnostic and therapeutic procedures. This article will review both current options for intraoperative MRI operative suite arrangements and the current therapeutic/diagnostic uses of intraoperative MRI.

  15. Tethered propellant resupply technique for space stations

    NASA Technical Reports Server (NTRS)

    Kroll, K. R.

    1984-01-01

    One of the primary functions of the space station is related to the propellant resupply of orbital transfer vehicles, orbital maneuvering vehicles, and satellites. Difficulties arise in the case of an acquisition of cryogenic propellants by means of a use of zero-gravity techniques. The use of the 'tethered propellant resupply technique' is, therefore, considered. A study is being conducted to determine the feasibility, design requirements, and operational limitations of this technique. Attention is given to aspects of gravity feed, transfer method selection, requirements related to the orbital transfer vehicle, hazard clearance, attitude control, depot operations, end mass velocity, the microgravity laboratory, and concept evaluation activities.

  16. Cryogenic Size Reduction of Solid Propellant

    DTIC Science & Technology

    1993-03-01

    investigatedl: Hazard Class 1. 1 composite modified double base ( CMDB ), Hazard Class 1.1 cross-linked double base (XLDB), and Hazard Class 1.3 hydroxl...Three propellant types were investigated: Class 1.1 composite modified double base ( CMDB ), Class 1.1 cross linked double base (XLDB), and Class 1.3...Removal for HTPB (QDT) Propellant During Task 2B ...... 48 17 Mass Removal for XLDB (WAY) Propellant During Task 2B ..... 49 18 Mass Removal for CMDB

  17. 14 CFR 23.907 - Propeller vibration and fatigue.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Propeller vibration and fatigue. 23.907... General § 23.907 Propeller vibration and fatigue. This section does not apply to fixed-pitch wood propellers of conventional design. (a) The applicant must determine the magnitude of the propeller...

  18. 14 CFR 23.907 - Propeller vibration and fatigue.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Propeller vibration and fatigue. 23.907... General § 23.907 Propeller vibration and fatigue. This section does not apply to fixed-pitch wood propellers of conventional design. (a) The applicant must determine the magnitude of the propeller...

  19. 14 CFR 23.907 - Propeller vibration and fatigue.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Propeller vibration and fatigue. 23.907... General § 23.907 Propeller vibration and fatigue. This section does not apply to fixed-pitch wood propellers of conventional design. (a) The applicant must determine the magnitude of the propeller...

  20. 14 CFR 23.907 - Propeller vibration and fatigue.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Propeller vibration and fatigue. 23.907... General § 23.907 Propeller vibration and fatigue. This section does not apply to fixed-pitch wood propellers of conventional design. (a) The applicant must determine the magnitude of the propeller...

  1. 14 CFR 23.907 - Propeller vibration and fatigue.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Propeller vibration and fatigue. 23.907... General § 23.907 Propeller vibration and fatigue. This section does not apply to fixed-pitch wood propellers of conventional design. (a) The applicant must determine the magnitude of the propeller...

  2. 14 CFR 35.43 - Propeller hydraulic components.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Propeller hydraulic components. 35.43... AIRWORTHINESS STANDARDS: PROPELLERS Tests and Inspections § 35.43 Propeller hydraulic components. Applicants must show by test, validated analysis, or both, that propeller components that contain...

  3. 14 CFR 35.43 - Propeller hydraulic components.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Propeller hydraulic components. 35.43... AIRWORTHINESS STANDARDS: PROPELLERS Tests and Inspections § 35.43 Propeller hydraulic components. Applicants must show by test, validated analysis, or both, that propeller components that contain...

  4. 14 CFR 35.43 - Propeller hydraulic components.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Propeller hydraulic components. 35.43... AIRWORTHINESS STANDARDS: PROPELLERS Tests and Inspections § 35.43 Propeller hydraulic components. Applicants must show by test, validated analysis, or both, that propeller components that contain...

  5. 14 CFR 35.43 - Propeller hydraulic components.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Propeller hydraulic components. 35.43... AIRWORTHINESS STANDARDS: PROPELLERS Tests and Inspections § 35.43 Propeller hydraulic components. Applicants must show by test, validated analysis, or both, that propeller components that contain...

  6. 76 FR 74749 - Critical Parts for Airplane Propellers

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-01

    ... propeller critical parts by requiring a system of processes to identify and manage these parts throughout... propellers. Overview of Proposed Rule Part 35 does not specifically define the term propeller critical part... numerical terms. Propeller Critical Parts (New Sec. 35.16) Our proposed Sec. 35.16 would require...

  7. 14 CFR 35.5 - Propeller ratings and operating limitations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AIRCRAFT AIRWORTHINESS STANDARDS: PROPELLERS General § 35.5 Propeller ratings and operating limitations. (a) Propeller ratings and operating limitations must: (1) Be established by the applicant and approved by the... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Propeller ratings and operating...

  8. Portable propellant cutting assembly, and method of cutting propellant with assembly

    NASA Technical Reports Server (NTRS)

    Sharp, Roger A. (Inventor); Hoskins, Shawn W. (Inventor); Payne, Brett D. (Inventor)

    2002-01-01

    A propellant cutting assembly and method of using the assembly to cut samples of solid propellant in a repeatable and consistent manner is disclosed. The cutting assembly utilizes two parallel extension beams which are shorter than the diameter of a central bore of an annular solid propellant grain and can be loaded into the central bore. The assembly is equipped with retaining heads at its respective ends and an adjustment mechanism to position and wedge the assembly within the central bore. One end of the assembly is equipped with a cutting blade apparatus which can be extended beyond the end of the extension beams to cut into the solid propellant.

  9. DDT Behavior of Porous Propellant Models and Porous Samples of Commercial Propellants,

    DTIC Science & Technology

    1980-03-13

    base ( CMDB ) propellant and is also referred to as a cross-linked double base (XLDB) propellant. EXPERIMENTAL INSTRUMENTATION AND PROCEDURES The...binary AP mixtures that might be expected in composite or CMDB propellants. Each of the three charges was 80% AP. AP/wax was fired at 56.6 and 67.0% TMD...either a CMDB or a composite propellant to which RDX has been added. The Ak content was 9 or 20% and each composition was tested at 70 and 90% TMD; all

  10. Propellers of Minimum Induced Loss, and Water Tunnel Tests of Such a Propeller

    NASA Technical Reports Server (NTRS)

    Larrabee, E. E.

    1975-01-01

    The fundamental vortex theory for a single rotation propeller with a finite number of blades is reviewed. The theory leads to the specification of a radial distribution of bound circulation on each blade for minimum induced loss, analogous to the elliptic spanwise distribution of bound circulation on a wing for minimum induced drag. A propeller designed in accord with this theory has been tested in a water tunnel where it exhibited high efficiency in spite of localized cavitating flow. A knowledge of the flow field for an optimum propeller is of value to the airframe designer seeking to maximize the performance of the airplane-propeller combination.

  11. Development and implementation of a propeller test capability for GL-10 "Greased Lightning" propeller design

    NASA Astrophysics Data System (ADS)

    Duvall, Brian Edward

    Interest in small unmanned aerial vehicles has increased dramatically in recent years. Hybrid vehicles which allow forward flight as a fixed wing aircraft and a true vertical landing capability have always had applications. Management of the available energy and noise associated with electric propeller propulsion systems presents many challenges. NASA Langley has developed the Greased Lightning 10 (GL-10) vertical takeoff, unmanned aerial vehicle with ten individual motors and propellers. All are used for propulsion during takeoff and contribute to acoustic noise pollution which is an identified nuisance to the surrounding users. A propeller test capability was developed to gain an understanding of how the noise can be reduced while meeting minimum thrust requirements. The designed propeller test stand allowed for various commercially available propellers to be tested for potential direct replacement of the current GL-10 propellers and also supported testing of a newly designed propeller provided by the Georgia Institute of Technology. Results from the test program provided insight as to which factors affect the noise as well as performance characteristics. The outcome of the research effort showed that the current GL-10 propeller still represents the best choice of all the candidate propellers tested.

  12. Combustion characteristics of a solid propellant with a charring binder

    NASA Technical Reports Server (NTRS)

    Udlock, D. E.; Strand, L. D.

    1973-01-01

    A brief investigation of the combustion characteristics of a solid propellant containing a binder which chars, as opposed to melting or volatizing, has been made. The burning rate of the propellant with the charring binder was significantly higher than similar propellants containing non-charring binders. High speed motion pictures of the burning propellant showed that the aluminum burned on the regressing surface, rather than a short distance from it as is typical with composite propellants.

  13. An asymptotic theory of supersonic propeller noise

    NASA Astrophysics Data System (ADS)

    Envia, Edmane

    1992-05-01

    A theory for predicting the noise field of supersonic propellers with realistic blade geometries is presented. The theory, which utilizes a large-blade-count approximation, provides an efficient formula for predicting the radiation of sound from all three sources of propeller noise. Comparisons with a full numerical integration indicate that the levels predicted by this formula are quite accurate. Calculations also show that, for high speed propellers, the noise radiated by the Lighthill quadrupole source is rather substantial when compared with the noise radiated by the blade thickness and loading sources. Results from a preliminary application of the theory indicate that the peak noise level generated by a supersonic propeller initially increases with increasing tip helical Mach number, but is eventually reaches a plateau and does not increase further. The predicted trend shows qualitative agreement with the experimental observations.

  14. An asymptotic theory of supersonic propeller noise

    NASA Astrophysics Data System (ADS)

    Envia, Edmane

    A theory for predicting the noise field of a propeller with a realistic blade geometry is presented. The theory, which utilizes a large blade count approximation, provides an efficient formula for predicting the radiation of sound from all three sources of propeller noise. Comparisons with full numerical integration indicate that the noise levels predicted by this formula are quite accurate. Calculations based on this method also show that the radiation from the Lighthill quadrupole source is rather substantial when compared with thickness and loading noise for high speed propellers. A preliminary application of the theory to the problem of the sensitivity of the peak noise levels generated by a supersonic propeller to the variations in its tip helical Mach number has produced a trend that is in qualitative agreement with the experimental observations.

  15. 14 CFR 25.925 - Propeller clearance.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... attitude, whichever is most critical. In addition, there must be positive clearance between the propeller and the ground when in the level takeoff attitude with the critical tire(s) completely deflated...

  16. Catalytic ignition of hydrogen and oxygen propellants

    NASA Technical Reports Server (NTRS)

    Zurawski, Robert L.; Green, James M.

    1988-01-01

    An experimental program was conducted to evaluate the catalytic ignition of gaseous hydrogen and oxygen propellants. Shell 405 granular catalyst and a monolithic sponge catalyst were tested. Mixture ratio, mass flow rate, propellant temperature, and back pressure were varied parametrically in testing to determine the operational limits of the catalytic igniter. The test results show that the gaseous hydrogen and oxygen propellant combination can be ignited catalytically using Shell 405 catalyst over a wide range of mixture ratios, mass flow rates, and propellant injection temperatures. These operating conditions must be optimized to ensure reliable ignition for an extended period of time. A cyclic life of nearly 2000, 2 sec pulses at nominal operating conditions was demonstrated with the catalytic igniter. The results of the experimental program and the established operational limits for a catalytic igniter using the Shell 405 catalyst are presented.

  17. 14 CFR 23.905 - Propellers.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... must have a means to unfeather it in flight. (d) The propeller blade pitch control system must meet the..., and other removable items must be designed to ensure that they will not separate from the airplane...

  18. 14 CFR 23.905 - Propellers.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... must have a means to unfeather it in flight. (d) The propeller blade pitch control system must meet the..., and other removable items must be designed to ensure that they will not separate from the airplane...

  19. 14 CFR 23.905 - Propellers.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... must have a means to unfeather it in flight. (d) The propeller blade pitch control system must meet the..., and other removable items must be designed to ensure that they will not separate from the airplane...

  20. 14 CFR 23.905 - Propellers.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... must have a means to unfeather it in flight. (d) The propeller blade pitch control system must meet the..., and other removable items must be designed to ensure that they will not separate from the airplane...

  1. 14 CFR 23.905 - Propellers.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... must have a means to unfeather it in flight. (d) The propeller blade pitch control system must meet the..., and other removable items must be designed to ensure that they will not separate from the airplane...

  2. Nuclear thermal rockets using indigenous Martian propellants

    SciTech Connect

    Zubrin, R.M.

    1989-01-01

    This paper considers a novel concept for a Martian descent and ascent vehicle, called NIMF (for nuclear rocket using indigenous Martian fuel), the propulsion for which will be provided by a nuclear thermal reactor which will heat an indigenous Martian propellant gas to form a high-thrust rocket exhaust. The performance of each of the candidate Martian propellants, which include CO2, H2O, CH4, N2, CO, and Ar, is assessed, and the methods of propellant acquisition are examined. Attention is also given to the issues of chemical compatibility between candidate propellants and reactor fuel and cladding materials, and the potential of winged Mars supersonic aircraft driven by this type of engine. It is shown that, by utilizing the nuclear landing craft in combination with a hydrogen-fueled nuclear thermal interplanetary vehicle and a heavy lift booster, it is possible to achieve a manned Mars mission in one launch. 6 refs.

  3. An asymptotic theory of supersonic propeller noise

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    1992-01-01

    A theory for predicting the noise field of a propeller with a realistic blade geometry is presented. The theory, which utilizes a large blade count approximation, provides an efficient formula for predicting the radiation of sound from all three sources of propeller noise. Comparisons with full numerical integration indicate that the noise levels predicted by this formula are quite accurate. Calculations based on this method also show that the radiation from the Lighthill quadrupole source is rather substantial when compared with thickness and loading noise for high speed propellers. A preliminary application of the theory to the problem of the sensitivity of the peak noise levels generated by a supersonic propeller to the variations in its tip helical Mach number has produced a trend that is in qualitative agreement with the experimental observations.

  4. Welcome to the Saclay Propeller Testing Center

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The history, organization, purpose, and activities of the Saclay Propeller Testing Center is described. A list is provided of all facilities, current and planned, and the types of tests done in each facility are summarized.

  5. 14 CFR 35.22 - Feathering propellers.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... intended to feather from all flight conditions, taking into account expected wear and leakage. Any... control systems that use engine oil to feather must incorporate a method to allow the propeller to...

  6. 14 CFR 35.22 - Feathering propellers.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... intended to feather from all flight conditions, taking into account expected wear and leakage. Any... control systems that use engine oil to feather must incorporate a method to allow the propeller to...

  7. 14 CFR 35.22 - Feathering propellers.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... intended to feather from all flight conditions, taking into account expected wear and leakage. Any... control systems that use engine oil to feather must incorporate a method to allow the propeller to...

  8. 14 CFR 35.22 - Feathering propellers.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... intended to feather from all flight conditions, taking into account expected wear and leakage. Any... control systems that use engine oil to feather must incorporate a method to allow the propeller to...

  9. 14 CFR 35.22 - Feathering propellers.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... intended to feather from all flight conditions, taking into account expected wear and leakage. Any... control systems that use engine oil to feather must incorporate a method to allow the propeller to...

  10. Active cooling requirements for propellant storage

    NASA Technical Reports Server (NTRS)

    Klein, G. A.

    1984-01-01

    Recent NASA and DOD mission models have indicated future needs for orbital cryogenic storage and supply systems. Two thermal control systems which show the greatest promise for improving propellant storage life were evaluated. One system was an open cycle thermodynamic vent type with a refrigeration system for partial hydrogen reliquefaction located at the LH2 tank and a vapor cooled shield for integrated and non-integrated tank designs to reduce boiloff. The other was a closed system with direct refrigeration at the LH2 tank. A reversed Brayton cycle unit was baselined for the propellant processor. It is concluded that: (1) reliquefaction systems are not attractive for minimizing propellant boiloff; (2) open cycle systems may not be economically attractive for long term storage; (3) a number of refrigeration systems are available to assist in the long term storage of cryogenic propellants; and (4) shields can significantly improve the performance of mechanical coolers.

  11. Investigations Into Tank Venting for Propellant Resupply

    NASA Technical Reports Server (NTRS)

    Hearn, H. C.; Harrison, Robert A. (Technical Monitor)

    2002-01-01

    Models and simulations have been developed and applied to the evaluation of propellant tank ullage venting, which is integral to one approach for propellant resupply. The analytical effort was instrumental in identifying issues associated with resupply objectives, and it was used to help develop an operational procedure to accomplish the desired propellant transfer for a particular storable bipropellant system. Work on the project was not completed, and several topics have been identified as requiring further study; these include the potential for liquid entrainment during the low-g and thermal/freezing effects in the vent line and orifice. Verification of the feasibility of this propellant venting and resupply approach still requires additional analyses as well as testing to investigate the fluid and thermodynamic phenomena involved.

  12. Catalytic ignition of hydrogen and oxygen propellants

    NASA Technical Reports Server (NTRS)

    Zurawski, Robert L.; Green, James M.

    1988-01-01

    An experimental program was conducted to evaluate the catalytic ignition of gaseous hydrogen and oxygen propellants. Shell 405 granular catalyst and a monolithic sponge catalyst were tested. Mixture ratio, mass flow rate, propellant temperature, and back pressure were varied parametrically in testing to determine the operational limits of the catalytic igniter. The test results show that the gaseous hydrogen and oxygen propellant combination can be ignited catalytically using Shell 405 catalyst over a wide range of mixture ratios, mass flow rates, and propellant injection temperatures. These operating conditions must be optimized to ensure reliable ignition for an extended period of time. A cyclic life of nearly 2000, 2 sec pulses at nominal operating conditions was demonstrated with the catalytic igniter. The results of the experimental program and the established operational limits for a catalytic igniter using the Shell 405 catalysts are presented.

  13. Propellers in Saturn A and B rings

    NASA Astrophysics Data System (ADS)

    Sremcevic, Miodrag; Stewart, Glen R.; Albers, Nicole; Esposito, Larry W.

    2014-11-01

    Propellers are gravitational signatures of small embedded moonlets within Saturn's rings. Even if the objects are too small to be directly observed, each body creates a much larger "S" shaped undulation on the rings. In this paper we present new results about by now classical A ring propellers and more enigmatic B ring population. In 2008 we obtained a UVIS occultation of the largest A ring propeller Bleriot. Utilizing Cassini ISS images we obtain Bleriot orbit and demonstrate that UVIS occultation did cut across Bleriot about 100km downstream from the center. The occultation itself shows a prominent partial gap and higher density outer flanking wakes, while their orientation is consistent with a downstream cut. Using simple model of the induced moonlet wakes we obtain that the size of the embedded body is about 400m, consistent with other estimates. While in the UVIS occultation the partial gap is more prominent than the flanking wakes, the features mostly seen in Bleriot images are actually flanking wakes. This result has been confirmed in another UVIS occultation from 2012.One of the most interesting aspects of the A ring propellers are their wanderings, or longitudinal deviations from a pure circular orbit We numerically investigated the possibility of simple moon driven librations. We adopted HNbody numerical integrator and checked forpossible influence of Saturnian satellites. We found that some of A ring propellers indeed respond to the satellites. Earhart and Sikorsky are strongly perturbed by 415:416 and 293:294 mean longitude resonances with Pan and propellers close to the Keeler gap are allperturbed by Daphnis.While the A ring propellers are not far from the Roche zone limit, propellers within the B ring come as a surprise. Simple expectation has been that the strong shear rate in the inner rings would tear bodies apart, which in turn requires stronger evidence for the B ring propellers. In B ring we discovered 12 propellers in 21 ISS NAC images (both

  14. Workshop on Explosive and Propellant Combustion Mechanisms

    DTIC Science & Technology

    1991-07-01

    REFERENCES; 1. J. H. Stufflebeam and A. C Eckbreth, "CARS Diagnostics of Solid Propellant Combustion at Elevated Pressure", Combustion Science and...Paper Number ATAA-89-0060, 1989; J. H. Stufflebeam , "Temperature and Multiple Species CARS Measurements of Solid Propellant Flames", 26th JANNAF...those of Stufflebeam (UTRC), Edwards (AFAL), Vanderhoff (BRL), Lengelle (ONERA, France), and other groups in the US, Netherlands, and Soviet Union

  15. Composite Propellant combustion and Transition to Detonation.

    DTIC Science & Technology

    1981-02-01

    I combustion BYU Brigham Young University I CMDB Composite-modified double-base propellant CPIA Chemical Propulsion Information Agency (at Johns...incorporate a model of active binder combustion and apply the model to composite-modified double-base ( CMDB ) propellants. The porous burner apparatus...Hercules composite-modified double-base ( CMDB ) pro- pellants, containing AP or HMX, but not containing aluminum. Qualita- tive effects of composition and

  16. Propeller/fan-pitch feathering apparatus

    NASA Technical Reports Server (NTRS)

    Schilling, Jan C. (Inventor); Adamson, Arthur P. (Inventor); Bathori, Julius (Inventor); Walker, Neil (Inventor)

    1990-01-01

    A pitch feathering system for a gas turbine driven aircraft propeller having multiple variable pitch blades utilizes a counter-weight linked to the blades. The weight is constrained to move, when effecting a pitch change, only in a radial plane and about an axis which rotates about the propeller axis. The system includes a linkage allowing the weight to move through a larger angle than the associated pitch change of the blade.

  17. Modelling the wash from a ship's propeller

    NASA Astrophysics Data System (ADS)

    Brewster, Paul Michael

    The characteristics of the velocity field produced by a ship's propeller were investigated using a commercial Computational Fluid Dynamics (CFD) software package. A CFD model of the propeller wash was developed using a sliding mesh technique to simulate the rotating blades of the propeller. Experimental measurements using Laser Doppler Anemometry and Pitot tube methods were used to validate the computational approach. Measurements and predictions of the axial and radial velocity fields for two propellers operating over a range of speeds were used in the validation. The results from the CFD simulation are in reasonable agreement. However, improvements to the approach used to model the turbulence in the flow may lead to a more accurate simulation. The validated CFD approach is used to investigate the propeller wash where an experimental study has been difficult or impossible to undertake. The velocity field close to the rotating blades was found to exhibit a pulsing behaviour. The characteristics of the pulsing are related to the speed of rotation and the geometrical characteristics of the rotating propeller. The tangential velocity field was found to be more prominent in the wash than the radial component of velocity. However, the axial component of velocity is the largest contributor to the resultant velocity field in the propeller wash. The formation of the tangential velocity field is related to the geometrical characteristics of the rotating blades. The diffusion characteristics of the tangential velocity field appear to be influenced by the behaviour of the axial velocity field. The maximum tangential velocity decays exponentially. The simulation of a full-size propeller was used to verify the scaling approach adopted for previous experimental investigations. The results indicated that scale effects due to viscosity were negligible, and the use of Froudian scaling for the experimental investigations was justified.

  18. Propellant for the NASA Standard Initiator

    NASA Technical Reports Server (NTRS)

    Hohmann, Carl; Tipton, Bill, Jr.; Dutton, Maureen

    2000-01-01

    This paper discusses processes employed in manufacturing zirconium-potassium perchlorate propellant for the NASA standard initiator. It provides both a historical background on the NSI device-detailing problem areas and their resolution--and on propellant blending techniques. Emphasis is placed on the precipitation blending method. The findings on mixing equipment, processing, and raw materials are described. Also detailed are findings on the bridgewire slurry operation, one of the critical steps in the production of the NASA standard initiator.

  19. Combustion Instability in Solid Propellant Rockets

    DTIC Science & Technology

    1989-03-21

    pressure oscillations. Unless the combustor is specially designed for such conditions, it can be destroyed by pressure excesses, severe heating , or...double base propellant charges that were ejected during nozzle release (due to over-pressure) were found to be heated in a way not attributable to any...Propellants are generally very poor heat conductors. Therefore, they can be heated rapidly to a surface temperature that leads to chemical reaction and flame at

  20. TU-F-CAMPUS-J-02: Evaluation of Textural Feature Extraction for Radiotherapy Response Assessment of Early Stage Breast Cancer Patients Using Diffusion Weighted MRI and Dynamic Contrast Enhanced MRI

    SciTech Connect

    Xie, Y; Wang, C; Horton, J; Chang, Z

    2015-06-15

    Purpose: To investigate the feasibility of using classic textural feature extraction in radiotherapy response assessment, we studied a unique cohort of early stage breast cancer patients with paired pre - and post-radiation Diffusion Weighted MRI (DWI-MRI) and Dynamic Contrast Enhanced MRI (DCE-MRI). Methods: 15 female patients from our prospective phase I trial evaluating preoperative radiotherapy were included in this retrospective study. Each patient received a single-fraction radiation treatment, and DWI and DCE scans were conducted before and after the radiotherapy. DWI scans were acquired using a spin-echo EPI sequence with diffusion weighting factors of b = 0 and b = 500 mm{sup 2} /s, and the apparent diffusion coefficient (ADC) maps were calculated. DCE-MRI scans were acquired using a T{sub 1}-weighted 3D SPGR sequence with a temporal resolution of about 1 minute. The contrast agent (CA) was intravenously injected with a 0.1 mmol/kg bodyweight dose at 2 ml/s. Two parameters, volume transfer constant (K{sup trans} ) and k{sub ep} were analyzed using the two-compartment Tofts kinetic model. For DCE parametric maps and ADC maps, 33 textural features were generated from the clinical target volume (CTV) in a 3D fashion using the classic gray level co-occurrence matrix (GLCOM) and gray level run length matrix (GLRLM). Wilcoxon signed-rank test was used to determine the significance of each texture feature’s change after the radiotherapy. The significance was set to 0.05 with Bonferroni correction. Results: For ADC maps calculated from DWI-MRI, 24 out of 33 CTV features changed significantly after the radiotherapy. For DCE-MRI pharmacokinetic parameters, all 33 CTV features of K{sup trans} and 33 features of k{sub ep} changed significantly. Conclusion: Initial results indicate that those significantly changed classic texture features are sensitive to radiation-induced changes and can be used for assessment of radiotherapy response in breast cancer.