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Sample records for intraprocedural diffusion-weighted propeller

  1. Intraprocedural Diffusion-Weighted PROPELLER MRI to Guide Percutaneous Biopsy Needle Placement within Rabbit VX2 Liver Tumors

    PubMed Central

    Deng, Jie; Virmani, Sumeet; Yang, Guang-Yu; Tang, Richard; Woloschak, Gayle; Omary, Reed A.; Larson, Andrew C.

    2010-01-01

    Purpose To test the hypothesis that diffusion-weighted (DW)-PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) magnetic resonance imaging (MRI) can be used to guide biopsy needle placement during percutaneous interventional procedures to selectively target viable and necrotic tissues within VX2 rabbit liver tumors. Materials and Methods Our institutional Animal Care and Use Committee approved all experiments. In six rabbits implanted with 15 VX2 liver tumors, baseline DWPROPELLER images acquired prior to the interventional procedure were used for apparent diffusion coefficient (ADC) measurements. Next, intraprocedural DW-PROPELLER scans were performed with needle position iteratively adjusted to target viable, necrotic, or intermediate border tissue regions. DW-PROPELLER ADC measurements at the selected needle tip locations were compared with the percentage of tumor necrosis qualitatively assessed at histopathology. Results DW-PROPELLER images demonstrated intratumoral tissue heterogeneity and clearly depicted the needle tip position within viable and necrotic tumor tissues. Mean ADC measurements within the region-of-interest encompassing the needle tip were highly correlated with histopathologic tumor necrotic tissue assessments. Conclusion DW-PROPELLER is an effective method to selectively position the biopsy needle tip within viable and necrotic tumor tissues. The DW-PROPELLER method may offer an important complementary tool for functional guidance during MR-guided percutaneous procedures. PMID:19629976

  2. Multishot diffusion-weighted SPLICE PROPELLER MRI of the abdomen.

    PubMed

    Deng, Jie; Omary, Reed A; Larson, Andrew C

    2008-05-01

    Multishot FSE (fast spin echo)-based diffusion-weighted (DW)-PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) MRI offers the potential to reduce susceptibility artifacts associated with single-shot DW-EPI (echo-planar imaging) approaches. However, DW-PROPELLER in the abdomen is challenging due to the large field-of-view and respiratory motion during DW preparation. Incoherent signal phase due to motion will violate the Carr-Purcell-Meiboom-Gill (CPMG) conditions, leading to destructive interference between spin echo and stimulated echo signals and consequent signal cancellation. The SPLICE (split-echo acquisition of FSE signals) technique can mitigate non-CPMG artifacts in FSE-based sequences. For SPLICE, spin echo and stimulated echo are separated by using imbalanced readout gradients and extended acquisition window. Two signal families each with coherent phase properties are acquired at different intervals within the readout window. Separate reconstruction of these two signal families can avoid destructive phase interference. Phantom studies were performed to validate signal phase properties with different initial magnetization phases. This study evaluated the feasibility of combining SPLICE and PROPELLER for DW imaging of the abdomen. It is demonstrated that DW-SPLICE-PROPELLER can effectively mitigate non-CPMG artifacts and improve DW image quality and apparent diffusion coefficient (ADC) map homogeneity. PMID:18429036

  3. X-PROP: a fast and robust diffusion-weighted propeller technique.

    PubMed

    Li, Zhiqiang; Pipe, James G; Lee, Chu-Yu; Debbins, Josef P; Karis, John P; Huo, Donglai

    2011-08-01

    Diffusion-weighted imaging (DWI) has shown great benefits in clinical MR exams. However, current DWI techniques have shortcomings of sensitivity to distortion or long scan times or combinations of the two. Diffusion-weighted echo-planar imaging (EPI) is fast but suffers from severe geometric distortion. Periodically rotated overlapping parallel lines with enhanced reconstruction diffusion-weighted imaging (PROPELLER DWI) is free of geometric distortion, but the scan time is usually long and imposes high Specific Absorption Rate (SAR) especially at high fields. TurboPROP was proposed to accelerate the scan by combining signal from gradient echoes, but the off-resonance artifacts from gradient echoes can still degrade the image quality. In this study, a new method called X-PROP is presented. Similar to TurboPROP, it uses gradient echoes to reduce the scan time. By separating the gradient and spin echoes into individual blades and removing the off-resonance phase, the off-resonance artifacts in X-PROP are minimized. Special reconstruction processes are applied on these blades to correct for the motion artifacts. In vivo results show its advantages over EPI, PROPELLER DWI, and TurboPROP techniques. PMID:21661046

  4. 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.

  5. 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. PMID:23008151

  6. Quality Control of Diffusion Weighted Images

    PubMed Central

    Liu, Zhexing; Wang, Yi; Gerig, Guido; Gouttard, Sylvain; Tao, Ran; Fletcher, Thomas; Styner, Martin

    2013-01-01

    Diffusion Tensor Imaging (DTI) has become an important MRI procedure to investigate the integrity of white matter in brain in vivo. DTI is estimated from a series of acquired Diffusion Weighted Imaging (DWI) volumes. DWI data suffers from inherent low SNR, overall long scanning time of multiple directional encoding with correspondingly large risk to encounter several kinds of artifacts. These artifacts can be too severe for a correct and stable estimation of the diffusion tensor. Thus, a quality control (QC) procedure is absolutely necessary for DTI studies. Currently, routine DTI QC procedures are conducted manually by visually checking the DWI data set in a gradient by gradient and slice by slice way. The results often suffer from low consistence across different data sets, lack of agreement of different experts, and difficulty to judge motion artifacts by qualitative inspection. Additionally considerable manpower is needed for this step due to the large number of images to QC, which is common for group comparison and longitudinal studies, especially with increasing number of diffusion gradient directions. We present a framework for automatic DWI QC. We developed a tool called DTIPrep which pipelines the QC steps with a detailed protocoling and reporting facility. And it is fully open source. This framework/tool has been successfully applied to several DTI studies with several hundred DWIs in our lab as well as collaborating labs in Utah and Iowa. In our studies, the tool provides a crucial piece for robust DTI analysis in brain white matter study. PMID:24353379

  7. Diffusion-weighted imaging of pancreatic cancer.

    PubMed

    De Robertis, Riccardo; Tinazzi Martini, Paolo; Demozzi, Emanuele; Dal Corso, Flavia; Bassi, Claudio; Pederzoli, Paolo; D'Onofrio, Mirko

    2015-10-28

    Magnetic resonance imaging (MRI) is a reliable and accurate imaging method for the evaluation of patients with pancreatic ductal adenocarcinoma (PDAC). Diffusion-weighted imaging (DWI) is a relatively recent technological improvement that expanded MRI capabilities, having brought functional aspects into conventional morphologic MRI evaluation. DWI can depict the random diffusion of water molecules within tissues (the so-called Brownian motions). Modifications of water diffusion induced by different factors acting on the extracellular and intracellular spaces, as increased cell density, edema, fibrosis, or altered functionality of cell membranes, can be detected using this MR sequence. The intravoxel incoherent motion (IVIM) model is an advanced DWI technique that consent a separate quantitative evaluation of all the microscopic random motions that contribute to DWI, which are essentially represented by molecular diffusion and blood microcirculation (perfusion). Technological improvements have made possible the routine use of DWI during abdominal MRI study. Several authors have reported that the addition of DWI sequence can be of value for the evaluation of patients with PDAC, especially improving the staging; nevertheless, it is still unclear whether and how DWI could be helpful for identification, characterization, prognostic stratification and follow-up during treatment. The aim of this paper is to review up-to-date literature data regarding the applications of DWI and IVIM to PDACs. PMID:26516428

  8. Diffusion-weighted imaging of pancreatic cancer

    PubMed Central

    De Robertis, Riccardo; Tinazzi Martini, Paolo; Demozzi, Emanuele; Dal Corso, Flavia; Bassi, Claudio; Pederzoli, Paolo; D’Onofrio, Mirko

    2015-01-01

    Magnetic resonance imaging (MRI) is a reliable and accurate imaging method for the evaluation of patients with pancreatic ductal adenocarcinoma (PDAC). Diffusion-weighted imaging (DWI) is a relatively recent technological improvement that expanded MRI capabilities, having brought functional aspects into conventional morphologic MRI evaluation. DWI can depict the random diffusion of water molecules within tissues (the so-called Brownian motions). Modifications of water diffusion induced by different factors acting on the extracellular and intracellular spaces, as increased cell density, edema, fibrosis, or altered functionality of cell membranes, can be detected using this MR sequence. The intravoxel incoherent motion (IVIM) model is an advanced DWI technique that consent a separate quantitative evaluation of all the microscopic random motions that contribute to DWI, which are essentially represented by molecular diffusion and blood microcirculation (perfusion). Technological improvements have made possible the routine use of DWI during abdominal MRI study. Several authors have reported that the addition of DWI sequence can be of value for the evaluation of patients with PDAC, especially improving the staging; nevertheless, it is still unclear whether and how DWI could be helpful for identification, characterization, prognostic stratification and follow-up during treatment. The aim of this paper is to review up-to-date literature data regarding the applications of DWI and IVIM to PDACs. PMID:26516428

  9. 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. PMID:25219332

  10. Technique of diffusion weighted imaging and its application in stroke

    NASA Astrophysics Data System (ADS)

    Li, Enzhong; Tian, Jie; Han, Ying; Wang, Huifang; Li, Wu; He, Huiguang

    2003-05-01

    To study the application of diffusion weighted imaging and image post processing in the diagnosis of stroke, especially in acute stroke, 205 patients were examined by 1.5 T or 1.0 T MRI scanner and the images such as T1, T2 and diffusion weighted images were obtained. Image post processing was done with "3D Med System" developed by our lab to analyze data and acquire the apparent diffusion coefficient (ADC) map. In acute and subacute stage of stroke, the signal in cerebral infarction areas changed to hyperintensity in T2- and diffusion-weighted images, normal or hypointensity in T1-weighted images. In hyperacute stage, however, the signal was hyperintense just in the diffusion weighted imaes; others were normal. In the chronic stage, the signal in T1- and diffusion-weighted imaging showed hypointensity and hyperintensity in T2 weighted imaging. Because ADC declined obviously in acute and subacute stage of stroke, the lesion area was hypointensity in ADC map. With the development of the disease, ADC gradually recovered and then changed to hyperintensity in ADC map in chronic stage. Using diffusion weighted imaging and ADC mapping can make a diagnosis of stroke, especially in the hyperacute stage of stroke, and can differentiate acute and chronic stroke.

  11. [Diffusion Weighted Magnetic Resonance Imaging and its Application in Ophthalmology].

    PubMed

    Lindner, T; Langner, S; Paul, K; Pohlmann, A; Hadlich, S; Niendorf, T; Jünemann, A; Guthoff, R F; Stachs, O

    2015-12-01

    The value of diffusion-weighted magnet resonance imaging (DWI-MRI) has been demonstrated for an ever growing range of clinical indications. DWI is sensitive to the diffusion of water molecules and probes their random displacement within tissue. DWI provides both qualitative and quantitative information on tissue characteristics, e.g. tissue cellularity. This review provides an overview of diffusion-weighted imaging and its emerging applications in ophthalmology. The basic physics and technical foundations of DWI are introduced. The emerging applications of DWI are surveyed, particularly in diseases of the eye, orbit and optical nerve. PMID:26678901

  12. Diffusion-weighted imaging in pediatric body magnetic resonance imaging.

    PubMed

    Chavhan, Govind B; Caro-Dominguez, Pablo

    2016-05-01

    Diffusion-weighted MRI is being increasingly used in pediatric body imaging. Its role is still emerging. It is used for detection of tumors and abscesses, differentiation of benign and malignant tumors, and detection of inflamed bowel segments in inflammatory bowel disease in children. It holds great promise in the assessment of therapy response in body tumors, with apparent diffusion coefficient (ADC) value as a potential biomarker. Significant overlap of ADC values of benign and malignant processes and less reproducibility of ADC measurements are hampering its widespread use in clinical practice. With standardization of the technique, diffusion-weighted imaging (DWI) is likely to be used more frequently in clinical practice. We discuss the principles and technique of DWI, selection of b value, qualitative and quantitative assessment, and current status of DWI in evaluation of disease processes in the pediatric body. PMID:27229502

  13. Reversible diffusion weighted imaging changes in propionic acidemia.

    PubMed

    Kandel, Amit; Amatya, Sirisa Kandel; Yeh, E Ann

    2013-01-01

    Propionic acidemia is an inborn error of metabolism with neurologic manifestations. We describe a 3-year-old boy with propionic acidemia presenting with a metabolic crisis including headache, vomiting, and altered mental status with metabolic acidosis. Electroencephalography showed focal slowing in right temporal region. Magnetic resonance imaging (MRI) of the brain showed restricted diffusion with apparent diffusion coefficient correlate in the right parietooccipital region. Correction of metabolic acidosis led to clinical improvement and normalization of MRI diffusion weighted imaging/apparent diffusion coefficient changes. This article suggests that restricted diffusion resulting from metabolic crises in propionic acidemia may be reversible in some cases. PMID:22532545

  14. DIFFUSION-WEIGHTED IMAGING OF THE LIVER: TECHNIQUES AND APPLICATIONS

    PubMed Central

    Lewis, Sara; Dyvorne, Hadrien; Cui, Yong; Taouli, Bachir

    2014-01-01

    SYNOPSIS Diffusion weighted MRI (DWI) is a technique that assesses the cellularity, tortuosity of the extracellular/extravascular space and cell membrane density based upon differences in water proton mobility in tissues. The strength of the diffusion weighting is reflected by the b-value. DWI using several b-values enables quantification of the apparent diffusion coefficient (ADC). DWI is increasingly employed in liver imaging for multiple reasons: it can add useful qualitative and quantitative information to conventional imaging sequences, it is acquired relatively quickly, it is easily incorporated into existing clinical protocols, and it is a non-contrast technique. DWI is useful for focal liver lesion detection and characterization, for the assessment of post-treatment tumor response and for evaluation of diffuse liver disease. ADC quantification can be used to characterize lesions as cystic/necrotic or solid and for predicting tumor response to therapy. Advanced diffusion methods such as IVIM (intravoxel incoherent motion) may have potential for detection, staging and evaluation of the progression of liver fibrosis and for liver lesion characterization. The lack of standardization of DWI technique including choice of b-values and sequence parameters has somewhat limited its widespread adoption. PMID:25086935

  15. Diffusion-weighted MR imaging in gynecologic cancers.

    PubMed

    Motoshima, Shigenobu; Irie, Hiroyuki; Nakazono, Takahiko; Kamura, Toshiharu; Kudo, Sho

    2011-12-01

    Diffusion-weighted imaging (DWI) reflects changes in proton mobility caused by pathological alterations of tissue cellularity, cellular membrane integrity, extracellular space perfusion, and fluid viscosity. Functional imaging is becoming increasingly important in the evaluation of cancer patients because of the limitations of morphologic imaging. DWI is being applied to the detection and characterization of tumors and the evaluation of treatment response in patients with cancer. The advantages of DWI include its cost-effectiveness and brevity of execution, its complete noninvasiveness, its lack of ionizing radiation, and the fact that it does not require injection of contrast material, thus enabling its use in patients with renal dysfunction. In this article, we describe the clinical application of DWI to gynecological disorders and its diagnostic efficacy therein. PMID:22247805

  16. Super-resolution in diffusion-weighted imaging.

    PubMed

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

    2011-01-01

    Diffusion-weighted imaging (DWI) enables non-invasive investigation and characterization of the white-matter but suffers from a relatively poor resolution. In this work we propose a super-resolution reconstruction (SRR) technique based on the acquisition of multiple anisotropic orthogonal DWI scans. We address the problem of patient motions by aligning the volumes both in space and in q-space. The SRR is formulated as a maximum a posteriori (MAP) problem. It relies on a volume acquisition model which describes the generation of the acquired scans from the unknown high-resolution image. It enables the introduction of image priors that exploit spatial homogeneity and enables regularized solutions. We detail our resulting SRR optimization procedure and report various experiments including numerical simulations, synthetic SRR scenario and real world SRR scenario. Super-resolution reconstruction in DWI may enable DWI to be performed with unprecedented resolution. PMID:21995021

  17. Diffusion weighted magnetic resonance imaging and its recent trend—a survey

    PubMed Central

    Chilla, Geetha Soujanya; Tan, Cher Heng

    2015-01-01

    Since its inception in 1985, diffusion weighted magnetic resonance imaging has been evolving and is becoming instrumental in diagnosis and investigation of tissue functions in various organs including brain, cartilage, and liver. Even though brain related pathology and/or investigation remains as the main application, diffusion weighted magnetic resonance imaging (DWI) is becoming a standard in oncology and in several other applications. This review article provides a brief introduction of diffusion weighted magnetic resonance imaging, challenges involved and recent advancements. PMID:26029644

  18. Diffusion-weighted MR imaging for characterizing musculoskeletal lesions.

    PubMed

    Subhawong, Ty K; Jacobs, Michael A; Fayad, Laura M

    2014-01-01

    Diffusion-weighted (DW) imaging is a functional magnetic resonance (MR) imaging technique that can readily be incorporated into a routine non-contrast material-enhanced MR imaging protocol with little additional scanning time. DW imaging is based on changes in the Brownian motion of water molecules caused by tissue microstructure. The apparent diffusion coefficient (ADC) is a quantitative measure of Brownian movement: Low ADC values typically reflect highly cellular microenvironments in which diffusion is restricted by the presence of cell membranes, whereas acellular regions allow free diffusion and result in elevated ADC values. Thus, with ADC mapping, one may derive useful quantitative information regarding the cellularity of a musculoskeletal lesion using a nonenhanced technique. The role of localized DW imaging in differentiating malignant from benign osseous and soft-tissue lesions is still evolving; when carefully applied, however, this modality has proved helpful in a subset of tumor types, such as nonmyxoid soft-tissue tumors. Studies of the use of DW imaging in assessing the treatment response of both osseous and soft-tissue tumors have shown that higher ADC values correlate with better response to cytotoxic therapy. Successful application of DW imaging in the evaluation of musculoskeletal lesions requires familiarity with potential diagnostic pitfalls that stem from technical artifacts and confounding factors unrelated to lesion cellularity. Further investigation is needed to evaluate the impact of DW imaging-ADC mapping on management and outcome in patients with musculoskeletal lesions. PMID:25208274

  19. Diffusion weighted imaging in gynecological malignancies - present and future

    PubMed Central

    Manoharan, Dinesh; Das, Chandan J; Aggarwal, Ankita; Gupta, Arun K

    2016-01-01

    The management of gynaecological malignancies has undergone a significant change in recent years with our improved understanding of cancer biogenetics, development of new treatment regimens and enhanced screening. Due to the rapid blooming of newer methods and techniques in gynaecology, surgery and oncology the scope and the role of imaging has also widened. Functional imaging in the form of diffusion weighted imaging (DWI) has been recently found to be very useful in assessing various tumours. Its ability to identify changes in the molecular level has dramatically changed the diagnostic approach of radiologists which was solely based on morphological criteria. It can improve the diagnostic accuracy of conventional magnetic resonance imaging, lend a hand in assessing tumour response to treatment regimens and detect tumour recurrence with better spatial resolution, negative radiation and diagnostic accuracy compared to positron emission tomography scan. The ability to quantify the diffusion has also lead to potential prediction of tumour aggressiveness and grade which directly correlate with the patient prognosis and management. Hence, it has become imperative for a radiologist to understand the concepts of DWI and its present and evolving role. In this article we present a brief description of the basics of DWI followed by its role in evaluation of female gynaecological malignancies. PMID:27027614

  20. Semiautomated spleen volumetry with diffusion-weighted MR imaging.

    PubMed

    Lee, Jeongjin; Kim, Kyoung Won; Lee, Ho; Lee, So Jung; Choi, Sanghyun; Jeong, Woo Kyoung; Kye, Heewon; Song, Gi-Won; Hwang, Shin; Lee, Sung-Gyu

    2012-07-01

    In this article, we determined the relative accuracy of semiautomated spleen volumetry with diffusion-weighted (DW) MR images compared to standard manual volumetry with DW-MR or CT images. Semiautomated spleen volumetry using simple thresholding followed by 3D and 2D connected component analysis was performed with DW-MR images. Manual spleen volumetry was performed on DW-MR and CT images. In this study, 35 potential live liver donor candidates were included. Semiautomated volumetry results were highly correlated with manual volumetry results using DW-MR (r = 0.99; P < 0.0001; mean percentage absolute difference, 1.43 ± 0.94) and CT (r = 0.99; P < 0.0001; 1.76 ± 1.07). Mean total processing time for semiautomated volumetry was significantly shorter compared to that of manual volumetry with DW-MR (P < 0.0001) and CT (P < 0.0001). In conclusion, semiautomated spleen volumetry with DW-MR images can be performed rapidly and accurately when compared with standard manual volumetry. PMID:22161960

  1. 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. PMID:21110195

  2. Diffusion weighted imaging in gynecological malignancies - present and future.

    PubMed

    Manoharan, Dinesh; Das, Chandan J; Aggarwal, Ankita; Gupta, Arun K

    2016-03-28

    The management of gynaecological malignancies has undergone a significant change in recent years with our improved understanding of cancer biogenetics, development of new treatment regimens and enhanced screening. Due to the rapid blooming of newer methods and techniques in gynaecology, surgery and oncology the scope and the role of imaging has also widened. Functional imaging in the form of diffusion weighted imaging (DWI) has been recently found to be very useful in assessing various tumours. Its ability to identify changes in the molecular level has dramatically changed the diagnostic approach of radiologists which was solely based on morphological criteria. It can improve the diagnostic accuracy of conventional magnetic resonance imaging, lend a hand in assessing tumour response to treatment regimens and detect tumour recurrence with better spatial resolution, negative radiation and diagnostic accuracy compared to positron emission tomography scan. The ability to quantify the diffusion has also lead to potential prediction of tumour aggressiveness and grade which directly correlate with the patient prognosis and management. Hence, it has become imperative for a radiologist to understand the concepts of DWI and its present and evolving role. In this article we present a brief description of the basics of DWI followed by its role in evaluation of female gynaecological malignancies. PMID:27027614

  3. 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.

  4. Resolution of early diffusion-weighted and FLAIR MRI abnormalities in a patient with TIA.

    PubMed

    Lecouvet, F E; Duprez, T P; Raymackers, J M; Peeters, A; Cosnard, G

    1999-03-23

    We report a patient with a clinical history and neurologic examination consistent with acute stroke. Diffusion-weighted and fast fluid-attenuated inversion recovery MRI obtained 4 hours after stroke onset detected focal abnormalities suggestive of acute ischemic brain damage. The neurologic deficit and the imaging abnormalities both resolved completely at follow-up. This patient illustrates complete resolution of early changes observed with diffusion-weighted MRI at the hyperacute phase in a TIA. PMID:10102438

  5. MR diffusion-weighted imaging of kidney: differentiation between hydronephrosis and pyonephrosis.

    PubMed

    Chan, J H; Tsui, E Y; Luk, S H; Fung, S L; Cheung, Y K; Chan, M S; Yuen, M K; Mak, S F; Wong, K P

    2001-01-01

    The objective of the study was to evaluate the capability and reliability of the magnetic resonance (MR) diffusion-weighted imaging (DWI) in differentiation between hydronephrosis and pyonephrosis. Single-shot echoplanar MR diffusion-weighted imaging was performed in 12 patients who had dilatation of the renal pelvis and calyces detected by ultrasonography (US). Microbiological tests confirmed that there were four cases of pyonephrosis and eight cases of hydronephrosis. Signal intensities of the collecting (pelvicalyceal) systems on the diffusion-weighted images and apparent diffusion coefficient (ADC) maps were noted. ADC values of the pelvicalyceal system in all patients were computed and compared using Student's t test. On diffusion-weighted images, the pelvicalyceal system of the hydronephrotic kidney was hypointense while the pelvicalyceal system of the pyonephrotic kidney was markedly hyperintense. The mean ADCs of the hydronephrotic and pyonephrotic renal pelvis were 2.98 +/- 0.65 x 10(-3) and 0.64 +/- 0.35 x 10(-3) mm(2)/s, respectively. The extremely low ADC of the renal pelvis of the pyonephrotic kidney accounted for its signal hyperintensity on diffusion-weighted images as well as signal hypointensity on ADC maps. In conclusion, the MR diffusion-weighted imaging may be a reliable tool to differentiate pyonephrosis from hydronephrosis. PMID:11483420

  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. Intraprocedural Angiographic CT as a Valuable Tool in the Course of Endovascular Treatment of Direct Sinus Cavernous Fistulas

    PubMed Central

    Gölitz, P.; Struffert, T.; Arc Saake, M.; Knossalla, F.; Doerfler, A.

    2012-01-01

    Summary This investigation aimed to demonstrate the potential of intraprocedural angiographic CT in monitoring complex endovascular coil embolization of direct carotid cavernous fistulas. Angiographic CT was performed as a dual rotational 5 s run with intraarterial contrast medium injection in two patients during endovascular coil embolization of direct carotid cavernous fistulas. Intraprocedural angiographic CT was considered helpful if conventional 2D series were not conclusive concerning coil position or if a precise delineation of the parent artery was impossible due to a complex anatomy or overlying coil material. During postprocessing multiplanar reformatted and dual volume images of angiographic CT were reconstructed. Angiographic CT turned out to be superior in the intraprocedural visualization of accidental coil migration into the parent artery where conventional 2D-DSA series failed to reliably detect coil protrusion. The delineation of coil protrusion by angiographic CT allowed immediate correct coil repositioning to prevent parent artery compromising. Angiographic CT can function as a valuable intraprocedurally feasible tool during complex coil embolizations of direct carotid cavernous fistulas. It allows the precise visualization of the cerebral vasculature and any accidental coil protrusion can be determined accurately in cases where conventional 2D-DSA series are unclear or compromised. Thus angiographic CT might contribute substantially to reduce procedural complications and to increase safety in the management of endovascular treatment of direct carotid cavernous fistulas. PMID:22958773

  9. Diffusion-weighted imaging of traumatic subdural hematoma in the subacute stage.

    PubMed

    Kuwahara, Seikou; Fukuoka, Masaaki; Koan, Yoko; Miyake, Hirohisa; Ono, Yuko; Moriki, Akihito; Mori, Koreaki; Mokudai, Toshihiko; Uchida, Yasufumi; Kumano, Osamu

    2005-09-01

    Five cases of traumatic subdural hematomas in the subacute stage (from 7 to 20 days after head injury) were treated in one male and four females, aged from 63 to 82 years, with evacuation via craniotomy in three and aspiration via burr hole surgery in two. All hematomas were evaluated by T1-, T2-, and diffusion-weighted magnetic resonance imaging, and measurement of the apparent diffusion coefficient (ADC). Diffusion-weighted imaging showed the hematoma as a crescent high intensity area with a low intensity rim close to the brain surface (two-layered structure) in four cases and as high intensity with low intensity components in one case. The high intensity areas under the dura mater on diffusion-weighted imaging appeared as homogeneous high intensity on T1- and T2-weighted imaging in four cases, and inhomogeneous high intensity on T1- and isointensity on T2-weighted imaging in one case. The mean ADC value of the high intensity areas was 0.58 +/- 0.23 (mean +/- standard deviation) x 10(-3) mm2/sec. The operative findings revealed the high intensity areas as solid clots. The low intensity areas on diffusion-weighted imaging appeared as homogeneous high intensity in four cases and inhomogeneous isointensity with high intensity components in one case on T1- and T2-weighted imaging. The mean ADC value of the low intensity areas was 2.03 +/- 0.27 x 10(-3) mm2/sec. The operative findings revealed the low intensity areas as mixtures of resolved clot and cerebrospinal fluid. Diffusion-weighted imaging showed the characteristic two-layered structure in traumatic subdural hematomas in the subacute stage, and analysis of the ADC values was useful for differentiating solid from liquid hematoma and for selection of the surgical procedure. PMID:16195646

  10. Usefulness of Intraprocedural Coronary Computed Tomographic Angiography During Intervention for Chronic Total Coronary Occlusion.

    PubMed

    Kim, Byeong-Keuk; Cho, Iksung; Hong, Myeong-Ki; Chang, Hyuk-Jae; Shin, Dong-Ho; Kim, Jung-Sun; Shin, Sanghoon; Ko, Young-Guk; Choi, Donghoon; Jang, Yangsoo

    2016-06-15

    Although intraprocedural coronary computed tomographic angiography (CCTA) allows for scanning during intervention without relocation of the patient, studies have yet to report on its use during chronic total occlusion (CTO) intervention. Therefore, we investigated the role of CCTA during CTO intervention, particularly whether CCTA could be used to evaluate the location of guidewires. A total of 61 patients scheduled for elective CTO intervention were consecutively enrolled and underwent CCTA and on-site analyses during intervention. Transverse axial and the curved multiplanar images in a 360-degree view were interactively used together to identify the location of guidewires, along with the adjustment of window condition. Intracoronary contrast injection was used for specific cases requiring enhancement of the distal part of the CTO. Most CCTAs were performed to confirm the location of a single guidewire; CCTA was also performed to evaluate parallel (3 patients) or retrograde wires (5 patients). The initial identification rate for guidewire location was 56% with immediate transaxial images, but it significantly increased to 87% after interactive on-site uses of the curved multiplanar images (p <0.001). Cases in which guidewire location could be predicted with CCTA evaluation show a numerically higher success rate than those that could not (83% vs 63%) but not statistical significance (p = 0.174). The mean time for CCTA evaluation and mean radiation dose were 8.6 minutes and 2.9 mSv, respectively. No specific complications occurred after CCTA and CTO procedures. Intraprocedural CCTA for identifying the location of the guidewires is feasible and safe when used for various CTO procedural steps. PMID:27134060

  11. Intra-procedural Transcatheter Intraarterial Perfusion MRI as a Predictor of Tumor Response to Chemoembolization for Hepatocellular Carcinoma

    PubMed Central

    Wang, Dingxin; Gaba, Ron C.; Jin, Brian; Riaz, Ahsun; Lewandowski, Robert J.; Ryu, Robert K.; Sato, Kent T.; Ragin, Ann B.; Kulik, Laura M.; Mulcahy, Mary F.; Salem, Riad; Larson, Andrew C.; Omary, Reed A.

    2011-01-01

    Rationale and Objectives To prospectively test the hypothesis that transcatheter intraarterial perfusion magnetic resonance imaging (TRIP-MRI) measured semi-quantitative perfusion reductions during transcatheter arterial chemoembolization of hepatocellular carcinoma (HCC) are associated with tumor response. Materials and Methods Twenty eight patients (mean age 63 years; range 47–87 years) with 29 tumors underwent chemoembolization in a combined MR-interventional radiology suite. Intra-procedural tumor perfusion reductions during chemoembolization were monitored using TRIP-MRI. Pre- and post-–chemoembolization semi-quantitative area under the time-signal enhancement curve (AUC) tumor perfusion was measured. Mean tumor perfusion pre- and post-chemoembolization were compared using a paired t-test. Imaging follow-up was performed one to three months after chemoembolization. We studied the relationship between short-term tumor imaging response and intra-procedural perfusion reductions using univariate and multivariate analysis. Results Intra-procedural AUC perfusion value decreased significantly after chemoembolization (342.1 versus 158.6 arbitrary unit, P < 0.001). Twenty six patients with 27 HCCs (n = 27) had follow-up imaging at mean 39 days post-chemoembolization. Favorable response was present in 67% of these treated tumors according to necrosis criteria. 15 of 16 (94%) tumors with 25–75% perfusion reductions showed necrosis treatment response compared to only 3 of 11 (27%) tumors with perfusion reductions outside the above range (P = 0.001). Multivariate logistic regression indicated that intra-procedural tumor perfusion reduction and Child-Pugh class were independent factors associated significantly with tumor response (P = 0.012 and 0.047, respectively). Conclusion TRIP-MRI can successfully measure semi-quantitative changes in HCC perfusion during chemoembolization. Intra-procedural tumor perfusion reductions are associated with future tumor response. PMID

  12. 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.

  13. Heidenhain variant of Creutzfeldt-Jakob disease: diffusion-weighted MRI and PET characteristics.

    PubMed

    Tsuji, Yoshihisa; Kanamori, Hiroshi; Murakami, Gaku; Yokode, Masayuki; Mezaki, Takahiro; Doh-ura, Katsumi; Taniguchi, Ken; Matsubayashi, Kozo; Fukuyama, Hidenao; Kita, Toru; Tanaka, Makoto

    2004-01-01

    Creutzfeldt-Jakob disease (CJD) is characterized by rapidly progressive dementia with a variety of neurological disorders and a fatal outcome. The authors present a case with visual disturbance as a leading symptom and rapid deterioration in global cognitive functions. The cerebrospinal fluid was positive for 14-3-3 protein, and diffusion-weighted magnetic resonance imaging (MRI) showed marked hyperintensity in the parieto-occipital cortices, where hypometabolism was clearly detected on positron emission tomography (PET). Pattern-reversal visual evoked potentials showed prolonged P100 latencies and increased N/5/P100 amplitudes. All these findings supported a diagnosis of the Heidenhain variant of CJD, whereas a long clinical course, a lack of myoclonus, and an absence of periodic synchronous discharges on electroencephalography were atypical. Diffusion-weighted MRI and PE1 in combination with visual evoked potential recording and 14-3-3 protein detection may be useful for the early diagnosis of CJD. PMID:14748211

  14. Separation of extra- and intracellular metabolites using hyperpolarized (13)C diffusion weighted MR.

    PubMed

    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 (13)C magnetic resonance spectroscopy. Using b-values of up to 15,000smm(-2), a multi-exponential signal response was measured for hyperpolarized [1-(13)C] 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 (13)C 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 (13)C 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. PMID:27434780

  15. COMPARISON OF THE COMPLETE FOURIER DIRECT MRI WITH EXISTING DIFFUSION WEIGHTED MRI METHODS

    PubMed Central

    Özcan, Alpay

    2011-01-01

    The Complete Fourier Direct (CFD) MRI method introduced in earlier work for modeling the diffusion weighted MRI signal is compared with the existing methods. The preservation of Hermitian symmetry in the diffusion weighted MRI signal without affecting its energy is the key point that differentiates CFD–MRI from the existing methods. By keeping the correct Fourier relationship intact, the joint distribution function is represented ‘as it is’, without any constraints, e.g. being symmetric. The necessity to model or assume models for spin motion and try to fit the model to the samples of the Fourier transform as in case of model matching methods is not required because the Discrete Fourier Transform applied to correctly processed signal in CFD–MRI gives more accurate results. PMID:21918715

  16. Diffusion weighted imaging of female pelvic cancers: concepts and clinical applications.

    PubMed

    Punwani, Shonit

    2011-04-01

    Early applications of diffusion weighted magnetic resonance imaging (DWI) were limited to neuroimaging, concentrating either on stroke or brain tumours. With recent advances in MRI hardware and software DWI is now increasingly being investigated for cancer assessment throughout the body. Clinical applications of DWI relating to female pelvic cancers have largely concentrated on detection, localisation and staging of disease. More recently investigators have started to evaluate the ability of DWI for determining tumour histology and even predicting the outcome of chemoradiation treatment. This article reviews the physical concepts of MR diffusion weighting, illustrates the biophysical basis of diffusion contrast and reports the clinical applications of DWI for cervical, endometrial, ovarian, rectal and bladder tumours. PMID:20801592

  17. The design of anisotropic diffusion phantoms for the validation of diffusion weighted magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Fieremans, Els; DeDeene, Yves; Delputte, Steven; Özdemir, Mahir S.; Achten, Eric; Lemahieu, Ignace

    2008-10-01

    Diffusion weighted magnetic resonance imaging offers a non-invasive tool to explore the three-dimensional structure of brain white matter in clinical practice. Anisotropic diffusion hardware phantoms are useful for the quantitative validation of this technique. This study provides guidelines on how to manufacture anisotropic fibre phantoms in a reproducible way and which fibre material to choose to obtain a good quality of the diffusion weighted images. Several fibre materials are compared regarding their effect on the diffusion MR measurements of the water molecules inside the phantoms. The diffusion anisotropy influencing material properties are the fibre density and diameter, while the fibre surface relaxivity and magnetic susceptibility determine the signal-to-noise ratio. The effect on the T2-relaxation time of water in the phantoms has been modelled and the diffusion behaviour inside the fibre phantoms has been quantitatively evaluated using Monte Carlo random walk simulations.

  18. Differentiation of Reactive and Tumor Metastatic Lymph Nodes with Diffusion-weighted and SPIO Enhanced MRI

    PubMed Central

    Zhang, Fan; Zhu, Lei; Huang, Xinglu; Niu, Gang; Chen, Siouan

    2012-01-01

    Objectives Determination of lymphatic metastasis is of great importance for both treatment planning and patient prognosis. We aim to distinguish tumor metastatic lymph nodes (TLNs) and reactive lymph nodes (RLNs) with diffusion-weighted and superparamagnetic iron oxide (SPIO) enhanced magnetic resonance imaging (MRI). Materials and methods Ipsilateral popliteal lymph node metastasis or lymphadenitis model was established by hock injection of either luciferase-expressing 4T1 murine breast cancer cells or Complete Freund Adjuvant (CFA) in male Balb/C mice. At different time points after inoculation, bioluminescence imaging, T2-weighted, diffusion-weighted and SPIO enhanced MRI were performed. Imaging findings were confirmed by histopathological staining. Results Size enlargement was observed in both TLNs and RLNs. At day 28, TLNs showed strong bioluminescence signal and bigger size than RLNs (p < 0.01). At early stages up to day 21, both TLNs and RLNs appeared homogeneous on diffusion-weighted imaging (DWI). At day 28, TLNs showed heterogeneous apparent diffusion coefficient (ADC) map with significantly higher average ADC value of 0.41 ± 0.03 × 10−3 mm2/s than that of RLNs (0.34 ± 0.02 10−3 mm2/s, p < 0.05). On SPIO enhanced MRI, both TLNs and RLNs showed distinct T2 signal reduction at day 21 after inoculation. At day 28, TLNs demonstrated partial uptake of the iron oxide particles, which was confirmed by Prussian blue staining. Conclusions Both diffusion-weighted and SPIO enhanced MRI can distinguish tumor metastatic lymph nodes from reactive lymph nodes. However, neither method is able to detect tumor metastasis to the draining lymph nodes at early stages. PMID:22588595

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

    PubMed

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

    2012-09-21

    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. PMID:22941943

  20. Evaluation of thermal and cryo lesions by diffusion-weighted MRI

    NASA Astrophysics Data System (ADS)

    Chen, Jing; Daniel, Bruce; Bouley, Donna; Sommer, Graham; Butts Pauly, Kim

    2007-02-01

    The purpose of this study is to further investigate the approach of DWI to estimate the cell viability immediately after treatment. In this work, we reported the result from 12 canine prostate experiments underwent cryoablation or hyperthermic therapy. The lesion detected by diffusion-weighted imaging was evaluated through apparent diffusion coefficient (ADC) value, image contrast, and lesion contour compared to contrast enhanced imaging and histology.

  1. Diffusion-weighted magnetic resonance imaging in tubo-ovarian abscess: a case report.

    PubMed

    Takeshita, Tohru; Ninoi, Teruhisa; Doh, Kunihiko; Hashimoto, Shigeo; Inoue, Yuichi

    2009-12-01

    In this report, we describe the magnetic resonance imaging appearance of tubo-ovarian abscess (TOA) in a patient who underwent diffusion-weighted imaging (DWI) of the pelvis and subsequent histologic analysis. The content of the TOA was markedly high signal intensity relative to the surrounding tissue on DWI, and it showed low signal intensity on the apparent diffusion coefficient map; these findings were consistent with those of published reports on brain and liver abscesses. PMID:20088410

  2. Non-oncologic applications of diffusion-weighted imaging (DWI) in the genitourinary system.

    PubMed

    Dunn, Dell P; Kelsey, Nathan R; Lee, Karen S; Smith, Martin P; Mortele, Koenraad J

    2015-08-01

    Diffusion-weighted imaging (DWI) has become an increasingly used tool in abdominal and pelvic magnetic resonance imaging (MRI), primarily in the oncologic setting. DWI sequences are being added to routine MRI protocols at many institutions, and as its use has spread, more non-oncologic applications have been explored. The purpose of this article is to provide a review of DWI applications in inflammatory, infectious, autoimmune-mediated, and ischemic processes affecting the genitourinary system. PMID:26109511

  3. A Computational Model for Diffusion Weighted Imaging of Myelinated White Matter

    PubMed Central

    Baxter, Gregory T.; Frank, Lawrence R.

    2013-01-01

    The signal for diffusion weighted magnetic resonance imaging has previously been represented analytically and simulated numerically for a variety of model problems with idealized geometries. Numerical simulations hold the promise of computing the diffusion weighted MR signal for more complex realistic tissue architectures and physiological models. This paper investigates a white matter model consisting of a matrix of coated cylinders with distinct diffusion coefficients and spin concentrations for each of the cylinder core, the coating, and the surrounding bath and compares results with an the analytical solution developed by Sen and Basser for the long diffusion time limit. Numerical simulations of diffusion weighted imaging experiments are performed for the three-medium model using a Monte Carlo diffusion simulation. Experiments are carried out for model parameters representing normal white matter. Pulse sequence parameters range from a low b value, long time limit, short pulse approximation to realistic clinical values. For simulations in the short pulse width, long diffusion time limit, numerical simulations agree with the Sen-Basser analytical result. When tested with realistic pulse sequence parameters, numerical simulations show lower anisotropy than the analytical model predicts. PMID:23507381

  4. Lower Intraprocedural Systolic Blood Pressure Predicts Good Outcome in Patients Undergoing Endovascular Therapy for Acute Ischemic Stroke

    PubMed Central

    John, Seby; Hazaa, Walaa; Uchino, Ken; Toth, Gabor; Bain, Mark; Thebo, Umera; Hussain, Muhammad S.

    2016-01-01

    Background It is unknown if intraprocedural blood pressure (BP) influences clinical outcomes and what BP parameter best predicts outcomes in acute ischemic stroke (AIS) patients who undergo intra-arterial therapy (IAT) for emergent large vessel occlusion. Methods We retrospectively reviewed 147 patients who underwent IAT for anterior circulation AIS from January 2008 to December 2012 at our institution. Baseline demographics, stroke treatment variables, and detailed intraprocedural hemodynamic variables were collected. Results The entire cohort consisted of 81 (55%) females with a mean age of 66.9 ± 15.6 years and a median National Institutes of Health Stroke Scale (NIHSS) score of 16 (IQR 11-21). Thirty-six (24.5%) patients died during hospitalization, 25 (17%) achieved a 30-day modified Rankin Scale score of 0-2, and 24 (16.3%) suffered symptomatic parenchymal hematoma type 1/2 hemorrhage. Patients who achieved a good outcome had a significantly lower admission NIHSS score, a higher baseline CT ASPECTS score, and a lower rate of ICA terminus occlusions. Successful recanalization was more frequent in the good-outcome group, while symptomatic hemorrhages occurred only in poor-outcome patients. The first systolic BP (SBP; 146.5 ± 0.2 vs. 157.7 ± 25.6 mm Hg, p = 0.042), first mean arterial pressure (MAP; 98.1 ± 20.8 vs. 109.7 ± 20.3 mm Hg, p = 0.024), maximum SBP (164.6 ± 27.6 vs. 180.9 ± 18.3 mm Hg, p = 0.0003), and maximum MAP (125.5 ± 18.6 vs. 138.5 ± 24.6 mm Hg, p = 0.0309) were all significantly lower in patients who achieved good outcomes. A lower maximum intraprocedural SBP was an independent predictor of good outcome (adjusted OR 0.929, 95% CI 0.886-0.963, p = 0.0005). Initial NIHSS score was the only other independent predictor of a good outcome. Conclusion Lower intraprocedural SBP was associated with good outcome in patients undergoing IAT for AIS, and maximum SBP was an independent predictor of good outcome. SBP may be the optimal hemodynamic

  5. Diffusion weighted MR imaging in the differential diagnosis of haemangiomas and metastases of the liver

    PubMed Central

    Inan, Nagihan; Kilinc, Furkan; Sarisoy, Tahsin; Gumustas, Sevtap; Akansel, Gur; Demirci, Ali

    2010-01-01

    Background The purpose of the study was to evaluate the value of diffusion-weighted imaging in the differential diagnosis of haemangiomas from metastases of the liver. Patients and methods. We analyzed 69 lesions in 38 patients (33 haemangiomas; 36 metastases) in the retrospective study. Diffusion-weighted imaging was performed using a breath-hold single-shot echo-planar spin echo sequence with three b factors (0, 500 and 1000 sec/mm2), and apparent diffusion coefficients (ADCs) were calculated. For the quantitative evaluation, signal intensity of the lesions, lesion-to-liver signal intensity ratios, ADC of the lesions, and lesion-to-liver ADC ratios were compared between the groups. The statistical significance was determined by student’s-t test. Results With the b factor 500 sec/mm2, no statistical significance was achieved (p>0.05). With the b factor of 1000 sec/mm2, both the signal intensity and lesion-to-liver signal intensity ratio of the metastases were significantly higher than those for haemangiomas (p<0.001). The cut-off value at 2.6 yielded a sensitivity of 86% and a specificity of 82% for the lesion-to-liver signal intensity ratio. The ADC, and lesion-to-liver ADC ratio of the metastases were significantly lower than those of haemangiomas (p<0.001). With cut-off value of 1.7, ADC ratio had a sensitivity of 88% and a specificity of 72% for ADC lesion/liver. Conclusions Diffusion-weighted imaging with high b value may help in the differential diagnosis of metastases from haemangiomas of the liver. PMID:22933887

  6. Imaging hypothalamic activity using diffusion weighted magnetic resonance imaging in the mouse and human brain.

    PubMed

    Lizarbe, Blanca; Benítez, Ania; Sánchez-Montañés, Manuel; Lago-Fernández, Luis F; Garcia-Martin, María L; López-Larrubia, Pilar; Cerdán, Sebastián

    2013-01-01

    Hypothalamic appetite regulation is a vital homeostatic process underlying global energy balance in animals and humans, its disturbances resulting in feeding disorders with high morbidity and mortality. The objective evaluation of appetite remains difficult, very often restricted to indirect measurements of food intake and body weight. We report here, the direct, non-invasive visualization of hypothalamic activation by fasting using diffusion weighted magnetic resonance imaging, in the mouse brain as well as in a preliminary study in the human brain. The brain of fed or fasted mice or humans were imaged at 7 or 1.5 Tesla, respectively, by diffusion weighted magnetic resonance imaging using a complete range of b values (10diffusion weighted image data sets were registered and analyzed pixel by pixel using a biexponential model of diffusion, or a model-free Linear Discriminant Analysis approach. Biexponential fittings revealed statistically significant increases in the slow diffusion parameters of the model, consistent with a neurocellular swelling response in the fasted hypothalamus. Increased resolution approaches allowed the detection of increases in the diffusion parameters within the Arcuate Nucleus, Ventromedial Nucleus and Dorsomedial Nucleus. Independently, Linear Discriminant Analysis was able to classify successfully the diffusion data sets from mice and humans between fed and fasted states. Present results are consistent with increased glutamatergic neurotransmission during orexigenic firing, a process resulting in increased ionic accumulation and concomitant osmotic neurocellular swelling. This swelling response is spatially extendable through surrounding astrocytic networks until it becomes MRI detectable. Present findings open new avenues for the direct, non-invasive, evaluation of appetite disorders and other hypothalamic pathologies helping potentially in the development of the corresponding therapies. PMID:23000787

  7. 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. PMID:26512584

  8. Diffusion Weighted Magnetic Resonance Imaging for the Characterization of Solitary Pulmonary Lesions

    PubMed Central

    Çakır, Çağlayan; Gençhellaç, Hakan; Temizöz, Osman; Polat, Ahmet; Şengül, Ersin; Duygulu, Gökhan

    2015-01-01

    Background: We evaluated the differential diagnosis of solitary pulmonary lesions on magnetic resonance imaging. Aims: To investigate the value of diffusion weighted imaging on the differential diagnosis of solitary pulmonary lesions. Study Design: Randomized prospective study. Methods: This prospective study included 48 solitary pulmonary nodules and masses (18 benign, 30 malignant). Single shot echo planar spin echo diffusion weighted imaging (DWI) was performed with two b factors (0 and 1000 s/mm2). Apparent diffusion coefficients (ADCs) were calculated. On diffusion weighted (DW) trace images, the signal intensities (SI) of the lesions were visually compared to the SI of the thoracic spinal cord using a 5-point scale: 1: hypointense, 2: moderately hypointense, 3: isointense, 4: moderately hyperintense, 5: significantly hyperintense. For the quantitative evaluation, the lesion to thoracic spinal signal intensity ratios and the ADCs of the lesions were compared between groups. Results: On visual evaluation, taking the density of the spinal cord as a reference, most benign lesions were found to be hypointense, while most of the malignant lesions were evaluated as hyperintense on DWI with a b factor of 1000 s/mm2. In contrast, on T2 weighted images, it was seen that the distinction of malignant lesions from benign lesions was not statistically significant. The ADCs of the malignant lesions were significantly lower than those of benign lesions (mean ADC was 2.02×10−3 mm2/s for malignant lesions, and 1.195×10−3±0.3 mm2/s for benign lesions). Setting the cut-off value at 1.5×10−3, ADC had a sensitivity of 86.7% and a specificity of 88.9% for the differentiation of benign lesions from malignant lesions. Conclusion: DWI may aid in the differential diagnosis of solitary pulmonary lesions. (ClinicalTrials.gov Identifier: NCT02482181) PMID:26740901

  9. Diffusion-weighted and diffusion tensor imaging of the brain, made easy.

    PubMed

    Huisman, T A G M

    2010-01-01

    Diffusion-weighted and diffusion tensor imaging (DWI/DTI) has revolutionized clinical neuroimaging. Pathology may be detected earlier and with greater specificity than with conventional magnetic resonance imaging sequences. In addition, DWI/DTI allows exploring the microarchitecture of the brain. A detailed knowledge of the basics of DWI/DTI is mandatory to better understand pathology encountered and to avoid misinterpretation of typical DWI/DTI artifacts. This article reviews the basic physics of DWI/DTI exemplified by several classical clinical cases. PMID:20880787

  10. The expanding landscape of diffusion-weighted MRI in prostate cancer.

    PubMed

    Wibmer, Andreas G; Sala, Evis; Hricak, Hedvig; Vargas, Hebert Alberto

    2016-05-01

    The added value of diffusion-weighted magnetic resonance imaging (DW-MRI) for the detection, localization, and staging of primary prostate cancer has been extensively reported in original studies and meta-analyses. More recently, DW-MRI and related techniques have been used to noninvasively assess prostate cancer aggressiveness and estimate its biological behavior. The present article aims to summarize the potential applications of DW-MRI for noninvasive optimization of pretherapeutic risk assessment, patient management decisions, and evaluation of treatment response. PMID:26814501

  11. Diffusion-weighted MR imaging of the kidneys and the urinary tract.

    PubMed

    Kim, Sooah; Naik, Mohit; Sigmund, Eric; Taouli, Bachir

    2008-11-01

    There is currently a growing interest in applications of diffusion-weighted imaging (DWI) in the abdomen and pelvis. DWI provides original functional information where the signal and contrast are determined by the microscopic mobility of water. DWI can provide additional information over conventional MR sequences, and could potentially be used as an alternative to contrast-enhanced sequences in patients with chronic renal insufficiency at risk of nephrogenic systemic fibrosis. We provide an overview on basic physics background on DWI applied to the kidneys, and we summarize the current available data, including our recent experience. PMID:18926424

  12. Diffusion-weighted MR imaging findings of ovarian adenocarcinofibromas and adenofibromas.

    PubMed

    Kozawa, Eito; Inoue, Kaiji; takahashi, Masahiro; Kato, Tomomi; Yasuda, Masanori; Kimura, Fumiko

    2014-01-01

    We retrospectively evaluated pelvic magnetic resonance imaging including diffusion-weighted imaging (DWI) of 16 ovarian lesions (5 adenocarcinofibromas, 2 borderline adenofibromas, and 9 benign adenofibromas). All adenocarcinofibromas were detected as large solid areas of strong high signal on DWI, and seven of nine benign adenofibromas and both borderline adenofibromas demonstrated no areas of high signal or small areas of weak high signal. Solid components that appear as areas of strong high signal on DWI might represent a characteristic finding of adenocarcinofibromas. PMID:24685607

  13. Diffusion-weighted magnetic resonance imaging findings in a patient with struma ovarii.

    PubMed

    Takeshita, Tohru; Ninoi, Teruhisa; Maebayashi, Tetunori; Doh, Kunihiko; Hashimoto, Shigeo; Mniki, Yumo

    2014-06-01

    In this report, the magnetic resonance imaging (MRI) appearance of struma ovarii (SO) in a patient who underwent diffusion-weighted imaging (DWI) of the pelvis and subsequent histological analysis is described. The solid portion of SO showed a high apparent diffusion coefficient (ADC) value, indicating unrestricted diffusion, and each loculus of SO showed different ADC values due to the different viscosity of the cyst contents in each loculus. These unique and characteristic DWI findings may serve as a helpful sign in making the correct diagnosis of SO when DWI findings are interpreted in conjunction with conventional MRI findings. PMID:25272567

  14. 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

  15. Quantitative Analysis of Diffusion Weighted MR Images of Brain Tumor Using Signal Intensity Gradient Technique

    PubMed Central

    Shanbhag, S. S.; Udupi, G. R.; Patil, K. M.; Ranganath, K.

    2014-01-01

    The purpose of this study was to evaluate the role of diffusion weighted-magnetic resonance imaging (DW-MRI) in the examination and classification of brain tumors, namely, glioma and meningioma. Our hypothesis was that as signal intensity variations on diffusion weighted (DW) images depend on histology and cellularity of the tumor, analysing the signal intensity characteristics on DW images may allow differentiating between the tumor types. Towards this end the signal intensity variations on DW images of the entire tumor volume data of 20 subjects with glioma and 12 subjects with meningioma were investigated and quantified using signal intensity gradient (SIG) parameter. The relative increase in the SIG values (RSIG) for the subjects with glioma and meningioma was in the range of 10.08–28.36 times and 5.60–9.86 times, respectively, compared to their corresponding SIG values on the contralateral hemisphere. The RSIG values were significantly different between the subjects with glioma and meningioma (P < 0.01), with no overlap between RSIG values across the two tumors. The results indicate that the quantitative changes in the RSIG values could be applied in the differential diagnosis of glioma and meningioma, and their adoption in clinical diagnosis and treatment could be helpful and informative. PMID:27006934

  16. Incidence and Predictors of Catheterization-Related Cerebral Infarction on Diffusion-Weighted Magnetic Resonance Imaging

    PubMed Central

    Okano, Mitsumasa; Suu, Kanae; Kimura, Masahiro; Minamino-Muta, Eri; Nakane, Eisaku; Izumi, Toshiaki; Miyamoto, Shoichi; Haruna, Tetsuya; Ueyama, Koji

    2016-01-01

    Introduction. The aim of this study was to examine the incidence and risk factors of catheterization-related CI in the contemporary era, using diffusion-weighted magnetic resonance imaging. Methods. We retrospectively analyzed consecutive 84 patients who underwent MRI (magnetic resonance imaging) after 2.81 ± 2.4 days (mean ± SD) of catheterization via aortic arch. We categorized the patients by the presence or absence of acute CI determined by diffusion-weighted MRI and analyzed the incidence and predictors. Results. Of 84 patients that underwent MRI after catheterization, acute CI was determined in 27 (32.1%) patients. In univariate analysis, dyslipidemia, age, coronary artery disease, antiplatelet agents, number of catheters used, urgent settings, and interventional procedures were significantly different. Multivariate analysis revealed dyslipidemia (odds ratio [OR], 4.46; 95% confidence interval [CI], 1.41–16.03; p = 0.01), higher age (OR, 1.09; 95% CI, 1.007–1.19; p = 0.03), and the number of catheters used (OR, 2.21; 95% CI, 1.21–4.36; p = 0.01) as independent predictors of the incidence of catheterization-related acute CI. Conclusions. Dyslipidemia, higher age, and number of catheters used were independent predictors for acute CI after catheterization. These findings imply that managing dyslipidemia and comprehensive planning to minimize the numbers of catheters are important. PMID:27127790

  17. 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.

  18. Diffusion-weighted magnetic resonance imaging of the normal canine brain.

    PubMed

    Hartmann, Antje; Söffler, Charlotte; Failing, Klaus; Schaubmar, Andreas; Kramer, Martin; Schmidt, Martin J

    2014-01-01

    Diffusion-weighted imaging (DWI) MRI has been primarily reported as a method for diagnosing cerebrovascular disease in veterinary patients. In humans, clinical applications for diffusion-weighted MRI have also included epilepsy, Alzheimer's, and Creutzfeld-Jakob disease. Before these applications can be developed in veterinary patients, more data on brain diffusion characteristics are needed. Therefore, the aim of this study was to evaluate the distribution of diffusion in the normal canine brain. Magnetic resonance imaging of the brain was performed in ten, clinically normal, purpose-bred beagle dogs. On apparent diffusion coefficient maps, regions of interest were drawn around the caudate nucleus, thalamus, piriform lobe, hippocampus, semioval center, and cerebral cortex. Statistically significant differences in mean apparent diffusion coefficient were found for the internal capsule, hippocampus, and thalamus. The highest apparent diffusion coefficient (1044.29 ± 165.21 μm(2)/s (mean ± SD (standard deviation)) was detected in the hippocampus. The lowest apparent diffusion coefficient was measured in the semioval center (721.39 ± 126.28 μm(2)/s (mean ± SD)). Significant differences in mean apparent diffusion coefficients of the caudate nucleus, thalamus, and piriform lobe were found by comparing right and left sides. Differences between brain regions may occur due to differences in myelination, neural density, or fiber orientation. The reason for the differences between right and left sides remains unclear. Data from the current study provide background for further studies of diffusion changes in dogs with brain disease. PMID:24798796

  19. Effect of b value on monitoring therapeutic response by diffusion-weighted imaging

    PubMed Central

    Jiang, Zhao-Xia; Peng, Wei-Jun; Li, Wen-Tao; Tang, Feng; Liu, Shi-Yuan; Qu, Xu-Dong; Wang, Jian-Hua; Lu, Hong-Feng

    2008-01-01

    AIM: To explore the diffusion gradient b-factor that optimizes both apparent diffusion coefficient (ADC) measurement and contrast-to-noise (CNR) for assessing tumor response to transarterial chemoembolization (TACE) in a rabbit model. METHODS: Twelve New Zealand white rabbits bearing VX2 tumors in the liver were treated with TACE. Diffusion-weighted imaging (DWI) with various b values was performed using the same protocol before and 3 d after treatment with TACE. ADC values and CNR of each tumor pre- and post-treatment with different b factors were analyzed. Correlation between ADC values and extent of necrosis in histological specimens was analyzed by a Pearson’s correlation test. RESULTS: The quality of diffusion-weighted images diminished as the b value increased. A substantial decrease in the mean lesion-to-liver CNR was observed on both pre- and post-treatment DW images, the largest difference in CNR pre- and post-treatment was manifested at a b value of 1000 s/mm2 (P = 0.036 ). The effect of therapy on diffusion early after treatment was shown by a significant increase in ADCs (P = 0.007), especially with large b factors (≥ 600 s/mm2). The mean percentage of necrotic cells present within the tumor was 76.3%-97.5%. A significant positive correlation was found between ADC values and the extent of necrosis with all b values except for b200, a higher relative coefficient between ADC values and percentage of necrosis was found on DWI with b1000 and b2000 (P = 0.002 and 0.006, respectively). CONCLUSION: An increasing b value of up to 600 s/mm2 would increase ADC contrast pre- and post-treatment, but decrease image quality. Taking into account both CNR and ADC measurement, diffusion-weighted imaging obtained with a b value of 1000 s/mm2 is recommended for monitoring early hepatic tumor response to TACE. PMID:18855990

  20. Diffusion-weighted MRI in the evaluation of renal lesions: preliminary results.

    PubMed

    Cova, M; Squillaci, E; Stacul, F; Manenti, G; Gava, S; Simonetti, G; Pozzi-Mucelli, R

    2004-10-01

    The purpose of this study was to evaluate the capability and the reliability of diffusion-weighted MRI in the evaluation of normal kidney and different renal lesions. 39 patients (10 normal volunteers and 29 patients with known renal lesions) underwent MRI of the kidneys by using a 1.5 T superconducting magnet. Axial fat suppressed turbo spin echo (TSE) T(2) and coronal fast field echo (FFE) T(1) or TSE T(1) weighted images were acquired for each patient. Diffusion-weighted (DW) images were obtained in the axial plane during breath-hold (17 s) with a spin-echo echo planar imaging (SE EPI) single shot sequence (repetition time (TR)=2883 ms, echo time (TE)=61 ms, flip angle=90 degrees ), with b value of 500 s mm(-2). 16 slices were produced with slice thickness of 7 mm and interslice gap of 1 mm. An apparent diffusion coefficient (ADC) map was obtained at each slice position. The ADC was measured in an approximately 1 cm region of interest (ROI) within the normal renal parenchyma, the detected renal lesions and the collecting system if dilated. ADC values in normal renal parenchyma ranged from 1.72 x 10(-3) mm(2) s(-1) to 2.65 x 10(-3) mm(2) s(-1), while ADC values in simple cysts (n=13) were higher (2.87 x 10(-3) mm(2) s(-1) to 4.00 x 10(-3) mm(2) s(-1)). In hydronephrotic kidneys (n=6) the ADC values of renal pelvis ranged from 3.39 x 10(-3) mm(2) s(-1) to 4.00 x 10(-3) mm(2) s(-1). In cases of pyonephrosis (n=3) ADC values of the renal pelvis were found to be lower than those of renal pelvis of hydronephrotic kidneys (0.77 x 10(-3) mm(2) s(-1) to 1.07 x 10(-3) mm(2) s(-1)). Solid benign and malignant renal tumours (n=7) showed ADC values ranging between 1.28 x 10(-3) mm(2) s(-1) and 1.83 x 10(-3) mm(2) s(-1). In conclusion diffusion-weighted MR imaging of the kidney seems to be a reliable way to differentiate normal renal parenchyma and different renal diseases. Clinical experience with this method is still preliminary and further studies are required. PMID

  1. 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

  2. Agitated saline sonography: a simple technique for intraprocedural feeder identification during transcatheter arterial chemoembolization of hepatocellular carcinoma

    PubMed Central

    Krishna Prasad, B. P.; Ray, Brijesh

    2016-01-01

    Transcatheter arterial chemoembolization (TACE) is the most widely used treatment modality for patients with hepatocellular carcinoma who are not eligible for surgery. Selective tumor embolization is very important, more so in patients with mild to moderate liver cell failure, but determining feeder vessels could be difficult with two-dimensional angiogram alone. Cone beam computed tomography and detection software are available for intraprocedural accurate feeder vessel detection; however, these facilities are not widely available. We have evaluated and successfully applied a very simple technique using only a portable ultrasonography machine to ensure superselective feeder cannulation prior to embolization. PMID:27015444

  3. Diffusion-weighted intensity magnetic resonance in the preoperative diagnosis of cholesteatoma.

    PubMed

    Cavaliere, Michele; Di Lullo, Antonella Miriam; Caruso, Antonia; Caliendo, Giandomenico; Elefante, Andrea; Brunetti, Arturo; Iengo, Maurizio

    2014-01-01

    We have analyzed the preoperative diagnosis of cholesteatoma through the use of diffusion-weighted intensity magnetic resonance (DWI-MR) in 16 consecutive patients suffering from chronic otitis media with clinical and radiological (by computed tomography) suspicion of cholesteatoma. In particular, we compared the radiological data with intraoperative ones, verifying the correspondence (in terms of sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy) between what is reported by DWI-MR and what is actually detectable at the time of surgery. Furthermore, we identified the most reliable DWI-MR sequence [single-shot (SSh) echo planar imaging (EPI) vs. multi-shot turbo spin-echo not-EPI] to detect cholesteatoma and reduce the time for examination. The obtained data on computed tomography scans revealed low diagnostic accuracy (56%); DWI-MR, instead, showed higher values, especially using not-EPI sequences (93.75 vs. 68.75% obtained by SSh-EPI sequences). PMID:25322773

  4. 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

  5. Diffusion-weighted imaging outside the brain: Consensus statement from an ISMRM-sponsored workshop.

    PubMed

    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

    2016-09-01

    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. J. Magn. Reson. Imaging 2016;44:521-540. PMID:26892827

  6. Diffusion weighted MRI of the breast: Protocol optimization, guidelines for interpretation, and potential clinical applications

    PubMed Central

    Partridge, Savannah C.; McDonald, Elizabeth S.

    2013-01-01

    Synopsis There has been increasing interest in the use of diffusion weighted MRI (DWI) for breast imaging. This technique has shown promise for improving the positive predictive value of breast MRI for detection of breast cancer, evaluating tumor response to neoadjuvant chemotherapy, and as a non-contrast MRI alternative for breast cancer screening. However, there is currently no standardized approach to DWI of the breast and data quality varies widely. Prior to implementing DWI into clinical practice, it is important to understand the pertinent technical considerations and current evidence of clinical applications of DWI of the breast. This article provides an overview of basic principles of DWI, optimization of breast DWI protocols, imaging features of benign and malignant breast lesions, promising clinical applications, and potential future directions. PMID:23928248

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

    PubMed

    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

  8. Diffusion-Weighted MRI for the Assessment of Liver Fibrosis: Principles and Applications

    PubMed Central

    Attinà, Giancarlo; Fuccio Sanzà, Giovanni; Foti, Pietro Valerio; Ettorre, Giovanni Carlo; Milone, Pietro

    2015-01-01

    The importance of an early identification of hepatic fibrosis has been emphasized, in order to start therapy and obtain fibrosis regression. Biopsy is the gold-standard method for the assessment of liver fibrosis in chronic liver diseases, but it is limited by complications, interobserver variability, and sampling errors. Several noninvasive methods have been recently introduced into clinical routine, in order to detect liver fibrosis early. One of the most diffuse approaches is represented by diffusion-weighted liver MRI. In this review, the main technical principles are briefly reported in order to explain the rationale for clinical applications. In addition, roles of apparent diffusion coefficient, intravoxel incoherent motion, and relative apparent diffusion coefficient are also reported, showing their advantages and limits. PMID:25866819

  9. 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.

  10. Diffusion-weighted imaging in musculoskeletal radiology—clinical applications and future directions

    PubMed Central

    Bhojwani, Nicholas; Szpakowski, Peter; Partovi, Sasan; Maurer, Martin H.; Grosse, Ulrich; von Tengg-Kobligk, Hendrik; Zipp-Partovi, Lisa; Fergus, Nathan; Kosmas, Christos; Nikolaou, Konstantin

    2015-01-01

    Diffusion-weighted imaging (DWI) is an established diagnostic tool with regards to the central nervous system (CNS) and research into its application in the musculoskeletal system has been growing. It has been shown that DWI has utility in differentiating vertebral compression fractures from malignant ones, assessing partial and complete tears of the anterior cruciate ligament (ACL), monitoring tumor response to therapy, and characterization of soft-tissue and bone tumors. DWI is however less useful in differentiating malignant vs. infectious processes. As of yet, no definitive qualitative or quantitative properties have been established due to reasons ranging from variability in acquisition protocols to overlapping imaging characteristics. Even with these limitations, DWI can still provide clinically useful information, increasing diagnostic accuracy and improving patient management when magnetic resonance imaging (MRI) findings are inconclusive. The purpose of this article is to summarize recent research into DWI applications in the musculoskeletal system. PMID:26682143

  11. 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

  12. [Ovarian metastases from ventricular cancer diagnosed using diffusion-weighted 3T magnetic resonance imaging].

    PubMed

    Røhl, Lisbeth; Nellemann, Hanne Marie; Ladekarl, Morten; Pedersen, Erik Morre

    2011-04-18

    A 58-year-old female with a non-resectable ventricular cancer was followed by conventional 3.0 T magnetic resonance imaging (MRI) of the pelvis and abdomen including diffusion-weighted MR imaging (DWI). B-values were 0 and 1,000 seconds/mm2, and the apparent diffusion coefficient was calculated. At one control, ovarian metastases were detected by DWI, but did not show on conventional T2 and T1. The ovarian metastases were surgically removed and histologically verified - even though metastasectomy is controversial. In conclusion, DWI at 3.0 T is feasible and can improve the detection of metastatic disease compared with conventional MRI. PMID:21501566

  13. Abdominal applications of diffusion-weighted magnetic resonance imaging: Where do we stand

    PubMed Central

    Morani, Ajaykumar C; Elsayes, Khaled M; Liu, Peter S; Weadock, William J; Szklaruk, Janio; Dillman, Jonathan Russell; Khan, Asra; Chenevert, Thomas L; Hussain, Hero K

    2013-01-01

    Diffusion-weighted imaging (DWI) is one of the magnetic resonance imaging (MRI) sequences providing qualitative as well as quantitative information at a cellular level. It has been widely used for various applications in the central nervous system. Over the past decade, various extracranial applications of DWI have been increasingly explored, as it may detect changes even before signal alterations or morphological abnormalities become apparent on other pulse sequences. Initial results from abdominal MRI applications are promising, particularly in oncological settings and for the detection of abscesses. The purpose of this article is to describe the clinically relevant basic concepts of DWI, techniques to perform abdominal DWI, its analysis and applications in abdominal visceral MR imaging, in addition to a brief overview of whole body DWI MRI. PMID:23671743

  14. Differentiation of malignant and benign lung lesions with diffusion-weighted MR imaging

    PubMed Central

    Gümüştaş, Sevtap; Inan, Nagihan; Akansel, Gür; Çiftçi, Ercüment; Demirci, Ali; Özkara, Sevgiye Kaçar

    2012-01-01

    Background The aim of the study was to evaluate the role of diffusion-weighted magnetic resonance imaging in the differential diagnosis of lung lesions. Patients and methods. Sixty-seven patients with lung lesions (48 malignant, 19 benign) were included in this prospective study. Signal intensities (SIs) were measured in diffusion-weighted MR images that were obtained with b=0, 500 and 1000 s/mm2 values. Apparent diffusion coefficient (ADC) maps were calculated by using images with b=0 and 1000 s/mm2 values. The statistical significance was determined using the Student-t test. Results The SIs of malignant lesions were significantly higher than those of benign lesions (p<0.004 for b=0 s/mm2 and p<0.000 for the other b values). Using b=500 s/mm2, SI≥391 indicated a malignant lesion with a sensitivity of 95%, specificity of 73% and positive predictive value of 87%. Using b=1000 s/mm2, SI≥277 indicated a malignant lesion with a sensitivity of 93%, specificity of 69% and positive predictive value of 85%. There was no significant difference between malignant and benign lesions regarding ADC values (p=0.675). There was no significant difference in SIs or ADC values between small cell carcinoma and non-small cell carcinoma. When comparing undifferentiated with well- partially differentiated cancers, SIs were higher with all b values, but the difference was statistically significant only with b=1000 s/mm2 (p<0.04). Conclusions Diffusion-weighteted MR trace image SI is useful for the differentiation of malignant versus benign lung lesions. PMID:23077446

  15. 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

  16. 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

  17. Evaluation of Hepatic Tumors Using Intravoxel Incoherent Motion Diffusion-Weighted MRI

    PubMed Central

    Wang, Mingjie; Li, Xudan; Zou, Jianxun; Chen, Xugao; Chen, Shuyan; Xiang, Wanqing

    2016-01-01

    Background This study aimed to evaluate the diagnostic value of the D value, D* value, and f magnitude for identifying benign and malignant hepatic tumors using intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI). Material/Methods Data of 89 cases (123 lesions) with hepatic tumor confirmed by surgical pathology and postoperative follow-up were retrospectively collected. Among these cases, 40 cases were benign hepatic tumors (57 lesions) and 49 cases were malignant hepatic tumors (66 lesions). All subjects underwent conventional MRI with T1WI, T2WI, multi-b-value DWI, and dynamic enhanced LAVA scan. Diffusion-weighted images with 11 b values (0, 10, 20, 30, 50, 80, 100, 200, 400, 800, and 1000 s/mm2) were obtained to calculate true molecular diffusion (D), perfusion-related diffusion coefficient (D*), and perfusion fraction (f). The diagnostic performance in differentiating between malignant and benign hepatic lesions was analyzed. Results Malignant lesions had a significantly lower D value ([1.04±0.34]×10−3 mm2/s) and D* value ([16.5±7.7]×10−3 mm2/s) compared to benign lesions (D value: [1.70±0.55]×10−3 mm2/s, P<0.01; D* value: [21.7±9.9]×10−3 mm2/s, P<0.01). There was no statistically significant difference in f values between malignant (23.3±9.5) and benign lesions (33.5±14.9, P=0.13). In addition, D exhibited a better diagnostic performance than D* in terms of the area under the curve, sensitivity, and specificity when identifying malignancies from benign lesions. Conclusions D and D* are significant parameters for diagnosing hepatic tumors. Moreover, the D value is a more reliable parameter in distinguishing benign and malignant hepatic tumors. PMID:26931063

  18. Diffusion-weighted magnetic resonance imaging in predicting the radiosensitivity of cervical cancer

    PubMed Central

    Ni, Xiaolei; Tong, Yuanhe; Xiao, Youping; Liao, Jiang; Chen, Yunbing; Wang, Min

    2015-01-01

    This study investigates the application value of diffusion-weighted magnetic resonance imaging in predicting cervical cancer radiosensitivity. Twenty-five patients who were newly diagnosed as cervical cancer and accepted simple radiotherapy were included in this study. Before external irradiation, 20 GY and at the end of irradiation, routine 1.5 T MRI and diffusion-weighted magnetic resonance imaging scanning were carried. Apparent diffusion coefficient (ADC) value of primary tumor was measured. Its correlation with tumor regression rate was analyzed. ADC values of before irradiation, 20 GY and at the end of irradiation was (0.93 ± 0.14) × 10-3 mm2/s, (1.25 ± 0.17) × 10-3 mm2/s and (1.55 ± 0.13) × 10-3 mm2/s, respectively. There were statistical significant differences (P< 0.01). D-value of ADC values between before and 20 GY external irradiation was (0.33 ± 0.16) mm2/s. The tumor volume before and at the end of external irradiation were (37.48 ± 26.83) cm3 and (4.41 ± 3.72) cm3 respectively, with tumor regression rate of before and after external irradiation of (0.86 ± 0.11). ADC values of before irradiation, 20 GY and at the end of irradiation did not correlate with tumor regression rate. D-value of ADC values between before and 20 GY external irradiation positively correlated with tumor regression rate (r = 0.423, P = 0.035). ADC value of cervical cancer increased after radiotherapy and early changes of ADC value was positively correlated with tumor regression rate, thus, ADC value could be used as a potential prediction factor for cervical cancer radiosensitivity. PMID:26550334

  19. Importance of b value in diffusion weighted imaging for the diagnosis of pancreatic cancer

    PubMed Central

    Hao, Jin-Gang; Wang, Jia-Ping; Gu, Ya-Lv; Lu, Ming-Liang

    2013-01-01

    AIM: To investigate the use of multi-b-value diffusion-weighted imaging in diagnosing pancreatic cancer. METHODS: We retrospectively analyzed 33 cases of pancreatic cancer and 12 cases of benign pancreatic tumors at the Second Affiliated Hospital of Kunming Medical University from December 2008 to January 2011. The demographic characteristics, clinical presentation, routine magnetic resonance imaging and diffusion weighted imaging (DWI) features with different b values were reviewed. Continuous data were expressed as mean ± SD. Comparisons between pancreatic cancer and benign pancreatic tumors were performed using the Student’s t test. A probability of P < 0.05 was considered statistically significant. RESULTS: Thirty-three patients with pancreatic cancer were identified. The mean age at diagnosis was 60 ± 5.6 years. The male: female ratio was 21:12. Twenty cases were confirmed by surgical resection and 13 by biopsy of metastases. T1 weighted images demonstrated a pancreatic head mass in 16 patients, a pancreatic body mass in 10 cases, and a pancreatic tail mass with pancreatic atrophy in 7 cases. Eight patients had hepatic metastases, 13 had invasion or envelopment of mesenteric vessels, 4 had bone metastases, and 8 had lymph node metastases. DWI demonstrated an irregular intense mass with unclear margins. Necrotic tissue demonstrated an uneven low signal. A b of 1100 s/mm2 was associated with a high intensity signal with poor anatomical delineation. A b of 700 s/mm2 was associated with apparent diffusion coefficients (ADCs) that were useful in distinguishing benign and malignant pancreatic tumors (P < 0.05). b values of 50, 350, 400, 450 and 1100 s/mm2 were associated with ADCs that did not differentiate the two tumors. CONCLUSION: Low b value images demonstrated superior anatomical details when compared to high b value images. Tumor tissue definition was high and contrast with the surrounding tissues was good. DWI was useful in diagnosing pancreatic cancer

  20. 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.

  1. Coronal Diffusion-weighted Magnetic Resonance Imaging of the Kidney: Agreement with Axial Diffusion-weighted Magnetic Imaging in Terms of Apparent Diffusion Coefficient Values

    PubMed Central

    Wang, Hai-Yi; Wang, Jia; Tang, Ye-Huan; Ye, Hui-Yi; Ma, Lin

    2015-01-01

    Background: Coronal diffusion-weighted magnetic resonance imaging (DW-MRI) and apparent diffusion coefficient (ADC) values have gradually become applied (following conventional axial DW-MRI) in the renal analysis. To explore whether data obtained using coronal DW-MRI are comparable with those derived using axial DW-MRI, this preliminary study sought to assess the agreement in renal ADC values between coronal DW-MRI and axial DW-MRI. Methods: Thirty-four healthy volunteers were enrolled in the study; written consents were obtained. All subjects underwent respiratory-triggered axial and coronal DW-MRI using a 1.5-MR system with b values of 0 and 800 s/mm2. The signal-to-noise ratios (SNRs) of the two DW-MRI sequences were measured and statistically compared using the paired t-test. The extent of agreement of ADC values of the upper pole, mid-pole, and lower pole of the kidney; the mean ADC values of the left kidney and right kidney; and the mean ADC values of the bilateral kidneys were evaluated via calculation of intraclass correlation coefficients (ICCs) or Bland–Altman method between the two DW-MRI sequences. Results: The SNR of coronal DW-MR images was statistically inferior to that of axial DW-MR images (P < 0.001). The ICCs of the ADC values of each region of interest, and the mean ADC values of bilateral kidneys, between the two sequences, were greater than 0.5, and the mean ADCs of the bilateral kidneys demonstrated the highest ICC (0.869; 95% confidence interval: 0.739–0.935). In addition, 94.1% (32/34), 94.1% (32/34), and 97.1% (31/34) of the ADC bias was inside the limits of agreement in terms of the mean ADC values of the left kidneys, right kidneys, and bilateral kidneys when coronal and axial DWI-MRI were compared. Conclusions: ADC values derived using coronal DW-MRI exhibited moderate-to-good agreement to those of axial DW-MRI, rendering the former an additional useful DW-MRI method, and causing the ADC values derived using the two types of DW

  2. Diffusion-weighted whole-body imaging with background body signal suppression (DWIBS): features and potential applications in oncology

    PubMed Central

    Takahara, Taro; Ochiai, Reiji; Nievelstein, Rutger A. J.; Luijten, Peter R.

    2008-01-01

    Diffusion-weighted magnetic resonance imaging (DWI) provides functional information and can be used for the detection and characterization of pathologic processes, including malignant tumors. The recently introduced concept of “diffusion-weighted whole-body imaging with background body signal suppression” (DWIBS) now allows acquisition of volumetric diffusion-weighted images of the entire body. This new concept has unique features different from conventional DWI and may play an important role in whole-body oncological imaging. This review describes and illustrates the basics of DWI, the features of DWIBS, and its potential applications in oncology. Electronic supplementary material The online version of this article (doi:10.1007/s00330-008-0968-z) contains supplementary material, which is available to authorized users. PMID:18446344

  3. Cyst infection in unilateral renal cystic disease and the role of diffusion-weighted magnetic resonance imaging.

    PubMed

    Takase, Yasukazu; Kodama, Koichi; Motoi, Isamu; Saito, Katsuhiko

    2012-11-01

    In multicystic renal diseases, cyst infection is a complex issue because of the absence of validated diagnostic methods. Unilateral renal cystic disease is a rare multicystic disease, believed to have an acquired maldevelopmental origin. Unilateral renal cystic disease is often confused with autosomal dominant polycystic kidney disease but has some distinguishing characteristics: unilateral localization, negative family history, and no progression to chronic renal failure. We describe a case of unilateral renal cystic disease with cyst infection that could be detected by diffusion-weighted magnetic resonance imaging, but not by conventional imaging techniques. Diffusion-weighted magnetic resonance imaging can be useful for detecting infected cysts, especially in multicystic renal diseases. PMID:22990058

  4. 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.

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

    PubMed

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

    2016-06-14

    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

  6. Anisotropy Induced by Macroscopic Boundaries: Surface-Normal Mapping using Diffusion-Weighted Imaging

    PubMed Central

    Özarslan, Evren; Nevo, Uri; Basser, Peter J.

    2008-01-01

    In MRI, macroscopic boundaries lead to a diffusion-related increase in signal intensity near them—an effect commonly referred to as edge-enhancement. In diffusion-weighted imaging protocols where the signal attenuation due to diffusion results predominantly from the application of magnetic field gradients, edge-enhancement will depend on the orientation of these diffusion gradients. The resulting diffusion anisotropy can be exploited to map the direction normal to the macroscopic boundary. Simulations suggest that the hypothesized anisotropy may be within observable limits even when the voxel contains no boundary itself—hence, the name remote-anisotropy. Moreover, for certain experimental parameters there may be significant phase cancellations within the voxel that may lead to an edge detraction effect. When this is avoided, the eigenvector corresponding to the smallest eigenvalue of the diffusion tensor obtained from diffusion-tensor imaging can be used to create surface-normal maps conveniently. Experiments performed on simple geometric constructs as well as real tissue demonstrate the feasibility of using the edge-enhancement mechanism to map orientations orthogonal to macroscopic surfaces, which may be used to assess the integrity of tissue and organ boundaries noninvasively. PMID:18065457

  7. Robust optimization of diffusion-weighted MRI protocols used for fiber reconstruction

    NASA Astrophysics Data System (ADS)

    Majumdar, S.; Udpa, S. S.; Raguin, L. G.

    2008-11-01

    Diffusion-weighted imaging (DWI) is a magnetic resonance imaging (MRI) technique that employs diffusion-encoding gradients to sensitize the signal to the diffusion of water molecules. DWI allows the noninvasive and quantitative probing of opaque structures such as fibrous soft tissues. Model-based DWI post-processing algorithms, such as diffusion tensor imaging (DTI), solve an inverse problem to estimate from a series of DWI data a set of model parameters representing the diffusion process and the environment of the water molecules. DWI models connect the model parameters (e.g., fiber orientations for fibrous soft tissues) with the experimental parameters (e.g., strengths and directions of the 3-D diffusion-encoding gradients). For spinal cord injuries and skeletal muscle characterization, the fiber orientations within the imaged region can be approximately known a priori using localizer images. Then, we propose and implement a model-based robust optimization framework for two axisymmetric diffusion models, producing robust DWI protocols with respect to the approximate knowledge of the fiber orientations within the images, thereby reducing the uncertainty in the parameter estimates caused by experimental noise. Our goal is to improve the yield of quantitative DWI diagnostics used in clinical and preclinical trials by minimizing the experimental uncertainty.

  8. 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.

  9. Intravoxel incoherent motion diffusion-weighted imaging in differentiating uterine fibroid from focal adenomyosis: initial results.

    PubMed

    Tian, Tao; Zhang, Guo-Fu; Zhang, He; Liu, Hui

    2016-01-01

    To evaluate the performance of intravoxel incoherent motion (IVIM)-diffusion-weighted imaging (DWI) in differentiating uterine fibroids from focal adenomyosises. Twenty-five uterine fibroids and 21 focal adenomyosises prospectively underwent IVIM-DWI examination prior to surgery. Four parameters including apparent diffusion coefficient total values (ADCtot), true diffusion coefficient (D), pseudodiffusion coefficient (D*) and perfusion fraction (f) derived from IVIM-DWI images were separately calculated and compared across four groups. There was a statistically significant difference in IVIM-derived f parameter between fibroid and focal adenomyosis (p = 0.01) and control group (p = 0.02). Uterine fibroids gave higher coefficient of variation (CV) of all IVIM-derived parameters than focal adenomyosises. IVIM-DWI could improve the sensitivity and specificity of detecting focal adenomyosis to 100 and 92.6 %, respectively. IVIM-f parameter could be potentially used to better distinguish uterine fibroid from focal adenomyosis. The higher CV of IVIM-derived parameters with acceptable range is often observed in the diseased group. PMID:26759748

  10. Diffusion-weighted imaging with apparent diffusion coefficient mapping and spectroscopy in prostate cancer.

    PubMed

    Jacobs, Michael A; Ouwerkerk, Ronald; Petrowski, Kyle; Macura, Katarzyna J

    2008-12-01

    Prostate cancer is a major health problem, and the exploration of noninvasive imaging methods that have the potential to improve specificity while maintaining high sensitivity is still critically needed. Tissue changes induced by tumor growth can be visualized by magnetic resonance imaging (MRI) methods. Current MRI methods include conventional T2-weighted imaging, diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping and magnetic resonance spectroscopy (MRS). Techniques such as DWI/ADC provide functional information about the behavior of water molecules in tissue; MRS can provide biochemical information about the presence or absence of certain metabolites, such as choline, creatine, and citrate. Finally, vascular parameters can be investigated using dynamic contrast-enhanced MRI. Moreover, with whole-body MRI and DWI, metastatic disease can be evaluated in 1 session and may provide a way to monitor treatment. Therefore, when combining these various methods, a multiparametric data set can be built to assist in the detection, localization, assessment of prostate cancer aggressiveness, and tumor staging. Such a comprehensive approach offers more power to evaluate prostate disease than any single measure alone. In this article, we focus on the role of DWI/ADC and MRS in the detection and characterization using both in vivo and ex vivo imaging of prostate pathology. PMID:19512848

  11. Diffusion-Weighted MRI Reflects Proliferative Activity in Primary CNS Lymphoma

    PubMed Central

    Meyer, Jonas; Gawlitza, Matthias; Frydrychowicz, Clara; Müller, Wolf; Preuss, Matthias; Bure, Lionel; Quäschling, Ulf; Hoffmann, Karl-Titus; Surov, Alexey

    2016-01-01

    Purpose To investigate if apparent diffusion coefficient (ADC) values within primary central nervous system lymphoma correlate with cellularity and proliferative activity in corresponding histological samples. Materials and Methods Echo-planar diffusion-weighted magnetic resonance images obtained from 21 patients with primary central nervous system lymphoma were reviewed retrospectively. Regions of interest were drawn on ADC maps corresponding to the contrast enhancing parts of the tumors. Biopsies from all 21 patients were histologically analyzed. Nuclei count, total nuclei area and average nuclei area were measured. The proliferation index was estimated as Ki-67 positive nuclei divided by total number of nuclei. Correlations of ADC values and histopathologic parameters were determined statistically. Results Ki-67 staining revealed a statistically significant correlation with ADCmin (r = -0.454, p = 0.038), ADCmean (r = -0.546, p = 0.010) and ADCmax (r = -0.515, p = 0.017). Furthermore, ADCmean correlated in a statistically significant manner with total nucleic area (r = -0.500, p = 0.021). Conclusion Low ADCmin, ADCmean and ADCmax values reflect a high proliferative activity of primary cental nervous system lymphoma. Low ADCmean values—in concordance with several previously published studies—indicate an increased cellularity within the tumor. PMID:27571268

  12. Diffusion-weighted imaging in pediatric body MR imaging: principles, technique, and emerging applications.

    PubMed

    Chavhan, Govind B; Alsabban, Zehour; Babyn, Paul S

    2014-01-01

    Diffusion-weighted (DW) imaging is an emerging technique in body imaging that provides indirect information about the microenvironment of tissues and lesions and helps detect, characterize, and follow up abnormalities. Two main challenges in the application of DW imaging to body imaging are the decreased signal-to-noise ratio of body tissues compared with neuronal tissues due to their shorter T2 relaxation time, and image degradation related to physiologic motion (eg, respiratory motion). Use of smaller b values and newer motion compensation techniques allow the evaluation of anatomic structures with DW imaging. DW imaging can be performed as a breath-hold sequence or a free-breathing sequence with or without respiratory triggering. Depending on the mobility of water molecules in their microenvironment, different normal tissues have different signals at DW imaging. Some normal tissues (eg, lymph nodes, spleen, ovarian and testicular parenchyma) are diffusion restricted, whereas others (eg, gallbladder, corpora cavernosa, endometrium, cartilage) show T2 shine-through. Epiphyses that contain fatty marrow and bone cortex appear dark on both DW images and apparent diffusion coefficient maps. Current and emerging applications of DW imaging in pediatric body imaging include tumor detection and characterization, assessment of therapy response and monitoring of tumors, noninvasive detection and grading of liver fibrosis and cirrhosis, detection of abscesses, and evaluation of inflammatory bowel disease. PMID:24819803

  13. Diagnostic utility of diffusion-weighted magnetic resonance imaging in two common renal tumors

    PubMed Central

    WEN, ZHAOXIA; SUN, ZHENCHAO; WANG, YUXING

    2015-01-01

    The aim of the present study was to evaluate the utility of diffusion-weighted magnetic resonance imaging (DWI) in the diagnosis of common renal tumors. Conventional magnetic resonance imaging and DWI were performed on 85 patients with renal lesions (54 renal carcinoma and 31 renal angiomyolipoma cases). The apparent diffusion coefficient (ADC) values in each case at b=800 sec/mm2 were measured in the ADC maps using a statistical software package. The 54 cases of renal cell carcinoma showed a high signal intensity in the parenchyma, and the 31 renal angiomyolipoma cases showed a well-defined mixed signal intensity on DWI. The soft-tissue component showed a high signal intensity and the fat tissue showed a low signal intensity on DWI. When the b-value was set to 800 sec/mm2, the mean ADC was significantly lower in the renal carcinoma cases than in the renal angiomyolipoma cases. In conclusion, the measurement of ADC on DWI can reveal the structure of renal tumors, which is beneficial in diagnosing and determining the prognosis of benign and malignant renal tumors. PMID:26622890

  14. Prognostic role for diffusion-weighted imaging of pediatric optic pathway glioma.

    PubMed

    Yeom, K W; Lober, R M; Andre, J B; Fisher, P G; Barnes, P D; Edwards, M S B; Partap, S

    2013-07-01

    Optic pathway glioma (OPG) has an unpredictable course, with poor correlation between conventional imaging features and tumor progression. We investigated whether diffusion-weighted MRI (DWI) predicts the clinical behavior of these tumors. Twelve children with OPG (median age 2.7 years; range 0.4-6.2 years) were followed for a median 4.4 years with DWI. Progression-free survival (time to requiring therapy) was compared between tumors stratified by apparent diffusion coefficient (ADC) from initial pre-treatment scans. Tumors with baseline ADC greater than 1,400 × 10(-6) mm(2)/s required treatment earlier than those with lower ADC (log-rank p = 0.002). In some cases, ADC increased leading up to treatment, and declined following treatment with surgery, chemotherapy, or radiation. Baseline ADC was higher in tumors that eventually required treatment (1,562 ± 192 × 10(-6) mm(2)/s), compared with those conservatively managed (1,123 ± 114 × 10(-6) mm(2)/s) (Kruskal-Wallis test p = 0.013). Higher ADC predicted earlier tumor progression in this cohort and in some cases declined after therapy. Evaluation of OPG with DWI may therefore be useful for predicting tumor behavior and assessing treatment response. PMID:23673514

  15. Updates in advanced diffusion-weighted magnetic resonance imaging techniques in the evaluation of prostate cancer

    PubMed Central

    Vargas, Hebert Alberto; Lawrence, Edward Malnor; Mazaheri, Yousef; Sala, Evis

    2015-01-01

    Diffusion-weighted magnetic resonance imaging (DW-MRI) is considered part of the standard imaging protocol for the evaluation of patients with prostate cancer. It has been proven valuable as a functional tool for qualitative and quantitative analysis of prostate cancer beyond anatomical MRI sequences such as T2-weighted imaging. This review discusses ongoing controversies in DW-MRI acquisition, including the optimal number of b-values to be used for prostate DWI, and summarizes the current literature on the use of advanced DW-MRI techniques. These include intravoxel incoherent motion imaging, which better accounts for the non-mono-exponential behavior of the apparent diffusion coefficient as a function of b-value and the influence of perfusion at low b-values. Another technique is diffusion kurtosis imaging (DKI). Metrics from DKI reflect excess kurtosis of tissues, representing its deviation from Gaussian diffusion behavior. Preliminary results suggest that DKI findings may have more value than findings from conventional DW-MRI for the assessment of prostate cancer. PMID:26339460

  16. Diffusion-weighted MRI findings and clinical correlations in sporadic Creutzfeldt-Jakob disease.

    PubMed

    Gao, Ting; Lyu, Jin-Hao; Zhang, Jia-Tang; Lou, Xin; Zhao, Wei; Xing, Xiao-Wei; Yang, Ming; Yao, Yan; Tan, Qing-Che; Tian, Cheng-Lin; Huang, Xu-Sheng; Ma, Lin; Yu, Sheng-Yuan

    2015-06-01

    The objective of this study is to investigate the hyperintense lesions on diffusion-weighted magnetic resonance imaging (DWI) and its clinical correlation in sporadic Creutzfeldt-Jakob disease (sCJD). Patients who suffered from sCJD and followed up at the Department of Neurology at the General Hospital of the People's Liberation Army during the period of June 1, 2007 to July 1, 2014 were reviewed. The location of the hyperintense lesions on DWI, apparent diffusion coefficient (ADC) values of the hyperintense lesions were correlated with symptoms and clinical course. A total of 58 sCJD patients and ten healthy controls were included. Hyperintense lesions on DWI were observed in all the patients. The patients with basal ganglia (BG) hyperintense lesions on DWI had shorter disease duration and higher incidence of myoclonus (92 versus 44 %) than those without BG hyperintense lesions. The patients with occipital cortex hyperintense lesions on DWI had shorter disease duration between symptom onset and akinetic mutism than those without these lesions. The lower of the BG ADC value the faster presence of akinetic mutism and the shorter disease duration the patients will have. The presence of BG and occipital cortex hyperintense lesions on DWI and BG ADC values is correlated with the clinical course and clinical symptoms. PMID:25860342

  17. Advanced Diffusion-Weighted Magnetic Resonance Imaging Techniques of the Human Spinal Cord

    PubMed Central

    Andre, Jalal B.; Bammer, Roland

    2012-01-01

    Unlike those of the brain, advances in diffusion-weighted imaging (DWI) of the human spinal cord have been challenged by the more complicated and inhomogeneous anatomy of the spine, the differences in magnetic susceptibility between adjacent air and fluid-filled structures and the surrounding soft tissues, and the inherent limitations of the initially used echo-planar imaging techniques used to image the spine. Interval advances in DWI techniques for imaging the human spinal cord, with the specific aims of improving the diagnostic quality of the images, and the simultaneous reduction in unwanted artifacts have resulted in higher-quality images that are now able to more accurately portray the complicated underlying anatomy and depict pathologic abnormality with improved sensitivity and specificity. Diffusion tensor imaging (DTI) has benefited from the advances in DWI techniques, as DWI images form the foundation for all tractography and DTI. This review provides a synopsis of the many recent advances in DWI of the human spinal cord, as well as some of the more common clinical uses for these techniques, including DTI and tractography. PMID:22158130

  18. Diffusion-weighted MRI for the detection of colorectal polyps: feasibility study.

    PubMed

    Leufkens, Anke M; Kwee, Thomas C; van den Bosch, Maurice A A J; Mali, Willem P Th M; Takahara, Taro; Siersema, Peter D

    2013-01-01

    The purpose of this study was to determine the feasibility of diffusion-weighted magnetic resonance imaging (DWI) for detecting colorectal polyps. DWI (high b-value of 1000 s/mm(2)) was prospectively performed in 26 symptomatic patients who were scheduled to undergo colonoscopy. DWI and colonoscopic findings were interpreted in a blinded manner. The sensitivity and positive predictive value (PPV) of DWI for the detection of clinically relevant polyps (≥6 mm) and colorectal cancer (CRC) were calculated on a per-lesion basis, using colonoscopy results as the standard of reference. Sensitivity, specificity, PPV and negative predictive value (NPV) on a per-patient basis were also calculated. Sensitivity and PPV on a per-lesion basis were 80.0% [95% confidence interval (CI): 49.0%-94.3%] and 72.7% (95% CI: 43.4%-90.3%) for polyps ≥6 mm and CRC. Sensitivity, specificity, PPV and NPV on a per-patient basis were 85.7% (95% CI: 48.7%-97.4%), 84.2% (95% CI: 62.4%-94.5%), 66.7% (95% CI: 35.4%-87.9%) and 94.1% (95% CI: 73.0%-99.0%) for polyps ≥6mm and CRC. In conclusion, DWI cannot yet be recommended in a clinical setting in which DWI is performed first and subsequent colonoscopy is only performed in patients with positive findings at DWI. Further (technical) developments are required to increase its diagnostic yield. PMID:22898697

  19. 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

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

    PubMed

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

    2007-08-01

    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

  1. Diffusion weighted magnetic resonance imaging for acute stroke: practical and popular

    PubMed Central

    Tan, P L; King, D; Durkin, C J; Meagher, T M; Briley, D

    2006-01-01

    Aim To evaluate the feasibility and impact of diffusion weighted magnetic resonance imaging (DW MRI) as the first line neuroimaging of stroke at a district general hospital. Methods Prospective audit of all in‐patients admitted with clinically suspected acute stroke and referred for imaging over a consecutive 17 week period. The data collected included scan type, time from cerebral event to imaging request, and time from formal radiological request to neuroimaging. Clinicians' (general physicians, neurologists, and radiologists) perceptions were assessed by a questionnaire. Results 148 patients had neuroimaging for clinically suspected stroke during this period. Eighty one per cent of patients (120 of 148) had DW MRI as first line. Ninety two per cent of these patients had DW MRI within 24 hours of the formal radiological request. Twenty eight patients did not undergo DW MRI because lack of MRI safety, clinical state, unavailability because of maintenance service or lack of trained staff. Clinicians found the introduction of the DW MRI based service a significant improvement on computed tomography, especially for equivocal cases. Conclusion DW based MRI service is both feasible and sustainable in the setting of a district general hospital and most clinicians feel that this is a significant improvement to stroke services. PMID:16597819

  2. 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

  3. Role of diffusion-weighted imaging in the diagnosis of gynecological diseases.

    PubMed

    Namimoto, Tomohiro; Awai, Kazuo; Nakaura, Takeshi; Yanaga, Yumi; Hirai, Toshinori; Yamashita, Yasuyuki

    2009-03-01

    Recent technical advances in diffusion-weighted imaging (DWI) greatly enhanced the clinical value of magnetic resonance imaging (MRI) of the body. DWI can provide excellent tissue contrast based on molecular diffusion and may be able to demonstrate malignant tumors. Quantitative measurement of the apparent diffusion coefficient (ADC) may be valuable in distinguishing between malignant and benign lesions. We reviewed DWI and conventional MRI of the female pelvis to study the utility of DWI in patients with gynecological diseases. Although the ADC can help to differentiate between normal and cancerous tissue in the uterine cervix and endometrium, its utility may be limited by the large overlap of the uterine myometrium and ovaries. On the other hand, the ADC may be useful for monitoring the therapeutic outcome after uterine arterial embolizati (UAE), chemotherapy and/or radiation therapy. In patients with ovarian cancer, DWI demonstrates high intensity not only at the primary cancer site but also in disseminated peritoneal implants. When added to conventional MRI findings, DWI and ADC values provide additional information and DWI may play an important role in the diagnosis of patients with gynecological diseases. PMID:18839179

  4. 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

  5. Meta-analysis of diffusion-weighted magnetic resonance imaging in identification of colorectal cancer

    PubMed Central

    Jia, Hongyuan; Ma, Xuelei; Zhao, Yang; Zhao, Jingyi; Liu, Rongjun; Chen, Zihang; Chen, Jinna; Huang, Jingwen; Li, Yanyan; Zhang, Jing; Wang, Feng

    2015-01-01

    Purpose: This meta-analysis aimed to evaluate the performance of diffusion-weighted magnetic resonance imaging (DWI) in identification of colorectal cancer. Methods: A systematic literature search was performed for studies that evaluated the diagnostic accuracy of DWI in identification of colorectal cancer. Methodological quality was assessed by Quality Assessment for Studies of Diagnostic Accuracy 2 (QUADAS 2) tool. After extracting data, we estimated the pooled sensitivity, specificity, likelihood ratios, and constructed summary receiver operating characteristics (SROC) curve. Results: Ten studies involving 367 malignant lesions and 178 benign lesions were considered eligible after full-text review. The pooled sensitivity and specificity were 0.95 (95% CI: 0.90-0.97) and 0.93 (95% CI: 0.85-0.97), respectively. Positive likelihood ratio and negative likelihood ratio were 12.8 (95% CI: 5.99-27.4) and 0.06 (95% CI: 0.03-0.11), respectively. The area under SROC curve was 0.98. Conclusions: Our meta-analysis indicates that DWI is a highly accurate diagnostic method in identification of colorectal cancer. PMID:26770325

  6. Hepatocellular Carcinoma and Diffusion-Weighted MRI: Detection and Evaluation of Treatment Response.

    PubMed

    Gluskin, Jill S; Chegai, Fabrizio; Monti, Serena; Squillaci, Ettore; Mannelli, Lorenzo

    2016-01-01

    Differentiating between cancerous tissue and healthy liver parenchyma could represent a challenge with the only conventional Magnetic Resonance (MR) imaging. Diffusion weighted imaging (DWI) exploits different tissue characteristics to conventional Magnetic Resonance Imaging (MRI) sequences that enhance hepatocellular carcinoma (HCC) detection, characterization, and post-treatment evaluation. Detection of HCC is improved by DWI, infact this technology increases conspicuity of lesions that might otherwise not be identified due to obscuration by adjacent vessels or due to low contrast between the lesion and background liver. It is important to remember that DWI combined with contrast-enhanced MRI has higher sensitivity than DWI alone, and that some patients are not eligible for use of contrast on CT and MRI; in these patients DWI has a prominent role. MRI has advanced beyond structural anatomic imaging to now showing pathophysiologic processes. DWI is a promising way to characterize lesions utilizing the inherent contrast within the liver and has the benefit of not requiring contrast injection. DWI improves detection and characterization of HCC. Proposed clinical uses for DWI include: assessing prognosis, predicting response, monitoring response to therapy, and distinguishing tumor recurrence from treatment effect. Ideally, DWI will help risk stratify patients and will participate in prognostic modeling. PMID:27471573

  7. 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.

  8. 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. PMID:26350492

  9. Hepatocellular Carcinoma and Diffusion-Weighted MRI: Detection and Evaluation of Treatment Response

    PubMed Central

    Gluskin, Jill S; Chegai, Fabrizio; Monti, Serena; Squillaci, Ettore; Mannelli, Lorenzo

    2016-01-01

    Differentiating between cancerous tissue and healthy liver parenchyma could represent a challenge with the only conventional Magnetic Resonance (MR) imaging. Diffusion weighted imaging (DWI) exploits different tissue characteristics to conventional Magnetic Resonance Imaging (MRI) sequences that enhance hepatocellular carcinoma (HCC) detection, characterization, and post-treatment evaluation. Detection of HCC is improved by DWI, infact this technology increases conspicuity of lesions that might otherwise not be identified due to obscuration by adjacent vessels or due to low contrast between the lesion and background liver. It is important to remember that DWI combined with contrast-enhanced MRI has higher sensitivity than DWI alone, and that some patients are not eligible for use of contrast on CT and MRI; in these patients DWI has a prominent role. MRI has advanced beyond structural anatomic imaging to now showing pathophysiologic processes. DWI is a promising way to characterize lesions utilizing the inherent contrast within the liver and has the benefit of not requiring contrast injection. DWI improves detection and characterization of HCC. Proposed clinical uses for DWI include: assessing prognosis, predicting response, monitoring response to therapy, and distinguishing tumor recurrence from treatment effect. Ideally, DWI will help risk stratify patients and will participate in prognostic modeling. PMID:27471573

  10. 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.

  11. 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.

  12. Characterization and Correction of Geometric Distortions in 814 Diffusion Weighted Images

    PubMed Central

    Treiber, Jeffrey Mark; White, Nathan S.; Steed, Tyler Christian; Bartsch, Hauke; Holland, Dominic; Farid, Nikdokht; McDonald, Carrie R.; Carter, Bob S.

    2016-01-01

    Introduction Diffusion Weighted Imaging (DWI), which is based on Echo Planar Imaging (EPI) protocols, is becoming increasingly important for neurosurgical applications. However, its use in this context is limited in part by significant spatial distortion inherent to EPI. Method We evaluated an efficient algorithm for EPI distortion correction (EPIC) across 814 DWI scans from 250 brain tumor patients and quantified the magnitude of geometric distortion for whole brain and multiple brain regions. Results Evaluation of the algorithm’s performance revealed significantly higher mutual information between T1-weighted pre-contrast images and corrected b = 0 images than the uncorrected b = 0 images (p < 0.001). The distortion magnitude across all voxels revealed a median EPI distortion effect of 2.1 mm, ranging from 1.2 mm to 5.9 mm, the 5th and 95th percentile, respectively. Regions adjacent to bone-air interfaces, such as the orbitofrontal cortex, temporal poles, and brain stem, were the regions most severely affected by DWI distortion. Conclusion Using EPIC to estimate the degree of distortion in 814 DWI brain tumor images enabled the creation of a topographic atlas of DWI distortion across the brain. The degree of displacement of tumors boundaries in uncorrected images is severe but can be corrected for using EPIC. Our results support the use of distortion correction to ensure accurate and careful application of DWI to neurosurgical practice. PMID:27027775

  13. 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

  14. Secondary neurolymphomatosis detected by whole-body diffusion-weighted magnetic resonance imaging: a case report.

    PubMed

    Tanaka, Hiroaki; Yoshino, Kazuhiro; Sakaida, Emiko; Hashimoto, Shinichiro; Takeda, Yusuke; Kawajiri, Chika; Takagi, Toshiyuki; Nakaseko, Chiaki

    2013-01-01

    Neurolymphomatosis (NL) is a rare clinical entity defined as peripheral nervous system infiltration by lymphoma. The diagnosis is difficult and often elusive. Whole-body diffusion-weighted magnetic resonance imaging (DW MRI) was developed to enhance the detection of vaguely delineated tumors. Here, we describe the case of a 71-year-old male with secondary NL of diffuse large B-cell lymphoma (DLBCL) that was successfully detected by whole-body DW MRI. The patient was diagnosed with DLBCL extending from the ethmoidal sinus to the nasal cavity, orbital cavity, and anterior cranial fossa. Although he was administered R-THP-COP chemotherapy and the tumor remarkably decreased in size, he developed painful paresthesia and weakness in the left upper and bilateral lower extremities during treatment. Because lymphoma cells were detected in his spinal fluid, high-dose methotrexate (MTX) and weekly intrathecal MTX and cytarabine injections were administered. Test results for lymphoma cells in the spinal fluid became negative ; however, the neurological disorders progressed. Whole-body DW MRI was performed as whole-body screening and could localize NL at the left cervical and bilateral lumbar nerve roots. Both cervical spine plain MRI and enhanced computed tomography performed around the same time could not detect the cervical lesion. Our case report suggests that whole-body DW MRI is a useful diagnostic imaging procedure, especially as whole-body screening in facilities where PET/CT is not available. PMID:24369224

  15. Improved diffusion-weighting efficiency of pulsed gradient stimulated echo MR measurements with background gradient cross-term suppression.

    PubMed

    Finsterbusch, Jürgen

    2008-04-01

    Accurate diffusion measurements with pulsed gradient NMR are hampered by cross-terms of the diffusion-weighting and background gradients. For experiments based on a stimulated echo pulse sequence, that is preferred for samples with a T2 short compared to the diffusion time, a diffusion-weighting scheme has been presented that avoids these cross-terms in each of the en- and decoding periods separately. However, this approach suffers from a reduced diffusion-weighting efficiency because the two gradients applied in each of the periods have effectively opposite polarities leading to a partial cancellation. An extension of this scheme is presented that involves an additional gradient pulse in each period and delivers an improved diffusion-weighting efficiency without sacrificing the cross-term compensation. Analytical expressions for the gradient pulse lengths and amplitudes are given for arbitrary timing parameters. MR measurements with artificial (switched) background gradients were performed to test the cross-term compensation capability of the proposed extension. The results show that considerably higher q and b values can be achieved with the extension without changing the timing parameters. The MR measurements yielded identical diffusion coefficients without, with the same, and with different background gradients in the en- and decoding periods demonstrating the cross-term compensation of the presented approach. PMID:18226941

  16. Improved diffusion-weighting efficiency of pulsed gradient stimulated echo MR measurements with background gradient cross-term suppression

    NASA Astrophysics Data System (ADS)

    Finsterbusch, Jürgen

    2008-04-01

    Accurate diffusion measurements with pulsed gradient NMR are hampered by cross-terms of the diffusion-weighting and background gradients. For experiments based on a stimulated echo pulse sequence, that is preferred for samples with a T2 short compared to the diffusion time, a diffusion-weighting scheme has been presented that avoids these cross-terms in each of the en- and decoding periods separately. However, this approach suffers from a reduced diffusion-weighting efficiency because the two gradients applied in each of the periods have effectively opposite polarities leading to a partial cancellation. An extension of this scheme is presented that involves an additional gradient pulse in each period and delivers an improved diffusion-weighting efficiency without sacrificing the cross-term compensation. Analytical expressions for the gradient pulse lengths and amplitudes are given for arbitrary timing parameters. MR measurements with artificial (switched) background gradients were performed to test the cross-term compensation capability of the proposed extension. The results show that considerably higher q and b values can be achieved with the extension without changing the timing parameters. The MR measurements yielded identical diffusion coefficients without, with the same, and with different background gradients in the en- and decoding periods demonstrating the cross-term compensation of the presented approach.

  17. 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. PMID:24375449

  18. Detection of electroporation-induced membrane permeabilization states in the brain using diffusion-weighted MRI

    PubMed Central

    Mahmood, Faisal; Hansen, Rasmus H.; Agerholm-Larsen, Birgit; Gissel, Hanne; Ibsen, Per

    2015-01-01

    Background Tissue permeabilization by electroporation (EP) is a promising technique to treat certain cancers. Non-invasive methods for verification of induced permeabilization are important, especially in deep-seated cancers. In this study we evaluated diffusion-weighted magnetic resonance imaging (DW-MRI) as a quantitative method for detecting EP-induced membrane permeabilization of brain tissue using a rat brain model. Material and methods Fifty-four anesthetized Sprague-Dawley male rats were electroporated in the right hemisphere, using different voltage levels to induce no permeabilization (NP), transient membrane permeabilization (TMP), and permanent membrane permeabilization (PMP), respectively. DW-MRI was acquired 5 minutes, 2 hours, 24 hours and 48 hours after EP. Histology was performed for validation of the permeabilization states. Tissue content of water, Na+, K+, Ca2+, and extracellular volume were determined. The Kruskal-Wallis test was used to compare the DW-MRI parameters, apparent diffusion coefficient (ADC) and kurtosis, at different voltage levels. The two-sample Mann- Whitney test with Holm's Bonferroni correction was used to identify pairs of significantly different groups. The study was approved by the Danish Animal Experiments Inspectorate. Results and conclusion Results showed significant difference in the ADC between TMP and PMP at 2 hours (p < 0.001) and 24 hours (p < 0.05) after EP. Kurtosis was significantly increased both at TMP (p < 0.05) and PMP (p < 0.001) 5 minutes after EP, compared to NP. Kurtosis was also significantly higher at 24 hours (p < 0.05) and 48 hours (p < 0.05) at PMP compared to NP. Physiological parameters indicated correlation with the permeabilization states, supporting the DW-MRI findings. We conclude that DW-MRI is capable of detecting EP-induced permeabilization of brain tissue and to some extent of differentiating NP, TMP and PMP using appropriate scan timing. PMID:25591820

  19. 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

  20. Clinically Confirmed Stroke With Negative Diffusion-Weighted Imaging Magnetic Resonance Imaging

    PubMed Central

    Makin, Stephen D.J.; Doubal, Fergus N.; Dennis, Martin S.

    2015-01-01

    Background and Purpose— We sought to establish whether the presence (versus absence) of a lesion on magnetic resonance imaging (MRI) with diffusion weighting (DWI-MRI) at presentation with acute stroke is associated with worse clinical outcomes at 1 year. Methods— We recruited consecutive patients with a nondisabling ischemic stroke and performed DWI-MRI. Patients were followed up at 1 year to establish stroke recurrence (clinical or on MRI), cognitive impairment (Addenbrooke Cognitive Assessment Revised,<88) and modified Rankin Scale. Results— A median of 4 days post stroke, one third (76/264; 29%) of patients did not have a DWI lesion (95% confidence interval, 23%–35%). There was no statistically significant difference between those with and without a DWI lesion with respect to age or vascular risk factors. Patients without a lesion were more likely to be women or have previous stroke. At 1 year, 11 of 76 (14%) patients with a DWI-negative index stroke had a clinical diagnosis of recurrent stroke or transient ischemic attack, 33% had cognitive impairment (Addenbrooke Cognitive Assessment Revised <88), and 40% still had modified Rankin Scale >1, no different from DWI-positive patients; DWI-positive patients were more likely to have a new lesion on MRI (14%), symptomatic or asymptomatic, than DWI-negative patients (2%; P=0.02). Our data were consistent with 6 other studies (total n=976), pooled proportion of DWI-negative patients was 21% (95% confidence interval, 12%–32%). Conclusions— Nearly one third of patients with nondisabling stroke do not have a relevant lesion on acute DWI-MRI. Patients with negative DWI-MRI had no better prognosis than patients with a lesion. DWI-negative stroke patients should receive secondary prevention. PMID:26419965

  1. 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

  2. Diffusion-weighted imaging in cancer: physical foundations and applications of restriction spectrum imaging.

    PubMed

    White, Nathan S; McDonald, Carrie; McDonald, Carrie R; 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, Christopher J; Kaine, Christopher J; Carter, Bob S; Bradley, William G; Dale, Anders M

    2014-09-01

    Diffusion-weighted imaging (DWI) has been at the forefront of cancer imaging since the early 2000s. Before 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 neurooncology, 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 about 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 neurooncology, 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 in diffusion MRI scans, may enable more precise spatial targeting of lesions, with implications for radiation oncology and surgical planning. See all articles in this

  3. Focal nodular hyperplasia: characterisation at gadoxetic acid-enhanced MRI and diffusion-weighted MRI

    PubMed Central

    An, H S; Kim, Y J; Jung, S I; Jeon, H J

    2013-01-01

    Purpose: The aim of this study was to assess the enhancement patterns of hepatic focal nodular hyperplasia (FNH) on gadoxetic acid-enhanced MRI and diffusion-weighted (DW) MRI. Methods: This retrospective study had institutional review board approval. Gadoxetic acid-enhanced and DW MR images were evaluated in 23 patients with 30 FNHs (26 histologically proven and 4 radiologically diagnosed). The lesion enhancement patterns of the hepatobiliary phase images were classified as heterogeneous or homogeneous signal intensity (SI), and as dominantly high/iso or low SI compared with those of adjacent liver parenchyma. Heterogeneous (any) SI lesions and homogeneous low SI lesions were categorised into the fibrosis group, whereas homogeneous high/iso SI lesions were categorised into the non-fibrosis group. Additionally, lesion SI on T2 weighted images, DW images and apparent diffusion coefficient (ADC) values were compared between the two groups. Results: The lesions showed heterogeneous high/iso SI (n=16), heterogeneous low SI (n=5), homogeneous high/iso SI (n=7) or homogeneous low SI (n=2) at the hepatobiliary phase MR images. The fibrosis group lesions were more likely to show high SI on DW images and T2 weighted images compared with those in the non-fibrosis group (p<0.05). ADC values tended to be lower in the fibrosis group than those in the non-fibrosis group without significance. Conclusion: FNH showed variable enhancement patterns on hepatobiliary phase images during gadoxetic acid-enhanced MRI. SI on DW and T2 weighted images differed according to the fibrosis component contained in the lesion. Advances in knowledge: FNH shows a wide spectrum of imaging findings on gadoxetic acid-enhanced MRI and DW MRI. PMID:23873903

  4. Prediction of background parenchymal enhancement on breast MRI using mammography, ultrasonography, and diffusion-weighted imaging

    PubMed Central

    Kawamura, Akiko; Satake, Hiroko; Ishigaki, Satoko; Ikeda, Mitsuru; Kimura, Reiko; Shimamoto, Kazuhiro; Naganawa, Shinji

    2015-01-01

    ABSTRACT This retrospective study assessed the effects of menopausal status and menstrual cycle on background parenchymal enhancement (BPE) of breast magnetic resonance imaging (MRI), and investigated whether the degree of BPE can be predicted by findings of mammography, ultrasonography (US), and diffusion-weighted MR imaging (DWI). There were 160 study patients (80 premenopausal, 80 postmenopausal). Degree of BPE was classified into minimal, mild, moderate, or marked. Mammographic density was classified into fatty, scattered, heterogeneously dense, and extremely dense. BP echotexture on US and BP intensity on DWI were visually classified as homogeneous or heterogeneous. Apparent diffusion coefficient (ADC) values of normal breast tissue were measured. Associations of the degree of BPE with menopausal status, menstrual cycle, or imaging features were evaluated by univariate and multivariate analyses. No significant correlation was found between mammographic density and BPE (p=0.085), whereas menopausal status (p=0.000), BP echotexture (p=0.000), and BP intensity on DWI (p= 0.000), and ADC values (p=0.000) showed significant correlations with BPE. Multivariate analysis showed that postmenopausal status was an independent predictor of minimal BPE (p=0.002, OR=3.743). In premenopausal women, there was no significant correlation between menstrual cycle and BPE, whereas BP echotexture was an independent predictor of whether BPE was less than mild or greater than moderate (p=0.001, OR=26.575). BPE on breast MRI is associated with menopausal status and the findings of US and DWI. Because premenopausal women with heterogeneous BP echotexture may be predicted to show moderate or marked BPE, scheduling of breast MRI should preferentially be adjusted to the menstrual cycle. PMID:26412889

  5. Diagnostic significance of diffusion-weighted MRI in patients with cervical cancer: a meta-analysis.

    PubMed

    Hou, Bo; Xiang, Shi-Feng; Yao, Gen-Dong; Yang, Su-Jun; Wang, Yu-Fang; Zhang, Yi-Xin; Wang, Jun-Wei

    2014-12-01

    The aim of this meta-analysis is to demonstrate whether diffusion-weighted magnetic resonance imaging (DWI) could assist in the precise diagnosis of cervical cancer or not. Both English and Chinese electronic databases were searched for potential relevant studies followed by a comprehensive literature search without any language restriction. Two reviewers independently assessed the methodological quality of the included trials. Standardized mean difference (SMD) and its corresponding 95 % confidence interval (95 % CI) were calculated in this meta-analysis. We chose Version 12.0 STATA statistical software to analyze our statistical data. Thirteen eligible cohort studies were selected for statistical analysis, including 645 tumor tissues and 504 normal tissues. Combined SMD of apparent diffusion coefficient (ADC) suggested that the ADC value in cervical cancer tissues was significantly lower than that of normal tissue (SMD = 2.80, 95 % CI = 2.64 ~ 2.96, P < 0.001). Subgroup analysis stratified by ethnicity indicated a higher ADC value in the normal tissues compared to the cancer tissues in both the Asian and Caucasian subgroups (Asians: SMD = 2.83, 95 % CI = 2.64 ~ 3.02, P < 0.001; Caucasians: SMD = 2.73, 95 % CI = 2.45 ~ 3.01, P < 0.001, respectively). The results from the subgroup analysis by MRI machine type revealed a statistically significant difference in ADC value between normal cervical tissue and tumor tissues among all of the six MRI machine type subgroups (all P < 0.05). The main finding from our meta-analysis revealed that increased signal intensity on DWI and decreased signal on ADC seem to be useful in the diagnosis of cervical cancer. DWI could therefore be an important imaging tool in potentially identifying patients with cervical cancer. PMID:25168365

  6. Prediction of Selective Serotonin Reuptake Inhibitor Response Using Diffusion-Weighted MRI

    PubMed Central

    DeLorenzo, Christine; Delaparte, Lauren; Thapa-Chhetry, Binod; Miller, Jeffrey M.; Mann, J. John; Parsey, Ramin V.

    2013-01-01

    Pre-treatment differences in serotonergic binding between those who remit to antidepressant treatment and those who do not have been found using Positron Emission Tomography (PET). To investigate these differences, an exploratory study was performed using a second imaging modality, diffusion-weighted MRI (DW-MRI). Eighteen antidepressant-free subjects with Major Depressive Disorder received a 25-direction DW-MRI scan prior to 8 weeks of selective serotonin reuptake inhibitor treatment. Probabilistic tractography was performed between the midbrain/raphe and two target regions implicated in depression pathophysiology (amygdala and hippocampus). Average fractional anisotropy (FA) within the derived tracts was compared between SSRI remitters and non-remitters, and correlation between pre-treatment FA values and SSRI treatment outcome was assessed. Results indicate that average FA in DW-MRI-derived tracts to the right amygdala was significantly lower in non-remitters (0.55 ± 0.04) than remitters (0.61 ± 0.04, p < 0.01). In addition, there was a significant correlation between average FA in tracts to the right amygdala and SSRI treatment response. These relationships were found at a trend level when using the left amygdala as a tractography target. No significant differences were observed when using the hippocampus as target. These regional differences, consistent with previous PET findings, suggest that the integrity and/or number of white matter fibers terminating in the right amygdala may be compromised in SSRI non-remitters. Further, this study points to the benefits of multimodal imaging and suggests that DW-MRI may provide a pre-treatment signature of SSRI depression remission at 8 weeks. PMID:23508528

  7. Spatially-constrained probability distribution model of incoherent motion (SPIM) for abdominal diffusion-weighted MRI.

    PubMed

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

    2016-08-01

    Quantitative diffusion-weighted MR imaging (DW-MRI) of the body enables characterization of the tissue microenvironment by measuring variations in the mobility of water molecules. The diffusion signal decay model parameters are increasingly used to evaluate various diseases of abdominal organs such as the liver and spleen. However, previous signal decay models (i.e., mono-exponential, bi-exponential intra-voxel incoherent motion (IVIM) and stretched exponential models) only provide insight into the average of the distribution of the signal decay rather than explicitly describe the entire range of diffusion scales. In this work, we propose a probability distribution model of incoherent motion that uses a mixture of Gamma distributions to fully characterize the multi-scale nature of diffusion within a voxel. Further, we improve the robustness of the distribution parameter estimates by integrating spatial homogeneity prior into the probability distribution model of incoherent motion (SPIM) and by using the fusion bootstrap solver (FBM) to estimate the model parameters. We evaluated the improvement in quantitative DW-MRI analysis achieved with the SPIM model in terms of accuracy, precision and reproducibility of parameter estimation in both simulated data and in 68 abdominal in-vivo DW-MRIs. Our results show that the SPIM model not only substantially reduced parameter estimation errors by up to 26%; it also significantly improved the robustness of the parameter estimates (paired Student's t-test, p < 0.0001) by reducing the coefficient of variation (CV) of estimated parameters compared to those produced by previous models. In addition, the SPIM model improves the parameter estimates reproducibility for both intra- (up to 47%) and inter-session (up to 30%) estimates compared to those generated by previous models. Thus, the SPIM model has the potential to improve accuracy, precision and robustness of quantitative abdominal DW-MRI analysis for clinical applications. PMID

  8. Magnetic resonance diffusion-weighted imaging: sensitivity and apparent diffusion constant in stroke.

    PubMed

    Jones, S C; Perez-Trepichio, A D; Xue, M; Furlan, A J; Awad, I A

    1994-01-01

    Magnetic resonance diffusion-weighted imaging (MR-DWI) is sensitive to the diffusibility of water and may offer characterization and anatomical localization of stroke leading to early tailored therapeutic intervention. We compared DWI, the apparent diffusion constant (ADC), and autoradiographic cerebral blood flow (CBF) in a model of focal cerebral ischemia in the rat. Sprague-Dawley rats were embolized with a single silicone cylinder injected into the internal carotid artery. Both common carotids were permanently ligated. The animals were anesthetized (isoflurane in O2), and paralyzed (gallamine). MR-DWI were obtained with a GE 4.7 T magnet (TE = 3 s, TR = 80 msec, b = 2393.10(-3) mm2/s, slice thickness 3 mm). DWI and CBF autoradiograms were compared visually. ADC was assessed in various regions, including ischemic cortex and a region homologous to ischemic cortex. Imaging times from stroke onset were 50 +/- 6 min (mean +/- SEM) for DWI, 185 +/- 17 min for a second DWI. CBF was determined at 258 +/- 15 min. The specificity was 100% at both 50 min and 185 min, indicating that there were no false positives; in 3 animals ischemia was not present. However, the sensitivity analysis indicated that early DWI yields some false negatives; at 50 min the sensitivity was 60%. We attribute our result of low early sensitivity to small infarcts in relation to the slice thickness. Later, at 185 min, sensitivity was 100%. The first ADCs were higher than the second ADC values in ischemic cortex. For infarcts larger than the slice thickness, early MR-DWI is highly sensitive for imaging evolving ischemia.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7976548

  9. 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

  10. Implementation and assessment of diffusion-weighted partial Fourier readout-segmented echo-planar imaging.

    PubMed

    Frost, Robert; Porter, David A; Miller, Karla L; Jezzard, Peter

    2012-08-01

    Single-shot echo-planar imaging has been used widely in diffusion magnetic resonance imaging due to the difficulties in correcting motion-induced phase corruption in multishot data. Readout-segmented EPI has addressed the multishot problem by introducing a two-dimensional nonlinear navigator correction with online reacquisition of uncorrectable data to enable acquisition of high-resolution diffusion data with reduced susceptibility artifact and T*(2) blurring. The primary shortcoming of readout-segmented EPI in its current form is its long acquisition time (longer than similar resolution single-shot echo-planar imaging protocols by approximately the number of readout segments), which limits the number of diffusion directions. By omitting readout segments at one side of k-space and using partial Fourier reconstruction, readout-segmented EPI imaging times could be reduced. In this study, the effects of homodyne and projection onto convex sets reconstructions on estimates of the fractional anisotropy, mean diffusivity, and diffusion orientation in fiber tracts and raw T(2)- and trace-weighted signal are compared, along with signal-to-noise ratio results. It is found that projections onto convex sets reconstruction with 3/5 segments in a 2 mm isotropic diffusion tensor image acquisition and 9/13 segments in a 0.9 × 0.9 × 4.0 mm(3) diffusion-weighted image acquisition provide good fidelity relative to the full k-space parameters. This allows application of readout-segmented EPI to tractography studies, and clinical stroke and oncology protocols. PMID:22535706

  11. The role of diffusion-weighted magnetic resonance imaging in the classification of hepatic hydatid cysts.

    PubMed

    Ceçe, Hasan; Gündoğan, Mehmet; Karakaş, Omer; Karakaş, Ekrem; Boyacı, Fatıma Nurefşan; Yıldız, Sema; Ozgönül, Abdullah; Karakaş, Emel Yiğit; Cullu, Neşat; Seker, Ahmet

    2013-01-01

    The aim of the study was to classify different types of hepatic hydatid cysts (HHCs) by measuring the mean apparent diffusion coefficient (ADC) using diffusion-weighted magnetic resonance imaging (DWI). This prospective study comprised 44 patients. The 44 HHCs were classified using Gharbi ultrasonographic classification (GUC) and then T2WIs and DWIs were obtained. The ADC values were measured of the hydatid cyst (HC) subtypes. The distribution of the ADC values in the cyst groups was compared using the Kruskal-Wallis test for multi groups and the Mann-Whitney U test for paired groups. To evaluate the efficacy of ADC values in cyst diagnosis, receiver operating characteristic (ROC) analysis was performed. According to the GUC, there were 15 type 1, 11 type 2, 7 type 3, 5 type 4 and 6 type 5 HHCs. According to the ADC values in the paired comparisons, while types 1, 2 and 5 HCs were statistically differentiated from all other groups except the type 3 group, the type 4 group was differentiated from all other groups and the type 3 group was only differentiated from the type 4 group. When two groups were formed from the HHC subtypes with types 1, 2, and 3 in one group and types 4 and 5 in the other, a statistically significant difference was determined in the mean ADC values of these new groups. In conclusion the measurement of ADC values can be considered a promising parameter as an alternative to ultrasonography in the determination of subtypes of HHCs. PMID:23177089

  12. Diffusion-weighted MRI for imaging cell death after cytotoxic or apoptosis-inducing therapy

    PubMed Central

    Papaevangelou, E; Almeida, G S; Jamin, Y; Robinson, S P; deSouza, N M

    2015-01-01

    Background: Non-invasive serial imaging is desirable to detect processes such as necrotic and apoptotic cell death in cancer patients undergoing treatment. This study investigated the use of diffusion-weighted (DW-) magnetic resonance imaging (MRI) for imaging cell death induced by either a cytotoxic drug (irinotecan), or the apoptosis-inducing agent birinapant, in human tumour xenografts in vivo. Methods: Nude mice bearing human SW620 colon carcinoma xenografts were treated with vehicle, irinotecan (50 mg kg−1) or birinapant (30 mg kg−1) for up to 5 days. DW-MRI was performed prior to and on days 1, 3 and 5 during treatment. Assessment of tumour apoptosis and necrosis ex vivo was used to validate the imaging findings. Results: Both irinotecan and birinapant induced significant tumour growth delay. Irinotecan induced a small increase in the tumour apparent diffusion coefficient (ADC) after 1 day, with a 20 and 30% increase at days 3 and 5 respectively. ADC was unchanged in the vehicle- and birinapant-treated tumours despite a growth delay in the latter. Histological analysis showed that irinotecan increased necrosis at days 3 and 5, and induced apoptosis after 1 day, compared with vehicle. Birinapant induced apoptosis after day 3, but had no effect on tumour necrosis. Conclusions: Tumour ADC changes after irinotecan treatment were associated with the induction of a mixture of necrotic and apoptotic cell death, whereas induction of apoptosis alone with birinapant was not sufficient to induce changes in tissue microstructure that were detectable with DW-MRI. ADC is a useful non-invasive biomarker for early detection of response to cytotoxic drugs, but false negatives may arise while detecting apoptotic response to birinapant. PMID:25880014

  13. Value of 3 Tesla diffusion-weighted magnetic resonance imaging for assessing liver fibrosis

    PubMed Central

    Papalavrentios, Lavrentios; Sinakos, Emmanouil; Chourmouzi, Danai; Hytiroglou, Prodromos; Drevelegas, Konstantinos; Constantinides, Manos; Drevelegas, Antonios; Talwalkar, Jayant; Akriviadis, Evangelos

    2015-01-01

    Background Limited data are available regarding the role of magnetic resonance imaging (MRI), particularly the new generation 3 Tesla technology, and especially diffusion-weighted imaging (DWI) in predicting liver fibrosis. The aim of our pilot study was to assess the clinical performance of the apparent diffusion coefficient (ADC) of liver parenchyma for the assessment of liver fibrosis in patients with non-alcoholic fatty liver disease (NAFLD). Methods 18 patients with biopsy-proven NAFLD underwent DWI with 3 Tesla MRI. DWI was performed with single-shot echo-planar technique at b values of 0-500 and 0-1000 s/mm2. ADC was measured in four locations in the liver and the mean ADC value was used for analysis. Staging of fibrosis was performed according to the METAVIR system. Results The median age of patients was 52 years (range 23-73). The distribution of patients in different fibrosis stages was: 0 (n=1), 1 (n=7), 2 (n=1), 3 (n=5), 4 (n=4). Fibrosis stage was poorly associated with ADC at b value of 0-500 s/mm2 (r= -0.30, P=0.27). However it was significantly associated with ADC at b value of 0-1000 s/mm2 (r= -0.57, P=0.01). For this b value (0-1000 s/mm2) the area under receiver-operating characteristic curve was 0.93 for fibrosis stage ≥3 and the optimal ADC cut-off value was 1.16 ×10-3 mm2/s. Conclusion 3 Tesla DWI can possibly predict the presence of advanced fibrosis in patients with NAFLD. PMID:25608776

  14. 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

  15. 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

  16. MR elastography and diffusion-weighted imaging of ex vivo prostate cancer: quantitative comparison to histopathology.

    PubMed

    Sahebjavaher, Ramin S; Nir, Guy; Gagnon, Louis O; Ischia, Joseph; Jones, Edward C; Chang, Silvia D; Yung, Andrew; Honarvar, Mohammad; Fazli, Ladan; Goldenberg, S Larry; Rohling, Robert; Sinkus, Ralph; Kozlowski, Piotr; Salcudean, Septimiu E

    2015-01-01

    The purpose of this work was (1) to develop a magnetic resonance elastography (MRE) system for imaging of the ex vivo human prostate and (2) to assess the diagnostic power of mono-frequency and multi-frequency MRE and diffusion weighted imaging (DWI) alone and combined as correlated with histopathology in a patient study. An electromagnetic driver was designed specifically for MRE studies in small-bore MR scanners. Ex vivo prostate specimens (post-fixation) of 14 patients who underwent radical prostatectomy were imaged with MRE at 7 T (nine cases had DWI). In six patients, the MRE examination was performed at three frequencies (600, 800, 1000 Hz) to extract the power-law exponent Gamma. The images were registered to wholemount pathology slides marked with the Gleason score. The areas under the receiver-operator-characteristic curves (AUC) were calculated. The methods were validated in a phantom study and it was demonstrated that (i) the driver does not interfere with the acquisition process and (ii) the driver can generate amplitudes greater than 100 µm for frequencies less than 1 kHz. In the quantitative study, cancerous tissue with Gleason score at least 3 + 3 was distinguished from normal tissue in the peripheral zone (PZ) with an average AUC of 0.75 (Gd ), 0.75 (Gl ), 0.70 (Gamma-Gd ), 0.68 (apparent diffusion coefficient, ADC), and 0.82 (Gd  + Gl  + ADC). The differentiation between PZ and central gland was modest for Gd (p < 0.07), Gl (p < 0.06) but not significant for Gamma (p < 0.2). A correlation of 0.4 kPa/h was found between the fixation time of the prostate specimen and the stiffness of the tissue, which could affect the diagnostic power results. DWI and MRE may provide complementary information; in fact MRE performed better than ADC in distinguishing normal from cancerous tissue in some cases. Multi-frequency (Gamma) analysis did not appear to improve the results. However, in light of the effect of tissue fixation, the

  17. 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

  18. Diffusion-weighted MRI in differentiating malignant from benign thyroid nodules: a meta-analysis

    PubMed Central

    Chen, Lihua; Xu, Jian; Bao, Jing; Huang, Xuequan; Hu, Xiaofei; Xia, Yunbao; Wang, Jian

    2016-01-01

    Objectives To perform a meta-analysis to evaluate the diagnostic efficacy of diffusion-weighted imaging (DWI) in differentiating malignant from benign thyroid nodules. Design A meta-analysis. Data sources and study selection Medical and scientific literature databases were searched for original articles published up to August 2015. Studies were selected if they (1) included diagnostic DWI for differentiating malignant from benign thyroid lesions, (2) included patients who later underwent biopsy and (3) presented sufficient data to enable the construction of contingency tables. Data synthesis For each study, the true-positive, false-positive, true-negative and false-negative values were extracted or derived, and 2×2 contingency tables were constructed. Methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) instrument. The heterogeneity test, threshold effect test, subgroup analyses and publication bias analyses were performed. Results From the 113 identified search results, 15 studies, representing a total of 765 lesions, were included in the meta-analysis. We detected heterogeneity between studies but found no evidence of publication bias. The methodological quality was moderate. The pooled weighted sensitivity was 0.90 (95% CI 0.85 to 0.93); the specificity was 0.95 (95% CI 0.88 to 0.98); the positive likelihood ratio was 16.49 (95% CI 7.37 to 36.86); the negative likelihood ratio was 0.11 (95% CI 0.08 to 0.16); and the diagnostic OR was 150.73 (95% CI 64.96 to 349.75). The area under the receiver operator characteristic curve was 0.95 (95% CI 0.93 to 0.97). Conclusions Quantitative DWI may be a non-invasive, non-radiative and accurate method of distinguishing malignant from benign thyroid nodules. Nevertheless, large-scale trials are necessary to assess its clinical value and to establish standards regarding b values and cut-off values for DWI-based diagnosis. PMID:26733564

  19. Integrative analysis of diffusion-weighted MRI and genomic data to inform treatment of glioblastoma.

    PubMed

    Jajamovich, Guido H; Valiathan, Chandni R; Cristescu, Razvan; Somayajula, Sangeetha

    2016-09-01

    Gene expression profiling from glioblastoma (GBM) patients enables characterization of cancer into subtypes that can be predictive of response to therapy. An integrative analysis of imaging and gene expression data can potentially be used to obtain novel biomarkers that are closely associated with the genetic subtype and gene signatures and thus provide a noninvasive approach to stratify GBM patients. In this retrospective study, we analyzed the expression of 12,042 genes for 558 patients from The Cancer Genome Atlas (TCGA). Among these patients, 50 patients had magnetic resonance imaging (MRI) studies including diffusion weighted (DW) MRI in The Cancer Imaging Archive (TCIA). We identified the contrast enhancing region of the tumors using the pre- and post-contrast T1-weighted MRI images and computed the apparent diffusion coefficient (ADC) histograms from the DW-MRI images. Using the gene expression data, we classified patients into four molecular subtypes, determined the number and composition of genes modules using the gap statistic, and computed gene signature scores. We used logistic regression to find significant predictors of GBM subtypes. We compared the predictors for different subtypes using Mann-Whitney U tests. We assessed detection power using area under the receiver operating characteristic (ROC) analysis. We computed Spearman correlations to determine the associations between ADC and each of the gene signatures. We performed gene enrichment analysis using Ingenuity Pathway Analysis (IPA). We adjusted all p values using the Benjamini and Hochberg method. The mean ADC was a significant predictor for the neural subtype. Neural tumors had a significantly lower mean ADC compared to non-neural tumors ([Formula: see text]), with mean ADC of [Formula: see text] and [Formula: see text] for neural and non-neural tumors, respectively. Mean ADC showed an area under the ROC of 0.75 for detecting neural tumors. We found eight gene modules in the GBM cohort. The

  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. Calculation methods for ventricular diffusion-weighted imaging thermometry: phantom and volunteer studies.

    PubMed

    Sakai, Koji; Yamada, Kei; Sugimoto, Naozo

    2012-02-01

    A method for the measurement of temperature in the lateral ventricle using diffusion-weighted imaging (DWI) has been proposed recently. This method uses predetermined arbitrary thresholds, but a more objective method of calculation would be useful. We therefore compared four different calculation methods, two of which were newly created and did not require predetermined thresholds. A rectangular polyethylene terephthalate bottle (8 × 10 × 28 cm(3)) was filled with heated water (35.0-38.8 °C) and used as a water phantom. The DWI data of 23 healthy subjects (aged 26-75 years; mean ± standard deviation, 50.13 ± 19.1 years) were used for this study. The temperature was calculated using the following equation: T(°C) = 2256.74/ln(4.39221/D) - 273.15, where D is the diffusion coefficient. The mean ventricular temperature was calculated by four methods: two thresholding methods and two histogram curve-fitting methods. As a reference, we used the temperature measured at the tympanic membrane, which is known to be approximately 1 °C lower than the brain temperature. The averaged differences in temperature between mercury thermometry and classical predetermined thresholding methods for the water phantom were 0.10 ± 0.42 and 0.05 ± 0.41 °C, respectively. The histogram curve-fitting methods, however, yielded temperatures a little lower (averaged differences of -0.24 ± 0.32 and -0.14 ± 0.31 °C, respectively) than mercury thermometry. There was very little difference in temperature between tympanic thermometry and classical predetermined thresholding methods (+0.01 and -0.07 °C, respectively). In humans, however, the histogram curve-fitting methods yielded temperatures approximately 1 °C higher (+1.04 °C and +1.36 °C, respectively), suggesting that temperatures measured in this way more closely approximate the true brain temperature. The histogram curve-fitting methods were more objective and better

  2. 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

  3. 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

  4. 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

  5. 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

  6. A finite difference method with periodic boundary conditions for simulations of diffusion-weighted magnetic resonance experiments in tissue

    NASA Astrophysics Data System (ADS)

    Russell, Greg; Harkins, Kevin D.; Secomb, Timothy W.; Galons, Jean-Philippe; Trouard, Theodore P.

    2012-02-01

    A new finite difference (FD) method for calculating the time evolution of complex transverse magnetization in diffusion-weighted magnetic resonance imaging and spectroscopy experiments is described that incorporates periodic boundary conditions. The new FD method relaxes restrictions on the allowable time step size employed in modeling which can significantly reduce computation time for simulations of large physical extent and allow for more complex, physiologically relevant, geometries to be simulated.

  7. 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

  8. 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.

  9. Fast burning propellants

    SciTech Connect

    Colgate, S.A.; Roos, G.E.

    1987-07-21

    A solid or semisolid propellant is described comprising grains of propellant or propellant components bonded together to create voids within the propellant volume. The grains are of near-uniform size and have less than about a 20% size variation between the largest and smallest grains, the voids comprising from about 10% to about 50% of the propellant volume. The grains are bonded together with sufficient strength to substantially delay the fluidization of the propellant by the onset of Taylor unstable burning. The propellant has a rapid burn rate of from about 10 cm sec/sup -1/ to about 10/sup 4/cm sec/sup -1/.

  10. Diffusion Weighted MR Imaging of Breast and Correlation of Prognostic Factors in Breast Cancer

    PubMed Central

    Kızıldağ Yırgın, İnci; Arslan, Gözde; Öztürk, Enis; Yırgın, Hakan; Taşdemir, Nihat; Gemici, Ayşegül Akdoğan; Kabul, Fatma Çelik; Kaya, Eyüp

    2016-01-01

    Background: Through Diffusion Weighted Imaging (DWI), information related to early molecular changes, changes in the permeability of cell membranes, and early morphologic and physiologic changes such as cell swelling can be obtained. Aims: We investigated the correlation between the prognostic factors of breast cancer and apparent diffusion coefficient (ADC) in DWI sequences of malignant lesions. Study Design: Retrospective cross-sectional study. Methods: Patients who were referred to our clinic between September 2012 and September 2013, who underwent dynamic breast MRI before or after biopsy and whose biopsy results were determined as malignant, were included in our study. Before the dynamic analysis, DWI sequences were taken. ADC relationship with all prognostic factors was investigated. Pearson correlation test was used to compare the numerical data, while Spearman correlation and Fisher exact tests were used to compare the categorical data. The advanced relationships were evaluated with linear regression analysis and univariate analysis. The efficiency of the parameters was evaluated using ROC analysis. The significance level (P) was accepted as 0.05. Results: In total, 41 female patients with an average age of 49.4 years (age interval 21–77) and 44 lesions were included into the study. In the Pearson correlation test, no statistically significant difference was determined between ADC and the patient’s age and tumor size. In the Spearman correlation test, a statistically significant difference was determined between nuclear grade (NG) and ADC (r=−0.424, p=0.04); no statistically significant correlation was observed between the other prognostic factors with each other and ADC values. In the linear regression analysis, the relationship of NG with ADC was found to be more significant alone than when comparing all parameters (corrected r2=0.196, p=0.005). Further evaluations between the NG and ADC correlation were carried out with ROC analysis. A

  11. Solid propellant rocket motor

    NASA Technical Reports Server (NTRS)

    Dowler, W. L.; Shafer, J. I.; Behm, J. W.; Strand, L. D. (Inventor)

    1973-01-01

    The characteristics of a solid propellant rocket engine with a controlled rate of thrust buildup to a desired thrust level are discussed. The engine uses a regressive burning controlled flow solid propellant igniter and a progressive burning main solid propellant charge. The igniter is capable of operating in a vacuum and sustains the burning of the propellant below its normal combustion limit until the burning propellant surface and combustion chamber pressure have increased sufficiently to provide a stable chamber pressure.

  12. Progression of striatal and extrastriatal degeneration in multiple system atrophy: a longitudinal diffusion-weighted MR study.

    PubMed

    Pellecchia, Maria Teresa; Barone, Paolo; Vicidomini, Caterina; Mollica, Carmine; Salvatore, Elena; Ianniciello, Marta; Liuzzi, Raffaele; Longo, Katia; Picillo, Marina; De Michele, Giuseppe; Filla, Alessandro; Brunetti, Arturo; Salvatore, Marco; Pappatà, Sabina

    2011-06-01

    Diffusion-weighted imaging has been largely used to detect and quantify early degenerative changes in patients with multiple system atrophy, but progression of neurodegeneration has been poorly investigated. We performed a serial diffusion-weighted imaging study in a population of multiple system atrophy patients and analyzed the evolution of diffusion properties in striatal and extrastriatal brain regions. Diffusion-weighted imaging was obtained in 11 multiple system atrophy patients at baseline and after a follow-up of 11.7 ± 1.2 months, and Trace (D) changes in different brain regions were correlated with disease duration and severity. A significant increase in Trace (D) was observed at follow-up in the putamen (P < .001), pons (P = .003), cerebellar white matter (P = .03), thalamus (P = .013), and frontal white matter (P = .021). Both Unified Multiple System Atrophy Rating Scale Part II and Unified Parkinson's Disease Rating Scale Part III scores significantly increased at follow-up (P = .003), but percent changes of Unified Parkinson's Disease Rating Scale Part III and Unified Multiple System Atrophy Rating Scale Part II did not correlate with percent changes of Trace (D) values in any brain region. This longitudinal study provides new insights into the progression of neurodegeneration in different brain regions in multiple system atrophy. Our results confirm that abnormal diffusivity in the putamen is sensitive to change over time in multiple system atrophy patients and show for the first time a progression of Trace (D) alterations in specific extrastriatal regions. Diffusivity changes in these regions may be useful for monitoring disease progression even after a short follow-up period. © 2011 Movement Disorder Society. PMID:21469200

  13. 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.

  14. Diffusion-weighted MRI derived apparent diffusion coefficient identifies prognostically distinct subgroups of pediatric diffuse intrinsic pontine glioma.

    PubMed

    Lober, Robert M; Cho, Yoon-Jae; Tang, Yujie; Barnes, Patrick D; Edwards, Michael S; Vogel, Hannes; Fisher, Paul G; Monje, Michelle; Yeom, Kristen W

    2014-03-01

    While pediatric diffuse intrinsic pontine gliomas (DIPG) remain fatal, recent data have shown subgroups with distinct molecular biology and clinical behavior. We hypothesized that diffusion-weighted MRI can be used as a prognostic marker to stratify DIPG subsets with distinct clinical behavior. Apparent diffusion coefficient (ADC) values derived from diffusion-weighted MRI were computed in 20 consecutive children with treatment-naïve DIPG tumors. The median ADC for the cohort was used to stratify the tumors into low and high ADC groups. Survival, gender, therapy, and potential steroid effects were compared between the ADC groups. Median age at diagnosis was 6.6 (range 2.3-13.2) years, with median follow-up seven (range 1-36) months. There were 14 boys and six girls. Seventeen patients received radiotherapy, five received chemotherapy, and six underwent cerebrospinal fluid diversion. The median ADC of 1,295 × 10(-6) mm(2)/s for the cohort partitioned tumors into low or high diffusion groups, which had distinct median survivals of 3 and 13 months, respectively (log-rank p < 0.001). Low ADC tumors were found only in boys, whereas high ADC tumors were found in both boys and girls. Available tissue specimens in three low ADC tumors demonstrated high-grade histology, whereas one high ADC tumor demonstrated low-grade histology with a histone H3.1 K27M mutation and high-grade metastatic lesion at autopsy. ADC derived from diffusion-weighted MRI may identify prognostically distinct subgroups of pediatric DIPG. PMID:24522717

  15. Diffusion-Weighted Imaging in Meningioma: Prediction of Tumor Grade and Association with Histopathological Parameters12

    PubMed Central

    Surov, Alexey; Gottschling, Sebastian; Mawrin, Christian; Prell, Julian; Spielmann, Rolf Peter; Wienke, Andreas; Fiedler, Eckhard

    2015-01-01

    OBJECTIVES: To analyze diffusion-weighted imaging (DWI) findings of meningiomas and to compare them with tumor grade, cell count, and proliferation index and to test a possibility of use of apparent diffusion coefficient (ADC) to differentiate benign from atypical/malignant tumors. METHODS: Forty-nine meningiomas were analyzed. DWI was done using a multislice single-shot echo-planar imaging sequence. A polygonal region of interest was drawn on ADC maps around the margin of the lesion. In all lesions, minimal ADC values (ADCmin) and mean ADC values (ADCmean) were estimated. Normalized ADC (NADC) was calculated in every case as a ratio ADCmean meningioma/ADCmean white matter. All meningiomas were surgically resected and analyzed histopathologically. The tumor proliferation index was estimated on Ki-67 antigen–stained specimens. Cell density was calculated. Collected data were evaluated by means of descriptive statistics. Analyses of ADC/NADC values were performed by means of two-sided t tests. RESULTS: The mean ADCmean value was higher in grade I meningiomas in comparison to grade II/III tumors (0.96 vs 0.80 × 10− 3 mm2s− 1, P = .006). Grade II/III meningiomas showed lower NADC values in comparison to grade I tumors (1.05 vs 1.26, P = .015). There was no significant difference in ADCmin values between grade I and II/III tumors (0.69 vs 0.63 × 10− 3 mm2s− 1, P = .539). The estimated cell count varied from 486 to 2091 (mean value, 1158.20 ± 333.74; median value, 1108). There were no significant differences in cell count between grade I and grade II/III tumors (1163.93 vs 1123.86 cells, P = .77). The mean level of the proliferation index was 4.78 ± 5.08%, the range was 1% to 18%, and the median value was 2%. The proliferation index was statistically significant higher in grade II/III meningiomas in comparison to grade I tumors (15.43% vs 3.00%, P = .001). Ki-67 was negatively associated with ADCmean (r = − 0.61, P < .001) and NADC (r = − 0.60, P

  16. 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

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

    PubMed Central

    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. PMID:27019851

  18. The utility of diffusion-weighted magnetic resonance imaging in differentiation of endometriomas from hemorrhagic ovarian cysts.

    PubMed

    Balaban, Mehtap; Idilman, Ilkay S; Toprak, Huseyin; Unal, Ozlem; Ipek, Ali; Kocakoc, Ercan

    2015-01-01

    The aim was to determine the utility of diffusion-weighted magnetic resonance imaging (DW MRI) and apparent diffusion coefficient (ADC) measurements in differentiation of endometrioma and hemorrhagic ovarian cyst. A total of 24 female patients who underwent pelvic MRI with an initial diagnosis of ovarian cyst were included in the study. The final diagnosis was endometrioma in 12 patients and hemorrhagic ovarian cyst in 12 patients. We observed significantly lower ADC values in endometriomas compared with hemorrhagic ovarian cysts in all b values. DW MRI with quantitative ADC measurements can be used for differentiation of endometrioma from hemorrhagic ovarian cysts. PMID:25986161

  19. 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

  20. Passive propellant system

    NASA Technical Reports Server (NTRS)

    Hess, D. A.; Regnier, W. W.; Jacobs, V. L. (Inventor)

    1979-01-01

    A passive propellant acquisition and feed system is disclosed which acquires and feeds gas-free propellant in low or zero-g environments during orbital maneuvers and retains this propellant under high axially directed acceleration such as may be experienced during launch of a space vehicle and orbit-to-orbit transfer is described. The propellant system includes a dual compartment propellant tank with independent surface tension acquisition channels in each compartment to provide gas-free flow of pressurized liquid propellant from one compartment to the other in one direction only.

  1. Tandem Air Propellers - II

    NASA Technical Reports Server (NTRS)

    Lesley, E. P.

    1939-01-01

    Tests of three-blade, adjustable-pitch counterrotating tandem model propellers, adjusted to absorb equal power at maximum efficiency of the combination, were made at Stanford University. The aerodynamic characteristics, for blade-angle settings of 15, 25, 35, 45, 55, and 65 degrees at 0.75R of the forward propeller and for diameters spacings of 8-1/2, 15 and 30% were compared with those of three-blade and six-blade propellers of the same blade form. It was found that, in order to realize the condition of equal power at maximum efficiency, the blade angles for the rear propeller must be generally less than for the forward propeller, the difference increasing the blade angle. The tests showed that, at maximum efficiency, the tandem propellers absorb about double the power of three-blade propellers and about 8% more power than six-blade propellers having the pitch of the forward propeller of the tandem combination. The maximum efficiency of the tandem propellers was found to be from 2-15% greater than for six-blade propellers, the difference varying directly with blade angle. It was also found that the maximum efficiency of the tandem propellers was greater than that of a three-blade propeller for blade angles at 0.75R of 25 degrees or more. The difference in maximum efficiency again varied directly with blade angle, being about 9% for 65 degrees at 0.75R.

  2. ADC values in diffusion-weighted MRI and their relationship with age, gender and BMI in healthy people's pancreases

    PubMed Central

    Faeghi, F; Abdkarimi, M H; Asghari JafarAbadi, M

    2015-01-01

    Objective: The aim of this study is to use diffusion-weighted MRI to assess the apparent diffusion coefficient (ADC) values in head, body and tail sections of the pancreas in healthy subjects and the relationships between these values and age, gender and body mass index (BMI) of these cases. Methods: This study was conducted on 82 participants who were referred to the Tabesh Medical Imaging Center, Tabriz, Islamic Republic of Iran, during 2013. Echo-planar diffusion-weighted imaging of the pancreas was carried out with b-values of 50, 400 and 800 s mm−2, and ADC values were assessed for the head, body and tail sections of the pancreas. Results: The ADC values for the head, body and tail sections of the pancreas in female participants were significantly greater than those in male subjects (p < 0.05). ADC values for these parts among subjects with different BMI differed significantly (p < 0.05). Regarding age, there were no statistically meaningful differences among the ADC values for the three parts (p > 0.05). Conclusion: Gender and BMI effect the ADC values of the three sections of the pancreas. Thus, knowledge of the basic values based on gender and BMI can improve diagnostics. Having looked at age factor, it seems that the ADC values were not significantly different. Advances in knowledge: According to the results pancreatic ADC values appear to be influenced by gender and BMI but not by age. PMID:25471056

  3. Usefulness of diffusion-weighted MRI with echo-planar technique in the evaluation of cellularity in gliomas.

    PubMed

    Sugahara, T; Korogi, Y; Kochi, M; Ikushima, I; Shigematu, Y; Hirai, T; Okuda, T; Liang, L; Ge, Y; Komohara, Y; Ushio, Y; Takahashi, M

    1999-01-01

    The purpose of this study was to evaluate the utility of diffusion-weighted magnetic resonance imaging (MRI) with echo-planar imaging (EPI) technique in depicting the tumor cellularity and grading of gliomas. Twenty consecutive patients (13 men and 7 women, ranging in age from 13 to 69 years) with histologically proven gliomas were examined using a 1.5 T superconducting imager. Tumor cellularity, analyzed with National Institutes of Health Image 1.60 software on a Macintosh computer, was compared with the minimum apparent diffusion coefficient (ADC) and the signal intensity on the T2-weighted images. The relationship of the minimum ADC to the tumor grade was also evaluated. Tumor cellularity correlated well with the minimum ADC value of the gliomas (P = 0.007), but not with the signal intensity on the T2-weighted images. The minimum ADC of the high-grade gliomas was significantly higher than that of the low-grade gliomas. Diffusion-weighted MRI with EPI is a useful technique for assessing the tumor cellularity and grading of gliomas. This information is not obtained with conventional MRI and is useful for the diagnosis and characterization of gliomas. PMID:10030650

  4. Information-based ranking of 10 compartment models of diffusion-weighted signal attenuation in fixed prostate tissue.

    PubMed

    Liang, Sisi; Panagiotaki, Eleftheria; Bongers, Andre; Shi, Peng; Sved, Paul; Watson, Geoffrey; Bourne, Roger

    2016-05-01

    This study compares the theoretical information content of single- and multi-compartment models of diffusion-weighted signal attenuation in prostate tissue. Diffusion-weighted imaging (DWI) was performed at 9.4 T with multiple diffusion times and an extended range of b values in four whole formalin-fixed prostates. Ten models, including different combinations of isotropic, anisotropic and restricted components, were tested. Models were ranked using the Akaike information criterion. In all four prostates, two-component models, comprising an anisotropic Gaussian component and an isotropic restricted component, ranked highest in the majority of voxels. Single-component models, whether isotropic (apparent diffusion coefficient, ADC) or anisotropic (diffusion tensor imaging, DTI), consistently ranked lower than multi-component models. Model ranking trends were independent of voxel size and maximum b value in the range tested (1.6-16 mm(3) and 3000-10 000 s/mm(2) ). This study characterizes the two major water components previously identified by biexponential models and shows that models incorporating both anisotropic and restricted components provide more information-rich descriptions of DWI signals in prostate tissue than single- or multi-component anisotropic models and models that do not account for restricted diffusion. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26999065

  5. Integration of diffusion-weighted MRI data and a simple mathematical model to predict breast tumor cellularity during neoadjuvant chemotherapy.

    PubMed

    Atuegwu, Nkiruka C; Arlinghaus, Lori R; Li, Xia; Welch, E Brian; Chakravarthy, Bapsi A; Gore, John C; Yankeelov, Thomas E

    2011-12-01

    Diffusion-weighted magnetic resonance imaging data obtained early in the course of therapy can be used to estimate tumor proliferation rates, and the estimated rates can be used to predict tumor cellularity at the conclusion of therapy. Six patients underwent diffusion-weighted magnetic resonance imaging immediately before, after one cycle, and after all cycles of neoadjuvant chemotherapy. Apparent diffusion coefficient values were calculated for each voxel and for a whole tumor region of interest. Proliferation rates were estimated using the apparent diffusion coefficient data from the first two time points and then used with the logistic model of tumor growth to predict cellularity after therapy. The predicted number of tumor cells was then correlated to the corresponding experimental data. Pearson's correlation coefficient for the region of interest analysis yielded 0.95 (P = 0.004), and, after applying a 3 × 3 mean filter to the apparent diffusion coefficient data, the voxel-by-voxel analysis yielded a Pearson correlation coefficient of 0.70 ± 0.10 (P < 0.05). PMID:21956404

  6. Predictive classification of pediatric bipolar disorder using atlas-based diffusion weighted imaging and support vector machines.

    PubMed

    Mwangi, Benson; Wu, Mon-Ju; Bauer, Isabelle E; Modi, Haina; Zeni, Cristian P; Zunta-Soares, Giovana B; Hasan, Khader M; Soares, Jair C

    2015-11-30

    Previous studies have reported abnormalities of white-matter diffusivity in pediatric bipolar disorder. However, it has not been established whether these abnormalities are able to distinguish individual subjects with pediatric bipolar disorder from healthy controls with a high specificity and sensitivity. Diffusion-weighted imaging scans were acquired from 16 youths diagnosed with DSM-IV bipolar disorder and 16 demographically matched healthy controls. Regional white matter tissue microstructural measurements such as fractional anisotropy, axial diffusivity and radial diffusivity were computed using an atlas-based approach. These measurements were used to 'train' a support vector machine (SVM) algorithm to predict new or 'unseen' subjects' diagnostic labels. The SVM algorithm predicted individual subjects with specificity=87.5%, sensitivity=68.75%, accuracy=78.12%, positive predictive value=84.62%, negative predictive value=73.68%, area under receiver operating characteristic curve (AUROC)=0.7812 and chi-square p-value=0.0012. A pattern of reduced regional white matter fractional anisotropy was observed in pediatric bipolar disorder patients. These results suggest that atlas-based diffusion weighted imaging measurements can distinguish individual pediatric bipolar disorder patients from healthy controls. Notably, from a clinical perspective these findings will contribute to the pathophysiological understanding of pediatric bipolar disorder. PMID:26459075

  7. Multi-modal pharmacokinetic modelling for DCE-MRI: using diffusion weighted imaging to constrain the local arterial input function

    NASA Astrophysics Data System (ADS)

    Hamy, Valentin; Modat, Marc; Shipley, Rebecca; Dikaios, Nikos; Cleary, Jon; Punwani, Shonit; Ourselin, Sebastien; Atkinson, David; Melbourne, Andrew

    2014-03-01

    The routine acquisition of multi-modal magnetic resonance imaging data in oncology yields the possibility of combined model fitting of traditionally separate models of tissue structure and function. In this work we hypothesise that diffusion weighted imaging data may help constrain the fitting of pharmacokinetic models to dynamic contrast enhanced (DCE) MRI data. Parameters related to tissue perfusion in the intra-voxel incoherent motion (IVIM) modelling of diffusion weighted MRI provide local information on how tissue is likely to perfuse that can be utilised to guide DCE modelling via local modification of the arterial input function (AIF). In this study we investigate, based on multi-parametric head and neck MRI of 8 subjects (4 with head and neck tumours), the benefit of incorporating parameters derived from the IVIM model within the DCE modelling procedure. Although we find the benefit of this procedure to be marginal on the data used in this work, it is conceivable that a technique of this type will be of greater use in a different application.

  8. Diffusion-weighted images (DWI) without ADC values in assessment of small focal nodules in cirrhotic liver

    PubMed Central

    Chen, Mai-Lin; Zhang, Xiao-Yan; Qi, Li-Ping; Shi, Qing-Lei; Chen, Bin

    2014-01-01

    Objective To assess if diffusion-weighted magnetic resonance (MR) imaging without apparent diffusion coefficient (ADC) values provides added diagnostic value in combination with conventional MR imaging in the detection and characterization of small nodules in cirrhotic liver. Methods Two observers retrospectively and independently analyzed 86 nodules (≤3 cm) certified pathologically in 33 patients with liver cirrhosis, including 48 hepatocellular carcinoma (HCC) nodules, 13 high-grade dysplastic nodules (HDN), 10 low-grade dysplastic nodules (LDNs) and 15 other benign nodules. All these focal nodules were evaluated with conventional MR images (T1-weighted, T2-weighted and dynamic gadolinium-enhanced images) and breath-hold diffusion-weighted images (DWI) (b=500 s/mm2). The nodules were classified by using a scale of 1-3 (1, not seen; 3, well seen) on DWI for qualitative assessment. These small nodules were characterized by two radiologists. ADC values weren’t measured. The diagnostic performance of the combined DWI-conventional images and the conventional images alone was evaluated using receiver operating characteristic (ROC) curves. The area under the curves (Az), sensitivity and specificity values for characterizing different small nodules were also calculated. Results Among 48 HCC nodules, 33 (68.8%) were graded as 3 (well seen), 6 (12.5%) were graded as 2 (partially obscured), and 9 weren’t seen on DWI. Among 13 HDNs, there were 3 (23.1%) and 4 (30.8%) graded as 3 and 2 respectively. Five (50%) of 10 benign nodules were partially obscured and slightly hyperintense. For 86 nodules, the average diagnostic accuracy of combined DWI-conventional images was 82.56%, which was increased significantly compared with conventional MR images with 76.17%. For HCC and HDN, the diagnostic accuracy of combined DWI-conventional images increased from 78.69% to 86.07%. Conclusions Diffusion-weighted MR imaging does provide added diagnostic value in the detection and

  9. 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.

  10. Passive propellant system

    NASA Technical Reports Server (NTRS)

    Hess, D. A.; Regnier, W. W.; Jacobs, V. L. (Inventor)

    1978-01-01

    The system utilizes a spherical tank structure A separated into two equal volume compartments by a flat bulkhead B. Each compartment has four similar gallery channel legs located in the principal vehicle axes, ensuring that bulk propellant will contact at least one gallery leg during vehicle maneuvers. The forward compartment gallery channel legs collect propellant and feed it into the aft compartment through communication screens which protrude into the aft compartment. The propellant is then collected by the screened gallery channels in the aft compartment and supplied to the propellant outlet. The invention resides in the independent gallery assembly and screen structure by means of which propellant flow from forward to aft compartments is maintained. Liquid surface tension of the liquid on the screens is used to control liquid flow. The system provides gas-free propellants in low or zero-g environments regardless of axial accelerations and propellant orientation in bulk regions of the vessel.

  11. Pitfalls in whole body MRI with diffusion weighted imaging performed on patients with lymphoma: What radiologists should know.

    PubMed

    Albano, Domenico; La Grutta, Ludovico; Grassedonio, Emanuele; Patti, Caterina; Lagalla, Roberto; Midiri, Massimo; Galia, Massimo

    2016-09-01

    The technological advances in radiological imaging and the relevance of a diagnostic tool that may reduce radiation-induced long-term effects have led to a widespread use of whole body magnetic resonance imaging (WB-MRI) with diffusion weighted imaging for oncologic patients. A lot of studies demonstrated the feasibility and reliability of WB-MRI as an alternative technique for lymphoma staging and response assessment during and after treatment. In this paper, taking advantage of our 2years of experience using WB-MRI for lymphoma, we discuss the main pitfalls and artifacts radiologists should know examining a WB-MRI performed on this typology of patients in order to avoid images misinterpretation. PMID:27114337

  12. Scan parameters and the diffusion emphasis effect in diffusion-weighted imaging using a motion-probing gradient preparation pulse.

    PubMed

    Takahashi, Daisuke; Tanji, Hajime; Yamaki, Tomoya; Obara, Makoto; Machida, Yoshio

    2014-07-01

    Diffusion-sensitized driven equilibrium preparation (DSDE) is a gradient echo (GRE) diffusion-weighted imaging (DWI) sequence that employs a motion-probing gradient (MPG) preparation pulse and phase cycling. In DSDE, several scan parameters of the MPG preparation pulse and the GRE sequence affect diffusion sensitivity. Our investigation of the relationship between these scan parameters and the diffusion emphasis effect revealed the importance of "prep.TE" in the MPG preparation pulse and "TFE shot interval" in the gradient echo sequence. Appropriate choice of these parameters allows DSDE to provide a similar DWI to that of conventional single-shot SEEPI DWI. We therefore concluded DSDE to be a useful DWI method. PMID:25055943

  13. lop-DWI: A Novel Scheme for Pre-Processing of Diffusion-Weighted Images in the Gradient Direction Domain

    PubMed Central

    Sepehrband, Farshid; Choupan, Jeiran; Caruyer, Emmanuel; Kurniawan, Nyoman D.; Gal, Yaniv; Tieng, Quang M.; McMahon, Katie L.; Vegh, Viktor; Reutens, David C.; Yang, Zhengyi

    2015-01-01

    We describe and evaluate a pre-processing method based on a periodic spiral sampling of diffusion-gradient directions for high angular resolution diffusion magnetic resonance imaging. Our pre-processing method incorporates prior knowledge about the acquired diffusion-weighted signal, facilitating noise reduction. Periodic spiral sampling of gradient direction encodings results in an acquired signal in each voxel that is pseudo-periodic with characteristics that allow separation of low-frequency signal from high frequency noise. Consequently, it enhances local reconstruction of the orientation distribution function used to define fiber tracks in the brain. Denoising with periodic spiral sampling was tested using synthetic data and in vivo human brain images. The level of improvement in signal-to-noise ratio and in the accuracy of local reconstruction of fiber tracks was significantly improved using our method. PMID:25628600

  14. 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

  15. Preoperative CT versus diffusion weighted magnetic resonance imaging of the liver in patients with rectal cancer; a prospective randomized trial

    PubMed Central

    Løgager, Vibeke B.; Skjoldbye, Bjørn; Møller, Jakob M.; Lorenzen, Torben; Rasmussen, Vera L.; Thomsen, Henrik S.; Mollerup, Talie H.; Okholm, Cecilie; Rosenberg, Jacob

    2016-01-01

    Introduction. Colorectal cancer is one of the most frequent cancers in the world and liver metastases are seen in up to 19% of patients with colorectal cancers. Detection of liver metastases is not only vital for sufficient treatment and survival, but also for a better estimation of prognosis. The aim of this study was to evaluate the feasibility of diffusion weighted MRI of the liver as part of a combined MR evaluation of patients with rectal cancers and compare it with the standard preoperative evaluation of the liver with CT. Methods. Consecutive patients diagnosed with rectal cancers were asked to participate in the study. Preoperative CT and diffusion weighted MR (DWMR) were compared to contrast enhanced laparoscopic ultrasound (CELUS). Results. A total of 35 patients were included, 15 patients in Group-1 having the standard CT evaluation of the liver and 20 patients in Group-2 having the standard CT evaluation of the liver and DWMR of the liver. Compared with CELUS, the per-patient sensitivity/specificity was 50/100% for CT, and for DWMR: 100/94% and 100/100% for Reader 1 and 2, respectively. The per-lesion sensitivity of CT and DWMR were 17% and 89%, respectively compared with CELUS. Furthermore, one patient had non-resectable metastases after DWMR despite being diagnosed with resectable metastases after CT. Another patient was diagnosed with multiple liver metastases during CELUS, despite a negative CT-scan. Discussion. DWMR is feasible for preoperative evaluation of liver metastases. The current standard preoperative evaluation with CT-scan results in disadvantages like missed metastases and futile operations. We recommend that patients with rectal cancer, who are scheduled for MR of the rectum, should have a DWMR of the liver performed at the same time. PMID:26793420

  16. Propeller tip vortex interactions

    NASA Technical Reports Server (NTRS)

    Johnston, Robert T.; Sullivan, John P.

    1990-01-01

    Propeller wakes interacting with aircraft aerodynamic surfaces are a source of noise and vibration. For this reason, flow visualization work on the motion of the helical tip vortex over a wing and through the second stage of a counterrotation propeller (CRP) has been pursued. Initially, work was done on the motion of a propeller helix as it passes over the center of a 9.0 aspect ratio wing. The propeller tip vortex experiences significant spanwise displacements when passing across a lifting wing. A stationary propeller blade or stator was installed behind the rotating propeller to model the blade vortex interaction in a CRP. The resulting vortex interaction was found to depend on the relative vortex strengths and vortex sign.

  17. Propeller design by optimization

    NASA Technical Reports Server (NTRS)

    Rizk, M. H.; Jou, W.-H.

    1986-01-01

    The feasibility of designing propellers by an optimization procedure is investigated. A scheme, which solves the full potential flow equation about a propeller by line relaxation, is modified so that the iterative solutions of the flow equation and the design parameters are updated simultaneously. Some technical problems in using optimization for designing propellers with maximum efficiency are identified. Approaches for overcoming these problems are presented.

  18. 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.

  19. Propeller flow visualization techniques

    NASA Technical Reports Server (NTRS)

    Stefko, G. L.; Paulovich, F. J.; Greissing, J. P.; Walker, E. D.

    1982-01-01

    Propeller flow visualization techniques were tested. The actual operating blade shape as it determines the actual propeller performance and noise was established. The ability to photographically determine the advanced propeller blade tip deflections, local flow field conditions, and gain insight into aeroelastic instability is demonstrated. The analytical prediction methods which are being developed can be compared with experimental data. These comparisons contribute to the verification of these improved methods and give improved capability for designing future advanced propellers with enhanced performance and noise characteristics.

  20. In vivo High Angular Resolution Diffusion-Weighted Imaging of Mouse Brain at 16.4 Tesla

    PubMed Central

    Alomair, Othman I.; Brereton, Ian M.; Smith, Maree T.; Galloway, Graham J.; Kurniawan, Nyoman D.

    2015-01-01

    Magnetic Resonance Imaging (MRI) of the rodent brain at ultra-high magnetic fields (> 9.4 Tesla) offers a higher signal-to-noise ratio that can be exploited to reduce image acquisition time or provide higher spatial resolution. However, significant challenges are presented due to a combination of longer T1 and shorter T2/T2* relaxation times and increased sensitivity to magnetic susceptibility resulting in severe local-field inhomogeneity artefacts from air pockets and bone/brain interfaces. The Stejskal-Tanner spin echo diffusion-weighted imaging (DWI) sequence is often used in high-field rodent brain MRI due to its immunity to these artefacts. To accurately determine diffusion-tensor or fibre-orientation distribution, high angular resolution diffusion imaging (HARDI) with strong diffusion weighting (b >3000 s/mm2) and at least 30 diffusion-encoding directions are required. However, this results in long image acquisition times unsuitable for live animal imaging. In this study, we describe the optimization of HARDI acquisition parameters at 16.4T using a Stejskal-Tanner sequence with echo-planar imaging (EPI) readout. EPI segmentation and partial Fourier encoding acceleration were applied to reduce the echo time (TE), thereby minimizing signal decay and distortion artefacts while maintaining a reasonably short acquisition time. The final HARDI acquisition protocol was achieved with the following parameters: 4 shot EPI, b = 3000 s/mm2, 64 diffusion-encoding directions, 125×150 μm2 in-plane resolution, 0.6 mm slice thickness, and 2h acquisition time. This protocol was used to image a cohort of adult C57BL/6 male mice, whereby the quality of the acquired data was assessed and diffusion tensor imaging (DTI) derived parameters were measured. High-quality images with high spatial and angular resolution, low distortion and low variability in DTI-derived parameters were obtained, indicating that EPI-DWI is feasible at 16.4T to study animal models of white matter (WM

  1. The role of pre-treatment diffusion-weighted MRI in predicting long-term outcome of colorectal liver metastasis

    PubMed Central

    Collins, D J; Brown, G; Chau, I; Cunningham, D; Leach, M O; Koh, D-M

    2013-01-01

    Objective: To determine the prognostic value of pre-treatment apparent diffusion coefficient (ADC) of colorectal liver metastases in predicting disease response, progression-free survival (PFS) and overall survival (OS). Methods: We retrospectively reviewed 102 patients who underwent pre-treatment diffusion-weighted MRI using a breath-hold (b=0, 150, 500) or a free-breathing (b=0, 50, 100, 250, 500, 750) technique. The mean ADC (b=0–500) and mean flow-insensitive ADC (ADChigh) values (breath-hold: b=150 and 500; free-breathing: b=100 and 500) of up to three hepatic lesions were evaluated in each patient. Clinical and laboratory parameters were recorded. Tumour response was assessed by Response Evaluation Criteria in Solid Tumors (RECIST) criteria at 12 weeks after treatment. Associations between tumour response, ADC values and clinical/laboratory parameters were examined by one-way analysis of variance. The relationship of ADC with PFS and OS was determined by Kaplan–Meier analysis. Results: 62 patients responded to chemotherapy at 12 weeks. The pre-treatment mean ADC and mean ADChigh were higher in the non-responding group than in the responding group (1.55 vs 1.36, p=0.033; 1.40 vs 1.16, p=0.024). However, the PFS and OS of the two groups of patients stratified by the median of mean ADC values or threshold derived by receiver operating characteristic analysis were not statistically significant. By multivariate Cox regression analysis, patients with ≤2 metastases and response to chemotherapy showed better PFS; white cell count ≤10 and surgical treatment were associated with better OS. Conclusion: Colorectal liver metastasis with higher pre-treatment mean ADC and mean ADChigh was associated with poorer response to chemotherapy. However, ADC and ADChigh values did not predict the patient outcome in this study cohort. Advances in knowledge: High mean ADC values of colorectal liver metastases on pre-treatment diffusion-weighted MRI is associated with poorer

  2. 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. PMID:27129076

  3. Diffusion Weighted MR Imaging of Primary and Recurrent Middle Ear Cholesteatoma: An Assessment by Readers with Different Expertise

    PubMed Central

    Elefante, A.; Cavaliere, M.; Russo, C.; Caliendo, G.; Marseglia, M.; Cicala, D.; Piccolo, D.; Di Lullo, A.; Brunetti, L.; Palma, A.; Iengo, M.; Brunetti, A.

    2015-01-01

    Introduction and Purpose. Diffusion weighted imaging (DWI) has been proven to be valuable in the diagnosis of middle ear cholesteatoma. The aims of our study were to evaluate the advantage of multi-shot turbo spin echo (MSh TSE) DWI compared to single-shot echo-planar (SSh EPI) DWI for the diagnosis of cholesteatoma. Material and Methods. Thirty-two patients with clinical suspicion of unilateral cholesteatoma underwent preoperative MRI (1.5T) with SSh EPI and MSh TSE. Images were separately analyzed by 4 readers with different expertise to confirm the presence of cholesteatoma. Sensitivity, specificity, diagnostic accuracy, and positive (PPV) and negative predictive values (NPV) were assessed for each observer and interrater agreement was assessed using kappa statistics. Diagnosis was obtained at surgery. Results. Overall MSh TSE showed higher diagnostic accuracy and lower negative predictive value (NPV) compared to conventional SSh EPI. Interreader agreement between the observers revealed the superiority of MSh TSE compared to SSh EPI. Interrater agreement among all the four observers was higher by using MSh TSE compared to SSh EPI. Conclusion. Our findings suggest that MSh TSE DWI has higher sensitivity for detection of cholesteatoma and lower probability of misdiagnosis. MSh TSE DWI is useful in guiding less experienced observers to the diagnosis. PMID:25722983

  4. Silent cerebral emboli following percutaneous closure of atrial septal defect in pediatric patients: a diffusion-weighted MRI study

    PubMed Central

    Koç, Gonca; Özyurt, Abdullah; Doğanay, Selim; Baykan, Ali; Görkem, S. Burcu; Doğan, M. Sait; Pamukçu, Özge; Üzüm, Kazım; Coşkun, Abdulhakim; Narin, Nazmi

    2016-01-01

    PURPOSE The aim of this prospective study was to investigate the incidence of silent cerebrovascular embolic events associated with percutaneous closure of atrial septal defect (ASD) in pediatric patients. METHODS A total of 23 consecutive pediatric patients (mean age, 10.4±3.8 years; range, 4–17 years) admitted for transcatheter closure of ASD were recruited in the study. The patients were scanned with a 1.5 Tesla clinical scanner. Two cranial magnetic resonance imaging (MRI) examinations were acquired before the procedure and within 24 hours following the catheterization. MRI included turbo spin-echo fluid-attenuated inversion recovery (FLAIR) sequence and diffusion-weighted imaging technique with single-shot echo-planar spin-echo sequence. The transcatheter closure of ASD was performed by three expert interventional cardiologists. Amplatzer septal occluder device was implemented for the closure of the defect. No contrast medium was administered in the course of the procedure. RESULTS None of the patients had diffusion restricted cerebral lesions resembling microembolic infarctions on postprocedural MRI. Preprocedural MRI of two patients revealed nonspecific hyperintense white matter lesions on FLAIR images with increased diffusion, which were considered to be older ischemic lesions associated with previously occurred paradoxical embolism. CONCLUSION The current study suggests that percutaneous closure of the ASD, when performed by experienced hands, may be free of cerebral microembolization in pediatric patients. However, due to the relatively small sample size, further studies with larger patient groups are needed for the validation of our preliminary results. PMID:26394443

  5. 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.

  6. Phantom for assessment of fat suppression in large field-of-view diffusion-weighted magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Winfield, J. M.; Douglas, N. H. M.; deSouza, N. M.; Collins, D. J.

    2014-05-01

    We present the development and application of a phantom for assessment and optimization of fat suppression over a large field-of-view in diffusion-weighted magnetic resonance imaging at 1.5 T and 3 T. A Perspex cylinder (inner diameter 185 mm, height 300 mm) which contains a second cylinder (inner diameter 140 mm) was constructed. The inner cylinder was filled with water doped with copper sulphate and sodium chloride and the annulus was filled with corn oil, which closely matches the spectrum and longitudinal relaxation times of subcutaneous abdominal fat. Placement of the phantom on the couch at 45° to the z-axis presented an elliptical cross-section, which was of a similar size and shape to axial abdominal images. The use of a phantom for optimization of fat suppression allowed quantitative comparison between studies without the differences introduced by variability between human subjects. We have demonstrated that the phantom is suitable for selection of inversion delay times, spectral adiabatic inversion recovery delays and assessment of combinatorial methods of fat suppression. The phantom is valuable in protocol development and the assessment of new techniques, particularly in multi-centre trials.

  7. ROBUST FAT SUPPRESSION AT 3T IN HIGH-RESOLUTION DIFFUSION-WEIGHTED SINGLE-SHOT EPI OF HUMAN BRAIN

    PubMed Central

    Sarlls, Joelle E.; Pierpaoli, Carlo; Talagala, S. Lalith; Luh, Wen-Ming

    2011-01-01

    Single-shot EPI is the most common acquisition technique for whole-brain diffusion tensor imaging (DTI) studies in vivo. Higher field MRI systems are readily available and advantageous for acquiring DTI due to increased signal. One of the practical issues for DTI with single-shot EPI at high field is incomplete fat suppression resulting in a chemically-shifted fat artifact within the brain image. Unsuppressed fat is especially detrimental in DTI because the diffusion coefficient of fat is two orders of magnitude lower than that of parenchyma, producing brighter appearing fat artifacts with greater diffusion weighting. In this work, several fat suppression techniques were tested alone and in combination with the goal of finding a method that provides robust fat suppression and can be utilized in high-resolution single-shot EPI DTI studies. Combination of chemical shift saturation with slice-select gradient reversal within a dual-spin-echo diffusion preparation period was found to provide robust fat suppression at 3T. PMID:21604298

  8. Diffusion-Weighted Magnetic Resonance Application in Response Prediction before, during, and after Neoadjuvant Radiochemotherapy in Primary Rectal Cancer Carcinoma

    PubMed Central

    Musio, Daniela; De Felice, Francesca; Magnante, Anna Lisa; Rengo, Marco; Redler, Adriano; Laghi, Andrea; Raffetto, Nicola; Tombolini, Vincenzo

    2013-01-01

    Introduction. Our interest was to monitor treatment response using ADC value to predict response of rectal tumour to preoperative radiochemotherapy. Materials and Methods. Twenty-two patients were treated with long course of radiochemotherapy, followed by surgery. Patients were examined by diffusion-weighted imaging MRI at three-time points (prior, during, and after radiochemotherapy) and were classified as responders and nonresponders. Results. A statistical significant correlation was found between preradiochemotherapy ADC values and during treatment ADC values, in responders (F = 21.50, P value <0.05). An increase in ADC value during treatment was predictive of at least a partial response. Discussion. Response of tumour to neoadjuvant therapy cannot be easily evaluated, and such capability might be of great importance in clinical practice, because the number of irradiated and operated patients may be superior to the number of who will really benefit from this multimodal treatment. A reliable prediction of the final clinical TN stage would allow radiotherapist to adapt multidisciplinary approach to a less invasive management, sparing surgical procedure in responder patients or even allowing an early surgery in nonresponders, which would significantly reduce radiochemotherapy related toxicity. Conclusion. Early evaluation of response during neoadjuvant radiochemotherapy treatment shows great promise to predict tumour response. PMID:23936841

  9. 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

  10. 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

  11. Thymoma of the left thymic lobe with a contralateral small pleural implant successfully detected with diffusion-weighted MRI.

    PubMed

    Priola, Adriano Massimiliano; Priola, Sandro Massimo

    2015-01-01

    Thymoma is the most common primary neoplasm of the anterior mediastinum. At diagnosis, up to 40% of patients present with advanced disease. Because advanced thymomas receive neoadjuvant chemotherapy, diagnostic imaging is crucial to plan the correct treatment. For characterizing thymomas, CT is the first choice modality, whereas 18F-FDG/PET is reserved for questionable cases and MRI is not routinely employed. Hereby, we describe a case of thymoma with a single contralateral pleural implant in a 30-year-old woman. The small pleural thickening detected at CT was correctly interpreted as pleural seeding related to thymoma at diffusion-weighted (DW)-MRI after a negative 18F-FDG/PET scan, and was subsequently confirmed at surgery. Precise diagnosis and accurate preoperative staging are crucial in managing thymic epithelial tumours in order to design the appropriate treatment and improve prognosis. Indeed, when stage IVa for pleural seeding is diagnosed preoperatively, a multimodality approach including primary chemotherapy followed by surgery and postoperative radiotherapy/chemotherapy is recommended. This is the first report that used DW-MRI for the characterization of pleural seeding in thymoma and demonstrates that DW-MRI could be useful for the correct pre-operatory staging in thymoma patients, especially in cases with indeterminate pleural thickenings at CT, in order to define the correct management. PMID:25702681

  12. Diffusion-Weighted Magnetic Resonance Imaging Findings of Kidneys with Obstructive Uropathy: Differentiation between Benign and Malignant Etiology

    PubMed Central

    Apaydin, Melda; Sönmezgöz, Fitnet; Çalık, Sinan; Bedel Koruyucu, Melike

    2014-01-01

    Purpose. In this study, we aimed to evaluate the capability of diffusion-weighted magnetic resonance imaging (DWI) in differentiation between benign and malignant etiology of obstructive uropathy. Materials and Methods. DWI was performed in 41 patients with hydronephrotic kidneys and 26 healthy volunteers. MR imaging was performed using a 1.5 T whole-body superconducting MR scanner. The signal intensities of the renal parenchyma on DWI and apparent diffusion coefficient (ADC) maps were noted. DWI was performed with the following diffusion gradient b values: 100, 600, and 1000 s/mm2. A large circular region of interest was placed in the corticomedullary junction of the kidneys. For statistical analysis, the independent-samples t test was used. Results. The mean renal ADC values for b100, b600, and b1000 in hydronephrosis patients with benign and malignant etiology and the healthy volunteers of the control group were analysed. ADC measurements of renal parenchyma in all hydronephrotic kidneys with benign and malignant etiology were found to be statistically low compared to those of normal kidneys (P < 0.05). Conclusions. There were significant differences in the ADC values of obstructed kidneys compared to those of normal kidneys. Obstructed kidneys with malignant etiology had lower ADC values for b1000 compared to obstructed kidneys with benign etiology, but these alterations were statistically insignificant. PMID:24764775

  13. Diffusion-weighted imaging and dynamic contrast-enhanced MRI in assessing response and recurrent disease in gynaecological malignancies.

    PubMed

    Hameeduddin, Ayshea; Sahdev, Anju

    2015-01-01

    Magnetic resonance imaging (MRI) has an established role in imaging pelvic gynaecological malignancies. It is routinely used in staging endometrial and cervical cancer, characterizing adnexal masses, selecting optimal treatment, monitoring treatment and detecting recurrent disease. MRI has also been shown to have an excellent performance and an evolving role in surveillance of patients after chemoradiotherapy in cervical cancer, post-trachelectomy, detecting early recurrence and planning exenterative surgery in isolated central recurrences in both cervical and endometrial cancer and in young patients on surveillance for medically managed endometrial cancer. However, conventional MRI still has limitations when the morphological appearance of early recurrent or residual disease overlaps with normal pelvic anatomy or treatment effects in the pelvis. In particular, after chemoradiotherapy for cervical cancer, distinguishing between radiotherapy changes and residual or early recurrent disease within the cervix or the vaginal vault can be challenging on conventional MRI alone. Therefore, there is an emerging need for functional imaging to overcome these limitations. The purpose of this paper is to discuss the emerging functional MRI techniques and their applications in predicting treatment response, detecting residual disease and early recurrent disease to optimize the treatment options available using diffusion-weighted imaging and dynamic contrast enhancement particularly in cervical and endometrial cancer. PMID:25889065

  14. Major mouse placental compartments revealed by diffusion-weighted MRI, contrast-enhanced MRI, and fluorescence imaging

    PubMed Central

    Solomon, Eddy; Avni, Reut; Hadas, Ron; Raz, Tal; Garbow, Joel Richard; Bendel, Peter; Frydman, Lucio; Neeman, Michal

    2014-01-01

    Mammalian models, and mouse studies in particular, play a central role in our understanding of placental development. Magnetic resonance imaging (MRI) could be a valuable tool to further these studies, providing both structural and functional information. As fluid dynamics throughout the placenta are driven by a variety of flow and diffusion processes, diffusion-weighted MRI could enhance our understanding of the exchange properties of maternal and fetal blood pools—and thereby of placental function. These studies, however, have so far been hindered by the small sizes, the unavoidable motions, and the challenging air/water/fat heterogeneities, associated with mouse placental environments. The present study demonstrates that emerging methods based on the spatiotemporal encoding (SPEN) of the MRI information can robustly overcome these obstacles. Using SPEN MRI in combination with albumin-based contrast agents, we analyzed the diffusion behavior of developing placentas in a cohort of mice. These studies successfully discriminated the maternal from the fetal blood flows; the two orders of magnitude differences measured in these fluids’ apparent diffusion coefficients suggest a nearly free diffusion behavior for the former and a strong flow-based component for the latter. An intermediate behavior was observed by these methods for a third compartment that, based on maternal albumin endocytosis, was associated with trophoblastic cells in the interphase labyrinth. Structural features associated with these dynamic measurements were consistent with independent intravital and ex vivo fluorescence microscopy studies and are discussed within the context of the anatomy of developing mouse placentas. PMID:24969421

  15. Major mouse placental compartments revealed by diffusion-weighted MRI, contrast-enhanced MRI, and fluorescence imaging.

    PubMed

    Solomon, Eddy; Avni, Reut; Hadas, Ron; Raz, Tal; Garbow, Joel Richard; Bendel, Peter; Frydman, Lucio; Neeman, Michal

    2014-07-15

    Mammalian models, and mouse studies in particular, play a central role in our understanding of placental development. Magnetic resonance imaging (MRI) could be a valuable tool to further these studies, providing both structural and functional information. As fluid dynamics throughout the placenta are driven by a variety of flow and diffusion processes, diffusion-weighted MRI could enhance our understanding of the exchange properties of maternal and fetal blood pools--and thereby of placental function. These studies, however, have so far been hindered by the small sizes, the unavoidable motions, and the challenging air/water/fat heterogeneities, associated with mouse placental environments. The present study demonstrates that emerging methods based on the spatiotemporal encoding (SPEN) of the MRI information can robustly overcome these obstacles. Using SPEN MRI in combination with albumin-based contrast agents, we analyzed the diffusion behavior of developing placentas in a cohort of mice. These studies successfully discriminated the maternal from the fetal blood flows; the two orders of magnitude differences measured in these fluids' apparent diffusion coefficients suggest a nearly free diffusion behavior for the former and a strong flow-based component for the latter. An intermediate behavior was observed by these methods for a third compartment that, based on maternal albumin endocytosis, was associated with trophoblastic cells in the interphase labyrinth. Structural features associated with these dynamic measurements were consistent with independent intravital and ex vivo fluorescence microscopy studies and are discussed within the context of the anatomy of developing mouse placentas. PMID:24969421

  16. Molecular imaging of water binding state and diffusion in breast cancer using diffuse optical spectroscopy and diffusion weighted MRI

    PubMed Central

    Yu, Hon; Su, Min-Ying; Cerussi, Albert E.; Tromberg, Bruce J.

    2012-01-01

    Abstract. Tissue water content and molecular microenvironment can provide important intrinsic contrast for cancer imaging. In this work, we examine the relationship between water optical spectroscopic features related to binding state and magnetic resonance imaging (MRI)-measured water diffusion dynamics. Broadband diffuse optical spectroscopic imaging (DOSI) and MR images were obtained from eight patients with locally-advanced infiltrating ductal carcinomas (tumor size=5.5±3.2  cm). A DOSI-derived bound water index (BWI) was compared to the apparent diffusion coefficient (ADC) of diffusion weighted (DW) MRI. BWI and ADC were positively correlated (R=0.90, p-value=0.003) and BWI and ADC both decreased as the bulk water content increased (R=−0.81 and −0.89, respectively). BWI correlated inversely with tumor size (R=−0.85, p-value=0.008). Our results suggest underlying sensitivity differences between BWI and ADC to water in different tissue compartments (e.g., extracellular vs cellular). These data highlight the potential complementary role of DOSI and DW-MRI in providing detailed information on the molecular disposition of water in breast tumors. Because DOSI is a portable technology that can be used at the bedside, BWI may provide a low-cost measure of tissue water properties related to breast cancer biology. PMID:22894465

  17. 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

  18. Pretreatment Diffusion-Weighted MRI Can Predict the Response to Neoadjuvant Chemotherapy in Patients with Nasopharyngeal Carcinoma

    PubMed Central

    Zhang, Guo-Yi; Wang, Yue-Jian; Liu, Jian-Ping; Zhou, Xin-Han; Xu, Zhi-Feng; Chen, Xiang-Ping; Xu, Tao; Wei, Wei-Hong; Zhang, Yang; Huang, Ying

    2015-01-01

    Purpose. To explore the potential of diffusion-weighted (DW) magnetic resonance imaging (MRI) using apparent diffusion coefficient (ADC) for predicting the response to neoadjuvant chemotherapy in nasopharyngeal carcinoma (NPC). Methods and Materials. Ninety-two consecutive patients with NPC who underwent three cycles of neoadjuvant chemotherapy were retrospectively analyzed. DW and anatomical MRI were performed before and after neoadjuvant chemotherapy prior to radiotherapy. Pretreatment ADCs and percentage increases in ADC after chemotherapy were calculated for the primary lesions and metastatic adenopathies. Receiver operating characteristic curve analysis was used to select optimal pretreatment ADCs. Results. Pretreatment mean ADCs were significantly lower for responders than for nonresponders (primary lesions, P = 0.012; metastatic adenopathies, P = 0.013). Mean percentage increases in ADC were higher for responders than for nonresponders (primary lesions, P = 0.008; metastatic adenopathies, P < 0.001). The optimal pretreatment primary lesion and metastatic adenopathy ADCs for differentiating responders from nonresponders were 0.897 × 10−3 mm2/sec and 1.031 × 10−3 mm2/sec, respectively. Conclusions. NPC patients with low pretreatment ADCs tend to respond better to neoadjuvant chemotherapy. Pretreatment ADCs could be used as a new pretreatment imaging biomarker of response to neoadjuvant chemotherapy. PMID:26413513

  19. [Aspects of FLAIR sequences, 3D-CISS and diffusion-weight MR imaging of intracranial epidermoid cysts].

    PubMed

    Doll, A; Abu Eid, M; Kehrli, P; Esposito, P; Gillis, C; Bogorin, A; Jacques, C; Dietemann, J L

    2000-06-01

    We propose to assess the usefulness of diffusion-weighted MR Imaging (DWI), fluid-attenuated inversion recovery (FLAIR) and constructive interference in steady state (CISS) sequences in depicting epidermoid cysts (EC). FLAIR, CISS and DWI were obtained in 7 patients among 22. All patients were studied with T1 and T2 sequences. On Spin Echo images, EC demonstrate signal similar to LCS, which may lead to difficult differentiation between EC and arachnoid cyst (AC), specially for inexperienced radiologists. EC appear with a heterogeneous signal on T1 images (32%), irregular limits (91%) and with extension through foramen of Pacchioni in 18% of cases. On FLAIR sequence, the tumors were heterogeneous, different from void signal of CSF in 86% of cases. On CISS sequence, the tumors appear heterogeneous, hyperintense but less than LCS and with irregular limits in all cases. Some more, CISS images allowed to appreciate exact tumor extension and their relations with nerves and vessels. On DWI images, signal is hyperintense in all cases. Our study exhibited the great usefulness of DWI, CISS and FLAIR sequences in diagnosis of EC and in differentiating EC from AC. PMID:10970961

  20. Confirmation of functional zones within the human subthalamic nucleus: Patterns of connectivity and sub-parcellation using diffusion weighted imaging

    PubMed Central

    Lambert, Christian; Zrinzo, Ludvic; Nagy, Zoltan; Lutti, Antoine; Hariz, Marwan; Foltynie, Thomas; Draganski, Bogdan; Ashburner, John; Frackowiak, Richard

    2012-01-01

    The subthalamic nucleus (STN) is a small, glutamatergic nucleus situated in the diencephalon. A critical component of normal motor function, it has become a key target for deep brain stimulation in the treatment of Parkinson's disease. Animal studies have demonstrated the existence of three functional sub-zones but these have never been shown conclusively in humans. In this work, a data driven method with diffusion weighted imaging demonstrated that three distinct clusters exist within the human STN based on brain connectivity profiles. The STN was successfully sub-parcellated into these regions, demonstrating good correspondence with that described in the animal literature. The local connectivity of each sub-region supported the hypothesis of bilateral limbic, associative and motor regions occupying the anterior, mid and posterior portions of the nucleus respectively. This study is the first to achieve in-vivo, non-invasive anatomical parcellation of the human STN into three anatomical zones within normal diagnostic scan times, which has important future implications for deep brain stimulation surgery. PMID:22173294

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

    PubMed Central

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

    2014-01-01

    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. PMID:25173414

  2. Pitfalls and Limitations of Diffusion-Weighted Magnetic Resonance Imaging in the Diagnosis of Urinary Bladder Cancer

    PubMed Central

    Lin, Wei-Ching; Chen, Jeon-Hor

    2015-01-01

    Adequately selecting a therapeutic approach for bladder cancer depends on accurate grading and staging. Substantial inaccuracy of clinical staging with bimanual examination, cystoscopy, and transurethral resection of bladder tumor has facilitated the increasing utility of magnetic resonance imaging to evaluate bladder cancer. Diffusion-weighted imaging (DWI) is a noninvasive functional magnetic resonance imaging technique. The high tissue contrast between cancers and surrounding tissues on DWI is derived from the difference of water molecules motion. DWI is potentially a useful tool for the detection, characterization, and staging of bladder cancers; it can also monitor posttreatment response and provide information on predicting tumor biophysical behaviors. Despite advancements in DWI techniques and the use of quantitative analysis to evaluate the apparent diffusion coefficient values, there are some inherent limitations in DWI interpretation related to relatively poor spatial resolution, lack of cancer specificity, and lack of standardized image acquisition protocols and data analysis procedures that restrict the application of DWI and reproducibility of apparent diffusion coefficient values. In addition, inadequate bladder distension, artifacts, thinness of bladder wall, cancerous mimickers of normal bladder wall and benign lesions, and variations in the manifestation of bladder cancer may interfere with diagnosis and monitoring of treatment. Recognition of these pitfalls and limitations can minimize their impact on image interpretation, and carefully applying the analyzed results and combining with pathologic grading and staging to clinical practice can contribute to the selection of an adequate treatment method to improve patient care. PMID:26055180

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Nitramine propellants. [gun propellant burning rate

    NASA Technical Reports Server (NTRS)

    Cohen, N. S.; Strand, L. D. (Inventor)

    1978-01-01

    Nitramine propellants without a pressure exponent shift in the burning rate curves are prepared by matching the burning rate of a selected nitramine or combination of nitramines within 10% of burning rate of a plasticized active binder so as to smooth out the break point appearance in the burning rate curve.

  9. Navy propeller section characteristics as used in propeller design

    NASA Technical Reports Server (NTRS)

    Weick, Fred E

    1926-01-01

    This report contains artificial aerodynamic characteristics of a set of propeller sections to be used in designing propellers by means of the blade element theory. Characteristics computed from model propeller tests for a single section are extended to cover sections of Navy propeller sections at high Reynolds Number in the variable density tunnel of the NACA.

  10. Usefulness of intra-procedural cone-beam computed tomography in modified balloon-occluded retrograde transvenous obliteration of gastric varices

    PubMed Central

    Lee, Edward Wolfgang; So, Naomi; Chapman, Ryan; McWilliams, Justin P; Loh, Christopher T; Busuttil, Ronald W; Kee, Stephen T

    2016-01-01

    AIM: To evaluate whether intra-procedural cone-beam computed tomography (CBCT) performed during modified balloon-occluded retrograde transvenous obliteration (mBRTO) can accurately determine technical success of complete variceal obliteration. METHODS: From June 2012 to December 2014, 15 patients who received CBCT during mBRTO for treatment of portal hypertensive gastric variceal bleeding were retrospectively evaluated. Three-dimensional (3D) CBCT images were performed and evaluated prior to the end of the procedure, and these were further analyzed and compared to the pre-procedure contrast-enhanced computed tomography to determine the technical success of mBRTO including: Complete occlusion/obliteration of: (1) gastrorenal shunt (GRS); (2) gastric varices; and (3) afferent feeding veins. Post-mBRTO contrast-enhanced CT was used to confirm the accuracy and diagnostic value of CBCT within 2-3 d. RESULTS: Intra-procedural 3D-CBCT images were 100% accurate in determining the technical success of mBRTO in all 15 cases. CBCT demonstrated complete occlusion/obliteration of GRS, gastric varices, collaterals and afferent feeding veins during mBRTO, which was confirmed with post-mBRTO CT. Two patients showed incomplete obliteration of gastric varices and feeding veins on CBCT, which therefore required additional gelfoam injections to complete the procedure. No patient required additional procedures or other interventions during their follow-up period (684 ± 279 d). CONCLUSION: CBCT during mBRTO appears to accurately and immediately determine the technical success of mBRTO. This may improve the technical and clinical success/outcome of mBRTO and reduce additional procedure time in the future. PMID:27158425

  11. 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.

  12. Autonomous production of propellants

    NASA Technical Reports Server (NTRS)

    Ramohalli, Kumar; Schallhorn, P. A.

    1990-01-01

    The autonomous production of propellants is addressed. Since 80 to 90 percent of a spacecraft's mass is typically propellants, it is advantageous to produce propellants in strategic locations en route to, and at, the desired mission destination. This reduces the weight of the spacecraft and the cost of each mission. Since one of the primary goals of the space program is safety, a totally automated propellant production system is desirable. This system would remove, from hostile, high-risk extraterrestrial environments, the constant human intervention currently required in the production of many propellants. This enables the exploration of space to be more than the search for and production of fuel. As a proof-of-concept demonstration, one specific case was chosen for this study. That case was a composite propellant processor (the principle is more important than the application), and the specific processor used saved SERC the considerable cost of acquiring a new liquid propellant processor that would also have required similar automation.

  13. 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.

  14. Whole-Body Diffusion-weighted Imaging in Hodgkin Lymphoma and Diffuse Large B-Cell Lymphoma.

    PubMed

    Toledano-Massiah, Sarah; Luciani, Alain; Itti, Emmanuel; Zerbib, Pierre; Vignaud, Alexandre; Belhadj, Karim; Baranes, Laurence; Haioun, Corinne; Lin, Chieh; Rahmouni, Alain

    2015-01-01

    Whole-body imaging, in particular molecular imaging with fluorine 18 ((18)F)-fluorodeoxyglucose (FDG) positron emission tomography (PET), is essential to management of lymphoma. The assessment of disease extent provided by use of whole-body imaging is mandatory for planning appropriate treatment and determining patient prognosis. Assessment of treatment response allows clinicians to tailor the treatment strategy during therapy if necessary and to document complete remission at the end of treatment. Because of rapid technical developments, such as echo-planar sequences, parallel imaging, multichannel phased-array surface coils, respiratory gating, and moving examination tables, whole-body diffusion-weighted (DW) magnetic resonance (MR) imaging that reflects cell density is now feasible in routine clinical practice. Whole-body DW MR imaging allows anatomic assessment as well as functional and quantitative evaluation of tumor sites by calculation of the apparent diffusion coefficient (ADC). Because of their high cellularity and high nucleus-to-cytoplasm ratio, lymphomatous lesions have low ADC values and appear hypointense on ADC maps. As a result, whole-body DW MR imaging with ADC mapping has become a promising tool for lymphoma staging and treatment response assessment. The authors review their 4 years of experience with 1.5-T and 3-T whole-body DW MR imaging used with (18)F-FDG PET/computed tomography at baseline, interim, and end of treatment in patients with Hodgkin lymphoma and diffuse large B-cell lymphoma and discuss the spectrum of imaging findings and potential pitfalls, limitations, and challenges associated with whole-body DW MR imaging in these patients. PMID:25815803

  15. Co-analysis of Brain Structure and Function using fMRI and Diffusion-weighted Imaging

    PubMed Central

    Phillips, Jeffrey S.; Greenberg, Adam S.; Pyles, John A.; Pathak, Sudhir K.; Behrmann, Marlene; Schneider, Walter; Tarr, Michael J.

    2012-01-01

    The study of complex computational systems is facilitated by network maps, such as circuit diagrams. Such mapping is particularly informative when studying the brain, as the functional role that a brain area fulfills may be largely defined by its connections to other brain areas. In this report, we describe a novel, non-invasive approach for relating brain structure and function using magnetic resonance imaging (MRI). This approach, a combination of structural imaging of long-range fiber connections and functional imaging data, is illustrated in two distinct cognitive domains, visual attention and face perception. Structural imaging is performed with diffusion-weighted imaging (DWI) and fiber tractography, which track the diffusion of water molecules along white-matter fiber tracts in the brain (Figure 1). By visualizing these fiber tracts, we are able to investigate the long-range connective architecture of the brain. The results compare favorably with one of the most widely-used techniques in DWI, diffusion tensor imaging (DTI). DTI is unable to resolve complex configurations of fiber tracts, limiting its utility for constructing detailed, anatomically-informed models of brain function. In contrast, our analyses reproduce known neuroanatomy with precision and accuracy. This advantage is partly due to data acquisition procedures: while many DTI protocols measure diffusion in a small number of directions (e.g., 6 or 12), we employ a diffusion spectrum imaging (DSI)1, 2 protocol which assesses diffusion in 257 directions and at a range of magnetic gradient strengths. Moreover, DSI data allow us to use more sophisticated methods for reconstructing acquired data. In two experiments (visual attention and face perception), tractography reveals that co-active areas of the human brain are anatomically connected, supporting extant hypotheses that they form functional networks. DWI allows us to create a "circuit diagram" and reproduce it on an individual-subject basis, for

  16. 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.

  17. Diffusion-weighted MRI with parallel imaging technique: apparent diffusion coefficient determination in normal kidneys and in nonmalignant renal diseases.

    PubMed

    Macarini, Luca; Stoppino, Luca Pio; Milillo, Paola; Ciuffreda, Pierpaolo; Fortunato, Francesca; Vinci, Roberta

    2010-01-01

    The purpose of the study was to assess the capability and the reliability of apparent diffusion coefficient (ADC) measurements in the evaluation of different benign renal abnormalities. Twenty-five healthy volunteers and 31 patients, divided into seven different groups (A-G) according to pathology, underwent diffusion-weighted magnetic resonance imaging (DW MRI) of the kidneys using 1.5-T system. DW images were obtained in the axial plane with a spin-echo echo planar imaging single-shot sequence with three b values (0, 300, and 600 s/mm²). Before acquisition of DW sequences, we performed in each patient a morphological study of the kidneys. ADC was 2.40±0.20×10⁻³ mm² s⁻¹ in volunteers. A significant difference was found between Groups A (cysts=3.39±0.51×10⁻³ mm² s⁻¹) and B (acute/chronic renal failure=1.38±0.40×10⁻³ mm² s⁻¹) and between Groups A and C (chronic pyelonephritis=1.53±0.21×10⁻³ mm² s⁻¹) (P<.05). An important difference was also observed among Group D (hydronephrosis=4.82±0.35×10⁻³ mm² s⁻¹) and Groups A, B, and C (P<.05), whereas no differences were found between Groups B and C (P>.05). A considerable correlation between glomerular filtration rate and ADC was found (P=.04). In conclusion, significant differences were detected among different patient groups, and this suggests that ADC measurements can be useful in differentiating normal renal parenchyma from most commonly encountered nonmalignant renal lesions. PMID:21092872

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

    PubMed

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

    2012-10-01

    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

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

    PubMed Central

    MENG, ZHAOWEI; ZHANG, GUIZHI; SUN, HAORAN; TAN, JIAN; YU, CHUNSHUN; TIAN, WEIJUN; LI, WEIDONG; YANG, ZHIQIANG; ZHU, MEI; HE, QING; ZHANG, YUJIE; HAN, SHUGAO

    2015-01-01

    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 mm2/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. PMID:26136954

  20. Sequential Cranial Ultrasound and Cerebellar Diffusion Weighted Imaging Contribute to the Early Prognosis of Neurodevelopmental Outcome in Preterm Infants

    PubMed Central

    Brouwer, Margaretha J.; van Kooij, Britt J. M.; van Haastert, Ingrid C.; Koopman-Esseboom, Corine; Groenendaal, Floris; de Vries, Linda S.; Benders, Manon J. N. L.

    2014-01-01

    Objective To evaluate the contribution of sequential cranial ultrasound (cUS) and term-equivalent age magnetic resonance imaging (TEA-MRI) including diffusion weighted imaging (DWI) to the early prognosis of neurodevelopmental outcome in a cohort of very preterm infants (gestational age [GA] <31 weeks). Study design In total, 93 preterm infants (median [range] GA in weeks: 28.3 [25.0–30.9]) were enrolled in this prospective cohort study and underwent early and term cUS as well as TEA-MRI including DWI. Early cUS abnormalities were classified as normal, mild, moderate or severe. Term cUS was evaluated for ex-vacuo ventriculomegaly (VM) and enlargement of the extracerebral cerebrospinal fluid (eCSF) space. Abnormalities on T1- and T2-weighted TEA-MRI were scored according to Kidokoro et al. Using DWI at TEA, apparent diffusion coefficients (ADCs) were measured in four white matter regions bilaterally and both cerebellar hemispheres. Neurodevelopmental outcome was assessed at two years’ corrected age (CA) using the Bayley Scales of Infant and Toddler Development, third edition. Linear regression analysis was conducted to explore the correlation between the different neuroimaging modalities and outcome. Results Moderate/severe abnormalities on early cUS, ex-vacuo VM and enlargement of the eCSF space on term cUS and increased cerebellar ADC values on term DWI were independently associated with worse motor outcome (p<.05). Ex-vacuo VM on term cUS was also related to worse cognitive performance at two years’ CA (p<.01). Conclusion These data support the clinical value of sequential cUS and recommend repeating cUS at TEA. In particular, assessment of moderate/severe early cUS abnormalities and ex-vacuo VM on term cUS provides important prognostic information. Cerebellar ADC values may further aid in the prognostication of gross motor function. PMID:25329772

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

    PubMed

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

    2016-07-01

    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. © 2016 Wiley Periodicals, Inc. PMID:26996400

  2. Perianal Fistula With and Without Abscess: Assessment of Fistula Activity Using Diffusion-Weighted Magnetic Resonance Imaging

    PubMed Central

    Bakan, Selim; Olgun, Deniz Cebi; Kandemirli, Sedat Giray; Tutar, Onur; Samanci, Cesur; Dikici, Suleyman; Simsek, Osman; Rafiee, Babak; Adaletli, Ibrahim; Mihmanli, Ismail

    2015-01-01

    Background: Magnetic resonance imaging (MRI) is highly accurate for the depiction of both the primary tract of fistula and abscesses, in patients with perianal disease. In addition, MRI can be used to evaluate the activity of fistulas, which is a significant factor for determining the therapeutic strategy. Objectives: This study aimed to determine the usefulness of diffusion-weighted (DW) MRI for assessing activity and visibility of perianal fistula. Patients and Methods: Fifty-three patients with 56 perianal fistulas were included in the current retrospective study. The T2-weighted imaging (T2WI) and DWMRI were performed and apparent diffusion coefficient (ADC) values of fistulas were measured. Fistulas were classified into two groups: only perianal fistulas and fistulas accompanied by abscess. Fistulas were also classified into two groups, based on clinical findings: positive inflammatory activity (PIA) and negative inflammatory activity (NIA). Results: Mean ADC value (mm2/s) of PIA group was significantly lower than that of NIA group, regarding lesions in patients with abscess-associated fistulas (1.371 × 10-3 ± 0.168 × 10-3 vs. 1.586 × 10-3 ± 0.136 × 10-3; P = 0.036). No statistically significant difference was found in mean ADC values between PIA and NIA groups, in patients with only perianal fistulas (P = 0.507). Perianal fistula visibility was greater with combined evaluation of T2WI and DWMRI than with T2WI, for two reviewers (P = 0.046 and P = 0.014). Conclusion: The DWMRI is a useful technique for evaluating activity of fistulas with abscess. Perianal fistula visibility is greater with combined T2WI and DWMRI than T2WI alone. PMID:26715982

  3. Convergent connectivity and graded specialization in the rostral human temporal lobe as revealed by diffusion-weighted imaging probabilistic tractography.

    PubMed

    Binney, Richard J; Parker, Geoffrey J M; Lambon Ralph, Matthew A

    2012-10-01

    In recent years, multiple independent neuroscience investigations have implicated critical roles for the rostral temporal lobe in auditory and visual perception, language, and semantic memory. Although arising in the context of different cognitive functions, most of these suggest that there is a gradual convergence of sensory information in the temporal lobe that culminates in modality- and perceptually invariant representations at the most rostral aspect. Currently, however, too little is known regarding connectivity within the human temporal lobe to be sure of exactly how and where convergence occurs; existing hypotheses are primarily derived on the basis of cross-species generalizations from invasive nonhuman primate studies, the validity of which is unclear, especially where language function is concerned. In this study, we map the connectivity of the human rostral temporal lobe in vivo for the first time using diffusion-weighted imaging probabilistic tractography. The results indicate that convergence of sensory information in the temporal lobe is in fact a graded process that occurs along both its longitudinal and lateral axes and culminates in the most rostral limits. We highlight the consistency of our results with those of prior functional neuroimaging, computational modeling, and patient studies. By going beyond simple fasciculus reconstruction, we systematically explored the connectivity of specific temporal lobe areas to frontal and parietal language regions. In contrast to the graded within-temporal lobe connectivity, this intertemporal connectivity was found to dissociate across caudal, mid, and rostral subregions. Furthermore, we identified a basal rostral temporal region with very limited connectivity to areas outside the temporal lobe, which aligns with recent evidence that this subregion underpins the extraction of modality- and context-invariant semantic representations. PMID:22721379

  4. Detection of acute nervous system injury with advanced diffusion-weighted MRI: a simulation and sensitivity analysis.

    PubMed

    Skinner, Nathan P; Kurpad, Shekar N; Schmit, Brian D; Budde, Matthew D

    2015-11-01

    Diffusion-weighted imaging (DWI) is a powerful tool to investigate the microscopic structure of the central nervous system (CNS). Diffusion tensor imaging (DTI), a common model of the DWI signal, has a demonstrated sensitivity to detect microscopic changes as a result of injury or disease. However, DTI and other similar models have inherent limitations that reduce their specificity for certain pathological features, particularly in tissues with complex fiber arrangements. Methods such as double pulsed field gradient (dPFG) and q-vector magic angle spinning (qMAS) have been proposed to specifically probe the underlying microscopic anisotropy without interference from the macroscopic tissue organization. This is particularly important for the study of acute injury, where abrupt changes in the microscopic morphology of axons and dendrites manifest as focal enlargements known as beading. The purpose of this work was to assess the relative sensitivity of DWI measures to beading in the context of macroscopic fiber organization and edema. Computational simulations of DWI experiments in normal and beaded axons demonstrated that, although DWI models can be highly specific for the simulated pathologies of beading and volume fraction changes in coherent fiber pathways, their sensitivity to a single idealized pathology is considerably reduced in crossing and dispersed fibers. However, dPFG and qMAS have a high sensitivity for beading, even in complex fiber tracts. Moreover, in tissues with coherent arrangements, such as the spinal cord or nerve fibers in which tract orientation is known a priori, a specific dPFG sequence variant decreases the effects of edema and improves specificity for beading. Collectively, the simulation results demonstrate that advanced DWI methods, particularly those which sample diffusion along multiple directions within a single acquisition, have improved sensitivity to acute axonal injury over conventional DTI metrics and hold promise for more

  5. Detection of chronic brain damage by diffusion-weighted imaging with multiple b values in patients with type 2 diabetes.

    PubMed

    Liu, Tieli; Han, Yunpeng; Tang, Lemei; Wu, Jianlin; Miao, Yanwei; Gao, Bingbing; Shang, Jin

    2016-08-01

    The aim of the study was to evaluate the performance of parameters obtained from diffusion-weighted imaging (DWI) with multiple b values in the detection of chronic brain damage in patients with type 2 diabetes.We enrolled 30 patients with or without abnormalities on brain magnetic resonance imaging (lacunar infarction, leukoaraiosis, and/or brain atrophy) and 15 nondiabetic controls; obtained DWI parameters that included apparent diffusion coefficient (ADC), fast ADC (ADCfast), slow ADC (ADCslow), fraction of fast ADC (f), distributed diffusion coefficient (DDC), and stretched exponential (α); and performed receiver operating characteristic (ROC) analysis to evaluate the performance of parameters for the detection of chronic brain damage.The parameters ADC, ADCslow, f, and DDC were increased, whereas parameters ADCfast and α were decreased in type 2 diabetes patients compared with controls without diabetes. The centrum semiovale showed the most significant change in the evaluated parameters, and the changes in parameters ADCslow, f, and DDC were greater than the changes in other parameters. There was no significance between parameters of the biexponential model (ADCfast, ADCslow, f) and parameters of the stretched model (DDC, α), but parameters of both these models were superior to the parameter of monoexponential model (ADC). Moreover, ROC analysis showed that ADCslow of the centrum semiovale supplied by the anterior cerebral artery had the highest performance for detection of chronic brain damage (area under the ROC curve of 0.987, 93.3% sensitivity, and 100% specificity).Our study shows that DWI with multiple b values can quantitatively access chronic brain damage and may be used for detection and monitoring in type 2 diabetes patients. PMID:27583912

  6. Texture-based and diffusion-weighted discrimination of parotid gland lesions on MR images at 3.0 Tesla.

    PubMed

    Fruehwald-Pallamar, Julia; Czerny, Christian; Holzer-Fruehwald, Laura; Nemec, Stefan F; Mueller-Mang, Christina; Weber, Michael; Mayerhoefer, Marius E

    2013-11-01

    The purpose of this study was to evaluate whether texture-based analysis of standard MRI sequences and diffusion-weighted imaging can help in the discrimination of parotid gland masses. The MR images of 38 patients with a biopsy- or surgery-proven parotid gland mass were retrospectively analyzed. All patients were examined on the same 3.0 Tesla MR unit, with one standard protocol. The ADC (apparent diffusion coefficient) values of the tumors were measured with three regions of interest (ROIs) covering the entire tumor. Texture-based analysis was performed with the texture analysis software MaZda (version 4.7), with ROI measurements covering the entire tumor in three slices. COC (co-occurrence matrix), RUN (run-length matrix), GRA (gradient), ARM (auto-regressive model), and WAV (wavelet transform) features were calculated for all ROIs. Three subsets of 10 texture features each were used for a linear discriminant analysis (LDA) in combination with k nearest neighbor classification (k-NN). Using histology as a standard of reference, benign tumors, including subtypes, and malignant tumors were compared with regard to ADC and texture-based values, with a one-way analysis of variance with post-hoc t-tests. Significant differences were found in the mean ADC values between Warthin tumors and pleomorphic adenomas, as well as between Warthin tumors and benign lesions. Contrast-enhanced T1-weighted images contained the most relevant textural information for the discrimination between benign and malignant parotid masses, and also for the discrimination between pleomorphic adenomas and Warthin tumors. STIR images contained the least relevant texture features, particularly for the discrimination between pleomorphic adenomas and Warthin tumors. Texture analysis proved to differentiate benign from malignant lesions, as well as pleomorphic adenomas from Warthin tumors, based on standard T(1w) sequences (without and with contrast). Of all benign parotid masses, Warthin tumors had

  7. 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

  8. 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

  9. Detection of chronic brain damage by diffusion-weighted imaging with multiple b values in patients with type 2 diabetes

    PubMed Central

    Liu, Tieli; Han, Yunpeng; Tang, Lemei; Wu, Jianlin; Miao, Yanwei; Gao, Bingbing; Shang, Jin

    2016-01-01

    Abstract The aim of the study was to evaluate the performance of parameters obtained from diffusion-weighted imaging (DWI) with multiple b values in the detection of chronic brain damage in patients with type 2 diabetes. We enrolled 30 patients with or without abnormalities on brain magnetic resonance imaging (lacunar infarction, leukoaraiosis, and/or brain atrophy) and 15 nondiabetic controls; obtained DWI parameters that included apparent diffusion coefficient (ADC), fast ADC (ADCfast), slow ADC (ADCslow), fraction of fast ADC (f), distributed diffusion coefficient (DDC), and stretched exponential (α); and performed receiver operating characteristic (ROC) analysis to evaluate the performance of parameters for the detection of chronic brain damage. The parameters ADC, ADCslow, f, and DDC were increased, whereas parameters ADCfast and α were decreased in type 2 diabetes patients compared with controls without diabetes. The centrum semiovale showed the most significant change in the evaluated parameters, and the changes in parameters ADCslow, f, and DDC were greater than the changes in other parameters. There was no significance between parameters of the biexponential model (ADCfast, ADCslow, f) and parameters of the stretched model (DDC, α), but parameters of both these models were superior to the parameter of monoexponential model (ADC). Moreover, ROC analysis showed that ADCslow of the centrum semiovale supplied by the anterior cerebral artery had the highest performance for detection of chronic brain damage (area under the ROC curve of 0.987, 93.3% sensitivity, and 100% specificity). Our study shows that DWI with multiple b values can quantitatively access chronic brain damage and may be used for detection and monitoring in type 2 diabetes patients. PMID:27583912

  10. 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.

  11. 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.

  12. High temperature propellant development

    NASA Technical Reports Server (NTRS)

    Anderson, F. A.

    1981-01-01

    It is reported that the neccessary technology has been developed and demonstrated for the manufacture of heat-sterilizable solid propellants which meet specific ballistic goals. It is shown that: (1) phosphate doping of ammonium perchlorate significantly enhances the thermal stability of the substance; (2) grinding the ammonium perchlorate to reduce particle size further increases thermal stability; and (3) unsaturated polymers such as the polybutadienes can be successfully used in a heat-sterilizable propellant system. Among the topics considered by the study are oxidizers, dopants, binders, and the thermal cycling of 70 lb and 600 lb propellant grains.

  13. 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.

  14. NASA propeller noise research

    NASA Technical Reports Server (NTRS)

    Greene, G. C.

    1980-01-01

    The research in propeller noise prediction, noise/performance optimization, and interior reduction is described. Selected results are presented to illustrate the status of the technology and the direction of future research.

  15. 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.

  16. The aerodynamics of propellers

    NASA Astrophysics Data System (ADS)

    Wald, Quentin R.

    2006-02-01

    The theory and the design of propellers of minimum induced loss is treated. The pioneer analysis of this problem was presented more than half a century ago by Theodorsen, but obscurities in his treatment and inaccuracies and limited coverage in his tables of the Goldstein circulation function for helicoidal vortex sheets have not been remedied until the present work which clarifies and extends his work. The inverse problem, the prediction of the performance of a given propeller of arbitrary form, is also treated. The theory of propellers of minimum energy loss is dependent on considerations of a regular helicoidal trailing vortex sheet; consequently, a more detailed discussion of the dynamics of vortex sheets and the consequences of their instability and roll up is presented than is usually found in treatments of propeller aerodynamics. Complete and accurate tables of the circulation function are presented. Interference effects between a fuselage or a nacelle and the propeller are considered. The regimes of propeller, vortex ring, and windmill operation are characterized.

  17. 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.

  18. 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.

  19. The value of diffusion-weighted MRI in the diagnosis of malignant and benign urinary bladder lesions

    PubMed Central

    Avcu, S; Koseoglu, M N; Ceylan, K; Dbulutand, M; Unal, O

    2011-01-01

    Objectives To investigate the role of diffusion-weighted MRI (DWI) in the diagnosis of urinary bladder (UB) tumours by means of measuring apparent diffusion coefficient (ADC) values. Methods A total of 83 people aged between 18 and 86 years were included in the study: 63 patients with UB pathology (46 malignant, 17 benign) constituted the case group; 20 individuals without any UB pathology constituted the control group. DWI was applied to all individuals. The ADC values were measured based on the tissue of the UB mass entities and normal UB wall in the control group. Results The mean ADC value in the UB carcinoma group was significantly lower than that in the control group: 1.0684 ± 0.26 × 10−3 mm2 s–1 and 2.010 ± 0.11 × 10−3 mm2 s–1, respectively (p<0.01). There was a significant difference among the mean ADC values of different grades of malignant tumours, corresponding to 0.9185 ± 0.20 mm2 s–1 and 1.281 ± 0.18 mm2 s–1 in high-grade and low-grade malignant UB carcinomas, respectively (p<0.01). The ADC value in the carcinoma group was significantly lower than that in the benign lesion group: 1.0684 ± 0.26 × 10−3 mm2 s–1 and 1.803 ± 0.19 × 10−3 mm2 s–1, respectively (p<0.01). All 46 malignant lesions displayed a restriction in diffusion; 4 of the 17 benign lesions displayed a mild restriction in diffusion. The sensitivity, specificity and accuracy of DWI in the diagnosis of malignant UB lesions was 100%, 76.5% and 93.65%, respectively. Conclusion DWI can be beneficial in the differentiation of benign and malignant UB lesions, as well as of high-grade and low-grade UB carcinomas, using quantitative ADC measurements. PMID:21224296

  20. 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

  1. Clinical Implications of Non-Steatotic Hepatic Fat Fractions on Quantitative Diffusion-Weighted Imaging of the Liver

    PubMed Central

    Dijkstra, Hildebrand; Handayani, Astri; Kappert, Peter; Oudkerk, Matthijs; Sijens, Paul E.

    2014-01-01

    Diffusion-weighted imaging (DWI) is an important diagnostic tool in the assessment of focal liver lesions and diffuse liver diseases such as cirrhosis and fibrosis. Quantitative DWI parameters such as molecular diffusion, microperfusion and their fractions, are known to be affected when hepatic fat fractions (HFF) are higher than 5.5% (steatosis). However, less is known about the effect on DWI for HFF in the normal non-steatotic range below 5.5%, which can be found in a large part of the population. The aim of this study was therefore to evaluate the diagnostic implications of non-steatotic HFF on quantitative DWI parameters in eight liver segments. For this purpose, eleven healthy volunteers (2 men, mean-age 31.0) were prospectively examined with DWI and three series of in-/out-of-phase dual-echo spoiled gradient-recalled MRI sequences to obtain the HFF and T2*. DWI data were analyzed using the intravoxel incoherent motion (IVIM) model. Four circular regions (ø22.3 mm) were drawn in each of eight liver segments and averaged. Measurements were divided in group 1 (HFF≤2.75%), group 2 (2.75< HFF ≤5.5%) and group 3 (HFF>5.5%). DWI parameters and T2* were compared between the three groups and between the segments. It was observed that the molecular diffusion (0.85, 0.72 and 0.49 ×10−3 mm2/s) and T2* (32.2, 27.2 and 21.0 ms) differed significantly between the three groups of increasing HFF (2.18, 3.50 and 19.91%). Microperfusion and its fraction remained similar for different HFF. Correlations with HFF were observed for the molecular diffusion (r = −0.514, p<0.001) and T2* (−0.714, p<0.001). Similar results were obtained for the majority of individual liver segments. It was concluded that fat significantly decreases molecular diffusion in the liver, also in absence of steatosis (HFF≤5.5%). Also, it was confirmed that fat influences T2*. Determination of HFF prior to quantitative DWI is therefore crucial. PMID:24505333

  2. Predicting liver metastasis of gastrointestinal tract cancer by diffusion-weighted imaging of apparent diffusion coefficient values

    PubMed Central

    Zheng, De-Xian; Meng, Shu-Chun; Liu, Qing-Jun; Li, Chuan-Ting; Shang, Xi-Dan; Zhu, Yu-Seng; Bai, Tian-Jun; Xu, Shi-Ming

    2016-01-01

    AIM: To determine if efficacy of chemotherapy on liver metastasis of gastrointestinal tract cancer can be predicted by apparent diffusion coefficient (ADC) values of diffusion-weighted imaging (DWI). METHODS: In total, 86 patients with liver metastasis of gastrointestinal tract cancer (156 metastatic lesions) diagnosed in our hospital were included in this study. The maximum diameters of these tumors were compared with each other before treatment, 2 wk after treatment, and 12 wk after treatment. Selected patients were classified as the effective group and the ineffective group, depending on the maximum diameter of the tumor after 12 wk of treatment; and the ADC values at different treatment times between the two groups were compared. Spearman rank correlation was used to analyze the relationship between ADC value and tumor diameter. Receiver operating characteristic curve (ROC curve) was used to analyze the ADC values before treatment to predict the patient’s sensitivity and specificity degree of efficacy to the chemotherapy. RESULTS: There was no difference in age between the two groups and in maximum tumor diameter before treatment and 2 wk after treatment. However, after 12 wk of treatment, maximum tumor diameter in the effective group was significantly lower than that in the ineffective group (P < 0.05). Before treatment, ADC values in the ineffective group were significantly higher than those in the effective group (P < 0.05). There was no difference in ADC values between the effective and ineffective groups after 2 and 12 wk of treatment. However, ADC values were significantly higher after 2 and 12 wk of treatment compared to before treatment in the effective group (P < 0.05). Spearman rank correlation analysis showed that ADC value before treatment and the reduced percentage of the maximum tumor diameter after 12 wk of treatment were negatively correlated, while the increase in the percentage of the ADC value 12 wk after treatment and the decrease in the

  3. 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

  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. WE-G-BRD-01: Diffusion Weighted MRI for Response Assessment of Inoperable Lung Tumors for Patients Undergoing SBRT Treatment

    SciTech Connect

    Tyagi, N; Wengler, K; Yorke, E; Hunt, M; Deasy, J; Rimner, A

    2014-06-15

    Purpose: To investigate early changes in tumor Apparent Diffusion Coefficients derived from diffusion weighted (DW)-MRI of lung cancer patients undergoing SBRT, as a possible early predictor of treatment response. Methods: DW-MRI scans were performed in this prospective phase I IRB-approved study of inoperable lung tumors at various time-points during the course of SBRT treatments. Axial DW scan using multi b-values ranging from 0–1000 s/mm{sup 2} were acquired in treatment position on a 3T Philips MR scanner during simulation, one hour after the first fraction (8 Gy), after a total of 5 fractions (40 Gy) and 4 weeks after SBRT delivery. A monoexponential model based on a least square fit from all b values was performed on a pixel-by-pixel basis and ADC was calculated. GTVs drawn on 4DCT for planning were mapped on the T2w MRI (acquired at exhale) after deformable registration. These volumes were then mapped on DWI scan for ADC calculation after rigid registration between the anatomical scan and diffusion scan. T2w scan on followup time points were deformably registered to the pretreatment T2 scan. Results: The first two patients in this study were analyzed. Median ADC values were 1.48, 1.48, 1.62 and 1.83 (10{sup −3}×) mm{sup 2}/s at pretreatment, after 8 Gy, after 40 Gy and 4 weeks posttreatment for the first patient and 1.57, 1.53, 1.66 and 1.72 (10{sup −3}×) mm{sup 2}/s for the second patient. ADC increased more significantly after 4 weeks of treatment rather than immediately post treatment, implying that late ADC value may be a better predictor of tumor response for SBRT treatment. The fraction of tumor pixels at high ADC values increased at 4 weeks post treatment. Conclusion: The observed increase in ADC values before the end of radiotherapy may be a surrogate for tumor response, but further patient accrual will be necessary to determine its value.

  6. The Value of Diffusion-Weighted Imaging in the Differential Diagnosis of Ovarian Lesions: A Meta-Analysis

    PubMed Central

    Shin, Yu Ri; Park, Chang Suk; Kim, Kijun

    2016-01-01

    Objectives The ability of contrast-enhanced MRI to distinguish between malignant and benign ovarian masses is limited. The aim of this meta-analysis is to evaluate the diagnostic performance of diffusion-weighted imaging (DWI) in differentiating malignant from benign ovarian masses. Methods A comprehensive literature search was performed in several authoritative databases to identify relevant articles. The weighted mean difference (WMD) and corresponding 95% confidence interval (95% CI) were calculated. We also used subgroup analysis to analyze study heterogeneity, and evaluated publication bias. Results The meta-analysis is based on 21 studies, which reported the findings for 731 malignant and 918 benign ovarian masses. There was no significant difference in apparent diffusion coefficient (ADC) values for DWI between benign and malignant lesions (WMD = 0.22, 95% CI = -0.02–0.47, p = 0.08). Subgroup analysis by benign tumor type revealed higher ADC values (or a trend toward higher values) for cysts, cystadenomas and other benign tumors compared to malignant masses (cyst: WMD = 0.54, 95% CI = -0.05–1.12, p = 0.07; cystadenoma: WMD = 0.73, 95% CI = 0.38–1.07, p < 0.0001; other benign tumor: WMD = 0.16, 95% CI = -0.13–0.46, p = 0.28). On the other hand, lower ADC values (or a trend toward lower values) were observed for endometrioma and teratoma compared to malignant masses (endometrioma: WMD = -0.09, 95% CI = -0.47–0.29, p = 0.64; teratoma: WMD = -0.49, 95% CI = -0.85–0.12, p = 0.009). Subgroup analysis by mass property revealed higher ADC values in cystic tumor types than in solid types for both benign and malignant tumors. Significant study heterogeneity was observed. There was no notable publication bias. Conclusions Quantitative DWI is not a reliable diagnostic method for differentiation between benign and malignant ovarian masses. This knowledge is essential in avoiding misdiagnosis of ovarian masses. PMID:26907919

  7. Diagnostic Performance of Diffusion-weighted Magnetic Resonance Imaging in Bone Malignancy: Evidence From a Meta-Analysis.

    PubMed

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

    2015-11-01

    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/mm 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 both basis. Our

  8. Quantitative Perfusion- and Diffusion-Weighted Magnetic Resonance Imaging of Gastrointestinal Cancers Treated With Multikinase Inhibitors: A Pilot Study

    PubMed Central

    Keene, Kimberly S.; Sarver, David B.; Lee, S. Kyle; Beasley, T. Mark; Morgan, Desiree E.; Posey, James A.

    2014-01-01

    ABSTRACT BACKGROUND: Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion-weighted imaging (DWI) are often used to detect the early response of solid tumors to an effective therapy. The early changes in intratumoral physiological parameters measured by DCE-MRI/DWI have been evaluated as surrogate biomarkers allowing a tailored treatment for the individual patient. METHODS: Patients with newly diagnosed, biopsy-proven, treatment-naïve gastrointestinal stromal tumor (GIST) or hepatocellular carcinoma (HCC) were enrolled prospectively after institutional review board (IRB)–approved informed consent (5 patients per tumor type). Patients with GIST were treated with sunitinib over 6 weeks. DCE-MRI/DWI was applied before therapy (baseline imaging) and at 2 and 6 weeks after therapy initiation. Patients with HCC were treated with radiation during the first 2 weeks and then with sorafenib for the next 6 weeks. DCE-MRI/DWI was applied in all patients with HCC before and after radiation therapy and at the end of sorafenib therapy. Tumor volume, perfusion parameters (Ktrans, the forward volume-transfer constant, and kep, the reverse reflux-rate constant) and the apparent diffusion coefficient (ADC) were measured. RESULTS: During 2 weeks of sunitinib therapy, GIST volume, Ktrans, and kep decreased 32 ± 13, 45 ± 24, and 42 ± 15%, respectively, whereas ADC increased 76 ± 24%. After 6 weeks of sunitinib therapy, GIST volume, Ktrans, and kep decreased 56 ± 7, 70 ± 7, and 50 ± 12%, respectively, whereas ADC increased 85 ± 33%. After completion of radiation therapy, HCC volume, Ktrans, and kep decreased 34 ± 14, 35 ± 12, and 4 ± 21%, respectively, but ADC increased 21 ± 9%. During the entire 10-week therapeutic period, HCC volume, Ktrans, and kep decreased 65 ± 15, 40 ± 9, and 26 ± 2%, respectively, whereas ADC increased 28 ± 10%. CONCLUSION: DCE-MRI/DWI can measure the perfusion and diffusion changes in GISTs or HCCs treated with

  9. 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.

  10. 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

  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. 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.

  13. 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.

  14. 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

  15. Propeller noise prediction

    NASA Technical Reports Server (NTRS)

    Zorumski, W. E.

    1983-01-01

    Analytic propeller noise prediction involves a sequence of computations culminating in the application of acoustic equations. The prediction sequence currently used by NASA in its ANOPP (aircraft noise prediction) program is described. The elements of the sequence are called program modules. The first group of modules analyzes the propeller geometry, the aerodynamics, including both potential and boundary layer flow, the propeller performance, and the surface loading distribution. This group of modules is based entirely on aerodynamic strip theory. The next group of modules deals with the actual noise prediction, based on data from the first group. Deterministic predictions of periodic thickness and loading noise are made using Farassat's time-domain methods. Broadband noise is predicted by the semi-empirical Schlinker-Amiet method. Near-field predictions of fuselage surface pressures include the effects of boundary layer refraction and (for a cylinder) scattering. Far-field predictions include atmospheric and ground effects. Experimental data from subsonic and transonic propellers are compared and NASA's future direction is propeller noise technology development are indicated.

  16. Aeroacoustics of advanced propellers

    NASA Astrophysics Data System (ADS)

    Groeneweg, John F.

    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.

  17. Inter- and Intra-Observer Repeatability of Quantitative Whole-Body, Diffusion-Weighted Imaging (WBDWI) in Metastatic Bone Disease

    PubMed Central

    Blackledge, Matthew D.; Tunariu, Nina; Orton, Matthew R.; Padhani, Anwar R.; Collins, David J.; Leach, Martin O.; Koh, Dow-Mu

    2016-01-01

    Quantitative whole-body diffusion-weighted MRI (WB-DWI) is now possible using semi-automatic segmentation techniques. The method enables whole-body estimates of global Apparent Diffusion Coefficient (gADC) and total Diffusion Volume (tDV), both of which have demonstrated considerable utility for assessing treatment response in patients with bone metastases from primary prostate and breast cancers. Here we investigate the agreement (inter-observer repeatability) between two radiologists in their definition of Volumes Of Interest (VOIs) and subsequent assessment of tDV and gADC on an exploratory patient cohort of nine. Furthermore, each radiologist was asked to repeat his or her measurements on the same patient data sets one month later to identify the intra-observer repeatability of the technique. Using a Markov Chain Monte Carlo (MCMC) estimation method provided full posterior probabilities of repeatability measures along with maximum a-posteriori values and 95% confidence intervals. Our estimates of the inter-observer Intraclass Correlation Coefficient (ICCinter) for log-tDV and median gADC were 1.00 (0.97–1.00) and 0.99 (0.89–0.99) respectively, indicating excellent observer agreement for these metrics. Mean gADC values were found to have ICCinter = 0.97 (0.81–0.99) indicating a slight sensitivity to outliers in the derived distributions of gADC. Of the higher order gADC statistics, skewness was demonstrated to have good inter-user agreement with ICCinter = 0.99 (0.86–1.00), whereas gADC variance and kurtosis performed relatively poorly: 0.89 (0.39–0.97) and 0.96 (0.69–0.99) respectively. Estimates of intra-observer repeatability (ICCintra) demonstrated similar results: 0.99 (0.95–1.00) for log-tDV, 0.98 (0.89–0.99) and 0.97 (0.83–0.99) for median and mean gADC respectively, 0.64 (0.25–0.88) for gADC variance, 0.85 (0.57–0.95) for gADC skewness and 0.85 (0.57–0.95) for gADC kurtosis. Further investigation of two anomalous patient cases

  18. 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.

  19. Optimum propeller wind turbines

    NASA Astrophysics Data System (ADS)

    Sanderson, R. J.; Archer, R. D.

    1983-12-01

    The Prandtl-Betz-Theodorsen theory of heavily loaded airscrews has been adapted to the design of propeller windmills which are to be optimized for maximum power coefficient. It is shown that the simpler, light-loading, constant-area wake assumption can generate significantly different 'optimum' performance and geometry, and that it is therefore not appropriate to the design of propeller wind turbines when operating in their normal range of high-tip-speed-to-wind-speed ratio. Design curves for optimum power coefficient are presented and an example of the design of a typical two-blade optimum rotor is given.

  20. 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.

  1. Active synchrophasing of propeller unbalance

    NASA Technical Reports Server (NTRS)

    Kaptein, Dick

    1992-01-01

    The results of a survey are presented to reduce the inflight propeller unbalance vibrations in the cabin of the Fokker 50 airplanes. Several approaches have been investigated. Active synchrophasing of the unbalance vibrations of both propellers appears to be successful.

  2. 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.

  3. Silicone containing solid propellant

    NASA Technical Reports Server (NTRS)

    Ramohalli, K. N. R. (Inventor)

    1980-01-01

    The addition of a small amount, for example 1% by weight, of a liquid silicone oil to a metal containing solid rocket propellant provides a significant reduction in heat transfer to the inert nozzle walls. Metal oxide slag collection and blockage of the nozzle are eliminated and the burning rate is increased by about 5% to 10% thus improving ballistic performance.

  4. 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.

  5. 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.

  6. Propeller Tip Flutter

    NASA Technical Reports Server (NTRS)

    Liebers, Fritz

    1932-01-01

    The present report is limited to a case of tip flutter recognized by experience as being important. It is the case where outside interferences force vibrations upon the propeller. Such interferences may be set up by the engine, or they may be the result of an unsymmetrical field of flow.

  7. New Propellants and Cryofuels

    NASA Technical Reports Server (NTRS)

    Palasezski, Bryan; Sullivan, Neil S.; Hamida, Jaha; Kokshenev, V.

    2006-01-01

    The proposed research will investigate the stability and cryogenic properties of solid propellants that are critical to NASA s goal of realizing practical propellant designs for future spacecraft. We will determine the stability and thermal properties of a solid hydrogen-liquid helium stabilizer in a laboratory environment in order to design a practical propellant. In particular, we will explore methods of embedding atomic species and metallic nano-particulates in hydrogen matrices suspended in liquid helium. We will also measure the characteristic lifetimes and diffusion of atomic species in these candidate cryofuels. The most promising large-scale advance in rocket propulsion is the use of atomic propellants; most notably atomic hydrogen stabilized in cryogenic environments, and metallized-gelled liquid hydrogen (MGH) or densified gelled hydrogen (DGH). The new propellants offer very significant improvements over classic liquid oxygen/hydrogen fuels because of two factors: (1) the high energy-release, and (ii) the density increase per unit energy release. These two changes can lead to significant reduced mission costs and increased payload to orbit weight ratios. An achievable 5 to 10 percent improvement in specific impulse for the atomic propellants or MGH fuels can result in a doubling or tripling of system payloads. The high-energy atomic propellants must be stored in a stabilizing medium such as solid hydrogen to inhibit or delay their recombination into molecules. The goal of the proposed research is to determine the stability and thermal properties of the solid hydrogen-liquid helium stabilizer. Magnetic resonance techniques will be used to measure the thermal lifetimes and the diffusive motions of atomic species stored in solid hydrogen grains. The properties of metallic nano-particulates embedded in hydrogen matrices will also be studied and analyzed. Dynamic polarization techniques will be developed to enhance signal/noise ratios in order to be able to

  8. Fusion of high b-value diffusion-weighted and T2-weighted MR images improves identification of lymph nodes in the pelvis.

    PubMed

    Mir, N; Sohaib, S A; Collins, D; Koh, D M

    2010-08-01

    Accurate identification of lymph nodes facilitates nodal assessment by size, morphological or MR lymphographic criteria. We compared the MR detection of lymph nodes in patients with pelvic cancers using T2-weighted imaging, and fusion of diffusion-weighted imaging (DWI) and T2-weighted imaging. Twenty patients with pelvic tumours underwent 5-mm axial T2-weighted and DWI (b-values 0-750 s/mm(2)) on a 1.5T system. Fusion images of b = 750 s/mm(2) diffusion-weighted MR and T2-weighted images were created. Two radiologists evaluated in consensus the T2-weighted images and fusion images independently. For each image set, the location and diameter of pelvic nodes were recorded, and nodal visibility was scored using a 4-point scale (0-3). Nodal visualisation was compared using Relative to an Identified Distribution (RIDIT) analysis. The mean RIDIT score describes the probability that a randomly selected node will be better visualised relative to the other image set. One hundred fourteen pelvic nodes (mean 5.9 mm; 2-10 mm) were identified on T2-weighted images and 161 nodes (mean 4.3 mm; 2-10 mm) on fusion images. Using fusion images, 47 additional nodes were detected compared with T2-weighted images alone (eight external iliac, 24 inguinal, 12 obturator, two peri-rectal, one presacral). Nodes detected only on fusion images were 2-9 mm (mean 3.7 mm). Nodal visualisation was better using fusion images compared with T2-weighted images (mean RIDIT score 0.689 vs 0.302). Fusion of diffusion-weighted MR with T2-weighted images improves identification of pelvic lymph nodes compared with T2-weighted images alone. The improved nodal identification may aid treatment planning and further nodal characterisation. PMID:20718916

  9. Improve the image quality of orbital 3 T diffusion-weighted magnetic resonance imaging with readout-segmented echo-planar imaging.

    PubMed

    Xu, Xiao-Quan; Liu, Jun; Hu, Hao; Su, Guo-Yi; Zhang, Yu-Dong; Shi, Hai-Bin; Wu, Fei-Yun

    2016-01-01

    The aim of our study is to compare the image quality of readout-segmented echo-planar imaging (rs-EPI) and that of standard single-shot EPI (ss-EPI) in orbital 3 T diffusion-weighted (DW) magnetic resonance (MR) imaging in healthy subjects. Forty-two volunteers underwent two sets of orbital DW imaging scan at a 3 T MR unit, and image quality was assessed qualitatively and quantitatively. As a result, we found that rs-EPI could provide better image quality than standard ss-EPI, while no significant difference was found on the apparent diffusion coefficient between the two sets of DW images. PMID:27317226

  10. 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

  11. Propeller design by numerical optimization

    NASA Technical Reports Server (NTRS)

    Mendoza, J. P.

    1977-01-01

    A computer program designed to optimize propeller characteristics was developed by combining two main programs: the first is the optimization program based on the gradient algorithm; the second is based on a propeller blade element theory and uses an aerodynamics subprogram to approximate the lift and drag characteristics of the NACA 16-series airfoil section. To evaluate the propeller program alone (with its aerodynamics subprogram), propeller characteristics were computed and compared to those from wind tunnel investigations conducted on three different NACA propellers. Although the thrust and power coefficients which were computed using the blade element theory were generally higher than the experimental results for two of the three propellers, the corresponding efficiencies showed good agreement for all three propellers. The propeller optimization program was then used to study the NACA 4-(5)(08)-03 propeller at various Mach numbers from 0.175 to 0.60. Improvements in propeller efficiency and thrust were obtained through the use of the propeller optimization program.

  12. Quantitative Multi-Parametric PROPELLER MRI of Diethylnitrosamine-Induced Hepatocarcinogenesis in Wister Rat model

    PubMed Central

    Deng, Jie; Jin, Ning; Yin, Xiaoming; Yang, Guang-Yu; Zhang, Zhuoli; Omary, Reed A.; Larson, Andrew C.

    2010-01-01

    PURPOSE To develop a quantitative multi-parametric PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) MRI approach and its application in a diethylnitrosamine (DEN) chemically-induced rodent model of hepatocarcinogensis for lesion characterization. MATERIALS AND METHODS In nine rabbits with 33 cirrhosis-associated hepatic nodules including regenerative nodule (RN), dysplastic nodule (DN), hepatocellular carcinoma (HCC) and cyst, multi-parametric PROPELLER MRI (diffusion-weighted, T2/M0 (proton density) mapping and T1-weighted) were performed. Apparent diffusion coefficient (ADC) maps, T2 and M0 maps of each tumor were generated. We compared ADC, T2 and M0 measurements for each type of hepatic nodule, confirmed at histopathology. RESULTS PROPELLER images and resultant parametric maps were inherently co-registered without image distortion or motion artifacts. All types of hepatic nodules demonstrated complex imaging characteristics within conventional T1- and T2-weighted images. Quantitatively, cysts were distinguished from RN, DN and HCC with significantly higher ADC and T2; however, there was no significant difference of ADC and T2 between HCC, DN and RN. Mean tumor M0 values of HCC were significantly higher than those of DN, RN and cysts. CONCLUSION This study exploited quantitative PROPELLER MRI and multi-dimensional analysis approaches in an attempt to differentiate hepatic nodules in the DEN rodent model of hepatocarcinogensis. This method offers great potential for parallel parameterization during non-invasive interrogation of hepatic tissue properties. PMID:20432363

  13. 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

    2016-08-01

    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. PMID:27385441

  14. 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.

  15. 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.

  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. 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.

  18. Optimal b value of diffusion-weighted imaging on a 3.0T magnetic resonance scanner in Crohn’s disease

    PubMed Central

    Feng, Qi; Yan, Yun-Qi; Zhu, Jiong; Tong, Jin-Lu; Xu, Jian-Rong

    2014-01-01

    AIM: To determine the optimal b value of diffusion-weighted imaging for detecting active inflammation in Crohn’s disease. METHODS: Thirty-one patients clinically diagnosed with active Crohn’s disease were referred for magnetic resonance examination. All patients were scanned on a 3.0T magnetic resonance scanner using the same protocol involving four different b values (800, 1500, 2000 and 2500 s/mm2). The diagnostic effect of diffusion-weighted imaging was evaluated and compared with endoscopic findings. The diffusion-weighted image quality of four b value groups was evaluated and apparent diffusion coefficient was measured for both normal and inflammatory intestinal segments. RESULTS: The contrast-to-noise ratio and signal-to-noise ratio were not satisfied when b value 2000 or 2500 s/mm2 was adopted (36.52 ± 14.95 vs 34.78 ± 24.83, P > 0.05; 53.58 ± 23.45 vs 47.58 ± 29.67, P > 0.05). The qualitative image quality was not enough to meet diagnostic requirement. No matter which b value was chosen, the apparent diffusion coefficient of inflammatory intestinal segments was significantly lower than that of normal intestinal segments (1.38 ± 0.28 vs 2.00 ± 0.38, P < 0.01; 1.09 ± 0.20 vs 1.50 ± 0.28, P < 0.01; 0.95 ± 0.19 vs 1.34 ± 0.28, P < 0.01; 0.88 ± 0.14 vs 1.20 ± 0.21, P < 0.01). The lesion detection rate (90.32%), diagnostic sensitivity (81.18%) and specificity (95.10%) would be appropriate when b value 1500 s/mm2 was adopted. CONCLUSION: High b value is suitable for intestinal DW examination on a high field MR scanner. PMID:25253967

  19. Resonance vibrations of aircraft propellers

    NASA Technical Reports Server (NTRS)

    Liebers, Fritz

    1932-01-01

    On the basis of the consideration of various possible kinds of propeller vibrations, the resonance vibrations caused by unequal impacts of the propeller blades appear to be the most important. Their theoretical investigation is made by separate analysis of torsional and bending vibrations. This method is justified by the very great difference in the two natural frequencies of aircraft propeller blades. The calculated data are illustrated by practical examples. Thereby the observed vibration phenomenon in the given examples is explained by a bending resonance, for which the bending frequency of the propeller is equal to twice the revolution speed.

  20. Composite propellant combustion modeling studies

    NASA Technical Reports Server (NTRS)

    Ramohalli, K.

    1977-01-01

    A review is presented of theoretical and experimental studies of composite propellant combustion. The theoretical investigations include a model of the combustion of a nonmetallized ammonium perchlorate (AP) propellant (noting time scales for vapor-phase combustion and the condensed phase) and response functions in pressure-coupled oscillations. The experimental studies are discussed with reference to scale-modeling apparatus, flame standoff distance versus velocity as a function of pressure, and results from T-burner firings of a nonmetallized AP/polysulfide propellant. Research applications including problems with nitramine propellants, the feasibility of stop-restart rockets with salt quench, and combustion problems in large boosters are outlined.

  1. A Spin Echo Sequence with a Single-Sided Bipolar Diffusion Gradient Pulse to Obtain Snapshot Diffusion Weighted Images in Moving Media

    PubMed Central

    Freidlin, R. Z.; Kakareka, J. W.; Pohida, T. J.; Komlosh, M. E.; Basser, P. J.

    2013-01-01

    In vivo MRI data can be corrupted by motion. Motion artifacts are particularly troublesome in Diffusion Weighted MRI (DWI), since the MR signal attenuation due to Brownian motion can be much less than the signal loss due to dephasing from other types of complex tissue motion, which can significantly degrade the estimation of self-diffusion coefficients, diffusion tensors, etc. This paper describes a snapshot DWI sequence, which utilizes a novel single-sided bipolar diffusion sensitizing gradient pulse within a spin echo sequence. The proposed method shortens the diffusion time by applying a single refocused bipolar diffusion gradient on one side of a refocusing RF pulse, instead of a set of diffusion sensitizing gradients, separated by a refocusing RF pulse, while reducing the impact of magnetic field inhomogeneity by using a spin echo sequence. A novel MRI phantom that can exhibit a range of complex motions was designed to demonstrate the robustness of the proposed DWI sequence. PMID:22743539

  2. Improving the Correction of Eddy Current-Induced Distortion in Diffusion-Weighted Images by Excluding Signals from the Cerebral Spinal Fluid

    PubMed Central

    Liu, Wei; Liu, Xiaozheng; Yang, Guang; Zhou, Zhenyu; Zhou, Yongdi; Li, Gengying; Dubin, Marc; Bansal, Ravi; Peterson, Bradley. S.; Xu, Dongrong

    2012-01-01

    Iterative Cross-Correlation (ICC) is the most popularly used schema for correcting eddy current (EC)-induced distortion in diffusion-weighted imaging data, however, it cannot process data acquired at high b-values. We analyzed the error sources and affecting factors in parameter estimation, and propose an efficient algorithm by expanding the ICC framework with a number of techniques: (1) Pattern recognition for excluding brain ventricles; (2) ICC with the extracted ventricle for parameter initialization; (3) Gradient-based Entropy Correlation Coefficient (GECC) for optimal and finer registration. Experiments demonstrated that our method is robust with high accuracy and error tolerance, and outperforms other ICC-family algorithms and popular approaches currently in use. PMID:22835646

  3. Diffusion Weighted MR Imaging to Evaluate Treatment Results after Volumetric MR-guided High Intensity Focused Ultrasound of Uterine Fibroids: Influence of Different B-values

    NASA Astrophysics Data System (ADS)

    Voogt, M. J.; Keserci, B.; Kim, Y. S.; Rhim, H.; Lim, H. K.; Mougenot, C.; Kohler, M. O.; van den Bosch, M. A.; Vincken, K. L.; Bartels, L. W.

    2011-09-01

    We have assessed the feasibility of using diffusion weighted MR imaging (DWI) and apparent diffusion coefficient (ADC) mapping using different b-value combinations to evaluate treatment results after volumetric magnetic resonance-guided high intensity focused ultrasound (MR-HIFU) for uterine fibroids. Pre-treatment, directly post-treatment and 1 month follow-up DW images were obtained using b-values 0, 200, 400, 600 and 800 s/mm2. ADC maps were constructed for quantitative analysis of ablation results. Four different combinations of b-values were used to calculate the ADC. Directly after treatment ADC values decreased. Low b-values (0 and 200 s/mm2) resulted in the best contrast between non-perfused and perfused tissue. One month after treatment the average ADC was increased, now showing the best contrast on the high b-value ADC maps.

  4. Role of Diffusion-weighted Imaging in Acute Stroke Management using Low-field Magnetic Resonance Imaging in Resource-limited Settings

    PubMed Central

    Okorie, Chinonye K; Ogbole, Godwin I; Owolabi, Mayowa O; Ogun, Olufunmilola; Adeyinka, Abiodun; Ogunniyi, Adesola

    2015-01-01

    A variety of imaging modalities exist for the diagnosis of stroke. Several studies have been carried out to ascertain their contribution to the management of acute stroke and to compare the benefits and limitations of each modality. Diffusion-weighted imaging (DWI) has been described as the optimal imaging technique for diagnosing acute ischemic stroke, yet limited evidence is available on the value of DWI in the management of ischemic stroke with low-field magnetic resonance (MR) systems. Although high-field MR imaging (MRI) is desirable for DWI, low-field scanners provide an acceptable clinical compromise which is of importance to developing countries posed with the challenge of limited availability of high-field units. The purpose of this paper was to systematically review the literature on the usefulness of DWI in acute stroke management with low-field MRI scanners and present the experience in Nigeria. PMID:26709342

  5. 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.

  6. 78 FR 18255 - Airworthiness Directives; Hartzell Propeller, Inc. Propellers

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-26

    ... 12866, (2) Is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034.... 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...

  7. FDG-MicroPET and Diffusion-Weighted MR Image Evaluation of Early Changes After Radiofrequency Ablation in Implanted VX2 Tumors in Rabbits

    SciTech Connect

    Ohira, Tomohiro Okuma, Tomohisa; Matsuoka, Toshiyuki; Wada, Yasuhiro; Nakamura, Kenji; Watanabe, Yasuyoshi; Inoue, Yuichi

    2009-01-15

    The objective of this study was to evaluate the early changes after radiofrequency ablation (RFA) in VX2 rabbit tumors implanted into the back muscles by diffusion-weighted magnetic resonance (MR) imaging and {sup 18}F-2-fluoro-2-deoxy-D-glucose positron emission tomography ({sup 18}F-FDG PET). Percutaneous CT-guided RFA was conducted in seven rabbits with implanted VX2 tumors. VX2 tumors on the other side were untreated and served as the control. MR imaging was performed with a clinical 1.5-T instrument 2 days after RFA, and FDG-PET, using a high-resolution PET scanner for small animals, was obtained 3 days after the procedure. The mean apparent diffusion coefficient (ADC) values and radioactivity count of untreated and ablated tumors were calculated. Untreated VX2 tumors showed hyperintensity on T1-, T2-, and diffusion-weighted MR images, ring-enhanced on contrast-enhanced T1-weighted imaging, and ring-shaped FDG accumulation on FDG-PET. Ablated VX2 tumors showed slight hyperintensity on T1-, T2-, and diffusion-weighed images, slight enhancement on contrast-enhanced T1-weighted images, and low accumulation on FDG-PET. The ADC value of ablated VX2 tumors (1.52 {+-} 0.24 x 10{sup -3} mm{sup 2}/s) was significantly higher than that of untreated tumors (1.09 {+-} 0.12 x 10{sup -3}; p < 0.05). The tumor/muscle ratio of ablated tumors (0.5 {+-} 0.3) was significantly lower than that of untreated tumors (11.6 {+-} 3.2; p < 0.05). Histopathological examination confirmed the lack of viable tumor cells in the ablated lesions. The results indicate that both ADC value and FDG-PET are potentially useful markers for monitoring the early effects of RFA.

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

    PubMed

    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/mm(2) in intervals of 500 s/mm(2). 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

  9. 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

  10. Differential Diagnosis of Axillary Inflammatory and Metastatic Lymph Nodes in Rabbit Models by Using Diffusion-Weighted Imaging: Compared with Conventional Magnetic Resonance Imaging

    PubMed Central

    Liao, Qian; Zhang, Yunting; Yu, Chunshui; Bai, Renju; Sun, Haoran

    2012-01-01

    Objective This experiment aims to determine the diagnostic value of diffusion-weighted imaging (DWI) in the differentiation of axillary inflammatory lymph nodes from metastatic lymph nodes in rabbit models in comparison with conventional magnetic resonance imaging (MRI). Materials and Methods Conventional MRI and DWI were performed at 4 weeks after successful inoculation into the forty female New Zealand white rabbits' mammary glands. The size-based and signal-intensity-based criteria and the relative apparent diffusion coefficient (rADC) value were compared between the axillary inflammatory lymph nodes and metastatic lymph nodes, with histopathological findings as the reference standard. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic performance of the aforementioned criteria and rADC value in differentiating the axillary inflammatory lymph nodes from metastatic lymph nodes. Results Thirty-two axillary inflammatory lymph nodes and 46 metastatic ones were successfully isolated and taken into pathological analysis. The differences of the aforementioned criteria between the two groups were not statistically significant (p > 0.05). However, the rADC value of the inflammatory lymph nodes (0.9 ± 0.14) was higher than that of metastatic ones (0.7 ± 0.18), with significant difference (p = 0.016). When the rADC value was chosen as 0.80, the area under the ROC curve is greater than all other criteria, and the sensitivity, specificity, accuracy, positive predictive value, and negative predictive value for differentiating two groups were 86.2%, 79.3%, 81.2%, 84.2%, and 85.6%, respectively. Conclusion Diffusion-weighted imaging is a promising new technique for differentiating axillary inflammatory lymph nodes from metastatic lymph nodes. Compared with routine magnetic resonance sequences, DWI could provide more useful physiological and functional information for diagnosis. PMID:22778568

  11. Increasing the Accuracy of Volume and ADC Delineation for Heterogeneous Tumor on Diffusion-Weighted MRI: Correlation with PET/CT

    SciTech Connect

    Gong, Nan-Jie; Wong, Chun-Sing; Chu, Yiu-Ching; Guo, Hua; Huang, Bingsheng; Chan, Queenie

    2013-10-01

    Purpose: To improve the accuracy of volume and apparent diffusion coefficient (ADC) measurements in diffusion-weighted magnetic resonance imaging (MRI), we proposed a method based on thresholding both the b0 images and the ADC maps. Methods and Materials: In 21 heterogeneous lesions from patients with metastatic gastrointestinal stromal tumors (GIST), gross lesion were manually contoured, and corresponding volumes and ADCs were denoted as gross tumor volume (GTV) and gross ADC (ADC{sub g}), respectively. Using a k-means clustering algorithm, the probable high-cellularity tumor tissues were selected based on b0 images and ADC maps. ADC and volume of the tissues selected using the proposed method were denoted as thresholded ADC (ADC{sub thr}) and high-cellularity tumor volume (HCTV), respectively. The metabolic tumor volume (MTV) in positron emission tomography (PET)/computed tomography (CT) was measured using 40% maximum standard uptake value (SUV{sub max}) as the lower threshold, and corresponding mean SUV (SUV{sub mean}) was also measured. Results: HCTV had excellent concordance with MTV according to Pearson's correlation (r=0.984, P<.001) and linear regression (slope = 1.085, intercept = −4.731). In contrast, GTV overestimated the volume and differed significantly from MTV (P=.005). ADC{sub thr} correlated significantly and strongly with SUV{sub mean} (r=−0.807, P<.001) and SUV{sub max} (r=−0.843, P<.001); both were stronger than those of ADC{sub g}. Conclusions: The proposed lesion-adaptive semiautomatic method can help segment high-cellularity tissues that match hypermetabolic tissues in PET/CT and enables more accurate volume and ADC delineation on diffusion-weighted MR images of GIST.

  12. Comparison of dynamic contrast-enhanced and diffusion weighted magnetic resonance image in staging and grading of carcinoma bladder with histopathological correlation

    PubMed Central

    Gupta, Neetika; Sureka, Binit; Kumar, Mittal Mahesh; Malik, Amita; Bhushan, Thukral Brij; Mohanty, N. K.

    2015-01-01

    Background: Bladder cancer is the second most common neoplasm of the urinary tract worldwide. Dynamic contrast-enhanced and diffusion-weighted MRI has been introduced in clinical MRI protocols of bladder cancer because of its accuracy in staging and grading. Aim: To evaluate and compare accuracy of Dynamic contrast enhanced (DCE) and Diffusion weighted (DW) MRI for preoperative T staging of urinary bladder cancer and find correlation between apparent diffusion coefficient (ADC) and maximum enhancement with histological grade. Materials and Methods: Sixty patients with bladder cancer were included in study. All patients underwent Magnetic Resonance Imaging (MRI) on a 1.5-T scanner with a phased-array pelvic coil. MR images were evaluated and assigned a stage which was compared with the histolopathological staging. ADC value and maximum enhancement curve were used based on previous studies. Subsequently histological grade was compared with MR characteristics. Results: The extent of agreement between the radiologic staging and histopathological staging was relatively greater with the DW-MRI (κ=0.669) than DCE-MRI (κ=0.619). The sensitivity, specificity, and accuracy are maximum and similar for stage T4 tumors in both DCEMRI (100.0, 96.2 and 96.7) and DW-MRI (100.0, 96.2 and 96.7) while minimum for stage T2 tumors - DCEMRI (83.3, 72.2, and 76.7) and DWI-MRI (91.7, 72.2, and 80). Conclusion: MRI is an effective tool for determining T stage and histological grade of urinary bladder cancers. Stage T2a and T2b can be differentiated only by DCE-MRI. Results were more accurate when both ADC and DCE-MRI were used together and hence a combined approach is suggested. PMID:25835087

  13. 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. PMID:24706159

  14. 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.

  15. Micarta propellers I : materials

    NASA Technical Reports Server (NTRS)

    Caldwell, F W; Clay, N S

    1924-01-01

    Here, values for tension, compression edgewise of laminations, and transverse flatwise of laminations are given for Micarta made with various kinds of sheet material. The corresponding values for white oak are given for comparison. It was found by destructive and service tests that Micarta made with a good grade of cotton duck will give satisfactory service with most designs. In propellers having detachable blades, it is desirable that the root of the blade be of a small cross section to decrease the weight of the metal hub. Here the use of the special fabric or wood veneer offers advantages due to greater tensile strength. These materials, especially the wood veneer, produce stiffer blades than duck. This is also a value in controllable and reversible pitch designs where it is desirable that the plan form of the blades be symmetrical.

  16. 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).

  17. 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.

  18. Propellant injection for MPD thrusters

    NASA Technical Reports Server (NTRS)

    Jones, R. M.

    1979-01-01

    The propellant gas for a pulsed self-field MPD thruster must be supplied by a valve which will necessarily be separated from the thruster injectors by some ullage volume. A model and experimental data are presented showing the effect of the ullage volume on the propellant pulse shape, along with a discussion of the proper location for the propellant flow choke point(s). Prospective MPD pulse valves are surveyed and the performance of two solenoid valves, one with a pulse length less than 2 milliseconds, is included. Pulse shape data is presented for a thruster specially modified to reduce the ullage volume.

  19. The Source of Propeller Noise

    NASA Technical Reports Server (NTRS)

    Ernsthausen, W

    1937-01-01

    A two blade propeller of 40 cm diameter and zero pitch was explored for its noise development; it could be whirled up to 17,000 rpm - i.e., a tip speed of 355 meters/second. To obtain the power loss N(sub m) of the propeller for comparison with the produced acoustical power N(sub A) the engine performance characteristics were measured with and without propeller. The result is the sought-for relation c, that is, curve c' after correction with the engine efficiency.

  20. A study on quantitative analyses before and after injection of contrast medium in spine examinations performed by using diffusion weighted image

    NASA Astrophysics Data System (ADS)

    Cho, Jae-Hwan; Lee, Hae-Kag; Kim, Yong-Kyun; Dong, Kyung-Rae; Chung, Woon-Kwan; Joo, Kyu-Ji

    2013-02-01

    This study examined the changes in the signal-to-noise ratio (SNR), the contrast-to-noise ratio (CNR) and the apparent diffusion coefficient (ADC) of metastatic cancer in the lumbar region by using diffusion weighted image taken with a 1.5 T (Tesla) magnetic resonance (MR) scanner before and after injecting a contrast medium. The study enrolled 30 healthy people and 30 patients with metastatic spine cancer from patients who underwent a lumbar MRI scan from January 2011 to October 2012. A 1.5 T MR scanner was used to obtain the diffusion weighted images (DWIs) before and after injecting the contrast medium. In the group with metastatic spine cancer, the SNR and the CNR were measured in three parts among the L1-L5 lumbar vertebrae, which included the part with metastatic spine cancer, the area of the spine with spine cancer, and the area of spine under the region with cancer. In the acquired ADC map image, the SNRs and the ADCs of the three parts were measured in ADC map images. Among the healthy subjects, the measurements were conducted for the lumbar regions of L3-L5. According to the results, in the group with metastatic spine cancer, the SNR in the DWI before the contrast medium had been injected was lowest in the part with spine cancer. In the DWI after the contrast medium had been injected, the SNR and the CNR were increased in all three parts. In the ADC map image after the contrast medium had been injected, the SNR decreased in all three parts compared to the SNR before the contrast had been injected. The ADC after had been injected the contrast medium was decreased in all three parts compared to that before the contrast medium had been injected. In the healthy group, the SNR was increased in the L3-L5 lumbar regions in the DWI. In the ADC map image, the SNR in all the three parts was decreased in the DWI after injecting the contrast medium had been injected. The ADC in the ADC map image was also decreased in all three parts.

  1. 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

  2. [Evaluation of diagnostic effectiveness of the method of diffusion-weighted MR-images in diagnosis of pathology of the uterine body].

    PubMed

    Stolyarova, I V; Yakovleva, E K; Sharakova, V V

    2015-01-01

    The purpose of this study was to evaluate diagnostic efficiency of methods of diffusion-weighted imaging (DWI) in the diagnosis of diseases of the body the uterus at the high and ultra high field MRI (1,5T1, 3,OT1). In total we examined 150 patients. In 72 patients (48%) there were histologically verified malignant changes; of these 70 patients (46.7%) had endome- trial cancer (EC), 2 (1.3%)--uterine sarcoma. 40 EC patients (57.2%) had of Stage I, 15 patients (21.4%)--Stage II, 11 patients (15.7%)--Stage III, and 4 patients (5.8%) of--stage IV. 48 patients (32%) had benign processes of the endometrium (uterine fibroids--27 patients, endometrial hyperplasia--12 patients, endometrial polyps--9 patients). The control group consisted of 30 (20%) healthy patients. All patients underwent MRI examination of the pelvic organs into high and ultra-high MRI (1,5T1, 3,0T1). All patients were required performance of SP DWI (diffusion-weighted images) in 2 projections (Ax and Sag) with different diffusion factors (50-500-1100). MRI data using DWI were compared with surgical material. To our opinion modern MRI techniques allow to reliably determine the size of the pathological process, its location, the extent of the parameters for endometrial cancer, as well as the degree of involvement in the pathological process of the bladder and rectum, to assess the condition of the pelvic lymph nodes. MRI, supplemented DWI, allowed differentiating benign and malignant lesions of the uterus. MRI data corresponded to a post mortem conclusion in the case, specificity 86%, sensitivity of 92% and a diagnostic accuracy of 91%, which significantly improved the diagnostic accuracy of a standard MRI. Thus the method DWI MRI using modern software improves the differential diagnosis of diseases of the body uterus, can reliably assess the extent of the pathological process, to fully assess the invasion of parametrial tissue, provide a comprehensive assessment of the status of the lymph nodes. PMID

  3. 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

  4. Reproducibility and optimization of in vivo human diffusion-weighted MRS of the corpus callosum at 3 T and 7 T.

    PubMed

    Wood, Emily T; Ercan, Ayse Ece; Branzoli, Francesca; Webb, Andrew; Sati, Pascal; Reich, Daniel S; Ronen, Itamar

    2015-08-01

    Diffusion-weighted MRS (DWS) of brain metabolites enables the study of cell-specific alterations in tissue microstructure by probing the diffusion of intracellular metabolites. In particular, the diffusion properties of neuronal N-acetylaspartate (NAA), typically co-measured with N-acetylaspartyl glutamate (NAAG) (NAA + NAAG = tNAA), have been shown to be sensitive to intraneuronal/axonal damage in pathologies such as stroke and multiple sclerosis. Lacking, so far, are empirical assessments of the reproducibility of DWS measures across time and subjects, as well as a systematic investigation of the optimal acquisition parameters for DWS experiments, both of which are sorely needed for clinical applications of the method. In this study, we acquired comprehensive single-volume DWS datasets of the human corpus callosum at 3 T and 7 T. We investigated the inter- and intra-subject variability of empirical and modeled diffusion properties of tNAA [D(avg) (tNAA) and D(model) (tNAA), respectively]. Subsequently, we used a jackknife-like resampling approach to explore the variance of these properties in partial data subsets reflecting different total scan durations. The coefficients of variation (C(V)) and repeatability coefficients (C(R)) for D(avg) (tNAA) and D(model) (tNAA) were calculated for both 3 T and 7 T, with overall lower variability in the 7 T results. Although this work is limited to the estimation of the diffusion properties in the corpus callosum, we show that a careful choice of diffusion-weighting conditions at both field strengths allows the accurate measurement of tNAA diffusion properties in clinically relevant experimental time. Based on the resampling results, we suggest optimized acquisition schemes of 13-min duration at 3T and 10-min duration at 7 T, whilst retaining low variability (C(V) ≈ 8%) for the tNAA diffusion measures. Power calculations for the estimation of D(model )(tNAA) and D(avg) (tNAA) based on the suggested schemes show that

  5. 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.

  6. Generic Propellants Transfer Unit (GPTU)

    NASA Technical Reports Server (NTRS)

    Cook, Christopher A.

    1992-01-01

    The Generic Propellants Transfer Unit (GPTU) is being designed to support spacecraft liquid propellant operations at the Kennedy Space Center (KSC) and Eastern Test Range (ETR). The GPTU will have a 500 gallon capacity and be Department Of Transportation (DOT) approved for over-the-road transportation of hypergolic propellants. The use of these containers will allow the users to increase efficiency and reduce the following costs: design/construction, transportation (to/from the launch site), propellant transfer operations, and decontamination operations. The user also acquires the flexibility of transporting to an offsite location for processing or storage without obtaining special exemptions or permits. These containers will incorporate their own quantity gaging and temperature sensing systems, and be integrated onto a transport trailer which contains work platforms and a fluid transfer system.

  7. 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.

  8. 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.

  9. Propellant gaging for geostationary satellites

    NASA Astrophysics Data System (ADS)

    Orazietti, A. J.; Orton, G. F.; Schreib, R.

    1986-06-01

    Evaluations were performed to select four gaging concepts for ground tests and low-g tests in the NASA KC-135 aircraft. The selected concepts were an ultrasonic point sensor system, a nucleonic gaging system, an ultrasonic torsional wave guide, and an ultrasonic flowmeter. The first three systems provide a direct measurement of propellant quantity remaining, while the fourth system integrates (totalizes) the propellant flow to the engines and infers propellant remaining based on a known initial propellant load. As a result of successful ground and KC-135 tests, two concepts (the ultrasonic point sensor and nucleonic systems) were selected for orbital test in a Shuttle Get-Away-Special experiment. These systems offer high end-of-life accuracy potential, are nonintrusive (external to the tanks and feedlines), and are low in risk because of their good technology base. The Shuttle Get-Away-Special experiment has been assembled and passed flight certification testing in late April 1986.

  10. 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.

  11. Preoperative diagnosis and staging of rectal cancer using diffusion-weighted and water imaging combined with dynamic contrast-enhanced scanning

    PubMed Central

    ZHAO, QILI; LIU, LIJIAN; WANG, QIUYAN; LIANG, ZEXIA; SHI, GAOFENG

    2014-01-01

    The aim of the present study was to evaluate the value of diffusion-weighted imaging (DWI) and water imaging combined with dynamic contrast-enhanced scanning for the preoperative diagnosis and staging of rectal cancer. In total, 72 patients with pathologically confirmed rectal cancer were selected for examination using magnetic resonance imaging (MRI) with phased-array coils, DWI, water imaging and dynamic contrast-enhanced scanning. The patients were divided into two groups, experimental (simple enhanced scanning plus diffusion combined with water imaging) and control (simple enhanced scanning), for the pathological observations. The sensitivity, specificity and accuracy for the T staging of the carcinomas using scan enhancement with DWI and the evaluation of cancer using water imaging were 98.5% (65/66), 66.7% (4/6) and 95.8% (69/72), respectively, and the accuracy for N staging was 89%. Whereas, the sensitivity, specificity and accuracy for the T staging of the carcinomas using simple scan enhancement were 85.7% (42/49), 78.3% (18/23) and 83.3% (60/72), respectively, and the accuracy for N staging was 61%. Therefore, the combination of multiple MRI techniques may be of high value for the early diagnosis and exact staging of rectal cancer. PMID:25360178

  12. Diffusion weighted MR and apparent diffusion coefficient measurement in classification and characterization of noncystic focal liver lesions: does a clinical role exist?

    PubMed

    Mungai, Francesco; Morone, Mario; Villanacci, Alberta; Bondioni, Maria Pia; Mazzoni, Lorenzo Nicola; Grazioli, Luigi; Colagrande, Stefano

    2014-07-01

    The objective of this study was to assess the clinical role of apparent diffusion coefficient (ADC) analysis in noncystic focal liver lesion (FLL) classification/characterization.Six hundred liver magnetic resonances with multi-b (b = 50, 400, 800 s/mm) diffusion-weighted imaging (DwI) were retrospectively reviewed. Mean ADC was measured in 388 lesions (195 benign and 193 malignant) excluding internal necrotic areas. Cystic benign lesions were excluded from analysis. Sensitivity and specificity in distinguishing benign from malignant lesions were calculated. Analysis of variance was performed to detect differences among subgroups of solid lesions.Mean ADC of malignant lesions was 0.980 × 10 mm/s, significantly (P < 0.05) lower than mean ADC of benign lesions (1.433 × 10 mm/s). Applying an ADC cutoff of 1.066 × 10 mm/s, specificity and sensitivity for malignancy were respectively 86.6% and 73.6%. Of all lesions, >1/3 (39.5%) presented values lower than 1 × 10 mm/s, with 90.0% chance of malignancy. Above 1.5 × 10 mm/s (about 20% of all lesions) chance of malignancy was 9.5%.DwI cannot assist in noncystic FLL characterization, but can help in FLL classification in about half the cases. PMID:25058143

  13. New Magnetic Resonance Imaging Index for Renal Fibrosis Assessment: A Comparison between Diffusion-Weighted Imaging and T1 Mapping with Histological Validation

    PubMed Central

    Friedli, I.; Crowe, L. A.; Berchtold, L.; Moll, S.; Hadaya, K.; de Perrot, T.; Vesin, C.; Martin, P.-Y.; de Seigneux, S.; Vallée, J.-P.

    2016-01-01

    A need exists to noninvasively assess renal interstitial fibrosis, a common process to all kidney diseases and predictive of renal prognosis. In this translational study, Magnetic Resonance Imaging (MRI) T1 mapping and a new segmented Diffusion-Weighted Imaging (DWI) technique, for Apparent Diffusion Coefficient (ADC), were first compared to renal fibrosis in two well-controlled animal models to assess detection limits. Validation against biopsy was then performed in 33 kidney allograft recipients (KARs). Predictive MRI indices, ΔT1 and ΔADC (defined as the cortico-medullary differences), were compared to histology. In rats, both T1 and ADC correlated well with fibrosis and inflammation showing a difference between normal and diseased kidneys. In KARs, MRI indices were not sensitive to interstitial inflammation. By contrast, ΔADC outperformed ΔT1 with a stronger negative correlation to fibrosis (R2 = 0.64 against R2 = 0.29 p < 0.001). ΔADC tends to negative values in KARs harboring cortical fibrosis of more than 40%. Using a discriminant analysis method, the ΔADC, as a marker to detect such level of fibrosis or higher, led to a specificity and sensitivity of 100% and 71%, respectively. This new index has potential for noninvasive assessment of fibrosis in the clinical setting. PMID:27439482

  14. Diffusion-weighted magnetic resonance imaging for prediction of tumor response to neoadjuvant chemoradiotherapy using irinotecan plus S-1 for rectal cancer

    PubMed Central

    DOI, HIROSHI; BEPPU, NAOHITO; KATO, TAKASHI; NODA, MASASHI; YANAGI, HIDENORI; TOMITA, NAOHIRO; KAMIKONYA, NORIHIKO; HIROTA, SHOZO

    2015-01-01

    The purpose of this study was to investigate the clinical value of diffusion-weighted (DW) magnetic resonance imaging (MRI) as a predictor of tumor response in patients receiving neoadjuvant chemoradiotherapy (NA-CRT) for rectal cancer (RC) through measurement of the apparent diffusion coefficient (ADC) value in each tumor. Neoadjuvant radiotherapy with a total dose of 45 Gy in 25 fractions was performed in all 16 patients with RC, combined with irinotecan and S-1. MRI was performed before and after NA-CRT. Multiple factors were assessed to predict the pathological response to NA-CRT. The pathological response rate was determined in 9 patients (56.3%). Statistical analyses indicated that the ADC value prior to NA-CRT was significantly lower in patients with a better response to NA-CRT (P=0.023). A cut-off value of 0.750×10−3 mm2/sec obtained by a receiver operating characteristic curve analysis indicated a sensitivity of 77.8% and specificity of 85.7% for pathological responders to NA-CRT. In addition, the patients with lower ADC values exhibited a greater pathological response to NA-CRT (P=0.041). In conclusion, the ADC value of MRI of RC patients treated with NA-CRT followed by surgery may provide valuable information to predict the response to NA-CRT. PMID:26623064

  15. Time course of diffusion weighted image and apparent diffusion coefficient in acute spinal cord infarction: A case report and review of the literature.

    PubMed

    Takeshita, Sho; Ogata, Toshiyasu; Mera, Hidekazu; Tsugawa, Jun; Fukae, Jiro; Tsuboi, Yoshio

    2016-05-31

    An 80-year-old woman was admitted to our hospital with acute onset of flaccid paraplegia and sensory and urinary disturbances that developed soon after acute pain in her lower back and leg. Neurological examination revealed, severe flaccid paraplegia, bladder and rectal disturbances and dissociated sensory loss below the level of L1 spinal cord segment. MR imaging with T2 weighted imaging (T2WI) and diffusion weighted imaging (DWI) on day 2 showed hyper signal intensity in the spinal cord at the vertebral level of L1 while initial apparent diffusion coefficient (ADC) showed decreased signal intensity in the lesion. We diagnosed spinal cord infarction, and anticoagulant and neuroprotective agents were administrated. Serial MRI findings revealed that the DWI signal of the lesion attenuated with time, and pseudo-normalization of the ADC occurred approximately 1 month after onset. These findings were similar to those seen in brain infarction. Our patient demonstrated serial MRI changes of spinal cord infarction showing anterior spinal cord syndrome. PMID:27098903

  16. Pyogenic and non-pyogenic spinal infections: emphasis on diffusion-weighted imaging for the detection of abscesses and pus collections.

    PubMed

    Moritani, T; Kim, J; Capizzano, A A; Kirby, P; Kademian, J; Sato, Y

    2014-09-01

    The incidence of spinal infections has increased in the past two decades, owing to the increasing number of elderly patients, immunocompromised conditions, spinal surgery and instrumentation, vascular access and intravenous drug use. Conventional MRI is the gold standard for diagnostic imaging; however, there are still a significant number of misdiagnosed cases. Diffusion-weighted imaging (DWI) with a b-value of 1000 and apparent diffusion coefficient (ADC) maps provide early and accurate detection of abscess and pus collection. Pyogenic infections are classified into four types of extension based on MRI and DWI findings: (1) epidural/paraspinal abscess with spondylodiscitis, (2) epidural/paraspinal abscess with facet joint infection, (3) epidural/paraspinal abscess without concomitant spondylodiscitis or facet joint infection and (4) intradural abscess (subdural abscess, purulent meningitis and spinal cord abscess). DWI easily detects abscesses and demonstrates the extension, multiplicity and remote disseminated infection. DWI is often a key image in the differential diagnosis. Important differential diagnoses include epidural, subdural or subarachnoid haemorrhage, cerebrospinal fluid leak, disc herniation, synovial cyst, granulation tissue, intra- or extradural tumour and post-surgical fluid collections. DWI and the ADC values are affected by susceptibility artefacts, incomplete fat suppression and volume-averaging artefacts. Recognition of artefacts is essential when interpreting DWI of spinal and paraspinal infections. DWI is not only useful for the diagnosis but also for the treatment planning of pyogenic and non-pyogenic spinal infections. PMID:24999081

  17. High-resolution three-dimensional diffusion-weighted MRI/CT image data fusion for cholesteatoma surgical planning: a feasibility study.

    PubMed

    Yamashita, Koji; Hiwatashi, Akio; Togao, Osamu; Kikuchi, Kazufumi; Matsumoto, Nozomu; Obara, Makoto; Yoshiura, Takashi; Honda, Hiroshi

    2015-12-01

    The aim of the study was to assess the feasibility of high-resolution three-dimensional diffusion-weighted images (HR3D-DWIs)/multi-detector row CT (MDCT) images' data fusion for surgical planning for cholesteatoma. A total of 12 patients (7 male and 5 female; age range 11-72 years; mean 38.1 years) with cholesteatoma underwent preoperative MRI using a 3.0-T clinical unit and an 8-channel array-head coil. For each subject, HR3D-DWIs were obtained using a turbo field-echo with diffusion-sensitized driven-equilibrium preparation with 1.5 mm iso-voxel dimension. These patients also underwent MDCT with a slice thickness of 0.5 mm. Fusion of the HR3D-DWIs and MDCT images was performed using an automated rigid registration and subsequent manual fine-tuning by a board-certified neuroradiologist on a workstation. Fused images were compared to CT and findings confirmed based on operation reports. On the fused images, the extent of the cholesteatoma, which was depicted as a conspicuous high-intensity lesion could be easily evaluated with background bony structures. In all patients, the location and extent of the cholesteatoma on the fused images corresponded well with the intraoperative findings. Image fusion between HR3D-DWIs and MDCT images is feasible, and provides valuable preoperative information for surgical planning to otorhinolaryngologists. PMID:25543305

  18. 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

  19. The Role of Diffusion-Weighted Imaging (DWI) in Locoregional Therapy Outcome Prediction and Response Assessment for Hepatocellular Carcinoma (HCC): The New Era of Functional Imaging Biomarkers.

    PubMed

    Ludwig, Johannes M; Camacho, Juan C; Kokabi, Nima; Xing, Minzhi; Kim, Hyun S

    2015-01-01

    Reliable response criteria are critical for the evaluation of therapeutic response in hepatocellular carcinoma (HCC). Current response assessment is mainly based on: (1) changes in size, which is at times unreliable and lag behind the result of therapy; and (2) contrast enhancement, which can be difficult to quantify in the presence of benign post-procedural changes and in tumors presenting with a heterogeneous pattern of enhancement. Given these challenges, functional magnetic resonance imaging (MRI) techniques, such as diffusion-weighted imaging (DWI) have been recently investigated, aiding specificity to locoregional therapy response assessment and outcome prediction. Briefly, DWI quantifies diffusion of water occurring naturally at a cellular level (Brownian movement), which is restricted in multiple neoplasms because of high cellularity. Disruption of cellular integrity secondary to therapy results in increased water diffusion across the injured membranes. This review will provide an overview of the current literature on DWI therapy response assessment and outcome prediction in HCC following treatment with locoregional therapies. PMID:26854170

  20. The Role of Diffusion-Weighted Imaging (DWI) in Locoregional Therapy Outcome Prediction and Response Assessment for Hepatocellular Carcinoma (HCC): The New Era of Functional Imaging Biomarkers

    PubMed Central

    Ludwig, Johannes M.; Camacho, Juan C.; Kokabi, Nima; Xing, Minzhi; Kim, Hyun S.

    2015-01-01

    Reliable response criteria are critical for the evaluation of therapeutic response in hepatocellular carcinoma (HCC). Current response assessment is mainly based on: (1) changes in size, which is at times unreliable and lag behind the result of therapy; and (2) contrast enhancement, which can be difficult to quantify in the presence of benign post-procedural changes and in tumors presenting with a heterogeneous pattern of enhancement. Given these challenges, functional magnetic resonance imaging (MRI) techniques, such as diffusion-weighted imaging (DWI) have been recently investigated, aiding specificity to locoregional therapy response assessment and outcome prediction. Briefly, DWI quantifies diffusion of water occurring naturally at a cellular level (Brownian movement), which is restricted in multiple neoplasms because of high cellularity. Disruption of cellular integrity secondary to therapy results in increased water diffusion across the injured membranes. This review will provide an overview of the current literature on DWI therapy response assessment and outcome prediction in HCC following treatment with locoregional therapies. PMID:26854170

  1. Accuracies and Contrasts of Models of the Diffusion-Weighted-Dependent Attenuation of the MRI Signal at Intermediate b-values

    PubMed Central

    Nicolas, Renaud; Sibon, Igor; Hiba, Bassem

    2015-01-01

    The diffusion-weighted-dependent attenuation of the MRI signal E(b) is extremely sensitive to microstructural features. The aim of this study was to determine which mathematical model of the E(b) signal most accurately describes it in the brain. The models compared were the monoexponential model, the stretched exponential model, the truncated cumulant expansion (TCE) model, the biexponential model, and the triexponential model. Acquisition was performed with nine b-values up to 2500 s/mm2 in 12 healthy volunteers. The goodness-of-fit was studied with F-tests and with the Akaike information criterion. Tissue contrasts were differentiated with a multiple comparison corrected nonparametric analysis of variance. F-test showed that the TCE model was better than the biexponential model in gray and white matter. Corrected Akaike information criterion showed that the TCE model has the best accuracy and produced the most reliable contrasts in white matter among all models studied. In conclusion, the TCE model was found to be the best model to infer the microstructural properties of brain tissue. PMID:26106263

  2. Development of Computerized Scheme for Adjustment of Display Grayscale in Brain Diffusion-Weighted Magnetic Resonance Images with Acute Ischemic Stroke

    NASA Astrophysics Data System (ADS)

    Nagashima, Hiroyuki; Harakawa, Tetsumi; Doi, Kunio

    We developed a computerized scheme for proper adjustment of display grayscale in brain diffusion-weighted magnetic resonance images (DWI) with acute ischemic stroke by using thalamic signal intensity on concurrent images (b0 image). In our computerized scheme, the gray level of b0 image was first normalized, and the brain region was segmented using thresholding and labeling techniques. The lateral inclination in b0 image was then corrected semi-automatically by rotating and shifting. Each of the thalamic positions was determined by using the coordinate information in the brain region. The average signal intensity of the thalamus was measured on the region of interest (ROI) selected, and the thalamus in one side with the low signal intensity was selected. The display grayscale in DWI was finally adjusted by using the signal intensity of the selected thalamus. The thalamus positions in all cases were confirmed to be included in the thalamic outline. In 30 training cases, the average error between the thalamic signal intensity obtained from the manual selection and the computerized scheme were 1.8%±1.5, and in 30 testing cases, 1.3%±1.2. Our computerized scheme has a potential in the determination of the display grayscale of brain DWI, and would be useful to radiologists in decision-making for radiological diagnosis.

  3. MR imaging of urinary bladder cancer for T-staging: a review and a pictorial essay of diffusion-weighted imaging.

    PubMed

    Takeuchi, Mitsuru; Sasaki, Shigeru; Naiki, Taku; Kawai, Noriyasu; Kohri, Kenjiro; Hara, Masaki; Shibamoto, Yuta

    2013-12-01

    Treatment decisions for bladder cancer patients are mainly based on the depth of bladder wall invasion by the tumor. In this article, we review the conventional MRI and exhibit a recently emerged diffusion-weighted imaging (DWI) of urinary bladder cancer for T-staging. We discuss limitations of conventional MRI, scanning protocols of DWI, normal pelvic findings on DWI, determination of T-stage using DWI, and pitfalls of DWI. DWI provides high contrast between bladder cancer and background tissue because the cancer shows markedly high SI. DWI has high sensitivity for detecting the stalk seen in stage Ta or T1. An inflammatory change or fibrosis surrounding the tumor mimics the invasion of bladder cancer on T2-weighted imaging or enhanced MRI and could lead to over-staging, but DWI could differentiate them clearly because these benign changes do not show high SI on DWI. DWI is also useful for detecting ureteral, urethral, and prostatic extension by means of the urethra. DWI provides more accurate information on the extent of bladder cancer and contributes to determination of the treatment strategy. PMID:24265260

  4. Diffusion-weighted imaging for non-invasive and quantitative monitoring of bone marrow infiltration in patients with monoclonal plasma cell disease: a comparative study with histology.

    PubMed

    Hillengass, Jens; Bäuerle, Tobias; Bartl, Reiner; Andrulis, Mindaugas; McClanahan, Fabienne; Laun, Frederik B; Zechmann, Christian Martin; Shah, Rajiv; Wagner-Gund, Barbara; Simon, Dirk; Heiss, Christiane; Neben, Kai; Ho, Anthony D; Schlemmer, Heinz-Peter; Goldschmidt, Hartmut; Delorme, Stefan; Stieltjes, Bram

    2011-06-01

    Bone marrow plasma cell infiltration is a crucial parameter of disease activity in monoclonal plasma cell disorders. Until now, the only way to quantify such infiltration was bone marrow biopsy or aspiration. Diffusion-weighted imaging (DWI) is a magnetic resonance imaging-technique that may mirror tissue cellularity by measuring random movements of water molecules. To investigate if DWI is capable of assessing bone marrow cellularity in monoclonal plasma cell disease, we investigated 56 patients with multiple myeloma or monoclonal gammopathy of undetermined significance, and 30 healthy controls using DWI of the pelvis and/or the lumbar spine. In 25 of 30 patients who underwent biopsy, bone marrow trephine and DWI could be compared. Of the patients with symptomatic disease 15 could be evaluated after systemic treatment. There was a positive correlation between the DWI-parameter apparent diffusion coefficient (ADC) and bone marrow cellularity as well as micro-vessel density (P<0·001 respectively). ADC was significantly different between patients and controls (P<0·01) and before and after systemic therapy (P<0·001). In conclusion, DWI enabled bone marrow infiltration to be monitored in a non-invasive, quantitative way, suggesting that after further investigations on larger patient groups this might become an useful tool in the clinical work-up to assess tumour burden. PMID:21517815

  5. Investigation of the optimal b-value to detect breast tumors with diffusion weighted imaging by 1.5-T MRI

    PubMed Central

    2014-01-01

    Background Previous studies have reported that the signal attenuation of diffusion-weighted magnetic resonance imaging (DWI) for normal breast tissue and tumor were well fitted by a monoexponential and a biexponential function, respectively. The aim of this study was to investigate the optimal b-value to detect breast tumors from DWI signal attenuations. Methods Sixty-four subjects with breast cancer underwent DWI using six b-values up to 3500 s/mm2. The signal attenuations of normal breast and tumor were fitted by mono- and biexponential functions, respectively. The maximum contrast b-values were estimated and compared in terms of frequency. Results In almost all cases, the contrast increased with a b-value from 0 to approximately 1500 s/mm2. For b > 1500 s/mm2, the contrast decreased. The highest contrast b-value in the range of 0 to 2500 s/mm2 most frequently was b = 1500 and the next most frequent was 1400 s/mm2. Comparing sensitivity and specificity between b = 700 and b = 1400 s/mm2, b =1400 s/mm2 was slightly superior. Conclusion Based on these results, DWI with a b-value of approximately 1400-1500 s/mm2 is recommended for optimizing breast tumor detectability. PMID:25608450

  6. Pyogenic and non-pyogenic spinal infections: emphasis on diffusion-weighted imaging for the detection of abscesses and pus collections

    PubMed Central

    Kim, J; Capizzano, A A; Kirby, P; Kademian, J; Sato, Y

    2014-01-01

    The incidence of spinal infections has increased in the past two decades, owing to the increasing number of elderly patients, immunocompromised conditions, spinal surgery and instrumentation, vascular access and intravenous drug use. Conventional MRI is the gold standard for diagnostic imaging; however, there are still a significant number of misdiagnosed cases. Diffusion-weighted imaging (DWI) with a b-value of 1000 and apparent diffusion coefficient (ADC) maps provide early and accurate detection of abscess and pus collection. Pyogenic infections are classified into four types of extension based on MRI and DWI findings: (1) epidural/paraspinal abscess with spondylodiscitis, (2) epidural/paraspinal abscess with facet joint infection, (3) epidural/paraspinal abscess without concomitant spondylodiscitis or facet joint infection and (4) intradural abscess (subdural abscess, purulent meningitis and spinal cord abscess). DWI easily detects abscesses and demonstrates the extension, multiplicity and remote disseminated infection. DWI is often a key image in the differential diagnosis. Important differential diagnoses include epidural, subdural or subarachnoid haemorrhage, cerebrospinal fluid leak, disc herniation, synovial cyst, granulation tissue, intra- or extradural tumour and post-surgical fluid collections. DWI and the ADC values are affected by susceptibility artefacts, incomplete fat suppression and volume-averaging artefacts. Recognition of artefacts is essential when interpreting DWI of spinal and paraspinal infections. DWI is not only useful for the diagnosis but also for the treatment planning of pyogenic and non-pyogenic spinal infections. PMID:24999081

  7. [An acute severe heat stroke patient showing abnormal diffuse high intensity of the cerebellar cortex in diffusion weighted image: a case report].

    PubMed

    Fujioka, Yusuke; Yasui, Keizo; Hasegawa, Yasuhiro; Takahashi, Akira; Sobue, Gen

    2009-10-01

    A 47-year-old man was admitted to the hospital because of general convulsion, loss of consciousness and hyperthermia. A diagnosis of acute heat stroke was made clinically and neuroradiologically. As the consciousness level ameliorated, he developed severe abulia and mutism, then cerebellar ataxic syndrome (viz. truncal ataxia, hypermetria, ataxic speech and nystagmus). An MRI (diffusion weighted image; DWI) disclosed abnormal diffuse high signal intensity of the cerebellar cortex with reduced apparent diffusion coefficient (ADC). Two months later after the onset, truncal ataxia and dysarthria significantly improved, while dysmetria of the extremities rather worsened. At that time, the abnormal signal intensity of the cerebellar cortex disappeared, and the cerebellum became atrophic. The cerebellar blood flow was significantly decreased on brain SPECT (99mTc-ECD). The abnormal DWI signal intensity of the cerebellar cortex in the present patient may represent the cytotoxic edema of Purkinje cells resulting from heat stroke-related hyperthermia It is essential to repeat MRI examination for cerebellar pathology and to obtain better insight into sequelae in patients with acute heat stroke. Protirelin tartrate seemed to be valid for improvement of abulia in the present patient. Further study is indicated. PMID:19999144

  8. Diffusion-weighted whole-body imaging with background body signal suppression/T2-weighted image fusion of gastrointestinal cancers

    PubMed Central

    TOMIZAWA, MINORU; SHINOZAKI, FUMINOBU; FUGO, KAZUNORI; SUNAOSHI, TAKAFUMI; KANO, DAISUKE; TANAKA, SATOMI; OZAKI, AIKA; SUGIYAMA, ERIKO; SHITE, MISAKI; HAGA, RYOUTA; BABA, AKIRA; FUKAMIZU, YOSHIYA; FUJITA, TOSHIYUKI; KAGAYAMA, SATOSHI; HASEGAWA, RUMIKO; TOGAWA, AKIRA; SHIRAI, YOSHINORI; ICHIKI, NOBORU; MOTOYOSHI, YASUFUMI; SUGIYAMA, TAKAO; YAMAMOTO, SHIGENORI; KISHIMOTO, TAKASHI; ISHIGE, NAOKI

    2016-01-01

    Diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) yields positive results for cancer against the surrounding tissues. The combination of DWIBS and T2-weighted images (DWIBS/T2) in the diagnosis of gastrointestinal tract cancers was retrospectively analyzed in the present study. Patients were subjected to magnetic resonance imaging after cancer was diagnosed through specimens obtained via biopsy or endoscopic mucosal resection. Sixteen patients were assessed between July, 2012 and June, 2013 and the correlation between detection with DWIBS/T2 and T staging was analyzed. Regarding patients who underwent surgery, the correlation between detection with DWIBS/T2 and the diameter or depth of invasion was analyzed. All cancers that had advanced to >T2 stage were detectable by DWIBS/T2, whereas all cancers staged as T2) or invading beyond the muscularis propria. PMID:27330763

  9. New Magnetic Resonance Imaging Index for Renal Fibrosis Assessment: A Comparison between Diffusion-Weighted Imaging and T1 Mapping with Histological Validation.

    PubMed

    Friedli, I; Crowe, L A; Berchtold, L; Moll, S; Hadaya, K; de Perrot, T; Vesin, C; Martin, P-Y; de Seigneux, S; Vallée, J-P

    2016-01-01

    A need exists to noninvasively assess renal interstitial fibrosis, a common process to all kidney diseases and predictive of renal prognosis. In this translational study, Magnetic Resonance Imaging (MRI) T1 mapping and a new segmented Diffusion-Weighted Imaging (DWI) technique, for Apparent Diffusion Coefficient (ADC), were first compared to renal fibrosis in two well-controlled animal models to assess detection limits. Validation against biopsy was then performed in 33 kidney allograft recipients (KARs). Predictive MRI indices, ΔT1 and ΔADC (defined as the cortico-medullary differences), were compared to histology. In rats, both T1 and ADC correlated well with fibrosis and inflammation showing a difference between normal and diseased kidneys. In KARs, MRI indices were not sensitive to interstitial inflammation. By contrast, ΔADC outperformed ΔT1 with a stronger negative correlation to fibrosis (R(2) = 0.64 against R(2) = 0.29 p < 0.001). ΔADC tends to negative values in KARs harboring cortical fibrosis of more than 40%. Using a discriminant analysis method, the ΔADC, as a marker to detect such level of fibrosis or higher, led to a specificity and sensitivity of 100% and 71%, respectively. This new index has potential for noninvasive assessment of fibrosis in the clinical setting. PMID:27439482

  10. A study of the relationship between gender/age and apparent diffusion coefficient values in spleen of healthy adults using diffusion-weighted magnetic resonance imaging

    PubMed Central

    Nazarlou, Ali Kiani; Abdolmohammadi, Jamil

    2015-01-01

    Background: Diffusion-weighted magnetic resonance imaging (DWI) systems are very effective in detecting strokes, and they also have shown significant promise in the detection of fibrosis and cirrhosis of the liver. However, such systems have the disadvantages of poor reproducibility and noise, which can diminish the accuracy of the apparent diffusion coefficients (ADCs) provided by the DWI process. The main aim of this study was to determine the relationship between the age and gender of healthy adults in terms of the ADC values of the spleen measured by DWI. Methods: Sixty-nine subjects selected for this study from people who were referred to the Tabesh Medical Imaging Center in Tabriz, Iran, in 2013. Each subject underwent echo-planar DWI for her or his ADC values of the spleen with b-values of 50, 400, and 800 s/mm2, and the resulting ADC values were evaluated. Results: No significant differences were observed in ADC values of the spleen among the female and male participants or those from various ages (P>0.05). Conclusions: Based on the findings of this study, it was concluded that the effect of age and gender on the spleen’s ADC values can be omitted from the spleen-diagnosis procedure. In other words, the spleen’s ADC values are not related to the age or the gender of healthy adults. PMID:26052412

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. Solid propellant environmental issues

    SciTech Connect

    Le, M.D.

    1998-07-01

    The objective of the Solid Propellant Environmental Issues (SPEI) project is to demonstrate environmentally acceptable technologies that will enhance the continued production of solid rocket motors (SRMs) by complying with current and anticipated environmental regulations. Phase 1 of the project identifies current and anticipated environmental regulations that may affect SRMs manufacturing in the future and identify emerging process technologies which comply with these regulations. Phase 2 of the project established a baseline database by fabricating a 363 kg motor using the current manufacturing process. In Phase 3, environmentally acceptable process technologies were evaluated, ranked, and selected for demonstration using criteria developed by the team. The results for Phase 1--3 have previously been presented. This paper will present data obtained to date on Phase 4. In Phase 4, the alternate process technologies were evaluated for compatibility, cleaning effectiveness, and waste minimization/pollution prevention. The best performing candidate for each application area was selected for demonstration. The selected process technologies will be inserted into the baseline manufacturing process from Phase 2. The new manufacturing process will be demonstrated and evaluated through the scale-up and fabrication of two 363 kg solid rocket motors.

  16. 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.

  17. 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.

  18. 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

  19. Diagnostic Performance of Fused Diffusion-Weighted Imaging Using Unenhanced or Postcontrast T1-Weighted MR Imaging in Patients With Breast Cancer

    PubMed Central

    Shin, Hee Jung; Chae, Eun Young; Choi, Woo Jung; Ha, Su Min; Park, Jin Young; Shin, Ki Chang; Cha, Joo Hee; Kim, Hak Hee

    2016-01-01

    Abstract To evaluate the diagnostic performance of fused diffusion-weighted imaging (DWI) using either unenhanced (UFMR) or early postcontrast T1-weighted imaging (PCFMR) to detect and characterize breast lesions in patients with breast cancer. This retrospective observational study was approved by institutional review board in our hospital and informed consents were waived. We retrospectively selected 87 consecutive patients who underwent preoperative breast magnetic resonance imaging, including DWI and definitive surgery. Both UFMR and PCFMR were reviewed by 5 radiologists for detection, lesion size, Breast Imaging Reporting and Data System final assessment, the probability of malignancy, lesion conspicuity, and apparent diffusion coefficients. A total of 129 lesions were identified by at least 2 readers on UFMR or PCFMR. Of 645 potentially detected lesions, there were 528 (82%) with UFMR and 554 (86%) with PCFMR. Malignant lesions or index cancers showed significantly higher detection rates than benign or additional lesions on both UFMR and PCFMR (P < 0.05). Area under the characteristic curves (AUCs) for predicting malignancy ranged 0.927 to 0.986 for UFMR, and 0.936 to 0.993 for PCFMR, which was not significantly different. Lesion conspicuity was significantly higher on PCFMR than UFMR (8.59 ± 1.67 vs 9.19 ± 1.36, respectively; P < 0.05) across 5 readers. Mean intraclass correlation coefficients for lesion size on UFMR and PCFMR were 0.89 and 0.92, respectively. Detection rates of index malignant lesions were similar for UFMR and PCFMR. Interobserver agreement for final assessments was reliable across 5 readers. Diagnostic accuracy for predicting malignancy with UFMR versus PCFMR was similar, although lesion conspicuity was significantly greater with the latter. PMID:27124054

  20. Diffusion Weighted MR and Apparent Diffusion Coefficient Measurement in Classification and Characterization of Noncystic Focal Liver Lesions: Does a Clinical Role Exist?

    PubMed Central

    Mungai, Francesco; Morone, Mario; Villanacci, Alberta; Bondioni, Maria Pia; Mazzoni, Lorenzo Nicola; Grazioli, Luigi; Colagrande, Stefano

    2014-01-01

    Abstract The objective of this study was to assess the clinical role of apparent diffusion coefficient (ADC) analysis in noncystic focal liver lesion (FLL) classification/characterization. Six hundred liver magnetic resonances with multi-b (b = 50, 400, 800 s/mm2) diffusion-weighted imaging (DwI) were retrospectively reviewed. Mean ADC was measured in 388 lesions (195 benign and 193 malignant) excluding internal necrotic areas. Cystic benign lesions were excluded from analysis. Sensitivity and specificity in distinguishing benign from malignant lesions were calculated. Analysis of variance was performed to detect differences among subgroups of solid lesions. Mean ADC of malignant lesions was 0.980 × 10−3 mm2/s, significantly (P < 0.05) lower than mean ADC of benign lesions (1.433 × 10−3 mm2/s). Applying an ADC cutoff of 1.066 × 10−3 mm2/s, specificity and sensitivity for malignancy were respectively 86.6% and 73.6%. Of all lesions, >1/3 (39.5%) presented values lower than 1 × 10−3 mm2/s, with 90.0% chance of malignancy. Above 1.5 × 10−3 mm2/s (about 20% of all lesions) chance of malignancy was 9.5%. DwI cannot assist in noncystic FLL characterization, but can help in FLL classification in about half the cases. PMID:25058143

  1. Intraventricular cerebrospinal fluid temperature analysis using MR diffusion-weighted imaging thermometry in Parkinson's disease patients, multiple system atrophy patients, and healthy subjects

    PubMed Central

    Sumida, Kaoru; Sato, Noriko; Ota, Miho; Sakai, Koji; Nippashi, Yasumasa; Sone, Daichi; Yokoyama, Kota; Ito, Kimiteru; Maikusa, Norihide; Imabayashi, Etsuko; Matsuda, Hiroshi; Yamada, Kei; Murata, Miho; Kunimatsu, Akira; Ohtomo, Kuni

    2015-01-01

    Purpose We examined the temperature of the intraventricular cerebrospinal fluid (Tv) in patients with Parkinson's disease (PD) and those with multiple system atrophy (MSA) in comparison with healthy subjects, and we examined normal changes in this temperature with aging. Methods Tv was estimated by magnetic resonance (MR) diffusion-weighted imaging (DWI) thermometry in 36 PD patients (19 males, 17 females), 34 MSA patients (17 males, 17 females), 64 age-matched controls (27 men, 37 women), and 114 all-age adult controls (47 men, 67 women; 28–89 years old). The volume of lateral ventricles was also estimated using FreeSurfer in all subjects. Tv and ventricular volume data were compared among the PD and MSA patients and age-matched controls. We also evaluated the relationship between Tv and age in the 114 all-age controls, controlling for ventricular volume. Men and women were analyzed separately. Results The male PD and MSA patients had significantly higher Tv values compared to the male controls, with no significant difference in ventricular volume among them. There was no significant difference in Tv between the female patients and controls. In the all-age male controls, there was a significant negative correlation between Tv and age controlling for ventricular volume, and this was not observed in the women. Conclusion DWI thermometry is a useful and easy method for demonstrating an altered intracranial environment in male patients and healthy controls, but not in females. DWI thermometry can thus be used to help to explore the pathophysiology of Parkinsonian syndromes and to differentiate individuals affected by neurodegenerative disease with autonomic dysfunction from those without it. PMID:26085965

  2. Analysis of factors influencing the degree of detectability on diffusion-weighted MRI and diffusion background signals in patients with invasive breast cancer.

    PubMed

    Hahn, Soo Yeon; Ko, Eun Sook; Han, Boo-Kyung; Lim, Yaeji; Gu, Seonhye; Ko, Eun Young

    2016-07-01

    To determine the factors influencing the degree of detectability of lesions and diffusion background signals on magnetic resonance diffusion-weighted imaging (DWI) in invasive breast cancer.Institutional review board approval was obtained and patient consent was waived. Patients with newly diagnosed invasive ductal carcinoma, who underwent preoperative breast magnetic resonance imaging with DWI were included in this study (n = 167). Lesion detectability on DWI and contrast-enhanced subtracted T1-weighted images, the degree of background parenchymal enhancement (BPE), and diffusion background signal were qualitatively rated. Detectability of lesions on DWI was compared with clinicopathological findings including menopausal status, mammographic density, and molecular subtype of breast cancer. Multivariate linear regression analysis was performed to determine variables independently associated with detectability of lesions on DWI and diffusion background signals.Univariate analysis showed that the detectability of lesions on DWI was significantly associated with lesion size (P = 0.001), diffuse background signal (P < 0.0001), and higher detectability scores for contrast-enhanced T1-weighted subtraction images (P = 0.000). The degree of diffusion background signal was significantly affected by age (P < 0.0001), BPE (P < 0.0001), mammographic density (P = 0.002), and menopausal status (P < 0.0001). On multivariate analysis, the diffusion background signal (P < 0.0001) and histologic grade (P < 0.0001) were correlated with the detectability on DWI of invasive breast cancer. Only BPE was correlated with the amount of diffusion background signal on DWI (P < 0.0001).For invasive breast cancers, detectability on DWI was significantly affected by the diffusion background signal. BPE, menopausal status, menstrual cycle, or mammographic density did not show statistically significant correlation with the diffusion detectability of lesions on DWI. PMID

  3. Bone metastases from prostate, breast and multiple myeloma: differences in lesion conspicuity at short-tau inversion recovery and diffusion-weighted MRI

    PubMed Central

    Pearce, T; Philip, S; Brown, J; Koh, D M; Burn, P R

    2012-01-01

    Objectives The objective of this study was to compare the relative conspicuity of bone metastases on short-tau inversion recovery (STIR) and diffusion-weighted MRI (DWI) whole-body MR sequences for breast, prostate and myeloma malignancies. Methods 44 whole-body MRI scans were reviewed retrospectively (coronal T1 weighted, STIR and DWI with b=800). On each scan, up to four of the largest bone lesions were identified on T1 weighting, and the region of interest signal intensity was measured on STIR and DWI, as well as the background signal intensity. The mean lesion signal to background ratio was calculated for each patient and then for each malignancy group. Results In prostate cancer patients, the DWI signal/background ratio was greater than that of STIR in 22 out of 24 patients (mean DWI lesion/background ratio 3.91, mean STIR lesion/background ratio 2.31; p=0.0001). In multiple myeloma, the DWI ratio was higher in 6/7 patients (DWI group mean ratio 7.59, STIR group mean ratio 3.7; p=0.0366). In 13 breast cancer patients, mean STIR and DWI signal/background were similar (DWI group mean ratio 4.13, group mean STIR ratio 4.26; p=0.8587). Conclusion Bone lesion conspicuity measured by lesion/background signal intensity was higher on DWI b=800 than on STIR in patients with prostate cancer and multiple myeloma. DWI should be used in whole-body MR oncology protocols in these conditions to maximise lesion detection. PMID:22457319

  4. Carotid Anatomy Does Not Predict the Risk of New Ischaemic Brain Lesions on Diffusion-Weighted Imaging after Carotid Artery Stenting in the ICSS-MRI Substudy

    PubMed Central

    Doig, D.; Hobson, B.M.; Müller, M.; Jäger, H.R.; Featherstone, R.L.; Brown, M.M.; Bonati, L.H.; Richards, T.

    2016-01-01

    Introduction The International Carotid Stenting Study (ICSS, ISRCTN25337470) randomized patients with recently symptomatic carotid artery stenosis > 50% to carotid artery stenting (CAS) or endarterectomy. CAS increased the risk of new brain lesions visible on diffusion-weighted magnetic resonance imaging (DWI-MRI) more than endarterectomy in the ICSS-MRI Substudy. The predictors of new post-stenting DWI lesions were assessed in these patients. Methods ICSS-MRI Substudy patients allocated to CAS were studied. Baseline or pre-stenting catheter angiograms were rated to determine carotid anatomy. Baseline patient demographics and the influence of plaque length, plaque morphology, internal carotid angulation, and external or common carotid atheroma were examined in negative binomial regression models. Results A total of 115 patients (70% male, average age 70.4) were included; 50.4% had at least one new DWI-MRI-positive lesion following CAS. Independent risk factors increasing the number of new lesions were a left-sided stenosis (incidence risk ratio [IRR] 1.59, 95% CI 1.04–2.44, p = .03), age (IRR 2.10 per 10-year increase in age, 95% CI 1.61–2.74, p < .01), male sex (IRR 2.83, 95% CI 1.72–4.67, p < .01), hypertension (IRR 2.04, 95% CI 1.25–3.33, p < .01) and absence of cardiac failure (IRR 6.58, 95% CI 1.23–35.07, p = .03). None of the carotid anatomical features significantly influenced the number of post-procedure lesions. Conclusion Carotid anatomy seen on pre-stenting catheter angiography did not predict of the number of ischaemic brain lesions following CAS. PMID:26481656

  5. Using Diffusion-Weighted MRI to Predict Aggressive Histological Features in Papillary Thyroid Carcinoma: A Novel Tool for Pre-Operative Risk Stratification in Thyroid Cancer

    PubMed Central

    Lu, Yonggang; Moreira, Andre L.; Hatzoglou, Vaios; Stambuk, Hilda E.; Gonen, Mithat; Mazaheri, Yousef; Deasy, Joseph O.; Shaha, Ashok R.

    2015-01-01

    Background: Initial management recommendations of papillary thyroid carcinoma (PTC) are very dependent on preoperative studies designed to evaluate the presence of PTC with aggressive features. The purpose of this study was to evaluate whether diffusion-weighted magnetic resonance imaging (DW-MRI) before surgery can be used as a tool to stratify tumor aggressiveness in patients with PTC. Methods: In this prospective study, 28 patients with PTC underwent DW-MRI studies on a three Tesla MR scanner prior to thyroidectomy. Due to image quality, 21 patients were finally suitable for further analysis. Apparent diffusion coefficients (ADCs) of normal thyroid tissues and PTCs for 21 patients were calculated. Tumor aggressiveness was defined by surgical histopathology. The Mann-Whitney U test was used to compare the difference in ADCs among groups of normal thyroid tissues and PTCs with and without features of tumor aggressiveness. Receiver operating characteristic (ROC) analysis was performed to assess the discriminative specificity, sensitivity, and accuracy of and determine the cutoff value for the ADC in stratifying PTCs with tumor aggressiveness. Results: There was no significant difference in ADC values between normal thyroid tissues and PTCs. However, ADC values of PTCs with extrathyroidal extension (ETE; 1.53±0.25×10–3 mm2/s) were significantly lower than corresponding values from PTCs without ETE (2.37±0.67×10–3 mm2/s; p<0.005). ADC values identified 3 papillary carcinoma patients with extrathyroidal extension that would have otherwise been candidates for observation based on ultrasound evaluations. The cutoff value of ADC to discriminate PTCs with and without ETE was determined at 1.85×10–3 mm2/s with a sensitivity of 85%, specificity of 85%, and ROC curve area of 0.85. Conclusion: ADC value derived from DW-MRI before surgery has the potential to stratify ETE in patients with PTCs. PMID:25809949

  6. 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.

  7. Diffusion Weighted Imaging for Differentiating Benign from Malignant Orbital Tumors: Diagnostic Performance of the Apparent Diffusion Coefficient Based on Region of Interest Selection Method

    PubMed Central

    Xu, Xiao-Quan; Hu, Hao; Su, Guo-Yi; Liu, Hu; Shi, Hai-Bin

    2016-01-01

    Objective To evaluate the differences in the apparent diffusion coefficient (ADC) measurements based on three different region of interest (ROI) selection methods, and compare their diagnostic performance in differentiating benign from malignant orbital tumors. Materials and Methods Diffusion-weighted imaging data of sixty-four patients with orbital tumors (33 benign and 31 malignant) were retrospectively analyzed. Two readers independently measured the ADC values using three different ROIs selection methods including whole-tumor (WT), single-slice (SS), and reader-defined small sample (RDSS). The differences of ADC values (ADC-ROIWT, ADC-ROISS, and ADC-ROIRDSS) between benign and malignant group were compared using unpaired t test. Receiver operating characteristic curve was used to determine and compare their diagnostic ability. The ADC measurement time was compared using ANOVA analysis and the measurement reproducibility was assessed using Bland-Altman method and intra-class correlation coefficient (ICC). Results Malignant group showed significantly lower ADC-ROIWT, ADC-ROISS, and ADC-ROIRDSS than benign group (all p < 0.05). The areas under the curve showed no significant difference when using ADC-ROIWT, ADC-ROISS, and ADC-ROIRDSS as differentiating index, respectively (all p > 0.05). The ROISS and ROIRDSS required comparable measurement time (p > 0.05), while significantly shorter than ROIWT (p < 0.05). The ROISS showed the best reproducibility (mean difference ± limits of agreement between two readers were 0.022 [-0.080–0.123] × 10-3 mm2/s; ICC, 0.997) among three ROI methods. Conclusion Apparent diffusion coefficient values based on the three different ROI selection methods can help to differentiate benign from malignant orbital tumors. The results of measurement time, reproducibility and diagnostic ability suggest that the ROISS method are potentially useful for clinical practice. PMID:27587953

  8. 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.

  9. 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.

  10. Intravoxel Incoherent Motion MR Imaging in the Head and Neck: Correlation with Dynamic Contrast-Enhanced MR Imaging and Diffusion-Weighted Imaging

    PubMed Central

    Xu, Xiao Quan; Choi, Young Jun; Sung, Yu Sub; Yoon, Ra Gyoung; Jang, Seung Won; Park, Ji Eun; Heo, Young Jin; Baek, Jung Hwan

    2016-01-01

    Objective To investigate the correlation between perfusion- and diffusion-related parameters from intravoxel incoherent motion (IVIM) and those from dynamic contrast-enhanced MR imaging (DCE-MRI) and diffusion-weighted imaging in tumors and normal muscles of the head and neck. Materials and Methods We retrospectively enrolled 20 consecutive patients with head and neck tumors with MR imaging performed using a 3T MR scanner. Tissue diffusivity (D), pseudo-diffusion coefficient (D*), and perfusion fraction (f) were derived from bi-exponential fitting of IVIM data obtained with 14 different b-values in three orthogonal directions. We investigated the correlation between D, f, and D* and model-free parameters from the DCE-MRI (wash-in, Tmax, Emax, initial AUC60, whole AUC) and the apparent diffusion coefficient (ADC) value in the tumor and normal masseter muscle using a whole volume-of-interest approach. Pearson's correlation test was used for statistical analysis. Results No correlation was found between f or D* and any of the parameters from the DCE-MRI in all patients or in patients with squamous cell carcinoma (p > 0.05). The ADC was significantly correlated with D values in the tumors (p < 0.001, r = 0.980) and muscles (p = 0.013, r = 0.542), despite its significantly higher value than D. The difference between ADC and D showed significant correlation with f values in the tumors (p = 0.017, r = 0.528) and muscles (p = 0.003, r = 0.630), but no correlation with D* (p > 0.05, respectively). Conclusion Intravoxel incoherent motion shows no significant correlation with model-free perfusion parameters derived from the DCE-MRI but is feasible for the analysis of diffusivity in both tumors and normal muscles of the head and neck. PMID:27587952

  11. Intravoxel Incoherent Motion Diffusion-Weighted MRI at 3.0 T Differentiates Malignant Breast Lesions From Benign Lesions and Breast Parenchyma

    PubMed Central

    Bokacheva, Louisa; Kaplan, Jennifer B.; Giri, Dilip D.; Patil, Sujata; Gnanasigamani, Merlin; Nyman, C. Gregory; Deasy, Joseph O.; Morris, Elizabeth A.; Thakur, Sunitha B.

    2016-01-01

    Purpose To study the differentiation of malignant breast lesions from benign lesions and fibroglandular tissue (FGT) using apparent diffusion coefficient (ADC) and intravoxel incoherent motion (IVIM) parameters. Materials and Methods This retrospective study included 26 malignant and 14 benign breast lesions in 35 patients who underwent diffusion-weighted MRI at 3.0T and nine b-values (0–1000 s/mm2). ADC and IVIM parameters (perfusion fraction fp, pseudodiffusion coefficient Dp, and true diffusion coefficient Dd) were determined in lesions and FGT. For comparison, IVIM was also measured in 16 high-risk normal patients. A predictive model was constructed using linear discriminant analysis. Lesion discrimination based on ADC and IVIM parameters was assessed using receiver operating characteristic (ROC) and area under the ROC curve (AUC). Results In FGT of normal subjects, fp was 1.1 ± 1.1%. In malignant lesions, fp (6.4 ± 3.1%) was significantly higher than in benign lesions (3.1 ± 3.3%, P = 0.0025) or FGT (1.5 ± 1.2%, P < 0.001), and Dd ((1.29 ± 0.28) × 10−3 mm2/s) was lower than in benign lesions ((1.56 ± 0.28) × 10−3 mm2/s, P = 0.011) or FGT ((1.86 ± 0.34) × 10−3 mm2/s, P < 0.001). A combination of Dd and fp provided higher AUC for discrimination between malignant and benign lesions (0.84) or FGT (0.97) than ADC (0.72 and 0.86, respectively). Conclusion The IVIM parameters provide accurate identification of malignant lesions. PMID:24273096

  12. Added value of diffusion-weighted MRI in detection of cervical cancer recurrence: comparison with morphologic and dynamic contrast-enhanced MRI sequences

    PubMed Central

    Lucas, Rita; Dias, João Lopes; Cunha, Teresa Margarida

    2015-01-01

    PURPOSE We aimed to evaluate the added value of diffusion-weighted imaging (DWI) to standard magnetic resonance imaging (MRI) for detecting post-treatment cervical cancer recurrence. The detection accuracy of T2-weighted (T2W) images was compared with that of T2W MRI combined with either dynamic contrast-enhanced (DCE) MRI or DWI. METHODS Thirty-eight women with clinically suspected uterine cervical cancer recurrence more than six months after treatment completion were examined with 1.5 Tesla MRI including T2W, DCE, and DWI sequences. Disease was confirmed histologically and correlated with MRI findings. The diagnostic performance of T2W imaging and its combination with either DCE or DWI were analyzed. Sensitivity, positive predictive value, and accuracy were calculated. RESULTS Thirty-six women had histologically proven recurrence. The accuracy for recurrence detection was 80% with T2W/DCE MRI and 92.1% with T2W/DWI. The addition of DCE sequences did not significantly improve the diagnostic ability of T2W imaging, and this sequence combination misclassified two patients as falsely positive and seven as falsely negative. The T2W/DWI combination revealed a positive predictive value of 100% and only three false negatives. CONCLUSION The addition of DWI to T2W sequences considerably improved the diagnostic ability of MRI. Our results support the inclusion of DWI in the initial MRI protocol for the detection of cervical cancer recurrence, leaving DCE sequences as an option for uncertain cases. PMID:26200480

  13. Assessment of treatment response by total tumor volume and global apparent diffusion coefficient using diffusion-weighted MRI in patients with metastatic bone disease: a feasibility study.

    PubMed

    Blackledge, Matthew D; Collins, David J; Tunariu, Nina; Orton, Matthew R; Padhani, Anwar R; Leach, Martin O; Koh, Dow-Mu

    2014-01-01

    We describe our semi-automatic segmentation of whole-body diffusion-weighted MRI (WBDWI) using a Markov random field (MRF) model to derive tumor total diffusion volume (tDV) and associated global apparent diffusion coefficient (gADC); and demonstrate the feasibility of using these indices for assessing tumor burden and response to treatment in patients with bone metastases. WBDWI was performed on eleven patients diagnosed with bone metastases from breast and prostate cancers before and after anti-cancer therapies. Semi-automatic segmentation incorporating a MRF model was performed in all patients below the C4 vertebra by an experienced radiologist with over eight years of clinical experience in body DWI. Changes in tDV and gADC distributions were compared with overall response determined by all imaging, tumor markers and clinical findings at serial follow up. The segmentation technique was possible in all patients although erroneous volumes of interest were generated in one patient because of poor fat suppression in the pelvis, requiring manual correction. Responding patients showed a larger increase in gADC (median change = +0.18, range = -0.07 to +0.78 × 10(-3) mm2/s) after treatment compared to non-responding patients (median change = -0.02, range = -0.10 to +0.05 × 10(-3) mm2/s, p = 0.05, Mann-Whitney test), whereas non-responding patients showed a significantly larger increase in tDV (median change = +26%, range = +3 to +284%) compared to responding patients (median change = -50%, range = -85 to +27%, p = 0.02, Mann-Whitney test). Semi-automatic segmentation of WBDWI is feasible for metastatic bone disease in this pilot cohort of 11 patients, and could be used to quantify tumor total diffusion volume and median global ADC for assessing response to treatment. PMID:24710083

  14. Improving background suppression in diffusion-weighted imaging of the abdomen and pelvis using STIR with single-axis diffusion encoding.

    PubMed

    Kwee, Thomas C; Takahara, Taro; Niwa, Tetsu; Yamashita, Tomohiro; Van Cauteren, Marc; Nievelstein, Rutger A J; Luijten, Peter R

    2011-07-01

    Bowel contents and peripheral nerves often show high signal intensity at diffusion-weighted imaging (DWI) of the abdomen and pelvis, obscuring or mimicking pathology. This study introduced and compared short tau inversion recovery (STIR) with single-axis DWI to the usual combination of spectral fat suppression (SFS) with trace DWI in the suppression of bowel contents and peripheral nerves. Five volunteers underwent both STIR with single-axis DWI and SFS with trace DWI of the abdomen and pelvis. Images were evaluated by two observers with respect to the suppression of signal of bowel contents and peripheral nerves using four-point grading scales (4=poor suppression; 3=moderate suppression; 2=good suppression; 1=excellent suppression). Mean scores (±S.D.) regarding the suppression of bowel contents were 1.60±0.55 and 1.40±0.89 for STIR with single-axis DWI and 3.40±0.55 and 3.00±1.00 for SFS with trace DWI for observers 1 and 2, respectively. Mean scores regarding the suppression of peripheral nerves were 1.20±0.45 and 1.20±0.45 for STIR with single-axis DWI and 2.40±0.89 and 2.80±0.84 for SFS with trace DWI for observers 1 and 2, respectively. In conclusion, STIR with single-axis DWI is superior to SFS with trace DWI in the suppression of bowel signal and peripheral nerves. PMID:21546187

  15. Diagnostic performance of diffusion-weighted MRI for detection of pelvic metastatic lymph nodes in patients with cervical cancer: a systematic review and meta-analysis

    PubMed Central

    Shen, G; Zhou, H; Deng, H

    2015-01-01

    In recent years, diffusion-weighted (DW) MRI has emerged as a new technique for detecting the pelvic lymph metastases in patients with cervical cancer. The aim of this meta-analysis was to assess the diagnostic value of DW imaging (DWI) for benign/malignant discrimination of pelvic lymph nodes (LNs). Studies about DWI for the detection of metastatic LNs were searched in the PubMed, EMBASE, Web of Science, EBSCO, the Cochrane Library and three Chinese databases. Based on the extracted data, we determined pooled sensitivities, specificities and diagnostic odds ratios (DORs) across studies, calculated positive and negative likelihood ratios (LRs) and constructed summary receiver operating characteristic curves with area under the curve (AUC) and Q* obtained. We also analysed the heterogeneity between studies based on subgroup analysis, threshold effect and publication bias. In total, 15 studies involving 1021 patients met the inclusion criteria. The pooled sensitivity, specificity and DOR of DWI were 0.86 [95% confidence interval (CI), 0.84–0.89], 0.84 (95% CI, 0.83–0.86) and 47.21 (95% CI, 25.67–86.81), respectively. LR syntheses yielded overall positive LR of 6.55 (95% CI, 4.77–9.01) and negative LR of 0.17 (95% CI, 0.12–0.23). The AUC and Q* index were 0.9384 and 0.8754, respectively. The heterogeneity was relatively high between studies; however, there was no evidence for threshold effect and publication bias. DWI is beneficial in the pelvic nodal assessment in patients with cervical cancer. Large-scale, high-quality trials with standard protocols are required to evaluate its clinical value for discrimination of metastatic from non-metastatic pelvic LNs in patients with cervical cancer. Advances in knowledge include providing evidence to assess the role of DWI in nodal staging of cervical cancer. PMID:26111112

  16. Diagnostic performance of diffusion-weighted MRI for detection of pelvic metastatic lymph nodes in patients with cervical cancer: a systematic review and meta-analysis.

    PubMed

    Shen, G; Zhou, H; Jia, Z; Deng, H

    2015-08-01

    In recent years, diffusion-weighted (DW) MRI has emerged as a new technique for detecting the pelvic lymph metastases in patients with cervical cancer. The aim of this meta-analysis was to assess the diagnostic value of DW imaging (DWI) for benign/malignant discrimination of pelvic lymph nodes (LNs). Studies about DWI for the detection of metastatic LNs were searched in the PubMed, EMBASE, Web of Science, EBSCO, the Cochrane Library and three Chinese databases. Based on the extracted data, we determined pooled sensitivities, specificities and diagnostic odds ratios (DORs) across studies, calculated positive and negative likelihood ratios (LRs) and constructed summary receiver operating characteristic curves with area under the curve (AUC) and Q* obtained. We also analysed the heterogeneity between studies based on subgroup analysis, threshold effect and publication bias. In total, 15 studies involving 1021 patients met the inclusion criteria. The pooled sensitivity, specificity and DOR of DWI were 0.86 [95% confidence interval (CI), 0.84-0.89], 0.84 (95% CI, 0.83-0.86) and 47.21 (95% CI, 25.67-86.81), respectively. LR syntheses yielded overall positive LR of 6.55 (95% CI, 4.77-9.01) and negative LR of 0.17 (95% CI, 0.12-0.23). The AUC and Q* index were 0.9384 and 0.8754, respectively. The heterogeneity was relatively high between studies; however, there was no evidence for threshold effect and publication bias. DWI is beneficial in the pelvic nodal assessment in patients with cervical cancer. Large-scale, high-quality trials with standard protocols are required to evaluate its clinical value for discrimination of metastatic from non-metastatic pelvic LNs in patients with cervical cancer. Advances in knowledge include providing evidence to assess the role of DWI in nodal staging of cervical cancer. PMID:26111112

  17. 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.

  18. Apparent diffusion coefficient of breast cancer and normal fibroglandular tissue in diffusion-weighted imaging: the effects of menstrual cycle and menopausal status.

    PubMed

    Kim, Jin You; Suh, Hie Bum; Kang, Hyun Jung; Shin, Jong Ki; Choo, Ki Seok; Nam, Kyung Jin; Lee, Seok Won; Jung, Young Lae; Bae, Young Tae

    2016-05-01

    The purpose of this study was to investigate prospectively whether the apparent diffusion coefficients (ADCs) of both breast cancer and normal fibroglandular tissue vary with the menstrual cycle and menopausal status. Institutional review board approval was obtained, and informed consent was obtained from each participant. Fifty-seven women (29 premenopausal, 28 postmenopausal) with newly diagnosed breast cancer underwent diffusion-weighted imaging twice (interval 12-20 days) before surgery. Two radiologists independently measured ADC of breast cancer and normal contralateral breast tissue, and we quantified the differences according to the phases of menstrual cycle and menopausal status. With normal fibroglandular tissue, ADC was significantly lower in postmenopausal than in premenopausal women (P = 0.035). In premenopausal women, ADC did not differ significantly between proliferative and secretory phases in either breast cancer or normal fibroglandular tissue (P = 0.969 and P = 0.519, respectively). In postmenopausal women, no significant differences were found between ADCs measured at different time intervals in either breast cancer or normal fibroglandular tissue (P = 0.948 and P = 0.961, respectively). The within-subject variability of the ADC measurements was quantified using the coefficient of variation (CV) and was small: the mean CVs of tumor ADC were 2.90 % (premenopausal) and 3.43 % (postmenopausal), and those of fibroglandular tissue ADC were 4.37 % (premenopausal) and 2.55 % (postmenopausal). Both intra- and interobserver agreements were excellent for ADC measurements, with intraclass correlation coefficients in the range of 0.834-0.974. In conclusion, the measured ADCs of breast cancer and normal fibroglandular tissue were not affected significantly by menstrual cycle, and the measurements were highly reproducible both within and between observers. PMID:27091644

  19. Evaluation of Cranial and Cervical Arteries and Brain Tissue in Transient Ischemic Attack Patients with Magnetic Resonance Angiography and Diffusion-Weighted Imaging

    PubMed Central

    Li, Jian-Long; Li, Chang-Shan; Fu, Jun-Hua; Zhang, Ke; Xu, Rui; Xu, Wen-Jian

    2015-01-01

    Background Magnetic resonance angiography (MRA) and diffusion-weighted imaging (DWI) have been widely used in the prediction of ischemic stroke; however, the differences of the 2 methods in detection the artery lesion differences between transient ischemic attack (TIA) and infarction patients have been long neglected. We performed the present study to investigate the differences between vessel characteristics detected by MRA and DWI in acute stroke and TIA patients. Material/Methods We classified 110 subjects into 2 groups and all the patients underwent both MRA and DWI. The degree of stenosis of cranial and cervical arteries, the distribution of the stenosis, the development and changes of the vessels, and the DWI scanning results of the brain tissue were all analyzed. Results We detected a significant difference in the number and the degree of stenosis of cranial and cervical arteries among the 3 groups (P=0.006). Compared with health controls, patients with TIA and cerebral infraction had much more severe stenosis and occlusive arteries (P<0.05). However, no significant difference was detected between TIA and cerebral infraction patients (P=0.148). Moreover, a higher rate of unilateral vertebral artery dysplasia was found in the vertebrobasilar TIA patients. Higher lesion signals were also observed by DWI in TIA patients of internal carotid artery system (4/8, 50%). Conclusions Vessel characteristics were not significantly different between TIA and infarction patients. Unilateral vertebral artery hypoplasia was a predisposing factor for vertebrobasilar TIA and ischemic focus in DWI detection was always caused by severe artery lesions. PMID:26073092

  20. 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. PMID:27114342

  1. Differentiating Laryngeal Carcinomas from Precursor Lesions by Diffusion-Weighted Magnetic Resonance Imaging at 3.0 T: A Preliminary Study

    PubMed Central

    Shang, De-Sheng; Ruan, Ling-Xiang; Zhou, Shui-Hong; Bao, Yang-Yang; Cheng, Ke-Jia; Wang, Qin-Ying

    2013-01-01

    Background Diffusion-weighted magnetic resonance imaging (DWI) has been introduced in head and neck cancers. Due to limitations in the performance of laryngeal DWI, including the complex anatomical structure of the larynx leading to susceptibility effects, the value of DWI in differentiating benign from malignant laryngeal lesions has largely been ignored. We assessed whether a threshold for the apparent diffusion coefficient (ADC) was useful in differentiating preoperative laryngeal carcinomas from precursor lesions by turbo spin-echo (TSE) DWI and 3.0-T magnetic resonance. Methods We evaluated DWI and the ADC value in 33 pathologically proven laryngeal carcinomas and 17 precancerous lesions. Results The sensitivity, specificity, and accuracy were 81.8%, 64.7%, 76.0% by laryngostroboscopy, respectively. The sensitivity, specificity, and accuracy of conventional magnetic resonance imaging were 90.9%, 76.5%, 86.0%, respectively. Qualitative DWI analysis produced sensitivity, specificity, and accuracy values of 100.0, 88.2, and 96.0%, respectively. The ADC values were lower for patients with laryngeal carcinoma (mean 1.195±0.32×10−3 mm2/s) versus those with laryngeal precancerous lesions (mean 1.780±0.32×10−3 mm2/s; P<0.001). ROC analysis showed that the area under the curve was 0.956 and the optimum threshold for the ADC was 1.455×10−3 mm2/s, resulting in a sensitivity of 94.1%, a specificity of 90.9%, and an accuracy of 92.9%. Conclusions Despite some limitations, including the small number of laryngeal carcinomas included, DWI may detect changes in tumor size and shape before they are visible by laryngostroboscopy. The ADC values were lower for patients with laryngeal carcinoma than for those with laryngeal precancerous lesions. The proposed cutoff for the ADC may help distinguish laryngeal carcinomas from laryngeal precancerous lesions. PMID:23874693

  2. The diagnostic value of 1.5-T diffusion-weighted MR imaging in detecting 5 to 10 mm metastatic cervical lymph nodes of nasopharyngeal carcinoma

    PubMed Central

    Jin, Guan Qiao; Yang, Jun; Liu, Li Dong; Su, Dan Ke; Wang, Duo Ping; Zhao, Sheng Fa; Liao, Zhi Ling

    2016-01-01

    Abstract The aim of the study was to prospectively assess the diagnostic accuracy of 1.5 T diffusion-weighted imaging (DWI) for 5 to 10 mm metastatic cervical lymph nodes of patients with nasopharyngeal carcinoma (NPC). All patients with histopathologically confirmed NPC underwent DWI with 2 b values of 0 and 800 s/mm2 were enrolled. The shortest axial diameter and mean apparent diffusion coefficient (ADC) value were recorded when lymph nodes with a shortest axial diameter from 5 to 10 mm were measured. The correlation between the pathological diagnoses and mean ADC values in the benign and metastatic lymph nodes were compared using the Z test. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic performance of DWI. Three hundred fourteen nodes of 52 patients with NPC consisted of 46.5% (146/314) metastatic lymph nodes and 53.5% (168/314) benign lymph nodes. The mean ADC value (×10–3 mm2/s) of benign lymph nodes was (1.110 ± 0.202), which was significantly higher than that of metastatic nodes (0.878 ± 0.159) (P < 0.05). The sensitivity, specificity, positive predictive value, and negative predictive value, accuracy for differentiating metastatic from benign lymph nodes using a cutoff ADC value of 0.924 × 10–3 mm2/s was 83.56%, 82.74%, 80.79%, 85.28%, and 82.80%, respectively. The area under the ROC curve was 0.851 (95% confidence intervals: 0.807–0.889). This study demonstrated that DWI is helpful in detecting 5 to 10 mm metastatic lymph nodes of patients with NPC. PMID:27512841

  3. 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.

  4. Erosive burning of solid propellants

    NASA Technical Reports Server (NTRS)

    King, Merrill K.

    1993-01-01

    Presented here is a review of the experimental and modeling work concerning erosive burning of solid propellants (augmentation of burning rate by flow of product gases across a burning surface). A brief introduction describes the motor design problems caused by this phenomenon, particularly for low port/throat area ratio motors and nozzleless motors. Various experimental techniques for measuring crossflow sensitivity of solid propellant burning rates are described, with the conclusion that accurate simulation of the flow, including upstream flow development, in actual motors is important since the degree of erosive burning depends not only on local mean crossflow velocity and propellant nature, but also upon this upstream development. In the modeling area, a brief review of simplified models and correlating equations is presented, followed by a description of more complex numerical analysis models. Both composite and double-base propellant models are reviewed. A second generation composite model is shown to give good agreement with data obtained in a series of tests in which composite propellant composition and heterogeneity (particle size distribution) were systematically varied. Finally, the use of numerical models for the development of erosive burning correlations is described, and a brief discussion of scaling is presented.

  5. 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.

  6. 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.

  7. 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.

  8. 14 CFR 23.905 - Propellers.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... pusher propeller that are likely to accumulate and shed ice into the propeller disc during any operating condition must be suitably protected to prevent ice formation, or it must be shown that any ice shed...

  9. Solid Propellant Grain Structural Integrity Analysis

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The structural properties of solid propellant rocket grains were studied to determine the propellant resistance to stresses. Grain geometry, thermal properties, mechanical properties, and failure modes are discussed along with design criteria and recommended practices.

  10. 14 CFR 23.905 - Propellers.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... pusher propeller that are likely to accumulate and shed ice into the propeller disc during any operating condition must be suitably protected to prevent ice formation, or it must be shown that any ice shed...

  11. 14 CFR 23.905 - Propellers.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... pusher propeller that are likely to accumulate and shed ice into the propeller disc during any operating condition must be suitably protected to prevent ice formation, or it must be shown that any ice shed...

  12. 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.

  13. 78 FR 9005 - Airworthiness Directives; Dowty Propellers Propellers

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-07

    .... Discussion On August 5, 2010, we issued AD 2010-17-11, Amendment 39-16403 (75 FR 51656, August 23, 2010), for... AD Was Issued Since we issued AD 2010-17-11 (75 FR 51656, August 23, 2010), Dowty Propellers... FR 51656, August 23, 2010). This proposed AD would add an optional terminating action to...

  14. 78 FR 45052 - Airworthiness Directives; Hartzell Propeller, Inc. Propellers

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-26

    ... specified products. The NPRM published in the Federal Register on March 26, 2013 (78 FR 18255). The NPRM... considered the comment received. Hartzell Propeller, Inc. supports the NPRM (78 FR 18255, dated March 26... ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979), (3) Will...

  15. 78 FR 41283 - Airworthiness Directives; Dowty Propellers Propellers

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-10

    ... (75 FR 51656, August 23, 2010). (c) Applicability This AD applies to Dowty Propellers R408/6-123-F/17... to revise AD 2010-17-11, Amendment 39-16403 (75 FR 51656, August 23, 2010). That AD applies to the specified products. The NPRM published in the Federal Register on February 7, 2013 (78 FR 9005). That...

  16. 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.

  17. 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.

  18. Diffusion-weighted EPI- and HASTE-MRI and 18F-FDG-PET-CT early during chemoradiotherapy in advanced head and neck cancer

    PubMed Central

    Schouten, Charlotte S.; de Bree, Remco; van der Putten, Lisa; Noij, Daniel P.; Hoekstra, Otto S.; Comans, Emile F.I.; Witte, Birgit I.; Doornaert, Patricia A.; Leemans, C. René

    2014-01-01

    Main problem Diffusion-weighted MRI (DW-MRI) has potential to predict chemoradiotherapy (CRT) response in head and neck squamous cell carcinoma (HNSCC) and is generally performed using echo-planar imaging (EPI). However, EPI-DWI is susceptible to geometric distortions. Half-fourier acquisition single-shot turbo spin-echo (HASTE)-DWI may be an alternative. This prospective pilot study evaluates the potential predictive value of EPI- and HASTE-DWI and 18F-fluorodeoxyglucose PET-CT (18F-FDG-PET-CT) early during CRT for locoregional outcome in HNSCC. Methods Eight patients with advanced HNSCC (7 primary tumors and 25 nodal metastases) scheduled for CRT, underwent DW-MRI (using both EPI- and HASTE-DWI) and 18F-FDG-PET(-CT) pretreatment, early during treatment and three months after treatment. Median follow-up time was 38 months. Results No local recurrences were detected during follow-up. Median Apparent Diffusion Coefficient (ADC)EPI-values in primary tumors increased from 77×10–5 mm2/s pretreatment, to 113×10–5 mm2/s during treatment (P=0.02), whereas ADCHASTE did not increase (74 and 74 mm2/s, respectively). Two regional recurrences were diagnosed. During treatment, ADCEPI tended to be higher for patients with regional control [(117.3±12.1)×10–5 mm2/s] than for patients with a recurrence [(98.0±4.2)×10–5 mm2/s]. This difference was not seen with ADCHASTE. No correlations between ΔADCEPI and ΔSUV (Standardized Uptake Value) were found in the primary tumor or nodal metastases. Conclusions HASTE-DWI seems to be inadequate in early CRT response prediction, compared to EPI-DWI which has potential to predict locoregional outcome. EPI-DWI and 18F-FDG-PET-CT potentially provide independent information in the early response to treatment, since no correlations were found between ΔADCEPI and ΔSUV. PMID:25202659

  19. Quantitative Sodium MR Imaging at 7 T: Initial Results and Comparison with Diffusion-weighted Imaging in Patients with Breast Tumors.

    PubMed

    Zaric, Olgica; Pinker, Katja; Zbyn, Stefan; Strasser, Bernhard; Robinson, Simon; Minarikova, Lenka; Gruber, Stephan; Farr, Alex; Singer, Christian; Helbich, Thomas H; Trattnig, Siegfried; Bogner, Wolfgang

    2016-07-01

    Purpose To investigate the clinical feasibility of a quantitative sodium 23 ((23)Na) magnetic resonance (MR) imaging protocol developed for breast tumor assessment and to compare it with 7-T diffusion-weighted imaging (DWI). Materials and Methods Written informed consent in this institutional review board-approved study was obtained from eight healthy volunteers and 17 patients with 20 breast tumors (five benign, 15 malignant). To achieve the best image quality and reproducibility, the (23)Na sequence was optimized and tested on phantoms and healthy volunteers. For in vivo quantification of absolute tissue sodium concentration (TSC), an external phantom was used. Static magnetic field, or B0, and combined transmit and receive radiofrequency field, or B1, maps were acquired, and image quality, measurement reproducibility, and accuracy testing were performed. Bilateral (23)Na and DWI sequences were performed before contrast material-enhanced MR imaging in patients with breast tumors. TSC and apparent diffusion coefficient (ADC) were calculated and correlated for healthy glandular tissue and benign and malignant lesions. Results The (23)Na MR imaging protocol is feasible, with 1.5-mm in-plane resolution and 16-minute imaging time. Good image quality was achieved, with high reproducibility (mean TSC values ± standard deviation for the test, 36 mmol per kilogram of wet weight ± 2 [range, 34-37 mmol/kg]; for the retest, 37 mmol/kg ± 1 [range, 35-39 mmol/kg]; P = .610) and accuracy (r = 0.998, P < .001). TSC values in normal glandular and adipose breast tissue were 35 mmol/kg ± 3 and 18 mmol/kg ± 3, respectively. In malignant lesions (mean size, 31 mm ± 24; range, 6-92 mm), the TSC of 69 mmol/kg ± 10 was, on average, 49% higher than that in benign lesions (mean size, 14 mm ± 12; range, 6-35 mm), with a TSC of 47 mmol/kg ± 8 (P = .002). There were similar ADC differences between benign ([1.78 ± 0.23] × 10(-3) mm(2)/sec) and malignant ([1.03 ± 0.23] × 10(-3) mm

  20. Quantitative diffusion-weighted magnetic resonance imaging in the assessment of myocardial fibrosis in hypertrophic cardiomyopathy compared with T1 mapping.

    PubMed

    Wu, Lian-Ming; Chen, Bing-Hua; Yao, Qiu-Ying; Ou, Yang-Rongzheng; Wu, Rui; Jiang, Meng; Hu, Jiani; An, Dong-Aolei; Xu, Jian-Rong

    2016-08-01

    To identify myocardial fibrosis in hypertrophic cardiomyopathy (HCM) subjects using quantitative cardiac diffusion-weighted imaging (DWI) and to compare its performance with native T1 mapping and extracellular volume (ECV). Thirty-eight HCM subjects (mean age, 53 ± 9 years) and 14 normal controls (mean age, 51 ± 8 years) underwent cardiac magnetic resonance imaging (CMRI) on a 3.0T magnetic resonance (MR) machine with DWI, T1 mapping and late gadolinium enhancement (LGE) imaging as the reference standard. The mean apparent diffusion coefficient (ADC), native T1 value and ECV were determined for each subject. Overall, the HCM subjects exhibited an increased native T1 value (1241.04 ± 78.50 ms), ECV (0.31 ± 0.03) and ADC (2.36 ± 0.34 s/mm(2)) compared with the normal controls (1114.60 ± 37.99 ms, 0.24 ± 0.04, and 1.62 ± 0.38 s/mm(2), respectively) (p < 0.05). DWI differentiated healthy and fibrotic myocardia with an area under the curve (AUC) of 0.93, while the AUCs of the native T1 values (0.93), (p > 0.05) and ECV (0.94), (p > 0.05) exhibited an equal differentiation ability. Both HCM LGE+ and HCM LGE- subjects had an increased native T1 value, ECV and ADC compared to the normal controls (p < 0.05). HCM LGE+ subjects exhibited an increased ECV (0.31 ± 0.04) and ADC (2.43 ± 0.36 s/mm(2)) compared to HCM LGE- subjects (p < 0.05). HCM LGE+ and HCM LGE- subjects had similar native T1 values (1250 ± 76.36 ms vs. 1213.98 ± 92.30 ms, respectively) (p > 0.05). ADC values were linearly associated with increased ECV (R(2) = 0.36) and native T1 values (R(2) = 0.40) among all subjects. DWI is a feasible alternative to native T1 mapping and ECV for the identification of myocardial fibrosis in patients with HCM. DWI and ECV can quantitatively characterize the extent of fibrosis in HCM LGE+ and HCM LGE- patients. PMID:27198892

  1. Assessing the Early Response of Advanced Cervical Cancer to Neoadjuvant Chemotherapy Using Intravoxel Incoherent Motion Diffusion-weighted Magnetic Resonance Imaging: A Pilot Study

    PubMed Central

    Wang, Yan-Chun; Hu, Dao-Yu; Hu, Xue-Mei; Shen, Ya-Qi; Meng, Xiao-Yan; Tang, Hao; Li, Zhen

    2016-01-01

    Background: Diffusion-weighted imaging (DWI) with the intravoxel incoherent motion (IVIM) model has shown promising results for providing both diffusion and perfusion information in cervical cancer; however, its use to predict and monitor the efficacy of neoadjuvant chemotherapy (NACT) in cervical cancer is relatively rare. The study aimed to evaluate the use of DWI with IVIM and monoexponential models to predict and monitor the efficacy of NACT in cervical cancer. Methods: Forty-two patients with primary cervical cancer underwent magnetic resonance exams at 3 time points (pre-NACT, 3 weeks after the first NACT cycle, and 3 weeks after the second NACT cycle). The response to treatment was determined according to the response evaluation criteria in solid tumors 3 weeks after the second NACT treatment, and the subjects were classified as two groups: responders and nonresponders groups. The apparent diffusion coefficient (ADC), true diffusion coefficient (D), perfusion-related pseudo-diffusion coefficient (D*), and perfusion fraction (f) values were determined. The differences in IVIM-derived variables and ADC between the different groups at the different time points were calculated using an independent samples t-test. Results: The D and ADC values were all significantly higher for the responders than for the nonresponders at all 3 time points, but no significant differences were observed in the D* and f values. An analysis of the receiver operating characteristic (ROC) curves indicated that a D value threshold <0.93 × 10−3 mm2/s and an ADC threshold <1.11 × 10−3 mm2/s could differentiate responders from nonresponders at pre-NACT time point, yielding area under the curve (AUC) of which were 0.771 and 0.806, respectively. The ROC indicated that the AUCs of D and ADC at the 3 weeks after the first NACT cycle and 3 weeks after the second NACT cycle were 0.823, 0.763, and 0.787, 0.794, respectively. The AUC values of D and ADC at these 3 time points were not

  2. 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

  3. Silent cerebral infarct after cardiac catheterization as detected by diffusion weighted Magnetic Resonance Imaging: a randomized comparison of radial and femoral arterial approaches

    PubMed Central

    Hamon, Michèle; Burzotta, Francesco; Oppenheim, Catherine; Morello, Rémy; Viader, Fausto; Hamon, Martial

    2007-01-01

    Background and objective Cerebral microembolism detected by transcranial Doppler (TCD) occurs systematically during cardiac catheterization, but its clinical relevance, remains unknown. Studies suggest that asymptomatic embolic cerebral infarction detectable by diffusion-weighted (DW) MRI might exist after percutaneous cardiac interventions with a frequency as high as 15 to 22% of cases. We have set up, for the first time, a prospective multicenter trial to assess the rate of silent cerebral infarction after cardiac catheterization and to compare the impact of the arterial access site, comparing radial and femoral access, on this phenomenon. Study design This prospective study will be performed in patients with severe aortic valve stenosis. To assess the occurrence of cerebral infarction, all patients will undergo cerebral DW-MRI and neurological assessment within 24 hours before, and 48 hours after cardiac catheterization and retrograde catheterization of the aortic valve. Randomization for the access site will be performed before coronary angiography. A subgroup will be monitored by transcranial power M-mode Doppler during cardiac catheterization to observe cerebral blood flow and track emboli. Neuropsychological tests will also be recorded in a subgroup of patients before and after the interventional procedures to assess the impact of silent brain injury on potential cognitive decline. The primary end-point of the study is a direct comparison of ischemic cerebral lesions as detected by serial cerebral DW-MRI between patients explored by radial access and patients explored by femoral access. Secondary end-points include comparison of neuropsychological test performance and number of microembolism signals observed in the two groups. Implications Using serial DW-MRI, silent cerebral infarction rate will be defined and the potential influence of vascular access site will be evaluated. Silent cerebral infarction might be a major concern during cardiac catheterization

  4. Diagnostic Utility of Diffusion-weighted Magnetic Resonance Imaging in Differentiating Small Solid Renal Tumors (≤4 cm) at 3.0T Magnetic Resonance Imaging

    PubMed Central

    Zhang, Han-Mei; Wu, Ying-Hua; Gan, Qi; Lyu, Xiao; Zhu, Xiang-Lan; Kuang, Min; Liu, Rong-Bo; Huang, Zi-Xing; Yuan, Fang; Liu, Xi-Jiao; Song, Bin

    2015-01-01

    Background: The aim of this study was to assess the performance of apparent diffusion coefficient (ADC) measurement obtained with diffusion-weighted magnetic resonance imaging (DW-MRI) to distinguish renal cell carcinomas (RCCs) from small benign solid renal tumors (≤4 cm). Methods: In this cross-sectional study, 49 consecutive patients with histopathologically confirmed small solid renal tumors, and seven healthy volunteers were imaged using nonenhanced MRI and DW-MRI. The ADC map was calculated using the b values of 0, 50, 400, and 600 s/mm2 and values compared via the Kruskal–Wallis and Mann–Whitney tests. The utility of ADC for differentiating RCCs and benign lesions was assessed using a receiver operating characteristic curve. Multiple nonenhanced MRI features were analyzed by Logistic regression. Results: The tumors consisted of 33 cases of clear-cell RCCs (ccRCCs) and 16 cases of benign tumors, including 14 cases of minimal fat angiomyolipomas and 2 cases of oncocytomas. The ADCs showed significant differences among benign tumors ([0.90 ± 0.52] × 10−3 mm2/s), ccRCCs ([1.53 ± 0.31] × 10−3 mm2/s) and the normal renal parenchyma ([2.22 ± 0.12] × 10−3 mm2/s) (P < 0.001). Moreover, there was statistically significant difference between high and low-grade ccRCCs (P = 0.004). Using a cut-off ADC of 1.36 × 10−3 mm2/s, DW-MRI resulted in an area under the curve (AUC), sensitivity, and specificity equal to 0.839, 75.8%, and 87.5%, respectively. Nonenhanced MRI alone and the combination of imaging methods led to an AUC, sensitivity and specificity equal to 0.919, 93.9%, and 81.2%, 0.998, 97%, and 100%, respectively. The Logistic regression showed that the location of the center of the tumor (inside the contour of the kidney) and appearance of stiff blood vessel were significantly helpful for diagnosing ccRCCs. Conclusions: DW-MRI has potential in distinguishing ccRCCs from benign lesions in human small solid renal tumors (≤4 cm), and in

  5. Potential of Diffusion-Weighted Imaging in the Characterization of Malignant, Benign, and Healthy Breast Tissues and Molecular Subtypes of Breast Cancer

    PubMed Central

    Sharma, Uma; Sah, Rani G.; Agarwal, Khushbu; Parshad, Rajinder; Seenu, Vurthaluru; Mathur, Sandeep R.; Hari, Smriti; Jagannathan, Naranamangalam R.

    2016-01-01

    The role of apparent diffusion coefficient (ADC) in the diagnosis of breast cancer and its association with molecular biomarkers was investigated in 259 patients with breast cancer, 67 with benign pathology, and 54 healthy volunteers using diffusion-weighted imaging (DWI) at 1.5 T. In 59 breast cancer patients, dynamic contrast-enhanced MRI (DCEMRI) was also acquired. Mean ADC of malignant lesions was significantly lower (1.02 ± 0.17 × 10−3 mm2/s) compared to benign (1.57 ± 0.26 × 10−3 mm2/s) and healthy (1.78 ± 0.13 × 10−3 mm2/s) breast tissues. A cutoff ADC value of 1.23 × 10−3 mm2/s (sensitivity 92.5%; specificity 91.1%; area under the curve 0.96) to differentiate malignant from benign diseases was arrived by receiver operating curve analysis. In 10/59 breast cancer patients, indeterminate DCE curve was seen, while their ADC value was indicative of malignancy, implying the potential of the addition of DWI in increasing the specificity of DCEMRI data. Further, the association of ADC with tumor volume, stage, hormonal receptors [estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor (HER2)], and menopausal status was investigated. A significant difference was seen in tumor volume between breast cancer patients of stages IIA and IIIA, IIB and IIIA, and IIB and III (B + C), respectively (P < 0.05). Patients with early breast cancer (n = 52) had significantly lower ADC and tumor volume than those with locally advanced breast cancer (n = 207). No association was found in ADC and tumor volume with the menopausal status. Breast cancers with ER−, PR−, and triple-negative (TN) status showed a significantly larger tumor volume compared to ER+, PR+, and non-triple-negative (nTN) cancers, respectively. Also, TN tumors showed a significantly higher ADC compared to ER+, PR+, and nTN cancers. Patients with ER− and TN cancers were younger than those with ER+ and nTN cancers

  6. Preoperative Diagnostic Strategy for Parotid Gland Tumors Using Diffusion-Weighted MRI and Technetium-99m Pertechnetate Scintigraphy: A Prospective Study

    PubMed Central

    Kikuchi, Masahiro; Koyasu, Sho; Shinohara, Shogo; Imai, Yukihiro; Hino, Megumu; Naito, Yasushi

    2016-01-01

    Objective Fine needle aspiration cytology (FNAC) for diagnosis of a parotid gland tumor is widely used but its sensitivity is low and non-diagnostic rate is relatively high. In contrast, core needle biopsy (CNB) has a higher sensitivity and lower rate of sampling errors but has a higher risk of injury to adjacent organs such as facial nerve than FNAC. Screening of patients with parotid gland tumors to identify cases of pleomorphic adenoma (PA) and Warthin tumor (WT) may allow CNB to be confined to patients without PA and WT. We established an algorithm for preoperative diagnosis and management of parotid gland tumor using diffusion-weighted MRI and 99mTc pertechnetate scintigraphy. This algorithm was developed with the goal of maximal reduction of the number of patients in whom CNB is required. The purpose of the study is to validate our algorithm prospectively. Methods A prospective study was conducted in 71 cases who were newly diagnosed with parotid gland tumor and 53 cases were enrolled in the study. In the algorithm, PA (high apparent diffusion coefficient (ADC) mean≥1.5×10−3 mm2/s) and non-PA (low ADCmean<1.5×10−3 mm2/s) cases are first distinguished based on the ADCmean on diffusion-weighed MRI. Second, among suspected non-PA cases, WT and non-WT are distinguished using technetium-99m pertechnetate scintigraphy. CNB is then performed only in probable non-PA and non-WT cases. Results Although CNB was only required in 40% (21/53) of all cases, we made a preoperative histopathological diagnosis with an accuracy of 87% (46/53) and we correctly diagnosed whether a tumor was benign or malignant with an accuracy of 96% (51/53). Preoperative surgical planning had to be changed during surgery in only one case (2%) Conclusions Our algorithm is valuable in terms of clinical practice with highly potential for preoperative diagnosis and with less risk of CNB procedure. PMID:26849569

  7. Value of the Diffusion-Weighted MRI in the Differential Diagnostics of Malignant and Benign Kidney Neoplasms – Our Clinical Experience

    PubMed Central

    Mytsyk, Yulian; Borys, Yuriy; Komnatska, Iryna; Dutka, Ihor; Shatynska-Mytsyk, Iryna

    2014-01-01

    Summary Background Diffusion-weighted imaging (DWI) is an MRI modality using strong bipolar gradients to create a sensitivity of the signal to the thermally-induced Brownian motions of water molecules and in vivo measurement of molecular diffusion. The apparent diffusion coefficient (ADC) is a quantitative parameter calculated from DWI images which is used as a measure of diffusion. DWI allows to obtain comprehensive information on morphological and functional state of the kidney during a single examination without contrast medium administration. The purpose of the study was to evaluate the value of DWI in differentiating benign and malignant solid kidney tumors based on the initial stage of the study. Material/Methods The study included 19 adult patients with pathologically verified renal tumors: 9 patients with clear cell subtype of the renal cell carcinoma, 5 patients with oncocytoma and 5 patients with angiomyolipoma (AML). In addition, 5 healthy volunteers with completely normal findings according to kidney ultrasound were included into this study and set as reference. All patients underwent renal MR imaging which included DWI with subsequent ADC measurement. MR imaging was performed with a 1.5 T body scanner using an eight-channel phased-array body coil. Results The mean ADC value of ccRCC was significantly lower than that of normal renal parenchyma (2.11±0.25×10−3 mm2/s vs. 3.36±0.41×10−3 mm2/s, p<0.01). There was a significant difference in ADC between the malignant and benign renal lesions: in patients with angiomyolipoma the ADC value was 2.36±0.32×10−3 mm2/s vs. 2.11±0.25×10−3 mm2/s; p<0.05 and in patients with oncocytoma – 2.75±0.27×10−3 mm2/s vs. 2.11±0.25×10−3 mm2/s; p<0.05. The difference in ADC values in patients with high and low ccRCC grades was observed. Conclusions DWI can be used to characterize renal lesions; the ADC of a renal lesion can be potentially used as an additional parameter to help determine the appropriate

  8. Characteristics of liver on magnetic resonance diffusion-weighted imaging: Dynamic and image pathological investigation in rabbit liver VX-2 tumor model

    PubMed Central

    Yuan, You-Hong; Xiao, En-Hua; Liu, Jian-Bin; He, Zhong; Jin, Ke; Ma, Cong; Xiang, Jun; Xiao, Jian-Hua; Chen, Wei-Jian

    2008-01-01

    AIM: To investigate dynamical and image pathological characteristics of the liver on magnetic resonance (MR) diffusion-weighted imaging (DWI) in the rabbit VX-2 tumor model. METHODS: Forty New Zealand rabbits were included in the study and VX-2 tumor piece was implanted intrahepatically. Fifteen animals received two intrahepatic implantations while 25 had one intrahepatical implantation. DWI, T1- and T2-weighted of magnetic resonance imaging (MRI) were carried out on the 7th and the 14th d after implantation and DWI was conducted, respectively on the 21th d. Ten VX-2 tumor samples were studied pathologically. RESULTS: The rate of lump detected by DWI, T1WI and T2WI was 78.7%, 10.7% and 53.5% (χ2 = 32.61, P < 0.001) on the 7th d after implantation and 95.8%, 54.3% and 82.9% (χ2 = 21.50, P < 0.001) on the 14th d. The signal of most VX-2 tumors on DWI was uniform and it was equal on the map of apparent diffusion coefficient (ADC). The signal of VX tumors did not decrease on the 7th d after implantation, most of them slowly growing during the week following implantation without significant cell dying within the tumor. VX-2 tumors grew increasingly within 14 d after implantation but the signal of most VX-2 tumors on DWI or on the map of ADC was uniform or uneven and ADC of VX tumors decreased obscurely or slightly because tumor necrosis was still not obvious. On the 21th d after implantation, the signal of most VX-2 tumors on DWI or on the map of ADC was uneven because tumor necrosis was evident and ADC of VX-2 tumor necrotic areas decreased. The areas of viable cells in VX-2 tumors manifested a high signal on DWI and a low signal on the map of ADC. The areas of dead cells or necrosis in VX-2 tumors manifested low signals on DWI and low, equal or high signals on the map of ADC but they manifested high signals on DWI and on the map of ADC at the same time when the areas of necrotic tumor became liquefied or cystic. The border of tumors on DWI appeared gradually

  9. 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

  10. Volume of Bone Metastasis Assessed with Whole-Body Diffusion-weighted Imaging Is Associated with Overall Survival in Metastatic Castration-resistant Prostate Cancer.

    PubMed

    Perez-Lopez, Raquel; Lorente, David; Blackledge, Matthew D; Collins, David J; Mateo, Joaquin; Bianchini, Diletta; Omlin, Aurelius; Zivi, Andrea; Leach, Martin O; de Bono, Johann S; Koh, Dow-Mu; Tunariu, Nina

    2016-07-01

    Purpose To determine the correlation between the volume of bone metastasis as assessed with diffusion-weighted (DW) imaging and established prognostic factors in metastatic castration-resistant prostate cancer (mCRPC) and the association with overall survival (OS). Materials and Methods This retrospective study was approved by the institutional review board; informed consent was obtained from all patients. The authors analyzed whole-body DW images obtained between June 2010 and February 2013 in 53 patients with mCRPC at the time of starting a new line of anticancer therapy. Bone metastases were identified and delineated on whole-body DW images in 43 eligible patients. Total tumor diffusion volume (tDV) was correlated with the bone scan index (BSI) and other prognostic factors by using the Pearson correlation coefficient (r). Survival analysis was performed with Kaplan-Meier analysis and Cox regression. Results The median tDV was 503.1 mL (range, 5.6-2242 mL), and the median OS was 12.9 months (95% confidence interval [CI]: 8.7, 16.1 months). There was a significant correlation between tDV and established prognostic factors, including hemoglobin level (r = -0.521, P < .001), prostate-specific antigen level (r = 0.556, P < .001), lactate dehydrogenase level (r = 0.534, P < .001), alkaline phosphatase level (r = 0.572, P < .001), circulating tumor cell count (r = 0.613, P = .004), and BSI (r = 0.565, P = .001). A higher tDV also showed a significant association with poorer OS (hazard ratio, 1.74; 95% CI: 1.02, 2.96; P = .035). Conclusion Metastatic bone disease from mCRPC can be evaluated and quantified with whole-body DW imaging. Whole-body DW imaging-generated tDV showed correlation with established prognostic biomarkers and is associated with OS in mCRPC. (©) RSNA, 2016 Online supplemental material is available for this article. PMID:26807894

  11. Potential of Diffusion-Weighted Imaging in the Characterization of Malignant, Benign, and Healthy Breast Tissues and Molecular Subtypes of Breast Cancer.

    PubMed

    Sharma, Uma; Sah, Rani G; Agarwal, Khushbu; Parshad, Rajinder; Seenu, Vurthaluru; Mathur, Sandeep R; Hari, Smriti; Jagannathan, Naranamangalam R

    2016-01-01

    The role of apparent diffusion coefficient (ADC) in the diagnosis of breast cancer and its association with molecular biomarkers was investigated in 259 patients with breast cancer, 67 with benign pathology, and 54 healthy volunteers using diffusion-weighted imaging (DWI) at 1.5 T. In 59 breast cancer patients, dynamic contrast-enhanced MRI (DCEMRI) was also acquired. Mean ADC of malignant lesions was significantly lower (1.02 ± 0.17 × 10(-3) mm(2)/s) compared to benign (1.57 ± 0.26 × 10(-3) mm(2)/s) and healthy (1.78 ± 0.13 × 10(-3) mm(2)/s) breast tissues. A cutoff ADC value of 1.23 × 10(-3) mm(2)/s (sensitivity 92.5%; specificity 91.1%; area under the curve 0.96) to differentiate malignant from benign diseases was arrived by receiver operating curve analysis. In 10/59 breast cancer patients, indeterminate DCE curve was seen, while their ADC value was indicative of malignancy, implying the potential of the addition of DWI in increasing the specificity of DCEMRI data. Further, the association of ADC with tumor volume, stage, hormonal receptors [estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor (HER2)], and menopausal status was investigated. A significant difference was seen in tumor volume between breast cancer patients of stages IIA and IIIA, IIB and IIIA, and IIB and III (B + C), respectively (P < 0.05). Patients with early breast cancer (n = 52) had significantly lower ADC and tumor volume than those with locally advanced breast cancer (n = 207). No association was found in ADC and tumor volume with the menopausal status. Breast cancers with ER-, PR-, and triple-negative (TN) status showed a significantly larger tumor volume compared to ER+, PR+, and non-triple-negative (nTN) cancers, respectively. Also, TN tumors showed a significantly higher ADC compared to ER+, PR+, and nTN cancers. Patients with ER- and TN cancers were younger than those with ER+ and n

  12. 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

  13. Predicting Prostate Biopsy Outcomes: A Preliminary Investigation on Screening with Ultrahigh B-Value Diffusion-Weighted Imaging as an Innovative Diagnostic Biomarker

    PubMed Central

    Zhang, Kun; Shen, Yanguang; Zhang, Xu; Ma, Lu; Wang, Haiyi; An, Ningyu; Guo, Aitao; Ye, Huiyi

    2016-01-01

    Background Routine screening of prostate specific antigen (PSA) is no longer recommended because of a high rate of over-diagnosis of prostate cancer (PCa). Objective To evaluate the efficacy of diffusion-weighted magnetic resonance imaging (DW-MRI) for PCa detection, and to explore the clinical utility of ultrahigh b-value DW-MRI in predicting prostate biopsy outcomes. Methodology 73 male patients were selected for the study. They underwent 3T MRI using T2WI conventional DW-MRI with b-value 1000 s/mm2, and ultrahigh b-value DW-MRI with b-values of 2000 s/mm2 and 3000 s/mm2. Two radiologists evaluated individual prostate gland images on a 5-point rating scale using PI-RADS, for the purpose of region-specific comparisons among modalities. Sensitivity, specificity, accuracy, positive predictive value (PPV), negative predictive value (NPV) and likelihood ratios (LR) were investigated for each MRI modality. The area under the receiver operating characteristic (ROC) curve (AUC) was also calculated. Results Results showed the improved diagnostic value of ultrahigh b-value DWI-MRI for detection of PCa when compared to other b values and conventional MRI protocols. Sensitivity values for 3000 s/mm2 in both peripheral zone (PZ) and transition zone (TZ) were significantly higher than those observed with conventional DW-MRI—Specificity values for 3000 s/mm2 in the TZ were significantly higher than other b-value images, whereas specificity values using 3000 s/mm2 in the PZ were not significantly higher than 2000 s/mm2 images. PPV and NPV between 3000 s/mm2 and the other three modalities were significantly higher for both PZ and TZ images. The PLRs and NLRs of b-value 3000 s/mm2 DW-MRI in the PZ and TZ were also recorded. ROC analysis showed greater AUCs for the b value 3000 s/mm2 DWI than for the other three modalities. Conclusions DW-MRI with a b-value of 3000 s/mm2 was found to be the most accurate and reliable MRI modality for PCa tumor detection and localization

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. 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...

  13. Refueling with In-Situ Produced Propellants

    NASA Technical Reports Server (NTRS)

    Chato, David J.

    2014-01-01

    In-situ produced propellants have been identified in many architecture studies as key to implementing feasible chemical propulsion missions to destinations beyond lunar orbit. Some of the more noteworthy ones include: launching from Mars to return to Earth (either direct from the surface, or via an orbital rendezvous); using the Earth-Moon Lagrange point as a place to refuel Mars transfer stages with Lunar surface produced propellants; and using Mars Moon Phobos as a place to produce propellants for descent and ascent stages bound for the Mars surface. However successful implementation of these strategies require an ability to successfully transfer propellants from the in-situ production equipment into the propellant tankage of the rocket stage used to move to the desired location. In many circumstances the most desirable location for this transfer to occur is in the low-gravity environment of space. In support of low earth orbit propellant depot concepts, extensive studies have been conducted on transferring propellants in-space. Most of these propellant transfer techniques will be applicable to low gravity operations in other locations. Even ground-based transfer operations on the Moon, Mars, and especially Phobos could benefit from the propellant conserving techniques used for depot refueling. This paper will review the literature of in-situ propellants and refueling to: assess the performance benefits of the use in-situ propellants for mission concepts; review the parallels with propellant depot efforts; assess the progress of the techniques required; and provide recommendations for future research.

  14. 14 CFR 25.905 - Propellers.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... a type certificate. (b) Engine power and propeller shaft rotational speed may not exceed the limits for which the propeller is certificated. (c) The propeller blade pitch control system must meet...

  15. 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.

  16. 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.

  17. 14 CFR 25.905 - Propellers.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Propellers. 25.905 Section 25.905 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Powerplant General § 25.905 Propellers. (a) Each propeller must have a type certificate. (b) Engine power...

  18. 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 the components, including references...

  19. 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.

  20. 14 CFR 35.2 - Propeller configuration.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 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...

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Propeller dynamic and aeroelastic effects

    NASA Technical Reports Server (NTRS)

    Mccormick, B. W.

    1980-01-01

    Various aspects of propeller blade dynamics are considered including those factors which are exciting the blades and the dynamic response of the blades to the excitations. Methods for treating this dynamic system are described and problems are discussed which may arise with advanced turboprop designs employing thin, swept blades.

  7. 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

  8. Viscoelastic propellant effects on Space Shuttle Dynamics

    NASA Technical Reports Server (NTRS)

    Bugg, F.

    1981-01-01

    The program of solid propellant research performed in support of the space shuttle dynamics modeling effort is described. Stiffness, damping, and compressibility of the propellant and the effects of many variables on these properties are discussed. The relationship between the propellant and solid rocket booster dynamics during liftoff and boost flight conditions and the effects of booster vibration and propellant stiffness on free free solid rocket booster modes are described. Coupled modes of the shuttle system and the effect of propellant stiffness on the interfaces of the booster and the external tank are described. A finite shell model of the solid rocket booster was developed.

  9. Vehicle propulsion system with external propellant supply

    SciTech Connect

    Criswell, D.R.

    1993-07-06

    A vehicle propulsion system is described, comprising: a vehicle designed for travel along an arranged travel path in a single extended surrounding medium; propellant depositing means for distributing propellant into a propellant trail having no structural constraint in the extended medium and extending along at least part of the travel path in advance of the vehicle; and the vehicle having combustion means for immediate combustion and expansion of at least some of the propellant distributed along the path to produce thrust on the vehicle, and exhaust means for expelling burnt propellant from the vehicle.

  10. Review of composite propellant burn rate modeling

    NASA Technical Reports Server (NTRS)

    Cohen, N. S.

    1979-01-01

    Steady-state combustion modeling of composite solid propellants is discussed with emphasis on the Beckstead-Derr-Price (BDP) model. The BDP model and some revisions are considered with respect to the analysis of monomodal ammonium perchlorate/inert binder propellants: topics examined include continuity relations, surface area relations, characteristic surface dimension, flame heights, and energy balance. Application of the BDP model to more complicated propellants containing multiple active ingredients is described. These propellants include multimodal, mixed oxidizer, active binder, aluminized, catalyzed, and nitramine propellants. Example cases of modeling (with comparison to experimental data) are presented, and strengths and weaknesses of current modeling approaches are evaluated.

  11. Monitoring Early Response to Anti-Angiogenic Therapy: Diffusion-Weighted Magnetic Resonance Imaging and Volume Measurements in Colon Carcinoma Xenografts

    PubMed Central

    Schneider, Moritz Jörg; Cyran, Clemens Christian; Nikolaou, Konstantin; Hirner, Heidrun; Reiser, Maximilian F.; Dietrich, Olaf

    2014-01-01

    Objectives To evaluate the use of diffusion-weighted MRI (DW-MRI) and volume measurements for early monitoring of antiangiogenic therapy in an experimental tumor model. Materials and Methods 23 athymic nude rats, bearing human colon carcinoma xenografts (HT-29) were examined before and after 6 days of treatment with regorafenib (n = 12) or placebo (n = 11) in a clinical 3-Tesla MRI. For DW-MRI, a single-shot EPI sequence with 9 b-values (10–800 s/mm2) was used. The apparent diffusion coefficient (ADC) was calculated voxelwise and its median value over a region of interest, covering the entire tumor, was defined as the tumor ADC. Tumor volume was determined using T2-weighted images. ADC and volume changes between first and second measurement were evaluated as classifiers by a receiver-operator-characteristic (ROC) analysis individually and combined using Fisher's linear discriminant analysis (FLDA). Results All ADCs and volumes are stated as median±standard deviation. Tumor ADC increased significantly in the therapy group (0.76±0.09×10−3 mm2/s to 0.90±0.12×10−3 mm2/s; p<0.001), with significantly higher changes of tumor ADC than in the control group (0.10±0.11×10−3 mm2/s vs. 0.03±0.09×10−3 mm2/s; p = 0.027). Tumor volume increased significantly in both groups (therapy: 347.8±449.1 to 405.3±823.6 mm3; p = 0.034; control: 219.7±79.5 to 443.7±141.5 mm3; p<0.001), however, the therapy group showed significantly reduced tumor growth (33.30±47.30% vs. 96.43±31.66%; p<0.001). Area under the curve and accuracy of the ADC-based ROC analysis were 0.773 and 78.3%; and for the volume change 0.886 and 82.6%. The FLDA approach yielded an AUC of 0.985 and an accuracy of 95.7%. Conclusions Regorafenib therapy significantly increased tumor ADC after 6 days of treatment and also significantly reduced tumor growth. However, ROC analyses using each parameter individually revealed a lack of accuracy in discriminating between therapy and control

  12. 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

  13. 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.

  14. 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.

  15. Processing solid propellants for recycling

    SciTech Connect

    Whinnery, L.L.; Griffiths, S.K.; Handrock, J.L.; Lipkin, J.

    1994-05-01

    Rapid evolution in the structure of military forces worldwide is resulting in the retirement of numerous weapon systems. Many of these systems include rocket motors containing highly energetic propellants based on hazardous nitrocellulose/nitroglycerin (NC/NG) mixtures. Even as the surplus quantities of such material increases, however, current disposal methods -- principally open burning and open detonation (OB/OD) -- are coming under close scrutiny from environmental regulators. Environmentally conscious alternatives to disposal of propellant and explosives are thus receiving renewed interest. Recycle and reuse alternatives to OB/OD appear particularly attractive because some of the energetic materials in the inventories of surplus weapon systems represent potentially valuable resources to the commercial explosives and chemical industries. The ability to reclaim such resources is therefore likely to be a key requirement of any successful technology of the future in rocket motor demilitarization. This document consists of view graphs from the poster session.

  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. 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.

  18. 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.

  19. Self-propelled Leidenfrost droplets.

    PubMed

    Linke, H; Alemán, B J; Melling, L D; Taormina, M J; Francis, M J; Dow-Hygelund, C C; Narayanan, V; Taylor, R P; Stout, A

    2006-04-21

    We report that liquids perform self-propelled motion when they are placed in contact with hot surfaces with asymmetric (ratchetlike) topology. The pumping effect is observed when the liquid is in the Leidenfrost regime (the film-boiling regime), for many liquids and over a wide temperature range. We propose that liquid motion is driven by a viscous force exerted by vapor flow between the solid and the liquid. PMID:16712160

  20. Self-Propelled Leidenfrost Droplets

    NASA Astrophysics Data System (ADS)

    Linke, H.; Alemán, B. J.; Melling, L. D.; Taormina, M. J.; Francis, M. J.; Dow-Hygelund, C. C.; Narayanan, V.; Taylor, R. P.; Stout, A.

    2006-04-01

    We report that liquids perform self-propelled motion when they are placed in contact with hot surfaces with asymmetric (ratchetlike) topology. The pumping effect is observed when the liquid is in the Leidenfrost regime (the film-boiling regime), for many liquids and over a wide temperature range. We propose that liquid motion is driven by a viscous force exerted by vapor flow between the solid and the liquid.

  1. Cubanes As Solid Propellant Ingredients

    NASA Astrophysics Data System (ADS)

    Cunkle, Glen T.; Willer, Rodney L.

    1988-05-01

    Nine diesters of cubane 1,4-dicarboxylic acid were synthesized and evaluated as advanced propellant plasticizers. Three energetic cubyl ammonium salts of amino and 1,4-diamino cubane were synthesized as models for more highly substituted cubyl ammonium salt oxidizers. Methyl carbamates of amino cubanes have been successfully nitrated with 100% HNO3/(CH3C0)20. These nitrated carbamates are precursors to unsubstituted nitramino cubanes.

  2. Combustion problems of nitramine propellants

    NASA Technical Reports Server (NTRS)

    Kumar, R. N.; Strand, L. D.

    1975-01-01

    This study has, as its distinctive feature, a detailed examination of the condensed-phase processes in the combustion of nitramine propellants. As a consequence of a recently developed model for the combustion of ammonium perchlorate (AP)/composite propellants, it is hypothesized that the condensed-phase degradation of the nitramine oxidizer particles to a vaporizable state is the overall rate-limiting step. It is also assumed that the gas-phase details are secondary in importance and need be studied only to the extent of supplying the correct boundary conditions on the condensed-phase/vapor-phase heat transfer. Because of imprecise understanding of the gas-phase processes in the presence of combustion, several plausible models are considered for the gas phase. It is found that all of the gas-phase models considered lead to predictions sufficiently close to experimental trends to conclude that the precise details of gas-phase processes are not of critical importance in determining propellant combustion behavior.

  3. Acoustical analysis capability for pusher propeller installations

    NASA Astrophysics Data System (ADS)

    Weir, Donald S.; Marsan, Mehmet; Lyon, Craig

    1990-01-01

    A new capability to predict the noise from pusher propeller installations has been developed. The pylon flowfield is modeled by potential flow theory for the outer solution and boundary layer theory for the inner solution. This flowfield is added to the performance prediction for a propeller contained in the NASA Aircraft Noise Prediction Program (ANOPP). Predictions of the noise are made using Farassat's method in the ANOPP Subsonic Propeller Noise Module. Comparisons of the predictions are made with noise data from a model scale SR-2 propeller in both tractor and pusher configurations taken in the NASA Langley Research Center Quiet Flow Facility. The results show good agreement near the plane of the propeller, but the quality of the agreement decreases toward the propeller axis.

  4. Pusher propeller noise directivity and trends

    NASA Technical Reports Server (NTRS)

    Block, P. J. W.

    1986-01-01

    The effects of pylon wake interaction on far-field propeller noise are studied using a model scale SR-2 propeller in a low-speed anechoic wind tunnel. The variation in the pusher noise penalty with axial angle theta and circumferential angle phi is compared to that of the tractor noise penalty; and the former exhibits minima occurring in the propeller plane and maxima occurring toward the propeller axis. The magnitude of the pusher installation noise penalty decreased with in increase in shaft horsepower and tip Mach number. Directivity comparisons revealed that both a noise reduction and a directivity pattern change resulted when the pylon was moved farther from the propeller. Noise emerging from the wake interaction was distinguished from that of the propeller by means of a modal decomposition.

  5. Pusher propeller noise directivity and trends

    NASA Astrophysics Data System (ADS)

    Block, P. J. W.

    1986-07-01

    The effects of pylon wake interaction on far-field propeller noise are studied using a model scale SR-2 propeller in a low-speed anechoic wind tunnel. The variation in the pusher noise penalty with axial angle theta and circumferential angle phi is compared to that of the tractor noise penalty; and the former exhibits minima occurring in the propeller plane and maxima occurring toward the propeller axis. The magnitude of the pusher installation noise penalty decreased with in increase in shaft horsepower and tip Mach number. Directivity comparisons revealed that both a noise reduction and a directivity pattern change resulted when the pylon was moved farther from the propeller. Noise emerging from the wake interaction was distinguished from that of the propeller by means of a modal decomposition.

  6. 14 CFR 25.1149 - Propeller speed and pitch controls.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Propeller speed and pitch controls. 25.1149... Accessories § 25.1149 Propeller speed and pitch controls. (a) There must be a separate propeller speed and... synchronization of all propellers. (d) The propeller speed and pitch controls must be to the right of, and...

  7. 14 CFR 25.1149 - Propeller speed and pitch controls.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Propeller speed and pitch controls. 25.1149... Accessories § 25.1149 Propeller speed and pitch controls. (a) There must be a separate propeller speed and... synchronization of all propellers. (d) The propeller speed and pitch controls must be to the right of, and...

  8. 14 CFR 25.1149 - Propeller speed and pitch controls.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Propeller speed and pitch controls. 25.1149... Accessories § 25.1149 Propeller speed and pitch controls. (a) There must be a separate propeller speed and... synchronization of all propellers. (d) The propeller speed and pitch controls must be to the right of, and...

  9. 14 CFR 25.875 - Reinforcement near propellers.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Reinforcement near propellers. 25.875....875 Reinforcement near propellers. (a) Each part of the airplane near the propeller tips must be... propeller. (b) No window may be near the propeller tips unless it can withstand the most severe ice...

  10. 14 CFR 25.1149 - Propeller speed and pitch controls.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Propeller speed and pitch controls. 25.1149... Accessories § 25.1149 Propeller speed and pitch controls. (a) There must be a separate propeller speed and... synchronization of all propellers. (d) The propeller speed and pitch controls must be to the right of, and...

  11. 14 CFR 25.1149 - Propeller speed and pitch controls.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Propeller speed and pitch controls. 25.1149... Accessories § 25.1149 Propeller speed and pitch controls. (a) There must be a separate propeller speed and... synchronization of all propellers. (d) The propeller speed and pitch controls must be to the right of, and...

  12. Electrochemical corrosion studies in low conductivity propellants

    NASA Technical Reports Server (NTRS)

    Blue, G. D.; Moran, C. M.; Distefano, S.

    1986-01-01

    The Jet Propulsion Laboratory is investigating the possibility of developing advanced electrochemical techniques as accelerated compatibility tests for metal/propellant systems which overcome the problems associated with the low conductivity of the liquid propellants (e.g., hydrazines, nitrogen tetroxide). Both DC techniques and AC electrochemical impedance spectroscopy are being evaluated. Progress has been made in experiments involving stainless steel with hydrazine and nitrogen tetroxide propellants.

  13. Explosive laser light initiation of propellants

    SciTech Connect

    Piltch, M.S.

    1992-12-31

    This invention is comprised of an 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.

  14. Dependence of propeller efficiency on angle of attack of propeller blade

    NASA Technical Reports Server (NTRS)

    Borck, Hermann

    1921-01-01

    In order to determine the maximum and the most favorable pitch for a propeller, it was found desirable to investigate the dependence of propeller efficiency on the angle of attack of the propeller blade. The results of a few experiments are given to show that propeller blades conduct themselves just like airplane wings with reference to the dependence of their efficiency on their angle of attack.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. The design of propeller blade roots

    NASA Technical Reports Server (NTRS)

    Cordes, G

    1942-01-01

    Predicated on the assumption of certain normal conditions for engine and propeller, simple expressions for the static and dynamic stresses of propeller blade roots are evolved. They, in combination with the fatigue strength diagram of the employed material, afford for each engine power one certain operating point by which the state of stress serving as a basis for the design of the root is defined. Different stress cases must be analyzed, depending on the vibration tendency of engine and use of propeller. The solution affords an insight into the possible introduction of different size classes of propeller.

  3. Propeller blade stresses caused by periodic displacement of the propeller shaft

    NASA Technical Reports Server (NTRS)

    Meyer, J

    1942-01-01

    The present report deals with different vibration stresses of the propeller and their removal by an elastic coupling of propeller and engine. A method is described for protecting the propeller from unstable oscillations and herewith from the thus excited alternating gyroscopic moments. The respective vibration equations are set down and the amount of elasticity required is deduced.

  4. 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

  5. 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.

  6. 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.

  7. Low-g propellant gaging

    NASA Astrophysics Data System (ADS)

    Orton, George

    1987-09-01

    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.

  8. High burn rate solid composite propellants

    NASA Astrophysics Data System (ADS)

    Manship, Timothy D.

    High burn rate propellants help maintain high levels of thrust without requiring complex, high surface area grain geometries. Utilizing high burn rate propellants allows for simplified grain geometries that not only make production of the grains easier, but the simplified grains tend to have better mechanical strength, which is important in missiles undergoing high-g accelerations. Additionally, high burn rate propellants allow for a higher volumetric loading which reduces the overall missile's size and weight. The purpose of this study is to present methods of achieving a high burn rate propellant and to develop a composite propellant formulation that burns at 1.5 inches per second at 1000 psia. In this study, several means of achieving a high burn rate propellant were presented. In addition, several candidate approaches were evaluated using the Kepner-Tregoe method with hydroxyl terminated polybutadiene (HTPB)-based propellants using burn rate modifiers and dicyclopentadiene (DCPD)-based propellants being selected for further evaluation. Propellants with varying levels of nano-aluminum, nano-iron oxide, FeBTA, and overall solids loading were produced using the HTPB binder and evaluated in order to determine the effect the various ingredients have on the burn rate and to find a formulation that provides the burn rate desired. Experiments were conducted to compare the burn rates of propellants using the binders HTPB and DCPD. The DCPD formulation matched that of the baseline HTPB mix. Finally, GAP-plasticized DCPD gumstock dogbones were attempted to be made for mechanical evaluation. Results from the study show that nano-additives have a substantial effect on propellant burn rate with nano-iron oxide having the largest influence. Of the formulations tested, the highest burn rate was a 84% solids loading mix using nano-aluminum nano-iron oxide, and ammonium perchlorate in a 3:1(20 micron: 200 micron) ratio which achieved a burn rate of 1.2 inches per second at 1000

  9. 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.

  10. 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...

  11. Destruction of propellant magazine, November 1982

    NASA Astrophysics Data System (ADS)

    Tozer, N. H.

    1984-08-01

    Details on the destruction of a propellant magazine are given. The properties of single base propellants are discussed. Although single base propellants have been around for one hundred years, production of this type of propellant in Australia only commenced during World War 2 when appropriate plant and know how were provided under the Lend Lease Scheme. Most of the single base propellants made at Mulwala Explosives Factory have been of the IMR type i.e., single perforated tubular granules with their surface coated with DNT for use in small to medium calibre ammunition. Since production started at Mulwala Explosives Factory in 1944 some fourteen different versions of style of propellant have been manufactured. Four versions only were made up until 1957 and these were identified with an IMR type number matching the US propellants from which they were copied. New varieties introduced since 1957 have been identified with an AR aeries number commencing with AR2001 - the original Australian 7.62 mm rifle propellant.

  12. 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.

  13. Identification of propellants of small arms ammunition.

    PubMed

    Nag, N K; Sengupta, D

    1987-02-01

    Existing methods seem inadequate to identify propellants of small arms ammunition. The present article describes that viscosity may be effectively used to differentiate and identify those. The temperature dependence, intra- and inter-batch variation and storage effect of propellants were studied. PMID:3557244

  14. 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.

  15. 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....

  16. 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.

  17. Tests on air propellers in yaw

    NASA Technical Reports Server (NTRS)

    Durand, W F; Lesley, E P

    1923-01-01

    This report contains the results of tests to determine the thrust (pull) and torque characteristics of air propellers in movement relative to the air in a line oblique to the line of the shaft, and specifically when such angle of obliquity is large, as in the case of helicopter flight with the propeller serving for both sustentation and traction.

  18. Feasibility of rocket propellant production on Mars

    NASA Technical Reports Server (NTRS)

    Ash, R. L.; Dowler, W. L.; Varsi, G.

    1978-01-01

    In situ production of rocket propellant to reduce landed mass requirements for Mars return missions has been investigated. The analysis has shown that a system which utilizes atmospheric carbon dioxide and soil moisture to produce liquid methane-oxygen propellant requires a landed mass which is less than half the mass of the ascent vehicle it produces.

  19. 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).

  20. 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....

  1. 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....

  2. 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.

  3. Effects of motion and b-matrix correction for high resolution DTI with short-axis PROPELLER-EPI

    PubMed Central

    Aksoy, Murat; Skare, Stefan; Holdsworth, Samantha; Bammer, Roland

    2010-01-01

    Short-axis PROPELLER-EPI (SAP-EPI) has been proven to be very effective in providing high-resolution diffusion-weighted and diffusion tensor data. The self-navigation capabilities of SAP-EPI allow one to correct for motion, phase errors, and geometric distortion. However, in the presence of patient motion, the change in the effective diffusion-encoding direction (i.e. the b-matrix) between successive PROPELLER ‘blades’ can decrease the accuracy of the estimated diffusion tensors, which might result in erroneous reconstruction of white matter tracts in the brain. In this study, we investigate the effects of alterations in the b-matrix as a result of patient motion on the example of SAP-EPI DTI and eliminate these effects by incorporating our novel single-step non-linear diffusion tensor estimation scheme into the SAP-EPI post-processing procedure. Our simulations and in-vivo studies showed that, in the presence of patient motion, correcting the b-matrix is necessary in order to get more accurate diffusion tensor and white matter pathway reconstructions. PMID:20222149

  4. 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

  5. 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.

  6. 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.

  7. Thrust engine and propellant exhaust arrangement therefor

    SciTech Connect

    Retallick, F.D.

    1981-01-27

    A nuclear engine and nozzle arrangement are described for a nuclear rocket comprising a cluster of elongated fissile fuel bearing and high temperature capacity modules suitably supported in a pressure vessel. The modules have a plurality of coolant-propellant channels extending therethrough, a convergent - divergent nozzle structure of fixed cross-sectional dimensions secured to the end portion of each of said modules, a divergent-only unitary skirt member connected directly to the propellant exit end of said modular cluster in series with and diverging from the divergent ends of said convergent-divergent nozzle structures. The modules are formed to conduct a compressible propellant therethrough at sub-sonic velocities, said nozzle structures being formed to develop supersonic velocities of the propellant and said divergent-only skirt being formed to develop further the supersonic velocities of said propellant.

  8. 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.

  9. 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.

  10. 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.

  11. SRM propellant, friction/ESD testing

    NASA Technical Reports Server (NTRS)

    Campbell, L. A.

    1989-01-01

    Following the Pershing 2 incident in 1985 and the Peacekeeper ignition during core removal in 1987, it was found that propellant can be much more sensitive to Electrostatic Discharges (ESD) than ever before realized. As a result of the Peacekeeper motor near miss incident, a friction machine was designed and fabricated, and used to determine friction hazards during core removal. Friction testing with and electrical charge being applied across the friction plates resulted in propellant ignitions at low friction pressures and extremely low ESD levels. The objective of this test series was to determine the sensitivity of solid rocket propellant to combined friction pressure and electrostatic stimuli and to compare the sensitivity of the SRM propellant to Peacekeeper propellant. The tests are fully discussed, summarized and conclusions drawn.

  12. 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

  13. 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

  14. 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.

  15. Random sphere packing model of heterogeneous propellants

    NASA Astrophysics Data System (ADS)

    Kochevets, Sergei Victorovich

    It is well recognized that combustion of heterogeneous propellants is strongly dependent on the propellant morphology. Recent developments in computing systems make it possible to start three-dimensional modeling of heterogeneous propellant combustion. A key component of such large scale computations is a realistic model of industrial propellants which retains the true morphology---a goal never achieved before. The research presented develops the Random Sphere Packing Model of heterogeneous propellants and generates numerical samples of actual industrial propellants. This is done by developing a sphere packing algorithm which randomly packs a large number of spheres with a polydisperse size distribution within a rectangular domain. First, the packing code is developed, optimized for performance, and parallelized using the OpenMP shared memory architecture. Second, the morphology and packing fraction of two simple cases of unimodal and bimodal packs are investigated computationally and analytically. It is shown that both the Loose Random Packing and Dense Random Packing limits are not well defined and the growth rate of the spheres is identified as the key parameter controlling the efficiency of the packing. For a properly chosen growth rate, computational results are found to be in excellent agreement with experimental data. Third, two strategies are developed to define numerical samples of polydisperse heterogeneous propellants: the Deterministic Strategy and the Random Selection Strategy. Using these strategies, numerical samples of industrial propellants are generated. The packing fraction is investigated and it is shown that the experimental values of the packing fraction can be achieved computationally. It is strongly believed that this Random Sphere Packing Model of propellants is a major step forward in the realistic computational modeling of heterogeneous propellant of combustion. In addition, a method of analysis of the morphology of heterogeneous

  16. High performance storable propellant resistojet

    NASA Technical Reports Server (NTRS)

    Vaughan, C. E.

    1992-01-01

    From 1965 until 1985 resistojets were used for a limited number of space missions. Capability increased in stages from an initial application using a 90 W gN2 thruster operating at 123 sec specific impulse (Isp) to a 830 W N2H4 thruster operating at 305 sec Isp. Prior to 1985 fewer than 100 resistojets were known to have been deployed on spacecraft. Building on this base NASA embarked upon the High Performance Storable Propellant Resistojet (HPSPR) program to significantly advance the resistojet state-of-the-art. Higher performance thrusters promised to increase the market demand for resistojets and enable space missions requiring higher performance. During the program three resistojets were fabricated and tested. High temperature wire and coupon materials tests were completed. A life test was conducted on an advanced gas generator.

  17. 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.

  18. Physiological response to aerosol propellants.

    PubMed Central

    Stewart, R D; Newton, P E; Baretta, E D; Herrmann, A A; Forster, H V; Soto, R J

    1978-01-01

    Acute exposures to isobutane, propane, F-12, and F-11 in concentrations of 250, 500, or 1000 ppm for periods of 1 min to 8 hr did not produce any untoward physiological effects as determined by the methods employed which included serial EKG's and continuous monitoring of modified V5 by telemetry during exposure. Repetitive exposures to these four propellants were also without measurable untoward physiological effect with the exception of the eight male subjects repetitively exposed to 1000 ppm, F-11, who did show minor decrements in several of the cognitive tests. Of particular importance is the observation that none of the subjects showed any decrement in pulmonary function or alteration in cardiac rhythm as the result of exposure to concentrations of the gases or vapors far greater than encountered in the normal use of aerosol products in the home. PMID:214300

  19. Noise reduction for model counterrotation propeller at cruise by reducing aft-propeller diameter

    NASA Technical Reports Server (NTRS)

    Dittmar, James H.; Stang, David B.

    1987-01-01

    The forward propeller of a model counterrotation propeller was tested with its original aft propeller and with a reduced diameter aft propeller. Noise reductions with the reduced diameter aft propeller were measured at simulated cruise conditions. Reductions were as large as 7.5 dB for the aft-propeller passing tone and 15 dB in the harmonics at specific angles. The interaction tones, mostly the first, were reduced probably because the reduced-diameter aft-propeller blades no longer interacted with the forward propeller tip vortex. The total noise (sum of primary and interaction noise) at each harmonic was significantly reduced. The chief noise reduction at each harmonic came from reduced aft-propeller-alone noise, with the interaction tones contributing little to the totals at cruise. Total cruise noise reductions were as much as 3 dB at given angles for the blade passing tone and 10 dB for some of the harmonics. These reductions would measurably improve the fuselage interior noise levels and represent a definite cruise noise benefit from using a reduced diameter aft propeller.

  20. 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.