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Stephen C. Textor - One of the best experts on this subject based on the ideXlab platform.

  • Blood Oxygen Level Dependent (BOLD) MR Analysis of Tissue Oxygenation in Atherosclerotic Renal Artery Stenosis
    Renal Vascular Disease, 2014
    Co-Authors: Ahmed Saad, Stephen C. Textor
    Abstract:

    While atherosclerotic Renal Artery Stenosis (ARAS) is a common cause of secondary hypertension and poses a threat to kidney viability, the degree to which reduced Blood flow to cortical or medullary segments leads to a reduction in tissue Oxygenation and/or increased overall Oxygen consumption is not well understood. These studies have been limited due to the lack of an adequate method to assess tissue Oxygenation in humans. BOLD (Blood Oxygen-Level-dependent) magnetic resonance imaging detects local Levels of tissue deoxyhemoglobin without requiring contrast. The normal kidney circulation consistently develops tissue Oxygen gradients, leaving some areas within the deep sections of medulla relatively hypoxic, reflected by corresponding differences in cortical and medullary R2* values. Moderate reductions in renal Blood flow that occur with ARAS do not invariably lead to renal hypoxia, likely due to both a surplus of Oxygenated Blood and a parallel decrease in GFR and tubular reabsorption of sodium that leads to decrease in Oxygen consumption. However, at some point, vascular occlusion threatens the viability of the kidney and can lead to loss of kidney function. In this chapter we will review the implementation of BOLD MRI in the diagnosis and management of renovascular disease.

  • Blood Oxygen Level dependent bold mri analysis in atherosclerotic renal artery stenosis
    Current Opinion in Nephrology and Hypertension, 2013
    Co-Authors: Monika L Gloviczki, Ahmed Saad, Stephen C. Textor
    Abstract:

    Purpose of review Blood Oxygen Level Dependent Magnetic Resonance Imaging (BOLD MRI) is a noninvasive tehnique evaluating kidney tissue Oxygenation that requires no contrast exposure with the potential to allow functional assessment for patients with Atherosclerotic Renal Artery Stenosis (ARAS). Normal cortical-to-medulla Oxygenation gradients are preserved in many patients treated for several years with medical antihypertensive therapy without restoring renal Blood flow. The current review is of particular interest as new methods were applied to the analyses of BOLD MRI opening perspective of its wider utilization in the clinical practice.

  • human r enovascular disease estimating fractional tissue hypoxia to analyze Blood Oxygen Level
    2013
    Co-Authors: Ahmed Saad, Lilach O. Lerman, Sandra M. Herrmann, John A Crane, James F Glockner, Hannah Friedman, Behzad Ebrahimi, Stephen C. Textor
    Abstract:

    To test the hypothesis that fractional kidney hypoxia, measured by using Blood Oxygen Level–dependent (BOLD) magnetic resonance (MR) imaging, correlates with renal Blood flow (RBF), tissue perfusion, and glomerular fil-tration rate (GFR) in patients with atherosclerotic renal artery stenosis (RAS) better than regionally selected re-gion of interest–based methods.

  • Blood Oxygen Level dependent magnetic resonance imaging identifies cortical hypoxia in severe renovascular disease
    Hypertension, 2011
    Co-Authors: Monika L Gloviczki, Lilach O. Lerman, John A Crane, James F Glockner, Michael A Mckusick, Sanjay Misra, Joseph P Grande, Stephen C. Textor
    Abstract:

    Atherosclerotic renal artery stenosis has a range of manifestations depending on the severity of vascular occlusion. The aim of this study was to examine whether exceeding the limits of adaptation to reduced Blood flow ultimately leads to tissue hypoxia, as determined by Blood Oxygen Level dependent MRI. We compared 3 groups of hypertensive patients, 24 with essential hypertension, 13 with “moderate” (Doppler velocities 200–384 cm/s), and 17 with “severe” atherosclerotic renal artery stenosis (ARAS; velocities >384 cm/s and loss of functional renal tissue). Cortical and medullary Blood flows and volumes were determined by multidetector computed tomography. Poststenotic kidney size and Blood flow were reduced with ARAS, and tissue perfusion fell in the most severe lesions. Tissue medullary deoxyhemoglobin, as reflected by R2* values, was higher as compared with the cortex for all of the groups and did not differ between subjects with renal artery lesions and essential hypertension. By contrast, cortical R2* Levels were elevated for severe ARAS (21.6±9.4 per second) as compared with either essential hypertension (17.8±2.3 per second; P P

  • Blood Oxygen Level dependent magnetic resonance imaging identifies cortical hypoxia in severe renovascular disease
    Hypertension, 2011
    Co-Authors: Monika L Gloviczki, Lilach O. Lerman, John A Crane, James F Glockner, Michael A Mckusick, Sanjay Misra, Joseph P Grande, Stephen C. Textor
    Abstract:

    Atherosclerotic renal artery stenosis has a range of manifestations depending on the severity of vascular occlusion. The aim of this study was to examine whether exceeding the limits of adaptation to reduced Blood flow ultimately leads to tissue hypoxia, as determined by Blood Oxygen Level dependent MRI. We compared 3 groups of hypertensive patients, 24 with essential hypertension, 13 with "moderate" (Doppler velocities 200-384 cm/s), and 17 with "severe" atherosclerotic renal artery stenosis (ARAS; velocities >384 cm/s and loss of functional renal tissue). Cortical and medullary Blood flows and volumes were determined by multidetector computed tomography. Poststenotic kidney size and Blood flow were reduced with ARAS, and tissue perfusion fell in the most severe lesions. Tissue medullary deoxyhemoglobin, as reflected by R2* values, was higher as compared with the cortex for all of the groups and did not differ between subjects with renal artery lesions and essential hypertension. By contrast, cortical R2* Levels were elevated for severe ARAS (21.6±9.4 per second) as compared with either essential hypertension (17.8±2.3 per second; P<0.01) or moderate ARAS (15.7±2.1 per second; P<0.01). Changes in medullary R2* after furosemide administration tended to be blunted in severe ARAS as compared with unaffected (contralateral) kidneys. These results demonstrate that severe vascular occlusion overwhelms the capacity of the kidney to adapt to reduced Blood flow, manifest as overt cortical hypoxia as measured by Blood Oxygen Level-dependent MRI. The Level of cortical hypoxia is out of proportion to the medulla and may provide a marker to identify irreversible parenchymal injury.

Howard J. Halpern - One of the best experts on this subject based on the ideXlab platform.

  • quantitative tumor oxymetric images from 4d electron paramagnetic resonance imaging epri methodology and comparison with Blood Oxygen Level dependent bold mri
    Magnetic Resonance in Medicine, 2003
    Co-Authors: Martyna Elas, Benjamin B. Williams, Adrian D. Parasca, Colin Mailer, Charles A. Pelizzari, Marta A. Lewis, Jonathan N. River, Gregory S. Karczmar, Eugene D. Barth, Howard J. Halpern
    Abstract:

    This work presents a methodology for obtaining quantitative Oxygen concentration images in the tumor-bearing legs of living C3H mice. The method uses high-resolution electron paramagnetic resonance imaging (EPRI). Enabling aspects of the methodology include the use of injectable, narrow, single-line triaryl methyl spin probes and an accurate model of overmodulated spectra. Both of these increase the signal-to-noise ratio (SNR), resulting in high resolution in space (1 mm)3 and Oxygen concentrations (∼3 torr). Thresholding at 15% the maximum spectral amplitude gives leg/tumor shapes that reproduce those in photographs. The EPRI appears to give reasonable Oxygen partial pressures, showing hypoxia (∼0–6 torr, 0–103 Pa) in many of the tumor voxels. EPRI was able to detect statistically significant changes in Oxygen concentrations in the tumor with administration of carbogen, although the changes were not increased uniformly. As a demonstration of the method, EPRI was compared with nearly concurrent (same anesthesia) T/Blood Oxygen Level-dependent (BOLD) MRI. There was a good spatial correlation between EPRI and MRI. Homogeneous and heterogeneous T/BOLD MRI correlated well with the quantitative EPRI. This work demonstrates the potential for EPRI to display, at high spatial resolution, quantitative Oxygen tension changes in the physiologic response to environmental changes. Magn Reson Med 49:682–691, 2003. © 2003 Wiley-Liss, Inc.

  • Quantitative tumor oxymetric images from 4D electron paramagnetic resonance imaging (EPRI): methodology and comparison with Blood Oxygen Level-dependent (BOLD) MRI.
    Magnetic resonance in medicine, 2003
    Co-Authors: Martyna Elas, Benjamin B. Williams, Adrian D. Parasca, Colin Mailer, Charles A. Pelizzari, Marta A. Lewis, Jonathan N. River, Gregory S. Karczmar, Eugene D. Barth, Howard J. Halpern
    Abstract:

    This work presents a methodology for obtaining quantitative Oxygen concentration images in the tumor-bearing legs of living C3H mice. The method uses high-resolution electron paramagnetic resonance imaging (EPRI). Enabling aspects of the methodology include the use of injectable, narrow, single-line triaryl methyl spin probes and an accurate model of overmodulated spectra. Both of these increase the signal-to-noise ratio (SNR), resulting in high resolution in space (1 mm)(3) and Oxygen concentrations (approximately 3 torr). Thresholding at 15% the maximum spectral amplitude gives leg/tumor shapes that reproduce those in photographs. The EPRI appears to give reasonable Oxygen partial pressures, showing hypoxia (approximately 0-6 torr, 0-10(3) Pa) in many of the tumor voxels. EPRI was able to detect statistically significant changes in Oxygen concentrations in the tumor with administration of carbogen, although the changes were not increased uniformly. As a demonstration of the method, EPRI was compared with nearly concurrent (same anesthesia) T(2)*/Blood Oxygen Level-dependent (BOLD) MRI. There was a good spatial correlation between EPRI and MRI. Homogeneous and heterogeneous T(2)*/BOLD MRI correlated well with the quantitative EPRI. This work demonstrates the potential for EPRI to display, at high spatial resolution, quantitative Oxygen tension changes in the physiologic response to environmental changes.

Richard Tang - One of the best experts on this subject based on the ideXlab platform.

  • heart rate independent 3d myocardial Blood Oxygen Level dependent mri at 3 0 t with simultaneous 13n ammonia pet validation
    Radiology, 2020
    Co-Authors: Hsinjung Yang, Richard Tang, Ivan Cokic, Jane Sykes, John Butler, Heather Biernaski, Michael S Kovacs, Xiaoming Bi, Behzad Sharif, Piotr J Slomka
    Abstract:

    Three-dimensional Blood Oxygen Level−dependent cardiac MRI at 3.0 T allowed for assessment of whole-heart myocardial perfusion change between rest and stress.

  • heart rate independent 3d myocardial Blood Oxygen Level dependent mri at 3 0 t with simultaneous 13n ammonia pet validation
    Radiology, 2020
    Co-Authors: Hsinjung Yang, Richard Tang, Ivan Cokic, Jane Sykes, John Butler, Heather Biernaski, Michael S Kovacs, Behzad Sharif, Damini Dey, Piotr J Slomka
    Abstract:

    Background Despite advances, Blood Oxygen Level-dependent (BOLD) cardiac MRI for myocardial perfusion is limited by inadequate spatial coverage, imaging speed, multiple breath holds, and imaging artifacts, particularly at 3.0 T. Purpose To develop and validate a robust, contrast agent-unenhanced, free-breathing three-dimensional (3D) cardiac MRI approach for reliably examining changes in myocardial perfusion between rest and adenosine stress. Materials and Methods A heart rate-independent, free-breathing 3D T2 mapping technique at 3.0 T that can be completed within the period of adenosine stress (≤4 minutes) was developed by using computer simulations, ex vivo heart preparations, and dogs. Studies in dogs were performed with and without coronary stenosis and validated with simultaneously acquired nitrogen 13 (13N) ammonia PET perfusion in a clinical PET/MRI system. The MRI approach was also prospectively evaluated in healthy human volunteers (from January 2017 to September 2017). Myocardial BOLD responses (MBRs) between normal and ischemic myocardium were compared with mixed model analysis. Results Dogs (n = 10; weight range, 20-25 kg; mongrel dogs) and healthy human volunteers (n = 10; age range, 22-53 years; seven men) were evaluated. In healthy dogs, T2 MRI at adenosine stress was greater than at rest (mean rest vs stress, 38.7 msec ± 2.5 [standard deviation] vs 45.4 msec ± 3.3, respectively; MBR, 1.19 ± 0.08; both, P < .001). At the same conditions, mean rest versus stress PET perfusion was 1.1 mL/mg/min ± 0.11 versus 2.3 mL/mg/min ± 0.82, respectively (P < .001); myocardial perfusion reserve (MPR) was 2.4 ± 0.82 (P < .001). The BOLD response and PET MPR were positively correlated (R = 0.67; P < .001). In dogs with coronary stenosis, perfusion anomalies were detected on the basis of MBR (normal vs ischemic, 1.09 ± 0.05 vs 1.00 ± 0.04, respectively; P < .001) and MPR (normal vs ischemic, 2.7 ± 0.08 vs 1.7 ± 1.1, respectively; P < .001). Human volunteers showed increased myocardial T2 at stress (rest vs stress, 44.5 msec ± 2.6 vs 49.0 msec ± 5.5, respectively; P = .004; MBR, 1.1 msec ± 8.08). Conclusion This three-dimensional cardiac Blood Oxygen Level-dependent (BOLD) MRI approach overcame key limitations associated with conventional cardiac BOLD MRI by enabling whole-heart coverage within the standard duration of adenosine infusion, and increased the magnitude and reliability of BOLD contrast, which may be performed without requiring breath holds. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Almeida in this issue.

  • assessment of myocardial reactivity to controlled hypercapnia with free breathing t2 prepared cardiac Blood Oxygen Level dependent mr imaging
    Radiology, 2014
    Co-Authors: Hsinjung Yang, Roya Yumul, Richard Tang, Ivan Cokic, Michael Klein, Avinash Kali, Olivia Sobczyk
    Abstract:

    Free-breathing T2-prepared myocardial Blood Oxygen Level–dependent MR responses under hypercapnia of 10 mm Hg and adenosine are not different.

  • detecting myocardial ischemia at rest with cardiac phase resolved Blood Oxygen Level dependent cardiovascular magnetic resonance
    Circulation-cardiovascular Imaging, 2013
    Co-Authors: Sotirios A Tsaftaris, Richard Tang, Xiangzhi Zhou, Rohan Dharmakumar
    Abstract:

    Background— Fast noninvasive identification of ischemic territories at rest (before tissue-specific changes) and assessment of functional status can be valuable in the management of severe coronary artery disease. This study investigated the use of cardiac phase–resolved Blood Oxygen Level–dependent (CP-BOLD) cardiovascular magnetic resonance in detecting myocardial ischemia at rest secondary to severe coronary artery stenosis. Methods and Results— CP-BOLD, standard cine, and T2-weighted images were acquired in canines (n=11) at baseline and within 20 minutes of ischemia induction (severe left anterior descending stenosis) at rest. After 3 hours of ischemia, left anterior descending stenosis was removed, and T2-weighted and late-gadolinium-enhancement images were acquired. From standard cine and CP-BOLD images, end-systolic and end-diastolic myocardium was segmented. Affected and remote sections of the myocardium were identified from postreperfusion late-gadolinium-enhancement images. Systolic-to-diastolic ratio (S/D), quotient of mean end-systolic and end-diastolic signal intensities (on CP-BOLD and standard cine), was computed for affected and remote segments at baseline and ischemia. Ejection fraction and segmental wall thickening were derived from CP-BOLD images at baseline and ischemia. On CP-BOLD images, S/D was >1 (remote and affected territories) at baseline; S/D was diminished only in affected territories during ischemia, and the findings were statistically significant (ANOVA, post hoc P <0.01). The dependence of S/D on ischemia was not observed in standard cine images. Computer simulations confirmed the experimental findings. Receiver-operating characteristic analysis showed that S/D identifies affected regions with performance (area under the curve, 0.87) similar to ejection fraction (area under the curve, 0.89) and segmental wall thickening (area under the curve, 0.75). Conclusions— Preclinical studies and computer simulations showed that CP-BOLD cardiovascular magnetic resonance could be useful in detecting myocardial ischemia at rest. Patient studies are needed for clinical translation.

  • artifact reduced two dimensional cine steady state free precession for myocardial Blood Oxygen Level dependent imaging
    Journal of Magnetic Resonance Imaging, 2010
    Co-Authors: Xiangzhi Zhou, Rachel Klein, Richard Tang, Sotirios A Tsaftaris, Ying Liu, Sven Zuehlsdorff, Rohan Dharmakumar
    Abstract:

    Purpose—To minimize image artifacts in long TR cardiac phase-resolved steady state free precession (SSFP) based Blood-Oxygen-Level-dependent (BOLD) imaging. Materials and Methods—Nine healthy dogs (4 male, 5 female, 20–25kg) were studied in a clinical 1.5T MRI scanner to investigate the effect of temporal resolution, readout bandwidth, and motion compensation on long TR SSFP images. Breath-held 2D SSFP cine sequences with various temporal resolutions (10 ms – 204 ms), bandwidths (239 Hz/pixel – 930 Hz/pixel), with and without first-order motion compensation were prescribed in the basal, mid-ventricular, and apical along the short axis. Preliminary myocardial BOLD studies in dogs with controllable coronary stenosis were performed to assess the benefits of artifact-reduction strategies. Results—Shortening the readout time via increasing readout bandwidth had no observable reduction in image artifacts. However, increasing the temporal resolution in the presence of firstorder motion compensation led to significant reduction in image artifacts. Preliminary studies demonstrated that BOLD signal changes can be reliably detected throughout the cardiac cycle. Conclusion—Artifact-reduction methods employed in this study provide significant improvement in image quality compared to conventional long TR SSFP BOLD MRI. It is envisioned that the methods proposed here may enable reliable detection of myocardial Oxygenation changes throughout the cardiac cycle with long TR SSFP-based myocardial BOLD MRI.

Reed A Omary - One of the best experts on this subject based on the ideXlab platform.

  • gas challenge Blood Oxygen Level dependent gc bold mri in the rat novikoff hepatoma model
    Magnetic Resonance Imaging, 2012
    Co-Authors: Rachel Klein, Reed A Omary, Jurgen Nicolai, Guangyu Yang, Andrew C Larson
    Abstract:

    Abstract Purpose The purpose of the study was to investigate the relationship between gas challenge–Blood Oxygen Level-dependent (GC-BOLD) response angiogenesis and tumor size in rat Novikoff hepatoma model. Materials and Methods Twenty adult male Sprague–Dawley rats (weighting 301–325 g) were used for our Animal Care and Use Committee-approved experiments. N1-S1 Novikoff hepatomas were grown in 14 rats with sizes ranging from 0.42 to 2.81 cm. All experiments were performed at 3.0 T using a custom-built rodent receiver coil. A multiple gradient-echo sequence was used for R2 ⁎ measurements, first during room air (78% N 2 /20% O 2 ) breathing and then after 10 min of carbogen (95% O 2 /5% CO 2 ) breathing. After image acquisition, rats were euthanized, and the tumors were harvested for histological evaluation. Results The R2 ⁎ change between air and carbogen breathing for small hepatomas was positive; R2 ⁎ changes changed to negative values for larger hepatomas. We found a significant positive correlation between tumor R2 ⁎ change and tumor microvessel density (MVD) ( r =0.798, P =.001) and a significant inverse correlation between tumor R2 ⁎ change and tumor size ( r =−0.840, P Conclusions GC-BOLD magnetic resonance imaging measurements are well correlated to MVD Levels and tumor size in the N1-S1 Novikoff hepatoma model; GC-BOLD measurements may serve as noninvasive biomarkers for evaluating angiogenesis and disease progression and/or therapy response.

  • t2 prepared steady state free precession Blood Oxygen Level dependent mr imaging of myocardial perfusion in a dog stenosis model
    Radiology, 2005
    Co-Authors: Steven Shea, David S Fieno, Brian E Schirf, Jie Huang, Reed A Omary
    Abstract:

    PURPOSE: To assess the ability of a T2-prepared steady-state free precession Blood Oxygen Level–dependent (BOLD) magnetic resonance (MR) imaging sequence to depict changes in myocardial perfusion during stress testing in a dog stenosis model. MATERIALS AND METHODS: Study was approved by the institutional Animal Care and Use Committee. A hydraulic occluder was placed in the left circumflex coronary artery (LCX) in 10 dogs. Adenosine was administered intravenously to increase coronary Blood flow, and stenosis was achieved in the LCX with the occluder. A T2-prepared two-dimensional steady-state free precession sequence was used for BOLD imaging at a spatial resolution of 1.5 × 1.2 × 5.0 mm3, and first-pass perfusion images were acquired for visual comparison. Microspheres were injected to provide regional perfusion information. Mixed-effect regression analysis was performed to assess normalized MR signal intensity ratios and microsphere-measured perfusion differences. For the same data, 95% prediction interv...

Steven Shea - One of the best experts on this subject based on the ideXlab platform.

  • t2 prepared steady state free precession Blood Oxygen Level dependent mr imaging of myocardial perfusion in a dog stenosis model
    Radiology, 2005
    Co-Authors: Steven Shea, David S Fieno, Brian E Schirf, Jie Huang, Reed A Omary
    Abstract:

    PURPOSE: To assess the ability of a T2-prepared steady-state free precession Blood Oxygen Level–dependent (BOLD) magnetic resonance (MR) imaging sequence to depict changes in myocardial perfusion during stress testing in a dog stenosis model. MATERIALS AND METHODS: Study was approved by the institutional Animal Care and Use Committee. A hydraulic occluder was placed in the left circumflex coronary artery (LCX) in 10 dogs. Adenosine was administered intravenously to increase coronary Blood flow, and stenosis was achieved in the LCX with the occluder. A T2-prepared two-dimensional steady-state free precession sequence was used for BOLD imaging at a spatial resolution of 1.5 × 1.2 × 5.0 mm3, and first-pass perfusion images were acquired for visual comparison. Microspheres were injected to provide regional perfusion information. Mixed-effect regression analysis was performed to assess normalized MR signal intensity ratios and microsphere-measured perfusion differences. For the same data, 95% prediction interv...

  • myocardial perfusion imaging based on the Blood Oxygen Level dependent effect using t2 prepared steady state free precession magnetic resonance imaging
    Circulation, 2004
    Co-Authors: David S Fieno, Steven Shea, Kathleen R Harris, Paul J Finn
    Abstract:

    Background— The decision to perform coronary revascularization procedures may hinge on assessment of myocardial perfusion reserve. Blood Oxygen Level–dependent (BOLD) MRI is a potential method to detect the effects of regional variations in myocardial Blood flow during vasodilation. Methods and Results— We imaged dogs (n=13) on a 1.5-T whole-body MRI scanner using a new T2-prepared steady-state free-precession (SSFP) MRI pulse sequence sensitive to BOLD contrast. Images (in-plane resolution ≈1 mm2) of 5 short-axis and 2 long-axis slices of the heart were acquired during graded Levels of adenosine infusion via a surgically placed left circumflex (LCx) catheter (n=11) or via a right atrial catheter in animals with an LCx occluder (n=2). Relative myocardial perfusion was measured with the use of fluorescent microspheres. Signal intensity changes in myocardium subtended by the left anterior descending coronary artery were compared with those in the LCx region. Unprocessed T2-weighted images revealed changes i...