The overall objective of this application is to develop and validate methods for vastly undersampled radial acquisitions and constrained reconstructions for phase contrast MR angiography of the renal arteries. Coupled with novel strategies addressing respiratory motion, we aim to reduce the total scan time necessary for a high resolution mapping of 3D velocity fields, time-resolved with the cardiac cycle, and with volumetric coverage within a clinically acceptable duration. This data set will have a spatial resolution comparable or superior to single breath-hold contrast-enhanced MR angiography, the current clinical standard in MRI. In addition to information on the vessel geometry, functional parameters derived from the velocity fields, such as flow and trans-stenotic pressure gradients are available to identify hemodynamically significant stenoses. Disadvantages of current phase contrast MRA approaches include inaccuracies and artifacts from intra-voxel dephasing and extensive scan times. These issues will be overcome by the superior spatial resolution to decrease voxel size and by the combination of a 3D radial undersampling method called VIPR (Vastly undersampled Isotropic Projection Reconstruction) with a highly constrained reconstruction method called HYPR (HighlY constrained back PRojection) and motion compensation techniques to reduce scan times. We hypothesize that the availability of information on the anatomy and trans-stenotic pressure gradients could significantly improve the non-invasive assessment of patients currently identified by MRI with a moderate renal artery stenosis (50-75%). Currently, these patients undergo invasive X-ray angiography with intraarterial pressure measurements and a significant number of patients is found to not have a hemodynamically significant stenosis and does not receive surgical treatment. PC HYPR VIPR has the potential to identify these patients in a non-invasive fashion. In addition, the injection of a contrast agent is not required for PC HYPR VIPR. Therefore, patients that would currently be excluded from standard MRA exams because of the potential development of nephrogenic systemic fibrosis (NSF) could still be diagnosed with this approach. The first specific aim is to develop the techniques necessary to extend the PC VIPR method to anatomical regions where respiratory motion is present. This will include gating and motion analysis and correction techniques. Advanced processing and visualization tools will be developed to facilitate efficient data handling and diagnosis from the large data sets. The second specific aim is the development of phase sensitive HYPR processing for the processing of velocity measurements. The third specific aim is the validation of measurements of degree of stenosis, flow, and pressure gradients in the renal arteries of an animal model. In this approach, the pressure measurements are obtained from two tandem pressure-sensitive intravascular fiberoptic sensors. The fourth specific aim is the validation of PC HYPR VIPR imaging in healthy volunteers and patients with renal artery stenosis and kidney transplants. Measurements of degree of stenosis, flow, pressure gradients, and image quality will be evaluated.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
Project #
Application #
Study Section
Biomedical Imaging Technology Study Section (BMIT)
Program Officer
Evans, Frank
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Wisconsin Madison
Schools of Medicine
United States
Zip Code
Barker, Alex J; Roldán-Alzate, Alejandro; Entezari, Pegah et al. (2015) Four-dimensional flow assessment of pulmonary artery flow and wall shear stress in adult pulmonary arterial hypertension: results from two institutions. Magn Reson Med 73:1904-13
Landgraf, Benjamin R; Johnson, Kevin M; Roldán-Alzate, Alejandro et al. (2014) Effect of temporal resolution on 4D flow MRI in the portal circulation. J Magn Reson Imaging 39:819-26
Roldán-Alzate, Alejandro; Frydrychowicz, Alex; Johnson, Kevin M et al. (2014) Non-invasive assessment of cardiac function and pulmonary vascular resistance in an canine model of acute thromboembolic pulmonary hypertension using 4D flow cardiovascular magnetic resonance. J Cardiovasc Magn Reson 16:23
Frydrychowicz, Alex; Wieben, Oliver; Niespodzany, Eric et al. (2013) Quantification of thoracic blood flow using volumetric magnetic resonance imaging with radial velocity encoding: in vivo validation. Invest Radiol 48:819-25
Roldan-Alzate, Alejandro; Frydrychowicz, Alex; Niespodzany, Eric et al. (2013) In vivo validation of 4D flow MRI for assessing the hemodynamics of portal hypertension. J Magn Reson Imaging 37:1100-8
Johnson, Kevin M; Block, Walter F; Reeder, Scott B et al. (2012) Improved least squares MR image reconstruction using estimates of k-space data consistency. Magn Reson Med 67:1600-8
Nett, Elizabeth J; Johnson, Kevin M; Frydrychowicz, Alex et al. (2012) Four-dimensional phase contrast MRI with accelerated dual velocity encoding. J Magn Reson Imaging 35:1462-71
Kecskemeti, Steven; Johnson, Kevin; Wu, Yijing et al. (2012) High resolution three-dimensional cine phase contrast MRI of small intracranial aneurysms using a stack of stars k-space trajectory. J Magn Reson Imaging 35:518-27
Chang, W; Landgraf, B; Johnson, K M et al. (2011) Velocity measurements in the middle cerebral arteries of healthy volunteers using 3D radial phase-contrast HYPRFlow: comparison with transcranial Doppler sonography and 2D phase-contrast MR imaging. AJNR Am J Neuroradiol 32:54-9
Francois, Christopher J; Lum, Darren P; Johnson, Kevin M et al. (2011) Renal arteries: isotropic, high-spatial-resolution, unenhanced MR angiography with three-dimensional radial phase contrast. Radiology 258:254-60

Showing the most recent 10 out of 19 publications