Exciting developments in doppler ultrasound have demonstrated that many vascular diseases can be distinguished by characteristic blood flow patterns. These include carotid artery disease, peripheral vascular disease, cardiac valve stenosis and regurgitation, aneurysms, A-V shunts, and portal vein abnormalities. However, many vessels of interest are not accessible to ultrasound or show poor reproducibility. Although a number of MR imaging techniques have been developed which overcome many of the limitations of ultrasound, there is at present no standard procedure for measuring flow velocities using MRl. The Pl has developed a novel MR imaging sequence that slice-selectively inverts longitudinal magnetization thereby tagging consecutive boli of material as they enter the selected slice. This technique provides a method for quantitating flow velocities that has many attractive features. The specificity and sensitivity of the bolus tagging technique and conventional MR flow quantitation techniques will be examined to determine the method most suitable for velocity quantitation. This will be accomplished by: Simulating the flow patterns and magnetization distribution for steady and pulsatile flow through regular and irregular vessels in response to velocity quantitation pulse sequences. Conducting phantom studies with accurately controlled flow phantoms to validate the conclusions of the simulation studies. Demonstrating the viability of these sequences in studies on human volunteers. 3D display strategies and thick-slab multi-slice methods will be used to derive quantitative measures of velocity for material moving through tortuous vessels. Measures of the velocity at multiple points in the pulsatile cycle where either the cycle period is not known a priori or where the flow amplitude may vary from cycle to cycle will be obtained with post-hoc rebinding methods. Methods to determine the presence of turbulent flow a to distinguish between the various contributions to intra-voxel mixing and signal loss in disturbed flow will be examined. The significance of this project is that, in clinical studies, this will provide the capability to noninvasively determine the dynamic and spatial variation of the velocity of blood flow (and thus total blood flow) through the body vessels. Those quantities could then be related to the disease state of the vessel and would aid in the diagnosis and treatment of flow-related dysfunction.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
5R29HL042506-04
Application #
3472593
Study Section
Diagnostic Radiology Study Section (RNM)
Project Start
1989-04-01
Project End
1994-03-31
Budget Start
1992-04-01
Budget End
1993-03-31
Support Year
4
Fiscal Year
1992
Total Cost
Indirect Cost
Name
University of California San Francisco
Department
Type
Schools of Medicine
DUNS #
073133571
City
San Francisco
State
CA
Country
United States
Zip Code
94143
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Franck, A; Selby, K; van Tyen, R et al. (1995) Cardiac-gated MR angiography of pulsatile flow: k-space strategies. J Magn Reson Imaging 5:297-307
Saloner, D; Selby, K; Anderson, C M (1994) MRA studies of arterial stenosis: improvements by diastolic acquisition. Magn Reson Med 31:196-203
van Tyen, R; Saloner, D; Jou, L D et al. (1994) MR imaging of flow through tortuous vessels: a numerical simulation. Magn Reson Med 31:184-95
Schaefer, S; van Tyen, R; Saloner, D (1992) Evaluation of myocardial perfusion abnormalities with gadolinium-enhanced snapshot MR imaging in humans. Work in progress. Radiology 185:795-801
Saloner, D; Anderson, C M (1992) Instrumentation for magnetic resonance angiography. Cardiovasc Intervent Radiol 15:14-22
Selby, K; Saloner, D; Anderson, C M et al. (1992) MR angiography with a cardiac-phase--specific acquisition window. J Magn Reson Imaging 2:637-43
Pan, X M; Anderson, C M; Reilly, L M et al. (1992) Magnetic resonance angiography of the carotid artery combining two- and three-dimensional acquisitions. J Vasc Surg 16:609-15;discussion 615-8
Saloner, D; Hanson, W A; Tsuruda, J S et al. (1991) Application of a connected-voxel algorithm to MR angiographic data. J Magn Reson Imaging 1:423-30
Saloner, D; Anderson, C M (1990) Flow velocity quantitation using inversion tagging. Magn Reson Med 16:269-79