Project: Research project

Project Details


We propose to study in detail the technical characteristics, advantages,
and limitations of limited flip angle (LFA) magnetic resonance imaging and
apply it to the specific task of projection imaging of blood vessels.
Expected signal levels of LFA imaging will be predicted from theoretical
grounds and measured experimentally. Repetition times and flip angles will
be optimized for distinguishing prescribed pairs of materials. Algorithms
will be devised for determining images of the T1 relaxation time from
measurements acquired at several different flip angles. Contrast-to-noise
ratios (CNR) and efficiency (CNR divided by the square root of time) of LFA
imaging will be compared rigorously with conventional spin-warp methods.
Limited flip angle methods will also be applied to the different imaging of
blood vessels in projection format. The basis of the signal will be the
randomization in phase and hence reduction in signal caused by the motion
of flowing blood along a magnetic gradient. Data for a high velocity
(systolic) and low velocity (diastolic) image will be acquired in
interleaved fashion over approximately ten cardiac cycles and assigned
respectively to the phase destructive and phase coherent images. Such
assignment will be determined from an additional simultaneous measurement
of blood pressure pulses. Velocity profiles in vessels at various phases
of the cardiac cycle will be measured in dogs with Doppler ultrasound.
Such measurements will be used to optimize the MR technique. LFA MR
angiographic images of dogs will be compared with results from IV-DSA.
Effective start/end date12/1/867/31/04


  • Medicine(all)