Determining exercise-induced blood flow reserve in lower extremities using phase contrast MRI

Area of Science:

• Cardiovascular physiology
• Medical imaging
• Vascular dynamics

Background:

• Understanding limb blood flow changes during exercise is crucial for assessing vascular health.
• Phase contrast MRI (PC-MRI) offers a non-invasive method to quantify blood flow dynamics.

Purpose of the Study:

• To investigate alterations in lower extremity blood flow during exercise using PC-MRI.
• To characterize changes in the superficial femoral artery (SFA) waveform and flow reserve.

Main Methods:

• Healthy volunteers underwent PC-MRI of the SFA during a four-minute plantar flexion exercise protocol.
• Measurements were taken at rest, immediately post-exercise, during recovery, and post-recovery.
• Cardiac-gated, cine PC-MRI sequences were employed on a 3T scanner.

Main Results:

• The resting SFA exhibited a triphasic flow waveform, which shifted to a monophasic pattern during exercise.
• Total blood flow increased during exercise, with variable changes in vessel size and velocity.
• The exercise-induced flow reserve (FR) was measured at 167 +/- 90%.

Conclusions:

• PC-MRI effectively visualizes the transformation of the SFA flow waveform from triphasic to monophasic with submaximal exercise.
• The resting waveform pattern is restored upon recovery.
• This technique enables the measurement of exercise-induced FR in the SFA, providing insights into regional blood flow regulation.