- Poster presentation
- Open Access
ASL demonstrates higher and more homogenous calf muscle perfusion with post-occlusion hyperemia than with exercise
© Lopez et al; licensee BioMed Central Ltd. 2013
- Published: 30 January 2013
- Peripheral Arterial Disease
- Calf Muscle
- Peripheral Arterial Disease Patient
- Thigh Cuff
- Pulse Arterial Spin Label
Pulsed arterial spin labeling (PASL) is a non-contrast MRI technique capable of quantifying calf muscle perfusion with comparable accuracy to contrast enhanced-MRI perfusion in normal subjects and peripheral arterial disease (PAD) patients. Peak perfusion can be achieved with exercise or during post-occlusion hyperemia. However, exercise stress may underestimate peak perfusion because of submaximal effort and/or heterogeneous flow. We hypothesized that post-occlusion hyperemia would yield higher peak calf muscle flow compared to peak exercise calf muscle flow measured with PASL.
Twenty-five normal subjects with no PAD risk factors or exertional symptoms were enrolled. Peak calf muscle perfusion was measured in 15 volunteers at peak exercise (Ex-PASL) and in 10 volunteers during post-cuff occlusion hyperemia (Cuff-PASL). Ex-PASL volunteers performed supine plantar flexion exercise using a pedal ergometer until exhaustion. Cuff-PASL volunteers had a thigh cuff inflated to 200 mmHg for 5 minutes. At end-exercise or immediately after cuff deflation, 15 averaged PASL images were acquired using a single-shot echo-planar pulse sequence (Total scan time 62s, FOV 200x200 mm, matrix 64x64, TR 4000 ms, TE 32 ms, 10 mm thick). PASL was performed using the proximal inversion with control for off-resonance effects technique and proximal blood labeling. The QUIPSS II with thin-slice TI1 periodic saturation technique minimized errors from variable transit delay of spins from labeling region to imaging slice and contamination of perfusion signal by intravascular blood. Peak perfusion was measured by placing a region of interest in the calf muscle group with the greatest signal intensity.
Post-cuff occlusion hyperemia yields higher and more homogeneous peak calf muscle perfusion compared to peak exercise in normal volunteers. These characteristics make cuff occlusion an attractive form of stress for patients with PAD in whom peak perfusion may be underestimated due to exercise limiting symptoms. However, exercise does allow testing of specific muscle groups used in the exercise and is a more physiologic stress. Further studies are needed to compare the performance and reproducibility of the two techniques in PAD patients.
R01 HL075792, 5T32EB003841
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.