Hyperemic flow heterogeneity within the calf, foot, and forearm measured with continuous arterial spin labeling MRI.
Arterial spin labeling (ASL) is a noninvasive magnetic resonance imaging (MRI) technique for microvascular blood flow measurement. We used a continuous ASL scheme (CASL) to investigate the hyperemic flow difference between major muscle groups in human extremities. Twenty-four healthy subjects with no evidence of vascular disease were recruited. MRI was conducted on a 3.0 Tesla Siemens Trio whole body system with a transmit/receive knee coil. A nonmagnetic orthopedic tourniquet system was used to create a 5-min period of ischemia followed by a period of hyperemic flow (occlusion pressure = 250 mmHg). CASL imaging, lasting from 2 min before cuff inflation to 3 min after cuff deflation, was performed on the midcalf, midfoot, and midforearm in separate sessions from which blood flow was quantified with an effective temporal resolution of 16 s. When muscles in the same anatomic location were compared, hyperemic flow was found to be significantly higher in the compartments containing muscles known to have relatively higher slow-twitch type I fiber compositions, such as the soleus muscle in the calf and the extensors in the forearm. In the foot, the plantar flexors exhibited a slightly delayed hyperemic response relative to that of the dorsal compartment, but no between-group flow difference was observed. These results demonstrate that CASL is sensitive to flow heterogeneity between diverse muscle groups and that nonuniform hyperemic flow patterns following an ischemic paradigm correlate with relative fiber-type predominance.
Wu
Wen-Chau
WC
Department of Radiology, The Hospital of University of Pennsylvania, 3400 Spruce St., Philadelphia, PA 19104, USA.
Wang
Jiongjiong
J
Detre
John A
JA
Wehrli
Felix W
FW
Mohler
Emile
E
Ratcliffe
Sarah J
SJ
Floyd
Thomas F
TF
D000328:Adult; D001158:Arteries / Q000503:physiopathology; D001783:Blood Flow Velocity; D005260:Female; D005528:Foot / Q000098:blood supply*; D005542:Forearm / Q000098:blood supply*; D006801:Humans; D006940:Hyperemia / Q000473:pathology / Q000503:physiopathology*; D007866:Leg / Q000098:blood supply*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000473:pathology; D012039:Regional Blood Flow; D013113:Spin Labels; D013997:Time Factors; D014111:Tourniquets
D013113:Spin Labels