Simultaneous Dynamic Blood Oxygen Level-Dependent Magnetic Resonance Imaging of Foot and Calf Muscles: Aging Effects at Ischemia and Postocclusive Hyperemia in Healthy Volunteers

PURPOSE:To demonstrate the feasibility of simultaneous blood oxygen level-dependent (BOLD) magnetic resonance imaging of calf and foot muscles and investigate age-related changes of BOLD signal changes during ischemia and postocclusive hyperemia in healthy volunteers. MATERIAL AND METHODS:In this study, 15 healthy elderly volunteers (mean age69.0 ± 7.4 years) and 15 healthy young volunteers (mean age26.1 ± 3.9 years) were enrolled. In both legs, simultaneous BOLD imaging of calf and foot muscles was performed at 1.5 Tesla. Short-term ischemia and consecutive reactive hyperemia were provoked by a cuff-compression paradigm. T2*-weighted signal time courses were obtained from foot and calf muscles simultaneously. Ischemia was assessed by T2* minimum ischemic value (MIV) and the time to half ischemic minimum (THIM). Reperfusion was assessed by the time to reach T2* half hyperemia peak (THHP). Reactive hyperemia was characterized by hyperemia peak value (HPV), time to peak (TTP), and relative T2* change from end of ischemia to HPV (δS). Parameter differences were assessed using a 2-sided Student t test. RESULTS:Dynamic BOLD measurement of foot and calf muscles was techniqually feasible and successful in all volunteers.In comparison, THIM was significantly longer in elderly than in young volunteers for calf (P < 0.01) muscles (young28.9 ± 3.7 seconds; elderly57.8 ± 31.4 seconds) and foot (P = 0.01) muscles (young36.8 ± 25.5 seconds; elderly56.6 ± 31.7 seconds). MIV relative to baseline T2*-signal was significantly (P < 0.01) lower in the elderly for calf (young96.0% ± 2.6%; elderly91.3% ± 4.4%) and foot (young95.8% ± 2.5%; elderly91.1% ± 8.2%) muscles. TTP was significantly (calfP = 0.01; footP = 0.02) delayed in the elderly (elderly calf103.0 ± 92.7 seconds and foot157.1 ± 109.9 seconds vs. young calf54.8 ± 42.1 seconds and foot95.1 ± 77.6 seconds). HPV was significantly (calfP < 0.01 and footP = 0.03) higher in (young calf114.1% ± 7.2% and foot105.8% ± 3.3% vs. elderly calf104.0% ± 2.1% and foot103.9% ± 3.2% seconds) young volunteers.In a muscle-group comparison, no significant differences in THIM and MIV were observed between calf and foot.THHP was significantly (P = 0.02) longer in foot muscles (foot young32.5 ± 29.8 seconds and elderly34.1 ± 25.0 seconds vs. calf young16.8 ± 14.1 seconds and elderly23.6 ± 14.1 seconds) of both age groups. TTP was significantly (P = 0.01 and 0.02) longer in foot muscles (foot young95.1 ± 77.6 seconds and elderly157.1 ± 109.9