Simultaneous Dynamic Blood Oxygen Level-Dependent Magnetic Resonance Imaging of Foot and Calf Muscles

Abstract

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. In this study, 15 healthy elderly volunteers (mean age: 69.0 +/- 7.4 years) and 15 healthy young volunteers (mean age: 26.1 +/- 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 (deltaS). Parameter differences were assessed using a 2-sided Student t test. 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 (young: 28.9 +/- 3.7 seconds; elderly: 57.8 +/- 31.4 seconds) and foot (P = 0.01) muscles (young: 36.8 +/- 25.5 seconds; elderly: 56.6 +/- 31.7 seconds). MIV relative to baseline T2*-signal was significantly (P < 0.01) lower in the elderly for calf (young: 96.0% +/- 2.6%; elderly: 91.3% +/- 4.4%) and foot (young: 95.8% +/- 2.5%; elderly: 91.1% +/- 8.2%) muscles. TTP was significantly (calf: P = 0.01; foot: P = 0.02) delayed in the elderly (elderly calf: 103.0 +/- 92.7 seconds and foot: 157.1 +/- 109.9 seconds vs. young calf: 54.8 +/- 42.1 seconds and foot: 95.1 +/- 77.6 seconds). HPV was significantly (calf: P < 0.01 and foot: P = 0.03) higher in (young calf: 114.1% +/- 7.2% and foot: 105.8% +/- 3.3% vs. elderly calf: 104.0% +/- 2.1% and foot: 103.9% +/- 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 young: 32.5 +/- 29.8 seconds and elderly: 34.1 +/- 25.0 seconds vs. calf young: 16.8 +/- 14.1 seconds and elderly: 23.6 +/- 14.1 seconds) of both age groups. TTP was significantly (P = 0.01 and 0.02) longer in foot muscles (foot young: 95.1 +/- 77.6 seconds and elderly: 157.1 +/- 109.9 seconds vs. calf young: 54.8 +/- 42.1 seconds and elderly: 103.0 +/- 92.7 seconds) of both age groups. HPV was lower (P < 0.01) in foot muscles of the young (calf: 114.1% +/- 7.2% vs. foot: 105.8 +/- 3.3%). Simultaneous BOLD-imaging of calf and foot muscles is feasible and reveals statistically significant age-related differences during ischemia and postocclusive hyperemia in healthy volunteers.