Calf Muscles Imaged at BOLD MR: Correlation with TcPo2and Flowmetry Measurements during Ischemia and Reactive Hyperemia—Initial Experience

Abstract

To prospectively compare the blood oxygen level-dependent (BOLD) magnetic resonance (MR) signal intensity of calf muscle during ischemia and reactive hyperemia with laser Doppler flowmetry (LDF) and transcutaneous oxygen pressure (TcPo2) measurements, two parameters routinely used to evaluate peripheral arterial occlusive disease. The study was institutional review board approved; all volunteers gave informed consent. Fifteen healthy volunteers (eight male, seven female; mean age, 33.0 years +/- 6.1 [standard deviation]) underwent LDF, TcPo2 measurement, and BOLD MR imaging of the calf during ischemia and reactive hyperemia. The BOLD signal intensity of the gastrocnemius muscle was measured at 1.5-T single-shot multiecho gradient-echo echo-planar imaging. Time to half ischemia minimum (THIM), time to half hyperemia peak (THHP), and time to peak (TTP) after cuff deflation were measured with each method. Correlation coefficients (CCs) for associations of BOLD response with LDF and TcPo2 time courses were calculated. Student t testing of key BOLD MR, LDF, and TcPo2 measurement parameters was performed. During ischemia, normalized LDF and TcPo2 measurements decreased similarly to BOLD MR signal intensity (CCs: 0.86 and 0.96 for associations with LDF and TcPo2 measurements, respectively). Mean THIM values were 136.0, 82.5, and 121.3 seconds for BOLD MR, LDF (P < .01), and TcPo2 (P > .05) measurements, respectively. During early reactive hyperemia, LDF and TcPo2 measurements increased rapidly to peak values, similarly to BOLD MR signal intensity (CCs: 0.81 and 0.78, respectively). Mean THHP values were 26.0, 12.5, and 44.0 seconds for BOLD MR, LDF (P < .01), and TcPo2 (P < .01) measurements, respectively. Mean TTP values were 48.7, 47.5, and 98.0 seconds for BOLD MR, LDF (P > .05), and TcPo2 (P < .01) measurements, respectively. BOLD MR imaging of calf muscles-depending on underlying key parameters-has moderate to good correlation with LDF and TcPo2 measurements during ischemia and reactive hyperemia.