title: Dual gradient-echo MRI of post-contraction changes in skeletal muscle blood volume and oxygenation.
abstract: Analysis of post-contraction MRI signal intensity (SI) transients may allow noninvasive studies of microvascular reactivity and blood oxygenation recovery. The purpose of this study was to determine the physiological basis for post-contraction changes in short-echo (6 ms) and long-echo (46 ms) gradient-echo (GRE) MRI signals (S(6) and S(46), respectively). Six healthy subjects were studied with the use of dual GRE MRI and near-infrared spectroscopy (NIRS). S(6), S(46), total hemoglobin concentration ([THb]), and oxyhemoglobin saturation (%HbO(2)) were measured before, during, and after 2 and 8 s dorsiflexion maximal voluntary contractions, and 5 min of proximal arterial occlusion. The changes in S(6) and [THb] after the 2-s contractions were similar to those following 8-s contractions, but changes in %HbO(2) and S(46) were greater following 8-s contractions than after the 2-s contractions. [THb] and S(6) did not change during and following 5 min of arterial occlusion, but %HbO(2) and S(46) were both significantly depressed at similar occlusion durations. Also, distance measures indicated similarity between S(6) and [THb] and between S(46) and %HbO(2). We conclude that following brief human skeletal muscle contractions, changes in S(6) primarily reflect changes in blood volume and changes in S(46) primarily reflect changes in blood oxygenation.
authors: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA. bruce.damon@vanderbilt.edu
authors: Bruce M
authors: BM
authors: Damon
authors: Jennifer L
authors: JL
authors: Hornberger
authors: Megan C
authors: MC
authors: Wadington
authors: Drew A
authors: DA
authors: Lansdown
authors: Jane A
authors: JA
authors: Kent-Braun
mesh_terms: D000704:Analysis of Variance; D001810:Blood Volume; D005260:Female; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008833:Microcirculation; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000502:physiology*; D010100:Oxygen / Q000097:blood*; D012039:Regional Blood Flow / Q000502:physiology; D019265:Spectroscopy, Near-Infrared
chemical_list: D006454:Hemoglobins; D010100:Oxygen