Dual gradient-echo MRI of post-contraction changes in skeletal muscle blood volume and oxygenation

✍ Scribed by Bruce M. Damon; Jennifer L. Hornberger; Megan C. Wadington; Drew A. Lansdown; Jane A. Kent-Braun

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 547 KB
• Volume: 57
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.21191

✦ Synopsis

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. Magn Reson Med 57:670–679, 2007. © 2007 Wiley‐Liss, Inc.