Repeatability of multinuclear interleaved acquisitions with nuclear Overhauser enhancement effect in dynamic experiments in the calf muscle at 3T

Abstract

Purpose To evaluate the repeatability of multinuclear interleaved ¹H/³¹P NMR dynamic acquisitions in skeletal muscle and the impact of nuclear Overhauser enhancement (nOe) on the ³¹P results at 3T in exercise‐recovery and ischemia‐hyperemia paradigms. Methods A ¹H/³¹P interleaved pulse sequence was used to measure every 2.5 s a perfusion‐weighted image, a map, a ³¹P spectrum and 32 ¹H spectra sensitive to deoxymyoglobin. 21 subjects performed a plantar flexion exercise and after recovery underwent an 8‐min lower leg ischemia. The procedure was repeated in visit 2 with 12 subjects. An additional exercise bout without ¹H excitation was appended to visit 1. Individual ¹H RF pulse nOe was measured at rest in every visit. Results Repeatability scores (coefficient of variation, Bland‐Altman analysis) were similar to those found in the literature using similar mono‐nuclear acquisitions. |Pi]/[PCr], pH drop, creatine rephosphorylation rate (τ_PCr), maximum perfusion, time to peak perfusion, and blood flow post‐exercise showed high reliability (intraclass correlation coefficient > 0.7), whereas hemodynamic results from reactive hyperemia showed higher repeatability. After accounting for nOe, which increased Pi and PCr signal‐to‐noise ratio by 30%, no differences in ³¹P results were observed between interleaved and ³¹P MRS‐only acquisitions. τ_PCr was unaffected by nOe. Conclusion The method shows good repeatability for both paradigms while simultaneously providing multiple dynamic data sets on a clinical scanner. The nOe effects were accounted for on a per‐subject and per‐visit basis using a short ³¹P reference scan. This multiparametric approach has a multitude of applications for the study of oxygen utilization and ATP turnover in the muscle.