Repeatability of multinuclear interleaved acquisitions with nuclear Overhauser enhancement effect in dynamic experiments in the calf muscle at 3T
Alfredo L. Lopez Kolkovsky, Benjamin Marty, Eric Giacomini, Martin Meyerspeer, Pierre G. Carlier
Abstract
Purpose To evaluate the repeatability of multinuclear interleaved 1 H/ 31 P NMR dynamic acquisitions in skeletal muscle and the impact of nuclear Overhauser enhancement (nOe) on the 31 P results at 3T in exercise‐recovery and ischemia‐hyperemia paradigms. Methods A 1 H/ 31 P interleaved pulse sequence was used to measure every 2.5 s a perfusion‐weighted image, a map, a 31 P spectrum and 32 1 H 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 1 H excitation was appended to visit 1. Individual 1 H 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 31 P results were observed between interleaved and 31 P 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 31 P reference scan. This multiparametric approach has a multitude of applications for the study of oxygen utilization and ATP turnover in the muscle.