Repeatability of multinuclear interleaved acquisitions with nuclear Overhauser enhancement effect in dynamic...

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.

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.

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.

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.