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

Abstract

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 ischemiahyperemia paradigms. Methods: A 1 H/ 31 P interleaved pulse sequence was used to measure every 2.5 s a perfusion-weighted image, a T * 2 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.

Interleaved and simultaneous multi‐nuclear magnetic resonance in vivo. Review of principles, applications and potential

“…[56][57][58] While such 'interleaved' techniques are not per se the topic of this review, they can be and have been combined with multi-nuclear interleaved measurements. 32,34,55,59,60 Finally, the terms 'interleaved' and 'simultaneous' have sometimes been used in the literature to describe measurements with different nuclei that were actually performed in consecutive scans 61,62 and not even necessarily in the same scan session.…”

“…Conversely, unintended heteronuclear nOe can be generated by the application of on-resonance RF-intensive 1 H pulses, which is typically the case of magnetization-preparation modules or in sequences employing adiabatic pulses. 60,71,102 Furthermore, a larger signal enhancement will result if the complete volume of interest of the X-nucleus measurement is irradiated. 60 While nOe can increase SNR and repeatability 103 and provide biological information by itself, 104 its magnitude will depend on the experimental setting but also on the tissue type and potentially on the pathological state.…”

“…60,71,102 Furthermore, a larger signal enhancement will result if the complete volume of interest of the X-nucleus measurement is irradiated. 60 While nOe can increase SNR and repeatability 103 and provide biological information by itself, 104 its magnitude will depend on the experimental setting but also on the tissue type and potentially on the pathological state. 97 Therefore, similar nOe values between studies can be assumed only if the sequence parameters and experimental conditions are largely conserved.…”

“…Estimating nOe in preparatory measurements is recommended, 6,96 and will allow calculation of 'nOe-free' metabolite concentrations and ratios. 60…”

Motion‐corrected 23Na MRI of the human brain using interleaved 1H 3D navigator images

“…Interleaved or simultaneous dual-nuclear MR acquisitions, where data of two different nuclei are acquired within the same sequence, have been performed at different magnetic field strengths, recently even at modern 3 Tesla clinical systems without the need of hardware modification. 15,16 At 7 Tesla human scanners, however, interleaved dual-nuclear MRI has always been conducted on research systems using additional hardware modifications 17,18 or a special software interface developed by the user. 19 With the recent generation of clinically approved 7 Tesla platforms, interleaved MRI measurements have also been enabled by the manufacturer, which has been demonstrated recently with interleaved 31 P/ 1 H MR spectroscopy.…”