N Sanchez¹*, A Moody¹, G Clarke¹, (1)University of Texas Health Science Center - San Antonio, San Antonio, TX

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  N Sanchez

MO-C930-IePD-F9-6 (Monday, 7/11/2022) 9:30 AM - 10:00 AM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 9

Purpose: To evaluate differences between exercise modalities in measurements of phosphocreatine (PCr) recovery constants of vastus lateralis (VL) using 31P-MRS to determine intrasubject reproducibility. It is hypothesized that physiological and practical differences with different exercise setups affects measurement reproducibility.

Methods: Healthy subjects were studied (2F/2M, avg. 27 y/o). 31P-MRS spectra were obtained on a Siemens 3T TIMTrio scanner using a localized STEAM sequence with TR = 1500 ms, TE = 2.3 ms, NSA = 4, voxel size = 200×200×25 mm, TA = 12’ with the VOI parasagittal along the VL. In isometric studies, subjects were placed supine and instructed to kick against straps at low and high frequencies while spectra were acquired using a TX/RX 1H/31P coil. Exercises were repeated in an isotonic system. Spectral analysis was performed using jMRUI. PCr recovery data was fit to non-linear least squares models for the recovery constant, k. NLS and Bland Altman analyses were done using R.

Results: Differences between recovery time constants for different exercise frequency groups as well as SKM contraction type are supported by precious studies. From preliminary data, we obtained large limits of agreements (LoA) of -0.053 s-1 & 0.074 s-1, bias of 0.01 s-1 using Bland Altman analysis for our comparison between contraction types. We obtained LoA of 0.050 s-1 & -0.055 s-1 and a bias of -0.002 s-1 for contraction duration. It is anticipated that there will be differences in PCr recovery rates in both comparisons with a larger sample size.

Conclusion: Differences between the two modalities can be attributed to practical issues such as positioning of the TX/RX coil, thus shimming capabilities and intrasubject variability. Differences between the frequency groups are thought to exist due to differences in intracellular pH as it has been shown that the level of acidosis differs amongst varying intensity.

Keywords

MRS

Taxonomy

IM- MRI : Spectroscopy

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