Reliability of In Vivo Creatine-Weighted Chemical Exchange Saturation Transfer (CrCEST) MRI in Calf Skeletal Muscle of Healthy Volunteers at 3 T.

Abstract

Background: Skeletal muscle mitochondrial oxidative phosphorylation (mtOXPHOS) is important for ATP generation and its dysfunction leads to exercise intolerance. Phosphorus magnetic resonance spectroscopy (³¹P-MRS) is a useful, noninvasive technique for mtOXPHOS assessment but has limitations. Creatine-weighted chemical exchange saturation transfer (CrCEST) MRI is a potential alternative to assess muscle bioenergetics.

Purpose: To evaluate the interscan repeatability, intra- and interobserver reproducibility of CrCEST during mild plantar flexion exercise.

Study type: Retrospective.

Subjects: Twenty healthy volunteers (age 37.6 ± 12.4 years, 11 females).

Field strength/sequence: 3 T/CEST imaging using gradient echo readout.

Assessment: τCrCEST (postexercise Cr recovery time) was assessed in two scans for each participant, following mild plantar flexion exercises targeting the medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus (Sol) muscles. Three observers measured τCrCEST for interobserver reproducibility. Three readings by one observer were used to measure intraobserver reproducibility. Two scans were used for within-participant interscan repeatability.

Statistical tests: Paired t tests, intraclass correlation coefficient (ICC), and Pearson correlation were conducted. Bland-Altman plots were used to analyze the interobserver variability. A P-value of 0.05 was considered statistically significant.

Results: There was excellent intra- (ICC $\in \left(0.94-0.98\right)$ ) and interobserver (ICC $\in \left(0.9-0.98\right)$ ) reproducibility, with moderate interscan repeatability for τCrCEST in LG and MG (ICC $\in \left(0.54-0.74\right)$ ) and poor-to-moderate interscan repeatability in Sol (ICC $\in \left(0.24-0.53\right)$ ). Excellent interobserver reproducibility was confirmed by Bland-Altman plots (fixed bias P-value $\in \left(0.08-0.87\right)$ ).

Data conclusion: CrCEST MRI shows promise in assessing muscle bioenergetics by evaluating τCrCEST during mild plantar flexion exercise with reasonable reliability, particularly in LG and MG.

Level of evidence: 4 TECHNICAL EFFICACY: Stage 1.