Abstract 12812: Creatine Chemical Exchange Transfer MRI Demonstrates Abnormal Calf Muscle Energetics in Peripheral Arterial Disease

Abstract

Introduction: Creatine chemical exchange saturation transfer (CrCEST) is a novel MRI technique utilizing radiofrequency pulses to monitor creatine concentrations at high spatial resolution. The study utilized CrCEST kinetics to compare post-exercise creatine decay in peripheral arterial disease (PAD) patients to normal subjects and to validate against phosphocreatine (PCr) recovery by 31 phosphorus (P) MR spectroscopy (MRS). Methods: 23 subjects with PAD (claudication and ankle-brachial index<0.9) and 28 healthy subjects were enrolled. All underwent 3T MRI (Siemens Prisma) using a knee coil around the calf. Pre- and post-exercise images were obtained around plantar flexion ergometry (Ergospect) until exhaustion. Regions of interests were drawn around major muscle groups. Creatine decay times were obtained by fitting an exponential curve to the CrCEST values. 31 P spectra were obtained 20 minutes later at peak exercise using a surface-coil localized, free induction decay acquisition with 25 signal averages at a repetition time of 550s with calculation of PCr recovery time constant. Results: 23 PAD subjects (mean ABI 0.66 ± 0.11, age 64 ± 8, 17% females) had prolonged median overall calf muscle creatine decay time of 286 seconds (s) (Interquartile Range (IQR) 134 to 370) versus 152 s (IQR 114 to 193) in controls (age 63 ± 9, 70% females), p = 0.009. The gastrocnemius muscle demonstrated a creatine decay time of 316 s in PAD (IQR 189 to 510) versus 181 s in controls (IQR 102 to 236), p = 0.003 and the posterior tibialis muscle, 186 s (IQR 119 to 653) versus 125 s (IQR 72 to 221), p = 0.013. 8 PAD patients and 6 controls underwent CrCEST and 31 P MRS which were compared over the entire calf. Bland-Altman analysis (Figure 1B) yielded a mean difference of 71s (SD 109). Conclusions: Imaging with CrCEST demonstrates prolonged creatine kinetics in PAD patients compared to normal subjects with high spatial resolution and good agreement with 31 P MRS, although PCr recovery appears faster.