Simultaneous Observation of Distinct Phosphocreatine and Creatine CEST Peaks in Exercised Human Skeletal Muscle at 5T

Motivation: PCrCEST and CrCEST contrasts are weak and indiscernible in clinical settings (≤ 3 T), limiting the accuracy of quantification. Goal(s): To develop an accurate and reliable PCrCEST and CrCEST method in human skeletal muscle at 5 T. Approach: The optimal saturation scheme was investigated. Two-peak PLOF method was employed for quantification. Plantar flexion exercise was conducted to validate the performance of the proposed method. Results: Distinct PCrCEST and CrCEST peaks can be observed simultaneously at 5T. The transition between PCr and Cr was clearly observed in a volunteer during and after exercise. Impact: Improved accuracy and reliability of PCrCEST and CrCEST in human skeletal muscle can be obtained at 5T. The distinct CEST peak at 2.0 ppm immediately after exercise suggests that the in vivo CrCEST is a slow-exchanging process.