Towards patient-friendly arterial-spin-labeling MRI in muscle: Effect of exercise intensity and standardisation on perfusion parameters

Perfusion is fundamental to muscle function, and is limited in muscular dystrophies—representing a promising biomarker for clinical trials. However, in-magnet exercise paradigms for measuring ASL perfusion are seldom standardised and require high-intensity exercise, which is impracticable in patients. In volunteers, we tested the acceptability of three protocols: two standardised paradigms with different intensities, and a non-standardised paradigm at a single intensity. Exercise standardisation improved SNR. In general, muscle blood flow, T2*, and SNR decreased, while arterial transit time increased with time after exercise; T2* was higher after high-intensity exercise. SNR at lower exercise-intensity was insufficient for robust perfusion-parameter estimation.