Biexponential analysis of intravoxel incoherent motion in calf muscle before and after exercise: Comparisons with arterial spin labeling perfusion and T2

Abstract

PurposeThis study aimed to clarify exercise-induced changes in intravoxel incoherent motion (IVIM) parameters obtained from diffusion-weighted imaging (DWI) of the calf muscle, as well as the relationships between IVIM parameters, perfusion, and water content in muscle tissue. Materials and methodsThirteen healthy volunteers underwent IVIM-DWI, arterial spin labeling (ASL), and multi-echo spin-echo T2 mapping of the right calf on a 3.0-T magnetic resonance imaging scanner before and after performing dorsiflexion exercise. From the data, we derived the perfusion-related diffusion coefficient (D⁎), perfusion component fraction (F), blood flow parameter (FD⁎), and restricted diffusion coefficient (D) in the tibialis anterior muscle. The muscle blood flow (MBF) and transverse relaxation time (T2) were also calculated from the ASL and multi-echo spin-echo data, respectively. We compared the parameters measured before and after exercise and assessed the relationship of each IVIM-derived perfusion parameter (D⁎, F, and FD⁎) with MBF and each diffusion parameter (D and ADC) or F with T2. ResultsNotably, all these parameters were significantly increased after exercise. Before exercise, the FD⁎ exhibited a significant positive correlation with the MBF, whereas no significant correlation was observed between D⁎ or F and MBF. After exercise, both D⁎ and FD⁎ exhibited significant positive correlations with MBF, whereas F was not significantly correlated with MBF. Additionally, D was significantly correlated with T2 after exercise, but not before exercise. No significant correlations were found between ADC and T2 either before or after exercise. ConclusionsThe IVIM analyses before and after exercise enable the simultaneous evaluation of exercise-induced changes in perfusion and water diffusion in the muscle and increases the body of information on muscle physiology.