The dynamic course of spontaneous muscular contractions assessed using multiple-point acquisition in diffusion-weighted stimulated echo imaging.

Purpose: The temporal course of spontaneous mechanical activities of musculature (SMAMs) is investigated using a novel multiple-point diffusion-weighted stimulated echo imaging sequence (MP-DW-STE) with adapted spatial and temporal resolution. For this purpose, different sequence settings and measurement parameters are applied.

Methods: A single-shot MP-DW-STE imaging sequence with multiple signal rephasing by small flip angle RF pulses was developed to acquire image series during spontaneous muscle contractions with duration of several hundred milliseconds. Measurements were conducted on an incoherent motion phantom and in the calf muscles of eight healthy volunteers. The number and cross-sectional area of SMAM visualizations as well as the contractile behavior in terms of onset and duration of visible SMAMs was analyzed.

Results: Measurements on the incoherent motion phantom confirmed the ability of the proposed technique to characterize dynamic incoherent motion as signal voids in series of images with a high temporal resolution of approximately 40 ms. All human subjects showed SMAMs with a median duration of 120 ms, therefore, visible in several diffusion-weighted images in a row. Contraction time of SMAMs was in the range of 80 to 120 ms for the soleus muscle. The MP-DW-STE sequence settings have shown to significantly influence the mean frequency and cross-sectional area of SMAMs.

Conclusion: MP-DW-STE imaging allows for time-resolved recording of spontaneous muscular contractions and provides new insights into their dynamic course. This new feature can be used for better characterization of physiological SMAMs in healthy subjects and pathological SMAMs in patients suffering from neuromuscular diseases.