Readout-segmented echo-planar diffusion-weighted MR at 3.0 T for the evaluation the effect of low-intensity transcranial ultrasound on stroke in a rat model

ObjectiveTo investigate the feasibility of the relative apparent diffusion coefficient (rADC) values based on readout-segmented echo-planar diffusion sequence in evaluation the effects of low-intensity transcranial ultrasound (LIPUS) on ischemic stroke in rat models at different onset times.MethodsSixty Sprague-Dawley rats (weight, 250 ± 10 g) were divided randomly into six groups (n = 10) to establish a permanent model of distal middle cerebral artery occlusion (dMCAO). The rats were stimulated with ultrasound for 10 min in the LIPUS groups at 0.5 h, 1 h, 3 h, 6 h, and 9 h after dMCAO (denoted as the LIPUS group (0.5 h), LIPUS group (1 h), LIPUS group (3 h), LIPUS group (6 h), LIPUS group (9 h), and Control group without ultrasound stimulation). Magnetic resonance imaging was acquired at 0.5 h and 1 h after dMCAO and then at 1-hour intervals until 12 h. The rADC values were then measured and calculated. The pathological results from the rat brains were obtained after the experiment.ResultsWhen LIPUS was applied 0.5 h after dMCAO, the rate of decline of rADC values in the early stages were significantly reduced and the final rADC values were significantly increased. When LIPUS were applied at 1 h, 3 h, and 6 h, the final rADC values only increased slightly and did not prevent early declines. No significant difference of ultrasound stimulation at 9 h was found.ConclusionThe rADC values demonstrated difference at different time points after dMCAO between with and without LIPUS groups.