Characterization of Macrolesions Induced by Myocardial Contrast Enabled Therapy (MCET)

摘要

Intermittent high intensity ultrasound pulses with circulating contrast agent microbubbles can induce scattered cavitation microlesions of potential value for myocardial reduction therapy. In this study, a computer-aided evaluation scheme of the effective treated volume was implemented in order to optimize ultrasound pulse parameters, exposure duration, and contrast agent dose. Rats with Evans blue injections were treated with 1.5 MHz focused ultrasound bursts. Evans blue staining indicates lethal cardiomyocytic injury. After frozen in compound on dry ice, each heart was sectioned to provide samples covering the entire exposed myocardial volume. Both brightfield and fluorescence images of 25 tissue sections were taken. Tissue detection and microlesion detection were first done based on the 2D images to form microlesion masks containing the outline of the heart and the dead cell regions. Image registration was then performed on the microlesion masks to reconstruct a volume-based model according to the morphology of the heart. The therapeutic beam path was estimated from 3D stacked microlesions, and finally the total impacted volume with microlesions, here termed macrolesion, was characterized along the therapeutic beam axis. Radially symmetric fractional macrolesions were characterized via stepping disks of variable radius determined by the local distribution of microlesions. Treated groups show significant macrolesions with approximately 100 μL volume, an average radius of 2.5 mm, 6 mm length, and 13% lesion density compared to zero radius, length and lesion density for the sham group.