Ultrasound Skull Imaging for Guiding Noninvasive Ultrasound Brain Therapy in Rodent

Abstract

Noninvasive ultrasound (US) brain therapies, including US brain stimulation, US drug delivery by BBB opening, or US thrombolysis, have great potential in clinical applications. But target positioning is a challenge. Dual-mode US system provides a promising solution, which can carry out US therapy function under the guidance of US imaging. However, the brain skull usually deteriorates the brain image seriously, because of the great amplitude of US echoes reflected from the skull. In order to improve the guidance function of US image, we investigated the relationship of skull structures and US image in rodents. Computerized tomography (CT) images of the heads of four rats were scanned by a micro-CT system. US skull imaging was carried out by a custom-built US imaging and stimulation system with a dual-mode 2D matrix array with 1 MHz center frequency and 256 elements. The features of the CT images and the US images of rat skulls were carefully recognized, which were used to identify the coordinates of the rat brain from US images. After the US imaging and brain position was determined, multi-target BBB opening was carried out based on the identified coordinate. The result indicated that the deviation of the coordinate was less than 1 mm. US skull imaging will be a useful method for image-guided noninvasive therapy applications.