A method for automated detection of high intensity focused ultrasound (HIFU) beams in 3D space

In HIFU therapy, it is critical to determine the HIFU beam path and its focus before the therapy-level dose is administered into tissue. In this work, we adapted echo-strain methods to construct the HIFU beam information and developed an automated detection method using 3D data segmentation, beam trajectory estimation, and focal point localization. A series of 3D volume ultrasound data acquisitions was interleaved in time with a testing pulse with low intensity (Isppa ~200 W/cm²) and small duty cycle (4.7%). 3D echo-strain was derived from tissue apparent displacement and was segmented based on a volume growing technique. Our methods were tested on tissue mimicking phantom materials with acoustic properties similar to human muscle. Testing was done to show repeatability and accuracy for HIFU beams focused at varying depths and steering angles. The error from thirteen (13) different focal positions was 5.7 ± 2.3 mm (mean ± std) in 3D space, with error defined as the Euclidian distance between the estimated focal location and the experimentally determined focal location. Experimental location was determined via a thermocouple embedded in the phantom, and the location of the thermocouple was determined by the highest temperature rise location when moving the HIFU 2D array transducer through a 3D volume using a short (1 second) and low power (Isppa ~40W/cm²) focused beam sonication. It was concluded that an automated HIFU beam focal point detection method was developed and provides accurate localization of the HIFU beam focus.