Photoacoustic-guided Transcranial HIFU with Combined Time-reversal and Genetic Algorithm.

High intensity focused ultrasound (HIFU) is a noninvasive therapy used to induce tissue ablation for treating malignant tissues. Photoacoustic (PA) has recently been proposed as an alternative method to guide HIFU. In this paper, we present a method of HIFU guided by time-reversing the transcranial PA signals of an optically selective target in a nonselective background. To improve the focus performance on target area, we further propose to utilize the time-reversed PA signals as the initial population of Genetic Algorithm (GA) to optimize the focusing iteratively. In particular, we mimic both optical and acoustic parameters of the human brain and intracranial media in the simulation study. Experimental results show that the focusing accuracy of the proposed method has been significantly improved compared to just one-step PA time-reversal. At the same time, the combination of TR and GA makes the iteration time consumption of the optimization process less than other traditional algorithms without TR, showing its potential HIFU in clinical scenarios.