An Optimal Control Approach for {HIFU} Self-Scanning Treatment Planning

In noninvasive abdominal tumor treatment, research has focused on canceling organ motion either by gating, breath holding or tracking of the target. This paper is based on the novel self-scanning method which combines the advantages of the gated and the tracking method. This approach leverages the respiratory organ motion by holding the focal spot of the high intensity focused ultrasound (HIFU) device static for a given time, while it passively scans the tumor due to respiratory motion. This enables to use a lower-cost HIFU device. We present a planning method for such a system that is based on optimal control theory which optimizes the scanning path and the sonication intensities simultaneously. The method minimizes treatment time and ensures complete tumor ablation according to the thermal dose under free-breathing. To verify our method, we simulated a tumor in two dimensions. The achieved treatment time performs on par to the gold-standard tracking method. Moreover, we measured the temperature profile of the HIFU device in a tissue-mimicking phantom to verify our temperature model