Towards real-time tracking of anatomic features for HIFU beam steering

Introduction A challenge for High Intensity Focused Ultrasound (HIFU) therapy in the upper abdomen is maintaining the ultrasound focal spot on the target during free breathing. Normal breathing can cause liver tissue to move by as much as 5.5 cm[1]. Consequently, current approaches require the patient to hold their breath during the deposition of focused ultrasound[2]. This practice assumes that the target lesion will return to the same location in each breath hold throughout the treatment. While consistent breath holding may be possible with patient training and feedback mechanisms, a more significant limitation to this approach is that gating ultrasound delivery to the respiratory cycle reduces the treatment duty cycle to the point where perfusion results in a significant dissipation of the ablation energy.