Laparoscopic High Intensity Focused Ultrasound: Application to Kidney Ablation

This work demonstrates the feasibility of using high intensity focused ultrasound (HIFU) for selective ablation of renal tissue through laparoscopic procedures. Two laparoscopic HIFU probe prototypes were developed and tested. Probe 1: It is a hand-held probe with no integrated ultrasound imaging capability. It consists of two focused rectangular HIFU piezoceramic crystals mounted on a stainless steel tube for side and front firing configurations working at 4 and 5MHz respectively. During laparoscopic operation a separate video camera imaging channel is used for treatment monitoring. Probe 2: It is a computer-controlled probe with an integrated ultrasound imaging working in conjunction with the Sonablate HIFU system. It consists of a 4MHz focused rectangular HIFU piezoceramic transducer confocally coupled with a circular central element used for real-time pulse-echo imaging. Precise bi-plane mechanical movements of the transducer enable it to treat targeted tissue volumes under ultrasound imaging guidance. Both prototypes were fully characterized for electrical impedances, acoustic fields, and total acoustic power outputs. They were then tested in an in vivo animal experimental study in which 20 pigs were treated through both open and sterile laparoscopic HIFU surgery procedures. Gross pathology and histology results demonstrated the feasibility of the laparoscopic HIFU to generate selective homogenous well-delineated necrotic lesions in a lobe of the kidney. Specifically, when treating under real-time ultrasound imaging guidance (probe 2) the ablated tissue region agrees with the planed lesion size and position within ± 1mm. Moreover, it can be used as a hemostasis tool during standard partial nephrectomy to significantly reduce bleeding associate to these procedures.