Introduction

High intensity focused ultrasound (HIFU) has established itself clinically as a viable, safe, effective, and non-invasive tissue ablation modality. Previous studies have shown that HIFU delivered laparoscopically can be used to ablate kidney tumors, potentially enabling a lower morbidity treatment with faster recovery time as compared to partial nephrectomy procedures. Challenges remain, however, including ensuring full tissue necrosis and consistent energy coupling to the target volume. The objective of this study was to evaluate whether a newly developed laparoscopic HIFU probe is able to address these challenges.

Methods

A laparoscopic porcine kidney model was used to investigate the safety and efficacy of the new 15mm HIFU probe. Under ultrasound guidance, kidneys of 12 pigs were targeted and ablated with HIFU, creating on average 2 ablation zones per kidney of varying sizes and locations in order to quantify the probe&[prime]s ability to deliver HIFU to any location on the kidney. Efficacy was evaluated via the analysis of ablation volume histology slides, real-time ultrasound images collected during HIFU delivery, and MRI and ultrasound contrast images. Safety was evaluated by surviving a subgroup of the animals (2w). Gross-pathological data, sonication parameters, and workflow feedback was also collected during the study.

Results

Repeatable lesions could be created at a rate of 0.48cm³/min and average energy densities of 584cal/cm³. Histological evaluation indicated contiguous ablated volumes using these delivery parameters, extending from the transducer&[prime]s focal zone to the kidney surface, with a maximum treatment depth of 27mm. Ablated target volumes ranged from 5.1cm³ to 24.5cm³.

Conclusions

The results confirm the ability of the new probe to deliver HIFU in a consistent and reliable manner. Initial dose requirements for ablating tissue at various depths were also determined. Workflow feedback has resulted in additional system user interface improvements, with all of these results paving the way for a future clinical study.

Funding

This work was supported by a Young Investigator Award (S.C.).