MRI-compatible mechatronic needle guidance system for focal thermal laser ablation in localized prostate cancer

Abstract

Prostate cancer is the most frequently diagnosed non-cutaneous cancer and the second leading cause of cancer-related deaths in men. Whole gland surgical and radiation treatments for prostate cancer are highly effective for long-term cancer control. However, these are often associated with overtreatment, resulting in urinary complications and sexual dysfunction, adversely impacting the quality of life. Focal laser ablation (FLA) under magnetic resonance imaging (MRI)-guidance is an alternative minimally invasive treatment method for localized prostate tumors while preserving surrounding structures and healthy tissues. Accurate needle positioning and delivery are critical for the therapeutic success of MRI-guided FLA. We propose an MRI-compatible mechatronic system for in-bore transperineal FLA needle guidance to localized prostate lesions. This paper presents the mechatronic system design, including a remotely actuated, four degree-of-freedom transperineal positioning and needle guidance mechanism, and adaptable needle guide. We demonstrate its MR compatibility and evaluated its mechanical bias in free-space testing using an external optical tracking system with several measurement points (N=40) over its range-of-motion. Free-space testing resulted in a root-mean-square error of 0.71 ± 0.30 mm. Within an MR environment, in-bore testing to virtual targets (N=10) with projected needle trajectories resulted in a mean needle tip error of 1.81 ± 0.56 mm and needle trajectory error of 0.78 ± 0.75°. This suggests that localized ablation regions can be accurately targeted within 2.16 mm within 95% confidence. An extensive in-bore analysis and correction for systematic bias across the range-of-motion may improve this accuracy. This study shows that our proposed mechatronic needle guidance system may be a feasible alternative for accurate MR-guided FLA for localized prostate therapy.