Junichi Tokuda

Robot-assisted needle insertion is widely employed in minimally invasive percutaneous interventions such as biopsy, brachytherapy, or ablation; however, most existing systems predominantly emphasize needle dexterity and manipulation within the soft tissue, neglecting the significant challenge of percutaneous access. In practice, conventional needle insertions often require excessive force that causes significant deformation of both tissue and needle, particularly when penetrating stiff skin or fibrotic tumors. To address this, we develop a novel tapping mechanism that generates instantaneous momentum at the needle tip to achieve efficient tissue penetration. Theoretical models are formulated to describe the force–deformation behavior and fracture mechanics induced by the tapping motion. Experiments on porcine tissue demonstrated that the tapping motion reduced the mean rupture force and tissue deformation from 9.75 N and 34.44 mm obtained via the conventional continuous insertion to 2.79 N and 19.85 mm, respectively. Furthermore, the tapping mechanism enabled successful insertion into the two-barrier porcine tissue using compliant needles that would otherwise buckle under continuous insertion, increasing the second-barrier successful penetration rate from 0/15 to 13/15.

Magnetic resonance imaging (MRI)-guided transperineal targeted prostate biopsy has the potential to provide a precise cancer diagnosis. However, it is challenged by targeting errors and needle deflection. The main issue is that the traditional needle guides have limited degrees of freedom (DoF) and therefore restrict insertion path options. Thus, the targeting error can be larger than 5[ ]mm. This study evaluates the performance of a custom-built 4-DoF needle guiding device designed to enable alternative insertion paths. The 4-DoF Smart Template was designed to improve image quality and stability, including redesigned fiducials and titanium positioning frames. Four MRI-guided biopsy cases were conducted. Targets were identified on T2-weighted images, and insertion paths were planned and adjusted to avoid critical structures. The targeting error was measured as the in-plane distance between the target and the actual needle position. The average targeting error of the best insertion attempt was 3.7[ ]mm ± 2.6[ ]mm (mean ± standard deviation). When discarding the case where the device had to be removed due to patient anatomy, the average targeting error was reduced to 2.7[ ]mm ± 1.1[ ]mm. No adverse events were reported. The new 4-DoF Smart Template device has demonstrated improved accuracy as compared to the traditional needle guide device, successfully reaching the target location with just one insertion in four out of six targets.

Objective. Focal therapy offers a middle ground between active surveillance and whole-gland treatment for patients with low- and intermediate-risk prostate cancer, aiming to eliminate tumor tissue while preserving surrounding structures. Among available focal therapy approaches, magnetic resonance imaging (MRI)-guided focal cryoablation offers some technical advantages, including real-time monitoring of iceball formation and intraoperative images with excellent soft-tissue contrast. Despite its minimally invasive nature, prior studies have reported postoperative urinary and sexual dysfunction, raising concerns about unintended injury to critical anatomical structures such as the external urethral sphincter (EUS) and neurovascular bundles (NVBs). However, the direct relationship between anatomical injury and postoperative symptoms remains unclear. We hypothesize that damage to the EUS or NVBs during MRI-guided focal cryoablation increases the risk of postoperative urinary or erectile dysfunction. Approach. We analyzed 402 multi-slice MRI image sets from 42 procedures. We developed an AI-assisted tool for automatic segmentation of anatomical structures and iceballs. Quantitative metrics were proposed to estimate tissue damage based on spatial overlap, exposure time, and temperature dynamics. These metrics were then statistically correlated with postoperative urinary and erectile outcomes. Main results. Significant associations were observed between injury metrics and postoperative dysfunctions, with EUS involvement predictive of urinary dysfunction in both time-based ( p < 0.05 ) and temperature-proxy models ( p < 0.05 ) , and NVB involvement associated with erectile dysfunction in the time-based model ( p < 0.05 ) . Significance. Our findings demonstrate that EUS and NVB injuries are quantifiable predictors of postoperative morbidity with medium-to-large effect sizes. The developed AI-assisted framework supports objective evaluation of cryo-dose and establishes a preliminary basis for a quantitative injury metric designed to minimize side effects and enhance the safety of focal cryoablation.

Radiofrequency ablation is widely used to prevent ventricular tachycardia (VT) by creating lesions to inhibit arrhythmias; however, the current surface ablation catheters are limited in creating lesions that are deeper within the left ventricle (LV) wall. Intramyocardial needle ablation (INA) addresses this limitation by penetrating the myocardium and delivering energy from within. Yet, existing INA catheters lack adequate dexterity to navigate the highly asymmetric, trabeculated LV chamber and steer around papillary structures, limiting precise targeting. This work presents a novel dexterous INA (d-INA) toolset designed to enable effective manipulation and creation of deep ablation lesions. The system consists of an outer sheath and an inner catheter, both bidirectionally steerable, along with an integrated ablation needle assembly. Benchtop tests demonstrated that the sheath and catheter reached maximum bending curvatures of 0.088~mm$^{-1}$ and 0.114~mm$^{-1}$, respectively, and achieved stable C-, S-, and non-planar S-shaped configurations. Ex-vivo studies validated the system's stiffness modulation and lesion-creation capabilities. In-vivo experiments in two swine demonstrated the device's ability to reach previously challenging regions such as the LV summit, and achieved a 219\% increase in ablation depth compared with a standard ablation catheter. These results establish the proposed d-INA as a promising platform for achieving deep ablation with enhanced dexterity, advancing VT treatment.

Purpose Minimally invasive needle-based interventions are commonly used in cancer diagnosis and treatment, including procedures, such as biopsy, brachytherapy, and microwave ablation. Although MR-guided needle placement offers several distinct advantages, such as high-resolution target visualization and accurate device tracking, one of the primary limitations that affect its widespread adoption is the ergonomic constraints of the closed-bore MRI environment, requiring the patients to be frequently moved in and out to perform the needle-based procedures. This paper introduces a low-profile, body-mounted, MR-guided robot designed to address this limitation by streamlining the operation workflow and enabling accurate needle placement within the MRI scanner. Methods The robot employs piezoelectric linear actuators and stacked Cartesian XY stages to precisely control the position and orientation of a needle guide. A kinematic model and control framework was developed to facilitate accurate targeting. Additionally, clinical workflow for the liver interventions was developed to demonstrate the robot’s capability to replicate existing procedures. The proposed system was validated in benchtop environment and 3T MRI scanner to quantify the system performance. Results Experimental validations conducted in free space demonstrated a position accuracy of 2.38 ± 0.94 mm and orientation error of 1.40 ± 2.89°. Additional tests to confirm MR-conditionality and MR-guided phantom placements were carried out to assess the system’s performance and safety in MRI suite, yielding a position error of 2.01 ± 0.77 mm and an orientation error of 1.57 ± 1.31°. Conclusion The presented robot shows exceptional compatibility with a wide range of patients and bore sizes while maintaining clinically significant accuracy. Future work will focus on the validations in dynamic liver environments.

Image-guided robotic interventions involve the use of medical imaging in tandem with robotics. SlicerROS2 is a software module that combines 3D Slicer and robot operating system (ROS) in pursuit of a standard integration approach for medical robotics research. The first release of SlicerROS2 demonstrated the feasibility of using the C++ API from 3D Slicer and ROS to load and visualize robots in real time. Since this initial release, we’ve rewritten and redesigned the module to offer greater modularity, access to low-level features, access to 3D Slicer’s Python API, and better data transfer protocols. In this paper, we introduce this new design as well as four applications that leverage the core functionalities of SlicerROS2 in realistic image-guided robotics scenarios.

This letter addresses the targeting challenges in MRI-guided transperineal needle placement for prostate cancer (PCa) diagnosis and treatment, a procedure where accuracy is crucial for effective outcomes. We introduce a parameter-agnostic trajectory correction approach incorporating a data-driven closed-loop strategy by radial displacement and an FBG-based shape sensing to enable autonomous needle steering. In an animal study designed to emulate clinical complexity and assess MRI compatibility through a PCa mock biopsy procedure, our approach demonstrated a significant improvement in targeting accuracy (p < 0.05), with mean target error of only 2.2 $\pm$ 1.9 mm on first insertion attempts, without needle reinsertions. To the best of our knowledge, this work represents the first in vivo evaluation of robotic needle steering with FBG-sensor feedback, marking a significant step towards its clinical translation.