Evaluation of a New CT-Guided Robotic System for Percutaneous Needle Insertion for Thermal Ablation of Liver Tumors: A Prospective Pilot Study

Percutaneous thermal ablation is one of the treatments of choice for liver tumors less than 3 cm in size [1, 2]. Radiofrequency ablation (RFA) and microwave ablation (MWA) are the most frequently used modalities and are well documented in the current literature [3, 4]. They have shown favorable outcomes for tumor control, with low associated morbidity, and low local tumor progression (LTP) rate [5]. CT-guided freehand insertion of percutaneous needles sometimes requires numerous CT acquisitions for needle progression control, moreover tumor localization itself and/or poor tumor visibility can lead to a challenging procedure with reduced odds of ablation success.

The development of robotic needle guidance in interventional radiology can help to improve needle insertion, reducing the need for needle adjustments. It also allows the physician to set and visualize the planned ablation margin, to obtain more precise ablation zones with less rates of tumor persistence or recurrence. Lastly, robotic solutions generally offer better positioning results compared with freehand needle insertion [6‐10].

We herein report our first in human trial with a CT-guided robotic which is designed to assist interventional radiologists in performing percutaneous procedures in the abdomen. The objective of our work was to assess feasibility and safety for needle insertion.

No adverse events were reported in this study in relation with the use of the device, confirming the safety data collected in animal pre-clinical studies [11, 12]. Only few other devices are available for robotic needle placements, and no specific complications were reported in prospective clinical investigations involving these devices [3, 7, 17‐19]. The short hospital stay with quick recovery of our patients is similar to results reported in the literature on navigational devices for liver ablations [10, 20‐23].

In our cohort, feasibility was achieved for 95.7% of the lesions. This result is consistent with the rate of 89% in 28 lesions reported by Engstrand et al. with another navigation device [20]. In our PP population, we observed one case of non-feasibility, whereas the first trajectory could not be reached by the robot arm which was stopped before a possible contact with the patient, the second attempt resulted in the sliding of the needle along the liver capsule due to a steep approach angle. Therefore, in future it would be relevant to plan trajectories as perpendicular as possible to the liver capsule. In our study, the mean number of needle adjustment per lesion was 0.4 (± 0.7) and 29.2% of lesions requiring needle adjustment. It is lower than rates from other reports of robotic needle placement with manual repositioning required in 48.7% to 60% of the interventions, and a mean number of adjustment from 0.8 (± 0.8) to 1.1 (± 0.7) per lesion [7, 17]. Needle placement has a major impact on the treatment outcomes since any adjustment may increase radiation dose, procedure time, tissue trauma, and possibly the risk of bleeding and tumor seeding; but moreover approximative needle placement will decrease the probability of local tumor control [20, 22, 24, 25].

The targeting potentialities are highly dependent on tumor visibility and location of the lesion within the liver, with a third of lesions judged “unablatable” in the clinical setting [21, 26]. We reported that 46% of our patients had tumors judged as challenging to target (Fig. 5), but tumor location did not influence feasibility. Lachenmayer et al. [21] and Tinguely et al. [22] using a CT-guided percutaneous system, and Odisio et al. [27] using freehand insertion under CT guidance for liver ablations recently reported similar results. Tinguely et al. showed complex targeting trajectories such as intercostal trajectories and steep trajectory angles have no impact on targeting accuracy [22]. In our study, eighteen (75%) trajectories were out of plane with a minimum and maximum craniocaudal angulations from − 16.9 to 61.4°, demonstrating the ability of the device to target lesions requiring significant angulation without impacting feasibility.

There are several limitations and potential shortcomings to the present study. First and foremost, this is not a comparative and randomized trial. We chose to design a single-arm study to collect the first data in Human with a new robotic device. A simple design was therefore preferred to demonstrate the main outcomes which were feasibility and safety. Additionally, the number of patients and lesions may be too small to allow robust statistical analyses and identify differences in our results compared to other data from the literature. Furthermore, the radiation dose received by the patient was not analyzed in the present study although the low rate of needle adjustment demonstrated in this study highlights the fact that the majority of patients had only 3 CT-scan acquisitions (treatment planning CT, needle placement assessment CT, and post-ablation CT), and no radiation was delivered to the operator. These could be interesting parameter to evaluate in the future.

Robotic arm assistance for needle positioning during thermal ablation was safe and allowed a single insertion in 70.8% of targeted tumors, with an overall mean number of adjustments of 0.4 ± 0.7 per lesion.

Our present first-in-human limited series suggests both feasibility and safety of a stereotactic CT-guided device for the percutaneous needle insertion for liver tumors treatment. Other CT-guided interventions such as biopsies and other organs in abdomen might benefit from such needle guidance.