Percutaneous radiofrequency thermal ablation of primary and metastatic hepatic tumors: current concepts and review of the literature

Augmented reality navigation with ultrasound-assisted point cloud registration for percutaneous ablation of liver tumors

PURPOSE

We present a novel augmented reality (AR) surgical navigation method with ultrasound-assisted point cloud registration for percutaneous ablation of liver tumors. A preliminary study is carried out to verify its feasibility.

METHODS

Two three-dimensional (3D) point clouds of the liver surface are derived from the preoperative images and intraoperative tracked US images, respectively. To compensate for the soft tissue deformation, the point cloud registration between the preoperative images and the liver is performed using the non-rigid iterative closest point (ICP) algorithm. A 3D AR device based on integral videography technology is designed to accurately display naked-eye 3D images for surgical navigation. Based on the above registration, naked-eye 3D images of the liver surface, planning path, entry points, and tumor can be overlaid in situ through our 3D AR device. Finally, the AR-guided targeting accuracy is evaluated through entry point positioning.

RESULTS

Experiments on both the liver phantom and in vitro pork liver were conducted. Several entry points on the liver surface were used to evaluate the targeting accuracy. The preliminary validation on the liver phantom showed average entry-point errors (EPEs) of 2.34 ± 0.45 mm, 2.25 ± 0.72 mm, 2.71 ± 0.82 mm, and 2.50 ± 1.11 mm at distinct US point cloud coverage rates of 100%, 75%, 50%, and 25%, respectively. The average EPEs of the deformed pork liver were 4.49 ± 1.88 mm and 5.02 ± 2.03 mm at the coverage rates of 100% and 75%, and the average covered-entry-point errors (CEPEs) were 4.96 ± 2.05 mm and 2.97 ± 1.37 mm at 50% and 25%, respectively.

CONCLUSION

Experimental outcomes demonstrate that the proposed AR navigation method based on US-assisted point cloud registration has achieved an acceptable targeting accuracy on the liver surface even in the case of liver deformation.

Optimizing Loco Regional Management of Oligometastatic Colorectal Cancer: Technical Aspects and Biomarkers, Two Sides of the Same Coin

Colorectal cancer (CRC) is the third most common cancer worldwide and has a high rate of metastatic disease which is the main cause of CRC-related death. Oligometastatic disease is a clinical condition recently included in ESMO guidelines that can benefit from a more aggressive locoregional approach. This review focuses the attention on colorectal liver metastases (CRLM) and highlights recommendations and therapeutic locoregional strategies drawn from the current literature and consensus conferences. The different percutaneous therapies (radiofrequency ablation, microwave ablation, irreversible electroporation) as well as trans-arterial approaches (chemoembolization and radioembolization) are discussed. Ablation margins, the choice of the imaging guidance as well as characteristics of the different ablation techniques and other technical aspects are analyzed. A specific attention is then paid to the increasing role of biomarkers (in particular molecular profiling) and their role in the selection of the proper treatment for the right patient. In conclusion, in this review an up-to-date state of the art of the application of locoregional treatments on CRLM is provided, highlighting both technical aspects and the role of biomarkers, two sides of the same coin.

Follow-up of percutaneous microwave (MW) ablation of hepatic lesion: predictive value of CT at 24-h compared with CT at 1 month

To retrospectively assess the predictive value of the CT performed at 24 h, compared with the CT performed at 1 month, in the evaluation of the technical success of microwave (MW) ablation of hepatic lesions. In a single center, 50 patients with HCC underwent percutaneous MW ablation between November 2016 and March 2019. Each patient underwent a contrast-enhanced CT exam at 24 h and at 1 month after the procedure. For each patient, was assessed the presence or absence of residual disease, the appearance of a new lesion, complications, and the involvement of the hepatic capsule, both at 24-h and at 1 month. Overall correlation between residual disease, appearance of a new nodule and complications was also assessed. A total of 50 hepatic lesions were treated with US-guided MW ablation. Patients' mean age was 70.9 years (range 28-87 years). Mean nodule diameter was 17.6 mm (range 7-35 mm). Contingency tables and the χ² test showed a strong association when looking at capsule involvement (accuracy: 100%), residual disease (accuracy: 90%; p-value 0.003), and the appearance of a new HCC nodule (accuracy: 88%; p-value 0.007); regarding complications, the accuracy was 78% (p-value 0.014). Optimal correlation was reached in 62% of cases, moderate correlation in 26%, minimum correlation in 10% of cases; no cases of zero correlation were recorded. CT at 24 h and 1 month showed comparable efficacy in evaluating residual disease after MW thermal ablation of liver lesions. However, further studies are needed to assess which factors may cause false-negative results at the 24-h CT.

Imaging guided percutaneous interventions in hepatic dome lesions: Tips and tricks

Percutaneous hepatic interventions are generally safe given the fact that liver closely abuts the abdominal wall and hence it is easily accessible. However, the superior portion of liver, adjacent to the diaphragm, commonly referred as the “hepatic dome”, presents unique challenges for interventionists. Percutaneous access to the hepatic dome may be restricted by anatomical factors and special considerations may be required to avoid injury to the surrounding organs. The purpose of this review article is to discuss certain specific maneuvers and techniques that can enhance the success and safety of interventions in the hepatic dome.

Highly Articulated Robotic Needle Achieves Distributed Ablation of Liver Tissue

Robotic needle steering will improve percutaneous radio-frequency ablation (RFA) in the liver by performing distributed ablations without requiring multiple punctures of the liver capsule, thus enabling the treatment of large or multifocal tumors. However, state-of-the-art asymmetric-tip robotic needle steering systems do not yet achieve clinically relevant curvature. This work presents the design and development of a highly articulated needle that enables distributed RFA in liver tissue under ultrasound (US) image guidance. Our new needle design attains the target curvature required for liver procedures while meeting important clinical requirements, such as the use of fixed diameter needle introducers, presence of a free needle working channel, robustness for repeated insertions, and conductivity for the delivery of RF current for tissue ablation. The new needle tip includes two important design features: A tendon-actuated Nitinol asymmetric flexure joint, which allows for an active amplification of the needle steering force, and a steel back-bevel tip profile, which decreases the risk of needle jamming. The needle's resulting curvature was evaluated in both phantom and ex vivo liver tissues using segmented US images. The average radius of minimum curvature in ex vivo liver tissue was found to be 33.6 mm, the smallest reported to date. Furthermore, RFA in ex vivo porcine liver tissue tests were performed to demonstrate that distributedablation with a single puncture of the liver capsule is possible via robotic needle steering.

Ablation techniques for primary and metastatic liver tumors

Ablative treatment methods have emerged as safe and effective therapies for patients with primary and secondary liver tumors who are not surgical candidates at the time of diagnosis. This article reviews the current literature and describes the techniques, complications and results for radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation.

Unintended thermal injuries from radiofrequency ablation: organ protection with an angioplasty balloon catheter in an animal model

OBJECTIVES

The aim of this study was to investigate a novel approach of using a balloon catheter as a protective device to separate liver from the diaphragm or nearby bowel during radiofrequency ablation (RFA) of hepatic dome tumors in an animal model.

MATERIALS AND METHODS

All experimental procedures were approved by animal Institutional Review Board. Using a 3 cm RF needle electrode, 70 hepatic ablation zones were created using ultrasound in 7 pigs. 50 lesions were created using balloon interposition between liver and diaphragm; 20 lesions were created using the balloon device interposed posteriorly between liver and bowel. Additional 21 control lesions were performed. Animals were sacrificed immediately; diaphragm and bowel were then visually inspected and sectioned. Diaphragmatic and bowel injury was then classified according to the depth of thickness.

RESULTS

Control lesions caused full thickness injury, either to diaphragm or bowel. During ablation of lesions with balloon interposition, there was significantly less diaphragmatic injury, P < 0.001 and less bowel injury, P < 0.01.

CONCLUSION

Using balloon interposition as a protective device has advantages over previous saline infusion or CO2 insufflation, providing a safe way to expand percutaneous RFA of liver tumors located on the undersurface of the diaphragm. In addition, this method may be used in protection of other organs adjacent to areas being ablated.