Adjunctive Thermoprotection During Percutaneous Thermal Ablation Procedures: Review of Current Techniques

Hydrodissection of the Retro-Sternal Space to Protect the Pericardium During Sternal Cryoablation

PURPOSE

To report the retro-sternal space hydrodissection technique used to displace the heart and the pericardium posteriorly for thermoprotection ahead of sternal cryoablation (CA).

METHODS AND MATERIALS

Between May 2015 and March 2020, hydrodissection of the retro-sternal space was performed in 5 consecutive patients (5 female; mean age 55.2 ± 9.3 years, range 41-65) who underwent percutaneous image-guided cryoablation of the sternum. The number of needles required, the implemented approach, volume of injectate to achieve hydrodissection, hydrodissection procedure time, distance between the lesion and the pericardium before and after hydrodissection, distance between the ice-ball and the pericardium, technical success and complications were retrospectively assessed.

RESULTS

Technical success, defined as the completion of a full dual freeze protocol without contact between the ice-ball and the pericardium, was achieved in all cases (5/5, 100%). One to two needles were used to perform hydrodissection via a perpendicular (3/5) or an anterior oblique approach (2/5) and a mean hydrodissection procedure time of 10.4 ± 2.6 min (range 8-14). Minimum distance between the lesion and the pericardium increased from mean 5.8 ± 3.8 mm (range 0-10) before hydrodissection to a mean 22.2 ± 5.8 mm (range 18-32) after, with a mean distance between the final ice-ball and the pericardium of 11.6 ± 8.7 mm (range 7-27). A mean of 198 ± 79.8 mL (range 90-290) of iodinated contrast was injected. There were no immediate, short- or medium-term complication noted.

CONCLUSION

Hydrodissection of the retro-sternal space is a feasible technique for sternal cryoablation in order to protect the pericardium from freezing for sternal cryoablation.

Image-Guided Thermal Ablation for Colorectal Liver Metastases

Image-guided percutaneous thermal ablation is a widely acceptable local therapy for patients with colorectal liver metastases who are noneligible for surgery or present with recurrence after hepatectomy. The increasing knowledge of factors that affect oncologic outcomes has allowed selected patients with resectable small volume colorectal liver metastases to be treated by thermal ablation with curative intent. The continuous technological evolutions in imaging and image-guidance and the wide implementation of microwave ablation that overcomes most of the limitations of radiofrequency ablation have contributed to this paradigm shift. The importance of patient selection, ablation margin evaluation, and confirmation of complete tumor ablation (A0) are discussed in this article.

Trends in Musculoskeletal Ablation: Emerging Indications and Techniques

Image-guided percutaneous thermal ablation plays an increasingly important role in the multidisciplinary management of musculoskeletal lesions. Established indications for ablation in this setting include the treatment of osteoid osteomas, palliation of painful skeletal metastases, local control of oligometastatic disease, and consolidation of bone tumors at risk for fracture. Emerging indications include the treatment of symptomatic soft tissue masses such as extra-abdominal desmoid tumors and abdominal wall endometriosis. This review will discuss considerations in patient selection and preprocedural workup, ablation technology and techniques, strategies to avoid complications, and expected outcomes of ablation in the musculoskeletal system.

CIRSE Standards of Practice on Thermal Ablation of Liver Tumours

This CIRSE Standards of Practice document reviews current literature and provides best practices for image guided thermal ablation of liver tumours, including radiofrequency, microwave and cryoablation techniques.

Performance of a New Blunt-Tip Needle for the Displacement of Critical Structure in Thermal Ablation

PURPOSE

To ascertain the performance of a new blunt-tip needle (HydroGuard^®), which allows injection of fluids during needle advancement in order to safely approach, displace and insulate nearby critical structures during thermal ablation (TA).

MATERIALS AND METHODS

This study included 27 consecutive patients treated by TA [cryoablation (CA), radiofrequency (RFA), and microwave MWA)] between April 2018 and January 2019. During TA, hydro- or gas dissection was performed with HydroGuard^® needle to displace and protect critical structures close to the tumor (< 10 mm). Technical and clinical success, distance between critical structure and tumor before and after hydro/gas dissection and complications were recorded.

RESULTS

Eighteen patients were treated by CA (66.7%), 7 by MWA (25.9%) and 2 by RFA (7.4%). Majority of patients were treated with a curative intent (24/27; 88.8%). Adjacent critical structures include vessels (n = 3), nerves (n = 10), ureter/renal pelvis (n = 3), bowel/rectum (n = 10), stomach: (n = 3), diaphragm (n = 2), and pleura (n = 1). Technical success was 100%. Clinical success was 88% (24/27). Median minimum distance to adjacent critical structures before hydro/gas dissection was 1 mm (range 0-9 mm; IQR: 0-3 mm) versus 10.5 mm (range 4-47 mm; IQR: 9.7-18 mm) after displacement. Of the 27 patients treated, four developed complications (14.8%; 95% CI: 1.4-28.2): 1 major (3.7%; 95% CI: 0-10.8) and 3 minors (11.1%; 95% CI: 0-23). Only one minor complication was related to inadequate hydro-dissection, resulting in close proximity of the critical structure to the ablation zone.

CONCLUSION

HydroGuard^® is a safe and effective needle when used to approach, displace and insulate nearby critical structures during TA.

Percutaneous MR-Guided Cryoablation of Low-Flow Vascular Malformation: Technical Feasibility, Safety and Clinical Efficacy

PURPOSE

To retrospectively assess the technical feasibility, safety and clinical efficacy of percutaneous MR-guided cryoablation of low-flow vascular malformations (LFVM).

MATERIALS AND METHODS

Between July 2013 and May 2019, 9 consecutive patients (5 male; 4 female; mean age 39.4 ± 15.3 years, range 15-68) underwent MR-guided cryoablation of LFVM. Patients were treated due to pain in all cases. Procedural data, complications and clinical results were analyzed.

RESULTS

Technical success defined as complete coverage of the LFVM by the iceball without involvement of nearby non-target thermal-sensitive structures was achieved in 9/9 (100%) cases. Mean procedure time was 122 ± 20 min (range 90-150); 2-6 cryoprobes (mean 3.7 ± 1.2) and 2-4 freezing cycles (mean freezing time 19.8 ± 11.8 min; range 4-40) were applied. No complications were noted. Mean time from the first treatment to the last follow-up was 548 days (range 30-1776). Persistent/recurring pain was noted in 3/9 cases (33%) 30, 133 and 639 days after cryoablation, respectively, and was related in all cases to MR-confirmed local residual/recurring disease. A second cryoablation treatment was performed in these 3 cases with complete pain control at the last available follow-up (153, 25, 91 days, respectively). In the whole population, at mean 161 days (range 25-413) after the last treatment, on the numerical pain rate scale, pain significantly dropped from mean 6.4 ± 2.1 (range 3-9/10) before CA to mean 0.3 ± 0.9 (range 0-3/10) after (p = 0.009).

CONCLUSIONS

Percutaneous MR-guided cryoablation is technically feasible, safe and effective for the treatment of symptomatic LFVM.

LEVEL OF EVIDENCE

Level 3b, retrospective cohort study.

Directional Microwave Ablation: Experimental Evaluation of a 2.45-GHz Applicator in Ex Vivo and In Vivo Liver

PURPOSE

To experimentally characterize a microwave (MW) ablation applicator designed to produce directional ablation zones.

MATERIALS AND METHODS

Using a 14-gauge, 2.45-GHz side-firing MW ablation applicator, 36 ex vivo bovine liver ablations were performed. Ablations were performed at 60 W, 80 W, and 100 W for 3, 5, and 10 minutes (n = 4 per combination). Ablation zone forward and backward depth and width were measured and directivity was calculated as the ratio of forward to backward depth. Thirteen in vivo ablations were performed in 2 domestic swine with the applicator either inserted into the liver (80 W, 5 min, n = 3; 100 W, 5 min, n = 3; 100 W, 10 min, n = 2) or placed on the surface of the liver with a nontarget tissue placed on the back side of the applicator (80 W, 5 min, n = 5). The animals were immediately euthanized after the procedure; the livers were harvested and sectioned perpendicular to the axis of the applicator. In vivo ablation zones were measured following viability staining and assessed on histopathology.

RESULTS

Mean ex vivo ablation forward depth was 8.3-15.5 mm. No backward heating was observed at 60 W, 3-5 minutes; directivity was 4.7-11.0 for the other power and time combinations. In vivo ablation forward depth was 10.3-11.5 mm, and directivity was 11.5-16.1. No visible or microscopic thermal damage to nontarget tissues in direct contact with the back side of the applicator was observed.

CONCLUSIONS

The side-firing MW ablation applicator can create directional ablation zones in ex vivo and in vivo tissues.

Risk factors of intrahepatic biloma and secondary infection after thermal ablation for malignant hepatic tumors

Objective: This study aimed to evaluate the risk factors of biloma formation and secondary infection after thermal ablation for malignant hepatic tumors. Patients and methods: A total of 58 patients with 68 bilomas after thermal ablation were recruited as the complication group, and 61 patients with 72 lesions without major complications were selected randomly as the control group. The potential risk factors for biloma formation were analyzed with the chi-square test and multivariate logistic regression analysis. To determine the optimum management method for biloma, patients with secondary infection were included for the subgroup analysis of risk factors. Results: A history of transcatheter arterial chemoembolization (TACE) treatment (odds ratio [OR]: 3.606, 95% confidence interval [CI]: 1.165-11.156, p = .026) and tumor location (OR: 37.734, 95% CI: 13.058-109.034, p = .000) were independent predictors of biloma formation. Among the 58 patients with biloma, 49 (84.5%) showed no symptoms (i.e., the asymptomatic group), while the remaining 9 (15.5%) developed symptoms related to secondary infections (i.e., the symptomatic group). There were significant differences in the history of biliary manipulation (p = .031) between the symptomatic and asymptomatic groups. Conclusion: A history of TACE treatment and the distance from the biliary tract were independent predictors of biloma formation after thermal ablation. Therefore, protecting the bile duct (i.e., cooling of the bile duct and combing thermal ablation with chemical ablation) should be considered for high-risk patients. Moreover, active monitoring and management should be performed for patients with bilomas who underwent biliary surgery before.

Cryoablation of Lung Metastases: Review of Recent Literature and Ablation Technique

This article reviews the current indications for image-guided thermal ablation of pulmonary metastatic disease. It also summarizes data regarding the efficacy and complications of lung cryoablation and present techniques for performing lung cryoablation as informed by the recent literature.

Large nearly spherical ablation zones are achieved with simultaneous multi-antenna microwave ablation applied to treat liver tumours

AIM

To investigate the shape and the volume of ablation zones obtained with microwave ablation (MWA) performed with multiple antennas in liver tumours.

MATERIALS AND METHODS

Tumour volume, number of antennas, size (long diameter (Dl), along the antenna axis; short diameter (Ds), perpendicular to the antenna axis; vertical diameter (Dv), vertical to both Dl and Ds) and shape (roundness index (RI); 1 corresponds to a sphere) of the ablation zone, ablation volume, and complications were evaluated.

RESULTS

Mean Dl, Ds, and Dv were 4.7 ± 1.4 cm, 3.9 ± 1.4 cm, and 3.8 ± 1.0 cm, respectively. Mean RIs (Ds/Dl, Dv/Dl, and Dv/Ds) were 0.83 ± 0.13, 0.83 ± 0.17, and 1.02 ± 0.23, respectively, without any difference between the mean RI obtained with the double (0.84 ± 0.01) and that with the triple-antenna (0.93 ± 0.13) approach (p = 0.25). Mean ablation volume was 41 ± 32 cm³ (vs. mean tumour volume 13 ± 10 cm³; range 1-40; p < 0.001). No complications were noted.

CONCLUSIONS

Simultaneous multi-antenna MWA of liver tumours results in large nearly spherical ablation zones.

KEY POINTS

• Simultaneous multi-antenna microwave ablation of liver tumours results in nearly spherical ablation zones. • The multi-antenna approach generates oversized ablation volumes compared with the target tumour volume. • The multi-antenna approach is safe.

Percutaneous image-guided ablation: From techniques to treatments

Image-guided ablation is performed by percutaneously introducing ablation probes to deliver energy into a tumor to destroy it in a controlled and localized fashion. Ablation modalities can be broadly classified as thermal or non-thermal based on the mechanism of tumor destruction and are performed using different types of image guidance for planning, delivering and follow-up of the treatment. Ablation is performed in a minimally invasive fashion, providing greater residual organ preservation with minimal morbidity to the patient. Image-guided ablation is being used in the clinic for the treatment of primary and metastatic tumors, and this article reviews state of the art for the treatment of malignancies in the liver, lung, kidney and musculoskeletal tissue.

Videolaparoscopic microwave ablation in patients with HCC at a European high-volume center: Results of 815 procedures

BACKGROUND

Videolaparoscopic (VL) microwave ablation (MWA) is not included in most of the international guidelines as a therapeutic option for hepatocellular carcinoma (HCC). Aim of this study was to assess the safety of VL MWA in patients with HCC for whom resection or percutaneous ablation is unsuitable.

METHODS

A retrospective analysis was performed on a prospective database of patients with HCC treated with VL MWA at our institution from 2009 to 2016. Patient demographics, operational characteristics, and complications were recorded. Statistical analysis was performed to identify safety profile, overall survival and recurrence rate.

RESULTS

A total of 815 VL MWA were performed in 674 patients with a mean age of 64 years. Patients had a mean Model for End-stage Liver Disease score of 10 (±3); 32.8% were Child B, 44.1% Barcelona Clinic Liver Cancer B-C. Perioperative mortality was 0.4%. Overall morbidity was 30.8%, with Dindo-Clavien complications ≥3 in 2%. The median length of stay was 2 days. In 43.1% VL MWA was the first-line therapy. Overall 1-, 3-, and 5-year survival rates were 81.9%, 54.9%, and 35.9%.

CONCLUSIONS

The present is the largest series of VL ablation and the bigger number of patients with HCC treated with MW reported nowadays. It confirms the safety of a minimally invasive procedure for patients with HCC when resection or percutaneous ablation is not feasible.

Protection from injury of organs adjacent to a renal tumor during percutaneous cryoablation

Renal cryoablation has become accepted as treatment for small renal tumors as an alternative to surgery. However, parallel with the increase in the use of this therapy, there also has been increases in the number of reports of complications related to renal cryoablation. One potential complication is injury to important non-renal structures adjacent to the ablated renal tumor, such as the colon, duodenum, ureter, psoas muscle and so on. To prevent injury of adjacent organs, separating organs from the tumor is desirable. Over the past 15 years, several techniques have been developed to protect against injury of organs adjacent to renal tumors that are targets of cryoablation. The most commonly used technique for this purpose has been hydrodissection. Others include dissection with gas, balloon dissection and probe traction. To avoid injury of a ureter running near the renal tumor, pyeloperfusion is known to be useful. The rate of cases necessitating avoidance of organ injury by using these techniques is relatively high. In some cases, more than two techniques are combined. In the present review, we provided an overview of techniques currently available to protect against organ injuries, and discussed the advantages and disadvantages of each technique.

Hydrodissection of the Retrohepatic Space: A Technique to Physically Separate a Liver Tumour from the Inferior Vena Cava and the Ostia of the Hepatic Veins

OBJECTIVE

To report a technique of percutaneous retrohepatic hydrodissection, highlighting its potential to physically separate liver tumours from the inferior vena cava (IVC) and the ostia of the hepatic veins (HV).

MATERIALS AND METHODS

Between December 2017 and April 2018, hydrodissection of the retrohepatic IVC was performed in 5 patients (5 females; mean age 64.5 years) undergoing percutaneous ablation of 5 liver metastases (mean size: 3.6 cm) located adjacent to the IVC. Number of hydrodissection needles, volume of hydrodissection, separation of tumour/liver parenchyma from IVC/HV post-hydrodissection; technical success of ablation; and complications were tabulated.

RESULTS

Two to three 22G spinal needles were required per case for adequate dissection. Mean volume to obtain sufficient hydrodissection was 410 ml on average. Physical separation of the IVC and tumour/hepatic parenchyma was successful in all cases, by 9 mm on average (range 5-12 mm). It also leaded to physical separation of the ostia of the right and middle HV in all cases. There was no early or delayed complication, notably no venous thrombosis in the post-operative period. All lesions but one were completely ablated after one session at 3-month follow-up. The patient with residual tumour was successfully retreated.

CONCLUSION

Retrohepatic hydrodissection is a feasible technique to separate a tumour from the IVC and/or ostia of the HV. This could potentially limit the heat-sink effect/reduce the risk of thrombosis. Larger follow-up studies are required to assess efficacy on a long-term basis.