Fundamentals of microwave physics: application to hepatic ablation

Vessel-Sealing Capability of Novel Microwave Sealer: Experimental Study in Animal Models

Background. Ultrasonically activated dissectors (UADs) and radiofrequency-based devices have been considered excellent surgical devices because of their reliability and flexibility. Meanwhile, microwave-based devices have demonstrated potential with their unique heating mechanism. This study aims to compare the sealing function of a newly invented forceps-like microwave sealer (MS) with that of currently available UADs. Materials and Methods. MS and 2 examples of UADs (Harmonic Focus+ [HF+] and Sonicision [SNC]) were employed to perform mesenterectomies (in vivo) and sealing sizable vessels (ex vivo). Vessel diameter, seal time, burst pressure (BP), sealing completion, and instrument sticking were recorded. The samples underwent histological investigation for thermal damage evaluation. Results. During mesenterectomies, MS required 3 seconds and 30 W to secure a complete seal. The BP achieved by the MS seal was higher than that of HF+ and SNC on arteries (851 ± 203.7 vs 682.4 ± 287.3, P < .05; vs 833.1 ± 251.2 mmHg, P = .4523, respectively) but was not statistically different on veins (324.9 ± 203.5 vs 460.1 ± 320.3 vs 508.3 ± 350.7 mmHg, P = .215). In all trials, MS caused less sticking but exhibited similar heat-induced alterations to UADs. MS's thermal spread was not statistically more extended than that of UADs on either arteries or veins. Conclusions. MS was capable of not only sealing tiny vessels but also achieving high-pressure endurance on sizable vessels. Its forceful grasping and synchronous heating process helped create solid stumps with an acceptable thermal spread.

Efficacy of a Laparoscopic Saline-Coupled Bipolar Sealer in Minimally Invasive Hepatobiliary Surgery

Hepatic resection presents unique surgical challenges to reduce blood loss during parenchymal division. The development of saline-coupled bipolar devices, in which hemostasis is achieved at lower temperatures than electrocautery or other bipolar sealing devices, have been employed for open hepatic resection. Saline-coupled bipolar devices have now become available for minimally invasive use. The goals of this study were to evaluate the feasibility and safety of a laparoscopic saline-coupled bipolar device for minimally invasive hepatectomy. Seventeen patients (median age 66 years, range 36-81) were consented for inclusion and enrolled. Patient demographics, intraoperative data, and surgeon feedback were collected. Seven robot-assisted partial hepatectomies, 9 laparoscopic partial hepatectomies, and 1 laparoscopic cholecystectomy with liver abscess resection were performed. Average operating time was 222 ± 33 minutes (median 188 minutes; range 61-564 minutes) with no difference between robotic versus laparoscopic time. Successful seals were achieved in all cases following application of 150 to 200 J energy (average 179 ± 3 J, average time to achieve a successful seal 9.3 ± 2.7 minutes). Estimated blood loss was 362 ± 74 mL (median 300 mL, range 5-1200 mL) and 3/17 patients received intraoperative blood transfusion. No bile leaks were detected in any of the patients. Median length of stay was 5 days (range 1-20 days), and there were no readmissions within 30 days. Postoperative morbidity occurred in 5/17 patients, all of which were Clavien Grade 1. There was no mortality within 90 days or complications requiring a return to the operating room, and there were no liver-specific morbidities. These data suggest the laparoscopic Aquamantys device represents a useful device for use in minimally invasive liver resection.

The invention of microwave surgical scissors for seamless coagulation and cutting

PURPOSE

We developed a microwave energy-based scissors device (MWCX) that is capable of performing cutting and coagulation using 2.45 GHz microwave energy. This paper aims to present the concept of the device and assess the basic functions including the hemostasis, cutting, and sealing abilities.

METHODS

Seven beagle dogs were used in our experiments. In six dogs, we measured the coagulation time (CT), lateral thermal injury (LTI), bursting pressure (BP). The dogs were then subjected to re-laparotomy 1 week later to allow us to investigate the results. In one dog, the same factors and the quantities of smoke and mist emitted were compared to those observed when using a Harmonic Focus (HF) device.

RESULTS

At 60 W, the MWCX could cut and seal small (5 s, diameter 1-2 mm) and medium-sized (10 s, 3-4 mm) vessels with complete hemostasis. The liver (length 2 cm) was cut for 30 s. Harvested vessels were sealed for 10 s (artery, 17 times; vein, six times). The mean BP was 887. 8 ± 41.5 mmHg in the medium arteries and 457.2 ± 118.0 mmHg in veins, with a mean diameter of 4.5 ± 1.3 mm. In a comparative study, the MWCX showed similar results to the HF with regard to the CT, BP and LTI, and emitted less smoke and mist.

CONCLUSION

The MWCX showed similar levels of functionality and safety to HF, as well as the advantages offered by the use of microwave energy. Microwave devices might be used in the majority of applications for which traditional energy devices are used.

Ablation therapy for hepatocellular carcinoma: past, present and future perspectives

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death worldwide, and is most commonly found in the setting of liver cirrhosis. Treatment of HCC must consider both the tumors present, as well as the remaining dysfunctional liver that both hinders treatment and can produce additional HCC over time. Ablation is an evolving part of the multimodality treatment approach to HCC that can effectively destroy tumors while preserving surrounding liver parenchyma. New technologies have made ablation an indispensable tool in the treatment of all stages of HCC. This review presents the history, present technologies and future potential of ablation in the treatment of HCC.