Christopher Paul Hancock

Microwave ablation of ex vivo human liver and colorectal liver metastases with a novel 14.5 GHz generator

Purpose: This study assessed the relationship between time, power and ablation size using a novel high-frequency 14.5 GHz microwave applicator in ex vivo human hepatic parenchyma and colorectal liver metastases. Previous examination has demonstrated structurally normal but non-viable cells within the ablation zone. This study aimed to further investigate how ablation affects these cells, and to confirm non-viability. Materials and methods: Ablations were performed in ex vivo human hepatic parenchyma and tumour for a variety of time (10–180 s) and power (10–50 W) settings. Histological examination was performed to assess cellular anatomy, whilst enzyme histochemistry was used to confirm cellular non-viability. Transmission electron microscopy was used to investigate the subcellular structural effects of ablation within these fixed cells. Preliminary proteomic analysis was also performed to explore the mechanism of microwave cell death. Results: Increasing time and power settings led to a predictable and reproducible increase in size of ablation. At 50 W and 180 s application, a maximum ablation diameter of 38.8 mm (±1.3) was produced. Ablations were produced rapidly, and at all time and power settings ablations remained spherical (longest:shortest diameter <1.2). Routine histological analysis using haematoxylin-eosin (H&E) confirmed well preserved cellular anatomy despite ablation. Transmission electron microscopy demonstrated marked subcellular damage. Enzyme histochemistry showed complete absence of viability in ablated tissue. Conclusions: Large spherical ablation zones can be rapidly and reproducibly achieved in ex vivo human hepatic parenchyma and colorectal liver metastases using a 14.5 GHz microwave generator. Despite well preserved cellular appearance, ablated tissue is non-viable.

A non-invasive monitoring system

This paper describes a preliminary study carried out using microwave resonant cavities to measure variations in blood-glucose concentrations by observing changes in Q and frequency shifts in a minima occurring in the magnitude response due to variations in the complex permittivity of the blood-glucose mixture. The measurement system presented in this work makes use of low power microwave energy over the frequency range of between 10GHz and 20GHz and resonant cavity structures. One potential future application for this work is to non-invasively monitor variations in concentrations of various constituents contained within biological fluid contained within the human biological system. The measurement data presented here was obtained using laboratory test and measurement equipment, test cells developed specifically for this study, and representative blood-glucose concentrations. The results obtained from this study indicate a variation in blood-glucose concentration representative of the normal and hyperglycaemic states causes a marked shift in the resonant frequency and the Q of the system.

A New Wave in Electrosurgery : A Review of Existing and Introduction to New Radio-Frequency and Microwave Therapeutic Systems

A review of experimentally and commercially available therapeutic systems that use radio-frequency (RF) and microwave energy is provided in the first part of this article. The second part considers new advanced electrosurgical systems that combine the advantages associated with the use of low-frequency RF energy and high-frequency microwave energy to enhance the overall clinical effect and discusses how the frequency of operation and the design of the antenna structure can be optimized to ensure the desired tissue effects are achieved. Consideration is also given to how the latest developments in high-frequency semiconductor power technology developed for the communications sector are enabling new microwave and millimeter-wave energy-based electrosurgical systems to be developed and commercialized at an affordable cost.

A novel multimodality endoscopic device for colonic submucosal dissection using a combination of bipolar radiofrequency and microwave modalities.

BACKGROUND AND STUDY AIMS Current submucosal dissection devices are technically challenging to use, resulting in long and sometimes incomplete colonic polyp resections. The aim of this feasibility preclinical study was to evaluate a new, multimodality instrument with novel electrocautery properties. METHODS Six female adult pigs underwent colonic submucosal resections. The novel device was used to cut mucosa and submucosa using bipolar radiofrequency (BRF; at 400 KHz), provide hemostasis with microwave coagulation (MWC; at 5.8 GHz), and inject fluid via a retractable needle. The main outcomes measured were safety (histological analysis post-recovery), performance, and time needed to achieve complete resection. RESULTS A total of 12 consecutive colonic pseudopolyps were completely excised (two per subject) using BRF cutting. The median time to complete resection was 44.3 minutes (SD 8.9). The median defect size was 32.8 mm (SD 4.3). MWC was applied on 37 occasions for pre-coagulation or treatment of bleeding vessels. One microperforation was treated successfully with endoscopic clips. All animals recovered uneventfully during the 28-day survival period. Histology confirmed adequate healing in all postmortem defects. CONCLUSIONS In this preclinical evaluation, the novel multimodality endoscopic device facilitated rapid and safe en bloc resection of colonic pseudopolyps.

14.5GHz energy for dermatological applications - initial in-vivo data with histology

This paper presents the first use of Ku band energy at the spot frequency of 14.5GHz for the treatment of a range of dermatological conditions. Initial in-vivo and ex-vivo results are presented, together with histology and data analysis. The outcome from this work indicates that 14.5GHz energy has a strong potential for future use in treating a number of dermatological conditions, where control of depth in the millimeter range, and uniformity over the area of the heating profile, are of paramount importance.