title: Microwave ablation of ex vivo human liver and colorectal liver metastases with a novel 14.5 GHz generator.
abstract: OBJECTIVE
  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.
  
  
  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.
authors.affiliation: Centre for Drug Safety Science, Department of Pharmacology, University of Liverpool, UK. robjones@liv.ac.uk
authors.forename: Robert P
authors.initials: RP
authors.lastname: Jones
authors.forename: Neil R
authors.initials: NR
authors.lastname: Kitteringham
authors.forename: Monica
authors.initials: M
authors.lastname: Terlizzo
authors.forename: Christopher
authors.initials: C
authors.lastname: Hancock
authors.forename: Declan
authors.initials: D
authors.lastname: Dunne
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Fenwick
authors.forename: Graeme J
authors.initials: GJ
authors.lastname: Poston
authors.forename: Paula
authors.initials: P
authors.lastname: Ghaneh
authors.forename: Hassan Z
authors.initials: HZ
authors.lastname: Malik
mesh_terms: D055011:Ablation Techniques; D000368:Aged; D015179:Colorectal Neoplasms / Q000473:pathology; D005260:Female; D006801:Humans; D008099:Liver / Q000473:pathology / Q000601:surgery*; D008113:Liver Neoplasms / Q000556:secondary / Q000601:surgery*; D008297:Male; D008872:Microwaves / Q000627:therapeutic use*; D008875:Middle Aged