Microwave ablation of the liver:  a description of lesion evolution over time and an investigation of the heat sink effect.
OBJECTIVE
Microwave ablation has been successfully used to treat unresectable liver tumours for many years. However, despite its widespread use, there seems to be a relative paucity of experimental data regarding lesion evolution and the effects of any surrounding vasculature on ablation morphology. The aim of this study was to investigate the principal pathological changes in the liver following microwave ablation, in particular the heat sink effect. In addition we carefully reviewed the available literature to provide an overview of all relevant pathological studies.


METHODS
Microwave ablation was carried out on male rats at various distances from the hilum. Histological (H&E) and immunocytochemical (caspase 3) analyses of the lesion were performed at various time points; 0, 4, 24, 48  hours, 2 weeks and 1 month. A literature review was carried out using Medline, Embase and the Cochrane database to identify all relevant histological studies.


RESULTS
The lesion underwent complete coagulative necrosis and was extremely regular at the ablation edge with no evidence of any influence from surrounding blood vessels at all time points. H&E and caspase 3 results were consistent and microwave caused little collateral damage outside the intended ablation zone.


CONCLUSIONS
This study suggests that microwave ablation is extremely concise and is minimally affected by the heat sink effect. Comparative investigations with other treatment modalities are required.
Department of Hepatobiliary Surgery, Leicester General Hospital, Leicester, United Kingdom. neilbhardwaj@yahoo.co.uk
N
N
Bhardwaj
J
J
Dormer
F
F
Ahmad
A D
AD
Strickland
G
G
Gravante
K
K
West
A R
AR
Dennison
D M
DM
Lloyd
D000818:Animals; D017115:Catheter Ablation / Q000379:methods*; D008099:Liver / Q000528:radiation effects* / Q000601:surgery*; D008297:Male; D008872:Microwaves / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley