Porcine liver: morphologic characteristics and cell viability at experimental radiofrequency ablation with internally cooled electrodes.
OBJECTIVE
To evaluate morphologic characteristics and cell viability of radiofrequency ablation zones in porcine liver.


METHODS
Approval of the study protocol was obtained from the Ethics Committee on Use of Live Animals for Teaching and Research at University of Hong Kong. Internally cooled electrodes were used to produce 120 ablated zones ex vivo and 60 ablated zones in vivo with single electrodes (1-, 2-, and 3-cm exposed lengths) or clustered electrodes (1.0-, 2.0-, and 2.5-cm exposed lengths) at 4, 8, 12, and 16 minutes of ablation (ex vivo) and 8 and 12 minutes of ablation (in vivo). Morphologic measurements of each ablated zone were performed. Cell viability in each ablated zone was assessed qualitatively with histochemical staining and quantitatively with measurement of intracellular adenosine 5'-triphosphate (ATP) concentration.


RESULTS
Exposed length of electrode (coefficient = 0.79, standard error = 0.04, P < .001), duration of ablation (coefficient = 0.14, standard error = 0.01, P < .001), and clustered electrode design (coefficient = 1.21, standard error = 0.05, P < .001) were independent factors that affected minimal transverse diameter and volume of ablated zone in ex vivo study. Similar morphologic characteristics existed among ablated zones in in vivo study. Mean distance of ablation beyond the electrode tip remained constant (ex vivo, 1.0 cm +/- 0.08 [standard deviation]; in vivo, 0.5 cm +/- 0.05) regardless of different ablation conditions. Histochemical staining revealed no viable hepatocytes from center to margins of white zone in each ablated area. Mean intracellular ATP concentration in margins of white zone (9.5 x 10(-12) mol/microg DNA +/- 1.43) was lower than that in red zone (4088 x 10(-12) mol/microg DNA +/- 65.97, P < .001) and in adjacent normal liver (4528 x 10(-12) mol/microg DNA +/- 52.74, P < .001).


CONCLUSIONS
Distance of ablation beyond the tip of the electrode remained constant (ex vivo, 1.0 cm; in vivo, 0.5 cm) with different conditions of ablation. Complete and uniform cellular destruction was achieved in the white zone of ablated area.
Ng
Kelvin K
KK
Departments of Surgery and Pathology and Centre for the Study of Liver Disease, University of Hong Kong, Queen Mary Hospital, 102 Pokfulam Road, Hong Kong, China. kcng66@yahoo.com
Lam
Chi Ming
CM
Poon
Ronnie T
RT
Shek
Tony W
TW
Yu
Wan Ching
WC
To
Jensen Y
JY
Wo
Yim Hung
YH
Lau
Cecilia P
CP
Tang
Terence C
TC
Ho
David W
DW
Fan
Sheung Tat
ST
D000255:Adenosine Triphosphate / Q000032:analysis; D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation* / Q000379:methods; D002470:Cell Survival / Q000502:physiology*; D004566:Electrodes; D004867:Equipment Design; D008099:Liver / Q000473:pathology / Q000601:surgery*; D009924:Organ Culture Techniques; D013552:Swine; D013696:Temperature; D046509:Tissue Culture Techniques; D016896:Treatment Outcome
D000255:Adenosine Triphosphate