History, ethics, advantages and limitations of experimental models for hepatic ablation

Table 1 Advantages and limitations of ex vivo and in vivo models for experimental study of hepatic ablation

Models	Applications	Advantages	Limitations
Ex vivo (non perfused) models	Compare the efficacy of different antenna configurations	Allow histological examination of whole lesion to study zones of ablation	Non-physiological
	Trial of different energy setting	Cheap	Homogenous parenchyma
		Larger study sample size	Absence of respiratory excursion and subject motions
		Easy to manipulate during experiment	Lack of cooling effect secondary to tissue perfusion
		Does not require ethical approval/animal license	Unable to study heat sink effect
In vivo models	Study of lesion evolution over time	Small animals
	Histological examination of lesion	Easier to handle	Small animals
	Study of heat sink effect and the effect of bile duct cooling	Cheaper	Small volume of liver
	Study of systemic responses to ablation	Ability to have larger sample size	Limit number of ablation on each liver
	Study of the effect of large volume ablation (in larger animals)		Not suitable for the study of large volume ablation
		Large animals	Large animals
		Closer resemblance to human liver in terms of size and physiology	Size and temperament poses challenges during anesthesia
		More ablations can be carried out in each liver	Difficult vascular access in porcine models
			Also limited by strict ethic regulation
			Small study sample size
			Common limitations
			Expensive
			Expertise in animal handling and anesthesia is required
Isolated perfused ex vivo liver models	Study of lesion evolution over time	Cheaper than in vivo experiments	Duration of study is limited to the lifespan of the model
	Study of heat sink effect and the effect of bile duct cooling	Sophisticated and accurate manipulation of hepatic inflow (e.g., Pringle manoeuvre)	Absence of interacting organ systems which may have a role in generating systemic response
	Study of early inflammatory response	Does not require ethical approval	Unable to assess the impact of ablation on end organs
		Greater control of perfusion characteristics (e.g., portal vein and hepatic arterial flows and pressures)	Perfusion circuit itself may activate some degree of systemic response