Table 2.

The relative biological effectiveness (RBE) for SPE-like protons compared with standard reference radiations (gamma or electron) in animal models

Animal	WBC	Neutrophil
Mouse	1	1
Ferret	1.16–1.6	1.9–2
Mini-Pig	2.4–4.1	2.2–5

Source: Refs.^45,56,71,72

The RBE of proton exposure varies greatly for total white blood cells (WBC) and specifically for neutrophils when comparing animal models. Note that ferret RBE values were determined 48 h after exposure; mini-pig values were determined 4 days post-irradiation