Table 1. Geometrical and dosimetric path lengths of materials in the beam path.

Material in beam path	Protons			6 MV Photons
	Conv. factor	WEPL /mm		Conv. factor	WEPL /mm
		Plateau	Mid-SOBP
Cell phantom entrance window, 12.0 mm PMMA	1.163	13.96		1.136	13.63
Plastic bottom of 96 well plate, 1.1 mm polystyrene	1.023	1.12		1.0	1.1
Water	1.0	13.9	88.4	1.0	88.4
Embryo mediuma, 1.5 mm water	1.0	1.5		1.0	1.5
Position of zebrafish embryo in depth of water		30.5	105.0		104.6

Overview of geometrical and dosimetric parameters of the different materials in the beam path from beam entrance into the cell phantom through to the respective positions of the zebrafish embryos. The corresponding conversion factors (stopping power ratios, [21]) are given for completeness.

^aEmbryos were considered as water equivalent and positioned halfway through the 3 mm available space.