Institute for Radiological Protection and Nuclear Safety (IRSN) 1 article published in JoVE Biology Dosimetry for Cell Irradiation using Orthovoltage (40-300 kV) X-Ray Facilities Morgane Dos Santos1, Vincent Paget2, François Trompier3, Gaëtan Gruel1, Fabien Milliat2 1Department of RAdiobiology and Regenerative MEDicine (SERAMED), Laboratory of Radiobiology of Accidental Exposures (LRAcc), Institute for Radiological Protection and Nuclear Safety (IRSN), 2Department of RAdiobiology and Regenerative MEDicine (SERAMED), Laboratory of MEDical Radiobialogy (LRMed), Institute for Radiological Protection and Nuclear Safety (IRSN), 3Department of DOSimetry (SDOS), Ionizing Radiation Dosimetry Laboratory (LDRI), Institute for Radiological Protection and Nuclear Safety (IRSN) This document describes a new dosimetry protocol for cell irradiations using low energy X-ray equipment. Measurements are performed in conditions simulating real cell irradiation conditions as much as possible.