A cartridge, medical apparatus and method are disclosed. The cartridge and a holding element are for operable connection with each other to form a phototherapy apparatus. The cartridge includes a radiation source for emitting radiation towards an area to be treated of a user； a mount element for positioning the radiation source in a predetermined position relative to the area to be treated； wherein the mount element comprises a locating portion configured for locating the cartridge at a predetermined position with respect to a body portion of the user.
