Radiation detectors are used for a variety of purposes including medical diagnoses, radioactive dating measurements, measurement of background radiation, activity level and radiation dose. Radiation passing through matter can cause severe damage. The degree and type of damage depends on several factors including the type and energy of the radiation and the properties of the medium. Radiation damage in biological organisms is primarily due to ionization effects in cells. The normal operation of the cell may be disrupted when highly reactive ions or radicals, thought to lead to cancers, are formed as the result of ionizing radiation. Radiation detectors can be used to monitor area or personal exposure.