Ionizing radiation (IR) therapy induces a variety of DNA lesions in cancer cells using photon beams (low-linear energy transfer (LET) radiations such as x- or γ-rays) and heavy ion particle beams (high-LET radiations such as carbon ions). It is crucial to ascertain the consequences of IR-induced DNA damage to improve treatment approaches. Especially, DNA double-strand breaks (DSBs) are considered the major cause of cellular lethality. Failure to repair DSBs can lead to deleterious consequences, such as chromatid breaks and micronuclei, which are detectable biomarkers after both low- and high-LET irradiation. The methodology outlined here offers a systematic way to detect these biomarkers postirradiation.