Biological Effects of Ionizing Radiation

Citation : Arun Kanmanthareddy, Avanija Buddam, Madhu Reddy, Pramod Janga, Ajay Vallakati, Vivek Yarlagadda, Sudharani Bommana, Dhanunjaya Lakkireddy, Andrea Natale

Ionizing radiation (IR) is electromagnetic wave of high frequency and small wavelength capable of ionizing tissues and damages cells in multiple ways. Components of radiation are used for diagnostic studies such as X-rays, CT scans and fluoroscopy and therapeutically for treating malignancy. Unfortunate incidents like atomic bombing in Japan, Chernobyl nuclear leak, nuclear weapons testing sites in various countries have exposed people to radiation on a large scale. The long-term effects of IR in these population groups are still being studied. IR causes damage to the cells by producing free radicals and causes alterations in the DNA. The resulting oxidative stress causes production of cytokines, which mediate the inflammatory process. DNA alterations can result in mutated cells and neoplastic transformation. Deterministic effects occur at a particular threshold level of radiation and their severity increases with increasing dose, while stochastic effects such as malignancy may occur at a threshold dose, but the severity of effect is independent of the dose.

Acute radiation syndrome occurs when subjects are exposed to high dose radiation over a short period of time and can have devastating outcomes. Bone marrow failure occurs at doses >2Gy and gastrointestinal and neurovascular complications occurs with doses >5-10Gy. Chronic effects of radiation depend on the tissue, the dose and duration of exposure. Different tissues vary in their sensitivity to radiation; hematopoietic and reproductive systems are the most sensitive to radiation. Leukemia was the first non-acute effect observed in atom-bomb survivors, followed by solid tumors over the course of several years. Cardiovascular events such as myocardial infarction and stroke were also increased in populations exposed to radiation. Radiation therapy used in the treatment of malignancies also causes multiple adverse effects involving several organ systems. Medical radiation used for diagnostic purposes is considered safe, but repeated exposures to patients and personnel might increase the cumulative risk for adverse effects. Thus it is important to understand the harmful biological effects of radiation and every possible effort should be made to minimize radiation risk to patients and operators administering and performing these procedures.