A method for assessing the radiation risk of medical exposure after computed tomography scan of children and adolescents based on data from scanning protocols

Computed tomography (CT) scan is a fairly accurate and reliable method for diagnosing various diseases, however, based on irradiation of the patient with ionizing radiation, it can lead to an excess risk of developing malignant neoplasms. According to the safety standards of the International Atomic Energy Agency, no patient can be exposed to medical radiation unless he or she has been informed of the risks associated with radiation exposure. This requirement is also contained in the Russian Radiation Safety Standards (NRB-99/2009). Radiation risk is estimated on the basis of calculated values of equivalent doses in the patient's organs and tissues using radiation risk models of the International Commission on Radiological Protection. This article is devoted to the improvement of the method for calculating equivalent doses in the organs and tissues of patients with computed tomography scan for further assessment of radiation risks. For 15 modern computed tomography scanners, with different geometry of patient scanning, the data necessary for calculating the equivalent doses in organs and tissues based on the parameters of the children's phantom were updated. The coefficients of conversion of the surrogate measure of the patient's radiation dose for the entire CT scan study, namely, the value of the "Dose Length Product" (DLP), into the values of equivalent doses in individual organs and tissues exposed to radiation were determined. The results of the calculation are given for five typical scan areas: chest, abdomen, pelvis, head and neck. In the course of simulation numerical modeling, organs and tissues with the highest equivalent doses were determined during CT scan examinations of children and adolescents. Unlike adult patients, for children and adolescents, the dose load on the surface of the bone is significantly lower and does not stand out in any of the considered types of CT scan examinations. It should be noted that with CT scan of the cervical spine, due to the specifics of the geometry of scanning new types of tomography scanners, the dose load on the thyroid gland of boys increased. The dose conversion factors obtained in this paper with estimates of standard deviations make it possible to assess the radiation risks of children and adolescents during examinations on modern CT scanners and optimize their dose loads.