Long-term health hazards from diagnostic X-ray exposure

Sammanfattning: Medical imaging is an important function in the diagnosis and management of disease and its use have been increasing with technological advancements. A large part of medical imaging uses ionizing radiation as medium for imaging although it does pose potential risks to the patient. Computed Tomography (CT) uses a larger radiation dose than conventional X-rays and technological advances has led to more complex examinations increasing radiation doses even higher. The increased availability of CT machines has also facilitated the increased usage. This means that the population as a whole receives an increasing radiation dose and CT is now the most important contributor to radiation dose from medical examinations. The potential damage from ionizing radiation concerns long-term risks and includes cancer but other effects are known and includes cognitive difficulties amongst children. In study I we investigated the relationship between pelvimetry and negative effects from ionizing radiation on cognitive function expressed as changes in school grades. We examined 1 536 children exposed to pelvimetry in utero and compared them to 44 530 unexposed children. We found no negative effect on school grades when controlling for sex, birth order, mother’s education and birth position. In study II and III we examined the risk of ionizing radiation from CT of the head. We gathered data from a radiological archive in Sweden and collected 26 370 patients. Patients were then matched on age, sex and residence to 4 controls, both cohorts were then linked to national registries in order to gather outcome data. The outcome in study II was meningioma and in study III glioma. We found no evidence of increased risk for neither meningioma nor glioma after CT examinations. However, information in national registries were not enough for exclusion of prevalent tumor at time of first CT or radiotherapy, referral notes were necessary in order to minimize bias. Study IV is a method article and is a description of the international EPI-CT study that aims to investigate children who have had a CT examination. As part of EPI-CT we have collected RIS and PACS data from hospitals in order to assemble the Swedish cohort. This data will then be linked to national registries in order to investigate adverse effects from CT examinations. In conclusion we have not found any negative result on school performance after pelvimetry nor have we found any increased risk for meningioma or glial tumors after CT examination of the head.