During lateral cephalometric radiography, the whole brain and cervical spine may become irradiated, depending on the size of the X-ray beam ( 2 ), and exposure of salivary glands and oral mucosa cannot be avoided. The thyroid gland may also become partly exposed if the beam area is not restricted to the level of inferior mandibular border. This has rightly placed them under special protection in radiation protection legislation ( 1, 2 ).ĭuring dental panoramic tomography, the X-ray beam passes through salivary glands, oral mucosa, and part of orbits ( 8 ). It is believed that children are at particular risk from these unintended effects of radiographic examination due to their increased rate of cellular division and by having a long remaining lifespan. Dental radiography has been indicated as a risk factor for cancer of salivary gland and even for intracranial tumours ( 6, 7 ). This highlights the risk posed to the individual due to routine intra-oral and extra-oral radiographic examination ( 1, 5 ). In 2007, tissue weighting factors were also introduced for the brain, salivary glands, and the oral mucosa. Tissue weighting factors have been given for these sensitive areas of the body. Irradiation of the eyes even at low doses results in an elevated risk of cataract formation ( 4 ). Its irradiation leads to an increased risk of hypothyroidism, thyroid nodules, and thyroid cancer, particularly in children ( 3 ). Lead shields are used to protect particularly sensitive organs such as the thyroid gland.
Radiographic examinations can be optimized by adjustment of image field-size, exposure parameters, and filtration, and by use of protective lead aprons ( 2 ). The organ-specific sensitivity is expressed by tissue weighting factor ( 1 ). It takes into account not only the absorbed energy, but also the specific radio-sensitivity of the different organs situated in the irradiated field. Effective dose is a dose quantity that represents the probability of stochastic health risk, cancer or genetic effects, of ionizing radiation. It means that the radiation dose should be kept as low as reasonably achievable (‘ALARA’) while still being adequate for diagnostic image quality. Optimization forms one of the three fundamental and universally accepted principles of radiation protection.