This study was aimed at the estimation of the effective doses and radiation risks from dental X-ray examinations based on the data collection in St. Petersburg and the Leningrad Region. The range of mean values of effective doses for intraoral examinations on the X-ray units with film detectors was from 3.5 to 8.2 μSv and for the units with digital detectors—from 1.2 to 2.5 μSv. The mean effective doses for panoramic examinations were 22.9 μSv and for cone-beam computed tomography (CBCT)—530.6 μSv, respectively. The highest detriment-adjusted lifetime risk values were estimated for the 20–24-year-old age group: 40.8 × 10−6 in females and 32.7 × 10−6 in males for CBCT. Effective doses in St. Petersburg and Leningrad region were comparable or higher compared with the published data.

Purpose: To evaluate the impact of CT scan protocol parameters on patient dose and image quality for optimization of protocols for newborn patients. Materials and methods: Three anatomical areas (chest, abdomen and combined chest + abdomen area) of a newborn PH-50 Newborn Whole-Body Phantom (Kyoto Kagaku Co, LTD, Japan) were scanned on Ingenuity 128 CT scanner (Philips) using different scan parameters. The values of weighted CT dose index (CTDIvol) and dose length product (DLP) were used as dose characteristics and the noise of CT image was chosen to estimate the image quality. The noise was determined in the soft tissues in the areas of shoulder girdle and diaphragm in images with the reconstruction kernel B, as well as in lung tissue of lung apices for images with the reconstruction kernel YC for chest and chest + abdomen; and in soft tissues (for reconstruction kernel B) in the area of the diaphragm for abdomen. Results: The analysis of the impact of tube voltage and dose right index (DRI) on dose characteristics and image quality made it possible to determine the optimal parameters of CT protocols for selected CT department: chest – 80 kV at DRI -– 19, abdomen – 100 kV at DRI – 22, chest + abdomen – 120 kV at DRI – 22. These protocol parameters provide an effective dose of newborn patients – 1.4, 1.7 and 2,8 mSv for chest, abdomen and chest + abdomen scans, respectively. Conclusion: The impact of different scan parameters (tube voltage and DRI) of chest, abdomen and chest + abdomen protocols on patient dose and image noise was evaluated. The study allowed setting optimized protocol parameters to improve the image quality.

An important part of the justification process is assessment of the radiation risks caused by exposure of a patient during examination. The authors developed official national methodology both for medical doctors and sanitary inspectors called 'assessment of radiation risks of patients undergoing diagnostic examinations with the use of ionizing radiation'. The document addresses patients of various age groups and a wide spectrum of modern X-ray and nuclear medicine examinations. International scale of risk categorisation was implemented by the use of effective dose with account for age dependence of radiation risk. The survey of effective doses in radiology, including CT, mammography, and intervention radiology, and nuclear medicine, including singlephoton emission tomography and positron emission tomography, for patients of various age groups from several regions of Russia was used for the risk assessment. The output of the methodology is a series of tables for each diagnostic technology with lists of examinations for three age groups (children/adolescents, adults and seniors) corresponding to various radiation risk categories.

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