USE OF ANTHROPOMORPHIC HETEROGENEOUS PHYSICAL PHANTOMS FOR VALIDATION OF COMPUTATIONAL DOSIMETRY OF MEDICAL PERSONNEL AND PATIENTS

In the dosimetry of ionizing radiation, the phantoms of the human body, which are used as a replacement for thehuman body in physical measurements and calculations, play an important, but sometimes underestimated, role.There are physical phantoms used directly for measurements, and mathematical phantoms for computationaldosimetry. Their complexity varies from simple geometry applied for calibration purposes up to very complex, whichsimulates in detail the shapes of organs and tissues of the human body. The use of physical anthropomorphic phantoms makes it possible to effectively optimize radiation doses by adjusting the parameters of CT-scanning (computed tomography) in accordance with the characteristics of the patient without compromising image quality. The useof phantoms is an indispensable approach to estimate the actual doses to the organs or to determine the effectivedose of workers - values that are regulated, but cannot be directly measured.The article contains an overview of types, designs and the fields of application of anthropomorphic heterogeneousphysical phantoms of a human with special emphasis on their use for validation of models and methods of computational dosimetry.

THE REQUIREMENTS FOR PERSONAL MONITORING OF OCCUPATIONAL EXPOSURE: INTERNATIONAL EXPERIENCE AND UKRAINIAN REALITIES

The article includes analysis and generalizations about international and national experience as well as regulatory requirements for the organization and performance of occupational monitoring for radiation exposure (category A personnel), filling of the national dose registries. It is shown that for practical reasons it is justifiable to provide universal individual monitoring of category A personnel, regardless of the expected dose of radiation. The establish ment and functioning the national dose registry should not be limited to the mechanical collection and accumulation of data of non-guaranteed quality. Instead, both a quality management program and a scientific and methodological center should become components of the dose monitoring and registration system ensuring the quality and reliability of data on occupational exposure doses. Besides the dose records, the data sets should include information about methods used, work conditions, employees' health status. Information exchange infrastructure and data protection policies should be built in accordance with national approaches under the auspices of the State Agency for E-Governance in Ukraine.

RADIATION RISKS OF THYROID CANCER IN CHORNOBYL CLEAN-UP WORKERS USING THE ALTERNATIVE ESTIMATES OF DOSES OF EXTERNAL EXPOSURE

OBJECTIVE

The objective of this study was to estimate the thyroid cancer radiation risks - excess absolute risk(EAR), excess relative risk (ERR) and attributable fraction of risk (AR) in the cohort of 150,813 Ukrainian male clean-up workers during the 1986-2012 period (more than 25 years after the Chornobyl accident).

MATERIALS AND METHODS

The cohort under study of 150,813 Ukrainian men who participated emergency and clean-up work in 1986-1990 was formed based on the data of the Ukrainian State Register of persons affected due toChornobyl accident (SRU). The identification of thyroid cancer cases (216) was carried out by linking the SRU data-base with the National Cancer Registry of Ukraine (NCRU) data. Standardised incidence ratios (SIR) were estimatedcomparing thyroid cancer incidence in the cohort with the corresponding national indices. Excess absolute risk(EAR), excess relative risk (ERR) and attributable fraction of risk (AR) were calculated accounting for the alterna-tive dose estimates. The following sources of the average dose values for Ukrainian liquidators were used: officialtotal external dose records according to UNSCEAR 2008 report and results of external red bone marrow dose recon-struction by the RADRUE method for the cohort sample. For the radiation risk evaluation, these estimates were con-versed to the average external thyroid dose.

RESULTS

Results of the long term study (1986-2012) of thyroid cancer risks in a cohort of 150813 Chornobyl clean-up workers («liquidators») from Ukraine are presented. Two options for the average thyroid dose estimates were usedfor radiation risks evaluation. According to the SRU and NCRU 216 incident thyroid cancers were diagnosed in 1986-2012 within the studied cohort with an overall SIR of 3.35 (95 % confidence interval (CI) 2.51-3.80). The SIR esti-mates were elevated throughout the entire follow-up period. Investigation of a contribution of the external expo-sure (according to the alternative values) showed the elevated dose associated thyroid cancer rates in the studiedcohort. Alternatively estimated EAR/104 PY Gy were of 1.86 (95 % CI 0.47-3.24) and 2.07 (95 % CI 0.53-3.62);ERR/Gy - 2.38 (95 % CI 0.60-4.15) and 2.66 (95 % CI 0.68-4.64) and AR % (Gy) 70.4 % and 72.7 % Gy.

CONCLUSIONS

Obtained results prove the dose dependent increase of thyroid cancer incidence among UkrainianChornobyl clean-up workers. These conclusions are consistent with those received for combined cohort of Belarus,Russia and Baltic States liquidators.

Testing and validation of methods for dose measuring in anisotropic fields under occupational exposure in interventional cardiology

STUDY OBJECTIVE

Experimental testing of the practical application of methodology developed for the individual effective doses assay in an NPP staff by means of 4 dosimeters in case of non-uniform external γ-exposure with known angular characteristics of the radiation field.

MATERIALS AND METHODS

Two series of experimental phantom measurements were held at the workplaces of interventional cardiologists during a procedures in an X-ray operating room.

RESULTS AND CONCLUSIONS

Dose fields in a body of healthcare professional are characterized by the high gradients and readings of individual dosimeters depending on location can differ from 1.5 to 10 times. Thus a single dosimeter is not a source of sufficient information for accurate estimation of an effective dose. Studies have confirmed the possibility of NPP technique application at the workplace of interventional cardiologist. The essential need for a strict control of the eye lens doses is demonstrated.

Methodological approach to developing of double dosimetry algorithms and its application in the interventional cardiology

STUDY OBJECTIVES

to develop taking into account the specifity of exposure conditions a new algorithm for interventional cardiologists who use the X-ray protective clothes.

MATERIALS AND METHODS

modelling of the typical conditions of radiation exposure of interventional cardiologist wearing protective clothes during the interventions, providing Monte-Carlo computations of organ doses and dosimeters readouts.

RESULTS

partial dose values for all possible radiation conditions and relative frequency weight coefficients for each condition were obtained by Monte-Carlo method.

CONCLUSIONS

flexible and adaptive methodology for algorithm developing was proposed, a more specific algorithm was obtained for typical radiation conditions occuring under the interventional cardiology procedures. This algorithm well corresponded to experimental measurements demonstrating at that less conservatism comparing to other known algorithms.