DETERMINATION OF THE PATIENTS' EFFECTIVE DOSES FOR MOST COMMON X-RAY EXAMINATIONS BY PHANTOM SIMULATION

The objective of investigation is the determination of conversion factors from measured dosimetric values to equivalent organ / tissue doses by phantom modeling of the exposure conditions and assessment the effective doses of the «standard» patient for the most common types of radiographic examinations in Ukraine.

The simulation of patients' exposure for 7 most common types of radiographic exams and fluorography in Ukraine was carried out on a heterogeneous anthropomorphic phantom of a «standard» person. For phantom modeling two groups of X-ray units (modern digital and analogue units which have been in use for more than 15 years) were used. The measurements of entrance surface and absorbed doses in organs and tissues were per- formed using thermoluminescent dosimetry method.

The conversional factors from the entrance surface doses (ESDs) to the equivalent doses for most radiosen- sitive organs / tissues of the «standard» patient were determined for the selected types of radiographic exams from the results of phantom simulations. The estimation of conversional factors from the ESDs to the effective doses was carried out in the working range of voltage values of two groups of X-ray units for the same radiographic examina- tions. A total of 116 phantom simulations were performed with 2-3 measurement repetitions for each irradiation model on each X-ray unit.

The obtained values of conversion factors from ESD to the patients' effective doses for selected types of X-ray diagnostic exams can be used for assessing the effective doses of «standard» patients in the various X-ray rooms and for assessing the collective doses and radiation risks of the population of Ukraine due to the most com- mon radiographic examinations.