Individual dosimetric monitoring (IDM) is performed to control doses of personnel who are involved in work with radiation sources. Monitoring is carried out continuously, the measurement results are recorded once a quarter. Individual annual personnel exposure doses are recorded in a card for accounting of personnel individual dose and in an electronic database. Personnel who directly (permanently or temporarily) works with radiation sources (“Category A”) and can receive half of the annual dose rate during one year, as well as women under the age of 45 regardless of the expected annual dose are subjected to obligatory individual dose control.
The main objective of centralized IDM for medical workers in Ukraine who work with radiation sources is:
- quarterly monitoring of individual exposure doses of different categories of medical personnel during the main types of activities with radiation sources, collection, generalization and analysis of the information on IDM results of medical occupational exposure, assessment of collective and average annual doses of personnel of different professional groups;
- identification of high-risk groups with the largest individual and average annual exposure doses;
- analysis of cases when medical personnel received exposure doses exceeding the reference levels of quarterly/annual doses established for the purposes of IDM
- risk assessment of long-term effects due to occupational exposure for different professional groups of health workers;
- justification of a range of necessary measures aimed at improving the radiation protection of medical personnel during the work with radiation sources, especially in high-risk groups.
A simplified scheme of individual dose control is as follows: during work hours, workers use individual dosimeters consisting of a plastic case and two phosphor crystals inside (a substance that converts stored energy into light). All dosimeters are sent to the laboratory to read information once a quarter, and another set of the same dosimeters is received instead of them. The Central Laboratory of Radiation Safety and Dosimetry of Medical Exposure of S. P. Grigoriev Institute for Medical Radiology performs IDM for the majority of medical workers in Ukraine. It uses the thermoluminescent dosimetry method (TLD) including the laboratory measurement of light intensity emitted by a crystal of an individual detector when heated. Light intensity depends on quantitative characteristics of the received radiation exposure (“thermoluminescence” phenomenon).
IDM analysis results are sent to all medical institutions of Ukraine in the form of annual reports with the information on individual and accumulated exposure doses of each medical worker. Generalized annual reports on all medical institutions of Ukraine subjected to the centralized IDM are sent to the Ministry of Health of Ukraine, the State Nuclear Regulatory Inspectorate of Ukraine and the National Academy of Medical Sciences of Ukraine.
6053 people of category A personnel from 710 medical institutions/establishments of Ukraine from 23 regions were subjected to the centralized IDM in the Central Laboratory of Radiation Safety and Dosimetry of Medical Exposure based on the analysis results in 2018, among them are:
– 4796 people working with x-ray sources for diagnostic and therapeutic purposes, (X-ray diagnostics, X-ray therapy and interventional radiology);
– 1257 people working with radionuclide sources (contact radiation therapy with sealed radionuclides, remote radiation therapy on gamma-therapeutic devices and linear accelerators, radionuclide therapy and radionuclide diagnostics with unsealed radiation sources, radon therapy).
The distribution of the number of medical personnel subjected to the centralized IDM in 2018 according to the main types of activities dealing with radiation sources in medicine is as follows:
Effective dose limit for category A personnel for one year is 20 mSv. Average annual doses in different medical institutions varied within the range of:
– 0.40 – 2.0 mSv for personnel of radiological departments working with gamma-radiation sources;
– 0.40 – 8.9 mSv for personnel of X-ray diagnostic departments.
The generalized average annual dose of medical personnel in all medical institutions of Ukraine during the work with gamma-radiation sources was 0.58 mSv, while the one during the work with X-ray sources was 0.54 mSv.
The contribution to the total collective exposure dose to medical personnel involved into the interventional radiology is gradually increasing. Thus, the increase of the collective dose of this group of personnel ranged from 4.9% to 13.4% for 2015 – 2018.
Distribution of average annual doses for the selected professional groups of medical personnel of Ukraine according to the main types of work with radiation sources:
The highest average annual doses were observed for the medical personnel of the units with sealed radiation sources in the radiology departments who perform manual contact gamma-therapy:
– keepers of radioactive substances – 1.54 mSv;
– radio-manipulation nurses – 1.40 mSv.
The highest average annual doses of medical personnel working with X-ray sources were revealed for specialists performing complex interventions under X-ray control (angiography, coronary angiography, endoscopy, lithotripsy, etc.):
– surgeons, cardiac surgeons and anesthesiologists – 1.06 mSv;
– anesthetist nurses, operating nurses – 0.90 mSv.
These groups of medical personnel are referred to the high-risk groups.
The data on distribution of individual annual doses of medical personnel according to the main activity types in radiotherapy and radio-diagnostics:
87.7% of medical personnel employed in interventional radiology received doses below 2.0 mSv, while personnel who received doses within 2.0-5.0 mSv made up 8.8%.
Three cases of received individual annual doses that exceeded half of the annual dose limit were registered in 2018. Doses were received by surgeons who work in the interventional radiology departments.
The existing radiation protection systems meet the radiation safety requirements based on the results of the centralized IDM in 2018 for the most of the groups of medical personnel working with radiation sources. Further improvement of the radiation protection system in medicine during the work with radiation sources should be aimed at decreasing personnel exposure doses in:
– units with sealed radiation sources in radiotherapy/radiology departments, namely: the keepers of radioactive substances and radio manipulation nurses involved into the contact (intracavitary and interstitial) manual gamma therapy;
– nuclear medicine departments during radionuclide diagnostics and therapy with unsealed radiation sources (manipulative nurses).
– departments of interventional radiology involved in complex interventions under X-ray radiation control (surgeons, cardiac surgeons and others).
According to the report of the Central Laboratory of Radiation Safety and Dosimetry of Medical Exposure for 2018