ID-02M Small X-Ray Dosimeter for Monitoring Radiation Output

Abstract

Scientific-Research Institute of Introscopy. Spektr ScientificManufacturing Association, Moscow, Russia; E-mail: spektr@co.ru New regulations for hygiene and sanitation (SanPiN 2.6.1.802-99: Ionizing Radiation, Radiation Safety. Hygienic Requirements for Medical X-Ray Rooms, XRay Apparatuses, and X-Ray Examination Procedure) for the first time impose requirements on the following parameters: – reproducibility of radiation dose in manual and automatic modes of X-ray photography; – dose linearity in relation to anode current or quantity of electricity; – monitoring of radiation output. It is recommended to normalize the radiation output H to the focal distance of 1 m and the anode current of 1 mA. Within the anode voltage range from 40 to 200 kV, it is recommended to install an additional Al filter 2 mm thick. At the anode voltage of 250 kV, an additional filter 0.5 mm Cu should be installed. According to the recommendations of SanPiN 2.6.1.802-99, the radiation output H should be measured in mGy⋅m/mA⋅min. Reference data on radiation output for various anode voltages are given in Supplement 7 to SanPiN 2.6.1.80299 [3]. For anode voltage of 40, 50, 75, 100, 150, 200, and 250 kV, the radiation output is 2, 3, 6.3, 9, 18, 25, and 20 mGy⋅m/mA⋅min, respectively. In the majority of X-ray diagnostic apparatuses, the exposure time in the mode of X-ray photography does not exceed 5 sec. In addition, X-ray photographs are often made in the mode of reduction of the radiation load [2]: during exposure, the anode voltage remains constant, while the anode current decreases according to a certain algorithm. Thus, it is expedient to normalize the radiation output to the value of the quantity of electricity (mA⋅sec) given on the control panel. Parameters of X-ray radiation in a direct beam are measured using the following models of X-ray dosimeters: VA-J-18, 27012 (Germany), PTW-Freiburg, PTWUnidos (Germany), Diados, Nomex, Multidos, etc. These dosimeters have good metrological characteristics. However, rather large size and heavy weight hinder their use for periodic testing of X-ray diagnostic apparatuses at the radiologists’ workplaces. To solve this problem, the ID-02M portable small-size dosimeter (Fig. 1) was developed at the Scientific-Research Institute of Introscopy. The metrological characteristics of the ID-02M dosimeter meet the requirements of SanPiN 2.6.1.802-99, ch.10/13. The functional diagram of the dosimeter is shown in Fig. 2. The control panel of the dosimeter contains two feather-touch buttons: Reset/Measurement and mGy/ μGy. The Reset/Measurement button is supplied with a red-green LED indicator (red light indicates resetting; green, measurement). The mGy/μGy button is supplied with two red LED indicators. A third button (Control) activates the mode of the dosimeter operation testing before measurement.