Improving the approach to calculating shielding in computed tomography rooms

The study assessed the acceptability of the currently existing approach to calculating shielding in computed tomography rooms and formulated proposals for its improvement, taking into account the parameters of research in domestic medical practice. It is proposed to use the dose-length product as the main measured parameter in the new approach to calculating shielding. Typical tomograph workload values of dose-length product, typical for examinations in the Russian Federation, were assessed. Using thermoluminescent detectors, the experimental assessment of the distribution of absorbed dose in the air in a computed tomography room was carried out. The experimental results showed that the distribution of of X-ray exposure in the central plane is not isotropic. Due to the attenuation of exposure by the gantry design, “shadow” zones are observed, where  the  absorbed  dose  reduction  in  the  air  reaches  10-13  times  compared  to  its  level  in  the  direction  of couch movement. Based on the results of measurements of the distribution of absorbed dose in air, the relative scatter coefficients were calculated. The workload was determined for 7 tomographs (1 in St. Petersburg and 6 in Moscow). For each tomograph, the average weekly number of head and body examinations and the values    of dose-length product for these areas were assessed, taking into account the number of multiphase examinations. The obtained workload values   turned out to be one or two orders of magnitude higher than those currently used in calculating shielding. Based on the results of the study and literature data, the work proposes a  new  approach  to  calculating  shielding  in  computed  tomography  rooms,  based  on  the  value  of  measured dose-length product during the examination and allowing to take into account the specifics of the operation of the device.

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