X-Ray Tubes Quality Control in the Optimization of Doses to Patients and Personnel in Conventional Radiology

Abstract

Objective: To report the place of the quality control of X-ray tubes in the search for optimization of doses delivered by these installations. Materials and methods:Descriptive cross-sectional study carried out in the imaging departments of the Yopougon, Cocody and Treichville teaching centers in Abidjan from 06/15/2011 to 08/15/2011. All conventional radiology equipment of the various university hospitals, in working order during the study period, was surveyed. The quality control of the X-ray tubes concerned the technical characteristics of the acquisition and the quality of the radiation by alignment, collimation, linearity, accuracy, reproducibility and tube tension as well as focal spot and homogeneity of the x-ray beam. The means of evaluation were a RMI Beam model 162 A, a RMI Collimator model 161 B, a DIAVOLT Universal type 43014, a PTW-DensiX densitometer and a Focal test tool model 162 A. Tension and accuracy were measured and values compared to those displayed by the manufacturer. All other parameters have been compared with current international standards. These results were related to the age of the installations and the duration of activity.Results: 4 posts were in operation during the study period. Post office 1 of the emergency department of Yopougon University Hospital and posts 2, 3 and 4 respectively of the outpatient clinics, the 3rd floor and the remote control room of Cocody University Hospital. The calibration of the devices, carried out by the vendor, deemed them to comply with European standards of functionality. None of the quality parameters of the emitted radiation were checked after the devices was switched on. The tubes displayed maximum voltages of 150 kilovolts (kV). Post 3, was the oldest at the time of the study with 14 years of age and 12 years of activity. The other items (1, 2 and 4) were respectively 3 years, 4 years, and 8 years of age and 2 years, 4 years and 3 years of activity. With the following parameters, 80 kilovolts (kV), 250 milliamperes second (mAs), 50 milliseconds (ms) and 100 centimeters (cm) focal-film distance, the three stations aged four years and older had failures related to the reproducibility of the current voltage across the tube. The one with the greatest number of years of activity (12 years) had, in addition, a lack of precision in tension and alignment of the X-ray beam. On the other hand, for the other two, a linearity defect of the x-ray beam was observed, with a dose delivered below the expected dose values when amperage was less than 250 milliamperes (mA). Conclusion:Our study demonstrates the value of X-ray tube quality control for radioprotection in conventional radiology. In this way, the oldest installations will present, failures related to the reproducibility of the current voltage across the tub, lack of precision in tension and alignment of the X-ray beam and linearity defect of the x-ray beam. Failures increases with the duration of activity. All these things contribute to an excessive radiation exposure by increasing the scatt...