Chest Radiography: Optimising The Dose At Industrial Mines In The Northern Cape

Abstract

Occupational medical testing requires an employee to perform certain medical tests before he/she can be classified as fit for duty. A chest x-ray is part of such medical tests. Contracted employees are employed over different periods of time to complete a contract on a mine. When they enter and leave the site, a medical examination is required, which includes a chest x-ray (CXR). The aim of the study was to establish whether certain contracted employees receive more than one CXR per annum, and to determine a baseline for dose reference level (DRL) for a posterior-anterior (PA) CXR for the four clinics that participated in the study and ensures the researcher and the study collaborates with radiation protection. The research questions that were addressed were: (1) are contracted employees referred for more chest imaging than permanent employees, and (2) are contracted employees receiving a higher than necessary radiation dose compared to permanent employees, due to unnecessary repetition of chest imaging at the different clinics contracted by mining companies. A (1) technical parameters sheet, a (2) checklist of x-rays and a (3) formulae and calculations sheet were compiled in order to approach the research questions. (1) was the part of data collection the radiographer had to complete, with the permission of the employee, due to the fact that they interact with the employees when medical testing is done. (2) was done by the researcher where a search was done for previous CXRs, other x-rays and rejects/repeats. (3) was done by the researcher with the assistance of a medical physicist to calculate the Entrance Surface Dose (ESD) of each employee and ultimately determine DRL for that clinic. A univariate procedure was used to test for normality for the ESD by utilising the Schapiro-Wilk test, and presented with a statistic of 0.907037, all four clinics combined. Firstly, the researcher conducted a pilot study to determine the research instruments’ credibility, and they proved to be user friendly. The large scale study started after all required permissions were granted and the technical parameter information were recorded by the radiographer on duty. The study found that the median patient thickness was between 21 to 25 cm. With this information the (1) ESD and DRL were calculated. The results of the checklist showed that there were no employees who had x-ray examinations at the other three clinics. (2) Clinic 1, 2 and 4 reported contracted employees only had one chest x-ray done per annum, whilst clinic 3 had 5 contracted employees who had more than one chest x-ray done per annum. The total of all four clinics combined that had only one chest x-ray done per annum were 54.25 % (217 employees) of the study population (n = 400), 2 chest x-rays = 22.50 % (89 employees), 3 chest x-rays = 8.50 % (34 employees), 4 chest x-rays = 3.50 % (14 employees), 5 chest x-rays = 3.25 % (13 employees), 6 chest x-rays = 3.25 % (13 employees), 7 chest x-rays = 3.50 % (14 employees), 8 chest x-rays = 1.25 % (5 employees) and 10 chest x-rays = 0.25 % (1 employee). There was no specific employee identified who had x-rays at another participating clinic in one year, but it was evident that certain employees received multiple x-ray examinations. Other projections of all four clinics combined were reported as employees that had one other anatomical projection AP/PA = 2.75 %, 2 other projections AP/PA = 0.50 %, and 1 other projections AP/PA = 0.25 %. One other projection lateral = 2 %, 2 other projections lateral = 0.50 %, and 3 other projections lateral = 0.25 %. One other projection oblique = 0.50 %, and 2 other projections oblique = 0.25 %. Rejects/repeats for PA CXR for all four clinics combined reported as 1 repeat = 4.25 %, 2 PA CXR repeats = 0.25 %, and 3 PA CXR repeats = 0.50 %. There were no CXR lateral repeats. Other repeats of all four clinics combined for AP/PA were reported as 1 other repeat AP/PA = 0.50 %. Other repeats lateral was reported as 1 other repeat lateral = 0.50 %, and 2 other repeats as 0.25 %. Repeats for other projections oblique were 0. Potential diagnostic reference levels (DRLs) for PA CXR established through research studies for an adult chest examination in four countries are included in this study, and the values were as follows: a study done in South Africa established a DRL: 0.10; Ireland a DRL: 0.16; Iran a DRL: 0.26; and Slovenia a DRL: 0.16. (3) The DRLs of this study of the four clinics were calculated and reported as Clinic 1: 0.204, Clinic 2: 0.292, Clinic 3: 0.391 and Clinic 4: 0.144. The study results can be utilised to assist radiographers with a baseline DRL for chest imaging to optimise dose, and to assist the mines to focus on limiting unnecessary exposure to ionizing radiation by enforcing only one chest image per annum. It was evident that a DRL value assisted the radiographer to limit exposure and if mining clinics share the images, less annual imaging is needed per employee.