Local Diagnostic Reference Levels (Ldrls) For Routine Chest X-Ray Examinations At A Government Hospital In The Northern Cape

Abstract

BACKGROUND The use of ionising radiation in the medical field accounts for the largest contribution of radiation exposure to the human population. The extent of radiation received by patients undergoing X-ray examinations needs to be quantified to estimate the possibility of harm. The focal point of the research is chest X-ray examinations since these examinations are the most commonly performed worldwide. The chest contains two radiosensitive organs, namely the thyroid and breast tissue. This research study is deemed critical because it demonstrates how dose optimisation can be achieved. Dose optimisation is achieved when the local diagnostic reference levels (LDRLs) of chest X-ray examinations of the research site are less than the international values. The Directorate of Radiation Control (DRC) has not yet established LDRLs for radiological examinations. The data generated by this research could assist the organisation to baseline diagnostic reference levels (DRLs) for adult chest X-ray examinations in the Northern Cape. RESEARCH QUESTION The research question is: What are the LDRLs for routine chest X-ray examinations at a government hospital in the Northern Cape? OVERALL GOAL OF THE STUDY The overall goal of this study was to determine LDRLs values for adult chest X-ray examinations. AIM OF THE STUDY The aim of the study was to determine LDRLs for routine chest X-ray examinations in a diagnostic radiology department at a government hospital in the Northern Cape, in the absence of published values about this important concept in Republic South Africa. OBJECTIVES OF THE STUDY The objectives of this study were: To calculate the entrance surface air kerma (ESAK) for routine chest X-ray examinations’ postero-anterior (PA) and lateral (LAT) images. To establish LDRLs for routine chest X-ray examinations (PA and LAT images) at the research site. To compare LDRLs and the typical dose of chest X-ray examinations with relevant international organisations and values cited in the literature. To propose changes to the specific research site to optimise and justify patient dose if there are significant differences in LDRLs compared to the values from cited literature. METHOD This research study was a cross-sectional study, which is used to examine data at a point in time, that is, the data at/on one occasion only with different participants. It was also a quantitative research study. Quantitative data are numerically measurable, for example, how many, how much or how often. This method determined how much radiation dose a patient receives for each projection. An indirect method was utilised to determine patients’ dose. The research site was a radiology department in the Northern Cape. Three general radiographic rooms were used, namely, two x-ray rooms equipped with computed radiography (CR) and the third room utilised digital radiography (flat panel detector) [(DR (FPD)]. The methodology was divided into three phases, namely quality control, imaging procedure and ESAK calculation. The quality control was performed by a medical physicist. Radiographers executed the imaging procedure at the research site. The radiographers adhere to the Declaration of Helsinki with regard to ethical standards and behaviour. The radiographers had to obey the International Declaration of Helsinki to select patients, obtain chest X-ray radiographs and data for the research. The data recorded by the radiographers were kilo-voltage peak (kVp), focus film distance (FFD), patients’ weight and patients’ thickness at the centring point. These data were used to determine the ESAK of each projection of the participating patients. The indirect method recommended by International Atomic Energy Agency (IAEA) was used to determine the ESAK. A statistician used a statistical application (SAS version 9.2) to determine the LDRLs for chest X-ray examinations of the three X-ray rooms, radiographic systems and the research site. The first sixty patients referred for chest X-ray examinations who met the inclusion criteria participated in this study. The patients selected were 18 years and above, accepted to sign the consent form, were referred for chest X-ray examinations, weighed 60 kilograms (kg) to 80 kg and the exposure index of chest X-ray images were within the prescribed manufacturer range. The ESAK were measured using the indirect method recommended by the IAEA. A statistical application (SAS Version 9.2) was used to determine the LDRLs for chest X-ray examinations of three X-ray rooms, radiographic systems, and the research site. The instruments that were used for this research were valid because weighing scale measures the weight of a patient in kilograms and a calliper measures the thickness of the patient at the centring point in centimetres (cm). The formula and procedure that were used to estimate dose to patients are recommended by IAEA and other researches have successfully used this formula and procedure to estimate patient dose. This research study utilised instruments that were reliable. A known weight of 70 kg was placed on the weighing scale. The reading on the weighing scale and the value of the known weight correlated; the weighing scale was deemed reliable. The calliper measurement was compared to a measuring meter. The measurements were the same; the calliper was deemed reliable. Quality assurance (QA) and quality control (QC) were performed on the X-ray machines at regular intervals as per the QA guidelines to ensure the exposure parameters were reliable. The specific tests were: accuracy and reproducibility of kVp, accuracy and reproducibility of exposure time and linearity of the output with milli-ampere (mA) and time. RESULTS AND DISCUSSION The following LDRLs for chest X-ray examinations were established; Room 1, postero-anterior projection (PA) (0.3 milli-Gray (mGy) and lateral projection (LAT) (0.8 mGy), Room 2, PA (0.3 mGy) and LAT (0.7 mGy), Room 3, PA (0.2 mGy) and LAT (0.8 mGy), computed radiography (CR), PA (0.3 mGy) and LAT (0.8 mGy), digital radiography (DR), PA (0.2 mGy) and LAT (0.8 mGy) and research site, PA (0.3 mGy) and LAT (0.8 mGy). The results showed that there were wide ranges for exposure parameters and ESAK for chest examinations at the research site. These wide ranges could be attributed to patients’ weight range and thickness, radiographer skill, knowledge and training and the use of automatic and manual exposure settings. CONCLUSION The LDRLs for chest X-ray examinations were established at this research site. The LDRLs for chest X-ray examinations were lower than the published international diagnostic reference levels. The recommendation is LDRLs for routine chest X-ray examinations should be repeated after three years according to ICRP. The latest results should then be compared with the results of this research study. This study did not demonstrate the LDRLs for routine chest X-ray examinations of patients whose weights are less than 60 kg or more than 80 kg. As a result, many patients had to be excluded from this research study because their weight was not within the required weight range of this research study. This is the significant limitation of the research study.