Determination of effective dose and entrance skin dose from dose area product values for barium studies in adult patients at a large tertiary hospital in the Western Cape

Abstract

Background and objectives The issue of patient doses received during fluoroscopy procedures, raised concerns for the researcher, as there may have been probable past skin injuries or deterministic injuries that may not have been documented. Amongst the radiology staff, there was very little understanding of what the actual dose area product (DAP) value means in real terms of effective dose and entrance skin dose. The aims of the study were to: i) Measure the radiation doses received by the patient and determine a simple means of defining the DAP value to the radiographer in terms of the dose received by the patient. ii) Determine the effective dose, entrance skin dose and the relationship with the DAP value to assist with developing a conversion co-efficient for dose indicators. Method Direct radiation dose measurements can be obtained through DAP meters attached to the diagnostic equipment, but the DAP value is not an direct indication of the effective dose received by the patient. The DAP values captured from the DICOM header information for barium fluoroscopic procedures at a large tertiary was analysed and Diagnostic Reference levels (DRL) were determined for barium swallow, meal and enema procedures. The effective and skin doses were calculated by means of the Monte Carlo program. The results were compared to published values. The relationship between the entrance skin dose and the DAP value was determined and conversion factors were calculated. Results Correlation between the DAP and entrance skin dose and comparative 75th percentile threshold values were determined for barium swallow (BaS), barium meal (BaM) and barium enema (BaE) procedures. Effective to DAP conversation factors for BaS, BaM and BaE are 0.19, 0.26 and 0.60 respectively and 0.15, 0.11 and 0.14 for entrance skin to DAP. Conclusion The the research showed the relationship between the effective dose, entrance skin dose and DAP value and a simple, practical and applicable explanation of the DAP value by means of conversion factors.