LOW BMI PATIENT DOSE IN DIGITAL RADIOGRAPHY.

In this study, the radiation dose received by 364 low body mass index (BMI) adult patients undergoing chest, abdomen, lumbar spine, kidneys and urinary bladder (KUB) and pelvis X-ray examinations in an X-ray room with a digital radiography system was evaluated. The patients' kerma area product (KAP) values were recorded, and the entrance surface air kerma (ESAK) was calculated based on the X-ray tube output, exposure parameters and technical data. The 75th percentiles of the distribution of ESAK and KAP values were also estimated. The dose values were compared with the corresponding values for normal patients obtained from a previous survey in our hospital, as well as with the national and UK diagnostic reference levels (DRLs). The correlation of dose values with patient size metrics (mass, height, BMI) was also investigated. A statistically significant difference was found in KAP and the ESAK values between low BMI and normal patients (Mann-Whitney test, p < 0.05), for all examinations studied. The percentage difference for chest PA, chest LAT, abdomen PA, lumbar spine AP, lumbar spine LAT, pelvis AP and KUB AP examinations was 40, 36, 48, 68, 57, 46 and 67% for median KAP and 26, 43, 52, 48, 19, 44 and 51% for median ESAK, respectively. The corresponding 75th percentiles for low BMI patients were 0.065, 0.349, 0.683, 1.54, 3.92, 1.11, 0.67 mGy and 0.042, 0.218, 0.450, 0.280, 0.598, 0.597, 0.267 Gycm2 in terms of ESAK and KAP values, respectively. They were 74-90% lower compared to the national diagnostic reference levels (DRLs), 35-84% and 58-82% compared to the UK DRLs, for ESAK and KAP values, respectively. Regarding the gender of the patients, no statistically significant difference was found in the dose values between female and male patients (Mann-Whitney test, p > 0.05), for all examinations studied. A statistically significant correlation was found between ESAK and KAP values with BMI for KUB AP, pelvis AP, lumbar spine AP, lumbar spine LAT and chest PA, while for chest LAT examinations, only the ESAK were significantly correlated with BMI. They also significantly correlated with the mass for KUB AP, lumbar spine LAT, abdomen PA and chest PA examinations, while no significant correlation was found between the dose values and patients' height. It can be concluded that the low BMI patients received a significantly reduced radiation dose compared to normal patients. Additional studies need to be conducted for these patient groups, which could contribute to the further development of a radiation protection culture in diagnostic radiography.