Evaluation of patients' Body Mass Index and weight as a simpler alternative method for calculating size-specific dose estimation in patients with lung computed tomography

Background : Evaluation of Size-Specific Dose Estimation (SSDE) by patient's weight and Body Mass Index (BMI) instead of Anterior-Posterior (AP) and Lateral (LAT) diameter measurements in patient's images for lung computed tomography (CT). Materials and Methods: Before the examination, the weight and BMI of all patients were measured and calculated. All AP and LAT diameters were measured from the axial images, and localizer and conversion factors (f(size)) were calculated based on them. Volume Computed Tomography Dose Index (CTDIvol) and Dose Length Product (DLP) values were also recorded from the patient's examination summary. In this way, different SSDEs based on effective diameter (SSDEeff), water equivalent diameter (SSDEw), AP diameter (SSDEAP), LAT diameter (SSDELAT), sum of the AP and LAT diameters (SSDEAP+LAT), AP diameter in scout view (SSDEAPscout ) and LAT diameter in scout view (SSDELATscout ) are obtained. By Pearson statistical test the correlation between patients' BMI and weight with all types of SSDE calculation methods was examined. Results: There was a statistically significant correlation between all measured and compared parameters, but the most correlation between BMI and weight with SSDEs was obtained with SSDEeff (R=0.825, P<0.05) and SSDEw (R=0.777, P<0.05), respectively. Also, the correlation between BMI and effective diameter (d(eff )) (R=0913, P<0.05) is the highest among all types of diameters measured. The correlation of BMI with SSDEw and water equivalent diameter (d(w) ) was (R=0.807, P<0.05), (R=0.909, P<0.05), respectively. Conclusion: There seems to be a significant correlation between BMI andf_size so that we can estimate patients' SSDE without measuring AP and LAT diameters, even before a CT scan.