Applying the AAPM 293 report to estimate the absorbed dose during head computed tomography: using head circumference for rapid dose estimation

BACKGROUND: The American Association of Physicists in Medicine (AAPM) report 293 is more accurate than report 220 in evaluating the absorbed radiation dose during head computed tomography (CT) examination. We aimed to investigate the associations between age, head circumference (HC), the conversion factor (f(293)), and specific-size dose estimation (SSDE(293)) during these procedures. The rapid radiation dose was also estimated based on the AAPM report 293. METHODS: In this retrospective, cross-sectional study, unenhanced CT images of the head were retrospectively collected from 1,222 participants from Union Hospital and Hubei Cancer Hospital between December 2018 and September 2019. Scan parameters, including age, HC, water-equivalent diameter (D(W)), and volumetric computed tomography dose index (CTDI(vol)), were generated automatically using indigenously-developed image processing software. The corresponding f(293) and SSDE(293) were calculated according to the AAPM report 293. The analyses were performed using linear regression. RESULTS: In the younger group, age and HC were significantly negatively correlated with SSDE(293) (r=−0.33 and −0.44, respectively; both P values ≤0.001). No significant correlation was reported between age, HC, and SSDE(293) in the older group. Moreover, age was significantly negatively associated with f(293) in the younger and older groups (r=−0.80 and −0.13, respectively; both P values ≤0.001). A significantly negative association was seen between f(293) and increased HC in both age groups (r=−0.92 and −0.82, respectively; both P values ≤0.001). CONCLUSIONS: The HC of patients was associated with head conversion. HC is a feasible indicator for rapidly estimating the radiation dose in head CT examinations based on the AAPM report 293.