Application value of the two estimation methods in evaluating the radiation dose of adult chest CT

Objective To investigate the application value of CTDIvol and size-specific dose estimate(SSDE) in evaluating the radiation dose of adult chest CT. Methods A retrospective analysis was made on the CTDIvoland SSDE of 128 patients who underwent chest CT scanning in the First Affiliated Hospital of Zhejiang Chinese Medical University from March to April 2017 and all images are adequate for diagnosis. The subjects were divided into three groups according to body mass index (BMI): Group A, 38 cases with 16≤BMI<21.1 kg/m2; Group B, 53 cases with 21.1≤BMI<23.9 kg/m2; Group C, 37 cases with 23.9≤BMI<34.1 kg/m2. The diameters of anterior-posterior (AP) and left-right (LAT) of each patient were measured in the slice of nipple level, and CTDIvol, effective diameter (ED), conversion factor (fsize) and SSDE of each patient were recorded and calculated. Meanwhile, the differences between CTDIvol and SSDE in different BMI groups were compared. Results SSDE of each group was higher than CTDIvol, and increased by 50.13%, 42.83% and 33.68% in group A, B and C, respectively. There were significant differences in radiation dose between CTDIvol and SSDE in the three groups (t=-48.873, -57.001, -32.651, P<0.05). There were significant differences in ED, fsize, CTDIvol and SSDE among the three groups (F=51.456, 47.749, 113.916, 106.449, P<0.05). Conclusions SSDE can evaluate the radiation dose absorbed by patients with different body types in chest CT, while CTDIvol underestimated the radiation dose.The lower BMI, the greater the underestimated dose value, the more radiation dose absorbed. Key words: Radiation dose; Chest; CT; Size-specific dose estimate