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Automatic Exposure Control Or Fixed Tube Current? : Evaluating Dose Effectiveness of AEC in Pediatric Chest CT Examinations with CTDIvol, SSDE, and Water-Equivalent SSDE

M CHUN¹*, C Heo¹, J Cheon², J Kim^1,2,3, (1) Seoul National University College of Medicine, Seoul, Korea (2) Seoul National University Hospital, Seoul, Korea, (3) Program in Biomedical Radiation Sciences, Department of Transdisciplinary Stdudies, Graduate School of Convergence Science and Technology, Seoul National University, Suwon, Korea

SU-E-I-43 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To investigate the effectiveness of automatic exposure control (AEC) in pediatric CT examinations in terms of volume CT dose index (CTDIvol), size-specific dose estimates (SSDE), and water-equivalent size-specific dose estimates (SSDEw).
Methods: We selected 179 pediatric chest CT examinations of patient ages 1 ~ 15 taken with or without AEC (AEC: 88, FIXED: 91). A 16 slice MDCT(Sensation 16, Siemens) was used with tube potentials of 80kVp. The reference level for AEC was different for each patient. We assigned CT exams into one of four age groups: under 2, 2-5, 6-10, and under 15. We segmented body regions using a seeded region growing method. The effective diameter (Deff) and the water-equivalent diameter (DW) were calculated at each slice. CTDIvol was extracted from the conventional DICOM dose report image using optical character recognition (OCR) technique, and then SSDE and SSDEw were derived according to AAPM TG 204 based on Deff and DW. The patient dose was compared for with and without AEC exams using those 3 CT dose metrics.
Results: Patient dose of exams with AEC was lower in all age groups regardless of the 3 CT dose metrics. CTDIvol, SSDE, and SSDEw with AEC were 1.61±1.13, 2.85±1.29, and 3.23±1.53 mGy and those without AEC were 2.86±1.34, 5.42±2.61, and 6.21±1.93 mGy, which represent dose reduction of AEC exams by 56.3%, 52.6%, and 52.0%, respectively.
Conclusions: Our study revealed that patient dose of exams with AEC was substantially lower than that without AEC by 52 ~ 56.3 % in pediatric chest CT examinations. Our study results suggest that AEC technique is recommended in pediatric CT exams.

Funding Support, Disclosures, and Conflict of Interest: The research was supported by the Converging Research Center Program through the Ministry of Education, Science and Technology (2012K001498)

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