Evaluation of Acceptable Quality Dose Based on Size-Specific Dose Estimate in Chest and Abdomen/Pelvis CT Examinations

Purpose: To determine the Acceptable quality dose (AQD) based on the size-specific dose estimate (SSDE) for chest and abdomen/pelvis CT examinations in a 16 slice CT scanner equipped to the dose modulation technology.Method: The AQD values of patients’ weight groups with acceptable image quality were obtained for the dose indices displayed on the CT scanner console, i.e. volume CT dose index (CTDIVol) for chest and abdomen/pelvis examinations. On the other hand, the SSDE was calculated by measuring the patients’ lateral diameter and applying the corresponding correction factors to the CTDIVol. Then, the AQD values were also calculated based on the SSDE for the same weight groups and examination types.Results: The patients’ weight range from 36-103 kg classified into 7 groups. The AQD ranges of SSDE were 7.67-11.94 mGy for chest and 10.5-21.49 mGy for abdomen/pelvis examination. The corresponding AQD ranges of CTDIVol were 4.08-16.2 mGy for chest and 6.46-25.6 mGy for abdomen/pelvis examination. Conclusion: The difference between the AQD obtained for the SSDE and CTDIVol in each weight group show that although the dose modulation applied in our CT scanner is based on the adjustment of the average mAs for a phantom with closest diameter to the patient dimension, the CTDIVol does not adequately address the patient specific dose. Therefore, applying the AQD based on the SSDE instead of CTDIVol can be a simple, precise and applicable method for optimizing the patients dose in CT examinations.

کلیدواژه ها:

CT dose optimization ، Size-specific dose estimate ، patient dose