Breast dose reduction for chest CT by modifying the scanning parameters based on the pre-scan size-specific dose estimate (SSDE).

Abstract

To investigate the usefulness of modifying scanning parameters based on the size-specific dose estimate (SSDE) for a breast-dose reduction for chest CT. We scanned 26 women with a fixed volume CT dose index (CTDIvol) (15mGy) and another 26 with a fixed SSDE (15mGy) protocol (protocol 1 and 2, respectively). In protocol 2, tube current was calculated based on the patient habitus obtained on scout images. We compared the mean breast dose and the inter-patient breast dose variability and performed linear regression analysis of the breast dose and the body mass index (BMI) of the two protocols. The mean breast dose was about 35% lower under protocol 2 than protocol 1 (10.9mGy vs. 16.8mGy, p < 0.01). The inter-patient breast dose variability was significantly lower under protocol 2 than 1 (1.2mGy vs. 2.5mGy, p < 0.01). We observed a moderate negative correlation between the breast dose and the BMI under protocol 1 (r = 0.43, p < 0.01); there was no significant correlation (r = 0.06, p = 0.35) under protocol 2. TheSSDE-based protocol achieved a reduction in breast dose and in inter-patient breast dose variability. • CT scan parameters can be modified based on the pre-scan SSDE. • The pre-scan SSDE is useful for a breast dose reduction. • The fixed SSDE protocol reduced individual variations in the breast dose.