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

OBJECTIVE

To investigate the usefulness of modifying scanning parameters based on the size-specific dose estimate (SSDE) for a breast-dose reduction for chest CT.

MATERIALS AND METHODS

We scanned 26 women with a fixed volume CT dose index (CTDI) (15 mGy) and another 26 with a fixed SSDE (15 mGy) 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.

RESULTS

The mean breast dose was about 35 % lower under protocol 2 than protocol 1 (10.9 mGy vs. 16.8 mGy, p < 0.01). The inter-patient breast dose variability was significantly lower under protocol 2 than 1 (1.2 mGy vs. 2.5 mGy, 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.

CONCLUSION

The SSDE-based protocol achieved a reduction in breast dose and in inter-patient breast dose variability.

KEY POINTS

• 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.