Purpose:

To evaluate whether combining a polychromatic reconstruction algorithm for breast CT with projection data acquired using alternating high and low energy spectra allows a significant dose reduction while maintaining image quality.

Materials and Methods:

A breast phantom was scanned on a clinical breast CT scanner using the automatic exposure control selected exposure at the regular spectrum with a tube voltage of 49 kV and a 1.576 mm aluminum filter and with a second, higher energy spectrum created by adding a 0.254 mm copper filter. An acquisition with spectrum switching was simulated by interleaving projections from the standard and high energy datasets, and a previously developed polychromatic reconstruction algorithm was modified to reconstruct the breast CT images. Image quality was assessed using the signal difference-to-noise ratio (SDNR) of a high and a low contrast target present in the phantom. A Monte Carlo simulation was performed to determine the mean glandular dose (MGD) of each scan.

Results:

Acquisition of the simulated scan with spectrum switching would result in an MGD of 6.57 mGy, compared to the standard acquisition MGD of 10.4 mGy, a reduction of 37%. At the same time, the measured SDNR of the mixed spectrum reconstructions was slightly higher than that of the standard acquisition, with an increase in SDNR of 6.6% (p < 0.01) for the high contrast target and 5.3% (p = 0.12) for the low contrast target.

Conclusion:

Our approach combining a polychromatic reconstruction algorithm for breast CT with an advanced acquisition protocol using alternating high and low energy spectra can lower dose by at least a third without loss of target SDNR