Abstract Introduction: Cone Beam CT (CBCT) imaging is used for accurate patient positioning in radiotherapy; however, excess frame acquisition increases the patient dose from the imaging procedure unnecessarily. Previous investigations identified that breast imaging was most affected by excessive frames. Methods: Comparing all protocols, a modification was introduced to adjust the gantry start angle ± 5 degrees to ensure acquisitions commenced after acceleration, which aimed to reduce static frames and minimise unnecessary dose. Results: The protocol optimisation reduced the acquired frames by an average of 7 across Left and Right Breast Fast protocols and lowered delivered mAs by up to 4%. Using PCXMC simulation, the effective dose decreased from 3·0 to 2·8 mSv for the Left Breast protocol and from 2·9 to 2·8 mSv for the Right Breast, which is equivalent to 14 and 7 chest X-rays, respectively. Image quality metrics from the Catphan 503 phantom showed minimal changes in uniformity and contrast. Conclusion: The optimisation technique reduced excess CBCT frame acquisition and dose while maintaining image quality. The maximum deviations above tolerance reduced substantially from 16·1 to 8·5% for the Left Breast Fast S20 protocol and from18·6% to 12·1% for the Right Breast Fast S20 protocol.
Jenkins et al. (Thu,) studied this question.