A Novel Approach to Reduce Breast Radiation Exposure with Coronary CTA: Angled Axial Image Acquisition

Rationale and Objectives. To determine whether angled gantry acquisition might be used to image the heart with a shorter scan length and reduced breast exposure during coronary computed tomography angiography. Materials and Methods. One hundred consecutive coronary computed tomography angiography examinations of female patients were retrospectively evaluated to define the angle between the long axis of the left heart and the axial imaging plane. The scan length required to image the entire left ventricle along with the coronary arteries was measured for an axial scan plane as well as for a scan plane parallel to the long axis of the left heart. The overlap between these imaging volumes and the lower portion of the breast was measured. Results. The long axis of the left heart varied from 7 degrees to 54 degrees off the axial plane (mean 32 degrees +/- 7 degrees). The required scan length to include the entire left ventricle and coronary arteries ranged from 8.2 to 12.4 cm (mean, 10.0 +/- 0.9 cm) for the axial scan plane and 5.6-10.1 cm (mean, 7.5 +/- 0.8 cm) for a scan plane parallel to the long axis of the heart (P < .001). cCTA in the axial plane required a 7.4 +/- 1.6 cm overlap with the lower breast, whereas cCTA in the long axis of the heart reduced the overlap to 4.5 +/- 1.8 cm (P < .001). Conclusions. Using an angled gantry approach, the coronary arteries can be fully imaged in a plane along the long axis of the left heart with a single 10-cm acquisition and with substantial reduction in amount of breast tissue within the irradiated field.