Angled gantry technique reduces breast radiation exposure during CTA

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A novel angled gantry approach to coronary CT angiography (CCTA) reduced radiation exposure to the breast by more than 50 percent, according to research presented at the 2008 Radiological Society of North America meeting in Chicago.

Breast radiation exposure with helical coronary CTA may be 10 to 30 times greater than the dose from mammography screening and is a concern for young women as the dose may increase the risk for breast cancer, according to lead author Ethan Halpern, MD, an associate professor of radiology at Jefferson Medical College of Thomas Jefferson University in Philadelphia

Halpern and colleagues retrospectively reviewed 100 consecutive 64-slice CCTA images. They evaluated sagittal images:
  • to define the position of the breasts and the gantry angulation required to perform a CT exam parallel to the long axis of the heart, and
  • to determine the reduction in breast exposure to radiation that might be accomplished by imaging the heart with an angled gantry acquisition.
The scan length required to image the entire left ventricle along with the coronary arteries was measured at this angle. The extent of overlap between this imaging volume and the lower portion of the breast was measured.

The standard axial imaging plane for CCTA required a 6.5cm overlap with the lower portion of the breast. The overlap with the lower portion of the breast using the angled scan was reduced in half to 3.2 cm. The difference was significant.

Furthermore, the thickness of breast tissue exposed along the inferior margin of the breast with the angled scan was less than the thickness of breast tissue exposed with a standard axial scan orientation, according to researchers.

Investigators concluded that a variable gantry angle, ranging from 4-41°, is required to acquire a CTA image along the long axis of the heart. Using an angled gantry approach, the coronary arteries can be imaged with a single 6.4 cm to 10.4 cm acquisition, and breast exposure can be reduced by more than 50 percent compared with a standard axial acquisition.

"These results warrant the development of machines that can perform this technique," Halpern said.