Proposed standard for CAC CT screening reduces dose and improves diagnosis

December 1, 2003

A new standard proposed by a consortium of researchers and manufacturers at the RSNA meeting would make coronary artery calcium (CAC) screening with CT safer and more useful in assessing early heart disease.

 

A new standard proposed by a consortium of researchers and manufacturers at the RSNA meeting would make coronary artery calcium (CAC) screening with CT safer and more useful in assessing early heart disease.

The proposed standards would ensure that all manufacturers play by the same rules, said Cynthia McCollough, Ph.D., an associate professor of radiologic physics at the Mayo Clinic in Rochester, MN.

"The problem has been in the variability of the scoring in CAC screening," she said. "There are a variety of CT scanners using different scoring systems to produce CAC screening results. In order for these numbers to be meaningful and comparable, we need to be measuring and scoring in the same way."

The consortium developed a calcium calibration phantom for testing CAC screening on all major manufacturers' CT scanners. In addition, the group set standards for body size that will help reduce the radiation dose to small and medium-sized patients.

The new standard uses a physically based score to evaluate calcification, which will allow portability of screening between machines. Instead of using a CT number, it measures the actual density of calcium in the artery. Any amount greater than 100 mg/cc is considered significant.

McCollough cautioned that the new standard has some drawbacks; for example, it becomes less accurate as more motion is introduced into the study.

The consortium included researchers from the Mayo Clinic, the Cleveland Clinic, and the Institute for Medical Physics in Erlangen, Germany, as well as participants from the medical divisions of GE, Philips, Siemens, and Toshiba.