High cardiac CT exposures fall with help of Michigan consortium

May 22, 2009

A Blue Cross Blue Shield of Michigan consortium has shown that adopting common radiation reduction techniques can help community-based cardiac CT practices break the habit of exposing patients to extraordinary amounts of radiation.

A Blue Cross Blue Shield of Michigan consortium has shown that adopting common radiation reduction techniques can help community-based cardiac CT practices break the habit of exposing patients to extraordinary amounts of radiation.

Dr. Gilbert Raff, medical director of advanced cardiovascular imaging at William Beaumont Hospital in Royal Oak, MI, did not believe the critical findings of Dr. Andrew Einstein and others about the potential dangers associated with CT and radiation exposure until he became involved with the BCBS program. He admitted during a presentation at the 2009 International Symposium on Multidetector-Row CT that it has been the source of a personal epiphany.

The BCBS quality-improvement program involves 40 CCT imaging services in Michigan. During an initiation period that began in July 2007, the clinical results of more than 4800 patient scans were collected and evaluated. The initial phase established that the median baseline exposure involved an effective dose of 21 mSv, despite the use of EKG-gated tube current modulation to reduce dose in 93% of the procedures.

"I took the position that very few patients were exposed to as much radiation as was discussed in the Einstein paper (Estimating risk of cancer associated with radiation exposure from 64-slice computed tomography coronary angiography). I was wrong," Raff said.

He now believes that the 21 mSv at Michigan's hospitals probably reflects the reality of practice for most of the country.

The finding led to a consensus improvement project and agreement among Michigan providers to participate in a radiation dose intervention program. A best practices model was developed over eight months in 2008. The group's scan acquisition model did not include many of the available radiation reduction strategies. Raff described it as a "non-sequential, non-ASIR (adaptive statistical iterative reconstruction), and non-Flash technique."

The clinical experience of about 5000 patients was subsequently evaluated. Confidential quarterly reports covering individual site experiences were sent to each site's clinical investigator. The project was initiated with a seminar to teach dose reduction methods to the participants. It covered scan length minimization, use of EKG dose modulation, the use of 100 kVp for lower body-mass patients, and the use of narrow-window retrospective gating.

Results accumulated during 12 months encouraged Raff as much as the initial experience discouraged him. The average radiation dose of CCT procedures performed at the 15 facilities fell 53% to less than 10 mSv. At the beginning of the program, the most frequent dose range was 25 to 29 mSv. At the end of the first year, it had fallen to 5 to 9 mSv.

The Michigan experience has encouraged the American College of Radiology and American College of Cardiology to work together on a national program applying the same radiation reduction principles, Raff said. They have applied for a federal "Grand Opportunity" economic stimulation grant to establish a multimodality cardiac registry involving CT, echocardiography, and nuclear imaging.

If approved, it will feature a randomized controlled trial of dose reduction comparing the relative values of passive and active instruction to persuade cardiac CT users to adopt radiation reduction strategies, he said.