Cardiac scientific sessions examine outcomes, contrast media use

Cardiac imaging researchers are expanding the scope of topics considered at the 2009 RSNA meeting to include iodinated contrast media administration as a safety issue and clinical outcomes studies that weigh the relative merits of cost and clinical efficacy.

The 23 scientific sessions devoted to cardiac imaging will investigate clinical questions relevant to cardiac CT, MR, nuclear perfusion imaging, and echocardiography. The overall quality of those studies has improved significantly, according to cardiac scientific program chair Dr. Andre J. Duerinckx.

"In past years, a lot of the papers were limited to just slight improvements in technical performance, whereas now people are looking at all aspects: clinical applications, utilization, new frontiers, and comparisons between techniques," he said in an interview. "It is a much broader and relevant approach."

Cardiac CT is again playing a starring role. Scientific inquiries this year, however, will place relatively less emphasis on using the modality to mimic x-ray angiography. Instead they will pay more attention to using it to examine myocardial perfusion, a role now mainly fulfilled with perfusion SPECT, MRI, or PET imaging, according to Dr. Suhny Abbara, associate director of cardiovascular imaging at Massachusetts General Hospital.

"We will see a lot of plaque characterization studies," Abbara said in an interview. "In the past, we would limit our inquiries to just determining the presence or absence of stenosis. A number of papers will concentrate on the location of the plaque, the plaque's composition, and whether it predicts ischemia with SPECT, for example."

Radiologists attending the cardiac scientific sessions should come away with a better understanding about the cost-effectiveness of cardiac CT compared with alternative imaging modalities.

On Wednesday morning (SSK03, 10:30 a.m., Room S502AB), Dr. Ethan Halpern, vice-chair of research at Thomas Jefferson University Hospital in Philadelphia, will present results from a decision analysis comparing the cost and radiation dose for coronary CTA and nuclear stress perfusion imaging.

Dr. Gudrun Feuchtner, a radiologist from Innsbruck Medical University in Austria, will describe findings from a cohort study, involving 1157 chest pain patients, to investigate the relative cost- and clinical effectiveness of CTA and myocardial perfusion scintigraphy.

A Dutch study of 2038 asymptomatic patients drawn from the longitudinal Rotterdam cardiology study will establish a strong association between the extent of coronary calcium and the risk of future coronary events.

"It is nice to see these topics considered in a radiology meeting as opposed to a cardiology meeting. We are getting some very good data discussed and published," Duerinckx said.

A Tuesday morning session will be devoted to contrast media use during cardiac imaging (SSG02, 10:30 a.m., Room S503AB). Highlights will include a German study using a 320-slice CT scanner that suggests optimal contrast dosages. A Chinese study of 64-slice CTA will describe how substantial dose reductions are possible by tailoring dose and injection rate to patient body weight. And Dr. Geoffrey D. Rubin, a professor of radiology at Stanford University, will lecture on how to plan dose volumes for cardiac CTA.

Radiation reduction will again be a major theme, though many specific strategies have already been examined extensively at previous RSNA meetings. Abstracts will evaluate the value of prospectively and retrospectively triggered gating, tube modulation reduction, and strategies that concentrate on patient weight and body mass when choosing exposure settings.

"The principle is an old one, the ALARA principle (as low as reasonably achievable), but there is pressure from RSNA members to do better, and vendors have further improved the tools that allow us to reduce radiation," Abbara said.

On Tuesday afternoon (SSJ03, 3 p.m., Room S502AB) researchers will present results from several large studies investigating cardiac imaging safety and outcomes. Dr. James P. Earls, medical director of Fairfax Radiological Consultants in Fairfax, VA, will present results from a cohort study involving 1150 patients to evaluate the effect of adaptive statistical iterative reconstruction on radiation dose.

In another Tuesday afternoon session (SSJ04, 3 p.m., Room S503AB), Dr. Jonathan Leipsic, codirector of advanced cardiac imaging at the University of British Columbia in Vancouver, will describe the effect on radiation dose of reducing the padding in the field-of-view during cardiac CTA. His findings are based on a multicenter trial involving 517 consecutive patients.

Dr. Michael Lell from Dr. Stephan Achenbach's group at the University of Erlangen in Germany will explain how a radiation exposure of 1 mSv can be achieved for patients weighing 220 pounds with high-pitched, prospectively triggered cardiac CT.

And Cynthia H. McCollough, Ph.D., a medical physicist at Mayo Clinic in Rochester, MN, will describe how a high-pitched (flash) scan during dual-source imaging allows 75 msec temporal resolution at doses 25% lower than previously reported.