Core64, Core320 coronary CTA trials cross paths at meeting

The 2008 RSNA meeting serves as a reference point of sorts for two important trials testing the clinical efficacy of multislice cardiac CT. Results from the Core64 trials of 64-slice coronary CTA were published Nov. 28 in the New England Journal of Medicine while plans for a Core320 trial were announced in Chicago at the RSNA show.

Though sponsored by Toshiba America Medical Systems, the two prospective, international multicenter clinical trials are structured to offer scientifically valid insights into the fast-advancing technologies.

Supervised by João Lima, an associate professor of medicine and radiology at the Johns Hopkins University Heart Institute, the nine-center Core64 trial compared the diagnostic accuracy of 64-slice coronary CT angiography and conventional x-ray angiography for 291 intermediate-risk patients with calcium scores of 600 or less. Occlusions of greater than 50% were considered clinically significant. Patients received a maximum effective dose of 20 mSv for the CTA, calcium scoring, and angiographic procedures.

The study found that on a per-patient basis, 64-slice CTA was 85% sensitive and 90% specific for the presence of significant coronary disease. CTA was nearly equivalent to conventional angiography for identifying patients who later would undergo revascularization. The area under the curve (AUC) for CTA was 0.84 compared with 0.82 for conventional angiography.

Only nine of 3782 coronary segments were excluded from review. The sensitivity and specificity for the overall vessel-based analysis were 75% and 93% respectively. The AUC associated with vessel-specific revascularization was 0.84 for CTA, which correlated fairly closely with 0.89 for coronary angiography.

The results of Core64 were initially reported at the 2007 American Heart Association meeting.

The Core320 trial will compare perfusion CT performed on Toshiba's Aquilion One 320-slice scanners and myocardial perfusion SPECT for identifying stenoses less than 50%. Lima is again the primary investigator, with Johns Hopkins serving as the core site for CT imaging. Dr. Marcelo Di Carli, chief of nuclear medicine at Brigham and Women's Hospital, will collaborate with Lima, with his department serving as the core site for the perfusion SPECT portion of the trial. Additional sites will be announced later.

Toshiba is showcasing Aquilion One at the 2008 RSNA conference. Its performance differs radically from the Aquilion 64 used in the Core64 trial, according to the company's Doug Ryan. While helical scanning is required to visualize the entire heart at the imaging acquisition speeds of a 64-slice scanner, dynamic volume acquisition of the whole heart is routinely possible in a single camera rotation with the 320-slice scanner, he said.