Report from ARRS: Researchers maximize performance with 64-slice cardiac CT

Coronary artery stenosis detection with 64-slice CT can get a big boost in accuracy if intravenous contrast protocols aim for maximum intravascular attenuation, according to research presented today at the American Roentgen Ray Society meeting in Orlando.

Researchers from the Erasmus Medical Center in Rotterdam, the Netherlands, and Azienda Ospedaliero-Universitaria in Parma, Italy, found that high-attenuation protocols yield a sensitivity and specificity of 96.3% and 97.6%, compared with 82.8% and 93.2%, respectively, for low-attenuation protocols.

High attenuation was particularly useful for evaluation of distal segments, said Dr. Erica Maffei of the Azienda Ospedaliero-Universitaria, who presented the results.

The European study involved 170 patients with known or suspected artery disease who were scheduled to undergo conventional angiography. All patients first underwent CTA on a Philips Brilliance Pro 64-slice unit. Significant stenosis was defined as reduction of the lumen by at least 50%.

Patient groups were similar in body mass index, coronary calcium score, heart rate, and age. Half had low-attenuation protocols (average intracoronary attenuation, 297), and half had high attenuation (average intracoronary attenuation, 388).

Of 2050 segments evaluated, coronary angiography found 323 significant lesions.

"Sensitivity and specificity are significantly higher with high attenuation than low attenuation. Contrast material administration protocols should aim at higher intravascular iodine concentration," Maffei said.

"High attentuation is not as common as it should be. Most people think that intermediate attenuation is fine. Instead, a high intracoronary attenuation is the goal for better diagnostic accuracy," said lead author Dr. Filippo Cademartiri of the Azienda Ospedaliero-Universitaria.

In a study from the U.S. presented during the same session, Thomas Jefferson University researchers obtained excellent results with 64-slice CT in assessment of coronary artery disease.

Significant disease was defined as more than a 50% reduction in the diameter of the lumen. In the study, 57 patients underwent cardiac-gated CTA and then proceeded to undergo conventional angiography within one month.

Images were assessed in a double-blind fashion. Of 855 segments, significant stenosis was found in 96 (57 patients evaluated) on coronary CTA. Coronary angiography revealed that 23 cases had been underestimated or overestimated by CTA and only 73 had significant stenosis.

Results with CTA were as follows:

• sensitivity: 90%

• specificity: 93%

• positive predictive value: 93%

• negative predictive value: 89%

• accuracy: 91%

"Our study demonstrates that coronary CTA using MSCT is an excellent noninvasive method of detecting significant artery disease, with high accuracy compared with basic angiography," said Dr. Shaoxiong Zhang, an assistant professor of radiology at Jefferson, who presented study results.