Report from MDCT: Dual-source technology challenges 64-slice CT in coronary angiography

Dual-source CT provides fast, optimal quality heart images without the need to administer the beta blockers that are often required with 64-slice CT scanners, according to a report Saturday at the 8th Annual International Symposium on Multidetector-Row CT in San Francisco.

Initial experience with the technology presented by Dr. Stephan Achenbach included difficult cases made easier with dual-source CT.

"In the first 100 patients, image quality is extremely impressive," said Achenbach, an associate professor of cardiology at the University of Erlangen in Germany.

The dual-source scanner produced by Siemens features two tubes in a single gantry. It takes 330 msec for one-quarter of a rotation, with 83 msec temporal resolution. All data come from a single heartbeat, eliminating the need to take an average for multiple heartbeats.

When performing coronary CT angiography on the current generation of 64-slice scanners, it is typically necessary to slow the heart rate to under 65 bpm to avoid motion artifact and obtain good-quality images. Beta blockers are effective but inconvenient, and they are not possible in some patients, Achenbach said.

The 100 patients in the study had a range of heart rates from 53 to 109 bpm and a mean bpm of 71. No beta blockers were administered, although some patients were on chronic beta-blocker medication. Even without beta blockers, images were free of motion artifact, and 98% of vessel segments were visualized, Achenbach said. Visualization included the right coronary artery, which is typically most severely affected by motion artifacts.

Higher temporal resolution results in sharper images throughout the cardiac cycle. In patients with heart rates under 75 bpm, optimal images were obtained in 70% of the cardiac cycle. In patients with higher heart rates, it was sometimes necessary to reconstruct images taken during the systole phase.

Dual-source CT allows greater use of ECG pulsing techniques and reduces the window of time in which the full tube current is used, reducing radiation dose to the patient. Higher pitch values of up to 0.43 also result in lower radiation doses

"There is potential for a tremendous reduction in radiation dose," Achenbach said.

With the current generation of multislice CT scanners, motion artifacts are not always distinguishable and can lead to misinterpretations. Dual-source CT benefits from higher temporal resolution and fewer motion artifacts.

"Increasing temporal resolution is the key to improving CTA and increasing the number of applications with CTA," Achenbach said.

Experience at Erlangen suggests dual-source CT is very useful in challenging cases, such as patients with severe atherosclerosis. Calcium can also present problems in assessing presence of coronary artery stenosis. Motion increases the difficulty in seeing the lumen in severely calcified arteries. Achenbach demonstrated dual-source CT images of such patients with no artifact and clear visualization.

High temporal resolution also minimizes problems with stent artifacts.

"Dual-source CT offers a significant improvement in image quality, due to high temporal resolution, at a lower radiation dose," Achenbach concluded.

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