Radiology: Dual-source CT more accurate at segment-based analysis

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In patients with heart rates of 65 beats per minutes or less, dual-source CT angiography has a higher specificity and accuracy at segment-based analysis than 64-slice CT, but provides a comparable diagnostic accuracy on a patient-based level, according to a study in this month's Radiology. Both procedures were associated with a similar radiation dose.

Stephan Baumüller, MD, from the Institute of Diagnostic Radiology at University Hospital Zurich, Switzerland, and colleagues retrospectively studied 200 patients with heart rates of 65 beats per minute or less. All patients suffered from typical or atypical chest pain and had a low-to-intermediate risk of cardiovascular disease. Patients with nephropathy, known hypersensitivity to iodine-containing contrast media, nonsinus rhythm, previous aortocoronary bypass grafts, and previous coronary stent implantation were excluded. Of the participants, 100 underwent dual-source CT angiography and 100 underwent 64-slice CT coronary angiography.

All images were evaluated by two independent readers blinded to the clinical information and compared with results from catheter angiography. Image quality was graded according to a four-point scale and the reasons for poor image quality, such as motion artifacts or severe vessel wall calcifications, were noted.

All of the diagnostic coronary artery segments were assessed for the presence of significant stenoses. For estimation of radiation doses, the scan length, CT volume dose index, and dose-length product were recorded. The effective radiation dose from CT coronary angiography was derived by multiplying the dose-length product and a conversion coefficient.

No significant difference was found in image noise between 64-slice CT and dual-source CT angiography. Diagnostic image quality was found in 99 percent of all segments among the dual-source CT group and in 98.2 percent of all segments among the 64-slice CT group.

In the dual-source CT group, image quality was excellent in 59.9 percent of the segments, good in 31.4 percent, adequate in 7.7 percent and poor in 1 percent. In the 64-slice group, image quality was excellent in 52.6 percent of the segments, good in 36.1 percent, adequate in 9.4 percent and poor in 1.8 percent.

As for the catheter angiographic results, single-vessel disease was present in the dual-source CT group in 16 percent, two-vessel disease in 19 percent and three-vessel disease in 16 percent of patients. In the 64-slice CT group, single-vessel disease was present in 16 percent, two-vessel disease in 15 percent and three-vessel disease in 28 percent of patients.

According to the researchers, significant coronary stenoses could be excluded in 49 percent of the patients in the dual-source CT group and in 41 percent in the 64-slice CT group. There was no significant difference between the two groups regarding the extent of coronary artery disease.

The authors found no significant different between dual-source CT and 64-slice CT regarding effective radiation dose.

Baumüller and colleagues concluded that in patients with a heart rate of 65 beats or less 64-slice and dual-source CT coronary angiography have comparable diagnostic accuracy on a per patient basis, but dual-source was found to have a significantly higher specificity and accuracy at segment-based analysis for the diagnosis of coronary artery stenosis.