Dual-source CT lowers barriers to comprehensive exam

Innovative cardiovascular imagers are driving CT toward a golden era when a single comprehensive imaging exam can answer all the essential questions to diagnose and characterize coronary artery disease and then recommend appropriate treatment.

Dr. Balázs Ruzsics and colleagues at the Medical College of South Carolina have moved the field close to that goal with an imaging protocolperformed on a dual-source Definition CT scanner.

The contrast-enhanced CT angiographic dimension of the procedure diagnoses the presence and severity of sclerotic coronary artery disease. Myocardial blood pool mapping demonstrates the extent of myocardial ischemia associated with the occlusions. Amazingly, imaging data making both applications possible are gathered during the short breath-hold of a single 15-second scan.

The South Carolina group's experience with a 74-year-old woman with suspected CAD was described in the March 4 issue of Circulation (2008;117;1244-1245).

The retrospectively ECG-gated, contrast-enhanced procedure was performed with one-third-second gantry rotations, 0.2 pitch, and 32 × 2 × 0.6-mm collimation. One x-ray tube operated at 150 mA/rotation at 140 kV, while the other tube generated a 165 mA/rotation at 80 kV.

Investigators employed the unique differences in the x-ray absorption rates of separate sets of images based on 80 kV and 140 kV spectra to map the iodine content within the myocardium.

The resulting blood perfusion patterns were superimposed on gray-scale multiplanar reformats in short-axis and long-axis views.

A myocardial blood pool deficit (arrows in figures) associated with ischemia from the diagonal branch appears in the anteriolateral wall of the left ventricle. It correlated with a perfusion deficit that appeared in the short-axis view of a rest SPECT thallium perfusion study of the subject.

Though the protocol needs more testing, the case study demonstrates the Medical College of South Carolina group is close to making one fast dual-source scan play the role that is now clinically performed by several modalities to definitively diagnose coronary artery disease.

-By James Brice