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The CT angiogram, a noninvasive test, is becoming more effective as a diagnostic tool.
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The ultrafast CAT or CT (computerized tomography) scan, or EBCT (electron beam computerized tomography), and similarly the spiral CT scanner, can detect coronary artery calcium. A computer-driven process that utilizes the same underlying radiation-based technology as X-rays, CT scans can detect differences in density—highlighting calcified versus noncalcified areas. Arterial plaques calcify at a later stage in the development of arterial blockages. Advanced artery plaques are quite dense and therefore visible on CT scans, providing insights into previously unsuspected arterial disease.
Recent improvements in CT imaging—faster processing and the creation of an larger number of image “slices”—have made it more effective as a diagnostic tool. In the past, CT technology did not detect the initial, soft deposits of cholesterol on artery walls, which was a limitation in the CAT scan's usefulness in diagnosing disease in some patients. However advances in CT imaging have made it possible to identify softer plaques in CT angiograms (CTA) with contrast injection and measuring of the degree of stenosis or narrowing. By enabling us to find these softer plaques—which are potentially more dangerous—early, the improved CT scan puts us in a better position to treat patients who do not have symptoms and who may not yet have an abnormal stress test.
Even with advances in CT imaging, it has not completely replaced other testing methods such as the invasive coronary angiogram and the stress test. And CT scans still involve radiation exposure, though the newer CT scanners provide coronary angiograms with a lower degree of exposure. The contrast dye used in CT imaging also involves some risk to the kidneys and a risk of allergic reaction, although both are uncommon complications.
CT angiograms will likely replace diagnostic catheterization very soon. Ultimately the biggest challenge is not improving resolution of the images but in reducing the radiation/chemical exposure required to complete the exam.
 
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