Sixteen-Section Multi–Detector Row CT Scanners

I don’t think it is much of an exaggeration to say that the new generation of multi–detector row computed tomographic (CT) scanners—the 16-section scanners—changes everything. It’s not just that they are fast; although speed may be important for obtaining high-quality images of the chest or abdomen, it doesn’t add much quality in imaging of the brain or spine or other body parts that don’t move much. It’s not that they provide high resolution, because in fact the axial resolution is no better than that provided by even the single-section CT scanners introduced quite a few years ago. What makes these new scanners so different is that for the first time the image voxels are isotropic; the image resolution can be as good in the sagittal and coronal planes as it is in the axial plane. Unlike the situation with single-section or even four-section multi–detector row scanners, with 16-section scanners there is no preferred plane for image reconstruction. The fact that the images may have been acquired in the axial plane is irrelevant. All planes have equal resolution, and the viewer can choose the plane that best shows the anatomy. One of the advantages of magnetic resonance imaging over CT was that it was possible to acquire images in arbitrary planes, but that advantage was realized only when one knew, a priori, which plane would be best. With the new 16-section multi–detector row CT scanners, one can decide after the fact which plane is optimal—axial, sagittal, coronal, or oblique—and vary it at will. This means that CT studies are no longer a collection of axial sections to be viewed one section at a time, but now are three-dimensional volumes that can be manipulated and displayed in whatever fashion best suits the diagnostic problem. The fact that these scanners perform at high speed is an enormous bonus. Artifacts due to respiratory and peristaltic motion are reduced or eliminated, while cardiac synchronization becomes simpler and more accurate. These features open up entirely new applications for CT, perhaps the most important of which are in cardiology. With submillimeter isotropic resolution, it should be possible to detect critical lesions even in the distal portions of the coronary arteries. With fewer artifacts due to volume averaging, it might even be possible to see “vulnerable plaques” (cholesterol-filled lesions in the walls of the coronary and carotid arteries that are thought to be the cause of most heart attacks and strokes) (1–5). With the ability to synchronize cardiac motion and to reformat volumes in any plane for viewing from any angle, it will be easy to display cine loops of two-, three-, and four-chamber views showing ventricular wall motion and cardiac function in exquisite detail and with precise accuracy. It will be possible, in short, to achieve the holy grail of cardiac imaging—the one-stop cardiac study that could change the way acute or chronic heart disease is diagnosed and followed up. One can imagine, for example, CT scanning being the first and perhaps the only test performed on the patient presenting at the emergency room with chest pain. At one swoop, acute myocardial infarction, pulmonary embolus, aortic dissection, pneumothorax, or even pneumonia can be diagnosed or excluded in a matter of minutes and the patient either sent home or on to treatment, with full confidence that appropriate and cost-effective care has been given. Along with these opportunities come many challenges, some technical and some social. Acquisition of high-quality images will require an understanding of the technology and physics behind CT operation that extends well beyond what was necessary for operating prior generaAcad Radiol 2003; 10:351–352