Radiology 2004; 233:323-327.
Saini S.
Abdominal imaging with multi-detector row computed tomography (CT) can be performed during short breath holds. On 16-channel multi-detector row CT scanners, the effective detector row thickness, depending on the manufacturer, is typically 1.0-1.5 mm, which results in a beam collimation of 16-24 mm. At a gantry rotation speed of 0.5 second and a pitch of 1, the table travel speed will be 32-48 mm/sec. At a smaller effective detector row thickness and a narrower beam collimation, a slightly higher pitch may be needed to obtain short-breath-hold CT scans. Typically, transverse scans are viewed at a reconstructed section thickness of 3-5 mm, with thinner sections used for CT angiography and whenever off-axial reformations are obtained. The radiologic technique should be optimized according to the transverse section thickness used for interpretation, and the contrast material administration protocol should be optimized according to the clinical problem, with the scanning triggered for enhancement of a target organ.
In the era before the advent of spiral computed tomography (CT), the main parameters that radiologists considered when setting up abdominal CT scanning protocols were scanning area, or range; section thickness; and InterScan delay. With the introduction of spiral techniques, pitch became an additional important parameter because it affects scanning time and section thickness. Now, with the availability of multi-detect or row CT, scanning protocols have become even more complex owing to the larger number of interacting operator-defined parameters.
This article provides an overview of multi-detector row CT technology and a practical approach to setting up abdominal scanning protocols.