CT Scanning Techniques of Wrist Joints

Abstract

There is a large array of CT scanners currently operational in the public and private sectors. Scanning the entire wrist joint in one axial rotation is preferable, however most scanners in practice will need to scan the joint helically. When scanning helically, a number of factors must be considered: 1. Principle of Obliquity 2. Focal Spot Size 3. Splay Artifacts 4. Radiation Dose 1. Principles of Obliquity: Positioning of the wrist in an oblique position across the scan plan to increase the number of slices through the joint, and therefore increasing the sampling data across the joint. This also reduces metal artifacts. 2. Focal Spot Size: Reducing the focal spot to the smallest available setting improves resolution/detail. 3. Splay Artifacts: Occurs when there is a z-axis sampling error. The severity of the artifact depends on the magnitude of the high contrast transitions. This increases with slice width, pitch and detector rows. 4. Radiation Dose: The radiation dose commonly required for wrist scanning is very low. However, when there is metal fixation present, a small increase in radiation dose will counteract the beam hardening artifacts, thereby improving image quality. Once the data is obtained, the information should be reconstructed in a minimum of 3 planes (Axial, Coronal and Sagittal). With the correct settings and knowledge of the equipment, CT scanning of the wrist can be improved while keeping radiation dose to a minimum.L613470203 <br />