Sequential CT image acquisition
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In sequential scanning, the patient is moved forward along the longitudinal axis of the CT scanner, pausing at intervals to allow a trans-axial image to be captured at each position along the axis.
The tube gantry is restricted from rotating continuously by the use of high-tension cabling instead of slip ring technology seen in all modern CT scanners.
The disadvantages of sequential scanners include:
- uniplanar imaging (axial slices only)
- longer scan acquisition times
- increased motion artifact (secondary to longer scan times)
Helical scanners now comprise the vast majority of the installed CT base globally. However, helical scanners are also capable of sequential scanning, usually called "axial acquisition" in this context. Axial acquisitions are commonly used for head exams to minimize some helical artifacts, and are used in some gated cardiac exams. Axial acquisitions on modern scanners do allow reformatted images (e.g. sagittal, coronal, MIP), and can result in reduced dose compared to helical because they do not involve overranging.