glossaryCT

helical

CT acquisition mode where the patient table moves continuously through the gantry while the gantry rotates and the X-ray tube fires. Produces volumetric (3D) data instead of discrete axial slices. The architectural inflection that made multi-slice and clinical-CTA possible — first introduced commercially in 1989, became standard in the 4-slice / 16-slice multi-detector era.

Why it matters to buyers: Enables rapid whole-body scans — trauma pan-scan, chest, abdomen / pelvis, full-bore vascular CTA — in seconds. Non-helical "axial" (step-and-shoot) acquisition is reserved for specific protocols (cardiac retrospective gating in some modes, perfusion, dental specialty).

Why it matters to engineers: Pitch (table speed vs slice coverage) controls dose, temporal resolution, and helical artifact. Helical reconstruction artifacts (windmill, cone-beam) are inherent to the geometry — modern reconstruction algorithms (iterative, deep-learning) suppress them but don't eliminate the physics.

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