pre-scan
Low-dose localizer image acquired before the diagnostic CT scan. The X-ray tube parks in a fixed position (AP / lateral) while the table translates through the gantry, producing a 2D radiograph used to plan the diagnostic scan range. Vendor terminology: scout (GE), topogram (Siemens), scanogram (Philips / Canon).
Why it matters to buyers: Typically included in protocol automatically. Some protocols skip the scout (trauma, time-critical) at the cost of less precise scan-range planning.
Why it matters to engineers: Dose from the scout is small but included in DLP dose-tracking reports. Auto-positioning and scan-range automation features (CARE Position, Smart Prep) build on the scout.