CT Scanner

Overview

A computed tomography scanner reconstructs cross-sectional images of the body from a large set of X-ray projections acquired at many angles. An X-ray tube and an opposed detector arc spin continuously around the patient while the table advances through the bore, tracing a helical path that yields a volumetric dataset reconstructed into thin contiguous slices.

The rotating components live in the Gantry, whose disk turns on a large bearing at sub-second rotation times. Power and detector data cross the spinning interface through a slip ring, since cables cannot wrap around a continuously rotating rotor. Mounted on the rotor are the X-Ray Tube Assembly, a rotating-anode tube in an oil-cooled lead housing, and the opposed Detector Array array.

How it works

The High-Voltage Generator supplies up to ~140 kV across the tube through a high-frequency inverter and an oil-filled transformer-rectifier tank. The emitted fan beam passes through the Beam Shaping Assembly stage, where bowtie filters equalize dose across the fan, a motorized collimator sets the irradiated width and slice thickness, and a focused anti-scatter grid rejects scattered photons before they reach the detector. Each detector module converts X-rays to light in a pixelated scintillator, then to current in a photodiode array, and the data-acquisition system digitizes thousands of channels per view.

The Patient Couch indexes the patient through the bore on a low-attenuation carbon-fiber tabletop driven by a ball-screw. Digitized projections stream off the rotor to the Reconstruction Computer system, where filtered back-projection or iterative algorithms build the image volume, and the operator drives acquisition and review from the Operator Console. Tube and electronics heat is rejected by the Cooling System system, which circulates chilled coolant to the tube and HV tank.