Computerised tomography (CT) scanners use a sophisticated x-ray image intensifier to convert multiple two-dimensional x-ray “slices” of the body into visual 3D images. Advanced computer tomography software completes the process of image manipulation.
Specifications to look out for in a used CT scanner include:
Metal-Free Couch Specifications
Most CT scanners use carbon fibre patient couches, moving through the CT aperture at speeds of between 0.5 and 100 mm per second. Horizontal movement should be no greater than 0.25 mm, upward or downward. Maximum weight capacity is usually 200kg, with the width and length of the couch being no greater than 67.5cm by 273cm respectively.
CT Aperture Specifications
The C Arm technology is located here. It should include laser positioning lights to precisely position patients and the diameter of the aperture should be between 65.58 and 76.2cm.
A basic CT scanner can generate 6 x-ray image slices per single pass of the patient through the aperture. Higher-end scanners can make up to 64 image slices per single pass. Bear in mind that the greater the number of image slices, the better the detail in the three-dimensional images. Similarly, the faster the rotation time, the better the image quality, as this diminishes the artifacts produced by inadvertent patient movement.
Newer CT scanners include cone beam 3-D images, real-time moving two-dimensional images using fluoroscopy and two-dimensional radiography images. Scan times for partial mages are 0.5 seconds, whereas full body scans can be completed in three minutes.
Specifications for Radiation Levels and X-ray Tubes
Scanners using more than 50 kilovoltage must have a “source-skin distance” of 18cm. X-ray tubes should last for 1 year or 130,000 scans and the control room in which the scanner is housed should have a humidity level of 85 per cent. X-ray tube emissions released as air kinetic energy per unit mass should not exceed 0.26 micro-Gray units of radiation.