MODEL RELEASED. CT scanning. Anaesthetist (right) and radiologist talking to a female patient before an emergency CT (computed tomography) scan. The laser lines are used to align the scanner. On the patient's finger is a pulse oximeter. This measures her pulse rate and the amount of oxygen in her blood. CT scanning is a diagnostic technique in which numerous short bursts of low dose X-rays are passed through the body at different angles. A computer then produces a cross-sectional image of the tissues. A CT scan provides more detail than a normal X-ray, yet it reduces the patient's exposure to harmful radiation.