If an intravenous contrast agent will be used, the procedure will be explained and the patient will be asked to sign a consent form. The needle will then be placed and taped down.
The technologist settles the patient on the scanner's "couch." The technologist glides the couch into place within the opening of the gantry, using cross-hair positioning lights to put the "target" area (for example, the chest) in the path of the x-rays.
Some types of CT (involving the head, sinuses, throat, etc.) require that the head be immobilized during the procedure. In these cases, soft straps are used to extend the neck and hold the head in place.
After the patient is in position, the technologist usually leaves the CT room. The scanner is generally controlled by a computer in an adjacent room, which has a window facing the machine and patient. During this time, the technologist and patient can easily communicate through an intercom.
When images are being acquired, the patient is usually asked to hold his/her breath and remain motionless. Image acquisition typically lasts 20-30 seconds. When the scanner and patient couch move, the patient may hear whirring or clicking noises-this is normal. In addition, the scanner may tilt forward or back to capture images from the best angle during an examination of the head, sinus, inner ear, and spine.
It is very important to lie completely still while images are being taken. Any movement can reduce the clarity of the images, and the radiologist may then have difficulty interpreting them.