CT scanning (or computer tomography scanning) is a sophisticated form of an X-ray machine. The patient lies on a table that moves through the scanner, which itself is shaped like a donut. The subsequent images demonstrates the internal structures of the body as though a slice has been obtained from the patient. The CT scan images demonstrate the internal anatomy of the patient on a slice by slice basis.
Over the years CT scanners have continued to develop into highly sophisticated forms of imaging equipment, such that they are used to investigate patients with a wide variety of complaints. CT is an excellent imaging method for evaluating the liver, pancreas, spleen, and even most portions of the digestive tract. Examples of specific disease identified and particularly well evaluated by CT include: focal liver masses, pancreatic diseases such as pancreatitis or pancreatic tumors, abnormalities of the aorta (major blood vessel of the abdomen) and its branches.
When a CT is performed for gastrointestinal tract disorders patients are usually asked to drink contrast material which serves to outline the digestive tract. The contrast material is either dilute barium or water soluble iodinated contrast material (contrast material which contains iodine and no barium). The exact timing of the ingestion of this contrast material varies depending upon the examination but usually commences no more than 4 to 6 hours prior to the examination. The CT scan itself involves radiation and therefore should ideally be avoided for those patients that are pregnant or think they may be so. The technologist will also ascertain whether or not the patient has any allergies or is on any medications.
An intravenous injection of dye (contrast) is usually administered during the examination to outline the blood vessels. There are a small number of patients who may be allergic to dye and have had a reaction (i.e. hives, difficulty breathing). If a CT scan is indeed necessary it is usual for the patient to receive pre-medication with steroids. The use of the intravenous contrast can prevent a problem also in patients with impaired kidney function and in diabetics who are receiving particular types of medication.
The patient changes into a gown and remove all external metal objects such as belts or bra straps which may interfere with the scan. The patient lies on the CT scan table. Usually intravenous contrast is administered by a small IV placed in the patients hand or arm. The administration of the contrast material occasionally produces transient sensation of flushing or warmth within the patient but invariably no other adverse reactions. During the scan the patient will be instructed clearly by the technologist when to hold their breath. A very small minority of patients experience some claustrophobia during the examination. The patient is, at all times, in direct radio communication with the technologist who is situated behind the control panel in an adjacent room. The typical CT scan of the abdomen will last approximately 10 minutes, sometimes less.
What Will Happen Afterwards?
Upon final completion of the scan the radiologist will review the images and ensure that they are satisfactory. The IV will be removed and the patient discharged from the department. The patient is immediately free to resume all normal activities.
The oral contrast material is extremely safe. A very small number of patients do have an adverse reaction to the intravenous contrast agent. This is usually manifested within 15 or 20 minutes of the injection. Such patients are monitored within the department and usually discharged without any further treatment.
The CT scan does involve some radiation, however, this is kept to a minimum. The potential benefits of the procedure significantly outweigh the risks.