Diagnostic Investigation

X-rays or gamma rays are passed through a particular part of the body to generate an image, for example a chest X-ray or mammogram (Yarbro, Frogge and CANCER Goodman, 2005). In order to achieve a clearer image, especially in the gastrointestinal tract, lymphatic vessels, urinary tract and so on, a contrast medium can be used. This involves injecting or, in the case of gastrointestinal studies, asking the patient to swallow a contrast medium. This contrast medium enhances the structures, thereby providing clinicians with more detailed information (Yarbro, Frogge and Goodman, 2005).

MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of tissue and by certain diseases. A computer translates the pattern of radio waves given off by the tissues into a very detailed image of parts of the body. A contrast material might be injected just as with CT scans but is used less often. MRI scans are most helpful in looking at the brain. They take longer than CT scans — often up to an hour. The test is painless, but you must lie still inside a cylinder, the surface of which is just a few inches from your face. The machine makes a loud, thumping noise as the magnet switches on and off, so some facilities provide earplugs or headphones to block this sound out.

Nuclear medicine imaging involves the parenteral or enteral administration of radioactive compounds. The radioactive material concentrates in the organs or tissues under investigation. A special camera (gamma camera) is used to obtain images of the specific organ/tissues, for interpretation by the radiologist.

The CT scan is an x-ray procedure that produces detailed, cross-sectional images of your body. Instead of taking one picture, as does a conventional x-ray, a CT scanner takes many pictures as it rotates around you. A computer then combines these pictures into an image of a slice of your pelvis. The machine will take pictures of multiple slices of your abdomen. Often, after the first set of pictures is taken, you will receive an intravenous injection of a harmless contrast agent or dye that helps better outline structures in your body. A second set of pictures is then taken. You will need an (intravenous) line through which the contrast dye is injected. The injection can also cause a flushed feeling. Some people are allergic and get hives or, rarely, more serious reactions like trouble breathing and low blood pressure can occur. Be sure to tell the doctor if you have ever had a reaction to any contrast material used for x-rays.

PET scans involve the use of glucose (a form of sugar) that contains a radioactive atom. A small amount of the radioactive material is injected into your arm. Then you are put into the PET machine where a special camera can detect the radioactivity. Because of their high rate of metabolism, cancer cells absorb large amounts of the radioactive sugar. PET is useful when your doctor thinks the cancer has spread, but doesn’t know to where. PET scans can be used instead of several different x-rays because it scans your whole body and may find spread of the cancer where CT scans haven’t. PET scans have become more accurate because newer devices combine the PET scan with a CT scan.

involves the use of high frequency sound waves. The sound waves are directed over a particular area of the patient’s body, via a probe rubbed over the skin, and echoes are ‘bounced back’. These echoes can be interpreted to provide information relating to the density of the underlying structures. This is particularly useful in distinguishing cysts from more solid structures (Yarbro, Frogge and Goodman, 2005).