Problems With Dye in a CAT Scan

The use of an iodine-based contrast dye during certain medical tests has become an essential tool in the early detection of illnesses, such as cancer. A computerized tomography, or CT, scan is one method of looking into the body with nothing more invasive than an IV needle. A CT scan with dye can be lifesaving for a patient with an undiagnosed condition, but there can also be some problems with the use of dye.

How Computerized Tomography Works

• CT scans utilize X-rays to take pictures inside the body in exceptional detail. A patient will lie on the table of the CT scanner, which resembles a large doughnut. The inside of the machine rotates around the area being scanned, with each turn taking less than a second, snapping pictures of the area being scanned in cross sections. The pictures are then saved to be read by a radiologist.

Contrast Dye

• Contrast dye, made with iodine, makes objects of interest show up with better clarity on the CT scan. The metal content of iodine in the dye causes tumors and other problems to show up as radiopaque, or illuminated in white, giving the object of interest more detail. In many cases, CT scans incorporate images before contrast and after. Contrast is also used during Magnetic Resonance Imaging, or MRI, in addition to certain cardiac procedures, such as an angiogram to look for hardened arteries. Dye is administered in different ways: intravenously, or directly into a part of the body, such as the rectum, or in some cases it may need to be swallowed.

Contraindications to Contrast CT Scan

• The use of dye in CT scanning can be a problem for some patients. Because contrast dyes contain iodine, people with allergies to shellfish or a known allergy to iodine may not be able to have contrast as part of their CT scan. Likewise, patients taking certain medications, such as glucophage for diabetes, would need to give up their medication for a certain amount of time prior to using contrast. Anyone taking over-the-counter antacids containing bismuth cannot have contrast or a CT, as bismuth is radiopaque or white on the scan. Pregnant women, people with asthma, or those who have had heart failure or multiple myeloma must report these conditions to their doctor prior to having a CT with contrast. In most cases, the benefit outweighs the risk of the test for these people, but that decision can only come from a doctor.

Problems with Administration of Contrast

• Contrast is a relatively thick mixture, requiring a larger diameter IV needle, usually 18 or 20 gauge, for it to be administered during the procedure. People with small or sensitive veins may have problems that arise from getting an IV, for example, multiple needle sticks, or a vein collapsing because the needle is too large for it. In some cases, it may be necessary for the nurse to use the help of a Doppler machine to assist in locating a vein to accommodate the needle. Patients who receive contrast directly into the rectum may have difficulty holding it. Having to hold it can be painful in some cases, especially when the CT is to determine an appendix or rectal problem.

Problems with Claustrophobia

• Many people suffer from claustrophobia, or the fear of confining quarters. It does not get much tighter than a CT scanner. People with claustrophobia can be sedated for their CT scan. Doing this makes the procedure easier, and minimizes artifacts on the scan as a result of movement, which could necessitate the need for a second test to verify that the artifacts were a result of movement.