CT or CAT scan stands for computerized axial tomography. This type of imagery uses an X-ray tube that travels 360 degrees around your body while gathering information from multiple views to create cross-sectional images.

When to Get a CT Scan

A physical exam and bloodwork may not be enough for a physician to make a diagnose. Imaging and diagnostics, such as a CT scan, can be used to help a physician diagnose or assist with the following:

• See internal injuries or internal bleeding.
• Assist in surgery or biopsies.
• Diagnose and monitor conditions such as tumors, cancer, heart disease and more.
• Locate a blood clot, infection or tumor.

What to Expect During Your CT Scan

A board certified CT technologist performs your exam and the technologist will explain the entire procedure to you and provide any specific instructions for the CAT scan. You may need to hold your breath at times and an IV in your arm may be necessary if a contrast medium or dye is required.

Some exams require you to drink an oral contrast agent. If this is necessary, the technologist will provide you the contrast and inform you about when to drink it before the CAT scan.

It is very important not to move during the exam. You will be positioned on a scan table and then moved into the scanner. The technologist will have you in full view at all times and be in constant communication with you via two-way microphones and monitors. During this brief time, you will hear humming of the equipment as it produces the images and the scan table will move as different images are produced.

Risks of a CAT scan

Inform the technologist if you may be pregnant. If there is any possibility of pregnancy, a pregnancy test may be ordered before the exam. While the amount of radiation exposure during a CT Scan is low, there may still be adverse effects on a developing fetus. It is best to wait until you are no longer pregnant to have a CT scan. 

Please bring a list of your current medications as the technologist will ask you several questions regarding these before your exam. These questions will include any allergies (especially to iodine) you may have, a previous reaction to X-ray "dye," renal problems or diabetes. Inform the technologist if you are taking any medication for diabetes as these medications may react with the dye used for the test. You may be asked to temporarily stop taking your medication before the test.

CT Scan with Contrast

If your physician orders an IV contrast, the technologist will insert a small IV catheter into one of your arms for administration of the contrast. Contrast is a special dye that is dark in color. The dye blocks the x-rays and appears white on the images of the CT scan. Blocking certain areas can help emphasize areas of the body being scanned, like blood vessels and organs. If you feel any discomfort during a contrast injection, tell the technologist. A temporary wave of nausea or metallic taste in the mouth are common side effects but should be reported to the technologist.

If you observe any tenderness, swelling, or problems in the area of the injection site or arm where contrast was administered within 48 hours after injection, call the department and talk with a CT technologist or the radiology nurse.

Preparing for Your CAT Exam

The type of preparation required for a CT scan depends on the area on which the technician is focused:

• Abdomen/pelvis – You may be asked not to eat or drink for several hours prior to your exam. If ordered, the technologist will provide you with an oral contrast to drink. IV contrast is routinely administered through an IV in the arm. The exam takes 15 to 30 minutes.
• Chest – You may be asked not to eat or drink for several hours prior to your exam. IV contrast is routinely administered through an IV in the arm. The exam takes 15 to 30 minutes.
• Head scan with contrast – You may be asked not to eat or drink for several hours prior to your exam. IV contrast is routinely administered through an IV in the arm. The exam takes 15 to 30 minutes.
• Head scan without contrast - No preparation is required for this exam and you may eat up until the time of the exam. The exam takes 15 minutes.

Please arrive on time. You will be advised on your arrival time when your CT scan appointment is scheduled.

What to Expect after Your CT Scan

The CAT scan images will be reviewed and interpreted by a radiologist (a physician specializing in radiology), and a written report will be sent to the physician who ordered your exam. Your doctor will discuss the results of the exam with you at your next appointment.

Some possible side effects that can occur after a CT Scan include:

• A metallic taste in the mouth (if contrast dye is used)
• Headache
• Fatigue
• Weakness
• Constipation (if oral or rectal CT)

CAT scan vs. MRI

The main difference between a CAT scan and an MRI is the technology used to create the pictures. 

A CAT scan uses x-rays that scan the body in an arc to produce a picture from many different angles (think slices of bread in a loaf). Physicians can then view each picture out of the arc to review to help diagnose and treat. 

An MRI uses a magnetic field 20,000 times stronger than the Earth’s magnetic field to produce images of the body’s internal structures and organs. The magnetic field uses pulses of radio waves to align the water molecules into one dimension. When the radio waves are turned off, the molecules flip back to their original rotation and are picked up by a sensor which delivers the scanned body part as an image.