PATIENT INFORMATION FOR CT SCAN

What is a CT scan?
A CT scan (also known as a “CAT” scan) is a type of scan in which x-rays are sent through the body to form pictures of the inside of the body.

How is CT different to a regular x-ray?
A regular x-ray sends x-rays from a stationary machine through the body to make a “shadow” picture. In CT, the x-ray machine rotates around the body and makes pictures that are like “slices” through the body, giving much more information than a regular x-ray.

What are the benefits of CT?
The benefit of the study is that your doctor will use the results to better diagnose and manage your condition. CT may be used to check for many diseases, including cancer and causes of pain, such as blood clots in the lungs or appendicitis. Failure to diagnose and treat these conditions could seriously damage your health.

What are the risks of CT?
There is a very small risk from radiation, because CT uses x-rays and radiation can cause cancer. To put this in perspective, all of us are exposed to radiation every day, mainly from the sun and soil. The amount of radiation during a body CT scan is about the same as the radiation we each get in a year from these background sources, and the risk of getting a fatal cancer from this amount of radiation is about 1 in 4000. This is about the same excess risk of death as driving 10,000 miles in a car or living in New York City for 1.5 years.

How can the risk of cancer be reduced?
At UCSF, our scanners have the latest technology that allows us we use the lowest possible amount of radiation needed for each CT.

What is x-ray contrast, and why is it used?
X-ray contrast or “dye” is a special liquid that is often injected through a small tube placed in a vein in your forearm during a CT scan. This liquid shows up on the pictures, and provides much more information about the blood vessels and organs inside the body.

What are the risks of x-ray contrast?
The risks of x-ray contrast include nausea, vomiting, arm pain, allergy, kidney damage, and leakage of contrast from the blood vessel into the arm. All of these are uncommon and in the majority of cases are temporary and require no treatment or just simple “first aid” measures. However, you should be aware that:

• Kidney damage from contrast sometimes requires treatment by a Nephrologist (a doctor who specializes in kidney disease), and is occasionally irreversible. This occurs primarily in patients with known kidney ailments and diabetic patients.
• Surgery or surgical consultation for severe leakage of contrast into the tissues of the arm is required approximately once in every 6,000 injections.
• Allergic reactions can occur, and very rarely are severe enough to be life-threatening (about once in every 20,000 to 100,000 injections). *Allergic reactions may include headache, sneezing, vomiting, confusion, weakness, warmth, sweating, nervousness, trouble breathing (through mouth or nose), sickness in stomach, metallic taste, watery eyes, itchy eyes, itchy bumps on skin, sections of fluid-filled bumps on skin, red-colored skin, pale skin, or uncontrollable shaking. If you feel any of these symptoms during your CT scan, immediately tell your doctor or the department staff.

How can the risks of x-ray contrast be reduced?
Before contrast is injected, you will be asked to complete a special Contrast History and Evaluation Form so we can identify any risk factors that may place you at higher risk. If you are higher risk, your cases will be reviewed by the doctors in the Radiology Department. Alternatives to contrast or changes in the type and amount of contrast used may be considered or discussed with you and your referring doctor. It is important for your own safety that you complete this form as accurately as possible. Your information will be kept confidential (private). Sometimes, patients who have had a previous allergic reaction to contrast with be given special medicines to prevent this happening again (this is called “premedication”).

Are there alternatives to CT?
In a serious or emergency situation, it is important not to hesitate to have a CT. In these situations, the benefits clearly outweigh the risks. However, in other situations you may wish to discuss not having a CT scan or having another type of test (for example, ultrasound or MRI) with your referring doctor.

If my CT is normal, does that mean it should not have been done?
A normal CT provides valuable information, and does not mean the test was a “mistake”. It is as important for your doctor to know what you do not have as what you do have.

What if I still have questions or concerns?
You should discuss any remaining questions or concerns with either your referring doctor or with the staff of the Radiology Department.
What if I might be pregnant?
It is very important that you tell the Radiology Staff if there is even the slightest possibility that you may be pregnant, since x-rays can be harmful to the developing baby.

What can I expect before my CT scan?
Please arrive 30 minutes before the scheduled time of your CT scan, and sign in with the receptionist. You will be asked to remove important items and ALL jewelry, and to complete the Contrast History and Evaluation form.

What can I expect during my CT scan?
Your CT scan takes about 15 minutes, during which you be lying on a padded table. You may be asked to lie on your stomach, back, or side, and to hold your breath or stay very still. You may hear humming noises or feel the table move slowly through the CT scanner.

What can I expect after my CT scan?
After your CT scan, you should drink about 5 glasses of water to help flush out the contrast that was injected. If area where the plastic tube (IV tube) inside your vein was placed is red, swollen, or sore, you should put a warm, wet towel on the area four times a day for 15-20 minutes. If swelling continues for more than 48 hours, you should call your doctor. If you are breastfeeding, it is safe to continue to do so. If you feel any unusual symptoms after leaving the department, call your doctor or go to the nearest emergency room. If you feel your symptoms are life-threatening, call 911.

What are oral and rectal contrast?
Sometimes, because of known or suspected disease in the stomach or bowel, you may be asked to drink contrast mixture or water right before your CT scan, or contrast may be given in the rectum. This is only done if considered essential.

If you have any questions, please call the scheduling nurse at 415-353-4030.

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