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Department of Radiology

at Brigham and Women's Faulkner Hospital

Computed Tomography (CT)

Dan Glazer, MD

Dan Glazer, MD

Medical Director
Computed Tomography (CT)

Cross Sectional Interventional Radiology (CSIR)

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Computed tomography is commonly referred to as CT or a CAT scan. It combines an X-ray with a computer to produce very detailed images of the body. CT is used to help diagnose and treat medical conditions related to internal organs, soft tissue, bones and blood vessels. The images from a CT scan are “cross-sections” of your body, and can be thought of as if you were looking at individual slices from a loaf of bread.

The following information pertains to all patients having a CT scan. Where noted, special instructions are for patients receiving a contrast agent. A contrast agent is a substance that enhances the images taken during the CT scan.

Frequently Asked Questions About Computed Tomography

Types of CT Exams
  • CT scan of the chest
  • CT scan of the abdomen and pelvis
  • CT urogram
  • CT colonography (virtual colonoscopy)
  • CT angiography
  • CT scan of the head
  • CT scan of the paranasal sinuses
  • CT scan of the musculoskeletal system and joints
  • CT guided procedures: Biopsy, insertion of a catheter
  • Lung Cancer Screening
Is CT safe?

The benefits of CT are extraordinary in helping to diagnose or rule out conditions. CT is considered safe, but there are some things to know. CT uses radiation to produce images. At Brigham and Women’s Faulkner Hospital, we use state-of-the-art technology to minimize radiation dose. We also screen all patients for allergies and other conditions if they are receiving an intravenous contrast injection. You can be assured that the benefit of performing a CT scan outweighs the minimal risk of radiation exposure or contrast injection.

All CT exam requests are reviewed by a radiologist beforehand. Instructions are given to the technologists on how to perform the exam after the benefits and risks have been reviewed by the radiologist. Patients should inform staff if they are pregnant, have allergies or have impaired kidney function. The technologist or radiologist will answer any questions you may have at the time of your appointment.

Who is performing my CT scan? Who reads my CT exam?

A CT technologist will perform your exam. All CT technologists at Brigham and Women’s Faulkner Hospital have passed a certification exam in CT given by the American Registry of Radiologic Technologists and are licensed by the Massachusetts Department of Public Health’s Radiation Control Program. The technologist will perform the CT scan and answer any questions you may have.

The CT technologist will greet you after you have checked into the Radiology Department. You will be asked to complete a screening form if you are receiving an IV or oral contrast. The screening form provides information for your safety. It also assists the radiologist in the best scanning option for the best diagnosis. The screening form will need to be completed upon each CT exam return where IV or oral contrast is required.

Your completed exam will be read by a board-certified radiologist. A radiologist is a physician trained to diagnose conditions seen on medical imaging studies. The radiologist will send the report to your ordering provider.

Before Your CT
  • When to arrive: Patients should arrive at the Radiology front desk 15 minutes before their appointment time. Please note: some patients having abdominal or pelvic CT scans will need to drink oral contrast before their imaging study. The oral contrast coats your digestive tract to produce a more diagnostic study. The radiologist will determine if you need oral contrast. If you’re given oral contrast at the time of appointment check-in, the prep will take about 60 minutes. Please plan your time accordingly.
  • Diabetic patients: All insulin-dependent patients with diabetes who are scheduled for a CT scan should continue to take their insulin as prescribed. Drink extra fruit juices to make up for the two hour period when you will fast from solid foods.
    • Patients with diabetes should inform their doctor when an oral contrast is going to be part of the CT exam. Tell your doctor that instructions for after the exam were to stop taking medications for 48 hours after the exam.
  • Pregnant Patients: Women who are or think they may be pregnant should always consult with their doctor before a scan. If you are or think you may be pregnant, please let the CT technologist know ahead of time to ensure proper precautions are taken.
  • Food and drink: You should not eat solid foods for 2 hours prior to your test. You may drink plenty of fluids such as water, broth, clear soups, juice, or black decaf coffee or tea. We encourage you to drink plenty of fluids before your CT exam.   
  • What to wear: You should dress in comfortable clothing. It might be necessary for you to change into a hospital gown if there is metal in your clothing, such as a zipper, that covers the area of your body that will be examined. If you are wearing jewelry or anything that might interfere with the scan, we will ask you to remove it and store it with your other belongings. It is best that you leave valuable items at home.
  • Intravenous contrast preparation: Many patients receive an intravenous (IV) contrast agent for their CT exam. If the radiologist has determined that an IV contrast agent is necessary for your exam, the CT technologist will place an IV in your arm or hand prior to the exam.
During Your CT

The CT technologist will greet you in the waiting room and escort you into the exam room. The technologist will explain everything that will happen during the scan. You will be helped onto the table and positioned correctly. If you have difficulty staying very still, there is a safety belt that can help you remain in place. Even slight movement blurs the CT images.

The CT technologist controls the scanner from an adjacent room where they can still see and hear you. You will be moved slightly after each scan, although you may not notice this.

When the CT scan is complete, the technologist will make sure that all of the information the doctor will need has been collected.

Your time in the CT scan room will vary but is generally between 10 and 20 minutes. For multiple studies or procedures, times will be longer.  

After Your CT

Once the exam is complete, the technologist will help you off the table. You may leave the CT department immediately and resume your normal diet. If you have had a contrast media injection, drink plenty of fluids for the next two days unless instructed otherwise. Speak with your doctor if you have difficulty moving your bowels following a CT scan that used oral contrast agent.

Some patients experience an adverse reaction to the contrast agent, but this rarely happens. Contact your doctor if you develop a skin rash, difficulty breathing, nausea, or vomiting. If your symptoms are severe, call 911 or go to the nearest emergency room.

The technologist cannot discuss the results of the scan with you. Results for your exam are generally available for your provider to view on the same day of your exam. CT exams are interpreted by a board-certified radiologist and a detailed report will be sent to your ordering provider who will discuss them with you. Results are available in Mass General Brigham’s Patient Gateway.

Appointments are available Monday through Friday from 7 am to 8 pm. Saturday and Sunday appointments are available from 8 am to 5:15 pm.

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