What is a CT scan?

A computed tomography (CT) scan uses X-ray technology to produce computer-generated images of structures inside your body. Like X-rays, CT scans use ionizing radiation to capture the images. Because they are three-dimensional (3D), CT scans provide much more detail than typical X-rays.

CT scans are useful for detecting injuries, cancer, cardiovascular disease, and many other conditions. This type of imaging can be lifesaving in emergency situations.

How a CT scan works

A CT scanner rotates around your body and takes multiple pictures from different angles. The pictures are 2D (flat), cross-sectional images called slices. CT scanners take different numbers of slices, ranging from one to 640. In general, the higher the slice count the faster and more detailed the scan.

A computer takes all the slices and stacks them into a 3D image of the structure or organ being examined, a bit like a 3D printer. A radiologist may evaluate the 2D slices or the 3D images.

Types of CT scans

We use CT technology to evaluate many types of diseases and injuries in the head, abdomen, chest, pelvis, spine, and blood vessels. It can be combined with other diagnostic techniques for greater detail and accuracy. Surgeons and radiologists also use CT scans to guide and plan procedures and treatments.

Since CT scans use ionizing radiation, bones and other dense structures absorb the radiation well and appear white in images. Less dense structures like your brain, blood vessels, or organs in your digestive tract don’t show up with as much contrast.

In these cases, we often do a CT scan with a contrast agent. A contrast agent is a substance that absorbs ionizing radiation and illuminates organs and tissues. We may give you the contrast agent by mouth or through a vein in your arm.

Some of the CT scans we offer at Penn Medicine include:

  • Calcium score test: evaluates coronary arteries for narrowing or blockages to diagnose coronary artery disease
  • Chest CT: diagnoses symptoms such as chest pain or coughing and helps us spot lung nodules or early-stage cancers
  • CT angiography: uses contrast material to examine veins and arteries that supply blood to your heart, brain, kidneys, and other organs
  • CT biopsy: CT images precisely guide a needle when taking samples of abnormal tissue from lungs, lymph nodes, and other organs
  • CT enterography: detects problems in the small intestine and colon, including inflammation, bleeding, and tumors
  • Heart CT: uses contrast dye to create detailed images of heart valves, chambers, and blood vessels such as the aorta and pulmonary veins
  • Virtual colonoscopy (CT colonography): uses X-rays to examine the colon from outside the body instead of inserting a scope into the rectum
  • PET/CT: combines CT technology with a PET scan to pinpoint molecular activity in the body, which helps identify diseases

Dual-source CT scanner for cardiovascular imaging

Penn Medicine offers advanced CT technology that produces high-quality scans in half the time as a traditional CT scanner to diagnose heart and blood vessel conditions. A dual-source CT scanner takes pictures from two angles at once with a single scan, so we get clearer, faster images with less radiation exposure.

We may use this scan to diagnose chest pain, examine your coronary arteries for atherosclerosis, or assess your risk for a heart attack. Learn more about our expertise in cardiothoracic imaging.

Who might need a CT scan?

We may recommend a CT scan to diagnose:

  • Abdominal pain, intestinal blockages, or digestive diseases
  • Benign (noncancerous) tumors and cancer
  • Bone fractures and soft tissue injuries
  • Head, brain, and spine conditions
  • Traumatic injuries and internal bleeding
  • Vascular diseases such as aneurysms and blood clots
  • Other injuries and diseases in people who can’t have an MRI

What to expect during a CT scan

Most CT scans are painless and noninvasive. A CT technologist performs your exam. A radiologist (doctor who specializes in imaging) reviews and interprets the image.

CT scans are available at hospitals, emergency rooms, and some outpatient imaging facilities. The exam itself usually doesn’t last longer than 10 or 15 minutes.

Most scans don’t require any special preparation. However, you may not be able to eat solid foods or drink anything except clear liquids for several hours before certain scans. There may also be special instructions to prepare for a CT scan with a contrast agent. Your care team will tell you everything you need to know.

During a CT scan, here’s what you can expect:

  1. We ask you to remove your clothing and put on a hospital gown.
  2. You lie down on a comfortable table attached to the donut-shaped CT scanner.
  3. The CT technologist goes into another room and talks to you through an intercom.
  4. When the scan starts, the table slowly moves inside the CT scanner.
  5. An X-ray tube inside the scanner rotates around you and sends radiation through your body at different angles.
  6. The scanner doesn’t touch your body, and you won’t feel anything. It’s important to stay very still.
  7. When the scan is complete, the table you’re lying on moves out of the scanner.

After a CT scan

Most people don’t need any recovery time after a CT scan. If you had a CT scan with contrast dye, we may monitor you after the scan to make sure you feel well enough to go home. Some people experience mild and temporary side effects from the contrast agent, such as headache, dizziness, nausea, or an allergic reaction.

Does a CT scan have risks?

CT scans use ionizing radiation, which can damage tissue inside your body. Radiation also slightly increases your risk of cancer, particularly if you need repeated scans during your life. However, a CT scan’s potential to detect serious or life-threatening injuries and illnesses far outweighs the risks. Tell your care team before a CT scan if you’re pregnant or think you may be pregnant. If you need a pelvic or abdominal scan, we may recommend a different type of imaging that doesn’t use radiation.

CT scans at Penn Medicine: Precision imaging, expert care

Effective treatment starts with an accurate diagnosis. At Penn Medicine, you’ll find advanced imaging technology and an experienced, highly trained team. Our experts work together to select the right tests and imaging exams for your needs.

We offer:

  • Recognized expertise: We are fully accredited in computed tomography by the American College of Radiology. This seal of approval means our staff, equipment, and overall care meet rigorous quality and safety standards.
  • State-of-the-art imaging equipment: Our sophisticated CT scanners allow us to tailor scan settings for every patient. This customization improves accuracy and image quality while minimizing radiation doses.
  • Comfort and convenience: Our staff helps you feel at ease before, during, and after your exam. In addition, radiation technologists and radiologists work together to get clear scans the first time, which reduces repeat or unnecessary testing.
Panoramic shot of Penn Medicine's downtown campus

Locations

Our hospitals, multispecialty medical centers, pharmacies, labs and more offer outstanding, personalized care for patients all across the region.

Patient stories

How future cures begin as ideas in laboratories

The successes of CAR T research show the importance of the cycle of science—sparking new ideas and clinical trials that give patients better options.

How discoveries become cures, in a virtuous cycle

Public investments in biomedical research have an outsized effect, driving new scientific insights, economic growth, and ultimately treatments and cures.

Essential tremor patient finds relief

When his essential tremor symptoms became severe, Jim McDevitt turned to Dr. Iahn Cajigas and the team at Penn Medicine for help.

Actress returns to stage after struggling with seizures

Her seizure medications weren't helping, so actress Hannah Parke turned to Penn Medicine for the relief she needed to get back onstage.

‘You won the lottery’: The very first CAR T cell patient

Bill Ludwig will forever be known as the first person successfully treated with a cellular therapy that kills cancer cells with his own immune system.

A new way to treat Afib: Pulsed field ablation

Rick Smith chose pulsed field ablation for its precision and faster recovery. One month later, he’s back on the road, grateful for the care he received.

From bariatric surgery candidate to personal trainer

After bariatric surgery, a high school teacher reinvented himself as a trainer and coach, guiding others to their own health victories.

Finding triple-negative breast cancer at 33, she chose ‘Team Penn’

Shocked to learn she had stage III breast cancer, Kate Korson knew just where to go. She flew home to Penn Medicine, where a clinical trial saved her life.

Patient puts national spotlight on cancer clinical trials

As Kate Korson recently shared on Good Morning America, both she and her mother participated in clinical trials at Abramson Cancer Center.

A cancer dietitian, a survivor herself, keeps patients moving

Breast cancer treatments can upend a fitness routine. Cancer dietitian Dorris Piccinin, a survivor herself, is inspiring patients to keep at it.

Schedule an appointment

We can help you schedule an appointment or you can search our directory of specialists.