​Computed tomography (CT) scan

The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on April 1, 2021.

A doctor orders a computed tomography scan (CT scan), which is an X-ray that uses a computer to produce 3D cross-sectional images of inside the body, to get detailed pictures of internal organs, bones and soft tissues throughout the body. It’s different from a medical X-ray image in that it uses a doughnut-shaped machine to send X-ray beams at different angles, creating a cross-sectional image.

How is a CT scan performed?

A patient lies on a table that slides into the CT scanner, where an X-ray tube completes a full rotation. A technologist may inject a contrast material, usually an iodine or barium sulfate contrast dye, into a vein in the arm for even more detailed CT images. This painless outpatient procedure typically takes about 10 minutes.

What does the scan show?

We use CT imaging to determine the location of a tumor, the extent of the cancer and how well it has responded to treatment. This technology is sometimes used to guide treatment during a procedure or to gauge a patient’s response to a treatment.

What are the various types of CT scans?

3-D CT angiography

CT angiography (CTA) finds the location of tumors, determines whether the cancer has spread to other parts of the body and notes abnormal blood vessels that may be a health concern.

Advantages may include:

  • More detailed images than MRI or ultrasound
  • Shorter procedure than a standard angiogram
  • 3D images of almost every blood vessel in the body, as well as the brain, heart, lungs, pelvis, abdomen and extremities

Large bore CT scanner/RT with simulation

This health care tool produces detailed images of areas inside the body for diagnosing cancer and planning radiation therapy. It uses simulation, fluoroscopy and respiratory gating to plan and deliver radiation.

  • Advantages may include:
  • Locating abnormalities and guiding interventional radiology procedures, such as biopsies and radiation therapy
  • Planning treatment options based on a patients’ breathing patterns
  • Allowing for varying patient sizes and positioning  

Multi-detector CT scanner

This scanner provides multiple image slices in one rotation, allowing radiologists to view high-quality images in micro-level detail and faster. The CT machine's wide scanning space makes it more comfortable.


This nuclear imaging technique uses both positron emission tomography (PET) and computerized tomography (CT), providing detailed information about both the structure and function of cells and tissues in the body. The patient receives a glucose injection that has a small amount of radiation as a contrast agent. The radiation dose is absorbed by the organs or tissues being examined, making them visible in medical imaging. The radiation exposure from this procedure is minor. 

  • Advantages may include:
  • Locating damaged or cancerous cells where the glucose is being absorbed (cancer cells often use more glucose than normal cells)
  • Determining the tumor grade by measuring the rate at which the tumor is using the glucose
  • Providing a more detailed image of cancerous tissues than either test is able to do on its own
  • Capturing the both forms of diagnostic imaging in one scan