Mountain Range Background Image

Computed Tomography ​(CT) vs. Computed Tomography Angiography (CTA) Scans

Computed Tomography ​(CT) vs. Computed Tomography Angiography (CTA) Scans

Computed Tomography (CT Scan)

Computed tomography (CT) is a diagnostic imaging test used to create detailed images of internal organs, bones, soft tissue and blood vessels. The cross-sectional images generated during a CT scan can be reformatted in multiple planes, and can even generate three-dimensional images which can be viewed on a computer monitor, printed on film or transferred to electronic media. CT scanning is often the best method for detecting many different cancers since the images allow your doctor to confirm the presence of a tumor and determine its size and location. CT is fast, painless, noninvasive and accurate. In emergency cases, it can reveal internal injuries and bleeding quickly enough to help save lives.

How Does the Procedure Work?

Both CT and conventional x-rays take pictures of internal body structures. In conventional x-rays, the structures overlap. For example, the ribs overlay the lung and heart. In an x-ray, structures of medical concern are often obscured by other organs or bones, making diagnosis difficult.

In a CT image, overlapping structures are eliminated, making the internal anatomy more apparent.

During CT imaging, an x-ray tube rotates around the patient so that multiple images are collected from many angles. These images are stored in a computer that analyzes them to create a new image with the overlying structures removed.

CT images allow radiologists and other physicians to identify internal structures and see their shape, size, density and texture. This detailed information can be used to determine if there is a medical problem as well as the extent and exact location of the problem, and other important details. The images can also show if no abnormality is present.

Benefits of a CT Scan

Benefits of CT include more effective medical management by:

  • determining when surgeries are necessary
  • reducing the need for exploratory surgeries
  • improving cancer diagnosis and treatment
  • reducing the length of hospitalizations
  • guiding treatment of common conditions such as injury, cardiac disease and stroke
  • improving patient placement into appropriate areas of care, such as intensive care units

In an emergency room, patients can be scanned quickly so doctors can rapidly assess their condition. Emergency surgery might be necessary to stop internal bleeding. CT images show the surgeons exactly where to operate. Without this information, the success of surgery is greatly compromised. The risk of radiation exposure from CT is very small compared to the benefits of a well-planned surgery.

CT scanning provides medical information that is different from other imaging examinations, such as ultrasound, MRI, SPECT, PET or nuclear medicine. Each imaging technique has advantages and limitations. The principal advantages of CT are:

  • Rapid acquisition of images
  • A wealth of clear and specific information
  • A view of a large portion of the body

Computed Tomography Angiography (CTA Scan)

ComputedTomography Angiography (CTA) uses an injection of contrast material into your blood vessels and CT scanning to help diagnose and evaluate blood vessel disease or related conditions, such as aneurysms or blockages. CTA is typically performed in a radiology department or an outpatient imaging center.

How Does the Procedure Work?

There are many similarities between conventional x-ray imaging and CT scanning. During conventional x-ray imaging, a single x-ray beam source sends x-rays through the body. A detector plate captures the x-rays that come out of the body. Based on the amount of x-rays blocked by the body organs, the image will appear in different shades of gray. For example, bones appear white on the x-ray while air is relatively black.

For CT scans, multiple x-ray beam sources and sets of x-ray detectors spin around the body at high speed. The x-ray beam sources send multiple small high-energy x-ray beams through the body. The detectors capture those x-rays that come out of the body. During the examination, you will lie on a table that moves through the CT scanner so that the x-ray beams can examine different areas of the body. Then, a fast computer will take the information gathered from the scanner to produce images of the body. The computer processes a large volume of CT scan data to create two or three-dimensional images of the body.

Radiologists will analyze these images using sophisticated computer programs and high-quality monitors to detect diseases in the body.

When a contrast material is introduced to the bloodstream during the procedure, it clearly defines the blood vessels being examined by making them appear bright white.


  • Angiography may eliminate the need for surgery. If surgery remains necessary, it can be performed more accurately.
  • CT angiography is fast, non-invasive and may have fewer complications compared to conventional angiography.
  • CT angiography may provide more precise anatomical details than other angiography exams such as conventional catheter angiography and magnetic resonance imaging (MRI).
  • For CT Angiography, there is no need for sedation or general anesthesia.
  • CT angiography of the heart is a useful way of detecting blocked coronary arteries.
  • CT angiography may also cost less than catheter angiography.
  • No radiation remains in a patient's body after a CT examination.
  • X-rays used in CT scans should have no immediate side effects.