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
- improving patient placement into appropriate areas of care, such as intensive
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
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
- 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
- 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.