Computed Tomography (CT)

Fast, painless, noninvasive and quite accurate, Computed Tomography (CT) is often an invaluable tool used by doctors to make diagnoses in many situations. It works like a complex X-ray and is used to create detailed images of internal organs, bones, soft tissue and blood vessels.

If you have a CT scheduled, you may have many questions.

We’ve compiled the most common questions to help address any concerns you may have.

How does it work?
The CT scanner consists of an X-ray machine and a detector that spins around the body.  The detector records the X-ray information at every position. The complex computer system processes the information to produce a picture of what the inside of the body looks like.

Is there a risk from radiation?
Just like an X-ray, a CT scan can only work if the patient is administered a small dose of radiation.  While radiation exposure has been shown to increase the risk of getting cancer later in life, the increased risk to a person from one CT scan is extremely small. Most estimates suggest the increased lifetime risk of cancer from one CT scan would be between about 0.1 and 0.01%. 

St. Luke's takes radiation safety very seriously, adhering to all American College of Radiology guidelines. St. Luke’s continually updates technology so that we have the latest and safest CT scanners, and ensures the lowest radiation dose possible is used to get a patient's accurate diagnosis.

Will I need to drink contrast, or have contrast injected via an intravenous line?
There are two kinds of contrast – one taken by mouth and the other by intravenous catheter, or IV.  Each may be used as part of the CT scan study to help make a diagnosis by giving the radiologist and the referring doctor a clearer picture of what may be happening inside a patient's body.  

• The kind of contrast a patient drinks is often used when a doctor wants to know what is happening in a patient's abdomen and pelvis, because this contrast is visible in the stomach and intestines on the scan.  
• The kind of contrast injected into an IV catheter may be used for scans of practically any part of the body and can help a radiologist see tumors, infections or abnormalities that can cause a patient's symptoms.

Is contrast safe?
The contrast a patient drinks is extremely safe, and many patients even claim that it doesn’t taste as bad as they expected.

The contrast that is injected into an IV line is generally safe. In rare instances, some patients can have an allergic reaction to it.  For that reason, our trained technologists always ask about a history of allergies and keep a close watch for any symptoms of developing allergy.  We avoid giving intravenous contrast to patients who may have the onset of kidney failure.  Your doctor may ask that you get some labs drawn prior to getting a CT scan when IV contrast will be used.

How long will my CT scan take?
A CT scan will usually take less than one minute and is often performed in a few seconds.  Prior to the scan however, St. Luke’s technologists take the time to ask some questions and to make sure the scan is set up perfectly to get all the information your doctor needs to keep you healthy. An entire CT scan appointment may take up to 30 minutes.

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