What Is a Low Dose CT Scan?

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  • Written By: Mary McMahon
  • Edited By: Shereen Skola
  • Last Modified Date: 12 January 2020
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A low dose Computed Tomography (CT) scan provides an image of the inside of a patient’s body with minimal radiation. This reduces risks for the patient by limiting overall radiation exposure in association with the medical imaging study. The trade-off with a low dose CT scan is that the resolution of the images may not be sufficient to meet the needs of the test. Developments in CT technology have resulted in considerable improvements in low dose equipment, making higher doses of radiation increasingly unnecessary.

In this type of medical imaging study, the patient lies on a table while an X-ray takes a series of images, known as slices, of the inside of the body. The slices can be reassembled in a computer program to create a three dimensional image to reveal interesting structures, abnormal growths, and other features. One concern with CT technology is that it can involve a high dose of radiation to capture all the necessary slices, potentially increasing the risk of cancer or other problems later in life.


Patients who receive a low dose scan have a much lower amount of radiation exposure. The equipment can also use multiple detectors, allowing several slices to be captured at once. This reduces the amount of time the patient has to spend in the machine and also lowers the overall dose. Technicians can carefully compute the dosage settings on the equipment to tailor them to the patient, producing a low dose CT scan that will provide adequate resolution with the least risks for the patient.

The level of reduction in radiation exposure can depend on the equipment and the area of the body being scanned. A low dose CT scan can use as much as 90% less radiation in some cases, while in others it is less dramatic. Patients with questions or concerns about radiation exposure can discuss it with the technician as well as the medical provider ordering the test, to learn more about the risks and benefits of the CT scan.

There may be cases in which a low dose CT scan is not appropriate because it doesn’t offer enough image clarity. This can depend on why the study has been ordered, specific characteristics of the patient, and the type of equipment in use. Doctors can discuss options with patients and review the situation to determine which kind of testing would be most appropriate. They want to avoid the need to repeat the test for a second set of images.


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