What is a dual energy CT scan?

Standard computed tomography (CT) scanners use normal X-rays to make cross-sectional ‘slice-like’ pictures or images of the body (see InsideRadiology: Computed Tomography).

A dual energy CT scanner is fairly new technology that uses both the normal X-ray and also a second less powerful X-ray to make the images. This gives dual energy CT additional advantages over standard CT for a wide range of tests and procedures (see benefits of dual energy CT below).

Why would my doctor refer me to have this procedure?

Your doctor might refer you for a dual energy CT scan because:

  • It can selectively increase or decrease the effects of some chemical substances in the body, making some abnormalities clearer on the images taken; for example, iodine is a commonly used substance in X-ray contrast agents, and dual energy CT can selectively increase its effects to produce better images of blood vessels (CT angiography);
  • Images with and without contrast agents can be obtained using a single examination instead of two separate examinations;
  • It can detect particular substances in the body that can be useful for patients with kidney stones to see what type of stone is present and assist in deciding the type of treatment required;
  • It can significantly improve image quality if patients have metal in the area being scanned (e.g. joint replacements);
  • Your doctor might be following a recommendation for the test after discussions with a specialist radiologist.

How do I prepare for a dual energy CT scan?

Preparation for a dual energy CT scan is identical to that required for a standard CT scan (see: Computed Tomography). Your referring doctor and the radiology facility where you are having the dual energy CT scan will provide you with information on any specific preparation required.

What happens during a dual energy CT scan?

What happens during a dual energy CT scan is identical to that for a standard CT scan (see Computed Tomography). You will not notice any difference in the examination whether you have a single energy or dual energy CT.

Are there any after effects of a dual energy CT scan?

Dual energy CT itself is not associated with any immediate after effects. You should be able resume normal activities straight after the scan has been carried out.

Any potential after effects might be related to the injection of contrast medium if required (see Computed Tomography).

How long does a dual energy CT scan take?

The time taken for a dual energy CT scan is no different to a single energy CT examination (see Computed Tomography).

What are the risks of a dual energy CT scan?

There is no difference in the risks of dual energy CT when compared with single energy CT examinations (see Computed Tomography).

Some scanners using dual energy CT can use slightly higher radiation doses than single energy scanners. With newer computer ‘dose-saving’ techniques built into them, some dual energy CT scans use similar or even reduced radiation doses to standard single energy CT.

What are the benefits of a dual energy CT scan?

Most benefits of dual energy CT scans are no different to single energy CT scans (see Computed Tomography).

In addition, dual energy CT is better than standard CT by:

  • producing better pictures of blood vessels (CT angiography), which might allow the radiologist to obtain more accurate information about your condition;
  • improving the quality of images of metal that might have been used to repair bones or joints in the body;
  • reducing the number of scan images required to obtain the same information as a single energy study;
  • providing information about the chemical makeup of some diseases; for example, kidney stones, which could help your doctor to decide on the correct treatment.

Who does the a dual energy CT scan?

A radiologist (specialist doctor) decides on how the scan is to be carried out and whether dual energy scanning is appropriate for your problem. Sometimes this has already been decided following prior discussions with your own doctor. A radiographer (also known as medical imaging technologists) operates the dual energy CT scanner. The images taken by the radiographer are examined by the radiologist, who writes a report that is sent to your doctor.

Where is a dual energy CT scan done?

Dual energy CT scanners are a relatively new technology, and are mostly used in radiology departments within hospitals. A few large private radiology practices do have such machines.

When can I expect the results of my dual energy CT scan?

The time that it takes your doctor to receive a written report on the test or procedure you have had will vary, depending on:

  • the urgency with which the result is needed;
  • the complexity of the examination;
  • whether more information is needed from your doctor before the examination can be interpreted by the radiologist;
  • whether you have had previous X-rays or other medical imaging that needs to be compared with this new test or procedure (this is commonly the case if you have a disease or condition that is being followed to assess your progress);
  • how the report is conveyed from the practice or hospital to your doctor (in other words, email, fax or mail).

Please feel free to ask the private practice, clinic, or hospital where you are having your test or procedure when your doctor is likely to have the written report.

It is important that you discuss the results with the doctor who referred you, either in person or on the telephone, so that they can explain what the results mean for you.

Dr John Coucher

Last saved on 22 November 2016.

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