Answer to Question #12047 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
Is an abdominal magnetic resonance imaging (MRI) scan with and without contrast as accurate and clear as an abdominal computed tomography (CT) scan with and without contrast? If so, why would a patient risk the radiation output of a CT scan when an MRI scan could be just as effective?
Both an MRI scan and CT scan of the abdomen with and without contrast provide very good diagnostic information to clinicians. There are many reasons a health care provider may choose to order a CT examination instead of an MRI. A partial list is provided below:
- An MRI scan typically takes longer to complete than a CT scan. This can be a factor if the patient is in critical condition and clinical information from the scan is needed very quickly. It also means that there will be more breathing and other types of motion in the patient throughout the scan which may cause motion artifacts in the images. Artifacts degrade the quality of images. MRI scans are more susceptible to motion artifacts than CT scans.
- The type of anatomy the health care provider is trying to visualize may affect their decision to order an MRI or a CT scan. For example, anatomy that contains calcium or air may not be visualized as well on an MRI scan, as compared to a CT scan.
- There are safety risks associated with MRI. Patients with implanted medical devices have to undergo intensive safety screening to ensure the MRI scan will not interfere with the operation of the device or cause patient injury. Patients with certain implanted devices or objects may not receive MRI examinations due to significant safety concerns. Even when an implanted device or object is determined to be safe for MRI scanning, it may still cause significant artifacts which will degrade the quality of the images.
- The patient may not be able to receive the MRI contrast material due to other health concerns. This may limit the diagnostic value of the images to the health care provider.
- Patients may be claustrophobic. Many MRI scanners have a long, small tunnel (or bore) that the patient must remain in for an extended time period, which can cause severe anxiety. MRI scanners also make very loud banging or knocking noises which some patients cannot tolerate.
These are just a few of the many reasons a health care provider may order one type of imaging examination versus another. You should discuss imaging options with your provider so that you understand and are in agreement regarding which options are best for your specific situation.
Karen Brown, MHP, CHP, DABR
Editor's Note: I encourage you to check out the American Association of Physicists in Medicine's position statement on radiation risk from medical imaging procedures.