Why Would A Doctor Order A CT Scan Instead Of An MRI Scan?

January 16, 2023CT Scan Basics

If your doctor has recommended you get a CT scan, you might be wondering why they chose this scan over another popular medical scan: an MRI. There are many misconceptions about the differences, advantages, and disadvantages of MRI (magnetic resonance imaging) and CT (computed tomography) scans that your doctor keeps in mind when recommending a medical scan. Those differences – along with your medical history and the part of your body being scanned – are all part of why your doctor would order one scan over the other. 

An MRI uses radio frequency waves to scan the inside of your body, while a CT scan uses x-ray technology to capture images of your body. What this means is that an MRI uses magnets and a CT scan uses radiation. If you have questions about why your doctor chose one imaging technique over the other, talk to your doctor. 

A doctor would order an MRI as a follow-up scan if the CT scan results showed indefinite results. Getting an MRI would give your doctor a more detailed image that could answer any remaining questions before treatment recommendations. Doctors do not necessarily prefer one scan over the other: each scan has benefits and drawbacks, so your doctor will consider your medical history and the issue they are diagnosing or treating before deciding which scan they recommend.

What Are The Differences Between A CT Scan & MRI Scan?

MRI scans are considered the gold standard of medical imaging due to their detail and clarity, but they have their drawbacks. An MRI requires patients to lie still for a minimum of 30 minutes inside a giant metal tube that can sometimes be claustrophobic. CT scans only take about 30 minutes, and the machinery is more open and moves around your body. CT scans use a small amount of ionizing radiation to capture the images – everyone is exposed to a low level of ionizing radiation daily, and the radiation used for a CT scan is negligible. 

Both scans can produce accurate images, but depending on what part of the body is being scanned, one scan might be more accurate. A CT scan is better for showing bone and joint issues, blood clots, and some organ injuries, while an MRI is better for inflammation, torn ligaments, nerve and spinal problems, and soft tissues. 

Beyond accuracy, patient comfort is also a variable your doctor will keep in mind. MRI and CT scan machinery are different. An MRI machine is a loud, large metal tube your body goes inside for the scan, while a CT machine moves around your body to capture the images. A CT scan is a good alternative to an MRI if you are claustrophobic or unable to go inside an MRI machine for some reason (metal implants that cannot be removed). A CT scan can be an especially useful alternative if your doctor needs results faster than an MRI can provide. CT scans and MRIs use contrast agents to discover blockages and increase the variation between certain interior structures.

How Do I Prepare For Each Scan?

Your doctor may choose one scan over the other for any of the reasons described above, or based on what part of your body is being scanned. If you need a medical scan of the brain, it is better to get an MRI. For a medical scan of the pancreas, your doctor will likely recommend a CT scan. For a scan of the abdomen, an MRI scan is preferred. To diagnose a stroke, your doctor will likely recommend an MRI. However, in an emergency, a CT scan will be a better option since it is faster than an MRI. When getting a medical scan of bony structures, a CT scan is better. Either scan is capable of providing a detailed image of the heart. 

Preparing for your MRI requires some simple preparation. 

• Remember to take off any metal you may be wearing before your MRI. 
• Your doctor may recommend you fast to increase the clarity of your images. 
• Your MRI appointment will take between 30 minutes to 2 hours. 
• An MRI is capable of detecting many injuries and diseases, such as cancers, inflammation, internal bleeding, certain neurological conditions, and more. 

Preparing for your CT scan depends on what part of your body is being scanned and what your doctor is trying to diagnose. 

• Before your CT scan, don’t do anything out of your ordinary routine. 
• Your doctor may recommend you fast or be on a diet of clear liquids depending on what part of your body is being scanned. Drinking clear liquids before your CT scan can help increase the clarity of your results. 
• A recommended diet would be any clear liquids: water, fruit juice, broth, etc. 
• You might be asked to fast before your CT scan appointment so that your scans will be clear and uninhibited. 
• Your CT appointment will likely take between 30 and 45 minutes. 
• A CT scan is best for diagnosing damages or injuries to bony structures, soft tissues, and blood vessels. A CT can diagnose brain tumors, multiple sclerosis (MS), soft tissue damage, inflammation, and more. Like any type of medical imaging, there is a small margin of error wherein misdiagnosis can occur.

Should I Be Worried About Getting A CT Scan?

A CT scan does not necessarily mean something serious is wrong with you – you should not be stressed or concerned about your results. During and after your scan, your radiologist will not tell you if something is wrong based on your images. If your radiologist notices something on your scan that requires emergency treatment, they will get you that treatment immediately. Your doctor will receive your CT scan results within 24 hours of your scan. They will need some time to interpret your results and call you to set up a follow-up appointment to explain your results and potentially create a treatment plan. 

Getting any sort of medical imaging can be stressful. Asking questions ahead of time can help assuage that stress. Our team of trained professionals is ready and waiting to help answer your questions. At South Jersey Radiology, you and your comfort are our top priorities. Call us today to schedule an appointment at any of our following locations:

• Greentree Office – Marlton, NJ
• Haddonfield Office – Haddonfield, NJ
• Turnersville Office – Turnersville, NJ
• Voorhees Office – Voorhees Township, NJ
• Route 73 Office – Voorhees Township, NJ
• Washington Township Office – Sewell, NJ
• West Deptford Office – West Deptford, NJ

Learn more about the board-certified, sub-specialized radiologists who read and interpret studies at SJRA, here.