Differences between CT and MRI scans

To help diagnose possible conditions, your doctor may send you for a Computerized Tomography (CT) or Magnetic Resonance Imaging (MRI) scan.

While both types of scans take pictures of the inside of your body, they use different technology. Your doctor will choose what scan is right for you based on your symptoms and medical history.

Table comparing CT and MRI scans
DescriptionCT scanMRI scan
What it does
  • Takes many x-rays and puts them together to create a detailed picture
  • Uses magnetic fields and radio waves to take detailed pictures
Best use
  • Bones
  • Places where there’s a lot of movement ( e.g. chest)
  • Soft tissues ( e.g. ligaments, tendons, organs, tumors)
Scanning time
  • Usually a few seconds to a few minutes
  • 15 to 60+ minutes
  • Uses some radiation
  • Patients with metal in their body can get CT scan
  • Does not use any radiation
  • Because it uses strong magnets, an MRI may not be safe for people with metal in their body, such as pacemakers or metal plates/screws
  • Extra precautions are taken with patients who have medical implants
  • No pain
  • Possible discomfort if you are claustrophobic
  • The MRI itself is painless
  • You have to stay still and at least partially inside the machine for a long time, which can be hard – especially if you are claustrophobic
  • MRIs are very loud but you are given earplugs

Imaging wait times we track

You can see wait times for:

Understanding your journey

This is how you get a CT or MRI scan in Ontario and when you can expect to wait.

Learn how understanding the wait process helps you.

Seeing your family doctor

You go to your family doctor about a medical concern.

Your doctor would like you to have a diagnostic scan to help them determine the right course of treatment.

Your doctor determines which image (MRI or CT) is appropriate for you and sends a request to a hospital or imaging centre.

At the hospital/centre

The hospital/centre gets the request from your doctor and assigns a priority level based on the clinical information your doctor provided.

The hospital/centre schedules your appointment.

You wait for the hospital to contact you with your appointment time.

The hospital/centre contacts you or your doctor with:

  • the date and time for your imaging appointment
  • any information or instructions you’ll need before your scan ( e.g. stop medication, don’t eat for a certain period of time)

You wait for your appointment. You can see how long patients have waited where you have been referred.

You can view and compare wait times for MRI and CT scans across Ontario, and talk to your doctor about options for reducing your wait.

Getting your scan

You have your scan.

A radiologist analyzes the results of your scan and sends their report to your doctor.

You wait for your doctor to call you with the results or to set up an appointment to discuss the results.

We do not track this wait, but it’s usually less than a week. You can ask the technologist for an estimate before you leave.

What the numbers mean

When you check wait times for diagnostic imaging, you can access a lot of data. Here’s a preview of what the measurements mean and an example of how someone can use them to estimate their own wait time and inform discussions with their doctor.

Priority level

To help ensure patients most in need are seen first, a radiologist at the hospital/imaging centre assigns you a priority level of 1 to 4. For non-emergencies, priority 2 is the most urgent. (Priority 1 means emergency, so those patients get their scans immediately and are not included in wait times data.)

Your priority level will be based on:

  • your particular symptoms and medical history
  • the radiologist’s experience
  • medical research and best practices

Because priority levels are assigned based on specific criteria, you can be sure your wait time is appropriate for your condition.

Maya the patient

Meet Maya

Maya hasn’t been feeling well for the last two weeks and she’s concerned that there might be something wrong.

After an exam, Maya’s doctor suspects Maya may have small bowel disease (Crohn’s disease) and decides to send her for a CT scan of her small intestine to get more information. The doctor writes a referral that includes relevant medical information about Maya and what he found during his exam and sends it to the local hospital.

The radiologist at the hospital reviews the doctor’s referral and assigns her as Priority 4 for this CT scan.

Target time

A target time is the maximum wait time that patients should expect to wait to receive their diagnostic imaging (MRI or CT) scan. We established wait-time targets based on recommendations from clinical experts.

Maya can see that, at the hospital where her CT scan is scheduled:

  • Last month
    of priority 4 patients had their scan…
  • …within the target time of
  • the average wait time was
Maya the patient

That’s longer than I thought I’d have to wait. I wonder if I could go somewhere else and get in sooner?

Maya the patient

Average wait by hospital

This is the average number of days patients waited for a CT or MRI scan at particular hospitals or imaging centres. You can also see an average for the province.

  • To see if she could get her CT scan faster somewhere else, Maya checked the wait times at other hospitals and imaging centres in her area.

    She saw that a hospital about an hour’s drive away had a shorter wait time, so she asked her doctor if she could go there instead.

  • “Because you’re willing to travel, I can refer you to the out-of-town hospital instead. In addition, I can make sure you’re on a cancellation list in case an appointment becomes available sooner at the local hospital.”

    Maya’s doctor

Why some numbers are not available

If you see sections that say “no data,” there could be a few reasons why, such as:

  • the number of patients treated is too low to report
  • the service isn’t available at the hospital you’ve selected
  • there were no scans during the reporting period
  • the facility is new to reporting and has just started collecting data

Options for reducing your wait time

Talk to your family doctor about how you may be able to reduce your wait time. You can:

  • tell your doctor you’re willing to go for an appointment in the evening, night or weekend – those appointments may be available sooner
  • tell your doctor you’re willing to travel to a hospital or imaging centre with a shorter wait time
  • see if there is a cancellation list you could be added to, if you can be available on short notice when last-minute openings become available
  • make sure you follow any instructions about what to do before your appointment ( e.g. limiting what you eat or drink for a period of time) so you don’t risk having to reschedule

See wait times for diagnostic imaging