MRI, CT or Ultrasound?

Which is better:  MRI, CT or Ultrasound?

Should you have an MRI or a CT?  Why did your doctor order an ultrasound instead of another test?

The best scan depends on many things such as what your doctor is looking for, what exams you have had already and what your symptoms are.  Each type of scan has its strengths and weaknesses–at Canada Diagnostic, we have all three types of equipment and can help ensure that you get the best scan for your particular situation.


An MRI, or magnetic resonance imaging, is best for evaluating:

  • Head
  • Spine
  • Joints
  • Soft Tissue
  • Breasts

They provide excellent contrast resolution for soft tissue and MRI with contrast can be used when CT with contrast is contraindicated. The downsides of an MRI include the amount of time they take—about 30 to 60 minutes—and patients must remain incredibly still during this time. If you have claustrophobia, the MRI machine may increase symptoms. People who have pacemakers, aneurysm clips, are pregnant, or who are less than six weeks post-surgery cannot have an MRI.


A CT, or computed tomography, is best for evaluating:

  • Bones
  • Lungs
  • Intra-Abdominal Organs

A CT scan is incredibly fast—about 10 to 15 minutes—and is a great option for those whose MRIs were contraindicated. The negative aspects of CTs include low doses of radiation, a very small risk of an allergic reaction if contrast medium is used, and they cannot be done in patients who have renal insufficiency or any previous allergic reactions to CT contrast.