MRI vs CT Scan: What's the Difference?

Both MRI and CT produce detailed cross-sectional images, but they use different technology:

• CT scans use X-rays (ionising radiation) and are fast - usually 5-15 minutes • MRI uses magnets and radio waves (no radiation) and takes longer - usually 20-60 minutes

Neither is universally "better" - the right scan depends on what your doctor is looking for.

CT scans are preferred for:

• Emergency and trauma situations - CT is fast and shows fractures and internal bleeding quickly • Bone injuries and fractures - CT gives excellent bone detail • Chest imaging - lung conditions, pulmonary embolism, pneumonia • Abdominal emergencies - appendicitis, bowel obstruction, kidney stones • Cancer staging - whole-body scans to check for spread • Patients with metal implants - CT is safe with most metal (MRI is not) • Patients with claustrophobia - CT scanners are open and scans are quick

CT's speed makes it the go-to scan in emergency departments across Australia.

MRI is preferred for:

• Brain and spinal cord conditions - MRI gives far superior soft-tissue detail • Joint and ligament injuries - torn ACL, meniscus, rotator cuff, cartilage damage • Disc problems - herniated discs, spinal stenosis, nerve compression • Soft tissue tumours - MRI can characterise tissue better than CT • Breast imaging - as a supplement to mammography • Pelvic conditions - uterine, ovarian, and prostate conditions • When radiation must be avoided - children, pregnant women, patients needing repeated imaging

MRI's lack of radiation makes it preferred when multiple scans over time are needed.

This is one of the most significant differences:

• CT scan: Uses ionising radiation. A typical chest CT delivers about 7 mSv - equivalent to about 4 years of natural background radiation. • MRI: No radiation at all. Uses magnetic fields and radio waves.

For a single scan, the radiation from CT is not considered dangerous. But for patients who need frequent imaging (e.g., cancer monitoring), MRI may be preferred when it can provide the same diagnostic information.

In Australia:

• CT scan: Generally $0-$200 out-of-pocket with Medicare. CT scans have broader Medicare coverage. • MRI: $0-$250+ out-of-pocket with Medicare at approved sites. Not all MRI machines are Medicare-licensed, so costs can be higher.

CT scans are typically cheaper and more widely available. MRI availability and Medicare coverage have been expanding but remain more limited.

Use Radly to compare prices for both CT and MRI at clinics near you.

Your doctor considers several factors:

• What they suspect is wrong - soft tissue injury suggests MRI; fracture or emergency suggests CT • How urgent it is - CT is faster and more available for urgent cases • Whether radiation is a concern - children and pregnant women are steered toward MRI or ultrasound • Cost and availability - CT is more affordable and widely available • Your medical history - metal implants, claustrophobia, kidney function (for contrast)

Trust your doctor's recommendation. If you're curious about why a particular scan was chosen, ask - they'll be happy to explain.