Ultrasound vs X-Ray:
What's the Difference?
Ultrasound uses sound waves and no radiation; an X-Ray uses a very low dose of radiation. Here's how each works, what it's used for, and how the two differ on the day.
Key points
- Ultrasound uses sound waves, with no radiation. An X-Ray uses a very low dose of radiation, about 0.1 mSv for a chest X-Ray.
- Ultrasound shows organs, blood flow, soft tissue and pregnancy. An X-Ray shows bones, joints and the chest.
- Your doctor chooses the exam and writes the requisition. Both are covered by OHIP.
An Ultrasound makes pictures with sound waves and uses no radiation. An X-Ray makes pictures with a very low dose of radiation. Ultrasound is best for organs, blood flow, pregnancy and soft tissue. An X-Ray is best for bones, joints and the chest. Your doctor chooses the one that answers their question, and sometimes orders both.
Here’s how each works, what it’s used for, and what the visit is like.
How does an Ultrasound work?
A small handheld probe sends high-frequency sound waves into your body and listens for the echoes that bounce back. A computer turns those echoes into moving, real-time pictures. Health Canada describes it as real-time imaging of the fetus, internal organs, veins, arteries and blood flow.
On the day, the sonographer puts warm gel on your skin and moves the probe over the area. You feel gentle pressure, nothing more. There is no radiation, no needle and no dye, which is why Ultrasound is used throughout pregnancy and is safe for all ages. Our sonographers are registered with Sonography Canada.
How does an X-Ray work?
An X-Ray sends a very low dose of radiation through the part of your body being examined. Dense tissue such as bone absorbs more of it and shows up white, while air and soft tissue show up darker. The result is a still image, taken in a second or two.
How low is the dose? The Canadian Nuclear Safety Commission puts a typical chest X-Ray at 0.1 mSv, while the average Canadian receives 1.8 mSv a year from natural background radiation. A chest X-Ray is roughly the background radiation you get over a few days. Every X-Ray is done with a doctor’s requisition and at the lowest dose that produces a clear image. Lead shielding is no longer routinely used, because current guidelines show it isn’t needed and it can interfere with image quality.
What is each one used for?
| Ultrasound shows | X-Ray shows |
|---|---|
| Organs: liver, gall bladder, kidneys, pancreas, spleen | Bones and joints: fractures, arthritis, joint changes |
| Pregnancy: the baby, placenta and fluid | Chest and lungs: infections such as pneumonia, heart size |
| Blood flow in the carotid arteries, arms and legs (Doppler) | Head and neck: sinuses, jaw, skull |
| Breast lumps, often alongside Mammography | Spine and pelvis, arms and legs |
| Muscles, tendons and joints (MSK) | Some digestive concerns and swallowed objects |
Neither one is “better”. They answer different questions. A twisted ankle might get an X-Ray to rule out a broken bone and an Ultrasound to look at the tendon. A heart Ultrasound (an Echocardiogram) shows the heart’s valves and chambers, while a chest X-Ray shows the heart’s size and the lungs around it.
Which one do I need?
That’s your doctor’s or nurse practitioner’s call, and it’s written on your requisition. Bluewater accepts a valid requisition from any licensed Ontario healthcare provider, on any form. If your requisition lists an Ultrasound and an X-Ray, we book them back to back at one clinic so you come in once. Read Do you need a requisition for an X-Ray or Ultrasound in Ontario? if you’re not sure what counts.
How do they differ on the day?
| Ultrasound | X-Ray | |
|---|---|---|
| Preparation | Depends on the scan: an empty stomach for the abdomen, a full bladder for the pelvis or pregnancy, none for most others | None. Avoid clothing with metal zippers or snaps if you can |
| Time in the room | About 20 to 45 minutes | About 10 minutes |
| Booking | By appointment, at all ten clinics | Walk in with a signed requisition at nine clinics, or book ahead |
| What you feel | Warm gel and gentle pressure | Nothing |
| OHIP | Covered in full with a requisition | Covered in full with a requisition |
| Without OHIP (October 2026) | An abdominal or pelvic Ultrasound is $145 | A chest X-Ray is $85 |
Walk-in X-Ray is available at every Bluewater clinic that offers X-Ray, until 30 minutes before closing. At Belleville, X-Ray is available Tuesdays, 8:30am to 4:00pm only, and our University Heights clinic has no X-Ray. Read Can you walk in for an X-Ray? for the details.
Either way, a radiologist reads the images and the report reaches your doctor in 24 to 48 hours.
Is Ultrasound or X-Ray safer in pregnancy?
Ultrasound uses sound waves, not radiation, which is why it’s used throughout pregnancy. If you are pregnant or might be, tell us before any X-Ray. We’ll either reschedule, or confirm with your doctor that the exam is still the right choice. We ask every patient who could be pregnant, every time.
Book your Ultrasound or X-Ray
Both are offered across our ten clinics in Toronto, the GTA, Belleville and Port Hope. See our Ultrasound and X-Ray pages, find a clinic, then book online or call 416-462-0064. Most appointments are available within 48 hours.
This article is general information. Always follow the instructions from your doctor and your appointment confirmation.
Common questions
How does an Ultrasound work?
A handheld probe sends high-frequency sound waves into the body and listens for the echoes, which a computer turns into real-time pictures. There is no radiation, no needle and no dye.
How does an X-Ray work?
A very low dose of radiation passes through the body and makes an image on a detector. Dense tissue such as bone shows up white. A typical chest X-Ray is about 0.1 mSv, compared with 1.8 mSv a year from natural background radiation in Canada.
What is each one used for?
Ultrasound looks at organs such as the liver, gall bladder and kidneys, blood flow, pregnancy, the breast and soft tissue. An X-Ray looks at bones and joints, the chest and lungs, and some digestive concerns.
Which one do I need, Ultrasound or X-Ray?
Your doctor or nurse practitioner decides and writes it on your requisition. Sometimes both are ordered. Bluewater books them back to back at one clinic so you come in once.
Keep reading
Can You Walk In for an X-Ray?
Walk-In vs. Booking
Yes, you can walk in for an X-Ray at Bluewater with a signed requisition. Booking ahead is still a good idea. Here's how to decide, and what to bring either way.
Is My Ultrasound Covered by OHIP?
What's Free and What Isn't
With a valid Ontario health card and a requisition, a medically needed ultrasound costs you nothing. Here's what OHIP pays for, what it doesn't, and what to do if you're not covered.
Can You Get a Mammogram Without a Referral in Ontario?
Yes. Eligible women aged 40 and over can book their own screening Mammogram through the Ontario Breast Screening Program, with no doctor's visit and no cost. Here's who qualifies and how to book.