It is natural to feel uneasy before a scan. Many patients ask us the same questions: Is the radiation harmful? Is contrast dye safe? Can I be scanned if I am pregnant? Here are clear, honest answers, so you can come to your appointment with confidence.
First, which scans use radiation?
Not all of them do.
- Ultrasound and MRI use no ionising radiation at all. Ultrasound uses sound waves, and MRI uses magnets and radio waves.
- X-ray and CT use ionising radiation. X-ray uses a very small dose, and CT uses a higher dose because it takes many images.
How much radiation is involved?
We are all exposed to natural background radiation every day from the soil, air, food and the sun. As a rough guide, a chest X-ray gives about the same dose as a few days of natural background radiation. A CT scan gives more, comparable to a number of months or a few years of background exposure, depending on the body area scanned.
The dose from a single scan is small, and the risk it carries is very low. The benefit of finding a problem early, such as a fracture, an infection, a stone or a cancer, is almost always far greater than that small risk.
How do we keep your dose as low as possible?
Radiology teams follow a safety principle known as ALARA, meaning “as low as reasonably achievable.” In practice, this means:
- Scans are only done when your doctor and radiologist agree they are medically justified.
- The lowest dose that gives a clear, useful image is used.
- Radiographers focus the beam on the area being examined.
- Lead shielding is used where appropriate.
- Where a radiation-free test such as ultrasound or MRI can answer the question, it is considered first.
- Children receive adjusted, lower doses.
Is contrast dye safe?
Contrast is a special liquid that helps certain organs and blood vessels stand out on CT or MRI. It is given by injection into a vein, or sometimes as a drink.
For most people it is safe. You may feel a warm sensation, a metallic taste or mild nausea for a moment. Allergic reactions are uncommon, and they are usually mild, such as itching or a rash. Serious reactions are rare, and our team is trained to manage them.
Tell us before your scan if you have:
- a previous reaction to contrast dye
- asthma or other allergies
- kidney disease
- diabetes, especially if you take metformin
- thyroid problems
We may check your kidney function first, adjust your preparation or choose a different scan.
Can I have a scan if I am pregnant?
Yes, in many cases, but it depends on the scan and your stage of pregnancy.
- Ultrasound is safe throughout pregnancy and is the standard way to check on your baby.
- MRI is used when it is needed, and contrast is avoided unless it is essential.
- X-ray and CT are usually avoided, particularly of the abdomen and pelvis. If one is truly necessary, for example after a serious accident, the dose is kept as low as possible and your doctor will discuss the benefits and risks with you.
The most important step is to tell us before your scan if you are or might be pregnant. Never hide a possible pregnancy, as we will always find a safe option.
Are MRI scans safe?
MRI has an excellent safety record. The main risk comes from the very strong magnet, which can pull on metal objects and affect certain implants, such as some pacemakers and brain aneurysm clips. This is why every patient is carefully screened before an MRI, and why you must remove all metal and tell us about any implant. Some implants are MRI-safe, but we need to confirm this first.
What about children?
Children are more sensitive to radiation, so we scan them only when necessary, use child-sized doses and prefer ultrasound or MRI whenever they can answer the question. A parent or guardian is welcome to stay and comfort the child.
Can I have repeated scans?
Your doctor will advise you. Ultrasound can be repeated as often as needed. For X-ray and CT, repeat scans are only requested when the benefit is clear. Bring your earlier scans and reports, because they can help avoid repeating a test.
What you can do to stay safe
- Tell us if you are or might be pregnant.
- Share your medical history, allergies and medicines.
- Tell us about any implants or metal in your body.
- Bring previous scans and reports.
- Ask questions. We are happy to explain every step.
Safe, careful imaging at Primescan Radiology
At Primescan Radiology, your safety comes first. Our team explains each scan, screens every patient and keeps doses as low as reasonably possible. If you have concerns about an upcoming scan, contact our team through this website before your appointment.