Radiology is the medical field that uses imaging — X-ray, ultrasound, CT and MRI — to diagnose disease or injury and guide treatment. A closely related field, nuclear medicine, uses small amounts of radioactive tracer to show how organs are working. Together these are called 'medical imaging'. Some tests use ionising radiation (X-ray, CT, nuclear medicine); ultrasound and MRI do not. A radiologist — a specialist doctor — interprets the images.
Key takeaways
- Radiology uses X-ray, ultrasound, CT and MRI to diagnose and guide treatment.
- Nuclear medicine, a related field, shows how organs are working using tracers.
- X-ray, CT and nuclear medicine use ionising radiation; ultrasound and MRI do not.
- Radiologists (specialist doctors) interpret the images; radiographers and sonographers perform the scans.
Radiology is the medical specialty that uses imaging to help diagnose disease or injury, and to guide procedures that treat them.[2] When people talk about “having a scan,” they usually mean one of the main radiology tests. A closely related specialty, nuclear medicine, uses tiny amounts of radioactive medication to show how an organ is functioning. Together, these are referred to as medical imaging.
The main types of imaging
There are a few core technologies, and a key difference between them is whether they use ionising radiation:[2]
- X-ray — the simplest and fastest test; excellent for bones and the chest. Uses radiation.
- CT (computed tomography) — detailed cross-sectional images built from many X-ray “slices.” Uses radiation.
- Fluoroscopy — real-time, moving X-ray images. Uses radiation.
- Mammography — low-dose X-ray of the breast. Uses radiation.
- Ultrasound — real-time images made with sound waves. No radiation.
- MRI — very detailed images made with magnets and radio waves. No radiation.
- Nuclear medicine (including PET) — shows how organs work, using a radioactive tracer. Uses radiation.
Who’s involved
A radiologist is a medical doctor who has completed years of specialist training (in Australia, through the RANZCR — the Royal Australian and New Zealand College of Radiologists) to interpret images and write the report for your doctor.[1] You may never meet your radiologist, but they’re a critical part of your care team. The scans themselves are performed by trained professionals: radiographers (medical imaging technologists) for X-ray and CT, sonographers for ultrasound, and nuclear medicine technologists for nuclear medicine.[1]
Choosing the right test
No single test is best for everything. Your referring doctor — often in discussion with the radiologist — chooses the most appropriate scan for your symptoms, balancing what needs to be seen against keeping any radiation as low as possible.[1] Ultrasound and MRI are preferred where they can answer the question, especially for children and in pregnancy.
Frequently asked questions
What’s the difference between radiology and nuclear medicine?
Radiology (X-ray, ultrasound, CT, MRI) mainly shows what the body looks like; nuclear medicine uses a radioactive tracer to show how an organ is functioning. They’re often done in the same facility and together are called medical imaging.[2]
Is the person who does my scan the same as the one who reads it?
Usually not. A radiographer or sonographer performs the scan; a radiologist (a doctor) interprets it and writes the report.[1]
Which scans don’t use radiation?
Ultrasound and MRI use no ionising radiation. X-ray, CT, fluoroscopy, mammography and nuclear medicine do.[2]
Sources
- RadiologyInfo.org (RSNA & ACR) — What does a radiologist do? — www.radiologyinfo.org/en/info/article-your-radiologist
- RANZCR / InsideRadiology — Radiation risk of medical imaging — www.insideradiology.com.au/radiation-risk/
