Radiology is the branch of medicine that uses imaging technology to see inside the body, diagnose diseases, and in some cases treat them without surgery. It covers everything from a simple chest X-ray to guide a needle biopsy of a tumor, and it plays a role in nearly every area of modern healthcare.
Two Sides of Radiology
Radiology splits into two major branches. Diagnostic radiology focuses on capturing and interpreting images to identify what’s wrong. Interventional radiology uses those same imaging tools to guide minimally invasive treatments, like opening a blocked artery or placing a feeding tube, all through small incisions rather than open surgery.
A radiologist is a physician who has completed medical school plus years of specialized training in reading medical images. They interpret scans, write reports translating those images into words, and recommend next steps. A radiologic technologist is the person who actually operates the equipment and positions you for the scan, but does not make diagnoses or treatment decisions.
How Different Imaging Types Are Used
Each type of scan has strengths that make it better suited for certain problems.
- X-ray: The fastest and most common scan. It’s used primarily for detecting broken bones and lung conditions like pneumonia or tuberculosis. A chest X-ray delivers about 0.1 millisieverts of radiation, roughly the same amount you absorb from natural background radiation in a single day.
- CT scan: A series of X-ray images assembled into detailed cross-sections of the body. CT is the workhorse of emergency rooms, used to evaluate strokes, traumatic injuries, blood clots in the lungs, and cancers of the liver, kidney, and pancreas. It’s also used for pre-surgical planning and lung cancer screening.
- MRI: Uses magnetic fields instead of radiation, making it ideal for soft tissue. MRI excels at evaluating the brain and spinal cord (for conditions like multiple sclerosis or brain tumors), assessing heart structure, and diagnosing inflammatory bowel disease. Because it uses magnets, it’s incompatible with certain implants like pacemakers or aneurysm clips.
- Ultrasound: Uses sound waves to produce real-time images. It’s the go-to for pregnancy monitoring, but it’s also used to evaluate abdominal organs, assess trauma injuries, characterize liver lesions, and check thyroid nodules for signs of malignancy. No radiation is involved.
- Nuclear medicine (PET scans): Involves injecting a small amount of radioactive tracer to detect metabolic activity. PET scans are especially valuable in oncology for staging cancers and monitoring treatment response, and they can detect early metabolic changes in neurodegenerative diseases like Alzheimer’s and Parkinson’s.
What Interventional Radiologists Treat
Interventional radiologists use imaging as a live guide while performing procedures through catheters or needles. Common procedures include placing stents to open blocked blood vessels, inserting filters into large veins to catch blood clots before they reach the lungs, and injecting clot-dissolving medications to restore blood flow to limbs or organs. They also perform needle biopsies, guiding a small needle into almost any part of the body to collect tissue samples without surgery.
Other procedures include blocking blood flow to a vessel to stop internal bleeding (embolization), placing feeding tubes directly into the stomach for patients who can’t eat by mouth, and inserting catheters into large veins for chemotherapy, nutrition, or dialysis. Because these procedures are image-guided and minimally invasive, they typically involve shorter recovery times and lower complication rates than traditional surgery.
Radiology’s Role in Cancer Care
Radiology often serves as the entry point into the cancer care system. In breast cancer, for example, a screening mammogram may be the first step that leads to diagnosis. From there, the radiologist coordinates initial next steps: recommending additional imaging, performing image-guided biopsies, and making timely referrals to surgeons and oncologists. The radiologist doesn’t make treatment decisions but acts as what some in the field call a “quarterback” during the early phase of care, ensuring the right specialists get involved quickly.
Throughout treatment, imaging tracks whether tumors are shrinking, stable, or growing. CT and PET scans are used to measure tumor size and metabolic activity at regular intervals, giving oncologists the data they need to decide whether to continue, adjust, or change a treatment plan.
What Happens During a Radiology Visit
Preparation depends on the type of scan. For a CT scan, you’ll typically need to stop eating two hours beforehand and stick to clear liquids. If your scan requires contrast dye, you may need to arrive early to drink an oral contrast solution. For an MRI, you’ll be asked about any metal implants, pacemakers, or other devices that could be affected by the magnetic field. If you’re claustrophobic, your doctor can prescribe anti-anxiety medication to take beforehand, though you’ll need someone to drive you home.
Ultrasound preparation varies by the area being examined. A pelvic ultrasound requires you to drink about 32 ounces of water and arrive with a full bladder. An abdominal ultrasound requires fasting from midnight the night before. For a mammogram, skip deodorant, powder, and lotions on your chest and underarms, as these can interfere with the images.
The scan itself is usually quick. A chest X-ray takes minutes. A CT scan typically runs 10 to 30 minutes. An MRI can take 30 minutes to over an hour depending on what’s being examined. After the images are captured, a radiologist reviews them and generates a report for the doctor who ordered the scan. Critical findings, like signs of a stroke or internal bleeding, are communicated immediately.
Contrast Dye: What to Know
Many CT and MRI scans use contrast agents to make certain structures more visible. CT scans use iodine-based contrast, while MRI scans use gadolinium-based agents. Mild reactions to iodine contrast, such as itching, hives, or nausea, occur in fewer than 3% of cases. Severe reactions like difficulty breathing or cardiac symptoms are rare, occurring in less than 0.04% of patients.
Iodine-based contrast can also affect kidney function, particularly in people who already have reduced kidney health. This is why you may be asked about your kidney function or have blood work done before a contrast-enhanced CT. People with thyroid conditions, especially overactive thyroid, should mention this before receiving iodine contrast, as it can trigger or worsen thyroid problems. Gadolinium-based contrast used in MRI does not carry the same kidney risk but has its own safety profile that your care team will review with you. If you’ve had a prior contrast reaction, your ordering physician will typically prescribe medication to take before the scan to reduce the chance of another reaction.
How AI Is Changing Radiology
Artificial intelligence is increasingly used in radiology departments to flag urgent findings. In emergency settings, AI can immediately identify signs of stroke or blood clots in the lungs and bump those cases to the top of the reading queue, shaving critical minutes off diagnosis. AI also assists radiologists by spotting abnormalities through pattern recognition, serving as a second set of eyes that complements human expertise.
Beyond interpretation, AI algorithms are helping reduce radiation exposure. Deep learning techniques can reconstruct high-quality images from lower-dose scans, meaning patients receive less radiation without sacrificing diagnostic accuracy. AI also speeds up time-consuming measurements, like calculating liver volume before a transplant or tracking changes in tumor size across multiple scans, tasks that previously required significant manual effort from radiologists.