Medical Term Glossary
Plain-language explanations of the medical terms that appear on CT, MRI and X-ray reports — what each one means, when it matters, and what to ask your doctor.
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Abscess
A walled-off pocket of pus that the body builds around an infection to stop it spreading. It is the immune system's way of containing trouble, but once it forms it usually cannot drain on its own. Most need either antibiotics, a drain placed under image guidance, or a small procedure to clear them properly.
Also: infected cavity, infected fluid collection, pocket of pus
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Aneurysm
A focal bulge in the wall of an artery, where the vessel has stretched outwards into a balloon-like pouch. Most are found by chance on scans done for another reason and are watched over years rather than treated immediately. Size, location, and growth rate decide whether monitoring, medication, or repair is the right plan.
Also: AAA, arterial aneurysm, ballooning artery
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Aorta
The body's largest artery. It carries oxygen-rich blood out of the heart, arches over the top of the chest, and then runs straight down through the chest and belly, branching off to supply every organ and limb along the way. Reports often mention it when measuring its width or describing changes in its wall.
Also: abdominal aorta, aortic vessel, great artery
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Atrophy
Loss of size or volume in a tissue or organ. It can affect the brain, muscles, kidneys, a gland, or almost anywhere else. Some volume loss is part of normal ageing; some reflects a specific condition such as disuse, nerve damage, reduced blood supply, or a longstanding disease. The pattern matters more than the word alone.
Also: atrophic change, reduced volume, shrinkage
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Calcification
A small deposit of calcium that has built up in soft tissue, blood vessels, or an old healed area. On a CT scan it shows up as a very bright white spot because calcium blocks x-rays. Most deposits are old, stable, and harmless — they are essentially scars made of mineral.
Also: calcifications, calcified, calcified lesion
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Chronic
A radiology word meaning a finding has been present for a long time — usually weeks, months, or years — and looks stable rather than new. It is the opposite of acute, which describes something that has just appeared. The word says nothing about danger; it describes how long something has been there.
Also: chronic changes, established, long-standing
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Contrast enhancement
A special dye is injected into a vein during the scan to make blood vessels and certain tissues stand out more clearly. When an area soaks up the dye and looks brighter than its surroundings on the images, radiologists call that pattern enhancement. The pattern itself helps tell different kinds of tissue apart.
Also: IV contrast, contrast uptake, contrast-enhanced scan
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Cyst
A small sac filled with fluid, sitting inside an organ or in soft tissue. Most are harmless, very common, and pop up incidentally on scans done for other reasons. Radiologists describe them as simple when the fluid is clear and the walls are thin, which is the reassuring picture; complex ones earn a closer look.
Also: complex cyst, cystic lesion, fluid collection
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Focal
A descriptive word meaning a finding is limited to one specific spot rather than spread across a wider area. It is the opposite of diffuse, which means scattered or widespread. The word says where, not what — it tells you the finding is localised but says nothing on its own about whether it matters.
Also: circumscribed, discrete area, in one area
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Fracture
A break, crack, or other loss of continuity in a bone. It can be a hairline split that's barely visible, a clean snap across the middle, or a more complicated pattern with multiple pieces. The location, pattern, and whether nearby structures are involved all shape how it is treated.
Also: Fx, bone break, bony injury
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Imaging planes (axial, sagittal, coronal)
The three standard directions radiologists use to slice the body when reviewing a scan. Axial slices cut across like a horizontal cross-section, sagittal slices run from side to side splitting left from right, and coronal slices run front to back like opening a book. Looking at the same area in all three helps the radiologist see things any single direction would miss.
Also: axial, axial view, coronal
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Incidental finding
Something the radiologist noticed on a scan even though it was not what the scan was originally looking for. These pop-ups are very common in modern imaging because scans capture far more than the clinical question asked. Most are harmless background discoveries; a few deserve a closer look.
Also: additional finding, incidental lesion, incidentally noted
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Indeterminate
A careful word radiologists use when a finding doesn't fit neatly into the benign category or the worrying category. It means the current scan alone cannot decide what something is, so a follow-up scan or a different test is usually recommended. It does not mean the finding is dangerous.
Also: equivocal finding, incompletely characterised, indeterminate finding
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Lesion
A general word radiologists use for any spot, area, or region of tissue that looks different from what surrounds it. By itself it does not mean cancer, infection, or anything specific — it simply flags a finding that stood out. The report's other adjectives (focal, well-defined, suspicious, benign) carry most of the meaning.
Also: abnormal area, focal lesion, growth
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Lymph nodes
Small, bean-shaped filters that sit along the body's drainage network for tissue fluid. Hundreds of them are scattered through the neck, armpits, chest, abdomen, pelvis, and groin. They trap bacteria, viruses, debris, and stray cells, then mount an immune response. Their presence on a scan is normal; size, shape, and pattern decide whether they need attention.
Also: glands, lymph glands, lymph node
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Malignant
A heavy word in radiology meaning a finding has the appearance of cancer on imaging — irregular edges, invasion into nearby tissue, abnormal blood vessels, or other concerning features. It is a description of the picture, not a confirmed diagnosis. A biopsy is what actually proves cancer; imaging alone cannot.
Also: cancerous, concerning for cancer, concerning for malignancy
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Mass
A solid or partly solid lump of tissue, usually larger than three centimetres, that looks distinct from the tissue around it. The word flags something worth investigating, but it does not by itself mean cancer. Size, borders, growth over time, and how it behaves with contrast all carry far more meaning than the label alone.
Also: focal mass, growth, lump
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Metastasis
A spot on imaging that looks like cancer that has spread from another part of the body. The word on a report is a description of appearance, not always a diagnosis. Many suspected spreads turn out, after biopsy or follow-up, to be benign — cysts, scars, or unrelated lesions. Biopsy is the gold standard for confirmation.
Also: metastases, metastatic disease, metastatic lesion
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MRI signal intensity (T1, T2, FLAIR)
On an MRI scan, every tissue gives off a different brightness depending on which setting the scanner is using. The settings are called sequences — T1, T2, and FLAIR are the most common. Whether something looks bright or dark on each sequence is one of the main clues radiologists use to tell different tissues and problems apart.
Also: FLAIR, T1, T1 signal
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MRI vs CT — which does what
Two of the most common imaging tests, used for different jobs. CT is fast and great for bones, bleeding, and emergencies. MRI is slower but shows soft tissue, brain detail, and joints in much higher resolution. Neither is better overall — they answer different questions, and doctors choose based on what they need to see.
Also: CT or MRI, CT vs MRI, MRI or CT
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Mucosal thickening
A description used by radiologists when the soft inner lining of a hollow space looks puffier than usual. It is most commonly seen in the sinuses but also turns up in the bowel and other lined cavities. By itself it just means the lining is irritated; the cause varies from a recent cold to a more persistent inflammation.
Also: lining thickening, mucosal swelling, sinus lining thickening
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Nodule
A small, rounded spot of tissue, usually under three centimetres across, that looks different from what surrounds it. Most are harmless and very common — old scars, tiny benign growths, or healed inflammation. Size, shape, and behaviour over time decide whether one needs follow-up or can be ignored.
Also: pulmonary nodule, small focal lesion, small nodule
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Nonspecific
A hedging word radiologists use when a finding could be caused by several different things and the scan alone cannot decide between them. It is not a diagnosis — it is the radiologist being honest about the limits of imaging and asking your doctor to combine the picture with your symptoms and blood tests.
Also: etiology unclear, non-specific, nonspecific appearance
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Soft tissue mass
A lump in the soft parts of the body — muscle, fat, fibrous tissue, nerves, or vessels — rather than in bone. It is a description of what was seen, not a diagnosis. Most are benign (lipomas, cysts, fibrous lumps); some are inflammatory; a smaller number turn out to be tumours that warrant further imaging or biopsy.
Also: fatty lump, muscle mass, non-bony mass
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Study
In radiology, a single complete imaging examination of one patient on one day — for example, one MRI of the brain or one CT of the abdomen. A single examination is usually made up of several image sets, called series, captured from different angles or with different settings.
Also: DICOM study, current study, examination
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Suspicious
A hedging word radiologists use when a finding has some features that raise concern but the scan alone cannot prove a diagnosis. It usually triggers more workup — a follow-up scan, biopsy, or specialist referral — rather than a definite answer. The word is a flag, not a verdict.
Also: concerning, concerning for, raises concern for
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Ultrasound
An imaging test that uses high-frequency sound waves rather than X-rays to look inside the body. A handheld probe sends sound pulses through the skin and listens for the echoes, building a live picture on a screen. It involves no radiation, is widely available, and is especially good at looking at soft, fluid-filled, and moving structures.
Also: US, doppler scan, echo
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Unremarkable
A reassuring word in radiology. It means the radiologist looked carefully at a structure and found nothing worth pointing out — no swelling, no abnormal spots, no concerning changes. Despite how it sounds in everyday English, on a scan report this is good news.
Also: grossly normal, negative study, no abnormality detected
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