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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Carotid artery stenosis
Narrowing of one of the major neck arteries that supply blood to the brain, usually caused by a buildup of fatty plaque along the artery wall. It is one of the most important imaging findings for stroke risk and is graded by how much of the artery's opening is blocked.
Also: carotid artery blockage, carotid artery disease, carotid artery narrowing
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Cellulitis
A bacterial infection of the skin and the soft tissue just beneath it, causing redness, swelling, warmth, and pain. On a scan it shows up as thickened, inflamed tissue rather than a solid mass. It usually responds well to antibiotics, especially when caught early.
Also: SSTI, peri-incisional inflammation, skin and soft tissue infection
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Cholesteatoma
An abnormal growth of skin cells inside the middle ear, behind the eardrum, that can slowly enlarge and erode the delicate bones and structures nearby. It's not a cancer, but left untreated it can damage hearing, balance, or the facial nerve, so it's usually found on a CT scan of the temporal bone.
Also: choleastoma, cholesteatoma of the middle ear, cholesteotoma
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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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CT angiography (CTA)
An imaging test that pairs a CT scanner with a fast injection of contrast dye to produce detailed, three-dimensional pictures of blood vessels. It is commonly used to look for blockages, aneurysms, or blood clots in arteries throughout the body, and is usually completed within a few minutes.
Also: CT angiogram, CTA, angio CT
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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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Fine needle aspiration (FNA)
A minimally invasive test in which a very thin needle draws out a small sample of cells from a lump, node, or organ for examination under a microscope. It's typically done under local anesthetic, guided by ultrasound or CT, and results usually help determine whether further testing or treatment is needed.
Also: FNA, FNA biopsy, FNAC
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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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Hemangioma
A harmless tangle of blood vessels that forms a soft, benign growth, most often found in the liver or in a spinal bone. It is one of the most common incidental findings on imaging, almost never causes symptoms, and is generally left alone once its typical appearance confirms it is benign.
Also: angioma, benign vascular tumor, haemangioma
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Hematoma
A pocket of blood that has collected outside blood vessels, usually after an injury, procedure, or minor bleeding into soft tissue. Unlike an active bleed, a hematoma is blood that has already pooled and typically begins to break down and reabsorb naturally over the following weeks.
Also: blood clot collection, blood pocket, contained bleed
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Hemorrhage
Blood that has leaked outside the vessels meant to carry it. On a scan it shows up as a pool or streak of blood in tissue or a body cavity. Size, location, and whether the leak looks fresh or old all change how urgently it needs attention. Many small or old collections are watched rather than treated.
Also: active bleed, bleed, bleeding
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Hepatic
Anything to do with the liver. It is simply the medical adjective for 'relating to the liver', from the Greek word for liver. On its own it carries no good or bad meaning — it just tells you which organ a finding involves. The noun attached to it, like cyst or lesion, is what actually matters.
Also: liver, liver-related, of the liver
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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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Inferior vena cava
The body's largest vein in the lower half of the body. It collects oxygen-poor blood from the legs, belly, and pelvis and carries it up to the heart. Often shortened to IVC. Radiologists mention it when measuring its width or describing how full or collapsed it looks.
Also: IVC, great lower vein, lower vena cava
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Iodinated IV contrast
A dye injected into a vein during many CT scans to make blood vessels, organs, and abnormal tissue easier to distinguish from their surroundings. It contains iodine, is cleared by the kidneys within a day, and causes a serious allergic reaction in only a small fraction of people who receive it.
Also: CT contrast dye, IV contrast, contrast injection
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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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Lucency
A darker, less dense-looking area on an x-ray or CT, where more of the beam passed through than in the tissue around it. It is a neutral description of an appearance, not a diagnosis — common harmless causes include air or fat, while in bone it can sometimes need a closer look.
Also: dark area on x-ray, decreased density, low density area
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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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Lytic lesion
A spot where bone has been thinned or eaten away, leaving a darker hole-like area on an x-ray or CT. Many lytic areas are harmless cysts or normal variants, but because some have more serious causes, radiologists describe their edges carefully and often suggest a closer look.
Also: bone destruction, bone lysis, lucent bone lesion
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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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Mucous retention cyst
A small, fluid-filled dome that forms when a mucus-producing gland in the sinus lining becomes blocked and swells with trapped secretions. It's a very common, harmless finding on sinus imaging, often discovered by chance, and rarely causes any symptoms on its own.
Also: antral mucous cyst, benign sinus cyst, maxillary retention cyst
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Nasal septal deviation
A description of the thin wall of cartilage and bone inside the nose sitting off-center rather than perfectly straight. It's an extremely common variation seen on sinus and head scans, present in a large share of adults, and is usually unrelated to whatever prompted the imaging.
Also: bent nasal septum, crooked septum, deviated nasal septum
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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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Opacity
A whiter, denser-looking patch on an x-ray or CT, where something is blocking more of the beam than the surrounding tissue. It is a neutral description of an appearance, not a diagnosis — the cause can be anything from fluid or infection to scarring or a harmless overlap.
Also: dense area, density, increased density
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Osseous
A medical word that simply means "of the bone" or "made of bone." Radiologists use it as a precise adjective when describing structures, findings, or changes that involve the skeleton itself rather than the surrounding soft tissues — muscles, tendons, organs, or nerves. On its own it carries no good or bad meaning.
Also: bone, bone-related, bony
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Parenchyma
The working tissue of an organ — the part that actually does the organ's job, as opposed to its supporting structures like blood vessels, ducts, or capsule. The brain has its own working tissue; so do the kidneys, liver, lungs, and pancreas. Radiologists use the word to be precise about which part of an organ they are describing.
Also: brain parenchyma, functional tissue, hepatic parenchyma
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Parotid gland mass
A distinct lump found within the parotid gland, the largest salivary gland, which sits just in front of and below the ear. Most are discovered incidentally or noticed as painless swelling along the jawline, and the majority turn out to be benign.
Also: mass in parotid gland, parotid gland lesion, parotid lump
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Portable radiograph
An x-ray taken at the bedside with a wheeled machine, used when a patient is too unwell or immobile to travel to the x-ray department. The image is genuinely useful but a little less crisp than a film taken in the department, so reports often note this gently.
Also: bedside radiograph, bedside x-ray, mobile radiograph
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Projection views (AP, PA, lateral, oblique)
The named directions an x-ray beam travels through the body to make a picture. AP is front to back, PA is back to front, lateral is side on, and oblique is at an angle. Taking more than one direction lets the radiologist see a part from several sides.
Also: AP view, PA view, imaging projection
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Radiograph
The proper name for a plain x-ray picture — a single flat image made by passing a brief, low dose of x-rays through the body onto a detector. Dense things like bone show up white, air shows up black, and soft tissues sit in shades of grey in between.
Also: plain film, plain radiograph, plain x-ray
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Reactive lymph node
A lymph node that has enlarged simply because it is actively responding to a nearby infection or minor irritation, rather than to anything serious. Radiologists use this term when a node's size and shape match ordinary immune activity rather than a red flag, and it's one of the most common incidental findings on CT and MRI scans.
Also: benign reactive node, hyperplastic lymph node, inflammatory lymph node
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Renal
Anything to do with the kidneys. It is simply the medical adjective for 'relating to the kidney', from the Latin word for kidney. On its own it carries no good or bad meaning — it just tells you which organ a finding involves. The noun attached to it, like cyst or stone, is what actually matters.
Also: kidney, kidney-related, of the kidney
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Sclerosis
An area where bone has become thicker and denser than usual, showing up as a whiter patch on an x-ray or CT. It is often the body's way of reinforcing bone under stress or healing, and most cases are old, stable, and harmless rather than a sign of disease.
Also: bone hardening, bone sclerosis, dense bone
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Seroma
A pocket of clear, straw-colored fluid that collects under the skin, most often after surgery. It forms because tissue layers that were separated during an operation weep fluid as they heal, and it is a normal part of recovery rather than a sign of infection on its own.
Also: peri-incisional fluid collection, post-operative fluid collection, post-surgical seroma
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Sialolithiasis (salivary stone)
A hardened mineral deposit that forms inside a salivary gland or its draining duct, blocking the normal flow of saliva. It often causes pain and swelling that flares around mealtimes, when saliva production ramps up, and is a common reason for salivary-gland CT or a dedicated sialo-MRI.
Also: duct stone, salivary calculus, salivary duct stone
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Sinusitis
Inflammation of the lining inside the paranasal sinuses, the air-filled spaces around the nose and eyes, often seen with mucus or fluid buildup. It is one of the most frequent incidental findings on head, sinus, and even brain imaging, and is usually mild and unrelated to the reason the scan was ordered.
Also: mucosal thickening, paranasal sinusitis, rhinosinusitis
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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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Soft tissue swelling
Puffiness or thickening of the non-bony tissues — skin, muscle, fat, and the layers around a joint — seen as fullness around an area on a scan. It is the body's normal response to injury, inflammation, or infection, and very often settles as the underlying cause heals.
Also: puffiness, soft tissue edema, soft tissue oedema
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Splenic
Anything to do with the spleen. It is simply the medical adjective for 'relating to the spleen', the fist-sized organ in the upper left belly. On its own it carries no good or bad meaning — it just tells you which organ a finding involves. The noun attached to it, like cyst or vein, is what actually matters.
Also: of the spleen, pertaining to the spleen, relating to the spleen
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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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Thickening
A description that a wall, lining, or layer of tissue measures more than expected for that area. The word is purely a measurement — it does not say whether the cause is inflammation, infection, scarring, a benign change, or something more serious. The rest of the report and the clinical picture decide what it means.
Also: circumferential thickening, focal thickening, mural thickening
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Thyroid nodule
A small lump of tissue that has formed within the thyroid gland in the neck. These are very common, often found by chance on a scan done for an unrelated reason, and the large majority turn out to be non-cancerous.
Also: incidental thyroid nodule, nodular thyroid, thyroid cyst
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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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