Medical Imaging Glossary
Plain-language explanations of radiology terms — written for patients, not doctors
A
Aneurysm
An aneurysm is a balloon-like bulge in an artery — most small aneurysms found by chance are monitored with periodic imaging rather than treated right away.
Architectural Distortion
Architectural distortion on a mammogram means the normal pattern of breast tissue looks pulled or twisted without a clear lump — it is one of the findings that usually leads to a biopsy.
Artifact
An artifact is something that appears on your imaging scan but is not actually in your body — like a visual glitch that radiologists are trained to recognize.
Atelectasis
Atelectasis is a partial collapse or incomplete expansion of lung tissue — it is one of the most common incidental findings on chest imaging and is usually not a cause for concern.
B
Benign
Benign means a finding is not cancerous and is generally not harmful — it is the best outcome when something abnormal appears on a scan.
BI-RADS
BI-RADS is a scoring system (0–6) used to classify mammogram and breast ultrasound findings — the number tells your doctor what to do next.
Biopsy
A biopsy is the lab test that confirms what an imaging finding actually is — it is the only way to know for sure whether something is cancerous.
Breast Density
Breast density describes the ratio of fibroglandular tissue to fatty tissue in your breasts — about half of all women have dense breasts, and it affects how well mammograms can detect abnormalities.
Bulging Disc
A bulging disc is when the cushion between two spine bones spreads out beyond their edge in all directions — it is a normal part of aging and rarely the cause of pain by itself.
C
CAD-RADS
CAD-RADS (0–5) is a scoring system used on coronary CT angiography to grade the worst coronary artery narrowing — the number guides whether more testing or treatment is needed.
Calcification
Calcification refers to small deposits of calcium in tissue that show up as bright white spots on imaging — most are harmless.
Cardiomegaly
Cardiomegaly means an enlarged heart as seen on imaging — it is a finding, not a disease, and has many possible causes.
Clinical Correlation Recommended
Clinical correlation recommended means the radiologist is asking your doctor to combine the imaging findings with your symptoms, exam, and history to reach a complete interpretation.
Clinical Indication
Clinical indication is the 'reason for the exam' section on your imaging report — it tells the radiologist why your doctor ordered the scan.
Contrast / Contrast Dye
Contrast (or contrast dye) is a substance given before or during an imaging exam that makes certain structures in your body easier to see on the scan.
Cyst
A cyst is a fluid-filled sac that appears on imaging — the vast majority of cysts are benign and do not require treatment.
E
Edema
Edema on an imaging report means swelling caused by excess fluid in the tissue — it is often the body's natural response to injury or inflammation.
Effusion
An effusion is an abnormal collection of fluid in a body cavity — most often around the lungs, heart, or inside a joint — that can have many causes, from minor inflammation to conditions requiring treatment.
Enhancement
Enhancement means an area on your scan becomes brighter after contrast dye is given — it shows increased blood flow or a disrupted tissue barrier, not necessarily cancer.
F
Findings
The Findings section is the radiologist's organ-by-organ observation list — it is usually long, often includes normal entries, and is summarized in the Impression.
Fleischner Criteria
The Fleischner Criteria are guidelines that tell doctors how to follow up on small lung nodules found on CT scans — most small nodules need only monitoring.
Follow-Up Recommended
Follow-up recommended means the radiologist wants you to have a repeat scan at a specific time interval to monitor a finding — it usually does not mean something is wrong.
Further Evaluation Recommended
'Further evaluation recommended' means the radiologist has enough information to ask a question but not enough to answer it — the next step is more imaging, a specialist visit, or clinical correlation.
G
Gadolinium
Gadolinium is the contrast metal used to make tissues and blood vessels show up on an MRI — for most patients it is uncommonly associated with reactions, and modern formulations have largely eliminated the historical kidney-related risk.
Ground-Glass Opacity
Ground-glass opacity (GGO) is a hazy, translucent area on a lung CT scan — it can be caused by infection, inflammation, or other conditions.
H
Herniation
A herniation means tissue has pushed out of its normal space — most commonly a spinal disc — and is extremely common on MRI, often found even in people with no symptoms.
Heterogeneous
Heterogeneous means a tissue or structure has a mixed or varied internal appearance on imaging — it is a neutral descriptive term, not a diagnosis.
Hyperintensity
Hyperintensity refers to a bright area on an MRI scan — it indicates tissue with different properties but does not automatically mean something is wrong.
Hypodense
Hypodense means an area appears darker than surrounding tissue on a CT scan — it is a very common descriptor and most often represents benign findings like simple cysts.
Hypoechoic
Hypoechoic means an area appears darker than surrounding tissue on ultrasound — it describes how the tissue reflects sound waves, not whether it is dangerous.
I
Impression
The Impression is the radiologist's summary at the end of your imaging report — it contains the most important findings and recommendations.
Incidental Finding
An incidental finding is something unexpected that shows up on your scan when the doctor was looking for something else — most are harmless.
L
Lesion
A lesion is any area of abnormal tissue found on a medical imaging scan — it does not automatically mean cancer.
LI-RADS
LI-RADS (LR-1 to LR-5, plus LR-M, LR-TIV, LR-NC) is a scoring system used on liver CT and MRI in patients at high risk for liver cancer — the category tells your doctor what to do next.
Lung-RADS
Lung-RADS is a scoring system (1–4) used to classify findings on low-dose CT lung cancer screening — the category tells your doctor what follow-up is needed.
Lymphadenopathy
Lymphadenopathy means enlarged or abnormal-looking lymph nodes on imaging — the most common cause is reactive (infection or inflammation), not cancer.
M
Malignant
Malignant means a finding is cancerous or has the potential to spread — but imaging alone cannot confirm malignancy without a biopsy.
Mass
A mass is a lump or growth larger than 3 cm seen on imaging — it can be benign or malignant and usually requires further evaluation.
Mass Effect
Mass effect means something inside the body — such as a tumor, bleeding, or swelling — is pushing or shifting nearby structures out of their normal position.
Microcalcifications
Microcalcifications are tiny specks of calcium seen on a mammogram — whether they matter depends much more on their shape and pattern than on their presence, and most are benign.
O
O-RADS
O-RADS (0–5) is a scoring system used on ovarian and adnexal findings from ultrasound or MRI — the category estimates the chance a lesion is malignant and tells your doctor what to do next.
Opacity
An opacity is a white or hazy area on a chest X-ray — it can indicate fluid, infection, inflammation, or other conditions.
S
Spiculated
Spiculated means a mass or nodule has spiky, irregular projections radiating outward — this feature raises concern and typically warrants prompt further evaluation.
Spondylolisthesis
Spondylolisthesis is when one bone in your spine slips forward over the one below it — most slips are mild (Grade I), often painless, and treated without surgery.
Stable
Stable means a finding on your scan has not changed compared to a previous exam — it is one of the most reassuring words you can see on an imaging report.
Stenosis
Stenosis means narrowing of a body passage or channel — most commonly the spinal canal — and is often a normal part of aging that does not always cause symptoms.
T
T1 / T2 Weighted
T1 and T2 weighted are different MRI image settings that highlight different tissues — they are standard techniques, not findings to worry about.
TI-RADS
TI-RADS is a scoring system (TR1–TR5) used to classify thyroid nodules on ultrasound — the score guides whether a biopsy is needed.
Tumor
A tumor is an abnormal mass of tissue that can be benign (non-cancerous) or malignant (cancerous) — imaging alone cannot always tell the difference.
W
Well-Circumscribed
Well-circumscribed means a finding has smooth, clearly defined borders — this is generally a reassuring feature that suggests a benign process.
Within Normal Limits
Within Normal Limits (WNL) means the finding falls inside the expected range for a healthy person — it is the radiologist's way of saying 'normal.'
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