Glossary of Terms
- Radiology has its own dialect — a few dozen words do most of the heavy lifting.
- The big ones describe how bright something looks: dense/lucent on X-ray and CT, echogenic/anechoic on ultrasound, and the T1/T2 "signal" words on MRI.
- "Contrast" is overloaded: it means both the dye we inject and the difference in brightness between two things.
- This page is a dictionary, not a story — skim it, then come back whenever a word ambushes you.
Every field has its secret handshake, and radiology's is a pile of words that sound like a wizard describing the weather. Hypoattenuating. Anechoic. Hyperintense on T2. Translated, most of them just mean "darker" or "brighter" with extra syllables. Here's the cheat sheet I wish someone had handed me on day one. Skim it now, bookmark it, and let it bail you out later.
The "how bright is it" words
Almost every imaging term is secretly answering one question: is this spot brighter or darker than its neighbors, and why? The catch is that each modality uses a different word for the same idea, like four countries that all play soccer but refuse to call it the same thing.
If the underlying physics of "brighter vs. darker" feels shaky, the foundation is attenuation — how much of the beam gets eaten on the way through.
| Term | Modality | Plain meaning |
|---|---|---|
| Dense / opaque | X-ray, CT | Whiter — the beam got blocked (bone, metal, contrast). |
| Lucent / lucency | X-ray, CT | Blacker — the beam sailed through (air, fat, gas). |
| Attenuation | CT | How much the tissue blocks the beam; measured in Hounsfield units. |
| Hyperattenuating / hypoattenuating | CT | Brighter / darker than the reference tissue. |
| Echogenic / hyperechoic | Ultrasound | Bounces sound back well — shows up bright. |
| Anechoic | Ultrasound | Sends nothing back — pure black (classic for simple fluid). |
| Hypoechoic | Ultrasound | Darker than its surroundings, but not pure black. |
| Signal intensity | MRI | How bright a voxel is on a given sequence. |
| Hyperintense / hypointense | MRI | Bright / dark on the sequence you name (always say which). |
On MRI, "bright" is meaningless on its own. The same tissue can be dark on one sequence and glowing on the next, so the word is always glued to a sequence: hyperintense on T2, hypointense on T1. Saying something is "bright on MRI" is like saying a movie is "loud" — loud when?
The two MRI workhorses are worth memorizing as a pair, and they have their own home page: T1, T2 and weighting. The pocket version: on T2, water and most pathology shine bright; on T1, fat is bright and fluid goes dark.
Contrast: the most overloaded word in the building
"Contrast" means two completely different things and nobody warns you.
- The stuff we inject — the dye that lights up blood vessels and organs (see iodinated contrast for CT and gadolinium for MRI).
- The difference in brightness between two adjacent things — the reason you can tell the kidney from the fat around it.
So "this scan has poor contrast" might mean the IV dye was weak, or that two tissues look frustratingly similar. Context is everything.
"Enhancement" specifically means a tissue got brighter after contrast was given — usually a sign of blood flow reaching it. Don't confuse it with something that was already bright on its own (like fresh blood on CT or fat on T1). The trick: you only know it enhanced if you can compare a before-and-after pair.
Words for where you're standing
Cross-sectional imaging slices the body like a loaf of bread, and the slice direction has names.
| Term | What it means |
|---|---|
| Axial | Slices like deli meat — looking up from the patient's feet. The default CT view. |
| Coronal | Front-to-back slices, like a swinging saloon door. |
| Sagittal | Side slices, splitting left from right. |
| AP / PA | X-ray taken front-to-back (AP) or back-to-front (PA). |
| Supine / prone | Lying face-up / face-down. |
| Contralateral / ipsilateral | The opposite side / the same side. |
A reliable banana skin: on the image, the patient's left is on your right. You're looking at them as if they're facing you across a table. I have pointed confidently at the wrong side more times than I'll admit in writing.
Describing the thing you found
Once you spot something, there's a vocabulary for saying what it is without committing to a diagnosis.
- Lesion — a deliberately vague word for "an abnormal spot." It buys you time.
- Mass — a space-occupying lump that shoves its neighbors aside.
- Focal vs. diffuse — confined to one spot vs. smeared everywhere.
- Well-circumscribed vs. infiltrative — crisp borders (usually reassuring) vs. ragged ones (usually not).
- Cystic vs. solid — fluid-filled balloon vs. dense tissue. Ultrasound settles this argument fast.
- Calcification — calcium deposited where it doesn't belong; bright white on CT.
When you genuinely don't know what something is, "soft-tissue density lesion" or "indeterminate" are honest, legitimate answers. Radiology rewards calibrated uncertainty far more than a confident wrong guess.
A few odds and ends
- Incidental finding (incidentaloma) — something you weren't looking for that showed up uninvited, like finding a raccoon in the garage.
- Artifact — a fake-looking thing created by the machine or physics, not the patient. Real-looking, not real.
- Window / windowing — adjusting CT brightness and contrast on the fly to inspect bone vs. lung vs. soft tissue from the same scan.
- Reformat / reconstruction — rebuilding the raw data into different planes or slice thicknesses after the fact.
That's the starter dictionary. You don't need to memorize it cold — you need to recognize these words when they jump out of a report so they stop being a foreign language and start being signposts. Come back as often as you need; that's what a glossary is for.