CT Neck — Unenhanced
Skull base to thoracic inlet.
Timings, volumes and delays here are representative values drawn from published guidance. Scanner generation, injector, cardiac output and local preference all move them. Confirm against your department's own protocol before you rely on a number.
When to use it
- Suspected radio-opaque ingested or inhaled foreign body, including impacted fish or chicken bone.
- Suspected sialolithiasis where the question is the stone rather than the gland.
- Suspected surgical emphysema or airway perforation where free gas is the finding sought.
- A patient in whom iodinated contrast is genuinely not an option and the question is one that unenhanced imaging can still answer.
Technique
- Bone and sharp reformats are more useful than soft-tissue windows for a foreign body question.
- Coverage should extend low enough to include the upper oesophagus when ingestion is the history.
Where it goes wrong
- Using this protocol for an infection or cancer question wastes the study: without contrast, abscess and phlegmon look alike and nodes look like vessels.
- Calcified tonsilloliths and ossified thyroid cartilage are routinely mistaken for foreign bodies on unenhanced imaging; correlate with the reported level of symptoms.
Clinical questions that reach this study
Contrast
Acquisition
- Reconstruction
- Thin axial acquisition with soft-tissue and bone reformats in all three planes.
- Preparation
- Quiet respiration; no swallowing during the acquisition. Arms down by the sides — arms up drags shoulder artefact into the lower neck. Remove necklaces and dentures.
Phases
Each phase is authored once and shared across every protocol that uses it, so the physiology below is the same wherever you meet it.
- Non-contrast (unenhanced)No injection. Acquired before any contrast is given.
Shows intrinsic tissue attenuation, and nothing else. The transferable principle is that contrast is anti-signal for anything that is already dense: calcification, acute haemorrhage, urinary and biliary calculi, iodine-containing or haemorrhagic fluid, and intrinsic fat all lose conspicuity, or become uninterpretable, once surrounding tissue enhances. It is also the only baseline against which enhancement can be measured, so any protocol that quantifies enhancement or washout (a lesion "enhances by X HU", adrenal absolute washout, renal mass characterisation) is arithmetically impossible without it. Conversely, an unenhanced series adds dose and no information whenever the question is purely about vascularity or perfusion.
Safety checks this protocol carries
Derived from the contrast agent and phases above, not authored here — which is why they cannot drift apart from what the protocol actually does.
- Child-sized technique and contrast dose· radiographer at scan