CT Neck — Contrast-Enhanced Soft Tissue
Skull base to the thoracic inlet, extended into the upper mediastinum when the question is nodal or when a retropharyngeal collection may track inferiorly.
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 deep neck space infection, including peritonsillar, parapharyngeal and retropharyngeal abscess.
- Staging of known or suspected head and neck squamous cell carcinoma and assessment of cervical nodal disease.
- Neck lump of unclear nature, including suspected branchial or thyroglossal lesions.
- Salivary gland swelling, sialolithiasis with obstruction, and suspected sialadenitis.
- Suspected epiglottitis or airway compromise in a patient stable enough to be scanned.
Technique
- Delay conventions differ genuinely between centres and published protocols: reported delays for soft-tissue neck range from around 50 s to 90 s, with the shorter end favouring vascular differentiation and the longer end favouring mucosal and tumour enhancement.
- Delayed acquisitions of 3 minutes or more have been shown to improve conspicuity of squamous cell carcinoma in a substantial minority of cases, at the cost of vascular opacification.
- A puffed-cheek or modified Valsalva acquisition separates the buccal mucosal surfaces when an oral cavity lesion is the question.
- Arms down; a raised-arm position drives shoulder streak artefact through the lower neck.
Where it goes wrong
- An unenhanced neck CT cannot separate a node from a vessel and will under-call abscess; if contrast is genuinely contraindicated, the alternative study should be reconsidered rather than the contrast simply dropped.
- Swallowing during the acquisition produces motion through the larynx and hypopharynx that mimics or hides mucosal disease.
- Dental amalgam streak obscures the oral cavity and floor of mouth; a gantry-angled or reconstructed oblique series helps where the scanner allows it.
- Scanning too early leaves nodes and vessels equally dense and defeats nodal staging.
Clinical questions that reach this study
Contrast
Typically 80-100 mL of non-ionic iodinated contrast at around 1.5-3 mL/s, sometimes as a split injection to sustain mucosal enhancement.
Acquisition
- Breathing
- Quiet respiration, no swallowing, no phonation during the acquisition.
- Reconstruction
- Thin axial acquisition with coronal and sagittal soft-tissue reformats and a bone series.
- 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.
- Systemic venous (soft-tissue) phaseTypically ~45–90 s after the start of injection, with most published soft-tissue protocols sitting at ~60–80 s. Region-specific: reported neck delays span roughly 50–90 s, and routine contrast-enhanced chest work is conventionally ~60 s. Confirm locally.
Arteries and veins have equalised, and soft tissue outside the liver is at or near peak interstitial enhancement. The transferable principle is that away from the liver the purpose of a venous acquisition has nothing to do with portal delivery: it is that (a) every vessel is now uniformly dense, so a vessel stops being mistaken for a node or a mass, and (b) contrast has had time to leak into the expanded interstitium of inflamed or neoplastic tissue, which is what makes an abscess wall, a necrotic node, a mucosal tumour or a phlegmon declare itself against normal tissue. This is therefore the general-purpose soft-tissue phase for neck, chest, extremities and superficial structures. It is deliberately NOT called portal venous: the portal venous phase is a liver-timed acquisition that merely happens to fall in the same window, and borrowing its name for a neck or limb study imports a hepatic timing rationale that does not apply and hides the fact that the right delay is set by the target tissue. The errors are symmetrical — too early and arteries are far denser than nodes while an abscess rim has not yet enhanced; too late and everything equilibrates, collapsing the lesion-to-background difference the study depends on.
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.
- Prior contrast reaction and elective premedication· nurse pre scan
- Intravenous access adequate for the planned injection· radiographer at scan
- Metformin and iodinated contrast· radiographer at scan
- Child-sized technique and contrast dose· radiographer at scan
- Kidney function and intravenous iodinated contrast· radiographer at scan