When is a CT (Computed Tomography) neck with contrast indicated?

CT Neck with Contrast: Clinical Indications

CT neck with intravenous contrast is the preferred initial imaging modality for evaluating nonpulsatile neck masses in adults at increased risk for malignancy, deep neck infections, and localized cervical lymphadenopathy suspicious for disease. 1

Primary Clinical Indications

Suspected Head and Neck Malignancy

• Any patient with a neck mass at increased risk for malignancy should receive CT or MRI with contrast, with CT offering superior spatial resolution, shorter scan times, and better patient tolerance. 1
• Contrast enhancement is essential for distinguishing vessels from lymph nodes and identifying nodal necrosis, which helps guide the search for an unknown primary tumor. 1
• The standard protocol extends from skull base to thoracic inlet to adequately capture all structures and screen the upper aerodigestive tract for primary malignancy. 1
• Contrast material facilitates visualization of the carotid artery and jugular vein, helps delineate the full extent of neoplastic lesions, and can suggest a precise diagnosis based on enhancement patterns. 2

Salivary Gland Pathology

• CT with IV contrast is specifically indicated for suspected salivary gland cancer, particularly when there is concern for bone involvement, as CT provides superior evaluation of cortical erosion. 1
• IV contrast increases conspicuity of the primary lesion, characterizes necrotic or hypervascular tumors, improves detection of metastatic adenopathy, and evaluates vascular patency. 1

Deep Neck Infections

• IV contrast is essential for detecting neck abscesses, especially intramuscular abscesses that may not be apparent on non-contrast imaging. 1
• CT can identify dental sources of infection in febrile patients and is superior to ultrasound for evaluating the extent of deep neck inflammation. 1

Cervical Lymphadenopathy

• CT neck with IV contrast is indicated for localized neck findings such as lymphadenopathy suspicious for disease recurrence in patients with known malignancy. 3
• The presence and distribution of abnormal lymph nodes aids in differentiating reactive from malignant processes. 1

Cranial Neuropathy

• Contrast-enhanced CT neck is useful to characterize lesions in the carotid space or posterior cervical space along the extracranial course of cranial nerves, particularly CN XI (accessory nerve). 3
• CT can demonstrate atrophy of the trapezius or sternocleidomastoid muscles in accessory nerve palsy, though MRI offers superior soft tissue contrast for directly imaging features of neuritis. 3

Vascular Injuries

• CT angiography (CTA) of the neck with IV contrast is highly efficient for diagnosis of arterial and venous traumatic lesions in the acute setting and when patients develop delayed symptoms. 4
• Helical CT angiography can serve as the initial method for evaluation in patients with possible arterial injuries of the neck from penetrating trauma, with sensitivity and specificity approaching 100%. 5

When Non-Contrast CT May Be Sufficient

• Non-contrast CT may be helpful in a small minority of cases only, such as confirming fat-containing lesions or identifying sialoliths. 1
• There is no relevant literature supporting routine use of CT neck without IV contrast for most clinical scenarios including suspected disease recurrence, cranial neuropathy evaluation, or neck mass assessment. 3

When Dual-Phase Imaging Is NOT Indicated

• Dual-phase imaging (without and with contrast) is not usually necessary and doubles radiation exposure unnecessarily. 1
• There is no relevant literature supporting the use of CT neck without and with IV contrast for suspected disease recurrence or most other clinical indications. 3

Contraindications and Alternative Imaging

When to Choose MRI Instead

• Consider MRI instead of CT for: suspected nasopharyngeal primary tumor, cranial nerve abnormality, concern for perineural invasion or skull base involvement, or dental artifact obscuring the tonsillar fossa and tongue base. 1
• Contrast allergy and renal insufficiency are contraindications to contrast administration. 1
• In severe renal impairment, non-contrast MRI offers superior soft tissue characterization compared to non-contrast CT. 1

Limitations of CT

• CT has lower soft tissue resolution than MRI, which can be problematic for certain tumor types like adenoid cystic carcinoma that may lack significant contrast enhancement. 1
• MRI offers superior evaluation of the intracranial and high cervical portions of cranial nerves compared to CT. 3

Technical Considerations

Contrast Administration

• Adequate contrast enhancement of major neck vessels is more important than enhancement of the tumor itself because of the need to differentiate vessels from neck node metastases. 6
• A dose of 0.75 ml/kg of contrast medium (300 mg/ml concentration) appears sufficient for vascular opacification when the CT scan can be completed in approximately 120 seconds. 6
• Low tube voltage (80 kVp) with low concentration contrast media (270 mgI/ml) combined with iterative reconstruction can reduce radiation dose by 50% and iodine consumption by 15.6% while maintaining diagnostic image quality. 7

Radiation Exposure

• The average CT neck dose is approximately 3 mSv, considered acceptable in adults. 1
• All imaging should follow ALARA (as low as reasonably achievable) principles with modern low-dose protocols and reconstruction algorithms. 1

Common Pitfalls

• Do not order CT neck alone for tracheal pathology, as the limited z-axis coverage risks exclusion of the full extent of tracheal disease; combined neck and chest CT is preferred. 3
• Do not routinely order CTA for simple neck mass evaluation unless there is clinical suspicion of a pulsatile mass or vascular etiology. 3
• Conventional angiography is recommended only for therapeutic purposes or when the diagnosis remains unclear after cross-sectional imaging. 4