What is the recommended imaging protocol for a CT head and neck scan?

CT Head and Neck Imaging Protocol

The recommended imaging protocol for a CT head and neck scan includes non-contrast head CT followed by CTA of both the head and neck with IV contrast, which provides comprehensive evaluation of both vascular and non-vascular structures in a single examination. 1, 2

Standard Protocol Components

• Non-contrast head CT should be performed first to assess for hemorrhage, large infarcts, or other acute intracranial pathologies 1
• CTA head and neck with IV contrast should follow the non-contrast CT to evaluate vascular structures, which is particularly important for suspected vascular pathologies 1
• The protocol should cover from the aortic arch to the vertex of the skull to ensure complete visualization of the cerebrovascular system 3

Technical Considerations

• Modern 256-detector CT scanners allow for a "one-stop-shop" protocol that combines brain CT perfusion and head-and-neck CTA, reducing imaging time by approximately 43% and contrast dose by 40% compared to traditional separate examinations 4
• When evaluating for vascular pathologies, the CTA should be timed to coincide with peak arterial enhancement 4
• Radiation dose considerations are important, with the estimated contributions to total CTA scan dose from each body region being approximately: head (14%), neck (33%), and upper chest (53%) 3

Clinical Applications

• Acute stroke evaluation: Non-contrast head CT followed by CTA head and neck is the standard protocol 1
• Suspected vascular abnormalities: CTA head and neck is highly sensitive (>90%) for detecting aneurysms and arterial dissections 2
• Head trauma: Non-contrast head CT is the initial imaging of choice, with CTA indicated when there is suspicion for vascular injury 1
• Suspected CSF leak: Non-contrast head CT, maxillofacial CT, and temporal bone CT are recommended, with the specific protocol depending on the clinical setting (e.g., maxillofacial CT for CSF rhinorrhea, temporal bone CT for CSF otorrhea) 1

Optimization for Specific Clinical Scenarios

• For suspected cervical vascular dissection or injury, CTA neck or MRA neck without and with IV contrast are equally appropriate initial imaging options 1
• For evaluation of cerebrovascular disease, the protocol should include both head and neck imaging to ensure complete assessment of the vascular system 1
• In cases of suspected subarachnoid hemorrhage, non-contrast head CT should be performed first, followed by CTA if clinical suspicion remains high despite negative initial imaging 2

Potential Pitfalls and Considerations

• Simultaneous ordering of head and neck CT scans when injury is suspected in only one region may lead to unnecessary radiation exposure, as the yield for clinically significant injury in both regions is very low (0.5%) 5
• Relying solely on non-contrast CT head may miss vascular abnormalities, especially small aneurysms (<3mm) or those adjacent to bone 2
• While MRI offers superior soft tissue contrast and avoids radiation exposure, CT remains the first-line imaging tool for head and neck evaluation due to its availability, speed, and lower cost 6

Alternative Imaging Modalities

• MRI/MRA: Offers better soft tissue contrast and is more sensitive for detecting acute infarcts, but may not be readily available in emergency settings 1
• Ultrasound: Useful for evaluation of superficial neck structures but has limited utility for comprehensive head and neck assessment 6

By following this protocol, clinicians can obtain comprehensive anatomical and vascular information of the head and neck region in an efficient manner while minimizing radiation exposure and contrast dose.