CT Simulation Scanning Range for Brain Radiation Therapy
For CT simulation for radiation therapy to the brain, scan from vertex to the aortic arch, not just to C3.
Recommended Scanning Protocol
The evidence from stroke imaging guidelines, which extensively addresses cerebrovascular CT angiography protocols, consistently supports vertex-to-aortic arch scanning:
CT angiography should extend from the vertex to the aortic arch to comprehensively evaluate both intracranial and extracranial vasculature 1.
This scanning range is specifically recommended to assess the entire cerebrovascular axis, including the anterior (carotid) and posterior (vertebrobasilar) circulation, as well as the extracerebral carotid arteries 1.
The "aortic arch-to-vertex" protocol is the standard recommendation for comprehensive neurovascular imaging 1.
Rationale for Extended Coverage
Vascular Anatomy Considerations
Scanning to the aortic arch captures the origins of the great vessels (brachiocephalic, left common carotid, and left subclavian arteries), which is essential for understanding the complete vascular supply to the brain 1.
This extended coverage allows visualization of potential vascular anomalies, atherosclerotic disease, or anatomic variants at the aortic arch that could be clinically relevant 1.
Treatment Planning Benefits
Complete anatomic coverage ensures accurate patient positioning and treatment field design, particularly for cases where vascular structures may be dose-limiting organs at risk 1.
The extended scan range provides better anatomic landmarks for image registration and treatment setup verification 1.
Clinical Implementation
The vertex-to-aortic arch protocol can be efficiently performed during a single helical CT acquisition, adding minimal time to the simulation process 1.
Multidetector CT scanners are preferred for this extended coverage, as they provide faster acquisition with improved image quality 1.
Common Pitfall to Avoid
Scanning only to C3 is insufficient because it fails to capture the aortic arch and proximal great vessel origins, potentially missing important vascular anatomy that could impact treatment planning or patient positioning 1.