Exam category: Procedures → Head, Spine and Pelvis
Why it matters: Three eponym views — Towne, Caldwell, Waters — cover almost everything in this module, and each is defined by a specific structure it's built to isolate from everything around it.
The skull is a dense, overlapping 3D structure, so every specialized view here exists to move one specific structure into a clear, unobstructed spot on the image — usually by angling the CR or extending/tucking the chin to shift a dense structure (like the petrous pyramids) out of the way.
| Method | Projection | What it isolates |
|---|---|---|
| Towne | AP axial, CR angled caudad | Occipital bone, foramen magnum, posterior skull |
| Caldwell | PA axial, CR 15° caudad | Frontal bone, orbits |
| Waters | Parietoacanthial, chin extended | Facial bones, maxillary sinuses — extending the chin drops the petrous pyramids below the maxillary sinuses so they don't superimpose |
Routine skull series = Towne + lateral + Caldwell + PA — between them, these four views cover the whole skull from every necessary angle.
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On a Waters projection, what moves the petrous pyramids below the maxillary sinuses?
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