Which central landmark does the CR pass through in SMV projection?

Which central landmark does the CR pass through in SMV projection?

• A. Sella turcica
• B. Nasion
• C. External occipital protuberance
• D. Mastoid process

Answer: (A)

In the SMV projection, the central ray is aimed so it travels along the midline of the skull and passes through the sella turcica. This is set up by aligning the head so that the infraorbitomeatal line (IOML) is perpendicular to the beam, and directing the CR through the midline at the level of the skull base. The sella turcica — a midline, saddle-shaped part of the sphenoid bone that houses the pituitary gland — is the central landmark this projection targets. Imaging through this point ensures the cranial base structures around the sella, including the clivus and foramen magnum region, are captured clearly in a symmetrical view. Other surface landmarks like the nasion, external occipital protuberance, or mastoid process are off the central axis used for this view, so they don’t guide the beam through the center of the skull base in SMV.

In the SMV projection, the central ray is aimed so it travels along the midline of the skull and passes through the sella turcica. This is set up by aligning the head so that the infraorbitomeatal line (IOML) is perpendicular to the beam, and directing the CR through the midline at the level of the skull base. The sella turcica — a midline, saddle-shaped part of the sphenoid bone that houses the pituitary gland — is the central landmark this projection targets. Imaging through this point ensures the cranial base structures around the sella, including the clivus and foramen magnum region, are captured clearly in a symmetrical view.

Other surface landmarks like the nasion, external occipital protuberance, or mastoid process are off the central axis used for this view, so they don’t guide the beam through the center of the skull base in SMV.