Where should the CR be directed for a lateral projection of the nasal bones?

Where should the CR be directed for a lateral projection of the nasal bones?

• A. .5 inch (1 cm) inferior to nasion
• B. 1 inch inferior to nasion
• C. Through nasion
• D. 2 inches inferior to nasion

Answer: (A)

For a lateral projection of the nasal bones, the central ray should be directed perpendicular to the image receptor at a point just below the nasion. Specifically, about 0.5 inch (1 cm) inferior to the nasion places the beam through the midportion of the nasal bones, giving a true lateral view with minimal superimposition by adjacent structures. Aiming through the nasion would place the beam too high and not center the nasal bones properly, while directing the ray 1 inch or 2 inches below nasion would miss or underimage the nasal bones.

For a lateral projection of the nasal bones, the central ray should be directed perpendicular to the image receptor at a point just below the nasion. Specifically, about 0.5 inch (1 cm) inferior to the nasion places the beam through the midportion of the nasal bones, giving a true lateral view with minimal superimposition by adjacent structures. Aiming through the nasion would place the beam too high and not center the nasal bones properly, while directing the ray 1 inch or 2 inches below nasion would miss or underimage the nasal bones.