Which of the following statements is (are) true regarding a pa axial projection of the paranasal sinuses?
1. the oml is elevated 15 degrees from the horizontal.
2. the petrous pyramids completely fill the orbits.
3. the frontal and ethmoidal sinuses are visualized.
a 1 only
b 1 and 2 only
c 1 and 3 only
d 1, 2, and 3

C: 1, and 3 only

Explanation:

According to Caldwell view the use of PA axial projection radiograph of the skull is easier and best for visualization of the paranasal sinuses. The PA axial projection is utilized mostly for trauma patients and is acquired with the utilization of a 15 degrees cephalic point, with the orbit meatal line (OML) situated opposite to the image receptor (IR). During the PA axial projection, the petrous pyramids is anticipated to be at least 33% of the orbits and assist in visualization of the entire sinus of the meatuses of the nasal cavity, which means that if the petrous pyramids can fill the orbits the PA axial projection will not be able to visualize everything.