Skull projections

Question 1

AP axial (Towne) - Skull

Answer 1

Flex the patient’s neck enough to place the OML perpendicular to the plane of the IR.
CR: Directed through the foramen magnum at a caudal angle of 30 degrees to the OML or 37 degrees to the IOML. The CR enters approximately 2 ½ inches (6.3cm) above the glabella and passes through the level of the EAM

Question 2

PA axial (Caldwell) - Skull

Answer 2

Rest the patient’s forehead and nose against the bucky. Adjust the head so that the OML is perpendicular to the plane of the IR.
CR: Direct the CR to exit the nasion at an angle of 15 degrees caudad
*The petrous ridges are projected in the lower third of the orbits.

Question 3

Lateral - Skull

Answer 3

IOML is parallel to the long axis of the IR.

CR: Perpendicular, entering 2 inches (5 cm) superior to the EAM

Question 4

Parietoacanthial (Waters) - Sinuses

Answer 4

OML forms an angle of 37 degrees from the plane of the IR. The MML should be approximately perpendicular to the IR
CR: Horizontal to the IR and exiting the acanthion

Question 5

PA axial (Caldwell) - Sinuses

Answer 5

OML perpendicular when the grid is angled. If not, rest the tip of the nose on the grid and center to the nasion. We want the OML to form an angle of 15 degrees with the horizontal CR.
CR: Directed horizontal to exit the nasion. The 15 degrees relationship between the CR and the OML remains the same for both techniques.
*Shows the frontal sinuses, the anterior ethmoidal air cells and the inferior frontal sinuses. The petrous pyramids obscur the maxilary sinuses

Question 6

Lateral - Sinuses

Answer 6

IOML is horizontal.

CR: Directed horizontal, enter the patient’s head ½ - 1inch (1.3 – 2.5cm) posterior to the outer canthus

Question 7

PA axial (Caldwell) - Facial bones

Answer 7

OML is perpendicular.
CR: Directed the CR to exit at the nasion at an angle of 15 degrees caudad.
*Petrous ridges projected into the lower third of the orbits.

Question 8

Parietoacanthial (Waters) - Facial bones

Answer 8

OML forms a 37 degree angle with the plane of the IR. The MML is as perpendicular as possible .
CR: Perpendicular to exit acanthion
*Shows the orbits, maxillae, and zygomatic arches. The goal is to project the petrous ridges immediately below the maxillary sinuses

Question 9

Acanthioparietal (Reverse Waters) - Facial bones

Answer 9

OML forms a 37 degree angle with the plane of the IR. The MML is as perpendicular as possible.
CR: Perpendicular to enter the acanthion and centered to the IR
*Shows the superior facial bones. Petrous ridges below maxillary sinuses.

Question 10

Lateral - Facial bones

Answer 10

IOML is perpendicular.

CR: Perpendicular and entering the lateral surface of the zygomatic bone hallway between the outer canthus and the EAM

Question 11

PA axial - Orbits

Answer 11

Rest the forehead and nose on the IR. Center the IR 3/4 inch distal to the nasion
CR: Directed through the center of the orbits at a caudal angle of 30 degrees. This angulation is used to project the petrous portions of the temporal bones below the inferior margin of the orbits

Question 12

Parietoacanthial (modified Waters) - Orbits

Answer 12

Rest the patients chin on the holder. OML should form a 50 degree angle with the plane of the IR
CR: Perpendicular through the mid-orbits

Question 13

Lateral - Orbits

Answer 13

Midsagittal plane parralel with the IR.

CR: Perpendicular through the outer canthus

Question 14

Parietoacanthial (modified Waters) - Nasal bones

Answer 14

CR: Perpendicular to enter just above the base of the skull and exit at the nose

Question 15

Lateral - Nasal bones

Answer 15

IOML parallel with the IR

CR: Perpendicular to the bridge of the nose at a point ½ inch (1.3cm) distal to the nasion

Question 16

AP axial (modified Towne) - Mandible

Answer 16

OML is perpendicular
CR: Directed 35 degrees caudad, centered midway between the TMJs, and entering at a point approximately 3 inches (7.6cm) above the nasion

Question 17

PA axial - Mandible

Answer 17

AML nearly perpendicular (Body) or OML perpendicular (Rami)
CR: Directed midway between the TMJs at an angle of 30 degrees cephalad (Body) or 20 – 25 degrees cephalad to exit the acanthion (Rami)
*Shows medial or lateral displacement of fragments in rami fractures

Question 18

AP - Mandible

Answer 18

OML perpendicular to the IR.

CR: Perpendicular to enter the acanthion

Question 19

PA - Mandible

Answer 19

OML perpendicular to the IR (Rami) or AML perpendicular (Body).
CR: Rami: Perpendicular to exit the acanthion
Body: Perpendicular to the level of the lips
*Position of head varies between the two
*(1)Used to show medial or lateral displacement of fragment of the rami.

Question 20

Axiolateral - Mandible

Answer 20

Head in a true lateral position. IOML perpendicular.

CR: Directed 25 degrees cephalad to pass directly through the mandibular region of interest

Question 21

Axiolateral obliques - Mandible

Answer 21

Rotate the patients head 30 degrees toward the IR

CR: Directed 25 degrees cephalad to pass directly through the mandibular region of interest

Question 22

AP axial (modified Towne) - TM joints

Answer 22

OML perpendicular
CR: Directed 35 degrees caudad, centered midway between the TMJs, and entering at a point approximately 3 inches (7.6cm) above the nasion
*Shows the condyles of the mandible and the mandibular fossar of the temporal bones

Question 23

Axiolateral (open & closed mouth) - TM joints

Answer 23

IOML perpendicular. Head in a true lateral position.
CR: Directed to the midpoint of the IR at an angle of 25 or 30 degrees caudad. The CR enters about ½ inch (1.3cm) anterior and 2 inches (5cm) superior to the upside EAM