Chapter 11: Skull, Facial Bones, and Paranasal Sinuses

Question 1

Zygomatic Arches: Submentovertical (SMV)

SS/Eval: Zygomatic arches free from overlying structures. Arches projected beyond parietal eminences (unless flat or traumatic zygomas are present). No rotation or tilt by symmetric arches and without foreshortening.

Answer 1

POP: Supine or seated upright

POP: Hyperextend neck until vertex rests on table or on wall bucky with IOML parallel with IR

CR: Right angles to the IOML and 1” posterior to outer canthi

Collimation: No larger than 8x10” (1” laterally, superiorly to chin and inferiorly to gonions), can clip nose

Question 2

Zygomatic Arches: Tangential

SS/Eval: Tangential image of arch free from superimposition. Always do both sides for comparison.

Answer 2

POP: Supine or seated upright

POP: Hyperextend pt’s neck and rest head on vertex, adjust IOML as parallel as possible, rotate MSP 15-degrees toward side being examined AND tilt 15-degrees away from affected side.

CR: Perpendicular to IOML, centered to arch at 1” posterior to the outer canthus

Collimation: No larger than 6x10” (1” laterally, include tip of nose and inferiorly to include gonion)

Question 3

Zygomatic Arches: AP Axial
Modified Towne Method

SS: Symmetric arches free from superimposition by mandible and projected laterally from rami.

Answer 3

POP: Supine or seated upright

POP: MSP; OML perpendicular to IR

CR: Angle 30-degrees caudad. CR @ glabella (approx. 1” above the nasion)

Collimation: 8x10” (1” laterally include tip of nose and inferiorly to gonion)

Question 4

Mandible: AP Axial
(Modified Towne Method)

SS: Symmetrical mandibular body and rami, condyles, symmetrical cranium

Answer 4

POP: Supine or upright seated/standing

POP: OML is perpendicular to IR: MSP perpendicular; IPL to parallel to floor (When pt is upright)

IR: Top of IR approx. at top of ear

CR: 30-degrees caudad at level of mandibular condyles; passing approx. midway through EAMs and angle of mandible

Collimation: 8x10” to include superior orbital margins and soft tissue surrounding mandible

Question 5

Mandible: Modified Parietoacanthial
(Modified Waters)

SS: Petrous ridges projected midway through the maxillary sinuses; symmetrical mandibular body and rami; symmetrical cranium

Answer 5

POP: Prone or upright seated/ standing

POP: OML forms a 55-degree to IR: MSP is perpendicular to bucky; IPL is parallel to floor (when pt upright)

CR: perpendicular to IR at the level of the acanthion

Collimation: 8x10” (1” laterally and include supraorbital margin and inferiorly to chin)

Question 6

Mandibular Rami: PA

SS/Eval: Symmetrical mandibular body and rami. Central body of mandible not well demonstrated because of spine superimposition.

Answer 6

POP: Prone or upright, seated/standing

POP: Forehead and nose on IR; OML perpendicular to IR; MSP

CR: Perpendicular to acanthion

Collimation: No larger than 8x10” (1” laterally and superiorly to include TMJs and inferiorly to include chin)

Question 7

Mandibular Rami: PA Axial

SS/Eval: Symmetrical mandibular body and rami. Central body of mandible not well demonstrated because of spine superimposition. Includes condylar process.

Answer 7

POP: Prone or seated upright

POP: Forehead and nose on IR; OML perpendicular to IR; MSP

CR: 20-degree cephalad to exit acanthion

Collimation: No larger than 8x10” (1” laterally and superiorly to include TMJs and inferiorly to include chin)

Question 8

Mandibular Body: PA

SS: Symmetrical mandibular body

Answer 8

POP: Prone or seated upright

POP: Rest head on nose and chin; Mandibular symphysis parallel with IR (AML almost perpendicular)

CR: Perpendicular to level of lips

Collimation: No larger than 8x10” (1” laterally and superiorly to include TMJ’s and inferiorly to include chin)

Question 9

Mandibular Body: PA Axial

SS/Eval: Mandibular body and TMJs. TMJs inferior to mastoid process, symmetrical rami.

Answer 9

POP: Prone or seated upright

POP: Rest head on nose and chin; Mandibular symphysis parallel with IR (AML almost perpendicular)

CR: 30-degree cephalad directed between TMJs

Collimation: No larger than 8x10” (1” laterally and superiorly to include TMJs and inferiorly to include chin)

Question 10

Mandibular Rami: Axiolateral

SS: Mandibular ramus on side down; no overlap of ramus by opposite side, no superimposition of ramus with c-spine, no elongation or foreshortening.

Answer 10

POP: Seated or Semipronated

POP: True lateral position, IPL perpendicular, long axis of mandibular body parallel to floor to IR to avoid superimposition of cervical spine (*with approximate AML parallel); mouth closed and teeth together. Extend pt’s neck so that the mandibular body is not superimposed.

CR: 25-degree cephalad to ramus (side down) **10-degrees cephalad, tilting 15-degrees

Collimation: 8x10” (1” beyond anterior and inferior shadows and above TMJs)

Question 11

Mandibular Body: Axiolateral Oblique

SS: Mandibular body on the side down

Answer 11

POP: Seaterd or semipronated

POP: True lateral position, IPL perpendicular, mouth closed and teeth together; Extend neck so that mandibular body is parallel with transverse axis of IR and then rotate head 30-degrees toward IR.

CR: 25-degrees cephalad to pass through mandibular body (side down) **10-degrees cephalad, tilting 15-degrees, and obliquing

Collimation: 8x10” (1” beyond anterior and inferior shadows and above TMJs)

Question 12

Mandible: Submentovertical (SMV)

SS/Eval: Mandibular body, coronoid and condyloid process o the rami. Equidistant lateral borders of skull and mandible, condyles anterior to pars petrosal, symphysis extending to anterior border of face to avoid mandibular foreshortening.

Answer 12

POP: Supine or seated upright

POP: MSP; Hyperextend head until vertex rests on table or on wall buky with IOML parallel with the IR. When IOML not parallel, angle CR cephalic.

CR: Perpendicular to IOML and midway between the angles of the mandible.

Collimation: No larger than 8x10” (1” laterally and superiorly to tip of nose and inferiorly to gonions)

Question 13

TMJ: AP Axial

SS/Eval: Condyles of mandible and mandibular fossa of temporal bones. Minimal superimposition of petrosa on condyle in closed mouth. Condyle and TMJ below pars petrosa in open mouth. Condyle in fossa in closed mouth. Condyle inferior to articular tubercle in open mouth.

Answer 13

POP: Supine or seated upright

POP: MSP; OML perpendicular to IR

CR: Angle 35-degrees caudad entering 3” above the nasion and midway between the TMJs

Collimation: 8x10” (1” laterally and superiorly to glabella and inferiorly to lips)

Posterior teeth much be in contact

Question 14

TMJ: Axiolateral (R or L) (Modified Schuller)

SS/Eval: The TMJ on the side down is the side of interest. The TMJ is shown in the closed mouth and open mouth positions. TMJ anterior to EAM. Condyle in fossa in closed mouth. Condyle inferior to articular turbercle in open mouth.

Answer 14

POP: Semipronated or seated

POP: True lateral skull (IOML and MSP parallel, IPL perpendicular)

CR: Angle 25 or 30-degrees caudad. The CR enters about 1/2” anterior and 2” superior to the EAM on the side up.

Collimation: 8x10” (1” anteriorly and posteriorly, and inferior to TMJs)

Exact location of the TMJ is as follows: 1/2” anterior and 1” inferior to EAM.

Question 15

TMJ: Axiolateral Oblique (Modified Law Method)

SS: Condyles and necks of mandible on the side down is of interest. TMJs, condyle in fossa in closed mouth, condyle inferior to articular tubercle in open mouth.

Answer 15

POP: Semipronated or seated

POP: AML is parallel with the IR, rotate the MSP approx. 15-degrees toward the IR.

CR: Angle 15-degrees caudad and exiting TMJ closest to IR (CR enters about 1.5” superior to EAM on the side up)

Collimation: 5x5”, can increase collimation if necessary. (Outer canthus to posterior edge of auricle and from midparietal to bottom of ear)

Question 16

Paranasal sinuses: Lateral (R or L)

SS/Eval: All four sinus groups, sphenoid is best demonstrated. Clearly visible air-fluid levels, if present. Sella turcica in profile, superimposed orbital roofs and mandibular rami.

Answer 16

POP: Seated, Left preferred

POP: True lateral skull, IOML parallel to IR.

CR: Perpendicular 1/2” to 1” posterior to outer canthus.

Collimation: 8x10” (1” beyond tip of nose and 3” superior to nasion and inferiorly to include occlusal plane and posteriorly to include auricle)

Question 17

Frontal and Anterior Ethmoidal Sinuses: PA Axial (Caldwell Method)

SS/Eval: Primarly to show the frontal sinuses (lying superior to frontonasal suture) and anterior ethmoid sinuses (lying above petrous ridges and on each side of nasal fossa and inferior to frontal sinuses). Sphenoid sinuses projected through nasal fossa inferior to or between ethmoid air cells. Petrous pyramids extend from lower third of orbit to superior third of maxillary sinus. Symmetric petrous ridges, equal distance of lateral borders of skull and lateral orbits. Clearly visible air-fluid levels, if present.

Answer 17

POP: Seated or standing

• POP: Angled Grid Technique - Tilt grid 15-degrees caudad, OML perpendicular to IR; nose and forehead on IR.
• POP: Vertical Grid Technique - Rest tip of nose on IR; OML forms angle of 15-degrees with CR. Use sponge for support.

CR: Direct horizontal to exit nasion, 15-degree relationship between CR and OML for either technique

Collimation: 8x10” (1” laterally, superiorly include top of head and inferiorly for occlusal plane)

Question 18

Maxillary Sinuses: Parietoacanthial (Waters Method)

SS: Maxillary sinuses projected above the petrous ridges. Foramen rotundum also seen

Answer 18

**Same as the Waters method for the facial bones

Collimation: 8x10” (1” laterally and top of head shadow to occlusal plane)

CR: acanthion

Question 19

Maxillary and Sphenoidal Sinuses: Parietoacanthial (Open-mouth Waters Method)

SS/Eval: sphenoidal sinuses projected through the open mouth, maxillary sinuses. Clearly visible air-fluid levels. Petrous pyramids lying inferior to floor of maxillary sinuses. Equidistant lateral skull borders and lateral orbits, orbits and maxillary sinuses symmetric.

Answer 19

POP: Seated PA

POP: Same as for Waters Method (OML forms 37-degree relationship with plane of IR), except that the mouth will be open; MML will NOT be perpendicular

CR: Perpendicular to exit acanthion

Collimation: 8x10” (1” laterally and top of head shadow to occlusal plane)

Question 20

Ethmoid adn Sphenoidal Sinuses: Submentovertical (SMV) (Schuller Method)

SS/Eval: Sphenoidal sinus and ethmoid air cells are shown. Equidistant lateral skull borders to mandibular condyles. IOML position demonstrated by superimposed anterior frontal bone by mental protruberance. Improper positioning cuases mandible to superimpose ethomoid sinuses. Mandibular condyles anterior to petrous pyramids.

Answer 20

POP: Supine or seated upright

POP: Extend head until vertex rests on table or on wall bucky. MSP perpendicular and IOML parallel to IR. When IOML not parallel, angle CR cephalic.

CR: Perpendicular to the IOML through sella turcica (3/4” anterior to EAM).

Collimation: 8x10” (1” beyond tip of nose and laterally)