Textbook of Radiographic Positioning and Related Anatomy

PA Axial Projection: Skull Series

Haas Method

Clinical Indications

• Skull fractures (medial and lateral displacement), neoplastic processes, and Paget's disease

This is an alternative projection for patients who cannot flex the neck sufficiently for AP axial (Towne). It results in magnification of the occipital area but in lower doses to facial structures and the thyroid gland.

This projection is not recommended when the occipital bone is the area of interest because of excessive magnification.

Skull Series

Special

• SMV

• PA axial (Haas method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—24 × 30 cm (10 × 12 inches), lengthwise

• Grid

• Analog—70 to 80 kV range

• Digital systems—80 to 85 kV range

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from patient's head and neck. Take radiograph with patient in the erect or prone position.

Part Position

• Rest patient's nose and forehead against the table/imaging device surface.

• Flex neck, bringing OML perpendicular to IR.

• Align MSP to CR and to the midline of the grid or table/imaging device surface.

• Ensure that no rotation or tilt exists (MSP perpendicular to IR).

• Angle CR 25° cephalad to OML.

• Center CR to MSP to pass through level of EAM and exit inches (4 cm) superior to the nasion.

• Center IR to projected CR.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration.

Evaluation Criteria

Anatomy Demonstrated:

• Occipital bone, petrous pyramids, and foramen magnum are demonstrated, with the dorsum sellae and posterior clinoid processes visualized in the shadow of the foramen magnum.

Position:

• No rotation is evident, as indicated by bilateral symmetric petrous ridges. • Dorsum sellae and posterior clinoid processes are visualized in the foramen magnum, which indicates correct CR angle and proper neck flexion and extension. • No tilt as evidenced by correct placement of anterior clinoid processes within the middle of the foramen magnum • Collimation to area of interest.

Exposure:

• Density (brightness) and contrast are sufficient to visualize occipital bone and sellar structures within foramen magnum. • Sharp bony margins indicate no motion.

Fig. 11-119 PA axial—CR 25° cephalad to OML.

Part V: Radiographic Positioning of Facial Bones and Paranasal Sinuses

Skull Series

Routine

• AP axial (Towne method), 411

• Lateral, 412

• PA axial 15° (Caldwell method) or PA axial 25° to 30°, 413

• PA 0°, 414

Special

• Submentovertex (SMV), 415

• PA axial (Haas method), 416

Facial Bones (Orbits)

Routine

• Lateral, 419

• Parietoacanthial (Waters method), 419

• PA axial (Caldwell method), 420

Special

• Modified parietoacanthial (modified Waters method), 421

Nasal Bones

Routine

• Lateral, 422

• Parietoacanthial (Waters method), 422

Special

• Superoinferior (axial), 423

Zygomatic Arches

Routine

• Submentovertex (SMV), 424

• Oblique inferosuperior (tangential), 425

• AP axial (modified Towne method), 426

• Parietoacanthial (Waters method), 426

Optic Foramina and Orbits

Routine

• Parieto-orbital oblique (Rhese method), 427

• Parietoacanthial (Waters method), 419

Special

• Modified parietoacanthial (modified Waters method), 421

Mandible

Routine

• Axiolateral oblique, 428

• PA 0° and 20° to 25° cephalad, 429

• AP axial (Towne method), 430

Special

• Submentovertex (SMV), 431

• Orthopantomography (panoramic tomography), 432

TMJs

Routine

• AP axial (modified Towne method), 433

Special

• Axiolateral 15° oblique (modified Law method), 434

• Axiolateral (Schuller method), 435

Paranasal Sinuses

Routine

• Lateral, 436

• PA (Caldwell method), 437

• Parietoacanthial (Waters method), 438

Special

• Submentovertex (SMV), 439

• Parietoacanthial transoral (open mouth Waters method), 440

Lateral Position—Right or Left Lateral: Facial Bones

Clinical Indications

Fractures and neoplastic or inflammatory processes of the facial bones, orbits, and mandible

Facial Bones

Routine

• Lateral

• Parietoacanthial (Waters method)

• PA axial (Caldwell method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), lengthwise

• Grid

• Analog—65 to 75 kV range

• Digital systems—70 to 80 kV range

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Patient position is erect or recumbent semiprone.

Part Position

• Rest lateral aspect of head against table or upright imaging device surface, with side of interest closest to IR.

• Adjust head into a true lateral position and oblique body as needed for patient's comfort. (Palpate external occipital protuberance posteriorly and nasion or glabella anteriorly to ensure that these two points are equidistant from tabletop.) Place support sponge under chin if needed.

• Align MSP parallel to IR.

• Align IPL perpendicular to IR.

• Adjust chin to bring IOML perpendicular to front edge of IR.

• Align CR perpendicular to IR.

• Center CR to zygoma (prominence of the cheek), midway between outer canthus and EAM.

• Center IR to CR.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration.

NOTE: Use radiolucent support under the head if needed to bring IPL perpendicular to tabletop on patient with a large chest.

Evaluation Criteria

Anatomy Demonstrated:

• Superimposed facial bones, greater wings of the sphenoid, orbital roofs, sella turcica, zygoma, and mandible are demonstrated.

Position:

• An accurately positioned lateral image of the facial bones demonstrates no rotation or tilt. • Rotation is evident by anterior and posterior separation of symmetric vertical bilateral structures such as the mandibular rami and greater wings of the sphenoid. • Tilt is evident by superior and inferior separation of symmetric horizontal structures such as the orbital roofs (plates) and greater wings of sphenoid. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize the maxillary region. • Sharp bony margins indicate no motion.

Parietoacanthial Projection: Facial Bones

Waters Method

Clinical Indications

• Fractures (particularly tripod and Le Fort fractures) and neoplastic or inflammatory processes

• Foreign bodies in the eye

Facial Bones

Routine

• Lateral

• Parietoacanthial (Waters method)

• PA axial (Caldwell method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), or 24 × 30 cm (10 × 12 inches), lengthwise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 85 kV range

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Patient position is erect or prone (erect is preferred if patient's condition allows).

Part Position

• Extend neck, resting chin against table/upright imaging device surface.

• Adjust head until MML is perpendicular to plane of IR. OML forms a 37° angle with the table/imaging device surface.

• Position MSP perpendicular to midline of grid or table/imaging device surface, preventing rotation or tilting of head. (One way to check for rotation is to palpate the mastoid processes on each side and the lateral orbital margins with the thumb and fingertips to ensure that these lines are equidistant from the tabletop.)

• Align CR perpendicular to IR, to exit at acanthion.

• Center IR to CR.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration.

Evaluation Criteria

Anatomy Demonstrated:

• IOMs, maxillae, nasal septum, zygomatic bones, zygomatic arches, and anterior nasal spine.

Position:

• Correct neck extension demonstrates petrous ridges just inferior to the maxillary sinuses. • No patient rotation exists, as indicated by equal distance from the midlateral orbital margin to the lateral cortex of cranium on each side. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize maxillary region. • Sharp bony margins indicate no motion.

Fig. 11-126 Parietoacanthial (Waters)—**MML perpendicular** (OML 37°).

Fig. 11-127 Parietoacanthial (Waters) projection.

Fig. 11-128 Parietoacanthial (Waters) projection.

PA Axial Projection: Facial Bones

Caldwell Method

Clinical Indications

• Fractures and neoplastic or inflammatory processes of the facial bones

Facial Bones

Routine

• Lateral

• Parietoacanthial (Waters method)

• PA axial (Caldwell method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), or 24 × 30 cm (10 × 12 inches), lengthwise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 85 kV range

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Patient position is erect or prone (erect is preferred if patient's condition allows).

Part Position

• Rest patient's nose and forehead against tabletop.

• Tuck chin, bringing OML perpendicular to IR.

• Align MSP perpendicular to midline of grid or table/imaging device surface. Ensure no rotation or tilt of head.

• Angle CR 15° caudad, to exit at nasion (see Note).

• Center CR to IR.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration.

NOTE: If area of interest is the orbital floors, use a 30° caudad angle to project the petrous ridges below the IOM.

Evaluation Criteria

Anatomy Demonstrated:

• Orbital rim, maxillae, nasal septum, zygomatic bones, and anterior nasal spine.

Position:

• Correct patient position/CR angulation is indicated by petrous ridges projected into the lower one-third of orbits with 15° caudad CR. If the orbital floors are the area of interest, 30° caudad angle projects the petrous ridges below the IOMs. • No rotation of cranium is indicated by equal distance from midlateral orbital margin to the lateral cortex of the cranium; superior orbital fissures are symmetric. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize maxillary region and orbital floor. • Sharp bony margins indicate no motion.

Fig. 11-129 PA axial Caldwell—**OML perpendicular, CR 15° caudad.**

Modified Parietoacanthial Projection: Facial Bones

Modified Waters Method

Clinical Indications

• Orbital fractures (e.g., blowout) and neoplastic or inflammatory processes

• Foreign bodies in the eye

Facial Bones

Special

• Modified parietoacanthial (modified Waters method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), lengthwise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 85 kV range

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from the head and neck. Patient position is erect or prone (erect is preferred if patient's condition allows).

Part Position

• Extend neck, resting chin and nose against table/upright imaging device surface.

• Adjust head until LML is perpendicular; OML forms a 55° angle with IR.

• Position MSP perpendicular to midline of grid or table/upright imaging device surface. Ensure no rotation or tilt of head.

• Align CR perpendicular, centered to exit at acanthion.

• Center IR to CR.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration during exposure.

Evaluation Criteria

Anatomy Demonstrated:

• Orbital floors (plates) are perpendicular to IR, which also provides a less distorted view of the orbital rims than a parietoacanthial (Waters) projection.

Position:

• Correct position/CR angulation is indicated by petrous ridges projected into the lower half of the maxillary sinuses, below the IOMs. • No rotation of the cranium is indicated by equal distance from the midlateral orbital margin to the lateral cortex of the cranium. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize the orbital floors. • Sharp bony margins indicate no motion.

Fig. 11-132 Modified parietoacanthial (Waters)—**LML perpendicular (OML 55°).**

Fig. 11-133 Modified parietoacanthial (Waters).

Fig. 11-134 Modified parietoacanthial (Waters).

Lateral Position: Nasal Bones

Clinical Indications

• Nasal bone fractures

Both sides should be examined for comparison, with side closest to IR best demonstrated.

Nasal Bones

Routine

• Lateral

• Parietoacanthial (Waters method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), crosswise (split*)

• Nongrid

• Analog—50 to 60 kV range

• Digital systems—60 to 70 kV range

• Automatic exposure control (AEC) not recommended because of small exposure field

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Patient position is prone or erect.

Part Position

• Rest lateral aspect of head against the table/upright imaging device surface, with side of interest closest to IR.

• Position nasal bones to center of IR.

• Adjust head into a true lateral position and oblique body as needed for patient's comfort (place sponge block under chin if needed).

• Align MSP parallel with a table/upright imaging device surface.

• Align IPL perpendicular to table/upright imaging device surface.

• Position IOML perpendicular to front edge of IR.

• Align CR perpendicular to IR.

• Center CR to inch (1.25 cm) inferior to nasion.

Recommended Collimation

Collimate on all sides to within 2 inches (5 cm) of nasal bone.

Respiration

Suspend respiration during exposure.

Evaluation Criteria

Anatomy Demonstrated:

• Nasal bones with soft tissue nasal structures, the frontonasal suture, and the anterior nasal spine are demonstrated.

Position:

• Nasal bones are demonstrated without rotation. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize nasal bone and soft tissue structures. • Sharp bony structures indicate no motion.

Fig. 11-135 Left lateral—prone or erect.

Superoinferior Tangential (Axial) Projection: Nasal Bones

Clinical Indications

• Fractures of the nasal bones (medial-lateral displacement)

Nasal Bones

Special

• Superoinferior (axial)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), crosswise

• Nongrid

• Analog—50 to 60 kV range

• Digital systems—60 to 70 kV range

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Patient is seated erect in a chair at end of table or in the prone position on table.

Part Position

• Extend and rest chin on IR. Place angled support under IR, as demonstrated, to place IR perpendicular to GAL.

• Align MSP perpendicular to CR and to IR midline.

• Center CR to nasion and angle as needed to ensure that it is parallel to GAL. (CR must just skim glabella and anterior upper front teeth.)

Recommended Collimation

Collimate on all sides to nasal bones.

Respiration

Suspend respiration during exposure.

Evaluation Criteria

Anatomy Demonstrated:

• Tangential projection of midnasal and distal nasal bones (with little superimposition of the glabella or alveolar ridge) and nasal soft tissue. Petrous ridges are inferior to maxillary sinuses.

Position:

• No patient rotation is evident, as indicated by equal distance from anterior nasal spine to outer soft tissue borders on each side. • Incorrect neck position is indicated by visualization of alveolar ridge (excessive extension) or visualization of too much glabella (excessive flexion).

Exposure:

• Contrast and density (brightness) are sufficient to visualize nasal bones and nasal soft tissue. • Sharp bony margins indicate no motion.

SMV Projection: Zygomatic Arches

Clinical Indications

• Fractures of zygomatic arch

• Neoplastic or inflammatory processes

Zygomatic Arches

Routine

• SMV

• Oblique tangential

• AP axial (modified Towne method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10inches), crosswise

• Grid

• Analog—60 to 70 kV range

• Digital systems—70 to 80 kV range

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. This projection may be taken with the patient erect or supine. The erect position may be easier for the patient.

Part Position

• Raise chin, hyperextend neck until IOML is parallel to IR (see Notes).

• Rest head on vertex of skull.

• Align MSP perpendicular to midline of the grid or the table/upright imaging device surface, avoiding all tilt or rotation.

• Align CR perpendicular to IR (see Notes).

• Center CR midway between zygomatic arches, at a level inches (4 cm) inferior to mandibular symphysis.

• Center IR to CR, with plane of IR parallel to IOML.

Recommended Collimation

Collimate to outer margins of zygomatic arches.

Respiration

Suspend respiration during exposure.

NOTES: If patient is unable to extend neck adequately, angle CR perpendicular to IOML. If equipment allows, IR should be angled to maintain CR/IR perpendicular relationship (see Fig. 11-140, inset).

This position is very uncomfortable for patients; complete the projection as quickly as possible.

Evaluation Criteria

Anatomy Demonstrated:

• Zygomatic arches are demonstrated laterally from each mandibular ramus.

Position:

• Correct IOML/CR relationship, as indicated by superimposition of mandibular symphysis on frontal bone. • No patient rotation, as indicated by zygomatic arches visualized symmetrically. • Collimation to area of interest.

Exposure:

• Sufficient contrast and density (brightness) to visualize zygomatic arches. • Sharp bony margins indicate no motion.

Fig. 11-140 SMV projection, supine or erect—**IOML parallel to IR; CR perpendicular to IOML.**

Oblique Inferosuperior (Tangential) Projection: Zygomatic Arches

Clinical Indications

• Fractures of zygomatic arch

• Especially useful for depressed zygomatic arches caused by trauma or skull morphology

Radiographs of both sides generally are taken for comparison.

Zygomatic Arches

Routine

• SMV

• Oblique tangential

• AP axial (modified Towne method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), lengthwise

• Grid

• Analog—60 to 70 kV range

• Digital systems—70 to 80 kV range

• AEC not recommended

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Patient position is erect or supine. Erect, which is easier for the patient, may be done with erect table or upright imaging device.

Part Position

• Raise chin, hyperextending neck until IOML is parallel to IR (see Notes).

• Rest head on vertex of skull.

• Rotate head 15° toward side to be examined; also tilt chin 15° toward side of interest.

• Align CR perpendicular to IR and IOML (see Notes).

• Center CR to zygomatic arch of interest (CR skims mandibular ramus, passes through arch, and skims parietal eminence on the downside).

• Adjust IR so it is parallel to IOML and perpendicular to CR.

Recommended Collimation

Collimate closely to zygomatic bone and arch.

Respiration

Suspend respiration.

NOTES: If patient is unable to extend neck sufficiently, angle CR perpendicular to IOML. If equipment allows, IR should be angled to maintain CR/IR perpendicular relationship.

This position is very uncomfortable for the patient; complete the projection as quickly as possible.

Evaluation Criteria

Anatomy Demonstrated:

• Single zygomatic arch, free of superimposition, is shown.

Position:

• Correct patient position provides for demonstration of zygomatic arch without superimposition of parietal bone or mandible. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize zygomatic arch. • Sharp bony margins indicate no motion.

Fig. 11-143 Oblique tangential, upright imaging device (15° tilt, 15° rotation, CR perpendicular to IOML).

AP Axial Projection: Zygomatic Arches

Modified Towne Method

Clinical Indications

• Fractures and neoplastic or inflammatory processes of zygomatic arch

Zygomatic Arches

Routine

• SMV

• Oblique axial (tangential)

• AP axial (modified Towne method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), crosswise

• Grid

• Analog—60 to 70 kV range

• Digital systems—70 to 80 kV range

• AEC not recommended

Shielding

Shield radiosensitive tissues outside region of interest

Patient Position

Remove all metallic or plastic objects from head and neck. Patient position is erect or supine.

Part Position

• Rest patient's posterior skull against table/upright imaging device surface.

• Tuck chin, bringing OML (or IOML) perpendicular to IR (see Note).

• Align MSP perpendicular to midline of grid or table/upright imaging device surface to prevent head rotation or tilt.

• Angle CR 30° caudad to OML or 37° to IOML (see Note).

• Center CR to 2.5 cm (1 inch) superior to glabella (to pass through midarches) at level of the gonion.

• Center IR to projected CR.

Recommended Collimation

Collimate to outer margins of zygomatic arches.

Respiration

Suspend respiration during exposure.

NOTE: If patient is unable to depress the chin sufficiently to bring OML perpendicular to IR, IOML can be placed perpendicular instead and CR angle increased to 37° caudad. This positioning maintains the 30° angle between OML and CR and demonstrates the same anatomic relationships. (A 7° difference is noted between OML and IOML.)

Evaluation Criteria

Anatomy Demonstrated:

• Bilateral zygomatic arches, free of superimposition, are shown.

Position:

• Zygomatic arches are visualized without patient rotation as indicated by symmetric appearance of arches bilaterally. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize zygomatic arches. • Sharp bony margins indicate no motion.

Fig. 11-146 AP axial—**CR 30° to OML** (37° to IOML).

Parieto-Orbital Oblique Projection: Optic Foramina

Rhese Method

Clinical Indications

• Bony abnormalities of the optic foramen

• Demonstrate lateral margins of orbits and foreign bodies within eye

CT is the preferred modality for a detailed investigation of the optic foramina. Radiographs of both sides generally are taken for comparison.

Optic Foramina

Routine

• Parieto-orbital (Rhese)

• Parietoacanthial (Waters method)

Special

• Modified parietoacanthial (modified Waters method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), crosswise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 85 kV range

• AEC is not recommended

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Position patient erect or supine.

Part Position

• As a starting reference, position patient's head in a prone position with MSP perpendicular to IR. Adjust flexion and extension so that AML is perpendicular to IR. Adjust the patient's head so that the chin, cheek, and nose touch the table/upright imaging device surface.

• Rotate the head 37° toward the affected side. The angle formed between MSP and plane of IR measures 53°. (An angle indicator should be used to obtain an accurate angle of 37° from CR to MSP.)

• Align CR perpendicular to IR at the midportion of the downside orbit.

Recommended Collimation

Collimate on all sides to yield a field size of approximately 4 inches (10 cm) square.

Respiration

Suspend respiration during exposure.

Evaluation Criteria

Anatomy Demonstrated:

• Bilateral, nondistorted view of the optic foramen. • Lateral orbital margins are demonstrated.

Position:

• Accurate positioning projects the optic foramen into the lower outer quadrant of the orbit. • Proper positioning results when AML is correctly placed perpendicular to IR and correct rotation of skull. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize the optic foramen. • Sharp bony margins indicate no motion.

Fig. 11-149 Parieto-orbital projection—53° rotation; AML perpendicular; CR perpendicular.

Fig. 11-150 Bilateral parieto-orbital projection.

Fig. 11-151 Bilateral parieto-orbital projection.

Axiolateral Oblique Projection: Mandible

Clinical Indications

• Fractures and neoplastic or inflammatory processes of mandible

Both sides of mandible are examined for comparison.

Mandible

Routine

• Axiolateral oblique

• PA (or PA axial)

• AP axial (Towne method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), crosswise

• Grid (often performed nongrid)

• Analog—70 to 80 kV range

• Digital systems—75 to 80 kV range

• AEC not used

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Patient position is erect or recumbent. If supine for trauma patients, place IR on wedge sponge to minimize object image receptor distance (OID) (see Fig. 11-152), or position IR (and grid if used) lengthwise for horizontal beam trauma position (see Fig. 11-154).

Part Position

• Place head in a true lateral position, with side of interest against IR.

• If possible, have patient close mouth and bring teeth together.

• Extend neck slightly to prevent superimposition of the gonion over the cervical spine.

• Rotate head toward IR to place the mandibular area of interest parallel to IR. The degree of obliquity depends on which section of the mandible is of interest.

• Head in true lateral position best demonstrates ramus.

• 30° rotation toward IR best demonstrates body.

• 45° rotation best demonstrates mentum.

• 10° to 15° rotation best provides a general survey of the mandible.

• Three methods are suggested for demonstrating the specific region of the mandible of interest (side closest to IR) without superimposing the opposite side:

1. Angle CR 25° cephalad from IPL; for the horizontal beam trauma position, angle CR an additional 5° to 10° posteriorly.

2. Employ a combination of tilt on the head and CR angle not to exceed 25° (e.g., angle the tube 10° and add 15° of head tilt).

3. Employ 25° of head tilt toward IR, and use perpendicular CR.

• Direct CR to exit mandibular region of interest.

• Center IR to projected CR.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration.

Evaluation Criteria

Anatomy Demonstrated:

• Rami, condylar and coronoid processes, body, and mentum of mandible nearest the IR are demonstrated.

Position:

• The appearance of the image/position of the patient depends on the structures under examination. • For the ramus and body, the ramus of interest is demonstrated with no superimposition from the opposite mandible (indicating correct CR angulation). • No superimposition of the cervical spine by the ramus should occur (indicating sufficient extension of neck). • The ramus and body should be demonstrated without foreshortening (indicating correct rotation of head). • The area of interest is demonstrated with minimal superimposition and minimal foreshortening. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize the mandibular area of interest. • Sharp bony margins indicate no motion.

Fig. 11-152 Semisupine—**15° of head tilt** toward IR with 10° CR angle.

Fig. 11-153 Erect—15° head tilt toward IR and 10° CR angle.

Fig. 11-154 Horizontal beam trauma projection—**25° cephalad; 5° to 10° posteriorly;** left lateral.

Fig. 11-155 Axiolateral oblique (general survey).

Fig. 11-156 Axiolateral (general survey).

PA or PA Axial Projection: Mandible

Clinical Indications

• Fractures

• Neoplastic or inflammatory processes of mandible

Optional PA axial best demonstrates proximal rami and elongated view of condyloid processes.

Mandible

Routine

• Axiolateral oblique

• PA (or PA axial)

• AP axial (Towne method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), lengthwise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 85 kV range

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Patient position is erect or prone.

Part Position

• Rest patient's forehead and nose against table/upright imaging device surface.

• Tuck chin, bringing OML perpendicular to IR (see Note).

• Align MSP perpendicular to midline of grid or table/imaging device surface (ensuring no rotation or tilt of head).

• Center IR to projected CR (to junction of lips).

• PA: Align CR perpendicular to IR, centered to exit at junction of lips. For trauma patients, this position is best performed supine.

• Optional PA axial: Angle CR 20° to 25° cephalad, centered to exit at acanthion.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration during exposure.

NOTE: For a true PA projection of the body (if this is area of interest), raise chin to bring AML perpendicular to IR.

Evaluation Criteria

Anatomy Demonstrated:

• PA: Mandibular rami and lateral portion of body are visible. • Optional PA axial: TMJ region and heads of condyles are visible through mastoid processes; condyloid processes are well visualized (slightly elongated).

Position:

• No patient rotation exists, as indicated by mandibular rami visualized symmetrically, lateral to the cervical spine. • Midbody and mentum are faintly visualized, superimposed on cervical spine. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize mandibular body and rami. • Sharp bony margins indicate no motion.

Fig. 11-157 PA—CR perpendicular, exit at junction of lips. *Inset,* Optional PA axial—CR 20° to 25° cephalad, exit at acanthion.

Fig. 11-158 PA—CR 0°; fracture through left ramus.

Fig. 11-159 Optional PA axial—CR 20° cephalad.

AP Axial Projection: Mandible

Towne Method

Clinical Indications

• Fractures

• Neoplastic or inflammatory processes of condyloid processes of mandible

Mandible

Routine

• Axiolateral oblique

• PA (or PA axial)

• AP axial (Towne method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), lengthwise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 85 kV range

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Patient position is erect or supine.

Part Position

• Rest patient's posterior skull against table/upright imaging device surface.

• Tuck chin, bringing OML perpendicular to IR, or place IOML perpendicular and add 7° to CR angle (see Note).

• Align MSP perpendicular to midline of grid or table/upright imaging device surface to prevent head rotation or tilt.

• Angle CR 35° to 42° caudad (see Notes).

• Center CR to glabella.

• Center IR to CR.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration during exposure.

NOTES: If patient is unable to bring OML perpendicular to IR, align IOML perpendicular and increase CR angle by 7°.

If area of interest is the TM fossae, angle 40° to OML to reduce superimposition of TM fossae and mastoid portions of the temporal bone.

Evaluation Criteria

Anatomy Demonstrated:

• Condyloid processes of mandible and TM fossae.

Position:

• A correctly positioned image with no rotation demonstrates the following: condyloid processes visualized symmetrically, lateral to the cervical spine; clear visualization of condyle/TM fossae relationship, with minimal superimposition of the TM fossae and mastoid portions. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize condyloid process and TM fossa. • No motion exists, as indicated by sharp bony margins.

Fig. 11-160 AP axial—CR 35° to 40° to OML.

SMV Projection: Mandible

Clinical Indications

Fractures and neoplastic or inflammatory process of mandible

Mandible

Special

• SMV

• Orthopantomography (mandible or TMJs or both)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), lengthwise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 90 kV range

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Patient position is erect or supine (erect preferred, if patient's condition allows). Erect may be done with an erect table or an upright imaging device (see Fig. 11-163, inset).

Part Position

• Hyperextend neck until IOML is parallel to IR.

• Rest head on vertex of skull.

• Align MSP perpendicular to midline of grid or table/upright imaging device surface to prevent head rotation or tilt.

• Align CR perpendicular to IR or IOML (see Notes).

• Center CR to a point midway between angles of mandible or at a level inches (4 cm) inferior to mandibular symphysis.

• Center IR to projected CR.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration.

NOTES: If patient is unable to extend the neck sufficiently, angle tube to align CR perpendicular to IOML.

This position is very uncomfortable for the patient; complete the projection as quickly as possible.

Evaluation Criteria

Anatomy Demonstrated:

• Entire mandible and coronoid and condyloid processes are demonstrated.

Position:

• Correct neck extension is indicated by the following: mandibular symphysis superimposing frontal bone; mandibular condyles projected anterior to petrous ridges. • No patient rotation or tilt is indicated by the following: no tilt as evidenced by equal distance from mandible to lateral border of skull; no rotation as evidenced by symmetric mandibular condyles. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize the mandible superimposed on the skull. • Sharp bony margins indicate no motion.

Orthopantomography—Panoramic Tomography: Mandible

Clinical Indications

• Fractures or infectious processes of mandible

• Used as an adjuvant before bone marrow transplants

Mandible

Special

• SMV

• Orthopantomography (mandible or TMJs or both)

Technical Factors (Conventional Radiographic Systems)

• IR size—23 × 30 cm (9 × 12 inches), crosswise

• Curved nongrid cassette

• Analog: 70 to 80 kV range

• Digital system: 75 to 85 kV range

Unit Preparation

• Attach IR to panoramic unit.

• Position tube and IR at starting position.

• Raise chin rest to approximately same level as patient's chin.

Shielding

Wrap vest-type lead apron around patient.

Patient Position

• Remove all metal, plastic, and other removable objects from head and neck.

• Explain to patient how tube and IR rotate and the time span needed for exposure.

• Guide patient into unit, resting patient's chin on bite-block.

• Position patient's body, head, and neck as demonstrated in Figs. 11-168 and 11-169. Do not allow head and neck to stretch forward; have patient stand in close, with spine straight and hips forward.

Part Position

• Adjust height of chin rest until IOML is aligned parallel with floor. The occlusal plane (plane of biting surface of teeth) declines 10° from posterior to anterior.

• Align MSP with vertical center line of chin rest.

• Position bite-block between patient's front teeth (see Note).

• Instruct patient to place lips together and position tongue on roof of mouth.

• CR is fixed and directed slightly cephalic to project anatomic structures, positioned at the same height, on top of one another.

• Fixed SID, per panoramic unit.

Recommended Collimation

A narrow, vertical-slit diaphragm is attached to tube, providing collimation.

NOTE: When TMJs are of interest, a second panoramic image is taken with the mouth open. This requires placement of a larger bite-block between the patient's teeth.

Digital Orthopantomography

The first digital orthopantomography was developed in 1995. Since 1997, digital orthopantomography systems have been replacing the analog or systems. These systems do not require a cassette or chemical processing of images. They use charged couple device technology or a photostimulable phosphor to convert the analog signal into a digitized image. A key advantage of digital orthopantomography over film-based systems is increased exposure latitude and fewer repeat studies. This leads to reduced costs and patient exposure (Figs. 11-166 and 11-169).

Advantages of Orthopantomography Compared with Conventional Mandible Positioning

• More comprehensive image of the mandible, TMJs, surrounding facial bones, and teeth

• Low patient radiation dose (slit collimation reduces exposure to eyes and thyroid gland)

• Convenience of examination for patient (one position provides the panoramic view of entire mandible)

• Ability to image the teeth in a patient who cannot open the mouth or when the oral cavity is restricted

• Shorter examination time

Evaluation Criteria

Anatomy Demonstrated:

• A single image of the teeth, mandible, TMJs, nasal fossae, maxillary sinus, zygomatic arches, and maxillae is shown. • A portion of the cervical spine is visualized.

Position:

• The mandible visualized without rotation or tilting is indicated by the following: TMJs on the same horizontal plane in the image; rami and posterior teeth equally magnified on each side of the image; anterior and posterior teeth sharply visualized with uniform magnification. • Correct positioning of the patient is indicated by the following: mandibular symphysis projected slightly below the mandibular angles; mandible oval in shape; occlusal plane parallel with the long axis of the image; upper and lower teeth positioned slightly apart with no superimposition; cervical spine demonstrated with no superimposition of the TMJs.

Exposure:

• Density (brightness) of mandible and teeth is uniform across entire image; no density loss is evident at the center. • No artifacts are superimposed on the image.

Fig. 11-166 Digital orthopantomography—head correctly positioned.

Fig. 11-169 Digital orthopantomography—correct body position.

AP Axial Projection: TMJs

Modified Towne Method

WARNING: Opening the mouth should not be attempted with possible fracture.

Clinical Indications

• Fractures and abnormal relationship or range of motion between condyle and TM fossa.

See Note 1 on open mouth and closed mouth comparisons.

TMJs

ROUTINE

• AP axial (modified Towne method)

SPECIAL

• Axiolateral oblique (modified Law method)

• Axiolateral (Schuller method)

• Orthopantomography

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), crosswise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 90 kV range

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Position patient erect or supine.

Part Position

• Rest patient's posterior skull against table/upright imaging device surface.

• Tuck chin, bringing OML perpendicular to table/imaging device surface or bringing IOML perpendicular and increasing CR angle by 7°.

• Align MSP perpendicular to midline of the grid or the table/upright imaging device surface to prevent head rotation or tilt.

• Angle CR 35° caudad from OML or 42° from IOML.

• Direct CR 3 inches superior to the nasion. Center IR to projected CR.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration during exposure.

NOTE 1: Some departmental protocols indicate that these projections should be taken in both closed mouth and open mouth positions for comparison purposes when patient's condition allows.

NOTE 2: An additional 5° increase in CR may best demonstrate the TM fossae and TMJs.

Evaluation Criteria

Anatomy Demonstrated:

• Condyloid processes of mandible and TM fossae are demonstrated.

Position:

• Correctly positioned patient, with no rotation, is indicated by the following: condyloid processes visualized symmetrically, lateral to the cervical spine; clear visualization of condyle and TM fossae relationship. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize condyloid process and TM fossa. • Sharp bony margins indicate no motion.

Fig. 11-172 AP axial—CR 42° to IOML (closed mouth position).

Fig. 11-173 AP axial (closed mouth position).

Axiolateral Oblique Projection: TMJs

Modified Law Method

Clinical Indications

• Abnormal relationship or range of motion between condyle and TM fossa

Generally, images are obtained in the open mouth and closed mouth positions.

TMJs

Routine

• AP axial (modified Towne method)

Special

• Axiolateral 15° oblique (modified Law method)

• Axiolateral (Schuller)

• Orthopantomography

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), lengthwise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 85 kV range

• AEC not recommended

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Patient position is erect or semiprone (erect is preferred if patient's condition allows). Rest lateral aspect of head against table/upright imaging device surface, with side of interest closest to IR.

Part Position

• Prevent tilt by maintaining IPL perpendicular to IR. MSP is parallel to IR to start.

• Align IOML perpendicular to front edge of IR.

• From lateral position, rotate face toward IR 15° (with MSP of head rotated 15° from plane of IR).

• Angle CR 15° caudad, centered to inches (4 cm) superior to upside EAM (to pass through downside TMJ).

• Center IR to projected CR.

• Minimum SID is 40 inches (102 cm).

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration during exposure.

Evaluation Criteria

Anatomy Demonstrated:

• TMJ nearest IR is visible. • Closed mouth image demonstrates condyle within mandibular fossa; the condyle moves to the anterior margin (articular tubercle) of the mandibular fossa in the open mouth position.

Position:

• Correctly positioned images demonstrate TMJ closest to IR clearly, without superimposition of opposite TMJ (15° rotation prevents superimposition). • TMJ of interest is not superimposed by cervical spine. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize TMJ. • Sharp bony margins indicate no motion.

Fig. 11-174 Right TMJ—closed mouth; 15° oblique; CR 15° caudad.

Fig. 11-175 Right TMJ—open mouth; 15° oblique; CR 15° caudad.

Axiolateral Projection: TMJ

Schuller Method

Clinical Indications

• Abnormal relationship or range of motion between condyle and TM fossa

Generally, images are obtained in the open mouth and closed mouth positions.

TMJs

Routine

• AP axial (modified Towne method)

Special

• Axiolateral 15° oblique (modified Law method)

• Axiolateral (Schuller method)

• Orthopantomography

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), lengthwise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 85 kV range

• AEC not recommended

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Position patient erect or semiprone. Place the head in a true lateral position, with side of interest nearest IR.

Part Position

• Adjust head into true lateral position and move patient's body in an oblique direction, as needed for patient's comfort.

• Align IPL perpendicular to IR.

• Align MSP parallel with table/imaging device surface.

• Position IOML perpendicular to front edge of IR.

• Angle CR 25° to 30° caudad, centered to inch (1.3 cm) anterior and 2 inches (5 cm) superior to upside EAM.

• Center IR to projected TMJ.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration during exposure.

NOTE: This projection results in greater elongation of the condyle compared with the modified Law method.

Evaluation Criteria

Anatomy Demonstrated:

• TMJ nearest IR is visible. • Closed mouth image demonstrates the condyle within the mandibular fossa; the condyle moves to the anterior margin (articular tubercle) of fossa in the open mouth position.

Position:

• TMJs are demonstrated without rotation, as evidenced by superimposed lateral margins. • Collimation to area of interest.

Exposure:

• Contrast and density (brightness) are sufficient to visualize TMJ. • Sharp bony margins indicate no motion.

Fig. 11-178 Left TMJ—closed mouth; true lateral, CR 25° to 30° caudad angle.

Fig. 11-179 Left TMJ—open mouth; true lateral, CR 25° to 30° caudad angle.

Lateral Position—Right or Left Lateral: Sinuses

Clinical Indications

• Inflammatory conditions (sinusitis, secondary osteomyelitis)

• Sinus polyps or cysts

Sinuses

Routine

• Lateral

• PA (Caldwell method)

• Parietoacanthial (Waters method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), lengthwise

• Grid

• Analog—65 to 75 kV range

• Digital systems—75 to 85 kV range

• AEC not recommended

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metal, plastic, and other removable objects from head. Position patient erect (see Notes).

Part Position

• Place lateral aspect of head against table/upright imaging device surface, with side of interest closest to IR.

• Adjust head into true lateral position, moving body in an oblique direction as needed for patient's comfort (MSP parallel to IR).

• Align IPL perpendicular to IR (ensures no tilt).

• Adjust chin to align IOML perpendicular to front edge of IR.

• Align horizontal CR perpendicular to IR.

• Center CR to a point midway between outer canthus and EAM.

• Center IR to CR.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration during exposure.

NOTES: To visualize air-fluid levels, an erect position with a horizontal beam is required. Fluid within the paranasal sinus cavities is thick and gelatin-like, causing it to cling to the cavity walls. To visualize this fluid, allow a short time (at least 5 minutes) for the fluid to settle after patient's position has been changed (i.e., from recumbent to erect).

If patient is unable to be placed in the upright position, the image may be obtained with the use of a horizontal beam, similar to trauma lateral facial bones, as described in Chapter 15.

Evaluation Criteria

Anatomy Demonstrated:

• All four paranasal sinus groups are shown.

Position:

• Accurately positioned cranium without rotation or tilt. • Rotation is evident by anterior and posterior separation of symmetric bilateral structures such as the mandibular rami and greater wings of the sphenoid. • Tilt is evident by superior and inferior separation of symmetric horizontal structures such as the orbital roofs (plates) and greater wings of sphenoid • Collimation to area of interest.

Exposure:

• Density (brightness) and contrast are sufficient to visualize the sphenoid sinuses through the cranium without overexposing the maxillary and frontal sinuses. • Sharp bony margins indicate no motion.

Fig. 11-183 Erect left lateral (upright imaging device).

PA Projection: Sinuses

Caldwell Method

Clinical Indications

• Inflammatory conditions (sinusitis, secondary osteomyelitis)

• Sinus polyps or cysts

Sinuses

Routine

• Lateral

• PA (Caldwell method)

• Parietoacanthial (Waters method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), lengthwise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 85 kV range

• Upright imaging device angled 15° if possible, CR horizontal (see Note)

• AEC not recommended

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Position patient erect (see Note).

Part Position

• Place patient's nose and forehead against upright imaging device or table with neck extended to elevate OML 15° from horizontal. A radiolucent support between forehead and upright imaging device or table may be used to maintain this position. CR remains horizontal. (See alternative method if imaging device can be tilted 15°.)

• Align MSP perpendicular to midline of grid or upright imaging device surface.

• Center IR to CR and to nasion, ensuring no rotation.

• Align CR horizontal, parallel with floor (see Note).

• Center CR to exit at nasion.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration.

NOTE: To assess air-fluid levels accurately, CR must be horizontal, and the patient must be erect.

ALTERNATIVE METHOD: An alternative method if the imaging device can be tilted 15° is shown (Fig. 11-186, inset). The patient's forehead and nose can be supported directly against the imaging device with OML perpendicular to imaging device surface and 15° to horizontal CR.

Evaluation Criteria

Anatomy Demonstrated:

• Frontal sinuses projected above the frontonasal suture are demonstrated. • Anterior ethmoid air cells are visualized lateral to each nasal bone, directly below the frontal sinuses.

Position:

• Accurately positioned cranium with no rotation or tilt is indicated by the following: equal distance from the lateral margin of the orbit to the lateral cortex of the cranium on both sides; equal distance from the MSP (identified by the crista galli) to the lateral orbital margin on both sides; superior orbital fissures symmetrically visualized within the orbits. • Correct alignment of OML and CR projects petrous ridges into lower one-third of orbits. • Collimation to area of interest.

Exposure:

• Density (brightness) and contrast are sufficient to visualize the frontal and ethmoid sinuses. • Sharp bony margins indicate no motion.

Fig. 11-186 **CR horizontal,** OML 15° to CR (if cannot be tilted). *Inset,* If upright, imaging device can be tilted 15°.

Parietoacanthial Projection: Sinuses

Waters Method

Clinical Indications

• Inflammatory conditions (sinusitis, secondary osteomyelitis)

• Sinus polyps and cysts

Sinuses

Routine

• Lateral

• PA (Caldwell method)

• Parietoacanthial (Waters method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), lengthwise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 85 kV range

• AEC not recommended

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Position patient erect (see Note).

Part Position

• Extend neck, placing chin and nose against table/upright imaging device surface.

• Adjust head until MML is perpendicular to IR; OML forms a 37° angle with plane of IR.

• Position MSP perpendicular to midline of grid or table/upright imaging device surface.

• Ensure that no rotation or tilt exists.

• Center IR to CR and to acanthion.

• Align horizontal CR perpendicular to IR centered to exit at acanthion.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration during exposure.

NOTE: CR must be horizontal, and patient must be erect to demonstrate air-fluid levels within the paranasal sinus cavities.

Evaluation Criteria

Anatomy Demonstrated:

• Maxillary sinuses with the inferior aspect visualized free from superimposing alveolar processes and petrous ridges, the inferior orbital rim, and an oblique view of the frontal sinuses.

Position:

• No rotation of the cranium is indicated by the following: equal distance from MSP (identified by the bony nasal septum) to lateral orbital margin on both sides; equal distance from the lateral orbital margin to the lateral cortex of the cranium on both sides. • Adequate extension of neck demonstrates petrous ridges just inferior to the maxillary sinuses. • Collimation to area of interest.

Exposure:

• Density (brightness) and contrast are sufficient to visualize maxillary sinuses. • Sharp bony margins indicate no motion.

Fig. 11-189 Parietoacanthial projection (upright imaging device/table)—CR and MML perpendicular (OML 37° to IR).

Fig. 11-190 Parietoacanthial projection.

Fig. 11-191 Parietoacanthial projection.

SMV Projection: Sinuses

Clinical Indications

• Inflammatory conditions (sinusitis, secondary osteomyelitis)

• Sinus polyps and cysts

Sinuses

Special

• Submentovertex (SMV)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), lengthwise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 85 kV range

• AEC not recommended

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Position patient erect, if possible, to show air-fluid levels.

Part Position

• Raise chin, hyperextend neck if possible until IOML is parallel to table/upright imaging device surface. (See Notes.)

• Head rests on vertex of skull.

• Align MSP perpendicular to midline of the grid or table/upright imaging device surface; ensure no rotation or tilt.

• CR directed perpendicular to IOML (see Notes)

• CR centered midway between angles of mandible, at a level to 2 inches (4 to 5 cm) inferior to mandibular symphysis

• CR centered to IR

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration during exposure.

NOTES: If patient is unable to extend neck sufficiently, angle the tube from horizontal as needed to align CR perpendicular to IOML.

This position is very uncomfortable for the patient; have all factors set before positioning the patient, and complete the projection as quickly as possible.

Evaluation Criteria

Anatomy Demonstrated:

• Sphenoid sinuses, ethmoid sinuses, nasal fossae, and maxillary sinuses are demonstrated.

Position:

• Accurate IOML and CR relationship is demonstrated by the following: correct extension of neck and relationship between IOML and CR as indicated by mandibular mentum anterior to ethmoid sinuses. • No rotation evidenced by MSP parallel to edge of IR. • No tilt evidenced by equal distance between mandibular ramus and lateral cranial cortex. • Collimation to area of interest.

Exposure:

• Density (brightness) and contrast are sufficient to visualize sphenoid and ethmoid sinuses. • Sharp bony margins indicate no motion.

Fig. 11-192 SMV projection (upright imaging device/table).

Parietoacanthial Transoral Projection: Sinuses

Open Mouth Waters Method

Clinical Indications

• Inflammatory conditions (sinusitis, secondary osteomyelitis)

• Sinus polyps and cysts.

NOTE: Good alternative to demonstrate the sphenoid sinuses for patients who cannot perform the submentovertex (SMV) position.

Sinuses

Special

• Submentovertex (SMV)

• Parietoacanthial transoral (open mouth Waters method)

Technical Factors

• Minimum SID—40 inches (102 cm)

• IR size—18 × 24 cm (8 × 10 inches), lengthwise

• Grid

• Analog—70 to 80 kV range

• Digital systems—75 to 90 kV range

• AEC not recommended

Shielding

Shield radiosensitive tissues outside region of interest.

Patient Position

Remove all metallic or plastic objects from head and neck. Position patient erect (see Note).

Part Position

• Extend neck, placing chin and nose against table/upright imaging device surface.

• Adjust head until OML forms 37° angle with IR (MML is perpendicular with mouth closed).

• Position MSP perpendicular to the midline of grid or table/upright imaging device surface; ensure no rotation or tilt.

• Instruct patient to open mouth by instructing to “drop jaw without moving head.” (MML is no longer perpendicular.)

• Center IR to CR and to acanthion.

• Align horizontal CR perpendicular to IR.

• Center CR to exit at acanthion.

Recommended Collimation

Collimate on four sides to anatomy of interest.

Respiration

Suspend respiration during exposure.

Evaluation Criteria

Anatomy Demonstrated:

• Maxillary sinuses with the inferior aspect visualized, free from superimposing alveolar processes and petrous ridges, the inferior orbital rim, an oblique view of the frontal sinuses, and the sphenoid sinuses visualized through the open mouth.

Position:

• No rotation of the cranium is indicated by the following: equal distance from the MSP (identified by the bony nasal septum) to the lateral orbital margin on both sides; equal distance from the lateral orbital margin to the lateral cortex of the cranium on both sides; accurate extension of the neck demonstrating petrous ridges just inferior to the maxillary sinuses. • Collimation to area of interest.

Exposure:

• Density (brightness) and contrast are sufficient to visualize the maxillary and sphenoid sinuses. • Sharp bony margins indicate no motion.

Fig. 11-195 Parietoacanthial transoral projection (upright imaging device/table).

Fig. 11-196 Parietoacanthial transoral projection.

Fig. 11-197 Parietoacanthial transoral projection.

Radiographs for Critique—Cranium

Each of these skull radiographs demonstrates at least one repeatable error. See whether you can critique each of these radiographs based on the categories as described in the textbook and as outlined on the right. As a starting critique exercise, place a check mark in each category that demonstrates a repeatable error for that radiograph.

Answers are provided in the Appendix at the end of this textbook.

	RADIOGRAPHS
	A	B	C	D	E
1. Anatomy Demonstrated	______	______	______	______	_______
2. Positioning	______	______	______	______	_______
3. Collimation and CR	______	______	______	______	_______
4. Exposure	______	______	______	______	_______
5. Markers	______	______	______	______	_______

Fig. C11-198 Lateral skull—4-year-old patient.

Fig. C11-199 Lateral skull—54-year-old trauma patient.

Fig. C11-201 Is it a PA or AP axial projection?

Fig. C11-202 Caldwell: Is it a PA or AP axial projection?

Radiographs for Critique—Facial Bones

NOTE: Remember, CR must be horizontal and the patient erect to demonstrate air-fluid levels within the paranasal sinuses.

Students should determine whether they can critique each of these five radiographs based on the categories as described in the textbook and as outlined on the right. As a starting critique exercise, place a check in each category that demonstrates a repeatable error for that radiograph.

Answers are provided in the Appendix at the end of this textbook.

	RADIOGRAPHS
	A	B	C	D	E
1. Anatomy Demonstrated	______	______	______	______	______
2. Positioning	______	______	______	______	______
3. Collimation and CR	______	______	______	______	______
4. Exposure	______	______	______	______	______
5. Markers	______	______	______	______	______

Fig. C11-203 Parietoacanthial (Waters)—facial bones.

Fig. C11-205 Optic foramina—Rhese method.

Fig. C11-206 Optic foramina—Rhese method.

Radiographs for Critique—Sinuses

Students should determine whether they can critique each of these four radiographs based on the categories as described in the textbook and as outlined on the right. As a starting critique exercise, place a check in each category that demonstrates a repeatable error for that radiograph.

Answers are provided in the Appendix at the end of this textbook.

	RADIOGRAPHS
	A	B	C	D	E
1. Anatomy Demonstrated	______	______	______	______	______
2. Positioning	______	______	______	______	______
3. Collimation and CR	______	______	______	______	______
4. Exposure	______	______	______	______	______
5. Markers	______	______	______	______	______

Fig. C11-208 Sinuses—parietoacanthial transoral projection (open mouth Waters).

Fig. C11-209 Sinuses—parietoacanthial (Waters) projection.

Fig. C11-211 Sinuses—lateral projection.