Where is the center of the ir positioned for the ap projection of the dens, fuchs method?

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Chapter 6

Vertebral Column

• Intervertebral foramina and zygapophyseal joints

• Topographic landmarks

Cervical Spine

Thoracic Spine

Lumbar Spine

Sacrum and Coccyx

Sacroiliac Joints

(R) Routine, (S) Special

Intervertebral Foramina and Zygapophyseal Joints

Certain lateral and oblique projections best demonstrate these important foramina and joints of the spine as follows:

Topographic Landmarks

Fig. 6-1Cervical spine landmarks.

Fig. 6-2Sternum and thoracic spine landmarks.

Fig. 6-3Lower spine landmarks.

AP for C1-C2*

(Atlas and Axis)

Fig. 6-4 AP open mouth for C1-C2.

• 18 × 24 cm L.W. (8 × 10″)

• Grid

• AEC not recommended because of small field

Position

• Supine, patient centered to CR and centerline

• Adjust head without opening mouth—biting surface of upper incisors (junction of lips) aligned with base of skull (mastoid tips).

• Center IR to CR

• As a last step before making exposure—open mouth wide without moving head (make final check for head alignment).

Central Ray:

CR ⊥ through midportion of open mouth (to C1-C2)

SID:

40-44″ (102-113 cm)

Collimation:

Close collimation to C1-C2 region

Respiration:

Suspend during exposure.

AP for Dens (Odontoid Process)*

(AP Fuchs Method [and PA Judd Method])

Warning: Do not attempt on possible cervical trauma.

Fig. 6-5AP Fuchs for dens (within foramen magnum outline).

Fig. 6-6PA Judd method.

• 18 × 24 cm L.W. (8 × 10″)

• Grid

• AEC not recommended

Position

• Supine or erect, MSP aligned to centerline, no rotation

• Elevate chin until MML is near ⊥ to IR (may require some cephalic CR angle if chin cannot be elevated sufficiently)

Note:

May also be taken PA (Judd method) with chin against tabletop, with same CR alignment.

• Center IR to exiting CR.

Central Ray:

CR parallel to MML directed to tip of mandible (AP)

SID:

40-44″ (102-113 cm)

Collimation:

Close collimation to C1-C2 region

Respiration:

Suspend during exposure.

AP Open Mouth and AP (PA) Dens

Evaluation Criteria

Anatomy Demonstrated:

• Open mouth: Dens, lateral masses of C1, and C1-C2 zygapophyseal joints

• AP Fuchs: Dens within foramen magnum (odontoid process)

Fig. 6-7AP open mouth—dens.

Fig. 6-8AP (AP Fuchs—dens).

Position:

• Open mouth: Upper incisors and base of the skull superimposed. Entire dens demonstrated within foramen magnum

• AP Fuchs: Tip of mandible not superimposed over dens. Symmetric appearance of mandible

Exposure

• Optimal density (brightness) and contrast

• Sharp outline of dens; no motion

AP Axial Cervical Spine*

• 18 × 24 cm L.W. (8 × 10″)

• Grid

Fig. 6-9Erect (CR 15°–20° cephalad).

Position

• Supine or erect, center midsagittal plane to CR (and to centerline of IR)

• Raise chin slightly as needed so the CR angle superimposes the mentum of the mandible over the base of the skull (to prevent mandible from superimposing more than C1-C2).

• Center IR to projected CR.

Central Ray:

CR 15°–20° cephalad, to enter at C4 (inferior border of thyroid cartilage)

SID:

40-44″ (102-113 cm)

Collimation:

On four sides to C spine region

Respiration:

Suspend during exposure.

Fig. 6-10Supine (CR 15°–20° cephalad).

Oblique Projections, Cervical Spine*

Right and left obliques taken for comparison (as either posterior or anterior obli’s); anterior obli’s result in less thyroid dose.

• 18 × 24 cm (8 × 10″) or 24 × 30 cm (10 × 12″), L.W.

• Grid (screen optional for small patient or pediatrics)

Fig. 6-11LPO; CR 15° cephalad.

Fig. 6-12RAO; CR 15° caudad.

Position

• Erect preferred (sitting or standing), entire torso and head turned 45° to IR, C spine aligned to CR (and centerline of IR)

• Raise chin slightly, looking straight ahead (or turn head slightly toward IR to prevent superimposing C1 by mandible).

• Center IR to projected CR.

Central Ray (Posterior Obliques):

CR 15°–20° cephalad, to enter at C4. Caudal angle required for anterior obliques.

SID:

60-72″ (153-183 cm)

Collimation:

To C spine region

Respiration:

Suspend during exposure.

AP Axial and Oblique Cervical Spine

Fig. 6-13AP axial.

Fig. 6-14 RPO.

Evaluation Criteria

Anatomy Demonstrated:

• AP axial: C3 to T2 vertebral bodies and intervertebral joints

• Oblique: Intervertebral foramina open and pedicles

• LPO/RPO projections: Demonstrate upside intervertebral foramina

• LAO/RAO projections: Demonstrate downside intervertebral foramina

Position:

• AP axial: Intervertebral joints open and spinous processes equidistant to midline

• Oblique: 45° (AP or PA): Intervertebral foramina uniformly open and pedicles in profile

Exposure:

• Optimal density (brightness) and contrast; no motion

• Soft tissue and bony margins and trabecular markings sharp

Lateral Cervical Spine*

Fig. 6-15Erect lateral, 183 cm (72″) SID.

• 24 × 30 cm L.W. (10 × 12″)

• Grid (screen optional for small patient or pediatrics)

Position

• Erect (sitting or standing) in lateral position, C spine aligned and centered to CR (and centerline of IR)

• Top of IR ≈1-2″ (3-5 cm) above level of EAM

• Raise chin slightly (to remove mandible angles from spine).

• Relax and depress both shoulders evenly (weights in each hand may be necessary to visualize C7).

Note:

See following page for swimmer’s lateral if C7 is still not visualized.

Central Ray:

CR ⊥, to level of C4 (upper thyroid cartilage)

SID:

60-72″ (153-183 cm) (Longer SID provides for better visualization of C7 because of less divergent rays.)

Collimation:

On four sides to C spine region

Respiration:

Expose on complete expiration.

Lateral Cervicothoracic Spine*

Swimmer’s (Twining Method) C5-T3 Region

• 24 × 30 cm L.W. (10 × 12″)

• Grid

Fig. 6-16Cervicothoracic (swimmer’s) lateral.

Position

• Erect preferred, align C-spine to CR (and centerline of IR).

• Elevate arm and shoulder closest to IR and rotate this shoulder slightly anteriorly or posteriorly.

• Opposite arm down, relax and depress shoulder, with slight opposite rotation (from other shoulder) to separate humeral heads from vertebra. May also be taken in lateral recumbent position with one arm and shoulder down and one up—Pawlow method.

Central Ray:

CR ⊥, centered to T1 (approximately 1″ [2.5 cm] above level of jugular notch). Optional 3°–5° caudad to separate the two shoulders

SID:

60-72″ (153-183 cm)

Collimation:

Collimate closely to area of interest

Respiration:

Expose on full expiration or orthostatic (breathing) technique.

Erect Lateral and Cervicothoracic (Swimmer’s) Lateral

Fig. 6-17 Erect lateral.

Fig. 6-18Cervicothoracic (swimmer’s) lateral.

Evaluation Criteria

Anatomy Demonstrated:

• Lateral: C1-C7 (minimum) demonstrated

• Swimmer’s: Vertebral bodies from C5-T3 (minimum) demonstrated

Position:

• Lateral: Near superimposition of zygapophyseal joints; no superimposition of mandible on C spine

• Swimmer’s: Separation of humeral heads from C spine; vertebral bodies in lateral perspective

Exposure:

• Optimal density (brightness) and contrast of lower cervical and upper thoracic spine; no motion

• Soft tissue and bony anatomy visible

Lateral Cervical Spine Hyperflexion—Hyperextension*

Warning: Do NOT attempt on possible trauma patients.

• 24 × 30 cm L.W. (10 × 12″)

• Grid or nongrid

Fig. 6-19Hyperflexion.

Fig. 6-20Hyperextension.

Position

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