Panoramic Radiography Chapter 30 Panoramic Radiography

Objectives Define the key words. List uses of panoramic radiography. Compare the advantages and limitations of panoramic versus intraoral radiographs. Explain how the panoramic technique relates to the principles of tomography. Identify the three dimensions of the focal trough.

Objectives List the components of a panoramic x-ray machine. Explain how to use each of the head positioner guides found on a panoramic x-ray machine. Identify the planes used to position the dental arches correctly within the focal trough.

Objectives Explain the use of a cape-style lead/lead equivalent barrier or the use of an apron without an attached thyroid collar. List patient preparation errors and describe how these will affect the appearance of the panoramic radiograph. Match the patient-positioning errors with the characteristic affect on the appearance of the panoramic radiograph.

Objectives List exposure and image receptor handling errors and describe how these will affect the appearance of the panoramic radiograph. List and identify the anatomic landmarks of the maxilla and surrounding tissues as viewed on a panoramic radiograph.

Objectives List and identify the anatomic landmarks of the mandible and surrounding tissues as viewed on a panoramic radiograph. List and identify soft tissue images as viewed on a panoramic radiograph. List and identify three air space images as viewed on a panoramic radiograph.

Objectives List and identify machine part artifacts as viewed on a panoramic radiograph. List and identify ghost image artifacts as viewed on a panoramic radiograph. Identify in sequence the basic steps in the panoramic radiographic procedure.

Key Words Ala Ala-tragus line Cassette holder Focal trough (layer) Frankfort plane Ghost image Glossopharyngeal air space

Key Words Head positioner guides Midsagittal plane Nasopharyngeal air space Negative shadows Occult disease

Key Words Palatoglossal air space Panoramic Panoramic radiography Rotational center Tomography Tragus

Introduction The panoramic radiograph is probably the most common extraoral projection used in general oral health care practice.

Introduction Panoramic radiography refers to a technique for producing a broad view image of the entire dentition of the maxilla and mandible with the surrounding alveolar bone, the sinuses, and the temporomandibular joints on a single radiograph.

Figure 30-1 Panoramic radiograph Figure 30-1 Panoramic radiograph. Provides a broad view of the dental arches. Note, however, the inherent image distortion as the panoramic view broadens the arches. (Courtesy of Gendex Dental Systems/Imaging Sciences Intl.)

Purpose and Use Examining large areas of the face and jaws Locating impacted teeth or retained root tips Evaluating trauma, lesions, and diseases of the jaws Assessing growth and development

BOX 30-1 Advantages and Limitations of Panoramic Radiographs

Figure 30-2 Panoramic x-ray machine Figure 30-2 Panoramic x-ray machine. Radiographer positions the patient between the image receptor and the x-ray tube head of this digital panoramic dental x-ray machine.

Figure 30-3 Panoramic radiography Figure 30-3 Panoramic radiography. The moving x-ray source passes through the center of rotation in a horizontal plane toward the path of the moving image receptor. As the beam scans the object (the dental arches), a continuous image is recorded on the moving image receptor.

Figure 30-4 Moving rotational center allows the x-ray beam to continuously focus as the tube head and the image receptor simultaneously move.

Figure 30-5 Slit collimator (A) and slit opening (B) to the image receptor.

Figure 30-6 Plane of focus within the focal trough Figure 30-6 Plane of focus within the focal trough. The x-ray beam is focused on imaging the structures that are positioned closest to the image receptor. As the tube head and image receptor rotate, the x-ray beam is refocused to image the next section of anatomy. (A) Illustrated here is one moment in the continuous exposure. At this precise moment, the tube head is positioned on the right side, allowing the x-ray beam to penetrate the right side, then continue on to penetrate the left side and carry the images of the structures penetrated to the receptor. At this moment the right side is farther from the image receptor than the left side. At this moment in the exposure sequence, the left side will be recorded on the image, while the right side will be blurred out as a ghost image.

Figure 30-6 continued (B) As the tube head and image receptor rotate, the x-ray beam now penetrates the back of head (and the cervical vertebrae), then continues on to penetrate the anterior teeth. Because the anterior teeth at this moment are closer to the image receptor, the cervical vertebrae will most likely appear magnified and blurred out as a ghost image, while the anterior teeth will be more distinctly recorded onto the image.

Figure 30-6 continued (C) As the tube head and image receptor continue to rotate to the opposite side, the x-ray beam now penetrates the left side first, blurring it out of the image. The right side is now closer to the image receptor, so it will be imaged more clearly.

Figure 30-7 Diagram of the focal trough.

Components of the Panoramic X-ray Machine Rotational x-ray tube head Cassette holder (for film or phosphor plate) or digital image receptor Head positioner guides Exposure control panel

PROCEDURE 30-1 Panoramic radiographic procedure*

Procedure 30-1 (continued) Panoramic radiographic procedure*

Procedure 30-1 (continued) Panoramic radiographic procedure*

Procedure 30-1 (continued) Panoramic radiographic procedure*

Procedure 30-1 (continued) Panoramic radiographic procedure*

Procedure 30-1 (continued) Panoramic radiographic procedure*

Figure 30-8 Film-based panoramic x-ray machine.

Figure 30-9 Phosphor plates used for indirect digital panoramic x-ray machine. (Courtesy of Air Techniques.)

Figure 30-10 Digital panoramic x-ray machine Figure 30-10 Digital panoramic x-ray machine. (Courtesy of Gendex Dental Systems/Imaging Sciences Intl.)

Figure 30-11 Radiographer preparing to attach flexible cassette to the cassette holder carriage. Note the markings on the outside of the cassette that indicate the correct direction for attaching the cassette to the unit.

Figure 30-12 Head positioner guides Figure 30-12 Head positioner guides. A biteblock aids the radiographer in locating the correct forward and back dimension of the focal trough; side positioner guides aid with locating the correct left and right dimension; and a chin rest aids with locating the correct up and down dimension. Note the cape-style lead/lead equivalent apron without a thyroid collar for use with panoramic exposures.

Figure 30-13 Head positioner guides Figure 30-13 Head positioner guides. Beams of light shine on the patient’s face to aid the radiographer in positioning the arches in the focal trough. (Courtesy of Gendex Dental Corporation.)

Figure 30-14 The radiographer uses the control panel to set the exposure.

Importance of Correct Head Positioning Location of three facial landmarks to position patient correctly: Midsagittal plane Ala-tragus line Frankfort plane

Figure 30-15 Aligning the correct anterior–posterior position with the light beam guide illuminated over the interproximal space of the canine and the premolar.

Figure 30-16 Landmarks used to position the patient Figure 30-16 Landmarks used to position the patient. (A) When the ala–tragus line is positioned 5 degrees down, (B) the Frankfort plane will be in a position parallel to the floor.

Figure 30-17 Correct positioning Figure 30-17 Correct positioning. The arches are positioned correctly within the focal trough in all three dimensions: (A) Anterior–posterior and left–right; and (B) superior–inferior (up-down).

Panoramic Imaging Errors Patient preparation Positioning Exposure and film handling

Figure 30-18 Positioning of lips on the biteblock Figure 30-18 Positioning of lips on the biteblock. (A) The lips incorrectly open on the biteblock. (B) The lips correctly positioned closed around the biteblock.

Figure 30-19 Incorrect positioning Figure 30-19 Incorrect positioning. (A) Arches too far forward, causing the anterior teeth to be positioned outside and forward from the center of the focal trough. (B) Arches too far backward, causing the anterior teeth to be positioned outside and backward from the center of the focal trough. (C) Patient positioned too far forward. Note the incorrect position of the laser light beam. Compare with the correct position in Figure 30-15. (D) Radiographic image resulting from positioning the arches too far forward. Note the blurred and magnified anterior teeth and the prominent imaging of the spinal column on both sides. (E) Radiographic image resulting from positioning the arches too far backward. Note the widened and magnified anterior teeth.

Figure 30-20 Incorrect positioning: patient’s head is rotated Figure 30-20 Incorrect positioning: patient’s head is rotated. Midsaggital plane rotated to position the (A) left side of the arches closer to the image receptor and right side farther away from the x-ray tube head or (B) right side closer to the image receptor and left side farther away from the x-ray tube head. Diminution is apparent on the side malpositioned closer to the image receptor and magnification is apparent on the side malpositioned farther away from the x-ray tube head. (C) Patient positioned with the midsaggital plane rotated to the left. (D) Radiographic image resulting from a position rotated to the left. Note the arches, condyles, sinus, and teeth on the left appear narrowed, and these anatomical landmarks and teeth on the right appear widened and magnified. Note the higher position of the left condyle.

Figure 30-21 Incorrect positioning. (A) Patient’s chin too low Figure 30-21 Incorrect positioning. (A) Patient’s chin too low. The root apices of the mandibular anterior teeth slant out of the focal trough. (B) Frankfort plane/ala–tragus line incorrectly aligned to position the chin too low. (C) Patient’s chin too high. The root apices of the maxillary anterior teeth slant out of the focal trough. (D) Frankfort plane/ala–tragus line incorrectly aligned to position the chin too high. (E) Radiograph

Figure 30-22 Incorrect patient positioning (A) Patient not standing up straight. Compare with the correct straight posture illustrated in Figures 30-12 and 30-13. (B) Radiograph with wide radiopacity representing the compressed vertebrae superimposed over the anterior teeth. (C) Normal hand position on machine handles. (D) Altered hand position with arms crossed, left hand holding the right handle and right hand holding the left handle. (E) Altered hand position with arms crossed, left hand holding the right handle with palm facing up and right hand holding the left handle with palm facing up.

Figure 30-23 Drawing of panoramic radiograph showing the maxilla and surrounding normal anatomic landmarks. (1) Mastoid process, (2) styloid process, (3) external auditory meatus, (4) glenoid fossa, (5) articular eminence, (6) lateral pterygoid plate, (7) maxillary tuberosity, (8) infraorbital foramen, (9) orbit of the eye, (10) incisive canal, (11) incisive foramen, (12) anterior nasal spine, (13) nasal cavity, (14) nasal septum, (15) hard palate, (16) maxillary sinus, (17) zygomatic process of the zygoma, (18) zygoma, and (19) hamulus.

Figure 30-24 Panoramic radiograph showing the maxilla and surrounding normal anatomic landmarks. (1) Mastoid process, (2) external auditory meatus, (3) glenoid fossa, (4) articular eminence, (5) maxillary tuberosity, (6) orbit of the eye, (7) nasal cavity, (8) nasal septum, (9) incisive canal, (10) incisive foramen, (11) hard palate, (12) maxillary sinus, and (13) chin rest (machine part artifact).

Figure 30-25 Drawing of panoramic radiograph showing the mandible and surrounding normal anatomic landmarks. (1) Mandibular condyle, (2) mandibular notch, (3) coronoid process, (4) mandibular foramen, (5) lingula, (6) submandibular fossa, (7) mandibular canal, (8) mental foramen, (9) mental ridge, (10) mental fossa, (11) lingual foramen, (12) genial tubercles, (13) inferior border of the mandible, (14) mylohyoid ridge, (15) oblique ridge, (16) angle of the mandible, (17) cervical vertabrae.

Figure 30-26 Panoramic radiograph showing the mandible and surrounding normal anatomic landmarks. (1) Mandibular condyle, (2) mandibular notch, (3) coronoid process, (4) mandibular foramen, (5) lingula, (6) submandibular fossa, (7) mandibular canal, (8) mental foramen, (9) mental ridge, (10) mental fossa, (11) lingual foramen, (12) genial tubercles, (13) inferior border of the mandible, (14) mylohyoid ridge, (15) oblique ridge, (16) angle of the mandible, (17) cervical vertabrae.

Figure 30-27 Drawing of panoramic radiograph showing soft tissue images. (1) Tongue, (2) soft palate, (3) lipline, and (4) ear.

Figure 30-28 Panoramic radiograph showing soft tissue images Figure 30-28 Panoramic radiograph showing soft tissue images. (1) Tongue, (2) soft palate, and (3) ear.

Figure 30-29 Drawing of panoramic radiograph showing air space images Figure 30-29 Drawing of panoramic radiograph showing air space images. (1) Palatoglossal air space, (2) nasopharyngeal air space, and (3) glossopharyngeal air space.

Figure 30-30 Panoramic radiograph showing air space images Figure 30-30 Panoramic radiograph showing air space images. (1) Palatoglossal air space, (2) nasopharyngeal air space, and (3) glossopharyngeal air space.

Figure 30-31 Drawing of panoramic radiograph showing images of machine parts. (1) Biteblock, (2) chin rest, (3) side positioner guides.

Figure 30-32 Panoramic radiograph showing images of machine parts Figure 30-32 Panoramic radiograph showing images of machine parts. (1) Biteblock, (2) side positioner guides.

Figure 30-33 Drawing of panoramic radiograph showing ghost images Figure 30-33 Drawing of panoramic radiograph showing ghost images. (1) Ghost image of the spinal column (cervical vertebrae), (2) ghost image of the opposite side mandible.

Figure 30-34 Panoramic radiograph showing ghost images Figure 30-34 Panoramic radiograph showing ghost images. (1) Ghost image of the spinal column (cervical vertebrae), (2) ghost image of the opposite side mandible.

Review: Chapter Summary The greatest advantage of the panoramic radiograph is that it can image a large region of structures and provide an increased amount of diagnostic information when compared to a full mouth series of intraoral radiographs.

Review: Chapter Summary The greatest limitation of the panoramic radiograph is the image magnification and distortion that make interpreting the image difficult. The skilled radiographer should be able to identify normal radiographic anatomy of the maxilla and the mandible, including soft tissue images and air spaces that appear on a panoramic radiograph.

Review: Chapter Summary The radiographer should be able to distinguish normal radiographic anatomy from artifacts such as machine parts and ghost images that appear on the radiograph.

Recall: Study Questions General Chapter Review

Reflect: Case Study You have to expose a panoramic radiograph on the following patients today. Each of these patients presents with a characteristic that will make positioning the patient for the procedure a challenge. Carefully review each of the patient descriptions and answer the following questions:

Reflect: Case Study What patient positioning step do you anticipate having a problem with? What error is most likely to occur? What will the image look like?

Reflect: Case Study How can you prevent this error from occurring or minimize the result on the image? Write out the specific steps you plan to take to produce a diagnostic quality image.

Reflect: Case Study Case A A hyperactive 10-year-old child who seems to be having difficulty paying attention to your directions. Case B A young adult with multiple facial piercings, including a tongue ring and several earrings.

Reflect: Case Study Case C A young woman with fashionable hair extensions gathered into a large ponytail. Case D A middle-aged man who wears partial dentures that when removed reveal missing anterior teeth.

Reflect: Case Study Case E An older woman with osteoporosis who exhibits a pronounced stooped posture as a result of collapsed vertebrae.

Relate: Laboratory Application Proceed to Chapter 30, Laboratory Application, to complete this activity.