12 Panoramic Radiography










140
12
Panoramic Radiography
EDUCATIONAL OBJECTIVES
Upon completing this chapter, the student will be able to:
1. Dene the key terms listed at the beginning of the chapter.
2. Discuss the purpose of panoramic radiography.
3. Know the signicance of the slit beam in panoramic
radiography.
4. Explain the basics of panoramic radiography, including the
importance of a focal trough or image layer.
5. Describe concepts related to pantomograms:
• Describehowapanoramicimageisproduced.
• Listthepositioningrequirementsforpanoramicimages.
• Deneghost image, and explain its role in panoramic
radiography.
6. Listtheadvantagesanddisadvantagesofpanoramic
imaging.
7. Discuss the main indications for use of a panoramic
radiograph, and describe the interpretation of the images
produced.
8. Knowthecause,appearance,andremedyfortechnique
errors in panoramic radiography.
9. Discuss the common contemporary artifacts that can be
found on panoramic images.
KEY TERMS
ala-tragus line
centers of rotation
focal trough
Frankfort plane
ghost image
image layer
laminogram
midsagittal plane
panoramic image
Panorex
pantomogram
point of rotation
slit beam
tomogram
tomography
and digital panoramic radiography, as well as the basic
concepts, patient positioning, and errors involved with this
type of extraoral radiography.
The Basics of Panoramic Radiography
Tomography is a radiographic technique that allows
radiographing in one plane of an object while blurring or
eliminating images from structures in other planes. Tomo is
the Greek word for “section,” and sections or radiographic
slices of the object are seen. ese projections also could be
called laminograms, from the word lamina (layer), because
this is a layered radiographic technique. Tomography is
used extensively in medicine and is the basis for computed
tomography (CT) and magnetic resonance imaging (MRI),
both of which are discussed in Chapter 16.
A tomogram is made by moving the x-ray source and the
image receptor in opposite directions in a xed relationship
through one or a series of rotation points while the patient
remains stationary (Fig. 12.2). e plane of the object that
is not blurred on the radiograph is called the “plane of
acceptable detail” or focal trough. It is also called the image
Introduction
Panoramic dental x-ray units have become commonplace in
dental oces, and the panoramic radiograph is considered
to be an essential element in radiographic diagnosis. ere-
fore, dental professionals should be familiar with panoramic
x-ray machines, technique, and interpretation. As shown
in this chapter, the panoramic radiograph is not meant to
replace intraoral periapical and bitewing images but rather
to complement them in the diagnostic process. e term
panorama means “an unobstructed view of a region in any
direction;” thus, a panoramic image shows the mandible
and maxilla on one radiograph from condyle to condyle.
Panoramic radiography was introduced into the US
dental market in 1959 by the S. S. White Corporation as
their Panorex unit. e design of this unit was based mainly
on the work of Dr. Y. V. Paatero, a Finnish dentist, and was
published in 1949. e panoramic radiographic technique
makes use of a slit beam and curved or at-surface rotational
tomography. e term slit beam refers to the width, usually
1 to 2 mm, of the beam that is produced by the collimator
(Fig. 12.1). is chapter discusses the use of conventional

141CHAPTER 12 Panoramic Radiography
Figure 12.1 Slit beam collimator. Only the part of the receptor that
is in back of the narrow beam is exposed. (From Bird DL, Robinson
DS: Modern Dental Assisting, ed 12, St Louis, 2018, Elsevier.)
)RFDO
WURXJK
$
$
%
%
&
&
)LOP
;UD\
EHDP
7XEH
PRYHPHQW
)LOP
PRYHPHQW
Figure 12.2 Principles of tomography. Note that only objects in
the focal trough (square) project onto the same area of the image and
are not blurred out.
Figure 12.3 Image layer, or focal trough.
with the number of cuts varying according to the thickness
of the object (Fig. 12.4).
Some tomographic units are made combined with a
panoramic unit specically for use in the head and neck
region. ese units enable dentists to do tomography in
their own oces. Indications for dental oce tomography
include implant planning, temporomandibular joint (TMJ)
tomography, and diagnosis of pathologic lesions. e
majority of these tomographic units are computer-driven
(Fig. 12.5). is means that the computer controls the
motion of the tube head and receptor and other exposure
parameters based on choices and information entered by
the operator. In some of these computer-directed units, the
imaging system is still a lm screen combination. In these
Figure 12.4 Tomogram of the temporomandibular joint (TMJ). Note
the clarity of the condyle and the blurring of the rest of the image.
layer (Fig. 12.3). e image layer is an invisible area that
is located in the space between the source of radiation and
the image receptor. e shape of the image layer varies.
Clinically, this concept is very important, because many
of the errors in technique that are discussed later in this
chapter are caused by improper patient positioning, the
result of which is not having the desired area in the image
layer. e points of rotation around which the tube head
travels can be either inside or outside of the focal trough.
e width or thickness of the focal trough is governed by
many factors, including the angle of movement of the x-ray
beam, the width of the x-ray beam, and the size of the focal
spot. Any object that lies in the focal plane is shown clearly,
and objects above and below it appear blurred. By varying
the focal-object distance—the distance between the tube
head and the patient—on a tomographic series, dierent
focal troughs or “cuts” can be achieved. A tomographic
series is usually composed of multiple cuts, 0.5 cm apart,

142 CHAPTER 12 Panoramic Radiography
systems, the computer does not produce or store images as
in digital imaging; it simply directs the patient exposure,
after which the lm is processed to produce the diagnostic
image.
Pantomogram
A panoramic radiograph of the maxilla and the mandible
produced by using tomography is also called a pantomo-
gram. e pantomogram is a curved-surface tomogram
(Fig. 12.6), in contrast to the plane surface or straight-line
tomogram illustrated in Fig. 12.2. In common usage,
the term panoramic radiograph is usually substituted for
pantomogram. e term Panorex should never be used as
a substitute for a panoramic radiograph unless the Panorex
unit is being used. It is not a generic term but rather the
manufacturers name for the rst panoramic unit introduced
in the dental market.
Digital Radiography
Digital imaging is widely used in dental radiography for
intraoral periapical and bitewing projections, as well as for
digital panoramic imaging. Digital radiography is discussed
in detail in Chapter 15, in which the basic principles of
Figure 12.5 The Gendex GXDP 700 Series is a 3-in-1 system that provides digital panoramic,
cephalometric, and 3D radiography. (Courtesy KaVo Kerr, Orange, CA.)
intraoral digital imaging are shown to apply to panoramic
digital radiography. Basically, a digital complementary
metal oxide semiconductor (CMOS), charged-coupled
device (CCD), or phosphor storage plate (PSP) sensor
approximately the size of the slit beam collimating device
is in the carrier instead of a lm-screen combination. As the
carrier moves around the patient, the electronic impulses
are sent back to the computer, and an image is generated.
e digital panoramic image can be altered in the same
way as the digital intraoral image—the operator can change
NOTE
Dental professionals often use the term Panorex to describe
the panoramic radiographic technique, although it is actually
the name of the manufacturer that originated the rst
panoramic unit. Calling a panoramic radiograph a Panorex
is like calling a facial tissue a Kleenex and is not the actual
terminology that should be appropriately utilized in dental
radiography.
%HJLQ(QG
Figure 12.6 Rotational tomography. Note the slit opening in the
receptor carrier and that the receptor and the tube travel around the
patient in opposite directions.

143CHAPTER 12 Panoramic Radiography
Figure 12.7 The Orthophos XG 5 panoramic unit. (Courtesy
Dentsply Sirona, Charlotte, NC.)
Figure 12.8 PM 2002 CC Proline panoramic machine. (Courtesy
Planmeca, Inc., Roselle, IL.)
PROCEDURE 12.1 COMMON POSITIONING REQUIREMENTS FOR PANORAMIC UNITS
1. Midsagittal plane: The midsagittal plane should be
perpendicular to the oor (Fig. 12.9).
2. Frankfort plane: The Frankfort plane is the imaginary line
connecting the oor of the orbit and the external auditory
meatus. In most units, this plane should be parallel to the
oor (Fig. 12.10). Some units may use the ala-tragus line
(imaginary line connecting the lower border of the ala of
the nose to the upper border of the tragus of the ear) for
patient positioning.
3. Bite block position: The anterior teeth should be positioned
in the proper groove in the bite block (Fig. 12.11) and
not forward or posterior to the groove (Figs. 12.12 and
12.13). If the patient is edentulous, then some other type of
extraoral positioner should be used (Fig. 12.14).
4. Chin position: The chin should not be angled up or down
(Figs. 12.15 and 12.16).
5. Head position: The head-positioning devices should
be rm to prevent tipping or rotating during the
exposure and loss of proper midsagittal plane orientation
(Fig. 12.17).
6. Patient stabilization: The patient must not move during the
exposure or a blurred image will result.
7. Tongue position: The patient should place and maintain the
tongue against the roof of the mouth.
8 Posture: The patient should keep the spine erect and avoid
slumping during panoramic exposure.
9. Lead apron: A double-sided lead (or lead substitute) apron
is used without a thyroid collar, because the collar will block
the primary beam (Fig. 12.18). In addition, the lead apron
should be positioned below the level of the clavicles during
exposure.
Continued
various image qualities, including contrast, density, and
magnication.
Advantages and Disadvantages:
Panoramic Radiography
Like any technique, panoramic radiography has its advan-
tages and disadvantages when compared with conventional
intraoral techniques. e panoramic unit is expensive
(approximately four times the cost of a regular x-ray unit).
e standard x-ray unit is still necessary even in an oce
with a panoramic unit.
ere are many pantomographic units available on the
market today. ey dier primarily in the number and
locations of the centers of rotation, the choice of a xed
or adjustable focal trough, and the type and shape of the
receptor transport mechanism. All conventional panoramic
units use intensifying screens, with a lm size of either
5
1
2
or
6
1
2
inches. Design dierences in both conventional and
digital panoramic units include head-positioning devices,
manual or automatic setting controls, bite blocks, kilovolt-
age and milliamperage range, standing or sitting patient
positioning, and wall-mounted or freestanding units. Some
more advanced units oer the option of being able to do
other extraoral projections, cross-sectional tomography, or
digital panoramic imaging. Each manufacturers machine
has its own technique for operation, which can be learned
easily from the instruction manual (Figs. 12.7 and 12.8).
However, there are certain positioning requirements that
are common to all units, which are discussed in Procedure
Box 12.1.

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14012 Panoramic RadiographyEDUCATIONAL OBJECTIVESUpon completing this chapter, the student will be able to:1. Dene the key terms listed at the beginning of the chapter.2. Discuss the purpose of panoramic radiography.3. Know the signicance of the slit beam in panoramic radiography.4. Explain the basics of panoramic radiography, including the importance of a focal trough or image layer.5. Describe concepts related to pantomograms:• Describehowapanoramicimageisproduced.• Listthepositioningrequirementsforpanoramicimages.• Deneghost image, and explain its role in panoramic radiography.6. Listtheadvantagesanddisadvantagesofpanoramicimaging.7. Discuss the main indications for use of a panoramic radiograph, and describe the interpretation of the images produced.8. Knowthecause,appearance,andremedyfortechniqueerrors in panoramic radiography.9. Discuss the common contemporary artifacts that can be found on panoramic images.KEY TERMSala-tragus linecenters of rotationfocal troughFrankfort planeghost imageimage layerlaminogrammidsagittal planepanoramic imagePanorexpantomogrampoint of rotationslit beamtomogramtomographyand digital panoramic radiography, as well as the basic concepts, patient positioning, and errors involved with this type of extraoral radiography.The Basics of Panoramic RadiographyTomography is a radiographic technique that allows radiographing in one plane of an object while blurring or eliminating images from structures in other planes. Tomo is the Greek word for “section,” and sections or radiographic slices of the object are seen. ese projections also could be called laminograms, from the word lamina (layer), because this is a layered radiographic technique. Tomography is used extensively in medicine and is the basis for computed tomography (CT) and magnetic resonance imaging (MRI), both of which are discussed in Chapter 16.A tomogram is made by moving the x-ray source and the image receptor in opposite directions in a xed relationship through one or a series of rotation points while the patient remains stationary (Fig. 12.2). e plane of the object that is not blurred on the radiograph is called the “plane of acceptable detail” or focal trough. It is also called the image IntroductionPanoramic dental x-ray units have become commonplace in dental oces, and the panoramic radiograph is considered to be an essential element in radiographic diagnosis. ere-fore, dental professionals should be familiar with panoramic x-ray machines, technique, and interpretation. As shown in this chapter, the panoramic radiograph is not meant to replace intraoral periapical and bitewing images but rather to complement them in the diagnostic process. e term panorama means “an unobstructed view of a region in any direction;” thus, a panoramic image shows the mandible and maxilla on one radiograph from condyle to condyle.Panoramic radiography was introduced into the US dental market in 1959 by the S. S. White Corporation as their Panorex unit. e design of this unit was based mainly on the work of Dr. Y. V. Paatero, a Finnish dentist, and was published in 1949. e panoramic radiographic technique makes use of a slit beam and curved or at-surface rotational tomography. e term slit beam refers to the width, usually 1 to 2 mm, of the beam that is produced by the collimator (Fig. 12.1). is chapter discusses the use of conventional 141CHAPTER 12 Panoramic Radiography• Figure 12.1 Slit beam collimator. Only the part of the receptor that is in back of the narrow beam is exposed. (From Bird DL, Robinson DS: Modern Dental Assisting, ed 12, St Louis, 2018, Elsevier.))RFDOWURXJK$$%%&&)LOP;UD\EHDP7XEHPRYHPHQW)LOPPRYHPHQW• Figure 12.2 Principles of tomography. Note that only objects in the focal trough (square) project onto the same area of the image and are not blurred out. • Figure 12.3 Image layer, or focal trough. with the number of cuts varying according to the thickness of the object (Fig. 12.4).Some tomographic units are made combined with a panoramic unit specically for use in the head and neck region. ese units enable dentists to do tomography in their own oces. Indications for dental oce tomography include implant planning, temporomandibular joint (TMJ) tomography, and diagnosis of pathologic lesions. e majority of these tomographic units are computer-driven (Fig. 12.5). is means that the computer controls the motion of the tube head and receptor and other exposure parameters based on choices and information entered by the operator. In some of these computer-directed units, the imaging system is still a lm screen combination. In these • Figure 12.4 Tomogram of the temporomandibular joint (TMJ). Note the clarity of the condyle and the blurring of the rest of the image. layer (Fig. 12.3). e image layer is an invisible area that is located in the space between the source of radiation and the image receptor. e shape of the image layer varies. Clinically, this concept is very important, because many of the errors in technique that are discussed later in this chapter are caused by improper patient positioning, the result of which is not having the desired area in the image layer. e points of rotation around which the tube head travels can be either inside or outside of the focal trough. e width or thickness of the focal trough is governed by many factors, including the angle of movement of the x-ray beam, the width of the x-ray beam, and the size of the focal spot. Any object that lies in the focal plane is shown clearly, and objects above and below it appear blurred. By varying the focal-object distance—the distance between the tube head and the patient—on a tomographic series, dierent focal troughs or “cuts” can be achieved. A tomographic series is usually composed of multiple cuts, 0.5 cm apart, 142 CHAPTER 12 Panoramic Radiographysystems, the computer does not produce or store images as in digital imaging; it simply directs the patient exposure, after which the lm is processed to produce the diagnostic image.PantomogramA panoramic radiograph of the maxilla and the mandible produced by using tomography is also called a pantomo-gram. e pantomogram is a curved-surface tomogram (Fig. 12.6), in contrast to the plane surface or straight-line tomogram illustrated in Fig. 12.2. In common usage, the term panoramic radiograph is usually substituted for pantomogram. e term Panorex should never be used as a substitute for a panoramic radiograph unless the Panorex unit is being used. It is not a generic term but rather the manufacturer’s name for the rst panoramic unit introduced in the dental market.Digital RadiographyDigital imaging is widely used in dental radiography for intraoral periapical and bitewing projections, as well as for digital panoramic imaging. Digital radiography is discussed in detail in Chapter 15, in which the basic principles of • Figure 12.5 The Gendex GXDP 700 Series is a 3-in-1 system that provides digital panoramic, cephalometric, and 3D radiography. (Courtesy KaVo Kerr, Orange, CA.)intraoral digital imaging are shown to apply to panoramic digital radiography. Basically, a digital complementary metal oxide semiconductor (CMOS), charged-coupled device (CCD), or phosphor storage plate (PSP) sensor approximately the size of the slit beam collimating device is in the carrier instead of a lm-screen combination. As the carrier moves around the patient, the electronic impulses are sent back to the computer, and an image is generated. e digital panoramic image can be altered in the same way as the digital intraoral image—the operator can change NOTEDental professionals often use the term Panorex to describe the panoramic radiographic technique, although it is actually the name of the manufacturer that originated the rst panoramic unit. Calling a panoramic radiograph a Panorex is like calling a facial tissue a Kleenex and is not the actual terminology that should be appropriately utilized in dental radiography.%HJLQ(QG• Figure 12.6 Rotational tomography. Note the slit opening in the receptor carrier and that the receptor and the tube travel around the patient in opposite directions. 143CHAPTER 12 Panoramic Radiography• Figure 12.7 The Orthophos XG 5 panoramic unit. (Courtesy Dentsply Sirona, Charlotte, NC.)• Figure 12.8 PM 2002 CC Proline panoramic machine. (Courtesy Planmeca, Inc., Roselle, IL.)PROCEDURE 12.1 COMMON POSITIONING REQUIREMENTS FOR PANORAMIC UNITS1. Midsagittal plane: The midsagittal plane should be perpendicular to the oor (Fig. 12.9).2. Frankfort plane: The Frankfort plane is the imaginary line connecting the oor of the orbit and the external auditory meatus. In most units, this plane should be parallel to the oor (Fig. 12.10). Some units may use the ala-tragus line (imaginary line connecting the lower border of the ala of the nose to the upper border of the tragus of the ear) for patient positioning.3. Bite block position: The anterior teeth should be positioned in the proper groove in the bite block (Fig. 12.11) and not forward or posterior to the groove (Figs. 12.12 and 12.13). If the patient is edentulous, then some other type of extraoral positioner should be used (Fig. 12.14).4. Chin position: The chin should not be angled up or down (Figs. 12.15 and 12.16).5. Head position: The head-positioning devices should be rm to prevent tipping or rotating during the exposure and loss of proper midsagittal plane orientation (Fig. 12.17).6. Patient stabilization: The patient must not move during the exposure or a blurred image will result.7. Tongue position: The patient should place and maintain the tongue against the roof of the mouth.8 Posture: The patient should keep the spine erect and avoid slumping during panoramic exposure.9. Lead apron: A double-sided lead (or lead substitute) apron is used without a thyroid collar, because the collar will block the primary beam (Fig. 12.18). In addition, the lead apron should be positioned below the level of the clavicles during exposure.Continuedvarious image qualities, including contrast, density, and magnication.Advantages and Disadvantages: Panoramic RadiographyLike any technique, panoramic radiography has its advan-tages and disadvantages when compared with conventional intraoral techniques. e panoramic unit is expensive (approximately four times the cost of a regular x-ray unit). e standard x-ray unit is still necessary even in an oce with a panoramic unit.ere are many pantomographic units available on the market today. ey dier primarily in the number and locations of the centers of rotation, the choice of a xed or adjustable focal trough, and the type and shape of the receptor transport mechanism. All conventional panoramic units use intensifying screens, with a lm size of either 512 or 612 inches. Design dierences in both conventional and digital panoramic units include head-positioning devices, manual or automatic setting controls, bite blocks, kilovolt-age and milliamperage range, standing or sitting patient positioning, and wall-mounted or freestanding units. Some more advanced units oer the option of being able to do other extraoral projections, cross-sectional tomography, or digital panoramic imaging. Each manufacturer’s machine has its own technique for operation, which can be learned easily from the instruction manual (Figs. 12.7 and 12.8). However, there are certain positioning requirements that are common to all units, which are discussed in Procedure Box 12.1. 144 CHAPTER 12 Panoramic RadiographyPROCEDURE 12.1 COMMON POSITIONING REQUIREMENTS FOR PANORAMIC UNITS—cont’d• Figure 12.11 Patient positioned with anterior teeth in placement groove. • Figure 12.12 Patient positioned with anterior teeth forward of the groove in the bite block. • Figure 12.13 Patient positioned with anterior teeth posterior to the groove. NOTEPatient posture is very important. Without correct posture positioning, the structure to be radiographed may not be in or remain in the plane of focus (focal trough) and will appear blurred on the panoramic radiograph.2UELWRPHDWDO)UDQNIRUW3ODQH$ODWUDJXV/LQH• Figure 12.10 Anatomic horizontal positioning planes. • Figure 12.9 Midsagittal plane. 145CHAPTER 12 Panoramic RadiographyPROCEDURE 12.1 COMMON POSITIONING REQUIREMENTS FOR PANORAMIC UNITS—cont’d• Figure 12.16 Patient positioned incor-rectly with the chin down. • Figure 12.15 Patient positioned incor-rectly with the chin up. CAB• Figure 12.17 A, Anterior teeth positioned correctly. B, Broken line is focal plane, and unbroken line is mandibular arch, showing that neither side is in the focal plane. C, Patient positioned with head rotated. • Figure 12.18 Patient with lead apron in place. Note that there is no thyroid collar used. • Figure 12.14 Positioning of the edentu-lous patient. 146 CHAPTER 12 Panoramic Radiography• Figure 12.19 Ghost images of the opposite sides of the mandible, outlined by the arrows. • Figure 12.20 Radiopaque markings caused by the patient’s earring. Note the ghost image and the sharp image. • Figure 12.21 Pantomography of the temporomandibular joint (TMJ) done using a panoramic unit with an adjustable focal trough. The focal trough is set for the plane of the condyles instead of the body of the mandible. AdvantagesSize of the FieldField size is one of the major advantages of panoramic radi-ography. e full-mouth series is composed of radiographs of the entire mouth but only of the teeth, alveolar ridges, and part of the supporting bone. Panoramic radiography covers an area that includes all of the mandible from condyle to condyle and the maxillary regions extending superiorly to the maxillary sinus and nasal cavity (Figs. 12.22 and 12.23). Areas of the mandible—such as the condyles, inferior border, angle, ascending ramus, and coronoid process, as well as the entire maxillary arch, which are not visualized on Panoramic Imagee panoramic image shows the entire dentition and supporting bone from condyle to condyle on one image. However, the image does not have the same denition seen on an intraoral periapical or bitewing projection. is factor is inherent in the pantomographic process. ese images also have a signicant amount of horizontal distortion but less vertical distortion.All objects in the eld of the x-ray beam, even those out of the plane of focus, are projected onto the receptor, but most are not seen. e objects that have the greatest density (e.g., bone or metal objects) and are out of the plane of acceptable detail (focal trough) are shown in two places on the panoramic image. One place is the intended image or the usable image, and the other is referred to as the ghost image (Fig. 12.19). e ghost image always has less sharpness and is seen at a point higher on the radiograph than the desired image. e ghost image is always reversed; that is, the left appears on the right and vice versa. is can be best illustrated by an image in which the patient did not remove large earrings (Fig. 12.20).Some panoramic units can be used to take tomograms of the TMJ (Fig. 12.21). To accomplish this, the unit must have an adjustable focal plane. e plane is set for the position of the condyle instead of the usual focal plane, which is through the body of the mandible. By stopping the rotation and rewinding the receptor carrier, an open view and a closed view can be taken on each side with one receptor producing four images (R-closed position, R-open position, L-closed position, and L-open position). 147CHAPTER 12 Panoramic Radiography0LGGOH&UDQLDO)RVVD2UELW=\JRPDWLF$UFK3DODWH6W\ORLG3URFHVV6HSWDLQ0D[LOODU\6LQXV0D[LOODU\7XEHURVLW\([WHUQDO2EOLTXH5LGJH$QJOHRI0DQGLEOH+\RLG%RQH*OHQRLG)RVVD$UWLFXODU(PLQHQFH0DQGLEXODU&RQG\OH9HUWHEUD&RURQRLG3URFHVV3WHU\JRLG3ODWHV0D[LOODU\6LQXV(DU/REH0DQGLEXODU&DQDO0HQWDO)RUDPHQ• Figure 12.22 Panoramic radiograph and tracing showing numbered anatomic landmarks. (Courtesy KaVo Dental/GENDEX Imaging, Lake Zurich, IL.)• Figure 12.23 Panoramic radiograph with tracing of the area seen on a full-mouth survey (outlined). intraoral surveys—are seen routinely on panoramic images. Lesions that might be undetected on intraoral surveys may be seen in the enlarged eld size of the panoramic image.A contemporary indication for the use of panoramic images has been reported. Some patients who are at risk for cerebrovascular accidents because of the presence of atherosclerotic plaque in their carotid arteries can be identi-ed in the dental oce by appropriate evaluation of their panoramic images for calcications. Most panoramic images show the area adjacent to or below the intervertebral space between C3 and C4, which is the location of the carotid arteries that might show evidence of calcications (Fig. 12.24). Panoramic radiographs should not be taken solely to screen for carotid artery atherosclerotic plaque. However, their presence should be evaluated on every patient who has a pantomogram taken. It is your professional obligation to do this, and patients should be referred to a physician regardless of their symptoms. If a nding is observed on a radiograph that was not the primary purpose of the exposure, this nding is considered to be an incidental nding, and the appropriate referral is made based on the image produced.Quality ControlIn maintaining quality control, good chairside technique is essential so that the undistorted complete image is seen. Full visualization of all the teeth and surrounding bone, including the third molar area, is of prime importance. is is more easily done with a panoramic unit than an intraoral full-mouth series, because the technique, although not simple, is not as demanding as intraoral radiography. 148 CHAPTER 12 Panoramic Radiography• Figure 12.24 Panoramic radiograph showing calcications in the left carotid arteries distal and inferior to the angle of the mandible. (Courtesy Dr. Laurie Carter.)ere are fewer retakes, and quality control is easier to maintain. Quality control for processing of conventional panoramic lms is discussed in Chapter 11.SimplicityPanoramic procedures, as mentioned, are relatively simple to perform. With minimal training and strict attention to detail, any member of the dental team can become procient in taking these projections.Patient CooperationBecause panoramic radiography is an extraoral procedure, it requires a minimum of patient cooperation in comparison with intraoral techniques. Receptors are not placed in the patient’s mouth. e patient is asked to bite on a bite piece and is only required to sit or stand still for 12 to 22 seconds of exposure. When applicable, most units can be operated without radiation to demonstrate to an apprehensive patient what the procedure will be like.Panoramic radiography practically eliminates problems with intractable gaggers, patients with trismus, and fearful or uncooperative adults or children.TimeLess time is required for a panoramic radiographic examina-tion than an intraoral survey. e most skilled operator requires at least 15 to 20 minutes to expose an intraoral survey; panoramic radiographs can be taken in less than 5 minutes.Doseere seems to be general agreement that the radiation dose to the patient is less than that in intraoral radiography. e conventional panoramic dose is about equivalent to that received from four bitewing projections. is dose can be reduced even further by using digital panoramic units.DisadvantagesImage QualityPanoramic radiographs inherently show magnication, geometric distortion, and poor denition. Compared with an intraoral radiograph, the panoramic image does not give comparable denition. In addition to the tomographic process, other factors that tend to degrade the images as compared with intraoral images are (1) external placement of the receptor with resulting increased object-receptor distance, (2) the use of intensifying screens (in conventional panoramic radiography), and (3) faster lm with large grain size (in conventional panoramic radiography).Many diagnostic problems in dentistry require a high degree of radiographic denition. Early detection of condi-tions (such as, interproximal caries, disruption of the lamina dura, loss of crestal alveolar bone, and a thickened periodon-tal membrane) all require the maximum of radiographic denition. Because of these factors, panoramic images have very limited value in the diagnosis of periodontal disease and the detection of caries and early periapical lesions. ese are common diagnostic problems for practitioners, and the panoramic radiographic technique is lacking in these areas. If a panoramic image is used instead of a full-mouth series, it must be augmented with bitewings and selected periapical projections where indicated.Focal Trough (Image Layer)Areas that lie outside (either in front of or behind) the focal trough may be seen poorly or not at all. e focal trough or plane of acceptable detail is not as wide as either the mandible or maxilla, and only structures or changes that lie within the trough are visualized clearly. Pantomographic units that have adjustable focal troughs have far greater diagnostic capabili-ties than those that do not, but the cost is greater.OverlapPantomographic units have a tendency to produce overlap-ping images, particularly in the premolar area.SuperimpositionOften, superimposition of the spinal column shows up on the anterior portion of the pantomogram. If the patient is positioned properly, this should not happen. However, not all patients are in perfect physical condition, and some have physical problems that make proper positioning dicult. 149CHAPTER 12 Panoramic RadiographyFig. 12.22) the middle cranial fossa, orbit, styloid process septa in the maxillary sinus, palate, pterygomaxillary ssure, angle of the mandible, hyoid bone, TMJ, vertebra, coronoid process, pterygoid plate, the entire maxillary sinus, tonsillar tissue, ear lobe, mandibular foramen, and mandibular canal.TechniqueProcedure 12.2 presents the general rules of technique for preparing and positioning the patient for panoramic radi-ography. ese rules are valid for all units, but some slight technique changes may be necessary for individual units, depending on the manufacturer’s specic instructions.ProcessingConventional panoramic lms are processed with regular dental solutions either by hand processing or automatically if the processor can accommodate the panoramic size lm. e time-temperature method is used with the same xation and washing times as with intraoral lms. e lm used in panoramic radiography, as in other extraoral projections, is especially sensitive to excessive safelighting or exposure to cell phone light and may be fogged or completely ruined. One should make sure that the lm-screen combination used is compatible with the intensity and type of safelight used.One of the most common artifacts seen on conventional panoramic lms is caused in the darkroom by static electric-ity. Multiple black linear streaks resembling tree branches without leaves appear on the radiograph (Fig. 12.25). is artifact can be caused by pulling a piece of lm quickly and forcefully out of a tightly packed full box of lm or when loading or unloading lm between the intensifying screens of a cassette. Static electricity is produced most often on cold, dry days.e anterior teeth and periapical bone are the most dicult to interpret on pantomograms.Distortione amount of vertical and horizontal distortion varies from one part of the image to another, resulting in an uneven magnication of the image. erefore, structures, spaces, and distances may appear larger than they actually are. is is a critical factor, because some dentists use panoramic radiographs for bone evaluation and case planning involv-ing implant patients.OveruseOveruse is one of the prime concerns regarding patient ex-posure. e ease and convenience in obtaining the pan-oramic image might lead to careless substitution for other projections that would yield better results. e panoram-ic radiograph might be taken instead of a periapical pro-jection of an area.CostPanoramic units are not inexpensive, but they are a great aid to a practice. Costs vary depending on the manufacturer and design. It is very desirable to have a panoramic unit in a dental oce and, if not, to have a pathway for referrals.Indicationse main indication for panoramic radiography is attaining a larger eld size than is possible with periapical and bite-wing radiography. Clinical situations in which a panoramic unit is useful and helpful include detecting large areas of pathologic conditions, visualizing impacted teeth, jaw frac-tures, patients who cannot or will not open their mouths, evaluating tooth development and eruption patterns and timing for both the permanent and deciduous dentition, TMJ problems, foreign bodies, and implant evaluation.InterpretationBecause there is a larger eld size, it follows that it will be necessary to be able to identify more anatomic structures not seen on an intraoral survey. ere will be some struc-tures that will be seen on both. e new structures are (see NOTEAlways follow the manufacturer’s manual regarding which anatomic line is to be used for positioning the patient. For example, the ala-tragus line is tilted slightly down, about 5 degrees, from a parallel line to the oor, or the Frankfort plane is parallel to the oor.• Figure 12.25 Panoramic radiograph showing static marks. Text continued on p. 154 150 CHAPTER 12 Panoramic RadiographyPROCEDURE 12.2 RULES AND TECHNIQUES FOR PREPARING AND POSITIONING THE PATIENT FOR PANORAMIC RADIOGRAPHY1. Explain the procedure to the patient, pointing out the importance of not moving during the procedure. Point out the movement of the receptor and tube around the patient’s head and the possibility that the receptor may touch the shoulder or ear gently during the exposure rotation.2. Follow infection control procedures for panoramic imaging, including making sure that equipment barriers and personal protective infection control equipment are in place.3. Have the patient remove a jacket or any other bulky piece of clothing that might interfere with movement of the machine.4. Ask the patient to remove any dentures, eyeglasses, earrings, nose rings, necklaces, hearing aids, hairpins, and other metallic objects in the entire head and neck region to avoid their appearance on the panoramic image.5. Seat or stand the patient in the most erect position possible so that the spinal column is straight. Instruct the patient to hold the support handles on the unit, take one step forward, and keep the feet together.6. Align the patient’s head so that the midsagittal plane is perpendicular to the oor.7. Place the patient’s chin on the chin rest. Secure the head-positioning devices to prevent head movement.8. Drape the front and back of the patient with the lead apron. Do not use a thyroid collar or a bib chain, because it would be superimposed on the image.9. Place a cotton roll or a bite stick, if the unit has one, between the patient’s upper and lower incisors.10. Have the patient close the lips and place the at portion of the tongue against the roof of the mouth. In addition, instruct the patient to swallow and hold this position. These instructions help to prevent the formation of an airspace that is represented as a radiolucent area above the apices of the maxillary teeth.11. Properly set the exposure factors.12. Instruct the patient not to move during the exposure.13. Press the exposure button and keep your nger on the exposure button for the length of the appropriate exposure time.Panoramic Exposure ErrorsPatient Positioned Too Far Forward (Fig. 12.26). If the patient is positioned in front of the focal plane, the upper and lower anterior teeth appear blurred and narrow. The spinal column is superimposed on the ramus, and the premolars are overlapped.Remedy. The patient’s teeth or edentulous ridges must be in the proper position in the anteroposterior plane. Check the position of the teeth on the bite block and the position of the patient’s chin on the rest.Patient Positioned Too Far Back (Fig. 12.27). If the patient is positioned in back of the focal plane, the maxillary and mandibular anterior teeth appear blurred and widened. Increased ghosting of the mandible also appears.Remedy. The patient’s teeth or ridges must be in the proper position on the bite block. Check the position of the chin rest and the chin for the correct distance in the posterior-anterior plane.Patient’s Head Tilted Up (Fig. 12.28). If the patient’s head is tilted up, the forehead is too far back and the chin too far forward. This position causes the maxillary incisors to be out of focus, and the radiopaque hard palate is superimposed over the apices of the maxillary teeth. The condyles may be off the image.Remedy. The reference lines on the patient’s face, the Frankfort plane or the ala-tragus line, should be aligned parallel to the oor.Patient’s Head Tilted Down (Fig. 12.29). If the patient’s head is tilted down, then the chin is back and the forehead is forward. This position causes the mandibular incisors to be blurred. The radiopaque image of the hyoid bone is superimposed on the anterior part of the mandible. The superior portions of the condyles may be cut off the image, and the premolars are overlapped.Remedy. The reference lines on the patient’s face, the Frankfort plane or the ala-tragus line, should be aligned parallel to the oor.Patient Movement during Exposure (Fig. 12.30). If the patient moves anytime during the exposure, the part of the image that was being exposed at that time will appear blurred. This effect differs from that in intraoral radiography, in which patient movement blurs the entire image.Remedy. Talk to the patient during the exposure, reminding the patient not to move.Large Radiolucent Area below the Palate (Fig. 12.31). If the patient does not hold the at part of the tongue against the roof of the mouth, a radiolucent pharyngeal air space artifact is created that produces a dark shadow on the radiograph, obliterating the apices of the maxillary teeth.AB• Figure 12.26 Patient positioned too far forward. Anterior teeth appear blurred and narrow. Spinal column is superimposed on the ramus, and premolars are overlapped. A, Anterior teeth forward of the focal plane. B, Dental arch (solid line) anterior to focal plane (broken line). C, Radiograph. 151CHAPTER 12 Panoramic RadiographyContinuedPROCEDURE 12.2 RULES AND TECHNIQUES FOR PREPARING AND POSITIONING THE PATIENT FOR PANORAMIC RADIOGRAPHY—cont’dAB• Figure 12.28 Patient’s head tilted up. Hard palate (radiopaque band) image is superimposed on apices of upper teeth. A, Roots of maxillary incisors outside of focal plane. B, Mandibular arch (unbroken line) in focal trough. Maxillary arch (broken line) positioned in back of focal plane. C, Radiograph. AB• Figure 12.29 Patient’s head is tilted down. Lower incisors are blurred and image of the hyoid bone is superimposed on the mandible. A, Roots of mandibular teeth outside of focal plane. B, Maxillary arch (unbroken line) positioned in focal plane. Mandibular arch (broken line) positioned in back of focal plane. C, Radiograph. AB• Figure 12.27 Patient positioned too far back. Upper and lower anterior teeth appear blurred and widened. A, Anterior teeth positioned behind the focal plane. B, Dental arch (solid line) posterior to focal plane (broken line). C, Radiograph. 152 CHAPTER 12 Panoramic RadiographyPROCEDURE 12.2 RULES AND TECHNIQUES FOR PREPARING AND POSITIONING THE PATIENT FOR PANORAMIC RADIOGRAPHY—cont’dRemedy. Remind patients during the exposure to keep the tongue against the roof of the mouth.Patient Does Not Sit or Stand Erect (Fig. 12.32). If the patient slumps while standing or sitting, the spinal column causes a triangular radiopacity to be superimposed on the anterior teeth.Remedy. Keep the patient’s spine erect in the positioning process. In the seated position, the operator can place a cushion or support in the small of the patient’s back to help the patient sit upright.Failure to Remove Metal Objects from the Face, Head, Neck, and Mouth (Fig. 12.33). Metal objects (such as, dentures with metallic components, jewelry, eyeglasses, or other metallic objects), if not removed, cause ghosting on the opposite, superior side of the image and may obscure structures, making the image undiagnostic.Remedy. Remove all metallic objects from the patient’s mouth, head, and neck regions.Lead Apron Placed Too High on the Patient (Fig. 12.34). The lead apron cannot be placed on the patient • Figure 12.30 Patient movement during exposure. Note the blurred and sharp areas. • Figure 12.31 Tongue not against roof of the patient’s mouth. Note the large radiolucent band superimposed over apices of the maxillary teeth. • Figure 12.32 Patient slouching. Note superimposition of triangular radiopacity, representing the spinal column and not a lead apron. 153CHAPTER 12 Panoramic Radiographyabove the level of the clavicles, because it will create a large radiopacity on the image.Remedy. Keep the lead apron low on the patient, never use a thyroid collar, and remember to fasten both sides of the back of the double-sided lead apron evenly when taking a panoramic radiograph.Film Cassette Slowing Down Because of Patient Contact (Fig. 12.35). If the panoramic unit is slowed down or stopped for an instant during the exposure travel around the patient, dark vertical bands will appear on the image as a result of the localized overexposure.Remedy. Position the patient carefully. With large-framed patients, the operator should run the machine rst without radiation to acquaint the patient with the procedure and to check on the patient’s position, ensuring that the patient does not contact the rotating panoramic unit. PROCEDURE 12.2 RULES AND TECHNIQUES FOR PREPARING AND POSITIONING THE PATIENT FOR PANORAMIC RADIOGRAPHY—cont’d• Figure 12.33 Failure to remove metal earrings, maxillary denture, and eyeglasses from patient’s face. Note ghosting effect of the metal. • Figure 12.34 Placement of the lead apron too high on the patient’s neck. • Figure 12.35 Film cassette slowed because of patient contact. Note radiolucent band where the overexposure took place. 154 CHAPTER 12 Panoramic RadiographyContemporary Panoramic Imaging Artifactsere have been new ndings evident in dental panoramic imaging that reect changes in society over time. Although we may interpret these ndings as “artifacts,” they could simply be images that we cannot readily identify.One of these artifacts that accurately reects today’s lifestyle is cell phone fogging on panoramic images. Panoramic conventional lm is much more sensitive to light than intraoral lm, and it takes longer for the entire panoramic lm to be fed into an automatic lm processor. Although it may seem unlikely, when the operator exposes the panoramic lm to the light emitted from a cell phone, the lm becomes fogged and, therefore, is not acceptable for diagnostic use (Fig. 12.36).ere are several fashion trends that are common today, which are visible more often on panoramic dental images. Common among these are facial jewelry. ese items should be removed before dental radiographic exposure when pos-sible. If they are metallic in composition, they could be superimposed over images that need to be observed and/or they could cause ghosting on panoramic radiographs, interfering with the diagnostic capability of the image. In some instances, the patient is unable to remove the pierc-ings because, in keeping with contemporary body piercing procedures, they were soldered into place permanently. e artifacts will be visible, along with the ghosting caused by these objects, which appear more superior, reversed, and with less denition than the actual images (Fig. 12.37).Images that involve medical consideration and surgical intervention can also be seen on panoramic radiographs. ese images may include carotid stents, aneurysm clamps, and hearing aids (Figs. 12.38, 12.39, and 12.40).• Figure 12.37 Ghosting of various piercings on a panoramic radiograph. • Figure 12.36 Panoramic lm fogging because of exposure from cell-phone light. • Figure 12.38 Carotid artery stents on patient’s right side on a panoramic radiograph. • Figure 12.39 Aneurysm clamp seen on upper border of panoramic radiograph, on patient’s right side. • Figure 12.40 Hearing aid in patient’s left ear on a panoramic radiograph. 155CHAPTER 12 Panoramic RadiographyChapter Summary• Panoramic radiography was introduced into the U.S.dental market in 1959 by the S. S. White Corporation. e Panorex was the rst panoramic radiographic unit invented and used in extraoral radiography.• Panoramic radiography is based on the principles oftomography, which is a radiographic technique that allows radiographing in one plane of an object while blurring or eliminating images from structures in other planes.• e plane of the object that is not blurred on theradiograph is called the “plane of acceptable detail” or focal trough. It is also called the image layer and is an invisible area that is located in the space between the source of radiation and the image receptor. Many panoramic technique errors are caused by improper patient positioning, the result of which is not having the desired area in the image layer. Common positioning requirements for panoramic units include midsagittal plane orientation, Frankfort horizontal or ala-tragus plane orientation, bite-block positioning, chin position, head position, patient stabilization, tongue position, posture, and placement of the lead apron.• In panoramic imaging, objects that have the greatestdensity (e.g., metal objects) and are out of the plane of acceptable detail (focal trough) are shown in two places on the panoramic image. One place is the usable image, and the other is referred to as the ghost image. e ghost image is always reversed, has less sharpness, and is seen at a point higher on the radiograph than the desired image.• e advantagesofpanoramic radiography include: theeld size, quality control, simplicity, patient cooperation, minimal set-up and exposure time, and no signicant increase in radiation dose as compared with intraoral radiography, especially in the case of digital panoramic radiography.• e disadvantages of panoramic radiography includeissues with image quality; limitations of the focal trough (image layer); inherent overlapping, especially in the premolar regions; superimposition of structures, such as the spinal column; a certain amount of vertical and horizontal distortion; overuse of panoramic radiographs; and the cost of panoramic units.• e primary indication for use of a panoramic radio-graph is when a larger eld size is warranted for dental purposes. ese situations include visualizing impacted teeth, large pathologies, jaw fractures, tooth develop-ment, and other conditions.• Panoramicexposureerrorsaremostlydue to improperpatient positioning but can include static electricity artifacts, movement during exposure, failure to remove metallic objects, and incorrect lead apron placement as well.Chapter Review QuestionsMultiple Choice1. Radiopaquesuperimposedimagesresultfrom: a. e patient’s failure to place the tongue to the palate b. e patient’s failure to stay in one position during exposure c. e patient’s failure to remove metallic objects d. e patient’s failure to lift the chin e. e operator’s failure to avoid static electricity2. Panoramicradiographscanbeusedtodetect: a. Periodontal disease b. Incipient periapical lesions c. Impacted third molars d. Incipient interproximal caries e. Incipient widened periodontal ligament3. If the lead apron is placed too high on the patient during panoramicexposure: a. It will create a large RL artifact on the image b. It will create a large RO artifact on the maxilla only c. It will create a large RL artifact on the maxilla only d. It will create a large RO artifact on the image e. It will not create an artifact on the image4. e anatomic landmarks that are more visible on pan-oramic radiographs than intraoral radiographs are the (chooseallthatapply): a. Mandibular foramen b. Palate c. Mandibular condyle d. Hyoid bone e. Mental foramen5. Proper patient positioning for a panoramic exposure includesallofthefollowingexcept: a. e Frankfort plane parallel to the oor b. e tongue relaxed in the oor of the mouth c. e midsagittal plane perpendicular to the oor d. e patient’s chin in the chin rest e. e spinal column erect 156 CHAPTER 12 Panoramic RadiographyCase-Based Critical Thinking Exercise1. A patient presents for a routine dental examination. A panoramic radiograph is prescribed. e panoramic radiograph is exposed and exhibits a radiopacity inferior and distal to the angle of the mandible, as indicated by the arrows in the accompanying panoramic radiograph. a. Describe the nding, including the radiographic appearance and location. b. List the possibilities of what the nding could represent. c. Explain what the role of the dental professional is in identifying and managing this nding. d. Discuss the implications of this nding.Identifythefollowingpanoramicexposureerrors:1. e artifact on the accompanying panoramic radiograph isasaresultof: a. Underexposure b. Static electricity c. Overexposure d. e operator removing the lm from the box too slowly e. e operator placing the thyroid collar on the patient2. e panoramic error showing a horizontal radiolucent band above the apices of the maxillary teeth is generally causedby: a. A lead apron b. Static electricity c. e soft palate d. Cleft palate e. e patient’s tongue not being placed on the palate3. is panoramic image shows circular RO images on the lmthatarearesultof: a. Not removing bracelets b. Not removing facial jewelry c. Ghosting of facial jewelry d. Both a and c are correct e. Both b and c are correct4. e anterior teeth in the accompanying panoramic radiograph appear blurred and narrowed. In addition, the spinal column is superimposed on the ramus. e causeofthiserrorismostlikelythat: a. e lm cassette’s movement was interrupted b. e patient’s head was tilted up c. ere was static created d. e patient was positioned too far forward e. e patient is positioned too far back 157CHAPTER 12 Panoramic RadiographyBibliographyCarterLC,HallerAD,NadarajahV,etal:Useofpanoramicradiog-raphy among an ambulatory dental population to detect patients at risk of stroke, J Am Dent Assoc28:977–984,1997.FriedlanderAH,GarrettNR,NormanDC:eprevalenceofcalciedcarotid artery atheromas on the panoramic radiographs of patients with type 2 diabetes mellitus, J Am Dent Assoc133:1516–1523,2002.FrommerHIT,Stabulas-SavageJJ:Asignofthetimes:contemporarydental imaging artifacts, N Y State Dent J74:37–39,2008.IannucciJM,HowertonLJ:Dental radiography: Principles and tech-niques, ed 5, St Louis, MO, 2016, Elsevier Saunders.Langland OE, Langlais RP: Principles of dental imaging, Baltimore, MD, 1997, Williams & Wilkins.ompson EM, Johnson ON: Essentials of dental radiography for dental assistants and hygienists, ed 9, Upper Saddle River, NJ, 2012, Pearson Education, Inc.WhiteSC,PharoahMJ:Oral radiology: Principles and interpretation, ed 7, St Louis, MO, 2013, Mosby.5. e dark vertical band on the accompanying radiograph isdueto: a. Underexposure b. Fogged lm c. Interruption of the cassette movement d. Inadequate closure e. All of the above answers are incorrect

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