15 Digital Imaging










172
15
Digital Imaging
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 following related to digital imaging:
• Knowthebasicelementsthatarenecessarytoacquirea
digital image.
• Listthethreebasictypesofdigitalimagingsystemsand
how they dier from each other.
3. State the three types of digital sensors that can be used in
digital imaging.
4. Describe the following related to the nature of the image:
• Denewhatapixelis,andexplainitsroleinthe
formation of a digital image.
• Listtheadvantagesanddisadvantagesofdigitalimaging
whencomparedtoconventionallm-basedradiography.
5. Statethecomponentsofthedigitalimagingtechniqueand
be able to apply them to clinical practice.
6. Discussthetypesofdigitalsystems,aswellasthelegal
aspects of digital radiography in dentistry.
of digital imaging, as well as the technique, advantages, and
disadvantages of the system.
Digital Image
A digital image is an image formed by the use of an
electronic sensor that is connected in some manner to a
computer. Early in the development of digital imaging, it
was often referred to as lmless radiography, but that term
is no longer used to describe this imaging technique. e
basic elements necessary to acquire a digital image are (1) an
x-ray machine; (2) an electronic sensor or detector; (3) an
analogue-to-digital converter; (4) a computer, which can be
a laptop or desktop version; and (5) a monitor (Fig. 15.1).
Presently, there are three basic types of digital imaging
systems (Fig. 15.2):
Introduction
One of the most exciting technologies introduced in den-
tistry is digital imaging, along with the other computerized
aspects of a dental practice. Instead of lm or a lm-screen
combination, this digital imaging system uses electronic
sensors to record the penetration of the x-ray photons
and sends this information to a computer that digitizes
(converts to numbers) these electronic impulses. is allows
the computer to produce a diagnostic image on a monitor
almost instantaneously. Digital imaging was introduced into
dentistry in 1987 by Dr. Francois Mugnon with his RVG
system (RadioVisioGraphy). Since that time, the market
has exploded with numerous companies making compet-
ing products. is chapter does not focus on a particular
digital unit, but it attempts to explain the basic principles
KEY TERMS
analogue
charge-coupled device (CCD)
complementary metal oxide
semiconductor (CMOS)
detector
digital image
digitize
direct digital radiography
gray level
hard copies
image manipulation
imaging plate
indirect digital radiography
line pairs per millimeter
monitor
optically scanned digital radiography
paperless oce
photostimulable phosphor (PSP)
pixels
RVG system
sensor
storage phosphor

173CHAPTER 15 Digital Imaging
X-Ray Unit
e standard dental intraoral x-ray machine can be used
for digital radiography, so it is not necessary to purchase a
digital-specic unit. However, the unit must have a timer
that can be adjusted to accommodate the digital receptors
that require less time than conventional lm. ere are
units available that have an icon picturing a computer that,
when activated, automatically reduces the exposure time
and provides the image quality and reduction in exposure
times needed for digital radiography. ese units can be
utilized for both conventional and digital radiography.
ere are digital panoramic units available that combine the
advantages of digital imaging with those of pantomography.
Sensors
e most critical part of a digital radiography system is
the sensor that is placed in the patients mouth. Presently,
sensors are available that are equal in size to #0, #1, #2,
#4, and panoramic lms (Fig. 15.3). Direct sensors either
have wires or are wireless devices that are linked to the
image processor. e most common sensor in use is the
CCD, which is a chip of pure silicon that is divided into
a two-dimensional display called pixels. When either x-ray
or light photons interact with a CCD (depending on the
system used), an electric charge is created and stored. After
the exposure is completed, the charges on the CCD are
sequentially removed electrically, creating a continuous
analogue output signal. An analogue signal represents
data in a continuous mode, just like a wristwatch with
hour, minute, and second hands. is information must
be converted to digital units that can be assigned numbers.
Figure 15.1 A full-mouth series of digital images. (Courtesy DEXIS
LLC, Hateld, PA.)
X-ray
machine
Film
Film Processor
Laser Scanner
Sensor
Scanner
Computer
Printout
Storage
Figure 15.2 Different digital imaging systems.
1. Direct digital radiography. is system uses a sensor
wired directly (or through a WiFi system) to the com-
puter with the sensor either a charge-coupled device
(CCD) or a complementary metal oxide semiconduc-
tor (CMOS).
2. Indirect digital radiography (storage phosphor). is
wireless system employs a photostimulable phosphor
(PSP) plate and laser beam scanning to produce the
image.
3. Optically scanned digital radiography. In this system,
a nished processed radiograph is scanned and digitized
in much the same way that a document is scanned. e
new digitalized image can be manipulated in the same
manner that direct and indirect images are.

174 CHAPTER 15 Digital Imaging
Nature of the Image
A digital image is composed of structurally ordered areas
called pixels. A pixel would be the digital equivalent of a
silver halide crystal on conventional lm, with the dierence
being that silver halide crystals are randomly positioned in
the emulsion, whereas the pixel has a denite location that
can be assigned a number (digit). e pixel is a single dot
in a digital image; the image is made up of all the pixels or
dots on the image. An analogy would be a photograph in
a newspaper. In looking carefully at the newspaper image,
you see that it is composed of multiple dots with varying
degrees of black and white. When looking at the picture
without looking at it so carefully, however, you do not see
the dots but rather the entire picture.
Besides each pixel having a location, it also has a gray
level that represents the photon penetration of the object
(tooth) in that area. e pixel is represented in the computer
by a number that indicates its location and photon penetra-
tion, and the total image is a table of numbers that can be
manipulated (e.g., added or subtracted).
e pixels can be considered containers for numbers;
the numbers vary from 0 to 256 (black to white). Hence
there are usually 256 gray levels in an image. However, the
human eye can only discern 32 gray levels. Diagnosis relies
more on contrast discrimination (gray levels) than on spatial
relations and denition. e fact that digital images have
only 6 to 10 line pairs per millimeter discrimination as
compared with 12 to 15 line pairs per millimeter for lm
is not that important as a disadvantage of digital imaging.
Box 15.1 presents advantages and disadvantages of digital
imaging.
An analogue-to-digital converter is used to convert the
analogue output signal to a digital signal that is then sent
to the computer. e CMOS sensors are also wired directly
to the computer or are wireless devices that produce an
instantaneous image. CMOS sensors have less power and
are less expensive. CMOS sensors have more noise (lesser
image denition) than the CCD and hold less diagnostic
information. However, they are less fragile, and sensor
replacement is less common.
A storage phosphor sensor (or PSP) produces images
in a two-step process by using a reusable plastic imaging
plate that is not wired to the computer and is thinner,
less expensive, and less rigid than the CCD and CMOS
sensors. PSPs can be manufactured for both intraoral and
extraoral dental radiography. e phosphor material in
the sensor stores the x-ray energy until it is scanned by a
laser that digitizes the image and then transmits the image
to the computer. Acquiring the image from the laser can
take from 30 seconds to several minutes, depending on
the number of images being scanned. e light released
by the laser is captured as an electronic signal and is con-
verted to a digital image that is seen on the computer
monitor.
e sensors are reusable after the image has been erased
and disinfected. e PSP is placed in a barrier envelope for
infection control purposes before reusing it. It should be
noted that a dierent PSP is used for each exposure, much
like the use of lm packets in conventional radiography.
PSP sensors are also similar to conventional lm in that they
are exible and are comparable in size, shape, and thickness.
However, the laser scanning process and recharging of the
PSP sensor do not necessitate that the room be completely
dark like the use of standard lm does.
B
A
Figure 15.3 A, Wired direct digital sensor. B, Various sizes of digital sensors. (A, Courtesy Dentsply
Sirona, Charlotte, NC. B, Courtesy Dentsply Sirona, Charlotte, NC.)
Text continued on p. 182

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17215 Digital ImagingEDUCATIONAL 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 following related to digital imaging:• Knowthebasicelementsthatarenecessarytoacquireadigital image.• Listthethreebasictypesofdigitalimagingsystemsandhow they dier from each other.3. State the three types of digital sensors that can be used in digital imaging.4. Describe the following related to the nature of the image:• Denewhatapixelis,andexplainitsroleintheformation of a digital image.• Listtheadvantagesanddisadvantagesofdigitalimagingwhencomparedtoconventionallm-basedradiography.5. Statethecomponentsofthedigitalimagingtechniqueandbe able to apply them to clinical practice.6. Discussthetypesofdigitalsystems,aswellasthelegalaspects of digital radiography in dentistry.of digital imaging, as well as the technique, advantages, and disadvantages of the system.Digital ImageA digital image is an image formed by the use of an electronic sensor that is connected in some manner to a computer. Early in the development of digital imaging, it was often referred to as lmless radiography, but that term is no longer used to describe this imaging technique. e basic elements necessary to acquire a digital image are (1) an x-ray machine; (2) an electronic sensor or detector; (3) an analogue-to-digital converter; (4) a computer, which can be a laptop or desktop version; and (5) a monitor (Fig. 15.1).Presently, there are three basic types of digital imaging systems (Fig. 15.2):IntroductionOne of the most exciting technologies introduced in den-tistry is digital imaging, along with the other computerized aspects of a dental practice. Instead of lm or a lm-screen combination, this digital imaging system uses electronic sensors to record the penetration of the x-ray photons and sends this information to a computer that digitizes (converts to numbers) these electronic impulses. is allows the computer to produce a diagnostic image on a monitor almost instantaneously. Digital imaging was introduced into dentistry in 1987 by Dr. Francois Mugnon with his RVG system (RadioVisioGraphy). Since that time, the market has exploded with numerous companies making compet-ing products. is chapter does not focus on a particular digital unit, but it attempts to explain the basic principles KEY TERMSanaloguecharge-coupled device (CCD)complementary metal oxide semiconductor (CMOS)detectordigital imagedigitizedirect digital radiographygray levelhard copiesimage manipulationimaging plateindirect digital radiographyline pairs per millimetermonitoroptically scanned digital radiographypaperless ocephotostimulable phosphor (PSP)pixelsRVG systemsensorstorage phosphor 173CHAPTER 15 Digital ImagingX-Ray Unite standard dental intraoral x-ray machine can be used for digital radiography, so it is not necessary to purchase a digital-specic unit. However, the unit must have a timer that can be adjusted to accommodate the digital receptors that require less time than conventional lm. ere are units available that have an icon picturing a computer that, when activated, automatically reduces the exposure time and provides the image quality and reduction in exposure times needed for digital radiography. ese units can be utilized for both conventional and digital radiography. ere are digital panoramic units available that combine the advantages of digital imaging with those of pantomography.Sensorse most critical part of a digital radiography system is the sensor that is placed in the patient’s mouth. Presently, sensors are available that are equal in size to #0, #1, #2, #4, and panoramic lms (Fig. 15.3). Direct sensors either have wires or are wireless devices that are linked to the image processor. e most common sensor in use is the CCD, which is a chip of pure silicon that is divided into a two-dimensional display called pixels. When either x-ray or light photons interact with a CCD (depending on the system used), an electric charge is created and stored. After the exposure is completed, the charges on the CCD are sequentially removed electrically, creating a continuous analogue output signal. An analogue signal represents data in a continuous mode, just like a wristwatch with hour, minute, and second hands. is information must be converted to digital units that can be assigned numbers. • Figure 15.1 A full-mouth series of digital images. (Courtesy DEXIS LLC, Hateld, PA.)X-raymachineFilmFilm ProcessorLaser ScannerSensorScannerComputerPrintoutStorage• Figure 15.2 Different digital imaging systems. 1. Direct digital radiography. is system uses a sensor wired directly (or through a WiFi system) to the com-puter with the sensor either a charge-coupled device (CCD) or a complementary metal oxide semiconduc-tor (CMOS).2. Indirect digital radiography (storage phosphor). is wireless system employs a photostimulable phosphor (PSP) plate and laser beam scanning to produce the image.3. Optically scanned digital radiography. In this system, a nished processed radiograph is scanned and digitized in much the same way that a document is scanned. e new digitalized image can be manipulated in the same manner that direct and indirect images are. 174 CHAPTER 15 Digital ImagingNature of the ImageA digital image is composed of structurally ordered areas called pixels. A pixel would be the digital equivalent of a silver halide crystal on conventional lm, with the dierence being that silver halide crystals are randomly positioned in the emulsion, whereas the pixel has a denite location that can be assigned a number (digit). e pixel is a single dot in a digital image; the image is made up of all the pixels or dots on the image. An analogy would be a photograph in a newspaper. In looking carefully at the newspaper image, you see that it is composed of multiple dots with varying degrees of black and white. When looking at the picture without looking at it so carefully, however, you do not see the dots but rather the entire picture.Besides each pixel having a location, it also has a gray level that represents the photon penetration of the object (tooth) in that area. e pixel is represented in the computer by a number that indicates its location and photon penetra-tion, and the total image is a table of numbers that can be manipulated (e.g., added or subtracted).e pixels can be considered containers for numbers; the numbers vary from 0 to 256 (black to white). Hence there are usually 256 gray levels in an image. However, the human eye can only discern 32 gray levels. Diagnosis relies more on contrast discrimination (gray levels) than on spatial relations and denition. e fact that digital images have only 6 to 10 line pairs per millimeter discrimination as compared with 12 to 15 line pairs per millimeter for lm is not that important as a disadvantage of digital imaging. Box 15.1 presents advantages and disadvantages of digital imaging.An analogue-to-digital converter is used to convert the analogue output signal to a digital signal that is then sent to the computer. e CMOS sensors are also wired directly to the computer or are wireless devices that produce an instantaneous image. CMOS sensors have less power and are less expensive. CMOS sensors have more noise (lesser image denition) than the CCD and hold less diagnostic information. However, they are less fragile, and sensor replacement is less common.A storage phosphor sensor (or PSP) produces images in a two-step process by using a reusable plastic imaging plate that is not wired to the computer and is thinner, less expensive, and less rigid than the CCD and CMOS sensors. PSPs can be manufactured for both intraoral and extraoral dental radiography. e phosphor material in the sensor stores the x-ray energy until it is scanned by a laser that digitizes the image and then transmits the image to the computer. Acquiring the image from the laser can take from 30 seconds to several minutes, depending on the number of images being scanned. e light released by the laser is captured as an electronic signal and is con-verted to a digital image that is seen on the computer monitor.e sensors are reusable after the image has been erased and disinfected. e PSP is placed in a barrier envelope for infection control purposes before reusing it. It should be noted that a dierent PSP is used for each exposure, much like the use of lm packets in conventional radiography. PSP sensors are also similar to conventional lm in that they are exible and are comparable in size, shape, and thickness. However, the laser scanning process and recharging of the PSP sensor do not necessitate that the room be completely dark like the use of standard lm does.BA• Figure 15.3 A, Wired direct digital sensor. B, Various sizes of digital sensors. (A, Courtesy Dentsply Sirona, Charlotte, NC. B, Courtesy Dentsply Sirona, Charlotte, NC.)Text continued on p. 182 175CHAPTER 15 Digital Imaging• BOX 15.1 Advantages and Disadvantages of Digital RadiographyBefore discussing the technique for digital radiography, we will consider its advantages and disadvantages. The following lists utilize conventional radiography as the means of comparison.Advantages• Faster image acquisition. The growing acceptance of digital radiography can be contributed to the dental professional’s ability to view the digitized image on the monitor instantaneously or within minutes, depending on the digital method being utilized (i.e., direct or indirect digital radiography). This allows for immediate evaluation and interpretation of the digital image.• Overall procedure time is reduced. Digital radiography is more time efcient in multiple ways than conventional lm-based radiography. For example, in direct digital radiography, the same sensor and barrier sheath is used for all of the projections, the exposure time is reduced, and the processing and mounting steps are completely eliminated. Even though indirect digital radiography is not as time efcient as direct digital radiography, it does not take as long as conventional radiography.• Reduction in radiation dose. A great deal of attention has been given to the fact that digital imaging requires much less radiation than lm or lm-screen combinations. The reduction is about 90% when compared with the exposure from D-speed lm, about 60% when compared with E-speed lm, and there is a 50% reduction when compared to F-speed lm. This decrease in patient exposure is as a result of the increased sensitivity of the digital sensor to x-radiation.• Image adjustment and manipulation (Fig. 15.4). Once the image is acquired, the computer can alter it in many ways. The image can be enlarged, darkened, or lightened (varying the density and contrast) or have selected areas magnied, colorized, or reversed.• Image storage. Because the images are stored in digital form, the storage space required is minimal compared with mounted radiographs kept in a patient’s chart. If the dental facility has electronic health records (EHRs), the images are accessible through the patient’s EHR. In all available digital systems, stored images can be called up almost instantaneously. In addition, images taken at different times can be placed on the monitor side-by-side for comparison.• Remote consultation. The digital images can be transmitted to other dental ofces or insurance companies if the intended receiver has the ability to receive the images. Instead of duplication of radiographs and reliance on the mail, the images are sent immediately to another practitioner, saving valuable time and labor.• Hard copies. If teletransmission of the image is not possible, printouts, or hard copies, can be produced immediately, eliminating the need for duplication while preserving the integrity of the ofce records.• Patient education. Patients seem to relate better to a digital image on a monitor than a radiograph or a series of mounted radiographs on a viewbox when the dentist is using them as a visual aid for case presentation. The reason may be that this is an electronic age; thus, patients may be used to the screen and close-up views. The ability to look at clinical images or radiographs on the same screen at the same time also helps in case presentation.• Environmentally friendly. Because the silver salts found in lm emulsion and processing chemicals are not used in digital imaging, there are no environmental and waste disposal issues. As discussed in Chapter 11, many states have laws governing the disposal of processing chemicals. This environmental issue is very important and appealing to both patients and dentists. In addition, no lead foil is used in digital radiography, which can also be hazardous to the environment, especially in large quantities.• Paperless ofce. Most dental ofces and clinics are now using computers for record keeping. Software that started out as a means of billing has been expanded to include treatment records, insurance forms, recall systems, and more. The nal piece in the puzzle to make the use of the conventional dental chart obsolete is the digital image. With its addition, a paperless ofce makes every type of information about the patient available for immediate retrieval from the ofce electronic system. These records should be backed up by a duplicate disk that is stored at another location.Continued• Figure 15.4 Magnication of images is just one of the advantages of digital radiography, allowing the dental professional to take closer look at areas of concern. (Courtesy Dentsply Sirona, Charlotte, NC.) 176 CHAPTER 15 Digital ImagingBA• Figure 15.5 A, Charge-coupled device (CCD) sensor in patient’s mouth. B, Beam alignment devices manufactured with adhesive backing to hold sensors in place. (Courtesy Dentsply Rinn, York, PA.)• Figure 15.6 Intraoral phosphor sensors in various sizes. (Courtesy Air Techniques, Melville, NY.)• Figure 15.7 Sensor with plastic covering. • Cross-contamination. Computerized images are clean and sterile, because they are not touched by the operator’s contaminated gloves when mounting or removing them from the chart or viewbox during an operative procedure.Disadvantages• Sensor placement. The main disadvantage or difculty in digital radiography is sensor placement in the patient’s mouth (Fig. 15.5A). The direct digital sensors are the same size as the standard #0, #1, and #2 dental lm, but they are thicker and more rigid. Even though manufacturers have tried to make the sensors more user friendly, it may be difcult or impossible to obtain parallelism between the tooth and sensor in small or crowded mouths to follow the right angle/paralleling technique. However, paralleling instruments are available for use with direct digital sensors (see Fig. 15.5B). It should be noted that the storage phosphor systems use a thinner and slightly more adaptable sensor than the direct digital systems (Fig. 15.6); some practitioners feel that this gives the system a distinct advantage over the CCD-based (or CMOS-based) system.• Denition. As mentioned earlier, lm provides better detail (12 to 15 line pairs per millimeter) than do digital images (6 to 10 line pairs per millimeter). Although this may be the case, the human eye cannot usually make this distinction in clinical situations. Also, the digital image can be altered to improve the visual image on the monitor.• Cost. The initial cost of a digital system can be quite expensive. Although this may seem like a large expense at rst, over time the savings in space, labor, storage, and more justify and amortize the start-up costs. Digital panoramic units can cost $25,000 or more. It is also important to consider maintenance and repairs when discussing continued costs of digital systems.• Fragility of sensors. The intraoral sensors are really large silicon chips (Fig. 15.7); if dropped or abused, their replacement is costly. The cost of the sensor alone is considerably expensive. Therefore, careful handling of digital sensors should always be stressed in dental facilities.• BOX 15.1 Advantages and Disadvantages of Digital Radiography—cont’d 177CHAPTER 15 Digital ImagingPROCEDURE 15.1 THE DIGITAL IMAGING TECHNIQUEThe actual exposure technique for digital imaging at chairside is very similar to that of conventional radiography, with the exception of processing and the inclusion of computer knowledge and skills (Fig. 15.8).The main difference between direct and indirect digital radiography is that the direct digital sensors are wireless or have wires that connect the system to a computer, are less similar to the lm packet used in conventional radiography, and produce an instantaneous image on the monitor. The sensors used for both techniques are available in different sizes to accommodate varying patients. The operator should still maintain quality assurance in infection control, patient/operator protection, and chairside technique with digital exposures.Operators are expected to protect themselves and the patient against unnecessary radiation exposure. Each patient should be draped with a lead apron and thyroid collar (Fig. 15.9). Operators are also expected to use sensor-holding devices and not use the patient’s nger to stabilize the sensor when exposing images. Digital sensors should be covered with an infection control barrier and handled with extreme caution and care, because they are very sensitive devices. The operator’s position is maintained at least 6 feet from the source of radiation and behind an acceptable barrier.Optimal chairside technique is extremely important in producing quality images and preventing overexposure to the patient. The operator must avoid retakes as much as possible. The spontaneous image of an error causes retakes to be less time-consuming than conventional radiography, but it still adds to the radiation burden of the patient. Some of the errors previously mentioned do not apply to digital radiography (reversed lm, overbending of the lm packet, double exposure, static electricity artifacts, processing errors), but most exposure errors (collimator cutoff, foreshortening, elongation, overlap, improper receptor placement) are still possible.The Digital Full-Mouth SeriesThe digital full-mouth series is generally exposed using the paralleling technique with paralleling instruments. All principles of the paralleling technique are followed (refer to Chapter 9) with the digital sensor used as the receptor.The following account includes the sensor, paralleling instrument, and position-indicating device (PID) position for each projection constituent of a full-mouth series. The combination of the digital sensor, paralleling instruments, and a collimated x-ray beam contribute to a decrease in radiation exposure to the patient.Maxillary Central Incisors (Fig. 15.10)The sensor is placed parallel to the teeth in both the vertical and horizontal planes and as close to the teeth as possible. The sensor is placed in the holder in the vertical position. The sensor placement in the patient’s mouth may be difcult as a result of the rigidity of the digital sensors. However, the difculty in placement may be remedied by increasing the distance of the sensor from the central incisors and resting the bite piece on the mandibular arch instead of on the incisal edges of the maxillary incisors prior to the patient gently biting on the bite piece. The center of the sensor is aligned with the junction between the central incisors. The central ray is aimed at the center of the sensor. The PID is placed perpendicular to both the sensor and the tooth in the vertical and horizontal planes. When a localizing device is being used, make sure that the ring is placed as close to the patient’s face as possible and the PID is positioned as close to the ring as possible to decrease radiation exposure to the patient and to obtain proper contrast and density of the digital image.Maxillary Canines (Fig. 15.11)The sensor is placed parallel to the tooth in both the vertical and horizontal planes and as close to the tooth as possible. The sensor is placed in the holder in the vertical position for the canine projections. The placement of the sensor in the patient’s canine region may be difcult as a result of the rigidity of the digital sensors. However, the difculty in placement may be remedied by increasing the distance of the sensor from the canine and resting the bite piece on the mandibular arch away Continued• Figure 15.8 Operator accessing digital images. • Figure 15.9 Operator placing lead apron/collar on patient. NOTEThe operator may choose to place a cotton roll between the opposing arch and the bite piece to aid in patient comfort for any or all of the digital periapical projections. However, this technique is not recommended for bitewing projections. 178 CHAPTER 15 Digital Imagingfrom the incisal edges of the canines prior to the patient gently biting on the bite piece. The center of the sensor is aligned with the center of the canine. The central ray is aimed at the center of the sensor. The PID is placed perpendicular to both the sensor and the tooth in the vertical and horizontal planes. When a localizing device is being used, make sure that the ring is placed as close to the patient’s face as possible and the PID is positioned as close to the ring as possible to decrease radiation exposure to the patient and to obtain proper contrast and density of the digital image.Maxillary Premolars (Fig. 15.12)The sensor is placed parallel to the teeth in both the vertical and horizontal planes and as close to the tooth as possible. The sensor is placed in the holder in the horizontal position for the posterior projections. The placement of the sensor in PROCEDURE 15.1 THE DIGITAL IMAGING TECHNIQUE—cont’dA• Figure 15.10 Maxillary central incisors. A, Sensor-holding device and position-indicating device (PID). B, Digital image. A• Figure 15.11 Maxillary canines. A, Sensor-holding device and position-indicating device (PID). B, Digital image. • Figure 15.12 Maxillary premolars. A, Sensor-holding device and position-indicating device (PID). B, Digital image. A 179CHAPTER 15 Digital ImagingPROCEDURE 15.1 THE DIGITAL IMAGING TECHNIQUE—cont’dthe patient’s mouth may be difcult as a result of the rigidity of the digital sensors. However, the difculty in placement may be remedied by increasing the distance of the sensor from the premolars so that the sensor position may be in the middle of the palate. It is also helpful to rest the bite piece on the mandibular arch and guide the sensor into position as the patient closes their mouth. The center of the sensor is aligned with the center of the second premolar. The central ray is aimed at the center of the sensor. The PID is placed perpendicular to both the sensor and the tooth in the vertical and horizontal planes. Also, be sure that the sensor is parallel to the premolars in the horizontal plane to avoid overlapping of the premolar teeth on the digital image. When a localizing device is being used, make sure that the ring is placed as close to the patient’s face as possible and the PID is positioned as close to the ring as possible to decrease radiation exposure to the patient and to obtain proper contrast and density of the digital image.Maxillary Molars (Fig. 15.13)The sensor is placed parallel to the teeth in both the vertical and horizontal planes and as close to the teeth as possible. The sensor is placed in the holder in the horizontal position for the posterior projections. The placement of the sensor in the patient’s mouth may be difcult as a result of the rigidity of the digital sensors. However, the difculty in placement may be remedied by increasing the distance of the sensor from the molars so that the sensor position may be in the middle of the palate. It is also helpful to rest the bite piece on the mandibular arch and guide the sensor into position as the patient closes the mouth. The center of the sensor is aligned with the center of the rst molar, and the operator asks the patient to close down partially. Then, when the cheek is relaxed, the operator moves the sensor so that its center is aligned with the center of the second molar and asks the patient to close fully on the bite piece of the sensor-holding device.The central ray is aimed at the center of the sensor. The PID is placed perpendicular to both the lm and the tooth in the vertical and horizontal planes. When a localizing device is being used, make sure that the ring is placed as close to the patient’s face as possible and the PID is positioned as close to the ring as possible to decrease radiation exposure to the patient and to obtain proper contrast and density of the digital image.Bitewing Projections (Fig. 15.14)When the premolar bitewings are being radiographed, the center of the sensor is aligned with the center of the mandibular second premolar, and the biting surface of the sensor holder is held on the mandibular arch. While the operator holds the sensor in position, the patient is instructed to gently bite on the sensor-holding device. The operator should be sure that the patient is biting on the posterior teeth in centric occlusion and not holding the bite piece steady with the lips. The central ray is aimed at the center of the sensor. The PID is placed perpendicular to both the sensor and the tooth in the vertical and horizontal planes. Also, be sure that the sensor is parallel to the teeth being radiographed in the horizontal plane to avoid overlapping of the interproximal surfaces on the digital image. When a localizing device is being used, make sure that the ring is placed as close to the patient’s face as possible and the PID is positioned as close to the ring as possible to decrease radiation exposure to the patient and to obtain proper contrast and density of the digital image. The procedure for radiographing the molars is the same as that mentioned earlier, except that the biting surface of the sensor holder is centered and held on the mandibular second molar. It should also be noted that there are sensor-holding devices available for use with digital vertical bitewing projections.Mandibular Incisors (Fig. 15.15)The sensor is placed parallel to the teeth in both the vertical and horizontal planes and as close to the teeth as possible. The sensor is placed in the holder in the vertical position. The sensor placement in the patient’s mouth may be difcult as a result of the rigidity of the digital sensors. However, the difculty in placement may be remedied by increasing the distance of the sensor from the central incisors. In some cases, it may be necessary to position the sensor further back in the oor of the mouth at the level of the molars. The operator may also start out with the sensor on an angle and then slowly bring the sensor into a parallel position with the closure of the mandible. The operator may also place an opened gauze pad under the sensor covering the oor of the mouth to prevent it from irritating the tissue in this area. ContinuedA• Figure 15.13 Maxillary molars. A, Sensor-holding device and position-indicating device (PID). B, Digital image. HELPFUL HINTWhen exposing all bitewing and mandibular periapical projections, the operator must avoid placing the sensor on top of the tongue. The patient is asked to move their tongue away from the sensor. This tongue placement is requested to assure that the sensor is resting on the oor of the mouth and not on top of the tongue. If a receptor is placed on top of the tongue, the image will not show all of the radiographic information desired on the resultant image. 180 CHAPTER 15 Digital ImagingPROCEDURE 15.1 THE DIGITAL IMAGING TECHNIQUE—cont’dThe center of the sensor is aligned with the junction between the central incisors. The central ray is aimed at the center of the sensor. The PID is placed perpendicular to both the sensor and the tooth in the vertical and horizontal planes. When a localizing device is being used, make sure that the ring is placed as close to the patient’s face as possible and the PID is positioned as close to the ring as possible to decrease radiation exposure to the patient and to obtain proper contrast and density of the digital image.Mandibular Canines (Fig. 15.16)The sensor is placed parallel to the canines in both the vertical and horizontal planes and as close to the tooth as possible. The sensor is placed in the holder in the vertical position for CA• Figure 15.14 Bitewing projections. A, Sensor-holding device and position-indicating device (PID) for premolar bitewing. B, Digital image of premolar bitewing. C, Sensor-holding device and PID for molar bitewing. D, Digital image of molar bitewing. A• Figure 15.15 Mandibular incisors. A, Sensor-holding device and position-indicating device (PID). B, Digital image. 181CHAPTER 15 Digital ImagingPROCEDURE 15.1 THE DIGITAL IMAGING TECHNIQUE—cont’dthe anterior projections. The placement of the sensor in the patient’s mouth may be difcult as a result of the rigidity of the digital sensors. However, the difculty in placement may be remedied by increasing the distance of the sensor from the canine. In some cases, it may be necessary to position the sensor further back in the oor of the mouth. The operator may also start out with the sensor on an angle and then slowly bring the sensor into a parallel position with the closure of the mandible. The operator may also place an opened gauze pad under the sensor covering the oor of the mouth to prevent it from irritating the tissue in this area. Be sure that the sensor is placed below and not above the tongue. The center of the sensor is aligned with the center of the canine. The central ray is aimed at the center of the sensor. The PID is placed perpendicular to both the sensor and the tooth in the vertical and horizontal planes. When a localizing device is being used, make sure that the ring is placed as close to the patient’s face as possible and the PID is positioned as close to the ring as possible to decrease radiation exposure to the patient and to obtain proper contrast and density of the digital image.Mandibular Premolars (Fig. 15.17)The sensor is placed parallel to the teeth in both the vertical and horizontal planes and as close to the tooth as possible. The sensor is placed in the holder in the horizontal position for the posterior projections. The placement of the sensor in the patient’s mouth may be difcult as a result of the rigidity of the digital sensors. However, the difculty in placement may be remedied by increasing the distance of the sensor from the premolars so that the sensor position may be in the middle of the oor of the mouth. The operator may also place an opened gauze pad on the oor of the mouth, covering the entire mandibular arch, to prevent the sensor from irritating the tissue in this area. The anterior corner of the sensor will not curve to accommodate the arch; therefore, care must be taken to include the distal of the canine and the mesial of the rst premolar on the image without causing unnecessary discomfort to the patient. Also, be sure that the sensor is parallel to the premolars in the horizontal plane avoid overlapping of the premolars on the digital image. The center of the sensor is aligned with the center of the second premolar. The central ray is aimed at the center of the sensor. The PID is placed perpendicular to both the sensor and the tooth in the vertical and horizontal planes. When a localizing device is being used, make sure that the ring is placed as close to the patient’s face as possible and the PID is positioned as close to the ring as possible to decrease radiation exposure to the patient and to obtain proper contrast and density of the digital image.Mandibular Molars (Fig. 15.18)The sensor is placed parallel to the teeth in both the vertical and horizontal planes and as close to the teeth as possible. A• Figure 15.16 Mandibular canines. A, Sensor-holding device and position-indicating device (PID). B, Digital image. ContinuedA• Figure 15.17 Mandibular premolars. A, Sensor-holding device and position-indicating device (PID). B, Digital image. 182 CHAPTER 15 Digital ImagingPROCEDURE 15.1 THE DIGITAL IMAGING TECHNIQUE—cont’dThe sensor is placed in the holder in the horizontal position for the posterior projections. The placement of the sensor in the patient’s mouth may be difcult as a result of the rigidity of the digital sensors. However, the difculty in placement may be remedied by increasing the distance of the sensor from the molars so that the sensor position may be in the middle of the oor of the mouth. The operator may also place an opened gauze pad on the oor of the mouth, covering the entire mandibular arch, to prevent the sensor from irritating the tissue in this area. The center of the sensor is aligned with the center of the rst molar, and the operator asks the patient to close down partially. Then, when the cheek is relaxed, the operator moves the sensor so that its center is aligned with the center of the second molar and asks the patient to close fully on the bite piece of the sensor-holding device. The central ray is aimed at the center of the sensor. The PID is placed perpendicular to both the receptor and the tooth in the vertical and horizontal planes. When a localizing device is being used, make sure that the ring is placed as close to the patient’s face as possible and the PID is positioned as close to the ring as possible to decrease radiation exposure to the patient and to obtain proper contrast and density of the digital image.A• Figure 15.18 Mandibular molars. A, Sensor-holding device and position-indicating device (PID). B, Digital image. Types of Digital SystemsAll of the systems mentioned dier in how they acquire the digital image and in availability of receptor plate size (e.g., panoramic). Once acquired, the systems do not vary greatly in how they display, adjust, store, or transmit the image.Direct Digital RadiographyIn direct digital radiography systems, the sensor, which is placed in the patient’s mouth, is connected by a wire or a wireless device to the computer, and there is instantaneous image production on the monitor when the exposure is performed. Systems vary regarding the type of sensor used to capture the x-ray photons to aect the CCD or CMOS sensor. Some acquire the photons directly, whereas others use a beroptically coupled sensor that operates like a lm-screen system, sending light photons to aect the CCD or CMOS sensor.Indirect Digital Radiography (Storage Phosphor)In indirect digital radiography (storage phosphor), a slightly exible sensor, which is not connected by a wire or cable to the computer, is placed in the patient’s mouth, and an exposure is made (Fig. 15.19). e sensor is then exposed, removed from the mouth, and processed by a laser beam with electronic data sent to the computer, which generates a digital image in 112 to 5 minutes, depending on the number and types of sensor plates being processed. e plates can then be recharged and used again. Some types of digital scanners have a built-in heat sealer and bag cutter to maintain the sterility of the imaging plates.Optically Scanned Digital RadiographyIn optically scanned digital radiography systems, regular dental lm is used to acquire the image with conventional lm-based intraoral techniques. e lm is then pro-cessed in the darkroom, the nished dry lm is scanned, and the digital image is produced. is digitized image can be used in the same way as those that have been directly digitally acquired. With this method, it takes a great deal of time to acquire a digitized image, because complete lm processing must be done before the image can be scanned and digitized. e most advantageous use of optically scanned digital imaging is in ling and storage of conventional images when EHRs are being utilized in the dental facility. 183CHAPTER 15 Digital Imaging• Figure 15.19 Storage phosphor imaging system. (Courtesy Apixia Digital Imaging, Industry, CA.)Legal AspectsOne of the major concerns raised about all electronic infor-mation, including digital images, has been the reliability of the information and the possibility of image manipulation.For example, conventional radiographs have been regu-larly admitted in court as evidence in cases for many years. With digital imaging, however, there is a possibility that if a jury learns that images can be altered, they may no longer look at the digital images as hard evidence. is concern has been largely overcome by the major manufacturers of digital radiographic systems by including “audit indicators” into their units that signal if and when an image has been altered.Chapter Summary• Digitalradiographyutilizeselectronicsensorstorecordthe penetration of x-radiation and transmits this infor-mation to a computer that digitizes these electronic impulses.• ereare three types ofdigital systems used in dentalradiography: (1) direct digital radiography, (2) indirect digital radiography, and (3) optically scanned digital radiography.• In intraoral digital imaging, an electronic sensor isplaced inside the patient’s mouth and is then exposed to x-radiation generated from a conventional dental x-ray unit. An electronic charge is produced on the sensor and is converted to a digital format. e image is then viewed on a computer monitor. Digital imaging and electronic sensors are also utilized in extraoral digital radiography. Infection control and radiation safety procedures are employed with both intraoral and extraoral digital radiography.• e advantages of digital radiography when comparedto conventional lm-based radiography include faster image acquisition, an overall decrease in procedure time, reduced radiation exposure, image adjustment and manipulation, easier image storage, remote consulta-tion, hard copy production, more convenient patient education, is environmentally friendly, creates a paper-less oce with EHRs, and more eciency in avoiding cross-contamination.• edisadvantagesofdigitalradiographywhencomparedto conventional lm-based radiography include dicult sensor placement, less image denition, expensive initial costs, and fragility of the expensive sensors.Chapter Review QuestionsMultiple Choice1. Direct digital and indirect digital radiography dier in: a. e type of sensors used b. e time it takes for an image to appear on the computer monitor c. e thickness of the sensor d. e radiographic unit used e. All of the above except d2. When compared to D speed lm, digital radiography reduces patient exposure by: a. 50% b. 60% c. 99% d. 90% e. 85%3. All of the following statements regarding digital radio-graphy are true except: a. e sensors are more sensitive to radiation than conventional lm b. e image is best seen on the computer c. Direct digital sensors are dicult to place d. e conventional x-ray unit cannot be used e. e image can be altered 184 CHAPTER 15 Digital ImagingMouyen F, Benz C, Sonnabend E, et al: Presentation and physical evaluation of radiovisiography, Oral Surg Oral Med Oral Pathol 68:238–242, 1989.Tsang A, Sweet D, Wood RE: Potential for fraudulent use of digital radiography, J Am Dent Assoc 130:1325–1329, 1999.White SC, Pharoah MJ: Oral radiology: Principles and interpretation, ed 7, St Louis, MO, 2013, Mosby.BibliographyDunn SM, Kantor ML: Digital radiology, facts and ctions, J Am Dent Assoc 124:38–47, 1993.Iannucci JM, Howerton LJ: Dental radiography: Principles and tech-niques, ed 5, St Louis, MO, 2016, Elsevier Saunders.Jones GA, Behrents RG, Bailey GP: Legal considerations for digitized images, Gen Dent 44:242–244, 1996.Critical Thinking Exercise1. You are asked to give a presentation on the topic of digital radiography to a group of dental professionals. e following is a list of questions that was submitted by the audience members and compiled by the organization you are speaking on behalf of, be sure to include the answers to these questions in your presentation: a. What is the dierence between direct and indirect digital radiography? b. Do I have to replace the radiographic unit in our dental facility if our facility is transitioning from conventional to digital radiography? c. Does digital radiography decrease radiation exposure to the patient? Please explain. d. Can I dispose of the lead apron and thyroid collar in my oce when switching to digital radiography? e. What are photostimulable phosphor (PSP) plates, and how are they used in dental radiography? f. What is the dierence between CCD and CMOS sensors? g. Can the digital image be altered? h. Can digital images be used as evidence in a court of law? i. What is the laser scanner used for in indirect digital radiography? j. Can I scan my conventional radiographic images and incorporate them in my electronic health records (EHRs)? Please explain. k. Are digital images more useful for patient education than conventional lm images? l. How does the placement of CCD sensors dier from lm placement in the patient’s mouth? m. What are some helpful hints we can use when placing and exposing digital sensors? n. Is a digital system expensive to set up in a dental oce? If so, how do you justify the initial costs? o. What is the advantage of using PSP rather than CCD sensors? p. What other facts could you provide in support of our switching from conventional to digital radiography?4. Pixels are considered containers for numbers, and the numbers vary from 0 to 256 (black to white), which means that there are usually 256 gray levels in an image. However, the human eye can only discern 52 gray levels. (Indicate all that apply.) a. Both statements are true. b. Both statements are false. c. e rst statement is true, and the second statement is false. d. e rst statement is false, and the second statement is true. e. e statements are related.

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