Volume 3, Issue 4 US $6.00

Editor: Allan G. Farman, BDS, PhD (odont.), Digital Options for Panoramic Radiology DSc (odont.), Diplomate of the American Board of Oral and By Dr. Allan G. Farman in conjunction commercial dental intraoral sensor Maxillofacial Radiology, Professor of with William Jacobs became available in the U.S. market in Radiology and Imaging Sciences, 1991. Since that year, a number of Department of Surgical and Hospital Digital x-ray imaging is making different systems have become Dentistry, The University of substantial inroads into the dental available, and picking the right system Louisville School of Dentistry, practice. The purpose of this article is for the job is not an easy task. Louisville, KY. to provide a succinct overview of Systems are different in nature, and Contributor: current digital options for panoramic comparison is made difficult because William R. Jacobs, President, WRJ & dental radiography. physical specifications do not easily Associates, Dental Marketing translate into day-to-day dental Consultants, Homer Glen, Illinois Introduction operations. The move to panoramic digital An image is said to be digital Featured Article: radiography in dentistry has been when it is composed of separate Digital Options for Panoramic slower than the move toward intraoral (distinct) elements [1,2]. Each element Radiology digital radiography for a variety of is called a “picture element” or pixel. If reasons. Every dental practice is an image is displayed on the monitor, In The Recent Literature: different and has unique needs and and the pixel is smaller than the Radiation Dosage – Solid State wants. Before making a decision on smallest detail the viewer’s eye can Imaging digital panoramic radiography, you see, it is hard to determine that the Third Molar Assessment must weigh carefully your unique image is indeed a digital one. If this is operation, the type of practice and not the case, that is the individual Soft Versus Hard Copy patient mix, your staffing, your goals pixels can be spotted, the eye views and objectives, the systems available, the image as a mosaic of pixels. Learning Objectives: the overall economics and costs Each pixel can only take on a Gain understanding of digital involved, the timing, the state of the limited number of gray shades. The system options available for technology, and anticipated changes number of possible gray shades panoramic radiography. in technology. If you already have a depends on the number of bits (binary digital intraoral system the move may digits) that are used to store a pixel. A Learn the basic concept behind make sense. If you do not, then one-bit pixel can only take two values each approach along with the maybe going to digital intraoral first is (0 or 1 - that is black or white). An 8- advantages and disadvantages of best. Perhaps it is something you want bit pixel can take any one of 256 (28) each option. to delay to see how things develop values. A 16-bit pixel can take more and what new technologies are than sixty-five thousand grayscale Review points to consider in introduced in the next year or so. values (216). It is generally accepted analyzing options for your practice. Perhaps you wish to take small steps, that the human eye can only distin- first incorporating secondary capture guish about 20 magnitudes of light using a scanner to help you determine intensity, and is certainly unable to the best long-term approach for your discern all 256 gray levels that a practice. The decision is not an easy standard computer monitor can one and takes much thought and display. The total number of bits that investigation. This newsletter will are used to store an image is the address the basics of digital radiogra- number of pixels times the number of phy and show the alternative ap- bits per pixel. proaches available today. There are three methods avail- Digital radiography encompasses able to produce digital images. First, all the techniques that produce digital it is possible to digitize conventional (or computerized) images, as op- radiographs through secondary posed to conventional radiography, capture using transparency scanners which uses x-ray films. The first or specialized digital cameras. “ Film scanners and digital cameras can be used to produce a digital image from a film radiograph.”

Alternatively, digital images can • No changes or additional be produced using storage phosphor training required plates or with solid-state systems, • Known entity — proven output usually involving use of a charge- • Relatively low cost of operation coupled device (CCD) comparable to • Excellent diagnostic clarity the computer chip found in a digital possible if exposed and pro- camera. cessed optimally Properties essential for digital • Widely accepted panoramic radiography include: • Images of diagnostic quality Digital X-ray Imaging • Radiation dose similar or Disadvantages reduced compared to film The following are some of the key radiography disadvantages of digital radiography: • Compatibility with existing • Added initial cost for equipment panoramic x-ray generators given you are presently using • Lossless archiving (storage of film the full original radiographicim- • Need for additional computers, age) monitors, networking and • Interoperability of image backup storage format so that the patient’s • Sensors (both solid-state and Fig. 1: Nikon CoolPixTM scanner with information can be conveniently phosphor systems) can add transparency adaptor in lid sufficient shared when professionally $15,000 to $25,000 to the cost for extraoral radiograph duplication. necessary. of the panoramic system • Changes in operations, sys- • Digital images allow perfect Film Disadvantages tems and procedures require an “clone” duplication and The following are some of the key investment in time and involve a backup disadvantages to using film radiogra- learning curve • Post-processing can help phy: • Not all digital image formats are optimize the diagnostic • Cost of consumables such as identical at this moment so yield film and processing solutions interoperability can be problem- • Digital radiology eliminates • Cost of processing equipment atic both in the same office and environmental silver and darkroom space when making outside referrals contamination from spent • Time consumption in film • Eventual hardware obsoles- fixer processing and processor cence maintenance If I decide to go digital, how do I • Processed film images are Digital X-ray Imaging get into it? What systems are rarely optimal Advantages available? • Used processing chemicals are The following are some of the key There are two ways to get toxic to the environment advantages of digital radiography: into digital panoramic radiography; • Film radiograph storage and • Digital x-ray imaging saves time (1) buy a totally new integrated retrieval can be problematic as there is no chemical pro- digital system; or (2) use your • Duplicates made from film cessing current panoramic system [3-5]. radiographs are invariably • Digital images are more If you use your current inferior to the original radio- consistent in quality for the panoramic system, undoubtedly graph same reason the most economical method, • Digital images ease communi- there are three alternatives to look Film Advantages cation with patients at: (1) Secondary Capture of The following are some of the key • Digital images are readily analog film images using scan- advantages to using film radiography: stored and retrieved ners, (2) photostimulable phos- • Low initial cost, especially for • Digital radiology opens the way phor plates and (3) retrofit (add- manual processing to electronic interchange on) solid- state systems with • Often already in place • Consultation can be expedited digital detectors[6]. TABLE 1.

2 DIGITAL METHODS Film scanners and cameras Table 1: Alternative digital approaches. Film scanners and digital cameras can be used to produce EXISTING PANORAMIC GENERATOR a digital image from a film radiograph. In general, secondary Film Based System capture is best achieved with a good quality scanner having a radiograph adaptor (i.e. scanning SECONDARY PHOSPHOR ADD ON/ light in the lid to pass light through CAPTURE PLATE RETROFIT CCD the radiograph, Fig. 1). Nikon and Epson produce excellent scan- • Scanner • Phosphor Plate • Sensor replaces film ners for this purpose with the costs varying from around $600 • Digital Camera • Plate reader/scanner • Sensor linked directly to $1,500 for a quality system. A linked to computer to computer sharp black and white photograph setting is preferred. Scanners are preferred to digital cameras as they practically eliminate optical BENEFITS BENEFITS BENEFITS distortion and the reflection from the surface of the radiograph that • No change to • Similar exposure • Directly digital would otherwise reduce image radiography procedures quality. Film scanners do not generator or •“Instant” image on exposure • No machine changes change the need to continue screen making radiographs with x-ray • Try digital out • Easy transition • Speed film. They introduce additional time-consuming activity to scan • Low cost • Can be used with • No consumables (film the images, but that is the price multiple machines and solutions) you pay to continue to use film • Digitize all file radiographs while digitally storing radiographs images. No matter how good your film scanner is, scanned images can only be as good as the original film radiographs. The COSTS COSTS COSTS advantage here is that you can scan and archive your existing • Added procedure • Scanning high • Initial outlay: film files over time and you can (time) resolution takes time ~$20,000 for System also determine if digital pan- oramic is for you without spending • Attributes less • Plates expensive and • System dedicated to a lot of money in purchasing reliable than with readily damaged one generator type sophisticated equipment. While other methods Schultz et al (2002) found the sensitivity for detection of low- contrast simulated bone lesions was greater with film than after PANORAMIC SYSTEM digitization, the absolute differ- Integrated Digital ences were small [7].

Photostimulable phosphor Multiple Systems Available plates A phosphor plate reader works very much like a film

3 scanner, except that an imaging plate capture. So x-ray photons is used instead of film (Fig. 2 & 3). need to be converted to Fig. 2A: Air Techniques (Hicksville, NY) ScanXTM Such reusable plates can have the visible photons for an image phosphor plate laser same sizes as dental panoramic films. to be captured by the system. scanner. They contain a phosphor layer that This is done by a scintillator “remembers” the image; hence, the layer, similar to the scintillators name “storage phosphor”. To read the that are used as intensifying image, phosphor plates need to be screens in analog film illuminated by a Helium-Neon laser panoramic radiography (Fig. beam. When a portion of the plate is 4). An example of one of the illuminated, it emits light that is earliest commercialized digital photomultiplied and collected by a panoramic systems was that digital imaging chip. of the Trophy Digipan adaptor Photostimulable phosphor for the Instrumentarium OP systems dedicated to dentistry are 100 (Fig. 5A). available from a number of manufac- As with analog film, the turers. Each system is comprised of panoramic image is pieced the phosphor plates and a laser together during the scan. Unlike scanner that interfaces with a com- analog film radiography, the receptor puter. The plates can be quite expen- is stationary and the image for each sive, costing $500 to $1,000 each for segment is read-out in appropriate extraoral purposes. While extraoral sequence. Solid-state systems are plates are not as sensitive to scratch- available both to retrofit an existing ing as are the intraoral plates, care panoramic system and as integrated must still be taken not to scratch or units dedicated to a specific pan- contaminate them. The plates are very oramic x-ray generator (Table 1). A sensitive to ambient light, which can potential concern with retrofitting a erase much of the latent image. unit is that if something does go Furthermore, they need extensive wrong you may find yourself working exposure to light in order to completely with the manufacturer of the pan- erase the image before reuse. On the oramic system, the manufacturer of other hand, storage phosphor sys- the retrofit system and the installer. TM tems are versatile in that they can be Fig. 2B: DenOptix (Dentsply/ Gendex, Des Plaines, IL) laser scanner with used with a wide range of different Radiation Dose phosphor plate attached to drum ready x-ray systems. Unlike intraoral radiology, the for processing. Solid-state digital x-ray detectors switch to digital panoramic imaging are based on a silicon chip that permits the acquisition of an image. Such a chip consists of a myriad of pixels; each pixel captures a small Fig. 2C: Loading a quantity of energy (usually light from a phosphor plate scintillator) and converts this radiant into a soft cassette. energy into electricity. For panoramic radiography, this generally involves a charge-coupled device (CCD) of sufficient dimensions to cover the secondary slit of the panoramic machine (i.e. tall and narrow). The CCD converts radiant photons into electrons. The ability of the current detectors to capture radiant energy is presently limited to visible photon

4 “ Storage phosphor systems (photostimulable phosphors) specific to dentistry are available from a number of different manufacturers.”

does not generally result in a substan- storage of secondary images. This is tial dose reduction to the patient. In certainly an inexpensive way to fact it is sometimes necessary to become familiar with digital images — actually increase dosage to optimize and it also replaces the need to use image quality when using digital duplicating film and a duplicator to systems [6]. create duplicates. Such a system With intraoral film radiography, the could be worthwhile in any dental emulsion is directly sensitive to x-rays, office regardless of whether or not so adding a scintillating screen can other digital methods are also to be improve the efficiency with which incorporated. Furthermore, a scanner x-rays are detected. However, for allows you to incorporate prior extraoral radiography, an intensifying radiographic images into the elec- screen is generally employed – tronic patient record. Problems with and this is not so very different from relying on scanning are (1) this does Fig. 2D: Orex’s Paxorama Xi™ the scintillating layer used with solid- not remove the darkroom issues that works with existing X-ray and state detectors. Gijbels et al (2001) often lead to suboptimal analog phosphor plate. found no difference in exposure radiographs, and (2) scanning is an settings or organ doses between added task for your assistants to analog film and indirect digital pan- perform; time for which you are not oramic radiography using being additionally reimbursed. photostimulable phosphor plates [9]. Storage phosphor systems (photostimulable phosphors) specific Costs to dentistry are available from a Determining the true cost of number of different manufacturers. In system ownership is not an easy most cases the cost of the basic matter. Certainly the basic expenditure package is roughly $20,000 — but on the system is easily measured. that price can escalate if you pur- However, one also needs to factor in chase multiple extraoral phosphor possible savings in terms of plates at as much as $1,000 each. In consumables such as film and most instances, the plate cassette is processing solutions, the possible loaded and unloaded manually. value of time-savings, or of the Without using caution, this can lead to increased time used. Even more wear of the expensive plates — and difficult to determine is the diagnostic also can lead to suboptimal images gain or loss. through the effects of ambient lighting A good quality on exposed plates being loaded into scanner will cost the scanner. Further, processing of between $600 and extraoral plates in medium to high $1,500 and can be resolution can be quite time consum- used for general ing — no big time savings, if any, over scanning purposes film processing. The advantage of beyond radio- such a system is that the images are graphs. The system stored digitally in computer memory can be attached to and can be easily duplicated for safe the practice storage and retrieval. Moreover, a management single storage phosphor processor computer, and can be used with multiple x-ray many practice generators. management Retrofit solid-state digital pan- software packages oramic imagers have the advantage Fig. 3: Imaging using storage include modules for of providing a virtually instant image phosphor plate. the capturing and on the screen – so if you are in a high

5 “ There are several excellent dedicated digital panoramic systems on the market, however, the costs of such systems range from $25,000 to $60,000 depending on the degree of sophistication desired.”

volume practice or have other reasons new media as they for needing immediate images, these become accepted. are an excellent alternative (Fig. 5; For example, you Table 1). They can provide most, if not cannot play music all, of the digital capabilities of the from an old record integrated digital units without the cost directly using a tape of buying a new machine. Retrofit player or 8-track – systems generally cost around and you cannot $20,000. If you have a relatively play a music tape inexpensive panoramic system and do on a CD or MP3 not utilize it to a substantial degree, player. Similarly, it is then this added cost might not be now difficult to find warranted given your business a computer with a situation. 5.25” floppy disk There are several excellent drive and standard dedicated digital panoramic systems “A” drives are on the market (Fig. 6; Table 1), rapidly disappear- however, the costs of such systems ing to be replaced range from $25,000 to $60,000 by CD-R, DVD-R, Fig. 4: Schematic representation of a depending on the degree of sophisti- Flash Memory and solid-state detector. cation desired. To select such a unit USB-Mass Storage requires a careful assessment of your Devices. If you practice and an individualized cost- intend to use digital Fig. 5A: One of the earliest benefit analysis. It should be remem- images then you commercialized digital panoramics was the Trophy bered that reimbursements per should expect to DigipanTM used with the panoramic procedure are not gener- make periodic Instrumentarium OP 100TM ally proportional to your investment. storage hardware panoramic system in place Whatever device you select should fit upgrades. of the film cassette. A with the type of practice and patients Regarding the variety of “add-on” systems from several different you serve. matter of software/ vendor sources are now file format available for most Interoperability interoperability, the panoramic systems. It is not unusual to review film digital x-ray industry radiographs that are decades old – and practice especially when demonstrating management system vendors are “classical” radiographic features of presently working together to facilitate disease entities at a continuing digital image interoperability using education forum [10]. Archived film specifications from the DICOM (Digital images that are decades old are Image Communication) standards that usually still of high quality and can be were developed initially for medical viewed by anyone who happens to radiology. This specification includes have a view box to transmit light image format rules and associated through the radiographs. One might information for transmission of question whether the digitized radiographs used in dentistry includ- versions will be as readily accessible ing intraoral surveys and panoramic as the analog film versions decades images. Working Group 12.1 of the into the future. The likelihood of being American Dental Association has able to retrieve digital images is been tasked with developing appropri- Fig. 5B: Schick CDRPanTM (Long Island dependent upon both hardware and ate specifications. It must be cau- City, NY) digital retrofits are available for software/file format considerations. tioned, however, that no guidelines or a number of panoramic systems Regarding hardware issues, one specifications will guarantee including the Panoramic Corporation simply needs to back up all files on interoperability. PC-1000TM.

6 Fig 5C: Interoperability imaging. Dentomaxillofac Radiol Components needs to be demon- 1994;23:5-9. ® of the DXIS strated practically. 2. Farman AG, Farman TT. Extraoral (Direct X-ray Such practical and panoramic digital radiography. Imaging demonstrations were System). Dent Clin N Amer 2000; 44:257- initiated at the ADA 272. Annual Congress in 3. Farman TT, Farman AG, Kelly MS. New Orleans in 2002 The OP 100 Digipan: Evaluation of where 10 companies the image layer, magnification demonstrated that factors and dosimetry. Oral Surg interoperability of Oral Med Oral Pathol Oral Radiol their image files Endod 1997;83:281-287. could be achieved satisfactorily. 4. Farman AG, Farman TT. Panoramic Interoperability within the DICOM dental radiography using a charge- coupled device receptor. J Digit standards is important so that the Imaging 1998;11(Suppl. 1):166- dentist can integrate data from different 168. digital sources and read diagnostic images referred from outside sources 5. Farman TT, Farman AG. Clinical trial where different systems may have been of panoramic dental radiography us- used. Otherwise there could be incon- ing a CCD receptor. J Digit Imaging venience both for the patient and for the 1998;11(Suppl. 1):169-171. practitioner. 6. Farman AG, Farman TT. A compari- son of image characteristics and REFERENCES convenience in panoramic radiogra- Fig. 5D: DXIS® system 1. Farman AG, Scarfe WC. Pixel percep- phy using charge-coupled device, installed on a Panoramic storage phosphor and film. J Digit Corporation PC-1000. tion and voxel vision: constructs for a new paradigm in dento-maxillofacial Imaging 2001;14(Suppl. 1): 48-51. 7. Schultz RK, Rosing ST, D’Hoedt B. Contrast perception in digitized panoramic radiographs compared with film-based originals. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;94:388-394. 8. Benediktsdottir IS, Hintze H, Petersen JK, Wenzel A. Image quality of two solid-state and three photostimulable phosphor plate digital panoramic systems, and treatment planning of mandibular third molar removal. Dentomaxillofac Radiol Fig. 6A: An example of a dedicated 3003;32:39-45. solid-state digital panoramic system is the Instrumentarium OP 100-DTM 9. Gijbels F, Sanderink G, Serhal CB, (Tuusula, Finland). Pauwels H, Jacobs R. Organ doses and subjective image quality of in direct digital panoramic radiography. Dentomaxillofac Radiol Fig. 6B: Another dedicated solid- 2001;30:308-313. state panoramic system is the TrophyPanTM (PracticeWorks/Trophy, 10. Farman AG. Use and implication of Atlanta, GA). the DICOM standard in dentistry. Dent Clin N Amer 2002;46:565-573.

7 In The Recent Literature:

Dosage: It is possible to reduce niques, patient exposure was reduced pathologies determined with the two radiation dose by substituting solid- by solid-state digital panoramic radiogra- modalities was similar. The five digital state imaging devices for analog film phy. The extent of dose reduction panoramic systems evaluated in this during panoramic radiography; depended on the device employed and study were evaluated to be equally however, dose savings from solid- was generally smaller than the dose as useful for third molar treatment state panoramic imagers are not as reduction that can be achieved by digital planning and diagnosis of dental large as found when changing to imaging devices in intraoral radiography. anomalies and pathologies as digital imaging for intraoral radiogra- conventional film-based panoramic phy. Third molar assessment: Digital radiographs. Visser H, Hermann KP, Bredemeier S, panoramic radiography proved equal Kohler B. Dose measurements to film imaging for assessing Soft versus hard copy: Digital comparing conventional and digital unerupted third molar teeth. panoramic images were judged to panoramic radiography. Mund Kiefer Benediktsdottir IS, Hintze H, Petersen have better quality when viewed Gesichtschir 2000;4:213-216. [From JK, Wenzel A. Accuracy of digital and on the computer monitor than the Abteilung Parodontologie, film panoramic radiographs for when printed; however, diagnostic Georg-August-Universitat Gottingen, assessment of position and morphol- utility was found to be comparable Germany.] ogy of mandibular third molars and when it came to viewing anatomic prevalence of dental anomalies and features. This study measured and compared pathologies. Dentomaxillofac Radiol. Guerrant GH, Moore WS, patient exposure by digital and conven- 2003;32:109-115. [From Department Murchison DF. Diagnostic utility of tional panoramic radiography. Dose of Oral Radiology, Royal Dental thermal printed panographs measurements were carried out on an College, Faculty of Health Sciences, compared with corresponding anthropomorphic phantom, which was University of Aarhus, Denmark.] computer monitor images. Gen specially developed for dental radiogra- Dent 2001;49:190-196. [From the phy. Panoramic radiographs were taken This study compared the accuracy of Wilford Hall USAF Medical Center, with three different conventional digital and film panoramic radiographs Lackland AFB, Texas, USA.] devices and two solid-state digital for determining (1) the position and devices The exposure conditions shape of mandibular third molars before Digital panoramic radiographs can followed clinical routine. The energy surgical removal and (2) the prevalence be either viewed on computer dose was measured at 28 places inside of dental anomalies and pathologies. monitors or archived as thermal or and on the surface of the phantom by Three hundred and eighty-eight third laser prints. To compare the available using a set of 108 thermoluminescence mandibular molars were available for diagnostic information from thermal detectors. Additionally, exposure time, examination. Position and morphology of print images to that of corresponding tube voltage, central-beam dose, and third molars observed on film radio- computer monitor images, four dose-area products were measured. graphs and on digital panoramic images calibrated evaluators performed a The effective doses were calculated on from five different systems were qualitative analysis of 13 specified the basis of the absorbed doses. In recorded by two observers and were anatomic features in 60 pairs of each case, the highest energy doses compared with surgeons’ findings at the digital panoramic images presented were recorded at the parotid gland, the time of the operation. One observer in random order on a computer mandibular angle, the submandibular further recorded the prevalence of monitor and as thermal printed gland, and the skin in the neck. Pan- dental anomalies and pathologies on images. Each anatomic site was oramic radiographs made with the both imaging modalities. Few differences rated both for subjective diagnostic conventional units yielded effective were found between the digital and film- quality and diagnostic utility using a doses in the range of 16-21 µ Sv, the based panoramic systems in the nominal scale. Computer monitor digital units yielded 5-14 µ Sv. Hence, in assessment of accuracy of position and images more often were subjectively comparison with conventional tech- morphology of mandibular third molars. judged to have better quality. Within The prevalence of dental anomalies and the parameters of this study, both formats had acceptable diagnostic utility for the majority of the anatomic features evaluated.

©2003 Panoramic Corporation (10-03)

8 Volume 3, Issue 4 CE TEST: Digital Options for Panoramic Radiology 1. Duplicate images of digital radiographs made with 7. Scanning, generally using a He-Ne laser, is necessary charge-coupled devices or photostimulable to process the latent image when using phosphors are inferior to the original image. photostimulable phosphors for panoramic ! True ! False radiography. ! True ! False 2. Digital imaging systems not utilizing analog film are environmentally friendly. 8. Achievement of digital imaging using an existing ! True ! False panoramic unit is possible using secondary capture, phosphor plate or retrofit (add-on) solid-state 3. Solid-state digital technologies include systems. photostimulable phosphor plates. ! True ! False ! True ! False 9. For digital panoramic radiography using a solid-state 4. Digital panoramic radiographs generally require a system, the solid-state sensor moves in a similar reduced dosage in comparison with traditional film/ manner to analog film during the exposure. screen radiography. ! True ! False ! True ! False 10. Gijbels et al (2001) found a substantial difference in 5. Strict adherence to DICOM file formats is a exposure settings and organ doses between analog guarantee of interoperability between different film and indirect digital panoramic radiography digital systems used in dentistry. using photostimulable phosphor plates. ! True ! False ! True ! False

6. Hardware upgrades in storage devices are likely to be needed periodically to preserve the availability of digital images. ! True ! False

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