Integration of multiple direct digital imaging sources in a picture archiving and communication system (PACS)

(2003) 32, 337 342 q 2003 The British Institute of Radiology http://dmfr.birjournals.org TECHNICAL REPORT Integration of multiple direct digital imaging sources in a picture archiving and communication system (PACS) E Gotfredsen* and A Wenzel Department of Oral Radiology, Royal Dental College, University of Aarhus, Denmark Introduction Objectives: The aim of this report was to describe a flexible picture archiving and communication system (PACS) able to handle and communicate digital image data from various radiography systems and other sources. Methods: The radiographic image is acquired using the vendor s own software. Following image capture, a request for update message (appending a record to an Access database) activates our PACS engine, DigiMerge. Images from sources with no patient-related organizing software, e.g. TWAIN-compatible scanners and digital cameras, are handled by a self-developed program, MedCom-T. DigiMerge generates and maintains one database based on all manufacturers databases (software: VixWin 2000, Digora for Windows, Dimaxis Pro, Sidexis, CDR DICOM for Windows, Trophy for Windows). This database contains patient information, image information and image path. The program DigiView searches a patient and displays patient and image data from the database generated by DigiMerge. With DigiView, images can be viewed at any workstation in the dental school, but only temporary changes can be made (contrast, brightness, etc.) and no image can be deleted. Results: The PACS is currently installed on 86 workstations. Statistics collected by DigiMerge reveal that approximately 2000 new digital images are recorded each month, half of which are radiographs and the other half are clinical photographs. Statistics collected by DigiView reveal that 500 800 digital images are opened per week. Conclusions: The self-developed PACS is able to manage images from a range of digital modalities each providing its own image data format. (2003) 32, 337 342. doi: 10.1259/dmfr/29383573 Keywords: radiology information systems; radiography, digital Dental schools worldwide now consider implementing digital radiography for routine patient examination and student education, but few reports have described how to integrate a picture archiving and communication system (PACS) in dental schools and hospitals. 1,2 There may be several approaches to digital imaging implementation in large institutions. A technically simple solution may be to collaborate with a single vendor for hardware and software. The format for storing and communicating image files is then given. On the other hand, dental schools may not wish to rely on one producer of digital radiographic systems. Available digital systems *Correspondence to: Erik Gotfredsen, Department of Oral Radiology, Royal Dental College, Faculty of Health Sciences, University of Aarhus, Vennelyst Boulevard, DK-8000 Aarhus C, Denmark; E-mail: egotfred@odont.au.dk Received 6 February 2003; revised 25 April 2003; accepted 3 July 2003 all have their limitations, and ideally the best system for any given diagnostic task should be used. Moreover, it may be proper in an educational environment to expose students to various concepts for digital imaging. There may therefore be the need to integrate heterogeneous systems enabling transparent access to all sources from all workplaces. Vendors of direct digital radiography systems unfortunately do not adhere to one standard for image file formats, but often provide their own image storage solutions. Commercially available software for image acquisition and viewing of images originating from multiple digital sources seems to be limited and may not be able to handle any future system. Relying on commercial software may limit the choice of hardware and may shift the focus from the diagnostic process to the handling of the image. There is little information in the literature on the use of PACS by dentists, but at least one

338 A multiple source PACS E Gotfredsen and A Wenzel dental hospital 2 has chosen the DICOM (Digital Imaging and Communication in Medicine) standard. 3 5 However, it is questionable whether the mammoth DICOM definition is the solution for dentistry, and not all vendors of digital systems for dentistry offer a DICOM-compatible solution. The last option may therefore be use of self-developed software for the integration of images from various commercially available digital sources. The aim of this report was to describe a flexible PACS, developed and implemented in our dental school. The PACS is able to handle and communicate digital image data from various radiography systems and other sources. The considerations and discussions leading to the choice of the particular digital systems chosen will initiate the report. Radiographic image sources The digital systems included in our routine radiographic examinations are shown in Table 1. They have been selected on the basis of the examination types that they provide, their user friendliness, image quality and diagnostic accuracy. Evidence for their diagnostic accuracy is available in the literature, but will not be provided in this report. Since there are advantages of charge-coupled device (CCD)-based sensor systems over photostimulable phosphor plates (PSPs), and vice versa, we decided to implement both types of systems for different intraoral and extraoral examinations. For those not acquainted with CCD and PSP systems, reviews are available by Sanderink and Miles, 6 Farman and Farman 7 and Hildebolt et al. 8 The digital radiographic image sources are displayed in the left-hand column of Figure 1. Systems selected for intraoral examinations Digital intraoral full-mouth surveys and bitewings are performed with the Digora fmx (PSP) system. Bitewings obtained with a PSP system contain fewer positioning errors than those obtained with CCD sensor systems; moreover, owing to their thickness it is not easy to image the most posterior teeth with the CCD sensors. 9 Occlusal plane examination for localization of, for example, impacted canines, is performed with the DenOptix PSP system since this is the only system that provides this plate size. Periapical images that orthodontists use for control of root length before and during orthodontic treatment are performed with the Trophy RVG and the Sidexis sensors since the sensors provide fully acceptable images in the frontal regions. The Schick sensor is used for radiographic control of an inserted implant and is installed in the operating theatre in the surgical department. On the other hand, intraoral radiographic examination of the third molars is also performed in the surgical department with the Digora PSP plate since it is cumbersome to work with sensors in this region. Systems selected for extraoral examinations The Orthophos DS Ceph CCD-based unit is in use for panoramic imaging and in some cases for lateral and frontal skull examinations. This panoramic image has a resolution of 282 dots per inch (dpi). The waiting time is approximately 90 s from termination of the exposure to display of the image on the monitor. Owing to the image size (18 cm 24 cm), a lateral cephalogram may lack part of the neck, which is claimed by orthodontists for some patient categories. Recently, the Promax Ceph Dimax3 (CCD unit) from Planmeca (Table 1) has been accepted for evaluation. The unit operates with a different collimation principle and sensor concept than the Orthophos DS Ceph, and there are not yet any reports on the performance of this unit. The CCD-based units offer a number of programs for other examination categories, e.g. tomography, but the CCD technology can only provide linear tomography. We therefore chose units with the ability for narrow beam radiography and spiral tomography, Cranex Tome and Scanora (Soredex; Orion Corporation, Helsinki, Finland), Table 1 Dental digital radiography systems in daily use, with company name and address Model Type Manufacturer Address URL DenOptix Ceph PSP; combination Gendex Dental Systems Via Capelli 12, www.dentsply.it intraoral/extraoral 20126 Milano, Italy Digora fmx PSP; intraoral, extraoral Orion Corporation, Soredex Nilsiänkatu 10 14, www.soredex.com Digora pct PO Box 79, 00510 Helsinki, Finland ProMax Ceph Dimax3 CCD; extraoral Planmeca Asentajankatu 6, www.planmeca.com 00880 Helsinki, Finland Sidexis CCD; intraoral, extraoral Sirona Dental Systems GmbH Fabrikstrasse 31, www.sirona.de Orthophos DS Ceph D-64625 Bensheim, Germany Schick CCD; intraoral Schick Technologies Inc. 30-00 47th Avenue, www.schicktech.com Long Island City, NY 11101, USA Trophy RVG CCD; intraoral Trophy Radiologie 4, rue F. Pelloutier, www.trophy-imaging.com Croissy-Beaubourg, 77437, Marne la Vallee Cedex 2, France PSP, photostimulable phosphor plate; CCD, charge-coupled device

A multiple source PACS E Gotfredsen and A Wenzel 339 Figure 1 Schematic drawing of the logical structure of the picture archiving and communication system (PACS). Left section: upper part, the Klips patient database program; middle part, illustrates the digital radiographic image sources; lower part, defines other image sources (scanners, digital camera). Middle section: displays the DigiMerge program, which retrieves images from all sources enabling their integrated display via DigiView at all workstations. Right section: illustrates links to other programs and to image export facilities from DigiView. The system is independent of communication protocol for more advanced examinations such as cross-sectional tomography and scanography. Such examinations in the Cranex Tome/Scanora unit are combined with a PSP system. The PSP imaging systems can in principle work with any available conventional radiographic equipment since the phosphor plates may be installed in the same cassette type as film. The intensifying screens are removed and the plate is installed. A PSP system is also used for cephalometric examinations in combination with a 40-year-old cephalostat, which still provides excellent images (focus-to-film distance 190 cm and secondary collimation). The image size routinely used for cephalograms is 24 cm 30 cm. There is a limit to the size of the plates for some of the PSP systems, 18 cm 24 cm being the largest possible image size with the DenOptix unit while the Digora system allows for 24 cm 30 cm images similar to film. In the CCD-based units the maximum height of a cephalogram is 24 cm. After exposure, PSP plates are read out in a scanner. The scanner may in principle be placed anywhere in the clinic, but it should be remembered that the plates are to some extent sensitive to room light (since light erases the information). For the Digora system, the plate is fed into the slot in the rather large scanner, protected by a black plastic envelope until it is safely placed in the scanner. This takes a few seconds and exposure to light is therefore not a problem. The DenOptix system operates with a drum-like scanner that takes up less space than the Digora scanner. The operator must mount the plates in the drum. This takes time, which may be critical owing to the sensitivity of the plates to light. In practice, this means that the light has to be dimmed or turned off in the room when mounting the plates. Another time consuming factor for the DenOptix scanner is that the plate is not erased by light after the

340 A multiple source PACS E Gotfredsen and A Wenzel scanning procedure, which is the case for the Digora scanner. This means that the plate must be transferred to a conventional light box and left in strong light for some minutes before it can be used again. Another consideration on resources may be the differences in scan time between the makes. The fastest scan time is obtained with the Digora pct scanner, which takes approximately 90 s to scan a panoramic image (in 300 dpi resolution) compared with 3 6 min depending on the resolution with the DenOptix system (150 dpi or 300 dpi). These considerations have resulted in the fact that the DenOptix system is used merely for occlusal plane examinations. Image sources other than radiography Film-based radiographs may be scanned using various TWAIN-compatible scanners (www.twain.org) in the dental school to facilitate their use together with more recent digital images of the same patient. Clinical images of the patients, both facial and intraoral images, are taken in many departments. In the orthodontic department, all clinical photographs are recorded with digital cameras (Nikon D1, connected by fire-wire) situated in the clinics and connected to a stationary computer. Such images from sources with no patient-related organizing software are handled by a self-developed program, MedCom-T (Figure 1, bottom left). This program organizes images from various sources using a relational database with a table for patient information and another for image data. The images are organized into one folder per patient. Patient data (Klips) Klips is the self-developed clinical patient system used at our dental school. All patients accepted in the dental school are drawn up in Klips, which controls patient data (name, address, etc.). Klips stores information on patient treatment needs and is used by the students to find specific treatment categories. Relevant data from new patients entered into this program are delivered within 2 min (as a comma-separated text file) to our PACS, and once a day a full extract of all relevant patient data is delivered. This means that information on a new patient, who has been registered in Klips at patient entry, is available at the radiology clinic before the patient arrives physically. When the radiographic examination of the patient is to begin, the patient s data are transferred from our PACS to the software of the recording system. How the data are delivered depends on the ability of the vendor s software. The Planmeca system has a system called PMBridge, which by sending a string of patient information to a program called DxStart, transfers the data to the Planmeca system. The Digora system communicates by writing/ reading codes and patient data to the Clipboard. For the DenOptix, Sirona and Trophy systems we communicate simply by substituting keyboard input of data. Among other advantages, these procedures ensure that, for example, patients names are spelled identically at all recording units. The procedure also saves time since patient information does not need to be re-entered into each radiographic system s software. Acquisition of digital images using the commercial system s software At the unit where the digital image is acquired, the vendor s own software is installed and set up to store all data on the local area network. The software version and how the systems store their images can be seen in Table 2. The relationship between the digital receptor and the software used for image acquisition and display is close, and we believe that the manufacturers have sought to optimize this interconnection. We have therefore decided not to interfere with the developers integration between image receptor and display software. The radiographers in our department were therefore trained to use the individual systems, software for image acquisition. Following image capture, a request for update message (appending a record to an Access database) activates our PACS engine, DigiMerge (Figure 1). We have decided not to use irreversible data compression (e.g. JPEG) for standard storage of radiographic images, 10 whilst clinical photographs are compressed using JPEG compression before storage. Communication of digital images using a self-developed PACS engine, DigiMerge The PACS programs were developed for the Windows platform in Microsoft Visual Basic 6.0, using Microsoft Table 2 Dental digital radiography systems in daily use, with software version and image storage Model Type Software Software version Image storage Image conversion DenOptix Ceph PSP VixWin 2000 v1.2 TIFF Digora PSP Digora for Windows 2.1 rev 2, Single User, Build 45 Own file format DigiView makes a temporary file before view Promax Ceph Dimax3 CCD Dimaxis Pro Version 3.1.2 Inside database Export of image using Dimax Pro Sidexis CCD Sidexis Version 5.52 TIFF Schick CCD CDR DICOM for Windows 3.0.0.1025 DICOM file DigiView makes a temporary file before view Trophy RVG CCD Trophy for Windows Version 4.0i TIFF PSP, photostimulable phosphor plate; CCD, charge-coupled device; TIFF, tagged image file format; DICOM, Digital Imaging and Communication in Medicine

A multiple source PACS E Gotfredsen and A Wenzel 341 Access 97 as the database engine. The program, LeadTools 11.5 (www.leadtools.com), was chosen for image display and manipulation. The program DigiMerge generates and maintains one database based on all manufacturers databases and images. The database contains patient information, image information and image path. This means that all data are gathered in one database, and that radiographers do not export images after acquisition (except from the Planmeca unit, which is under evaluation). Display of digital images using a self-developed program, DigiView The DigiView program searches a patient and displays patient and image data from the database generated by DigiMerge. With DigiView, images can be viewed at any workstation in the dental school, but only temporary changes can be made (contrast, brightness, etc.) and no image can be deleted. The essential function of the program is therefore equivalent to a conventional light box with adjustment facilities. The program has been described briefly in a previous report. 11 A discussion on monitors for image display throughout the dental school resulted in the following recommendations. A so-called clinical workstation comprising a compact PC with flat screen (Mermaid Ventura 150), usually wall hung, was installed in the clinics. A larger, so-called treatment planning workstation with a 19 00 high quality monitor (IBM P96) was recommended in each department, since the dentists receiving the digital images did not agree that the quality of the displayed image was as high on the flat screens as on the large monitors. In the orthodontic department, some postgraduate students make use of a portable PC to display their patients records, including images at the chair side. Wireless networks are available for these students. External communication of the digital images is usually performed by attaching the image (as an encrypted file) to an e-mail. Parties who are not able to receive and display an electronic image may need a hard copy, which is made on glossy paper or transparent film on an inkjet printer (Kodak 1200, Distributed Medical Imager). Links from DigiView to task-specific tools In conventional film radiography, various measurements are performed on the film in connection with treatment planning tasks. When using the Scanora unit, for example for cross-sectional tomography of the jaws, a panoramic image constitutes the basis for selecting the correct program for the region to be sectioned. The measurements are performed on the Scanora light box using a particular Scanora ruler. When switching to digital imaging, the ruler in the Digora for Windows software can be used only with Digora images, and therefore a program that can be used with all digital systems was developed to substitute the ruler ( ScanoraLightBox ; Figure 1). When a full-mouth survey or other series of intraoral images is taken of the same patient, the convention for film is to mount them in a frame. When the images are digital and stored individually, it may be time consuming to have to select each image individually, and the overview is lost when they are displayed as a stack of separate windows. We therefore developed a program ( Image Template Mounter ; Figure 1) that enables the user to mount digital images in self-defined templates, fitted to the number of images needed. When defining the template, a JPEG compression rate is chosen (for a full-mouth survey the compression is 1:12). 12 After mounting, the template with all images is stored as a single image file, named, for example, full-mouth survey. The individual images are of course still available in their original format. This has satisfied the dentists in the clinics, who found it cumbersome to retrieve and view each periapical image individually. ImplantPlanner is a program by which the surgeon can measure enlargement of the region of interest by calibration to a body of known dimensions, for example a steel ball. Flexible links to other task-specific programs facilitate use of the digital images for linear and angular measurements. PorDiosW (www.pordios.com), a program that has been described previously, 13 is used for cephalometric analysis in orthodontic treatment planning. X-PoseIt (www.x-poseit.adsl.dk) is a program for subtraction of information in two digital images. Other image handling programs, such as PhotoShop (www.adobe.com), may also be called from DigiView. Figure 1 (right-hand column) illustrates links to other programs and to image export facilities from DigiView. Results The PACS is currently installed on 86 workstations. The main users are the radiology, surgery and orthodontic departments. The statistics collected by DigiMerge reveal that approximately 2000 new digital images are recorded each month, half of which are radiographs and the other half are clinical photographs. The statistics collected by DigiView reveal that 500 800 digital images are opened and viewed per week. The production can be followed at our homepage: www.odont.au.dk/rad/digiview/status.htm. Moreover, a frequently updated graphical presentation of recorded digital images can be seen at www.odont.au.dk/ rad/implement.htm#patients. Discussion In the year 2000, we began to switch from conventional radiography to digital imaging in connection with the pregraduate and postgraduate student curriculum. We decided to switch gradually, starting with the surgical department, then the orthodontic department, the implant clinic and the temporomandibular joint clinic, and this year we will implement digital equipment in the large clinics for operative dentistry and endodontics. The reasons for the

342 A multiple source PACS E Gotfredsen and A Wenzel stepwise introduction of digital imaging a reverse salami technique was partly economical and partly owing to the fact that we were able to solve the problems that may arise for each department one at a time. Starting with clinics needing mainly extraoral images was a smaller economical strain (e.g. the orthodontists do not need a monitor for image display at the chair side). We needed to be able to manage a range of digital radiography modalities each providing their own data formats. Easy usage of the digital images is unfortunately hindered in many of the present digital radiography systems by the way the developers store the images. In some systems the images are stored inside the database, with the result that the dentist does not have immediate access to them but will have to export them to a proper file format (e.g. TIFF) before they can be used in other programs. Digora for Windows software does not store images in a standard format, meaning that the images must be pre-processed before display. Dimaxis Pro software stores images inside the database, meaning that they must be exported after exposure. Among other inexpediencies, this means that in some cases redundant information is stored at the server. The company is working on a solution to this problem. Schick images are stored as DICOM files. We have not yet invested in tools to handle DICOM, meaning that these images are handled as any non-standard format and pre-processed before display. Sidexis, Trophy for Windows and VixWin 2000 software store their images in a format (TIFF) that can be used directly as stored. It may be much more user friendly if the developers of software for digital radiography would store their images outside the database, obey standard file formats and show the name of the image file in their software. Having to export images acquired with a particular system is time consuming and, even worse, redundant information is stored. It is an ongoing discussion whether dentistry and manufacturers who develop digital systems for dentistry should await and implement the DICOM standard for their PACS. 4 This may be the solution for some institutions, but it should be considered that DICOM often runs on expensive licenses, further increasing costs for digital radiography. If the DICOM standard is recognized for dentistry, our PACS is flexible enough to manage this as well. A further advantage of the present PACS is that from his workstation the user has merely reading access to data and therefore cannot by accident delete or permanently change images and patient information. It may be seen as an increase in data security compared with using the vendor s software. References 1. Analoui M, Buckwalter K. Digital radiographic image archival, retrieval, and management. Dent Clin North Am 2000; 44: 339 358. 2. Okamura K, Tanaka T, Yoshiura K, Tokumori K, Yuasa K, Kanda S. Integration of a picture archiving and communication system with videocapture and computed radiography in a dental hospital. Dentomaxillofac Radiol 2001; 30: 172 178. 3. ACR NEMA. Digital Imaging and Communications in Medicine (DICOM), ACR NEMA standards Publication No. 300-1994. National Electrical Manufacturer s Association, 1994. 4. Bidgood WD, Horii SC. Modular extension of the ACR NEMA DICOM standard to support new diagnostic imaging modalities and services. J Digit Imaging 1996; 9: 67 77. 5. Benn DK, Bidgood WD Jr, Pettigrew JC Jr. An imaging standard for dentistry. Extension of the radiological DICOM standard. Oral Surg Oral Med Oral Pathol 1993; 76: 262 265. 6. Sanderink GCH, Miles DA. Intraoral detectors: CCD, CMOS, TFT, and other devices. Dent Clin North Am 2000; 44: 249 256. 7. Farman AG, Farman TT. Extraoral and panoramic systems. Dent Clin North Am 2000; 44: 257 272. 8. Hildebolt C, Couture RA, Whiting BR. Dental photostimulable phosphor radiography. Dent Clin North Am 2000; 44: 273 297. 9. Bahrami G, Hagstrøm C, Wenzel A. Bitewing examination with four digital receptors. Dentomaxillofac Radiol 2003 [in press]. 10. Gotfredsen E, Wenzel A. Image compression in storing and communicating digital radiographs. Int J Comput Dent 2001; 4: 273 279. 11. Gotfredsen E. A non-dicom based system for distributing and viewing digital images from multiple sources in dentistry. In: Lemke HV, Vannier MW, Inamura K, Farman AG (eds). Computer assisted radiology and surgery 99. Amsterdam, The Netherlands: Elsevier Science B.V., 1999, pp 964 967. 12. Wenzel A, Gotfredsen E, Borg E, Gröndahl H-G. Impact of lossy image compression (JPEG) on accuracy of caries detection in digital images taken with a storage phosphor system. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996; 81: 351 355. 13. Gotfredsen E, Kragskov J, Wenzel A. Development of a system for craniofacial analyses from monitor-displayed digital images. Dentomaxillofac Radiol 1999; 28: 123 126.