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Clinical Technique: Digital Radiography in Exotic Pets—Important Practical Differences Compared with Traditional Radiography

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Abstract

The future of radiography will be digital. In exotic pet radiography, where some of the animals have a very low body weight and anatomic structures can be small, detail rendition plays an important feature in image quality. Veterinarians should be familiar with the technical principles, image quality criteria, and radiation exposure issues associated with the various types of digital systems currently available. This article discusses basic principles of digital radiography, technical solutions, and selected parameters characterizing detectors, processing, and monitors. An overview of reported experiences is given, and results from experimental clinical studies are reviewed to evaluate the current options and limitations in applying digital radiography to exotic pet medicine.

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... Eine Erhö- hung der Röhrenspannung führt zu einer größeren Durchdringungsfähigkeit der Strahlung und damit zu einer Erhöhung der Dosis auf dem Film/Detektor. Aller- dings führt eine Erhöhung der Strahlungsenergie immer zu einer Kontrastverminderung. Um einen guten Kontrast zu erhalten, kann gerade bei kleinen Patienten die kV- Zahl niedrig gewählt werden [9,11]. Die damit einher- gehende Verringerung der Strahlendosis auf dem Bild- detektor kann in der Regel durch die Wahl des passenden Röhrenstrom-Zeit-Produkts (mAs-Produkt) ausgegli- chen werden. ...
... Das mAs-Produkt ist ein Maß für die Strahlendosis pro Aufnahme [11]. Bei Röntgenanlagen, die mit einem kon- stanten Röhrenstrom arbeiten, ergibt es sich einfach als ...
... screen-film systems are contrast limited 3 . In digital radiography two different approaches have been developed. ...
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This method comparison study used radiographs of 20 mice and 20 budgerigars to investigate comparability between computed radiography (CR) and high-resolution screen-film systems and study the effects of reduced radiation doses on image quality of digital radiographs of small patients. Exposure settings used with the mammography screen-film system (SF) were taken as baseline settings. A powder-based storage-phosphor system (CRP) and a needle-based storage-phosphor system (CRN) were used with the same settings (D/100%) and half the detector dose (D/50%). Using a scoring system four reviewers assessed five criteria per species covering soft tissue and bone structures. Results were evaluated for differences between reviewers (interobserver variability), systems and settings (intersystem variability, using visual grading characteristic analysis). Correlations were significant (p ≤ 0.05) for interobserver variability in 86.7% of the cases. Correlation coefficients ranged from 0.206 to 0.772. For mice and budgerigars, the CRN system was rated as superior to the SF and CRP system for most criteria, being significant in two cases each. Comparing the SF and CRP system, the conventional method scored higher for all criteria, in one case significantly. For both species and both digital systems, dose reduction to 50% resulted in significantly worse scores for most criteria. In summary, the needle-based storage-phosphor technique proved to be superior compared to the conventional storage-phosphor and mammography screen-film system. Needle-based detector systems are suitable substitutes for high-resolution screen–film systems when performing diagnostic imaging of small patients. Dose reduction to 50% of the corresponding dose needed in high-resolution film-screen systems cannot be recommended.
... 27 The low body weight (240 to 850 g) of these animals also influences MR image quality. 26 MRI and CT are popular 3D imaging methods in experiments involving animal models (rats, mice, rabbits) to investigate the pathophysiology of human diseases. 25 For example, MRI has been used experimentally in small mammals to study pyelonephritis, spinal abscesses, synovitis, and bacterial sinusitis in rabbits. ...
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Erwartungen, die man anfnglich in die digitale Projektionsradiographie gesetzt hat, haben sich in der Kinderradiologie erst verzgert oder teilweise gar nicht erfllt. Insbesondere Hoffnungen, dass man die Strahlenbelastung bei gleich bleibender oder gar verbesserter Bildqualitt reduzieren knnte, wurden bald enttuscht. Das einzige portable digitale System waren lange Zeit Phosphorplatten, die aber im Vergleich zu den Festplattendetektoren eine uerst limitierte Dosisquanteneffizienz (DQE) hatten. Durch neue Entwicklungen und v.a. durch die Einfhrung des Dual-reading-Systems kann eine Bildqualitt erreicht werden, die an hochauflsende Film-Folien-Systeme heranreicht, ohne die Dosis erhhen zu mssen. Teilweise ist nun auch eine Dosisreduktion mglich. In einem Tiermodell konnte gezeigt werden, dass diese Systeme auch bei Frhgeborenen mit einem sehr niedrigen Geburtgewicht einsetzbar sind. Hoffnung wird in ein neues portables Festplattendetektorsystem gesetzt, welches in der pdiatrischen digitalen Thoraxradiographie evtl. neue Mastbe setzen knnte.The hopes placed in digital radiography have been fulfilled only partly in pediatric radiology. Specifically, the option of gaining reduced radiation exposure in combination with a similar or even improved image quality was hard to realize. The only portable digital system available for a long time were storage phosphors which were disadvantaged by an extremely limited dose-quantum-efficiency (DQE) in comparison to digital flat panel detectors. New developments and the introduction of the dual-reading system led to image qualities comparable to film-screen-systems with high resolution and achievable without dose increase, sometimes even with dose reduction. A study using an animal model suggests that these systems can even be used in preterm infants with very low birth weights. A new portable flat panel detector by Canon may improve digital chest radiography in pediatric patients.
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Seit 110Jahren werden Rntgenstrahlen in Verbindung mit Rntgenfilmen zur medizinischen Diagnostik eingesetzt. Fortschritte auf dem Gebiet der Rntgen- und insbesondere der Computertechnik fhrten in den letzten Jahrzehnten zu neuen Bild gebenden Verfahren, die das Spektrum radiologischer Untersuchungsmglichkeiten wesentlich erweitert haben. Trotz erheblicher technologischer und diagnostischer Fortschritte auf dem Gebiet der MRT und der Multidetektor-CT stellen groflchige radiographische Aufnahmen von Lunge, Skelett und Organen mit bis zu 80% der Untersuchungen noch immer die grte Sule im radiologischen Routinebetrieb dar. Die zunehmende Verbreitung digitaler Detektoren lst hierbei mehr und mehr die Film-/Folienradiographie ab, wobei versptet, bedingt durch die hheren Anforderungen an die Ortsauflsung, auch die digitale Mammographie hinzukam. Seit etwa 2Jahren stehen als Ersatz des seit etwa 40Jahren verwendeten Bildverstrkers neue dynamische Festkrperdetektoren fr die Fluoroskopie zur Verfgung.For 110years, x-rays and special x-ray films have been used in medical diagnostics. New developments in the field of x-ray techniques, and especially new computer applications, have led to new imaging techniques which have substantially expanded the spectrum of radiological examinations. In spite of significant technological and medical advances in the field of MRI and multidetector-CT, radiographic images of the lungs, skeleton and organs still comprise up to 80% of the routine radiological workload. The increasing availability of digital detectors has led to the continual replacement of conventional film/screen systems. The inclusion of digital mammography was delayed due to the higher requirements for spatial resolution. For about 2years, dynamic flat panel detectors have started to replace the image intensifier which has been used in fluoroscopy for 40years.
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Digital X-ray detector technologies provide several advantages when compared with screen-film (SF) systems: better diagnostic quality of the radiographic image, increased dose efficiency, better dynamic range and possible reduction of radiation exposure to the patient. The transition from traditional SF systems to digital technology-based systems highlights the importance of the discussion around technical factors such as image acquisition, the management of patient dose and diagnostic image quality. Radiographers should be aware of these aspects concerning their clinical practice regarding the advantages and limitations of digital detectors. New digital technologies require an up-to-date of scientific knowledge concerning their use in projection radiography.This is the second of a two-part review article focused on a technical overview of digital radiography detectors. This article provides a discussion about the issues related to the image acquisition requirements and advantages of digital technologies, the management of patient dose and the diagnostic image quality.
Article
Objective: The aim of the study was to compare the image quality of radiographs obtained with a storage phosphor (SP) system and a flat-panel detector (FD). Furthermore, the influence of different exposure settings was investigated. Material and methods: In a prospective study a series of lateral thoracic radiographs of 45 normal cats were acquired by use of a standard SP-system and an opto-direct FD. From each animal four radiographs were taken with exposure settings adjusted to achieve sensitivity (S)-values of the system-specific dose indicator of S180 and S360. In a blind study, five observers rated the presentation of anatomical structures (trachea, cranial lung field, sternum, cardiac silhouette, caudal thoracic field) by use of a four-point scale (1 - excellent; 4 - insufficient). Results: Independent of the detector-type and the exposure level applied the mean values of the ratings of the respective image criteria ranged from 1.14 to 1.67. In both systems higher doses related to better rating results. While comparing the detectors on the basis of identical exposure settings the FD demonstrated superior performance. Conclusion and clinical relevance: At the dose levels investigated both detectors reveal an image quality sufficient for the depiction of subtle, low-contrast thoracic structures in cats. Therefore, the detectors can be recommended for practical use in small animal radiology. In both systems a dose reduction of 50% in comparison to the original level (S180) is possible without a substantial loss of information. Because of the superior quantum efficiency the dose saving potential of the FD might be even higher. Alternatively, the higher dose efficiency can be utilised to improve image quality in comparison to the SP-system with identical exposure settings.
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A conventional high-resolution screen-film system was compared with a digital detector system. A total of 20 birds (14 pigeons and six psittacine birds) with an average body mass of 533g were examined in dorsoventral as well as lateral projections. Digital radiographs were acquired with the same mAs as well as half the mAs used for the conventional radiographs. Three criteria and one overall assessment were defined for each of four anatomic regions and assessed by five veterinarians using a score system. Comparison of the ratings was done by visual grading analysis. For the majority of criteria, there was no significant difference regarding image quality between the digital and screen-film projections. However, for certain criteria the quality of the digital images was significantly superior. Using the same mAs as for the conventional radiographs, the humeral joint surfaces and the honeycomb structure of the lung were assessed as superior with the digital imaging system. The tracheal rings and the delineation of the trachea from the surrounding tissue were also superior with the digital system. Assessment of the trabecular structure of the humerus was superior when the full mAs was used compared with the reduced mAs. In conclusion the digital technique is equal or superior to the conventional screen-film high-resolution system for pet birds of a medium size. With some limitations, a dose reduction is possible with the digital system.
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In human medical imaging, the performance of the monitor used for image reporting has a substantial impact on the diagnostic performance of the entire digital system. Our purpose was to compare the display quality of different monitors used in veterinary practice. Two medical-grade gray scale monitors (one cathode-ray tube [CRT], one liquid crystal display [LCD]) and two standard consumer-grade color monitors (one CRT, one LCD) were compared in the ability to display anatomic structures in cats. Radiographs of the stifle joint and the thorax of 30 normal domestic shorthair cats were acquired by use of a storage phosphor system. Two anatomic features of the stifle joint and five anatomic structures of the thorax were evaluated. The two medical-grade monitors had superior display quality compared with standard PC monitors. No differences were seen between the monochrome monitors. In comparison with the color CRT, the ratings of the color LCD were significantly worse. The ranking order was uniform for both the region and the criteria investigated. Differences in monitor luminance, bit depth, and screen size were presumed to be the reasons for the observed varying performance. The observed differences between monitors place an emphasis on the need for guidelines defining minimum requirements for the acceptance of monitors and for quality control in veterinary radiography.
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A conventional high-resolution screen-film-system (film Kodak MIN-R S, screen Kodak MIN-R 2000) was compared to a digital detector system (Varian PaxScan 4030E) for the evaluation of the respiratory tract in snakes. Digital radiographs were taken with the same dose as well as with half the dose used for the conventional radiographs. A total of 20 Burmese pythons (Python molurus) were examined in dorsoventral and lateral projection. Four criteria (three features, one overall assessment) were defined for each of the anatomical structures lung, trachea and spinal column and assessed by five veterinarians in a semi-blinded study using a score system. Comparison of the ratings between the techniques used was done using a visual grading analysis. For the lung, two of the three features as well as the overall assessment were rated significantly superior using the digital system. The trachea was rated significantly superior using the conventional system for the overall assessment as well as for one feature. For the spinal column, the overall assessment was significantly superior using the digital system with the full dose. Conventional radiography as well as digital radiography using half the dose was rated significantly inferior for one feature each. The of the relatively low-contrast respiratory tract. A limiting factor is the demonstration of particularly small structures. Generally, a dose reduction (compared to a conventional high-resolution film-screen-system) is possible for the evaluation of the respiratory system.
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After some initial reluctance, nowadays transition from conventional analogue-to-digital radiographic technique is realized in the vast majority of institutions. The eventual triumph of digital over conventional technique is related to its undoubted advantages with respect to image quality and improved image handling in the context of a picture archiving and communication system. CR represents the older system, which matured over decades and experienced some important recent improvements with respect to dose efficiency and work-flow efficiency that strengthened its position. It represents a very versatile, economically attractive system that is equally suited for integrated systems as well as for cassette-based imaging at the bedside. DR systems offer superb image quality and realistic options for dose reduction based on their high dose efficiency. While for a long time only integrated systems were on the market suited for a large patient throughput, also mobile DR systems became recently available. While for the next years, it is likely that DR and CR systems will coexist, the long term perspective of CR will depend on further innovations with respect to dose efficiency and signal-to-noise characteristics while for DR economical aspects and broader availability of mobile systems will play a role.
Article
LANGUAGE="EN">Summary. The image quality of a radiograph is determined by the local contrast, spatial resolution, latitude and the image noise. The goal of digital processing is to improve the visualisation of pathology by optimising these physical parameters. Processing parameters need to be chosen correctly in order to overcome the inverse relationship between contrast and latitude while producing images that retain a conventional appearance. Unsharp mask filtering (UMF) is a simple technique for improving image quality. This technique, however, suffers from serious drawbacks, such as the suppression of pathologic lesions or artifacts that may simulate pathology. Manufacturers have developed different approaches in order to overcome problems and artifacts derived from this technique.
Article
Electronically readable, large-area x-ray detectors that promise rapid access to the image for diagnosis, improved image quality relative to that of screen-film and storage phosphor-based radiography, reduced patient examination time, a reduction of consumable agents, and possibilities for reduced patient exposure will soon be commercially available for digital radiography.
Article
Image processing has a major impact on image quality and diagnostic performance of digital chest radiographs. Goals of processing are to reduce the dynamic range of the image data to capture the full range of attenuation differences between lungs and mediastinum, to improve the modulation transfer function to optimize spatial resolution, to enhance structural contrast, and to suppress image noise. Image processing comprises look-up table operations and spatial filtering. Look-up table operations allow for automated signal normalization and arbitrary choice of image gradation. The most simple and still widely applied spatial filtering algorithms are based on unsharp masking. Various modifications were introduced for dynamic range reduction and MTF restoration. More elaborate and more effective are multi-scale frequency processing algorithms. They are based on the subdivision of an image in multiple frequency bands according to its structural composition. This allows for a wide range of image manipulations including a size-independent enhancement of low-contrast structures. Principles of the various algorithms will be explained and their impact on image appearance will be illustrated by clinical examples. Optimum and sub-optimum parameter settings are discussed and pitfalls will be explained.
Article
Substantial advances in detector technology characterize digital chest radiography. This article compares the various systems from a radiologist's point of view. Computed radiography (CR) is a well-established system that is robust, has good reproducibility, and is relatively inexpensive. Image quality has been continuously improved in recent years while the physical size of the readout units has been reduced and the throughput increased. CR is the only digital system that can be used for bedside chest radiographs. Improved detector properties and dual reading have made it a dose-efficient system. Although now widely available, a 4K image matrix does not appear to offer a general diagnostic improvement for imaging the chest. New developments with respect to detector composition and readout process can be expected in the future. Direct radiography (DR) is the common name for different technologies that are characterized by a direct readout matrix that covers the whole exposure area. Conversion of x-ray intensity into electric signals can either be direct (selenium-based systems) or indirect (scintillator/photodiode systems). Advantages of DR systems are a high image quality and the potential for dose reduction. The role of selenium radiography (Thoravision) has decreased after the advent of DR systems although this dedicated chest unit offers high image quality at 400 speed acquisition dose. Especially in a PACS environment, CR and DR systems will increasingly substitute for conventional radiography with advantages for CR for bedside chest radiographs and for DR for high-end chest stands.
Article
We sought to evaluate the performance of dual-readout and single-readout computed radiography compared with direct radiography for detecting subtle lung abnormalities with a standard and a low-dose technique. Posteroanterior radiographs of an anthropomorphic chest phantom were obtained with a single-readout storage phosphor radiography system (CRS, pixel size 200 microm), a dual-readout storage phosphor radiography system (CRD, pixel size 100 microm), and a direct detector (DR, pixel size 143 microm) at dose levels of 400 and 800 speed. Ten templates were superimposed to project 4 types of lesions over low- and high-attenuation areas, simulating nodules, micronodules, lines, and patchy opacities. Six radiologists evaluated 60 hard-copy images for the presence or absence of lesions. Statistical significance of differences was evaluated using receiver operating characteristic analysis and analysis of variance. For both low- and high-attenuation areas, CRD (Az = 0.85 and 0.66) was superior to CRS (Az = 0.75 and 0.58) for overall performance and all lesion subtypes (P < 0.05). DR (Az = 0.87 and 0.67) performed slightly better than CRD, being significant only for the detection of micronodules. Acquisition dose significantly affected only the detection of lines and micronodules, whereas the detection of nodules and patchy opacities was not significantly different with reduced exposure, regardless of the system used. The dual-readout CR system significantly outperformed the single-readout CR and almost equaled the performance of DR. Dose reduction was more critical for small-sized lesions (micronodules, lines) than for nodular or patchy opacifications and affected mainly the lesions in high attenuation areas.
Article
For 110 years, x-rays and special x-ray films have been used in medical diagnostics. New developments in the field of x-ray techniques, and especially new computer applications, have led to new imaging techniques which have substantially expanded the spectrum of radiological examinations. In spite of significant technological and medical advances in the field of MRI and multidetector-CT, radiographic images of the lungs, skeleton and organs still comprise up to 80% of the routine radiological workload. The increasing availability of digital detectors has led to the continual replacement of conventional film/screen systems. The inclusion of digital mammography was delayed due to the higher requirements for spatial resolution. For about 2 years, dynamic flat panel detectors have started to replace the image intensifier which has been used in fluoroscopy for 40 years.
Article
Digital radiography has been used in human medical imaging since the 1980s with recent and rapid acceptance into the veterinary profession. Using advanced image capture and computer technology, radiographic images are viewed on a computer monitor. This is advantageous because radiographic images can be adjusted using dedicated computer software to maximize diagnostic image quality. Digital images can be accessed at computer workstations throughout the hospital, instantly retrieved from computer archives, and transmitted via the internet for consultation or case referral. Digital radiographic data can also be incorporated into a hospital information system, making record keeping an entirely paperless process. Digital image acquisition is faster when compared to conventional screen-film radiography, improving workflow and patient throughput. Digital radiography greatly reduces the need for 'retake' radiographs because of wide latitude in exposure factors. Also eliminated are costs associated with radiographic film and x-ray film development. Computed radiography, charged coupled devices, and flat panel detectors are types of digital radiography systems currently available.
Article
Choosing a workstation for daily use in the interpretation of digital radiologic images can be a daunting task. There are numerous products available on the market, but differentiating among them and deciding on what is best for a particular environment can be confusing and frustrating. There is no "one-size-fits-all" workstation, so users must consider a variety of factors when choosing a workstation. This review summarizes the critical elements in a radiology workstation and the characteristics one should be aware of and look for in the selection of a workstation. Issues pertaining to both hardware and software aspects of medical workstations, including interface design, are reviewed, particularly as they may affect the interpretation process.
Article
During the past two decades, digital radiography has supplanted screen-film radiography in many radiology departments. Today, manufacturers provide a variety of digital imaging solutions based on various detector and readout technologies. Digital detectors allow implementation of a fully digital picture archiving and communication system, in which images are stored digitally and are available anytime. Image distribution in hospitals can now be achieved electronically by means of web-based technology with no risk of losing images. Other advantages of digital radiography include higher patient throughput, increased dose efficiency, and the greater dynamic range of digital detectors with possible reduction of radiation exposure to the patient. The future of radiography will be digital, and it behooves radiologists to be familiar with the technical principles, image quality criteria, and radiation exposure issues associated with the various digital radiography systems that are currently available.
Article
This article on digital radiography image processing and display is the second of two articles written as part of an intersociety effort to establish image quality standards for digital and computed radiography. The topic of the other paper is digital radiography image acquisition. The articles were developed collaboratively by the ACR, the American Association of Physicists in Medicine, and the Society for Imaging Informatics in Medicine. Increasingly, medical imaging and patient information are being managed using digital data during acquisition, transmission, storage, display, interpretation, and consultation. The management of data during each of these operations may have an impact on the quality of patient care. These articles describe what is known to improve image quality for digital and computed radiography and to make recommendations on optimal acquisition, processing, and display. The practice of digital radiography is a rapidly evolving technology that will require timely revision of any guidelines and standards.
Article
Radiographic artifacts may mimic a clinical feature, impair image quality, or obscure abnormalities. With the development of digital radiography (DR), a new set of artifacts is introduced. Regardless of the technology, the classic technical errors that occur with film screen radiography still occur using DR. Artifacts created using computed radiography, DR, and incorrect image processing are discussed. Methods for correction of the artifacts are presented.
Article
Use of digital radiography is growing rapidly in veterinary medicine. Two basic digital imaging systems are available, computed radiography (CR) and direct digital radiography (DDR). Computed radiographic detectors use a two-step process for image capture and processing. Image capture is by X-ray sensitive phosphors in the image plate. The image plate reader transforms the latent phosphor image to light photons that are converted to an analog electrical signal. An analog to digital converter is used to digitize the electrical signal before computer analysis. Direct digital detectors provide digital data by direct readout after image capture--a reader unnecessary. Types of DDR detectors are flat panel detectors and charge coupled device (CCD) detectors. Flat panel detectors are composed of layers of semiconductors for image capture with transistor and microscopic circuitry embedded in a pixel array. Direct converting flat panel detectors convert incident X-rays directly into electrical charges. Indirect detectors convert X-rays to visible light, then to electrical charges. All flat panel detectors send a digitized electrical signal to a computer using a direct link. Charge coupled device detectors have a small chip similar to those used in digital cameras. A scintillator first converts X-rays to a light signal that is minified by an optical system before reaching the chip. The chip sends a digital signal directly to a computer. Both CR and DDR provide quality diagnostic images. CR is a mature technology while DDR is an emerging technology.
Article
Solid-state, digital radiography (DR) detectors, designed specifically for standard projection radiography, emerged just before the turn of the millennium. This new generation of digital image detector comprises a thin layer of x-ray absorptive material combined with an electronic active matrix array fabricated in a thin film of hydrogenated amorphous silicon (a-Si:H). DR detectors can offer both efficient (low-dose) x-ray image acquisition plus on-line readout of the latent image as electronic data. To date, solid-state, flat-panel, DR detectors have come in two principal designs, the indirect-conversion (x-ray scintillator-based) and the direct-conversion (x-ray photoconductor-based) types. This review describes the underlying principles and enabling technologies exploited by these designs of detector, and evaluates their physical imaging characteristics, comparing performance both against each other and computed radiography (CR). In standard projection radiography indirect conversion DR detectors currently offer superior physical image quality and dose efficiency compared with direct conversion DR and modern point-scan CR. These conclusions have been confirmed in the findings of clinical evaluations of DR detectors. Future trends in solid-state DR detector technologies are also briefly considered. Salient innovations include WiFi-enabled, portable DR detectors, improvements in x-ray absorber layers and developments in alternative electronic media to a-Si:H.
Article
The basic scheme of modern medical imaging consists of the following steps: (1) data acquisition, (2) data (image) processing, (3) further data processing by the computer graphic system, (4) image display, and finally (5) visual perception and interpretation. Medical monitors represent a forgotten part of the whole chain. The purpose of this review is to present the key facts about the display technologies used today, as well as their characterization and quality assurance.
Digitale radiographie und fluoroskopie: technische grundlagen, abbildungsei-genschaften und anwendungen
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Vergleichende röntgenologische darstellung des respira-tionstraktes von schlangen mittels konventioneller mam-mographietechnik und einem digitalen detektorsystem
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