Photostimulable Storage Phosphor Research Articles

Work flow with digital intraoral radiography: A systematic review

Objective. This systematic review evaluates the six most frequently emphasized advantages of working with digital radiography: less working time, lower radiation dose to the patient, fewer retakes and errors, wider dynamic range, easier access to patient information and easier image storage and communication. Moreover, some clinical aspects and possible disadvantages of digital imaging that were not foreseen at the beginning of the digital era, such as patient discomfort, damage to the receptor, degradation of the image, cross-contamination and viewing conditions, were assessed. Material and methods. The literature search used the PubMed database with no limits and was performed during June to August 2009. Search strategies are described in the text for each of the mentioned tasks. A hand search of task-specific journals supplemented the search strategies. Results. Time seems to be saved when switching from film to digital imaging in dental practice, a dose reduction may not be obtained, retakes and errors may be increased, the dynamic range may be wider with photostimulable storage phosphor (PSP) plates but not with sensors, the effect on patient information has not been well studied and storage and communication create new challenges with regard to handling large files and image compression. In addition, patient discomfort seems to be pronounced with sensors compared with PSP plates and film, the PSP plate may be scratched in clinical use and a two-layer barrier seems to be needed to prevent contamination of the receptor. The type of monitor may not be of major concern if the image is viewed in a room with subdued light. Conclusions. Not all of the predicted advantages with digital compared to film-based radiography hold true in daily clinical work. Of particular interest is the relationship between number of images, retakes and the dose given to the patient.

Advances in Computed Radiography: Dual-Side Readout

Computed radiography is the generic term given to the class of digital radiographic detectors that use photostimulable storage phosphors (PSPs) to absorb incident x-ray energy with the subsequent storage of proportional charge at localized energy traps and subsequent laser-moderated photostimulated luminescence (PSL) to measure and convert the trapped energy into a corresponding digital image. Recent advances in computed radiographic (CR) detector and readout technology have been the introduction of dual-side readout methods, structured PSP detectors, and parallel readout methods [ 1 Cowen A.R. Davies A.G. Kengylics S.M. Advances in computed radiography systems and their physical imaging characteristics. Clin Radiol. 2007; 62: 1132-1141 Abstract Full Text Full Text PDF PubMed Scopus (45) Google Scholar ]. This technical note reviews the characteristics and benefits of dual-side readout methods for CR imaging, which were first introduced with prototype digital mammographic cassette-based systems in about 2001 and subsequently with clinical radiographic systems from 2004 to the present.

The Influence of Tube Potential on Periodontal Bone Level Measurements and Subjective Image Quality Using a Digital Photostimulable Storage Phosphor Sensor

ABSTRACTObjectivesThe purpose of the present study was to determine the measurement accuracy and subjective image quality for periodontal disease diagnosis when using two X-ray tube voltages with a digital photostimulable storage phosphor sensor.Material and MethodsA digital photostimulable storage phosphor (PSP) sensor (Vistascan) and a multipulse X-ray generator (Prostyle Intra) with two tube voltages were used in this study. The front, premolar and molar region of two adult human cadaver skulls jaws were imaged using the X-ray tube at 63 kV and 70 kV, both at 8 mA and decreasing exposure times (160 ms, 120 ms and 80 ms). A standardized exposure protocol containing waxed occlusal keys and an aiming device ensured proper and reproducible beam alignment. Three observers assessed the digital radiographs for 31 selected periodontal bone loss sites. Radiographic measurements were compared to physical measurements (Standard). Subjective ratings of lamina dura, crater defect and furcation involvement visibility, contrast perception and bone quality were also performed.ResultsMultiple regression equation of the variables kV and exposure time demonstrated no significant difference for the periodontal bone level measurements (P > 0.05). In 90.3% and 96.7% of the measurements for 70 kV and 63 kV respectively, deviation was within 1 mm. The subjective ratings produced similar findings in terms of image quality for both tube voltages and the three exposure times.ConclusionsThe results of the present study revealed that tube voltages of 63 kV and 70 kV provided similar accuracy and image quality for periodontal disease diagnosis.

The Influence of Tube Potential on Periodontal Bone Level Measurements and Subjective Image Quality Using a Digital Photostimulable Storage Phosphor Sensor

The purpose of the present study was to determine the measurement accuracy and subjective image quality for periodontal disease diagnosis when using two X-ray tube voltages with a digital photostimulable storage phosphor sensor.

The Influence of Tube Potential on Periodontal Bone Level Measurements and Subjective Image Quality Using a Digital Photostimulable Storage Phosphor Sensor

The purpose of the present study was to determine the measurement accuracy and subjective image quality for periodontal disease diagnosis when using two X-ray tube voltages with a digital photostimulable storage phosphor sensor.

Variable-resolution cone-beam computerized tomography with enhancement filtration compared with intraoral photostimulable phosphor radiography in detection of transverse root fractures in an in vitro model

The aim of this study was to compare the diagnostic accuracy of an intraoral photostimulable storage phosphor (PSP) plate system and cone-beam computerized tomography scanning (CBCT) for detection of experimentally induced transverse root fractures and to evaluate differences between original images and images enhanced with high-pass filters. Sixty-nine extracted human teeth, 34 with root fractures and 35 without, were examined under standardized conditions using an intraoral PSP system (Digora Optime; Soredex). The images were saved in original 8-bit format and in a version sharpened with a high-pass filter. The teeth were examined with CBCT (i-Cat; Imaging Sciences) in 2 resolutions: 0.125 mm and 0.25 mm voxel size. Original images were saved together with images enhanced with 2 high-pass filters, sharpen and angio-sharpen. Six observers scored the presence of a root fracture in all modalities in random order. Sensitivity, specificity, and accuracy [(true positives + true negatives)/all scores] were calculated for each modality and each observer. Differences were estimated by analyzing the binary data, assuming additive effects of observer and modality in a generalized linear model. High-resolution original CBCT images had higher sensitivity (P < .05) than lower-resolution images and PSP images (0.125 mm resolution 87%, 0.25 mm resolution 72%, and PSP 74%). Angio-sharpen-filtered images for both CBCT resolutions had higher sensitivities (P < .02) than the original images (0.125 mm resolution: 95% vs. 87%; 0.25 mm resolution: 81% vs. 72%). There was no significant difference between the lower-resolution CBCT and PSP images. Only small differences in specificity were seen between modalities, and accuracy was higher for high-resolution CBCT than for the other modalities (P < .03). High-resolution i-Cat CBCT images resulted in an increase in sensitivity without jeopardizing specificity for detection of transverse root fractures compared with lower-resolution CBCT images, which were not more accurate than periapical PSP images. The angio-sharpen high-pass filter improved sensitivity in the high-resolution CBCT images in this in vitro model.

An exposure indicator for digital radiography: AAPM Task Group 116 (Executive Summary)

Digital radiographic imaging systems, such as those using photostimulable storage phosphor, amorphous selenium, amorphous silicon, CCD, and MOSFET technology, can produce adequate image quality over a much broader range of exposure levels than that of screen/film imaging systems. In screen/film imaging, the final image brightness and contrast are indicative of over- and underexposure. In digital imaging, brightness and contrast are often determined entirely by digital postprocessing of the acquired image data. Overexposure and underexposures are not readily recognizable. As a result, patient dose has a tendency to gradually increase over time after a department converts from screen/film-based imaging to digital radiographic imaging. The purpose of this report is to recommend a standard indicator which reflects the radiation exposure that is incident on a detector after every exposure event and that reflects the noise levels present in the image data. The intent is to facilitate the production of consistent, high quality digital radiographic images at acceptable patient doses. This should be based not on image optical density or brightness but on feedback regarding the detector exposure provided and actively monitored by the imaging system. A standard beam calibration condition is recommended that is based on RQA5 but uses filtration materials that are commonly available and simple to use. Recommendations on clinical implementation of the indices to control image quality and patient dose are derived from historical tolerance limits and presented as guidelines.

The use of high-resolution digital imaging technology for small diameter K-file length determination in endodontics

To assess the reliability of high resolution intra-oral photostimulable storage phosphor (PSP) and complementary metal-oxide semiconductor (CMOS) imaging systems for working length (WL) assessment of small K-files in narrow and curved root canals. Eleven narrow and curved canals from extracted molars were used as pre-test for sample-size calculation. Nineteen canals from four cadavers were used for endodontic length assessment in the final study. Small K-files (ISO size 6, 8, and 10) were introduced into the canals at prepared length. Digital intra-oral radiographs were obtained using high-resolution Vistascan PSP plates and Sigma M CMOS active pixel sensor with a DC X-ray tube at 70 kV, 7 mA, and 0.16 s. Both image series were assessed with and without use of a dedicated endodontic filter. Three observers measured WLs for comparison to the gold standards of a digital millimeter ruler. Multiple regression analysis of the dependent measurements revealed no significant influence of imaging sensor (PSP or CMOS, p = 0.34) and image processing (p = 0.97). For ISO file size, however, there was a significant difference (p = 0.08) at a level of 10%. Observers mostly underestimated lengths using PSP but overestimated them on CMOS. Almost all radiographic measurements (96-98%) were within 2-mm deviation, while 71% to 82% deviated within 1 mm. Dedicated filtering and sensor type did not influence the outcome of WL determination of small file sizes when using high-resolution imaging sensors. WL determination with ISO file 6 did show a significant difference compared to ISO 8 and 10 but mostly for deviations <1.5 mm.

Synthesis and functionality of the storage phosphor BaFBr:Eu2+

The present paper relates to a method for synthesizing the photostimulable storage phosphor BaFBr:Eu2+ that features high stimulation characteristics for use in image plates. All previous synthesis routes consist of a multistep process whereas the presented route is a one-step synthesis. Starting compounds are BaCO3, NH4F, and NH4Br, as well as EuF3 where the ammonium compounds are highly volatile at temperatures below 300°C. Their reaction products initiate the decomposition of BaCO3 and form BaFBr. The incorporation of F-centers and europium ions occurs at temperature exceeding 550°C. The individual reaction steps are monitored by simultaneous thermal analysis (thermogravimetry/differential thermal analysis) and the gaseous reaction products are detected by in situ mass spectroscopy. Intermediate and final products are characterized by x-ray diffraction techniques to determine the involved phases. Photoluminescence spectra reveal the typical emission peak of Eu2+ accompanied by a redshifted emission band at 470nm, which was assigned to oxygen incorporated into the BaFBr lattice. The synthesized powders exhibit small grain sizes well suited for the use in image plates.

A comparison of older and newer versions of intraoral digital radiography systems: Diagnosing noncavitated proximal carious lesions

The authors conducted a study to compare the accuracy of an older and newer version of two intraoral digital systems in terms of radiographic detection of proximal carious lesions. Under in vitro and standardized conditions, the authors obtained radiographs of 160 noncavitated proximal surfaces using the Digora FMX (Soredex, Tuusula, Finland), the Digora Optime, the Schick CDR (Schick Technologies, Long Island City, N.Y.) and the Schick CDR Wireless (Schick Technologies) systems. Eight observers recorded proximal carious lesions on a five-point confidence scale. The presence of caries was validated histologically. The new digital systems (Digora Optime and Schick CDR Wireless) had significantly higher sensitivities than their predecessors. The authors found no significant differences in specificity among the Digora FMX, Schick CDR and Schick CDR Wireless systems, all of which had a significantly higher specificity than did the Digora Optime system (P < .02). The positive predictive value for the Digora Optime system was affected by its high sensitivity and low specificity, and it was lower than that for the two CDR systems (P < .02). Regarding overall accuracy, the difference between the older and newer versions of the photostimulable storage phosphor and complementary metal oxide semiconductor systems was not statistically significant. However, the authors found more false-positive diagnoses made with the Digora Optime system than with the Digora FMX system. Though the difference in specificities was statistically significant, the authors question whether the difference between the Digora Optime and the other systems is clinically relevant. Therefore, dentists can purchase any of these systems after considering factors other than those evaluated in this study.

How does signal fade on photo-stimulable storage phosphor imaging plates when scanned with a delay and what is the effect on image quality?

The goals of this in vitro study were to determine the effect of signal fading of DenOptix photo-stimulable storage phosphor imaging plates scanned with a delay and to determine the effect on the diagnostic quality of the image. In addition, we sought to correlate signal fading with image spatial resolution and average pixel intensity values. Forty-eight images were obtained of a test specimen apparatus and scanned at 6 delayed time intervals: immediately scanned, 1 hour, 8 hours, 24 hours, 72 hours, and 168 hours. Six general dentists using Vixwin2000 software performed a measuring task to determine the location of an endodontic file tip and root apex. One-way ANOVA with repeated measures was used to determine the effect of signal fading (delayed scan time) on diagnostic image quality and average pixel intensity value. There was no statistically significant difference in diagnostic image quality resulting from signal fading. No difference was observed in spatial resolution of the images. There was a statistically significant difference in the pixel intensity analysis of an 8-step aluminum wedge between immediate scanning and 24-hour delayed scan time. There was an effect of delayed scanning on the average pixel intensity value. However, there was no effect on image quality and raters' ability to perform a clinical identification task. Proprietary software of the DenOptix digital imaging system demonstrates an excellent ability to process a delayed scan time signal and create an image of diagnostic quality.

TU‐C‐224C‐04: Computed Radiography for Helical Tomotherapy Quality Assurance

Purpose: To determine if a CR system that had been used for radiation therapy digital imaging since 2001 could also be used for IMRT quality assurance, and if the system could be used in helical tomotherapy quality assurance. Methods and Materials: The CR system used consisted of a desktop CR reader that utilizes storage phosphor plates, a 650 nm laser diode scanning beam source, and a high luminance light box for plate erasure. The CR plates are made of phosphor, coated with a photostimulable storage phosphor (BaFBR:Eu2+). Three types of dose‐to‐response calibrations were performed 1.) Static square fields; 2.) An IMRT step‐wedge; and 3.) A rotational helical tomotherapy delivery with concentric rings of known dose. All readings were taken with 6 MV beams. Like TLDs, some of the trapped charge carriers in the storage phosphor gradually decay with time. Because of the decay effect, it was important to determine the best time to wait between exposure and scanning. Five helical tomotherapy patients were selected as test cases for the CR dosimetry. Measurements were made in a cylindrical phantom with the CR plate and again with radiographic film. Calibration techniques #1, #2, and #3 were applied to the CR images to determine which was the most appropriate. Dose differences and gamma comparisons were made between the calculated and measured doses. Results: A time and field size dependence was observed. After comparing readings from different time intervals, ranging from one to twenty minutes, it was decided that four minutes was an optimal time to wait between exposure and scanning. Also, gamma for the CR images was significantly worse than the film images taken for the same patient. Conclusions: The field‐size dependences, inconsistencies between calibration techniques, and plate decay make the CR system used in this study non‐usable for IMRT dosimetry.

MO‐B‐I‐618‐02: Overview of Digital Detector Technology

There are various technologies available for the acquisition and display of digital radiographic images. A division has historically existed between “computed radiography” (CR) using photostimulable storage phosphors placed in a cassette holder with subsequent processing in a reader, and “direct radiography” (DR) using a detector with integrated electronics and direct readout and image display. In 2005, these distinctions are less obvious, as some storage phosphor (PSP) devices are automated with direct image display, and some direct flat‐panel devices are used like a portable cassette. Generally speaking, rather than distinguishing digital detectors based on “CR versus DR”, consideration of cassette versus cassetteless digital radiography is perhaps warranted as the technology advances. Besides the venerable cassette‐based PSP detector and plate reader for large field of view imaging (35 × 43 cm), digital detector technologies now available include PSP line‐scan systems in a cassetteless enclosure, optically coupled CCD‐camera systems, fiber‐optically coupled slot‐scan CCD array detectors, indirect x‐ray conversion scintillators and thin‐film‐transistor (TFT) photodiode arrays, and direct x‐ray conversion semiconductors layered on TFT detector arrays. Dedicated digital mammography detectors use similar technologies, with appropriate tuning for resolution and speed. Detective quantum efficiency measurements, equipment specifications, unique acquisition techniques (e.g., digital tomosynthesis and dual energy radiography), PACS/RIS integration and quality control issues are reviewed in the presentation.Educational Objectives:1. To describe digital radiography in general terms, and compare with screen‐film detectors2. To understand acquisition and information flow of digital radiography devices3. To compare cassette and cassetteless operation in terms of resolution, dose efficiency and signal to noise ratio4. To describe new data acquisition and image processing techniques5. To consider PACS/RIS interface and design features for digital radiography

Digital detectors for mammography: the technical challenges

This paper reviews the different techniques available and competing for full-field digital mammography. The detectors are described in their principles: photostimulable storage phosphor plates inserted as a cassette in a conventional mammography unit, dedicated active matrix detectors (i.e., flat-panel, thin-film transistor-based detectors) and scanning systems, using indirect and direct X-ray conversion. The main parameters that characterize the performances of the current systems and influence the quality of digital images are briefly explained: spatial resolution, detective quantum efficiency and modulation transfer function. Overall performances are often the result of compromises in the choice of technology.

Cassette-based digital mammography.

Over the past several years, digital mammography systems have been installed clinically across North America in small but growing numbers. A photostimulable phosphor-based full-field digital mammography image was evaluated in this investigation. Commonly known as computed radiography (CR), its use closely mimics the screen-film mammography paradigm. System performance using modulation transfer function (MTF) and detective quantum efficiency (DQE) metrics show MTF(2.5 mm(-1)) = 0.5, DQE(2.5 mm(-1)) = 0.3, and MTF(5.0 mm(-1)) = 0.2, DQE(5.0 mm(-1)) = 0.05, for a 26 kVp beam, 0.03 mm molybdenum tube filtration, 4.5 cm tissue attenuation, and 15 mR incident exposure to the detector. Slightly higher DQE values were measured at 32 kVp with 0.025 mm rhodium tube filtration. CR mammography advantages include the ability to use existing mammography machines, where multiple rooms can be converted to "digital" operation, which allows overall cost savings compared to integrated digital mammography systems. Chief disadvantages include the labor-intensive handling of the cassettes prior to and after the imaging exam, lack of a direct interface to the x-ray system for recording technique parameters, and relatively slow processing time. Clinical experience in an IRB-approved research trial has suggested that digital mammography with photostimulable storage phosphors and a dedicated CR reader is a viable alternative to conventional screen-film mammography.

The effect of X-ray tube potential on the image quality of PA chest radiographs when using digital image acquisition devices

The rapid development in digital acquisition technology in radiography has not been accompanied by information regarding optimum radiographic technique for use with newly developed systems. Three of the most common technologies for digital radiographic examinations of the chest are flat panel amorphous Silicon Caesium Iodide systems (FPD), amorphous Selenium drums (DSD) and photostimulable storage phosphor computed radiography (CR). Published data on the effect of X-ray beam energy on image quality and patient dose when using these digital image acquisition devices are reviewed. It is important that radiographers are aware of optimum kVp selection for these systems, particularly for the commonly performed chest examination.

Investigation of beam quality for digital chest radiography with RbBr:Tl(+) photostimulable storage phosphors

Beam quality for digital chest radiography in digital radiography systems (DR systems) with RbBr:Tl(+) photostimulable storage phosphors was investigated. Measurements of overall Wiener spectrum (overall WS) and observer performance experiments by means of Scheffé's method of paired comparisons were performed under the same exposure (5.16x10(-7)C/kg) at the X-ray detector of DR systems (sampling distance: 175 micro m, 2,048x2,048 pixels, 12 bits, look-up table: THX2) with a phantom lung and metacryl plates. Overall WS values were indicated to be inferior at higher tube voltages. All of the overall WS values were greater than those of screen film systems (HGM/UR1:S/F) at radiographic density 0.50, which was considered the density of the mediastinum and the area below the diaphragm (low density area), and at radiographic densities 1.00 and 1.50, considered as lung, WS values of S/F were located between the overall WS values of 80 kV and 100 kV, and 120 kV and 140 kV, respectively. Evaluation of visibility including mediastinum, lung, and total were indicated to be superior at the lower tube voltages. In evaluation of the mediastinum, the base image, which was obtained by 100 kV tube voltage (effective energy: 46.0 kV) in this study, was not significant from 90 kV to 110 kV tube voltages (range, +/-10 kV), and in-lung and total evaluations were not significant from 90 kV to 120 kV (range, -10 kV to +20 kV), and from 80 kV to 120 kV (range, +/-20 kV) tube voltages by 99% confidence interval. In conclusion, optimal beam quality for digital chest radiography with RbBr:Tl(+) photostimulable storage phosphors was considered to be less than 110 kV tube voltage (effective energy, 47.9 keV) in 0.1 mm copper and 3.8 mm aluminum total filtration. In this case, the granularity in low-density areas were inferior to those of S/F systems but nearly equal to the middle and high-density areas of chest images, and exposure dose was 14.3% lower than that of the base image obtained by 100 kV (effective energy, 46.0 keV) tube voltage in this study.

RbBr:Tl&lt;sup&gt;+&lt;/sup&gt;輝尽性蛍光体を用いたdigital radiography 装置による胸部X線写真の評価

RbBr:Tl&lt;sup&gt;+&lt;/sup&gt;輝尽性蛍光体を用いたdigital radiography 装置による胸部X線写真の評価

Photostimulable storage phosphor image acquisition: Evaluation of three commercially available state-of-the-art systems

Photostimulable storage phosphor (PSP) image acquisition systems have been available for several years. The technology has had the opportunity to mature; however, there has not been an independent comparison of recently marketed commercial systems. For this study, three computed radiography (CR) systems using PSP technology (Kodak CR System 400 with autoloader [Eastman Kodak, Rochester, NY], Fuji FCR AC-3CS [Fuji Medical Systems, Stamford, CT], and Agfa ADC Compact [Bayer Corp, Ridgefield Park, NJ]) were connected to an IBM RadWorks diagnostic radiology workstation (IBM Corp, White Plains, NY) and evaluated for conformance to their performance specifications using guidance provided in the most recent draft acceptance testing protocol from Task Group No. 10, American Association of Physicists in Medicine. In addition, the physical requirements (e.g., space and power) and connectivity to another manufacturer's diagnostic workstation were examined. X-ray technologist comfort with each PSP imaging system and an assessment by our supporting biomedical equipment maintenance activity of their ability to service each PSP imaging system were also considered.

Principles of digital radiography with large-area, electronically readable detectors: a review of the basics.

The practice of digital radiographic imaging is poised to undergo dramatic change in the very near future owing to a rapid proliferation of electronically readable x-ray detectors. Although self-scanning, direct-readout digital detectors have been in use since the introduction of the charged-coupled device (CCD) almost 30 years ago, recent advances in manufacturing technology have made possible a new generation of large-area, flat-panel detectors with integrated, thin-film transistor readout mechanisms. The excitement surrounding this new technology is based on two factors—the promise of very rapid access to digital images wherever radiography with stationary x-ray equipment is performed and the anticipation of image quality that exceeds that of both screen-film receptors and photostimulable storage phosphor computed radiographic systems because of improvements in x-ray detector technology. As digital radiography continues this rapid evolution, it is likely that radiologists will be inundated with information concerning a wide variety of large-area, flat-panel electronic detectors. Unfortunately, it is also likely that there will be a tendency to think of these devices as equivalent, interchangeable commodities because they will be similar in physical size, appearance, and targeted applications. It must be emphasized, however, that important differences exist among these detectors, and differences in digital image quality among the various systems are inevitable and may be quite large. To minimize confusion, therefore, it is important that radiologists have a working understanding of this emerging technology. In this report, we provide an overview of digital electronic x-ray detectors, including two broad classes of detectors based on thin-film transistor arrays and the older, CCD-based designs. Computed radiographic systems based on photostimulable storage phosphors are omitted from this report because they do not contain integrated readout mechanisms (1). Our goal is to provide a brief review of the basic methods, designs, and materials used in direct-readout radiographic systems and to emphasize important characteristics that may affect system performance and image quality. The advantages and disadvantages of the different detectors, as well as the important factors that should be considered when performing a critical analysis of these new digital imaging systems, are discussed.