Photostimulable Storage Phosphor Research Articles

The Effect of Different Storage Conditions and Scan Delays on the Mean Gray Value (MGV) on Photostimulable Storage Phosphor (PSP) Plate Images

Amaç: Bu çalışmanın amacı, ışıkla uyarılabilen fosfor (Photostimulable Storage Phosphor, PSP) plakalarının ışınlama-tarama süreçleri arasındaki farklı tarama gecikmeleri (bekletme süresi) ve saklama koşullarının görüntülerindeki Ortalama Gri Değer (OGD) değişimine etkisini değerlendirmekti. Gereç ve Yöntem: Saklama koşuluna göre oluşturulan dört grupta [Tek Kılıf Aydınlık (TKA), Tek Kılıf Karanlık (TKK), Tek Kılıf Karton Aydınlık (TKKA), Tek Kılıf Karton Karanlık (TKKK)] farklı bekletme sürelerinde toplam 40 görüntü elde edildi. ImageJ (National Institutes of Health, Bethesda, MD) programı ile görüntülerin OGD’leri ölçüldü. Saklama koşullarını karşılaştırmak için tek yönlü, bekletme sürelerini karşılaştırmak için iki yönlü tekrarlı ölçümlü ANOVA testleri kullanıldı. Her bir gruptaki bekletme süreleri ile 0 dk. (altın standart) OGD’lerin karşılaştırılması için eşleştirilmiş örneklemler t-testi uygulandı. p<0.05 istatistiksel olarak anlamlı kabul edildi. BULGULAR: On dk. ile altın standart arasındaki OGD farkı sadece TKA grubunda istatistiksel olarak anlamlıydı (p<0.05). Herhangi bir bekletme süresinde, saklama koşulları OGD’leri arasında istatistiksel olarak anlamlı fark yoktu (p>0.05). Altın standart dışındaki diğer bekletme süreleri karşılaştırıldığında, 24 saat bekletme süresi ile diğer bekletme süreleri OGD’leri arasında istatistiksel olarak anlamlı fark vardı (p<0.05). Sonuç: Plakların ışınlama sonrası karanlık ortamda ve karton koruyucu içinde 10 dk.’yı geçmeyen bekletme süresi ile bekletilmesinin OGD’ye etkisi önemsizdi. Sadece plastik bariyerde ve 24 saat sürede bekletilen plakların görüntülerdeki OGD artışı dikkat çekiciydi.

Hypochlorous acid and white vinegar: Artifact-free COVID-19 disinfection options for photostimulable storage phosphor plates

To examine the artifacts on intraoral photostimulable storage phosphor (PSP) plate images caused by 3 different disinfectants that are effective against pathogens including SARS-CoV-2. Nine new PSP plates, to be wiped with hypochlorous acid (HOCl) in group A, alcohol in group B, and white vinegar in group C, were distributed in 3 groups. Twelve images of each PSP plate with increasing numbers of wipes were examined for artifacts. The comparisons were evaluated by Kruskal-Wallis and post hoc tests. The reliability of the measurements was evaluated using the intraclass correlation coefficient (ICC) and Cohen kappa statistic. Artifacts were observed only on group B images. In terms of artifact scores, the difference between group A and group C was not statistically significant (P > .05), whereas group B artifact scores were significantly higher than group A and group C (P < .05). Intraobserver reliability was perfect (ICC and kappa of 1.0) and interobserver reliability was considered excellent (ICC=0.985) or almost perfect (kappa=0.956). HOCl and white vinegar can be alternative disinfection options for PSP plates tested in this study. Unlike alcohol, they did not produce artifacts. Additional research evaluating their effects on image quality is needed to determine if they are appropriate for disinfection.

Artificial intelligence for detection of periapical lesions on intraoral radiographs: Comparison between convolutional neural networks and human observers

The aim of this study was to compare the diagnostic performance of convolutional neural networks (CNNs) with the performance of human observers for the detection of simulated periapical lesions on periapical radiographs. Ten sockets were prepared in bovine ribs. Periapical defects of 3 sizes were sequentially created. Periapical radiographs were acquired of each socket with no lesion and with each lesion size with a photostimulable storage phosphor system. Radiographs were evaluated with no filter and with 6 image filter settings. A CNN architecture was set up using Keras-TensorFlow. Separate CNNs were evaluated for randomly sampled training/validation data and for data split up by socket (5-fold cross-validation) and filter (7-fold cross-validation). CNN performance on validation data was compared with that of 3 oral radiologists for sensitivity, specificity, and area under the receiver operating characteristic curve (ROC-AUC). Using random sampling, the CNN showed perfect accuracy for the validation data. When data were split up by socket, the mean sensitivity, specificity, and ROC-AUC values were 0.79, 0.88, and 0.86, respectively; when split up by filter, they were 0.87, 0.98, and 0.93, respectively. For radiologists, the values were 0.58, 0.83, and 0.75, respectively. CNNs show promise in periapical lesion detection. The pretrained CNN model yielded in this study can be used for further training on larger samples and/or clinical radiographs.

Benefits of using a photostimulable phosphor plate protective device.

To develop and test a protective device (PD) to increase the resistance of photostimulable storage phosphor (PSP) plate to compressive load, and assess the resulting image quality. Two prototypes, polyvinylchloride sheets of 0.3 mm and 0.7 mm each, were developed for PSP plate size 2. The resistance to compressive load was tested using eight new PSPs divided into four test groups: (1) PSP, (2) PSP and paperboard protector, (3) PSP and 0.3 mm PD, and (4) PSP and 0.7 mm PD. The resulting images were analyzed by three oral radiologists, based on the consensus for image artifacts. Additionally, the objective image quality test was performed with four new PSPs, using an 8-step wedge aluminum scale. The mean gray values and standard deviation were measured in a total of 240 images, and the data were analyzed using analysis of variance with Bonferroni post-hoc test. Artifacts were seen in the PSP control group starting at 40 n, and at 150 n, 175 n and 300 n in 0.3 mm PD, paperboard protector and 0.7 mm PD, respectively. Although there was no statistical difference among groups, there were differences between exposure times (0.06-0.25 s, 0.06-0.40 s, and 0.10-0.40 s). Scanning resolution of 20 lp/mm showed higher mean gray value than 25 and 40 lp/mm (p < 0.05). The developed PDs improved the PSP resistance to compressive forces, with low interference on the pixel gray values, regardless of exposure time and spatial resolution. Nevertheless, the 0.7 mm PD could withstand the maximum compressive load.

Influence of VistaScan image enhancement filters on diagnosis of simulated periapical lesions on intraoral radiographs

To evaluate whether image enhancement filters of VistaScan system improve the diagnostic accuracy of simulated periapical lesions. 10 sockets were prepared on bovine ribs to fit a bovine tooth. Bone defects were created and successively enlarged providing four groups (n = 10): Group 0, absence of lesions; Group 1, periapical lesions with 1.6  mm in diameter; Group 2, with 1.8  mm in diameter; and Group 3, with 2.1  mm in diameter. Periapical radiographs were taken using a photostimulable storage phosphor plate and DBSWIN software. VistaScan filters were applied and the images were allocated into seven groups: Nonfiltered, Fine, Caries 1, Caries 2, Endodontic, Periodontal and Noise Reduction. All the 280 images were assessed about the presence or absence of periapical lesions. Pixel intensities standard deviation were compared between nonfiltered and filtered images. Two-Way Analysis of Variance and the post hoc Tukey's test were used to compare area under the ROC curve, sensitivity and specificity. VistaScan filters showed no significant difference for area under receiver operating characteristic curve (p = 0.124), sensitivity (p = 0.835) and specificity (p = 0.832). Area under receiver operating characteristic curve (p = 0.000) and sensitivity (p = 0.000) in 2.1  mm lesions size were significantly higher than in 1.6  mm and 1.8  mm lesions size. Pixel intensities standard deviation was significantly changed in the filtered images compared to nonfiltered ones (p < 0.01), except for Fine in the bone region (p > 0.05). VistaScan enhancement filters do not influence the diagnostic accuracy of simulated periapical lesions. On the other hand, larger lesions were more frequently detected. The filters change the pixel intensities reducing or intensifying the differences between similar regions.

Diagnostic accuracy of a charge-coupled device and a photostimulable phosphor plate in detection of non-cavitated proximal caries

Objective: The aim of this study was to compare the diagnostic accuracy of two direct digital radiography systems: the charge-coupled device (CCD) XIOS XG Sirona® and the photostimulable storage phosphor (PSP) VistaScan DürrDental®, in the detection of non-cavitated proximal caries lesions. Materials and methods: in this experimental and cross-sectional study 112 proximal surfaces from 27 molars and 31 premolars with or without proximal caries lesions were evaluated and randomly allocated in a study unit. Bitewing radiographs were acquired with a CCD XIOS XG and with the PSP VistaScan. A single X-ray unit was used for both systems. Radiographic images were assessed independently by two calibrated radiologists. Histological evaluation on a stereomicroscope was used as gold standard. Results: Sensitivity values were found to be 0.35 for CCD and 0.31 for PSP. Specificity values were found to be similar for both systems (0.867). Az values showed a low diagnostic accuracy for both sensors: 0.61 for CCD and 0.59 for PSP, no statistical difference was found between these two values (p=0.78). Conclusion: Both digital radiology systems have a high diagnostic accuracy to detect sound surfaces but low diagnostic accuracy to detect proximal carious lesions.

Photostimulable Storage Phosphor Materials and Their Application to Radiation Monitoring

Photostimulable Storage Phosphor Materials and Their Application to Radiation Monitoring

Effectiveness of Periapical Radiography Versus Cone Beam Computed Tomography with Different Kilovoltage Settings in the Detection of Chemically Created Peri-implant Bone Defects: An In Vitro Study.

To determine the effectiveness of cone beam computed tomography (CBCT) images obtained with different kilovoltage settings compared with intraoral periapical photostimulable storage phosphor (PSP) plate images in the detection of chemically created peri-implant defects utilizing a bovine rib bone model in vitro. After placing 80 implants in bovine ribs, peri-implant circumferential bone defects of different sizes were created with 70% perchloric acid. CBCT images (3D Accuitomo 170) were acquired at 90 and 75 kVp, and intraoral periapical images were acquired using a PSP system (Carestream KODAK, CS 7600). Using a 5-point Likert scale, two oral and maxillofacial radiologists (OMR) and two oral and maxillofacial surgeons (OMS) evaluated the likelihood of a bone defect being absent or present. The kappa statistic was used to compare observer agreement, and area under the curve values were compared using analysis of variance and the post hoc Tukey test. Significance was set at P ≤ .05. PSP reliability ranged from discordance to slight for small defects and fair to moderate for larger defects. For CBCT, OMRs had good agreement for defects using 90 kVp, and slight to fair using 75 kVp. Agreement for OMS observations was fair for 75 kVp, and varied from slight to good for 90 kVp. Small lesions were detected more effectively by CBCT than by PSP, and larger lesions were detected more effectively by CBCT at 90 kVp than by CBCT at 75 kVp or by PSP. CBCT imaging at 90 kVp was associated with a significantly higher rate of detection of both small and large chemically simulated bone defects than PSP or CBCT at 75 kVp. CBCT imaging at 75 kVp proved better than PSP for the detection of small defects.

Aluminum Nitride Ceramic as an Optically Stimulable Luminescence Dosimeter Plate

Photostimulable storage phosphors have been used in a wide range of applications including radiation measurements in one- and two-dimensional spaces, called point dosimetry and radiography. In this work, we report that an aluminum nitride (AlN) ceramic plate, which is practically used as a heat sink (SHAPAL®, Tokuyama Corp., Yamaguchi, Japan), shows good optically-stimulated luminescence (OSL) properties with sufficiently large signal and capability for imaging applications, and we have characterized the AlN plate for OSL applications. Upon interaction with X-rays, the sample color turns yellowish, due to a radiation-induced photoabsorption band in the UV-blue range below ~500 nm. After irradiating the sample with X-rays, an intense OSL emission can be observed in the UV (360 nm) spectral region during stimulation by red light. Although our measurement setup is not optimized, dose detection was confirmed as low as ~3 mGy to over 20 Gy. Furthermore, we have successfully demonstrated that the SHAPAL® AlN ceramic plate has great potential to be used as an imaging plate in radiography.

輝尽性蛍光体板を用いた Winston-Lutzテスト自動解析法の開発

Stereotactic radiosurgery (SRS) and radiotherapy (SRT) are intricate techniques that deliver a highly precise radiation dose to a localized target, usually a tumor. At our hospital, we perform SRS and SRT on brain tumors using a linear accelerator (linac) mounted with an external micro multi-leaf system. The Task Group TG-142 Report by the American Association of Physicists in Medicine recommends the coincidence of the radiation and mechanical isocenter to be within ±1 mm. The Winston-Lutz test is commonly used to verify the linac isocenter position: it has the advantages of being a simple method that uses a film or electronic portal imaging device (EPID). However, the film method requires a higher radiation dose, which makes it more time-consuming than the EPID method, and the results are highly dependent on the skills of the observer. The EPID method has certain advantages over the film method, but it has low resolution and can only be used for a few combinations of gantry and couch angles. This prompted us to develop an in-house-designed radiation receptor system based on digital radiography, using a photostimulable storage phosphor and automated analysis algorithm for Winston-Lutz test images using a template-matching technique based on cross-correlation coefficients. Our proposed method shows a maximum average absolute error of 0.222 mm (less than 2 pixels) for 0.5 mm and 1.0 mm displacement from the isocenter toward the inline and crossline directions. Our proposed method is thus potentially useful for verifying the Linac isocenter position with a small error and good reproducibility, as demonstrated by improved accuracy of evaluation.

Mechanochemical synthesis of nanocrystalline BaFCl:Sm3+ storage phosphor by ball milling

The mechanochemical preparation of nanocrystalline BaFCl:Sm3+ by ball milling BaCl2 or BaCl2·2H2O, BaF2 and SmF3 is reported. Photoluminescence shows predominantly Sm3+4GJ–6HJ luminescence whereas cathodoluminescence comprises of both the Sm3+4GJ–6HJ and Sm2+5DJ–7FJ emissions. In comparison with the co-precipitated phosphor, the storage efficiency, as measured by the conversion of Sm3+ to Sm2+ upon X-irradiation, is 15 and 6 times lower for the samples prepared by using BaCl2 or BaCl2·2H2O, respectively. Importantly, the present result points to the possibility of preparing the entire class of photoluminescent and photostimulable storage phosphors BaFX:RE2+/3+ (X=Cl, Br, I; RE=rare earth element) by ball milling.

Photostimulated near-infrared persistent luminescence as a new optical read-out from Cr³⁺-doped LiGa₅O₈.

In conventional photostimulable storage phosphors, the optical information written by x-ray or ultraviolet irradiation is usually read out as a visible photostimulated luminescence (PSL) signal under the stimulation of a low-energy light with appropriate wavelength. Unlike the transient PSL, here we report a new optical read-out form, photostimulated persistent luminescence (PSPL) in the near-infrared (NIR), from a Cr3+-doped LiGa5O8 NIR persistent phosphor exhibiting a super-long NIR persistent luminescence of more than 1,000 h. An intense PSPL signal peaking at 716 nm can be repeatedly obtained in a period of more than 1,000 h when an ultraviolet-light (250–360 nm) pre-irradiated LiGa5O8:Cr3+ phosphor is repeatedly stimulated with a visible light or a NIR light. The LiGa5O8:Cr3+ phosphor has promising applications in optical information storage, night-vision surveillance, and in vivo bio-imaging.

Advantages of fitting contrast curves using logistic function: a technical note

The aim of this article is to demonstrate how the contrast properties of an imaging system can be ideally fitted with the use of stripe patterns and the logistic function. Stripe patterns with defined amounts of line pairs (lp/mm) per mm (10-20 lp/mm) were recorded with the use of digital photostimulable storage phosphor. Scan data and normalized image data were analyzed with the use of ImageJ and MatLab to calculate different contrast curves. For original scan data, the goodness of fit was 0.0000019 (sum of squared error [SSE]). The R-square was 0.9998. For normalized data the goodness of fit was 0.0007 (SSE) and the R-square 0.998. An amount of 50% contrast could be calculated to be found on 11.67 lp/mm in normalized images. This article addresses a potentially new approach to compare digital x-ray modalities using a direct assessment of a known technical target.

Performance of a photostimulable storage phosphor digital system with or without the sharpen filter and cone beam CT for detecting approximal enamel subsurface demineralization

The aim of this study was to assess the performance of photostimulable storage phosphor (PSP) radiographs with or without using the sharpen filter and cone beam CT (CBCT) for detecting enamel subsurface demineralization. Enamel subsurface demineralization was induced on one of the approximal surfaces of 120 sound human teeth. Standardized images of all teeth were acquired after the demineralization phase using the Digora(®) Optime (Orion Corp./Soredex, Helsinki, Finland) (PSP) and the i-CAT™ (Imaging Sciences International, Hatfield, PA) (CBCT) systems. Three calibrated observers interpreted the images using a five-point scale (1, demineralization definitely absent; 2, demineralization probably absent; 3, unsure; 4, demineralization probably present; and 5, demineralization definitely present). Diagnoses were validated by cross-sectional microhardness profiling in the test areas of the approximal surfaces. Interobserver agreement was analysed using kappa statistics. Accuracy was estimated by the areas under the receiver operating characteristic curves (Az), which were compared using the Kruskal-Wallis test (α = 5%). Interobserver agreement was higher for CBCT (κ = 0.7-0.8), followed by sharpen-filtered (κ = 0.6-0.7) and original (κ = 0.5-0.6) images. CBCT presented the highest accuracy value (Az = 0.897) compared with the original (Az = 0.792) and sharpen-filtered (Az = 0.712) images. However, no statistical differences were observed between the imaging modalities (p = 0.0794). It can be concluded that PSP radiographs with or without using the sharpen filter and the CBCT images may be useful adjuncts for detecting subtle approximal enamel demineralization.

Development of a micro-size dosimeter using an optical fiber probe based on photostimulable phosphorescence

Abstract We have developed a novel micro-size dosimeter using an optical fiber probe coupled with a photostimulable storage phosphor, such as BaFBr:Eu 2+ . Our micro-size dosimeter is based on the concept in which the radiation dose response is temporally compressed by using integrating-type dosimeter elements, such as a photostimulable storage phosphor, and the signal-to-noise ratio is improved to downsize the dosimeter probe. We fabricate the prototype dosimeter probe which has the detectable volume of 100 μm thick and 400 μm diameter and the outer diameter of 900 μm. The lower limit of detectable dose, which is defined as three times the noise level, is evaluated to be 0.9 mGy. This value is much smaller than the typical irradiation dose (a few Gy per treatment) in the radiotherapy. We, therefore, conclude that the proposed micro-size dosimeter can be a promising candidate of in-vivo and on-line dose monitor in the radiotherapy.

ACR–AAPM–SIIM Practice Guideline for Digital Radiography

This guideline was developed collaboratively by the American College of Radiology (ACR), the American Association of Physicists in Medicine (AAPM), and the Society for Imaging Informatics in Medicine (SIIM). Increasingly, medical imaging and patient information are being managed using digital data during acquisition, transmission, storage, display, interpretation, and consultation. The management of these data during each of these operations may have an impact on the quality of patient care. “CR” and “DR” are the commonly used terms for digital radiography detectors. CR is the acronym for computed radiography, and DR is an acronym for digital radiography. CR uses a photostimulable storage phosphor that stores the latent image, which is subsequently read out using a stimulating laser beam. It can be easily adapted to a cassette-based system analogous to that used in screen-film (SF) radiography. Historically, the acronym DR has been used to describe a flat-panel digital X-ray imaging system that reads the transmitted X-ray signal immediately after exposure with the detector in place. Generically, the term CR is applied to passive detector systems, while the term DR is applied to active detectors. This guideline is applicable to the practice of digital radiography. It defines motivations, qualifications of personnel, equipment guidelines, data manipulation and management, and quality control (QC) and quality improvement procedures for the use of digital radiography that should result in high-quality radiological patient care. In all cases for which an ACR practice guideline or technical standard exists for the modality being used or the specific examination being performed, that guideline or standard will continue to apply when digital image data management systems are used.

The visibility of secondary caries under bonding agents with two different imaging modalities

This study investigated the visibility of secondary caries lesions associated with two different adhesive systems of composite restorations (Optibond Solo Plus and Clearfil SE Bond) using a conventional dental x-ray film (Kodak D Speed) and a digital system (Digora) based on storage phosphor-plate technology for detection of secondary caries. For imaging techniques and adhesive systems, false positive scores were high. Intraobserver agreements ranged between 0.432 and 0.778, while interobserver agreements for the readings ranged 0.321-0.731 and 0.411-0.701, respectively. No statistical difference was found between the Az (area under curve) values obtained from PSP (photostimulable storage phosphor) and film images with the exception of the second observer's first reading for total etch adhesive system (Optibond Solo Plus) (p=0.0258). Furthermore, no statistical difference was found between both the bonding systems assessed (p>0.05). Adhesive materials should also have enough radiopacity to facilitate diagnosis of secondary caries.

Accuracy of scanography using storage phosphor plate systems and film for assessment of mandibular third molars

The aim of this study was to compare the diagnostic accuracy of two digital photostimulable storage phosphor (PSP) systems and film for assessment of mandibular third molars before surgery. 110 patients were referred to have both their mandibular third molars removed. Each patient underwent a radiographic examination with scanography using either Digora (Soredex, Helsinki, Finland) and film or VistaScan (Dürr Dental, Beitigheim-Bissingen, Germany) and film in a randomized paired design. Two observers examined the following variables on the scanograms: bone coverage, angulation of the tooth in the bone, number of roots, root morphology and the relationship to the mandibular canal. In 75 of the pairs (Digora/film pair = 38 and Vista/film pair = 37) both third molars were eventually removed. During and after surgery the same variables were assessed, which served as reference standard for the radiographic assessments. The Wilcoxon signed-rank test tested differences in accuracy (radiographic compared with surgical findings) between Digora/film and between Vista/film. There was no statistically significant difference between the diagnostic accuracy of film and either of the two digital receptors for assessment of mandibular third molars before surgery (P > 0.05), although Digora obtained a higher accuracy than film. Scanography is a valuable method for examination of mandibular third molars before removal and the PSP digital receptors in this study were equal to film for this purpose.

A comprehensive in vitro study of image accuracy and quality for periodontal diagnosis. PART 1: The influence of X-ray generator on periodontal measurements using conventional and digital receptors

The aim of this study was the determination of image accuracy and quality for periodontal diagnosis using various X-ray generators with conventional and digital radiographs. Thirty-one in vitro periodontal defects were evaluated on intraoral conventional (E-, F/E-speed) and digital images (three indirect, two direct sensors). Standardised radiographs were made with an alternating current (AC), a high-frequency (HF) and a direct current (DC) X-ray unit at rising exposure times (20-160ms with 20-ms interval) with a constant kV of 70. Three observers assessed bone levels for comparison to the gold standard. Lamina dura, contrast, trabecularisation, crater and furcation involvements were evaluated. Irrespective X-ray generator-type, measurement deviations increased at higher exposure times for solid-state, but decreased for photostimulable storage phosphor (PSP) systems. Accuracy for HF or DC was significantly higher than AC (p < 0.0001), especially at low exposure times. At 0.5- to 1-mm clinical deviation, 27-53% and 32-55% dose savings were demonstrated when using HF or DC generators compared to AC, but only for PSP. No savings were found for solid-state sensors, indicating their higher sensitivity. The use of digital sensors compared to film allowed 15-90% dose savings using the AC tube, whilst solid-state sensors allowed approximately 50% savings compared to PSP, depending on tube type and threshold level.. Accuracy of periodontal diagnosis increases when using HF or DC generators and/or digital receptors with adequate diagnostic information at lower exposure times.

Rating the extent of surface scratches on photostimulable storage phosphor plates in a dental school environment

The aims of this study were (1) to subjectively quantify the degree of scratching and smudging that had taken place in the junior clinic in the 9 months following the implementation of digital radiology; (2) to compare the findings with a previously published report; and (3) to identify areas in the protocol and training that can be refined to minimize future scratching and smudging. Seven sets of blank clinical photostimulable storage phosphor (PSP) plates were scanned after exposing them at 65 kV and 7 mA for 0.80 s. Scanned plates were lightly wiped with a soft cloth and alcohol, repackaged in plastic sleeves, re-exposed and rescanned. The two sets of resulting images were subjectively rated independently by two investigators for artefacts and placed in five categories. Of all the images, approximately 75% were rated in the top 3 categories (most readable), leaving 17% and 8% in the poor and unsatisfactory categories, respectively. Mean rated values of the two image sets (before and after wiping) were not statistically different, but ratings slightly improved after cleaning the plates. Wiping all plates to remove surface contamination may not always be necessary or desirable. Systems that are designed to minimize handling of the plates may help minimize scratching of them.