Photostimulable Phosphor Imaging Plate Research Articles

Relationship between image information content and observer performance in digital intraoral radiography.

This study conducted a receiver operating characteristic (ROC) analysis by applying improved cluster signal-to-noise (CSN) analysis to digital intraoral radiographs and develop an observer-free method of analyzing image quality related to the observer performance in the detection task. Two aluminum step phantoms with a thickness interval of 1.0mm were used for this study. One phantom had holes of increasing depth (from 0.05 to 0.35mm) and the other had no holes. Phantom images were obtained under various exposure dose and image capture modes using a dental X-ray unit, a photostimulable phosphor imaging plate, and scanner system. These phantom images were analyzed using the FindFoci plugin in ImageJ software. Subsequently, true positive rates (TPRs) and false positive rates (FPRs) were calculated by analyzing phantom images with and without holes. We constructed ROC curves by plotting the TPRs against the FPRs and calculated the area under the ROC curve (AUC). Using the same phantom images with holes, eight observers assessed the number of detectable holes. Correlations between observer detection performance and AUC values were evaluated. AUC values increased as the exposure dose increased and showed different tendencies depending on the image capture mode. The AUC values showed a high correlation with observer detection performance (r = 0.76). AUC values obtained from CSN analysis reflect image quality and replace the observer detection performance test of image quality.

Effect of differences in pixel size on image characteristics of digital intraoral radiographic systems: a physical and visual evaluation.

To quantify and validate the effect of pixel size on a digital intraoral radiographic system according to International Electrotechnical Commission standards through physical and visual evaluations. The digital intraoral radiographic system used was the photostimulable phosphor imaging plate and scanner system. The system had three image capture modes: high-speed (HS), high-resolution (HR), and super high-resolution (SHR) with different pixels. The physical characteristics of the system were evaluated using presampled modulation transfer function (MTF) and the normalized noise power spectrum (NNPS). An aluminum (Al) step phantom with different depths of holes was used to acquire images under various exposure conditions. The average number of perceptible holes from all steps was plotted against each exposure dose. The results were compared to analyze the effects of pixel size on image quality of intraoral radiographs. The MTF was slightly higher with SHR than with HR and HS. The NNPS with SHR showed about a 40% decrease in magnitude compared to HS. The total number of perceptible holes in the Al step phantom was higher with SHR than with HS and HR in all exposure conditions. The MTF and NNPS obtained with different pixel size could be quantified by physical evaluation, and the differences were visually validated with Al step phantom. The SHR mode has the potential to decrease the radiation dose without compromising the image quality.

OA083] Toward 4d micro-CT and radiotherapy of small animals using all-optical, ultrashort X-ray sources: feasibility study and preliminary experimental results

Purpose All-optical, laser-driven X/gamma-ray sources, based on the primary electron acceleration via the Laser WakeField Acceleration (LWFA) process, have now entered a mature phase in terms of beam parameters, shot-to-shot stability, and reliability, so as to be considered as promising tools in medical physics. The high electron acceleration gradient results in the possibility of accelerating electrons up to the 100s MeV range over very short distances and thus opening the way to the generation of high energy photons using “table-top” machines. The PRELUDE (PREclinical Laser-based Ultrafast Diagnostics and therapy) project is ongoing, as a collaboration among different Italian Institutions aimed at studying the application of a laser-driven X-ray source for 4D micro-CT and radiotherapy of small animals. Methods As a first step, the exploitation of a Bremsstrahlung source driven by a LWFA, plasma-based accelerator is investigated, both theoretically and experimentally. The preliminary experimental results focused on characterizing the photon source, based on a 10TW ultrashort laser system for micro-CT of small animals is discussed. Issues related to both the primary electron acceleration and the generation of secondary photons via the Bremsstrahlung process will be discussed, including both numerical and experimental results. Results The X-ray spectrum, beam intensity, e- contamination and photon dosimetry have been simulated using the GEANT4 toolkit on top of experimental measurements of the e- spectrum obtained using our setup and numerical estimations of the accelerated charge per pulse. Proof-of-principle radiographic images of physical phantoms obtained with photostimulable phosphor image plates are presented. Conclusions We presented a system for small animal 4D-CT and radiotherapy based on a laser-driven X-ray source. The results of a theoretical and numerical study of a 4D micro-CT device based on a more advanced all-optical X-ray source based on Thomson scattering will be presented.

Measurement of activity distribution using photostimulable phosphor imaging plates in decommissioned 10 MV medical linear accelerator.

Photonuclear reactions generate neutrons in the head of the linear accelerator. Therefore, some parts of the linear accelerator can become activated. Such activated materials must be handled as radioactive waste. The authors attempted to investigate the distribution of induced radioactivity using photostimulable phosphor imaging plates. Autoradiographs were produced from some parts of the linear accelerator (the target, upper jaw, multileaf collimator and shielding). The levels of induced radioactivity were confirmed to be non-uniform within each part from the autoradiographs. The method was a simple and highly sensitive approach to evaluating the relative degree of activation of the linear accelerators, so that appropriate materials management procedures can be carried out.

Comparison of the accuracy of cone-beam computed tomography, photostimulable phosphor imaging plate, charge coupled device, and conventional intraoral radiography in the diagnosis of internal root resorption: an in vitro study

Objective: Various radiographic methods are used to identify the internal root resorption. The aim of this study was to assess and compare the diagnostic accuracy of cone-beam computed tomography (CBCT), photostimulable phosphor (PSP) imaging plate, charge coupled device (CCD), and conventional intraoral radiography (CIR), for internal root resorption.Methods: This experimental study was conducted in Hamadan in 2012. Fifty seven carries-free anterior teeth were divided into three intervention groups of 15 teeth and one control group of 12 teeth. Teeth were split into two parts using a disk. Cavities of 0.5, 1 and 1.5 mm in depth were created in root canal of teeth to simulate internal root resorption artificially. Finally, the teeth fragments were fused. All teeth were examined with four different procedures and the results were compared with known simulated internal root resorption as the gold standard to determine the sensitivity and specificity of the procedures.Results: The sensitivity of CBCT, PSP, CCD, and CIR for diagnosis internal root resorption of 0.5 mm in depth was 93%, 73%, 60%, and 53% respectively. The sensitivity of all four procedures for diagnosis of internal root resorption with 1 and 1.5 mm in depth was the same and equal to 100%. Specificity of the four radiology procedures for diagnosis of internal root resorption of any depth was 100%, 100%, 83% and 75% respectively.Conclusion: CBCT provides the most accurate information on the depth and location of root resorption followed by the PSP and CCD respectively. Accordingly, conventional intraoral radiography was the least accurate procedure.

Integrating Photo–Stimulable Phosphor Plates into Dental and Dental Hygiene Radiography Curricula

It is not known whether the integration of photo-stimulable phosphor (PSP) plates into dental and dental hygiene curricula creates unique learning challenges for students. The purpose of this two-year study was to determine if dental hygiene students had more and/or different types of errors when using PSP plates compared to film and whether the PSP imaging plates had any particular characteristics that needed to be addressed in the learning process. Fifty-nine first-year dental hygiene students at one Canadian dental school were randomly assigned to two groups (PSP or film) before exposing their initial full mouth series on a teaching manikin using the parallel technique. The principal investigator determined the number and types of errors based on a specific set of performance criteria. The two groups (PSP vs. film) were compared for total number and type of errors made. Results of the study indicated the difference in the total number of errors made using PSP or film was not statistically significant; however, there was a difference in the types of errors made, with the PSP group having more horizontal errors than the film group. In addition, the study identified a number of unique characteristics of the PSP plates that required special consideration for teaching this technology.

Comparison of cone-beam computed tomography with intraoral photostimulable phosphor imaging plate for diagnosis of endodontic complications: a simulation study

With great interest we read the article by Eskandarloo et al.,1 entitled “Comparison of cone-beam computed tomography with intraoral photostimulable phosphor imaging plate for diagnosis of endodontic complications: a simulation study” in Oral Surg Oral Med Oral Pathol Oral Radiol. This study employed a method very similar to a study performed by our group.2 We congratulate the authors for their work but we would also like to discuss the topic with some of our observations.

Comparison of cone-beam computed tomography with intraoral photostimulable phosphor imaging plate for diagnosis of endodontic complications: a simulation study

The objective of this study was to compare the sensitivity and reliability of cone-beam computed tomography (CBCT) and intraoral photostimulable phosphor (PSP) imaging plate for diagnosis of endodontic complications. Seventy-two human mandibular teeth were used, including 24 incisors/canines, 24 premolars, and 24 molars. Three images were taken from each group of teeth with intraoral PSP, CBCT-NewTom, and CBCT-ProMax. The sensitivity of PSP, CBCT-NewTom, and CBCT-ProMax was 76.39%, 80.56%, and 94.44% for detecting cast post deviation; 98.61%, 100%, and 100% for external root resorption; 86.11%, 31.94%, and 36.11% for fractured file; and 66.67%, 90.28%, and 86.11% for lateral root perforation respectively. The intertechnique reliability (kappa statistics) was 58.4% for the 2 CBCT techniques, 20.1% and 18.8% for CBCT-NewTom and CBCT-ProMax versus PSP respectively. Given strengths and weaknesses of the techniques as well as the cost, CBCT is recommended as a complementary but not routinely used diagnostic method for endodontic complications not usually detected by conventional methods.

Evaluation of the Response of the Modulation Transfer Function to a Computed Radiography Photostimulable Phosphor Imaging Plate for Various Numbers of X-ray Exposures

The purpose of this project was to analyze the modulation transfer function (MTF) responses to a computed radiography (CR) imaging plate (IP) for various numbers of X-ray exposures and to determine whether or not the MTF response may be used as an indicator of image quality degradation. A measurement facility, which complies with the IEC 62220-1 international standard, has been set up to determine the MTF for computed X-ray detetor systems. The international standard (IEC 62220-1) was demonstrated to allows accurate and reliable measurements of the MTF, and the standardized radiation quality RQA 5 was applied for the measurements. The MTF is the modulation transfer function of the detector. The MTF was obtained from the images that were exposed using an opaque tungsten edge test device (2-mm thick). The presampled MTFs were deduced from the acquired images by using fast Fourier transform analysis techniques, and

X-ray modulation transfer functions of photostimulable phosphor image plates and scanners

The modulation transfer functions of two types of photostimulable phosphor image plates were determined in the 10 keV to 50 keV x-ray energy range using a resolution test pattern with up to 10 line pairs per mm (LP/mm) and a wavelength dispersive x-ray spectrometer. Techniques were developed for correcting for the partial transmittance of the high energy x rays through the lead bars of the resolution test pattern, and the modulation transfer function (MTF) was determined from the measured change in contrast with LP/mm values. The MTF was convolved with the slit function of the image plate scanner, and the resulting point spread functions (PSFs) were in good agreement with the observed shapes and widths of x-ray spectral lines and with the PSF derived from edge spread functions. The shapes and the full width at half-maximum (FWHM) values of the PSF curves of the Fuji Superior Resolution (SR) and Fuji Maximum Sensitivity (MS) image plate detectors, consisting of the image plate and the scanner, determined by the three methods gave consistent results: The SR PSF is Gaussian with 0.13 mm FWHM, and the MS PSF is Lorentzian with 0.19 mm FWHM. These techniques result in the accurate determination of the spatial resolution achievable using image plate and scanner combinations and enable the optimization of spatial resolution for x-ray spectroscopy and radiography.

High-resolution imaging spectrometer for recording absolutely calibrated far ultraviolet spectra from laser-produced plasmas

An imaging spectrometer was designed and fabricated for recording far ultraviolet spectra from laser-produced plasmas with wavelengths as short as 155 nm. The spectrometer implements a Cassegrain telescope and two gratings in a tandem Wadsworth optical configuration that provides diffraction limited resolution. Spectral images were recorded from plasmas produced by the irradiation of various target materials by intense KrF laser radiation with 248 nm wavelength. Two pairs of high-resolution gratings can be selected for the coverage of two wavebands, one grating pair with 1800 grooves/mm and covering approximately 155-175 nm and another grating pair with 1200 grooves/mm covering 230-260 nm. The latter waveband includes the 248 nm KrF laser wavelength, and the former waveband includes the wavelength of the two-plasmon decay instability at 23 the KrF laser wavelength (165 nm). The detection media consist of a complementary metal oxide semiconductor imager, photostimulable phosphor image plates, and a linear array of 1 mm(2) square silicon photodiodes with 0.4 ns rise time. The telescope mirrors, spectrometer gratings, and 1 mm(2) photodiode were calibrated using synchrotron radiation, and this enables the measurement of the absolute emission from the laser-produced plasmas with temporal, spatial, and spectral resolutions. The spectrometer is capable of measuring absolute spectral emissions at 165 nm wavelength as small as 5x10(-7) J/nm from a plasma source area of 0.37 mm(2) and with 0.4 ns time resolution.

Enhanced x-ray resolving power achieved behind the focal circles of Cauchois spectrometers

Maintaining high resolving power is a primary challenge in hard x-ray spectroscopy of newly developed bright and transient x-ray sources such as laser-produced plasmas. To address this challenge, the line widths in x-ray spectra with energies in the 17 keV to 70 keV range were recorded by positioning the detectors on and behind the focal circles of Cauchois type transmission-crystal spectrometers. To analyze and understand the observed line widths, we developed a geometrical model that accounts for source broadening and various instrumental broadening mechanisms. The x-ray sources were laboratory Mo or W electron-bombarded anodes, and the spectra were recorded on photostimulable phosphor image plates. For these relatively small x-ray sources, it was found that when the detector was placed on or near the focal circle, the line widths were dominated by the effective spatial resolution of the detector. When the detector was positioned beyond the focal circle, the line widths were determined primarily by source-size broadening. Moreover, the separation between the spectral lines increased with distance behind the focal circle faster than the line widths, resulting in increased resolving power with distance. Contributions to line broadenings caused by the crystal thickness, crystal rocking curve width, geometrical aberrations, and natural widths of the x-ray transitions were in all cases smaller than detector and source broadening, but were significant for some spectrometer geometries. The various contributions to the line widths, calculated using simple analytical expressions, were in good agreement with the measured line widths for a variety of spectrometer and source conditions. These modeling and experimental results enable the design of hard x-ray spectrometers that are optimized for high resolving power and for the measurement of the x-ray source size from the line widths recorded behind the focal circle.

K-shell spectra from Ag, Sn, Sm, Ta, and Au generated by intense femtosecond laser pulses

K-shell X-ray spectra were recorded by the Dual Crystal Spectrometer (DCS) from Ag, Sn, Sm, Ta, and Au planar foil targets irradiated by single intense femtosecond pulses from the Titan laser at Lawrence Livermore National Laboratory. DCS implements two quartz crystals in transmission (Laué) geometry covering the X-ray energy range 10–50 keV and 20–120 keV. The spectral images were recorded on photo-stimulable phosphor image plates and on film/phosphor cassettes. The Kα and Kβ spectral lines of Ag with energies 22 keV and 25 keV, Sn at 25 keV and 28 keV, Sm at 40 keV and 46 keV, Ta at 57 keV and 66 keV, and Au at 67 keV and 79 keV were clearly resolved. The observation of these spectral lines, resulting from 1s electron vacancies created by electrons with energies up to at least 80 keV, enables the implementation of K-shell spectroscopy diagnostic techniques for understanding the laser energy deposition, energetic electron generation, ionization distribution, and X-ray conversion efficiency in plasmas produced by an intense femtosecond laser pulse. Based on the measured energies of the Au K-shell transitions, we conclude that the observed Au K-shell transitions are from ionization stages lower than Au +44, and are most likely from neutral Au atoms, that the Titan plasmas and the hard X-ray emissions are dominated by electrons with energies exceeding 80 keV, and that thermal processes play a minor role.

Effects of scanning resolution and digital image magnification on photostimulable phosphor imaging system

To examine the effects of changes in scanning resolution and digital magnification on the image quality and diagnostic ability of the photostimulable phosphor imaging system. Using a photostimulable phosphor imaging system, images of a human adult dried mandible phantom embedded in a 25 mm-thick epoxy resin block were made. The latent images on the photostimulable phosphor imaging plate were scanned using four different pixel sizes as follows: 25μm×25μm, 50μm×50μm, 100μm×100μm and 200μm×200μm. A primary image was produced for each pixel size. These images were also digitally magnified at powers of 2, 4 and 8 times. The gradient range, brightness and contrast of each image were adjusted to optimum levels on a cathode ray tube display, and hard copies were produced with a writing pixel size of 60μm×60μm. The granularity, sharpness and anatomical diagnostic ability of the images were assessed subjectively by eight dentists. Increasing the scanning resolution tended to generally improve image quality and diagnostic ability. Visual image quality was maintained up to a pixel size of 50 μm, and diagnostic ability was maintained up to a pixel size of 100μm. Digital image magnification degrated image quality, and more than 2-times magnification degraded diagnostic ability. Under the present experimental conditions, increasing the scanning resolution did not always lead to an improvement in image quality or diagnostic ability, and digital image magnification degraded image quality and diagnostic ability.

Effect of different background lighting conditions on diagnostic performance of digital and film images.

To compare the performance of a photostimulable phosphor (PSP) imaging system with radiographic film for the detection of approximal lesions under two background lighting conditions. Bitewing exposures were made of the extracted human teeth with artificial approximal lesions using D-speed and E-speed radiographic film and a PSP imaging plate. Eight dentists rated 12 approximal surfaces in each image on a 5-point scale. Images were viewed with overhead fluorescent room lighting on and off. ROC curves were generated for each image receptor and lighting condition. Repeated measures analysis of variance ANOVA tested differences between observers, lesion size, image receptor, lighting condition. Mean ROC curve areas for D-speed film viewed in full ambient light scored highest (0.8030) followed by E-speed film using dark conditions (0.7386). The lowest mean curve area was found when PSP (enhanced mode) images were viewed in a dark room (0.6726). Significant differences were found between observers, lesion size, image receptor and image receptor-lesion size interaction. No significant difference was found with background lighting. Background lighting does not appear to effect the ability to detect artificial approximal lesions.