Screen-film Systems Research Articles

COMPARISON OF THE IMAGE QUALITY OF A HIGH‐RESOLUTION SCREEN–FILM SYSTEM AND A DIGITAL FLAT PANEL DETECTOR SYSTEM IN AVIAN RADIOGRAPHY

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.

Breast computed tomography with the PICASSO detector: A feasibility study

The SYRMEP (Synchrotron Radiation for Medical Physics) collaboration has performed, for the first time in the world, a clinical program of mammography with synchrotron radiation. This program provided excellent results, although utilizing a commercial screen-film system as a detector. The PICASSO (Phase Imaging for Clinical Application with Silicon detector and Synchrotron radiation) project has developed a detector prototype capable of fully exploiting the peculiar characteristics of the synchrotron source, utilizing silicon microstrip sensors illuminated in the edge-on geometry and operated in single-photon counting. In this paper the potential of the PICASSO detector in breast computed tomography was evaluated by means of custom phantoms. Very encouraging results have been obtained with severe dose constrains as far as both spatial and contrast resolution are concerned. Moreover, the capability of detecting phase contrast effects was demonstrated, albeit with a higher delivered dose.

Integration of flat panel X-ray detector for high resolution diagnostic medical imaging

In these days, flat panel X-ray image detectors have shown their potential for replacing traditional screen-film systems. To detect the X-ray photon energy, there are two main methods known as a direct method and an indirect method. The X-rays are converted immediately into electrical signal with the direct method. The indirect method has two conversion steps: the scintillator absorbs the X-rays and converts them to visible light. And then the visible light is converted to electrical signal (e.g. by photodiodes). In this work, the flat panel digital X-ray image detector based on direct method with a high atomic number material was designed and evaluated. The high atomic number material for X-ray conversion is deposited by a rubbing method with about 300 μm. The rubbing method is similar to the screen printing method. It consists of two elements: the screen and the squeegee. The method uses a proper stiff bar stretched tightly over a frame made of wood or metal. Proper tension is essential for proper laminated structure. The detector prototype has 139 μm pixel pitch, total 1280×1536 pixels and 86% fill factor. Twelve readout ICs are installed on digital X-ray detector and simultaneously operated to reach short readout time. The electronics integrated: the preamplifier to amplify generated signal, the Analog to Digital converter and the source of bias voltage (1 V/μm). The system board and interface use an NI-camera program. Finally, we achieved images from this flat panel X-ray image detector.

Methods for monitoring patient dose in dental radiology

Different types of X-ray equipment are used in dental radiology, such as intra-oral, panoramic, cephalometric, cone-beam computed tomography (CBCT) and multi-slice computed tomography (MSCT) units. Digital receptors have replaced film and screen-film systems and other technical developments have been made. The radiation doses arising from different types of examination are sparsely documented and often expressed in different radiation quantities. In order to allow the comparison of radiation doses using conventional techniques, i.e. intra-oral, panoramic and cephalometric units, with those obtained using, CBCT or MSCT techniques, the same quantities and units of dose must be used. Dose determination should be straightforward and reproducible, and data should be stored for each image and clinical examination. It is shown here that air kerma-area product (P(KA)) values can be used to monitor the radiation doses used in all types of dental examinations including CBCT and MSCT. However, for the CBCT and MSCT techniques, the methods for the estimation of dose must be more thoroughly investigated. The values recorded can be used to determine the diagnostic standard doses and to set diagnostic reference levels for each type of clinical examination and equipment used. It should also be possible to use these values for the estimation and documentation of organ or effective doses.

An Autosteresoscopic 3D Display System Based on Prism Patterned Projection Screen

Using a 2-view Autostereoscopic 3D Projection display system, a radically designed projection screen film system coupled with a conventional projection display is herein presented and shown to produce a superior 3D effect than most current autostereoscopic and non-autostereo 3D display systems.

599 Does radiopharmaceutical molecule size change number of sentinel lymph node in breast cancer patients?

To investigate the impact of breast density on the performance of radiologists when mammograms are digitally acquired and displayed.A total of 150 craniocaudal digital mammograms including 75 cases with cancer were examined by 14 radiologists divided into two groups: those who read more (six) and less (eight) than 2000 mammograms per year. Cases were classified as low or high mammographic density. For both types of cases, detection of cancers within and outside the dense fibroglandular tissue was investigated. The performance of radiologist was measured using jack-knife free-response receiver operating characteristic (JAFROC) figure of merit (FOM).Radiologists with over 2000 annual reads had significantly higher JAFROC FOM (P = .03) for high (0.76) mammographic density compared to low (0.70) mammographic density cases. When lesions overlaid the fibroglandular tissue, cases with high mammographic density compared to low mammographic density displayed increased location sensitivity for all radiologists (P = .03) and for those radiologists reading more than 2000 mammograms annually (P = .04), whereas JAFROC FOMs increased for all radiologists (P = .05). No significant changes were observed when the lesion was outside the fibroglandular region.Increased mammographic density improves the performance of experienced radiologists when using digital mammograms. This finding, which does not align with those previously reported for film screen systems, may be because of windowing/leveling opportunities available with digital images.

Current status and issues of screening digital mammography in Japan

Digital systems have replaced screen-film systems, and have already been used for a screening program. The diagnostic performance of digital systems has been compared with that of screen-film systems, as the golden standard of breast cancer screening. Several studies have demonstrated they are superior to screen-film mammography; others have shown performance is comparable. The validity of digital screening mammography has been demonstrated. Regarding the method of interpretation of digital screening mammograms, the performance of hard-copy and soft-copy reading has been reported to be comparable, although the environment of soft-copy reading was premature. Soft-copy reading seems more promising in the future as a result of the development of both hardware and software. However, many aspects of quality assurance of soft-copy reading (e.g. standard specifications of viewing workstation, contrast visibility and resolution, ambient light) which remain undetermined should be clarified in the Japanese guideline. In Japan the average glandular dose in screening digital mammography is higher than that in screen-film mammography. Most (93.2%) are under 2 mGy for each radiation exposure. The risk of breast cancer by radiation exposure is regarded as higher than before in the 2007 recommendations of the ICRP. Management of radiation exposure is a continuing challenge.

Reduction of patient dose in medical radiography by utilizing scattered X-rays: Relation between permissible limit of scatter fraction, viewer brightness, and perceptibility of vision

This paper proposes a new technique for reducing the patient dose when employing medical radiographs prepared by using screen-film systems. In this technique the patient dose can be reduced by employing scattered X-rays in order to obtain the same film density as that realized without the use of scattered X-rays. The minimum perceptible thickness difference Δ X min, which can be recognized by liminal vision, was psychophysically calculated by considering the energy spectrum of incident X-ray, sensitivity spectrum of the screen layer, and the perception capability of human vision. From the calculated Δ X mins in various conditions, the permissible upper limit of scatter fraction for obtaining the same Δ X min for three kinds of luminances, and the fraction of reduction in the primary X-rays were determined. As an example of the results, when the object size required for perception is 1.3 mm, a scatter fraction up to 42% can be permitted at a density D of 1.0 for a luminance of 2548 cd m −2. When we increase the luminance of the viewer from 478 cd m −2 to 2548 cd m −2, the upper limit of the permitted scatter fraction varies from 30% to 42% at a D of 1.0, i.e., the patient dose can be reduced by 17% under the same perceptibility of Δ X min by utilizing scattered X-rays. This reduction can be successfully achieved by changing the lead content of the grid from 0.45 to 0.38 g cm −2.

Visualisation of uric acid renal calculi (UARC) using computed radiography (CR)

Aim To investigate the capability of CR to visualise UARC through inverse image post-processing technique. Methods. A patient-equivalent phantom (PEP) consisting of six 2.5-cm thick Perspex layers and one 1-mm thick aluminium layer was used to represent human tissues and bones respectively. A total of eight exposures were made on PEP to radiograph 1 mm, 2 mm and 3 mm UARC located between three layers of 2-cm thick cattle muscle, positioned inside the PEP. After each exposure, a layer of Perspex was removed, and another exposure was made until only one Perspex layer and one layer of muscle (containing the three UARC) remained. For each exposure, two images (a positive and an inverse image) were produced for comparison using Fuji XG1 computed radiography system with IP0 type C-ST-VI Fuji imaging plate (equivalent to 400 speed radiographic screen-film systems). Results In positive image, UARC of all three sizes (1 mm, 2 mm and 3 mm) located in the cattle muscle, cannot be visualised when the PEP consists of more than one layer of Perspex. In inverse image, the 3-mm UARC can be seen even when the PEP consists of five layers of Perspex. Conclusion This study revealed the post-processing capability of CR to increase the visualisation of UARC which has been categorised as radiolucent. A further study of clinical image quality should be performed using blinded observers to test diagnostic accuracy, which was not included in this study.

Physical and clinical comparison between a screen-film system and a dual-side reading mammography-dedicated computed radiography system

Digital mammography systems, thanks to a physical performance better than conventional screen-film units, have the potential of reducing the dose to patients, without decreasing the diagnostic accuracy. To achieve a physical and clinical comparison between two systems: a screen-film plate and a dual-side computed radiography system (CRM; FUJIFILM FCR 5000 MA). A unique feature of the FCR 5000 MA system is that it has a clear support medium, allowing light emitted during the scanning process to be detected on the "back" of the storage phosphor plate, considerably improving the system's efficiency. The system's physical performance was tested by means of a quantitative analysis, with calculation of the modulation transfer function, detective quantum efficiency, and contrast-detail analysis; subsequently, the results were compared with those achieved using a screen-film system (SFM; Eastmann Kodak MinR-MinR 2000). A receiver operating characteristic (ROC) analysis was then performed on 120 paired clinical images obtained in a craniocaudal projection with the conventional SFM system under standard exposure conditions and also with the CRM system working with a dose reduced by 35% (average breast thickness: 4.3 cm; mean glandular dose: 1.45 mGy). CRM clinical images were interpreted both in hard copy and in soft copy. The ROC analysis revealed that the performances of the two systems (SFM and CRM with reduced dose) were similar (P>0.05): the diagnostic accuracy of the two systems, when valued in terms of the area underneath the ROC curve, was found to be 0.74 for the SFM, 0.78 for the CRM (hard copy), and 0.79 for the CRM (soft copy). The outcome obtained from our experiments shows that the use of the dual-side CRM system is a very good alternative to the screen-film system.

COMPARISON OF FLAT‐PANEL DIGITAL TO CONVENTIONAL FILM‐SCREEN RADIOGRAPHY IN DETECTION OF EXPERIMENTALLY CREATED LESIONS OF THE EQUINE THIRD METACARPAL BONE

Radiographic diagnosis of equine bone disease using digital radiography is prevalent in veterinary practice. However, the diagnostic quality of digital vs. conventional radiography has not been compared systematically. We hypothesized that digital radiography would be superior to film-screen radiography for detection of subtle lesions of the equine third metacarpal bone. Twenty-four third metacarpal bones were collected from horses euthanized for reasons other than orthopedic disease. Bones were dissected free of soft tissue and computed tomography was performed to ensure that no osseous abnormalities were present. Subtle osseous lesions were produced in the dorsal cortex of the third metacarpal bones, and the bones were radiographed in a soft tissue phantom using indirect digital and conventional radiography at standard exposures. Digital radiographs were printed onto film. Three Diplomates of the American College of Veterinary Radiology evaluated the radiographs for the presence or absence of a lesion. Receiver operator characteristic curves were constructed, and the area under these curves were compared to assess the ability of the digital and film-screen radiographic systems to detect lesions. The area under the ROC curves for film-screen and digital radiography were 0.87 and 0.90, respectively (P = 0.59). We concluded that the digital radiographic system was comparable to the film-screen system for detection of subtle lesions of the equine third metacarpal bone.

A comparative investigation of Lu2SiO5:Ce and Gd2O2S:Eu powder scintillators for use in x-ray mammography detectors

The dominant powder scintillator in most medical imaging modalities for decades has been Gd2O2S:Tb due to the very good intrinsic properties and overall efficiency. Apart from Gd2O2S:Tb, there are alternative powder phosphor scintillators such as Lu2SiO5:Ce and Gd2O2S:Eu that have been suggested for use in various medical imaging modalities. Gd2O2S:Eu emits red light and can be combined mainly with digital mammography detectors such as CCDs. Lu2SiO5:Ce emits blue light and can be combined with blue sensitivity films, photocathodes and some photodiodes. For the purposes of the present study, two scintillating screens, one from Lu2SiO5:Ce and the other from Gd2O2S:Eu powders, were prepared using the method of sedimentation. The screen coating thicknesses were 25.0 and 33.1 mg cm−2 respectively. The screens were investigated by evaluating the following parameters: the output signal, the modulation transfer function, the noise equivalent passband, the informational efficiency, the quantum detection efficiency and the zero-frequency detective quantum efficiency. Furthermore, the spectral compatibility of those materials with various optical detectors was determined. Results were compared to published data for the commercially employed ‘Kodak Min-R film-screen system’, based on a 31.7 mg cm−2 thick Gd2O2S:Tb phosphor. For Gd2O2S:Eu, MTF data were found comparable to those of Gd2O2S:Tb, while the MTF of Lu2SiO5:Ce was even higher resulting in better spatial resolution and image sharpness properties. On the other hand, Gd2O2S:Eu was found to exhibit higher output signal and zero-frequency detective quantum efficiency than Lu2SiO5:Ce.

Optimisation of patient radiation protection in conventional X-ray imaging procedures using film reject analysis: a demonstration of the importance of rare earth screen-film systems

The optimisation of patient protection was studied using a conventional film screen of speed class 200 and a rare earth film screen of speed class 400. The entrance surface dose (ESD) for the two film-screen systems was determined for patients undergoing some common diagnostic procedures (chest, lumbar spine and pelvis series). The ESD was the optimising parameter and its trade off with the image quality assessment of the radiographs. The estimated ESDs were compared with reference levels set by the Commission of the European Communities for a typical standard adult patient. A mean dose reduction of 17-33 % was achieved upon adoption of a rare earth film screen of speed class 400. Regular assessment of patient dose, quality control (QC) of parameters that affect the patient dose and image quality, adoption of faster rare earth screens and optimum radiographic technique are recommended in order to achieve optimisation goals.

Radiographic method for measuring the continuum hard X-ray output spectrum of a Plasma Focus device

A radiographic method is proposed and then applied to infer the continuum part of the hard X-ray spectrum of a 4.7 kJ Plasma Focus from differential absorption measurements on metals. Copper, nickel, titanium and silver samples with thicknesses spanning between 0.1 and 10 mm were employed as filters. The X-ray radiation was detected using a standard radiographic screen-film system. The results show the presence of a dominant peak around 75 keV with significant spectral components in the range of 40 to 200 keV. The method is easy to follow, inexpensive, and allows for calibrated, single shot, spectral measurements.

41.3: Zero Barrier, Zero Crosstalk Autosteresoscopic 3D Display System for Cinema & Home Theater Multi‐User Settings

AbstractUsing a 4‐viewer Autostereoscopic 3D Home Theater display system, a radically designed projection screen film system coupled with a conventional projection display is herein presented and shown to produce a superior 3D effect than most current autostereoscopic and non‐autostereo 3D Display systems. The proposed design's goals were specifically aimed at tackling the, until now, mutually exclusive properties of most parallax based autostereoscopic 3D Displays i.e. staggeringly high Display Optical Efficiency and drastically low levels of image Crosstalk. By uniquely patterning a film stack onto a projection screen so that the projected left and right images are reflected to their respective viewers locations without the need for barrier or lenticular lens, we were able to achieve a 0% Image Crosstalk at ∼90% Optical Efficiency in a 4 concurrent autostereosocopic 3D viewers Home Theater Display System.

Ｉｍａｇｅ ｑｕａｌｉｔｙ ｆｉｇｕｒｅの閾値によるＣｏｍｐｕｔｅｄ Ｒａｄｉｏｇｒａｐｈｙでの適正線量の推定

We estimated the optimum dose for imaging with a computed radiography (CR) system at two different pixel sizes based on the area under curve (AUC) in receiver operating characteristic (ROC) analysis and image quality figure (IQF). Samples for ROC analysis were prepared as follows. Acryl beads, 2.0 mm in diameter, were placed on a 50.0 mm tough water phantom that was fitted with a 20.0 mm Al filter (SID 200 cm, tube voltage 80 kV). The dose level at which the film density of the screen-film system (SRO250/SRG) was 1.0+/-0.05 served as the reference dose (0.69microC/kg). Five samples were prepared by multiplying the reference dose by 1/4, 1/2, 1, 2, and 4. The samples for image quality evaluation on the basis of IQF were prepared under identical conditions. A contrast-detail (C-D) phantom was placed on a 50.0 mm tough water phantom and images were taken. The contrast threshold of these samples was determined by 10 film readers, the same as those for the ROC analysis. When the significance of differences in the AUC was tested by the paired t-test (two-sided) and the Jackknife method, significant differences were noted between the reference dose and the 1/4 or 4-times dose at the standard pixel size (0.175 mm) and smaller pixel size (0.0875 mm) size, while no significant difference was noted between the reference dose and the 1/2 or 2-times dose. In terms of IQF, no significant difference was noted between standard and smaller pixel sizes (paired t-test). The IQF data indicate that the dose level for imaging with CR can be reduced by about 30% from the reference dose.

Determination of radiotherapy X-ray spectra using a screen-film system

A method to determine the X-ray spectrum delivered by a medical linear accelerator is presented. This method consists of an analytical calculation of the primary spectrum using the Schiff bremsstrahlung cross-section formula. A correction factor that accounts for the scatter component of the spectrum is estimated by comparing the signal in two screen-film systems to a theoretical prediction using a model of energy deposition in such detectors. The model makes use of the quantum absorption efficiency and the average energy deposited per interacting photon concepts. These two quantities are calculated by means of Monte Carlo simulations of the screen-film systems used. This method is capable of determining the spectrum as a function of the spatial position across a plane perpendicular to the beam central axis. It does not, however, render information about the direction cosines of the X-ray fluence crossing such a plane, a requirement in order to produce a full phase-space file that can be used in conjunction with a Monte Carlo dose calculation engine.

The mammography project at the SYRMEP beamline

A clinical program for X-ray phase contrast (PhC) mammography with synchrotron radiation (SR) has been started in March 2006 at the SYRMEP beamline of Elettra, the SR facility in Trieste, Italy. The original beamline layout has been modified substantially and a clinical facility has been realized. In order to fulfill all security requirements, dedicated systems have been designed and implemented, following redundancy criteria and “fail safe” philosophy. Planar radiographic images are obtained by scanning simultaneously the patient and the detector through the stationary and laminar SR beam. In this first phase of the project a commercial screen-film system has been used as image receptor. Upon approval by the respective authorities, the mammography program is about half way to conclusion. Up to now about 50 patients have been examined. The patients are volunteers recruited by the radiologist after conventional examinations at the hospital resulted in an uncertain diagnosis. As an example one case of PhC SR mammography is shown and compared to conventional digital mammography. Preliminary analysis shows the high diagnostic quality of the PhC SR images that were acquired with equal or less delivered dose compared to the conventional ones.

Full field digital mammography: which equipment?

A wide variety of digital mammography systems are now commercially available. These include digital radiography (DR) systems such as the CSi/amorphous silicon detector (for example, GE Senographe 2000D, DS and Essential models), amorphous selenium (for example, LoRad Selenia, Siemens Novation and Inspiration models, IMS Giotto, Planmed Nuance) and a scanning system with silicon detectors (for example, Sectra Micro Dose Mammography). A variety of computerised radiography (CR) systems for mammography are also available (for example, Fuji Profect, Kodak DirectView, Konica Regius 190, Agfa CR 85-X). Recently the CR manufacturers have introduced new designs of phosphor plates. Such a wide variety of systems raises the question of how the performances of these systems compare with each other and with film-screen technology. Another factor to be considered is the radiation dose required by each system to reach an acceptable level of image quality. To help answer these questions, the National Health Service Breast Screening Programme and European Guidelines specify minimum and achievable standards for dose and image quality. The minimum standard is designed to ensure that new digital systems are at least as good as the previous film-screen systems. This lecture compares the measurements on a wide range of digital systems against the standards in the European Guidelines. The overall conclusion is that the DR systems can generally meet the achievable image quality standards for a dose lower than that used for film-screen systems. While the new designs of CR plate have brought about measurable improvements, most CR systems still require doses higher than film-screen systems to meet the minimum standards for image quality.

An evaluation of the Film–Based and Digital Panoramic Radiographic Quality

Aims: To compare the image quality of panoramic radiographs obtained with charge–coupled device(CCD) and screen–film systems. Materials and methods: True Panoramic radiographs were taken in26 patients each with both screen–film and CCD systems. The images were obtained with TRATO2000, CE by VILLA SISTEMI MEDICALIS–ITALY with regular intensifying screen typeKodak Lanex and 6 x 12 inch screen type film used for film–based projection, while Dimax3digital system pan/ceph, PLANMECA, Helsinki, Finland with CCD X–ray image sensor (thesize of the panoramic sensor was 15 x 30 cm and the resolution of the panoramic image was around230 dpi, used for digital projection. Both X–ray machines were operated at range of 70–80kV and 10–12 mA, according to the patient age. Altogether, the digital images files weredisplayed on 17 inch monitor, brightness and contrast were fixed and no enhancement wasmade before the digital images files were saved. While the film–based images after processingwere viewed on the viewer box. Image quality was assessed by rating the visibilityof five anatomical landmarks commonly found on panoramic radiographs: The superior andinferior cortex of the mandibular canal, the superior and inferior margin of the mentalforamen, the lower and anterior border of the maxillary sinus, the lower border of themandible, and the articular eminence. For each image, the given landmark was rated as good(image of excellent diagnostic quality), acceptable (image of diagnostic quality but shouldbe improved), or unacceptable (image not of diagnostic quality). Each image was then givenan overall evaluation rating of good, acceptable, or unacceptable. Results: The data collectedfrom the evaluation of the digital and film–based images by the three examiners, were analyzedby t–test. The image quality, as represented by each of the five anatomical landmarks,and the overall rating for each system were expressed as the mean scores of the threeexaminers. The difference between the film–based and the digital images systems was not statisticallysignificant (P>0.05). Conclusions: It was concluded that digital panoramic radiographs are equivalentto film–based images for the five anatomical landmarks.