Conventional Screen-film System Research Articles

Assessment of image quality and radiation dose in some models of digital radiography systems – A Pehamed FLUORAD A + D phantom study

Digital radiography (DR) systems have been recently introduced as a developed technology that is replacing conventional film–screen systems in many countries around the world. Ideal situation in radiography is to maximize the image quality while minimizing the patient dose. The purpose of this study was to compare image quality and radiation dose in different digital radiography systems. Four different digital systems are compared in terms of their image quality performance and dose area product (DAP). Images of Pehamed FLUORAD A + D phantom were obtained for each DR system. Image quality parameters (contrast resolution (CR), spatial resolution (SR), and contrast-to-noise ratio (CNR)) and DAP were significantly different between different digital systems. It was shown that all four quantities increased with increasing exposure parameters in all systems. Image quality parameters of the SEDECAL system were higher than that in other systems (p ≤ 0.05). At the stable DAP (100 mGy.cm2), means of CR, CNR, and SR in the SEDECAL system were 6.38 ± 0.797, 29.70 ± 0.85 and 3.10 ± 0.38 lp/mm, respectively. The results of this investigation can be taken into consideration in the selection and purchasing of new systems in order to preserve patients as well as radiographers from unnecessary radiation dose.

Exploratory survey of image quality on CR digital mammography imaging systems in Mexico

The purpose of this study was to assess the current status of image quality and dose in computed radiographic digital mammography (CRDM) systems. Studies included CRDM systems of various models and manufacturers which dose and image quality comparisons were performed. Due to the recent rise in the use of digital radiographic systems in Mexico, CRDM systems are rapidly replacing conventional film-screen systems without any regard to quality control or image quality standards. Study was conducted in 65 mammography facilities which use CRDM systems in the Mexico City and surrounding States. The systems were tested as used clinically. This means that the dose and beam qualities were selected using the automatic beam selection and photo-timed features. All systems surveyed generate laser film hardcopies for the radiologist to read on a scope or mammographic high luminance light box. It was found that 51 of CRDM systems presented a variety of image artefacts and non-uniformities arising from inadequate acquisition and processing, as well as from the laser printer itself. Undisciplined alteration of image processing settings by the technologist was found to be a serious prevalent problem in 42 facilities. Only four of them showed an image QC program which is periodically monitored by a medical physicist. The Average Glandular Dose (AGD) in the surveyed systems was estimated to have a mean value of 2.4mGy. To improve image quality in mammography and make more efficient screening mammographic in early detection of breast cancer is required new legislation.

Patient dose, gray level and exposure index with a computed radiography system

Computed radiography (CR) is gradually replacing conventional screen-film system in Brazil. To assess image quality, manufactures provide the calculation of an exposure index through the acquisition software of the CR system. The objective of this study is to verify if the CR image can be used as an evaluator of patient absorbed dose too, through a relationship between the entrance skin dose and the exposure index or the gray level values obtained in the image. The CR system used for this study (Agfa model 30-X with NX acquisition software) calculates an exposure index called Log of the Median (lgM), related to the absorbed dose to the IP. The lgM value depends on the average gray level (called Scan Average Level (SAL)) of the segmented pixel value histogram of the whole image. A Rando male phantom was used to simulate a human body (chest and head), and was irradiated with an X-ray equipment, using usual radiologic techniques for chest exams. Thermoluminescent dosimeters (LiF, TLD100) were used to evaluate entrance skin dose and exit dose. The results showed a logarithm relation between entrance dose and SAL in the image center, regardless of the beam filtration. The exposure index varies linearly with the entrance dose, but the angular coefficient is beam quality dependent. We conclude that, with an adequate calibration, the CR system can be used to evaluate the patient absorbed dose.

Optimisation of radiological protocols for chest imaging using computed radiography and flat-panel X-ray detectors

Digital radiography technology has replaced conventional screen-film systems in many hospitals. Despite the different characteristics of new detector materials, frequently, the same radiological protocols previously optimised for screen film are still used with digital equipment without any critical review. This study addressed optimisation of exposure settings for chest examinations with digital systems, considering both image quality and patient dose. Images acquired with direct digital radiography equipment and a computed radiography system were analysed with specially developed commercial software with a four-alternative forced-choice method: the most promising protocols were then scored by two senior radiologists. Digital technology offers a wide dynamic range and the ability to postprocess images, allowing use of lower tube potentials in chest examinations. The computed radiography system showed both better image quality and lower dose at lower energies (85 kVp and 95 kVp) than those currently used (125 kVp). Direct digital radiography equipment confirmed both its superior image quality and lower dose requirements compared with the storage phosphor plate system. Generally, lowering tube potentials in chest examinations seems to allow better image quality/effective dose ratio when using digital equipment.

Radiography in veterinary practice – a review and update

ABSTRACT:Radiography is a commonly used diagnostic tool in veterinary practice. A fundamental understanding of how radiographs are created enables the user to select the most appropriate exposure factor settings during radiograph production, in order to achieve optimal image quality. There are currently three types of radiography systems available for use in veterinary practice including conventional film-screen radiography, computed radiography (CR) and direct digital radiography (DR). Digital radiography systems, including both CR and DR, offer a number of distinct advantages over conventional film-screen radiography systems.

Comparison to Images from a Computed Radiography System for Non-destructive Testing Using Selenium-75, Iridium-192, and X-rays

A computed radiography (CR) system using reusable image plates (IPs) offers a convenient and reliable way to replace a conventional film-screen system for non-destructive testing field. The ability of radiography to detect a defect in welded objects depends on the procedure and embraces several factors such as the measurement conditions, the image plate type/class, the radiation energy, the radiation type, and the source-to-image plate distance. Also, the ability of images to detect a flaw decreases with increasing object thickness. In the study, images of welded objects were acquired with a CR system manufactured by FUJI by using selenium-75, iridium-192, and X-ray with and were obtained through MCNP5 simulations under the same conditions as the given experiments conditions.

Optimal steel thickness combined with computed radiography for portal imaging of nasopharyngeal cancer patients

The poor image quality of conventional metal screen-film portal imaging system has long been of concern, and various methods have been investigated in an attempt to enhance the quality of portal images. Computed radiography (CR) used in combination with a steel plate displays image enhancement. The optimal thickness of the steel plate had been studied by measuring the modulation transfer function (MTF) characteristics. Portal images of nasopharyngeal carcinoma patients were taken by both a conventional metal screen-film system and this optimal steel and CR plate combination system. Compared with a conventional metal screen-film system, the CR-metal screen system achieves a much higher image contrast. The measured modulation transfer function (MTF) of the CR combination is greater than conventional film-screen portal imaging systems and also results in superior image performance, as demonstrated by receiver operator characteristic (ROC) analysis. This optimal combination steel CR plate portal imaging system is capable of producing high contrast portal images conveniently.

Edge on silicon microstrip detectors for medical imaging

Silicon microstrip detectors in the edge on geometry, i.e. oriented with the strips parallel to the incoming beam, allow a high absorption efficiency for X-rays in the 10–100 keV energy range. In medical imaging, this results in a significant reduction of the dose given to the patient with respect to conventional screen-film systems. This geometrical configuration was first proposed in the early 90s and since then it has been applied to several medical imaging projects. In this short review, an overview of some medical imaging applications using edge on detectors will be presented, focusing the attention on the main characteristics of the detection systems. The studies performed in Trieste in order to optimize such detectors for digital mammography with synchrotron radiation will be described in detail. In particular, novel imaging techniques (phase contrast, refraction and scatter imaging, computed tomography) implemented and tested at the Trieste synchrotron light source will be shortly discussed.

Objective assessment of image quality in conventional and digital mammography taking into account dynamic range

The goal of this work is to develop a method to objectively compare the performance of a digital and a screen-film mammography system in terms of image quality. The method takes into account the dynamic range of the image detector, the detection of high and low contrast structures, the visualisation of the images and the observer response. A test object, designed to represent a compressed breast, was constructed from various tissue equivalent materials ranging from purely adipose to purely glandular composition. Different areas within the test object permitted the evaluation of low and high contrast detection, spatial resolution and image noise. All the images (digital and conventional) were captured using a CCD camera to include the visualisation process in the image quality assessment. A mathematical model observer (non-prewhitening matched filter), that calculates the detectability of high and low contrast structures using spatial resolution, noise and contrast, was used to compare the two technologies. Our results show that for a given patient dose, the detection of high and low contrast structures is significantly better for the digital system than for the conventional screen-film system studied. The method of using a test object with a large tissue composition range combined with a camera to compare conventional and digital imaging modalities can be applied to other radiological imaging techniques. In particular it could be used to optimise the process of radiographic reading of soft copy images.

Phantomstudie zur Detektion simulierter Läsionen an fünf verschiedenen digitalen und einem konventionellen Mammographiesystem

Purpose: Experimental phantom study for the detection of simulated lesions with five different digital and one conventional screen-film mammography system. Materials and Methods: Three radiographs were obtained at variousconfigurations of the phantom with one conventional screen-film system (Mammomat 3000 N) (Siemens), five digital systems (high resolution computed radiography system [Fuji/Siemens], one a-Si detector [GE Medical Systems], two a-Se detectors [Siemens; Hologic / Lorad] and one CCD detector [Fischer Imaging]), applying the same exposure parameters. The Wisconsin Mammographic Random Phantom, Model 152 A, was used. Five investigators with different experience in mammography (3 months to more than 4 years) evaluated the 18 randomly selected radiographs. Results: No significant differences were found in the detection rate of simulated breast lesions for conventional screen-film mammography (84.9%), high resolution computed radiography (86.7%) and digital mammography with an a-Si detector (89.8%). Highly significantly better results (p<0.001) were found with the two a-Se systems (97.3%) and the CCD system (100%). Conclusion: Conventional screen-film mammography can be replaced by high resolution computed radiography and digital mammography with a-Si-, a-Se- and CCD-detectors. This has to be confirmed in further clinical studies.

The ALARA Concept in Pediatric CR and DR: Dose Reduction in Pediatric Radiographic Exams — A White Paper Conference

Charles E. Willis1 Thomas L. Slovis2 ALARA, an acronym for as low as reasonably achievable, is a philosophy of radiation-dose management. As the SPR continues to promote ALARA in pediatric CT, we have begun to examine other imaging modalities where the potential for dose reduction exists. Computed radiography (CR) and digital radiography (DR) are acquisition systems that replace conventional screen-film (SF) systems for projection radiography. In conventional radiography, the amount of radiation needed to produce an acceptable image is specific to the SF system and chemical processing conditions. In CR and DR, the acquisition process is separated from the display process, allowing these systems to produce acceptable images over a wide range of exposures. Unfortunately, the disconnection of acquisition from display also introduces the potential for systematic overexposure. In order to examine the risk that CR and DR pose in pediatric radiography and the potential for dose reduction, the SPR organized a second ALARA Conference. The conference, held in Houston, Texas, February 28, 2004 and was attended by 77 pediatric radiologists, medical physicists, radiologic technologists, imaging scientists, and engineers. The conference was made possible by unrestricted grants from 6 CR and DR manufacturers. The faculty consisted of four academic speakers, five industry speakers, and a speaker from the Food and Drug Administration. The industry speakers were provided a list of questions in order to focus their lectures on specific features of their products that were relevant to dose management in pediatric radiography.

Performance comparison of an active matrix flat panel imager, computed radiography system, and a screen-film system at four standard radiation qualities

Four standard radiation qualities (from RQA 3 to RQA 9) were used to compare the imaging performance of a computed radiography (CR) system (general purpose and high resolution phosphor plates of a Kodak CR 9000 system), a selenium-based direct flat panel detector (Kodak Direct View DR 9000), and a conventional screen-film system (Kodak T-MAT L/RA film with a 3M Trimax Regular screen of speed 400) in conventional radiography. Reference exposure levels were chosen according to the manufacturer's recommendations to be representative of clinical practice (exposure index of 1700 for digital systems and a film optical density of 1.4). With the exception of the RQA 3 beam quality, the exposure levels needed to produce a mean digital signal of 1700 were higher than those needed to obtain a mean film optical density of 1.4. In spite of intense developments in the field of digital detectors, screen-film systems are still very efficient detectors for most of the beam qualities used in radiology. An important outcome of this study is the behavior of the detective quantum efficiency of the digital radiography (DR) system as a function of beam energy. The practice of users to increase beam energy when switching from a screen-film system to a CR system, in order to improve the compromise between patient dose and image quality, might not be appropriate when switching from screen-film to selenium-based DR systems.

Phantom study for the detection of simulated lesions in five different digital and one conventional mammography system

Experimental phantom study for the detection of simulated lesions with five different digital and one conventional screen-film mammography system. Three radiographs were obtained at various configurations of the phantom with one conventional screen-film system (Mammomat 3000 N) (Siemens), five digital systems (high resolution computed radiography system [Fuji/Siemens], one a-Si detector [GE Medical Systems], two a-Se detectors [Siemens; Hologic / Lorad] and one CCD detector [Fischer Imaging]), applying the same exposure parameters. The Wisconsin Mammographic Random Phantom, Model 152 A, was used. Five investigators with different experience in mammography (3 months to more than 4 years) evaluated the 18 randomly selected radiographs. No significant differences were found in the detection rate of simulated breast lesions for conventional screen-film mammography (84.9 %), high resolution computed radiography (86.7 %) and digital mammography with an a-Si detector (89.8 %). Highly significantly better results (p < 0.001) were found with the two a-Se systems (97.3 %) and the CCD system (100 %). Conventional screen-film mammography can be replaced by high resolution computed radiography and digital mammography with a-Si-, a-Se- and CCD-detectors. This has to be confirmed in further clinical studies.

Experimental in vitro study to evaluate a flat-panel detector system

To evaluate the contrast-detail performance of a flat-panel detector system, we performed a comparative study of this flat-panel system versus storage phosphor and conventional screen-film systems. Bone models made of human humeri were prepared with foreign bodies, fracture lines and drilled holes to create artificial fractures, osteolyses or metastases. Immersed in a water bath, hard copy images of these models were acquired with the same exposure dose (55 kV; 3.2 mAs) on the flat-panel detector, two state-of-the-art storage phosphor systems (PCR, ADC) and two conventional screen-film systems (Insight, T-Mat). Using a standardized protocol with a 4-point scale for a lesion, 220 different images were analyzed as to their appearance by 5 independent radiologists. The statistical significance of the differences between the used modalities and the observers was determined with a sign test. Especially the drilled holes showed differences between the modalities. The flat-panel detector showed significantly slightly better results locally than the two storage phosphor systems. The same applied to the Insight screen-film systems, but the intraindividual differences between the modalities were not clinically relevant. Under the conditions of the chosen experimental design, the flat-panel detector showed results comparable to the conventional screen-film and the state of the art storage phosphor radiographs. The use in skeletal radiography is possible.

Dose Reduction in Patients Undergoing Chest Imaging: Digital Amorphous Silicon Flat-Panel Detector Radiography Versus Conventional Film-Screen Radiography and Phosphor-Based Computed Radiography

We sought to compare the radiation dose delivered to patients undergoing clinical chest imaging on a full-field digital amorphous silicon flat-panel detector radiography system with the doses delivered by a state-of-the-art conventional film-screen radiography system and a storage phosphor-based computed radiography system. Image quality was evaluated to ensure that the potential reduction in radiation dose did not result in decreased image acuity. SUBJECTS AND METHODS. Three groups of 100 patients each were examined using the amorphous silicon flat-panel detector, film-screen, or computed radiography systems. All patient groups were matched for body mass index, sex, and age. To measure the entrance skin dose, we attached 24 calibrated thermoluminescent dosimeters to every patient. The calculation of the effective dose, which represents the risk of late radiation-induced effects, was based on measurements on an anthropomorphic phantom. Image quality of all three systems was evaluated by five experienced radiologists, using the European Quality Criteria for Chest Radiology. In addition, a contrast-detail phantom study was set up to assess the low-contrast detection of all three systems. The amorphous silicon flat-panel detector radiography system allowed an important and significant reduction in both entrance skin dose and effective dose compared with the film-screen radiography (x 2.7 decrease) or computed radiography (x 1.7 decrease) system. In addition, image quality produced by the amorphous silicon flat-panel detector radiography system was significantly better than the image quality produced by the film-screen or computed radiography systems, confirming that the dose reduction was not detrimental to image quality. The introduction of digital flat-panel radiography systems based on amorphous silicon and cesium iodide is an important step forward in chest imaging that offers improved image quality combined with a significant reduction in the patient radiation dose.

Digital chest radiography: quality assurance.

Digital chest radiography: quality assurance.

Radiation Dose Reduction in Chest Radiography using a Flat-Panel Amorphous Silicon Detector

AIM: The aim of this study was to evaluate the image quality and the potential for radiation dose reduction with a digital flat-panel amorphous silicon detector radiography system. MATERIAL AND METHODS: Using flat-panel technology, radiographs of an anthropomorphic thorax phantom were taken with a range of technical parameters (125kV, 200mA and 5, 4, 3.2, 2, 1, 0.5, and 0.25mAs) which were equivalent to a radiation dose of 332, 263, 209, 127, 58.7, 29, and 14μGy, respectively. These images were compared to radiographs obtained by a conventional film-screen radiography system at 125kV, 200mA and 5mAs (equivalent to 252μGy) which served as reference. Three observers evaluated independently the visibility of simulated rounded lesions and anatomical structures, comparing printed films from the flat-panel amorphous silicon detector and conventional x-ray system films. RESULTS: With flat-panel technology, the visibility of rounded lesions and normal anatomical structures at 5, 4, and 3.2mAs was superior compared to the conventional film-screen radiography system. (P⩽0.0001). At 2mAs, improvement was only marginal (P=0.19). At 1.0, 0.5 and 0.25mAs, the visibility of simulated rounded lesions was worse (P⩽0.004). Comparing fine lung parenchymal structures, the flat-panel amorphous silicon detector showed improvement for all exposure levels down to 2mAs and equality at 1mAs. CONCLUSION: Compared to a conventional x-ray film system, the flat-panel amorphous silicon detector demonstrated improved image quality and the possibility for a reduction of the radiation dose by 50% without loss in image quality. Hosch, W. P. etal. (2002). Clinical Radiology57, 902–907.

Experimentelle Untersuchungen zur Bildgüte konventioneller Film-Folien-Mammographie, digitaler Mammographie mit Speicherfolien in Vergrößerungstechnik und voll digitaler Mammographie in CCD-Technik

Comparison of image quality between conventional film screen system, digital phosphor storage plate mammography in magnification technique and digital mammography in CCD-technique. Radiograms of a RMI-mammography phantom were acquired using a conventional film screen system, two digital storage plate systems and two digital systems in CCD-technique. Additionally, the radiograms of one digital phosphor storage plate system were postprocessed emphasizing contrast and included in the comparison. The detectability of details was the best with the digital mammography in CCD-technique in comparison with the conventional film screen technique resp. digital phosphor storage plate in magnification technique. Based on these results there is the possibility to replace the conventional film screen system by further studies--this has to be confirmed.

Synchrotron light and imaging systems for medical radiology

In the past years several successful experimental studies have proven the suitability of synchrotron light in the field of medical radiology and in diagnostic medical imaging. To be mentioned and reviewed in the following are transvenous coronary angiography with synchrotron radiation, bronchography, single- or multi-energy tomography and synchrotron radiation-based mammography. Amongst those the most demanding application is X-ray mammography. Here, a dedicated system has to fulfil the demanding requirements on the source and the X-ray detector. Synchrotron radiation-based mammography, which enables improved image quality maintaining a low dose level, takes advantage of the tunable monochromatic energy and of the peculiar laminar geometry of the beam. In addition, further improvements can be achieved with the development of novel detectors for full-field digital mammography in order to overcome the intrinsic limitations of the conventional screen–film systems. Encouraging results in digital mammography have been obtained at the medical beamline of the synchrotron radiation facility ELETTRA, Trieste. Besides, the high degree of the spatial coherence of the synchrotron source allows new imaging modalities based on phase contrast effects that produce superior radiographs featuring highly enhanced contrast with a low delivered dose.

Digital radiography with a large-area, amorphous-silicon, flat-panel X-ray detector system.

To investigate the image quality of a digital radiography system with an amorphous-silicon, large-area, digital flat-panel detector. A flat-panel detector based on a matrix of amorphous silicon was integrated into a projection radiography system. The scintillator consisted of a layer of structured cesium iodide. The active matrix size of 30002 pixels together with a pixel size of 143 microm provided a large image area of 43 x 43 cm2. Basic image quality parameters such as detective quantum efficiency (DQE) and modulation transfer function (MTF) were measured and compared with those obtained with conventional systems. The measurement of DQE yielded a high value of 70% at zero spatial frequency. At a system dose equivalent to 400 speed, the DQE of the digital system was a factor of two larger than the DQE of a storage phosphor or screen-film system within the entire spatial frequency range between zero and the Nyquist limit of 3.5 line pairs per millimeter. The flat-panel detector furthermore has an MTF that is superior to that in regular screen-film systems and also provides a substantially larger dynamic range. This new technology demonstrates its potential to provide equal or superior image quality to conventional screen-film systems and to reduce patient exposure to radiation dose. The advantages of digital radiography systems, based on a flat-panel detector as an instant image display, facilitation of work flow in the radiology department, and digital networking and archiving, are well in sight.