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Recently, for medical imaging, digital radiography systems are widely used in clinical practices. However, a study in the past reported that a patient radiation exposure level by digital radiography is in fact not lower than that by analog radiography system. High level of attention needs to be paid for over-exposure when using the conventional analog radiography with a screen and a film, as it results in high density of the film. However, for digital radiography systems, since the automatic adjusting function of image density is equipped with them, no attention for radiation dose need to be paid. Thus technologists tend to be careless and results in higher chance for over-exposure. Current digital radiography systems are high-performance in the image properties and capable of patient dose reduction. Especially, the image quality of the flat panel detector system is recognized, higher than that of the computed radiography system by imaging plates, in both objective and subjective evaluations. Therefore, we technologists are responsible for optimizing the balance between the image quality of the digital radiogram and the radiation dose required for each case. Moreover, it is also required for us as medical technologists to make effective use of such evaluation result of medical images for patients.

Because of an accident of the nuclear power plants in the Fukushima, many radioisotopes (RI) have been diffused to the environment. As a result, black spots were appearing on the medical images which were taken by the phosphor plate. The aim of this study is to evaluate the activity (Bq) of radioactive contaminated IP based on the experiment using RI. The radioactive material ((134)Cs and/or (137)Cs) in the form of liquid was dropped on filter paper (25 mm(2)), and radioactive sources having 40-240 Bq activities were made. These sources were closely attached to the IP with irradiation times of 2-22 h. Then, we obtained the relationship between pixel values and products of activities and irradiation times. Using these relationships, we evaluated the activity in the contaminated IP. The evaluated value of approximately 7 Bq was in good agreement with a value which was inhered in a chemical wiper used for the decontamination of the IP. Based on the results, we summarized that almost all black spots were created by the RI adhered directly to the IP.

We investigated whether the use of a newly developed columnar-crystal-type photostimulable-phosphor plate (CP1M200, referred to as system C) helps to provide improved edge-enhanced effect in phase contrast imaging. Physical characteristics of 2 conventional particulate-crystal-type photostimulable-phosphor plates (RP-5PM, referred to as system A and RP-6M, referred to as system B) and system C were measured. Then, an acrylic plate phantom and RMI152 phantom were imaged using 3 types of plates, and the edge-enhancement effects were evaluated based on the profile curve of the acrylic plate phantom. Visual evaluation of the RMI152 phantom images was conducted. The results showed that the modulation transfer function (MTF) of system C was superior to those of the other systems. The WS of system C was superior to those of the other systems in the low frequency band region, and inferior to those of the other systems in the high frequency band region. The presence of an edge-enhanced image was not detectable in the profile curve of the acrylic plate in system A, although that was shown in systems B and C due to their excellent sharpness. In the visual image evaluation of the RMI152 phantom, image quality of system C was superior to those of the other systems. Phase contrast imaging with a digital detector of a columnar-crystal-type photostimulable-phosphor plate is considered to provide improved edge-enhancement over that of conventional plates.

Philips DigitalDiagnost, a digital radiographic system mounting flat panel detector (FPD), can display dose area data (DiDi dose) calculated by examination parameters. We evaluated its fundamental characteristics and compared the values of DiDi dose andactual measured data obtained by the area dose product meter (PD-4100L). Tendency of varied values of mAs, X-ray tube values and exposure area from both the area dose product meter and the DiDi dose were coincided. Further, in clinical images of chest PA 100 cases, chest lateral 50 cases and abdomen stand 25 cases, the determination coefficient was overly high as R(2)=0.99. Based on these results, it is clear that the DiDi dose can be treated the same as the area dose product meter. Under increasing of patient X-ray exposure dose is a concern in digital general radiography, this research indicates that maximum values of histogram obtained by DiDi dose contributes dose awareness for radiographer.

The purpose of this study was to investigate image quality identification methods among direct- and indirect-type flat panel detectors (FPDs) and a computed radiography (CR) system using two radiation qualities RQA3 and RQA5 defined in the IEC 61267 standard. For each system, the digital characteristic curve, the presampled modulation transfer function (MTF), and the normalized noise power spectrum (NNPS) were measured. Images for a burger phantom and a foot-bone phantom were processed by resolution identification utilizing two-dimensional Fourier transform, and then contrast-to-noise ratio (CNR) for each image was measured. For the RQA3, the direct FPD system indicated the highest DQE value, and for the RQA5 DQE value of indirect FPD system, it was a little higher than that of direct FPD system. The CNR results with the resolution identification displayed good accordance with the DQE results in both phantoms. From the DQE results, dose ratios for image quality identification were determined, and the CNRs of the dose-adjusted images were measured. The results for, the CNRs of all systems showed good coincidence. From these findings, they indicated that the DQE measurement is effective to determine the exposure parameters for equalizing the image quality of different types of radiographic systems.

Angiographic equipment has tended toward using flat-panel detector (FPD). However, the radiation dose varies depending on the size of field of view (FOV) in the FPD. Although we were using 7 inch FOV in cardiac procedures, we examined a way to reduce the patients' radiation dose by using 8 inch FOV utilizing a digital zoom processing. We measured the absorbed dose rates at an interventional reference point (IRP) with 20 cm acrylic board to compare 8 inch FOV using a digital zoom processing with 7 inch FOV. Additionally we visually evaluated these phantom images. Result of comparison of absorbed dose rates at IRP, 8 inch FOV using a digital zoom processing was reduced more than 7 inch FOV (fluoroscopic 29.0% and digital cine 37.5%). These phantom images were of equivalent quality. The method to use 8 inch FOV utilizing a digital zoom processing technique in cardiac procedures is one of the effective radiation exposure reduction methods.

Soft copy reading of digital images has been practiced commonly in the PACS environment. In this study, we compared liquid-crystal display (LCD) and cathode-ray tube (CRT) monitors for detection of pulmonary nodules and interstitial lung diseases on digital chest radiographs by using receiver operating characteristic (ROC) analysis. Digital chest images with a 1000x1000 matrix size and a 8 bit grayscale were displayed on LCD/CRT monitor with 2M pixels in each observer test. Eight and ten radiologists participated in the observer tests for detection of nodules and interstitial diseases, respectively. In each observer test, radiologists marked their confidence levels for diagnosis of pulmonary nodules or interstitial diseases. The detection performance of radiologists was evaluated by ROC analyses. The average Az values (area under the ROC curve) in detecting pulmonary nodules with LCD and CRT monitors were 0.792 and 0.814, respectively. In addition, the average Az values in detecting interstitial diseases with LCD and CRT monitors were 0.951 and 0.953, respectively. There was no statistically significant difference between LCD and CRT for both detection of pulmonary nodules (P=0.522) and interstitial lung diseases (P=0.869). Therefore, we believe that the LCD monitor instead of the CRT monitor can be used for the diagnosis of pulmonary nodules and interstitial lung diseases in digital chest images.

The physical characteristics of a direct amorphous Selenium (a-Se) digital fluoroscopy and radiography system were investigated. Pre-sampled modulation transfer functions (MTF) were measured using a slit method. Noise power spectra were determined for different input exposures by fast Fourier transform of uniformly exposed samples. The MTFs of direct digital radiography systems showed significantly higher values than those of indirect digital radiography and screen-film systems. The direct digital radiography systems showed higher noise levels compared with those of indirect systems under roughly the same exposure conditions. Contrast-detail analysis was performed to compare detection by direct digital radiography systems with that of the screen-film (FUJI HG-M2/UR2) systems. The average contrast-detail curves of digital and film images were obtained from the results of observation. Image quality figures (IQF) were also calculated from the individual observer performance tests. The results indicated that digital contrast-detail curves and IQF are, on average, are equal those of the screen-film system.

With the recent great advances in technology, the use of flat panel displays (FPD) is tending to increase. However, there is concern that the physical properties are not understood well enough by physicians to take advantage of the improved physical properties to assist them with diagnosis. Because displays of differing physical properties are being used in clinics, we have not seen enough research about the relationship between diagnostic ability and the physical properties of displays. The purpose of this study was to evaluate radiologists' performance in the diagnosis of nodules in chest radiographs with three kinds of flat panel displays: 3M- and 5M-pixel monochrome flat panel displays, and a 3M-pixel color flat panel display. Nine radiologists participated in this observer study. Sixty chest radiographs were used. Thirty-five images depicted malignant nodules, and 25 images were normal. We set for an 8-bit gray scale in advance. The radiologists' performance was evaluated with receiver operating characteristic (ROC) analysis by using a computer program (ROCKIT; Charles E. Metz, University of Chicago) . Observer performance for the diagnosis of nodules in chest radiographs was not significantly different using 3M- and 5M-pixel monochrome, and 3M-pixel color flat panel displays. Further investigation of frequent spatial patterns requiring higher resolutions such as the interstitial infiltrate pattern in chest images and the microcalcifications in mammographs will be needed.

Recently, a few types of step-wedges for bootstrap sensitometry with a mammographic screen-film system have been proposed. In this study, the bootstrap sensitometry with the mammographic screen-film system was studied for two types of aluminum step-wedges. Characteristic X-ray energy curves were determined using mammographic and general radiographic aluminum step-wedges devised to prevent scattered X-rays generated from one step penetrating into the region of another one, and dependence of the characteristic curves on the wedges was also discussed. No difference was found in the characteristic curves due to the difference in the step-wedges for mammography and general radiography although there was a slight difference in shape at the shoulder portion for the two types of step-wedges. Therefore, it was concluded that aluminum step-wedges for mammography and general radiography could be employed in bootstrap sensitometry with the mammographic screen-film system.

We investigated the relationship between average glandular tissue dose and imaging properties such as image density, contrast, and visual image quality, varying the tube voltage and subject parameters (glandular fraction and breast thickness) The wax inserts of 156 phantom and disk of polymethyl methacrylate (PMMA) were arranged between the BR-12 breast-equivalent phantoms. These phantoms were radiographed using automatic exposure control (AEC) for the various combinations of tube voltage and subject parameters. In addition, exposures were measured at the same time. The results showed that the average glandular tissue dose increased when the high glandular fraction and/or thick phantom were being radiographed with the low tube voltage. We found that the criteria of the Japanese Mammography Screening Accreditation Program for image quality were not satisfied when breast thickness was greater than 6 cm.

For physicians who monitor images during interventional radiology (VR), we have built and been using a system that employs a liquid crystal display (LCD) instead of the conventional cathode ray tube (CRT). The system incorporates a ceiling-suspension-type monitor (three-display monitor) with an LCD on each of the three displays for the head and abdominal regions and another ceiling-suspension-type monitor (5-display monitor) with an LCD on each display for the cardiac region. As these monitors are made to be thin and light in weight, they can be placed in a high position in the room, thereby saving space and allowing for more effective use of space in the X-ray room. The system has also improved the efficiency of operators in the IVR room. The three-display folding mechanism allows the displays to be viewed from multiple directions, thereby improving the environment so that the performance of IVR can be observed.

We have been using an X-ray angiography system that incorporates a flat panel detector (FPD) since December 2001. This system is equipped with the scintillator-type FPD PaxScan 4030A from Varian Medical Systems, and for objective comparison of the image intensifier (I.I.) and FPD, the system is constructed so that these detectors can be used alternatively. Using this system and other X-ray angiography systems, visual studies have been conducted on the digital subtraction angiography (DSA) images acquired by FPD and I.I. We have found from the clinical images that the FPD is superior to the I.I. in depiction of fine blood vessels as well as of physical characteristics. Fluoroscopy images acquired by the FPD were not entirely satisfactory, however the improvement made in its performance now permits equal use of the FPD and I.I. systems.

Comparisons of focal-spot size measurements with a direct-exposure X-ray film, screen-film (S/F) system, and imaging plate (IP) were carried out for slit and star resolution pattern camera techniques. The focal-spot measurements of X-ray units with the nominal size of 0.1-1 mm were performed, and measurement using the computed radiography (CR) system was investigated. Compared with the direct-exposure X-ray film method, the measurements of focal-spot size by the S/F system were slightly small for all focal spots. The measurements obtained with IP were slightly large for large and small focal spots, although the measurement of micro focal-spot size was overestimated, extending the tolerance level owing to the sampling. With the star pattern camera technique, differences between the three kinds of detectors were minimal. Therefore, it was thought that measurement of focal-spot size using the CR system would be practical for both large and small focal spots if this method were used for quality control in medical facilities.

The current method of verification for external beam radiation therapy visually compares a simulation image with a portal image. However, because this method depends largely upon the observer's experience, it sometimes results in inter-observer differences. In this study, we developed software to measure atomatically the quantitative difference between the simulation image and portal image using an image-analysis method. The feasibility of this software was evaluated on a rectangular field in the pelvic region. We took 12 simulation images of a pelvic phantom, setting 4 different field shapes on each of 3 isocenters. We then obtained 84 portal images setting 7 known distances from each of the 12 simulation images. Using this software, the direction of shift was detected correctly, and the distance of shift was detected correctly to within less than 3 mm. We consider that this software could be a useful method of verification.

We compared the INNOVA2000 (INNOVA), which has a flat panel detector system, and the Advantx LCLP (LCLP), which has a conventional I. I. system, in terms of the dependence of phantom thickness on patient surface dose (surface dose) and receptor entrance dose (entrance dose). We examined the reduction in surface dose and entrance dose by using an additional filter and shortening the patient detector distance (PDD). The surface dose rate for fluoroscopy with INNOVA was 73.8-63.5%, and the reduction rate was high at a phantom thickness of less than 20 cm compared with LCLP, but such a reduction could not be expected at a phantom thickness of more than 30 cm, depending on maximum dose rate. The rate of reduction in surface dose in the case of exposure was considerably low at a phantom thickness of about 20 cm, while the other's (5, 10, 15, 25, 30 cm) reduction rates were about 40%. The length of PDD with INNOVA was shortened by 5 cm compared with LCLP. As a result, we obtained a reduction rate of surface dose of 11-15%, while the entrance dose was 10% lower. The reduction rate achieved with an additional filter was 43-60% in surface dose rate in fluoroscopy, whereas that of surface dose for exposure was about 50% at phantom thicknesses up to 20 cm, but remained just 25% thereafter. The results indicated that the reduction of surface dose with INNOVA could be changed by means of the phantom thickness, and we consider the effect achieved by the addition of a filter to be the main factor.

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

The flat-panel detector (FPD) has been introduced into clinical practice. A modified FPD, which has the ability to obtain dynamic chest radiographs, was introduced into our hospital, and clinical testing is ongoing. Both the inspiratory and expiratory phases have to be included in dynamic chest radiographs. The purpose of this study was to investigate the most appropriate chest radiography signal for observation of the respiratory process. We prepared ten protocol patterns that differed in terms of respiratory phase at X-ray exposure, exposure duration, and signal multiplicity. We also performed preliminary experiments and administered several questionnaires to ten volunteers. The volunteers breathed according to vocal and visual signals, and their respiratory waves were recorded by spirometer. The most appropriate protocol was similar to the method used for conventional chest radiography.

A new imaging plate (IP) with a transparent support and reading system that can detect emissions from both sides of the IP has been developed and has already been introduced in some facilities. In this study, low contrast threshold detectability was investigated experimentally for a CR system with a two-sided reading system (new CR) and for a conventional CR system. Images of a Contrast-Detail phantom were obtained with the new and conventional CR systems at dose levels corresponding to 26%, 49%, 82%, 103%, and 164% of the dose used for the screen-film system. Using an observer performance study of Contrast-Detail phantom images, the threshold contrast of disk-shaped objects ranging from 0.3 mm to 4.0 mm in diameter was determined. We also calculated image quality figure (IQF) from the results of observation. The new CR system showed significantly better contrast detectability than the conventional CR system. The use of a new CR system provided a reduction of approximately 25% in radiographic dose while providing comparable IQF.

To develop a method of kinetic radiography and a computer-aided diagnosis (CAD) system for quantitative evaluation of the temporomandibular joint (TMJ), dynamic images of the TMJ from one healthy volunteer were obtained by fluoroscopy in the lateral view on the right and left sides. The accumulated image subtraction technique extracted the condyle in each image. A sequential similarity detection algorithm (SSDA) was employed to trace the movement path and the velocity of the condyle. The shape of the path of the right condyle was smoother than that of the left condyle. The size of the maximum vertical and horizontal movements of the condyle were 4.6+/-0.1 mm and 15.0+/-0.2 mm, respectively. The velocity of the movement of the condyle was higher in the area close to the articular eminence than in any other area during the opening and closing of the mouth. This CAD system will contribute to the kinetic analysis of the TMJ for screening, follow-up study, and informed consent, providing speed, quantitation, and cost-effectiveness.

We had the chance of clinical studies by new proto-type Digital Subtraction Angiography (DSA) System with the Flat Panel Detector (FPD). That system has two types of detector, FPD and I.I.-CCD camera, and we can compare with image quality in clinical. We measured and discussed about the physical characteristic data of both detectors. Up to physical characteristic evaluation, FPD has good MTF and SNR performance, comparing with I.I.-CCD camera. In clinical evaluation, DSA image of FPD was superior to that of I.I.-CCD camera by visual comparison of medical doctors. Finally we discussed about the feasibility of replacement of detectors. We expect that DSA system will accept FPD in near future.

Present status of development of flat panel detectors and their clinical application in the world have been surveyed, and future trends are also explored especially in the field of material researches and methods of manufacturing. Also the importance of role of medical physicists on user side is described because characteristic physics measurement of a detector assembly is unavoidable and essential in quality assurance in clinical routine and acceptance test in hospitals. Even though physics measurements and clinical evaluations on flat panel detectors have shown remarkable progress and advances in these several years, future problems of cost down in manufacturing and quality assurance to prevent individual differences between detector assemblies must be resolved. Results of evaluation in mammography, chest radiography, fluoroscopy for cardiovascular examination, bone tumor examination and radiotherapy application indicate that flat panel detectors are future promising materials. Their systematic operation is contributing to heighten accuracy of image examinations and preciseness of radiation therapy. Encouragement to medical physicists relevant to flat panel detectors is also raised in this paper.

We measured and evaluated digital, pre-sampling and overall imaging properties (characteristic curve, modulation transfer function (MTF), Wiener spectrum (WS), noise equivalent quanta (NEQ) ) for Cannon's flat-panel detector (FPD), Fuji computed radiography (FCR) and screen-film (S/F) systems, respectively. First, the digital and overall characteristic curves of FPD and FCR systems were more wide dynamic range than that of the S/F system. Second, the pre-sampling and overall MTF of FPD system were better than those of FCR system a little at lower spatial frequencies than 0.8 mm(-1), but the overall MTF of FPD and FCR systems were worse than that of S/F system a little at all spatial frequencies. Third, the digital and overall WS of FPD system were similar or better than those of FCR system, but the overall WS of FPD and FCR systems were worse than that of S/F system. Fourth, the pre-sampling and overall NEQ of FPD system were better than those of FCR system a little at lower spatial frequencies than 1.6 mm(-1), but the overall NEQ of FPD and FCR systems were worse than that of S/F system at all spatial frequencies. Comparison of chest phantom images showed that the FPD produced images with quality comparable to or higher than those of the FCR system. From these results, we can expect that the FPD is useful machine by using digital image processing and so on in the radiology department.

We report the physical imaging properties of a flat panel detector (FPD) designed for radiographic imaging applications (Revolution XQ/i digital chest imaging system, G.E. Medical Systems). The imaging properties of the detector were evaluated through measurements of the characteristic curve, modulation transfer function (MTF), and Wiener spectrum. The digital characteristic curves of the FPD system were measured for the two tube voltages (80 kV and 120 kV). They showed that the correlation between the pixel values of FPD and the incident exposure to the FPD was a linear correlation. The dynamic range of characteristic curves had a range from about 0.003 to 2 microC/kg at the exposure. The presampling MTFs for different tube voltage were almost the same, when we measured the MTFs at 80 kV and 120 kV. And also, there was no significant difference between the MTFs measured with the slit in the direction parallel to the horizontal direction and with the slit in the perpendicular direction. The relative resolution of the FPD system was a 46% higher than that of ST-V imaging plate of FCR (Fuji Computed Radiography) system at 2 cycles/mm. The digital Wiener spectrum of the FPD system was about 1/10 lower than that of the CR system. Thus the FPD system can provide superior imaging performance due to both high resolution and low noise.

We measured and evaluated digital, pre-sampling and overall imaging properties (characteristic curve, Modulation Transfer Function (MTF), Wiener spectrum (WS), Noise Equivalent Quanta (NEQ) and Detective Quantum Efficiency (DQE)) for Hologic's direct type and Cannon's indirect type of Flat-Panel Detector (FPD). First, the digital and overall characteristic curves of both types of FPD were more wide dynamic range than that of the S/F system. Second, the pre-sampling and overall MTF of the direct-type FPD system were superior to those of the indirect-type FPD system. Third, for identical exposures, the digital and overall WS of the direct-type FPD system were similar or worse than those of the indirect-type FPD system, and for larger exposure, the digital WS of the both types of FPD system were smaller, but the overall WS of the both types of FPD systems were larger. Fourth, the digital and overall NEQ and DQE of the direct-type FPD system were worse than those of the indirect-type FPD system at lower spatial frequencies than 1.75 - 2.0 mm(-1), but were worse at higher spatial frequencies than 1.75 - 2.0 mm(-1). We show radiographs made with the direct type of FPD system. Radiographs of square wave chart show the difference in MTF and contrast of the both types of FPD systems. As the result of evaluation of radiographs of chest phantom in point of noise by radiologists and radiological technologists, the direct type of FPD system needed double or more exposure dose than own standard condition, this dose was same as the indirect-type FPD system. And radiologists evaluated radiographs of human body, spatial resolution was very good, but contrast was much more likely to high at standard parameter. Therefore we have to consider exposure condition and image processing for the direct type of FPD system.

We introduced digital X-ray diagnostic systems with Flat panel detector both in general X-ray systems and in Angiography systems. Our introduced Flat Panel Detector has the latest technology and has Cesium Iodide (CsI) that absorbs X-ray energy and generates visible light. Detected light signals make digital X-ray images. CsI is the most important material because its absorption rate of X-ray influences the strength of output digital signal. The purpose in this paper is checking that is latest Flat Panel Detector pulls out enough capability CsI has. Especially the thickness of CsI relates to X-ray absorption. X-ray absorption rate depended on the thickness of CsI was calculated by using simulated X-ray model and the future direction of Flat Panel Detector system was discussed.

In our country, the introduction of flat panel detector is carried out in the diagnosis region since before several years. In flat panel detector with the high image characteristic, large expectation is being placed. In this paper, image characteristic of flat panel detector and effectiveness of clinical application were reviewed. It is anticipated that flat panel detector with the excellent image characteristic gives large effect in the radiological diagnosis.

A flat-panel detector (FPD) is a long-awaited technology to implement the digital X-ray imaging technology into the radiological department. This paper describes the state-of-the-art technology and future prospects on the FPD technology. State-of-the-art technology was reviewed taking the CXDI series as an example. Several FPD-based systems have been introduced into the Japanese market since CXDI-11 opened it in November 1998. Accompanying CXDI-C2 for control, CXDI-22 for table position and CXDI-31 for portable, the CXDI series fulfills the requirement of the radiography room being a fully digitalized room. The FPD on the CXDI series is comprised of a scintillator (Gd(2)O(2)S:Tb(3+)) as a primary sensor in which the X-ray is captured and an amorphous silicon detector (LANMIT) as a secondary sensor in which the fluorescent light is detected. Since the scintillator is identical to that of the screen-film systems, it can be said as proven, durable and chemically stable and it is expected to produce the same image quality as the screen-film systems. CXDI-31, a portable FPD-based system, was developed targeting thinner dimensions, lightweight, durability and high spatial resolution. Thoroughly re-designing the mechanical structure and reducing the power consumption at the readout IC realized thinner dimensions. Introducing the portable note PC technologies successfully combined lightweight with durability. Improving the sensor process and re-designing the layout made the sensor high resolution without compromising the signal-to-noise ratio. Future prospects were overviewed in the aspect of technology and applications. Sensitivity, spatial resolution, frame rate and portability were described as the upcoming technology. Increasing gain and reducing noise will realize higher sensitivity, especially by adopting the PbI(2), HgI(2) or such photoconductor materials as the primary sensor. Pixelized amplifier will also achieve higher sensitivity. Layered sensor designed such that TFT layer and sensitive layer are constructed separately will decrease the pixel pitch lower than 100 microm. The FPD has been applied in radiography, mammography and angiography. It will expand the applications into low-dose fluoroscopy to replace the X-ray image intensifiers and into cone-beam computer tomography. What the FPD brought was mainly the efficient workflow of the X-ray technologist. However, diagnosis efficiency and patient benefit must be improved further more by combining FPD technology into computer-aided diagnosis, tele-radiography or other IT-based technologies. Such prospect may come true in the near future.

The imaging characteristics (contrast and noise) of x-ray film/screen combinations were examined for their suitability in the detection of faint nodules of lung cancer. Two hundred conventional chest radiographs of a human chest phantom were obtained with 5 mm or 10 mm spherically or hemispherically shaped simulated nodules placed on the posterior surface of an anthropomorphic chest phantom. Nodules were placed on several selected lung areas, and were overlain by the intercostal spaces, ribs or mediastinum. Five combinations of film/screen systems that differed in their contrast (characteristic curve) and noise were used to obtain the radiographs. The detectability of simulated nodules shown on the radiographs was evaluated based on the results obtained by an interpretive study by 6 observers utilizing receiver operating characteristic (ROC) analysis and calculating the average area under the ROC curve (Az). The system with standard contrast and improved noise reduction was favorable in detecting nodules of 5 mm in diameter. The system with latitude-type contrast was not suitable for the detection of nodules placed in the intercostal spaces. Systems with degraded noise or low contrast showed poor performance in detecting hemispheric nodules, since ill-defined nodules were overlain by the ribs. For the detection of nodules on the mediastinum or diaphragm, display of these regions with sufficient density and improved contrast appeared mandatory. The combination of a high contrast x-ray film, Iow noise x-ray film/screen combination, high voltage x-ray exposure, and the addition of a compensatory x-ray filter or screen appears suitable for improved recognition of a small, faint, lung nodules.

The usefulness and clinical applicability of computed radiography (FCR) in X-ray examination of the stomach were evaluated in comparison with film-screen (FS) radiography by both phantom experiments and clinical studies. Receiver operating characteristic (ROC) curve analysis consisting of 25 normal and 25 artificially created simulated lesions on an originally created Styrofoam phantom showed no difference in lesion detectability between FCR and FS radiography. Both were also equal in evaluation of the internal structure and margin of the 25 lesions by visual ranking. ROC curve analysis of clinical cases was performed in 30 cases, 20 normal and 10 abnormal, while evaluation by visual ranking was performed on 18 lesions. There was no significant difference between FCR and FS radiography either with ROC curve analysis or visual ranking, although the variations were somewhat greater in the clinical cases than in the phantom studies. I conclude that FCR is equal to FS radiography in X-ray examination of the stomach regarding both the detectability and visual conspicuity of the lesion. In view of the other advantages of FCR, it can safely replace conventional FS radiography in X-ray examination of the stomach.

We compared the ability of standard film-screen chest radiographs to detect simulated pulmonary nodules. The radiographs were taken with different X-ray filters and tube voltages. Detection capability was analyzed utilizing receiver operating characteristic (ROC) curves formed from the interpretation of six readers. Nodule detection was slightly better in images obtained with a tube voltage of 135 kVp than with one of 100 kVp (not statistically significant). Approximately equal detection performance was shown by a conventional film-screen system and FCR with three X-ray filter sets: a copper filter backed by aluminium, a tungsten filter backed by yttrium and aluminium, and a lead filter backed by yttrium and aluminium. Results showed less X-ray exposure with the two latter filter sets. Unenhanced FCR images taken with approximately the same X-ray exposure as conventional radiographs showed nearly equal ability to detect the simulated nodules.

The thorax has a wide dynamic range from low (lung fields) to high X-ray absorption (mediastinum, retrocardiac and retrodiaphragmatic areas). The conventional screen/film system cannot visualize each area of the thorax with good contrast on a single sheet of film with the wide latitude. To solve this problem, advanced multiple-beam equalization radiography (AMBER), a type of scanning equalization radiography, has been developed. The present studies were designed to evaluate the usefulness of AMBER for the chest from the experimental and clinical aspects. In the experimental study, an imaging technology assessment of density and contrast properties and a phantom study for detecting a simulated pulmonary nodule were carried out. In the clinical study, visualization of the normal structures and abnormal shadows in chest radiographs was assessed. X-ray findings in the AMBER films were compared with those of conventional chest radiographs using the screen/film system. In the analysis of density and contrast properties, AMBER showed more favorable contrast properties than the conventional system, regardless of background density. In the phantom study, the detectability of the nodule in the retrocardiac or retrodiaphragmatic region in an AMBER film was superior to that of the conventional system, and there was no reduction in detectability in other regions of the peripheral lung field. In the clinical assessment, AMBER was excellent for visualization of the mediastinum and the normal structures and lesions in the retrocardiac and retrodiaphragmatic areas. AMBER can be concluded to be excellent in visualizing not only the high absorption area, which is difficult to observe with the conventional system, but also the low absorption area.

We investigated the clinical usefulness of the asymmetric film-screen system on postero-anterior chest roentgenograms for thoracic lesions. The asymmetric film-screen system, the so-called Kodak Insight thoracic imaging system, records a different image on each side of double-emulsion film. An image displaying the lung field is captured on the anterior side of the film, while one displaying the mediastinal, retrocardiac and retrodiaphragmatic structures is captured on the posterior side. The clinical usefulness of the asymmetric film was evaluated in 20 patients for visibility of the anatomical structures and abnormal lesions in comparison with conventional film. In the asymmetric film-screen system, the front and rear screens were HC (high contrast) and Regular, respectively. Chest radiography was performed at 200mA and 100kVp. As conventional film, we used SRC film (Konica, orthotype film), and chest radiography was performed at 100mA and 130kVp. The chest roentgenograms obtained with the asymmetric film-screen system provided better information on normal structures and abnormal lesions in the lung field, but slightly inferior information on mediastinal structures. In conclusion, it was considered that the asymmetric film-screen system was useful for thoracic lesions.

The physical imaging properties of asymmetric systems and a conventional system were evaluated by measuring characteristic curves, resolution properties and noise Wiener spectra. The potential clinical application of asymmetric screen-film systems was studied by evaluating the visibility of the anatomical structures and various types of abnormalities in comparison with those of a conventional screen-film system. The asymmetric systems showed a wider dynamic range than the conventional system. The resolution properties of asymmetric systems depend on the combination of front and back screens used. Chest radiographs obtained with asymmetric systems improved the visibility of the mediastinal area. The visibility of the lung field in the asymmetric systems was slightly inferior to that with the conventional system when the same tube potential was used. However, the image quality and visibility of various abnormalities showed greater improvement with the asymmetric systems when a lower tube potential was applied. We conclude that the selection of radiographic techniques and combination of screens are important for the clinical use of asymmetric systems.

Image quality of digital chest radiography using FCR (Fuji Computed Radiography) was evaluated experimentally and clinically, comparing with the conventional radiography using regular film-screen system (F-S system). 1. In experimental study, Burger's phantom and Hawlet chart were used. The results were as follows: 1) Almost same amount of incident X-ray exposure was necessary for FCR to obtain the same resolution power as F-S system. 2) Contrast enhancement processing did not improve resolution power in FCR. It was improved by the processing of spatial frequency enhancement in the range of lower than 0.5 c/mm, but was decreased by the same processing in the range of higher than 0.5 c/mm. 2. In clinical study, chest radiograms of FCR and F-S system which were taken at the same day were evaluated. The results were as follows. 1) Firstly, the visibility of abnormal shadows which were classified into nine types was evaluated subjectively by two chest-radiologists. As the results, FCR was superior to F-S system in visibility of the lesions overlapping mediastinum and diaphragm, calcifications and bone lesions. FCR was, however, inferior to F-S system in visibility of ground glass shadows, fine reticular shadows and granular shadows. 2) In the second step, the detectability of those interstitial shadows was evaluated using ROC curve analysis. As the results, FCR was statistically inferior to F-S system in detectability of those interstitial shadows.

Conventional Radiography, Fuji Computed Radiography (FCR) hardcopy and CRT images were evaluated about the detectability of pulmonary nodule using the chest phantom. Conventional and digitized chest radiographs (FCR) were used, including 45 normal cases and 45 abnormal cases with a variety pulmonary nodule. Observer performance tests were conducted to compare the effects on diagnostic accuracy of Conventional Radiography, FCR hardcopy and CRT images, and diagnostic accuracy was determined with receiver operating characteristic (ROC) analysis. ROC study was performed in which six radiologists were asked to locate nodule on three modalities. Two CRT monitors were used to observed CRT images. The left side CRT monitor was divided into two parts and displayed two images which were done as same image processing as FCR hardcopy. The right side CRT monitor was divided into four parts and displayed four images as a subsidiary diagnosis. The upper two images were displayed to diagnose the nodule of cardiac and diaphragmatic area, and lower two images were displayed to diagnose the nodule of the lung field. The results were summarized as follows: 1) CRT images were superior in sensitivity (78.5%) to the others, and FCR hardcopys were superior in specificity (95.9%). 2) About the accuracy of 5 and 8 mm in diameter nodule detection, there was no significant difference among three modalities. 3) Diagnostic accuracy of 3 mm in diameter nodule detection was significantly greater with digitized radiographs (FCR 44.4%, CRT images 54.4%) than with conventional radiograph (17.7%).(ABSTRACT TRUNCATED AT 250 WORDS)

Threshold contrasts of low-contrast objects were compared between screen-film and computed radiography (CR) systems. Effects of incident exposure to the imaging plate (IP) and contrast enhancement on the detectability of low-contrast objects were also studied. We employed 18-alternative forced-choice (18AFC) experiments to study the dependence of the threshold contrasts of the test objects on the incident exposure, object size, and contrast enhancement. The results indicated that the threshold contrasts of CR system were comparable to that of the medium-speed screen-film system and increased by decreasing x-ray exposures. Although threshold contrasts decreased by contrast enhancement, the magnitude of improvement depended on the object size and incident exposure.