Image quality for five modern chest radiography techniques: a modified FROC study with an anthropomorphic chest phantom

The purpose of the study was to compare the image quality for one conventional and four digital chest radiography techniques. Three storage phosphor systems, one selenium drum system, and one film-screen system were compared using a modified receiver-operating-characteristics method. Simulated pathology was randomly positioned over the parenchymal regions and the mediastinum of an anthropomorphic phantom. Eight observers (four chest radiologists, one specialist in general radiology, one hospital physicist, and two radiographers) evaluated 60 images for each technique. The selenium drum system (Philips, Eindhoven, The Netherlands) rated best for the detection of parenchymal nodules. Together with the storage phosphor system of generation IIIN (Philips/Fuji), the selenium drum system also rated best for detection of thin linear structures. The storage phosphor system of generation V (Fuji) rated best for the detection of mediastinal nodules. The first generation of the storage phosphor system from Agfa (Mortsel, Belgium) rated worst for the detection of parenchymal nodules and thin linear structures. These differences were significant (p < 0.0001). Averaging the results for all test objects, the selenium drum system and the storage phosphor system of generation V were significantly better than the other systems tested. The film/screen system performed significantly better than the first-generation storage phosphor system from Agfa, equal to the generation IIIN storage phosphor system (Philips/Fuji) and significantly worse than the selenium drum system (Philips) and the generation-V storage phosphor system (Fuji). The conclusion is therefore that the image quality of selenium-based digital technique and of the more recent generations of storage phosphor systems is superior to both conventional technique and storage phosphor systems using image plates of older types. Received: 11 September 1997; Revised: 25 June 1998; Accepted: 18 February 1999     

Experimental investigations of image quality in X-ray mammography with conventional screen film system (SFS), digital phosphor storage plate in/without magnification technique (CR) and digital CCD-technique (CCD)

Comparison of image quality in X-ray mammography between conventional film screen film system (SFS), digital phosphor storage plate in and without magnification technique (CR) and digital CCD-technique (CCD). Radiograms of an RMI-mammography phantom were acquired using a conventional screen film system, three digital storage plate systems and two digital systems in CCD-technique. Additionally, the radiograms of one digital phosphor storage plate system were post-processed regarding contrast and included in the comparison. The detectability of details was best with the digital mammography in CCD-technique. After confirming these promising results in clinical studies, digital mammography should be able to replace conventional screen film technique.     

Digital chest radiography with a large image intensifier. An ROC study with an anthropomorphic phantom

The diagnostic performance of two systems for chest radiography was studied. One system was based on a large image intensifier, the other was a conventional film-screen system. The images from the image intensifier were studied either on a digital TV screen or on 100 mm photofluorograms. Receiver operating characteristic curve analysis was performed on images of an anthropomorphic chest phantom. Low-contrast MMAP (methyl methacrylate polymer) nodules and simulated vessels were positioned over the parenchymal and the mediastinal region of the phantom. Five observers assessed the digital monitor images, photofluorograms, and conventional full-size radiograms. The results showed a significantly superior detectability for the full-size radiograms over the digital monitor images both in the parenchyma and in the mediastinum. No significant difference was found between photofluorograms and digital images.     

Patient absorbed doses in digital grey-scale fluorography

This article describes a preliminary comparison between the levels of patient dose used in digital grey-scale fluorography (DGF) and screen-film radiography. Patient doses were measured in three common radiographic examinations, postero-anterior chest, antero-posterior lumbar spine and lateral lumbo-sacral junction, using thermoluminescent dose-meters and an anthropomorphic phantom. Within the limitations of the image quality currently available in DGF, the findings indicate that digital radiography with the large-field X-ray image intensifier promises significant savings in patient dose compared with conventional radiography.     

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

Purpose

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.

Materials and methods

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.

Results

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.

Conclusions

Generally, lowering tube potentials in chest examinations seems to allow better image quality/effective dose ratio when using digital equipment.     

Digital radiography und fluoroscopy. Basics of technology, imaging properties and applications

For 110 years, x-rays and special x-ray films have been used in medical diagnostics. New developments in the field of x-ray techniques, and especially new computer applications, have led to new imaging techniques which have substantially expanded the spectrum of radiological examinations. In spite of significant technological and medical advances in the field of MRI and multidetector-CT, radiographic images of the lungs, skeleton and organs still comprise up to 80% of the routine radiological workload. The increasing availability of digital detectors has led to the continual replacement of conventional film/screen systems. The inclusion of digital mammography was delayed due to the higher requirements for spatial resolution. For about 2 years, dynamic flat panel detectors have started to replace the image intensifier which has been used in fluoroscopy for 40 years.     

Digitale Radiographie und Fluoroskopie

For 110 years, x-rays and special x-ray films have been used in medical diagnostics. New developments in the field of x-ray techniques, and especially new computer applications, have led to new imaging techniques which have substantially expanded the spectrum of radiological examinations. In spite of significant technological and medical advances in the field of MRI and multidetector-CT, radiographic images of the lungs, skeleton and organs still comprise up to 80% of the routine radiological workload. The increasing availability of digital detectors has led to the continual replacement of conventional film/screen systems. The inclusion of digital mammography was delayed due to the higher requirements for spatial resolution. For about 2 years, dynamic flat panel detectors have started to replace the image intensifier which has been used in fluoroscopy for 40 years.     

Image quality vs. radiation dose for a flat-panel amorphous silicon detector: a phantom study

The aim of this study was to investigate the image quality for a flat-panel amorphous silicon detector at various radiation dose settings and to compare the results with storage phosphor plates and a screen-film system. A CDRAD 2.0 contrast-detail phantom was imaged with a flat-panel detector (Philips Medical Systems, Eindhoven, The Netherlands) at three different dose levels with settings for intravenous urography. The same phantom was imaged with storage phosphor plates at a simulated system speed of 200 and a screen-film system with a system speed of 160. Entrance surface doses were recorded for all images. At each setting, three images were read by four independent observers. The flat-panel detector had equal image quality at less than half the radiation dose compared with storage phosphor plates. The difference was even larger when compared with film with the flat-panel detector having equal image quality at approximately one-fifth the dose. The flat-panel detector has a very favourable combination of image quality vs radiation dose compared with storage phosphor plates and screen film.     

Aktuelle Entwicklungen auf dem Gebiet der digitalen Thoraxradiographie

All three currently commercially available systems for digital radiography of the chest such as the selenium drum, storage phosphor plates and the flat panel direct detector systems provide an excellent image quality that is at least equivalent or superior to that of conventional film. Reasons for that are the continuously improved detective or dose efficiency of the detector systems and an improved image processing. The new direct detector systems have the largest potential for dose reduction while storage phosphor and selenium radiographs are usually obtained with a dose comparable to that of a 400 speed system. Improved image processing algorithms allow for the production of digital images that are adapted to the conventional image characteristics within the lung regions combined with an increased transparency of the high absorption areas such as the retrocardial and retrodiaphragmatic regions.     

Storage phosphor radiographs vs conventional films: interpreters' perceptions of diagnostic quality

We compared storage phosphor images with high-quality conventional film-screen images by evaluating physicians' perceptions of image quality and their levels of confidence in making diagnostic interpretations. Eight physicians each examined 11 posteroanterior storage phosphor chest images (obtained with an experimental high-resolution storage phosphor system) side by side with conventional film images of the same patients. The storage phosphor images were obtained only minutes after the conventional radiographs were obtained. Storage phosphor images were digitally printed onto films in two different formats: a full-size (12 X 14 in. [30.5 X 35.6 cm]) and a half-size format of four computer-processed, minified images (6 X 7 in. [15.2 X 17.8 cm] each). Most of the responses rated the quality and resolution/sharpness of conventional images, as well as their ability to display the complete lung field, as either "excellent" or "good"; however, the storage phosphor images received significantly better ratings (p less than .05). Computer-processed minified versions of the storage phosphor images also received better ratings than did the conventional images. When the physicians were asked to rate their confidence level in making diagnoses with each of the two techniques, in 74 of 88 cases they indicated that their level of confidence would be at least as high when using the storage phosphor images as when using the conventional images.     

Stimulable phosphor plates in chest radiology

LANGUAGE="EN">Summary. The stimulable phosphor plate technique has revolutionised radiology with portable equipment. The image quality permits diagnosis under difficult control conditions (ICUs). In order to achieve a signal-to-noise ratio, and therefore a contrast resolution similar to the commonly used film/screen systems, a higher radiation dose is needed. However, overall, with this technique a radiation dose reduction may be achieved as a result of the elimination of the need for retakes. The available stimulable phosphor plate systems, with adequate image processing are reliable, and at least as good as conventional film/screen systems for diagnosis in chest radiography. There are, however, other aspects that make the stimulable phosphor plate technique particularly appealing. Firstly, its reproducibility, which particularly in chest radiography allows images to be obtained with the same grey scale and darkness. Secondly, as this technique permits digital archiving and visualisation of images on screen, images can be rapidly distributed over a network making them available when and where they are needed.     

Preliminary results with digital luminescence radiography in radiotherapy

Port films in radiation therapy suffer from low image contrast und exposure errors. We examined the potential of computed radiography with a storage phosphor system (FCR-901/Siemens Digiscan) to overcome these drawbacks. Port films of various treatment sites were obtained for both, conventional films and digital storage phosphor screens with a DuPont cassette and steel intensifier screens under identical exposure settings. We examined port films from a linear accelerator and from a 60Co source. We found a superior contrast in the digital images and an almost total elimination of exposure errors. The differences between digital and conventional images, however, were less pronounced with films from the 60Co source. Unsharp mask filtering (medium kernel size, moderate enhancement) further improved image quality. Several sources of artefacts in the digital images could be described.     

Efficacy of daily bedside chest radiography as visualized by digital luminescence radiography

To determine the diagnostic impact of daily bedside chest radiography in comparison with digital luminescence technique (DLR; storage phosphor radiography) and conventional film screen radiography, a prospective randomized study was completed in 210 mechanically ventilated patients with a total of 420 analysed radiographs. The patients were allocated to two groups: 150 patients underwent DLR, and 60 patients underwent conventional film screen radiography. Radiological analysis was performed consensually and therapeutic efficacy was assessed by the clinicians. There was no statistical significant difference between the frequency of abnormal findings seen on DLR and conventional film screen radiography. In total, 448 abnormal findings were present in 249 of 300 DLR and 97 of 120 conventional film screen radiographs. The most common findings were signs of overhydration (41%), pleural effusion (31%), partial collapse of the lung (11%) and pneumothorax (2%). One hundred and twenty-three of 448 (27%) of these abnormal findings were thought to have a considerable impact on patient management. The high rate of abnormal findings with significant impact on patient management suggests that the use of daily bedside chest radiography may be reasonable.     

Large-screen image intensifier photofluorography compared with full-size screen-film technique in chest radiography

Large-screen image intensifier photofluorography revealed a radiation dose and exposure time of about one third of those of a medium speed rare-earth screen/film (Trimax T4/XD) combination for full-size chest radiography. The resolving power of the former technique is somewhat poorer and there is a moderate electron-òptical distortion in the peripheral field. In clinical chest radiography photospot films showed excellent demonstration of the central areas of the image but slight deterioration in peripheral parts. The minification effect of the photofluorographic films is advantageous for visual perception of many anatomic details on chest radiographs. The type of viewing device for photospot films is important.     

Comparing image quality of flat-panel chest radiography with storage phosphor radiography and film-screen radiography

OBJECTIVE: To evaluate image quality of a large-area direct-readout flat-panel detector system in chest radiography, we conducted an observer preference study. A clinical comparative study was conducted of the flat-panel system versus the storage phosphor and standard film-screen systems. MATERIALS AND METHODS: Routine chest radiographs (posteroanterior) of 30 patients that were obtained using flat-panel, storage phosphor, and film screen systems were compared. The visibility of 10 anatomic regions and the overall image quality criteria were rated independently by three radiologists using a 5-point scale. The significance of the differences in diagnostic performance was tested with a Wilcoxon's signed rank test. Dose measurements for the three modalities were performed. RESULTS: The flat-panel radiography system showed an improved visibility in most anatomic structures when compared with a state-of-the-art conventional film-screen system and an equal visibility when compared with a storage phosphor system. The flat-panel system showed the greatest enhancement in the depiction of small detailed structures (p < 0.05) and achieved this with a reduction in overall radiation dose of more than 50%. CONCLUSION: The visibility of anatomic structures provided by this flat-panel detector system is as good as if not better than that provided by conventional or storage phosphor systems while emitting a reduced radiation dose.     

Clinical comparative study with a large-area amorphous silicon flat-panel detector: image quality and visibility of anatomic structures on chest radiography.

OBJECTIVE: The objective of this study was to compare clinical chest radiographs of a large-area, flat-panel digital radiography system and a conventional film-screen radiography system. The comparison was based on an observer preference study of image quality and visibility of anatomic structures. MATERIALS AND METHODS: Routine follow-up chest radiographs were obtained from 100 consecutive oncology patients using a large-area, amorphous silicon flat-panel detector digital radiography system (dose equivalent to a 400-speed film system). Hard-copy images were compared with previous examinations of the same individuals taken on a conventional film-screen system (200-speed). Patients were excluded if changes in the chest anatomy were detected or if the time interval between the examinations exceeded 1 year. Observer preference was evaluated for the image quality and the visibility of 15 anatomic structures using a five-point scale. RESULTS: Dose measurements with a chest phantom showed a dose reduction of approximately 50% with the digital radiography system compared with the film-screen radiography system. The image quality and the visibility of all but one anatomic structure of the images obtained with the digital flat-panel detector system were rated significantly superior (p < or = 0.0003) to those obtained with the conventional film-screen radiography system. CONCLUSION: The image quality and visibility of anatomic structures on the images obtained by the flat-panel detector system were perceived as equal or superior to the images from conventional film-screen chest radiography. This was true even though the radiation dose was reduced approximately 50% with the digital flat-panel detector system.     

High frequency edge enhancement in the detection of fine pulmonary lines. Parity between storage phosphor digital images and conventional chest radiography

Fine linear structures represent a severe test of the minimum spatial resolution that is needed for digital chest imaging. We studied the comparative observer performance of storage phosphor digital imaging (1760 X 2140 pixel matrix, 10 bits deep), and conventional radiography (Lanex medium screen, Ortho C film) in the detection of simulated fine pulmonary lines superimposed on the normal chest when exposure factors were identical (20mR skin entrance dose at 141 kVp). Receiver operating characteristics analysis of 2160 observations by six readers found that high frequency edge-enhanced digital images (ROC area: 0.78 +/- 0.06) performed better than unenhanced digital images (ROC area: 0.70 +/- 0.07) (P less than 0.01 for paired t-test), and that edge enhanced digital images performed on a par with conventional radiography (ROC area: 0.78 +/- 0.09). We conclude that for the detection of fine linear structures, storage phosphor digital images can perform on a par with higher resolution conventional chest radiographs when a high frequency edge-enhancement algorithm is employed.     

AMBER and conventional chest radiography: comparison of radiation dose and image quality.

The authors compared the radiation dose to the patient and the image quality in advanced multiple-beam equalization radiography (AMBER) with those in conventional chest radiography. Organ doses were estimated for an anthropomorphic phantom from measurements with thermoluminescence dosimeters. These measurements were supplemented with area-air kerma products obtained during chest examinations of 223 patients. Image quality was determined by means of a contrast-detail image evaluation test. An improvement in image quality in regions of high absorption and an increased dose to the patient were found for the AMBER technique compared with the conventional technique. However, for both techniques, the radiation exposure was relatively low compared with other reported values of patient dose during chest radiography. The estimated effective dose for an average-size patient during chest radiography with posteroanterior and lateral projections is 0.085 mSv for the conventional and 0.14 mSv for the AMBER technique.     

Single exposure simultaneous acquisition of digital and conventional radiographs utilizing unaltered dose

We describe the simultaneous acquisition of digital and conventional radiographs with a single standard radiographic exposure. A digitizable storage phosphor (ST Imaging Plate, FujiTM) is sandwiched into a radiographic cassette (X-Omatic, KodakTM) behind a conventional radiographic film-screen combination (Lanex medium screens, OC film, KodakTM). The barium fluorohalide storage phosphor is digitized with a helium-neon laser scanner (TCR 201, ToshibaTM), and the conventional radiograph is processed in the standard fashion (M7B, KodakTM). The storage phosphor is exposed by the "wasted" radiation normally exiting the back of the film-screen combination (32% of the cassette entrance dose at 141 kVp). At a standard exposure (6.3 mAs), the conventional radiograph is of unaltered quality, and the digital image appears to have an adequate signal-to-noise ratio for chest studies despite the lower exposure dose. This technique produces twin images of identical spatial and temporal registration and avoids the added radiation exposure normally required to carry out comparative studies.     

Digital radiology. Clinical experience

The authors report the experience achieved at the Stanford University (USA) with a digital radiography system which allows the digitization of the film and of the images collected with photostimulable phosphors. The phosphor is essentially an intensifying screen where a latent image is stored after exposure to X-rays and is extracted by a laser scanning. The images collected with the digitized film and with the phosphor (chest, breast, bone) have been analyzed. The digitized film offers potential diagnostic advantages over the conventional film, because of the contrast manipulation and many other processing options. The possibility to recover the information of overexposed films appears very attractive. The photostimulable phosphors allow to get good quality images, with a consistent reduction of dose and costs. These plates offer the possibility, in the next future, to replace the conventional screen-film systems.