Digital radiography versus conventional radiography during excretory urography: our experience

The authors describe a computed radiographic system employed to generate and archive digital images in intravenous urography. For each exposure the system produces two digital images: the first (left image) simulates a conventional screen-film radiograph, the second (right image); enhances some spatial frequencies and emphasizes the margins of the structures. These images can be modified in their chief parameters and then printed by a laser-printer and archived on optical disks. Four experienced radiologists evaluated digital images with regard to some chief diagnostic parameters and, in 50 patients, they compared digital images with conventional screen-film radiographs and submitted the results to statistical analysis. For some of the chosen parameters, particularly for the evaluation of renal margins before and after contrast medium injection, digital images gave statistically better results than conventional films, while, no statistically significant different was observed for the other parameters. From the results of this preliminary study digital radiography was found to be useful in intravenous urography by reducing the patient's exposition dose, by always obtaining images of good quality, and by enhancing some particular features of the standard image; on the other hand there were many unsolved problems regarding the communicating and archiving system (PACS), because of the slowness of the image transfer procedure, difficulties in data transmission and complexity of referential procedures.     

Diagnostic quality of portable abdominal radiographs in neonates with necrotizing enterocolitis: digitized vs nondigitized images

Digital manipulation of radiographic images has prompted significant interest because of the potential for improving image quality and diagnostic accuracy. We compared conventional and digital radiographs in the evaluation of neonatal necrotizing enterocolitis (NEC). Fifty abdominal radiographs in neonates with suspected or autopsy-confirmed NEC and 50 similar radiographs of neonates without suspicion of NEC were digitized. Definition of intraabdominal anatomy was optimized by window width and level adjustment. Hard-copy radiographs of the digitally manipulated images were then produced by a laser printer. Twelve general radiologists each evaluated, without benefit of clinical information, a random mixture of 50 cases of NEC and normal controls, with both conventional and digital images for each case, for a total of 100 radiographs reviewed. Each image was evaluated for overall suspicion of NEC and the presence and severity of six radiographic signs of NEC. The radiologists also rated their confidence in their assessments. The results were compared with those from a similar analysis by an experienced pediatric radiologist to ensure validity of image evaluation. No statistically significant differences were found between the conventional and digital imaging formats for the assessment of the signs of NEC (p = .15) or for determination of the overall suspicion of NEC (p = .07). Our results show the digitized and the conventional, nondigitized radiographs to be at least equally useful for evaluating the radiographic signs of NEC and suggesting an appropriate diagnosis.     

The effect of varying high pass filter parameters on the detectability of isolated pulmonary nodules in digitized chest images

The effect of image processing of digital radiographic data on lesion detectability in clinical images has not been systematically studied. In this experiment, we evaluated a low frequency suppression filter program applied to CT digital radiographic localization images (General Electric Scoutview). Three different filter parameters affecting edge enhancement and local image contrast were applied to a set of digital chest images. A standard observer detection experiment comparing the variously filtered digital images and standard chest radiographs in the detection of lung nodules (11 peripheral lung fields, one superimposed on aortic arch) was performed. Standard chest radiography was more sensitive than the digital chest images, although some improvement was noted with increase in local image contrast and edge enhancement. Both image formats were equally specific. Image processing would be better evaluated using a digital imaging system with better performance parameters.     

Double-contrast arthrography of the knee: a digital technique study

From October 1989, in our Radiology Department, digital radiographic techniques have been applied to double-contrast arthrography of the knee. In this preliminary work we examine the diagnostic contribution of computed radiography to arthrographic findings by comparing image quality of conventional and digital radiographs using a dedicated Philips unit. The digital unit is compatible with all the extant radiographic equipment in our department and automatically supplies two images, the first one resembling a conventional radiograph, the second one characterized by a broader exposure range that allows a clear visualization of soft tissues. To obtain high-quality radiographs the processing curves of the system were modified, in particular by shifting the curve leftward, thus reducing its slope, and by amending the parameters related to spatial frequencies. The changes in the reading curves made these images more useful: they were more homogeneous and allowed a better evaluation of fine details. Relative to the second type of images, characterized by both edge enhancement and a broader recording range, it was enough to shift the curve along the X-axis to compensate for a moderate image overexposure. Keeping in mind that the aim of this preliminary work was not compare the two techniques from a diagnostic point of view, in the authors' opinion the two yield similar information for the diagnostic evaluation of meniscal traumas. On the contrary, if the same principles are applied to the evaluation of capsulo-ligamentous components, digital arthrography appears to be more accurate than the conventional technique, the latter being deceptive especially in the evaluation of cruciate ligaments.     

Conventional radiography and digital radiography of the thorax: evaluation of anatomo-radiological parameters

We report the results of a comparative study of digital and conventional chest radiographs to detect normal anatomical structures of the thorax. A digital Toshiba unit (TCR 201) was used to examine 100 selected patients who were diagnosed with no chest pathologic conditions. The images in both modes were submitted for interpretation to five radiologists. The depiction of nine normal anatomical structures was more accurate on digital than on conventional radiographs. The mean confidence levels achieved in viewing digital images were higher than those obtained with conventional radiographs. This difference was statistically significant (p = 0.002).     

Digital chest radiography with a large-area flat-panel silicon X-ray detector: clinical comparison with conventional radiography

This was a radiologists' preference study to compare a digital chest radiography system that utilizes a large-area silicon flat-panel detector with conventional radiography for visualizing anatomic regions of the chest. Conventional and digital posteroanterior (PA) and lateral chest radiographs were obtained in 115 patients. The PA and lateral image pairs were compared independently by three radiologists rating the overall appearance, 11 anatomic regions in the PA, and 9 in the lateral views. Statistical analysis was performed with the Wilcoxon signed-rank test with Bonferroni-Holm adjustment (p=0.05). For the PA view, the digital system performed significantly better for the overall appearance and for all anatomic regions except for the peripheral pulmonary vasculature and hilum, where no significant difference was found. For the lateral digital images, the regions trachea, costodiaphragmatic recess, and hilum were rated significantly worse. The regions retrosternal and retrocardiac lung were rated significantly better. The other regions and the overall appearance showed no significant differences. The described digital chest radiography system showed statistically superior visualization of anatomic regions for PA and an ambiguous performance for lateral images as compared with conventional radiography. After changing some image processing parameters for the lateral view, this system may be suitable for digitalization of chest radiography.     

Digital radiography of the chest: clinical experience with a prototype unit

A prototype digital unit dedicated to chest radiography was used to examine 50 selected patients for a comparison study of the capability of digital images and conventional chest radiographs to reveal normal anatomic structures and a variety of pathologic states. The images in both modes were submitted for interpretation to seven experienced radiologists and a standardized questionnaire completed for each. Visibility of seven anatomic structures in the mediastinum was consistently better on the digital images than on the conventional radiographs. With minor exceptions, pathologic states were equally well seen in the two systems. Despite the less familiar viewing format of the digital images, the mean confidence levels achieved were higher than for those on the conventional radiographs; this difference was statistically significant both for normal anatomic structures (p = 0.001) and pathologic states (p = 0.01). The advantages and disadvantages of the digital technique are discussed.     

Report on a new type of trauma full-body digital X-ray machine

The purpose of this study was to evaluate the diagnostic equivalence, radiation dose, clinical usefulness and radiographic aspects of a low-dose, full-body digital X-ray machine in a busy trauma unit. A digital trauma X-ray machine known as "LODOX" was compared with conventional radiography between June 1999 and November 2001 in the Groote Schuur Hospital Trauma Unit, Cape Town. Digital images of a variety of body regions commonly imaged in trauma were compared for diagnostic image quality in a number of categories with equivalent conventional radiographs. A seven-point equivalence scoring system ranging from much inferior (−3) through equivalent (0) to much superior (+3) was used in each category. Radiation dose was recorded and compared with that in conventional measurements. Turnaround times of patients undergoing digital and conventional X-rays were evaluated. Clinical and radiographic issues were assessed by staff feedback. The digital images when compared with conventional film had an overall mean equivalence score of −0.429, with a standard deviation (SD) of 0.77. The best digital performance was in the mediastinum (mean 0.346, SD 0.49) and the weakest was for bony detail (mean −0.654, SD 0.81). Relative digital radiation dose compared to conventional varied from 72% (chest) to 2% (pelvis), with a simple average of 6%. Radiographic points included full-body imaging capability and differing positioning, penetration, workflow and practicality considerations. The digital images required overall patient times of 5–6 min, compared with 8–48 min for conventional X-rays. New installations are under way, and computed tomography and angiography applications are being explored. FDA approval is awaited. Projected cost is similar to that of flat-panel digital units. This digital unit was felt to be diagnostically substantially equivalent to conventional radiographs, with low-dose full-body imaging, improved workflow, digital technology and long-term cost benefits as potentially favourable contributions to trauma imaging. Electronic Publication     

Film tomography compared with film and digital bitewing radiography for proximal caries detection

OBJECTIVES: The purpose of this study was to evaluate the efficiency of conventional tomography for proximal caries detection compared with conventional bitewing and digital intraoral radiography. METHODS: In this study, 48 extracted human posterior permanent teeth were used. Conventional bitewing radiographs, digital intraoral radiographs and conventional tomograms were obtained of the teeth. The presence or absence of caries was scored according to a five-point scale by two oral and maxillofacial radiologists. True caries depth was determined by histological examination. The diagnostic accuracy of each radiographic system was assessed by means of receiver operating characteristic (ROC) curve analysis. The mean of areas under the ROC curve (A(z)) was analysed by pairwise comparison of ROC curve. The interobserver agreement was evaluated using a t-test. RESULTS: The statistical analysis of A(z) scores has shown no significant difference for three imaging modalities (P>0.05). There was no statistically significant difference between interobserver agreement (P>0.05). CONCLUSIONS: This study has demonstrated that the diagnostic accuracy of conventional tomograms is comparable to that of conventional bitewing and digital intraoral radiographs for proximal caries detection.     

Effects of optimization and image processing in digital chest radiography: an ROC study with an anthropomorphic phantom.

A digital system for chest radiography based on a large image intensifier was compared to a conventional film-screen system. The digital system was optimized with regard to spatial and contrast resolution and dose. The images were digitally processed for contrast and edge enhancement. A simulated pneumothorax and two simulated nodules were positioned over the lungs and the mediastinum of an anthropomorphic phantom. Observer performance was evaluated with ROC analysis. Five observers assessed the processed digital images and the conventional full-size radiographs. The time spent viewing the full-size radiographs and the digital images was recorded. For the simulated pneumothorax, the results showed perfect performance for the full-size radiographs and detectability was high also for the processed digital images. No significant difference in the detectability of the simulated nodules was seen between the two imaging systems. The results for the digital images showed a significantly improved detectability for the nodules in the mediastinum as compared to a previous ROC study where no optimization and image processing was available. No significant difference in detectability was seen between the former and the present ROC study for small nodules in the lung. No difference was seen in the time spent assessing the conventional full-size radiographs and the digital images. The study indicates that processed digital images produced by a large image intensifier are equal in image quality to conventional full-size radiographs for low-contrast objects such as nodules.     

Efficacy of digital radiography for the detection of pneumothorax: comparison with conventional chest radiography.

As part of our continuing evaluation of the clinical applicability of digital radiography, we compared the abilities of radiologists to detect pneumothoraces on conventional chest radiographs with their performances when using three formats of digitally obtained images. Twenty-three frontal-view chest radiographs with pneumothoraces and 22 other chest radiographs, either normal or showing miscellaneous abnormalities, were interpreted by five experienced radiologists in each of four formats: conventional film-screen chest radiographs, small-format (17.8 x 21.6 cm) computed radiographs, large-format (35.6 x 43.1 cm) computed radiographs, and digital images viewed on an interactive electronic workstation. The receiver-operating-characteristic curve areas for each observer for the four types of images were compared by a z test on a critical ratio, and the mean sensitivity and specificity values were compared by the sign rank test. The mean areas under the receiver-operating-characteristic curves ranged from 0.869 for the digital workstation to 0.915 for film-screen images. The differences observed among formats were not statistically significant. Mean specificities also were not significantly different, ranging from 0.90 for large-format computed radiographs to 0.96 for the digital workstation. Mean sensitivity ranged from 0.65 for the digital workstation to 0.82 for film-screen images. Radiologists interpreting digital workstation images were significantly less sensitive in detecting pneumothoraces than with film-screen and small-format computed images (p = .06). In this study, radiologists detected pneumothoraces equally well on conventional film-screen radiographs and digital images printed on film; however, they detected pneumothoraces less well on electronic viewing consoles. This latter finding reflects an important practical difference in the working behavior of radiologists interacting with a digital workstation.     

Clinical evaluation of digital radiography based on a large-area cesium iodide-amorphous silicon flat-panel detector compared with screen-film radiography for skeletal system and abdomen

The aim of this clinical study was to compare the image quality of digital radiography using the new digital Bucky system based on a flat-panel detector with that of a conventional screen-film system for the skeletal structure and the abdomen. Fifty patients were examined using digital radiography with a flat-panel detector and screen-film systems, 25 for the skeletal structures and 25 for the abdomen. Six radiologists judged each paired image acquired under the same exposure parameters concerning three observation items for the bone and six items for the abdomen. Digital radiographic images for the bone were evaluated to be similar to screen-film images at the mean of 42.2%, to be superior at 50.2%, and to be inferior at 7.6%. Digital radiographic images for the abdomen were judged to be similar to screen-film images at the mean of 43.4%, superior at 52.4%, and inferior at 4.2%; thus, digital radiographic images were estimated to be either similar as or superior to screen-film images at over 92% for the bone and abdomen. On the statistical analysis, digital radiographic images were also judged to be preferred significantly in the most items for the bone and abdomen. In conclusion, the image quality of digital radiography with a flat-panel detector was superior to that of a screen-film system under the same exposure parameters, suggesting that dose reduction is possible with digital radiography.     

Computed radiography in musculoskeletal imaging: state of the art.

Computed radiography is a 2K x 2K x 10 bit digital radiographic system that replaces the film-screen combination with a photo-stimulable phosphor plate. The advantages of this relatively new technology include linear detector response, improved detector efficiency, and digital processing capabilities. Musculoskeletal applications benefit significantly from these attributes, which result clinically in the ability to reduce both radiation dose and number of exposures. Studies of observers' performance have shown no statistically significant difference in diagnostic accuracy between film-screen and computed radiographic musculoskeletal images. Computed radiography is particularly useful in the evaluation of the musculoskeletal system in traumatized patients with portable radiographs, spine radiographs, scoliosis studies, and depiction of soft-tissue abnormalities. Limitations include change in image format and size, high cost, decreased spatial resolution, restricted throughput, increased perception of noise, and new artifacts that must be recognized. Spatial resolution limitations of computed radiography in identification of fine detail information can be improved by using magnification techniques. Radiation dose reduction with an exposure decrease of 25-50% can be achieved without loss of diagnostic accuracy, although this depends on the examination and the abnormality. An interactive workstation is important in the use of a computed radiographic system with capabilities to adjust display parameters to best depict images and disease. We conclude that computed radiography is an alternative to film-screen radiography without significant differences in diagnostic quality in the evaluation of musculoskeletal images.     

Low-dose digital computed radiography in pediatric chest imaging

A prototype digital computed radiographic imaging system that uses laser-stimulated luminescence was evaluated for its ability to achieve reproducible, high-detail, low-dose pediatric chest radiographs. Using this system, we performed a total of 401 examinations in infants and children, and achieved an 85% reduction in radiation dose, as compared with that delivered when film-screen techniques were used. We also achieved satisfactory image resolution, and the images obtained were of acceptable diagnostic quality. A direct comparison of analog and digital radiographs showed that comparable quality and clinical acceptability could be readily maintained between the two techniques. This study shows that high-quality images can be produced by this system at radiation doses reduced by 85% when compared with doses from standard radiographic techniques.     

Accuracy of direct digital radiography for detecting occlusal caries in primary teeth compared with conventional radiography and visual inspection: an in vitro study

Objectives

The diagnosis of caries lesions is still a matter of concern in dentistry. The diagnosis of dental caries by digital radiography has a number of advantages over conventional radiography; however, this method has not been explored fully in the field of paediatric dentistry. This in vitro research evaluated the accuracy of direct digital radiography compared with visual inspection and conventional radiography in the diagnosis of occlusal caries lesions in primary molars.

Methods

50 molars were selected and evaluated under standardized conditions by 2 previously calibrated examiners according to 3 diagnostic methods (visual inspection, conventional radiography and direct digital radiography). Direct digital radiographs were obtained with the Dixi3 system (Planmeca, Helsinki, Finland) and the conventional radiographs with InSight film (Kodak Eastman Co., Rochester, NY). The images were scored and a reference standard was obtained histologically. The interexaminer reliability was calculated using Cohen''s kappa test and the specificity, sensitivity and accuracy of the methods were calculated.

Results

Examiner reliability was good. For lesions limited to the enamel, visual inspection showed significantly higher sensitivity and accuracy than both radiographic methods, but no significant difference was found in specificity. For teeth with dentinal caries, no significant differences were found for any parameter when comparing visual and radiographic evaluation.

Conclusions

Although less accurate than the visual method for detecting caries lesions confined to the enamel, the direct digital radiographic method is as effective as conventional radiographic examination and visual inspection of primary teeth with occlusal caries when the dentine is involved.     

Digital radiography in urography

The clinical utility was evaluated of a computed radiographic system in urography. The system (FCR 101, Philips Medical Systems, Inc., Shelton, CT) is based on a photo-stimulatable phosphor screen (imaging plate) for X-ray image detection and storage. The X-ray information recorded on the imaging plate is converted into digital from and processed by means of a computer. After processing is completed, the digitized image is reversed back to analogic signals, which modulate the intensity of a laser beam scanning the image on a single-emulsion film (Fuji CR 633). Two hundred IVP's were obtained in four groups, of 50 patients each, with normal azotemic values by rapid infusion of a low osmolality contrast medium (iopamidol 150 mgI/ml). While conventional radiographs were performed on the first group of patients with the injection of 0.6 gI/kg body weight of contrast medium, digital examinations were carried out, in the remaining three groups, with the injection of 0.6, 0.3 and 0.12 gI/kg, respectively. The digital images were processed with the "Abdomen-routine" program. A specific algorithm was implemented in order to reduce the excessive contrast resolution of the bladder, which is due to the characteristics of the nonionic contrast medium and enhanced by the reading program. The image details were evaluated by two observers and then statistically analyzed with nonparametric tests. Statistical analysis did not show any difference in the quality of digital and screen-film images. Image processing improved some inadequate images, by reducing the contrast resolution of the bladder, and allowed a better detection of some details. Low doses (0.3 gI/kg) of a low osmolality (150 mgI/kg) contrast medium were enough to obtain good images. Another biological advantage was obtained by a consistent radiation dose reduction (about 40%).     

A comparison of conventional intra-oral radiography and computer imaging techniques for the detection of proximal surface dental caries.

The detection of proximal surface caries by the visual interpretation of bitewing radiographs is known to be relatively inaccurate. The present study was designed to examine whether computer image processing could improve the diagnostic accuracy. A computer-aided, software-driven, TV-based system was used to digitize conventional radiographs and digitally process the images using histogram equalization and grey-scale inversion to enhance the images. The computer-enhanced images were compared with conventional intra-oral radiographs for the detection of proximal surface caries using receiver operating characteristic analysis. The results indicate that the digital image processing techniques used did not improve the diagnostic accuracy of dental radiographs. No significant difference in diagnostic accuracy could be detected between the non-enhanced digital images and conventional film-based images for the detection of proximal surface caries.     

Digital subtraction radiography in artificial recurrent caries detection.

The diagnostic accuracy of digital subtraction radiography in detection of artificial recurrent caries lesions was assessed in this project. The use of digital subtraction radiography has been shown to markedly increase the accuracy of the detection of destruction in the periodontal bone, but the method has not been evaluated in secondary caries detection. Defects of three different sizes, simulating recurrent caries, were sequentially prepared in the interproximal cavity preparation margins of 28 teeth. Two composite restorative materials with different radiographic densities were used as posterior restorations, and a radiograph was obtained of each defect size and restorative material. The radiographs were digitized and subtracted from the reference images, and the conventional radiographs and the subtraction images were evaluated by seven observers. The data were analysed with ROC statistics. Subtraction radiography was found to be superior to conventional radiography in recurrent caries detection, mainly by reducing the false-positive diagnoses. The radiopacity of the restorative material had a significant effect on accuracy with conventional but not with subtraction radiography.     

Quantification of axial alignment of the lower extremity on conventional and digital total leg radiographs

The purpose was to assess axial alignment of the lower limb using mechanical axis measurements on conventional and digital radiographs. Total-leg radiographs of 24 patients, 8 male and 16 female, with a mean age of 68.6±10.2 years, were performed in a standardized anterior-posterior projection and standing position using a conventional and digital phosphor storage film screen radiography system. Knee joint angulation was assessed by measuring the angle between a line drawn from the center of the femoral head to the middle of the femoral condyles and a line drawn from the middle of the tibial condyles to the midpoint of the malleolus. On conventional leg radiographs, line drawing and angle measurement were performed manually with a transparent goniometer. Angle measurement on digital leg radiographs was performed on a PACS workstation using computer-assisted measurement software (IMPAX, AGFA-GEVAERT, Belgium). Evaluation time for both measurements was recorded. We diagnosed 14 varus and 10 valgus angulations of the knee joint. The mean individual difference between axis deviation of conventional digital leg radiographs was 0.93+0.6°(min 0°, max 2°), the mean difference in varus angulation was 1.13±0.45° (min 0.3°, max 2°), and the mean difference in valgus angulation was 0.65±0.71° (min 0°, max 2°). Angle measurements on conventional and digital radiographs did not show any statistically significant difference. Mean time exposure was 4.9 min/patient for manual and 1.08 min/patient for computer-assisted angle measurement (P<0.001). Computer-assisted angle measurement on digital total-leg radiographs represents a reliable method with no significant angle differences compared to conventional radiographic systems and offers a significantly lower evaluation time.     

Intra-oral storage phosphor and conventional radiography in the assessment of alveolar bone structures

OBJECTIVES: To compare storage phosphor (SP) with conventional film radiography for accuracy of linear measurements of the marginal alveolar bone and visibility of anatomical structures. METHODS: Linear measurements were made in paired SP and conventional images of dried human mandibles with a metal pin fixed 10 mm below the alveolar crest. One observer measured the distance from the alveolar crest to the reference point on the radiographs. The difference between the measured and the true distance was calculated. Two observers rated the visibility of bony structures (periodontal ligament space, periapical bone tissue, alveolar crest) in 51 paired digital and conventional images of 21 patients on a 3-point scale. Overall agreement and Kappa index were calculated. RESULTS: Accuracy of linear measurements was higher in digital radiography (mean difference 0.17 mm) than in conventional radiography (mean difference 0.59 mm). Overall, the two observers rated visibility higher in conventional radiographs. The Kappa indices for the periodontal ligament space and periapical bone indicated fair to almost perfect agreement (kappa = 0.38 and 0.5; kappa = 0.39 and 0.84) while for the alveolar crest there was only poor or moderate agreement (kappa = 0.2 and 0.5). CONCLUSIONS: The small differences in linear measurements indicate that the Digora system is suitable for clinical assessment of periodontal and peri-implant bone loss. The visibility of dental structures depends as much on the individual features assessed, as the radiographic system.