Radiography using film has been an established method for imaging the internal organs of the body for over 100 years. Surveys carried out during the 1980s identified a wide range in patient doses showing that there was scope for dosage reduction in many hospitals. This paper discusses factors that need to be considered in optimising the performance of radiographic equipment. The most important factor is choice of the screen/film combination, and the preparation of automatic exposure control devices to suit its characteristics. Tube potential determines the photon energies in the X-ray beam, with the selection involving a compromise between image contrast and the dose to the patient. Allied to this is the choice of anti-scatter grid, as a high grid ratio effectively removes the larger component of scatter when using higher tube potentials. However, a high grid ratio attenuates the X-ray beam more heavily. Decisions about grids and use of low attenuation components are particularly important for paediatric radiography, which uses lower energy X-ray beams. Another factor which can reduce patient dose is the use of copper filtration to remove more low-energy X-rays. Regular surveys of patient dose and comparisons with diagnostic reference levels that provide a guide representing good practice enable units for which doses are higher to be identified. Causes can then be investigated and changes implemented to address any shortfalls. Application of these methods has led to a gradual reduction in doses in many countries.
Radiography; dental radiography; X-ray film; automatic exposure control; anti-scatter grid
Computed tomography (CT; both conventional (CCT) and high resolution (HRCT)) scans of the thorax were evaluated to detect early asbestosis in 61 subjects exposed to asbestos dust in Québec for an average of 22(3) years and in five controls. The study was limited to consecutive cases with chest radiographs of the International Labour Organisation categories 0 or 1 determined independently. All subjects had a standard high kilovoltage posteroanterior and lateral chest radiograph, a set of 10-15 1 cm collimation CCT scans and a set of three to five 2 mm collimation HRCT scans in the upper, middle, and lower lung fields. Five experienced readers independently read each chest radiograph and sets of CT scans. On the basis of three to five readers agreeing for small opacities of the lung parenchyma, 12/46 (26%) negative chest radiographs were positive on CT scans, but 6/18 (33%) positive chest radiographs were negative on CT scan. On the basis of four to five readers agreeing on a chest radiograph, 36/66 (54%) subjects were normal (group A), 17/66 (26%) were indeterminate (group B), and 13/66 (20%) were abnormal (group C). By the combined readings of CCT and HRCT, 4/31 (13%) asbestos exposed subjects of group A were abnormal (p < 0.001), 6/17 (35%) of group B were abnormal, and in group C, 1/13 (8%) was normal, 2/13 were indeterminate, and 10/13 (77%) were abnormal. Separate readings of CCT and HRCT on distinct films in 14 subjects showed that all cases of asbestosis were abnormal on both CCT and HRCT. Inter-reader analyses by kappa statistics showed significantly better agreement for the readings of CT than the chest radiographs (p < 0.001), and for the reading of CCT than HRCT (p < 0.01). Thus CT scans of the thorax identifies significantly more irregular opacities consistent with the diagnosis of asbestosis than the chest radiograph (20 cases on CT scans v 13 on chest radiographs when four to five readers agreed, 13% of asbestos exposed subjects with normal chest radiographs or 21% of asbestos exposed subjects with normal or near normal chest radiographs. It decreased the number of indeterminate cases significantly from 17 on chest radiographs to 13 on CT scans. All cases of asbestosis detected only on CT scans were similarly seen on CCT and HRCT and did not have significant changes in lung function. The CT scans significantly reduced the inter-reader variability, despite the absence of ILO type reference films for these scans.
Four chest radiographs (14 in. × 14 in. postero-anterior) for each of 86 coal-miners were taken (in a trial to compare ϰ-ray sets) and assessed by a number of experienced readers for both quality and pneumoconiosis. All films were developed by one technician under standard conditions so that variations in the quality of the films produced for one subject arose because of differences in the sets and in the way they were used by the radiographers taking the films. The data thus obtained allowed a study of film quality to be made (a) in relation to the subject and (b) as it affected the reading of simple pneumoconiosis.
The subjects were selected to include a high proportion whose earlier radiographs showed pneumoconiosis; they were thus substantially older than a normal colliery population.
The assessments of quality were found to be reasonably consistent both between observers and on different occasions for the same observer.
A clear tendency was found for the quality of a film to depend on the subject. Men with no radiological evidence of pneumoconiosis tended to produce films which were assessed as of better quality than those of men with pneumoconiosis, however slight. Among the latter, chest thickness had an important effect on film quality; men with thicker chests produced poorer films. The subject's age did not appear to have any effect on the quality of his film.
Film quality was found to introduce only slight biases into the reading of pneumoconiosis. Individual readers varied considerably so that, although on average the readers tended to overcorrect for technical faults, i.e. to read more abnormality in black films than in good ones, and less in grey, some readers undercorrected slightly.
What little evidence was available did not suggest that poor quality of films introduced any excess variability into film reading.
Computed radiography (CR) has many advantages such as filmless operations, efficiency, and convenience. Furthermore, it is easier to integrate with the picture archiving and communication systems. Another important advantage is that CR images generally have a wider dynamic range than conventional screen film. Unfortunately, grid artifacts and moiré pattern artifacts may be present in CR images. These artifacts become a more serious problem when viewing CR images on a computer monitor when a clinic grade monitor is not available. Images produced using a grid with higher frequency or a Potter–Bucky grid (i.e., a moving grid, Bucky for short) can reduce occurrence but cannot guarantee elimination of these artifacts [CR & PACS (2000); Detrick F (2001), pp 7–8]. In this paper, the formation of the artifacts is studied. We show that the grid artifacts occur in a narrow band of frequency in the frequency domain. The frequency can be determined, accurately located, and thus removed from the frequency domain. When comparing the results obtained from the proposed method against the results obtained using previous computer methods, we show that our method can achieve better image quality.
Moiré; aliasing; computed radiography; grid; Bucky
Bedside chest radiography (bCXR) represents a substantial fraction of the volume of medical imaging for inpatient healthcare facilities. However, its image quality is limited compared to posterior-anterior/lateral (PA/LAT) acquisitions taken radiographic rooms. We evaluated utilization of bCXR and other chest imaging modalities before and after placing a radiography room within our thoracic surgical inpatient ward.
Institutional review board approval was obtained for this HIPAA-compliant. We retrospectively identified all patient admissions (3,852) to the thoracic surgical units between April 1, 2007 and December 31, 2010. All chest imaging tests performed for these patients including computed tomography (CT) scans, magnetic resonance imaging (MRI), ultrasound (US), bedside and PA/LAT radiographs were counted. Our primary outcome measure was chest imaging utilization, defined as the number of chest examinations per admission, pre- and post-establishment of the digital radiography room on January, 10th 2010. Statistical analysis was performed using an independent-samples t-test to evaluate changes in chest imaging utilization.
We observed a 2.61 fold increase in the number of PA/LAT CXR per admission (p<0.01) and a 1.96 fold decrease in the number of bCXR per admission (p<0.01) post radiography room implementation. The number of chest CT, MRI and US per admission did not change significantly.
Establishing a radiography room physically within thoracic surgery units or in close proximity can significantly shift CXR utilization from bedside to PA/LAT acquisitions, which may enable opportunities for improvement in efficiency, quality, and safety in patient care.
Chest imaging; workflow improvement; imaging utilization; radiography room; radiology resource optimization
Problem: The purpose of the investigation was a comparison of two different digital X-ray techniques with conventional standing full spine films. Evaluation of dose area product, image quality and inter-observer error of Cobb-angle measurement in patients with scoliosis and kyphoscoliosis were studied.
Methods: A consecutive series of 150 patients were prospectively randomized into three groups. Patients in group 1 (n=53) received a conventional standing postero-anterior full spine radiograph. All films were evaluated on the light box. Patients in group 2 (n=48) received a X-ray using the digital storage phosphor plate system (CR). For group 3 (n=49) digital pulsed fluoroscopy was used. In groups 2 and 3 images were exported to a picture archiving and communicating system (PACS) workstation and viewed on a monitor (Siemens SMM 21140P, Germany). Dose area product measurements were performed in all three groups (Diamentor-M, PTW, Freiburg). Three experienced investigators independently reviewed all pictures. Pedicles and endplates were counted. Cobb-angles of the main curves were measured.
Results: The mean dose area product was 97.0 cGy cm² (37.0–380.0 cGy cm²) for conventional films, 31.5 cGy cm² (6.0–66.0 cGy cm²) for CR imaging and 5.0 cGy cm² (1.0–29.0 cGy cm²) for digital fluoroscopy. The differences of Cobb-angle measurements were not significantly different for the three methods. Differences in the count of pedicles and endplates between the investigators were significantly lower for the conventional film as an indicator for the best detail presentation.
Conclusion: A significant reduction in dose area product is possible with modern digital X-ray methods. The inter-observer error of Cobb-angle measurement is not significantly altered. The detail information is decreased in comparison to conventional films.
X-ray; AIS; Dose area product; Digital; Exposure
An objective assessment and comparison of computed radiography (CR) versus digital radiography (DR) and screen-film for performing upright chest examinations on outpatients is presented in terms of workflow, productivity, speed of service, and potential cost justification. Perceived ease of use and workflow of each device is collected via a technologist opinion survey. Productivity is measured as the rate of patient throughput from normalized timing studies. The overall speed of service is calculated from the time of examination ordering as stamped in the radiology information system (RIS), to the time of image availability on the picture archiving and communication system (PACS), to the time of interpretation rendered (from the RIS). A cost comparison is discussed in terms of potential productivity gains and device expenditures. Comparative results of a screen-film (analog) dedicated chest unit versus a CR reader and a DR dedicated chest unit show a higher patient throughput for the digital systems. A mean of 8.2 patients were moved through the analog chest room per hour, versus 9.2 patients per hour using the CR system and 10.7 patients per hour with the DR system. This represents a 12% increase in patient throughput for CR over screen-film; a 30% increase in patient throughput for DR over screen-film, which is statistically significant; and a 16% increase in patient throughput for DR over CR, which is not statistically significant. Measured time to image availability for interpretation is much faster for both CR and DR versus screen-film, with the mean minutes to image availability calculated as 29.2 ± 14.3 min for screen-film, 6.7 ± 1.5 min for CR, and 5.7 ± 2.5 min for DR. This represents an improved time to image availability of 77% for CR over screen-film, 80% for DR over screen-film, and 15% for DR over CR. These results are statistically significant (P <.0001) for both CR over screen-film and DR over screen-film but not statistically significant for DR over CR. A comparison of the digital technology costs illustrates that the high cost of DR may not be justifiable unless a facility has a steady high patient volume to run the device at or near 100% productivity. Both CR and DR can improve workflow and productivity over analog screen-film in a PACS for delivery of projection radiography services in an outpatient environment. Cost justification for DR over CR appears to be tied predominantly to high patient volume and continuous rather than sporadic use patterns.
The role chest radiography plays in intensive care units (ICU) is unlike its role elsewhere because in the ICU a patient's underlying disease is usually known. Furthermore, additional diseases that develop in the ICU—such as pneumonia, hemorrhage, edema, lung collapse and effusion—often are radiographically indistinguishable. Nevertheless, an ICU radiograph of the chest is valuable, mainly in identifying such complications as malpositioned intravenous catheters, Swan-Ganz catheters, pacemakers, nasogastric tubes, endotracheal tubes, chest tubes, and mediastinal tubes, and ectopic gas related to mechanical ventilation. Understanding the limitations of the portable ICU chest film in the diagnosis of specific diseases and being alert to possible iatrogenic complications will increase the usefulness of ICU chest radiography.
Even though facilities using computed radiography (CR) operate in an electronic environment, the production of hard-copy films is still necessary during the transition period, as well as for particular needs following complete implementation. We have implemented a quantitative technique to match the response of printed CR film with that of previous screen/film combinations. A stepwedge is radiographed using the conventional system. The same stepwedge is then radiographed (same geometry and technique) using the CR system. Following processing and printing, the plot of optical density versus step for the CR system is compared with that of the screen/film system. Adjustments are made to the printing parameters until the response curves are identical. All other translation tables in the system are set to be linear. This has proven to be a valuable technique for us and provides CR printed image quality that is equivalent to that of our previous screen/film combinations.
To ascertain current chest radiography practice in intensive care units (ICUs) in the Netherlands.
Postal survey: a questionnaire was sent to all ICUs with > 5 beds suitable for mechanical ventilation; pediatric ICUs were excluded. When an ICU performed daily-routine chest radiographs in any group of patients it was considered to be a "daily-routine chest radiography" ICU.
From the number of ICUs responding, 63% practice a daily-routine strategy, in which chest radiographs are obtained on a daily basis without any specific reason. A daily-routine chest radiography strategy is practiced less frequently in university-affiliated ICUs (50%) as compared to other ICUs (68%), as well as in larger ICUs (> 20 beds, 50%) as compared to smaller ICUs (< 20 beds, 65%) (P > 0.05). Remarkably, physicians that practice a daily-routine strategy consider daily-routine radiographs helpful in guiding daily practice in less than 30% of all performed radiographs. Chest radiographs are considered essential for verification of the position of invasive devices (81%) and for diagnosing pneumothorax, pneumonia or acute respiratory distress syndrome (82%, 74% and 69%, respectively). On demand chest radiographs are obtained after introduction of thoracic drains, central venous lines and endotracheal tubes in 98%, 84% and 75% of responding ICUs, respectively. Chest films are also obtained in case of ventilatory deterioration (49% of responding ICUs), and after cardiopulmonary resuscitation (59%), tracheotomy (58%) and mini-tracheotomy (23%).
There is notable lack of consensus on chest radiography practice in the Netherlands. This survey suggests that a large number of intensivists may doubt the value of daily-routine chest radiography, but still practice a daily-routine strategy.
Computer programs for measuring simple pneumoconiosis in radiographs are described and assessed. The 36 films studied had been read by 11 skilled human observers and a 'radiological score' of pneumoconiotic severity was therefore available for each film. The computer assigns to each square grid of side 3-6 mm a measure which reflects the unevenness of the density distribution in that grid. The 'computed score' is defined as the mean diversity over all relevant grids in both lung fields. On the set of 36 films the correlation between radiological score and computed score was 0-88. By contrast, the correlation between the score assigned by a single observer and the average of the scores assigned by the other 10 was in the range 0-95 to 0-98. The program can use the computed score to classify a film into one of the four major International Labour Office (ILO) U/C categories, the success rate of this process being 80% compared with those quoted by other workers in the range 45%-65%. If the films used in this study be typical, then the program described may form the basis of an automatic method for measuring pneumoconiosis in epidemiological work.
The purpose of this study was to compare the conventional and digital radiography in the estimation of working length in mandibular molars.
Materials and Methods
Sixty molar teeth were selected and divided into three groups in the basis of canal curves (0-15°, 15-30°, >30°). After the placement of a 15 K-file, radiographs were taken with a conventional film (F-speed) and a digital sensor. Canal lengths were measured in these images by two observers. Statistical analysis was performed with repeated measures of ANOVA and paired sample t-test with 95% confidence.
There was a high inter-observer agreement on the measurements of working length in conventional and digital radiographs. There was no significant difference between the mean values of measurements in conventional and digital radiography. Moreover, there was no significant difference between conventional and digital radiography with the actual values in the basis of canal curves.
The accuracy of conventional and digital radiography in the determination of the working length was in an acceptable range.
Dental Digital Radiography; Measurement; Root Canal
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.
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.
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.
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.
direct digital radiography; conventional radiography; dental caries; primary teeth
A series of artifact images, obtained over 5 years of performance testing, of both computed radiography (CR) and integrated digital radiographic X-ray imaging detectors are presented. The images presented are all either flat field or test object images and show artifacts previously either undescribed in the existing literature or meriting further comment. The artifacts described are caused by incorrect flat field corrections, a failing amplifier, damaged detector lines affecting their neighbors, lost information between neighboring detector tiles, image retention, delamination of a detector, poor setup of mechanical movements in CR, suckers damaging a CR plate, inappropriate use of grid suppression software, inappropriate use of a low pass spatial frequency filter, and unsharp masking filters. The causes and significance of the artifacts are explained and categorized as software or hardware related. Actions taken to correct the artifacts are described and explained. This work will help physicists, radiographers, and radiologists identify various image quality problems and shows that quality assurance is useful in identifying artifacts.
Computed radiography; digital radiology; image artifact; radiography; quality assurance; diagnostic image quality
Computed Radiography (CR) has become a major digital imaging modality in a modern radiological department. CR system changes workflow from the conventional way of using film/screen by employing photostimulable phosphor plate technology. This results in the changing perspectives of technical, artefacts and quality control issues in radiology departments. Guidelines for better image quality in digital medical enterprise include professional guidelines for users and the quality control programme specifically designed to serve the best quality of clinical images. Radiographers who understand technological shift of the CR from conventional method can employ optimization of CR images. Proper anatomic collimation and exposure techniques for each radiographic projection are crucial steps in producing quality digital images. Matching image processing with specific anatomy is also important factor that radiographers should realise. Successful shift from conventional to fully digitised radiology department requires skilful radiographers who utilise the technology and a successful quality control program from teamwork in the department.
Computed radiography; image quality; quality control
Coherent X-ray scattering is related to the electron density distribution by a Fourier transform, and therefore a window into the microscopic structures of biological samples. Current techniques of scattering rely on small-angle measurements from highly collimated X-ray beams produced from synchrotron light sources. Imaging of the distribution of scattering provides a new contrast mechanism which is different from absorption radiography, but is a lengthy process of raster or flue scans of the beam over the object. Here, we describe an imaging technique in the spatial frequency domain capable of acquiring both the scattering and absorption distributions in a single exposure. We present first results obtained with conventional X-ray equipment. This method interposes a grid between the X-ray source and the imaged object, so that the grid-modulated image contains a primary image and a grid harmonic image. The ratio between the harmonic and primary images is shown to be a pure scattering image. It is the auto-correlation of the electron density distribution at a specific distance. We tested a number of samples at 60–200 nm autocorrelation distance, and found the scattering images to be distinct from the absorption images and reveal new features. This technique is simple to implement, and should help broaden the imaging applications of X-ray scattering.
Diffraction; imaging; scatter; X-ray
Modern portable x-ray units are light enough to be easily carried to the ill patient in his home; their output is sufficient for radiographs containing useful diagnostic information to be made of the chest, hip, and other regions, especially if a grid is employed. The skull is considered to be beyond the range of this method of examination, because of the long exposure times required, but gross lesions can be demonstrated in the oesophagus and stomach if barium is given. The radiation hazard is not considered to be a contraindication if appropriate precautions are taken.
Recent advances in technology and the use of image archiving and communication systems (PACS) has led some institutions to abandon conventional plain film radiography and rely solely on digital computed radiography. The level of accuracy of digital radiography in measuring distances for orthopaedic applications is unclear.
Is it possible to accurately measure small distances using digital radiographs and PACS software?
Materials and Methods
A model for measuring articular step-off was created using a commercially produced radiographic phantom with predetermined markings at known distances. Radiographs were taken using both indirect and direct computed radiography systems, then uploaded to a PACS system. Eighteen observers measured the distance between standardized, preselected points on the radiographic phantom. The measured values were compared with the known values for each measurement.
The mean measured values differed by 0 and 0.1 mm (SD, 0.5 mm) for indirect and direct radiographs, respectively, when measuring short distances and 1.4 mm and 2.6 mm (SD, 1.0 mm) for indirect and direct radiographs, respectively, when measuring longer distances. The intraclass correlation coefficient (ICC) for interobserver reliability was 0.82 for indirect and 0.75 for direct digital radiography. The ICC for intraobserver reliability was 0.94 for indirect and 0.90 for direct digital radiography.
Although the mean measured values were very accurate (within 0.1 mm for a known distance of 3.2 mm), the SD of measurements (0.5 mm) could affect the interpretation of data, especially in clinical situations such as evaluating the quality of fracture reduction.
Introduction: With the steady increase in public and professional concern regarding the biological effects of ionising radiation, there is a need for both the Chiropractic and Radiography professions to improve imaging techniques for the lowering of patient radiation doses. Lumbar radiographs are essential in chiropractic general practice for biomechanical diagnosis and postural analysis. Detailed anatomical measurements are taken from spinal radiographs for the determination of various biomechanical alterations for clinical purposes. The quality of spinal radiograph is dependent on a number of factors, including Focus Film Distance (FFD), magnification ratios, penumbra, contrast and density. Variation in FFD will vary magnification factor (MF) and Penumbra.
Objectives: The study aims to investigate the relationship between FFD and received radiation dose to patients, where the radiation dose to the testes may be significantly lowered whilst still maintaining acceptable image quality.
Methods: Radiographic images and dosimetry were obtained with a Seimans wall-mounted X-ray unit. All anterior/posterior (AP) and lateral lumbar-pelvic radiographs were taken of an anthromorphological phantom that resembles human tissues, at both 100cm and 200cm FFD. Five central beam air doses were measured for all parameters to demonstrate patient entrance doses.
Results: For AP lumbar-pelvic radiography, increasing FFD by a factor of two resulted in an approximately 30% decrease in entrance dose to the testes. For lateral lumbar-pelvic radiography a two fold increase in FFD resulted in a 70% reduction in entrance dose.
Conclusions: The study suggests for the first time that an FFD of 200 cm, which is largely utilised by the chiropractic profession, is an efficient method of minimising radiation dose to patient, during lumbar radiography.
Chiropractic; radiography; focus film distance; lumbar spine
The anti-scatter grid has been widely used to reject scatter and increase the perceptibility of low contrast object in chest radiography; however it also attenuate the primary x-rays, resulting in a substantial loss of information and an increased relative noise level in heavily attenuated regions. A more dose efficient approach to scatter rejection is the slot-scan imaging technique. Another problem in chest radiography is the low transmitted x-ray intensity in heavily attenuating regions. It results in higher relative noise level and subject the contrast sensitivity to limitation by the system noises. A solution to this problem is through the exposure equalization technique with which the incident x-ray intensity is regionally modulated to compensate for the differences of x-ray attenuation due to the anatomic variation. We are in the process of implementing the scan equalization digital radiography (SEDR) technique which combines the advantages of slot-scan imaging and exposure equalization. However, associated with the use of exposure equalization is a re-distribution of scattered radiation at the detector which may impact on the benefit of using exposure equalization in conjunction with the slot-scan imaging geometry. In order to understand the scatter properties and their impact in SEDR, we have used spot collimated aSi FP images to synthesize simulated SEDR images with which scatter components, primary signals, and scatter-to-primary ratios (SPRs) were measured. Using a simple model for scatter effects, we have also estimated and compared the contrast-to-noise ratio degradation factors (CNRDFs). It was found that for quantum limited situations the slot-scan technique has resulted in a substantial improvement of the image quality as indicated by higher estimated CNRDFs. Compared to slot-scan imaging, SEDR resulted in higher SPRs in the lungs and lower SPRs in the mediastinum. In the sub-diaphragmatic regions, the SPRs remain about the same. This correspond to lower CNRDFs in the lungs, higher CNRDFs in the mediastinum, and about the same CNRDFs in the sub-diaphragmatic regions. It was shown that although SEDR has resulted in minimum improvement over slot-scan imaging in reducing the SPRs, it could improve the contrast sensitivity by raising the primary signal levels in heavily attenuating regions. This advantage needs to be further investigated in our continuing study of the SEDR technique.
Scattered radiation; scatter rejection; slot-scan imaging; exposure equalization; digital radiography; flat-panel detector
A dedicated chest computed radiography (CR) system has an option of energy subtraction (ES) acquisition. Two imaging plates, rather than one, are separated by a copper filter to give a high-energy and low-energy image. This study compares the diagnostic accuracy of conventional computed radiography to that of ES obtained with two radiographic techniques. One soft tissue only image was obtained at the conventional CR technique (s=254) and the second was obtained at twice the radiation exposure (s=131) to reduce noise. An anthropomorphic phantom with superimposed low-contrast lung nodules was imaged 53 times for each radiographic technique. Fifteen images had no nodules; 38 images had a total of 90 nodules placed on the phantom. Three chest radiologists read the three sets of images in a receiver operating characteristic (ROC) study. Significant differences in Az were only found between (1) the higher exposure energy subtracted images and the conventional dose energy subtracted images (P=.095, 90% confidence), and (2) the conventional CR and the energy subtracted image obtained at the same technique (P=.024, 98% confidence). As a result of this study, energy subtracted images cannot be substituted for conventional CR images when detecting low-contrast nodules, even when twice the exposure is used to obtain them.
lung nodules; computerized radiography; energy subtraction; ROC
The relation between the macroscopic pathology of the lungs of coal-workers and the radiological category of pneumoconiosis on a chest film taken not more than two years before death has been investigated in 238 coal-miners in South Wales. Large lung sections were shown to provide more accurate and convenient material than wet lungs for this comparison and were used to assess the number and character of dust foci and the degree of emphysema. The profusion of dust foci was classified into four grades—very sparse, sparse, moderate, and numerous—using standard lung sections. Emphysema was graded slight, moderate, and severe. The chest radiographs were categorized according to the I.L.O. Classification, 1953.
The comparison shows that there is a fairly good correlation between the radiological category and the number and character of dust foci in the lungs at necropsy. The higher the radiological category the greater the likelihood that the lungs will show a large number of dust foci and particularly a higher proportion of fibrotic nodules, and vice versa. Only about 10% of the films read as category 1 showed sparse fibrotic nodules on the lung section, and none showed more than this. Fibrotic nodules occurred more frequently when early complicated pneumoconiosis (category A) was also present. There was no evidence that emphysema was obscuring the recognition of the severity of simple pneumoconiosis on the radiograph. The commonest cause of localized areas of consolidation detected radiologically was progressive massive fibrosis; less commonly, apical scars. Other causes were lung cancer, bronchiectasis, and interstitial fibrosis.
The aim of this study was to determine any increase in the incidence of cone cut errors that adversely affected diagnostic yield resulting in more retakes using rectangular collimation with film holders in bitewing radiography. Comparisons were also made with other positioning errors that occurred when bitewings were taken with circular collimation, with and without film holders.
A preliminary questionnaire was used to determine the year that rectangular collimation was adopted by military dental practice. 3 time-framed subsets, each of 1000 bitewing radiographs, were identified: subset 1, films taken with circular collimators without film holders; subset 2, films taken with circular collimators with film holders; and subset 3, films taken with rectangular collimators with film holders. Each subset was assessed for positioning errors of cone cut, horizontal overlap, vertical distortion and film centring. The χ2 test was used to test significant differences amongst the three subsets.
The use of film holders with circular collimation significantly reduced the incidence of cone cut errors from 21.7% to 3.3%. There was an increase in the incidence of cone cut errors from 3.3% to 20.9% when rectangular collimation was used, but the actual number considered “rejects” was very small, only 0.1% (1 in 1000 films) in subset 2 and 0.3% (3 of 1000 films) in subset 3, when assessed for diagnostic yield.
This study provides evidence that rectangular collimation did not significantly affect the diagnostic yield of bitewing radiographs despite the presence of cone cut. Therefore, all practitioners should adopt rectangular collimation.
bitewing radiography; rectangular collimation; circular collimation; cone cut
Computer Analysis of Mammography Phantom Images (CAMPI) is a method for making quantitative measurements of image quality. This article reports on a recent application of this method to a prototype full-field digital mammography (FFDM) machine. Images of a modified ACR phantom were acquired on the General Electric Diagnostic Molybdenum Rhodium (GE-DMR) FFDM machine at a number of x-ray techniques, both with and without the scatter reduction grid. The techniques were chosen so that one had sets of grid and non-grid images with matched doses (200 mrads) and matched gray-scale values (1500). A third set was acquired at constant 26 kVp and varying mAs for both grid conditions. Analyses of the images yielded signal-to-noise-ratio (SNR), contrast and noise corresponding to each target object, and a nonuniformity measure. The results showed that under conditions of equal gray-scale value the grid images were markedly superior, albeit at higher doses than the non-grid images. Under constant dose conditions, the non-grid images were slightly superior in SNR (7%) but markedly less uniform (60%). Overall, the grid images had substantially greater contrast and superior image uniformity. These conclusions applied to the whole kVp range studied for the Mo-Mo target filter combination and 4 cm of breast equivalent material of average composition. These results suggest that use of the non-grid technique in digital mammography with the GE-DMR-FFDM unit, is presently not warranted. With improved uniformity correction procedure, this conclusion would change and one should be able to realize a 14% reduction in patient dose at the same SNR by using a non-grid technique.
digital mammography; breast imaging; technique optimization; antiscatter grid
Successful endodontic therapy depends on adequate mechanical and chemical debridement of the canal which requires knowledge of the canal morphology. Conventional radiography has been used to evaluate the canal type; however, direct digital radiography has recently been practiced for this purpose due to the shortcomings of conventional radiography. The aim of the present study was to compare the accuracy of digital and conventional radiography taken at 0° and 30° angles in the diagnosis of the canal type of extracted maxillary premolars.
Materials and Methods:
This diagnostic study was performed on 90 extracted maxillary premolars. Conventional and digital radiographies were taken of all teeth at 0° and 30° horizontal angles. The images were assessed by an oral and maxillofacial radiologist. The clearing technique was used as the gold standard. The canal type was determined using Weine classification. The agreement between each one of the 4 radiographic modalities and gold standard was determined by kappa statistics.
The kappa values for the agreement of parallel conventional, 30° conventional, parallel digital and 30° digital modalities with the clearing technique were 0.059, 0.215, 0.043 and 0.391, respectively. Parallel modalities were unable to determine the tooth canal type. Radiographic images taken at 30° significantly determined the canal type, although only a poor level of agreement was noted between the two modalities and the clearing technique.
All modalities had limited value to determine the root canal type in maxillary premolars. However, direct digital imaging taken at 30° angle showed the highest accuracy for canal type assessment.
Radiography, Dental; Digital; Root Canal Anatomy