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1.  UK Naval Dockyards Asbestosis Study: radiological methods in the surveillance of workers exposed to asbestos 
ABSTRACT In a survey of the effects of exposure to asbestos in the UK Naval Dockyards, small- and large-film chest radiographs of 674 men have been examined. These films have been read under survey conditions by two readers using a simple screening classification, and also in a controlled trial by five readers using the full ILO U/C classification. Comparison between the reading methods showed a deficiency, independent of the size of film, of at least 30% in the detection of asbestos-related radiographic abnormalities when the screening classification was used. For adequate diagnostic sensitivity the ILO U/C classification appears to be essential. There was a deficiency of 43% in significant abnormalities observed by a majority of readers in the small films when directly compared with large film readings. This deficiency could be reduced to 7% by using readings of the small films at any level of abnormality by any of the five readers. When the ILO U/C readings were related to the clinical diagnoses, the only abnormality missed was a small pleural plaque. Films with previously agreed coding were inserted at intervals during the reading trial and helped to maintain the consistency of reading. Right oblique views were taken for 1884 men, in addition to the full-sized postero-anterior view, but the contribution provided by this view proved insufficient to justify its use in large surveys. The cost of a survey when small films are used as a screening method is reduced to between one-third and one-half of the cost when large films are used, assuming that the abnormality rate is not more than 5%. However, this cost advantage for small films is likely to be overtaken by the development of automatic large-film units. The radiation dose when small films are used is increased by a factor of about 20, but is within the prescribed safety level. It is concluded that at least three readers should be involved, using the full ILO U/C classification. Small films may be of particular use in a large-scale survey, in which the abnormality rate is expected to be low, and which might otherwise be too expensive. A sensitive reading method and a high standard of film quality are essential factors in the use of this technique.
PMCID: PMC1008405  PMID: 698132
2.  The Effect of Film Quality on Reading Radiographs of Simple Pneumoconiosis in a trial of X-ray sets 
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.
PMCID: PMC1038146  PMID: 13761945
An investigation into the effect of variations in radiographic technical quality on pneumoconiosis reading standards in the Pneumoconiosis Field Research of the National Coal Board is reported. From the group of men for whom retake films had been obtained because of unsatisfactory technique of the originals, a trial series of pairs and triplets of films showing differing technique was assembled.
A total of 778 films was read for pneumoconiosis and assessed for technical quality by four readers. The quality was assessed in terms of three separate factors, viz., density (at high, medium, and low levels), contrast (satisfactory and unsatisfactory), and definition (satisfactory and unsatisfactory). The intra and inter observer consistency of this assessment was estimated, and the effect of techical quality on the reading of pneumoconiosis category was determined. A tendency for lower pneumoconiosis readings to be recorded on films with unsatisfactory technique was demonstrated.
A random 10% sample of the best available films (those on which routine pneumoconiosis readings have been made) for all men examined since the beginning of the research was also read for technical quality. Of the total of 4,188 films, 80% were considered satisfactory. It appeared that films taken on second surveys were, in general, of rather better quality than those taken on first surveys.
The physical attributes of the men examined had some effect on the technical standards, the proportion of unsatisfactory films rising with increasing values of the weight/sitting height ratio and being greater in men with pneumoconiosis categories 1 and A and in the middle age group.
The tendency for lower pneumoconiosis readings to be recorded on films with unsatisfactory technique is in contrast to the results of work previously published. Different criteria for the selection of films and the assessment of technical quality, and possibly differing reading conventions, make comparison with other work difficult.
PMCID: PMC1008254  PMID: 14278806
4.  Scan equalization digital radiography (SEDR) implemented with an amorphous Selenium flat-panel detector: initial experience 
Physics in medicine and biology  2009;54(22):6959-6978.
It is well recognized in projection radiography that low-contrast detectability suffered in heavily attenuating regions due to excessively low x-ray fluence to the image receptor and higher noise levels. Exposure equalization can improve image quality by increasing the x-ray exposure to heavily attenuating regions, resulting in a more uniform distribution of exposure to the detector. Image quality is also expected to be improved by using the slot-scan geometry to reject scattered radiation effectively without degrading primary x-rays. This paper describes the design of prototype scan equalization digital radiography (SEDR) system implemented with an amorphous silicon (a-Si) thin-film transistor (TFT) array based flat-panel detector. With this system, the slot-scan geometry with the alternate line erasure and readout (ALER) technique was used to achieve scatter rejection. A seven-segment beam height modulator assembly was mounted onto the fore-collimator to regulate exposure regionally for chest radiography. The beam modulator assembly, consisting of micro linear motors, lead screw cartridge with lead beam blocks attached, position feedback sensors, and motor driver circuitry, has been tested and found to have an acceptable response for exposure equalization in chest radiography. An anthropomorphic chest phantom was imaged in the posterior-anterior (PA) view under clinical conditions. Scatter component, primary x-rays, scatter-to-primary ratios (SPRs), and primary signal-to-noise ratios (PSNRs) were measured in the SEDR images to evaluate the rejection and redistribution of scattered radiation, and compared with those for conventional full-field imaging with and without anti-scatter grid methods. SPR reduction ratios (SPRRRs, defined as the differences between the non-grid full-field SPRs and the reduced SPRs divided by the former) yielded approximately 59% for the full-field imaging with grid and 82% for SEDR technique in the lungs; and 77% for the full-field imaging with grid and 95% for SEDR technique in the subdiaphragm. The SEDR technique demonstrated a substantial improvement in PSNRs over the anti-scatter grid technique. The improvements of PSNRs are varied with the regions and are more pronounced in the heavily attenuating regions.
PMCID: PMC2855213  PMID: 19887717
exposure equalization; slot-scan; digital radiography; flat-panel detector; scattered radiation; scatter rejection; signal-to-noise ratio
5.  Computed tomography in the early detection of asbestosis. 
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.
PMCID: PMC1012171  PMID: 8398855
6.  A Comparison of Some Alternative Procedures in the Classification of Chest Radiographs for Coal-workers' Pneumoconiosis 
This paper is concerned with the problem of reading individual chest radiographs for coal-workers' pneumoconiosis in terms of the I.L.O. (1953) classifications, using a group of four readers. It represents the first of a series of investigations by the National Coal Board's Pneumoconiosis Field Research into various aspects of the general subject of the classification of chest radiographs. Later papers in this series will cover related problems, including the effect of radiographic “technique” on reading standards, the classification of a series of radiographs of the same individual, and the use of the readings in the correlation of radiographic abnormality with environmental exposure.
The effect of the circumstances under which the readings must be made in the Pneumoconiosis Field Research, including the geographical separation of the four readers into two groups of two, is described, and it is shown that any acceptable procedure must involve two distinct stages. On the “first stage” every radiograph must be read by some or all of the doctors individually, and on the “second stage” a proportion of films (those on which the individual readings are “ambiguous”) must be classified by the four doctors reading together. The general conduct of the joint reading sessions is then considered, and a description is given of a trial which was held to compare some alternative procedures. On the basis of these results an optimum reading procedure is derived. This is as follows:-
(i) Every radiograph to be read independently by one or other of the doctors from each group, in such a way that each reads half of the total number of films. The doctors from the group producing the radiograph to read alternately consecutive batches of about 50 as they are taken during the survey; the doctors from the other group to read the first and second halves of the survey, respectively, the films being arranged in serial order.
(ii) If these two independent readings are consistent, the common reading to be taken as definitive. All other films to be classified by joint consultation between the four doctors reading together, their assessment being arrived at by general discussion with each of the readers in turn giving the first opinion of the category of the film.
PMCID: PMC1038382  PMID: 14072621
7.  Radiological findings as predictors of mortality in Quebec asbestos workers. 
Two cohorts of chrysotile miners and millers in Quebec were selected to study the extent to which chest radiographs taken while still employed predict mortality. The paper presents mainly findings in much the larger cohort, which consisted of 4559 men (two-thirds past workers) whose latest radiograph had been assessed by one of six experienced readers into what became the UICC/Cincinnati (U/C) classification; by the end of 1975 there had been 1543 deaths in this cohort. The findings were generally confirmed in the other cohort, comprising 988 current male workers, who had been examined in 1967-8 by questionnaires on respiratory symptoms and smoking and by lung function tests, and for whom all six readers had assessed their 1966 radiographs into the U/C classification; 130 men had died by the end of 1975. Men with any radiographic abnormality, heavy dust exposure, or a history of cigarette smoking had relative risks (RRs) of total mortality greater than unity. Death from pneumoconiosis was associated with small parenchymal opacities, usually irregular, of profusion l/l or more, and with heavy dust exposure but not with smoking. Most who died from lung cancer had smoked cigarettes, or had been heavily exposed to dust, or both. Small parenchymal opacities were present in most but not all the excess deaths due to lung cancer. Deaths from other malignant diseases showed no consistent dust or x-ray patterns. RRs of deaths from most other causes were raised for certain radiographic features. Failures in forecasting mortality were primarily due to deaths in which asbestos-related disease was not the primary cause but may have been a contributing factor. The main findings validated the U/C classification convincingly, particulary as the films had been taken as routine and were of modest quality. Despite objective rules for the reading and the fact that all six readers were contributing to the development of the classification, there was inevitably some observer variation. The importance of radiographic technique and the need for careful control of the reading is evident. Our results provide support for the use of the chest radiograph for surveillance of asbestos workers, and for environmental monitoring. Its protective value for individual workers, however, is limited to the extent that radiological progression continues after withdrawal from exposure, and by the carcinogenic risk associated with dust already retained.
PMCID: PMC1008705  PMID: 7426477
8.  Radiological progression and its predictive risk factors in silicosis 
OBJECTIVES—To investigate the risk factors predicting radiological progression in silicosis in a prospective cohort study of patients with silicosis who were previously exposed to silica from granite dust.
METHODS—From among a total of 260 patients with silicosis contracted from granite work, 141 with available serial chest x ray films of acceptable quality taken over a period of 2 to 17 (mean 7.5) years, were selected for study. Ninety four (66.7%) had ended exposure 5 or more years perviously (mean 10.1 years, maximum 28 years). Radiological progression was assessed by paired comparison of the initial and most recent radiographs, with two or more steps of increase in profusion of small opacities according to the 12 point scale of the International Labour Organisation (ILO) classification of radiographs of pneumoconiosis, taken from the majority reading by a panel of three independent readers.
RESULTS—Overall, 37% of patients with silicosis had radiological evidence of progression. From the initial radiographs, 24 (31.6%) of those with radiological profusion category 1, 15 (37.5%) of those with radiological profusion category 2, and 13 (52%) of those with complicated silicosis (including all seven with category 3 profusion of small opacities) showed radiological progression. As expected, progression was more likely to be found after longer periods of follow up (the interval between the two chest x ray films) with a 20% increased odds of progression for every additional year of follow up. After adjustment for varying intervals of follow up, the probability of radiological progression was found to be significant if large opacities were present in the initial chest x ray film. Progression was also less likely to be found among those who had ended exposure to silica longer ago, although the result was of borderline significance (p=0.07). Tuberculosis was also associated with increased likelihood of progression (borderline significance).
CONCLUSIONS—There is a high probability of radiological progression in silicosis after high levels of exposure to granite dust among workers who were followed up for up to 17 years. A significant risk factor is the extent of radiological opacities in the initial chest x ray film. The probability of progression is also likely to be reduced with longer periods after the end of exposure.

Keywords: silicosis; radiological progression; granite quarry
PMCID: PMC1740153  PMID: 11404452
9.  Diagnostic accuracy of cardiothoracic ratio on admission chest radiography to detect left or right ventricular systolic dysfunction: a retrospective study 
To determine the diagnostic accuracy of the cardiothoracic ratio on postero-anterior or antero-posterior chest radiographs in predicting left ventricular or right ventricular dysfunction on echocardiography in an inpatient population.
Retrospective study.
Two secondary care hospitals in the United Kingdom.
Four hundred consecutive inpatient echocardiograms were screened for inclusion along with chest radiographs (both postero-anterior and antero-posterior). The cardiothoracic ratio was calculated from chest radiographs along with quantitative and qualitative measures of left ventricular or right ventricular dysfunction on echocardiography.
Main outcome measures
Sensitivity and specificity of cardiothoracic ratio across a range of values to detect moderate/severe left ventricular and/or right ventricular dysfunction on echocardiography.
Overall, 272 records met inclusion criteria. The prevalence of left ventricular/right ventricular dysfunction on echocardiography was 26% in an inpatient population with high clinical suspicion of cardiac disease referred for echocardiography. Over a range of cardiothoracic ratio values on postero-anterior films, a value of >0.55 yielded the best sensitivity (62.5%) and specificity (76.5%) for diagnosing left ventricular/right ventricular impairment (positive likelihood ratio 2.56), with a positive predictive value of 29.5%. Cardiothoracic ratio on antero-posterior film was not predictive of left ventricular/right ventricular impairment on echocardiography.
In conclusion, in the context of an acute admission, cardiothoracic ratio measured on postero-anterior or antero-posterior films has limited value in detecting moderate left ventricular and/or right ventricular systolic dysfunction. Previously established absolute values may be unreliable by modern standards.
PMCID: PMC4535437  PMID: 26152673
cardiovascular disease; diagnosis; heart failure; hospital medicine; radiology
10.  The Study of Observer Variation in the Radiological Classification of Pneumoconiosis 
In a long-term investigation such as the National Coal Board's Pneumoconiosis Field Research (P.F.R.), it is essential to establish satisfactory and stable procedures for making the necessary observations and measurements. It is equally important regularly to apply suitable methods of checking the accuracy and consistency of the various observations and measurements. One aspect of vital importance in the P.F.R. is the classification of the series of chest radiographs taken, at intervals, of all the men under observation. This is inevitably a subjective process, and (as with other similar fields of work) it is desirable to obtain some understanding of the basic process behind the operation. This can usefully be done by the help of “models” designed to describe the process, if necessary in simplified terms. The problem of the radiological classification of pneumoconiosis has been studied hitherto in terms of coefficients of disagreement (inter-observer variation) and inconsistency (intra-observer variation), but for various reasons the method was not considered entirely satisfactory. New methods of approach were therefore developed for studying the performance of the two doctors responsible for the film reading in the Research, and two distinct “models” were derived. The advantages and disadvantages of each are described in the paper, together with the applications of the two models to the study of some of the problems arising in the course of the investigation.
The first model is based on the assumption that if a film is selected at random from a batch representing a whole colliery population, and that if the film is of “true” category i, the chance of its being read as another category (j) is a constant, Pij, which depends upon the observer concerned, the particular batch of films being read, and the values of i and j. This model enables the performance of the readers to be monitored satisfactorily, and it has also been used to investigate different methods for arriving at an agreed, or “definitive”, assessment of radiological abnormality. The Pij model suffers from the disadvantage of applying only to “average” films, and the assumptions made are such that it manifestly does not provide an entirely realistic representation of the reading process on any particular film.
The second “improved” model was therefore developed to overcome this criticism. Briefly, it is considered that each film is representative of a unique degree of abnormality, located on a continuum, or abnormality scale, which covers the whole range of simple pneumoconiosis. The scale of abnormality is then chosen in such a way that, whatever the true degree of abnormality of the film, the observer's readings will be normally distributed about the true value with constant bias and variability at all points along the scale. The very large number of readings available has been analysed to determine the optimum positions of the category boundaries on the abnormality scale and in this way the scale has been unambiguously defined. The model enables the routine reading standards to be monitored, and it has also been used to investigate the underlying distribution of abnormality at individual collieries. Its chief disadvantage is the extensive computational work required.
The “fit” of both models to the data collected in the Research is shown to be satisfactory and on balance it appears that both have applications in this field of study. The method chosen in any given circumstance will depend upon the particular requirement and the facilities available for computational work.
PMCID: PMC1038082  PMID: 13698433
11.  Absence of Visual Input Results in the Disruption of Grid Cell Firing in the Mouse 
Current Biology  2016;26(17):2335-2342.
Grid cells are spatially modulated neurons within the medial entorhinal cortex whose firing fields are arranged at the vertices of tessellating equilateral triangles [1]. The exquisite periodicity of their firing has led to the suggestion that they represent a path integration signal, tracking the organism’s position by integrating speed and direction of movement [2, 3, 4, 5, 6, 7, 8, 9, 10]. External sensory inputs are required to reset any errors that the path integrator would inevitably accumulate. Here we probe the nature of the external sensory inputs required to sustain grid firing, by recording grid cells as mice explore familiar environments in complete darkness. The absence of visual cues results in a significant disruption of grid cell firing patterns, even when the quality of the directional information provided by head direction cells is largely preserved. Darkness alters the expression of velocity signaling within the entorhinal cortex, with changes evident in grid cell firing rate and the local field potential theta frequency. Short-term (<1.5 s) spike timing relationships between grid cell pairs are preserved in the dark, indicating that network patterns of excitatory and inhibitory coupling between grid cells exist independently of visual input and of spatially periodic firing. However, we find no evidence of preserved hexagonal symmetry in the spatial firing of single grid cells at comparable short timescales. Taken together, these results demonstrate that visual input is required to sustain grid cell periodicity and stability in mice and suggest that grid cells in mice cannot perform accurate path integration in the absence of reliable visual cues.
•Grid cell firing patterns are disrupted in darkness in the mouse•Grid cells are disrupted even when head direction cell signaling is preserved•Absence of visual input alters movement velocity modulation of theta frequency•Temporal firing relationships between grid cell pairs are preserved in the dark
Chen et al. show in the mouse that lack of visual input results in severe disruption of grid cell firing, and that this is not caused by instability in the head direction signal but may be due to changed velocity signaling. Temporal firing relationships between grid cells are preserved, even when their spatial firing patterns are disrupted.
PMCID: PMC5026695  PMID: 27498565
12.  Comparison of chest radiograph reading methods for assessing progress of pneumoconiosis over 10 years in Wittenoom crocidolite workers. 
Thirty three pairs of chest radiographs taken up to 10 years apart were obtained for 33 subjects suffering from asbestosis who had applied for compensation to the Pneumoconiosis Medical Board of Western Australia. Multiple films from the period before the first radiograph in each pair, from the intervening period between the two, and from the period subsequent to the second radiograph were also available and all films were read by two independent readers according to the 1980 ILO classification of pneumoconiosis. Films were read twice as side by side pairs ten years apart, twice as two separate randomly ordered films ten years apart, and once as part of the full series of all available chest radiographs on each subject to assess which method provided the best consistency (between reader variation) and repeatability (within reader variation). Judging by consistency, the full series method performed as well as either of the other methods when assessing radiographic changes and significantly better when assessing the level of profusion of small opacities. There was little to choose between the other two methods either judging by consistency or repeatability, which could not be estimated for the full series method. Use of all available films for a subject is recommended for assessing single films, as in a prevalence study, as well as for documenting change in a longitudinal study.
PMCID: PMC1035114  PMID: 2155650
13.  An elaboration of the I.L.O. classification of simple pneumoconiosis 
Liddell, F. D. K., and Lindars, D. C. (1969).Brit. J. industr. Med.,26, 89-100. An elaboration of the I.L.O. classification of simple pneumoconiosis. Simple pneumoconiosis in chest radiographs presents a continuum of increasing abnormality. Liddell (1963) introduced a 12-point scale obtained by dividing each of the four I.L.O. categories (International Labour Office, 1959) into one central and two marginal zones. In this system, which has come to be known as the N.C.B. elaboration, readers record for each radiograph the I.L.O. category of choice (0, 1, 2 or 3), followed by an adjacent I.L.O. category if that had been seriously considered; otherwise, the same category is repeated. Very clear normals are denoted as 0/-, and `high' category 3 films as 3/4.
This paper reviews the evidence from seven reading trials in which 12 National Coal Board (N.C.B.) film readers have taken part. About 28,000 assessments on a total of well over 2,000 single radiographs have been analysed. (The reading of serial radiographs to assess progression is dealt with elsewhere.)
All readers used the elaboration successfully, but they differed in the extents to which they placed films in central and in marginal zones; they were more consistent when preliminary briefing had been given. Film quality had little influence on the use of the zones, except that 0/- tended to be reserved for films of good quality.
Despite the variation in the use of the zones, marked improvements accrued from the use of the elaboration in both intra- and inter-observer error for all readers, and for films of poor quality as well as for good films. The validity of expressing simple pneumoconiosis prevalence rates in terms of I.L.O. categories derived from N.C.B. elaboration readings was confirmed. Although the exact widths of the zones along the continuum remain to be determined, all the evidence suggests that they represent steadily increasing abnormality.
Thus, the N.C.B. elaboration is a practical procedure which amplifies, but neither distorts nor supplants, the I.L.O. classification. It is reported to be easier to use.
PMCID: PMC1008901  PMID: 5780111
14.  Productivity and Cost Assessment of Computed Radiography, Digital Radiography, and Screen-Film for Outpatient Chest Examinations  
Journal of Digital Imaging  2003;15(3):161-169.
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.
PMCID: PMC3613258  PMID: 12532253
15.  Investigating the use of an antiscatter grid in chest radiography for average adults with a computed radiography imaging system 
The British Journal of Radiology  2015;88(1047):20140613.
The aim of this study was to investigate via simulation a proposed change to clinical practice for chest radiography. The validity of using a scatter rejection grid across the diagnostic energy range (60–125 kVp), in conjunction with appropriate tube current–time product (mAs) for imaging with a computed radiography (CR) system was investigated.
A digitally reconstructed radiograph algorithm was used, which was capable of simulating CR chest radiographs with various tube voltages, receptor doses and scatter rejection methods. Four experienced image evaluators graded images with a grid (n = 80) at tube voltages across the diagnostic energy range and varying detector air kermas. These were scored against corresponding images reconstructed without a grid, as per current clinical protocol.
For all patients, diagnostic image quality improved with the use of a grid, without the need to increase tube mAs (and therefore patient dose), irrespective of the tube voltage used. Increasing tube mAs by an amount determined by the Bucky factor made little difference to image quality.
A virtual clinical trial has been performed with simulated chest CR images. Results indicate that the use of a grid improves diagnostic image quality for average adults, without the need to increase tube mAs, even at low tube voltages.
Advances in knowledge:
Validated with images containing realistic anatomical noise, it is possible to improve image quality by utilizing grids for chest radiography with CR systems without increasing patient exposure. Increasing tube mAs by an amount determined by the Bucky factor is not justified.
PMCID: PMC4651192  PMID: 25571914
16.  The Evaluation of Effect of Developer Age in the Detection of Approximal Caries Using Three Speed Dental X-Ray Films: An In-Vitro Study 
Background and Objectives: Ever since the first radiograph was taken in 1895, radiographs have become an essential part of dental practice. Since radiation exposure for the patients is a major concern, it is important for us to reduce the radiation exposure to the patient and surrounding environment, without compromising the quality of image. Since improper film processing is one of the major causes of poor image quality, it is very important to test dental films under a variety of processing conditions. So this study was conducted to compare the diagnostic accuracy between Kodak Ultraspeed, Ektaspeed and Agfa Dentus M2 Comfort films for the detection of approximal caries in fresh as well as in aged processing solution.
Methods: Hundred extracted unrestored maxillary and mandibular teeth were aligned in a group of five teeth in each plaster model. Total of 20 plaster models were constructed and only 3 teeth in the middle were utilized for the study. The final sample consisted of 60 teeth in the study. The exposure time for Ultraspeed film was standardized at 0.5 seconds and for Ektaspeed and Agfa Dentus M2 films, the exposure time was 0.32 seconds. For each radiograph two blocks were used simulating bitewing radiograph. All 20 plaster blocks were exposed using three film types at standardized exposure timings with 30 radiographs each week. The procedure was repeated every week until 6 weeks. Radiographs were evaluated by an observer and assessed by following four point scale 0- sound tooth, 1- lesion in enamel, 2- lesion in amelodentinal junction, 3- dentinal lesion. Only distal surfaces were assessed. Thereafter all the teeth were subjected for histological study and actual depth of the lesion was recorded which acted as gold standard and this reading was subtracted in observer readings after radiographic examination. All data collected were analyzed statistically using ANOVA, paired and unpaired t-tests.
Results: Ektaspeed and Agfa films required less exposure compared to Ultraspeed film. With respect to film, all films had equal diagnostic accuracy upto three weeks. From fourth week Ultraspeed and Agfa films were considerably better than E speed film. E speed film was inferior in the depleted solution compared to other two solutions. With respect to lesion detection Agfa film was inferior to other two films.
Conclusion: All three films had equal diagnostic accuracy in fresh solution. Considering the significant reduction in patient radiation with Ektaspeed film, this should be the film of choice whenever possible. As far as the diagnosis of approximal caries is concerned processing solutions should not be used longer than 3 weeks.
PMCID: PMC4003653  PMID: 24783146
Kodak Ultraspeed; Kodak Ektaspeed; Agfa Dentus M2 Comfort; Processing solution; Proximal caries
17.  A survey of digital radiography practice in four South African teaching hospitals: an illuminative study 
The purpose of this study was to assess radiographer familiarity and preferences with digital radiography in four teaching hospitals and thereafter make recommendations in line with the migration from screen film to digital radiography.
Materials and methods:
A questionnaire was designed to collect data from either qualified or student radiographers from four teaching hospitals. From the four teaching hospitals, there were a total of 205 potential respondents. Among other things, responses regarding experiences and preferences with digital radiography, quality control procedures, patient dose, advantages and disadvantages of digital radiography were sought. The information collected was based on self-reporting by the participants. The study is exploratory in nature and descriptive statistics were generated from the collected data using Microsoft Excel 2007 and StatsDirect software.
Sixty-three out of 205 (31%) radiographers from all the four radiology centers responded to the circulated questionnaire. Only 15% (8) of the qualified radiographers had 4 or more years of experience with digital radiography compared to 68% (36) for the same amount of experience with screen-film radiography. Sixty-one percent (38) of the participants had been exposed to digital radiography during their lectures while at university. A small proportion, 16% (10) of the respondents underwent formal training in quality control procedures on the digital X-ray units they were using. Slightly more than half (55%) of the participants felt it was easier for them to retake an image in digital radiography than in screen film radiography.
The results of this survey showed that the participants are familiar with digital radiography and have embraced this relatively new technology as shown by the fact that they can identify both its advantages and disadvantages as applied to clinical practice. However, there are minimal quality control procedures specific to digital radiography being undertaken as such there is need for formal education, continuing education and manufacturer training with respect to quality control as institutions make the transition from conventional screen film radiology to digital radiology.
PMCID: PMC3097796  PMID: 21611065
Digital radiography; radiography practice; quality control
18.  A Comparison of the effectiveness of Mammographic Film-Screen and Standard Film-Screen in the Detection of Small Bone Fractures 
The use of mammography film-screen is limited in general radiography. The purpose of this study was to compare the effectiveness of mammographic film-screen and standard film-screen systems in the detection of small bone fractures. Radiographs were taken from patients' extremities and neck areas using mammography film-screen and standard film-screen (n=57 each). Fourteen other radiographs were taken from other views (predominantly oblique views), making a total number of 128 radiographs. Paired radiographs, taken from the same areas, were compared by two radiologists in terms of image visual sharpness, presence of bony fractures, and soft tissue injuries. The surface dose received by patients in the two systems was also compared. The radiographs taken by mammography film-screen had a statistically better visual sharpness compared to those taken by the standard film-screen system. However, there was no statistically significant difference between the diagnostic accuracy of the two systems. Mammography film-screen was able to detect only one out of 57 lesions, whereas standard film-screen system did not detec any lesion. The surface dose received by patients in mammography film-screen was higher than that in standard film-screen system. The findings of the present study suggest that mammography film-screen may be recommended as a diagnostic tool for the detection of small fractures of tinny parts of body such as fingers, hand or foot. They also suggest that mammography film-screen has no advantage over standard film-screen for radiography of thick body parts such as neck and knee.
PMCID: PMC3470282  PMID: 23115417
Bone fracture; mammography; diagnostic techniques; surface dose; X-Ray screen system
19.  Support line and tube visibility in chest examinations using computed radiography 
Journal of Digital Imaging  1997;10(3):126-131.
The visibility of support lines and tubes was compared in computed radiography (CR) and screen-film adult chest radiographs. Parameters investigated were radiation dose, image minification, and the use of unsharp mask enhancement. Five radiologists rated the visibility of support lines and tubes on a five-point scale ranging from 1 (entire course of line visible) to 5 (line not visible or only small portion seen). These CR results were compared with the visibility of support lines and tubes as assessed by the same readers for conventional screen-film radiographs (600 speed). Support line and tube visibility improved with image enhancement, image minification, and increasing radiation dose. At the same radiation exposure, support line and tube visibility of the screen-film combination was superior to that of standard CR images. Application of an unsharp mask enhancement algorithm to CR images, however, significantly improved support line and tube visibility in comparison to that obtained with the screen-film combination. It was concluded that unsharp mask processing is a valuable tool for improving the visibility of support lines and tubes in CR chest radiographs.
PMCID: PMC3452951  PMID: 9268908
Chest radiology; computed radiography; image enhancement; patient doses; support lines and tubes; computers; radiology
20.  Some factors influencing interobserver variation in classifying simple pneumoconiosis. 
Three experienced physician readers assessed the chest radiographs of 743 men from a coal mining community in West Virginia for the signs of simple pneumoconiosis, using the ILO U/C 1971 Classification of Radiographs of the Pneumoconioses. The number of films categorised by each reader as showing evidence of simple pneumoconiosis varied from 63 (8.5%) to 114 (15.3%) of the 743 films classified. The effect of film quality and obesity on interobserver agreement was assessed by use of kappa-type analytic procedures for measuring agreement on categorical data. Poor film quality and obesity both affected agreement adversely. Poor quality films were disproportionately frequent in obese individuals, as defined by the Quetelet index. On control of film quality by stratification, the effect of obesity on interobserver profusion agreement was no longer evident.
PMCID: PMC1007483  PMID: 3986146
21.  Use of a digitally reconstructed radiograph-based computer simulation for the optimisation of chest radiographic techniques for computed radiography imaging systems 
The British Journal of Radiology  2012;85(1017):e630-e639.
The purpose of this study was to derive an optimum radiographic technique for computed radiography (CR) chest imaging using a digitally reconstructed radiograph computer simulator. The simulator is capable of producing CR chest radiographs of adults with various tube potentials, receptor doses and scatter rejection.
Four experienced image evaluators graded images of average and obese adult patients at different potentials (average-sized, n=50; obese, n=20), receptor doses (n=10) and scatter rejection techniques (average-sized, n=20; obese, n=20). The quality of the images was evaluated using visually graded analysis. The influence of rib contrast was also assessed.
For average-sized patients, image quality improved when tube potential was reduced compared with the reference (102 kVp). No scatter rejection was indicated. For obese patients, it has been shown that an antiscatter grid is indicated, and should be used in conjunction with as low a tube potential as possible (while allowing exposure times <20 ms). It is also possible to reduce receptor air kerma by 50% without adversely influencing image quality. Rib contrast did not interfere at any tube potential.
A virtual clinical trial has been performed with simulated chest CR images. Results indicate that low tube potentials (<102 kVp) are optimal for average and obese adults, the former acquired without scatter rejection, the latter with an anti-scatter grid. Lower receptor (and therefore patient doses) than those used clinically are possible while maintaining adequate image quality.
PMCID: PMC3487078  PMID: 22253349
22.  Correlation of the clinical and physical image quality in chest radiography for average adults with a computed radiography imaging system 
The British Journal of Radiology  2013;86(1027):20130077.
The purpose of this study was to examine the correlation between the quality of visually graded patient (clinical) chest images and a quantitative assessment of chest phantom (physical) images acquired with a computed radiography (CR) imaging system.
The results of a previously published study, in which four experienced image evaluators graded computer-simulated postero-anterior chest images using a visual grading analysis scoring (VGAS) scheme, were used for the clinical image quality measurement. Contrast-to-noise ratio (CNR) and effective dose efficiency (eDE) were used as physical image quality metrics measured in a uniform chest phantom. Although optimal values of these physical metrics for chest radiography were not derived in this work, their correlation with VGAS in images acquired without an antiscatter grid across the diagnostic range of X-ray tube voltages was determined using Pearson’s correlation coefficient.
Clinical and physical image quality metrics increased with decreasing tube voltage. Statistically significant correlations between VGAS and CNR (R=0.87, p<0.033) and eDE (R=0.77, p<0.008) were observed.
Medical physics experts may use the physical image quality metrics described here in quality assurance programmes and optimisation studies with a degree of confidence that they reflect the clinical image quality in chest CR images acquired without an antiscatter grid.
Advances in knowledge:
A statistically significant correlation has been found between the clinical and physical image quality in CR chest imaging. The results support the value of using CNR and eDE in the evaluation of quality in clinical thorax radiography.
PMCID: PMC3922182  PMID: 23568362
23.  Radiological survey of past and present vermiculite miners exposed to tremolite. 
Chest radiographs taken by a standard technique were obtained from 173 current employees (164 men, 9 women) of a vermiculite mine in Montana, from 80 of 110 past employees resident within 200 miles, and from 47 men from the same area without known exposure to dust. In 43 of the 80 and 24 of the 47 an earlier chest x ray film was retrieved from the hospital archives. All 367 films were assessed blind and independently by three experienced readers using the ILO 1980 classification. Median radiographic assessment scores were analysed in relation to estimated cumulative exposure to the amphibole fibres that contaminate the vermiculite. Logistic regression analyses showed independent effects of age, smoking, and exposure on the prevalence of small opacities and of age and probably of exposure on pleural thickening. Overall, the data suggest that by retirement age the increase in prevalence of small opacities (greater than or equal to 1/0) lies between 5% and 10% per 100 f/ml years. This gradient may be somewhat steeper than for chrysotile miners and millers, but not much so.
PMCID: PMC1007683  PMID: 3013279
24.  Utility of a Newly Designed Film Holder for Premolar Bitewing Radiography 
Bitewing radiography is a valuable technique for assessment of proximal caries, alveolar crest and periodontal status. Technical errors during radiography result in erroneous radiographic interpretation, misdiagnosis, possible mistreatment or unnecessary exposure of patient for taking a repeat radiograph.
In this study, we aimed to evaluate the efficacy of a film holder modified from the conventional one and compared it with that of conventional film holder.
Materials and Methods
Our study population comprised of 70 patients who were referred to the Radiology Department for bilateral premolar bitewing radiographs as requested by their attending clinician. Bitewing radiographs in each patient were taken using the newly designed holder in one side and the conventional holder in the other side. The acceptability of the two holders from the perspectives of the technician and patients was determined using a 0-20 point scale. The frequency of overlap and film positioning errors was calculated for each method.
The conventional holder had greater acceptability among patients compared to the newly designed holder (mean score of 16.59 versus 13.37). From the technicians’ point of view, the newly designed holder was superior to the conventional holder (mean score of 17.33 versus 16.44). The frequency of overlap was lower using the newly designed holder (p<0.001) and it allowed more accurate film positioning (p=0.005).
The newly designed holder may facilitate the process of radiography for technicians and may be associated with less frequency of radiographic errors compared to the conventional holder.
PMCID: PMC4668503  PMID: 26675339
Cheek; Digital radiography; Inter-proximal radiographs
25.  Validation of the International Labour Office Digitized Standard Images for Recognition and Classification of Radiographs of Pneumoconiosis 
Academic radiology  2014;21(3):305-311.
Rationale and Objectives
Chest radiographs are recommended for prevention and detection of pneumoconiosis. In 2011, the International Labour Office (ILO) released a revision of the International Classification of Radiographs of Pneumoconioses that included a digitized standard images set. The present study compared results of classifications of digital chest images performed using the new ILO 2011 digitized standard images to classification approaches used in the past.
Materials and Methods
Underground coal miners (N = 172) were examined using both digital and film-screen radiography (FSR) on the same day. Seven National Institute for Occupational Safety and Health-certified B Readers independently classified all 172 digital radiographs, once using the ILO 2011 digitized standard images (DRILO2011-D) and once using digitized standard images used in the previous research (DRRES). The same seven B Readers classified all the miners’ chest films using the ILO film-based standards.
Agreement between classifications of FSR and digital radiography was identical, using a standard image set (either DRILO2011-D or DRRES). The overall weighted κ value was 0.58.Somespecific differences in the results were seen and noted. However, intrareader variability in this study was similar to the published values and did not appear to be affected by the use of the new ILO 2011 digitized standard images.
These findings validate the use of the ILO digitized standard images for classification of small pneumoconiotic opacities. When digital chest radiographs are obtained and displayed appropriately, results of pneumoconiosis classifications using the 2011 ILO digitized standards are comparable to film-based ILO classifications and to classifications using earlier research standards.
PMCID: PMC4564115  PMID: 24507420
Pneumoconiosis; digital radiography; imaging; chest radiograph

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