This article was downloaded by: [130.132.123.28] On: 03 January 2015, At: 00:53 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Archives of Environmental Health: An International Journal Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/vzeh20
The Chest Roentgenogram as an Epidemiologic Tool Hans Weill MD & Robert Jones MD Published online: 02 May 2013.
To cite this article: Hans Weill MD & Robert Jones MD (1975) The Chest Roentgenogram as an Epidemiologic Tool, Archives of Environmental Health: An International Journal, 30:9, 435-439, DOI: 10.1080/00039896.1975.10666744 To link to this article: http://dx.doi.org/10.1080/00039896.1975.10666744
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions
The Chest Roentgenogram as an Epidemiologic Tool Downloaded by [] at 00:53 03 January 2015
Report of a Workshop Hans Weill, MD, Robert Jones, MD (Editors)
November 1973, the Division of I n Lung Diseases, National Heart and Lung Institute (NHLI), sponsored a workshop on the epidemiology of respiratory diseases that included a discussion of problems associated with the use of standardized procedures in chest roentgenography. There was a consensus that the chest roentgenogram was useful in epidemiologic studies involving occupational diseases or specific pulmonary diseases other than the obstructive diseases. Furthermore, it was agreed that investigators should use standardized procedures to minimize variability of readings and to insure comparability of results from different studies. Use of the International Office UICC/Cincinnati Labour (ILO U IC) classification of radiography of pneumoconiosis was recommended. 1 To address these problems of vari-
ability in interpretation, the Division of Lung Diseases sponsored a workshop on chest roentgenography held on March 25 and 26, 1974, in New Orleans. Hans Weill, MD, was the chairman. The workshop brought together experts in the use of the ILO U/C classification (some of whom had served on the committee that developed it), and also experts in population studies of nonspecific chronic respiratory diseases and in standardizing methodology and automated reading analyses. Workshop sessions were addressed to (1) problems in use of the ILO U IC classification; (2) correlation of roentgenographic indexes with lung function and pathology; (3) use of roentgenography in diseases associated with exposure to occupational dusts and in community studies; and (4) technical and methodologic considerations. The final session was devoted to a discussion of conclusions and recommendations. INTRODUCTION
Submitted for publication Nov 21, 1974; accepted Feb 3, 1975. The workshop, held in New Orleans on March 25-26,1974, was sponsored by the National Heart and Lung Institute. Reprint requests to Pulmonary Disease Section, Department of Medicine, Tulane University School of Medicine, 1700 Perdido St, New Orleans, LA 70112 (Dr. Weill).
Arch Environ Health-Vol 3D, Sept 1975
The ILO U IC classification is a classification of roentgenograms of pneumoconioses. 1 The classification provides for systematic recording of roentgenographic appearances; describes the natural history of the Chest Roentgenogram-Weill & Jones
435
changes; and, by use of verbal descriptions and standard films, permits semiquantitative assessments. Features that are recorded include (1) type of opacity (eg, small or large, rounded or irregular, calcified); (2) profusion of opacities (number of opacities per unit area); (3) extent of involvement (areas of the lung field affected); and (4) other features, such as pleural thickness, ill-defined diaphragm, ill-defined cardiac outline, and pleural calcification.
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HIGHLIGHTS OF WORKSHOP DISCUSSIONS Problems in Use of ILO UIC Classification
Although participants agreed on the advantages of the ILO DIe classification, they were cdttcerned particularly about problems of interobserver variability in grading small opacities and in the development of standad reference films. The category of small irregular opacities l1aS led to fundamental disagreements in film interpretation. Lack of agreement relates both to what constitutes a small irregular opacity and to how they should be interpreted when a film also contains small rounded opacities. In coal pneumOCOnIOSIS small worker's rounded opacities have well-established significance as indexes of dust content in the lung and hence as measures of past dust exposure. Small irregular opacities are at present of undetermined meaning in coal workers, but are highly relevant in those workers exposed to asbestos. However, mixed mineral dust exposures are the rule rather than the exception, so there are good grounds for having a simple classification with appropriate subdivisions to classify all types of patterns seen in all kinds of pneumoconioses. Recording the level of profusion also presents problems because it may be based on whichever type of small opacity (rounded or irregular) is higher or it may be based on their combination. The choice between these alternatives may be influenced by the nature of the disease under study. Workshop participants agreed that, even when the combination of 436
both rounded and irregular nodules is to be taken as the measure of profusion, the profusion of small rounded and of small irregular opacities should be separately recorded. Some participants questioned the validity of dividing small irregular opacities into types "s" (fine), "t" (medium), and "u" (coarse), because at present these terms are purely descriptive (although future work may prove these distinctions to be important). On the other hand, some advocated extending the system of recording profusion to cover cases in which the vascular pattern is obscured but in which no small (neither rounded nor irregular) opacities can be discerned, a condition often described as a "ground glass pattern." However, there was no agreement as to whether this should merely be a notation or should be a mandatory category in profusion grading. Because the histopathology of this change is not understood, it is difficult to assess its importance in the classification. The goal of a roentgenographic study will influence the way films are studied. For example, when films are read for clinical surveillance, they should be arranged in order and read side by side to provide an assessment of the progression of abnormalities in a single patient. On the other hand, when films are read for epidemiologic studies, it is essential that each film be interpreted independently from a randomized series. Only in this way is it possible to avoid biased readings of progression, a bias that will be introduced if the order of pairing or the severity of the disease is known. 2 As presently used, the ILO DIe classification is difficult to apply to diseases that evolve rapidly or that have marked tendencies to regression or exacerbation. For this reason, a classification scheme suited to a very short time-frame would be needed to study diffuse parenchymal diseases due to organic dusts or other agents. For studies of chronic obstructive pulmonary disease or respiratory diseases caused by air pollution, the classification could be a useful tool, but a roentgenographic category for estimating lung volume would be needed, a feature not included in the
Arch Environ Health-Vol 30, Sept 1975
ILO DIe classification. Correlation of Roentgenographic Changes With Indexes of Dust Exposure, Lung Abnormality and Lung Function
Roentgenographic Indexes of Dust Exposure.-When roentgenographic changes are used to derive a dose-response curve, the detection of the earliest changes is especially important. To quantify the roentgenographic response, it is necessary to use a graded scale, such as the ILO DIe 12-point system. This is particularly useful in epidemiologic studies, where counting the persons in each category can provide a measure of the number of affected persons in the population at risk. In progression from the lower categories in the grading scale to the higher (ie, more extensive roentgenographic changes), smaller numbers of affected persons should be found. The largest number (including normal subjects) will be found in the lowest grading categories. However, the reliability of roentgenographic changes as a measure of dust exposure depends on the type of dust. In coal worker's pneumoconiosis, data show that roentgenographic progression is probably directly proportional to dust exposure (as estimated from dust content of lungs at autopsy)." But with dusts such as silica, which evoke a tissue response, the correlation between level of exposure and roentgenographic response may be poorer. This is probably because greater variability in the appearance of the roentgenographic results from the enhanced biologic response. Correlation With Pathologic Findings.-Pathologists have tried to grade tissue response and to correlate it with other measures of morbidity in interstitial lung diseases. One system, using a six-point scale to grade severity, correlates well with pulmonary function data when the pathologist concentrates on extent and severity of infiltration of alveolar walls but ignores nodules.' A grade corresponding to severe abnormality showed good correlation with severe Chest Roentgenogram-Weill & Jones
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functional impairment and "ground glass" type of roentgenographic appearance. However, beyond category 2 small irregular opacities on the roentgenographic scale there was little difference in the pathologic reactions, which were rather marked. The grades of pathology correlated better with the profusion of small rounded opacities in the x-ray film. Pathologic grades indicating severe tissue changes correlated with the roentgenographic finding of "small lungs." These studies, based in most cases on patients referred on account of disability, need to be interpreted with caution as generalizations. Correlations With Measures of Lung Function.-In attempts to relate altered pulmonary function in coal worker's pneumoconiosis to roentgenographic changes, it was found that indexes of air flow derived from the forced expiratory spirogram (forced expiratory volume in one second and forced vital capacity) did not correlate with roentgenographic grades until the stage of progressive massive fibrosis was reached. 5 However, residual volume correlated with roentgenographic changes even in subjects free of airways obstruction. In nonsmoking subjects with category 2 or 3 roentgenographic changes, frequency dependence of compliance can be demonstrated regardless of whether or not the subject has bronchitic symptoms. Although flow-volume loops and closing volume determinations can be used to distinguish miners from nonminers, these data do not correlate with roentgenographic severity in affected miners. And the presence of "type p" (up to 1.5 mm) small rounded opacities correlates with modest reduction in gas transfer but not with disability. These studies are based on representative and large samples of working miners. In general they agree clearly with similar studies in the United Kingdom and other European countries. Regional differences have been a feature in the US and United Kingdom studies; they are not at present fully explained. In a group of subjects exposed to asbestos and free silica in manufacturing, pulmonary function was Arch Environ Health-Vol 30, Sept 1975
related to the profusion of small opacities. 6 In subjects with small irregular opacities in category 2 or greater, mean values of total lung capacity, vital capacity, and pulmonary diffusing capacity were considerably lower than in subjects with similar profusion of small rounded opacities. But residual volume was substantially higher in the group with rounded opacities. In this population, dust exposure data correlated with profusion of both small irregular and rounded opacities, with pleural changes, and with reduction in lung volume and expiratory flow rates. 7 Lung function and roentgenographic abnormalities were equally sensitive in detecting any adverse effects of dust. Although reduced gas transfer correlated poorly with dust exposure, it reliably separated the group of subjects with roentgenographic changes from those without them. These studies provide support for the use of profusion categories in quantifying response to dust. Moreover, they support the separation of irregular from rounded opacities, although there is no direct validation of the division of irregular opacities into different types or sizes (s, t, and u). While the workshop participants agreed that chest roentgenography should be included with other modes of investigation, it should not be used as an indirect substitute for measurements of pulmonary function. Even when roentgenographic changes correlate well with function data, this does not always establish the value of the chest roentgenogram in determining clinical status and disability. For example, in coal worker's pneumocomOSIS, increasing roentgenographic changes correlate well with increased abnormality of certain function tests (eg, the alveolar-arterial gradient), but these are functional changes of low magnitude that do not correlate with symptoms, disability, or mortality.8 It is thus clear that the nature of the disease will determine whether roentgenographic data will prove helpful to clinicians or to those charged with determining disability compensation. But, the chest x-ray film may still be of use in preventive medicine; for example, in
coal worker's pneumoconiosis, to determine those who, if permitted to continue in their previous dust exposure, might develop complicated pneumoconiosis. Special Considerations Relating to Type of Exposure
Exposure to Asbestos.-Special problems arise when the same roentgenogram includes manifestations of different diseases that are present in different extents and degrees of severity. These difficulties are especially evident in exposures to asbestos because mixed types of fibers as well as other dusts, such as free silica, are present. To meet these problems, the classification has been broadened to include a number of the effects of asbestos exposure, namely, ill-defined diaphragm and ill-defined cardiac outline ("shaggy heart"), but their significance is at present not known. Pleural thickening as a single feature is much more common in some types of asbestos exposure than was appreciated before the recent epidemiologic surveys of exposed groups. The pleural thickening is associated with a small functional impairment, but its significance in terms of mortality and risk of development of mesothelioma will only be established by prospective epidemiologic studies that follow the classification. Attempts to define dust exposure accurately, or to determine the relative effects of sustained low exposures, in contast to intermittent heavy exposures, have presented major difficulties. And the problem of variability in tissue response remains formidable. Exposure to Coal Dust.-The difficulty of correlating degree of roentgenographic involvement with in-· dexes of disability or mortality from coal worker's pneumoconiosis has been alluded to above. Recent efforts have been addressed to examining the validity of readings of progression of disease and to introducing special measures that may effectively reduce interreader variability and bias." No single method of reading serial films has been shown to be best. Exposure to Silica.-In complicated silicosis, special problems arise in inChest Roentgenogram-Weill & Jones
437
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terpreting roentgenographic data. When basilar emphysema develops in the wake of progressive massive fibrosis, it may spread and obscure small opacities. Interpretative problems also may arise when typical and atypical mycobacterial infections occur. 9 Other sources of difficulty are that all aspects of the disease may progress even after exposure to dust has terminated, and that massive exposures for a few years may have effects that are either similar to or very different from the effects of the same total dose over many years. In accelerated silicosis, there may be an atypical distribution of roentgenographic abnormalities with predominant involvement of the lower lung zones with obscured nodulation, raising difficulties in classification. Exposure to Organic Dusts.-In diseases produced by organic dusts, the evanescent roentgenographic changes, presence of air-space filling patterns, and tendency to regress present a set of problems that are quite different from those in diseases caused by mineral dusts. To characterize diseases produced by organic dusts may require inhalation challenge with dusts, as well as immunologic tests and studies of the pattern of functional disturbance, which may be of greater use than roentgenograms. Other Diseases.-In considering the value of the chest roentgenogram in disorders other than those caused by dust inhalation, it was noted that there is a disappointing paucity of data with regard to such conditions as chronic obstructive lung disease and sarcoidosis and also with regard to such adverse environmental factors as smoking and air pollution. Technical Considerations and Newer Methodology
Film Quality.-Experience gained in the survey of coal miners makes it clear that constant attention must be given to film quality if roentgenograms are to yield useful data. It is essential to enforce basic standards for certifying personnel and establishing equipment capabilities and exposure techniques. Use of a set of standard films would help to deter438
mine the acceptable exposure range on a "dark-light" scale, but tests to define the range over which classification is little altered have not yet been reported. Automated Methods of Film Reading.-In an effort to minimize observer variability as well as to reduce the sheer magnitude of reading loads in epidemiologic studies, attempts are being made to develop automated film reading technology. For example, this technique might be used to assess film quality and discount for variations in exposure techniques. It may prove easier to decide by machine than by man whether a single characteristic (for example, small opacities) distinguishes normal subjects from abnormal subjects. The grading of profusion, which calls for multiple discriminations, averaging, and spatial perception, seems ideally suited to automation. Automated approaches to detecting and grading the small opacities of the pneumoconioses include use of optical and digital methods to extract textural features of the roentgenogram that would distinguish small opacities from vascular markings of the lung. The digital approach has extracted textural features from individual posterior rib interface fields. The optical method-using domain features-is capable of measuring the global aspects of texture. While digital measures seem to yield a slightly better estimate of profusion and could be extended to measure features other than texture, the optical method is fast and hence suitable for texture screening. Both methods give results (when analyzed by the method of confusion matrices) that compare favorably with film readings by those experienced in the use of the classification. Digital Processing for Assessing Progression of Disease.-Digital image correlation is believed to be a method of potentially great sensitivity in detecting changes in serial roentgenograms. Image scanners are used to sample two films and assign readings from each point in terms of shades of gray, and a digital computer is used to compare the images for differences in gray-scale values. The differences
Arch Environ Health-Vol 30, Sept 1975
can be displayed and enhanced by several techniques. WORKSHOP CONCLUSIONS AND RECOMMENDATIONS
The ILO U Ie classification of roentgenograms of pneumoconiosis measures responses to dusts, indicates the presence of disease, and correlates well with assessments of pathologic and functional changes. It can be used to set acceptable standards for dust levels and also to monitor the biologic response at safe-or nearly safe-levels of dust. However, it has not been adequately extended to other diseases. The workshop recommended that, Additional work should be done on the use of chest roentgenograms for epidemiologic investigations of nonoccupational interstitial diseases and chronic obstructive lung disease.
Several years of experience with the classification have uncovered problems relative to (1) distinguishing between small rounded and small irregular opacities when both are present; (2) obtaining measures of profusion that correlate well with lung function; (3) assessing progression of disease; and (4) avoiding biased readings in epidemiologic studies. The workshop recommended that, Instructions should be developed to enable readers to distinguish between small rounded and small irregular opacities when both are present. Methods should be developed to improve the measurement of profusion and alternate methods should be explored to achieve better correlation with measures of lung function. When assessing progression of disease, combined profusion of small rounded and small irregular opacities should not be used alone; all information, including types of opacities, should be recorded. Paired films, obtained in longitudinal studies, should be assessed by both independent randomized and side-by-side methods. In epidemiologic studies, several experienced readers (at least three) should be used to minimize observer variability, and their comparability should be established initially as well as checked periodically. In addition, standard films should be used continuously by all readers, chest films of unexposed workers should be included for Chest Roentgenogram-Weill & Jones
purposes of control, and a proportion of films should be fed back to the reader periodically to check repeatability.
Technical problems in obtaining suitable films can interfere with effective use of the classification system. The workshop recommended that, High priority should be given to defining in objective terms what is meant by a "good film," and illustrative standard chest x-ray films should be provided to insure film quality.
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It is anticipated that in the foreseeable future automated image transformation and recognition, and nonphysician describers or classifiers, may be used in epidemiologic investigations of occupational dust diseases. However, there are still technical problems to be overcome. The workshop recommended that, Further study should be addressed to developing information about sensory perception in pattern recognition of pneumoconioses. The participants in the workshop were as follows: Charles Carrington, MD, Professor of Pathology, Yale University, School of Medicine; Sally Cowles, MD, Epidemiologist, Division of Lung Diseases, National Heart and Lung Insti-
tute; John C. Gilson, FRCP, Director, MRC Pneumoconiosis Unit, Llandough Hospital, Penarth, Giamorgan, UK; Gareth Green, MD, Professor of Medicine, University of Vermont, School of Medicine; Ernest Hall, PhD, Professor of Electrical Engineering, University of Southern California; Ian Higgins, MD, FRCP, Professor and Chairman, Department of Epidemiology, University of Michigan, School of Public Health; George Jacobson, MD, Professor and Chairman, Department of Radiology, University of Southern California, School of Medicine; Robert Jones, MD, Assistant Professor of Medicine, Tulane University, School of Medicine; William Lainhart, MD, Deputy Associate Director, National Institute of Occupational Safety and Health; Robert Lillestrand, Director, Electrooptics Research, Control Data Corporation, Minneapolis; Raymond Moore, MD, Associate Director, National Institute of Occupational Safety and Health; W. Keith C. Morgan, MD, Director, Appalachian Laboratory for Occupational Respiratory Disease, National Institute of Occupational Safety and Health; Raymond Murphy, MD, Assistant Professor of Physiology, Harvard School of Public Health; Peter Oldham, DSc, MRC Pneumoconiosis Unit, Llandough Hospital, Penarth, Glamorgan, UK; Robert Reger, MS, Appalachian Laboratory for Occupational Respiratory Disease, National Institute of Occupational Safety and Health; Charles Rossiter, MA, RMC Pneumoconiosis Unit, Llandough Hospital, Penarth, Glamorgan, UK; Gerard Scanlon, MD, Associate Professor of Radiology, Milwaukee County General Hospital; Hans Weill, MD, Professor of Medicine, TulaRe University, School of Medicine; Lynn Blake, PhD, Bioengineering Program, Division of Lung Diseases, National Heart and Lung Institute; George Wright, MD, Greenwood Plaza, Denver; Morton Ziskind, MD, Professor of Medicine, Tulane University, School of Medicine.
John C. Gilson, FRCP, director of the Medical Research Council, Pneumoconiosis Unit, and his colleagues provided assistance in this study.
MYTHOLOGY 1. ILO
Ule Internaticmal Classification of Ra-
diography of Pneumoconioses: 1971, pUblication No. 22 (revised). Geneva, International Labour Office, Occupational Safety and Health Service, 1972. 2. Reger RB, Butcher DF, Morgan WKC: Assessing change in the pneumoconioses using serial radiographs. Am J Epidemiol 98:243-254, 1973.
3. Rossiter CEo Relation between content and composition of coal workers' lungs and radiological appearances. Br J Ind Med 29:31-44, 1972. 4. Gaensler EA, Carrington CB, Contu RE, et al: Pathological, physiological, and radiological correlations in the pneumoconioses. Ann NY Acad Sci 200:574-607, 1972. 5. Morgan WKC, Handelsman L, Kibelstis J, et al: Ventilatory capacity and lung volumes of US coal miners. Arch Envircm Health 28:182-189, 1974. 6. Weill H, Waggenspack C, Bailey W, et al: Radiographic and physiologic patterns among workers engaged in manufacture of asbestos cement products. J Occup Med 15:248-252, 1973. 7. Weill H, Ziskind MM, Waggenspack C, et al: Lung function consequences of dust exposure in asbestos cement manufacturing plants. Arch Environ Health 30:88-97, 1975. 8. Lapp NL, Seaton A: Pulmcmary Reactions to Coal Dust. New York, Academic Press Inc, 1971, p 153. 9. Bailey WC, Brown M, Buechner HA, et al: Silico-mycobacterial disease in sandblasters. Am Rev Respir Dis 110:115-125, 1974.
MYTHOLOGY Index to Gods and Hemes Vulcan The blacksmith Vulcan is the same Hephaestus, by his Grecian name, Whom Venus knew and by "knew" I mean The same as ancient prophets. The unclean Old god provides us with a word or two Straight from his shop. "Vulcanize" will do To signify a heated piece of rubber while Volcano means his smithy underground and vile. Unlucky fellow to survive hedabbled. Who once the goddess' gown unscrabbled.
Ceres Ceres, patroness of wheat and barley, Goddess of rural amplitude, With cornucopia pictured nude And kindly-advertising treats you hardly: From sunburst tropiC to chill Boreal It steals your name to put on breakfast cereal.
Rusticatus
Arch Environ Health-Vol 30, Sept 1975
Chest Roentgenogram-Weill Ii Jones
4139
Archives of Environmental Health: An International Journal Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/vzeh20
The Chest Roentgenogram as an Epidemiologic Tool Hans Weill MD & Robert Jones MD Published online: 02 May 2013.
To cite this article: Hans Weill MD & Robert Jones MD (1975) The Chest Roentgenogram as an Epidemiologic Tool, Archives of Environmental Health: An International Journal, 30:9, 435-439, DOI: 10.1080/00039896.1975.10666744 To link to this article: http://dx.doi.org/10.1080/00039896.1975.10666744
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions
The Chest Roentgenogram as an Epidemiologic Tool Downloaded by [] at 00:53 03 January 2015
Report of a Workshop Hans Weill, MD, Robert Jones, MD (Editors)
November 1973, the Division of I n Lung Diseases, National Heart and Lung Institute (NHLI), sponsored a workshop on the epidemiology of respiratory diseases that included a discussion of problems associated with the use of standardized procedures in chest roentgenography. There was a consensus that the chest roentgenogram was useful in epidemiologic studies involving occupational diseases or specific pulmonary diseases other than the obstructive diseases. Furthermore, it was agreed that investigators should use standardized procedures to minimize variability of readings and to insure comparability of results from different studies. Use of the International Office UICC/Cincinnati Labour (ILO U IC) classification of radiography of pneumoconiosis was recommended. 1 To address these problems of vari-
ability in interpretation, the Division of Lung Diseases sponsored a workshop on chest roentgenography held on March 25 and 26, 1974, in New Orleans. Hans Weill, MD, was the chairman. The workshop brought together experts in the use of the ILO U/C classification (some of whom had served on the committee that developed it), and also experts in population studies of nonspecific chronic respiratory diseases and in standardizing methodology and automated reading analyses. Workshop sessions were addressed to (1) problems in use of the ILO U IC classification; (2) correlation of roentgenographic indexes with lung function and pathology; (3) use of roentgenography in diseases associated with exposure to occupational dusts and in community studies; and (4) technical and methodologic considerations. The final session was devoted to a discussion of conclusions and recommendations. INTRODUCTION
Submitted for publication Nov 21, 1974; accepted Feb 3, 1975. The workshop, held in New Orleans on March 25-26,1974, was sponsored by the National Heart and Lung Institute. Reprint requests to Pulmonary Disease Section, Department of Medicine, Tulane University School of Medicine, 1700 Perdido St, New Orleans, LA 70112 (Dr. Weill).
Arch Environ Health-Vol 3D, Sept 1975
The ILO U IC classification is a classification of roentgenograms of pneumoconioses. 1 The classification provides for systematic recording of roentgenographic appearances; describes the natural history of the Chest Roentgenogram-Weill & Jones
435
changes; and, by use of verbal descriptions and standard films, permits semiquantitative assessments. Features that are recorded include (1) type of opacity (eg, small or large, rounded or irregular, calcified); (2) profusion of opacities (number of opacities per unit area); (3) extent of involvement (areas of the lung field affected); and (4) other features, such as pleural thickness, ill-defined diaphragm, ill-defined cardiac outline, and pleural calcification.
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HIGHLIGHTS OF WORKSHOP DISCUSSIONS Problems in Use of ILO UIC Classification
Although participants agreed on the advantages of the ILO DIe classification, they were cdttcerned particularly about problems of interobserver variability in grading small opacities and in the development of standad reference films. The category of small irregular opacities l1aS led to fundamental disagreements in film interpretation. Lack of agreement relates both to what constitutes a small irregular opacity and to how they should be interpreted when a film also contains small rounded opacities. In coal pneumOCOnIOSIS small worker's rounded opacities have well-established significance as indexes of dust content in the lung and hence as measures of past dust exposure. Small irregular opacities are at present of undetermined meaning in coal workers, but are highly relevant in those workers exposed to asbestos. However, mixed mineral dust exposures are the rule rather than the exception, so there are good grounds for having a simple classification with appropriate subdivisions to classify all types of patterns seen in all kinds of pneumoconioses. Recording the level of profusion also presents problems because it may be based on whichever type of small opacity (rounded or irregular) is higher or it may be based on their combination. The choice between these alternatives may be influenced by the nature of the disease under study. Workshop participants agreed that, even when the combination of 436
both rounded and irregular nodules is to be taken as the measure of profusion, the profusion of small rounded and of small irregular opacities should be separately recorded. Some participants questioned the validity of dividing small irregular opacities into types "s" (fine), "t" (medium), and "u" (coarse), because at present these terms are purely descriptive (although future work may prove these distinctions to be important). On the other hand, some advocated extending the system of recording profusion to cover cases in which the vascular pattern is obscured but in which no small (neither rounded nor irregular) opacities can be discerned, a condition often described as a "ground glass pattern." However, there was no agreement as to whether this should merely be a notation or should be a mandatory category in profusion grading. Because the histopathology of this change is not understood, it is difficult to assess its importance in the classification. The goal of a roentgenographic study will influence the way films are studied. For example, when films are read for clinical surveillance, they should be arranged in order and read side by side to provide an assessment of the progression of abnormalities in a single patient. On the other hand, when films are read for epidemiologic studies, it is essential that each film be interpreted independently from a randomized series. Only in this way is it possible to avoid biased readings of progression, a bias that will be introduced if the order of pairing or the severity of the disease is known. 2 As presently used, the ILO DIe classification is difficult to apply to diseases that evolve rapidly or that have marked tendencies to regression or exacerbation. For this reason, a classification scheme suited to a very short time-frame would be needed to study diffuse parenchymal diseases due to organic dusts or other agents. For studies of chronic obstructive pulmonary disease or respiratory diseases caused by air pollution, the classification could be a useful tool, but a roentgenographic category for estimating lung volume would be needed, a feature not included in the
Arch Environ Health-Vol 30, Sept 1975
ILO DIe classification. Correlation of Roentgenographic Changes With Indexes of Dust Exposure, Lung Abnormality and Lung Function
Roentgenographic Indexes of Dust Exposure.-When roentgenographic changes are used to derive a dose-response curve, the detection of the earliest changes is especially important. To quantify the roentgenographic response, it is necessary to use a graded scale, such as the ILO DIe 12-point system. This is particularly useful in epidemiologic studies, where counting the persons in each category can provide a measure of the number of affected persons in the population at risk. In progression from the lower categories in the grading scale to the higher (ie, more extensive roentgenographic changes), smaller numbers of affected persons should be found. The largest number (including normal subjects) will be found in the lowest grading categories. However, the reliability of roentgenographic changes as a measure of dust exposure depends on the type of dust. In coal worker's pneumoconiosis, data show that roentgenographic progression is probably directly proportional to dust exposure (as estimated from dust content of lungs at autopsy)." But with dusts such as silica, which evoke a tissue response, the correlation between level of exposure and roentgenographic response may be poorer. This is probably because greater variability in the appearance of the roentgenographic results from the enhanced biologic response. Correlation With Pathologic Findings.-Pathologists have tried to grade tissue response and to correlate it with other measures of morbidity in interstitial lung diseases. One system, using a six-point scale to grade severity, correlates well with pulmonary function data when the pathologist concentrates on extent and severity of infiltration of alveolar walls but ignores nodules.' A grade corresponding to severe abnormality showed good correlation with severe Chest Roentgenogram-Weill & Jones
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functional impairment and "ground glass" type of roentgenographic appearance. However, beyond category 2 small irregular opacities on the roentgenographic scale there was little difference in the pathologic reactions, which were rather marked. The grades of pathology correlated better with the profusion of small rounded opacities in the x-ray film. Pathologic grades indicating severe tissue changes correlated with the roentgenographic finding of "small lungs." These studies, based in most cases on patients referred on account of disability, need to be interpreted with caution as generalizations. Correlations With Measures of Lung Function.-In attempts to relate altered pulmonary function in coal worker's pneumoconiosis to roentgenographic changes, it was found that indexes of air flow derived from the forced expiratory spirogram (forced expiratory volume in one second and forced vital capacity) did not correlate with roentgenographic grades until the stage of progressive massive fibrosis was reached. 5 However, residual volume correlated with roentgenographic changes even in subjects free of airways obstruction. In nonsmoking subjects with category 2 or 3 roentgenographic changes, frequency dependence of compliance can be demonstrated regardless of whether or not the subject has bronchitic symptoms. Although flow-volume loops and closing volume determinations can be used to distinguish miners from nonminers, these data do not correlate with roentgenographic severity in affected miners. And the presence of "type p" (up to 1.5 mm) small rounded opacities correlates with modest reduction in gas transfer but not with disability. These studies are based on representative and large samples of working miners. In general they agree clearly with similar studies in the United Kingdom and other European countries. Regional differences have been a feature in the US and United Kingdom studies; they are not at present fully explained. In a group of subjects exposed to asbestos and free silica in manufacturing, pulmonary function was Arch Environ Health-Vol 30, Sept 1975
related to the profusion of small opacities. 6 In subjects with small irregular opacities in category 2 or greater, mean values of total lung capacity, vital capacity, and pulmonary diffusing capacity were considerably lower than in subjects with similar profusion of small rounded opacities. But residual volume was substantially higher in the group with rounded opacities. In this population, dust exposure data correlated with profusion of both small irregular and rounded opacities, with pleural changes, and with reduction in lung volume and expiratory flow rates. 7 Lung function and roentgenographic abnormalities were equally sensitive in detecting any adverse effects of dust. Although reduced gas transfer correlated poorly with dust exposure, it reliably separated the group of subjects with roentgenographic changes from those without them. These studies provide support for the use of profusion categories in quantifying response to dust. Moreover, they support the separation of irregular from rounded opacities, although there is no direct validation of the division of irregular opacities into different types or sizes (s, t, and u). While the workshop participants agreed that chest roentgenography should be included with other modes of investigation, it should not be used as an indirect substitute for measurements of pulmonary function. Even when roentgenographic changes correlate well with function data, this does not always establish the value of the chest roentgenogram in determining clinical status and disability. For example, in coal worker's pneumocomOSIS, increasing roentgenographic changes correlate well with increased abnormality of certain function tests (eg, the alveolar-arterial gradient), but these are functional changes of low magnitude that do not correlate with symptoms, disability, or mortality.8 It is thus clear that the nature of the disease will determine whether roentgenographic data will prove helpful to clinicians or to those charged with determining disability compensation. But, the chest x-ray film may still be of use in preventive medicine; for example, in
coal worker's pneumoconiosis, to determine those who, if permitted to continue in their previous dust exposure, might develop complicated pneumoconiosis. Special Considerations Relating to Type of Exposure
Exposure to Asbestos.-Special problems arise when the same roentgenogram includes manifestations of different diseases that are present in different extents and degrees of severity. These difficulties are especially evident in exposures to asbestos because mixed types of fibers as well as other dusts, such as free silica, are present. To meet these problems, the classification has been broadened to include a number of the effects of asbestos exposure, namely, ill-defined diaphragm and ill-defined cardiac outline ("shaggy heart"), but their significance is at present not known. Pleural thickening as a single feature is much more common in some types of asbestos exposure than was appreciated before the recent epidemiologic surveys of exposed groups. The pleural thickening is associated with a small functional impairment, but its significance in terms of mortality and risk of development of mesothelioma will only be established by prospective epidemiologic studies that follow the classification. Attempts to define dust exposure accurately, or to determine the relative effects of sustained low exposures, in contast to intermittent heavy exposures, have presented major difficulties. And the problem of variability in tissue response remains formidable. Exposure to Coal Dust.-The difficulty of correlating degree of roentgenographic involvement with in-· dexes of disability or mortality from coal worker's pneumoconiosis has been alluded to above. Recent efforts have been addressed to examining the validity of readings of progression of disease and to introducing special measures that may effectively reduce interreader variability and bias." No single method of reading serial films has been shown to be best. Exposure to Silica.-In complicated silicosis, special problems arise in inChest Roentgenogram-Weill & Jones
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terpreting roentgenographic data. When basilar emphysema develops in the wake of progressive massive fibrosis, it may spread and obscure small opacities. Interpretative problems also may arise when typical and atypical mycobacterial infections occur. 9 Other sources of difficulty are that all aspects of the disease may progress even after exposure to dust has terminated, and that massive exposures for a few years may have effects that are either similar to or very different from the effects of the same total dose over many years. In accelerated silicosis, there may be an atypical distribution of roentgenographic abnormalities with predominant involvement of the lower lung zones with obscured nodulation, raising difficulties in classification. Exposure to Organic Dusts.-In diseases produced by organic dusts, the evanescent roentgenographic changes, presence of air-space filling patterns, and tendency to regress present a set of problems that are quite different from those in diseases caused by mineral dusts. To characterize diseases produced by organic dusts may require inhalation challenge with dusts, as well as immunologic tests and studies of the pattern of functional disturbance, which may be of greater use than roentgenograms. Other Diseases.-In considering the value of the chest roentgenogram in disorders other than those caused by dust inhalation, it was noted that there is a disappointing paucity of data with regard to such conditions as chronic obstructive lung disease and sarcoidosis and also with regard to such adverse environmental factors as smoking and air pollution. Technical Considerations and Newer Methodology
Film Quality.-Experience gained in the survey of coal miners makes it clear that constant attention must be given to film quality if roentgenograms are to yield useful data. It is essential to enforce basic standards for certifying personnel and establishing equipment capabilities and exposure techniques. Use of a set of standard films would help to deter438
mine the acceptable exposure range on a "dark-light" scale, but tests to define the range over which classification is little altered have not yet been reported. Automated Methods of Film Reading.-In an effort to minimize observer variability as well as to reduce the sheer magnitude of reading loads in epidemiologic studies, attempts are being made to develop automated film reading technology. For example, this technique might be used to assess film quality and discount for variations in exposure techniques. It may prove easier to decide by machine than by man whether a single characteristic (for example, small opacities) distinguishes normal subjects from abnormal subjects. The grading of profusion, which calls for multiple discriminations, averaging, and spatial perception, seems ideally suited to automation. Automated approaches to detecting and grading the small opacities of the pneumoconioses include use of optical and digital methods to extract textural features of the roentgenogram that would distinguish small opacities from vascular markings of the lung. The digital approach has extracted textural features from individual posterior rib interface fields. The optical method-using domain features-is capable of measuring the global aspects of texture. While digital measures seem to yield a slightly better estimate of profusion and could be extended to measure features other than texture, the optical method is fast and hence suitable for texture screening. Both methods give results (when analyzed by the method of confusion matrices) that compare favorably with film readings by those experienced in the use of the classification. Digital Processing for Assessing Progression of Disease.-Digital image correlation is believed to be a method of potentially great sensitivity in detecting changes in serial roentgenograms. Image scanners are used to sample two films and assign readings from each point in terms of shades of gray, and a digital computer is used to compare the images for differences in gray-scale values. The differences
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can be displayed and enhanced by several techniques. WORKSHOP CONCLUSIONS AND RECOMMENDATIONS
The ILO U Ie classification of roentgenograms of pneumoconiosis measures responses to dusts, indicates the presence of disease, and correlates well with assessments of pathologic and functional changes. It can be used to set acceptable standards for dust levels and also to monitor the biologic response at safe-or nearly safe-levels of dust. However, it has not been adequately extended to other diseases. The workshop recommended that, Additional work should be done on the use of chest roentgenograms for epidemiologic investigations of nonoccupational interstitial diseases and chronic obstructive lung disease.
Several years of experience with the classification have uncovered problems relative to (1) distinguishing between small rounded and small irregular opacities when both are present; (2) obtaining measures of profusion that correlate well with lung function; (3) assessing progression of disease; and (4) avoiding biased readings in epidemiologic studies. The workshop recommended that, Instructions should be developed to enable readers to distinguish between small rounded and small irregular opacities when both are present. Methods should be developed to improve the measurement of profusion and alternate methods should be explored to achieve better correlation with measures of lung function. When assessing progression of disease, combined profusion of small rounded and small irregular opacities should not be used alone; all information, including types of opacities, should be recorded. Paired films, obtained in longitudinal studies, should be assessed by both independent randomized and side-by-side methods. In epidemiologic studies, several experienced readers (at least three) should be used to minimize observer variability, and their comparability should be established initially as well as checked periodically. In addition, standard films should be used continuously by all readers, chest films of unexposed workers should be included for Chest Roentgenogram-Weill & Jones
purposes of control, and a proportion of films should be fed back to the reader periodically to check repeatability.
Technical problems in obtaining suitable films can interfere with effective use of the classification system. The workshop recommended that, High priority should be given to defining in objective terms what is meant by a "good film," and illustrative standard chest x-ray films should be provided to insure film quality.
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It is anticipated that in the foreseeable future automated image transformation and recognition, and nonphysician describers or classifiers, may be used in epidemiologic investigations of occupational dust diseases. However, there are still technical problems to be overcome. The workshop recommended that, Further study should be addressed to developing information about sensory perception in pattern recognition of pneumoconioses. The participants in the workshop were as follows: Charles Carrington, MD, Professor of Pathology, Yale University, School of Medicine; Sally Cowles, MD, Epidemiologist, Division of Lung Diseases, National Heart and Lung Insti-
tute; John C. Gilson, FRCP, Director, MRC Pneumoconiosis Unit, Llandough Hospital, Penarth, Giamorgan, UK; Gareth Green, MD, Professor of Medicine, University of Vermont, School of Medicine; Ernest Hall, PhD, Professor of Electrical Engineering, University of Southern California; Ian Higgins, MD, FRCP, Professor and Chairman, Department of Epidemiology, University of Michigan, School of Public Health; George Jacobson, MD, Professor and Chairman, Department of Radiology, University of Southern California, School of Medicine; Robert Jones, MD, Assistant Professor of Medicine, Tulane University, School of Medicine; William Lainhart, MD, Deputy Associate Director, National Institute of Occupational Safety and Health; Robert Lillestrand, Director, Electrooptics Research, Control Data Corporation, Minneapolis; Raymond Moore, MD, Associate Director, National Institute of Occupational Safety and Health; W. Keith C. Morgan, MD, Director, Appalachian Laboratory for Occupational Respiratory Disease, National Institute of Occupational Safety and Health; Raymond Murphy, MD, Assistant Professor of Physiology, Harvard School of Public Health; Peter Oldham, DSc, MRC Pneumoconiosis Unit, Llandough Hospital, Penarth, Glamorgan, UK; Robert Reger, MS, Appalachian Laboratory for Occupational Respiratory Disease, National Institute of Occupational Safety and Health; Charles Rossiter, MA, RMC Pneumoconiosis Unit, Llandough Hospital, Penarth, Glamorgan, UK; Gerard Scanlon, MD, Associate Professor of Radiology, Milwaukee County General Hospital; Hans Weill, MD, Professor of Medicine, TulaRe University, School of Medicine; Lynn Blake, PhD, Bioengineering Program, Division of Lung Diseases, National Heart and Lung Institute; George Wright, MD, Greenwood Plaza, Denver; Morton Ziskind, MD, Professor of Medicine, Tulane University, School of Medicine.
John C. Gilson, FRCP, director of the Medical Research Council, Pneumoconiosis Unit, and his colleagues provided assistance in this study.
MYTHOLOGY 1. ILO
Ule Internaticmal Classification of Ra-
diography of Pneumoconioses: 1971, pUblication No. 22 (revised). Geneva, International Labour Office, Occupational Safety and Health Service, 1972. 2. Reger RB, Butcher DF, Morgan WKC: Assessing change in the pneumoconioses using serial radiographs. Am J Epidemiol 98:243-254, 1973.
3. Rossiter CEo Relation between content and composition of coal workers' lungs and radiological appearances. Br J Ind Med 29:31-44, 1972. 4. Gaensler EA, Carrington CB, Contu RE, et al: Pathological, physiological, and radiological correlations in the pneumoconioses. Ann NY Acad Sci 200:574-607, 1972. 5. Morgan WKC, Handelsman L, Kibelstis J, et al: Ventilatory capacity and lung volumes of US coal miners. Arch Envircm Health 28:182-189, 1974. 6. Weill H, Waggenspack C, Bailey W, et al: Radiographic and physiologic patterns among workers engaged in manufacture of asbestos cement products. J Occup Med 15:248-252, 1973. 7. Weill H, Ziskind MM, Waggenspack C, et al: Lung function consequences of dust exposure in asbestos cement manufacturing plants. Arch Environ Health 30:88-97, 1975. 8. Lapp NL, Seaton A: Pulmcmary Reactions to Coal Dust. New York, Academic Press Inc, 1971, p 153. 9. Bailey WC, Brown M, Buechner HA, et al: Silico-mycobacterial disease in sandblasters. Am Rev Respir Dis 110:115-125, 1974.
MYTHOLOGY Index to Gods and Hemes Vulcan The blacksmith Vulcan is the same Hephaestus, by his Grecian name, Whom Venus knew and by "knew" I mean The same as ancient prophets. The unclean Old god provides us with a word or two Straight from his shop. "Vulcanize" will do To signify a heated piece of rubber while Volcano means his smithy underground and vile. Unlucky fellow to survive hedabbled. Who once the goddess' gown unscrabbled.
Ceres Ceres, patroness of wheat and barley, Goddess of rural amplitude, With cornucopia pictured nude And kindly-advertising treats you hardly: From sunburst tropiC to chill Boreal It steals your name to put on breakfast cereal.
Rusticatus
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