Supervoltage and Multiple Simultaneous Roentgenography—New Technics for Roentgen Examination of the Chest

Abstract

While the survey chest roentgenogram is one of our best diagnostic tools, experience has shown that conventional roentgenographic methods fail to record some significant lesions, most notably those which occur within the mediastinum (1). Bronchogenic carcinoma frequently involves the structures of the mediastinum before peripheral roentgenographic evidence of disease is apparent. It is felt, therefore, that the development of a roentgenographic technic adaptable to mass screening methods, which would demonstrate the lung fields and the mediastinal structures, would be of great value in the early detection of cancer of the lung. It is possible, to be sure, to study both the mediastinum and the lung fields with conventional technics. The authors believe, however, that these conventional methods are not satisfactory for mass survey studies, since they require multiple exposures. As the number of exposures needed per patient increases, the cost of the examination rises, the roentgen dose to the patient becomes larger, and the number of patients that a given diagnostic unit can serve decreases. Added to these difficulties, is the very considerable problem of the interpretation of a greatly increased number of roentgenograms. For these reasons, a mass screening program based on multiple exposure technics appears to be impractical, and the advantage of a procedure with which more diagnostic information might be recorded in a single exposure appears obvious. The purpose of this discussion is to consider new approaches to the solution of this problem, and to present early clinical impressions of supervoltage roentgenography, which appears to be the most promising new technic that we have studied. Multiple Simultaneous Roentgenography New methods are perhaps best suggested by a consideration of the inadequacies of conventional roentgenograms. One major defect in the present survey chest study is that the mediastinal shadow is an area of “under-exposure” and is therefore characterized by a very low film contrast factor (2). This makes impossible the demonstration of critical details in this area. In more heavily exposed roentgenograms, the mediastinal details can be recorded much more adequately (provided a grid is employed), but in such a study the lung fields are said to be “burned out,” i.e., they are sufficiently bright for optimum contrast perception when viewed on a conventional illuminator (8). In brief, the roentgen-ray absorption of the mediastinum is so great, relative to that of the lung fields, that it is impossible to record both satisfactorily on a single sheet of film if conventional radiation is employed. A possible solution to this problem lies in the use of a cassette containing two pairs of fluorescent intensifying screens, one pair of which is coated with a “faster” phosphor than the other (Fig. 1).