. The principles and practice of roentgenological technique . w irt)ni within protective booth ofserial plate changing apparatus. (Hirsch.) shift of the tube to the right should be marked(R) and the other (L). After the two ex-posures have been developed, the images maybe optically combined by the many forms ofstereoscopes, the \Mieatstone reflecting mirrorbeing most commonly used. By means of re-ductions, a hand prism stereoscope may beutilized. 134 POLYGRAMS Teleroentgenography By orthoroentgenoscopy it is possible, ashas been shown, to minimize tlie distortion inthe shadow of an organ, resu
. The principles and practice of roentgenological technique . w irt)ni within protective booth ofserial plate changing apparatus. (Hirsch.) shift of the tube to the right should be marked(R) and the other (L). After the two ex-posures have been developed, the images maybe optically combined by the many forms ofstereoscopes, the \Mieatstone reflecting mirrorbeing most commonly used. By means of re-ductions, a hand prism stereoscope may beutilized. 134 POLYGRAMS Teleroentgenography By orthoroentgenoscopy it is possible, ashas been shown, to minimize tlie distortion inthe shadow of an organ, resulting in the diver-gence of the rays, by outlining the structuresby the central ray. The disadvantages whichattend this method may be overcome by mak-ing a permanent record on a sensitive plate bya ray, which for practical purposes, is rela-tively parallel. This may be attained by in-creasing the target plate distance to twometers or eighty inches. While the differencebetween the size of the heart shadow made atthe usual distance, fifty centimeters, and the. Fig. i8i.—Back of plate holding pan. The pin ismade to move on a -|- track, this bringing thevarious quarters of the plate under the hole inthe table for exposure. (Hirsch.) shadow at two meters, is over one centimeter,the distortion at the latter distance isnegligible. In chest examinations a dorso-ventral exposure is the one usually madewith the object of determining the heart tube is focused at the sixth dorsal ver-tebra. It is an advantage to place lead markers,in the supra-sternal notch, or at the zi-phoid. It is not necessary that the exposures bevery short, since it is the purpose to obtain themaximum dimension, as in diastole. The useof an intensifying screen and a relatively high tube is necessary, if detail and sharpnessis to be obtained. By the use of a film be-tween two screens, satisfactory teleroentgeno-grams may be made with small apparatus.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectradiogr, bookyear1920
