. The principles and practice of roentgenological technique . Fig. 197.—Compression of the abdomen with cylin-der. No actual compression has really takenplace, because of sagging of the abdomen. axis parallel to the central ray. \Mien theobject lies obliquely to the horizontal planethere is distortion of the shadow, and the re- IMMOBILIZATION 145 cording surface should be placed ])arallel to itand the central ray directed at right angles tothe recording surface, if a centric view is to beobtained (Fig. 196-b). The shadow of an object which lies with itslong axis parallel to the plane of the re
. The principles and practice of roentgenological technique . Fig. 197.—Compression of the abdomen with cylin-der. No actual compression has really takenplace, because of sagging of the abdomen. axis parallel to the central ray. \Mien theobject lies obliquely to the horizontal planethere is distortion of the shadow, and the re- IMMOBILIZATION 145 cording surface should be placed ])arallel to itand the central ray directed at right angles tothe recording surface, if a centric view is to beobtained (Fig. 196-b). The shadow of an object which lies with itslong axis parallel to the plane of the recordingsurface will show a minimum alteration bytube deviation, as compared to an object Fig. 198.—The interposition of a permeable material,loofah sponge, rubber ball or pad permits actualcompression. The factors, therefore, upon which thedefinition of the shadow depends (referringto arrangement only) are: 1. Proximity of the tube to the object. 2. Proximity of the object to the recordingsurface. 3. Immobility of tube, part and recordiiigsurface. The first will be discussed under exposureand the second and third will be discussed to-gether under immobilization. The Part is Iiiiiiiobiliccd. Immobilization may be active, as when thechest walls, lung structures or kidneys arevokmtarily immobilized by the cessation ofrespiration, or passive, as when the part isplaced in a certain posture and kept in a fixedposition by the use of immobilization ap-paratus. It is advisable to always practise passiveimmobilization even when instantaneous ex-posure is made. The immobilization shouldaim to bring the part in as close proximity to the recording surface as possible. To ac-complish
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectradiogr, bookyear1920
