. Roentgen interpretation; a manual for students and practitioners . Fig. 99.—The water-bottle shape of the heart shadow seen in pericardialeffusion with the patient upright. After the fluoroscopic observations are completed, a mark is placedon the patients chest opposite the center of the heart shadow toserve as a point upon which to focus the tube for the plate which istaken with the patient standing. The focal spot of the tube shouldbe at a distance of at least six feet from the plate. Special care must be taken so to place the patient that the centralrays from the tube pass through the che
. Roentgen interpretation; a manual for students and practitioners . Fig. 99.—The water-bottle shape of the heart shadow seen in pericardialeffusion with the patient upright. After the fluoroscopic observations are completed, a mark is placedon the patients chest opposite the center of the heart shadow toserve as a point upon which to focus the tube for the plate which istaken with the patient standing. The focal spot of the tube shouldbe at a distance of at least six feet from the plate. Special care must be taken so to place the patient that the centralrays from the tube pass through the chest at right angles to its THE HEART AND GREAT VESSELS 121 transverse diameter. At this distance a small amount of displace-ment of the tube to the right or the left from the median line doesnot appreciably distort the heart shadow, but a slight rotation ofthe patient does produce definite distortion. In stout patients it is better to have the plate in contact with thechest wall and the patient standing erect. If the plate is placed at. Fig. 100.—The same as Fig. 99, but taken with the patient prone. Notethe change in the shape of the heart shadow, due to the .shifting of the fluid withinthe pericardium. right angles to the central ray from the tube, its upper portionmay be some distance from the chest wall; and as we are notdealing with absolutely parallel rays, a slight amount of magnifica-tion of the aorta will result. On the other hand, if the patient is allowed to lean forward tobring the chest entirely in contact with the plate, there will be acertain amount of apparent sagging of the contents of the chest. The time of exposure should be sufficiently long to cover one full 122 THE CHEST heart cycle, so that the shadow obtained will be the shadow of theheart in diastole. Where very rapid exposures are made the result-ing picture may represent the heart either in systole or diastole orat some phase between. The period of diastole is the one from whichestimates of t
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