. American quarterly of roentgenology . (to the end marked R if the radiographs are madeof the right eye, and to L if of the left eye). The upper shutteris moved to cover the exposed central portion of the plate anduncover the upper unexposed portion. The current is againturned on and the second exposure made. The time of expos-ure for the second picture should be about one and a halftimes that of the first, to allow for the increased distance ofthe tube from the eye. After the plate is developed it is placed in the frame P.(Fig. 1), containing the key plate or focal coordinates (Fig. 5),with
. American quarterly of roentgenology . (to the end marked R if the radiographs are madeof the right eye, and to L if of the left eye). The upper shutteris moved to cover the exposed central portion of the plate anduncover the upper unexposed portion. The current is againturned on and the second exposure made. The time of expos-ure for the second picture should be about one and a halftimes that of the first, to allow for the increased distance ofthe tube from the eye. After the plate is developed it is placed in the frame P.(Fig. 1), containing the key plate or focal coordinates (Fig. 5),with the film side of the radiograph next to the key plate. Theradiograph is moved until the shadow of the indicating ball of 76 American Quarterly of Roentgenology the first exposure is in apposition with the middle ball on thekey plate and the heavy horizontal line of the radiograph paral-lel with the horizontal line on the plate. Holding the frame to Focal Co-ordinates for Dr. SweetsImproved Eye Localizer BiCHT Lett 10 20 Ctq 30 10 ±-50. T 10 B 10 10 10 20 *A 30 MO SO Fig. 5.—Plate showing focal coordinates (three-fourths actual size). the light, there is noted the position occupied, by the shadowof the foreign body with respect to the vertical lines of C andD. A reading is made of the line or lines, which passthrough the body, and this is transferred to the correspondinglines of the C or D scale of the chart, to the right or leftside, depending on which eye is under examination; Withoutremoving the plate the E reading is similarly made and trans-ferred to the chart. To take the A or B reading the plateis shifted slightly until the image of the indicating ball on thesecond exposure coincides with the Right or Left ball ofthe vertical coordinates A or B. The line or lines of theA or B coordinates which cross the shadow of the body arenoted and indicated on the A or B lines of the chart. The American Quarterly of Roentgenology . horizontal coordinate E should he the same in both
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