. Radiography and radio-therapeutics . ble, and make the exposure. All exposures should, if possible, be made at a uniform distance of, say, 60 cm. between the anti-cathode and the plate. ^ Technique with the Coolidge Tube, in the American Journal of Roentgenology,May 1916. ESTIMATION OF THE EXPOSURE 135 gives the following table for the three kinds of plates he uses: Thicknessof Part. Paragon Plate. Time (Sec.) u 23 4567891012131416171820222426 Seed Plate. Cramer Plate. Time (Sec.) 2 3 4 5 6 7 8 9 10 11 12 15 16 17 19 21 23 25 27 29 Time (Sec.) 2i
. Radiography and radio-therapeutics . ble, and make the exposure. All exposures should, if possible, be made at a uniform distance of, say, 60 cm. between the anti-cathode and the plate. ^ Technique with the Coolidge Tube, in the American Journal of Roentgenology,May 1916. ESTIMATION OF THE EXPOSURE 135 gives the following table for the three kinds of plates he uses: Thicknessof Part. Paragon Plate. Time (Sec.) u 23 4567891012131416171820222426 Seed Plate. Cramer Plate. Time (Sec.) 2 3 4 5 6 7 8 9 10 11 12 15 16 17 19 21 23 25 27 29 Time (Sec.) 2i 4 5 6 8 9 10 11 12 14 16 17 19 21 22 23 25 27 29 31 Screen. 2 2\ 3 H 4 5 5i 7 910111213 Gregory Cole gives the following data for exposure mth a Coolidge tube Part of Body. Hand, soft parts .Hand, bone .Foot, soft tissues, lateralFoot, bone, lateralKnee, soft parts .Knee, bone and soft tissueKnee, bone only .Shoulder, soft tissues Shoulder, bone Hip, bone Kidney . Spine, bone, detail Head, lateral . Head, Lungs Stomach (Screen). Exposure TablesComparison of Different Radiometers Benoist .Benoist-WalterWalter .WehneltBauer . 2 1 2-3 1-81 2i2 3-43-3 2 3 4 5 6 7 3 4 4i 5 5^ 4-5 5-6 6 6-7 7 4-9 6-5 7-2 8 9 3 4 5 6 7 6 7-810-5 9 10 13 15 9 10 TI«> IntensUy of the X-rays varies wUh the Distame between the Mi-cathode and the ^e intensity of the X-rays is m mverse proportion 136 RADIOGEAPHY to the square of the distance. If we have to expose for a certain object3 seconds, with a distance of 10 inches between the anti-cathode and theplate, the time of exposure required with 10, 12, 16, 20, 25, 30, 40, 50,60, 80 inches will be 3, 4-32, 7-68, 12, 18-75, 27, 48, 75, 108, 192 seconds ;or, expressed in other figures : Distance 10 14-1 17-3 20 22-4 24-5 26-4 28-3 30 10 20 30 40 50 60 70 80 90 seconds. The distances usually chosen are : For teeth, toes, fingers, or hands . 10 to 12 inches. Arms, neck, leg, or foot . . 12 „ 15 „ Nose, head, shoulder, knee
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