THRESHOLD ERYTHEMA DOSE OF LOW VOLTAGE ROENTGEN RAYS

[摘要] 111 individuals were tested with low voltage roentgen rays to determine erythema dose. The Philips Contact roentgen apparatus and the Machlett AEG-50 tube with a General Electric generator were used. The dose required to produce erythema in at least 80% of those tested with the Philips apparatus was 150 r (un-filtered, target skin dose (TSD) 3. 8 cm or 10 cm). The Machlett tube at 50 kv and TSD of 10 cm produced erythema in 80% of the subjects with 150 r or less. At 25 kv, the Machlett tube required 200 r or less to produce an erythema in 80%. The following conclusions are derived from these tests: (1) There is scarcely any latent period between delivery of low voltage roentgen rays to the skin and appearance of erythema. (2) The effect of roentgen rays of longer wavelengths usually appears within 1 to 6 hrs. (3) It is impossible to divide the threshold erythema of the skin into primary and secondary erythema as may be done when higher voltages are used. The erythema that appears within the first 6 hrs. persists and goes imperceptibly into pigmentation, usually within 7 days. This pigmentation may persist as long as 4 months.