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When a physicist calibrates an x-ray machine for the dermatologist, he determines the output at a voltage usually of 80 to 100 kv., skin-target distance of from 20 to 60 cm., amperage of 3 to 5 ma., and filtration varying from nothing to 3 mm. Al. The output is then given in roentgens per minute. For 100 kv., 20-cm. distance, 3 ma., and no filtration, the output may vary from 40 to 75 r or more per minute depending on the machine. If the dermatologist then desires to apply 70 r to a lesion, he must calculate the corresponding time interval which will then vary in different machines from 55 to 155 seconds, more or less.
In order to simplify the procedure of determining the time interval required for a definite dosage, I have the physicist determine the factors required to produce an output of 1 r per second. If,
MONASH S. SIMPLIFIED METHOD OF CALCULATING DOSAGE IN SUPERFICIAL X-RAY THERAPY. AMA Arch Derm Syphilol. 1951;64(6):792. doi:10.1001/archderm.1951.01570120127018
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