Dr. Hamson's Roentgen Radiometer (ca. 1910 - 1920) |
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| At the time that it was produced (ca. 1910-1920) Dr. Hamson's Roentgen Radiometer was marketed as an improvement over the other colorometric methods for determining the dose from x-rays. Whereas the Sabouraud dosimeter had only two color gradations (Tint A and Tint B) and the dosimeter of Bordier had four or five, Dr. Hamson's Radiometer employed 25 "very carefully graded tints." | |
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| The above photograph shows six semi-circular pastilles (ca. 3/8" across) coated with barium platinocyanide on top of the calibration wheel (3 1/4" x 3 1/2"). After the exposure to radiation, the pastille would be placed in the window just above the exposed portion of the top of the wheel. The wheel was then turned until the numbered shade on the wheel matched the color of the pastille. A shade equivalent to number 16 corresponded to Sabouraud's tint B | |
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A shade of 4 on the Hamson scale corresponded to a "full erythema dose," the standard exposure used by dermatologists. One of the advantages of the Hamson radiometer was that an exposed pastille could be reused immediately. The physician simply subtracted the number for the first exposure from the number obtained from the second exposure. As such, two standard treatments in a row would result in a final shade of 8 on the Hamson scale.
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