Victoreen X-ray Filters (1936) |
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| This is a set of five x-ray filters
manufactured by the Victoreen Instrument Company. Three of the filters are
made of 5 3/8" x 6 1/4" sheets of copper; two of these are
0.5 mm thick and the other is 0.25 mm thick. The other two filters are
made of aluminum; one is 6 1/4" x 6 1/4" and 1 mm
thick, while the other is 4 1/4" x 6" and 1 mm thick.
These types of filters were positioned between the x-ray tube and the patient. More specifically, they were placed between the x-ray tube and the unit's diaphragm. Their purpose was to alter the effective energy (quality) of the x-ray beam. For example, if the deeper portions of the body were to be exposed, low energy x-rays would be undesirable since they would simply result in a dose to the outer tissues of the patient's body without exposing the deeper tissues being treated. The use of a filter in an x-ray beam increases the effective energy of the x-rays, and the higher the atomic number of the filter, the higher the effective x-ray energy. Sometimes different filters were used in combination. When that was done, the filter with the higher atomic number (e.g., Cu) was placed closest to the x-ray tube while the lower atomic numbered material was placed on the patient's side. Of course, the use of filtration also reduced the intensity of the x-rays, but this could be compensated for by increasing the tube current. The calibration curves that came with the filters are dated December 22, 1936. |
