Letter: Ardran/Crooks penetrameter cassette - necessity for re-calibration.
We have frequently been asked if the penetrameter cassette described by us (1968) requires frequent re-calibration. When this cassette was first designed it was our opinion that calcium tungstate intensifying screens did not alter in speed with time or use unless obviously worn, abraided, stained or dirty; we still hold this view.
Checking diagnostic x-ray beam quality.
Abstract A radiographic method is described for comparing the effective kilovoltage and inherent nitration of diagnostic X-ray machines. The apparatus consists of a modified Xray cassette covered by a sheet of lead perforated with two rows of holes; one row is associated with a strip of slow intensifying screen and provides a reference exposure, the other row has a strip of fast intensifying screen and a copper step wedge. The thickness of copper needed to give a film density which matches that of the reference exposure is called the copper reference number and provides an index of the beam quality. The device is calibrated against a constant potential generator for which the kV values are accurately known. For determining the effective kV of machine the beam is attenuated and hardened at source by means of a filter of 1·5 mm of Cu, corresponding approximately to the filtration (of the primary beam) provided by an abdomen plus Bucky grid, plus table top. The method is relatively independent of processing,...
A Photoelectric Instrument Measuring Quality and Quantity of X Rays for Radiographic Purposes
Applications of barrier layer photocells to X-ray technique are described, and a photoelectric instrument is shown which is capable of filling gaps in the technique of X-ray measurement. Quality and quantity and the photographically effective dosage may be measured simultaneously with the deflection of “one” light spot, the movement of which is caused by two ballistic galvanometers. The position of the spot on the scale defines the photographically effective dosage, and at the same time the quality and the quantity of the incident X rays independent of the type of generator used, and hence provides a basis for standardisation of exposure technique.