[Radiological meneral equivalent determinations in bone. The problems of build-up factor (author's transl)]

The apparatus for measuring mineral equivalents described by Gebhardt, Heinen and Zwicker in 1973 was subjected to theoretical and experimental investigations; as a result, changes were introduced which significantly improved the basis for exact absorption measurments on phalanges. 1.The CuK alpha radiation (8.5 kV) produced the Hohannson monochromator was replaced by higher energy AgK alpha radiation (22.2 kV). The total spectrum was improved by using a palladium filter and an impulse height discriminator. 2. A slit collimator was used giving a beam area of 3 mm X 0.5 mm with improved paralleism ofthe beam and an incident angle alpha of 0.1 degrees compared with a previous angle of alpha approximately 1 degrees. 3. Correction of attenuation N = No. e-ux by a correction factor B to allow for "build-up factor" in the required area of measurement is no longer necessary. Measurements at four of hydroxyle apatite (Reiss) provide the required mineral absorption. 4.AgK alpha radiation permits measurement of thicker bones such as radius and calcaneus and provides adequate impulses for short periods of measurement which is useful in practice.