The purpose of the test procedure based on the PET sensitivity phantom is to measure the sensitivity or ability of positron emission tomographs to detect positrons. The phantom used for this purpose is a set of five metal tubes of 700 mm length and 2.5 mm wall thickness each. The outside diameters are 9.5 mm, 12.7 mm, 15.9 mm, 19.1 mm and 22.2 mm. A plastic tube homogeneously filled with 18F liquid is inserted for the measurement. This line source has an outside diameter of approx. 5 mm and a length of approx. 800 mm. Successive measurements are made by accumulating the sleeve wall thickness with the uniform line source surrounded by known absorbers.