The MTFs of three different gamma camera systems have been measured using two methods. In one method a step function was used as the object and the calculations were made by means of a pocket calculator. This method has been compared with a conventional line source method, where a computer is needed in performing the calculations. The methods give the same results with a fairly good accuracy. Both of the methods are well suited to a regular control of the condition and functioning of a gamma camera, provided that the camera is connected to a data-processing system so that the profile curves measured can be converted into the digital form.
Owing to contamination by long-lived radio-isotopes, the residual activity of an old 99Mo-99mTc generator may be large enough to prevent its disposal. The long-lived impurities of one generator were determined by energy spectrum and half-life measurements. In this generator 46Sc, 51Cr, 60 Co, 92mNb, 95Nb and 124Sb nuclides were found. Only the half-life of 60Co exceeds 3 months, thus a moderately long storage of the generator reduces the activity, and its disposal is then safe.
The impurities present after use in 99Mo- 99mTc-generators produced by four different manufacturers were investigated by means of the energy spectrum and half-life measurements. The generators produced with fission contained only a few impurities, and the half-lives of their nuclides were relatively short. The only generator manufactured using neutron bombardment contained several nuclides whose half-lives were in a range of a few months, but also a 60Co nuclide whose long half-life may give rise to difficulties in destroying the generator.
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