Testing the count rate performance of the scintillation camera by exponential attenuation: Decaying source; Multiple filters

An algorithm and two fortran programs have been developed to evaluate the count rate performance of scintillation cameras from count rates reduced exponentially, either by a decaying source or by filtration. The first method is used with short‐lived radionuclides such as 191 m Ir or 191 m Au. The second implements a National Electrical Manufacturers’ Association (NEMA) protocol in which the count rate from a source of 191 m Tc is attenuated by a varying number of copper filters stacked over it. The count rate at each data point is corrected for deadtime loss after assigning an arbitrary deadtime (τ). A second‐order polynomial equation is fitted to the logarithms of net count rate values: ln( R )= A + BT + CT 2 where R is the net corrected count rate (cps), and T is the elapsed time (or the filter thickness in the NEMA method). Depending on C , τ is incremented or decremented iteratively, and the count rate corrections and curve fittings are repeated until C approaches zero, indicating a correct value of the deadtime (τ). The program then plots the measured count rate versus the corrected count rate values.