Estimation and Measurement of Data Accuracy

Two intrinsic random events are associated with tracer position measurement in the CAPTF. One is the random emission of gamma photons 

Consider a gamma source at a distance r from the detector. By assuming that the scintillation crystal is sufficiently small, an approximate relationship between the source activity S and the rate of scintillation n at the crystal is 

the first factor at the right-hand-side, which represents the fraction of gamma photons intercepted by the scintillating crystal, is equal to the solid angle extended by the detector crystal to the source, with dc denoting the crystal diameter. The efficiency of the crystal t depends on both the material and the size of the crystal. 

In the radioactive-particle tracking methodology, the distance is inferred by measuring the scintillation rate n. Thus, the approximate relationship between the accuracy of the distance measurement and the scintillation rate from Eq. 9.20 is 

Because of the finite length of the output pulses from the scintillation detectors (on the order of 1 ps), the maximum practical count rate nmax is 10s counts/s for the gamma photon energies in the vicinity of 1 MeV. 

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