A robust conversion method of radioactivities between plastic and NaI scintillation well counters for long-term quality control and quality assurance

PURPOSE: The purpose of this study is to specify a simple procedure for a robust data conversion of radioactivity value between plastic scintillator (PL) and NaI scintillator (NaI) devices. MATERIALS AND METHODS: The radioactivity estimate of 100 blood samples was measured by the two devices. The two radioactivities were plotted on the same graph. The least-squares method was applied to obtain the conversion function. The differences between the actual radioradioy (N) from the NaI device and the estimated radioactivity for NaI (N’) from the PL device activity (P) were statistically analyzed. RESULTS: N’ was determined from P as N’ = 4.45 P + 6.28 with high correlation (r = 0.997). The Bland-Altman analysis between N’ and N showed no fixed bias and no proportional bias. CONCLUSIONS: A hundred blood samples using a fixed type of sample tubes and a fixed radionuclide may be required to set up the robust conversion function.