Accuracy of organ radioactivity quantification comparing the geometrical mean and channel ratio techniques

The accuracy of quantification of radioactivity in organs is determined by scatter and attenuation. The standard Geometrical mean Method is inaccurate since scatter correction is not performed. Accuracy can be improved by expressing the organ activity as a percentage of a reference source of the same size and at the same depth as the organ of interest. The Channel Ratio Method corrects for scatter but is according to Monte Carlo simulations dependent on depth of organ and on energy spectrum shift during rotation of the scintillation camera head. The purpose of this work was to compare the experimental accuracy of organ quantification by using the Geometrical Mean and Channel Ratio Methods. The influence of organ and reference source depths and sizes on accuracy was determined.