The influence of geometrical factors in 131-I-hippuran renography

Using a particular collimated NaI scintillation detector and a kidney phantom containing 131-I, the dependence of the resulting count rates on collimator-kidney geometry has been determined. These results have been used to calculate the geometrical contribution to the error in the measurement of relative effective renal plasma flow (REP) by 131-I-Hippuran renography. When radiographic and ultrasonic methods of localizing the kidneys are employed, this error has been found to follow a normal distribution with a SD of 2.6% in the case of equally divided function. Combination of this error with that from natural movement and statistical fluctuations, as observed using a dose of 10 muCi 131-I-Hippuran, has led to the estimation of a corresponding potential error 11%. Values of the potential error, which is defined as the 99% probability range, have been calculated covering the range of RFP.