Research

Comparison of methods to determine accurate dose calibrator activity measurements

Lidia Strigari¹ , Marcello Benassi^{* 1} , Pierino De Felice^{* 2} , Marco D'Andrea^{* 1} , Aldo Fazio^{* 2} , Sandro Nocentini^{* 1} , Annelisa d'Angelo^{* 1} and Alessia Ceccatelli^1,2

¹Laboratory of Medical Physics and Expert Systems, National Cancer Institute Regina Elena, Rome, Italy

²ENEA – Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, C.R. Casaccia, P.O. Box 2400 – I-00100, Rome, Italy

author email corresponding author email* Contributed equally

Journal of Experimental & Clinical Cancer Research 2008, 27:14doi:10.1186/1756-9966-27-14

Published:	1 July 2008

Abstract

Background

In nuclear medicine, liquid radiopharmaceuticals for diagnostic or therapeutic purposes are administered to patients by using various types of syringes with different volumes. The activity of each "dose" must be carefully measured and documented prior to administration using an activity calibrator.

Methods

Calibrator response is a function of the measurement geometry and, in particular, it depends on the syringe type and filling volume. To minimize the uncertainty associated with the measured activity of the syringe, it is necessary to calculate a calibration curve depending on filling volume for each syringe type. This curve can be obtained by fitting experimentally determined volume correction factors.

Results

A theoretical evaluation of volume correction factors for syringes is reported for three different experimental methods. The aim is to determine the most accurate experimental method among those considered, by examining the expression of uncertainty for the correction factor. This theoretical analysis was then tested experimentally.

Conclusion

The agreement between the experimental data obtained in the constant activity method and gravimetric method at constant specific activity and the small associated uncertainties show the accuracy of these two procedures; while the volumetric method at constant specific activity could lead to a wrong evaluation of the correction factors.