Measurement of the effect of scintillation camera dead time on the quantification of 131I

Overview

Introduction: With the growing importance of quantitative evaluation of nuclear medicine images, it is necessary to account for the influence of the dead time of the detector in the case of measurements at high count rates, especially for ¹³¹I dosimetry.

Methods: Two dead time models (parylazble and paralyzable-nonparalyzable) were verified and four different methods (method of multiple sources, method of two sources at various distances, shielding method and method of radiactiove decay of short-living radionuclide) for determining the effect of dead time for ¹³¹I were compared in this work. Their accuracy and difficulty were assessed in relation to the reference method of radioactive decay.

Results: The paralyzable-nonparalyzable dead time model better describes the measured data compared to the paralyzable model. Among the methods examined, only the multi-source method with or without the collimator shows results comparable to the reference radioactive decay method.

Conclusions: The multi-source method without the use of collimators with low activities shows a maximum deviation from the reference method of up to 10%.

Keywords:

quantification – dead time measurement – high count rate – dosimetry 131I