Detection and quantification of 223Ra uptake in bone metastases of patients with castration-resistant prostate carcinoma, with the aim of determining the absorbed dose in the metastases

Abstract

PurposesTo obtain the necessary acquisition and calibration parameters in order to evaluate the possibility of detecting and quantifying 223Ra uptake in bone metastases of patients treated for castration resistant prostate carcinoma. Furthermore, in the cases in which the activity can be quantified, to determine the absorbed dose. Material and methodsAcquisitions from a Petri dish filled with 223Ra were performed in the gamma camera. Monte Carlo simulations were also performed to study the partial volume effect. Formulae to obtain the detection and quantification limits of 223Ra uptake were applied to planar images of two patients 7 days post-administration of 55kBq/kg of 223Ra. In order to locate the lesions in advance, whole-body scans and SPECT/CT images were acquired after injecting 99mTc-HDP. ResultsThe optimal energy window was found to be at 82keV with a medium-energy collimator MEGP. Of the lesions found in the patients, only those that had been detected in both the anterior and posterior projections could be quantified. These lesions were those which had shown a higher 99mTc-HDP uptake. The estimated values of absorbed doses ranged between 0.7Gy and 7.8Gy. ConclusionsOf the lesions that can be detected, it is not possible to quantify the activity uptake in some of them, which means that the absorbed dose cannot be determined either. This does not mean that the absorbed dose in these lesions can be regarded as negligible.