Dosimetric Evaluation of Extravasated Activity in Nuclear Medicine Scans

During the course of a typical nuclear medicine diagnostic test, a patient may receive a radiopharmaceutical intravenous injection with the typical extravasation risk. For radiopharmaceuticals, the absorbed dose at the injection site can be high, and it is critical in the case of children. To estimate the extravasation risk, patients are selected randomly for the typical tests carried out in our service. These patients were injected with 99mTc-DMSA, 99mTc-MAG3 or 99mTc-MDP. The frequency and magnitude of extravasations were calculated in all cases. To calculate the extravasation percentage of the administered dose we used two methods: control of the administration site through a manual external detector and regions of interest in acquired images. The results for DMSA injected patients showed six complete extravasations, all of them children. We also found that in 47% of these patients the remaining activity at the injection site was up to 80%. For the MAG3 and MDP injected patients there was none with complete extravasation. However, in 33% of these patients the remaining activity was up to 2%. The local mean absorbed doses in these diagnostically investigated patients were estimated with the MIRD formalism to be up to 10mGy. (Author)