Occupational radiation exposure during blood sample collection post I-131 therapeutic administration in thyroid cancer patients

The blood sampling required for the verification of dose delivered during radioactive iodine (I-131) therapy is a source of radiation exposure for healthcare staff. This study aims to estimate staff exposures, using Monte Carlo modelling, as well as experimental measurements. The study further aimed to validate the models with staff exposure measurements and examine the impact of protective measures on the procedure. The clinical set-up of blood sampling post I-131 patient administration, within a dedicated I-131 ablation therapy suite, was modelled using EGSnrc Monte Carlo simulations (MCSs). The dose scoring regions representing deep dose (Hp(10)) and skin dose (Hp(0.07)) were estimated and validated with an experimental approach and clinical monitoring of staff members using electronic personal dosimeters. MCSs and experimental values did not show significant differences between the two approaches (p > 0.05), with simulated values having lower uncertainties. It is demonstrated that the model is capable of being tailored to clinical scenarios at any centre. The simulations were corroborated with dosimetry data of blood sampling from 14 patients post administering 3.7 GBq I-131, amounting to a total of 54 measurements from 14 staff members. With the employed protective shielding, none of the staff were exposed to a dose rate approaching the annual dose constraint of 0.3 mSv.yr(-1). The experimental and MCS data show good agreement with the clinical data, demonstrating the advantages of MCS approaches for providing useful information for planning and carrying out risk assessments before implementing a new dosimetry practice.