Red bone marrow dose estimation using several internal dosimetry models for prospective dosimetry-oriented radioiodine therapy.

The aim of the present study was to review the available models developed for calculating red bone marrow dose in radioiodine therapy using clinical data. The study includes 18 patients (12 females and six males) with metastatic differentiated thyroid cancer. Radioiodine tracer of 73 ± 16 MBq 131I was orally administered, followed by blood sampling (2 ml) and whole-body scans (WBSs) done at several time points (2, 6, 24, 48, 72, and ≥ 96 h). Red bone marrow dose was estimated using the OLINDA/EXM 1.0, IDAC-Dose 2.1, and EANM models, the models developed by Shen and co-workers, Keizer and co-workers and Siegel and co-workers, and Traino and co-workers, as well as the single measurement model (SMM). The results were then compared to the standard reference model Revised Sgouros Model (RSM) reported by Wessels and co-workers. The mean dose deviations of the Traino, Siegel, Shen, Keizer, OLINDA/EXM, EANM, SMM, and IDAC-Dose 2.1 models from the RSM were - 17%, - 24%, 6%, - 29%, - 15%, 40%, 48%, and - 8%, respectively. The statistical analysis demonstrated no significant difference between the results obtained with the RSM and with those obtained with the Shen, Traino, OLINDA/EXM, and IDAC-Dose 2.1 models (t test; pvalue > 0.05). However, a significant difference was found between RSM doses and those obtained with the EANM, SMM, and Keizer models (t test; pvalue < 0.05). The correlation between red marrow dose from the SMM and EANM models was modest (R2 = 0.65), while the crossfire dose calculated with the OLINDA/EXM and IDAC-Dose 2.1 models were in good agreement with each other and with the reference model. The findings obtained indicate that most of the dosimetry models can be used for a reliable dosimetry, and the calculated total body doses can be considered as a reliable non-invasive option for a conservative activity planning. In addition, the excellent performance of the IDAC-Dose 2.1 model will be of particular importance for a practical and accurate dosimetry, with the advantages of allowing for the use of realistic advanced phantoms and updated dose fractions, and of providing information about the blood dose contribution to the red bone marrow.