Figure 3 Mean absorbed dose for different distributions of radioiodine in the human multiple follicle model.
A multiple thyroid follicle model was used to calculate the contribution from surrounding layers of follicles to the follicle cell nuclei in a centrally placed follicle, based on the previously published multiple follicle model [[19]].
For radioiodine homogeneously distributed in the follicle cells and lumens, calculations for our human multiple follicle model gave up to 18% higher mean absorbed dose.
The mean absorbed dose calculated for our human thyroid multiple follicle model, assuming homogenous distribution of for 123I, 125I, or 131I within the follicle lumens and follicle cells, was 9%, 18% and 4% higher, respectively, compared with the mean absorbed dose according to Medical Internal Radiation Dose (MIRD) formalism and nuclear decay data.
To compare if microdosimetry would give other absorbed doses than conventional macrodosimetry, we calculated the absorbed dose to the follicle cell nuclei from the amount of 211At homogeneously distributed in the lumens (multiple follicle model) that gives a mean absorbed dose of 1 Gy.
The multiple follicle thyroid model used in this work is a simplification, with a single spherical layer of follicle cells surrounding the central follicle and the neighbouring follicle lumen simulated as a spherical shell around the outer cell layer.
Figure 2 Schematic illustration of the multiple thyroid follicle model.
The mean absorbed dose to the central follicle cell nuclei in the human multiple thyroid follicle model for different relations in radioiodine concentration (homogeneous in each compartment) between follicle lumens and/or follicle cells for (a 123I, (b 125I and (c 131I.
The calculated S values and the relative contributions to the mean absorbed dose to the inner follicle cell nuclei are presented in Table 2 with 123I, 125I and 131I homogeneously distributed within various source compartments (the follicle lumens and cells) in the human multiple thyroid follicle model (S values for the mouse and rat models, see Additional file 1).
All the follicle models were assumed to consist of liquid water with unit density (1.0 g/cm3).
