Dosimetric analysis of 123I, 125I and 131I in thyroid follicle models

EJNMMI Research

Table 2 S values for radioiodine in the human multiple thyroid models

Source compartment	r ₁	r ₂	Svalue	Relative contribution^a	Relative contribution^b	Relative contribution^c
	(μm)	(μm)	(Gy/Bq·s)	(%)	(%)	(%)
123I
Lumen 1	0	75	2.54E-07	9.6	15.0	-
Cell layer 1	75	85	1.60E-06	27.6	-	77.3
Cell layer 2a	85	95	2.77E-07	6.1	-	16.9
Lumen layer 2	95	245	4.23E-08	52.7	82.0	-
Cell layer 2b + 3a	245	265	5.86E-09	2.1	-	5.8
Lumen layer 3	265	415	3.97E-10	1.9	2.9	-
Cell layer 3b	415	425	7.50E-12	0.0	-	0.0
				100	100	100
¹²⁵I
Lumen 1	0	75	1.37E-07	7.7	93.6	-
Cells layer 1	75	85	3.21E-06	82.5	-	89.9
Cells layer 2a	85	95	2.85E-07	9.3	-	10.1
Lumen layer 2	95	245	2.86E-10	0.5	6.4	-
Cell layer 2b	245	255	0.00E + 00	0.0	-	0.0
				100	100	100
¹³¹I
Lumen 1	0	75	1.03E-06	5.7	6.9	-
Cells layer 1	75	85	1.98E-06	5.0	-	30.0
Cells layer 2a	85	95	1.02E-06	3.3	-	19.6
Lumen layer 2	95	245	1.44E-07	26.4	31.6	-
Cells layer 2b + 3a	245	265	5.14E-08	2.6	-	15.8
Lumen layer 3	265	415	2.36E-08	16.4	19.7	-
Cells layer 3b + 4a	415	435	1.35E-08	1.9	-	11.6
Lumen layer 4	435	585	7.68E-09	11.9	14.3	-
Cells layer 4b + 5a	585	605	5.39E-09	1.5	-	9.0
Lumen layer 5	605	755	3.28E-09	9.0	10.8	-
Cells layer 5b + 6a	755	775	2.08E-09	1.0	-	5.8
Lumen layer 6	775	925	1.31E-09	5.6	6.8	-
Cells layer 6b + 7a	925	945	9.70E-10	0.7	-	4.0
Lumen layer 7	945	1,095	6.81E-10	4.2	5.1	-
Cells layer 7b + 8a	1,095	1,115	3.67E-10	0.4	-	2.1
Lumen layer 8	1,115	1,265	3.30E-10	2.8	3.3	-
Cells layer 8b + 9a	1,265	1,285	2.21E-10	0.3	-	1.7
Lumen layer 9	1,285	1,435	1.12E-10	1.2	1.5	-
Cell layer 9b	1,435	1,445	6.30E-11	0.1	-	0.3
				100	100	100

The S values for the innermost follicle cell nuclei from radioiodine homogeneously distributed in the different source compartments in the human multiple thyroid follicle models (spherical compartments with r₁ = inner radius and r₂ = outer radius). The relative contributions to the mean absorbed dose to the innermost follicle cell nuclei from each compartment are shown for three radionuclide distributions: for ¹²³I with two surrounding layers of follicles contributing, ¹²⁵I with one surrounding layer of follicles contributing, and ¹³¹I with eight surrounding layers of follicles contributing. Follicle layers beyond these contributed with <1%. ^aRadioiodine homogeneously distributed within the follicle lumens and follicle cells (the entire thyroid model). ^bRadioiodine homogeneously distributed within the follicle lumens. ^cRadioiodine homogeneously distributed within the follicle cells.