Biokinetic model of radioiodine I-131 in nine thyroid cancer patients subjected to in-vivo gamma camera scanning: A simplified five-compartmental model

Abstract

A five-compartmental biokinetic model of I-131 radioiodine based on in-vivo gamma camera scanning results was developed and successfully applied to nine thyroid cancer patients who were administered 1,110 MBq I-131 in capsules for the residual thyroid gland ablation. The I-131 solution activity among internal organs was analyzed via the revised biokinetic model of iodine recommended by the ICRP-30 and-56 reports. Accordingly, a five-compartmental (stomach, body fluid, thyroid, whole body, and excretion) model was established to simulate the metabolic mechanism of I-131 in thyroid cancer patients, whereas the respective four simultaneous differential equations were solved via a self-developed program run in MATLAB. This made it possible to provide a close correlation between MATLAB simulation results and empirical data. The latter data were collected through in-vivo gamma camera scans of nine patients obtained after 1, 4, 24, 48, 72, and 168 hours after radioactive I-131 administration. The average biological half-life values for the stomach, body fluid, thyroid, and whole body of thyroid cancer patients under study were 0.54±0.32, 12.6±1.8, 42.8±5.1, and 12.6±1.8 h, respectively. The corresponding branching ratios I 12 , I 23 , I 25 , I 34 , I 42 , and I 45 as denoted in the biokinetic model of iodine were 1.0, 0.21±0.14, 0.79±0.14, 1.0, 0.1, and 0.9, respectively. The average values of the AT dimensionless index used to verify the agreement between empirical and numerical simulation results were 0.056±0.017, 0.017±0.014, 0.044±0.023, and 0.045±0.009 for the stomach, thyroid, body fluid + whole body, and total, respectively. The results obtained were considered quite instrumental in the elucidation of metabolic mechanisms in the human body, particularly in thyroid cancer patients.

Monte Carlo Method Estimates for Internal Dosimetry of Well Differentiated Thyroid Cancer Patients

“…[9], Oktajianto H, Setiawati E, 2016 [2], the obtained total absorbed doses per administrated activity in the present study were greatly compatible using the same thyroid uptake values. Few differences with the comparative studies [2,9] may be noticed as two sources were implanted in different locations in our present study (thyroid and abdomen) based on SPECT/CT imaging of patients [4][5][6][7][8] while one source was set in the thyroid gland only in the comparative literatures. Also, the difference may be due to differences in geometry and design of organs.…”

“…Most of the administrated activity is excreted throw the bladder and the remaining 131 I activity slowly migrates to its target organ in the thyroid gland. After 24h post administration, all the remaining activity is concentrated in the thyroid gland tissues with few traces of 131 Istill present in the abdomen [4][5][6][7][8].…”

Quantitative Prediction of SYNTAX Score for Cardiovascular Artery Disease Patients via the Inverse Problem Algorithm Technique as Artificial Intelligence Assessment in Diagnostics

“…Specifically, the defined agreement (AT) equals [(actual − prediction)/actual] of the SYNTAX score. Therefore, the average AT avg and standard deviation of the 105 ATs are 0.308 and 0.193, respectively, implying high agreement between the actual and predicted values of the SYNTAX score [ 12 , 13 , 14 ]. Figure 6 illustrates the distribution of 105 individual ATs in this study.…”

A practical individualized radiation precaution based on the dose rate at release time after inpatient 131I ablation therapy

“…First, the actual effective half-life of remnant thyroid tissue is shorter than 7.3 days. It has been noted in previous articles that 131 I clears more rapidly from remnant thyroid tissue [ 11 , 12 , 22 – 24 ]. The shorter half-life of RAI can be explained by radiation-induced thyroiditis which can cause the release of radioiodinated Tg and thyroxine [ 25 ].…”