Standard and Iterative Two Stage Approaches for Estimation of Area Under the Curve in Thyroid Disease Dosimetry
Hany Putri Yuliati (a), Bisma Barron Patrianesha (b), Deni Hardiansyah (a*)

a) Medical Physics and Biophysics, Physics Department, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia
*denihardiansyah[at]ui.ac.id
b) Research Center for Safety, Metrology, and Nuclear Quality Technology, National Research and Innovation Agency (BRIN), Tangerang Selatan

Abstract

Background:
The optimal dose estimation of 131I for thyroid disease depends on the accuracy of the area under the curve (AUC) of time-activity curve. The individual fitting (IF) method is commonly used as the standard for AUC estimation. However, fitting with inclusion of population-information such as the Standard Two Stage (STS) and Iterative Two Stage (ITS) methods might provide alternatives. This study aims to evaluate and compare the calculated AUC from STS and ITS methods.
Methods:
Biokinetic data of 131I from 50 patients were simulated using a sum-of-exponential function as being measured at 2, 6, 24, 48, 96, and 120 h after administration. Individual AUC (AUCind) was obtained from IF of each patient. The same dataset was then analyzed using both the STS and ITS methods. The root mean square error (RMSE) of the relative deviation was calculated by comparing AUC values obtained from STS (AUCSTS) and ITS (AUCITS) against the AUCind.
Results:
The comparison between the AUCSTS and AUCind resulted in an RMSE of 0%, while the comparison between the AUCITS and AUCind resulted in an RMSE of 8%.
Conclusion:
The individual fitting approach demonstrated only marginal differences compared to the STS method, while the ITS approach exhibited a slightly higher deviation from the individual fitting than that of the STS.

Keywords: 131I, Standard Two Stage (STS), Iterative Two Stage (ITS)

Topic: Medical Physics and Biophysics