THE EFFECTS OF INTRA-INDIVIDUAL VARIABILITY SETTING ON THE ACCURACY OF TIME-INTEGRATED ACTIVITY CALCULATIONS USING NONLINEAR MIXED-EFFECTS MODELING

Authors

  • Fira Dwi Ananda Medical Physics and Biophysics, Physics Department, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia.
  • Assyifa Rahman Hakim Medical Physics and Biophysics, Physics Department, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia.
  • Indra Budiansah Medical Physics and Biophysics, Physics Department, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia.
  • Rien Ritawidya Research Center for Radioisotope Technology, Radiopharmaceuticals, and Biodosimetry, Nuclear Power Research Organization, National Research and Innovation Agency, South Tangerang, Indonesia
  • Deni Hardiansyah Medical Physics and Biophysics, Physics Department, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia.

DOI:

https://doi.org/10.21009/03.1401.FA04

Abstract

Estimasi yang akurat terhadap time-integrated activity (TIA) penting untuk perencanaan pengobatan pada peptide receptor radionuclide therapy (PRRT). Dalam konteks pemodelan farmakokinetik, intra-individual variability (IAV) — yang berkaitan dengan ketidakpastian pengukuran — dapat memengaruhi estimasi nilai TIA. Penelitian ini bertujuan untuk meneliti dampak variasi pengaturan IAV terhadap perhitungan TIA. Data biokinetik ginjal (PMID: 33443063) dari 10 pasien tumor neuroendokrin setelah pemberian [¹⁷⁷Lu]Lu-DOTATATE dianalisis menggunakan SPECT/CT. Estimasi TIA dilakukan menggunakan Nonlinear Mixed-Effects Modeling (NLMEM) dengan error model proporsional. Metode 1: TIA referensi (rTIA) dihitung dengan mengestimasi inter-individual variability (IIV) and IAV. Metode 2: Nilai IAV kemudian ditetapkan menjadi setengah (hTIA) dan dua kali lipat (tTIA) dari nilai yang diperoleh pada Metode 1. Pengaruh perubahan IAV terhadap akurasi TIA dievaluasi dengan membandingkan hTIA dan tTIA terhadap rTIA menggunakan relative deviation (RD), root-mean-square error (RMSE), dan mean absolute percentage error (MAPE). Hasil menunjukkan bahwa penetapan IAV menjadi setengah dari nilai referensi menghasilkan RMSE sebesar 5% dan MAPE sebesar 3%. Sementara itu, perubahan dua kali nilai IAV menghasilkan RMSE sebesar 7% dan MAPE sebesar 6%. Secara keseluruhan, perubahan pengaturan IAV memberikan dampak yang sangat kecil, karena perhitungan TIA tetap stabil dan tidak sensitif terhadap variasi IAV, baik ketika nilainya dikurangi setengah maupun digandakan dalam data biokinetik populasi ini.

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Published

2025-12-07

How to Cite

Fira Dwi Ananda, Assyifa Rahman Hakim, Indra Budiansah, Rien Ritawidya, & Deni Hardiansyah. (2025). THE EFFECTS OF INTRA-INDIVIDUAL VARIABILITY SETTING ON THE ACCURACY OF TIME-INTEGRATED ACTIVITY CALCULATIONS USING NONLINEAR MIXED-EFFECTS MODELING. Joint Prosiding IPS Dan Seminar Nasional Fisika, 14(1), FA 24–31. https://doi.org/10.21009/03.1401.FA04

Issue

Vol. 14 No. 1 (2026): Joint Prosiding IPS dan Seminar Nasional Fisika

Section

Fisika dan Aplikasinya