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Rien Ritawidya
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Electrical & Electronics Engineering Energy Physics Other

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THE EFFECTS OF INTRA-INDIVIDUAL VARIABILITY SETTING ON THE ACCURACY OF TIME-INTEGRATED ACTIVITY CALCULATIONS USING NONLINEAR MIXED-EFFECTS MODELING Fira Dwi Ananda; Assyifa Rahman Hakim; Indra Budiansah; Rien Ritawidya; Deni Hardiansyah
Joint Prosiding IPS dan Seminar Nasional Fisika Vol. 14 No. 1 (2026): Joint Prosiding IPS dan Seminar Nasional Fisika
Publisher : Program Studi Pendidikan Fisika dan Program Studi Fisika Universitas Negeri Jakarta, LPPM Universitas Negeri Jakarta, HFI Jakarta, HFI

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 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.
EFFECT OF PATIENT’S GENDER ON THE CALCULATION OF TIME-INTEGRATED ACTIVITY COEFFICIENT IN RADIONUCLIDE THERAPY: STUDY WITH NON-LINEAR MIXED-EFFECTS MODEL Assyifa Rahman Hakim; Fira Dwi Ananda; Indra Budiansah; Rien Ritawidya; Deni Hardiansyah
Joint Prosiding IPS dan Seminar Nasional Fisika Vol. 14 No. 1 (2026): Joint Prosiding IPS dan Seminar Nasional Fisika
Publisher : Program Studi Pendidikan Fisika dan Program Studi Fisika Universitas Negeri Jakarta, LPPM Universitas Negeri Jakarta, HFI Jakarta, HFI

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21009/03.1401.FA03

Abstract

Purpose: This study investigates the influence of patient gender on the calculation of the Time-Integrated Activity Coefficient (TIAC) in radionuclide therapy. Methods: Kidney biokinetic data (PMID: 33443063) from 10 patients (6 males and 4 females) treated with [¹⁷⁷Lu]Lu-DOTATATE were analysed. A bi-exponential function was used to model both uptake and clearance phases. The reference TIAC (rTIAC) was obtained by fitting the bi-exponential parameters to the complete dataset using a Non-Linear Mixed-Effects Model (NLMEM). To assess the impact of gender, separate NLMEM fits were performed for male and female subgroups to generate estimated TIACs (eTIACs). rTIAC and eTIAC values were compared using the Relative Deviation (RD) and the Root-Mean-Square Error (RMSE). Gender was considered influential if RD or RMSE exceeded 27%. Results: For male patients, the RD was −4.1% ± 7.2% and the RMSE was 8.3%. For female patients, the RD was 5.2% ± 7.8% and the RMSE was 9.4%. Conclusions: Based on the analysed [¹⁷⁷Lu]Lu-DOTATATE biokinetic data, gender does not appear to be a major determinant in TIAC calculation. The deviations between rTIAC and eTIAC remain within an acceptable range for both male and female patients.
Co-Authors Assyifa Rahman Hakim Deni Hardiansyah Fira Dwi Ananda Indra Budiansah