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"Latar Belakang: Delineasi merupakan proses yang penting dalam radioterapi, namun dilaporkan adanya variabilitas dan inkonsistensi. Jenis modalitas dan kualitas pencitraan serta observer merupakan faktor yang mempengaruhi variabilitas delineasi. Variabilitas interobserver dapat digunakan untuk mengetahui adanya variasi delineasi. Saat ini delineasi kanker serviks menggunakan CT Scan. MRI lebih baik dalam memvisualisasikan jaringan lunak pada pelvis, namun belum digunakan rutin untuk delineasi kanker serviks.Tujuan: Membandingkan perbedaan variabilitas interobserver dalam mengidentiifkasi GTV pada kanker serviks.Metode: Sembilan pasien kanker serviks stadium lokal lanjut didelineasi oleh lima observer. Observer adalah peserta didik program studi onkologi radiasi tahap mandiri dengan kriteria tertentu. Modalitas pencitraan yang digunakan adalah CT Scan dan MRI. Struktur yang didelineasi adalah GTV, parametrium, uterus dan vagina. Hasil delineasi dibandingkan dengan menggunakan koefisien kesesuaian Dice Similarity Coefficient (DSC). Variabilitas delineasi akan dibandingkan antar kelompok modalitas menggunakan perbandingan dua rerata berpasangan menggunakan uji t berpasangan dan uji wilcoxon.Hasil: DSC delineasi GTV pada kelompok CT Scan adalah 0,74 (0,71-0,76 IK 95%). Sedangkan pada kelompok MRI adalah 0,79 (0,77-0,81 IK 95%). Rerata DSC didapatkan lebih tinggi pada kelompok MRI dibandingkan dengan kelompok CT Scan dan signifikan secara statisitik.Kesimpulan: Variabilitas interobserver delineasi GTV didapatkan baik menggunakan MRI maupun CT Scan dengan tingkat kesesuaian deliniasi baik (substantial agreement). Variabilitas interobserver delineasi GTV lebih kecil pada MRI dibandingkan CT Scan secara signifikan.

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Background: Delineation is an important process in radiotherapy, but variability and inconsistency have been reported in almost all tumor sites. The type of modality and quality of imaging as well as observers are factors that affect delineation variability. Interobserver variability can determine the variation of delineation. Currently delineation of cervical cancer using CT Scan. MRI is better at visualizing the soft tissues of the pelvis, but has not been used routinely for cervical cancer delineation.

Aim: Comparing interobserver differences in identifying GTV in cervical cancer.

Methods: Nine locally advanced cervical cancer patients were delineated by five observers. Observers were senior resident of the radiation oncology study program with certain criteria. The modalities used were CT Scan and MRI. The structures delineated were the GTV, parametrium, uterus and vagina. The results of the delineation were compared using the Dice Similarity Coefficient (DSC). Delineation variability will be compared between modality groups using a comparison of two paired means using paired tests and Wilcoxon's test.

Result: Mean DSC of GTV delineation in the CT scan group was 0.74 (0.71-0.76 95% CI). Meanwhile, the mean DSC in the MRI group was 0.79 (0.77-0.81 95% CI). The mean DSC was found to be higher in the MRI group. That the interobserver variability of GTV delineation using MRI is smaller than CT scan and statistically significant.

Conclusion: Interobserver variability of GTV delineation was obtained using either MRI or CT Scan with substantial agreement. Interobserver variability of delineation was significantly smaller on MRI than CT.

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"Tujuan: Mengetahui hubungan nilai DSC (Dice Similarity Coefficient) GTVMRI dan GTVCT dengan jarak waktu MRI sebelum radiasi dan CT Simulator dalam radiasi eksterna kanker serviks. Metode: Dilakukan studi potong lintang pada 25 pasien kanker serviks yang belum mendapatkan terapi definitif sebelumnya, dan sudah dilakukan MRI pelvis diagnostik dan CT Simulator pelvis pada periode Januari 2018 – Februari 2021. Dilakukan registrasi/fusi antara MRI dan CT, dilakukan delineasi GTV primer pada T2WI MRI dan CT Simulator. Dihitung nilai DSC dan dilakukan analisis korelasi antara nilai DSC dan jarak waktu. Batasan waktu dihitung menggunakan kurva ROC (Receiving Operator Characteristic). Hasil: Median jarak waktu MRI dan CT Simulator 24 (1-71) hari. Volume GTVMRI 104.35±66.23, GTVCT 167.79±97.15. Nilai DSC sebesar 0.53±0.16. Korelasi antara DSC dan jarak waktu r = -0.421, p = 0.036. Kurva ROC dengan sensitivitas 85.7%, spesifitas 54.5%, dengan indeks Youden yang paling optimal dan Area Under Curve (AUC) 0.682, 95% CI 0.461-0.902 didapatkan pada 10 hari. Kesimpulan: Semakin lama jarak waktu antara pemeriksaan MRI dan CT akan menurunkan nilai DSC. Diperlukan pertimbangan lebih jika akan dilakukan fusi antara MRI dan CT pada delineasi GTV primer kanker serviks dengan jarak waktu antara pemeriksaan lebih dari 10 hari.

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Objective: The aim of this study is to assess the correlation between DSC (Dice Similarity Coefficient) values of GTVMRI and GTVCT ​​with the MRI time interval before radiation and CT Simulator.

Method: A cross-sectional study was conducted on 25 cervical cancer patients who had not previously received definitive therapy, and already had a diagnostic pelvic MRI and pelvic CT simulator in periode January 2018 – February 2021. Rigid Body Registration/fusion between MRI and CT was carried out, primary GTV delineate on T2WI MRI and CT Simulator. The DSC value was calculated and a correlation analysis was performed between the DSC value and the interval time. The time limit was calculated using the ROC (Receiving Operator Characteristic) curve.

Result: Median time interval between MRI and CT Simulator was 24 (1-71) days. GTVMRI volume 104.35±66.23, GTVCT 167.79±97.15. Mean DSC value was 0.53±0.16. Correlation between DSC and time interval r = -0.421, p = 0.036. ROC curve with sensitivity 85.7%, specificity 54.5%, with the most optimal Youden index and Area Under Curve (AUC) 0.682, 95% CI 0.461-0.902 obtained at 10 days.

Conclusion: The longer the time interval between the MRI and CT planning, the lower the DSC value. Need to be more caution in doing the fusion if the time interval between MRI and CT is more than 10 days."