Perbandingan Metode Clipbox dan Mask Pada Teknik Volumetric Modulated Arc Therapy Untuk Verifikasi Pada Kasus Kanker Nasofaring

Abstract

Background : In 3D radiotherapy using the VMAT technique, verification is crucial to ensure precise patient positioning and target volume alignment, especially in nasopharyngeal cancer cases surrounded by many organs at risk. This study aims to compare the accuracy of two image matching methods clipbox and mask used in Cone Beam Computed Tomography (CBCT) verification during irradiation.

Method : This quantitative, quasi experimental study analyzed irradiation verification data from 31 nasopharyngeal cancer patients during their fourth treatment. The verification process used CBCT with both clipbox and mask methods, measuring shift values on the X, Y, and Z axes. Data were analyzed using the Shapiro Wilk test for normality, followed by the Wilcoxon and Mean Rank tests for comparison.

Results : The mask method was more sensitive in detecting positional shifts on the Y and Z axes. However, the clipbox method showed better overall precision, with a higher Mean Rank score (44.96 vs. 42.93) and smaller standard deviations, indicating more consistent results. Both methods detected minimal average shifts of approximately 0.1 cm, reflecting high verification accuracy.

Conclusion : While the mask method is more accurate in detecting shifts on certain axes, the clipbox method provides greater overall precision and consistency across all axes. Therefore, the clipbox method is considered more suitable for irradiation verification in VMAT based nasopharyngeal cancer treatment.