3753 - Quantification of Three-Dimensional Morphometric Parameters of the High-Risk Clinical Target Volume before and after Brachytherapy Applicator Placement Using MRI for Patients with Cervical Cancer
Presenter(s)
D. Ross1, U. G. Gardner Jr1, G. Kim1, K. Sheikh1, M. Antaki1, E. Schmidt2, M. B. Roumeliotis2, J. Lee2, and A. N. Viswanathan2; 1Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, 2Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins Medicine, Baltimore, MD
Purpose/Objective(s): We set out to quantify volumetric morphometric parameters in the three-dimensional (3D) shape of the high-risk clinical target volume (HR-CTV) before and after applicator placement.
Materials/Methods: Patients diagnosed with cervical cancer and treated at a single institution with brachytherapy between January 2019 and December 2024 were included. Patients were treated and imaged under an approved institutional review board protocol. Each patient, on their scheduled brachytherapy treatment day, underwent both pre- and post-brachytherapy applicator insertion MRI. HR-CTV volumes were contoured on T2-weighted sequences. Quantification of 3D shape was performed using 3D-Slicer (v5.6.2) software. Paired two-sided t-tests with alpha set to p<0.05 were performed to assess statistical significance of the HR-CTV shape using variables of volume, roundness, flatness, elongation, and principal moments (defined as force required in given dimension for equilibrium to be obtained) in x (Left-Right), y (Anterior-Posterior), and z (Superior-Inferior) coordinates.
Results: Sixty-one patients were included in this analysis. The median (interquartile range, IQR) HR-CTV volume before and after insertion was 41.3cc (22.9-59.6) and 49.4cc (22.2-76.6), respectively (p=0.21). The elongation component of the volume was significantly increased after insertion (p=0.002). The roundness significantly decreased after insertion (p=0.007). The flatness of the volume remained unchanged (p=0.097). Furthermore, the principal x-moment was significantly different after insertion (p=0.019). The y- and z-moments were not significantly changed after insertion (p=0.189 and 0.194, respectively), denoting integrity in anterior-posterior and inferior-superior dimensions of the volume.
Conclusion: This analysis provides quantitative evidence of significant geometric changes of the HR-CTV volume after brachytherapy applicator insertion for the treatment of cervical cancer. With elongation increasing, roundness decreasing, and the x coordinate principal moment changes, the volume appears significantly stretched after insertion. This may be clinically significant as acquiring pre-insertion MRIs only may inadequately depict tumor volume and lead to inadequate coverage of critical areas if used for treatment planning.