Dose distribution for gynecological brachytherapy with dose accumulation between insertions: Feasibility study

Area of Science:

• Medical physics
• Radiation oncology
• Image analysis

Background:

• Standard gynecological treatment planning uses daily CT/MR imaging for dose calculation.
• Current methods conservatively estimate cumulative dose, potentially limiting treatment efficacy.
• Accurate dose assessment is crucial for optimizing radiation therapy outcomes.

Purpose of the Study:

• To investigate deformable image registration (DIR) for assessing cumulative dose in gynecological brachytherapy.
• To evaluate methods for improving DIR accuracy in the pelvic region.
• To explore DIR as an alternative to standard dose accumulation methods.

Main Methods:

• Rigid registration of CT images followed by DIR.
• DIR guided by 3D images, organ contours, or artificially modified contrast.
• Deformation of dose matrices from previous fractions using calculated deformation fields.

Main Results:

• DIR, guided by contrast enhancement or contours, enables dose accumulation from multiple fractions.
• Despite improvements, dose uncertainty remains 5-10% due to high dose gradients.
• Local errors in DIR can significantly impact dose distribution, especially with contour matching.

Conclusions:

• Deformable image registration (DIR) offers a method for accumulating dose across brachytherapy fractions.
• Image features and contours enhance DIR accuracy for dose assessment.
• Further development of robust validation procedures is essential for clinical implementation.