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Analytical HDR prostate brachytherapy planning with automatic catheter and isotope selection
Catherine Holly Frank1, Pavitra Ramesh1, Qihui Lyu1
1Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California, USA.
Medical Physics
|August 31, 2023
Summary
This study introduces a new analytical approach for high dose rate (HDR) brachytherapy planning, optimizing catheter placement and dual-isotope selection for prostate cancer treatment. While results show minimal clinical differences, the method aids in planning and isotope selection for specific treatment goals.
Area of Science:
- Medical Physics
- Radiation Oncology
- Computational Biology
Background:
- High dose rate (HDR) brachytherapy is a standard treatment for prostate cancer.
- Current HDR planning systems are limited by predetermined catheter positions and single energy sources.
- Optimizing catheter placement and incorporating multiple isotopes can potentially improve treatment conformity and spare organs at risk.
Purpose of the Study:
- To present a novel analytical approach for HDR planning, addressing catheter and dual-energy source selection.
- To investigate the dosimetric benefits of flexible catheter placement and multiple isotope options, particularly for urethra sparing.
- To solve the HDR planning problem with enhanced degrees of freedom for improved treatment outcomes.
Main Methods:
- A constrained optimization problem was formulated for catheter and dual-energy source selection, employing non-convex group sparsity regularization.
- The Fast Iterative Shrinkage-Thresholding Algorithm (FISTA) was used to solve the optimization problem.
- Dose rates for Ytterbium (Yb-169) and Iridium (Ir-192) sources were modeled, and plans were compared against clinical Ir-192 only (IRO) plans in 22 retrospective prostate cancer cases.
Main Results:
- Dual-source (DS) plans predominantly selected Ir-192 as the sole source.
- IRO plans demonstrated superior organ at risk (OAR) sparing compared to Ytterbium (Yb-169) only (YBO) plans, with statistically significant reductions in urethra, bladder, and rectum dose metrics.
- While IRO plans improved OAR sparing over clinical plans, they also led to increased CTV V150% and D90%, with overall minimal clinical differences observed between all evaluated plans.
Conclusions:
- The developed analytical HDR planning algorithm effectively integrates catheter and isotope selection with dwell time optimization for diverse clinical objectives, including urethra sparing.
- This planning methodology can guide HDR implant procedures and identify optimal isotopes for specific clinical goals, such as enhancing target conformity or maximizing OAR sparing.
- The approach offers a flexible framework for advancing HDR brachytherapy treatment planning.
