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PLANER: Development and validation of a real-time image-guided dynamic dosimetric framework for I-125 seed
Jun-Ru Xiong1, Liang-Yu Deng1, Feng Zhang2
1Department of Nuclear Medicine (Treatment Center of Minimally Invasive Intervention and Radioactive Particles), First Affiliated Hospital of Army Medical University, Chongqing, China.
Brachytherapy
|May 28, 2026
Summary
This study introduces a real-time image-guided adaptive dosimetry workflow for I-125 seed brachytherapy. The PLANER workflow ensures the delivered radiation dose closely matches the planned dose, improving treatment consistency.
Area of Science:
- Radiation Oncology
- Medical Physics
- Image-Guided Therapy
Background:
- Brachytherapy, particularly Iodine-125 (I-125) seed implants, is a key treatment for localized prostate cancer.
- Achieving accurate and consistent dose delivery is crucial for maximizing tumor control and minimizing side effects.
- Current static treatment planning may not account for intraoperative anatomical changes, potentially leading to dose discrepancies.
Purpose of the Study:
- To develop and validate a novel real-time image-guided adaptive dosimetry workflow (PLANER) for I-125 seed brachytherapy.
- To enhance the consistency between planned and delivered dose distributions on the day of implantation.
- To assess the impact of adaptive re-planning on key dosimetric parameters.
Main Methods:
- Retrospective analysis of 34 patients undergoing CT-guided I-125 seed brachytherapy using the PLANER workflow.
- Utilized a laser navigation system for precise needle placement based on pre-plans.
- Implemented intraoperative dosimetry checks with adaptive re-planning if deviations exceeded thresholds.
- Compared dosimetric indices (D90, V90, V200) across treatment stages; mediation analysis evaluated adaptive planning's effect.
Main Results:
- The PLANER workflow was successfully implemented in all cases, with a slight increase in median seed count (38 to 40) but no change in median needle count (11).
- Target D90 remained within ~5% of planned values throughout all stages.
- V90 coverage consistently met or exceeded 95%, recovering to ~97% after optimization.
- High-dose V200 levels were effectively controlled. Mediation analysis confirmed adaptive re-planning significantly influenced final D90 and V90 outcomes.
Conclusions:
- The real-time image-guided PLANER dosimetry workflow achieved excellent agreement between planned and delivered dose distributions for I-125 seed brachytherapy.
- Intraoperative adaptive planning proved essential for maintaining target coverage and limiting dose to organs at risk.
- This dynamic approach is feasible and offers potential for improved tumor control and reduced toxicity compared to traditional static planning.
