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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.
Purpose:
To develop and clinically validate a novel real-time image-guided adaptive dosimetry workflow for I-125 seed brachytherapy, aiming to improve consistency between planned and actually delivered dose distributions on the day of implantation.
Materials And Methods:
We retrospectively analyzed 34 patients who underwent CT-guided I-125 seed brachytherapy using a four-stage PLANER workflow. A laser navigation system guided needle placement per the preplan. If intraoperative dosimetry deviated beyond preset thresholds, an adaptive re-plan was immediately generated. Key dosimetric indices (D90, V90, V200) were compared across stages, and mediation analysis evaluated the contribution of adaptive re-planning to final dosimetry.
Results:
The PLANER workflow was completed in all cases. Median seed count increased from 38 to 40 (p < 0.001) with no change in median needle number (11), indicating additional seeds without more needles. Target D90 remained within ∼5% of the planned value at all stages. V90 coverage was ≥95% throughout, with a slight dip after initial placement and recovery to ∼97% after optimization. High-dose hotspots (V200) were well controlled with no significant increase. Mediation analysis confirmed that the adaptive re-plan stage had a significant mediating effect on final D90 and V90, effectively transmitting the preplan's dose influence to the delivered dose.
Conclusion:
A real-time image-guided PLANER dosimetry workflow achieved a near-identical match between planned and delivered dose distributions on the day of implantation. Intraoperative adaptive planning was crucial for maintaining target coverage and limiting hotspots. This dynamic approach is feasible and has the potential to improve tumor control and reduce toxicity compared to static preplanning.
