Normal Tissue Objective Parameter Optimization in Eclipse Treatment Planning System: Enhancing Stereotactic...

Area of Science:

• Radiation Oncology
• Medical Physics
• Neurosurgery

Background:

• Stereotactic radiosurgery (SRS) is a precise radiation therapy technique.
• Noncoplanar RapidArc (RA) and HyperArc (HA) are advanced treatment delivery technologies.
• Optimizing normal tissue objective parameters is crucial for minimizing radiation-induced toxicity.

Purpose of the Study:

• To identify optimal manual normal tissue objective (mNTO) parameters for noncoplanar RA SRS plans.
• To compare the performance of these optimized RA plans against HA plans for single brain metastasis treatment.

Main Methods:

• Retrospective analysis of 28 patients with single brain metastasis treated with 21 Gy SRS.
• Generation of noncoplanar RA plans with varying mNTO parameters (dose fall-offs 0.1-5.0 mm^-1, end doses 50%, 25%, 10%).
• Comparison with two HA plans (HA-sNTO and HA-mNTO) using integrated scoring (CI, GI, HI, MUs, normal brain doses, delivery accuracy).

Main Results:

• The optimized RA-mNTO plan (25% end-dose, 0.5 mm^-1 dose fall-off) demonstrated significantly better CI, GI, and HI compared to HA plans (P < 0.05).
• RA-mNTO significantly reduced normal brain doses (V18Gy, V15Gy, V12Gy) and monitor units (MUs) compared to both HA plans (P < 0.05).
• RA-mNTO achieved higher gamma pass rates (99.8% ± 0.39) than HA-sNTO (98.9% ± 0.68) and HA-mNTO (99.0% ± 0.51).

Conclusions:

• Optimized mNTO-based noncoplanar RA plans provide superior plan quality and dose distribution for single brain metastasis SRS.
• This approach outperforms HA in key dosimetric and delivery accuracy metrics.
• RA-mNTO represents a highly effective strategy for SRS treatment of brain metastases.