Plan Assessment Metrics for Dose Painting in Stereotactic Radiosurgery

Area of Science:

• Radiation Oncology
• Medical Physics
• Image-Guided Therapy

Background:

• Advancements in radiation therapy precision enable dose painting, delivering nonuniform radiation doses to targets.
• Stereotactic radiosurgery (SRS) is well-suited for dose painting due to its high precision.
• Existing dose painting metrics are not optimized for SRS, which prioritizes avoiding target underdose and considers single prescriptions.

Purpose of the Study:

• To develop and propose a novel set of metrics for assessing dose painting SRS treatment plans.
• To address the clinical need for metrics that accommodate nonuniform dose prescriptions in SRS.
• To create metrics suitable for SRS plans that avoid target underdose and consider dose fall-off.

Main Methods:

• Dose painting SRS prescriptions were generated using Gamma Knife SRS cases and MRI data.
• Treatment plans were optimized using semi-infinite linear programming.
• Existing SRS metrics were modified, and new metrics like integral dose ratio were proposed and evaluated.

Main Results:

• Modified conformity and efficiency indices were found to be suitable replacements for existing SRS metrics in dose painting scenarios.
• A modified conformity index is appropriate for integral or maximum boost methods in dose painting SRS.
• Modified efficiency indices can effectively replace the existing gradient index for dose painting SRS.

Conclusions:

• The proposed modified SRS metrics accurately assess the quality of dose painting SRS plans.
• These new metrics provide equivalent values to original SRS metrics when applied to single-prescription plans.
• The developed metrics meet clinical needs for evaluating complex, nonuniform dose distributions in SRS.