A practical strategy for incorporating the convolution algorithm in Leksell GammaPlan for routine treatment planning^†

Area of Science:

• Medical Physics
• Radiotherapy
• Radiation Oncology

Background:

• Accurate dose calculation is essential for effective and safe radiosurgery.
• Heterogeneity in tissue density can significantly impact dose distribution in radiation therapy.

Purpose of the Study:

• To establish criteria for convolution dose calculations in GammaKnife radiosurgery (GKRS).
• To develop an efficient procedure for incorporating heterogeneity effects into GKRS treatment plans.

Main Methods:

• Analyzed 114 GKRS cases with 205 tumors of varying characteristics.
• Compared dose calculations using the TMR10 algorithm with the convolution (Conv) algorithm.
• Evaluated dose ratios (Conv/TMR10) for treatment volume, dose metrics, and isodose coverage.
• Categorized results based on tumor proximity to the skull surface (distC and distE).

Main Results:

• Dose calculation ratios generally increased with greater distance from the skull surface.
• A statistically significant difference in minimum dose ratio was observed for tumors with distE < 2 cm versus distE ≥ 2 cm.
• The TMR10 algorithm showed a potential overestimation of delivered dose by approximately 6.1% compared to the convolution algorithm.

Conclusions:

• Heterogeneity effects are significant for GKRS dose calculations.
• The convolution algorithm should be applied for tumors within 2 cm of the skull surface to achieve <3% accuracy.
• This approach enhances the precision of GammaKnife radiosurgery treatment planning.