Analytic characterization of linear accelerator radiosurgery dose distributions for fast optimization.

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiosurgery

Background:

• Linear accelerator (linac) radiosurgery typically uses non-coplanar arc therapy with circular collimators, leading to spherical dose distributions.
• Conforming these dose distributions to irregular lesions requires complex manipulation of treatment planning parameters.
• Current methods are time-consuming due to the complexity of parameter effects and computationally expensive 3D dose calculations.

Purpose of the Study:

• To simplify and improve the efficiency of radiosurgery treatment planning.
• To develop a method for real-time approximation of 3D dose distributions.
• To enable faster iterative plan optimization for radiosurgery.

Main Methods:

• Empirically determined the effects of treatment planning parameters on isodose surface dimensions.
• Fitted these dimensions to analytic functions, modeling dose distributions as conic sections.
• Developed analytic functions for real-time approximation of the 3D isodose surface.

Main Results:

• The prescription isodose surface for single isocenter distributions can be approximated by conic sections.
• Analytic functions were derived to represent these conic sections in real-time.
• This approach allows for efficient iterative plan optimization using a pseudo-inverse method based on geometric considerations.

Conclusions:

• A novel pseudo-inverse approach to radiosurgery optimization based on geometric considerations was developed.
• Real-time approximation of the 3D isodose surface significantly enhances the efficiency of iterative plan optimization.
• This method simplifies the complex process of dose conformation for irregular lesions in linac radiosurgery.