The dosimetric consequences of weighted fields using the same isocenter in radiosurgery

Area of Science:

• Neurosurgery
• Radiation Oncology
• Medical Physics

Background:

• Gamma Knife radiosurgery relies on precise dosimetry for effective treatment.
• Standard collimator sizes in Gamma Knife (4, 8, 14, 18 mm) limit optimal isodose line matching to diverse lesion sizes.
• Achieving ideal dosimetry is crucial for maximizing therapeutic effect and minimizing off-target radiation exposure.

Purpose of the Study:

• To present a novel technique for creating 50% or higher isodose lines in Gamma Knife radiosurgery.
• To improve the matching of isodose lines to lesion diameters using a combination of different collimator sizes and weights.
• To evaluate the dosimetric accuracy of this new technique in three dimensions.

Main Methods:

• Utilized a single isocenter for treatment delivery.
• Employed a combination of different sized and weighted collimators to generate custom isodose distributions.
• Compared the resulting 3D dosimetry of combination fields with standard collimator sizes (8 mm and 14 mm).

Main Results:

• The developed technique enables the creation of 50% or higher isodose lines for effective collimator sizes ranging from 4 to 18 mm.
• This approach enhances the ability to match isodose line diameters to lesion dimensions in a defined plane.
• Significant discrepancies in three-dimensional dosimetry were observed when comparing combination fields to standard Gamma Knife collimator sizes.

Conclusions:

• The described Gamma Knife dosimetry technique offers improved matching of isodose lines to lesion sizes in a 2D plane.
• Further investigation is needed to address the observed three-dimensional dosimetric differences for clinical application.
• This method provides a potential strategy to overcome limitations of fixed collimator sizes in Gamma Knife radiosurgery.