New dosimetric approach for multidimensional dose evaluation in gamma knife radiosurgery. Technical note

Area of Science:

• Medical Physics
• Radiotherapy
• Dosimetry

Background:

• Gamma knife radiosurgery has advanced with smaller collimators for precise treatment.
• Traditional ionization chambers are unsuitable for calibrating small (4 mm) gamma knife collimators due to size mismatch.
• Development of novel dosimeters is crucial for accurate calibration in advanced radiosurgery.

Purpose of the Study:

• To introduce and validate the FriXyGel method as a suitable dosimeter for gamma knife radiosurgery.
• To enable accurate absorbed dose measurement and 3D dose distribution mapping with small collimators.
• To provide a reliable calibration tool for advanced gamma knife treatment planning.

Main Methods:

• The FriXyGel method utilizes a phantom with agarose gel incorporating ferrous sulphate and xylenol orange.
• Absorbed dose is measured via visible light transmission changes detected by a charge-coupled device camera.
• Three-dimensional dose representation is achieved through imaging gel layers before and after irradiation, followed by image processing and calibration.

Main Results:

• The FriXyGel method successfully measures absorbed doses in a 3D format.
• Image processing software corrects for optical factors and enables accurate dose value determination.
• The system allows for spatial representation of absorbed dose, facilitating comparison with theoretical calculations.

Conclusions:

• The FriXyGel method offers a viable solution for dosimetric calibration in gamma knife radiosurgery, particularly with small collimators.
• This novel approach enhances the accuracy of radiation therapy planning and delivery.
• The developed software and phantom system provide a comprehensive tool for 3D dose verification.