HyperArc^TM Dosimetric Validation for Multiple Targets Using Ionization Chamber and RT-100 Polymer Gel.

Area of Science:

• Radiotherapy Physics
• Medical Imaging
• Radiation Oncology

Background:

• Single-isocenter stereotactic radiosurgery (SRS) is emerging for treating multiple brain metastases.
• Pre-clinical end-to-end testing is crucial before implementing new radiotherapy techniques into clinical practice.

Purpose of the Study:

• To validate the accuracy of HyperArcTM single-isocenter SRS treatment plans for multiple brain metastases.
• To assess the feasibility of using polymer gel dosimetry and magnetic resonance imaging (MRI) for end-to-end verification.

Main Methods:

• Five HyperArcTM treatment plans were evaluated using ionization chambers and polymer gel dosimetry.
• End-to-end tests were conducted in a Mobius Verification Phantom (MVP) and a 3D-printed PseudoPatient® (PP) head phantom.
• Dose distributions were measured using 1.5T MRI and analyzed with gamma index criteria (e.g., 5% 2 mm, 3% 2 mm).

Main Results:

• Mean point dose differences were minimal: 1.01% in MVP and 0.23% in PP phantom.
• Gamma index passing rates exceeded 95% for both 2D and 3D dose distributions across tested criteria.
• High agreement was observed between calculated and measured dose distributions.

Conclusions:

• Single-isocenter SRS effectively reduces treatment time for multiple brain metastases.
• The study confirms the accuracy and reliability of this technique, even for targets distant from the isocenter.
• Polymer gel dosimetry with MRI provides a robust method for end-to-end verification of complex SRS plans.