Commissioning cranial single-isocenter multi-target radiosurgery for the Versa HD

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Single-isocenter multi-target (SIMT) cranial stereotactic radiosurgery (SRS) requires specialized treatment planning.
• Brainlab's Elements Multiple Brain Mets SRS (MBMS) is designed for these complex treatments.

Purpose of the Study:

• To document the commissioning process of the MBMS system on an Elekta Versa HD linear accelerator.
• To evaluate the accuracy and safety of MBMS for cranial SRS.

Main Methods:

• Commissioning involved collecting beam data (output factors, PDDs, profiles) for 6 MV, 6 MV FFF, and 10 MV FFF photon beams.
• Treatment plans were created for patient data and evaluated using conformity and gradient indices.
• Dosimetric accuracy was verified using microDiamond, Gafchromic film, and SRS Mapcheck, with end-to-end testing for the entire workflow.

Main Results:

• Beam model parameters were within acceptable tolerances.
• MBMS plans achieved excellent conformity (ICI < 1.5) and gradient indices (GI < 5.0) for targets > 10 mm.
• Measurements confirmed high dosimetric accuracy, with end-to-end tests showing dose agreement within 1.5%.

Conclusions:

• The commissioning of Brainlab's MBMS on the Elekta Versa HD was successful.
• This experience provides a valuable guide for implementing safe and accurate SIMT cranial SRS treatments.