Changes in Patient Marker Coordinates with High-Definition Motion Management System during Frameless Gamma Knife...

Area of Science:

• Neurosurgery
• Radiation Oncology
• Medical Physics

Background:

• The Leksell Gamma Knife (LGK) Icon™ enables frameless gamma knife radiosurgery (GKRS) using a high-definition motion management (HDMM) system.
• The HDMM system tracks intra-fractional motion but does not specify directional shifts (X, Y, Z axes).

Purpose of the Study:

• To investigate coordinate shifts in patient markers during frameless GKRS using the HDMM system.
• To analyze intra-fractional motion along the X, Y, and Z axes in patients with meningioma and metastases.

Main Methods:

• Retrospective analysis of patients undergoing frameless GKRS with LGK Icon™ between January and September 2023.
• Immobilization using Nanor thermoplastic masks; sequential analysis of nose marker coordinates (X, Y, Z).

Main Results:

• Meningioma patients (n=30) showed no significant intra-fractional displacements (X: 0.07±0.06 mm, Y: 0.08±0.46 mm, Z: 0.08±0.04 mm).
• Metastases patients (n=30) exhibited significant Y-axis displacement (0.57±0.37 mm, p<0.05) compared to the X-axis (0.33±0.23 mm).
• Y-axis displacement increased significantly after 30 minutes of beam-on time in metastases patients.

Conclusions:

• Y-axis movement is most prominent in metastases patients during frameless GKRS.
• Recommendations include pressing the forehead during mask application to minimize nose marker movement.
• Suggest adding a 0.5 mm margin to the Y-axis for treatment plans in metastases patients treated with LGK Icon™.