Intrafraction motion during frameless radiosurgery using Varian HyperArc^TM and BrainLab Elements^TM immobilization...

Area of Science:

• Neurosurgery
• Radiation Oncology
• Medical Physics

Background:

• Advanced radiosurgery systems enable single-isocenter treatment for multiple brain metastases.
• These systems necessitate specialized frameless immobilization techniques.

Purpose of the Study:

• To compare the intrafraction motion and immobilization accuracy of two distinct frameless mask systems used with Varian HyperArcTM and BrainLab Elements MultiMetTM radiosurgery platforms.
• To evaluate the clinical implications of intrafraction motion for frameless radiosurgery of multiple brain metastases.

Main Methods:

• Retrospective analysis of patients undergoing single-isocenter radiosurgery for brain metastases.
• Utilized cone-beam CT scans and image registration to quantify intrafraction translational and rotational motion for two immobilization systems (QFix-Encompass and BrainLab frameless-mask).

Main Results:

• No statistically significant differences were observed in mean absolute translational shifts (approx. 0.43 mm 3D-vector) between the QFix-Encompass and BrainLab frameless-mask systems.
• No statistically significant differences were found in mean absolute rotational shifts between the two immobilization systems.
• Individual maximum shifts, particularly rotational, warrant attention due to potential lesion misalignment, especially at greater distances from the isocenter.

Conclusions:

• Both the QFix-Encompass and BrainLab frameless-mask systems provide comparable intrafraction motion control for single-isocenter radiosurgery of multiple brain metastases.
• While average motion is insignificant, careful consideration of maximum rotational shifts and real-time patient monitoring is crucial for optimizing treatment accuracy and safety.