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Performance of a Novel Frameless and Maskless Robotic Head Motion Compensation System for Stereotactic Radiosurgery
Xinmin Liu1, Ahmad Sakaamini2, Wenbo Gu2
1Department of Radiation Oncology, University of California, Los Angeles, California.
Purpose:
Stereotactic radiosurgery (SRS) is a nonsurgical method for treating brain abnormalities and small tumors. Traditional high-accuracy SRS requires a rigid metal head frame screwed into the skull, which causes discomfort and reduces patient compliance. Thermoplastic masks offer a less invasive alternative but compromise accuracy because of flexing and are often still uncomfortable. To address these issues, we developed a novel robotic head motion compensation (RHMC) device that enables frameless and maskless SRS.
Methods And Materials:
A compact, portable RHMC device was developed that can be quickly attached to or detached from the end of a linear accelerator treatment table. Real-time 6° head position tracking was performed using 3-dimensional surface-guided radiation therapy imaging, which was fed into the robot control computer. Device performance was evaluated by administering virtual SRS treatments to a phantom and 20 healthy volunteers, simulating a clinical environment but without delivering radiation. The primary success metric was defined as maintaining the 6D target position under a 1.0 mm and 1.0° threshold for more than 95% of beam-on time (denoted as DC95%_1.0 mm and 1.0°).
Results:
Two of the 20 volunteers were excluded because of incompatibility with the RHMC device. Among the remaining 18 volunteers, the DC95%_1.0 mm and 1.0° success metric was achieved in all cases. Without the RHMC device, 9 of the 18 volunteers were able to meet this metric. For a tighter tolerance of DC95%_1.0 mm and 0.5°, 17 volunteers achieved the metric with the RHMC device, compared with 4 without. For a tolerance of 1.0 mm and 1.0°, across all 18 volunteers, the mean and range were 99% and 96% to 100% using the RHMC device, respectively, compared with 73% and 9% to 100% without the RHMC device.
Conclusions:
The RHMC device effectively maintained accurate head motion control under simulated clinical conditions, achieving the DC95%_1.0 mm and 1.0° success metric for all suitable candidates. This technology has the potential to enable frameless and maskless SRS delivery within or better than current standard-of-care tolerance guidelines.
