Performance of a Novel Frameless and Maskless Robotic Head Motion Compensation System for Stereotactic Radiosurgery in a Realistic Clinical Environment with Healthy Volunteers.

Abstract

PurposeStereotactic 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 materialsA 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°).ResultsTwo 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.ConclusionsThe 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.