Direct comparison between surface imaging and orthogonal radiographic imaging for SRS localization in phantom

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Image Guidance

Background:

• Radiographic imaging poses risks due to ionizing radiation.
• Surface imaging (SI) presents a nonionizing, real-time alternative for radiosurgery localization.
• Accurate intrafraction localization is critical for effective radiotherapy delivery.

Purpose of the Study:

• To systematically compare a commercial SI system against a commercial room-mounted X-ray (RM) localization system.
• To evaluate the accuracy and feasibility of SI for intrafraction radiosurgery localization using phantom measurements.
• To assess system performance under various couch angles, head tilts, and isocenter positions.

Main Methods:

• An anthropomorphic head phantom with fiducial markers was used for comparative imaging.
• Three imaging systems were employed: linear accelerator on-board X-ray imaging (ground truth), SI, and RM.
• Measurements were taken at 72 different positions, varying couch angles (±45°, ±90°), head tilts, and isocenters.

Main Results:

• Both RM and SI systems demonstrated comparable accuracy, with displacement vectors of 0.7 ± 0.3 mm relative to on-board imaging.
• Accuracy for both systems remained within 1.1 mm of ground truth across all couch angles.
• SI showed submillimeter average accuracy, with minimal performance degradation even when camera pods were partially blocked.

Conclusions:

• Surface imaging (SI) and room-mounted X-ray (RM) systems exhibit similar accuracy for intrafraction radiosurgery localization.
• SI is a feasible and effective nonionizing imaging modality for real-time localization during radiosurgery.
• SI maintains high accuracy with minimal performance loss under challenging imaging conditions.