Technical note: Surface imaging for real-time patient positioning in external radiation therapy.

Area of Science:

• Medical Physics
• Radiation Oncology
• Imaging Technology

Background:

• Surface imaging is increasingly utilized for patient positioning in external radiation therapy.
• Accurate patient alignment is critical for effective radiation delivery and minimizing off-target dose.

Purpose of the Study:

• To evaluate the accuracy of the Azure Kinect surface imaging system for daily patient positioning in external radiation therapy.
• To assess the system's performance across various anatomical locations and treatment sites.

Main Methods:

• A total of 50 treatment fractions from 10 patients (lung, pelvic, head and neck tumors) were analyzed.
• A rigid registration algorithm using the iterative closest point (ICP) approach estimated patient position in 6 degrees of freedom (DOF).
• Positioning accuracy was compared against reference values obtained via radiograph imaging.

Main Results:

• Mean setup errors were: lateral 1.1 ± 1.1 mm, longitudinal 1.8 ± 2.1 mm, vertical 0.8 ± 1.1 mm.
• Angular errors included yaw 0.3°± 0.4°, pitch 0.2°± 0.2°, and roll 0.2°± 0.2°.
• The largest setup errors were observed in pelvic region treatments.

Conclusions:

• The Azure Kinect surface imaging system provides accurate patient positioning in a radiotherapy setting.
• The system effectively handles 6 DOF couch motion across diverse patient anatomies.
• This technology enables precise patient alignment without requiring skin markings or increasing radiation dose.