Patient positioning in radiotherapy based on surface imaging using time of flight cameras

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Image Processing

Background:

• Accurate patient positioning is crucial for effective radiotherapy delivery.
• Traditional patient setup verification methods can be time-consuming and may not capture intrafraction motion.
• Advancements in imaging technology are needed to improve radiotherapy precision.

Purpose of the Study:

• To evaluate the accuracy and efficiency of a stereo-time of flight (ToF)-camera system for patient positioning in radiotherapy.
• To assess the system's ability to detect interfraction and intrafraction motion.

Main Methods:

• A stereo-ToF camera system was employed to scan patient surfaces for daily positioning on the treatment couch.
• Point cloud registration was used to detect table translations and predict necessary displacements for accurate patient alignment.
• The system's measurements were compared against actual applied translations across 150 radiotherapy fractions.

Main Results:

• The system demonstrated high accuracy in displacement detection, with small absolute errors (0.7-0.8 mm) across all axes.
• Lung cancer patients showed slightly larger mean errors (up to 1.1 mm) compared to other patient groups.
• The stereo-ToF system proved effective in identifying both interfraction and intrafraction patient movements.

Conclusions:

• The stereo-time of flight (ToF) system provides sufficient accuracy for patient positioning in radiotherapy, leading to faster setup times.
• Real-time tracking of the entire patient surface offers potential for enhanced intrafraction motion management, including involuntary and breathing movements.
• This technology represents a significant advancement in improving radiotherapy precision and patient safety.