A simple and accurate coordinate transformation for a stereotactic radiotherapy system

Area of Science:

• Medical Physics
• Radiotherapy
• Image Guidance

Background:

• Accurate coordinate transformation is crucial for stereotactic radiation therapy.
• Current methods often require digitization of reference points across multiple CT slices.
• Approximations or linear interpolations can introduce inaccuracies in target point determination.

Purpose of the Study:

• To develop and validate a global registration algorithm using only two CT slices.
• To simplify the coordinate transformation process from the Brown-Roberts-Wells (BRW) frame to the CT-simulator coordinate system.
• To eliminate the need for digitization of BRW pins in every CT slice and avoid approximations for points between slices.

Main Methods:

• Developed a global registration algorithm utilizing exact solutions based on BRW pins in two CT slices.
• Algorithm transforms target points from the BRW frame to the CT-simulator coordinate system.
• Validated the algorithm's performance in 60 clinical cases.

Main Results:

• The algorithm accurately determines points of interest using only two CT slices.
• Eliminates the need for digitization in every slice and avoids interpolation errors.
• Achieved accuracy and precision in isocentric positions within digitization uncertainty.

Conclusions:

• The developed global image registration algorithm simplifies coordinate transformation in stereotactic radiation therapy.
• Offers improved accuracy and efficiency compared to slice-by-slice methods.
• Facilitates precise targeting for radiation treatment planning.