Cone-beam CT using a mobile C-arm: a registration solution for IGRT with an optical tracking system

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Image Registration

Background:

• Accurate image registration is crucial for image-guided radiation therapy (IGRT).
• Mobile C-arms with kilovoltage cone-beam computed tomography (kV-CBCT) offer advanced imaging capabilities.
• Integrating C-arm imaging with linear accelerator (LINAC) targeting requires precise spatial calibration.

Purpose of the Study:

• To develop and evaluate a method for registering kV-CBCT images from a mobile C-arm to a LINAC isocenter.
• To establish a transformation for mapping image voxels to room coordinates for IGRT applications.

Main Methods:

• A calibration procedure using reflective markers on the C-arm and a phantom.
• An optical tracking system to locate markers in room coordinates relative to the LINAC isocenter.
• kV-CBCT imaging to determine marker positions in image coordinates.
• Singular value decomposition (SVD) algorithm to establish the coordinate system relationship.

Main Results:

• A transformation was calculated to map image voxels to room coordinates.
• The method achieved a mean absolute distance of 1.4+/-0.5 mm in phantom evaluations.
• This accuracy is comparable to existing systems used in IGRT.

Conclusions:

• The presented method enables accurate registration of C-arm kV-CBCT images to the LINAC isocenter.
• This technique facilitates precise patient positioning and treatment delivery in IGRT.
• The developed calibration method offers a viable solution for advanced image guidance in radiotherapy.