Image-guided radiotherapy using a mobile kilovoltage x-ray device

Area of Science:

• Medical Imaging
• Radiotherapy Physics
• Image-Guided Interventions

Background:

• Image-guided radiotherapy (IGRT) requires precise patient and tumor localization.
• Mobile C-arm imagers offer potential for flexible IGRT setups.
• Cone-beam computed tomography (CBCT) is a developing imaging technique for IGRT.

Purpose of the Study:

• To evaluate a mobile isocentric C-arm kilovoltage imager for IGRT applications.
• To assess the system's imaging performance, including resolution and contrast.
• To investigate methods for accurate C-arm positioning and address motion artifacts.

Main Methods:

• Utilized an amorphous silicon flat panel C-arm with modified Feldkamp algorithm for CBCT.
• Acquired volumetric data over a 180-degree arc with varying projections (100-1000).
• Compared image quality to conventional CT and evaluated two C-arm registration methods: fiducial markers and infrared navigation tracking.

Main Results:

• Achieved spatial resolution > or = 10 lp/cm, comparable to conventional CT, with near-isotropic resolution.
• Subject contrast was lower than conventional CT due to scatter and noise.
• Navigation-based positioning accuracy was 1.0-1.5 mm, superior to fiducial-based (1.5-2.5 mm).
• Respiratory motion degraded image quality, but retrospective gating improved it.

Conclusions:

• The mobile C-arm kilovoltage imager is a viable tool for IGRT, providing comparable spatial resolution to conventional CT.
• Navigation-based registration offers superior accuracy for daily patient positioning.
• Retrospective gating is effective in mitigating respiratory motion artifacts for improved CBCT quality.