Triggered kV Imaging During Spine SBRT for Intrafraction Motion Management

Area of Science:

• Medical Physics
• Radiation Oncology
• Image-Guided Therapy

Background:

• Intrafraction motion during spine stereotactic body radiotherapy (SBRT) can compromise treatment accuracy.
• Monitoring this motion requires efficient and readily available technology.

Purpose of the Study:

• To implement and evaluate triggered kV imaging for intrafraction motion monitoring during spine SBRT.
• To assess the feasibility and clinical utility of this technique using on-board imager (OBI) technology.

Main Methods:

• Triggered kV imaging was tested using an anthropomorphic phantom and simulated spine SBRT treatments.
• Image-guided radiotherapy (IGRT) structures (vertebral bodies, spinous processes) were contoured.
• 2D projections of IGRT structures were automatically calculated and displayed on kV images.
• Gantry-angle-based (45°) and time-based (15s) triggering were employed, alongside a survey of physicists/physicians.

Main Results:

• Image-guided radiotherapy (IGRT) structure accuracy improved with smaller CT slice thickness.
• Detectability of shifts was proportional to shift size and inversely related to CT slice thickness.
• Appreciable intrafraction motion was detected in 11.7% of clinically treated fractions.

Conclusions:

• Triggered kV imaging is a feasible technique for spine SBRT intrafraction motion management.
• This method provides efficient, non-invasive patient position monitoring using OBI and patient anatomy.
• The technique enhances the robustness of patient immobilization assessment during treatment.