SU-E-J-210: Lung Tumor Target Volume Contours on EPID Cine Mode Images.

Area of Science:

• Medical Physics
• Radiation Oncology
• Image Registration

Background:

• Electronic portal imaging devices (EPIDs) offer real-time treatment monitoring but have limitations in field of view and contrast.
• Physician assessment of EPID images is challenging due to inherent limitations, particularly for lung tumors with potential movement.

Purpose of the Study:

• To develop and validate a method for registering and projecting internal target volume (ITV) and planning target volume (PTV) contours onto cine mode EPID images.
• To improve the interpretation of real-time treatment images for physicians, aiding in accurate tumor targeting.

Main Methods:

• EPID images were registered to planning CT using machine geometry and cone-beam CT (CBCT) for patient setup.
• Digitally reconstructed radiographs (DRRs) were generated from the CT, with ITV and PTV structures projected onto them.
• DRRs were registered to EPID images using cross-correlation, and contours were transferred for visualization.

Main Results:

• Successful registration of MV DRRs to EPID images was achieved, enabling the display of projected target volumes.
• Geometric registration and CBCT-guided setup were sufficient for sub-pixel contour registration in static cases.
• The developed method is expected to be crucial for managing cases with significant tumor motion.

Conclusions:

• Visualizing target volumes on EPID images provides a valuable tool for treatment assessment, particularly for moving tumors.
• The implemented methods form the foundation for a clinical tool that offers real-time contour visualization during radiation therapy.