Analysis of image quality for real-time target tracking using simultaneous kV-MV imaging

Area of Science:

• Medical Physics
• Radiotherapy Imaging
• Image Quality Assessment

Background:

• Real-time tracking is crucial for accurate radiation delivery to moving targets.
• Simultaneous kV-MV imaging uses on-board imagers for 3D localization.
• Beam scatter between kV and MV imaging modalities degrades image quality and target visibility.

Purpose of the Study:

• To investigate the impact of MV beam scatter on kV image quality.
• To assess target visibility using contrast-to-noise ratio (CNR).
• To determine the feasibility of simultaneous kV-MV imaging for real-time target tracking.

Main Methods:

• Acquired simultaneous kV-MV images of a gold marker in thorax and pelvis phantoms.
• Quantitatively assessed target visibility using Contrast-to-Noise Ratio (CNR).
• Evaluated the effect of MV beam scatter on kV images and vice versa.

Main Results:

• MV beam scatter significantly reduced target visibility in kV images (R=0.47).
• kV beam scatter had a minor effect on MV images (R=0.93).
• Optimized kV imaging parameters achieved CNR values between 1.3 and 4.2, ensuring adequate target visibility.

Conclusions:

• CNR is a critical metric for assessing target visibility and image quality in kV-MV imaging.
• Simultaneous kV-MV imaging, with parameter optimization, can achieve sufficient target visibility for real-time tracking.
• This technique shows promise for improving accuracy in image-guided radiation therapy.