Prior image constrained scatter correction in cone-beam computed tomography image-guided radiation therapy

Area of Science:

• Medical Physics
• Radiological Imaging
• Computational Imaging

Background:

• X-ray scatter in cone-beam CT (CBCT) degrades image quality, causing reduced contrast and CT number inaccuracy, especially with thicker objects and larger cone angles.
• Prior image-based reconstruction methods have improved X-ray computed tomography (CT) but need adaptation for scatter correction in CBCT image-guided radiation therapy.

Purpose of the Study:

• To develop and evaluate a new algorithm for correcting scatter-induced shading artifacts in CBCT images acquired under high scatter conditions.
• To leverage prior image information to mitigate artifacts in CBCT for image-guided radiation therapy applications.

Main Methods:

• A novel scatter correction algorithm was proposed, utilizing a prior image with low scatter artifacts.
• The algorithm hypothesizes the target image as a weighted sum of basis images derived from raw CBCT projection data.
• Basis images were reconstructed using filtered backprojection, and weights were optimized by minimizing the difference between the target and prior images.

Main Results:

• The proposed algorithm demonstrated substantial mitigation of scatter-induced shading artifacts in CBCT images.
• Qualitative and quantitative evaluations using phantom studies confirmed the algorithm's effectiveness.
• The correction was successful in both full-fan and half-fan acquisition modes.

Conclusions:

• The developed scatter correction algorithm effectively reduces shading artifacts in CBCT images.
• Utilizing a low-scatter prior image is a viable strategy for scatter correction in CBCT-guided radiation therapy.
• The method shows promise for improving image quality in CBCT applications.