Two-dimensional antiscatter grid: A novel scatter rejection device for Cone-beam computed tomography

Area of Science:

• Medical Imaging
• Radiological Physics
• Cone-Beam Computed Tomography

Background:

• Scattered radiation is a primary factor degrading image quality in Flat Panel Detector (FPD)-based Cone-beam computed tomography (CBCT).
• Reducing scatter intensity is crucial for improving CBCT image fidelity and diagnostic accuracy.

Purpose of the Study:

• To investigate a novel two-dimensional antiscatter grid (2D-ASG) for scatter reduction in CBCT.
• To demonstrate the efficacy of a 2D-ASG prototype in enhancing CBCT image quality.

Main Methods:

• A 2D-ASG prototype made of tungsten was additively manufactured and mounted on a Varian TrueBeam CBCT system.
• CBCT projections were acquired using an offset detector geometry, with angle-specific gain correction applied.
• Image quality was assessed by measuring contrast-to-noise ratio (CNR) and CT number accuracy, comparing 2D-ASG with no antiscatter grid (NO-ASG) and 1D-ASG.

Main Results:

• The 2D-ASG prototype achieved significant improvements in contrast resolution compared to NO-ASG and 1D-ASG.
• CNR of material inserts improved by up to 86% (vs. NO-ASG) and 54% (vs. 1D-ASG).
• CT number underestimation in water-equivalent material was reduced by up to 325 HU (vs. NO-ASG) and 179 HU (vs. 1D-ASG) with the 2D-ASG.

Conclusions:

• The first CBCT imaging experiments with a 2D-ASG prototype were successfully conducted.
• The 2D-ASG demonstrated significantly higher CT number accuracy, improved CNR, and reduced scatter-induced artifacts.
• The 2D-ASG holds potential for enhanced soft tissue visualization and novel clinical applications in CBCT.