A general framework and review of scatter correction methods in cone beam CT. Part 2: Scatter estimation approaches

Abstract

The main components of scatter correction procedures are scatter estimation and a scatter compensation algorithm. This paper completes a previous paper where a general framework for scatter compensation was presented under the prerequisite that a scatter estimation method is already available. In the current paper, the authors give a systematic review of the variety of scatter estimation approaches. Scatter estimation methods are based on measurements, mathematical-physical models, or combinations of both. For completeness they present an overview of measurement-based methods, but the main topic is the theoretically more demanding models, as analytical, Monte-Carlo, and hybrid models. Further classifications are 3D image-based and 2D projection-based approaches. The authors present a system-theoretic framework, which allows to proceed top-down from a general 3D formulation, by successive approximations, to efficient 2D approaches. A widely useful method is the beam-scatter-kernel superposition approach. Together with the review of standard methods, the authors discuss their limitations and how to take into account the issues of object dependency, spatial variance, deformation of scatter kernels, external and internal absorbers. Open questions for further investigations are indicated. Finally, the authors refer on some special issues and applications, such as bow-tie filter, offset detector, truncated data, and dual-source CT.

Optimizing the target detectability of cone beam CT performed in image‐guided radiation therapy for patients of different body sizes

“…Scatter is a very important artifact causing factor in CBCT. The scatter‐to‐primary ratio (SPR) is about 0.01 for single‐ray CT and 0.05–0.15 for fan‐beam and spiral CT, and may be as large as 0.4–2.0 in CBCT 10, 11, 12, 13, 29, 30, 31. Typical scatter artifacts show as shading or streaks, which would result in reduced contrast resolution and increased noise in CBCT imaging.…”

“…Typical scatter artifacts show as shading or streaks, which would result in reduced contrast resolution and increased noise in CBCT imaging. Several scatter correction algorithms have been proposed to compensate for the shading artifacts in CBCT, but there is no uniformly accepted solution yet 30, 31. Because of the heavier attenuation caused by larger calibration phantoms, the statistical fluctuations in their CBCT imaging become greater.…”

Contrast enhancement for portal images by combination of subtraction and reprojection processes for Compton scattering

“…Scatter correction methods that comprise scatter estimation and compensation have been reported 9, 1011…”

An energy minimization method for the correction of cupping artifacts in cone‐beam CT

“…Many correction methods that have been developed to reduce the cupping artifacts focus on reducing the scattered photons on the projective image. One such hardware‐based method involves physical scatter rejection techniques in the data acquisition system, such as the use of an air gap, (1) antiscatter grid, (2) or bowtie filter (3) . The second category of software‐based approaches are based on Monte Carlo simulation, 4 , 5 which use Monte Carlo (MC) simulations to model the scatter distribution by tracing the history of photons from the source to the detector.…”