3D VSHARP®, a general-purpose CBCT scatter correction tool that uses the Linear Boltzmann Transport Equation

High quality cone-beam tomography (CBCT) reconstruction requires accurately estimating and subtracting the (often) large amount of scatter from the raw projection data. Although considerable attention has been paid to scatter correction algorithm development over the past several years, there still exists the need for a practical, general-purpose tool that is accurate, fast, and requires minimal calibration. Here, we introduce 3D VSHARP® which utilizes a finite element solver of the Linear Boltzmann Transport Equation (LBTE) to accurately and rapidly simulate photon transport through a model of the object being scanned and then scale and subtract the estimated scatter from raw projections. 3D VSHARP has been incorporated into the commercially available reconstruction software development toolkit, CST (Varex Imaging, Salt Lake City, UT) enabling scatter correction to be applied to arbitrary scanner configurations and geometries as part of an entire reconstruction pipeline. To set parameters for 3D VSHARP, the user chooses from a library of files that describe key physical aspects of the CT system, including its x-ray spectrum, detector response, and, if they exist, bowtie filter, and anti-scatter grid. The object model, which characterizes the spatial distribution of the atomic number and density of the scanned object, is automatically generated from the first-pass reconstruction which may, if desired, include CST’s existing kernel-based scatter correction 2D VSHARP®. We describe the new correction tool and show example reconstructions. High accuracy of scatter correction and excellent image quality were achieved with total reconstruction times on the order of 1 minute.