Target-specific dose and scatter estimation in CT images

Inventors

Hennix, Marcus • Nordstrom, Hakan • Eriksson, Markus • ADLER, Jonas • Jaffray, David • Bootsma, Gregory • VERHAEGEN, Frank • NUTTI, Bjorn

Assignees

University Health Network • Elekta AB

Abstract

Embodiments disclose a method performed by at least one processor for processing a plurality of x-ray projection images of a subject, the method comprising a plurality of operations including reconstructing the projection images to yield a volume reconstruction; segmenting the reconstructed volume by assigning a material type to each voxel; estimating a first set of scatter images corresponding to a subset of the projection images by calculating probabilistic predictions of interactions of x-rays with the subject and applying a low pass spatial filter to the scatter images; estimating a second set of scatter images corresponding to projection images not included in the subset, based on the first set of scatter images; and subtracting, for each projection image, the corresponding scatter image to yield a corrected projection image. Applying the plurality of operations of the method in an iterative process on graphics-processor-quality computational hardware enables real-time scatter correction and reconstruction of CT volume images.

Core Innovation

A method for processing a plurality of x-ray projection images of a subject reconstructs the projection images to yield a volume reconstruction or generates a CT volume image based on the plurality of projection images. The plurality of projection images comprises at least a first subset and a second subset not included in the first subset, and the reconstructed volume is segmented by assigning a material type to each voxel.

Scatter images corresponding to the first subset are estimated by calculating probabilistic predictions of interactions of x-rays with the subject using a Monte Carlo process. A first threshold and a second threshold are determined for completing the Monte Carlo process, where the first threshold represents a first number of photons and the second threshold represents a second number of photons lower than the first number of photons, and the Monte Carlo process is interrupted when the process reaches the second threshold.

A low pass spatial filter is applied to the estimated scatter images, and a second set of scatter images corresponding to the second subset is estimated based on interpolation from the first set of scatter images. Scatter images from the first set and the second set are subtracted from the corresponding projection images to yield corrected projection images, and an updated CT volume image is generated based on the corrected projection images.

Claims Coverage

The independent claims cover a processor-implemented scatter correction workflow for x-ray projection images with five inventive features. The workflow includes subset-based scatter estimation, Monte Carlo-based scatter estimation with photon-threshold early completion, low-pass filtering of estimated scatter, interpolation-based estimation for a second projection subset, and generation of an updated CT volume image from corrected projection images.

Across the independent claims, scatter correction is achieved by estimating scatter images via Monte Carlo probabilistic interaction predictions with photon-threshold interruption, filtering the estimated scatter with a low pass spatial filter, interpolating scatter for a second projection subset, subtracting the estimated scatter from corresponding projection images to produce corrected projection images, and generating an updated CT volume image from the corrected projection images.

Stated Advantages

Documented Applications