Pme IP Australia Pty Ltd

Mercury Computer Systems, Inc.

Scott A Thieret

Ari Peter Berman

Joseph Goddard

Malte Westerhoff

Detlev Stalling

Valeri Kotlov

In one aspect, the invention provides improvements in a digital data processor of the type that renders a three-dimensional (3D) volume image data into a two-dimensional (2D) image suitable for display. The improvements include a graphics processing unit (GPU) that comprises a plurality of programmable vertex shaders that are coupled to a plurality of programmable pixel shaders, where one or more of the vertex and pixel shaders are adapted to determine intensities of a plurality of pixels in the 2D image as an iterative function of intensities of sample points in the 3D image through which a plurality viewing rays associated with those pixels are passed. The pixel shaders compute, for each ray, multiple iteration steps of the iterative function prior to computing respective steps for a subsequent ray.

Method and apparatus for visualizing three-dimensional and higher-dimensional image data sets

The invention provides in one aspect methods and apparatus for use with C-arm and other CT systems, e.g., with non-rigid geometries. In such systems, by way of example, calibration can be performed to determine the exact position of the x-ray source and the exact orientation of the detector where each projection measurement is made. Next, a weighting coefficient can be determined for the voxels in each plane of a reconstruction volume at every possible projection. Finally, the order in which to process the voxels during image reconstruction can be determined. Following an actual CT scan procedure in which scans are obtained of a volume to be constructed, a system according to these and related aspects of the invention can use an optimal, pre-calculated processing method, while utilizing offsets and weighting coefficients determined during calibration, for performing backprojection image reconstruction.

Method of reconstructing computed tomography (CT) volumes suitable for execution on commodity central processing units (CPUS) and graphics processors, and apparatus operating in accord with those methods (rotational X-ray on GPUs)

Method of reconstructing computed tomography (CT) volumes suitable for execution on commodity central processing units (CPUs) and graphics processors, and apparatus operating in accord with those methods (rotational X-ray on GPUs)

The invention provides, in some aspects, methods and apparatus for signal and/or image processing which perform convolution-based filtering utilizing a graphics processing unit (GPU, also called 'graphics card') to compute multiple output pixels at once. This has the advantage of saving memory bandwidth, while leveraging the GPUs vector multiplication and dot product units during the calculation. Related aspects of the invention provide such methods and apparatus in which multiple output pixels are computed simultaneously by using render targets with more than one channel, e.g., an RGBA render target, or multiple render targets, or a combination thereof. By way of non-limiting example, methods and apparatus according to the invention implement convolution on a GPU by executing the steps of defining input image I(x,y) as input texture of size N&#xd7;N; defining an RGBA render target (output) of size N/4&#xd7;N; and, for each RGBA output pixel aggregating o(x,y) by (i) reading all input pixels I(x*4+i,y), with i=&#x2212;4,0,4, and computing o(x,y) for the all four components of the output tuple.

Method and apparatus for digital image filtering with discrete filter kernels using graphics hardware

The invention provides improvements in reconstructive imaging of the type in which a volume is reconstructed from a series of measured projection images (or other two-dimensional representations) generated by projection of a point x-ray source (or other radiation source), positioned at a distinct focus, through the volume to a plane at which the respective projection image is acquired ('detector plane'). In one aspect, the improvements are with respect to back-projecting a two-dimensional representation lying in the detector plane (representing, for example, a difference between an originally-acquired measured projection image and a subsequently-generated estimate thereof) to generate three-dimensional representation (which can be used, for example, to update an estimate of the volume). According to this aspect, for each of one or more slices of the 3D representation parallel to the projection plane and for each distinct focus at which a projection is generated, the following steps are performed in connection with the back-projection: (i) warping the first 2D representation to generate a second 2D representation by applying to the first 2D representation a selected linear mapping, where that selected linear mapping would map, in order to match dimensions of the respective slice within the 3D representation, a region defined by projection, at the respective focus, of corners of that slice onto the detector plane, and (ii) incrementing values of each of one or more voxels of the respective slice by an amount that is a function of a value of a correspondingly indexed pixel of the second 2D representation. A related aspect provides improvements with respect to forward-projecting, as well as in iterative (and non-iterative) methodologies that incorporate both back-projection and forward-projection.

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Nashua, NH, United States of America

Scott A Thieret