194 results about "Filtered backprojection" patented technology

A scanning method for scanning samples of biological cells using optical tomography includes preparing, acquiring, reconstructing and viewing three-dimensional images of cell samples. Concentration and enrichment of the cell sample follows. The cell sample is stained. Cells are isolated from the cell sample and purified. A cell/solvent mixture is injected into a gel by centrifugation. A cell/gel mixture is injected into a capillary tube until a cell appears centered in a field of view using a step flow method. An optical imaging system, such as a fixed or variable motion optical tomography system acquires a projection image. The sample is rotated about a tube axis to generate additional projections. Once image acquisition is completed, the acquired shawdowgrams or image projections are corrected for errors. A computer or other equivalent processor is used to compute filtered backprojection information for 3D reconstruction.

We present an iterative method for reducing artifacts in computed tomography (CT) images. First, a filter is applied to the experimental projection data that adaptively expands the detector element size in regions with low photon counts, until the desired number of photons are detected. The initial image is then calculated using an existing reconstruction technique. In each iteration, artifacts and noise in the current image are reduced by using an edge-preserving blur filter. Metal pixels (determined from the initial image) are replaced with smaller values. The resulting image is forward projected. Rays that go through metal are replaced with the forward projected values. Rays that do not pass near metal are kept at the experimental values. Filtered backprojection is then performed on the new projection data to determine the updated image. Finally, after the last iteration, metal pixels are copied from the initial image.

A method of obtaining a computed tomography image of an object includes determining linear terms and non-linear beam hardening terms in a pair of line integral equations for dual-energy projection data from inserting average and difference from average attenuation terms, obtaining an initial solution of the line integral equation by setting the non-linear beam hardening terms to zero, and iteratively solving the line integral equations to obtain one line integral equations for each basis material. Attenuation by the first basis material corresponds to a photoelectric attenuation process, and attenuation by the second basis material corresponds to a Compton attenuation process. The line integral equations can be inverted by an inverse Radon procedure such as filtered backprojection to give images of each basis material. The images of each basis material can then be optionally combined to give monochromatic images, density and effective atomic number images, or photoelectric and Compton processes images.

Provided herein are methods of reconstructing an image from projection data provided by a tomography scanner that is based on geometric optics comprising scanning an object in a cone-beam imaging geometry following a non-standard spiral path or a general piecewise smooth scanning path wherein projection data is generated and reconstructing an image according to a closed-form formula that is either in the filtered backprojection (FBP) or backprojection filtration (or backprojected filtration, BPF) formats. Also provided herein are associated systems and apparatuses for tomographic imaging.

Systems, methods and apparatus are provided through which a specialized back-projection process reconstructs a finely detailed and crisp three-dimensional image (3-D ) from a series of two-dimensional (2-D) images by pre-filtering the 2-D images with a first group of settings before back-projecting the 2-D images into a 3-D image, and then post-filtering the 3-D image with another group of settings. In some embodiments, the first group of settings and the second group of settings are synergistically optimized in relation to each other to provide emphasis on a structure of interest in the object.

A system and method for image reconstruction is disclosed. The method divides iterative image reconstruction into two stages, in the image and Radon space, respectively. In the first stage, filtered back projection and adaptive filtering in the image space are combined to generate a refined reconstructed image of a sinogram residue. This reconstructed image represents an update direction in the image space. In the second stage, the update direction is transformed to the Radon space, and a step size is determined to minimize a difference between the sinogram residue and a Radon transform of the refined reconstructed image of the sinogram residue in the Radon space. These stages are repeated iteratively until the solution converges.

A tomographic image reconstruction method produces either 2D or 3D images from fan beam or cone beam projection data by filtering the backprojection image of differentiated projection data. The reconstruction is mathematically exact if sufficient projection data is acquired. A cone beam embodiment and both a symmetric and asymmetric fan beam embodiment are described.

The invention discloses a CT image iteration reconstruction method based on compressed sensing and particularly relates to a CT image reconstruction method for carrying out minimization algebra iteration (algebraic reconstruction technique, ART) of the total variation (TV) in a wavelet domain. The method mainly comprises the steps that (1) imaging parameters of a CT system and projection data collected by a scanning system are obtained; (2) the projection data are initialized, and namely, Wiener filtering noise reduction processing and wavelet sparsity conversion are carried out on the projection data; (3) algebra iteration reconstruction is carried out on the initialized projection data on the basis of minimization of the image total variation (TV), and whether the iteration result meets a convergence condition is judged, if not, the iteration reconstruction image data are used as initial values, and iteration continues to be carried out; if yes, reconstructed images are used as final output images. Compared with the traditional filtering back projection and algebra iteration CT image reconstruction technology, the method finishes reconstructing the images with the fewer projection data, the speed for reconstructing the images can be increased, the radiation dose is reduced, and the image reconstruction quality can be improved.

An image is reconstructed based upon a filtered backprojection (FBP) technique using a reconstruction filter which is customized or shaped by parameters including a weight value that is determined for weighing projection data according to a predetermined noise model. The weight value is determined based upon rays or views in the projection data. A regularization term is also combined with the noise-weighted FBP.

Provided is a pipeline flow-velocity imaging and flow measuring method based on ultrasonic. Ultrasonic probes composed of three piezoelectricity units are processed and used for sending and receiving ultrasonic signals. The ultrasonic probes are respectively arranged on two oblique sections which form 45 degrees with the pipeline axis, measure flight time of fair-current and adverse-current transmission of the ultrasonic on each sound track and calculate average flow velocity of pipeline fluid on each sound track. Uniformly-spaced interpolation is performed to each group of sound tracks, the average flow velocity on each sound track after interpolation is obtained, the flow velocity distribution profile is rebuilt from average flow velocity data on the basis of a filtering back projectionmethod of parallel beam projection, flow velocity points are selected at a uniformly-spaced mode on the basis of a flow velocity distribution profile map obtained by rebuilding, and the flow velocityof each point is simply averaged and then multiplied with the sectional area of the pipeline so that pipeline flow values are obtained. The pipeline flow-velocity imaging and flow measuring method based on the ultrasonic can monitor distribution of flow field in the pipeline under complex flow state and reduces model errors of an ultrasonic flowmeter, and the accurate flow values are obtained finally.

A method for obtaining a reconstruction of a tomographic dataset by filtering and combining the projection images, followed by a backprojection step. In one embodiment, the method can yield a reconstruction equivalent to an additive ART reconstruction, while in another embodiment the method represents a filtered back-projection type reconstruction. The computations do not require an iterative backprojection/re-projection step.

An augmented lagrangian iterative reconstruction method of an X-ray image and a CI image is characterized by comprising the following steps: (1) acquiring system parameters and projecting data under a low dose scanning protocol of CI equipment; (2) carrying out one-by-one data point variance estimation on the projecting data in the step (1), and conducting filtered back projection on the projected data in the step (1) to obtain an initial pattern; (3) taking the initial pattern obtained from the step (2) as an iterative initial pattern to be subjected to iterative reconstruction, and obtaining the final reconstruction pattern through loop iteration according to the iterative formula. The invention provides an algorithm for optimizing the iterative formula. The method has the advantages of wide application range, less iterative times, and high imaging quality.

In the present invention, the fast high-resolution image reconstruction of PET projection data is realized by introducing the organic combination of super-laxation speeding factor and variable background constraint, the reconstruction speed and spatial resolution are superior to available ordered subset expectation maximum (OSEM) process, and the antijamming capacity is superior to traditional filtering back projection (FBP) process. The present invention is the improvement of OSEM, and said algorithm combines several kinds of data processing technology in the reconstruction of the heat source image to obtain reconstructed image with high spatial resolution and low noise.

The invention relates to the technical field of X-ray CT imaging testing, which discloses a CT imaging method using a tilted multi-cone-beam linear track. The imaging method comprises the steps of: projection acquisition, wave filtering and back-projection reconstruction, wherein during the projection acquisition, a detector receives rays from a ray source so as to obtain the sequence of digital ray projective images; during the wave filtering, specified filter function and ray projection are subjected to convolution operation to obtain the data of the filtered projection; and during back-projection reconstruction, the weighted back-projection reconstruction of the data of the filtered projection is conducted according to the system parameters. In the method of the invention, a scanning mode using the tilted multi-cone-beam linear track is adopted, multiple cone beams are aslant installed in different places, an object to be tested passes through all the cone beams in linear motion, the detector collects the rays which pass through the object in different directions, and thus the scanning process is simple, and the scanning rate is high; because of the back-projection reconstruction method, the reconstruction rate is high, and the problems of low detecting rate and large object volume are solved.

General scheme processes and systems for constructing algorithms for reconstructing images of objects that have been scanned in a spiral or non-spiral fashions with detectors. Application of the scheme requires finding of a weight function, which would lead to the required reconstruction algorithm. This general scheme can use a C-arm scan with the closed x-ray source trajectory and gives a new, theoretically exact and efficient (i.e., with the convolution-based FBP structure) reconstruction algorithm. The invention can also utilize the algorithms disclosed in an earlier application U.S. application Ser. No. 10/143,160 filed May 10, 2002, entitled: Exact Filtered Back Projection (FBP) Algorithm For Spiral Computer Tomography, which claims the benefit of U.S. Provisional Application No. 60/312,827 filed Aug. 16, 2001, also fit into the general scheme.

The invention relates to a three-dimensional digital imaging method of the large view field cone-beam X-ray tilting scanning of a biased detector, belonging to the technical field of X-ray computerized tomography (CT). In the three-dimensional digital imaging method, the area array detector is placed to be biased, and an X-ray source is used for generating cone-beam X-rays which irradiate a member imaging area with a certain angle in a penetrating and tilting way relative to the length and width surface of a member; in the scanning process, the X-ray source and the area array detector are static, the member rotates in an angle of 360 degrees in an equal angle and step length way surrounding a rotating shaft, and the area array detector acquires an X-ray signal modulated by the member under each rotation angle. A three-dimensional computerized tomography image of a scanning area can be reestablished and obtained by a data truncation smoothing preprocessing method and a filtering back projection reestablishing arithmetic according to data obtained by the area array detector under the scanning angle of 360 degrees. Compared with the traditional tilting scanning method, the three-dimensional digital imaging method can double the tilting scanning imaging view field without changing the system hardware and the scanning speed and has high reestablishment quality, simple process and high efficiency.

A method for obtaining a 3D image dataset of an object of interest is proposed. A plurality of 2D X-ray images are captured and a 3D reconstruction is carried out using filtered back projection. The projection parameters have been measured with the aid of a calibrating phantom, possibly using an interpolation or extrapolation of such measurements. A model of effect strings of the components in an X-ray imaging device is obtained, and the model parameters are identified based on imaging of a calibrating phantom. A projection matrix can then be calculated for any positions on any desired trajectories, without having to use imaging of a calibrating phantom at precisely that position and desired trajectory.

In a tomographical image reconstruction method and apparatus to generate an image of an examination subject from a number of digital projection data acquired at different projection angles, a first analytical filter kernel (formed by a first analytical function) is determined for a filtered back projection in the spatial frequency range, this first analytical filter kernel approximating, at least in a range of the spatial frequency, a discrete filter kernel iteratively determined for a model. Back projection is implemented with a second analytical filter kernel calculated from the analytical filter kernel and formed by a second analytical function.