Abstract: A human torso phantom and its construction, wherein the phantom mimics respiratory and cardiac cycles in a human allowing acquisition of medical imaging data under conditions simulating patient cardiac and respiratory motion.

Abstract: A human torso phantom and its construction, wherein the phantom mimics respiratory and cardiac cycles in a human allowing acquisition of medical imaging data under conditions simulating patient cardiac and respiratory motion.

Abstract: A method of constructing a non-uniform attenuation map (460) of a subject for use in image reconstruction of SPECT data is provided. It includes collecting a population of a priori transmission images and storing them in an a priori image memory (400). The transmission images not of the subject. Next, a cross-correlation matrix (410) is generated from the population of transmission images. The eigenvectors (420) of the cross-correlation matrix (410) are calculated. A set of orthonormal basis vectors (430) is generated from the eigenvectors (420). A linear combination of the basis vectors (420) is constructed (440), and coefficients for the basis vectors are determined (450) such that the linear combination thereof defines the non-uniform attenuation map (460).

Abstract: A method for using factor analysis to improve the resolution and remove undesired biological activity from medical device imagery employs a Penalized Least Squares Factor Analysis of Dynamic Structures technique. Non-uniqueness correction is provided, based on minimizing the overlaps between images of different factor coefficient images. This invention finds application in the image processing of the full range of medical imaging devices and systems.

Abstract: A method of modeling 3D first-order scatter, non-uniform attenuation, and 3D system geometric point response in an ML-EM algorithm to reconstruction SPECT data is provided. It includes performing an initial slice-to-slice blurring operation (112) on a volume of estimated emission source data. The volume of estimated emission source data is represented by a 3D array of voxels. A voxel-by-voxel multiplying (114) of the results from the initial slice-to-slice blurring operation (112) by a volume of attenuation coefficients yields a volume of effective scatter source data (116). The volume of effective scatter source data (116) is voxel-by-voxel added (118) to the volume of estimated emission source data to produce a volume of combined estimated emission and scatter source data. Finally, a secondary slice-to-slice blurring operation (120) is performed on the volume of combined estimated emission and scatter source data.

Abstract: A diagnostic imaging system includes a Compton camera (14) disposed on a gantry (16). The camera (14) includes linear detectors (30a, 30b) for detecting radiation emanating from a subject to be imaged. A data processor (32) collects and processes radiation data in accordance with the detected radiation. Position and energy resolving circuitry (34) determines positions and energy deposited by photons striking the detectors. A cone projection generator (40) generates cone projection data or cone integrals based on the collected data which determine a possible location of a gamma source of the detected radiation. A conversion processor (41) converts the cone projection data into plane projection data. The conversion processor (41) includes a line integral processor (42) which determines line integrals representing the cone projection data and applies a spherical harmonic expansion to the line integrals.

Abstract: A SPECT system includes a Compton camera (14) disposed on a gantry (16). The camera (14) includes linear detectors (30a, 30b) operating without mechanical collimation for detecting radiation emanating from a subject to be imaged. A data processor (22) collects and processes radiation data in accordance with the detected radiation. Position and energy resolving circuitry (24) determines positions and energy deposited by photons striking the detectors. A projection generator (34) generates divergent projections or V-projections based on the collected data which determine a possible location of a gamma source of the detected radiation. A conversion processor (36) converts the V-projections into parallel projection data such as a Radon transformation. A reconstruction processor (38) reconstructs an image representation of a region of interest from the subject from the parallel projection data using filtered back projection.

Abstract: A SPECT system includes three gam camera heads (22a), (22b), (22c) which are mounted to a gantry (20) for rotation about a subject (12). The subject is injected with a source of emission radiation, which emission radiation is received by the camera heads. Camera head (22a) has a fan-beam collimator (24a) mounted on a radiation receiving face and generates fan-beam data indicative of the received emission radiation. The camera heads (22b) and (22c) each have a cone-beam collimator (24b), (24c) mounted respectively on their radiation receiving face and generate cone-beam data indicative of the received emission radiation. A transmission radiation source (26) is mounted opposite the camera head (22a) having the fan-beam collimator (24a). The fan-beam detector head (22a) further receives transmission radiation and generates fan-beam transmission radiation indicative thereof. A transmission data reconstruction processor (50) reconstructs the fan-beam transmission data.

Abstract: A subject (12) in an examination region is injected with a radioisotope that emits radiation. A detector head (18) receives emission radiation projections (28a) from the radioisotope and transmission radiation projections (28b) from a transmission radiation source (22) disposed opposite the subject from the detector head. A volume memory (50) stores an estimated volume image. For each actually collected image emission data projection set, a projector (52) reprojects a set of projection of the volume image from the image memory (50) along each of the same projection directions as the emission data projections. Each projection is rotated (80) and warped (82) such that rays which converge with the same angle as the convergence of the collimator on the detector head become parallel. The layers are each convolved with a point response function (84) weighted in accordance with a depth of the corresponding layer in the volume image and corresponding points are summed (92) to create a reprojected projection.

Abstract: A SPECT camera system has three detector heads (12a, 12b, 12c). Each of the detectors have a fan-beam collimator (14) disposed toward an examination region (10). The detectors receive radiation travelling along a fan of rays from an apex (x.sub.f,y.sub.f) to a planar face of the detectors. The detectors generate electronic data indicative of a location (x.sub.s,y.sub.s) on the detector at which a radiation event is received along a ray q.sub..beta. (s). The detectors in a selected orbit R(.beta.) around a subject within the examination region (10). A backprojector (56) includes a backprojection trajectory calculating processor (60) that calculates a trajectory through image space, hence through an image memory (58), corresponding to each radiation ray q.sub..beta. (s). The backprojector weights (68) each data value (x.sub.s,y.sub.s) with a weighting function, preferably a Jacobian J(r,.phi.,.beta.), and adds (64) each weighted data value to a corresponding memory cell of the image memory (58).

Abstract: A SPECT camera (A) includes a plurality of detector heads (12a, 12b, 12c) which rotate around an examination region (10). A reconstruction processor (50) reconstructs output projection data from the detector heads into a three-dimensional image representation which is stored in an image memory (62). Selected data from the image memory (62) is converted to a human-readable display on a video monitor (66). To adjust automatically for detector head misalignment, a calibration phantom (B) which has two orthogonal lines of scintillators (20.sub.1, 20.sub.2, 20.sub.3, 20.sub.4, 20.sub.5) arranged orthogonal to each other with a common scintillator in both lines is positioned in the examination region. As the detector heads rotate around the phantom, a misalignment parameter generator (40) generates the displacement distance of the actual rotation from the theoretical rotation axis (.zeta.

Abstract: Radiation passing through a cone beam collimator is received by a radiation detector (10) such as a gamma camera head, as the gamma camera head is moved in a helical orbit. Data g(n,u,v) collected during the helical orbit is scaled (42) to scaled data G(n,u,v). A first partial derivative .differential.G (n,u,v)/.differential.u is taken (46u) with respect to a horizontal direction and a second partial derivative .differential.G (n,u,v)/.differential.v is taken (46v) with respect to a vertical direction. The partial derivatives are linearly combined (48) by being multiplied by sine and cosine values of an angle .alpha. between the horizontal direction u and an arbitrary direction p in the detector plane to form partial derivatives .differential.G(n,u,v)/.differential.p. The coordinate system of the derivatives is converted (60) from the (n,u,v) coordinate system to an (n,.alpha.,p) coordinate system. The first derivatives are projected (62) i.e.

Abstract: A SPECT system includes three gamma camera heads (22a), (22b), (22c) which are mounted to a gantry (20) for rotation about a subject (12). The subject is injected with a source of emission radiation, which emission radiation is received by the camera heads. Transmission radiation from a transmission radiation source (30) is truncated to pass through a central portion of the subject but not peripheral portions and is received by one of the camera heads (22a) concurrently with the emission data. As the heads and radiation source rotate, the transmitted radiation passes through different parts or none of the peripheral portions at different angular orientations. An ultrasonic range arranger (152) measures an actual periphery of the subject. Attenuation properties of the subject are determined by reconstructing (90") the transmission data using an iterative approximation technique and the measured actual subject periphery.

Abstract: A SPECT system includes three gamma camera heads (22a), (22b), (22c) which are mounted to a gantry (20) for rotation about a subject (12). The subject is injected with a source of emission radiation, which emission radiation is received by the camera heads. A reconstruction processor (112) reconstructs the emission projection data into a distribution of emission radiation sources in the subject. Transmission radiation from a radiation source (30) passes through the subject and is received by one of the camera heads (22a) concurrently with the emission radiation. The transmission radiation data is reconstructed into a three-dimensional CT type image representation of radiation attenuation characteristics of each pixel of the subject. An attenuation correction processor (118) corrects the emission projection data to compensate for attenuation along the path or ray that it traversed. In this manner, an attenuation corrected distribution of emission sources is generated.

Abstract: Radiation passing through a cone-beam collimator is received by a radiation detector, such as a gamma camera head, as the gamma camera head is moved in a circular orbit and in a line orbit. Data collected during the circular orbit is stored (42c), transformed (50c) into the frequency domain and redundant data removed (52c, 52c), and transformed (56c) back to the spatial domain. The data collected during the line orbit is stored (42l). The line orbit data is transformed to the frequency domain and repeatedly filtered with a family of filter functions (52l, 54) to remove redundant data. Each filter function corresponds to a different row through the examination region. The filtered frequency domain slice data sets (62.sub.1, 62.sub.2, . . . , 62.sub.n) are transformed (56l) back to the spatial domain and transferred to a central portion of a spatial domain memory (58l). Empty memory cells of the memory (58l) are filled with zeros.

Abstract: A method and means is presented to estimate the contour of a body to compensate for attenuation in the production of a reconstructed image in fan beam computed tomographic systems having a detector system for taking a plurality of projections of a scanned body at a plurality of angles. The method and means defines a set of variable parameters representing an arbitrary ellipse and projects the arbitrary ellipse into fan beam projection space to determine the expected edges of the arbitrary ellipse at each angle in terms of the variable parameters. A series of fan beam projections is taken having sufficient information for reconstructing a cross-sectional image of the scanned body, and the fan beam coordinates of the apparent body edges in each of the projections are determined.

Abstract: Method and means for determining and compensating for a shift in the center of rotation of a fan beam CT reconstruction apparatus. Known reconstruction algorithms for fan beam computed tomography are based on the assumption that the center of rotation of the source or detector is on the midline of the fan. In certain cases due, for example, to machine inaccuracies, the center of rotation can be shifted from the assumed center, and such shift can cause artifacts in the reconstruction. The present invention provides a procedure for estimating the magnitude of the shift and also accommodates for the shift by applying a series of weighting factors to the projection information which are dependent on the magnitude of the shift. The weighted projections are then processed by the usual convolution operation, and the convolved projection sets back projected using a geometry modified to account for the shift.

Abstract: A method for shimming a magnet in a nuclear magnetic resonance (NMR) system employs measurements of the magnetic field obtained from chemical shift imaging (CSI) of a homogeneous phantom. The data are acquired, in one embodiment, in four planes parallel to, and rotated about, the axis of the magnet. A special volume subset of data are expanded in an orthonormal basis set (associated Legendre polynomials in one embodiment) for N+1 separate experiments, where N is the number of shim coils to be adjusted. The result is an N.times.N matrix of calibration coefficients for the shim coil set and a vector of shim current changes which must be applied to null out the measured field inhomogeneity.

Abstract: Method and means for determining and compensating for a shift in the center of rotation of a fan beam CT reconstruction apparatus. Known reconstruction algorithms for fan beam computed tomography are based on the assumption that the center of rotation of the source or detector is on the midline of the fan. In certain cases due, for example, to machine inaccuracies, the center of rotation can be shifted from the assumed center, and such shift can cause artifacts in the reconstruction. The present invention provides a procedure for estimating the magnitude of the shift and also accommodates for the shift by applying a series of weighting factors to the projection information which are dependent on the magnitude of the shift. The weighted projections are then processed by the usual convolution operation, and the convolved projection sets back projected using a geometry modified to account for the shift.

Abstract: Method and apparatus for quickly and efficiently producing ECT (emission computed tomography) images corrected at least in part for attenuation in which a plurality of stored attenuation coefficients are used directly in the projection and back projection operations which produce the ECT image. The evaluation of attentuation factors as needed during the course of projection and back projection avoids the need for precalculation and storage of attenuation factors, thus achieving the reasonably fast reconstruction times needed for efficient diagnostic imaging.