X-ray detectors (24) of a CT scanner (10) generate data values which are preprocessed and assembled (26) into binary data lines. The binary data lines are convolved by a convolver (30) which convolves a plurality of data lines concurrently. A backprojector (32) includes a parametric cubic spline preinterpolator (40) which performs a high order interpolation on the convolved data lines and a linear interpolator (42) which performs a linear interpolation on the high order preinterpolated data lines. The interpolated data lines are backprojected into an image memory (34). Data from the image memory (34) is converted (36) to appropriate format for display on a video monitor (38). The parametric cubic spline preinterpolator (40) includes a first adder (52) which adds most adjacent data lines and a second adder (54) which adds next most adjacent data lines. A first barrel shifter (58) shifts the binary sum of the most adjacent data lines by 1-N spaces, where N is an integer, 4 in the preferred embodiment. The shifting is done in a direction which effectively multiplies the data by 2.sup.N-1. The difference between the sum of the adjacent and next most adjacent data lines is determined (56) and the difference is added (60) to the output of the first barrel shifter. A second barrel shifter (62) shifts the output of the third adder by N bits in the opposite direction, effectively dividing by 2.sup.N to create a higher order interpolated data line between each received convolved data line.
The present invention comprises a system and method for producing images of an object utilizing an x-ray computed tomography (CT) system. Detector elements within the CT system provide raw projection data representing the attenuated x-rays. A data corrector modifies the raw projection data to account for errors to produce corrected projection data. A high order interpolator operates on the corrected projection data to provide estimated projection data at the exact spatial position of the desired image. The high order interpolator utilizes a cubic spline function to determine the estimated projection data. The estimated projection data are used by an image reconstructor to perform high speed image reconstruction.
A method of diagnostic image reconstruction from projection data is provided. It includes generating projection data followed by a convolution of the same. The convolved projection data is then scaled into unsigned, fixed precision words of a predetermined number of bits. The words are then split into a predetermined number of color channels corresponding to color channels of a multi-color rendering engine (150). Simultaneously and independently, the split words are backprojected along each of the color channels to obtain backprojected views for each color channel. The backprojected views for each color channel are accumulated to produce separate color images corresponding to each color channel. Finally, the separate color images are recombined to produce an output image. In a preferred embodiment, prior to the convolution of the projection data, a rebinning operation is performed to ensure that the projection data is in a parallel format. In addition, after convolving the projection data, a selective pre-interpolating step of linear or higher order is optionally performed on the projection data.
A computed tomography method and system where a voxel of a subject irradiated with x-rays is divided into an plurality of sub-voxels, and backprojection data is obtained for the sub-voxels. Projection data for the sub-voxels can be weighted before backprojecting, or the projection data can be backprojected and then weighted. With the method according to the invention, instead of backprojecting data on a straight line passing through the center of a voxel, the beam passing through the entire voxel is backprojected. Also, the method and system weights the sub-voxels using a space-variant function. The weighting can be applied to discrete sub-voxels or integration can be used with infinitely thin sub-voxels. The present invention is a more accurate method and can take into account of spreading of the x-ray beam.
A temperature sensor which can achieve accurate temperature measurement in a magnetic field and accurate temperature measurement over a broader temperature range and, further, provides a temperature sensor which, in the correction of a temperature characteristic on a resistance value of the present temperature sensor, can reduce, to a minimal possible extent, an error between a value found from an approximation equation and a measured value, includes a cylindrical type sensor including a temperature-sensitive device having a micro-crystalline semiconductor thin film formed over an insulating substrate and four electrodes connected to the thin film, a cylindrical container made of a nonmagnetic metal and holding the temperature-sensitive device, together with a helium gas, hermetically sealed therein and four conductors hermetically mounted at the bottom of the container and connected to the corresponding electrodes of the temperature-sensitive device, with the micro-crystalline semiconductor thin film 2 being formed of an n-type silicon germanium and having a silicon composition ratio exceeding 50% but less than 100% and a conductivity of 0.1 to 50 S/cm.
A method for converting a specified color value from a first color space to a second color space identifies the specified color value in the first color space. A converted color space value is received from a final lookup table. The converted color space value is previously determined as a function of the specified color value and a mid-point interpolation and represents the specified color in the second color space. The converted color space value is stored in a memory device.
