Abstract: A system for X-ray geometry calibration comprises a calibration frame adapted for mounting proximate to at least a portion of a patient's body, such as a patient's head. An X-ray source cooperates with a target at a given orientation and distance from the portion of a patient's body for forming an image of the portion of a patient's body and of at least an associated portion of the calibration frame. The calibration frame includes encoding arrangement for uniquely determining correspondence between the image of the associated portion of the calibration frame and the calibration frame such that the orientation and distance can be determined uniquely from the image of the associated portion of the calibration frame.

Abstract: An x-ray or gamma ray image that is produced as an array of pixels is treated for reduction or elimination of white spot noise. Two or more successive images in registry are produced and the pixel values at each pixel location are inspected for the respective images. The pixel values are considered according to rank, e.g. from dark to bright, and the lowest ranking pixel value is selected for each pixel location. This creates an output image that is substantially free of the spot noise that results from direct impingement of the x-ray photons on the imaging device. This technique is especially useful in portal imaging for radiation therapy, dental imaging, or industrial imaging.

Abstract: The present invention, in one form, is a system for reducing noise artifacts in three-dimensional image reconstruction using data acquired in a helical scan. More specifically, a standard deviation ratio of reconstructed images with and without helical weighting is identified. Such standard deviation ratio is then used to generate filter coefficients, which are then applied to the data in an adaptive smoothing algorithm.

Abstract: The invention relates to an examination method whereby a respective spectrum with a number of spectral values is measured for a number of locations. Collective evaluation of the old spectra is enabled by the following steps:a) formation of a data matrix from the spectral vectors formed by the series of spectral values of a respective spectrum, the spectral vectors being arranged in the columns (or in the rows) of the data matrix in a location-dependent manner,b) singular value decomposition of the data matrix in order to obtain three matrices whose product corresponds to the data matrix, the first (third) matrix consisting of spectrally dependent vectors, whereas the second matrix is a diagonal matrix and the third (first) matrix consists of location-dependent vectors,c) evaluation of at least one of the three matrices.

Abstract: The Invention provides practical apparatus and methods for significant improvements to conventional radiography practice. It can image objects having negligible x-ray absorption contrast e.g. otherwise x-ray transparent low-Z artifacts such as human soft-tissue, by obtaining edge-enhanced contrast from an object's (BDY) x-ray refractive-index gradients. In mammography, the contrast of small micro-calcifications is increased typically 4-fold, or more. It can be "tuned" to obtain element-selective refractive-index enhanced contrast to resonantly image minute quantities of a specific element with Z.apprxeq.35-56 and only that element. With only a single brief x-ray exposure it can produce two independent images, e.g. of the object's x-ray absorption and refractive-index distributions. It virtually eliminates the blurring and contrast reducing effects of x-ray scatter, especially of very small-angle scatter.

Abstract: The present invention, in one form, is a method for detecting a partial volume artifact in scan data acquired during a tomographic scan. In accordance with one embodiment of the algorithm, an object of interest is scanned to generate scan data. Sampling pairs of the scan data are identified and used to generate an inconsistency map. The inconsistency map is weighted and filtered to generate a partial volume signature which identifies partial volume artifacts.

Abstract: An x-ray fluorographic system produces frame images at a low dose rate for both on-line and off-line use. Background noise is filtered by first producing a mask which defines the boundaries of the structural features of interest. The mask is used to select the background pixels for filtering, while enabling the structural pixels to pass unfiltered to the display.

Abstract: A scanning and data acquisition method and apparatus for three-dimensional computerized tomographic imaging of a region of interest (ROI) of an object which is smaller than the object itself and having upper and lower boundaries which are completely within a field of view of an imaging system comprises merely a continuation of the scan trajectory used for scanning the main portion of the ROI so as to extend past its upper and lower boundaries. In a preferred embodiment, the scan path of the present invention consists of a main spiral scan path comprising a plurality of spiral turns, or stages, for scanning between upper and lower boundaries of the ROI, and at least a portion of an extra single spiral turn of the scan path at each end thereof.

Abstract: An X-ray exposure apparatus has an X-ray exposure system that rotates during an image exposure wherein sharp images are generated despite the motion employs a digital filtering of the image information ensues taking the exposure time and the motion of the X-ray exposure system into consideration, thereby eliminating motion artifacts.

Abstract: An arithmetic unit for a computed tomography apparatus has special hardware in the form of a processor, a median filter ASIC, an angle clipping ASIC and two memories are employed. In the median filter ASIC, for each pixel a determination of increments for generating a supporting point address are made by the processor, the access addresses are calculated and the supporting points are addressed from a first of the memories and a median value formation is undertaken in the median filter ASIC, followed by a difference image production in the median filter ASIC. In the angle clipping ASIC, a determination is made of the coordinates of each pixel with reference to a rotational center in the processor, and supporting points are generated and accumulated from the difference image resulting from the median filtering, and a resultant image is generated in the angle clipping ASIC.

Abstract: An x-ray or neutron optic configuration includes a plurality of single crystal portions (25) formed with respective spaced x-ray or neutron reflection faces (21,22,23) formed at predetermined asymmetry angles to a Bragg diffraction plane in the respective crystal portion. The crystal portions are interconnected (25) to maintain a first and second (21,22) of these faces spaced apart for receipt of a sample (8) between them and to allow small adjustments of the relative angle of the faces about the normal to the plane of diffraction while maintaining the normals to the Bragg planes for the first and second faces (21,22) substantially in the plane of diffraction. First face (21) is arranged to be a monochromator and collimator with respect to x-rays or neutrons of appropriate wavelength incident reflected through the sample for receipt by the second face (22), which thereby serves as an analyzer face.

Abstract: A nutating slice CT image reconstruction apparatus and method generates a set of projection data using helical cone-beam scanning. The three-dimensional projection data is used to reconstruct a series of planar image slices. The slices are selected such that they define a tilt angle and a rotation angle with respect to the longitudinal axes of the object being scanned. Successive slices have equal tilt angles but changing rotation angles such that normal axes of successive slices define a nutation and precession about the longitudinal axis of the object. Projection data for the tilted slices are formed of selected one-dimensional fan-beam data. As such, the projection data can be applied to conventional two-dimensional reconstruction approaches to generate an image.

Abstract: An apparatus and method is provided for coordinating two fluoroscope images, which permits accurate computer-based planning of the insertion point and angle of approach of a needle, drill, screw, nail, wire or other surgical instrumentation into the body of a patient, and subsequently guides the surgeon in performing the insertion in accordance with the plan.

Abstract: In an approximative image reconstruction method for a computed tomography apparatus with a multi-row detector in spiral operation, a reinterpolation from fan data to parallel data (rebinning) is first carried out independently for all rows of the detector. With the parallel data, an image is reconstructed by having each beam contribute to the image with a weight that depends on the respective distance of the beam to the image plane. Each beam thereby receives a weight that, in general, changes along the beam. By approximating these weighting functions by a short Fourier series, an efficient Fourier reconstruction results.

Abstract: A multiple angle tomographic system includes a rotating gantry with a source, e.g., an x-ray source, and detector array combination mounted thereon so as to acquire a plurality of projections of objects passing through the gantry. A pre-screen subsystem utilizes a subset of the projections from those that can be acquired during a full scan so as to define a first plurality of projections--e.g., eight projections--that are sufficient analyze whether there is a likelihood that a targeted object, e.g., a firearm and/or plastic explosives is present. If there is a likelihood that a targeted object is present, a full-image CT reconstruction is commanded, automatically or manually, so as to verify and more fully assess the detected object. This combination of pre-screen and selective full-image CT reconstruction provides thorough inspection of closed containers, e.g., passenger luggage, by providing multiple angle and perspective viewing of targeted objects.

Abstract: A high-energy photon imaging system including an imaging head, a signal processor, a data acquisition system and an image processing computer. The imaging head includes a detector comprising a plurality of closely-packed detection modules. Each detection module comprises a plurality of detection elements mounted to a circuit carrier. The detection elements produce electrical pulses having amplitudes indicative of the magnitude of radiation absorbed by the detection elements. The circuit carrier includes channels for conditioning and processing the signals generated by corresponding detection elements and for preparing the processed signals for further processing by a signal processor. Each conditioning and processing channel stores the amplitudes of the detection element electrical pulses exceeding a predetermined threshold. The detection modules employ a fall-through circuit which automatically finds only those detection elements that have a stored pulse amplitude exceeding the threshold.

Abstract: X-ray images such as radiotherapy portal images and simulation images are matched by apparatus which digitizes the images and automatically processes the digitized signals to generate matched digitized signals which can be displayed for comparison. The digitized images are first coarse aligned using a transform generated from seed points selected interactively from the two images or through detection and identification of x-ray opaque fiducials placed on the patient. A fine alignment is then performed by first selecting intersecting regions of the two images and enhancing those regions. Secondly, an updated transform is generated using robust motion flow in these regions at successive ascending levels of resolution. The updated transform is then used to align the images which are displayed for comparison. The updated transform can also be used to control the radiotherapy equipment.

Abstract: A novel x-ray image receptor holder physically links to the collimated tube of a lightweight, portable and preferably hand-held X-ray generator for use in intraoral and other X-ray applications. The image receptor holder has a horizontal member with a vertical member attached to the distal end of the horizontal member. The image receptor is held between the vertical member and a sliding member which is also mounted on the horizontal member.

Abstract: In a computed tomography apparatus with a volume reconstruction by a three-dimensional gridding algorithm an arithmetic unit and method for operating same are provided for efficiently implementing the three-dimensional gridding algorithm. In this arithmetic unit and method, randomly-distributed supporting points SP are weighted in the frequency space in order to be able to apply a 3D gridding algorithm for a three-dimensional Fourier reconstruction for a computed tomography apparatus. An ASIC is provided wherein the supporting point weighting and the 3D gridding algorithm are efficiently implemented.

Abstract: An improved computerized tomography method and an apparatus for performing the method are used for construction of visual images of a subject utilizing a Radon transform inversion scheme of lower computational complexity. A multiscale backprojection with a postprocessing step is utilized instead of a conventional backprojection algorithm or direct Fourier method to obtain improved images. Multilevel methods can be applied under weaker regularity requirements than Fourier methods, so the present algorithm can be adjusted to provide different resolutions for different parts of the reconstruction, whether or not the Radon data are equally spaced.