Abstract: A method and apparatus are disclosed for predicting prior to injection an organ specific contrast enhancement in a patient for a preselected contrast injection protocol for pre-determining a computed tomography scan. The invention is preferably implemented in a computer program which creates a mathematical model of human cardiovascular physiology in a hypothetical patient with a specific body habitus subjected to the pre-selected contrast injection protocol. The predicted contrast enhancement is then displayed for operator approval and may be then used to control a CT scanner or contrast injector system, to perform the injection and scan with the pre-selected injection protocol and scan parameters. The mathematical model includes models of organs and vessels using differential equations to describe mass transport of contrast agent through the cardiovascular system.

Abstract: The object's transmission function is expressed as a finite power expansion of a reference-material reference thickness, each expansion power being equal to a ratio of a reference-material thickness to the reference thickness; the expansion coefficients are determined from the measurements of the intensities transmitted by the selected various thicknesses, including zero thickness, of the reference material exposed to a test beam evincing consecutively several energy spectra and from the measurements of the intensity transmitted by the object exposed to this same variable-spectrum test beam; the attenuation function is derived from the determination of the transmission function.

Abstract: A high speed, digitally based, signal processing system which accepts input data from a detector-preamplifier and produces a spectral analysis of the x-rays illuminating the detector. The system achieves high throughputs at low cost by dividing the required digital processing steps between a "hardwired" processor implemented in combinatorial digital logic, which detects the presence of the x-ray signals in the digitized data stream and extracts filtered estimates of their amplitudes, and a programmable digital signal processing computer, which refines the filtered amplitude estimates and bins them to produce the desired spectral analysis. One set of algorithms allow this hybrid system to match the resolution of analog systems while operating at much higher data rates. A second set of algorithms implemented in the processor allow the system to be self calibrating as well. The same processor also handles the interface to an external control computer.

Abstract: The disclosed streak suppression filter is for use with a Computed Tomography (CT) system. The CT system generates a plurality of projection data signals each of which is representative of the density of a portion of an object. The streak suppression filter includes a spatial filter for receiving the projection data signals and for generating therefrom a low frequency signal and a high frequency signal. The streak suppression filter further includes a non-linear filter for generating a filtered signal from the high frequency signal. The streak suppression filter further includes a device for combining the low frequency and filtered signals to generate a streak corrected signal. The streak suppression filter may form the low frequency signal by low pass filtering the raw density signals and may form the high frequency signal by subtracting the low frequency signal from the corresponding raw density signal.

Abstract: A system and method for evaluating a geological formation is described which compares actual wireline log measurements from a number of wireline logging tools to predicted tool response logs. The system and method uses a forward model of each tool response, given a formation description, to predict a set of wireline logs. Comparing the predicted logs with the actual measured logs yields a mismatch error. The system and method iteratively adjusts the formation description to minimize the mismatch error to obtain a "best" formation description. In one form, the formation description includes petrophysical properties (porosity, density, saturation) and geometry properties (dip, bedding, invasion). In a more complicated form, the formation description also includes a model of petrophysical mixing laws and formation material content. In the special case of a horizontally layered formation and linear tool response models, there exists a computationally efficient version of the system and method.

Abstract: A method for aligning a patient for radiation treatment based on an earlier tomographic scan of the patient uses projection images used to reconstruct a tomographic image rather than reconstructed images and compares the projection images directly to projection images taken at the time of the radiation therapy to determine a series of offsets of the patient which may be used to characterize and correct for motion of the patient between the initial tomographic scan, used for treatment planning, and one or a series of subsequent radiation treatment sessions.

Abstract: The disclosed motion artifact filter generates motion corrected signals from projection data signals to compensate for motion artifacts in CT images. Each measurement of the projection data signals is representative of the density of all the mass occupying a volume between an X-ray source and a detector at a particular projection angle. The motion artifact filter includes a high pass filter for generating high frequency signals representative of patient movement. Each measurement of the high frequency signals is generated by combining groups of measurements of the projection data signals corresponding to volumes that are proximal to each other. Each measurement of the motion corrected signals is generated by subtracting a portion of a measurement of a high frequency signal from its associated measurement of a projection data signal. The portions increase as the projection angle approaches a starting angle and the portions decrease as the projection angle approaches an intermediate angle.

Abstract: This invention provides a method for infrared and near-infrared estimations of properties of materials with improved model stability against random and pseudo-random effects and improved assessment of the appropriateness of the model for an unknown sample. Statistical tests are defined for quantifying the model's stability against random effects (B-statistic) and the probability of substantial interpolation error (I-statistic). The method of this invention involves building many different infrared models for each property of interest, either randomly or by other strategies. The models with the lowest calibration errors for their respective calibration sets whose errors are least correlated to one another are averaged to create a composite model. Such composite models have improved stability and accuracy. The consistency with which the individual models (making up the composite model) estimate the same property value for an unknown sample is a measure of the improbability of substantial interpolation error.

Abstract: In a CT scanning system having an x-ray source, a plurality of x-ray detector modules, and a plurality of anti-scatter plate modules, signal instability and the associated introduction of artifacts into the reconstructed images are prevented by an alignment assembly which permits the anti-scatter plates to be substantially aligned with regions of substantially constant maximum sensitivity of corresponding detectors. Shadows cast by the anti-scatter plates fall entirely within these regions of substantially constant maximum sensitivity to radiation, thereby minimizing signal modulation due to thermal effects or relative movement of the source, the detectors and the anti-scatter plates between scans.

Abstract: This invention provides methods and apparatus for determining the presence or absence of a specific constituent in a mixture. The method includes the steps of (a) applying energy to the mixture to cause constituents in the mixture to produce characteristic patterns of spectral lines and detecting quantity values at the spectral lines, wherein a quantity value may represent a contribution of two or more constituents; (b) comparing detected quantity values for a number N of spectral lines from a pattern of spectral lines characteristic of the specific constituent with known quantity values for the N spectral lines; (c) determining whether the detected quantity values for the N spectral lines fall within a predetermined error range, and; (d) determining the presence of the constituent in the mixture when detected quantity values of a number of spectral lines less than N fall within the predetermined error range.

Abstract: A system and method of determining porosity and water saturation of a formation surrounding a wellbore is disclosed. Well logs are taken to obtain near and far thermal and epithermal neutron log measurements, and to obtain pulsed neutron capture log measurements, at varying depths along the borehole, with the results stored in a computer memory. The computer is then operated, using an assumed porosity value, to calculate the matrix diffusion length according to two independent methods. If the two matrix diffusion lengths do not closely match, the assumed porosity value is adjusted, and the method repeated. Upon convergence of the matrix diffusion lengths, the adjusted assumed porosity value is used to determine the water saturation of the formation. A set of three equations in three unknowns is solved, where the three equations are indicative of the pulsed neutron capture cross-section, and also the near and far thermal neutron absorption.

Abstract: A method and apparatus to facilitate avoiding failure of a computed tomography x-ray source while performing a patient scan permits detection of the onset of a potential x-ray source failure and estimation of the x-ray source life expectancy. The information obtained can be used in deciding whether to repair or replace an x-ray source prior to failure. In one embodiment, signals I(x,y) representative of the x-ray beam optical focal spot detected by a detector array are sampled, and a wavelet transform is applied to the sampled signals I(x,y) to generate at least one energy level F.sub.new for a wavelet band. The energy level P.sub.new is compared with stored energy levels P.sub.stored to identify one of the energy levels P.sub.stored which, when subtracted from energy level P.sub.new, results in a statistically non-significant value. The remaining life of the x-ray source is estimated as being equal to the life expectancy value corresponding to the identified energy level P.sub.stored.

Abstract: In step s1, X-ray imaging is performed, and an image signal linear to the intensity of X-rays is stored in an image memory 7. Next, in step s2, the maximum from among image data is detected, and the maximum is set as reference value N0. In step s3, image data N is logarithmically converted in accordance with the following equation (a), and the converted data is stored in an image memory 7.d=.beta..multidot.log(N0/N) . . . (a)where d is image data after correction and has a logarithmic relationship to the X-ray intensity, and .beta. is a constant. Then, the image data logarithmically converted for density correction is displayed by a display unit 6 in step 4.

Abstract: Radiation indicative of an object being imaged is detected and a data set indicative of the detected radiation is generated. Negative cells within the data set are located and ordered for processing. A negative cell is selected for processing. A mask region is defined in relation to the selected cell, and positive cells within the mask region are identified. A correction factor is determined, the value of the positive cells is adjusted accordingly. The value of the selected cell is also adjusted so that the count value of the data set remains constant. If the value of the selected cell is still negative, new correction factors are determined and the values of the positive cells and the selected cell are again adjusted. The process is repeated until all of the negative cells within the data set have been processed. An image indicative of the object is then generated.

Abstract: A method for reconstructing an image in a computed tomography system performing a cone beam helical scan is described. In accordance with one embodiment, a point is selected for which image data is to be generated and a ray pair is identified wherein each ray passes through the selected point. Further, each ray in the ray pair is related according to view angle and detector angle associated with each ray. Projection data of each ray is then weighted to generate image data for the selected point.

Abstract: A human interface to be used with irradiation machine in a computed tomography machine wherein x-ray computed tomography images are individually display on a computer screen and an operator uses a manual cursor control device to trace various irradiation zones on the image, identify desired dose within each zone, verify the accuracy of the therapy treatment plan prior to an irradiation session, and verify irradiation delivered after a therapy treatment session.

Abstract: A method and system for the automated detection of lesions such as masses and/or tissue (parenchymal) distortions in medical images such as mammograms. Dense regions and subcutaneous fat regions within a mammogram are segmented. A background correction may be performed within the dense regions. Hough spectrum within ROIs placed in the breast region of a mammogram are calculated and thresholded using the intensity value .eta. in order to increase sensitivity and reduce the number of false-positive detections. Lesions are detected based on the thresholded Hough spectra. The thresholded Hough spectra are also used to differentiate between benign and malignant masses.

Abstract: Method and system for reproducing or displaying a medical image with a text box having a lay out that can easily be adapted to the specifications of the customer. A file comprising parameters relating to the lay out of a text box is downloaded into a storage unit, part of an image acquisition station or a workstation, the parameters are selected from the file and used for the composition of the text box to be reproduced on a hard copy of said medical image or to be displayed on a soft copy of the medical image.

Abstract: There is provided a radiotherapy system comprising: a radiotherapy planning CT system integratedly having an X-ray scanner member for acquiring image data of a diagnostic portion of a subject by irradiating X-rays to the subject, said diagnostic portion including a lesion, a radiotherapy planner member for displaying the image data and producing radiotherapy plan data including a position data of an isocenter and a contour data of a radiation field limiting radiations from a virtual radiation source irradiated into the diagnostic portion, and a positioning member for automatically pointing a marking position on the subject based on the position data of the isocenter; and a radiotherapy apparatus for carrying out radiotherapy on the basis of the therapy plan data.

Abstract: Radiologists may protect their subjects against unnecessary exposure to X-rays by use of X-ray opaque material. They may also use X-ray opaque material to permit multiple exposures on a single image. The resulting image contains relatively unexposed regions resulting from the shadow cast by the X-ray opaque material. This invention discloses a method for the automatic determination of the location of the boundary between multiple exposures and the boundary between signal and shadow regions within each exposure. Many hypotheses as to the location of such boundaries are generated and the final decision as to the correct hypothesis is contingent on the results of a rule-based reasoning network.