Abstract: An improved method for obtaining a multi-slice acquisition in which images from several slices are simultaneously acquired at preselected repetition times. One scan allows for the acquiring of images from multiple slices, at multiple repetition times TR and multiple echo times TE in such a manner that all available readout time is utilized when both the first repetition time TR1 and the second repetition time TR2 are both appropriate combinations of defined measurement intervals.

Abstract: A method of calculating the intrinsic parameters including the spin-lattice relaxation time T1 and the spin-spin relaxation time T2 for Nuclear Magnetic Resonance (NMR) technique which utilizes calculations of derived algorithms by a series of passthroughs of a digital video processor. The use of a digital video processor to accomplish the algorithm construction provides a significant increase in the speed with which the intrinsic parameters can be calculated.

Abstract: A method for providing improved estimates of the spin-lattice relaxation time T1 of an image in a Nuclear Magnetic Resonance (NMR) technique on a human body is disclosed which utilizes the application of a multiple spin-echo pulse sequence technique at two different pulse repetition times TR1 and TR2. The signals for each of the different repetition times are measured by first setting the longitudinal magnetization to an initial value and then waiting the appropriate repetition time in order to provide the measured signal. The magnetization is "flipped" into the x-y plane and the relationship between the measured values for each of the repetition times is utilized to form an algorithm whereby the calculated ratio of the measured signals allows for an initial estimate of T1.

Abstract: Intrinsic parameters T.sub.1, T.sub.2 and M.sub.o of the materials in a body under NMR examination are determined by conducting a small number of actual NMR measurements and analyzing the derived data, the measurements being made at different repetition and delay times. The intrinsic parameters are then used to synthesize images which simulate those which would have been generated using other delay and repetition times in an actual measurement process. A processing apparatus is disclosed which operates in real time, permitting an operator to interactively modify the delay and repetition times while observing successive displays which simulates measurements made using those times.

Abstract: Intrinsic parameters T.sub.1, T.sub.2 and M.sub.o of the materials in a body under NMR examination are determined by conducting a small number of actually NMR measurements and analyzing the derived data, the measurements being made at different repetition and delay times. The intrinsic parameters are then used to synthesize images which simulate those which would have been generated using other delay and repetition times in an actual measurement process. A processing apparatus is disclosed which operates in real time, permitting an operator to interactively modify the delay and repetition times while observing successive displays which simulates measurements made using those times.

Abstract: In a subtraction angiography hybrid difference images are generated and reviewed visually. Hybrid images that exhibit no x-ray contrast medium and are free of artifacts are identified and selected for forming an integrated mask image. Hybrid images that exhibit contrast medium and are free of artifacts are identified and selected for forming an integrated contrast medium image. The selected images that exhibit no contrast medium are integrated and those that exhibit contrast medium are integrated separately. The result of one integration is subtracted from the other to yield a single final image that exhibits substantially only the contrast medium in a blood vessel. In an alternate method temporal difference images are reviewed and a similar selection of some that exhibit no contrast medium and some that exhibit contrast medium is made. These images are separately integrated and subtracted to yield a single final image that exhibits substantially only contrast medium in the blood vessel.

Abstract: Low and high energy x-ray exposures are made before and after an injected x-ray contrast medium arrives at a blood vessel of interest. In one mode, low and high energy mask images are made and these are subtracted from subsequent low and high energy images, respectively, to yield temporal difference images. The projected intensities of the contrast medium with respect to time constitute matched filter coefficients by which the difference images are mulitplied. The matched filtered images are summed, multiplied by weighting factors and subtracted from each other to yield a final hybrid image. In an alternative mode, successive pairs of low and high energy images are subtracted to yield energy difference images. The difference images are subjected to matched filtering and summed and the results subtracted to produce a final hybrid image.

Abstract: A matched filtering method for X-ray image subtraction procedures in which an X-ray contrast medium is injected intravenously. A sequence of pre-contrast X-ray images are made during a period before the medium arrives in a blood vessel that is to be imaged and the sequence is continued through the post-contrast period and in some cases, an after-contrast period. A curve or plot of how projected intensity of the contrast medium varies as a function, h, at times (t) is determined at some prior time based on characteristic patients or, in the alternative, by using the post-contrast image data obtained from the patient presently undergoing examination. In either case a sequence of coefficients or weighting factors are produced that are proportioned to the value of the function h at the time (t) at which the corresponding image in the post-contrast sequence was acquired.

Abstract: In a digital fluorography system a television (TV) camera converts X-ray images to analog video signals that are converted to digital pixel words in an analog-to-digital converter (ADC). The sync signals for the TV camera and the sample clock signals for the ADC are derived from a novel resettable crystal controlled sync generator. A phase-locked loop provides an ac reference signal at one-half power line frequency which is equivalent to TV frame rate. The sync generator is reset to start a new frame and an ensuing sequence of crystal controlled horizontal sync pulses only in response to occurrence of ac reference signals so every frame is in registration. A digital video processor (DVP) subtracts a mask image from each image in a sequence of images that are acquired while an X-ray contrast medium is appearing in and disappearing from a blood vessel. The resulting difference images are stored in analog video signal format in an analog video disk recorder.

Abstract: Apparatus and methods are provided for performing temporal and hybrid subtraction of X-ray images. In one mode, using three memories, a pair of low and high energy X-ray exposures are made before an X-ray contrast medium arrives in a blood vessel to provide mask images. After contrast arrival additional high and low energy exposures are made and the low energy mask is subtracted from the low energy post-contrast images and the high energy mask is subtracted from the high energy post-contrast images and the resulting sequence of low and high energy temporal difference images are stored. The low energy temporal difference images are displayed. If motion artifacts are perceived, hybrid subtraction of low and high energy temporal difference images is undertaken to produce an image data set in which motion artifacts are removed. In an alternate mode, which uses four memories, low and high energy pre-contrast mask images are stored in one pair of memories.

Abstract: A radiographic phantom is comprised of only two materials, a non-iodinated material composing the base and an iodinated material disposed in a channel simulating a blood vessel, thus providing for a resultant signal attributable only to the iodinated material when a radiographic subtraction process is conducted to test an apparatus for contrast sensitivity. The phantom is fabricated by forming the base of a plastic material, forming a channel in the base, and then filling in the channel with the same kind of plastic material but with minute amounts of iodine suspended uniformly therein.

Abstract: In a digital fluoroscopy system, analog video signals representative of successive x-ray image frames are converted to digital pixel values that are used as addresses, respectively. A digital memory stores at its respective locations a digital value corresponding to the logarithm of an address value so that when a digital pixel value represented by an address is fed from the analog-to-digital converter to the memory the memory will output the logarithm of the pixel value in digital form. Pixel values for successive x-ray images are subtracted in-phase on a pixel-by-pixel basis to produce digital difference pixel signals which are converted to analog video signals for driving a television monitor that displays an image representative of the difference between x-ray images.

Abstract: Apparatus for reducing the effect of x-ray statistical noise and electronic noise in a fluorographic system that displays an x-ray image on a television screen. Analog video signals based on the x-ray image are amplified logarithmically and digitized to yield live pixel signals. Processed pixel signals are averaged in a full image store or memory. Motion is detected by subtracting the stored pixels from the live pixels on a pixel-by-pixel basis in an ALU. The difference resulting from subtraction is used as part of an address to a look-up table (LUT) which contains values equivalent to the difference signals times a noise reduction multiplicative factor, K. The other part of the addresses is the live pixel value. There are several replications of the look-up tables each relating to a particular brightness level range. The one selected is determined by the live signal part of the address which relates to brightness.