Abstract: In an improved CT scanner calibration method and apparatus, a radiation beam, for example an x-ray beam, is directed at a plurality of radiation detectors. The beam is attenuated by a phantom of known attenuation characteristics. The detectors generate measured attenuation data from the attenuated beam. The measured attenuation data is back-projected to generate a measured phantom image. The measured phantom image is converted to an ideal phantom image. The ideal phantom image is forward projected to generate ideal attenuation data. Calibration values for each detector channel in the scanner are generated by cross-referencing the ideal and measured attenuation data. In a preferred embodiment, this cross-referenced data is compressed and stored in a look-up table for referencing during later interrogation of subjects.

Abstract: A CT scanner (10) includes a reconstruction processor (82) for reconstructing an image from digital signals from detector arrays (20). Each detector array includes scintillation crystals (22) arranged in an array for converting x-ray radiation into visible light. An array of photodetectors (24) is mounted beneath the scintillation crystal array for converting light emitted from the scintillation crystals into electrical charge. The combination scintillation crystal, photodetector array is mounted to and preferably integral with an integrated circuit (26) having charge storage devices (32, 34). Electrical charge generated by each photodetector is integrated and stored alternately by a corresponding pair of charge storage devices. The charge storage devices operate as a double buffer in which one charge storage device accumulates charge while the other holds an accumulated charge until read out by downstream circuitry.

Abstract: A CT scanner (10) has an x-ray source (12) which transmits a plurality (N) of x-ray fans across an examination region (14) to a plurality of rings of radiation detectors (28). An adjustable septum (80) adjusts a gap between the fan beams and outer collimators (82) adjust the width of the fan beams such that the effective spacing and width are adjusted. The x-ray source rotates around the examination region as a subject support (32) moves longitudinally through the examination region such that the x-ray fans move along interleaved spiral trajectories. Radiation attenuation data from each of the x-ray fans is combined and reconstructed into a plurality of images along parallel slices orthogonal to the longitudinal axis. The spacing between the x-ray beams is adjusted relative to the effective pitch of the spirals such that the leading edges of the x-ray fans intersect a common transverse plane at 180.degree./N angular intervals around the longitudinal axis.

Abstract: A patient breathing through a mask (34) receives breathing air from a breathing air system (A). A xenon gas supply (12) selectively supplies xenon or other enhancement gases into the breathing air. During each exhalation portion of a respiratory cycle, a portion of the exhaled gas passes through a narrow tube (40) to a xenon concentration detector (44) and a carbon dioxide concentration detector (46). A carbon dioxide concentration comparing circuit (54) compares the carbon dioxide concentration values with characteristics (56) of carbon dioxide concentration during an end-tidal portion of the exhalation respiratory cycle. Xenon concentrations read during the end-tidal portion of the respiratory cycle (62) are utilized to project a blood absorption curve (64). A plurality of CT images are generated by a CT scanner (B) as the blood xenon concentration increases.

Abstract: A patient is disposed within a scan circle or examination region (62) of a CT scanner (B). As the patient starts breathing air from a xenon gas supply (A), a flow image and a lambda image are created and stored in a flow image memory (90) and a lambda image memory (92). The flow and lambda images, as well as a standard CT image, are displayed in quadrants of a video monitor (102). A joystick (106) enables the operator to designate a region of interest on the displayed image representations. Corresponding flow and lambda values are retrieved from the flow and lambda image memories for each spatial location or pixel within the region of interest. The flow and lambda values are loaded into a flow vs. lambda image memory (112) which is addressed in one direction by the flow values and in another by the lambda values to create a count of the flow and lambda value pairs. The information in the flow vs. lambda image memory is displayed as a histogram in one quadrant of the video display.

Abstract: A medical diagnostic imaging apparatus (A) creates an image representation which is stored in an image memory (24). A video processor (26) generates a monochrome video signal from the data stored in the image memory. A monochrome to color video signal converter (B) converts the gray scale designations of the monochrome video signal to hue scale designations of a color video signal. More specifically, the gray scale values of the monochrome signal are digitized by an analog-to-digital (32) and used as addresses for a plurality of look up tables (36r, 36g, 36b, 64r, 64g, 64b). Each set of three look up tables (30, 60, 66) is preprogrammed with appropriate transfer functions, such as the transfer functions (40, 42, 44) of FIG. 2. Each look up table puts out an appropriate intensity designation for one of the three color components of the video signal. A digital-to-analog converter (50) converts the look up table outputs to three components of an RGB or other appropriate color video signal.

Abstract: A xenon gas system (B) introduces xenon gas into a patient's blood. The xenon concentration in the patient's blood is monitored (26) periodically as the concentration builds toward a saturation level (32). The absorption data is divided into at least three curved segments (32, 34, 36) each of which are approximated by a curve segment to determine absorption curve characteristics. The amplitude of the saturation curve segment is determined as first characteristic; the slope of the second curve segment is a second characteristic; and an end amplitude and time constant of an exponential third curve segment provide third and fourth characteristics indicative of blood xenon absorption. A CT scanner (A) generates a plurality of time displaced image representations, each of which is subtracted (52) from a reference image (30) to determine difference image representations. Each image representation includes a plurality of pixels that correspond to subregions of a region of interest within the patient.

Abstract: A xenon gas system (B) introduces xenon gas into a patients's blood. The xenon gas concentration in the patient's blood is monitored and the characteristics of the patient's blood absorption curve are determined (34). A look-up table array (60) includes a plurality of look-up tables, each look-up table corresponding to one of a plurality of preselected blood absorption curves. A look-up table selection circuit (36) selects the look-up table which most closely corresponds to the projected blood absorption curve. A CT scanner (A) generates a plurality of image representations at preselected intervals after commencement of xenon gas interpolation, which images are stored in an image memory array (44). Xenon gas concentration values from corresponding pixels of each image representation are utilized to address the look-up table corresponding most closely to the patient's blood absorption curve in order to retrieve precalculated partition coefficient, blood flow rate, and confidence values.