Abstract: In an NMR imaging system, two-pulse excitation sequences are used to acquire lines of NMR signal information. Artifact signal components may also be present during the times of NMR signal acquisition. In order to remove these artifacts from the center of the image, the artifact signals are alternately phase-encoded from line to line by alternating the phase of one of said excitation pulses from line to line. Fourier transformation is performed on the lines of information in at least the direction of alternate phasing of the artifact components, which relocates the artifacts to the edge of the resulting image.

Abstract: The effects of particle motion or flow within a sample may be measured by applying a motion-encoding gradient to the sample, along with spatial encoding gradients. The motion-encoding gradient applies two gradient fields of respective opposite sense to the spins of the sample so as to encode motion as a net phase component resulting from the two fields. Two image data sequences, one with motion encoding and one without, may be compared to measure the effects of motion, or a plurality of image data sequences may be taken, each with a different value motion-encoding gradient. A Fourier transformation performed on the sequence data in the latter case with respect to the variation in the motion-encoding gradient pulses will yield a plurality of images, each representing the amount of material which exhibits a different velocity.

Abstract: Real time acquisition of cardiac or other gated cyclical data using a scintillation camera with image formulation utilizing only such data that satisfied a preselected time frame for each cycle. The technique provides real time processing of gated data without the need for specialized hardware equipment or for post processing of the data. Unwanted information corresponding to cycles falling outside a preselected time frame are deleted in real time and hence do not contribute to the cumulative cardiac image.

Abstract: Compensation is provided for a gradient field of an NMR imaging system which compensates for the effects of eddy fields developed in the static magnetic field from metallic components during gradient field switching. The compensation comprises providing current overshoot to the gradient coil during gradient switching. The overshoot current decays with a time constant chosen to substantially offset the decay of eddy fields following gradient switching. In a preferred embodiment, a time constant network representative of eddy field decay is coupled in combination with a feedback signal from a current sampling resistor of the gradient coil.

Abstract: The invention relates to a method for processing attenuation data to produce a tomographic image which requires only that each point within the scan circle be viewed from 180.degree. in order to produce a full set of data. Data from views beyond 180.degree. are redundant and do not improve the picture quality. The invention further relates to an X-ray source and detector arrangement in which the X-ray source is a fan-shaped beam of X-rays and the detectors are arranged about the scan circle for 180.degree. plus approximately the angle of the fan beam. The invention further relates to method and apparatus for back projecting data from a polar coordinate system into a rectangular coordinate system in which the matrix points in the rectangular coordinate system can be loaded sequentially with the appropriate density value from the data line expressed in the polar coordinate system.

Abstract: A method for correcting predictable errors in the location of detected scintillation events acquired during emission computed tomography by a rotational scintillation gamma camera system. The method includes calibrating the rotational scintillation camera system and generating a look-up table comprising a set of pairs of x and y offset values, one pair for each viewing angle. The calibration reflects systemic deviations in the location of the rotating camera head detector measured in terms of x and y coordinates in the frame of reference of the detector for a plurality of view angles relative to the geometric ideal expected path. Once a look-up table is generated for a camera system, the detected location of each gamma event is altered in real time by adjusting in the camera head the x,y coordinate location of each event by the x,y offset values previously generated for the corresponding viewing angle associated with the detected event.

Abstract: An all metal and ceramic high vacuum rotary anode X-ray tube adapted for mounting on a gantry of a rotational type CT scanner. The evacuated region where X-rays are generated is maintained at about 10.sup.-7 Torr. Vacuum sealing about the rotating shaft of the anode is provided by a magnetic fluid. No bearings are utilized within the evacuated region. Large, long wearing ball bearings that transmit rotation through the vacuum seal are provided about the shaft outside of the high vacuum region where conventional lubricants may be applied. Circulating coolant is applied internally through the anode assuring continual operation of the tube without the need for frequent cool-down waits.

Abstract: Dual focus ultrasonic transducers are provided for a diagnostic imaging effective aspheric radiating surface. The transducers are formed of disc-shaped piezoelectric material. An annular groove separates the piezoelectric material into an inner disc region and an outer annular region for simultaneous activation or activation of the inner disc alone. The focus is changed by a reed switch connection to the two transducer regions, which permits proximity switch control of the transducer operation in a shielded environment for good noise performance.

Abstract: In an ultrasonic scanning and display system, lines of pixel values to be displayed comprise pixel values resulting from reception of echoes separated by pixels for which no echo information was received. The "holes" between pixels representing echo information are selectively filled in with interpolated values when the length of the sequence of holes is less than a selected number, and sequence of holes greater than the selected number are blanked for display. This arrangement permits the system operator to select the degree to which the display contains interpolated information.

Abstract: The patient's ECG signal is employed in a traverse-and-rotate type CT scanner as a time base for triggering the beginning of a traverse such that the traveling beam reaches the heart at a desired phase of the cardiac cycle. For a purely-rotational-type CT scanner, continuously generated scan data is only stored for corresponding phases of successive cardiac cycles. Alternatively, gating of the beams themselves can be controlled by the ECG signal. The use of a pacemaker to stabilize the cardiac period is described along with a system for recognizing unacceptable variations in the cardiac period. In a traverse-and-rotate-type fan-beam CT scanner, the effective beam width is narrowed to hasten the traverse of the heart.

Abstract: An ultrasonic emulsion fluid is provided for use in ultrasonic probes of medical ultrasonic diagnostic systems, in which the fluid couples ultrasonic energy between a transducer and human tissue. The emulsion outer phase is a water and velocity enhancer mixture. Suitable enhancers include alcohols such as ethylene glycol, propylene glycol, or glycerol. The suspended phase of the emulsion is an oil phase such as a silicone fluid. The silicone fluid droplets in the emulsion exhibit an average size which provides the emulsion with desired attenuation characteristics over a given band of ultrasonic frequencies.

Abstract: An annular array ultrasonic transducer is provided which comprises a plurality of concentric rings of piezoelectric material having widths chosen for operation at different depths of focus. The total aperture of the transducer is divided into a plurality of contiguous focal depths. In the near field only the inner element or elements are activated, and rings of increasing radius are added as the depth of focus is increased. The widths of the rings are chosen to keep phase errors across each ring within acceptable limits over the depth of field for which they are energized. The transition depths at which the aperture is changed are chosen to allow rings of manufacturable widths to be employed while maintaining aperture transitions which prevent banding in the ultrasonic image.

Abstract: An ultrasonic diagnostic imaging system is described in which a multi-element transducer array transmits a focused beam of energy from the transducer elements. As the depth of focus is varied between near and far field focusing under operator control, the nominal frequency of the transmitted ultrasound energy is varied correspondingly by the system, from relatively high frequency transmission in the near field to relatively low frequency transmission in the far field.

Abstract: Method and apparatus for increasing the effective data storage transfer rate in a system to permit the recording of a rapid sequence of high resolution images by eliminating and hence not transferring designated portions of each image in the sequence.

Abstract: A hybrid collimator for tomographic imaging with a scintillation camera comprising a coded aperture plate and a parallel plate collimator. The code plate includes a plurality of lateral slits each of which is radiopaque or radiotransparent pursuant to a time modulated code. The parallel plates define a plurality of radiotransparent channels whose lengthwise orientation is orthogonal to the lateral slits of the code plate. In a preferred embodiment, the code plate is advanced across the channels of the collimator in a direction parallel to their lengthwise orientation rendering a time coded pattern that is identical for each channel.

Abstract: A radiation imaging system including a rotatable scintillation detector for non-circular emission computed tomography. The radiation imaging system includes a rotatable scintillation detector and a linearly movable detector stand. With the stand stationary, the scintillation detector is capable of circularly orbiting about the longitudinal axis of the patient for emission computed tomography and with the detector stationary the detector stand may be linearly displaced for whole body scanning with the patient aligned parallel to the detector stand path in an orientation orthogonal to the tomographic orientation. The circular rotational motion is combined with the linear translation such that the detector orbits about a section of the patient in a non-circular path. The path assures a minimum distance between the face of the scintillation detector and the boundary of the patient during the entire tomographic orbit to thereby improve resolution of the tomogram.

Abstract: A method of vacuum assembling a rotating anode X-ray tube of the type having a rotor and a shaft extending therefrom with a magnetic fluid for vacuum sealing about the shaft. The tube is subjected to a high temperature bake-out whereby gases are sufficiently evolved from exposed metal parts that a stable low pressure region is created. A static seal is used to temporarily seal the region during bake-out with the anode temporarily rendered non-rotatable and the permanent magnetic vacuum seal protected from the high temperature. The system is then allowed to cool off before the permanent magnetic vacuum seal is moved into its operational position within the high vacuum. Assembly tooling is provided ensuring that the high vacuum is maintained throughout the installation. Bearings are installed external to the region of high vacuum to transmit rotary motion of the shaft through the permanent seal. Finally, the tube is rendered operational by displacing the static seal thereby permitting the anode to be rotated.

Abstract: An ultrasound phantom is provided which simulates human tissue containing tissue masses viable for biopsy. The phantom is used to demonstrate or teach the performance of a biopsy procedure assisted by real-time ultrasonic imaging. The phantom comprises a plurality of small balloons, filled with a viscous substance, and tied shut. The balloons are distributed through and surrounded by a gelatinous substance comprising tissue equivalent material. During a simulated biopsy procedure, a section of the phantom is imaged as a biopsy needle penetrates through the tissue equivalent material, pierces one of the balloons, and aspirates some of the viscous substance from the balloon.

Abstract: An ultrasound imaging system is provided having an articulated arm for holding a transducer. Signals representative of the angular position of the arm joints are scaled up to a voltage range over which the restricted range of movement of each joint is distributed. The scaled signals are combined to produce a plurality of combined angular signals, which then may be digitized and used to compute the X-Y position of the transducer.