Abstract: A dual energy method for CT scanning. Scanning is carried out at low and high energy levels, S.sub.2 and S.sub.1 respectively, each at a preselected dose level. Detected electronic signals (I.sub.2,I.sub.1) are digitized. A look up table is used to generate a pair of values from each pair of signals, one a photoelectric component and the other a Compton component. Each of these values are subjected to spatial filtering by a convolution filter function for each signal specially designed to increase the signal to noise ratio in the resultant combined image by exploiting the correlation in noise in the two values.

Abstract: In scintillation cameras, spatial or linearity correction is accomplished utilizing a weighted average of correction vectors in the region of the apparent location of scintillation events. Such vectors are developed in a calibration step using a pinhole or slot apertured mask. On the fly, vectors beyond those next adjacent the apparent location are used for correction, which are constrained to exhibit continuity in both the functional value, and at a minimum the first derivative, but which may include continuity in higher order derivatives also. One such correction function, which insures continuity in both the functional value and its first derivative, is called a Hermite interpolation function.

Abstract: A mechanical in-line sector scanner is provided in which the ultrasonic transducer pivots about an axis. The transducer is oscillated through an arc about the axis by reciprocating pins, which alternately push the transducer in opposite directions of scanning. The pins are reciprocated by a continuously turning cam having a cam surface obliquely oriented with respect to the longitudinal axis of the pins.

Abstract: A patient handling system for an NMR imaging system includes a portable patient table having a bottom portion and a top portion. The table is docked adjacent to the magnet of an NMR system. The top portion may be elevated to align the top portion with the magnet bore. A patient pallet, located on the top portion of the table, is then moved into and out of the magnet bore. The pallet includes a number of modules upon which the patient reclines. At least one module includes a radio frequency coil for NMR imaging. The other modules are dummy modules which do not contain r.f. coils and support other parts of the patients's body.

Abstract: Radio frequency apparatus for a magnetic resonance system is provided which includes an r.f. coil and DC controlled circuitry for selectively altering the characteristics of the coil. A loading coil is provided which is selectively activated to de-Q the coil during r.f. transmission so as to minimize the loading effects of the subject and their effect on coil impedance. A switched network is provided which selectively destroys the normal resonant condition of the coil when a second r.f. coil is operative to minimize interaction between the two coils.

Abstract: A technique for producing multiple spin echo signals following an initial excitation pulse is provided. A first inverting pulse is applied a given time interval following the initial excitation pulse, resulting in the formation of the usual first spin echo signal after passage of the given time interval. At a later point in time, a second inverting pulse is applied. The time interval between the initial excitation pulse and this second inverting pulse is not required to be harmonically related to the first given time interval. This results in the production of at least a second, later occurring spin echo signal which does not contain harmonically-related artifact components of the earlier pulses and spin echo signals.

Abstract: A mechanical transducer probe assembly is provided which is both rugged and easy to assemble. The probe mechanism is located inside a hollow probe case. A reference point for assembly is located on the inner surface of the case. A motor assembly and a transducer mounting assembly are located within the case and are fixedly joined together. At the jointure of the two, the motor and transducer assemblies are in contact with the reference point, thereby positionally locating the transducer and its drive mechanism within the case. Means are provided for urging the motor and transducer assemblies against the reference point, which means also provides shock mounting for the probe mechanism.

Abstract: In a magnetic resonance imaging system, the same reference signal is used for both radio frequency transmission and phase sensitive detection. The use of the same reference signal for both transmission and reception prevents phase unlock between the two events. However, this technique results in variation in the demodulated, frequency encoded information, which is corrected by digitally filtering the received signal information as a function of the demodulation frequency used.

Abstract: In a magnetic resonance imaging system, a multiplexing technique is used to image volumetric regions by performing a number of scans within the recovery time of the spin systems. The multiple scans acquire signal information from sub-regional volumes by phase-encoding in the direction of the excitation gradient.

Abstract: In an NMR system, two chemical shift components are separated by correcting NMR data for field inhomogeneity. A first image data set is acquired which contains no chemical shift information or field inhomogeneity. A second image data set is acquired which contains both chemical shift information and field inhomogeneity. A third image data set is acquired which contains field inhomogeneity information. The first and third image data sets are combined to identify the field inhomogeneity information. This intermediate field image is then used to correct the second image data set for field inhomogeneity. The first image data set and corrected second image data set may then be combined by magnitude reconstruction of complex sums and differences to separate the two chemical shift components.

Abstract: A mechanical support structure which coordinates patient positioning and medical diagnostic equipment positioning in a unified system. More particularly, the system includes a vertically adjustable patient table supported at both ends by substantial upright end support members. Also suspended between these two end supports is a radiation detector such as a scintillation camera head whose position relative to the patient table is conveniently and accurately adjustable from an operator control panel provided on one end support. Each degree of freedom afforded the detector is accomplished independently of the other and, if desired, simultaneously, or in any desired combination. To perform static imaging the separation between the detector and the patient table is adjustable, as is the lateral position of the detector between the two end stands and hence along the span of the patient table. In a detector having a non-symmetrical field of view, its length and width orientation may be reversed.

Abstract: An ultrasonic transducer probe is provided, in which the transducer is oscillated by a crank shaft for sector scanning. The crank shaft is driven by a motor having a moving magnet stack assembly in a tubular set of electromagnetic coils. The motor also moves a bimetallic pin through a position sensor coil so that the position of the transducer is represented by the detected inductance change of the coil.

Abstract: A family of high Q radio frequency coils for an NMR imaging system is provided. The coil family includes a transmitting coil for transmitting an r.f. field aligned with a given plane. The transmitting coil is used with one of the described receiving coils, each of which is responsive to NMR signals in a plane oriented orthogonally to said given plane. The receiving coils employ an open, arcuate configuration, which alleviates sensations of confinement characteristic of fully enclosing coil forms. Arcuate sections of the receiving coils are curved away from the patient, to decrease signal reception at areas from which meaningful signals cannot be gathered. To prevent interaction between the transmitting and receiving coils, means are provided for rendering each coil nonresponsive to NMR and radio signal frequencies when the coils are not being operated.

Abstract: In an NMR imaging system, an image plane is scanned and NMR signals are collected over a plurality of image lines. The experiment is repeated, with the timing of the excitation pulses changed. Images are formed by performing Fourier transformations of the signal values. A ratio image is then formed by performing a complex division of the two images on a pixel by pixel basis. The ratio values cancel phase error effects in the image data and the use of complex numbers maintains the proper pixel polarity.

Abstract: The null point in the gradient field of an NMR imaging system is offset from its nominal position in the static magnetic field by application of a bias field to the gradient field. The bias field produces a substantially uniform offset in the field intensity at every point in the gradient field. Alternatively, null point offset may be achieved by controllably superimposing two gradient fields of separately located null points.

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. A preferred embodiment discloses a modified path in the rotor for the coolant designed to disturb the conventional laminar type of flow which is heat transfer inefficient to one characterized by high turbulence resulting in approximately an order of magnitude improvement in the coefficient of heat transfer.

Abstract: A network for use in a fourth generation CT scanner for noise reduction. The network comprises an active low pass filter whose cutoff frequency is controlled by a scaled signal responsive to the angular velocity of the rotating radiation source of the scanner. In a preferred embodiment a raw signal is generated by an encoder that detects movement of the source. As the source speed changes either in response to an operator's selection of a different scan speed or to systemic variations in the scanner relative to expected performance, the filter's cutoff frequency will automatically change thereby assuring optimum performance regardless of scan speed.

Abstract: The effects of motion in a given direction of particles being imaged in an NMR imaging system are substantially reduced by using gradients in the given direction produced by gradient pulse sequences which exhibit a zero value first moment relative to the point in time at which phase determination of the particles occurs. This point in time is generally taken at the time at which the longitudinal magnetization is translated to the transverse plane, as that is the phase reference for the NMR signals produced by the particles.