摘要:
Separation of spectral components is achieved by acquiring radio frequency (RF) signals using a two dimensional scan sequence wherein the bandwidth of at least one of the RF pulses is less than or equal to the Larmor frequency difference of the spectral components. The slice select gradient pulse applied during the application of the RF pulse of limited frequency is smaller than the slice select gradient pulses applied during application of the other Rf pulses.
摘要:
Spatial separation of first and second spectral components in magnetic resonance imaging systems is accomplished by causing the first and second spectral components to generate first and second signals of different frequencies which are spatially separated and converting the spatially separated signals to image data for first and second images of said first and second spectral components respectively.
摘要:
A quadrature coil combiner for phase shifting the pulses and signals of a quadrature coil system used in magnetic resonance (MR) systems to selectively combine or cancel the pulses and signals transmitted and received. The combiner comprises a first and a second conductor for coupling a first and a second coil respectively of the quadrature coil system to a transmit-receive circuit of the MR system. The first conductor comprises an insertable .pi./2 radian delay. The second conductor includes a fixed .pi./2 radian delay. At least one of either the fixed delay or the insertable delay is a quarter wavelength cable whereby active elements are minimized.
摘要:
A slice orientation selection arrangement for magnetic resonance imaging in planes oblique to the normal cartesian coordinates. The coordinates are rotated to applying gradient signals using Euler computations.
摘要:
A waveguide has distal, medial and proximal sections. The distal and medial sections rotate relative to each other and to the proximal section. In a first configuration, the waveguide transforms linearly polarized electromagnetic radiation at the proximal end of the proximal section to linearly polarized electromagnetic radiation at the distal end of the distal section and vice versa. In a second configuration, the waveguide transforms linearly polarized radiation at the proximal end of the proximal section into circularly polarized electromagnetic radiation at the distal end of the distal section and vice versa. Preferably, the distal and medial sections include respective eight-wavelength polarizers and the proximal section includes a quarter-wavelength polarizer. A multi-band antenna feed includes two such waveguides, one nested inside the other, for transforming electromagnetic radiation of respective frequency bands.
摘要:
A system for measuring blood flow in an organ of a subject, particularly useful for non-invasive cardiac output monitoring (N.I.C.O.M.™), the system comprises: a radiofrequency generator for generating output radiofrequency signals; a plurality of electrodes, designed to be connectable to the skin of the subject, the electrodes being for transmitting the output radiofrequency signals to the organ and for sensing input radiofrequency signals of the organ. The system further comprises a mixer, electrically communicating with the radiofrequency generator and at least a portion of the plurality of electrodes, for mixing the output radiofrequency signals and the input radiofrequency signals, so as to provide a mixed radiofrequency signal being indicative of the blood flow. The system further comprises electronic circuitry, constructed and designed to filter out a portion of the mixed radiofrequency signal so as to substantially increase a signal-to-noise ratio of a remaining portion of the mixed radiofrequency signal.
摘要:
A method suitable for assessing the vascular condition of a subject is disclosed. The method comprises: measuring the transit time TT1 of a blood wavefront from the subject's heart to a distal point in a limb of the subject, and measuring the transit time TT2 of a blood wavefront from an intermediate point in the limb of the subject to the distal point of the subject's limb. The method further comprises computing the ratio TT2/TT1 and determining the likelihood that a small vessel disease condition exists when the ratio TT2/TT1 is above a preselected threshold.
摘要:
A method and apparatus for monitoring the presence of arteriosclerosis in an individual includes detecting an ECG signal of the individual's heart, detecting a blood front wave in a peripheral artery of the individual, and measuring the time lag between a predetermined reference point of the detected blood front wave and a predetermined reference point in the ECG signal to provide an indication of the cardiovascular condition of the individual, particularly arteriosclerosis or arterial obstruction.
摘要:
A device for delivering radiation to at least one preselected site in a vascular system of a patient, includes an elongated flexible catheter tube of a diameter for insertion into the patient's vascular system, and a flexible guide wire within the catheter tube and movable along its length. The guide wire includes a proximal end to be located externally of the patient's vascular system for moving the guide wire within the catheter tube, and a rounded distal tip at the opposite end to facilitate movement of the guide wire through the catheter tube. At least one radiation-producing element is fixed to the guide wire at an intermediate location spaced from the rounded distal tip.
摘要:
A slice orientation selection arrangement for magnetic resonance imaging in planes oblique to the normal cartesian coordinates. The coordinates are rotated to applying gradient signals using Euler computations.