Abstract: A magnetic resonance (MR) active invasive device system employs a radio-frequency (RF) coil embedded in an invasive device for the purpose of generating MR angiograms of a selected blood vessels. A subject is first placed in a polarizing magnetic field. The invasive device is then placed into a selected blood vessel of the subject such that the RF coil of the invasive device is located at or near the root of a vessel tree desired to be imaged. The RF coil is then used to alter the nuclear spin magnetization of blood flowing within the vessel. This is done by employing an RF excitation signal to the coil at the Larmor frequency of the blood. The nutation of spin magnetization can change the amount of longitudinal spin magnetization or the Amount of magnetization in the transverse plane. Because the size of the radio-frequency coil in the invasive device is small, the change in spin magnetization is limited to blood flowing by the invasive device.

Abstract: An invasive imaging system employs a self-contained RF transmitter attached to an invasive device which allows tracking of the invasive device within a subject without physical connections to a tracking/display system and without the use of ionizing rays. An imaging system obtains a medical diagnostic image of the subject. The self-contained RF transmitter is comprised of a power generator, a power conversion means such as an oscillator which converts the generated power to a radiofrequency (RF) signal, and a broadcasting means such as a tuned transmit coil for radiating the RF signal. The radiated RF signal is received by receive coils of a tracking/display means which calculates the location of the RF transmitter. The tracking/display means displays the medical diagnostic image on a monitor and superimposes a symbol on the image at a position corresponding to the calculated location of the RF transmitter.

Abstract: Magnetic resonance images of selected chemical species are generated by the application of a multi-band radio-frequency excitation pulse. The radio-frequency pulse excites an arbitrary number of spectral bands. As the imaging phase encoding gradient pulse is advanced, the phase of each excitation band is advanced by a unique amount. This causes the signals from the spins in a particular band to appear at a position in the phase encoding direction which is the stem of the spin position and an offset arising from the phase increment given to that excitation band. Additional selectivity of selected chemical species can be accomplished by combining the multi-band excitation with chemical shift selective saturation radio-frequency pulses and echo-time modulation.

Abstract: A method of magnetic resonance (MR) fluid flow measurement within a subject employs an invasive device with an RF transmit/receive coil and an RF transmit coil spaced a known distance apart. The subject is positioned in a static magnetic field. The invasive device is positioned in a vessel of a subject in which fluid flow is desired to be determined. A regular pattern of RF transmission pulses are radiated through the RF transmit/receive coil causing it to cause a steady-state MR response signal. Intermittently a second RF signal is transmitted from the RF coil positioned upstream which causes a change in the steady-state MR response signal sensed by the downstream transmit/receive coil. This is detected a short delay time later at the RF receive coil. The time delay and the distance between the RF coils leads directly to a fluid velocity. By exchanging the position of the RF transmit and transmit/receive coils, retrograde velocity may be measured. In another embodiment, more RF coils are employed.

Abstract: An invasive imaging system employs a self-contained RF transmitter attached to an invasive device which allows tracking of the invasive device within a subject without physical connections to a tracking/display system and without the use of ionizing rays. An imaging system obtains a medical diagnostic image of the subject. The self-contained RF transmitter is comprised of a power generator means, a power conversion means such as an oscillator which converts the generated power to a radiofrequency (RF) signal, and a broadcasting means such as a tuned transmit coil for radiating the RF signal. The radiated RF signal is received by receive coils of a tracing/display means which calculates the location of the RF transmitter. The tracking/display means displays the medical diagnostic image on a monitor and superimposes a symbol on the image at a position corresponding to the calculated location of the RF transmitter.

Abstract: RF tracking system employs a RF invasive device coupled to surgical tracking equipment for tracking the invasive device. An inductive coupling permits the device to be quickly coupled to, and decoupled from, the equipment. The coupling comprises an inducting coil which transmits a signal from the surgical tracking equipment to a communicating coil in the invasive device. The signal received by the communicating coil passes along leads to a tracked coil in a distal end of the invasive device. The tracked coil transmits the signal as RF energy which is received by the surgical tracking equipment which superimposes the position of the distal end of the invasive device on an X-ray image and displays it on a monitor A sterile shield is employed as a sterile barrier between the inducting coil and the equipment end of the invasive device to prevent contamination of the invasive device by the inducting coil.

Abstract: A motion imaging method uses magnetic resonance to detect the two or more components of motion such as velocity, acceleration or jerk within a subject. One component of motion is detected by computing differences of data obtained with modulated motion-encoding magnetic field gradient pulses. Distributions of at least one component of motion are measured responsive to a motion sensitive phase-encoding gradient pulse. The method can be used to obtain velocity and acceleration measurements in any of three mutually orthogonal directions.

Abstract: A magnetic resonance (MR) angiography system employs a Faraday catheter for generating MR angiograms of selected blood vessels. A subject is first placed in a polarizing magnetic field. The Faraday catheter is then inserted into a selected blood vessel of the subject at or near the root of a vessel tree desired to be imaged. An MR imaging pulse sequence is then applied to the subject to obtain image information from the region containing the desired vessel tree. Fluid inside the Faraday catheter is shielded from the RF pulses of the MR imaging sequence allowing the fluid to be in a relaxed state, while tissue outside the Faraday catheter is on a steady-state. As the fluid exits the catheter, and before it reaches steady-state, it produces an increased MR response signal causing the desired vessel tree to be imaged.

Abstract: A motion imaging method uses magnetic resonance to detect velocity, and an acceleration distribution within moving materials in a subject. Velocity encoding is performed by computing differences of data obtained with modulated motion-encoding magnetic field gradient pulses. Distributions of acceleration are measured responsive to a motion sensitive phase-encoding gradient pulse.

Abstract: A pulsed electromagnetic radiation (EMR) source and an interferometer are used to obtain spectra from the surface of a sample. The pulsed EMR source uses a broadband radiation source and a monochromator to generate monochromatic radiation. Alternatively, a tunable laser can be used as the monochromatic radiation source. The modulated radiation impinges on the surface of interest where it is absorbed. The absorption of radiation causes the surface of the sample to expand. This change in dimension is then detected by an interferometer which employs a monochromatic radiation source to measure the instantaneous distance between the sample surface and the interferometer. The detection system of the interferometer can be an imaging device such as a video camera to obtain the spatial distribution of chemical composition of the sample surface.

Abstract: A magnetic resonance system employs a sequence of radio frequency pulses and magnetic field gradients to detect and measure the spin-relaxation time T.sub.1 of a selected portion of a sample. Spin-lattice relaxation times are determined by first inverting longitudinal spin magnetization and then detecting the recovery of this magnetization with a series of detection radio frequency pulses. The inversion pulse is applied to the entire sample, but the detection pulses are applied to selected portions of the sample. Each detection pulse is applied in a unique location of the sample, thereby increasing the accuracy of the measurement and permitting the use of multiple detection pulses after a single inversion pulse.

Abstract: A tracking system in which radiofrequency signals emitted by an invasive device such as a catheter, are detected and used to measure the position and orientation of the invasive device. The invasive device has a transmit coil attached near its end and is driven by a low power RF source to produce a dipole electromagnetic field that can be detected by an array of receive coils distributed around a region of interest. The position and orientation of the device as determined by the tracking system are superimposed upon independently acquired Medical Diagnostic images, thereby minimizing the radiographic exposure times. One or more invasive devices can be simultaneously tracked.

Abstract: A shear rate imaging method uses magnetic resonance to detect the distribution of velocities within a subject. Distributions are measured responsive to at least two different field-of-views. Differences of the velocity distribution obtained with one field-of-view and the second field-of-view are computed to give a component of shear rate. The method can be used to obtain velocity measurements in any of three mutually orthogonal directions responsive to field-of-view shifts in as many as three mutually orthogonal directions to give a total of nine shear rate components. Data for each component can be acquired independently or data acquisition can be multiplexed to reduce data acquisition requirements.

Abstract: A magnetic resonance (MR) imaging system for use in a medical procedure employs an open main magnet allowing access to a portion of a patient within an imaging volume, for producing a main magnetic field over the imaging volume; a set of open gradient coils which provide magnetic fields gradients over the imaging volume without restricting access to the imaging volume; a radiofrequency coil set for transmitting RF energy into the imaging volume to nutate nuclear spins within the imaging volume and receive an MR response signal from the nuclear spins; and a pointing device for indicating the position and orientation of a plane in which an image is to be acquired; an image control means for operating power supplies for the gradient coils and the RF coils to acquire an MR signal from the desired imaging plane; and a computation unit for constructing an image of the desired imaging plane.

Abstract: A magnetic resonance imaging system employs a sequence of radio frequency pulses and magnetic field gradients to detect and measure the spin-relaxation time of moving blood within a subject. Spin-lattice relaxation times are determined by first inverting longitudinal spin magnetization and then detecting the recovery of this magnetization with a series of detection radio frequency pulses. The inversion pulse is applied to the entire subject, but the detection pulses are applied only to a selection portion of the subject. Blood motion causes the blood in the detection region to be replaced for each detection pulse, thereby increasing the accuracy of the measurement and permitting the use of multiple detection pulses after a single inversion pulse. In-vivo application of this invention can be used to assess renal function in individual kidneys.

Abstract: A tracking system employs magnetic resonance signals to monitor the position of a device such as a catheter within a subject. The device has a receiver coil which is sensitive to magnetic resonance signals generated in the subject. These signals are detected in the presence of magnetic field gradients and thus have frequencies which are substantially proportional to the location of the coil along the direction of the applied gradient. Signals are detected responsive to applied magnetic gradients to determine the position of the device in several dimensions. Sensitivity of the measured position to resonance offset conditions such as transmitter frequency misadjustment, chemical shift and the like is minimized by repeating the process a plurality of times with selected amplitudes and polarities for the applied magnetic field gradient.

Abstract: A magnetic resonance imaging system employs a sequence of radio frequency pulses and magnetic field gradients to detect and measure the spin-relaxation time of moving blood within a subject. Spin-lattice relaxation times are determined by first inverting longitudinal spin magnetization and then detecting the recovery of this magnetization with a series of detection radio frequency pulses. The inversion pulse is applied to the entire subject, but the detection pulses are applied only to a selection portion of the subject. Blood motion causes the blood in the detection region to be replaced for each detection pulse, thereby increasing the accuracy of the measurement and permitting the use of multiple detection pulses after a single inversion pulse. In-vivo application of this invention can be used to assess renal function in individual kidneys.

Abstract: A tracking system employs magnetic resonance signals to monitor the position and orientation of at least one device such as a catheter within a subject. The device has a plurality of receiver coils which are sensitive to magnetic resonance signals generated in the subject. These signals are detected in the presence of magnetic field gradients and thus have frequencies which are substantially proportional to the location of the coil along the direction of the applied gradient. Signals are detected responsive to sequentially applied mutually orthogonal magnetic gradients to determine the device's position and orientation in several dimensions. The position and orientation of the device as determined by the tracking system is superimposed upon independently acquired medical diagnostic images. One or more devices can be simultaneously tracked.

Abstract: A tracking system employs magnetic resonance signals to monitor the position of a device such as a catheter within a subject. The device has a receiver coil which is sensitive to magnetic resonance signals generated in the subject. These signals are detected in the presence of magnetic field gradients and thus have frequencies which are substantially proportional to the location of the coil along the direction of the applied gradient. Signals are detected responsive to sequentially applied mutually orthogonal magnetic gradients to determine the position of the device in several dimensions. The position of the device as determined by the tracking system is superimposed upon independently acquired medical diagnostic images.

Abstract: To obtain spectra from the surface of a sample, a first of a pair of interferometers includes a broadband radiation source and modulates the radiation at a frequency which is inversely proportional to wavelength. The modulated radiation impinges on the surface of interest where it is absorbed. The absorption of radiation causes the surface of the sample to expand. This change in dimension is then detected by a second interferometer which employs a monochromatic radiation source to measure the instantaneous distance between the sample surface and the second interferometer. The detection system of the second interferometer can be an imaging device such as a video camera to obtain the spatial distribution of chemical composition of the sample surface.