Abstract: A sweep generator 230 applies a range of frequencies to an rf coil 140 to detect the resonant frequency of a field generated by a magnet 125a,b. A frequency to current converter 220 applies an auxiliary magnetic field to tune an MRI apparatus to the resonant frequency of the rf coil. A flexible coil of one turn (300) or two or more turns (500) has a plurality of segments (301-307; 501-513). One of the belt has a contact k0, (k0′), which is electrically connectable to one or more contacts k1, (k1′), k2, (k2′), etc. located between the ends of the segments. For each connection to successive contacts, the length of the coil and its inductance increases by the added impedance DLij between contacts ki and kj. That increase of inductance is nullified by capacitors DCsij located between segments.

Abstract: An invasive probe for mapping the walls of a lumen employs a real-time tracking means and a wall distance measurement means. As the probe is advanced within the lumen, the real-time tracking means provides three-dimensional coordinates of the probe's position and orientation. Concurrent with probe localization, the distance between the probe and the lumen walls is measured. Both the probe position and the wall distance measurement are sent to a data acquisition system which in turn provides a graphic or numeric display to the operator. Probe tracking can be performed with radio-frequency, magnetic resonance, ultrasonic techniques or the like. If desired, lumen wall distance measurements can be performed with magnetic resonance or ultrasound methods. Lumen wall distance measurements can also be performed with mechanical devices such as balloons and/or expanding structures.

Abstract: A local RF antenna assembly for a magnetic resonance imaging (MRI) system includes a conducting RF antenna structure. First and second capacitors are connected in series with the inductance of the RF antenna structure to form a circuit that resonates at a Larmor frequency. An inductor has a first terminal connected to a node between the first and second capacitors and has a second terminal. A photosensitive first semiconductor switch is connected between the second terminal of the inductor and one terminal of the RF antenna inductance. A receive coil control selectively provides illumination that places the photosensitive first semiconductor switch in a conductive state. When the photosensitive first semiconductor switch is conductive, the inductor disables resonance of the RF antenna circuit at the Larmor frequency. This action inhibits the RF receive antenna from interacting with other antennae in the MRI system.

Abstract: An invasive probe for determining the morphological characteristics of walls of a lumen employs a real-time tracking means and an optical spectral measurement means. As the probe is advanced within the lumen, the real-time tracking means provides three-dimensional coordinates of the probe's position and orientation. Concurrent with probe localization, measurement of the spectral properties of the lumen wall are made by detecting the reflectance and/or absorption of light at the lumen wall. Both the probe position and the spectral measurement are sent to a data acquisition system which in turn provides an graphic or numeric display to the operator. Probe tracking can be performed with radio-frequency, magnetic resonance, ultrasonic techniques or the like. If desired, spectral measurements can be made in the visible, ultra-violet or infra-red spectral bands to provide optimized detection of chemical species of interest.

Abstract: A sweep generator 230 applies a range of frequencies to an rf coil 140 to detect the resonant frequency of a field generated by a magnet 125a,b. A frequency to current converter 220 applies an auxiliary magnetic field to tune an MRI apparatus to the resonant frequency of the rf coil. A flexible coil of one turn (300) or two or more turns (500) has a plurality of segments (301-307; 501-513). One of the belt has a contact k0, (k0'), which is electrically connectable to one or more contacts k1, (k1'), k2, (k2'), etc. located between the ends of the segments. For each connection to successive contacts, the length of the coil and its inductance increases by the added impedance .DELTA.L.sub.ij between contacts k.sub.i and k.sub.j. That increase of inductance is nullified by capacitors .DELTA.C.sub.sij located between segments.

Abstract: An optical coupling is incorporated into an invasive device used in magnetic resonance (MR) imaging. The coupling is incorporated into the invasive device between an imaging or tracking RF coil, and the MR receiver. The optical coupling has a first transducer circuit coupled to the RF which converts between optical and electrical signals. An optical fiber is coupled to the first transducer circuit and extends out of the invasive device to medical imaging equipment. Near this equipment, a second transducer circuit converts optical signals to electrical, and electrical signals to optical, just opposite that of the first transducer circuit. The present invention thereby replaces long lead wires which can cause heating during MR imaging, and may distort an MR image.

Abstract: A system for performing surgery by vibrational heating employs an ultrasonic transducer 80 for focusing a spherical ultrasound wave on a focal region. In one embodiment a refraction plate 410 having a spherical surface facing the transducer and a refracting surface with refracting pyramid elements 450 facing the subject causes the ultrasound beam to impinge on a plurality of overlapping focal regions and thereby expand the focal area of the transducer. In a second embodiment the refraction plate comprises a phased lens 600 having a constant thickness at any angular location but with its thickness varying linearly over 2.pi. radians or multiples thereof.

Abstract: A patient isolation device is used as a safety device to provide electrical insulation between medical electronic equipment and portions of the equipment which come in contact with the patient. In one implementation of the patient isolation device, an RF coil is incorporated in a catheter connected to medical electronic equipment which tracks the position of the catheter. Typically, there is also medical imaging electronics to provide internal images of the subject along with an indication of the location of the catheter. Typically, the signal from the RF coil is provided to a preamplifier to amplify the signal. The isolation device is placed between the RF coil and the preamplifier such that MR response signals may pass through to the preamplifiers but in the event of a short or electrical malfunction the line voltage will not pass backward into the RF coil causing damage to the patient.

Abstract: A system employing ultrasound imaging as a method to localize a patient's tissue volume to be treated prior to applying therapeutic levels of ultrasound energy includes a therapy transducer for producing high-intensity fields that cause necrosis and an imaging transducer for producing high-quality ultrasound images. The therapy transducer is a spheroidal piezoelectric element and the imaging transducer is made up of a plurality of piezoelectric elements mounted in fixed relationship to the therapy transducer. The therapy transducer transmits a beam that is focused at a location in the tissue to be treated. The imaging transducer is then steered to produce successive receive beams which scan the tissue, including the tissue at the focal point of the pulsed therapy transducer. The image of the focal point is then superimposed on an image of the tissue to be treated obtained by B-mode imaging using the imaging transducer to transmit and then receive.

Abstract: An electro optical circuit for transmitting an information bearing signal, such as a signal in the RF, AF or microwave frequency domains, to a predetermined location includes a laser for generating coherent light to be used as a carrier, and an electro optical modulator for receiving the information signal and the coherent light and generating first and second modulated light signals which respectively comprise the coherent light modulated by the information signal and the coherent light modulated by the inversion of the information signal. The first and second modulated light signals are supplied to a detector at the predetermined location through separate optical paths.

Abstract: A temperature monitoring system employs a temperature detection means incorporated into an invasive device intended to be placed within a body during a magnetic resonance procedure. The temperature monitoring system is used to monitor temperature rises in tissue arising from the creation of electric fields within the tissue. These electric fields are created by the application of RF pulses during the course of a magnetic resonance procedure which induce electrical current in the invasive device. It the detected temperature rise exceeds a selected threshold, the temperature monitoring system can cause the magnetic resonance imaging system to either reduce RF power or terminate the procedure. An optical coupling may be used between the imaging or tracking RF coil and the MR receiver to eliminate heating induced by the application of RF pulses during the procedure.

Abstract: A novel RF coil attached to an invasive device, such as a catheter, is used to detect magnetic resonance (MR) signals for monitoring the position of the device within a subject and for the acquisition of high-resolution magnetic resonance images of the tissue surrounding the device. The novel coil is sensitive to a small volume of MR active tissue during tracking procedures, but is sensitive to a larger volume during imaging procedures. During tracking, the MR 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 coil in several dimensions. The position of the novel coil, and hence the device, as determined by the tracking system is superimposed upon independently acquired medical diagnostic images.

Abstract: NMR images indicative of thermal changes in tissues undergoing therapy are produced using a gradient-recalled double-echo pulse sequence. A reference phase image is produced using a short echo time (TE.sub.1) and a measurement phase image is produced with a longer echo time (TE.sub.2). Temperature maps are produced during therapy using the phase difference information at corresponding pixels of the two phase images.