Abstract: Disclosed herein are portable ultrasound systems and methods. In an example, a portable ultrasound system can include a handheld computer, a case holding the handheld computer, a probe head coupled to the case, and a communicating means for communicating between the probe head and the handheld computer. The handheld computer can include a display. The case can also include an anterior opening framing the display of the handheld computer. The case can include a rechargeable battery integrated into the case opposite the anterior opening. The probe head can include an array of ultrasonic transducers powered by the battery. In another example, a method of the portable ultrasound system includes a method of using the portable ultrasound system.

Abstract: Disclosed are devices and methods for automated emergency arterial cannulation. The device comprises a hand-held automated emergency arterial sheath placement device having a body with a handle and an actuator, and an arterial sheath placement head at the distal end of the handle body configured for placement against the patient's skin. The arterial sheath placement head includes an arterial sheath insertion device configured to advance an arterial needle, guide wire, and arterial sheath into a patient's artery upon sequential operation of the actuator. The arterial sheath placement head also includes a non-invasive artery locator configured to locate an artery into which the arterial sheath is intended to be placed. The arterial sheath placement head also preferably includes a Doppler gel and antiseptic needle, a local anesthetic needle, and a scalpel, all of which are likewise configured to advance from the upper body portion upon sequential operation of the actuator.

Abstract: Disclosed are devices and methods for automated emergency arterial cannulation. The device comprises a hand-held automated emergency arterial sheath placement device having a body with a handle and an actuator, and an arterial sheath placement head at the distal end of the handle body configured for placement against the patient's skin. The arterial sheath placement head includes an arterial sheath insertion device configured to advance an arterial needle, guide wire, and arterial sheath into a patient's artery upon sequential operation of the actuator. The arterial sheath placement head also includes a non-invasive artery locator configured to locate an artery into which the arterial sheath is intended to be placed. The arterial sheath placement head also preferably includes a Doppler gel and antiseptic needle, a local anesthetic needle, and a scalpel, all of which are likewise configured to advance from the upper body portion upon sequential operation of the actuator.

Abstract: Systems and methods for autonomous intravenous needle insertion are disclosed herein. In an embodiment, a system for autonomous intravenous insertion include a robot arm, one or more sensors pivotally attached to the robot arm for gathering information about potential insertion sites in a subject arm, a medical device pivotally attached to the robot arm, and a controller in communication with the sensors and the robot arm, wherein the controller receives the information from the sensors about potential insertion sites, and the controller selects a target insertion site and directs the robot arm to insert the medical device into the target insertion site.

Abstract: Methods and systems for drilling to a target location include a control system that receives an input comprising a planned drilling path to a target location and determines a projected location of a bottom hole assembly of a drilling system. The projected location of the bottom hole assembly is compared to the planned drilling path to determine a deviation amount. A modified drilling path is created to the target location as selected based on the amount of deviation from the planned drilling path, and drilling rig control signals that steer the bottom hole assembly of the drilling system to the target location along the modified drilling path are generated to intersect the planned drilling path if the amount of deviation from the planned path exceeds a first threshold amount of deviation.

Abstract: An ultrasound medical treatment system includes an end effector insertable into a patient. The end effector includes a tissue-retaining device. The tissue-retaining device includes a first tissue-retaining member having an ultrasound medical-treatment transducer and includes a second tissue-retaining member. The first and second tissue-retaining members are operatively connected together to retain patient tissue between the first and second tissue-retaining members and to release patient tissue so retained. In one example, the second tissue-retaining member has an ultrasound reflector. In the same or a different example, the ultrasound medical-treatment transducer is an ultrasound imaging and medical-treatment transducer.

Abstract: In the biopsy system according to one embodiment, the needle tube of the treatment tool has the minor axis of the flattened portion and the bending plane of the bending portion parallel to each other. Accordingly, the needle tube is easily bent in the bending direction of the bending portion, and even in an endoscope that has few bendable directions and is bendable, for example, in only two directions (e.g., up and down), the bending operation of the bending portion is not easily hindered. As a result, even after the treatment tool for endoscopes is inserted into the endoscope, the bending portion can be easily bent with a predetermined bending amount, and a procedure can be easily performed.

Abstract: An embodiment in accordance with the present invention provides a device and method for a transrectal ultrasound (TRUS) guided prostate biopsy. The device includes an ultrasound wand equipped with a lateral fire ultrasound sensor. The ultrasound wand also defines a channel having an oblique path though the wand. The channel accommodates a biopsy needle, which can be pivoted as well inserted through the channel to different depths in order to perform a biopsy of the prostate. The device therefore uses only three degrees-of-freedom of movement in order to obtain the biopsy samples. Additionally, the ultrasound wand can be used to generate a three-dimensional image of the prostate.

Abstract: An apparatus for accessing the lumen of a vessel. The apparatus includes a main body and a disposable cartridge. The main body includes a imaging device attachment, wherein the imaging device attachment is utilized to secure an image capturing instrument to the main body; a cartridge carrier coupled to the imaging device attachment, wherein the cartridge carrier is adjustable to achieve a target insertion depth; and a first motor coupled to the cartridge carrier, wherein the first motor adjust the cartridge carrier to achieve the target insertion depth. The disposable cartridge is attached to the cartridge carrier and houses a sheath, needle, or guidewire to be inserted into the vessel to the target insertion depth.

Abstract: An apparatus for accessing the lumen of a vessel. The apparatus includes a reusable handheld device and a disposable cartridge. The reusable handheld device includes a imaging device attachment utilized to secure an image capturing instrument, an arm coupled to the imaging device attachment, and a depth scale coupled to the arm, wherein the depth scale provides a scale indicating an insertion depth. The disposable cartridge attaches to the reusable handheld device. The disposable cartridge includes a sheath, needle or guidewire coupled to the disposable cartridge. The sheath or needle extends to the insertion depth when fully advanced, thereby allowing the sheath, needle, or guidewire to access the lumen of a vessel.

Abstract: An endoventricular injection catheter with integrated echocardiographic capability enables injections into heart tissue under visualization. The catheter includes an elongated body having a distal end and an imaging core arranged to be inserted into a heart. The imaging core is arranged to transmit ultrasonic energy and to receive reflected ultrasonic energy at the distal end to provide electrical signals representing echocardiographic images to enable cardiac visualization. The catheter further includes an injector carried on the elongated body with the imaging core. The injector is arranged to inject a therapeutic agent into tissue of the heart visualized by the imaging core.

Abstract: An intraluminal endoscope inserting method according to the present invention is a method of forming a first opening in a wall of a first luminal organ while observing optical and ultrasonic images formed by an ultrasonic endoscope inserted into a first luminal organ through a natural opening, forming a second opening in a wall of a desired second luminal organ adjacent to the first luminal organ through an abdominal cavity space from the first opening, leading the ultrasonic endoscope into a second luminal organ from a second opening and performing observation and treatment, and after the treatment and the like, stitching the openings. This makes it possible to insert the endoscope with a skill same as that required for a normal endoscope test and makes it easy to insert the endoscope even into luminal organs irregularly connected to with one another in a body cavity.

Abstract: The invention includes a probe for imaging tissue within a body cavity. The probe includes a housing which has a first substantially narrow elongate distal portion insertable into a body cavity, and a second elongate portion proximal of the first elongate portion. The narrow distal portion houses a transducer which is longitudinally translatable and rotatable relative thereto. The second elongate portion houses a platform assembly and a movable member. The platform assembly includes a transmission system and a frame, both of which are coupled to the transducer by at least one connector such that rotational movement of the platform assembly within the second elongate portion effectuates rotation of the transducer within the first elongate portion, and translational movement of the moveable member within the second elongate portion effectuates translational movement of the transducer within the first elongate portion. The probe is used with a needle assembly and delivery system.

Abstract: An apparatus and method for guiding a needle in conjunction with a biopsy using a medical imaging device, where a non-reusable needle guide, which is relatively inexpensive which grasps the sheathed bracket firm, and holds the same in a set position based upon a bullet-nose lock.

Abstract: The ultrasound probe includes a first priority setting unit which sets a priority regarding which of temporal resolution and spatial resolution is given preference, and a measurement parameter setting unit which sets values of measurement parameters relating to the temporal resolution and the spatial resolution in accordance with the priority set by the first priority setting unit and a measurement depth set in advance such that power consumption falls within the allowable power consumption.

Abstract: Systems and methods for assisting/performing image-guided transjugular intrahepatic portosystemic shunt (TIPS) procedures in a portion of an anatomy of a patient include a guide needle portion having a hollow tube with a bend toward its distal tip, and a puncture needle portion that includes at least one position indicating element at its tip. The puncture needle is slidably mounted within the hollow tube of the guide needle such that a distal tip of the puncture needle can be extended from an opening in the distal tip of the guide needle and used to place a shunt between the portal and hepatic veins of a patient. The position indicating element of the puncture needle is used to produce a display of the puncture needle relative to a target vessel, including a projected path of the puncture needle that can be adjusted to accurately locate a shunt.

Abstract: A hyperechogenic needle includes a rigid shaft, which can be a hollow metal cannula, having a hyperechogenic particulate material affixed on an outer surface of the shaft that provides for visualization of the needle in two-dimensional (2D) ultrasound, particularly when the needle is in a position forming a non-90° angle between the longitudinal axis and the direction of the ultrasound waves in the two-dimensional ultrasound plane. The hyperechogenic particulate material can be covered by a polymeric coating or embedded in a polymeric material to provide a hyperechogenic layer. The polymeric coating and polymeric material can be electrically non-conductive or electrically conductive.

Abstract: Embodiments provided here generally relate to combinations of ultrasound aspects and antibodies. In some embodiments, antibodies are immobilized on a surface and binding of the antibodies to antigens can be detected by detecting changes in the vibrational properties of the surface.

Abstract: Needle guide systems for a sonography device are disclosed. The needle guide systems include both fixed and adjustable needle guides. In one embodiment, the needle guide includes a needle guide body that is rotatably mounted to a probe of a sonography device. A plurality of needle channels is disposed on a surface of the needle guide body. Each needle channel can be selectively rotated into position to guide a needle into a body of a patient at a predetermined needle insertion angle. If another needle insertion angle is desired, the needle guide is rotated to place a new needle channel defining the desired needle insertion angle into position.

Abstract: An intravascular ultrasound catheter system is provided and enables a simplified, economical technique for ultrasound visualization of a blood vessel. The catheter may include a park ablation system for crossing chronic total occlusions and severe stenoses. The catheter is advanceable and is oriented entirely under manual control of the clinician and the application of radiofrequency energy for spark erosion of the stenosis also is controlled manually by the clinician. The system enables the clinician to observe an ultrasound image sufficiently to determine where to orient the ablation electrode so as to reduce the risk of dissection or perforation of the blood vessel. The ultrasound image is generated in response to manual rotation of the catheter and the ablation spark is generated only when the physician is satisfied as to the orientation of the electrode within the vessel.

Abstract: A biopsy probe mechanism includes an elongate sample receiving member having a longitudinal axis and having a sample receiving notch. An elongate sample receiving member and a cutting cannula are movable relative to one another along a longitudinal axis between a first relative position and a second relative position. A first echogenic feature is established on the elongate sample receiving member and a second echogenic feature is established on the cutting cannula. The first echogenic feature is in longitudinal alignment with the second echogenic feature when the elongate sample receiving member and the cutting cannula are in the first relative position. The first echogenic feature is out of longitudinal alignment with the second echogenic feature when the elongate sample receiving member and the cutting cannula are in the second relative position.

Abstract: This invention relates to a pre-formed shape-memory trans-septal puncture catheter incorporating an intra cardiac echocardiography sensor and smart sheath and a related method of use

Abstract: A support tool for a supply assembly delivers a functional fluid to an implantable medical device. The supply assembly defines a supply axis. The support tool includes a support member defining an opening. The opening has a support axis, and the opening is configured to receive the supply assembly. The support member includes a three dimensionally contoured nesting surface that conforms to a corresponding three dimensionally contoured surface of the supply assembly. The corresponding surface of the supply assembly nests against the nesting surface to support the supply assembly such that the supply axis remains substantially fixed relative to and aligned with the support axis.

Abstract: An interventional medical device is provided that incorporates a forward-directed ultrasound imaging system integrated into a single device. The medical device can be in the form of sheaths, catheters, and interventional devices, particularly those suitable for minimally invasive procedures in the human or other mammalian body. The imaging system comprises one or more small ultrasound transducers that can be permanently integrated into the device or integrated into an interchangeable ultrasound transducer that can be inserted into and removed from the device to customize the device for a particular use. An ultrasound system can be provided in the device either alone or in combination with fiber optic imaging to provide a range of imaging and therapeutic capabilities of the device.

Abstract: An interventional medical device that incorporates an imaging system may be minimally invasive and equipped with an anchoring portion at a proximal end for securing the device to a human body. A luer lock may be utilized at the proximal end, for example, for introducing a syringe. The medical device can be in the form of sheaths, catheters, and interventional devices, particularly those suitable for minimally invasive procedures in the pericardium. The imaging system comprises one or more ultrasound transducers and can be used to guide the device to a target area and to perform a procedure and/or provide access to a target area for performing a procedure via a plurality of lumen. In one embodiment, a micro-electro-mechanical system may be utilized to monitor pressure within a human body.

Abstract: An apparatus and method for guiding a needle in which the apparatus comprises a locking button for coupling the needle guide to a transceiver bracket and an unlocking button for unlatching the locking button from a coupling position, where both buttons are pushed in the same direction to accomplish their respective locking and unlatching.

Abstract: An ultrasound endoscope has an ultrasound probe which is disposed at a distal end side of a distal end rigid portion configuring a distal end portion out of a flexible tube portion, a bending portion and the distal end rigid portion configuring an insertion portion, and forms an ultrasound scanning surface having a normal line in a direction orthogonal to an endoscope insertion axis L1, and a treatment instrument outlet of a treatment hole in the distal end rigid portion. The ultrasound probe is configured by a plurality of ultrasound transducers arranged in a convex circular arc shape, and a center of curvature of the plurality of ultrasound transducers is disposed at a proximal end side from the treatment instrument outlet.

Abstract: A medical device removal system includes a vessel filter repositioning or removal device to remove and/or reposition a medical device, such as a vessel filter. The system includes a gripper to grip a medical device that is located within a body vessel, and a detector, linked to the gripper, to detect the proximity of the medical device to the gripper. The system may also include an output to indicate a signal from the detector.

Abstract: Needles are deployed in tissue under direct ultrasonic or other imaging. To aid in deploying the needle, a visual needle guide is projected on to the image prior to needle deployment. Once the needle guide is properly aligned, the needle can be deployed. After needle deployment, a safety boundary and treatment region are projected on to the screen. After confirming that the safety boundary and treatment regions are sufficient, the patient can be treated using the needle.

Abstract: A compact ultrasound needle guidance system and method of use is described. The needle guidance system has components to adjustably target a needle's destination in the plane of a two-dimensional ultrasound image before insertion of a needle into a patient. Needle movement is tracked using a position detector that provides a visual display of the needle path on the ultrasonic image.

Abstract: An ultrasound diagnostic apparatus including an ultrasonic probe transmitting and receiving ultrasound toward and from a subject, a puncture adaptor configured to be fixed to the ultrasonic probe and to hold a puncture needle, wherein the puncture adaptor has moving part movable in relation to the ultrasonic probe with the puncture needle, and a sensor provided at the ultrasonic probe, and configured to detect the position of the moving part. As the puncture needle is moved relative to the probe, the movable part is correspondingly moved relative to the probe, and movement of the movable part, and therefore also of the puncture needle, is detected by the sensor.

Abstract: The present invention relates to an acoustic device for ultrasonic imaging of an object (21). The device comprises an acoustic transducer (10 and an acoustic lens (20) arranged to variably refract the said acoustic pulse to and/or from the acoustic transducer. The acoustic lens comprising a first (L1) and a second fluid (L2) being separated by an acoustic interface (7), the normal of the said acoustic interface forming a relative angle of incidence (AI) with the said acoustic pulse, e.g. an electrowetting lens. The first and the second fluid of the acoustic lens (20) are specifically chosen so that the acoustic interface (7) has a reflection minima at a non-zero relative angle of incidence (AI). The invention is advantageous for obtaining an improved acoustic device having a substantially lower reflection in a broader interval of incidence angles as compared to hitherto seen ultrasonic imaging utilising acoustic lenses with two or more fluids as the active acoustic refracting entities.

Abstract: Needles are deployed in tissue under direct ultrasonic or other imaging. To aid in deploying the needle, a visual needle guide is projected on to the image prior to needle deployment. Once the needle guide is properly aligned, the needle can be deployed. After needle deployment, a safety boundary and treatment region are projected on to the screen. After confirming that the safety boundary and treatment regions are sufficient, the patient can be treated using the needle.

Abstract: An ultrasound needle guide system for use with an ultrasound transducer and method of use of the guide system to provide predictable trajectories for puncture devices at various depths. The needle guide system basically consists of a bracket and a needle guide. The bracket is arranged to be releasably secured to the ultrasound transducer. The transducer/bracket assembly is then placed into an isolating sterile cover. The needle guide is arranged to be readily attached, e.g., snap-fit, to the transducer/bracket with the cover interposed therebetween. The needle guide can be provided in various versions for differing puncture device sizes and various entry angles in relation to the transducer. In one embodiment the needle guide is arranged to establish plural predetermined entry angles.

Abstract: A connectorized ultrasound probe includes a distal section that is configured for insertion into a patient's body and a proximal section configured to interface the distal section with an ultrasound system. The distal section is easily attachable and detachable from the proximal section using at least one set of connectors. When connected, a user-operated actuator located on the proximal section controls the bending of the distal section, and the ultrasound system sends driving signals to and receives return signals from the ultrasound transducer via the proximal section. This arrangement is particularly advantageous for long term monitoring, because the disconnectability of the proximal section makes it possible to leave the distal section in place in the patient for longer periods of time without undue discomfort.

Abstract: A method for discriminating particle groups comprises generating, by a particle analyzer, a particle characteristic distribution histogram in which the abscissa indicates respective channels for representing the characteristics of the particles, and the ordinate indicates the particle count; setting a valid area selection height in the particle characteristics distribution histogram; and generating an equivalent negative histogram based on the set height and the particle characteristic distribution histogram.

Abstract: A medical device removal system includes a vessel filter repositioning or removal device to remove and/or reposition a medical device, such as a vessel filter. The system includes a gripper to grip a medical device that is located within a body vessel, and a detector, linked to the gripper, to detect the proximity of the medical device to the gripper. The system may also include an output to indicate a signal from the detector.

Abstract: An ultrasound beacon is incorporated into a needle of a drug delivery system utilizing high intensity ultrasound energy during certain cancer treatments. The beacon is configured to generate a electrical feedback signal in response to an initial ultrasound signal sent by an ultrasound transmitter. The electrical feedback signal is then sent along two electrical conductors of the needle and further over a cable back to the electronic unit. The feedback signal is then used to generate high intensity focused ultrasound using time-reversal acoustics principles. Therapeutic application of the system of the invention includes applying high intensity focused ultrasound at the site of drug delivery to enhance local tissue uptake of injected medication.

Abstract: A needle biopsy guide system is disclosed for attachment to an endoluminal ultrasound probe or like sonographic instrument. The device includes a biopsy-guide attachment that allows for trocar catheter placement for abscess drainage or like procedures, using the transvaginal or transrectal route under sonographic control. The device has a base portion, which is attachable to an ultrasound probe. A removable retainer is provided that slides into the base unit to hold a biopsy needle in place. A physician may locate the target area in the body with the ultrasound probe, insert the biopsy needle into the target area, and then remove the insert (retainer) from the base unit and ultrasound probe, and leave the biopsy needle in place in the body.

Abstract: An apparatus and method for treating subcutaneous tissues using acoustic waves in the range of low acoustic pressure ultrasound waves is disclosed. The method includes injections of enhancing agents, wherein disruption of subcutaneous tissues and subcutaneous cavitational bioeffects are produced by ultrasound waves having a power that will not produce tissue cavitation in the absence of the enhancing agents. The apparatus and method of use is useful for treatment of subcutaneous abnormalities including cellulite, lipomas, and tumors.

Abstract: An improved probe guide and probe guide system for use in conjunction with a medical imaging device is disclosed. The medical imaging device may be any type of imaging device that generates a cross-sectional image of a portion of a patient's body in a single image plane, such as, ultrasound, CT, or MRI imaging devices. The probe guide allows maintaining the movement of the probe within the image plane and accurate placement of a probe, such as a biopsy needle, by allowing a range of angular translation of the probe. The probe guide system enables extrapolation of the penetration path of the probe held by the probe guide and superimpose it on to the cross-sectional image allowing the medical personnel to view the penetration path of the probe within the patient in advance.

Abstract: An ultrasonic probe with an ultrasonic head (K), which is arranged on or in a shaft (S) and is moveable with or in this shaft, and a positioning apparatus (P) for at least one examination or operating device is described, which is connected with the shaft. Also, medical operating apparatuses with examination probes and uses of the ultrasonic probe and the medical implements are described.

Abstract: A puncture adapter is provided for being mounted on an ultrasonic probe. The ultrasonic probe to be mounted comprises a rod-like insertion portion that is insertable into a subject and has a search unit for transmitting and receiving ultrasonic waves at the tip end of the insertion portion, and in which a guide channel for guiding a puncture needle is formed on a side surface of the insertion portion. This puncture adapter has a first tubular component on which a gap is provided on a side surface along the length direction, which gap is from one end to the other side of the side surface. The first tubular component is mounted so as to contact the outside of the insertion portion and cover the guide channel, and is turnable in the circumferential direction thereof.

Abstract: An electronic system includes a reader and a remotely powered and remotely interrogated sensor transponder. The sensor transponder includes a reader and a remotely powered and remotely interrogated sensor transponder. The sensor transponder includes a sensor and a radiation receiving device. Data from the sensor is conditioned to provide sensor data ratiometric with magnitude of excitation voltage provided by the radiation receiving device.

Abstract: An adapter for use in puncture (a puncture adapter) for performing puncture while an ultrasonic image is being observed. The puncture adapter is composed of a holder for holding a probe which transmits and receives an ultrasonic wave, and a base unit for movably supporting the holder. A guide mechanism provided in the base unit guides a puncture needle. Moving the probe held in the holder moves a beam scan plane, and the intersection between the beam scan plane and a puncture route can be moved along the puncture route. The base unit functions as a seat which is brought into contact with a surface of a living body. A plurality of projecting legs may be provided on the base unit. The plurality of projecting legs are provided along the periphery of the movement region in which the wave transmitting and receiving surface of the probe moves.

Abstract: A paracentesis needle holder attachable to an ultrasonic probe is provided. The holder includes a needle guide, an adjustment mechanism, and an open/close mechanism. The needle guide includes a first base and a second base and is configured to guide a needle in a plurality of directions between the first and second bases. The adjustment mechanism is provided at the needle guide and configured to adjust spacing between the first base and the second base in accordance with a diameter of the needle. The open/close mechanism is coupled with the needle guide and configured to close the first and second bases so that the needle is guided in one of the directions and to open the first and second bases so that the needle becomes releasable from the holder.

Abstract: A system and method for regional anesthesia using ultrasound to assist in locating the anesthetic needle are disclosed. One or more piezo-electric crystal transducers is placed either at the tip of the needle or near the tip of the needle on a stylet which is inserted into the lumen of the needle. The transducer(s) are pulsed with ultrasonic frequency, the reflected ultrasonic signals from structures are detected and converted into a digital signal and may be displayed in an oscilloscopic format to indicate anatomical structures forward to the needle and allow the medical professional to avoid errors and/or increase efficiency and accuracy. An array of transducers can be pulsed in a phased array fashion to generate a 2D image, or a single transducer can be pulsed to generate a 1D image.

Abstract: The needle injection catheter includes a delivery tube and at least one hypotube that fits slidably within the delivery tube. The hypotube has at least three hollow needle portions extending outwardly at its distal end. The needle portions curve outwardly and have ends shaped to penetrate tissue. At least one reference electrode is located on the delivery tube, spaced from the second end. At least one proximal electrode is located adjacent and spaced from the end of the needle portion. The proximal electrode is electrically connected to a first notification device. A microcircuit is electrically connected to the proximal electrode, the reference electrode and to a power supply. A distal electrode is located adjacent the end of the needle portion and electrically connected to the microcircuit. A tip electrode is located adjacent the second end of the delivery tube and electrically connected to a second notification device and the microcircuit.

Abstract: A method for discriminating particle groups comprises generating, by a particle analyzer, a particle characteristic distribution histogram in which the abscissa indicates respective channels for representing the characteristics of the particles, and the ordinate indicates the particle count; setting a valid area selection height in the particle characteristics distribution histogram; and generating an equivalent negative histogram based on the set height and the particle characteristic distribution histogram.

Abstract: Intravascular device for matching impedances of portions of an intravascular circuit and limiting RF signal-induced heating of intravascular conductors. An intravascular device includes alternating conductive and dielectric layers and an electrically conductive coil in a configuration that effects an impedance-matching circuit. Another embodiment of an intravascular device has cylindrical inner and outer walls formed of an expandable, electrically conductive material, the inner and outer walls being separated by a compressible dielectric material. Varying the pressure in the lumen defined by the inner wall changes the spacing between the inner and outer walls, thereby changing the capacitance between the inner and outer wall. Another embodiment of an intravascular device includes one or more coaxial chokes for limiting heating caused by currents induced by RF signals. A conductive shield of the choke is formed of a conductive polymer to further reduce heating effects.