Abstract: A method for sensing a disturbance in a transmission path of a converging ultrasound energy beam transmitted by a transducer in a focussed ultrasound system comprises transmitting a burst of ultrasound energy from the transducer, detecting whether a reflected portion of the ultrasound energy burst is received at the transducer within a certain time period following transmission of the burst, and, if so, analyzing the received reflected portion to determine a characteristic of the disturbance.

Abstract: Apparatus, systems, and methods are provided for measuring the power of acoustic energy transmitted by an ultrasound transducer. The apparatus includes a container including a liquid therein, and a buoyant body floating at a first level in the liquid. When acoustic energy is transmitted by the ultrasound transducer towards the buoyant body, the buoyant body floats at a second, different level in the liquid. The displaced volume of the buoyant body from the first level to the second level is directly related to the power of the acoustic energy transmitted by the ultrasound transducer. The apparatus may output signals corresponding to the level at which the buoyant body floats. The signal may be routed to a controller for adjusting the power output by the ultrasound transducer.

Abstract: A system for focusing ultrasonic energy through intervening tissue into a target site within a tissue region includes a transducer array including transducer element, an imager for imaging the tissue region, a processor receiving images from the imager to determine boundaries between different tissue types within the intervening tissue and generate correction factors for the transducer elements to compensate for refraction occurring at the boundaries between the tissue types and/or for variations in speed of sound. A controller is coupled to the processor and the transducer array to receive the correction factors and provide excitation signals to the transducer elements based upon the correction factors. The correction factors may include phase and/or amplitude correction factors, and the phases and/or amplitudes of excitation signals provided to the transducer elements may be adjusted based upon the phase correction factors to focus the ultrasonic energy to treat tissue at the target site.

Abstract: Systems and methods for performing a focused ultrasound procedure monitored using magnetic resonance imaging (MRI) is provided. An MRI system uses a timing sequence for transmitting radio frequency (RF) signals and detecting magnetic resonance (MR) response signals from a patient's body in response to the RF pulse sequences. A piezoelectric transducer is driven with drive signals such that the transducer emits acoustic energy towards a target tissue region within the patient's body. Parameters of the drive signals are changed at times during the timing sequence that minimize interference with the MRI system detecting MR response signals, e.g., during transmission of RF signals by the MRI system.

Abstract: Systems and methods for focussing an ultrasound energy beam transmitted from an array of transducer elements located outside the body through a non-uniform tissue medium, such as a skull, to a location (e.g., a tumor) located inside the body by monitoring a signal representing reflected portions of the beam at a desired focal point or zone through a portion of the medium that does not significantly distort the reflected signal. In one embodiment, a focussed ultrasound system includes a plurality of transmitting transducer elements configured to deliver respective energy waves from locations outside the skull to a focal zone within the skull, the energy waves collectively comprising an energy beam. The system further includes an ultrasound detector having a fixed position relative to the transmitting elements, the detector configured to receive a signal comprising a reflected portion of the beam along a line-of-sight axis through a portion of the skull.

Abstract: Cells are destroyed within a subcutaneous tissue region using a transducer disposed externally adjacent to a patient's skin. The transducer emits acoustic energy that is focused at a linear focal zone within the tissue region, the acoustic energy having sufficient intensity to rupture cells within the focal zone while minimizing heating. The transducer may include one or more transducer elements having a partial cylindrical shape, a single planar transducer element coupled to an acoustic lens, or a plurality of linear transducer elements disposed adjacent one another in an arcuate or planar configuration. The transducer may include detectors for sensing cavitation occurring with the focal zone, which is correlated to the extent of cell destruction. A frame may be provided for controlling movement of the transducer along the patient's skin, e.g., in response to the extent of cell destruction caused by the transducer.

Abstract: A system for performing a therapeutic procedure using focused ultrasound includes a piezoelectric transducer, drive circuitry coupled to the transducer for providing drive signals to the transducer, and a controller coupled to the drive circuitry for alternating an intensity of the drive signals between a plurality of intensities. Acoustic energy above a threshold intensity is transmitted by the transducer towards a target region to generate microbubbles in tissue within the target region. The intensity of the acoustic energy is reduced to discontinue generating microbubbles and heat the tissue, e.g., to necrose the tissue, without collapsing the generated microbubbles, the microbubbles enhancing the ability of the tissue in the target region to absorb the acoustic energy.

Abstract: Cells are destroyed within a subcutaneous tissue region using a transducer disposed externally adjacent to a patient's skin. The transducer emits acoustic energy that is focused at a linear focal zone within the tissue region, the acoustic energy having sufficient intensity to rupture cells within the focal zone while minimizing heating. The transducer may include one or more transducer elements having a partial cylindrical shape, a single planar transducer element coupled to an acoustic lens, or a plurality of linear transducer elements disposed adjacent one another in an arcuate or planar configuration. The transducer may include detectors for sensing cavitation occurring with the focal zone, which is correlated to the extent of cell destruction. A frame may be provided for controlling movement of the transducer along the patient's skin, e.g., in response to the extent of cell destruction caused by the transducer.

Abstract: Systems and methods are provided for positioning a therapy device, such as an ultrasound transducer, using a tilt sensor carried by the transducer and a positioner coupled to the transducer. The positioner provides roll and pitch control as well as translating the transducer in lateral and longitudinal directions. A processor receives signals from the tilt sensor corresponding to the actual rotational orientation of the transducer and controls the positioner to adjust the orientation of the therapy device until a desired position is achieved.

Abstract: A focused ultrasound system includes a transducer array including a plurality of sub-arrays, each sub-array defining an acoustic emission surface and including a plurality of transducer elements thereon. A mechanical controller is coupled to the sub-arrays that includes actuators for moving the sub-arrays to adjust an orientation of the acoustic emission surfaces of respective sub-arrays to facilitate steering of acoustic energy emitted by the transducer elements towards a target tissue region. Drive circuitry provides drive signals to the transducer elements, whereby the transducer elements emit acoustic energy from their respective acoustic emission surfaces to ablate the target region, such as a tumor within a patient's brain.

Abstract: A system for performing a therapeutic procedure using focused ultrasound includes a transducer array including a plurality of transducer elements, drive circuitry coupled to the transducer elements, and a controller coupled to the drive circuitry. The controller controls the drive circuitry to alternatively provide sets of the transducer elements with respective drive signals. Each of the sets of transducer elements are alternatively driven with the respective drive signals for a predetermined duration during a sonication, while substantially continuously focusing ultrasonic energy produced by the transducer elements of each set at a desired focal zone. The controller also controls a phase component of the respective drive signals to provide a predetermined size, shape, and/or location of the focal zone, and thereby necrose a target tissue region at the focal zone.

Abstract: Apparatus, systems, and methods are provided for measuring the power of acoustic energy transmitted by an ultrasound transducer. The apparatus includes a container including a liquid therein, and a buoyant body floating at a first level in the liquid. When acoustic energy is transmitted by the ultrasound transducer towards the buoyant body, the buoyant body floats at a second, different level in the liquid. The displaced volume of the buoyant body from the first level to the second level is directly related to the power of the acoustic energy transmitted by the ultrasound transducer. The apparatus may output signals corresponding to the level at which the buoyant body floats. The signal may be routed to a controller for adjusting the power output by the ultrasound transducer.

Abstract: Magnetic resonance temperature change monitoring of a heated portion of a tissue mass undergoing thermal treatment is more accurately accomplished by compensating for false temperature change measurements caused by movement of the mass and/or temporal changes of the magnetic field during the thermal MR Imaging, wherein the compensation is based on subtracting out “apparent temperature change” measurements of one or more unheated portions of the tissue mass located in a neighborhood of the heated portion, which form a temperature bias map of the tissue mass region.

Abstract: A method for sensing a disturbance in a transmission path of a converging ultrasound energy beam transmitted by a transducer in a focussed ultrasound system comprises transmitting a burst of ultrasound energy from the transducer, detecting whether a reflected portion of the ultrasound energy burst is received at the transducer within a certain time period following transmission of the burst, and, if so, analyzing the received reflected portion to determine a characteristic of the disturbance.

Abstract: Systems and methods for testing the performance of a focused ultrasound transducer array include transmitting ultrasonic energy from the transducer array towards an acoustic reflector, such as a planar air mirror, and receiving ultrasonic energy reflected off of the acoustic reflector using a sensing element. A characteristic of the reflected ultrasonic energy, such as amplitude and phase, is measured by processing circuitry, for example, by comparing the characteristic of the received ultrasonic energy to a corresponding characteristic of the transmitted ultrasonic energy to obtain an actual gain and phase shift for the received ultrasonic energy. A controller compares the actual gain and phase shift of the received ultrasonic energy to an expected gain and phase shift of the received ultrasonic energy. This information is used to calibrate the transducer array and/or to declare a system failure if the comparison indicates an error.

Abstract: Systems and methods using magnetic resonance imaging for monitoring the temperature of a tissue mass being heated by energy converging in a focal zone that is generally elongate and symmetrical about a focal axis. A first plurality of images of the tissue mass are acquired in a first image plane aligned substantially perpendicular to the focal axis. A cross-section of the focal zone in the first image plane is then defined from the first plurality of images. A second plurality of images are acquired of the tissue mass in a second image plane aligned substantially parallel to the focal axis, the second image plane bisecting the first image plane at approximately a midpoint of the defined focal zone cross-section.

Abstract: Systems and methods for controlling the phase and amplitude of individual drive sinus waves of a phased-array focused ultrasound transducer employ digitally controlled components to scale the amplitude of three or more bases sinuses into component sinus vectors. The component sinus vectors are linearly combined to generate the respective sinus of a selected phase and amplitude. The use of digitally controlled controlled components allows for digitally controlled switching between various distances, shapes and orientations (“characteristics”) of the focal zone of the transducer. The respective input parameters for any number of possible focal zone characteristics may be stored in a comprehensive table or memory for readily switching between focal zone characteristics in &mgr; seconds. Changes in the output frequency are accomplished without impacting on the specific focal zone characteristics of the transducer output.

Abstract: A focused ultrasound system includes a plurality of transducer elements disposed about and having an angular position with a central axis. Drive signals drive respective transducer elements that include phase shift values based upon the angular position of each respective transducer element. The phase shift values are based upon an oscillation function that oscillates about the central axis between minimal and maximal phase shift values such that a first on-axis focal zone and a second off-axis focal zone are created. An amplitude and frequency of the oscillation function are controlled to adjust relative acoustic energy levels of the first and second focal zones, and to adjust a radius of the second focal zone, respectively. In addition, the drive signals include an additional predetermined phase shift based upon a radial position of each respective transducer element to adjust a focal distance of the focal zones.

Abstract: Systems and methods for performing a focused ultrasound procedure monitored using magnetic resonance imaging (MRI) is provided. An MRI system uses a timing sequence for transmitting radio frequency (RF) signals and detecting magnetic resonance (MR) response signals from a patient's body in response to the RF pulse sequences. A piezoelectric transducer is driven with drive signals such that the transducer emits acoustic energy towards a target tissue region within the patient's body. Parameters of the drive signals are changed at times during the timing sequence that minimize interference with the MRI system detecting MR response signals, e.g., during transmission of RF signals by the MRI system.

Abstract: Magnetic resonance temperature change monitoring of a heated portion of a tissue mass undergoing thermal treatment is more accurately accomplished by compensating for false temperature change measurements caused by movement of the mass and/or temporal changes of the magnetic field during the thermal MR Imaging, wherein the compensation is based on subtracting out “apparent temperature change” measurements of one or more unheated portions of the tissue mass located in a neighborhood of the heated portion, which form a temperature bias map of the tissue mass region.