Patent Application
20110028845
The subject matter disclosed herein generally relates to reconfigurable sensor arrays and, in particular, to a reconfigurable ultrasound transducer array.
The present state of the art discloses a number of imaging systems having ultrasound sensor arrays configured to produce two-dimensional (2-D) images of a human heart in real-time inside a subject's body. Typical applications for such imaging systems include diagnosis and the monitoring of interventional procedures in, for example, Trans-Esophoegeal Echocardiography, Intra-Cardiac Echocardiography, and Intra-Vascular Ultrasound.
Imaging systems that are capable of producing three-dimensional (3-D) images in real-time typically utilize beam-forming electronics that occupy a larger volume than a corresponding 2-D imaging system and are thus not practical for placement inside the body to image the human heart. Some conventional ultrasound probes utilize micro-motors to actuate 2-D transducers placed inside the body to acquire 3-D imaging volumes in real time. However these micro-motor probes do not have the ultrasound beam agility of an electronically steered ultrasound probe and have not demonstrated the reliability offered by completely solid-state probes.
A reconfigurable sensor array offers a method to reduce the requirements on size and power for the beam-forming electronics, but uses high voltage switches at the transducer. Accordingly, such arrays suffer from the large size of such devices and are therefore limited to smaller sizes or higher on-resistance which leads to unwanted signal attenuation and delay. It is also possible to use a pulser switch matrix in which each transducer element is driven directly by a local pulser circuit while the transmit timing signal is distributed throughout the array using a low voltage switching network. While this solution can work well for B-mode imaging, it may not have adequate noise performance for high quality Doppler imaging.
The inventors herein have recognized a need for a high quality Doppler-capable reconfigurable ultrasound array for use in imaging the heart from inside the body.
An ultrasound transducer probe comprises: an array of ultrasound transducer elements, each ultrasound transducer element associated with a corresponding unit transducer cell for providing transmit and receive functions, each unit transducer cell including a cell transmit/receive switch connected to a low voltage switch matrix via a low voltage transmit path; and a plurality of microelectronic cross-point switches for switching an externally generated transmit control signal to one or more of the low voltage transmit paths.
An ultrasound transducer probe system comprising: a probe including, an array of ultrasound transducer elements; a plurality of unit transducer cells, each ultrasound transducer element coupled to a corresponding unit transducer cell; a transmit channel line for conducting transmit control signals from an ultrasound driver to a low voltage switch matrix in each of the unit transducer cells, the low voltage switch matrix for switchably providing the transmit control signal to a corresponding ultrasound transducer element via a low-voltage electrical path; and a programming circuit connected to each low voltage switch matrix by a system channel line.
A method for monitoring an interventional procedure inside a patient, the method comprising: providing an ultrasound transducer probe having a reconfigurable ultrasound transducer array; guiding the probe to a region of interest inside the patient; providing a transmit control signal to a transducer array through a switch matrix via a low-voltage electrical path; providing a control signal to the reconfigurable ultrasound transducer array for electronically steering an ultrasound beam produced by the ultrasound transducer probe; and imaging the interior of the patient via the ultrasound beam to obtain a three-dimensional, real-time image of the region of interest.
Other systems and/or methods according to the embodiments will become or are apparent to one with skill in the art upon review of the following drawings and detailed description. It is intended that all such additional systems and methods be within the scope of the present invention, and be protected by the accompanying claims.
This invention describes a reconfigurable switch matrix based ultrasound probe for producing high quality Doppler ultrasound images of the heart using a relatively compact and low-power ultrasound beamforming system. The system is especially useful for imaging the heart from inside the body. This method of imaging may provide an increased available image volume and an improved signal-to-noise ratio for use in catheter-based or endoscopy-based echo-cardiography imaging. The disclosed probe configuration may provide several advantages including, for example: 1) improved reliability as moving parts are not used; 2) lower power requirements; 3) smaller physical size; 4) greater ultrasound beam agility; 5) lower-cost solid-state implementation; and 6) higher quality Doppler imaging capabilities.
In particular, the reconfigurable ultrasound probe disclosed herein provides a reconfigurable array that can be adapted to, for example, an intercardiac echocardiography (ICE) probe, an intravascular ultrasound (IVUS) probe, or a trans-esophoegeal echocardiography (TEE) probe. The reconfigurable array utilizes timing signals both to control local high voltage pulsers and to drive the transducers themselves in a low voltage Continuous Wave (hereinafter CW) mode. A level-shifter circuit may be included to allow signals having voltage levels greater than logic levels to be passed through a low-voltage reconfigurable array switch network.
Standard B-mode imaging is accomplished by configuring the switch matrix for a given aperture to realize rings (or arcs for steering) which cause the beam to be focused in front of the array. An acoustic beam is transmitted by the array in response to a low voltage timing signal which is propagated throughout the switch matrix. Each of the rings corresponds to a unique ultrasound transmit channel where all elements connected to one ring will transmit sound at the same phase. Within each cell there is a discriminator which decodes the low voltage signal and generates drive signals to control a high voltage pulser which then drives the ultrasound transducer.
The invention also provides a switch gate drive level-shifter circuit which enables the ultrasound beamforming system to transmit continuous wave ultrasound pulses through the low voltage switch network which are larger than what might ordinarily be tolerated according to the required logic levels for the device. In this way, high quality, very low-noise transmit timing signals can be used to control blood flow imaging by circumventing local pulser and timing circuitry.
The reconfigurable ultrasound transducer array 30 may comprise a one-dimensional element array (not shown) or a two-dimensional array, as represented by the ultrasound transducer element array 32 of twelve ultrasound transducer elements 34, in
In an exemplary embodiment, each ultrasound transducer element 34 is substantially hexagonal in shape to provide for a close-packing configuration in the ultrasound transducer element array 32, although the present invention is not limited to this configuration and other one-dimensional or two-dimensional ultrasound transducer element array geometries may be used. An active surface 38 (i.e., the emitting surface of the ultrasound transducer element array 32) may be defined by the aggregate of the individual surfaces of the transducer elements 34 comprising the ultrasound transducer element array 32. The active surface 38 both emits ultrasound beams and receives ultrasound beam echoes, and may be substantially planar, convex, or concave to function with a specified ultrasound waveform configuration.
Alternatively, the active surface 38 may comprise connected planar, convex, or concave surface sections for greater flexibility in fabrication of the ultrasound transducer element array 32. The plurality of ultrasound transducer elements 34 in the ultrasound transducer element array 32 may be interconnected by a series of microelectronic switches in a switch matrix, as explained in greater detail below, and as disclosed in commonly-assigned U.S. Pat. No. 6,865,140 “Mosaic arrays using micro-machined ultrasound transducers,” incorporated in its entirety herein by reference.
In the exemplary embodiment shown, the ultrasound transducer element array 32 comprises twelve ultrasound transducer elements 34 arranged in three rows but it should be understood that any one- or two-dimensional configuration can be used for the ultrasound transducer element array 32, with more or fewer transducer element rows and more or fewer ultrasound transducer elements in each row, depending upon the particular ultrasound application desired. In an alternative exemplary embodiment (not shown), the transducer element array 32 may comprise a 32×32 array of ultrasound transducer elements 34. As appreciated by one skilled in the relevant art, the reconfigurable ultrasound transducer array 30 enables the dynamic connection and re-connection of groups of selected ultrasound transducer elements 34 so as to provide desired acoustic transmission and receiving patterns during operation of the ultrasound transducer probe 20 (shown in
Control signals may be provided to the reconfigurable ultrasound transducer array 30 via a plurality of microelectronic cross-point switches, here exemplified by cross-point switches 52, 54, and 56. That is, one cross-point switch may be used for each transducer element row 36. Each of the cross-point switches 52, 54, and 56 functions to connect one or more of the analog paths in the transmit channel line 14 to one or more transmit/receive (T/R) lines in respective T/R busses 22, 24, and 26. The T/R bus 24, for example, thus connects the transmit/receive system 12 to a series of unit transducer cells 40 associated with respective ultrasound transducer elements 34 in the common transducer element row 36.
As shown in greater detail in the exploded diagrammatical isometric illustration of
The transmit/receive switch 62 can change states to either allow the transmission of signals from the signal generator 64 to selected unit transducer cells 40 and ultrasound transducer elements 34, or to provide signals acquired to the ultrasound receiver 68. Each ultrasound transducer element 34 in the ultrasound transducer element row 36 may also have a local ground 58. It can be appreciated by one skilled in the relevant art that phase noise and timing errors may be produced in the reconfigurable ultrasound transducer array 30 as a result of decoding processes and the use of high-impedance high-voltage transmitters. Such phase noise and propagation errors can be especially detrimental when trying to image blood flow using Doppler processing, for example. Accordingly, it is advantageous that, to reduce noise, the low-voltage signal paths communicating with the system channel line 18 circumvent the high voltage electrical paths providing transmission signals to the ultrasound transducer elements 34, as disclosed below.
There is shown in
The low voltage switch matrix 46 may operate in the range of about 2.5 to 5.0 volts using, for example, CMOS devices. The low voltage switch matrix 46 can be switched to pass the analog transmit signal 84 to the cell T/R switch 48 in the unit transducer cell 40 and thereby control operation of the corresponding ultrasound transducer element 34. The electrical path connecting the transmit control signal generator 60 to the low voltage switch matrix 46 and to the cell T/R switch 48 may define a low-voltage transmit path 74. Accordingly, transmit/receive signals 88 may travel between the low voltage switch matrix 46 and the ultrasound transducer element 34 via the low voltage transmit path 74.
The local transmit control generator 42 in the unit transducer cell 40 may provide a pulse transmission signal 72 to control the high voltage pulse transmitter 44, which may operate in a B-mode or in a pulsed wave (PW) Doppler mode, for example. As understood in the relevant art, B-mode imaging includes transmitting a repeated pattern of a relatively small number of pulses, such as one to ten pulses, at a standard rate (i.e., Pulse Repetition Frequency), to acquire data for display as two-dimensional or three dimensional tomographic images. In comparison, PW Doppler operation can be used to obtain velocity data, such as blood flow information. It can be appreciated by one skilled in the art that B-mode imaging may be used to provide probe guidance prior to subsequent probe operation in the PW mode. The transmission signal 86 from the high voltage pulse transmitter 44 may range from about thirty to about five hundred volts. The electrical path from the local transmit control generator 42 to the cell T/R switch 48 may define a high-voltage transmit path 76. The cell T/R switch 48 may also function to isolate the low voltage switch matrix 46 from the high-voltage transmission signals generated by the high voltage pulse transmitter 44. It can be appreciated that high quality, low-noise transmit timing signals on the low voltage transmit path 74 thus circumvent the signals from the local transmit control generator 42 on the high-voltage transmit path 76.
In an exemplary mode of operation, the probe system 10 may function in accordance with a flow diagram 100, shown in
The programming circuit 16 next determines whether the reconfigurable ultrasound array 30 is to operate in a CW mode or in a PW mode, at decision block 108. For the CW mode, the analog transmit signal 84 is provided to the low voltage switch matrix 46, at step 110. If the corresponding switch is in the “ON” state in the low voltage switch matrix 46, the analog transmit signal 84 passes through the cell T/R switch 48 on the low voltage transmit path 74. For the PW mode, the high voltage pulse transmitter 44 sends a signal on the high voltage transmit path 86, at step 112. For either the CW or PW modes, the ultrasound transducer element 34 “fires,” at step 114. The receiver “listens” for the ultrasound echo, and the process repeats steps 108 through 114 if, at decision block 116, it is determined that the imaging session has not been completed. Otherwise, control returns to the programming circuit 16, at step 118.
There is shown in
The analog transmit signals 84 generated by the transmit control signal generator 60 may be provided to the low voltage switch 46 in the unit transducer cell 90. The low voltage switch 46 can be switched to a first configuration in which the analog transmit signal 84 is passed to the cell T/R switch 48. The analog transmit signal 84 functions as described in the flow diagram 100, as in
The low voltage switch matrix 46 may include a switch gate drive level shifter 122, as shown in greater detail in
The probe system 10 may function in accordance with a flow diagram 130, shown in
The programming circuit 16 next determines whether the reconfigurable ultrasound array 30 is to operate in a CW mode or in a PW mode, at decision block 136. For the CW mode, the analog transmit signal 84 is provided to the low voltage switch matrix 46, at step 138. If the corresponding switch is in the “ON” state in the low voltage switch matrix 46, the analog transmit signal 84 passes through the cell T/R switch 48 on the low voltage transmit path 74. For the PW mode, the low voltage transmit control signal 96 generated in the transmit control signal generator 60 propagates through the low voltage switch matrix 46 to the level shifter discriminator 92, at step 140. In response to receipt of the low voltage transmit control signal 96, the high voltage pulse transmitter 44 sends a signal on the high voltage transmit path 86, at step 142, and causes the ultrasound transducer element 34 to “fire,” at step 144. The receiver “listens” for the ultrasound echo, and the process repeats steps 136 through 144 if, at decision block 146, it is determined that the imaging session has not been completed. Otherwise, control returns to the programming circuit 16, at step 148.
While the invention is described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalence may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to the teachings of the invention to adapt to a particular situation without departing from the scope thereof. Therefore, it is intended that the invention not be limited to the embodiment disclosed for carrying out this invention, but that the invention includes all embodiments falling with the scope of the intended claims. Further, the use of the term “at least one” means one or more of the members of a group.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
