Patent Application
20130096436
Ultrasonic medical systems, such as ultrasonic diagnostic imaging systems and ultrasonic therapeutic systems, are in widespread use. Ultrasonic diagnostic imaging systems are used to perform ultrasonic imaging and measurements. For example, cardiologists, radiologists, and obstetricians use ultrasonic imaging systems to examine the heart, various abdominal organs, or a developing fetus, respectively. Diagnostic images are obtained from these systems by placing a scan head against the skin of a patient, and actuating an ultrasonic transducer located within the scan head to transmit ultrasonic energy through the skin and into the body of the patient. In response, ultrasonic echoes are reflected from the interior structure of the body, and the returning acoustic echoes are converted into electrical signals by the transducer in the scan head. Ultrasonic therapeutic systems apply ultrasonic emissions to a patient to produce a therapeutic effect, such as a cosmetic therapeutic effect involving the destruction an adipose tissue as described in U.S. Pat. No. 7,993,289, entitled “Systems and Methods for the Destruction of Adipose Tissue,” the entire disclosure of which is hereby incorporated by reference herein.
For an ultrasound system, the ideal impedance of a source (system based pulser and receiver) used to drive an ultrasound transducer depends on the impedance characteristics of the ultrasound transducer, with a resulting phase angle of zero degrees being ideal. The impedance values of ultrasound transducers, however, vary from unit to unit to some degree. Existing approaches for tuning a source to a transducer can be inconvenient (e.g., labor intensive). Additionally, high intensity ultrasound systems, such as used in some ultrasonic therapeutic systems, use power levels which may, over time, damage existing tuning networks.
Accordingly, improved approaches for inductively tuning an ultrasonic system are desirable. For example, improved approaches for tuning ultrasonic systems to account for the impedance characteristics of the particular ultrasound transducer employed are desirable. And improved tuning assemblies that can withstand prolonged exposure to the high power levels used in high intensity ultrasound systems are desirable.
The following presents a simplified summary of some embodiments of the invention in order to provide a basic understanding of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some embodiments of the invention in a simplified form as a prelude to the more detailed description that is presented later.
Tuning assemblies and related methods are disclosed for inductively tuning ultrasonic systems. The disclosed tuning assemblies and related methods can be used to in conjunction with ultrasound transducer configurations that exhibit unit to unit variation in impedance characteristics so as to adjust the impedance of the ultrasonic system appropriate to the impedance characteristics of the ultrasound transducer used in a particular ultrasonic system. The disclosed tuning assemblies and related methods provide for fast and convenient tuning of ultrasonic systems. And the disclosed tuning systems and methods may better tolerate the high power levels used to drive high intensity ultrasound transducers as compared to existing tuning networks.
Thus, in one aspect, an adjustable tuning network for a high intensity ultrasonic transducer is provided. The tuning network includes inductors and a multi-position (e.g., 16) rotary switch. The tuning network provides impedance matching for the transducer. The switch is used to vary the amount of inductance placed in parallel with the transducer to minimize phase angle. Tuning is accomplished by coupling the transducer to water and working through the rotary switch positions until the phase angle is closest to zero. The network primarily tunes phase angle.
In another aspect, a method is provided for forming a tuned ultrasound transducer assembly and assembling the tuned ultrasound transducer assembly into a medical device. The method includes selecting a tuning assembly that is adjustable to provide a selected inductance value from at least three different inductance values, electrically connecting an ultrasound transducer controller of the medical device with an input side of a transducer via an input electrical conductor, and electrically connecting the tuning assembly between the input electrical conductor and a ground potential so as to provide the selected inductance between the input electrical conductor and the ground potential. The ultrasound transducer controller and the transducer are electrically coupled with the ground potential. At least one of the at least three different inductance values is appropriate to the operation of the transducer. The transducer is operable to produce a cyclic sound pressure output with a frequency of at least 20 kilohertz. The tuning assembly includes a switch and a plurality of tuning inductors. The switch includes a first connection and a plurality of second connections. The switch has at least three positions, each position being operable to selectively connect the first connection with any one of at least three different combinations of the second connections including a combination connecting the first connection with at least two of the second connections. Each of the second connections is connected to at least one of the tuning inductors so that the switch is operable to select which subset of the tuning inductors is connected to the first connection so as to provide the selected inductance value. The switch can include a position selection feature that is rotated to select one of the positions.
In many embodiments, the tuning assembly is adjustable to provide the selected inductance value from at least six different inductance values, at least one of the six different inductance values being appropriate to the operation of the transducer. And the switch can include at least three of the second connections and have at least six positions, each of the six positions being operable to selectively connect the first connection with any one of at least six different combinations of the second connections.
In many embodiments, the tuning assembly is adjustable to provide the selected inductance value from at least ten different inductance values, at least one of the ten different inductance values being appropriate to the operation of the transducer. And the switch can have four to six of the second connections and have at least ten positions, each of the ten positions being operable to selectively connect the first connection with any one of at least ten different combinations of the second connections.
In many embodiments, the tuning assembly is adjustable to provide the selected inductance value from at least twelve different inductance values, at least one of the twelve different inductance values being appropriate to the operation of the transducer. And the switch can have four or five of the second connections and have at least twelve positions, each of the twelve positions being operable to selectively connect the first connection with any one of at least twelve different combinations of the second connections.
In many embodiments, the tuning assembly is adjustable to provide the selected inductance value from at least sixteen different inductance values, at least one of the sixteen different inductance values being appropriate to the operation of the transducer. And the switch can include at least four of the second connections and have at least sixteen positions, each of the sixteen positions being operable to selectively connect the first connection with any one of at least sixteen different combinations of the second connections.
The method can further include additional acts relating to the selection of a position for the tuning assembly switch. For example, the method can include: (a) measuring a phase angle of the ultrasound transducer assembly with the switch in a selected position; (b) operating the switch to change the switch to a different selected position to increase or decrease the selected inductance in response to whether the measured phase angle is positive or negative; (c) subsequent to act (b), re-measuring the phase angle of the ultrasound transducer assembly; and (d) repeating acts (b) and (c) until a change in sign of the measured phase angles occurs. And the method can include selecting a position for the switch that minimizes an absolute magnitude of the corresponding measured phase angle.
The method can include electrically connecting the tuning assembly to a printed circuit board (PCB) and electrically connecting the PCB between the input electrical conductor and the ground potential. The PCB can have a first lead and a second lead so that the PCB first lead and the tuning assembly switch first connection are electrically connected and the PCB second lead is electrically connected with the tuning inductors, each of the tuning inductors being electrically connected between the PCB second lead and a corresponding connection of the switch second connections. The PCB first lead and the input electrical conductor can be electrically connected and the PCB second lead and the ground potential can be electrically connected. Alternatively, the PCB first lead and the ground potential can be electrically connected and the PCB second lead and the input electrical conductor can be electrically connected. The PCB can be coupled to a housing. And the transducer can be secured to the housing so that a fluid tight seal is formed between the transducer and the housing.
In many embodiments, the transducer includes a high intensity focused ultrasound (HIFU) transducer operable to produce ultrasound output having a power level of at least 1 Watt average and typically higher than 10 Watts average to achieve a therapeutic effect in a timely manner. Peak power levels can range from the average power to many multiples of the average power to, for example, take advantage of non-linear effects such as associated heating. And the tuning assembly can include an inductor having an open core construction, which may better tolerate the power levels used to operate the HIFU transducer.
In many embodiments, the method further includes electrically connecting a plurality of fixed inductors in parallel between the input electrical conductor and the ground potential to provide a fixed inductance value between the input electrical conductor and the ground potential. The fixed inductance value and the selectable inductance values can have suitable values. For example, in many embodiments the fixed inductance value can be between 2.0 uH and 7.0 uH and the range of selectable inductance values can be within a range suitable for a particular transducer configuration, for example, between 0.15 uH and 150 uH.
In another aspect, a medical device having a tunable ultrasound transducer assembly is provided. The medical device includes an ultrasound transducer controller electrically connected with a ground potential, a transducer having an input side connected with the ultrasound transducer controller via an input electrical conductor, and a tuning assembly that is electrically connected between the input electrical conductor and the ground potential. The transducer is operable to produce a cyclic sound pressure output with a frequency of at least 20 kilohertz. The transducer is electrically connected with the ground potential. The tuning assembly is adjustable to provide a selected inductance from at least three different inductance values, at least one of the at least three different inductance values being appropriate to the operation of the transducer. The tuning assembly includes a switch and a plurality of tuning inductors. The switch includes a first connection and a plurality of second connections. The switch has at least three positions, each position being operable to selectively connect the first connection with any one of at least three different combinations of the second connections including a combination connecting the first connection with at least two of the second connections. Each of the second connections is connected to at least one of the tuning inductors so that the switch is operable to select which subset of the tuning inductors is connected to the first connection so as to provide the selected inductance value. The switch can include a position selection feature that is rotated to select one of the positions.
In many embodiments, the medical device tuning assembly is adjustable to provide the selected inductance value from at least six different inductance values, at least one of the six different inductance values being appropriate to the operation of the transducer. And the switch can include at least three of the second connections and have at least six positions, each of the six positions being operable to selectively connect the first connection with any one of at least six different combinations of the second connections.
In many embodiments, the medical device tuning assembly is adjustable to provide the selected inductance value from at least ten different inductance values, at least one of the ten different inductance values being appropriate to the operation of the transducer. And the switch can have four to six of the second connections and have at least ten positions, each of the ten positions being operable to selectively connect the first connection with any one of at least ten different combinations of the second connections.
In many embodiments, the medical device tuning assembly is adjustable to provide the selected inductance value from at least twelve different inductance values, at least one of the twelve different inductance values being appropriate to the operation of the transducer. And the switch can have four or five of the second connections and have at least twelve positions, each of the twelve positions being operable to selectively connect the first connection with any one of at least twelve different combinations of the second connections.
In many embodiments, the medical device tuning assembly is adjustable to provide the selected inductance value from at least sixteen different inductance values, at least one of the sixteen different inductance values being appropriate to the operation of the transducer. And the switch can include at least four of the second connections and have at least sixteen positions, each of the sixteen positions being operable to selectively connect the first connection with any one of at least sixteen different combinations of the second connections.
The medical device can include a housing and a printed circuit board (PCB) coupled with the housing. In many embodiments, the transducer is secured to the housing so that a fluid tight seal is formed between the transducer and the housing. The PCB can have a first lead and a second lead so that the PCB first lead and the tuning assembly switch first connection are electrically connected and the PCB second lead is electrically connected with the tuning inductors, each of the tuning inductors being electrically connected between the PCB second lead and a corresponding connection of the switch second connections. The PCB first lead and the input electrical conductor can be electrically connected and the PCB second lead and the ground potential can be electrically connected. Alternatively, the PCB first lead and the ground potential can be electrically connected and the PCB second lead and the input electrical conductor can be electrically connected.
In many embodiments, the medical device transducer includes a high intensity focused ultrasound (HIFU) transducer operable to produce ultrasound output having a power level of at least 1 Watt average and typically higher than 10 Watts average to achieve a therapeutic effect in a timely manner. Peak power levels can range from the average power to many multiples of the average power to, for example, take advantage of non-linear effects such as associated heating. And the medical device tuning assembly can include an inductor having an open core construction, which may better tolerate the power levels used to operate the HIFU transducer.
In many embodiments, the medical device includes a plurality of fixed inductors connected in parallel between the input electrical conductor and the ground potential to provide a fixed inductance value between the input electrical conductor and the ground potential. The fixed inductance value and the selected inductance value can have suitable values. For example, in many embodiments the fixed inductance value can be between 2.0 uH and 7.0 uH and the range of selectable inductance values can be within a range suitable for a particular transducer configuration, for example, between 0.15 uH and 150 uH.
For a fuller understanding of the nature and advantages of the present invention, reference should be made to the ensuing detailed description and accompanying drawings.
In the following description, various embodiments of the present invention will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the present invention can be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the embodiment being described.
Referring now to the drawings, in which like reference numerals represent like parts throughout the several views,
The tuning assembly 26 is adjustable to provide a selected inductance value between the input electrical conductor 30 and the ground potential 32 so that a phase angle of a signal used to drive the transducer 24 can be adjusted to be close to zero degrees. The tuning assembly 26 includes a switch 34 (e.g., a rotary Dual In-Line Package (DIP) switch), a plurality of tuning inductors (one or more first tuning inductors 36 through one or more nth tuning inductors 38), and optionally one or more fixed inductors 40. Each of the one or more first tuning inductors 36 through the one or more nth tuning inductors 38 can include, for example, a single inductor, two or more inductors connected in series, two or more inductors connected in parallel, and any suitable combination of single, series, and/or parallel connected inductors.
The switch 34 includes a first connection 42 and a plurality of second connections 44. The second connections 44 are connected to the one or more first tuning inductor(s) 36 through the one or more nth tuning inductor(s) 38. In many embodiments, the switch 34 has multiple positions including positions that connect the first connection 42 to only one of the second connections 44 and one or more positions that connect the first connection 42 to two or more of the second connections 44, thereby increasing the number of possible inductance values that can be connected to and between the input electrical conductor 30 and the ground potential 32.
Accordingly, the switch 34 is operable to connect a selected combination of the one or more first tuning inductors 36 through the one or more nth tuning inductors 38 to and between the input electrical conductor 30 and the ground potential 32. For example, in many embodiments, the switch 34 has a configuration (i.e., a position) that connects only the first tuning inductor(s) 36 to and between the input electrical conductor 30 and the ground potential 32, additional positions that each connect one of the second through the nth tuning inductors to and between the input electrical conductor 30 and the ground potential 32, and yet one or more additional positions that each connects a different combination of the first through the nth tuning inductors to and between the input electrical conductor 30 and the ground potential 32. In many embodiments, the one or more first tuning inductor(s) 36 through the one or more nth tuning inductor(s) 38 are selected so that each of the one or more first tuning inductor(s) 36 through the one or more nth tuning inductor(s) 32 provides a different inductance value between the switch 34 and the ground potential 32.
In many embodiments, the tuning assembly 26 includes the one or more fixed inductor(s) 40. The combination of the fixed inductance provided by the one or more fixed inductor(s) 40 and the range of selectable inductances provided by the switch 34 and the tuning inductors covers a desired range of total inductances suitable for the expected range of un-tuned transducer impedances for a population of transducers.
The tuning assembly 26 can be configured for use with a transducer operating at a relatively high power level (e.g., greater than 1 Watt average and typically greater than 10 Watts average), such as with a high intensity focused ultrasound (HIFU) transducer used in a therapeutic ultrasound system. For example, in many embodiments, the fixed inductors 40 include two or more inductors connected in parallel so as to reduce the current that any one of the fixed inductors is exposed to, thereby increasing the resulting life of the fixed inductors by reducing the power (and the resulting heat) generated by the fixed inductors. Likewise, the tuning inductors can also be to connected in series or parallel to a suitable extent so as to reduce the voltage or current that any one of the tuning inductors is exposed to, thereby increasing the resulting life of the tuning inductors by reducing the power (and resulting heat) generated by the tuning inductors. And the tuning assembly 26 can use inductors (for the fixed and/or the tuning inductors) having an open-core configuration, which are typically used for large rating power converters and may better tolerate the current levels associated with the operation of a high intensity ultrasound transducer as compared to inductors having a non-open-core configuration.
The fixed inductors 40 include thirteen 56 uH open-core inductors (e.g., Coilcraft part number ME3220-563KLB) connected in parallel. Accordingly, the thirteen fixed inductors provide an equivalent inductance of 4.31 uH. In many embodiments, surface mount inductors are used because they are suitable for automated assembly and are state of the art.
The tuning inductors 36, 38 include nine 56 uH open-core inductors connected in the illustrated ways, including two first tuning inductors 52 connected in series, a single second tuning inductor 54, two third tuning inductors 56 connected in parallel, and four fourth tuning inductors 58 connected in parallel. The two first tuning inductors 52 provide a combined inductance of 112 uH. The two third tuning inductors 56 provide an equivalent inductance of 28 uH. And the four fourth tuning inductors 58 provide an equivalent inductance of 14 uH.
The switch 34 is an RTE1600R44 low profile rotary dual in-line package (DIP) switch having 16 positions with a hexadecimal code switch function. The switch 34 includes a first connection 42 and four second connections 60, 62, 64, 66. Table 1 below illustrates the connections between the first connection 42 and the four second connections 60, 62, 64, 66, as well as the resulting tuning inductance and total inductance, for each of the 16 positions.
As shown in the resulting total inductances listed in Table 1, the tuning assembly 50 is operable to provide any one selected inductance between the input electrical conductor 30 and the ground potential 32 ranging from a low of 2.73 uH with the switch 34 in position 15 to a high of 4.31 uH with the switch 34 in position 0. The tuning assembly 50 is configured to provide a range of tuning suitable for the unit to unit transducer impedance variation exhibited in
Z
tuned=1/((1/Ztransducer)+(1/Ztuneinductor))
where: Ztuneinductor=j*2*pi*f*Ltuneinductor
Ltuneinductor=inductance of the tuning inductor
f=operating frequency
Setting the phase angle of Ztuned=0 for ideal tuning and solving for Ltuneinductor yields:
L
tuneinductor=Magnitude(Ztransducer)/(2*pi*f*sin(−Phase(Ztransducer)))
Table 2 below includes the values of transducer impedance, from
As in the tunable ultrasound transducer assembly 20 of
Tuned Ultrasound Transducer Assembly Methods
Other variations are within the spirit of the present invention. Thus, while the invention is susceptible to various modifications and alternative constructions, certain illustrated embodiments thereof are shown in the drawings and have been described above in detail. It should be understood, however, that there is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
