WO2019069113A1 - Modulation de phase en temps réel multicanal pour la réduction d'interférences électromagnétiques dans un dispositif ultrasonore - Google Patents

Modulation de phase en temps réel multicanal pour la réduction d'interférences électromagnétiques dans un dispositif ultrasonore Download PDF

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Publication number
WO2019069113A1
WO2019069113A1 PCT/IB2017/001388 IB2017001388W WO2019069113A1 WO 2019069113 A1 WO2019069113 A1 WO 2019069113A1 IB 2017001388 W IB2017001388 W IB 2017001388W WO 2019069113 A1 WO2019069113 A1 WO 2019069113A1
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Prior art keywords
vector
amplitudes
phase
array
transducers
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PCT/IB2017/001388
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English (en)
Inventor
Ron Kurtz
Patrick Leonard
Xiaoyu Zhang
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Profound Medical Inc.
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Application filed by Profound Medical Inc. filed Critical Profound Medical Inc.
Priority to JP2020519434A priority Critical patent/JP2020536626A/ja
Priority to CA3075451A priority patent/CA3075451A1/fr
Priority to CN201780095470.2A priority patent/CN111246916B/zh
Priority to PCT/IB2017/001388 priority patent/WO2019069113A1/fr
Publication of WO2019069113A1 publication Critical patent/WO2019069113A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N7/00—Ultrasound therapy
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N7/00—Ultrasound therapy
    • A61N7/02—Localised ultrasound hyperthermia
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N7/00—Ultrasound therapy
    • A61N2007/0073—Ultrasound therapy using multiple frequencies
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N7/00—Ultrasound therapy
    • A61N2007/0078—Ultrasound therapy with multiple treatment transducers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N7/00—Ultrasound therapy
    • A61N2007/0086—Beam steering
    • A61N2007/0095—Beam steering by modifying an excitation signal

Definitions

  • the present application generally relates to ultrasound therapy systems, and more particularly to methods for improving the effectiveness of ultrasound therapy by reducing electromagnetic interference (EMI) arising from ultrasound transducers through the use of phase modulation with respect to the electrical signals sent to such transducers.
  • EMI electromagnetic interference
  • Ultrasonic transducers have been employed in ultrasound therapy systems to achieve therapeutic heating of diseased and other tissues.
  • Arrays of ultrasound transducers operating to form a beam of ultrasonic energy cause a conversion of sound to thermal energy in the affected tissue areas or treatment volumes, and a subsequent beneficial rise in the temperature in the treatment volumes.
  • a patient and the ultrasound therapy apparatus are generally disposed in an imaging volume such as a magnetic resonance imaging (MRI) apparatus, which allows guidance of the applicator placement, and in addition allows monitoring of the treatment effect on the tissue by providing real-time data from which temperature maps can be calculated.
  • MRI magnetic resonance imaging
  • a clinical operator can then monitor the progress of the therapy within the treatment volume or diseased tissue and manual or automated changes can be made to the ultrasound power signals based on input from the results and progress of the treatment.
  • ultrasound therapy systems can be used to treat harmful cells and to controllably destroy tumors while minimizing damage to healthy tissue.
  • transurethral ultrasound therapy systems for treatment of disease such as prostate cancer in men. See, e.g., Chopra, et al., "MRI-compatible transurethral ultrasound system for the treatment of localized prostate cancer using rotational control," Med Phys 35(4):1346-1357, 2008. Also see, U.S. Pub. 2007/0239062; U.S. Pat. 6,589,174 “Technique and apparatus for ultrasound therapy," 2003; U.S. Pat. 7,771 ,41 8, “Treatment of diseased tissue using controlled ultrasonic heating,” 2010; U.S. Pat. 8,998,889, “System and method for control and monitoring of conformal thermal therapy," 2015; U.S. Pat. 9,707,413, “Ultrasonic therapy applicator,” 2017. Such systems, including cumulative published and patented work by or for the present applicant, all of which are hereby
  • transurethral ultrasonic energy to the diseased prostate to reach a desired target temperature in the diseased tissue to achieve the clinical result, which is usually the necrosis of the diseased tissue cells in the prostate.
  • MRI guidance and temperature monitoring of the treatment in real time enables control of the power to the ultrasound therapy transducers as well as control of the rotation of an array of such transducers disposed axially along an elongated applicator inserted into the patient's urethra in the vicinity of the diseased prostate.
  • transduction constructed and operated to take electrical power and produce ultrasound energy waves from a surface of a transducer element in a process generally referred to as transduction.
  • the nature and extent of the transduction depends on the material used to construct the transducers, transducer geometry, and the electrical input to the transducers.
  • a common material used in construction of ultrasound transducers is piezoelectric transducer crystal material (lead zirconate titanate, PZT), which comes in several forms.
  • RF radio frequency
  • the elements may be driven at a relatively high power, approximately 4 W and 2 W at the low and high bands, respectively, and it is known that PZT material can yield a non-linear response.
  • An effect of this is the generation of electromagnetic interference (EMI) in the form of harmonics that can contaminate MRI images and interfere with MRI thermometry when the transducers are used inside an MRI apparatus, which relies for its operation on RF electromagnetic signals.
  • EMI electromagnetic interference
  • EMI arises from electrical fields generated in the transducer elements, as well as magnetic fields generated by electrical currents flowing to and from the transducer elements, since time-varying electric and magnetic fields can generate electromagnetic radiation, as is well-known in the art.
  • Traditional shielding methods are not always feasible, or are of limited efficacy, when the sources of the EMI are deployed in narrow spaces inside the human body, for example in the male urethra and prostate.
  • Other methods of reducing EMI which do not increase the bulk of the apparatus deployed, and thus do not risk injury to the patient, are needed.
  • the present disclosure is directed to methods for reducing EMI arising from an array of ultrasound transducers, by adjusting the phase angles of the electrical signals sent to the different transducers in the array.
  • the present methods determine and implement phase offset angles for the signals sent to the respective transducers, so as to achieve an optimal degree of reduction of EMI through the mutual offsetting of electrical fields and currents generated by the respective transducers in the array.
  • An embodiment is directed to a method of reducing electromagnetic interference arising from a set of ultrasound transducers that are part of an array of ultrasound transducers in a thermal therapy apparatus, the set comprising N transducers, each transducer in the set corresponding to an active channel and being electrically driven with a driving signal at an amplitude, a frequency and a phase angle, the frequencies of the driving signals being the same for all transducers in the set, the method comprising a determination and setting of the phase angles ⁇ ⁇ , ⁇ 2 ,— - , ⁇ ⁇ of each driving signal, the determination and setting of such phase angles comprising determining the amplitudes A 1 , A 2 , ... , A N of the respective driving signals of each transducer, each amplitude being a
  • Another embodiment is directed to a method for reducing
  • electromagnetic interference when operating an electrically-driven ultrasound thermal therapy apparatus comprising positioning said apparatus including an ultrasound array of said apparatus with respect to a specified treatment zone; in a computer-based host unit coupled to said therapy apparatus, determining a common driving frequency and determining an amplitude with which to drive each of a plurality of transducer elements of said array; driving each of said plurality of transducer elements with a respective driving signal generated by a respective voltage source, the driving signal for each element comprising said common driving frequency, said amplitude, and a respective phase angle; and modifying the phase angle of at least one driving signal to reduce a net electromagnetic output of said thermal therapy apparatus.
  • the treatment zone may be an internal cavity, orifice or other natural or artificial volume within a patient's body, including a urethra, rectum or other organ or cavity.
  • the treatment is delivered internally (for example, trans- urethrally) in such cases.
  • the treatment is delivered externally to the body and ultrasonic energy is directed into the body, e.g., through the patient's skin and outer organs and tissue layers.
  • the treatment apparatus can therefore include an array that is linear (along a line or axis of a linear device), or can be a geometrically focused array with a curved, contoured or otherwise geometric arrangement.
  • Figure 1 illustrates an exemplary system for providing image-guided ultrasound therapy to a patient
  • Figure 2 illustrates an exemplary ultrasound array
  • Figure 3 is a schematic circuit diagram illustrating a simplified model of a two-transducer array, by which certain of the principles underlying the methods disclosed herein are demonstrated;
  • Figure 4 is a schematic representation of a two-tone mixing model, further demonstrating some of the principles underlying the methods described herein;
  • Figure 5 is an illustrative plot showing the results of two transducers driven both with and without using the methods disclosed herein, demonstrating results obtained from using such methods;
  • Figures 6A, 6B, 6C and 6D are vector diagrams demonstrating
  • Figure 7A, 7B, 7C, and 7D illustrate a flowchart showing the operation of the methods disclosed herein, according to an embodiment. Detailed Description
  • the disclosure herein is directed to methods for using phase modulation techniques to reduce EMI arising from a multi-element array of ultrasound transducers in an apparatus for ultrasound thermal therapy.
  • Fig. 1 illustrates an exemplary system 10 for providing image-guided ultrasound therapy to a patient.
  • the simplified illustration shows a master computer 100, such as a portable PC, workstation, or other processing device having a processor, memory, and coupled to some input/output apparatus.
  • a master computer 100 such as a portable PC, workstation, or other processing device having a processor, memory, and coupled to some input/output apparatus.
  • Master computer 100 may include a display and may support a user interface 1 10 to facilitate control of and observation of the thermal therapy treatment process.
  • Master computer 100 is adapted for coupling to other systems and components through a computer interface connector 120.
  • Connection 120 carries data and information to and from master computer 100 and may comprise standard or special-purpose electrical wiring connection cables, such as serial connection cables or the like. Also, connection 120 may be achieved wirelessly as known to those skilled in the art of wireless communication, and may further be achieved by way of multiple connections, over a network, or by another suitable method.
  • master computer 100 is coupled through connection 120 to a power control unit 130.
  • Power control unit 130 may be implemented as a stand-alone hardware apparatus but may be implemented as a part of master computer 100, e.g., by being built onto a special card in a computer or server system that accommodates such hardware components.
  • Power control unit 130 may specifically include at least a processor adapted for processing machine or program instructions, which may be provided to the processor from another component of system 10 and may be stored on a memory device in power control unit 130. Circuitry including analog and/ or digital circuitry may be operated within power control unit 130 so as to determine an output power to one or more ultrasound therapy transducer elements in an ultrasound therapy apparatus 150.
  • power control unit 130 may deliver controlled electrical driving signals to a plurality of ultrasound transducer elements (e.g., PZT array elements) in ultrasound therapy apparatus 150.
  • the driving signals may be controlled to deliver a programmed amount of power to each element or to groups of elements of therapy apparatus 150.
  • the driving signals may also be controlled so as to provide a determined driving voltage, current, amplitude, waveform, or frequency to said ultrasonic transducers of therapy apparatus 150.
  • the relative phase of the driving signals can also be controlled, for example to reduce EMI, as discussed herein.
  • Such electrical driving signals are carried from power control unit 130 to the ultrasound therapy apparatus 150 over suitable wires, cables, or buses 140. Appropriate plug interfaces or connectors may be included so as to mate the various ends of the connectors or buses to and from their associated components.
  • ultrasound therapy apparatus 150 includes a portion 155 that is inserted into a portion of a patient's body to deliver a suitable dose of ultrasound energy to tissue in a diseased region of the patient's body.
  • the patient and the ultrasound therapy apparatus 150 are generally disposed in an imaging volume 160 such as a magnetic resonance imaging (MRI) apparatus, which can provide real-time images of the relevant parts of the patient, e.g., the treatment volume to master computer 100 or display and user interface 1 10.
  • MRI magnetic resonance imaging
  • real-time monitoring of the thermal therapy is performed so that a clinical operator can monitor the progress of the therapy within the treatment volume or diseased tissue.
  • Manual or automated changes can be made to the power signals from power control unit 130 based on input from the results and progress of the treatment.
  • the feedback and coupling of the treatment system components to the control components in system 10 can be used to ensure that an optimum radio frequency (RF) power signal is provided to each element of an ultrasound array 155 used in treatment of diseased tissues.
  • RF radio frequency
  • Some examples include treatment of prostate cancer tumors in male patients using MRI guided ultrasound therapy applications.
  • RF power control unit 130 may include separate circuit cards having individual processors, amplifiers, filters and other components to achieve the desired driving power output to the elements of ultrasound array 155 of ultrasound treatment apparatus 150. Alternatively, a single processor may be employed to control the behavior of the various power channels to each array element.
  • Fig. 2 illustrates an ultrasound array 200, which can be the same as ultrasound array 155.
  • Each ultrasound transducer 205 in ultrasound array 200 is driven by a separate voltage source 210 via at least one electrical line 220.
  • the voltage source 210 are included in RF power control unit 230, which can be the same as RF power control unit 130.
  • RF power control unit 230 can include additional components, such as the circuitry, processors, amplifiers, filters, and other components as discussed above with respect to RF power control unit 130.
  • Each transducer 205 has 2 electrical terminals, the first of which is electrically connected to one terminal of its respective voltage source 210 via an electrical line called a drive line, and the second of which is electrically
  • the drive lines, one for each ultrasound transducer in the array 200, and the common return line are connected to the proximal end of the applicator and extend to the voltage sources 210.
  • the applicator When the apparatus is used for thermal therapy, in a typical arrangement, the applicator will be inserted inside a patient's body to be near a portion of the body receiving the therapy, e.g. inserted transureth rally to be near a diseased male prostate, with the patient inside an MRI machine.
  • the drive lines and return line typically bound together inside a single sheath, extend from the applicator to outside the MRI machine, where the voltage sources are located, along with the various means for controlling the apparatus, such as RF power control unit 230.
  • each transducer's voltage amplitude can be dynamically adjusted in response to feedback, in accordance with a treatment plan, to maintain an optimal level of ultrasound output for the location and direction of each transducer at any given time.
  • Each voltage source sends an alternating current (AC) signal, typically a sinusoidal signal, at a given frequency, called the driving frequency, to one of the transducers, at a given voltage amplitude, which amplitude at any given time is determined by the treatment plan and control algorithms and mechanisms of the system.
  • the AC voltage signal causes an oscillating electric field within the transducer, which in turn causes mechanical oscillations in the transducer by means of piezoelectric induction; it is these mechanical oscillations that transmit ultrasound acoustic energy into the tissue being treated, where such energy is ultimately converted into thermal energy to achieve the intended therapeutic effect.
  • EMI inside the MRI apparatus can arise from magnetic fields generated by electrical currents flowing though the driving and return lines, as well as electrical fields generated in the transducers.
  • transducers are driven at a common driving frequency by separate voltage sources, the EM I from these sources can be reduced by causing voltage signals to be out of phase with each other. I n this way, through the principle of
  • transducers are deployed in proximity to one another on a linear array, the electric fields generated by the transducers will partially overlap in space.
  • FIG. 3 is a simplified schematic diagram showing 2 transducers 301 and 302, each represented as a capacitor, each connected to and powered by one of sinusoidal voltage sources 31 1 and 312, connected by drive lines 321 and 322 and by shared return line 324. Electric fields within and around the transducers 301 and 302 are shown by field lines 331 and 332, respectively.
  • the sinusoidal voltage signals emanating from sources 31 1 and 31 2 can be described as a function of time as follows:
  • a and B are the voltage amplitudes of the respective signals
  • ⁇ 0 is the common driving frequency, measured in radians per second, or alternatively in degrees per second, based on a full cycle of 2 ⁇ radians or 360 degrees
  • ⁇ 1 and 0 2 a re the phase angles, or phase offsets, of each signal, measured in radians or alternatively in degrees.
  • a sinusoidal signal at a given frequency ⁇ can be thought of as a phase vector, or phasor, rotating counterclockwise in the complex plane at a rate of ⁇ radians (or degrees) per second, or one full cycle every 2 ⁇ radians (or 360 degrees); the length or magnitude of the vector is the amplitude of the signal, and the signal at any given time is equal to the projection of the phasor onto the horizontal (real) axis, i.e. the real part of the phasor.
  • vector arithmetic can be used to compute the combined effect of such signals. The methods disclosed herein make use of such computational techniques.
  • magnetic fields generated by the currents in the drive lines wil l be in opposite directions to each other, as a result of such currents being in opposite directions, and thus such magnetic fields wil l also superpose and offset each other, further reducing RF emissions.
  • Piezoelectric materials used in ultrasound transducers such as PZT have been observed to exhibit non-linear behavior in response to applied signals.
  • I n the simplified case of two active elements, a two-tone non-linear mixing model can be used to understand the resulting harmonic and intermodulation content:
  • I n the above equation, i and V 2 represent the signals applied to the two driven elements, in this case operating at a common frequency of ⁇ 0 .
  • the power level is free to vary.
  • V 0 is the output of the "mixer” containing the new harmonic and intermodulation content, represented here by a power series approximation of the PZT transfer function.
  • the RF voltage signals can be advanced or retarded, that is they can have their phase angle adjusted, without materially affecting the delivery of ultrasound acoustic energy to the target.
  • the ultrasound energy generated by a transducer depends on the amplitude and frequency of the voltage signal driving that transducer, but it does not depend on the phase of that signal; and such energy is transmitted in directions that depend on the location and geometry of the transducer and the surrounding tissue, but that do not depend on the phase of the signal.
  • the methods disclosed herein which involve selecting and implementing differing phase angles for the various signals driving an array of ultrasound transducers, are effective to reduce EMI from such signals while maintaining the effectiveness of such signals in driving the transducers to achieve the desired therapeutic ends.
  • the two-element model discussed above can easily be extended to multiple elements, where one or more subsets of such elements are driven at a common frequency.
  • a simple approach to assigning phase angles would be to set alternating elements at a common frequency to 0 / 1 80 / 0 / 1 80 ... degrees.
  • this approach is optimal only when the power output on all elements is identical.
  • the method disclosed herein is directed to determining and setting the phase angles of a set of sinusoidal voltage signals driving an array of ultrasound transducers, such that for each subset of signals at a given driving frequency, the vector sum of all signals in such subset is minimized.
  • each voltage signal at a given frequency is expressed as a phasor, that is as a vector in the complex plane with a length, or magnitude, equal to the amplitude of the signal , and at an angle, measured counterclockwise from the positive real axis, equal to the phase angle or phase offset of such signal .
  • the phasor could be represented by its components, i.e. its real and imaginary parts, as
  • the vector sum of al l signals at a given frequency wil l be a phasor representing the net signal being sent to al l transducers in the array that are being driven at that frequency.
  • net current in the drive and return lines whose currents are proportional to the voltage signals carried by such lines, wil l also be minimized.
  • the reduction of net current in the lines wil l reduce magnetic fields arising from such currents, and thus wil l reduce RF emissions.
  • the reduction of net voltage applied to ultrasound transducer elements that are disposed on a linear array, and thus physical ly parallel to one another will result in greater offsetting of electric fields generated by such transducers, and thus reduced RF emissions from such fields.
  • the algorithm disclosed herein can be used to optimize the respective phase angles of the signals to each transducer in the set.
  • N be the number of transducers in the subset, and let A , A 2 , etc. up to A N be the respective amplitudes (in voltage, or alternatively power) of the signals to be sent to the transducers in the set; such amplitudes would be determined and selected by whatever means is used for such purpose, in order to achieve the therapeutic and/or other goals of the ultrasound procedure. Note that all Ai's are
  • phase angles ⁇ 1 , ⁇ 2 , . . . , ⁇ ⁇ such that the vector sum of all of the phasors is minimized.
  • the algorithm proceeds as follows: Define an N-vector (that is, an ordered set of N scalar quantities) v consisting of the amplitudes:
  • phase angle of 1 80 degrees is equivalent to multiplying the signal by -1 , simplifying the calculations at this stage. Compute the sum of the amplitudes and determine the maximum amplitude:
  • the next step is to determine the combination of 0 and 1 80 degree phase angles, or equivalently 1 's and -1 's, respectively, that will yield the greatest offset of signals.
  • a phase offset vector as a N-vector consisting exclusively of 1 's and -1 's.
  • phase offset vector p the net amplitude, or residual amplitude, resulting from applying the phase angles (0 and 1 80 degrees) represented by p, can be computed as the scalar product, also known as the inner product or dot product, of v and p. This product is computed by multiplying the N pairs of corresponding elements in the 2 vectors, and then summing the resulting N products, yielding a scalar result:
  • pi [-1, -1, -1]
  • phase offset vector P is selected from these possible candidates based on other criteria, such as seeking to maximize the number of pairs of physically adjacent transducers that are driven in opposite phase to each other.
  • N-vector 0 the element-wise multiplication of v with P, with P selected as described above:
  • ⁇ will be negative. (If ⁇ were positive, then R min would not be the smallest possible residual, because it could be made smaller by reversing the signs of both P a and P b .) Note also that the magnitude of ⁇ will be less than the sum of a and ⁇ (if not, we would have R m i n ⁇ 0). The magnitude of ⁇ will be greater than the difference of a and ⁇ :
  • the quantity ⁇ represents the phasor of the resultant signal of the voltage signal from all the channels except those represented by a and ⁇ .
  • the next step is to set phase angles for those two channels so that they offset that resultant signal. These angles can be found geometrically by forming a triangle with sides of length a, ⁇ and ⁇ . Such a triangle can be formed because the three quantities satisfy the "triangle inequality," above.
  • phase angles A and B are used to compute phase angles A and B for the channels represented by a and ⁇ , respectively:
  • Channel a is assigned phase angle -B
  • channel b is assigned phase angle A, with the remaining channels assigned in the coarse-approximation step, i.e. either 0 degrees or 1 80 degrees depending on whether the corresponding element of P is + 1 or -1 , respectively.
  • phase angles may be illustrated with a numerical and graphical example.
  • P [— 1,— 1, +1,—1] will generate ?
  • the next step is to adjust the phase of the vectors and ⁇ to as to offset ⁇ , i.e. so that the 3 vectors will add vectorially to zero.
  • the phasors represented by the individual channels are shown with these phase angles in Fig. 6D.
  • the vector sum of the 4 phasors is zero, resulting in zero net current in the drive and return lines, and maximum offset of electric fields generated by the transducers.
  • the method disclosed herein is performed for each subset of transducers being driven at a given driving frequency.
  • the phase angle computation is repeated each time there is a change in any amplitude and/or frequency for any of the channels.
  • the phase angles corresponding to the new set of amplitudes and frequencies are computed as disclosed herein before the change in amplitudes and/or frequencies is implemented in the signals sent to the transducers. Then, when these signals are changed, the new frequencies and amplitudes are implemented concurrently with the new phase angles, determined as disclosed herein.
  • the method disclosed herein is illustrated in the flowchart 70 depicted in Figs. 7A-7D.
  • the method begins at step 702, where the N-vector v is defined, comprising each of the amplitudes of the N voltage signals at a given driving frequency to be sent to the respective ultrasound transducers in an array.
  • Such amplitudes are determined in accordance with the goals of the ultrasound procedure and in accordance with feedback received and other considerations. These amplitudes are not determined by the method disclosed herein, but are the inputs to such method.
  • step 704 the dot product (or scalar product) of v with each possible P vector, that is, each possible N-vector whose elements are either +1 or -1 , is computed.
  • R min There may be more than one possible P vector that yields R min ⁇ or - R min ), in which case one of such possible P vectors is chosen arbitrarily or based on other considerations, such as having adjacent channels with opposite phase offsets for maximal electric field cancellation.
  • ? min can be negative or positive.
  • R m i n and P may be determined by other methods that do not comprise computing all possible dot products with all possible permutations for P.
  • step 708 results in a "no," the flow chart proceeds to placeholder A.
  • a scalar quantity 0, which is used in computing phase angles, is set to be either 0 ° or 1 80 ° . Steps 720 and 730 then proceed to placeholders C and D, respectively.
  • Fig. 7C begins with placeholders C and D.
  • Step 540 The branches of the flowchart rejoin at step 540, where the residual ⁇ is defined as the sum of the remaining entries in 0 after removing O t and O j .
  • Step 540 then proceeds to placeholder E, which is also found in Fig. 7 D.
  • A cos _1 ([)3 2 + ⁇ 2 - ⁇ 2 ])/[2 ⁇
  • ]) and B cos -1 ([y 2 + a 2 - /? 2 ])/[2x
  • step 750 wherein the channels 1 through N are assigned phase angles in accordance with the vector ⁇ , and such phase angles are implemented in the voltage signals sent to the ultrasound transducers at the amplitudes given by v.
  • the flow chart 70 can repeat (i.e., return to step 502), at each hardware update interval, i.e. each time there is to be any change in the amplitudes and/or frequencies at which any of the transducers are driven, the method shown in the flowchart is to be followed in order to determine the optimal phase angles to be used with the driving signals, so that such phase angles can be implemented, to the greatest extent feasible, concurrently with the change in amplitudes and/or frequencies.

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Abstract

L'invention concerne des procédés de réduction d'une interférence électromagnétique résultant de l'utilisation de multiples transducteurs ultrasonores dans un réseau, en particulier dans un corps humain se trouvant à l'intérieur d'un dispositif d'imagerie par résonance magnétique. Des signaux électriques excitant les transducteurs sont décalés en phase l'un par rapport à l'autre de manière à obtenir un décalage maximal de champs électrique et magnétique résultant de tels signaux et transducteurs. Des décalages de phase sont réglés de manière dynamique pour répondre à des changements d'amplitudes et de fréquences d'excitation, de façon à maintenir une réduction optimale de l'interférence électromagnétique.
PCT/IB2017/001388 2017-10-03 2017-10-03 Modulation de phase en temps réel multicanal pour la réduction d'interférences électromagnétiques dans un dispositif ultrasonore WO2019069113A1 (fr)

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JP2020519434A JP2020536626A (ja) 2017-10-03 2017-10-03 超音波装置での電磁干渉（ｅｍｉ）低減のためのマルチチャネルリアルタイム位相変調
CA3075451A CA3075451A1 (fr) 2017-10-03 2017-10-03 Modulation de phase en temps reel multicanal pour la reduction d'interferences electromagnetiques dans un dispositif ultrasonore
CN201780095470.2A CN111246916B (zh) 2017-10-03 2017-10-03 用于超声装置中的emi减小的多信道实时相位调制
PCT/IB2017/001388 WO2019069113A1 (fr) 2017-10-03 2017-10-03 Modulation de phase en temps réel multicanal pour la réduction d'interférences électromagnétiques dans un dispositif ultrasonore

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