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United States Patent (10) Patent N0.: US 6,319,203 B1 Averkiou (45) Date of Patent: Nov

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United States Patent (10) Patent N0.: US 6,319,203 B1 Averkiou (45) Date of Patent: Nov US006319203B1 (12) United States Patent (10) Patent N0.: US 6,319,203 B1 Averkiou (45) Date of Patent: Nov. 20, 2001 (54) ULTRASONIC NONLINEAR IMAGING AT 5,833,613 11/1998 Averkiou et al. FUNDAMENTAL FREQUENCIES 5,848,968 12/1998 Takellchi~ 5,873,829 2/1999 Kamiyama et al. (75) Inventor: Michalakis Averkiou, Kirkland, WA 5,879,303 3/1999 Averkiou et a1- - (Us) 6,048,316 4/2000 Zhao et al. 6,186,949 * 2/2001 Hat?led et al. .................... .. 600/443 (73) Assigneez ATL Ultrasound, Bothell, WA (Us) 6,251,074 * 6/2001 Averkiou et al. .................. .. 600/447 * . ( * ) Notice: Subject to any disclaimer, the term of this cued by exammer patent is extended or adjusted under 35 _ _ _ U S C 154(k)) by 0 days Prtmary Examtner—Marvm M. Lateef ' i i ' Assistant Examiner—Maulin Patel (21) Appl NO _ 09/627 918 (74) Attorney, Agent, or Firm—W. Brinton Yorks, Jr. .. , (22) Filed: Jul. 28, 2000 (57) ABSTRACT 7 Nonlinear tissue or contrast agent effects are detected by (2;) ............................................ .gbbyhlss?onos?g Combining echoes from multiple, differently modulated ( ) _' ' ' ’ transmit pulses beloW the second harmonic band. The Fleld Of Search ................................... .. received eChoes may even Overlap the fundamental transmit 600/445’ 437’ 447’ 448’ 128/416 frequency band. The modulation may be amplitude modu , lation or phase or polarity modulation, and is preferably both (56) References Clted amplitude and phase or modulation. The present invention U_S_ PATENT DOCUMENTS affords the ability to utiliZe a majority of the transducer _ passband for both transmission and reception, and to trans lg ELOCk'FISh‘ZI ‘lat a1‘ ' mit pulses Which are less destructive to microbubble contrast , , apman e a . 5,694,937 12/1997 Kamiyama . agents‘ 5,706,819 1/1998 Hwang et al. 5,735,281 4/1998 Rafter et al. 7 Claims, 5 Drawing Sheets 120 104 105’ T/R L 102 _/- Swltch. Beamformer B_ 100 Freq. C t I . en r a 106/ Transmrtter Phase Controller B Mode Processor ,‘ —,_., 172 180 \ 150 190 \ 170\ Dis Ia Video Scan Doppler p y Processor Conv. Processor (—,_" _/-160 _/_ 3DMemory Image <_ Rendering3D Image _\ Cgntrastignal 184 182 Processor U.S. Patent Nov. 20, 2001 Sheet 1 0f5 US 6,319,203 B1 FIG. 1 Ampl. 10 12 I 11.25 14%2 2.5 3 4 FIG. 2 Ampl. 10 16 18 U.S. Patent Nov. 20, 2001 Sheet 2 0f5 US 6,319,203 B1 FIG. 3 Ampl. 1" 20 Ampl. Ampl. U.S. Patent Nov. 20, 2001 Sheet 3 0f5 US 6,319,203 B1 an .UER U.S. Patent Nov. 20, 2001 Sheet 4 0f5 US 6,319,203 B1 FIG. 8 Ampl. Ampl. US 6,319,203 B1 1 2 ULTRASONIC NONLINEAR IMAGING AT embodiment the nonlinear signals are detected by an ampli FUNDAMENTAL FREQUENCIES tude modulated tWo (or more) pulse technique. Preferably the transmit pulse Waveforms are of opposite phase and This invention relates to ultrasonic diagnostic imaging polarity and of different amplitudes. Upon reception the systems and, in particular, to ultrasonic diagnostic imaging echoes are normaliZed for the different transmit amplitudes systems Which image nonlinear signals in the fundamental and combined and the signals Within the fundamental band frequency band. are used for imaging. US. Pat. No. 5,879,303, of Which I am a co-inventor, In the draWings: describes methods and apparatus for doing harmonic ultra FIG. 1 illustrates conventional transmit and harmonic sound imaging. As eXplained in my patent, an ultrasonic receive spectra Within a transducer passband; Wave can be transmitted at a fundamental frequency to give FIG. 2 illustrates the location of a harmonic spectrum at rise to harmonic echo signals, in particular at the second the upper limit of the transducer passband; harmonic, from tWo distinct sources. One is the nonlinear FIG. 3 illustrates the fundamental transmit and second behavior of microbubble contrast agents. When these harmonic receive spectra of an embodiment of the present microbubble agents are insoni?ed by the transmit Wave, they 15 invention; Will oscillate or resonate nonlinearly, returning a spectrum of FIG. 4 illustrates the spectrum of fundamental nonlinear echo signals including those at the second harmonic of the echo signals resulting from the transmit spectrum of FIG. 3; transmit frequency. The strong harmonic echo components FIG. 5 illustrates receive passbands for the nonlinear uniquely distinguish echoes returning from the echo signals of FIG. 4; microbubbles, Which can be used to form B mode or FIGS. 6a—6g depict Waveforms illustrating the principle Doppler images of the blood?oW infused by the contrast of pulse inversion harmonic separation; agent. The other source of harmonic echo signals is the FIGS. 7a—7g depict Waveforms illustrating the principle nonlinear distortion Which ultrasonic Waves undergo as they of nonlinear echo signal detection in the fundamental band travel through tissue. The echoes returned from these dis in accordance With the principles of the present invention; torted Waves manifest harmonic components developed by 25 FIG. 8 illustrates the transmit and receive passbands of this distortion. one embodiment of the present invention; My aforementioned US. patent describes tWo Ways in FIG. 9 illustrates the transmit and receive passbands of Which the harmonic components of these echo signals may another embodiment of the present invention; and be detected. One is by use of a highpass ?lter, Which Will FIG. 10 illustrates an ultrasonic imaging system con pass signals in the harmonic band While attenuating the structed in accordance With the principles of the present stronger echo components in the fundamental band. The invention. other Way is by transmitting tWo or more pulses of opposite Referring ?rst to FIG. 1, typical fundamental and har phase or polarity and combining the echoes received in monic spectra of an ultrasound system are shoWn. This response from the tWo pulses. The fundamental components, draWing illustrates a passband 10 of an ultrasonic being of opposite phase or polarity by reason of that char 35 transducer/beamformer Which transmits the fundamental acteristic of the transmit pulses, Will cancel. The harmonic frequency pulses or Waves, and receives the harmonic echo components of the combined echoes, being quadratic in signals. In this eXample the transducer has a passband nature, Will additively combine, leaving the separated sec extending from 1 to 3 MHZ. When the same transducer is to ond harmonic signals. be used for both transmission and reception, both the fun As discussed in my aforementioned patent, harmonic damental transmit pulse and the harmonic receive echoes signals are advantageous in many imaging situations must be encompassed Within the passband 10 of the trans because of the distinctive Way in Which they identify echoes ducer. In this eXample the transmit pulse eXhibits a passband returned from harmonic contrast agents. When used Without 12 Which is centered around 1.25 MHZ. Second harmonic contrast agents the tissue harmonic signals are advantageous echo signals Will be received in a passband 14 centered because their development Within the body eliminates much 45 around 2.5 MHZ. It is seen that because the transmit band 12 of the clutter caused by near?eld effects. HoWever, harmonic is at the loWer end of the transducer passband 10, the signals are of a signi?cantly loWer amplitude than the harmonic receive passband Will fall in the upper portion of fundamental signal echoes, providing loWer signal to noise the passband 10 and thus both transmission and reception ratios and requiring greater ampli?cation. In addition, har can be performed by this particular transducer. monic signals require the use of relatively loW frequency As FIG. 1 shoWs, in order to get both the fundamental transmit pulses so that the second harmonic echo signal Will band 12 and the harmonic band 14 Within the same trans be of a frequency Which can be received Within the trans ducer passband it is often necessary to ?t one or the other or ducer’s passband. Generally, the transmit signal Will be both of the transmit or receive passbands at one of the cutoff centered at the loWer end of the transducer’s passband so eXtremes of the transducer passband. FIG. 2 shoWs another that the second harmonic return signal Will be beloW the 55 eXample of this, in Which the fundamental transmit band 16 upper cutoff of the transducer passband. This can place the is centered about a frequency of 1.5 MHZ and occupies the transmit and receive signals at the eXtremes Where broad entire loWer half of the transducer passband 10. The transmit band signals Will experience attenuating rolloff. It also band 16 thus is for a more broadband transmit signal than mandates loWer frequency transmit signals, Which can be that Which is transmitted by the passband 12 in FIG. 1, more disruptive to microbubble contrast agents than higher providing improved image detail and quality. HoWever the transmit frequencies Would be. Accordingly it is desirable to second harmonic receive passband 18 for this transmit pulse be able to overcome these de?ciencies and limitations of is centered at 3 MHZ at the upper eXtreme of the transducer harmonic imaging. passband 10. In this eXample the center of the harmonic In accordance With the principles of the present band is at the upper cutoff of the transducer band, resulting invention, the nonlinear signals returned from tissue and 65 in signi?cant attenuation of signals in the upper portion of contrast agents are detected in the fundamental frequency the band 18. Thus, broadband harmonic imaging is limited band rather than at harmonic frequencies. In a preferred by this transducer passband. US 6,319,203 B1 3 4 The passbands used in a ?rst embodiment of the present have been separated from the fundamental frequency com invention is shown in FIGS.
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