Acoustic nonlinearity parameter of tissue on echo mode: review and evaluation of the different approaches for B/A imaging (original) (raw)
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Study of acoustic nonlinearity parameter imaging methods in reflection mode for biological tissues
The Journal of the Acoustical Society of America, 2004
Three novel methods for acoustic nonlinearity parameter B/A imaging in reflection mode are developed in this paper. They are: ͑1͒ the acoustic nonlinearity parameter B/A tomography by detecting reflective second harmonic wave, ͑2͒ the B/A tomography in reflection mode via the measurement of the difference frequency wave generated by a parametric array, and ͑3͒ the C-scan imaging of B/A via the measurement of the echo second-harmonic signal. A theoretical analysis and the experimental imaging of normal and pathological biological tissues by using these methods are also present and discussed. Results show that using the acoustic nonlinearity parameter imaging we can more easily distinguish the diseased tissue from the normal one than using the linear acoustic parameters.
2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2014
The nonlinearity B/A parameter is an important parameter influencing the distortion of ultrasound waves in tissue. B/A has different values for normal and pathological media and can be used for tissue characterization. The extended comparative method (ECM) allows estimating the B/A parameter in echo mode configuration but presents some limitations. The limitations are the concentration of energy due to transmission focusing and the poor resolution in distinguishing areas with different B/A. This paper proposes to improve the estimation of B/A with the ECM approach using a high frame rate imaging approach based on plane wave transmission. The simulation results show that good performance in B/A estimation can be obtained through the analysis of the corresponding pressure field. Promising results are also achieved through the direct estimation of B/A from the B-Mode echo-mode images.
Extensions of nonlinear B/A parameter imaging methods for echo mode
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000
This paper investigates nonlinear B/A parameter imaging in ultrasound echo mode. First, the B/A estimation methods which can be extended to echo mode are identified. The finite amplitude approaches are found to be excellent candidates to assess the nonlinear parameter because of their experimental simplicity, supported by a strong mathematical background. Second, three nonlinear coefficient measurement methods, thus far proposed for applications in homogeneous media, are extended to heterogeneous media. In particular, the simulations show that the extended comparative method (ECM) offers the best results when the probe diffraction effects are taken into consideration. The first experimental images obtained by applying the ECM for two different phantoms are also presented, showing the feasibility of B/A imaging.
Higher order nonlinear ultrasound propagation in tissue-simulation study
2002 IEEE Ultrasonics Symposium, 2002. Proceedings., 2002
Nonlinear wave propagation in tissue has been simulated using typical propagation parameters for liver. The results indicate that the amplitude level of higher order harmonics can exceed the level of the second harmonic component. In that case detection of the higher order components can be achieved with increased signal to noise ratio due to the fact that the amplitude of the 3 rd order component can be higher than the 2 nd harmonic and the fact that the 3 rd order mixing component falls into the middle of the transducer bandwidth. Odd order harmonic components are of particular interest since they create spectral mixing products at the fundamental frequency. Therefore, transmission and reception can operate around the same center frequency.
Nonlinear propagation applied to the improvement of resolution in diagnostic medical ultrasound
The Journal of the Acoustical Society of America, 1997
Medical B-mode scanners operating under conditions typically encountered during clinical work produce ultrasonic wave fields that undergo nonlinear distortion. In general, the resulting harmonic beams are narrower and have lower sidelobe levels than the fundamental beam, making them ideal for imaging purposes. This work demonstrates the feasibility of nonlinear harmonic imaging in medical scanners using a simple broadband imaging arrangement in water. The ultrasonic system comprises a 2.25-MHz circular transducer with a diameter of 38 mm, a membrane hydrophone, also with a diameter of 38 mm, and a polymer lens with a focal length of 262 mm. These components are arranged coaxially giving an imaging geometry similar to that used in many commercial B-scanners, but with a receiver bandwidth sufficient to record the first four harmonics. A series of continuous wave and pulse-echo measurements are performed on a wire phantom to give 1-D transverse pressure profiles and 2-D B-mode images, respectively. The reflected beamwidths w n decrease as w n /w 1 ϭ1/n 0.78 , where n is the harmonic number, and the reflected sidelobe levels fall off quickly with increasing n. In imaging terms, these effects correspond to a large improvement in lateral resolution and signal-to-clutter ratio for the higher harmonics.
The Journal of the …, 1999
A study is presented in which the influence of the pressure amplitude of the incident pulse on the estimated frequency dependency of the attenuation coefficient is shown. First, the effect is demonstrated with a simple theoretical model for both transmission and reflection measurements. Simulations show that for both measurement techniques a high-amplitude incident pulse results in a biased estimate of the attenuation coefficient due to nonlinear interaction of the different frequency components of the incident pulse. It is shown that in transmission and reflection measurements the biases have opposite signs. The effect of bandwidth, central frequency, and phase of the incident pulse on this bias is investigated. Second, the effect is demonstrated both in vitro, using a broadband through-transmission substitution technique on a tissue mimicking gelatine phantom, and in vivo, using reflection measurements with standard clinical equipment. The experimental results agree well with the theoretical model. The relevance of this study for ultrasonic tissue characterization is shown.
Physics in Medicine and Biology, 2006
Nonlinear propagation has been demonstrated to have a significant impact on ultrasound imaging. An efficient computational algorithm is presented to simulate nonlinear ultrasound propagation through layered liquid and tissueequivalent media. Results are compared with hydrophone measurements. This study was undertaken to investigate the role of nonlinear propagation in high frequency ultrasound micro-imaging. The acoustic field of a focused transducer (20 MHz centre frequency, f-number 2.5) was simulated for layered media consisting of water and tissue-mimicking phantom, for several widebandwidth source pulses. The simulation model accounted for the effects of diffraction, attenuation and nonlinearity, with transmission and refraction at layer boundaries. The parameter of nonlinearity, B/A, of the water and tissue-mimicking phantom were assumed to be 5.2 and 7.4, respectively. The experimentally measured phantom B/A value found using a finite-amplitude insert-substitution method was shown to be 7.4 ± 0.6. Relative amounts of measured second and third harmonic pressures as a function of the fundamental pressures at the focus were in good agreement with simulations. Agreement within 3% was found between measurements and simulations of the beam widths of the fundamental and second harmonic signals following propagation through the tissue phantom. The results demonstrate significant nonlinear propagation effects for high frequency imaging beams.
Aberration in nonlinear acoustic wave propagation
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000
Theory and simulations are presented indicating that imaging at the second-harmonic frequency does not solve the problem of ultrasonic wave aberration. The nonlinearity of acoustic wave propagation in biological tissue is routinely exploited in medical imaging, since the improved contrast resolution leads to better image quality in many applications. The major sources of acoustic noise in ultrasound images are aberration and multiple reflections between the transducer and tissue structures (reverberations), both of which are the result of spatial variations in the acoustic properties of the tissue. These variations mainly occur close to the body surface, i.e. the body wall. As a result, the nonlinearly-generated second-harmonic is believed to alleviate both reverberation and aberration because it is assumed that the second-harmonic is mainly generated after the body wall. However, in the case of aberration, the second-harmonic is generated by an aberrated source. Thus the second-harmonic experiences considerable aberration at all depths, originating from this source. The results in this article show that the secondharmonic experiences similar aberration as its generating source; the first-harmonic.
Nonlinear acoustics in ultrasound metrology and other selected applications
Physics Procedia, 2010
A succinct background explaining why, initially, both the scientific community and industry were skeptical about the existence of the nonlinear (NL) wave propagation in tissue will be given and the design of an adequately wideband piezoelectric polymer hydrophone probe that was eventually used to verify that the 1-5 MHz probing wave then used in diagnostic ultrasound imaging was undergoing nonlinear distortion and generated harmonics in tissue will be discussed. The far-reaching implications of the advent of the piezoelectric PVDF polymer material will be reviewed and the advances in ultrasound metrology prompted by the regulatory agencies such as US Food and Drug Administration (FDA) and International Electrotechnical Commission (IEC) will be presented. These advances include the development of absolute calibration techniques for hydrophones along with the methods of accounting for spatial averaging corrections up to 100 MHz and the development of "point-receiver" hydrophone probes utilizing acousto-optic sensors. Next, selected therapeutic applications of nonlinear ultrasonics (NLU), including lithotripters will be briefly discussed. Also, the use of shock waves as pain relief tool and in abating penicillin resistant bacteria that develop rock hard "biofilm" that can be shattered by the finite amplitude wave will also be mentioned. The growing applications of NLU in cosmetic industry where it is used for redistribution and reduction of fatty tissue within the body will be briefly reviewed, and, finally, selected examples of NLU applications in retail and entertainment industry will also be pointed out.