CODED EXCITATION METHODS FOR ULTRASOUND HARMONIC IMAGING

Coded excitation methods offer the potential for improving the SNR without increasing the peak transmitted power and without sacrificing resolution. Our study examines the potential application of coded waveforms, specifically FM chirps, in harmonic imaging. Such a system, in which nonlinear echoes from tissue are used to form the image, requires the extraction and compression of the second harmonic portion of the echo signal. Our objective is to obtain the second harmonic using just one transmission, thereby avoiding problems of frame rate reduction and movement artifacts associated with multiple transmission schemes. With the help of an efficient method for predicting the transient nonlinear field from a focused transducer, design issues such as waveform and bandwidth selection, as well as filters for second harmonic extraction and compression are examined. Simulations reveal the presence of axial sidelobes in the compressed echo waveform as the bandwidth of the transmitted chirp is increased. These sidelobes, resulting from the overlap of the fundamental and third harmonic bands with the second harmonic, cannot be removed using conventional Fourier filtering. Alternative filtering techniques which utilize the separation of the harmonic bands of a backscattered chirp in the joint time-frequency domain are suggested.

[1]  Helmut Ermert,et al.  The optimum bandwidth of chirp signals in ultrasonic applications , 1993 .

[2]  Y Takeuchi.  An investigation of a spread energy method for medical ultrasound systems. Part two: proposed system and possible problems. , 1979, Ultrasonics.

[3]  P. Woodward,et al.  Probability and information theory , 2004 .

[4]  M. O'Donnell,et al.  Coded excitation system for improving the penetration of real-time phased-array imaging systems , 1992, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[5]  Y Takeuchi,et al.  An investigation of a spread energy method for medical ultrasound systems. Part one: theory and investigation. , 1979, Ultrasonics.

[6]  T. Misaridis,et al.  Use of modulated excitation signals in medical ultrasound. Part III: high frame rate imaging , 2005, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[7]  M. Gindre,et al.  Echography using correlation techniques: choice of coding signal , 1994, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[8]  R. Cobbold.  Foundations of Biomedical Ultrasound , 2006 .

[9]  Tai-Kyong Song,et al.  Ultrasound second harmonic imaging with a weighted chirp signal , 2001, 2001 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.01CH37263).

[10]  Klaus Krickeberg,et al.  Probability and information theory II , 1969 .

[11]  R. Y. Chiao,et al.  Coded excitation for diagnostic ultrasound: a system developer's perspective , 2003, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[12]  J.A. Jensen,et al.  Use of modulated excitation signals in medical ultrasound. Part I: basic concepts and expected benefits , 2005, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[13]  J. Tavakkoli,et al.  Modeling of nonlinear ultrasound propagation in tissue from array transducers. , 2003, The Journal of the Acoustical Society of America.

[14]  Philip M. Woodward,et al.  Probability and Information Theory with Applications to Radar , 1954 .

[15]  E.S. Ebbini,et al.  Post-beamforming second-order Volterra filter for pulse-echo ultrasonic imaging , 2003, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[16]  M. Kowatsch,et al.  Effect of Fresnel ripples on sidelobe suppression in low time-bandwidth product linear FM pulse compression , 1982 .

[17]  P. Burns,et al.  Pulse inversion Doppler: a new method for detecting nonlinear echoes from microbubble contrast agents , 1997, 1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118).

[18]  Pai-Chi Li,et al.  Pulse Compression for Finite Amplitude Distortion Based Harmonic Imaging Using Coded Waveforms , 1999, Ultrasonic imaging.

[19]  K. Parker,et al.  New approaches to nonlinear diffractive field propagation. , 1991, The Journal of the Acoustical Society of America.

[20]  T. Misaridis,et al.  Use of modulated excitation signals in medical ultrasound. Part II: design and performance for medical imaging applications , 2005, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[21]  Pai-Chi Li,et al.  Motion artifacts of pulse inversion-based tissue harmonic imaging. , 2002, IEEE transactions on ultrasonics, ferroelectrics, and frequency control.

[22]  M. J. Rycroft,et al.  Radar signals: An introduction to theory and application , 1995 .