Narendra D. Londhe R.S. Anand

(Dept. of Electrical Engineering, Indian Institute of Technology Roorkee Roorkee-247667 India)

Received Oct. 26, 2010

Revised Mar. 24, 2011

Abstract  The generation of tissue harmonics is due to nonlinear nature of ultrasound wave propagation in biological tissues. The tissue harmonics for imaging i.e. tissue harmonic imaging (THI) uses higher frequency components for imaging in which the resolution improves significantly but signal–to-noise ratio (SNR) and penetration depth remains low as compared to both fundamental and second harmonic imaging. The coded excitations have potential to improve the SNR which ultimately leads to improved penetration depth. In the present work, the linear frequency modulated (chirp/LFM) and nonlinear frequency modulated(NLFM) signals have been used to investigate the nonlinear ultrasound wave propagation and harmonic generation in biological tissues. The SNR has been found to be substantially improved for coded tissue harmonic imaging (CTHI) as well as for coded superharmonic imaging (CSHI).

PACS numbers: 40.35,43.25,43.60