Title :
Combining multi-pulse excitation and chirp coding in contrast enhanced echographic imaging
Author :
Crocco, Marco ; Pellegretti, Paolo ; Sciallero, Claudia ; Trucco, Andrea
Author_Institution :
Dept. of Biophys. & Electron. Eng. (DIBE), Univ. of Genoa, Genoa
Abstract :
Coded excitation is generally used in imaging to increase the signal to noise ratio (SNR) and the penetration depth. Only in recent years, coded excitation has been introduced for clinical ultrasound. The employment of this solution with contrast agents enhances the contrast to tissue ratio (CTR), since a signal with a long time duration is able to increase the backscattered echoes produced by microbubbles. However, nonlinear properties of contrast agents make decoding problematic in case of applying coded excitation to contrast imaging. An advantageous solution could be combining a multi-pulse technique, in particular one of the Contrast Pulse Sequences (CPS), with the chirp coding: a chirp excitation method for contrast agents based on the transmission and the opportune combination and post-processing of three chirp pulses is introduced (Chirp CPS3). The method proposed is compared to the Contrast Pulse Sequence technique based on the transmission of three uncoded signals (CPS3). Preliminary results are obtained considering simulated signals. The comparison of the methods reveals, under the same conditions, an increment of about 8 dB in the CTR and 17.5 dB in the SNR assured by the new technique. The simulation phase is followed by in-vitro tests that confirm the preliminary conclusions. The only drawback is represented in a loss of axial resolution: an 8 mm-diameter flow channel is overestimated of about 1 mm considering Chirp CPS3.
Keywords :
backscatter; biological tissues; biomedical ultrasonics; bubbles; chirp modulation; decoding; backscattered echoes; chirp coding; chirp pulses; clinical ultrasound; coded excitation; contrast agents; contrast enhanced echographic imaging; contrast pulse sequences; contrast-to-tissue ratio; decoding; flow channel; in-vitro tests; microbubbles; multipulse excitation; multipulse technique; nonlinear properties; penetration depth; signal-to-noise ratio; Bandwidth; Biological tissues; Chirp; Conferences; Energy resolution; Image quality; Linear approximation; Signal resolution; Signal to noise ratio; Ultrasonic imaging; chirp coding; contrast agents; echographic imaging; multi pulse techniques;
Conference_Titel :
Imaging Systems and Techniques, 2008. IST 2008. IEEE International Workshop on
Conference_Location :
Crete
Print_ISBN :
978-1-4244-2496-2
Electronic_ISBN :
978-1-4244-2497-9
DOI :
10.1109/IST.2008.4659938