Dual-pulse frequency compounded superharmonic imaging

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2011-11, Vol.58 (11), p.2316-2324
• Main Authors: van Neer, P. L. M. J., Danilouchkine, M. G., Matte, G. M., van der Steen, A. F. W., de Jong, N.
• Format: Article
• Language: English
• Subjects: Acoustic signal processing; Acoustics; Algorithms; Biological and medical sciences; Cardiovascular system; Elasticity Imaging Techniques - instrumentation; Elasticity Imaging Techniques - methods; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Harmonic analysis; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; Imaging; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Miscellaneous. Technology; Phantoms, Imaging; Physics; Power harmonic filters; Reproducibility of Results; Sensitivity and Specificity; Signal Processing, Computer-Assisted; Sonar equipment; Transducers; Transfer functions; Ultrasonic imaging; Ultrasonic investigative techniques
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2011.2089

Tissue second-harmonic imaging is currently the default mode in commercial diagnostic ultrasound systems. A new modality, superharmonic imaging (SHI), combines the third through fifth harmonics originating from nonlinear wave propagation through tissue. SHI could further improve the resolution and quality of echographic images. The superharmonics have gaps between the harmonics because the transducer has a limited bandwidth of about 70% to 80%. This causes ghost reflection artifacts in the superharmonic echo image. In this work, a new dual-pulse frequency compounding (DPFC) method to eliminate these artifacts is introduced. In the DPFC SHI method, each trace is constructed by summing two firings with slightly different center frequencies. The feasibility of the method was established using a single-element transducer. Its acoustic field was modeled in KZK simulations and compared with the corresponding measurements obtained with a hydrophone apparatus. Subsequently, the method was implemented on and optimized for a setup consisting of an interleaved phased-array transducer (44 elements at 1 MHz and 44 elements at 3.7 MHz, optimized for echocardiography) and a programmable ultrasound system. DPFC SHI effectively suppresses the ghost reflection artifacts associated with imaging using multiple harmonics. Moreover, compared with the single-pulse third harmonic, DPFC SHI improved the axial resolution by 3.1 and 1.6 times at the -6-dB and -20-dB levels, respectively. Hence, DPFC offers the possibility of generating harmonic images of a higher quality at a cost of a moderate frame rate reduction.