Abstract
Ultrasound imaging with the subharmonic component from contrast microbubbles provide improved CTR (Contrast-to-Tissue Ratio), however it is susceptible to the low amplitude of the subharmonic component. In this simulation study, NLFM (Nonlinear Frequency Modulated) signals are proposed in order to enhance the subharmonic response from microbubbles. NLFM signals having fractional bandwidths of 10, 20, and 40% with up and down sweeps were used as excitation. The performance of NLFM signals were compared with the reference tone-burst and LFM (Linear Frequency Modulated) signals. The results show that the ultrasound contrast microbubbles can produce subharmonic response which is dependent on the applied signal pressure and bandwidth. It is observed that the subharmonic component of the scattered NLFM signal is 3.2dB higher than the LFM signal, whereas it is 9dB higher compared to the sinusoidal tone-burst signal. The results are also presented which show that the up and down sweeps NLFM signals performed better than the LFM signals at the same acoustic pressure and bandwidth.
Highlights
Ultrasound imaging using contrast microbubbles has been widely used in diagnostic ultrasound [1]
Ultrasound imaging with the subharmonic component can provide improved CTR as it is exclusively produced by the contrast microbubbles at low applied pressures [5]
It is observed that the magnitude of the subharmonic component of the NLFM signal is always higher than the subharmonic magnitude of the reference tone-burst and LFM signals
Summary
Ultrasound imaging using contrast microbubbles has been widely used in diagnostic ultrasound [1]. When microbubbles are insonated at low acoustic pressure, they can produce the fundamental frequency as well as second harmonic, ultra-harmonic and subharmonic frequencies. These harmonic frequencies are used to improve the image contrast for blood detection from tissues [2]. Modern ultrasound scanners offer imaging with the second harmonic in order to enhance the image contrast with better axial resolution. The image quality can be degraded by the nonlinear second harmonic component produced by the tissue [3,4]. Ultrasound imaging with the subharmonic component can provide improved CTR as it is exclusively produced by the contrast microbubbles at low applied pressures [5].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
