Frequency modulated pulse for ultrasonic imaging in an attenuating medium
نویسنده
چکیده
Rao, Navalgund, "Frequency modulated pulse for ultrasonic imaging in an attenuating medium" (1990). IEEE,Accessed from ABSTRACT There is now increasing theoretical and experimental evidence that ultrasound used at intensities employed clinically, can produce effects characteristic of transient cavitation. Probability to cause bioeffects by transient cavitation is immensely greater above a threshold peak intensity of the interrogating ultrasound pulse. Within the framework of short pulses used in diagnostics, 1 is not possible to reduce the peak intensity without sacrificing signal to noise ratio. We have been investigating the usefulness of a frequency modulated interrogating pulse to resolve the above dilemma. Simulations and experiments in non attenuating medium show that a factor of 16 to 50 reduction in peak intensity is possible without sacrificing the signal primarily used for imaging or the resolution. This factor depends on the effective time-bandwidth product of the frequency modulated pulse. However, in a frequency dependent attenuating medium, such as sofl tissue, this advantage could diminish. We have incorporated a linear in frequency and linear phase model for attenuation in our simulation process. Time-band width product is evaluated for reflectors at various depths and also as a function of center frequency and bandwidth of the frequency modulated pulse.
منابع مشابه
Fast, tissue-realistic models of photoacoustic wave propagation for homogeneous attenuating media
Photoacoustic tomography is an emerging medical imaging modality based on the reconstruction of an initial internal pressure distribution from surface measurements of photoacoustic wave pulses over time. Current methods used for this image reconstruction assume that the propagation medium is acoustically non-attenuating. However, in soft biological tissue, the frequency dependent ultrasonic att...
متن کاملUltrasound Fields in an Attenuating
Ultrasound elds propagating in tissue will undergo changes in shape not only due to diiraction, but also due to the frequency dependent attenuation. Linear elds can be fairly well predicted for a non-attenuating medium like water by using the Tupholme-Stepanishen method for calculating the spatial impulse response, whereas the eld cannot readily be found for an attenuating medium. In this paper...
متن کاملExperimental point spread function of fm pulse imaging scheme.
In this paper, we have examined the possibility of incorporating pulse compression techniques into a conventional medical B-scan imaging scheme. Linear frequency modulation fm, one form of pulse coding among many others, has been used in this study. With this approach, one can overcome current peak intensity limitations. A theoretical framework that includes medium propagation effects, transduc...
متن کاملThe ultrasonic field in lossy media: some simulation and experimental results
The subject of the paper is simulation and measurements of an ultrasonic field in an isotropic homogeneous medium with attenuation. The complex problem of simultaneous influence of wave diffraction, attenuation, and velocity dispersion occurs. Only few publications can be mentioned on this subject. For example in [1] is presented an investigation of the complex problem of ultrasound field distr...
متن کاملCompensation of Ultrasound Attenuation in Photoacoustic Imaging
Photoacoustic imaging is a non-destructive method to obtain information about the distribution of optically absorbing structures inside a semitransparent medium. It is based on thermoelastic generation of ultrasonic waves by the absorption of a short laser pulse inside the sample. From the ultrasonic waves measured outside the object, the interior distribution of absorbed energy is reconstructe...
متن کامل