High-frequency backscatter and attenuation measurements of selected bovine tissues between 10 and 30 MHz.

There are now diagnostic ultrasonic imaging devices that operate at very high frequencies (VHF) of 20 MHz and beyond for clinical applications in ophthalmology, dermatology, vascular surgery, endoluminal imaging and small animal imaging. To be able to better interpret these images and to further the development of these devices, knowledge of ultrasonic attenuation and scattering of biological tissues in this frequency range is crucial. Attenuation and backscatter coefficients (BSCs) of bovine tissues in the frequency range of 10 to 30 MHz were measured, respectively, using a standard substitution method for attenuation measurements and a modified narrow-band substitution method for scattering measurements. A modified substitution method for scattering measurements has to be used at high frequencies because unfocused transducers due to their decreased sensitivity cannot be used in the simple substitution method. In the modified method, the flat reflector is substituted by a particulate reference medium whose BSC is well-known and documented; in this case, a red cell suspension. In this paper, experimental results on BSC and attenuation coefficient measured between 10 and 30 MHz are reported. The frequency dependence of backscatter of the selected bovine tissues ranges from 2.4 to 3.5, whereas attenuation is observed to be still approximately linearly proportional to frequency. The BSC measured with the modified method is in good agreement with those obtained with the standard method between 10 and 20 MHz.