In vivo measurement of attenuation

We propose a new technique for the in vivo measurement of attenuation. The method is conceptually simple and can also be easily implemented on a real-time ultrasound unit. The technique is suggested by an analysis of the propagation of a Gaussian pulse in a medium which has frequency-dependent attenuation as well as dispersion (frequency-dependent velocity). If the medium has a loss factor which can be described by H(f) = exp(-eta[f]pX), where f is the frequency and O less than or equal to p less than or equal to 2 (valid for tissues and other objects of interest), then the pulse retains its Gaussian shape, shifting only its centre frequency and bandwidth. This suggests that by measuring the mean frequency of the reflected rf waveform in a window which is moved in depth we can obtain an estimate of the attenuation. Here we describe a particular hardware implementation of this technique which we have completed (based on measurement of zero-crossings) and present some preliminary in vivo measurements.