High frequency ultrasound signal statistics from mouse mammary tissue during involution

We investigate the use of signal envelope statistics to monitor the tissue restructuring process during mouse mammary tissue involution. Using an f/3 transducer operating at a centre frequency of 20 MHz, ultrasound backscatter data were collected from mouse mammary tissue following removal of the litter. The signal envelope statistics were examined by fitting the Rayleigh and generalized gamma distributions. The goodness of fit of the distributions was evaluated by the Kolmogorov-Smirnov test. The goodness of fit of the Rayleigh distribution increased to a maximum at day 3 of involution, roughly corresponding to the peak of apoptosis in the tissue. Similarly, the fit parameters of the generalized gamma distribution indicate that at day 3 the distribution is most Rayleigh like. It is believed that the condensation of the nucleus and reorganization of the tissue structure produced these changes in the statistics of the signal envelope. The results demonstrate that high frequency ultrasound signal envelope statistics can be applied to monitor changes to tissue structure in vivo.