Measurements were made with the experimental configuration depicted in Figure 1. Tissue
samples were heated in an insulated tank that was filled with deionized water, which had been
degassed by vacuum pumping in an appropriate vessel. Tissue was placed in the focal zone (2
mm in diameter) of a focused, circular piston transducer. Center frequency of the transducer
was 7.5 MHz. Temperature in the tank was set by a heater that circulated the water in the tank.
The temperature in the tissue was monitored by a thermometer, which used an indwelling
needle thermocouple. After temperature in the tank reached equilibrium, the transducer was
pulsed with a MetroTek pulser and echoes recorded. The transducer was moved to the next
site of interest and a new echo signal recorded. After all sites of interest had been insonified,
the transducer was returned to its original position, so that the process could be repeated at the
next temperature. The temperature range covered was 37 to 50 oC in 0.5 oC increments.
Data were analyzed by identifying what appeared to be individual scatterers in the echo signal.
These žscatterersÓ were then tracked as there position shifted with temperature. We have
segmented the scatterers by hand and with a simple matched filter technique.
The matched-filter method used the hand segmented scatterers at the baseline temperature (37
oC) then automatically identified these scatterers at subsequent temperatures
Summary and Conclusions: