A reusable perfusion supporting tissue-mimicking material for ultrasound hyperthermia phantoms

A new ultrasonically and thermodynamically tissue-mimicking material is reported. The material is well suited for use in phantoms for testing ultrasound hyperthermia systems or related predictive models. Controlled convective heat transfer effects, mimicking to some extent perfusive heat transfer in tissues, can be instituted in the material with appropriate fluid sources and sinks. The material consists of closely packed agar spheres varying in diameters from 0.3-3.6 mm. The interstitial space between spheres is filled with 10% n-propanol solution. The material has two practical advantages over the solid-gel-type tissue-mimicking materials. The first advantage is that it allows rapid return of a hyperthermia phantom to thermal equilibrium following a heating test by rapid circulation of the perfusion fluid. The second advantage is that the material is in a "liquid" form. It can be easily siphoned in and out of phantom containers of any geometric shape for different purposes without change in its physical properties. Methods for measuring ultrasonic and thermodynamic properties of the material and the results of the measurements are reported. The physical parameters measured are the intensity attenuation and absorption coefficients, the ultrasonic speed, the thermal conductivity, specific-heat capacity and the mass density. Temperature measurements in a hyperthermia phantom made of the material are also reported.