  Therapeutic ultrasound is an investigational modality which could potentially
be used for minimally invasive treatment of prostate cancer. Computational
simulations were used to study the effect of natural physiological variations
in tissue parameters on the efficacy of therapeutic ultrasound treatment in the
prostate. The simulations were conducted on a clinical ultrasound therapy
system using patient computed tomography (CT) data. The values of attenuation,
perfusion, specific heat capacity and thermal conductivity were changed within
their biological ranges to determine their effect on peak temperature and
thermal dose volume. Increased attenuation was found to have the biggest effect
on peak temperature with a 6.9% rise. The smallest effect was seen with
perfusion with +-0.2% variation in peak temperature. Thermal dose was mostly
affected by specific heat capacity which showed a 20.7% increase in volume with
reduced heat capacity. Thermal conductivity had the smallest effect on thermal
dose with up to 2.1% increase in the volume with reduced thermal conductivity.
These results can be used to estimate the interpatient variation during the
therapeutic ultrasound treatment of the prostate.
