We have been working on the software development for the biomechanical simulations using supercomputer with VOXEL type medical image data. In this talk, as one of the software we developed for massively parallel computations, HIFU simulator is introduced and some of the numerical results are explained for the phased-array-type ultrasound transducers with the time reversal method. The procedure of designing the actual HIFU devices for the brain treatment is explained using the actual skull data of Macaque. The results indicated that there are different optimal designs for the number of arrays depending on the ultrasound frequency. In other words, in the practical range of ultrasound frequency, 500KHz-2MHz, lower frequency results might give better focal controllability in some actual situation of the reasonable number of arrays. More detail quantitative discussion will be given in the talk. This work is the joint project with Prof. Seki (NCNP) et al. and the part of study explained in his talk on Friday morning.