A NEW MODEL OF PRESSURE PROPAGATION IN HUMAN TISSUE IN HIFU APPLICATION SAEED REZA HAJIAN 1 , ALI ABBASPOUR TEHRANI FARD 2 , MAJID POULADIAN 3 , GHOLAM REZA HEMMASI 4 1 Medical Radiation Eng. Department, Engineering Faculty, Science and Research Branch, Islamic Azad University, Tehran, Iran 2 Assistant Professor, Department of Electrical Engineering, Sharif University of Technology, Tehran, Iran - 3 Chief of Biomedical Eng. Faculty, Science and Research Branch, Islamic Azad, University, Tehran, Iran - 4 Assistant professor, Research Centre of Gastroenterology & Hepatology of Firouzgar Hospital, Iran University of Medical Science, Tehran, Iran Introduction Ultrasound today is widely used for diagnosis in treatment process and monitoring. Cavitation is created continuously by HIFU waves around thera- peutic area because of water. With implementing HIFU waves in to the created cavitation tissue which as its result the amount of pressure and then heat will be increased in tissue, this effect can cause destruction and damaging of tissue so con- trolling that by system is crucially important for us. It is very important at the time of treatment with HIFU that bubbles to be monitored separately. Some believe that bubbles can produce heat there- for it is very important that pressure and heat are measured separately in this process. Chang-Yu Hsieh et al could obtain its amount of pressure using a hydrophane from bubble approximate model (1) . Because of heat and bubble making effects at the time of treating with HIFU both lead to biolog- ical effects on tissue. At the time of collision with the tissue, sound causes creating the effects of diffraction and scat- tering. A model can be proposed which obtain a bubble using KZK equation based on the amount of pressure. In this mood, wave’s harmonics can be achieved. A probe is used in this situation which is placed on a phantom and the amount of pressure is obtained by a hydrophane that is in the center of probe’s hypothetical line on phantom (2,3) . Propagating ultrasound’s waves which depend on time inside a tissue like liver causes that pres- sure inside this tissue changes depending on the time as well. When pressure changes inside a tissue causes heat and biological effect on that. Heat and pressure propagation beside each other and beside blood vessels will be effective on tissue. The importance of monitoring two parameters will be cleared here. Solving bio-heat equations is very important for special tissue and its comparison with obtained heat. By using laser wave the num- ber of bubbles can be counted and their diameter can be obtained as well. Shock waves which lead Acta Medica Mediterranea, 2015, 31: 1501 Received May 30, 2015; Accepted November 02, 2015 ABSTRACT This project is a new pressure model for propagating pressure inside one or several tissues at the time of treatment with high intensity focus ultrasound (HIFU). Pressure’s changes are converted to heat’s changes in tissue and this is done oscillatory. When the treatment is done in deeper tissues, obtained heat can affect surficial tissues. This pressure effect also can enter surficial tissues. Amount of pressure and heat possible injury can be controlled and reduced through this mechanical modelling. In this model we have used three layers and pressure also is obtained within these three layers and is investigated averagely. Obtained tissue in this mood is kidney tissue and it is tried to obtain the rate of pressure in these three layers. Key words: Mechanical Index, Hifu (High Intensity Focus Ultrasound), Mechanical ModellingYour article has been received and it will be reviewed but the process could take several time.