## 1 Introduction  
Cancer is one of the serious diseases that threatens the life and health of humans. According to cancer statistics released by the National Cancer Center of China, 3.804 million new cancer cases were diagnosed and 2.296 million cancer deaths were reported in 2014 [1]. Traditional therapies for cancer include surgery resection, chemotherapy, and radiotherapy. In recent years, other alternative therapies such as microwave ablation, laser ablation, cryoablation, and high-intensity focused ultrasound (HIFU) hyperthermia also have developed rapidly [2, 3]. HIFU therapy is a non-invasive technology in which an ultrasound beam carries sufficient energy, and the energy is focused onto the target area to cause a local temperature rise, which is sufficiently high to make the lesion tissue undergo coagulative necrosis without causing damage to the overlaying or surrounding tissue [4, 5]. It has many advantages such as non-invasive, non-contact, non-ionization, and low cost [6, 7], and has been successfully used in clinics to treat solid malignant tumors, including cancers of the prostate, liver, kidney, breast, and pancreas [8]. The clinical success of HIFU hyperthermia depends on the accurate thermal dose at the lesion location.  
Unfortunately, it is difficult to accurately measure the thermal dose at a depth of the tissue in most clinical situations. Instead, a numerical simulation method is usually used to predict the transient temperature profiles and thermal dose to assess the thermal damage that will occur in tissue during HIFU ablation [9].  
In the conventional method, the numerical simulation of HIFU hyperthermia is usually based on the acoustic model Westervelt equation and the thermal model Pennes bioheat transfer equation, and the tissue properties are set as constants. However, that the tissue properties varied with temperature had been observed in several experimental studies [10; 11; 12; 13]. Moreover, the temperature-dependent tissue properties in turn affect the acoustic field and temperature field. Several researchers have considered some temperature-dependent tissue properties to perform the numerical study of HIFU hyperthermia [9; 14; 15]. For example, [PERSON] [14] studied the effect of dynamic sound speed in the liver with and without a fat layer undergoing HIFU surgery. [PERSON] [15] examined the importance of the thermal lens effect with a phased array transducer in the liver with the fat layer when considering dynamic sound speed and a dynamic acoustic absorption coefficient in the HIFU hyperthermia study using three-dimensional model. [PERSON] [9] studied the influence of temperature-dependent thermal parameters on temperature during HIFU irradiation by comparing the conventional prediction of temperature and the thermal damage zone with that for different thermal parameters (i.e., specific heat capacity and thermal conductivity) at the given temperatures. However, only one or two dynamic tissue properties were considered in the above studies; to our knowledge, other dynamic tissue properties such as density and blood perfusion have never been considered. Furthermore, the joint effect of two dynamic tissue properties was investigated in the above studies, but the individual influence of each tissue property on HIFU hyperthermia is still unclear. Therefore, we first study the evolutions of the acoustic and temperature fields with each dynamic tissue property independently, and clarify the physical significance of each tissue property. In addition, we develop an acoustic-thermal model to evaluate the joint effect of all of the dynamic tissue properties on temperature distribution and thermal damage, including sound speed, acoustic absorption coefficient, non-linearity parameter, specific heat capacity, thermal conductivity, density, and blood perfusion. The results provide a more accurate prediction of temperature distribution and thermal damage, gaining insight into the complex dynamic processes during HIFU hyperthermia, which are useful for doctors making treatment planning.