The temperature field of HIFU piezo ultrasound

The temperature field of HIFU piezo ultrasound for tumor treatment can be generally divided into two types: thermotherapy and ablation therapy. The former is to heat the tumor about 43°C to 45°C,which keep it for several tens of minutes to inhibit tumor growth. The latter uses HIFU to make the target tissue temperature reach 70°C or more in a short time,It makes it coagulative necrosis. In the both treatments, real-time temperature measurement and control is necessary to ensure efficacy. According to the working principle of HIFU, H IFU is focused in the human body by the action of ultrasonic energy, and the tissue temperature instantly reaches 70°C or above. The coagulation necrosis of the lesion tissue is performed, and the non-invasive tumor treatment is performed. For sub-organic soft tissue, the ultrasonic energy is transformed into heat in a moment (seconds), the heat( t) is approximately non-diffusion, and the rising temperature T of the soft tissue can be simply expressed as: where p and c are the density and specific heat of the soft tissue, respectively. The sound intensity is related to the ultrasonic power of hifu and the number of irradiations. It is the tissue absorption coefficient that is related to the operating frequency of the 7Mhz high focusing piezo . Because the HIFU focused ultrasound focal has strict requirements, the side lobes around the focal region are much smaller than the Jiaocheng energy t. 

Therefore, we can think that the shape and size of the generated heat source are similar to those of the focused sound field.The formula shows that the biological effects of focused ultrasound in the tissue are intrinsically linked to the time of the tissue type, it is the ultrasonic frequency, the intensity of the ultrasound, and the number of irradiations. Controlling the temperature change of the 4Mhz ultrasonic high focus piezo treatment area and the influence of heat source on the periorbital tissue is the prerequisite for selecting a reasonable and optimal treatment plan to achieve non-invasive treatment. The HIFU temperature field side t is very necessary. At present, the use of lossy temperature measurement technology in clinical hyperthermia, using 3 to 4 or more thermocouples to the heated tissue.

About temperature measurement of 4Mhz hifu piezo transducer , this invasive temperature measurement technology can achieve the accuracy of 1°C, which undoubtedly cause new pain to the patient, and it is difficult to accurate locate. The measuring data does not represent the temperature field of the tumor heating zone,it is affecting treatment. The doctor's guidance to reduce the doctor's assessment of clinical safety effectiveness, in particular, which may also cause the displacement of cancer cells, so this method is not widely to use. Since 3Mhz hifu piezoelectric crystal uses point-to-line, line-to-face, and face-to-body treatments, the HIF U temperature field should be corrected based on the actual treatment characteristics of H I FU. 

The temperature probe (diameter is much smaller than the focal spot size) is inserted into the tissue, and the IG bamboo system guides the realization of the lattice treatment, thereby obtaining the temperature change of the treatment process, and the rising temperature of each row of the dot matrix on the the temperature probe is the highest. In the third cluster, the corresponding temperature 4Mhz hifu piezoelectric is located in the third row, that is, "each small peak in each cluster corresponds to each treatment point of each row, and the local data near the highest temperature in the temperature curve is expanded.