The Relationship Of Temperature, Hyperechoic And Coagulation Necrosis Induced By High Intensity Focused Ultrsound In Bovine Liver

BACKGROUNDHigh intensity focused ultrasound received attention began in the forties of last century, American scientists Lynn, Fry noted the possibility of using high intensity focused ultrasound treatment for patients from outside the body? Followed by the United States, Britain, France, Japan, China and other countries have invested significant human and material resources of research. Today High intensity focused ultrasound has become the research focus of acoustics and medical field. High intensity focused ultrasound focusing by a certain way (phased array focused, self-focusing, focusing mirror, etc.), the ultrasonic energy concentrated in an area called the focal areas of intense energy field, through the air, thermal, mechanical mechanism to target tissue leads to irreversible coagulation necrosis, thus achieving the purpose of injured target tissue. The current monitoring methods of HIFU treatment are US and MRI. Through monitoring changes in echogenicity and temperature to determine treatment respectively. However, the enhanced echogenicity caused by HIFU is primarily based on acoustic cavitation or vapor bubbles, temperature and coagulation necrosis, while the bubble will accelerate the temperature rise.then, What is the relationship between temperature, echo changes and coagulation necrosis of HIFU treatment?OBJECTIVE(1)The relationship of the temperature rise, gray-scale difference and changes in coagulation necrosis area When Bovine liver tissue reached the same temperature.(2)The changes of the temperature rise, gray-scale difference and changes in coagulation necrosis area When Bovine liver tissue under the same HIFU dose.(3)Different doses of radiation dose area under the heat, gray area and changes in coagulation necrosis area. The changes of integral area,echogenic area and in coagulation necrosis area of bovine liver tissue under different thermal dose irradiation of HIFU. MATERIALS AND METHODS1. The same temperature HIFU irradiation experiments in vitro bovine liver.1.1 Experiment Equipment: (1)MRIgHIFU treatment system, from the Chongqing Haifu Technology Co., Ltd. jointly developed and SIEMENS. Treatment of head parameters: diameter 200 mm, focal length 150 mm, frequency 1.0 MHz.(2) B-control section: HIFU treatment bed (and the first part of the HIFU treatment device is the same machine), B super-monitoring systems, industrial computer. Treatment of head and parameter system with MRIgHIFU.1.2 experiment object: The samples of bovine liver tissue in vitro (within 6 hours of slaughter), immersed in 0.9% saline, select the connective tissue and blood vessels less office cleaning, cut into 10 cm×8 cm×6 cm size, rewarming to 20℃, 30min spare conventional degassing.1.3 Experimental method: 1)MRI Part: HIFU irradiation depth 15mm, irradiation power were 300W, 250W, 200W, 150W, 100W, 50W. First of all, bovine liver tissue with t2_trufi_sag_pat2 sequence scan, get a set of images, select the level of less connective tissue and blood vessels as a target, and the focus moved to the level of HIFU, adjusted the treatment depth. Temperature sequence then GRE_TMap_phasediff_ref role HIFU levels to be scanned by a reference temperature phase diagram. HIFU with GRE_TMap_phasediff_ref scan upcoming irradiation level, collecting 1-2 clear image after HIFU exposure, while scanning the temperature graph, when 55℃appear immediately stop radiation. Records of irradiation time. Repeat each of six experimental power. 2)B-control parts: the depth and power ibid irradiation, irradiation time determined by the MRI monitoring section, the second B-scan probe the same direction and MRI were recorded before irradiation and irradiated immediately, 10s, 30s, 60s, 120s sound phase diagram. Observed temperature changes, changes in gray level difference, coagulation necrosis area and radiation dose.2.Three radiation dose at different temperatures, echo, experimental changes in coagulation necrosis2.1 The experimental apparatus: the same as the first part2.2 experiment object:the same as the first part2.3 Experimental Method: Irradiation depth of 15mm, and group parameters as shown below. Similar to the first part of the specific methods, not tired out. Radiation dose 1000 J 2000 J 3000 J 200W-5s 200W-10s 300W-10s 100W-10s 133W-15s 200W-15s 67W-15s 100W-20s 150W-20s 50W-20s 80W-25s 120W-25s power and time 40W-25s 67W-30s 100W-30sRESULTS1.The same temperature (55℃), as power increases, the time there 55℃gradually shorter, that is, the greater the temperature rise of power faster.2.Bovine coagulation necrosis of tissues of the area size and the total radiation dose, the greater the total radiation dose, the greater the area of coagulation necrosis.3.The radiation dose is fixed (3000J), 55℃with the power to increase the time gradually appear shorter to reach the same temperature when the power of larger radiation intensity generated by the difference immediately, the maximum temperature and anatomical area of coagulation necrosis are increased as the power increases.4.When HIFU radiation dose is large, thermal dose points (threshold 59.6min), gray scale monitor (the size of the irradiated 10s) method can reflect coagulation necrosis in the area, the temperature control method in certain extent, reflect the area of coagulation necrosis, but the heat sensitivity of different organizations with different, this method has some limitations. When HIFU radiation dose is small (1000J), integral thermal dose and temperature control can not be the appropriate size, then there is coagulation necrosis of bovine liver tissue, while the B-method can still monitor the higher power (200W , 100W, 67W) monitor changes to the echo.CONCLUSION1.Radiation dose on the formation of coagulation necrosis area play a decisive role, when the radiation dose when the power on a certain area of coagulation necrosis of the formation of a greater impact.2.HIFU exposure is constant, the maximum temperature rise produced by irradiation and the intensity difference and the coagulation necrosis area have increased with the power.3.MRI and HIFU treatment of B-control methods have advantages and disadvantages, when the HIFU radiation dose is large, with thermal dose integral method is more advantageous;When the radiation dose is small, the use of B-mode monitor more favorable, when the radiation dose is small, the thermal dose integration method can not be the appropriate size, the temperature may be monitored by MRI is the average temperature of a region can not reflect the temperature of each voxel, at a time when it can be observed B-enhanced echo and B-price is much lower compared to MRI, and can do real-time monitoring, the promotion of the use of clinical.