Recently, the phase compensation technique has allowed the ultrasound to propagate through the skull and focus into the brain. However, the temperature evolution during treatment is hard to control to achieve effectiv...Recently, the phase compensation technique has allowed the ultrasound to propagate through the skull and focus into the brain. However, the temperature evolution during treatment is hard to control to achieve effective treatment and avoid over-high temperature. Proposed in this paper is a method to modulate the temperature distribution in the focal region. It superimposes two signals which focus on two preset different targets with a certain distance. Then the temperature distribution is modulated by changing triggering time delay and amplitudes of the two signals. The simulation model is established based on an 82-element transducer and computed tomography （CT） data of a volunteer＇s head. A finite- difference time-domain （FDTD） method is used to calculate the temperature distributions. The results show that when the distances between the two targets respectively are 7.5-12.5 mm on the acoustic axis and 2.0-3.0 mm in the direction perpendicular to the acoustic axis, a focal region with a uniform temperature distribution （64-65 ℃） can be created. Moreover, the volume of the focal region formed by one irradiation can be adjusted （26.8-266.7 mm3） along with the uniform temperature distribution. This method may ensure the safety and efficacy of HIFU brain tumor therapy.展开更多
The hemispherical phased transducer maximizes the coverage of the skull and the ultrasonic energy per unit area of the skull is minimized,thereby reducing the risk of skull burns,but the transducer has a small focal a...The hemispherical phased transducer maximizes the coverage of the skull and the ultrasonic energy per unit area of the skull is minimized,thereby reducing the risk of skull burns,but the transducer has a small focal area adjustment range,increasing the focal length of treatment is an urgent question for this type of transducer.In this paper,a three-dimensional high-intensity focused ultrasound(HIFU)transcranial propagation model is established based on the human head structure.The finite difference time domain(FDTD)is combined with the Westervelt acoustic wave nonlinear propagation equation and Penne's biological heat conduction equation for numerical simulation of the sound pressure field and temperature field.Forming a treatable focal area in a small-opening hemispherical transducer with a small amount of numerical simulation calculation focusing at a set position to determine the minimum partial excitation area ratio of focusing.And then,applying these preliminary results to a large-opening diameter hemispherical transducer and the temperature field formed by it or full excitation is studied.The results show that the focus area with the excitation area ratio of less than 22%moves forward to the transducer side when the excitation sound is formed.When the excitation area ratio is greater than or equal to 23%,it focuses at the set position.In the case of partial incentives,using 23%of the partial array,the adjustable range of the treatable focal area formed in the three-dimensional space is larger than that of the full excitation.展开更多
In high intensity focused ultrasound(HIFU)treatment,it is crucial to accurately identify denatured and normal biological tissues.In this paper,a novel method based on compressed sensing(CS)and refined composite multi-...In high intensity focused ultrasound(HIFU)treatment,it is crucial to accurately identify denatured and normal biological tissues.In this paper,a novel method based on compressed sensing(CS)and refined composite multi-scale fuzzy entropy(RCMFE)is proposed.First,CS is used to denoise the HIFU echo signals.Then the multi-scale fuzzy entropy(MFE)and RCMFE of the denoised HIFU echo signals are calculated.This study analyzed 90 cases of HIFU echo signals,including 45 cases in normal status and 45 cases in denatured status,and the results show that although both MFE and RCMFE can be used to identify denatured tissues,the intra-class distance of RCMFE on each scale factor is smaller than MFE,and the inter-class distance is larger than MFE.Compared with MFE,RCMFE can calculate the complexity of the signal more accurately and improve the stability,compactness,and separability.When RCMFE is selected as the characteristic parameter,the RCMFE difference between denatured and normal biological tissues is more evident than that of MFE,which helps doctors evaluate the treatment effect more accurately.When the scale factor is selected as 16,the best distinguishing effect can be obtained.展开更多
Hyperthermia effects （39-44 ℃） induced by pulsed high-intensity focused ultrasound （HIFU） have been regarded as a promising therapeutic tool for boosting immune responses or enhancing drug delivery into a solid t...Hyperthermia effects （39-44 ℃） induced by pulsed high-intensity focused ultrasound （HIFU） have been regarded as a promising therapeutic tool for boosting immune responses or enhancing drug delivery into a solid tumor. However, previous studies also reported that the cell death occurs when cells are maintained at 43 ℃ for more than 20 minutes. The aim of this study is to investigate thermal responses inside in vivo rabbit auricular veins exposed to pulsed HIFU （1.17 MHz, 5300 W/cm2, with relatively low-duty ratios （0.2%-4.3%）. The results show that： （1） with constant pulse repetition frequency （PRF） （e.g., 1 Hz）, the thermal responses inside the vessel will increase with the increasing duty ratio; （2） a temperature elevation to 43 ℃ can be identified at the duty ratio of 4.3%; （3） with constant duty ratios, the change of PRF will not significantly affect the temperature measurement in the vessel; （4） as the duty ratios lower than 4.3%, the presence of microbubbles will not significantly enhance the thermal responses in the vessel, but will facilitate HIFU-induced inertial cavitation events.展开更多
When large tumors are treated,ablation of the entire volume of tumors requires multiple treatment spots formed by high intensity-focused ultrasound(HIFU)scanning therapy.The heating effect of HIFU on biological tissue...When large tumors are treated,ablation of the entire volume of tumors requires multiple treatment spots formed by high intensity-focused ultrasound(HIFU)scanning therapy.The heating effect of HIFU on biological tissue is mainly reflected in temperature elevation and tissue lesions.Tissue property parameters vary with temperature and,in turn,the distribution of temperature as well as the heating effects change accordingly.In this study,an HIFU scanning therapy model considering dynamic tissue properties is provided.The acoustic fields and temperature fields are solved combining the Helmholtz wave equation with Pennes bio-heat transfer equation based on the finite element method(FEM)to investigate the effects of various tissue properties(i.e.,the attenuation coefficient,acoustic velocity,thermal conductivity,specific heat capacity,density,and blood perfusion rate)on heating performance.Comparisons of the temperature distribution and thermal lesions under static and dynamic properties are made based on the data of tissue property parameters varying with temperature.The results show that the dynamic changes of thermal conductivity,specific heat capacity,and acoustic velocity may account for the decrease of temperature elevation in HIFU treatment,while the dynamic changes of attenuation coefficient,density,and blood perfusion rate aggravate the increase of temperature on treatment spots.Compared with other properties,the dynamic change of attenuation coefficient has a greater impact on tissue temperature elevation.During HIFU scanning therapy,the temperature elevation and tissue lesions of the first treatment spot are smaller than those of the subsequent treatment spots,but the temperature on the last treatment spot drops faster during the cooling period.The ellipsoidal tissue lesion is not symmetrical;specifically,the part facing toward the previous treatment spot tends to be larger.Under the condition of the same doses,the temperature elevation and the size of tissue lesions under dynamic properties present significant growth in comparison to static properties.Besides,the tissue lesion begins to form earlier with a more unsymmetrical shape and is connected to the tissue lesion around the previous treatment spot.As a result,lesions around all the treatment spots are connected with each other to form a closed lesion region.The findings in this study reveal the influence of dynamic tissue properties on temperature elevation and lesions during HIFU scanning therapy,providing useful support for the optimization of treatment programs to guarantee higher efficacy and safety.展开更多
目的探讨3.0 T MRI定量评估高强度聚焦超声(HIFU)射频消融对子宫肌瘤消融早期效果的可行性及对相关因素分析。方法选择2018年3月至9月在东莞市妇幼保健院行HIFU射频消融32例子宫肌瘤患者,年龄24~48岁,平均年龄38.3岁。分析HIFU射频消融...目的探讨3.0 T MRI定量评估高强度聚焦超声(HIFU)射频消融对子宫肌瘤消融早期效果的可行性及对相关因素分析。方法选择2018年3月至9月在东莞市妇幼保健院行HIFU射频消融32例子宫肌瘤患者,年龄24~48岁,平均年龄38.3岁。分析HIFU射频消融前后(消融后24 h内)MRI资料,将子宫肌瘤消融效果分3种,即完全消融、部分消融和增强信号减低。采用配对样本t检验比较各消融效果的HIFU射频消融前后T1加权成像(T1WI)、T2加权成像(T2WI)及增强序列信号强度差异。采用卡方检验分析子宫肌瘤大小、位置等因素对消融效果的影响。结果32例患者共56个子宫肌瘤,51个为实性,5个合并变性。肌瘤直径5~70 mm。位于子宫前壁36个,后壁20个。56个肌瘤中完全消融35个,部分消融12个,增强信号减低9个。完全消融:表现为全瘤信号发生上述改变,即T1WI呈等、稍高信号,T2WI呈稍高、高信号,增强无明显强化。部分消融:肌瘤的40%~90%发生上述信号改变。增强信号减低:T1WI、T2WI信号无明显变化,增强信号不同程度降低。射频消融前3种消融效果的T1WI信号强度与消融后比较,差异无统计学意义(P>0.05)。射频消融前3种消融效果的T2WI信号强度、增强序列信号强度与消融后比较,差异有显著统计学意义(P<0.01)或统计学意义(P<0.05)。消融效果与子宫肌瘤大小无相关性,差异无统计学意义(r=0.216,P>0.05),与子宫肌瘤前后壁位置有相关性,差异有统计学意义(r=0.389,P<0.05)。结论T2WI、增强序列信号强度的改变能评估子宫肌瘤的早期消融效果,为子宫肌瘤HIFU射频消融效果提供定量参考依据。子宫前壁射频消融效果优于后壁,提示临床对于后壁子宫肌瘤HIFU射频消融需要改进方法。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.81272495)the Natural Science Foundation of Tianjin,China(Grant No.16JC2DJC32200)
文摘Recently, the phase compensation technique has allowed the ultrasound to propagate through the skull and focus into the brain. However, the temperature evolution during treatment is hard to control to achieve effective treatment and avoid over-high temperature. Proposed in this paper is a method to modulate the temperature distribution in the focal region. It superimposes two signals which focus on two preset different targets with a certain distance. Then the temperature distribution is modulated by changing triggering time delay and amplitudes of the two signals. The simulation model is established based on an 82-element transducer and computed tomography （CT） data of a volunteer＇s head. A finite- difference time-domain （FDTD） method is used to calculate the temperature distributions. The results show that when the distances between the two targets respectively are 7.5-12.5 mm on the acoustic axis and 2.0-3.0 mm in the direction perpendicular to the acoustic axis, a focal region with a uniform temperature distribution （64-65 ℃） can be created. Moreover, the volume of the focal region formed by one irradiation can be adjusted （26.8-266.7 mm3） along with the uniform temperature distribution. This method may ensure the safety and efficacy of HIFU brain tumor therapy.
基金the National Natural Science Foundation of China(Grant No.81272495)the Natural Science Foundation of Tianjin(Grant No.16JC2DJC32200)。
文摘The hemispherical phased transducer maximizes the coverage of the skull and the ultrasonic energy per unit area of the skull is minimized,thereby reducing the risk of skull burns,but the transducer has a small focal area adjustment range,increasing the focal length of treatment is an urgent question for this type of transducer.In this paper,a three-dimensional high-intensity focused ultrasound(HIFU)transcranial propagation model is established based on the human head structure.The finite difference time domain(FDTD)is combined with the Westervelt acoustic wave nonlinear propagation equation and Penne's biological heat conduction equation for numerical simulation of the sound pressure field and temperature field.Forming a treatable focal area in a small-opening hemispherical transducer with a small amount of numerical simulation calculation focusing at a set position to determine the minimum partial excitation area ratio of focusing.And then,applying these preliminary results to a large-opening diameter hemispherical transducer and the temperature field formed by it or full excitation is studied.The results show that the focus area with the excitation area ratio of less than 22%moves forward to the transducer side when the excitation sound is formed.When the excitation area ratio is greater than or equal to 23%,it focuses at the set position.In the case of partial incentives,using 23%of the partial array,the adjustable range of the treatable focal area formed in the three-dimensional space is larger than that of the full excitation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11774088 and 11474090)。
文摘In high intensity focused ultrasound(HIFU)treatment,it is crucial to accurately identify denatured and normal biological tissues.In this paper,a novel method based on compressed sensing(CS)and refined composite multi-scale fuzzy entropy(RCMFE)is proposed.First,CS is used to denoise the HIFU echo signals.Then the multi-scale fuzzy entropy(MFE)and RCMFE of the denoised HIFU echo signals are calculated.This study analyzed 90 cases of HIFU echo signals,including 45 cases in normal status and 45 cases in denatured status,and the results show that although both MFE and RCMFE can be used to identify denatured tissues,the intra-class distance of RCMFE on each scale factor is smaller than MFE,and the inter-class distance is larger than MFE.Compared with MFE,RCMFE can calculate the complexity of the signal more accurately and improve the stability,compactness,and separability.When RCMFE is selected as the characteristic parameter,the RCMFE difference between denatured and normal biological tissues is more evident than that of MFE,which helps doctors evaluate the treatment effect more accurately.When the scale factor is selected as 16,the best distinguishing effect can be obtained.
基金Project supported by the National Basic Research Program of China (Grant No. 2011CB707900)the National Natural Science Foundation of China (Grant Nos. 11074123, 10974095, 10904068, and 10204014)+2 种基金the Fundamental Research Funds for the Central Universities of China (Grant Nos. 111602040 and 1095020409)the Natural Science Foundation of Jiangsu Province of China (Grant No. BK2011812)the Priority Academic Program Development of Jiangsu Higher Educaton Institutions of China
文摘Hyperthermia effects （39-44 ℃） induced by pulsed high-intensity focused ultrasound （HIFU） have been regarded as a promising therapeutic tool for boosting immune responses or enhancing drug delivery into a solid tumor. However, previous studies also reported that the cell death occurs when cells are maintained at 43 ℃ for more than 20 minutes. The aim of this study is to investigate thermal responses inside in vivo rabbit auricular veins exposed to pulsed HIFU （1.17 MHz, 5300 W/cm2, with relatively low-duty ratios （0.2%-4.3%）. The results show that： （1） with constant pulse repetition frequency （PRF） （e.g., 1 Hz）, the thermal responses inside the vessel will increase with the increasing duty ratio; （2） a temperature elevation to 43 ℃ can be identified at the duty ratio of 4.3%; （3） with constant duty ratios, the change of PRF will not significantly affect the temperature measurement in the vessel; （4） as the duty ratios lower than 4.3%, the presence of microbubbles will not significantly enhance the thermal responses in the vessel, but will facilitate HIFU-induced inertial cavitation events.
基金Project partially supported by the National Natural Science Foundation of China(Grant Nos.11774088 and 11474090)the Natural Science Foundation of Hunan Province,China(Grant Nos.2016JJ3090 and 2018JJ3557)the Scientific Research Fund of Hunan Provincial Education Department,China(Grant Nos.16B155 and 17B025)。
文摘When large tumors are treated,ablation of the entire volume of tumors requires multiple treatment spots formed by high intensity-focused ultrasound(HIFU)scanning therapy.The heating effect of HIFU on biological tissue is mainly reflected in temperature elevation and tissue lesions.Tissue property parameters vary with temperature and,in turn,the distribution of temperature as well as the heating effects change accordingly.In this study,an HIFU scanning therapy model considering dynamic tissue properties is provided.The acoustic fields and temperature fields are solved combining the Helmholtz wave equation with Pennes bio-heat transfer equation based on the finite element method(FEM)to investigate the effects of various tissue properties(i.e.,the attenuation coefficient,acoustic velocity,thermal conductivity,specific heat capacity,density,and blood perfusion rate)on heating performance.Comparisons of the temperature distribution and thermal lesions under static and dynamic properties are made based on the data of tissue property parameters varying with temperature.The results show that the dynamic changes of thermal conductivity,specific heat capacity,and acoustic velocity may account for the decrease of temperature elevation in HIFU treatment,while the dynamic changes of attenuation coefficient,density,and blood perfusion rate aggravate the increase of temperature on treatment spots.Compared with other properties,the dynamic change of attenuation coefficient has a greater impact on tissue temperature elevation.During HIFU scanning therapy,the temperature elevation and tissue lesions of the first treatment spot are smaller than those of the subsequent treatment spots,but the temperature on the last treatment spot drops faster during the cooling period.The ellipsoidal tissue lesion is not symmetrical;specifically,the part facing toward the previous treatment spot tends to be larger.Under the condition of the same doses,the temperature elevation and the size of tissue lesions under dynamic properties present significant growth in comparison to static properties.Besides,the tissue lesion begins to form earlier with a more unsymmetrical shape and is connected to the tissue lesion around the previous treatment spot.As a result,lesions around all the treatment spots are connected with each other to form a closed lesion region.The findings in this study reveal the influence of dynamic tissue properties on temperature elevation and lesions during HIFU scanning therapy,providing useful support for the optimization of treatment programs to guarantee higher efficacy and safety.
文摘目的探讨3.0 T MRI定量评估高强度聚焦超声(HIFU)射频消融对子宫肌瘤消融早期效果的可行性及对相关因素分析。方法选择2018年3月至9月在东莞市妇幼保健院行HIFU射频消融32例子宫肌瘤患者,年龄24~48岁,平均年龄38.3岁。分析HIFU射频消融前后(消融后24 h内)MRI资料,将子宫肌瘤消融效果分3种,即完全消融、部分消融和增强信号减低。采用配对样本t检验比较各消融效果的HIFU射频消融前后T1加权成像(T1WI)、T2加权成像(T2WI)及增强序列信号强度差异。采用卡方检验分析子宫肌瘤大小、位置等因素对消融效果的影响。结果32例患者共56个子宫肌瘤,51个为实性,5个合并变性。肌瘤直径5~70 mm。位于子宫前壁36个,后壁20个。56个肌瘤中完全消融35个,部分消融12个,增强信号减低9个。完全消融:表现为全瘤信号发生上述改变,即T1WI呈等、稍高信号,T2WI呈稍高、高信号,增强无明显强化。部分消融:肌瘤的40%~90%发生上述信号改变。增强信号减低:T1WI、T2WI信号无明显变化,增强信号不同程度降低。射频消融前3种消融效果的T1WI信号强度与消融后比较,差异无统计学意义(P>0.05)。射频消融前3种消融效果的T2WI信号强度、增强序列信号强度与消融后比较,差异有显著统计学意义(P<0.01)或统计学意义(P<0.05)。消融效果与子宫肌瘤大小无相关性,差异无统计学意义(r=0.216,P>0.05),与子宫肌瘤前后壁位置有相关性,差异有统计学意义(r=0.389,P<0.05)。结论T2WI、增强序列信号强度的改变能评估子宫肌瘤的早期消融效果,为子宫肌瘤HIFU射频消融效果提供定量参考依据。子宫前壁射频消融效果优于后壁,提示临床对于后壁子宫肌瘤HIFU射频消融需要改进方法。
