DWI监测子宫肌瘤HIFU术后早期疗效的价值

目的:探讨DWI评价子宫肌瘤高强度聚焦超声(high-intensity focused ultrasound,HIFU)术后早期疗效的价值。方法:24例患者共26个肌瘤在HIFU术前1周及消融后1周行DWI、CE-MRI检查,分析残留肌瘤组织的DWI信号特征,并比较DWI与CE-MRI测得的残留肌瘤组织体积。结果:24例DWI、CE-MRI均能发现残留肌瘤组织;HIFU术后1周子宫肌瘤残留区DWI信号较前略升高;术后1周残留部分平均ADC值为(1.552±0.142)×10-3 mm2/s,较术前有升高,且差异有统计学意义(P<0.005)。DWI与CE-MRI对术后1周残留组织平均体积的测量,差异无统计学意义(P>0.05)。Pearson法显示,DWI与CE-MRI测量肌瘤残留部分体积呈高度相关(r=0.95,P<0.005)。结论:DWI是监测早期子宫肌瘤HIFU术后不完全消融非常有效的方法。     

Current status and future potential of MRI-guided focused ultrasound surgery

The combination of the imaging abilities of magnetic resonance imaging (MRI) with the ability to delivery energy to targets deep in the body noninvasively with focused ultrasound presents a disruptive technology with the potential to significantly affect healthcare. MRI offers precise targeting, visualization, and quantification of temperature changes and the ability to immediately evaluate the treatment. By exploiting different mechanisms, focused ultrasound offers a range of therapies, ranging from thermal ablation to targeted drug delivery. This article reviews recent preclinical and tests clinical of this technology.     

DCE-MRI定量参数预测高强度超声消融术治疗症状性子宫肌瘤首次体积消融率价值

目的 探讨DCE-MRI定量渗透性与T1灌注分析预测高强度超声消融术(HIFU)治疗子宫肌瘤首次体积消融率价值.方法 搜集本院29例症状性子宫肌瘤行HIFU消融治疗患者(36个肌瘤,直径3.1 ～9.2 cm),治疗前、后3天内分别行DCE-MRI和常规MRI检查,术前测量子宫肌瘤DCE-MRI定量参数值(Ktrans、Kep、Ve、Vp、BF、BV),术后测量肌瘤首次体积消融率,根据体积消融率划分为消融70％以上组(H组)和70％以下组(L组),回顾性分析这两组病例术前渗透性与T1灌注定量参数值有无差别及其与体积消融率的相关性,然后采用ROC曲线评价各参数值的预测价值,寻找术前预测首次体积消融率的最佳临界值.结果 (1)H组(n=20)Ktrans、Kep、Ve、BF低于L组(n=16),差异有统计学意义(P值均＜0.05),余两组各参数间无统计学差异.(2)Ktrans、BF、BV与首次体积消融率呈负相关(r分别为-0.471、-0.452、-0.396,P值均＜0.05).(3)Ktrans、BF、BV值预测首次体积消融率ROC曲线下面积(AUC)分别为0.803、0.809、0.750(P值均＜0.05).以体积消融率70％分界,均获得较高的敏感性和特异性.结论 不同消融率组之间术前Ktrans、Kep、Ve、BF存在差异,Ktrans、BF、BV与首次体积消融率呈负相关,即术前Ktrans、BF、BV值越高,首次体积消融率越低,这三种参数中BF预测效能最好,Ktrans次之.术前DCE-MRI定量参数值可用于预测瘤灶的首次体积消融率,为HIFU消融治疗子宫肌瘤病例筛选和初步判断疗效提供依据.     

Optimization of encoding gradients for MR‐ARFI

MR acoustic radiation force imaging provides a promising method to monitor therapeutic ultrasound treatments. By measuring the displacement induced by the acoustic radiation force, MR acoustic radiation force imaging can locate the focal spot, without a significant temperature rise. In this work, the encoding gradient for MR acoustic radiation force imaging is optimized to achieve an enhanced accuracy and precision of the displacement measurement. By analyzing the sources of artifacts, bulk motion and eddy currents are shown to introduce errors to the measurement, and heavy diffusion‐weighting is shown to result in noisy displacement maps. To eliminate these problems, a new encoding scheme is proposed, which utilizes a pair of bipolar gradients. Improved precision is achieved with robustness against bulk motion and background phase distortion, and improved accuracy is achieved with reduced diffusion‐weighting and optimized encoding pulse width. The experiment result shows that the signal‐to‐noise ratio can be enhanced by more than 2‐fold. These significant improvements are obtained at no cost of scan time or encoding sensitivity, enabling the detection of a displacement less than 0.l μm in a gel phantom with MR acoustic radiation force imaging. Magn Reson Med 63:1050–1058, 2010. © 2010 Wiley‐Liss, Inc.     

Association between contrast‐enhanced MR images and blood–brain barrier disruption following transcranial focused ultrasound

Purpose:

To investigate the correlation between the contrast‐enhanced magnetic resonance imaging (MRI) signal and the duration of blood–brain barrier (BBB) disruption induced by focused ultrasound (FUS).

Materials and Methods:

FUS was applied to 45 rat brains in the presence of microbubbles, and these rats were scanned on a 3T MRI system at several timepoints. The rat brains were then studied using contrast‐enhanced spin echo T1‐weighted images. At the same time, BBB disruption was evaluated based on Evans blue (EB) extravasation. The relationship between the normalized signal intensity change of the MRI and EB extravasation was analyzed by least‐squares linear regression and the calculation of correlation coefficients.

Results:

When MRI enhancement was quantitatively evaluated by EB extravasation, a strong correlation between the normalized signal intensity change of the MRI and EB extravasation was identified during BBB disruption after sonication. However, the correlation coefficient decreased as BBB closure occurred after sonication ended.

Conclusion:

The contrast‐enhanced MRI signal can potentially be used to evaluate the amount of chemotherapeutic agents entering the targeted tissue, but the accuracy of the assessment will be affected by the time interval since sonication. J. Magn. Reson. Imaging 2010;32:593–599. © 2010 Wiley‐Liss, Inc.     

3.0 T MRI评价高强度聚焦超声治疗子宫肌瘤的疗效

目的 探讨使用3.0 T MRI评价高强度聚焦超声(HIFU)治疗子宫肌瘤的短期疗效价值.方法 对35例(共51个)子宫肌瘤患者HIFU治疗前后行MRI平扫和增强扫描,分别测量治疗前后子宫肌瘤及正常子宫壁T1WI、T2WI及T1WI增强的绝对信号强度(ASI),并计算治疗前后子宫肌瘤与正常子宫壁信号值的对比噪声比(CNR)、信号强度比(SIR).采用配对t检验.结果 子宫肌瘤在HIFU治疗前T1WI和T1WI增强的平均ASI、CNR、SIR及T2WI的平均ASI、SIR值与治疗后的差异有统计学意义[T1WI(ASI:t=-2.981,P=0.004;CNR:t=-2.147,P=0.037;SIR:t=-4.578,P=0.000),T1WI增强(ASI:t=13.868,P=0.000;CNR:t-9.084,P=0.000;SIR:t=19.676,P=0.000),T2WI(ASI:t=-2.569,P=0.013;SIR:t=-2.235,P=0.030)],而T2WI的平均CNR值在治疗前后的差异无统计学意义(t=0.860,P=0.394).正常子宫壁在HIFU治疗前T1WI、T2WI及T1WI增强的平均ASI值与治疗后的差异无统计学意义(T1WI:t1.361,P=0.180;T2WI:t=-0.518,P=0.607;T1WI增强:t=0.400,P=0.691).结论 MRI作为显示软组织最好的影像学技术,可作为评价HIFU治疗子宫肌瘤疗效的无创性检查方法.     

子宫平滑肌瘤的MRI诊断

目的　探讨子宫平滑肌瘤的MRI表现及其诊断价值。方法　全部病例均行MRI及超声检查。结合手术病理结果回顾性分析 32例 ( 71个病灶 )子宫平滑肌瘤的MRI表现 ,并与超声检查相对比。结果　所有病灶MRI均表现为T1WI中等或略低信号 ;T2 WI低信号 ,退变型肌瘤夹杂有斑片状高信号 ,肿瘤边界清楚 ,瘤周大多可见包膜 ( 5 5 / 71)。对发现 <2cm的肿瘤、判断肿瘤变性及肿瘤的定位MRI均优于超声检查。结论　子宫平滑肌瘤MRI表现颇具特征性 ,较B超检出率更高 ,可获得更精确的资料 ,对制定治疗方案及随访观察肿瘤的变化具有较大的临床意义     

Renal ablation using magnetic resonance-guided high intensity focused ultrasound: Magnetic resonance imaging and histopathology assessment

AIM: To use magnetic resonance-guided high intensity focused ultrasound (MRg-HIFU), magnetic resonance imaging (MRI) and histopathology for noninvasively ablating, quantifying and characterizing ablated renal tissue.METHODS: Six anesthetized/mechanically-ventilated pigs underwent single/double renal sonication (n = 24) using a 3T-MRg-HIFU (1.1 MHz frequency and 3000J-4400J energies). T2-weighted fast spin echo (T2-W), perfusion saturation recovery gradient echo and contrast enhanced (CE) T1-weighted (T1-W) sequences were used for treatment planning, temperature monitoring, lesion visualization, characterization and quantification, respectively. Histopathology was conducted in excised kidneys to quantify and characterize cellular and vascular changes. Paired Student’s t-test was used and a P-value < 0.05 was considered statistically significant.RESULTS: Ablated renal parenchyma could not be differentiated from normal parenchyma on T2-W or non-CE T1-W sequences. Ablated renal lesions were visible as hypoenhanced regions on perfusion and CE T1-W MRI sequences, suggesting perfusion deficits and necrosis. Volumes of ablated parenchyma on CE T1-W images in vivo (0.12-0.36 cm³ for single sonication 3000J, 0.50-0.84 cm³, for double 3000J, 0.75-0.78 cm³ for single 4400J and 0.12-2.65 cm³ for double 4400J) and at postmortem (0.23-0.52 cm³, 0.25-0.82 cm³, 0.45-0.68 cm³ and 0.29-1.80 cm³, respectively) were comparable. The ablated volumes on 3000J and 4400J double sonication were significantly larger than single (P < 0.01), thus, the volume and depth of ablated tissue depends on the applied energy and number of sonication. Macroscopic and microscopic examinations confirmed the locations and presence of coagulation necrosis, vascular damage and interstitial hemorrhage, respectively.CONCLUSION: Contrast enhanced MRI provides assessment of MRg-HIFU renal ablation. Histopathology demonstrated coagulation necrosis, vascular damage and confirmed the volume of damage seen on MRI.     

Volumetric MRI‐guided high‐intensity focused ultrasound for noninvasive,in vivo determination of tissue thermal conductivity: Initial experience in a pig model

Purpose:

To estimate the local thermal conductivity of porcine thigh muscle at temperatures required for magnetic resonance imaging (MRI)‐guided high‐intensity focused ultrasound (MRgHIFU) surgery (60–90°C).

Materials and Methods:

Using MRgHIFU, we performed 40 volumetric ablations in the thigh muscles of four pigs. Thirty‐five of the sonications were successful. We used MRI to monitor the resulting temperature increase. We then determined local thermal conductivity by analyzing the spatiotemporal spread of temperature during the cooling period.

Results:

The thermal conductivity of MRgHIFU‐treated porcine thigh muscle fell within a narrow range (0.52 ± 0.05 W/[m*K]), which is within the range reported for porcine thigh muscle at temperatures of <40°C (0.52 to 0.62 W/[m*K]). Thus, there was little change in the thermal conductivity of porcine thigh muscle at temperatures required for MRgHIFU surgery compared to lower temperatures.

Conclusion:

Our MRgHIFU‐based approach allowed us to estimate, with good reproducibility, the local thermal conductivity of in vivo deep tissue in real time at temperatures of 60°C to 90°C. Therefore, our method provides a valuable tool for quantifying the influence of thermal conductivity on temperature distribution in tissues and for optimizing thermal dose delivery during thermal ablation with clinical MRgHIFU. J. Magn. Reson. Imaging 2013;37:950–957. © 2012 Wiley Periodicals, Inc.     

Pulse sequence and timing of contrast‐enhanced MRI for assessing blood–brain barrier disruption after transcranial focused ultrasound in the presence of hemorrhage

Purpose:

To optimize the timing of contrast‐enhanced magnetic resonance imaging (MRI) that best indicates blood–brain barrier (BBB) disruption induced by focused ultrasound (FUS) along with an ultrasound contrast agent (UCA) and to verify that the contrast‐enhanced spin‐echo MRI sequence can indicate the degree and location of BBB disruption in the presence of hemorrhage better than a gradient‐echo sequence.

Materials and Methods:

Sonication was applied to 12 rat brains with four different doses of UCA to cause variable degrees of hemorrhage. Two imaging sequences were performed to acquire T1‐weighted (T1W) images at two time‐points after the administration of a T1‐shortening contrast agent. The contrast enhancement at the sonicated regions was quantified and correlated against Evans blue (EB) staining.

Results:

The spin‐echo T1W images at 10 minutes post–contrast enhancement showed the best correlation with EB staining in both quantity of EB extravasation (r = 0.812; P < 0.01) and spatial distribution (r = 0.528, P < 0.01). This capability was more robust than the gradient‐echo sequence.

Conclusion:

Our results suggest that contrast‐enhanced T1W spin‐echo sequence acquired in the early phase post–contrast enhancement should be considered to monitor the degree and location of BBB disruption under the possibility of hemorrhage induced by FUS. J. Magn. Reson. Imaging 2010;31:1323–1330. © 2010 Wiley‐Liss, Inc.     

Ultrasound and magnetic resonance imaging assessmentof active bowel segments in Crohn's disease

AIM: Determining bowel disease activity in Crohn's patients can be difficult on clinical and laboratory assessment. Endoscopy is invasive and barium studies use ionising radiation. The aim of this study was to compare ultrasound and magnetic resonance imaging (MRI) in detecting Crohn's disease activity in the small or large bowel. MATERIALS AND METHODS: Thirty patients, previously diagnosed with Crohn's disease, had bowel ultrasound and MR imaging, and were deemed active or inactive on each test. The 'gold standard' was based on clinical assessment and one or more of the following: endoscopy, barium studies or surgery. RESULTS: For determining Crohn's disease activity, the sensitivities and specificities of bowel ultrasound and MRI were 87 percent and 100 percent, and 87 percent and 71 percent, respectively. Significant parameters that defined disease activity were bowel wall thickening on ultrasound and MRI, and contrast enhancement of the bowel wall and mesenteric vascularity/stranding on MRI. CONCLUSION: Ultrasound and MRI were both sensitive for determining Crohn's disease activity in the bowel, but MRI with gadolinium enhancement was less specific.     

磁共振引导高强度聚焦超声完全消融子宫肌瘤:可行性、安全性和远期疗效

目的 评估MRI引导高强度聚焦超声(MRgHIFU)完全消融子宫肌瘤的可行性、安全性和远期疗效.方法 对43例(平均年龄41.4岁)共51个子宫肌瘤,平均大小为(7.1±1.4)em,均进行一次MRI引导高强度聚焦超声消融术.治疗后即刻MRI增强测量靶肌瘤的体积及其无灌注区的体积,子宫肌瘤无灌注区的完全覆盖靶肌瘤为完全消融.对完全消融的子宫肌瘤在治疗后3个月、6个月、1年、2年和3年通过MRI进行随访复查肌瘤的体积变化;在术前、3、6个月采用UFS-QOL症状评分方法对患者症状评分,并随访3年观察其症状的变化.同时对这些肌瘤的特征、治疗后不良事件、聚焦超声能量及治疗效率等进行了分析.结果 经MRgHIFU治疗后肌瘤平均消融率为84.3％±15.7％(范围33.8％～ 100％),肌瘤部分消融(消融率＜90％)、几乎完全消融(消融率为90％～99％)和完全消融的病例分别为23例、10例和10例,平均治疗时间为(2.2±0.8)h(范围1.0 ～ 4.3 h),治疗后均未发生并发症.10例13个完全消融的肌瘤术前MRI均为T2低信号表现而其血供类型不同;超声治疗的能效因子(EEF)为:(3.6±2.1)J/mm3(0.7 ～ 6.8 J/mm3).治疗后3、6个月症状严重程度评分(SSS)分别为从术前的33.9±7.1下降至16.6±9.0和8.1±3.4(P＜ 0.01),1年或2年后10例患者的症状完全消失.治疗后3、6个月和3年肌瘤体积分别缩小39.5％±10.2％、59.1％±9.0％和93.3％±3.1％(P＜0.01).治疗后3年随访肌瘤均未出现复发.结论 MRI引导高强度聚焦超声完全消融子宫肌瘤是可行的、安全的和有效的,MRI T2WI低信号肌瘤可在治疗后取得完全消融.     

磁共振常规序列在原发性肝癌高强度聚集超声疗效评估中的价值

目的探讨MR常规序列在原发性肝癌高强度聚集超声(HIFU)治疗后疗效评估中的价值。资料与方法采用1.5 T超导型MR成像系统及8通道体部相控阵线圈对75例原发性肝癌在HIFU治疗前、治疗后2周及3个月行MR常规平扫及动态增强扫描。扫描序列包括快速恢复快速自旋回波(FRFSE)序列横轴位T2WI;快速扰相梯度回波(FSPGR)序列结合饱和压脂技术横轴位T1WI;FSPGR序列横轴位双回波;冠状位稳态采集快速成像(FI-ESTA)以及肝脏快速容积采集(LAVA)序列行动态增强扫描。观察病灶HIFU治疗前后信号、大小、范围变化及强化特征,以此判断肿瘤坏死、残存或复发等情况。结果 79个(98.75%)病灶在HIFU治疗后2周内T2WI信号降低。1个(1.25%)病灶T2WI上病灶内部或周边仍可见结节状高信号。3个月后复查MRI,78个(97.5%)病灶T2WI信号无明显变化;2个(2.5%)病灶内部或周边出现不规则结节状高信号。在T2WI上,HIFU治疗后2周内原发肝癌病灶大小与治疗前比较无明显变化(t=-1.90,P>0.05);HIFU治疗后3个月,70个(87.5%)病灶大小与治疗后2周内比较无明显变化,8个...     

Simultaneous magnetic resonance phase and magnitude temperature maps in muscle

Noninvasive magnetic resonance temperature maps that are used to monitor thermal ablation of tissue are described. In magnetic resonance images, thermally induced proton nuclear magnetic resonance frequency shifts, and changes in the longitudinal relaxation time produce both phase and magnitude changes in the MR signal. Temperature maps with improved sensitivity are derived from the complex-difference nuclear magnetic resonance signal. Bovine muscle specimens were heated with focused ultrasound to model thermal surgery and create a known thermal distribution to test the method. Resulting MR images acquired in 2 s produce temperature maps with 1 mm resolution and 2°C temperature sensitivity. The temperature sensitivity was increased by extending the acquisition to 5 s, by decreasing the receiver bandwidth, and increasing the echo time.     

Detecting blood–brain barrier disruption within minimal hemorrhage following transcranial focused ultrasound: A correlation study with contrast‐enhanced MRI

Focused ultrasound combined with an intravascular ultrasound contrast agent can induce transient disruption of the blood–brain barrier, and the blood–brain barrier disruption can be detected by contrast‐enhanced MRI. There is, however, no study investigating the ability of various MR methods to detect focused ultrasound–induced blood–brain barrier disruption within minimal hemorrhage. Sonication was applied to 15 rat brains with four different doses of ultrasound contrast agent (0, 10, 30, or 50 μL/kg), and contrast‐enhanced T1‐weighted spin echo, gradient echo images, and longitudinal relaxation rate mapping along with effective transverse relaxation time–weighted and susceptibility‐weighted images were acquired. Volume‐of‐interest–based and threshold‐based analyses were performed to quantify the contrast enhancement, which was then correlated with the ultrasound contrast agent dose and with the amount of Evans blue extravasation. Both effective transverse relaxation time–weighted and susceptibility‐weighted images did not detect histology‐proved intracranial hemorrhage at 10 μL/kg, but MRI failed to detect mild intracranial hemorrhage at 30 μL/kg. All tested sequences showed detectable contrast enhancement increasing with ultrasound contrast agent dose. In correlating with Evans blue extravasation, the gradient echo sequence was slightly better than the spin echo sequence and was comparable to longitudinal relaxation rate mapping. In conclusion, both gradient echo and spin echo sequences were all reliable in indicating the degree of focused ultrasound–induced blood–brain barrier disruption within minimal hemorrhage. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.     

Evaluation of short-term response of high intensity focused ultrasound ablation for primary hepatic carcinoma: Utility of contrast-enhanced MRI and diffusion-weighted imaging

Objective

To explore the significance of contrast-enhanced MRI (CE-MRI) and diffusion-weighted imaging (DWI) in evaluating the short-term response of high intensity focused ultrasound (HIFU) ablation for primary hepatic carcinoma (PHC).

Methods

Thirty-nine lesions in the livers of 27 patients were performed HIFU ablation. Conventional MRI sequences, CE-MRI and DWI were performed 1 week before HIFU and 1 week, 3 months after the therapy, respectively. The short-term responses of HIFU for all lesions were evaluated with MRI.

Results

28 of the 39 lesions (28/39, 71.8%) showed complete necrosis with no enhancement 1 week and 3 months after HIFU. The apparent diffusion coefficient (ADC) values 1 week and 3 months after HIFU were significantly higher than those 1 week before treatment (p < 0.05). The tumor recurrence was detected in 7 of the 39 lesions (7/39, 17.9%) which had no significant enhancement 1 week after HIFU. On the 3 months follow-up, focal nodules were found on the inner aspects of the treated areas. The ADC values had no significant difference between 1 week before and after treatment (p > 0.05), however, they were significantly higher 3 months after HIFU (p < 0.05). The tumor residuals were detected in 4 of the 39 lesions (4/39, 10.3%) showing enhancement 1 week after treatment and increased size 3 months after HIFU. The ADC values had no significant difference among 1 week before HIFU, 1 week and 3 months after treatment (p > 0.05).

Conclusion

CE-MRI and DWI can be employed to evaluate the short-term response of HIFU ablation for PHC and to guide the patient management.