Ultrasound elastography using multiple images

Displacement estimation is an essential step for ultrasound elastography and numerous techniques have been proposed to improve its quality using two frames of ultrasound RF data. This paper introduces a technique for calculating a displacement field from three (or multiple) frames of ultrasound RF data. To calculate a displacement field using three images, we first derive constraints on variations of the displacement field with time using mechanics of materials. These constraints are then used to generate a regularized cost function that incorporates amplitude similarity of three ultrasound images and displacement continuity. We optimize the cost function in an expectation maximization (EM) framework. Iteratively reweighted least squares (IRLS) is used to minimize the effect of outliers. An alternative approach for utilizing multiple images is to only consider two frames at any time and sequentially calculate the strains, which are then accumulated. We formally show that, compared to using two images or accumulating strains, the new algorithm reduces the noise and eliminates ambiguities in displacement estimation. The displacement field is used to generate strain images for quasi-static elastography. Simulation, phantom experiments and in vivo patient trials of imaging liver tumors and monitoring ablation therapy of liver cancer are presented for validation. We show that even with the challenging patient data, where it is likely to have one frame among the three that is not optimal for strain estimation, the introduction of physics-based prior as well as the simultaneous consideration of three images significantly improves the quality of strain images. Average values for strain images of two frames versus ElastMI are: 43 versus 73 for SNR (signal to noise ratio) in simulation data, 11 versus 15 for CNR (contrast to noise ratio) in phantom data, and 5.7 versus 7.3 for CNR in patient data. In addition, the improvement of ElastMI over both utilizing two images and accumulating strains is statistically significant in the patient data, with p-values of respectively 0.006 and 0.012.     

剪切波弹性成像评价肝脏微波消融灶边界的实验研究

目的探讨超高速剪切波弹性成像（SWE）在定量评估肝脏微波消融边界中的可行性与准确性。 方法取健康雄性5月龄五指山猪15只,行开腹直视下肝脏微波消融术,消融功率选定40 W,根据消融时间分设为15 s、30 s、60 s三组。消融后即刻采用SWE测量消融灶的弹性模量值。术后利用HE染色、烟酰胺腺嘌呤二核苷酸（NADH）黄递酶组织化学染色评估肝组织的损伤程度。 结果本实验共进行有效消融156次,有效SWE测量740次,得到有效病理结果131个。消融灶弹性模量值呈阶梯式同心圆分布,从中心向外周可分为3个区域。同一消融时间下弹性模量值在周边正常组织区域、消融边界区域、消融中心区域阶梯式增高（P均<0.01）。消融功率40 W,消融时间15 s、30 s、60 s在周边正常组织区域和消融边界区域的弹性模量值差异无统计学意义（P均>0.05）,但在消融中心区域,其弹性模量值随消融时间的缩短而呈阶梯式降低,［60 s：（97.16±14.58）kPa>30 s：（77.84±9.64）kPa>15 s：（38.92±3.12）kPa］,差异有统计学意义（F=2 131.832,P<0.01）。不同消融时间的消融边界区域弹性模量值保持在22.68~23.56 kPa。 结论微波消融灶消融边界区域弹性模量值范围相对固定,SWE有助于定量评估肝脏微波消融边界,其在超声消融的监测与评估方面具有较强的实用价值。     

JSUM ultrasound elastography practice guidelines: liver

In diffuse liver disease, it is extremely important to make an accurate diagnosis of liver fibrosis prior to determining indications for therapy or predicting treatment outcome and malignant potential. Although liver biopsy has long been the gold standard in the diagnosis of liver fibrosis, it is still an invasive method. In addition, the sampling error is an intrinsic problem of liver biopsy. Non-invasive serological methods for the diagnosis of liver fibrosis can be affected by factors unrelated to the liver. Recently, after the introduction of FibroScan, it became possible to measure liver fibrosis directly and non-invasively by elastography, which has attracted attention as a non-invasive imaging diagnostic tool for liver fibrosis. In addition, real-time tissue elastography is currently being used to conduct clinical trials at many institutions. Moreover, virtual touch quantification enables the observation of liver stiffness at any location by simply observing B-mode images. Furthermore, the recently developed ShearWave elastography visualizes liver stiffness on a color map. Elastography is thought to be useful for all types of diffuse liver diseases. Because of its association with portal hypertension and liver carcinogenesis, elastography is expected to function as a novel prognostic tool for liver disease. Although various elastographic devices have been developed by multiple companies, each device has its own measurement principle, method, and outcome, creating confusion in clinical settings. Therefore, it is extremely important to understand the characteristics of each device in advance. The objective of this guideline, which describes the characteristics of each device based on the latest knowledge, is for all users to be able to make the correct diagnosis of hepatic fibrosis by ultrasound elastography.     

Ultrasound thyroid elastography using carotid artery pulsation: preliminary study.

OBJECTIVE: The purpose of this study was to evaluate the feasibility of ultrasound thyroid elastography using carotid artery pulsation as the compression source and its potential for differential diagnosis of thyroid nodules. METHODS: Baseband sonographic data were acquired for 16 thyroid nodules from 12 patients. The natural pulsation of the carotid artery was used as the compression source, and thyroid strain was estimated offline. For quantitative assessment of thyroid tissue stiffness, a new metric called the thyroid stiffness index (TSI) was computed as the ratio of strain near the carotid artery (high-strain region) to that of a stiff region (low-strain region) inside a thyroid nodule. The stiffness information from elastography was correlated with histopathologic findings. RESULTS: The TSI for papillary carcinoma (n = 9) was higher than the TSI for a benign nodular goiter (n = 6), indicating that papillary carcinoma is stiffer than a benign nodular goiter (P < .05). In 1 patient, we were able to distinguish a papillary carcinoma nodule and a benign nodular goiter located in the same thyroid lobe based on the stiffness information obtained from elastography. This suggests that elastography could be used for guiding fine-needle aspiration biopsy to a thyroid nodule with a high probability of cancer. CONCLUSIONS: The results from this preliminary study indicate the feasibility of the pulsation-induced thyroid elastography. Ultrasound thyroid elastography using carotid artery pulsation appears to have the potential for noninvasively differentiating papillary carcinoma from benign nodular goiter. Future studies are needed to evaluate the efficacy of elastography in detecting thyroid cancer and guiding thyroid biopsies.     

Time-Harmonic Ultrasound elastography of the Descending Abdominal Aorta: Initial Results

Stiffening of central large vessels is considered a key pathophysiologic factor within the cardiovascular system. Current diagnostic parameters such as pulse wave velocity (PWV) indirectly measure aortic stiffness, a hallmark of coronary diseases. The aim of the present study was to perform elastography of the proximal abdominal aorta based on externally induced time-harmonic shear waves. Experiments were performed in 30 healthy volunteers (25 young, 5 old, >50 y) and 5 patients with longstanding hypertension (PWV >10 m/s). B-Mode-guided sonographic time-harmonic elastography was used for measurement of externally induced shear waves at 30-Hz vibration frequency. Thirty-hertz shear wave amplitudes (SWAs) within the abdominal aorta were measured and displayed in real time and processed offline for differences in SWA between systole and diastole (ΔSWA). Data were analyzed using the Kruskal–Wallis test and receiver operating characteristic curve analysis. The change in SWA over the cardiac cycle was reduced significantly in all patients as assessed with ΔSWA (volunteers: mean = 10 ± 5 μm, patients: mean = 4 ± 1 μm; p < 0.001). The best separation of healthy volunteers from patients was obtained with a ΔSWA threshold of 4.7 μm, resulting in a sensitivity of 0.9 and a specificity of 1.0, with an overall area under the curve of 0.96. Time harmonic elastography of the abdominal aorta is feasible and shows promise for the exploitation of time-varying shear wave amplitudes as a diagnostic marker for aortic wall stiffening. Patients with elevated PWVs suggesting increased aortic wall stiffness were best identified by ΔSWA—a parameter that could be related to the ability of the vessel walls to distend on passages of the pulse wave.     

超声弹性成像在宫颈癌浸润范围评估中的应用研究

目的探讨超声弹性成像评估宫颈癌浸润范围的价值。方法对40例宫颈癌患者分别行经阴道常规二维超声和弹性成像,比较两种方法测量的宫颈癌病灶大小并评估宫颈癌浸润宫颈内口的情况,与病理测量结果进行比较。结果病灶大小的常规超声测值:长径35.35±10.16 mm、横径33.08±13.68 mm、前后径24.49±11.22 mm;弹性成像测值:长径37.86±9.93 mm、横径35.94±14.82 mm、前后径27.15±11.74 mm;病理测值:长径40.00±11.07 mm、横径37.08±14.99 mm、前后径27.50±11.88 mm;弹性成像测值大于常规超声测值,二者比较有统计学差异(P0.05)弹性成像测值与病理测值无差异(P0.05),常规超声测值与病理测值比较有明显差异(P0.01);弹性成像方法病灶大小测值与病理结果间呈显著正相关(r=0.992),常规超声病灶大小测值与病理结果间呈正相关(r=0.890)。在评价宫颈癌是否浸润宫体中,常规超声诊断宫体浸润9例,弹性成像诊断宫体浸润16例,病理诊断宫体浸润17例,弹性成像与常规超声诊断结果间有差异(P0.05)。结论经阴道实时弹性成像对宫颈癌浸润范围的评估优于常规超声。     

Ultrasound elastography for the differential diagnosis of nipple retraction

Purpose

Nipple retraction is difficult to diagnose radiologically and extremely worrisome for patients. It occurs most commonly due to pathologies such as previous mastitis or an infiltrative malignancy. With this in mind, the goal of this study was to differentiate benign from malignant lesions of nipple retraction, using the differential characteristics of retroareolar area stiffness, observed by means of the new technological modality of ultrasound elastography (USE).

Materials and methods

Nineteen unilateral nipple retraction cases, including five cases of mammary ductal carcinoma posteriorly infiltrated the areola, two cases of Paget disease, and 12 cases of mastitis, were investigated. Imaging findings [gray-scale ultrasound (US) and USE analyses of the breasts’ nipple–areolar complex], pathological evaluation, and the results of 4 years of follow-up treatment were obtained. The recorded images were evaluated by two different radiologists, and all data were analyzed statistically.

Results

Statistical analysis showed that there was a strong correlation between the two radiologists’ evaluations. The US images were not diagnostic for either the malignant or benign conditions. The correlation between the diagnosis using US and the final diagnosis was calculated as 0.436 (p = 0.006). However, the USE images were more informative since the correlation ratio between the USE results and the final diagnosis was found to be 0.723 (p < 0.001). While the area under the concentration curve (AUC) values that were used for the diagnostic determination of the US results were inconclusive at 0.274 (p < 0.021), the AUC values for USE were significant, with a diagnostic value of 0.866 for all cases (p < 0.01).

Conclusion

The USE modality, which is not commonly used in routine practice, has the potential to solve the problem of differentiation of nipple retraction etiologies in the near future.     

实时虚拟超声引导下冈上肌腱超声弹性成像

目的 探讨实时虚拟超声(RVS)引导下弹性成像诊断冈上肌腱损伤的价值。方法 24例肩关节疼痛患者,均经常规MR检查明确为一侧慢性冈上肌腱损伤。在RVS下进行MRI与超声图像融合,然后行超声弹性成像,对患侧和健侧相应部位进行弹性成像评分和统计学分析。评分标准:1分:弹性图像90%以上为绿色,可伴有10%以下的紫色或红色;2分:弹性图像50%~90%为绿色,其余以紫色为主,可伴有10%以下的红色;3分:弹性图像50%以上为紫色,其余为绿色与红色相间;或弹性图像90%以上为红色、绿色相间;4分:弹性图像50%~90%为红色,其余以紫色为主,可伴有10%以下的绿色;5分:弹性图像90%以上为红色,可伴有10%以下的紫色或绿色。结果 24例患者中,14例灰阶超声未见明显异常。对所有患者均可进行有效的实时虚拟导航,通过MRI引导超声定位病变的冈上肌腱。超声弹性成像患侧冈上肌腱3分3例,4分13例,5分8例;健侧冈上肌腱2分5例,3分16例,4分3例;患侧弹性评分高于健侧(P<0.05)。结论 借助于RVS,超声弹性成像有助于诊断慢性冈上肌腱损伤。     

对比声触诊弹性成像与可视化瞬时弹性成像检测肝脏弹性北大核心CSCD

目的对比观察声触诊弹性成像(STE)与可视化瞬时弹性成像(ViTE)检测肝脏弹性的价值。方法收集478名接受腹部超声检查的受检者,根据检查结果将其分为肝纤维化组(n=147)、肝硬化组(n=162)及健康组(n=169);采用STE和ViTE测量各组肝脏弹性值,观察2种方法检测的一致性、检测成功率、稳定性及其测值的差异。结果STE和ViTE检测成功率差异无统计学意义(P>0.05),其对肝纤维化组及健康组的检测一致性均较好,对肝硬化组的一致性较差。STE及ViTE针对肝纤维化组和健康组的测量结果的稳定性均较好;对肝硬化组,STE稳定性较好,而ViTE稳定性较差。STE与ViTE所测肝纤维化组及健康组肝脏弹性值差异均无统计学意义(P均>0.05),而STE测得肝硬化组肝脏弹性值显著低于ViTE(P<0.05)。STE及ViTE对男性受试者肝脏弹性值的测值均大于女性(P均<0.05),尤以25~50岁受检者为著(P均<0.05)。结论STE与ViTE检测肝脏弹性值的成功率均较高,且对肝纤维化患者和健康人群的一致性和稳定性均较好,而用于检测肝硬化患者的一致性较差;对肝硬化患者,STE检测稳定性较好,而ViTE较差。     

超声弹性成像观察正常成年女性乳腺组织

目的 探讨超声弹性成像在正常成年女性乳腺组织中的应用.方法 收集41名正常成年女性,根据年龄分为青年组(11名)、中青年组(10名)、中年组(10名)和老年组(10名),以弹性成像技术观察乳腺组织,采用乳腺整体5分评分法测量乳腺的皮下脂肪层、腺体层(中央区、内带、中带和外带)和胸壁肌层的弹性成像评分.结果 弹性评分:脂肪组织＜腺体层＜胸壁肌层.腺体层的弹性评分随年龄增加而增大(P＜0.05),而脂肪层和胸壁肌层的弹性评分不受年龄影响.除青年组外,乳腺中央区的弹性评分低于其他分区(P＜0.05),而内带、中带与外带间的弹性评分差异无统计学意义.结论 采用弹性成像技术可以很好地评判正常成年女性乳腺组织的硬度,半定量评价不同年龄段女性乳腺组织的差异.     

超声弹性成像在儿童肝脏中的应用进展

目前,超声弹性成像在成人肝脏中的应用相对较多,且日趋规范,在儿童肝脏中亦有一些应用,主要集中在胆道闭锁及慢性肝病方面,在正常儿童肝脏中的研究亦有少量报道。本文就超声弹性成像在儿童肝脏中的应用及其研究进展进行综述。     

超声弹性成像技术评估无水乙醇诱导肝脏凝固灶的实验研究

目的探讨超声弹性成像技术评估无水乙醇诱导肝脏凝固灶的价值。方法选取新鲜离体猪肝共25个肝叶,随机分为5组,每组各5个肝叶。分别行单点、两点相距0.5cm、两点相距1.0cm、两点相距1.5cm及两点相距2.0cm注射无水乙醇,各点无水乙醇注射量均为2.0ml。注射无水乙醇前、后观察实验区常规二维超声声像图及应变力弹性成像图（EI）变化,同时运用声触诊组织定量技术（VTQ）测定实验区剪切波速度。实验结束后剖开标本,记录凝固灶的形态、范围。采用配对t检验比较注射无水乙醇前后实验区肝组织剪切波速度差异。结果无水乙醇不同注射方式可形成不同形态的凝固灶,常规二维超声下局部区域出现短暂高回声,随之迅速消散,而EI图可显示较恒定红色硬变区,比常规二维超声更接近实际凝固灶;但对于间距小于0.3cm的双凝固灶,EI图难以分辨。凝固后的肝组织剪切波速度均明显增高,与注射无水乙醇前比较差异均有统计学意义（P〈0.01）,表明凝固性坏死的肝组织硬度增加。结论超声弹性成像技术可反映肝脏凝固灶力学变化,是常规二维超声的有力补充,但细微分辨力还有待提高。     

Ultrasound of focal liver masses

Detecting and characterizing focal liver lesions is one of the most difficult challenges in imaging today. All standard noninvasive imaging modalities are less sensitive than generally perceived, and characterization is imperfect. Liver sonography's main strengths are its ability to definitively characterize common benign lesions (eg, cysts and hemangiomas), safety, low cost, and its ability to guide biopsy. Sonography's weaknesses include its inability to image the entire liver in many patients and its inferiority to CT as a means of detecting extrahepatic malignant disease. Sonography is less sensitive than CT or MRI in detecting focal lesions. Ultrasound contrast agents will certainly improve liver lesion detection and characterization, but their impact is not yet clear.Typical findings in common focal liver lesions are discussed, and some hints to improve sonographic diagnosis are presented. Increased color Doppler flow should bring the possibility of hepatocellular carcinoma and focal nodular hyperplasia to mind, but Doppler diagnosis is ultimately not highly specific. Sonography, including Doppler analysis, is useful to assess the resectability of malignant masses. Intraoperative ultrasound is the most sensitive imaging modality in detecting focal liver lesions.     

肝移植超声检查

肝移植是治疗终末期肝病的最有效方法。影像学检查在肝移植术前、术中、术后检查中发挥着极其重要的作用。超声检查具有无创、简便、经济、可实时动态观察、能够获取丰富的肝脏血流信息动力学、可床边及术中进行检查等优势,已成为肝移植首选的影像学检查方法,其临床价值也越来越受到肝移植外科医师的重视。