Preliminary Results of Acoustic Radiation Force Impulse (ARFI) Ultrasound Imaging of Breast Lesions

The aim of this study was to determine the appearance of breast lesions using acoustic radiation force impulse imaging (ARFI) and to correlate the ARFI values with the pathologic results. The area ratio (AR) and virtual touch tissue quantification (VTQ) values were analyzed in 86 patients (mean age 45.6 years, range 17-78 years) with 92 breast lesions (65 benign, 27 malignant; mean size 25.7 mm). The diagnostic performance of ultrasound (US) alone and US plus ARFI values were compared with respect to sensitivity, specificity and area under the curve (AUC) using a receiver operating characteristic curve analysis. The mean AR of the benign lesions (1.08 ± 0.21) differed from that of the malignant lesions (1.99 ± 0.63; p < 0.0001), as did the mean VTQ values (3.25 ± 2.03 m/s vs. 8.22 ± 1.27 m/s; p < 0.0001). In conclusion, ARFI provides quantitative elasticity measurements, which may complement B-mode US and potentially improve the characterization of breast lesions.     

Impact of Food Intake, Ultrasound Transducer, Breathing Maneuvers and Body Position on Acoustic Radiation Force Impulse (ARFI) Elastometry of the Liver

Purpose: Since acoustic radiation force impulse (ARFI) elastometry is an increasingly popular method for the assessment of hepatic fibrosis and cirrhosis, we investigated factors possibly influencing hepatic elastometric measurements. Materials and Methods: 30 healthy volunteers (17 females, 13 males) were recruited. The shear wave velocity of the right liver lobe was determined in a fasting upright and supine position and after different breathing maneuvers with the convex array (4C1) and in a supine position with the linear (9L4) ultrasound transducer. In 18 volunteers, subsequent measurements were obtained in a fasting state and 30, 60, 90 and 120 min after ingestion of a standardized breakfast. A group of 8 patients (average age: 76 years) with right heart insufficiency was also evaluated. Results: In the fasting state, the ARFI shear wave velocities measured in an upright position were significantly higher than those in supine position (p< 0.0001). The supine ARFI values were significantly higher with the linear transducer than with the convex transducer (p = 0.0034). The results in deep inspiration, deep expiration and during Valsalva maneuver showed no differences. The food intake-related ARFI elastometric measurements were significantly elevated at time points 30 min (p = 0.019) and 60 min (p = 0.036) postprandial. In right heart insufficiency, the ARFI values were elevated. Conclusion: Hepatic ARFI elastometry is a well evaluated method. A standardized examination should include measuring in a supine position with the convex transducer (4C1) without specific breathing maneuvers. Since ARFI elastometry values increase after food intake, measurements should be performed in the fasting state, or not earlier than 2 hours postprandially. Heart dysfunction may impair ARFI accuracy.     

Factors Which Influence the Accuracy of Acoustic Radiation Force Impulse (ARFI) Elastography for the Diagnosis of Liver Fibrosis in Patients with Chronic Hepatitis C

Our study tried to identify the factors associated with discordance between liver stiffness values assessed by acoustic radiation force impulse (ARFI) elastography and histologic fibrosis in 106 chronic hepatitis C patients. Liver biopsy (LB) and ARFI measurements were performed in the same session. A discordance of at least two stages of fibrosis in the Metavir scoring system between ARFI results and LB was defined as significant. The performance of ARFI elastography was assessed using the following cut-offs: F1-1.19 m/s, F2-1.34 m/s, F3-1.55 m/s and F4-1.80 m/s. Discordance of at least two stages of fibrosis between ARFI results and histologic assessment were observed in 31.7% of the patients. In an univariate analysis, female sex (p = 0.004), interquartile range interval (IQR) ≥30% (p = 0.04), high alanine aminotransferases (p = 0.008) and high aspartate aminotransferases levels (p = 0.003) were associated with discordances. In a multivariate analysis, the female sex (p = 0.006) and IQR ≥30% (p = 0.004) were associated with discordances. Therefore, IQR parameter should be used for ARFI measurements.     

ARFI技术评估2型糖尿病患者非酒精性脂肪肝程度的应用价值

目的：探讨声辐射力脉冲成像技术(acoustic radiation force impulse imaging,ARFI)在无创定量评估2型糖尿病(type 2 diabetes mellitus ,T2DM)患者非酒精性脂肪肝(non-alcoholic fatty liver disease ,NAFLD)程度的临床应用价值。方法：对201例2型糖尿病患者进行常规肝脏彩超检查,分成NAFLD组(95例)及正常肝脏组(106例)。收集患者的相关资料及血液生化指标,根据肝功能相关指标将NAFLD组分为肝功能正常组(39例)和肝功能不全组(56例),运用ARFI技术对所有患者行肝脏弹性的测定,并进行统计学分析。结果：NAFLD组ARFI值较正常肝脏组减低(P<0.01)。NAFLD组中肝功能不全组较正常组的ARFI值升高(P=0.022)。NAFLD与正常肝脏ARFI值的受试者工作特征(ROC)曲线线下面积0.745,临界值为1.06m/s,95%的可信区间为0.616~0.814,敏感性88.7%,特异性45.7%。NAFLD组的患者中ARFI指数与甘油三酯、BMI指数相关。结论：ARFI技术可定量诊断2型糖尿病患者的非酒精性脂肪肝,有助于评估肝脏脂肪变性的程度,有着良好的临床应用价值。     

经直肠ARFI技术在前列腺病变中的研究

目的 探讨经直肠声辐射力脉冲成像技术(ARFI)对前列腺良恶性病变诊断的临床价值。方法 应用ARFI技术对72例前列腺占位性病变患者进行检查,测值与术后病理结果对照,鉴别其良恶性。结果 ARFI技术检测的前列腺恶性占位病变与前列腺良性占位病变组比较,剪切波速差异有显著性意义(P＜0.05);前列腺良性占位与前列腺正常组剪切波速比较差异具有显著性（P＜0.05）。以剪切波速大于2.94m/s作为前列腺恶性占位的诊断标准,ARFI诊断前列腺良恶性占位的敏感性为86.7%,特异性为66.7%。结论 ARFI技术可以做为前列腺病变早期诊断的一种重要手段。     

声辐射力脉冲成像技术对过敏性紫癜性肾炎诊断价值

目的探讨声辐射力脉冲成像技术在过敏性紫癜性肾炎定量诊断中的价值。方法选取89例首诊为过敏性紫癜性肾炎(HSPN)患者和40例年龄、性别与HSPN组基本匹配的健康志愿者为研究对象。采用声辐射力脉冲成像技术(ARFI)分别检测HSPN组和对照组肾皮质的剪切波速度(SWV),进行统计学分析。结果HSPN组与对照组SWV比较存在显著统计学差异(P=0.000 1)。1组、2组、3组、4组组间比较,均存在统计学差异(P0.01)。HSPN组肾皮质SWV与肾脏穿刺病理分级呈正相关(r=0.81,P=0.000 1)。HSPN组与对照组,1、2组,2、3组,3、4组SWV的诊断界点分别为2.07 m/s、2.46 m/s、3.33 m/s、3.84 m/s,特异度、灵敏度和诊断价值分别为67.5%、100%、0.892,66.7%、100%、0.883,100%、66.7%、0.883,100%、66.7%、0.778。结论HSPN患者肾脏SWV随肾脏病理损害程度加重而升高,ARFI技术可以无创、定量评估HSPN肾脏损害程度,用于疾病的早期诊断与分级诊断。     

声脉冲辐射力成像技术在IgA肾病中的初步应用

目的 评价声脉冲辐射力成像( ARFI)技术在评估IgA肾病(IgAN)患者肾脏弹性硬度中的作用.方法 65例肾脏组织活检病理证实为IgAN患者和35例健康志愿者进行了常规二维超声和ARFI弹性成像检查.结果 健康志愿者组和IgAN病理Iee氏分级弹性指数中位数分别为1.57 m/s; Lee I～Ⅱ级:2.06 m/s,Ⅲ级:2.52 m/s,Ⅳ:2.53 m/s,V级:2.84m/s;2组比较差异有统计学意义(P＜0.05).随着Lee氏分级程度加重,弹性指数数值不断增加.结论声脉冲辐射力成像技术可无创反映肾脏组织弹性硬度,对评估肾脏纤维化具有一定临床应用价值.     

声辐射力脉冲弹性成像在估测静脉血栓形成时间的研究

目的 本实验旨在通过声辐射力脉冲(acoustic radiation force impulse,ARFI)弹性技术在分析体外血栓模型形成时间中的应用价值.方法 利用人体大隐静脉作为血栓载体,分别向9段大隐静脉内注人健康人血,然后迅速结扎两端放人祸合剂箱内,同时使9根血栓模型处于近似高度,并依次Ⅰ～Ⅳ进行编号.利用ARM技术分别于1、3、6、9d的血栓模型进行弹性成像数据分析,并以病理检查结果进行验证.结果 使用ARM技术见血栓尚未形成时(1d)剪切波速度测量无反应;血栓形成至3、6、9d时,血栓内剪切波速度(SWV)逐渐增加,从3d的(0.76±0.12)m/s,增加至6d的(1.34±0.25)m/s及9d的(1.91±0.31)m/s;不同血栓形成时间血栓内SW V测值均存在统计学上的显著性差异(P<0.01).结论 ARM技术测定人体大隐静脉血栓模型的血栓SWV,对于预测血栓形成时间有一定的参考价值,它可能为今后弹性成像运用在人体静脉血栓中提供参考.     

Anisotropic Properties of Breast Tissue Measured by Acoustic Radiation Force Impulse Quantification

The goal of our study was to investigate the anisotropy of normal breast glandular and fatty tissue with acoustic radiation force impulse (ARFI) quantification. A total of 137 breasts in 137 women were enrolled. These breasts were divided into the duct-apparent group and the duct-inapparent group, divided into the ligament-apparent group and the ligament-inapparent group. Shear wave velocity (SWV) in the radial (SWV^r) and anti-radial (SWV^a-r) directions was measured. The elastic anisotropy of glandular tissue and fatty tissue was evaluated as the ratio between SWV^r and SWV^a-r. The SWV ratio was 1.30 ± 0.45 for glandular tissue and 1.27 ± 0.53 for fatty tissue in the total group. In glandular tissue, the SWV ratio of the duct-apparent group was higher than that of the duct-inapparent group (p = 0.011). In both glandular and fatty tissue, the SWV ratio was higher in the ligament-apparent group than in the ligament-inapparent group (p < 0.05 for both). SWV^r was higher than SWV^a-r in both glandular tissue and fatty tissue in all groups (p < 0.05 for all) except in breast fatty tissue in the ligament-inapparent group (p = 0.913). It is concluded that both breast glandular tissue and fatty tissue exhibited anisotropy of elastic behavior. To improve the diagnostic power of elastography in breast lesions, the elastic anisotropy of glandular tissue and fatty tissue should be taken into account in calculating strain ratio or elasticity ratio.     

Acoustic Radiation Force Impulse Imaging on ex vivo Abdominal Aortic Aneurysm Model

A method for reliable, noninvasive estimation of abdominal aortic aneurysms (AAA) wall mechanics may be a useful clinical tool for rupture prediction. An in vitro AAA model was developed from an excised porcine aorta with elastase treatment. The AAA model behaviour was analysed using acoustic radiation force impulse (ARFI) imaging techniques to generate and measure wave propagation in both aneurysmal and normal aortic tissue. Opening angle measurement showed a fourfold decrease from healthy aorta to AAA model and pathologic analysis verified this elastin degradation. Maximum wave velocity at 180 mm Hg was 7 mm/ms for healthy tissue and 8.26 mm/ms for the aneurysmal tissue. The mechanical changes produced in the artificially induced aneurysm were found to be detectable using ARFI imaging. (E-mail: tim.mcgloughlin@ul.ie)     

Non-invasive Measurement of Dynamic Myocardial Stiffness Using Acoustic Radiation Force Impulse Imaging

Myocardial stiffness exhibits cyclic variations over the course of the cardiac cycle. These trends are closely tied to the electromechanical and hemodynamic changes in the heart. Characterization of dynamic myocardialstiffness can provide insights into the functional state of the myocardium, as well as allow for differentiation between the underlying physiologic mechanisms that lead to congestive heart failure. Previous work has revealed the potential of acoustic radiation force impulse (ARFI) imaging to capture temporal trends in myocardial stiffness in experimental preparations such as the Langendorff heart, as well as on animals in open-chest and intracardiac settings. This study was aimed at investigating the potential of ARFI to measure dynamic myocardial stiffness in human subjects, in a non-invasive manner through transthoracic imaging windows. ARFI imaging was performed on 12 healthy volunteers to track stiffness changes within the interventricular septum in parasternal long-axis and short-axis views. Myocardial stiffness dynamics over the cardiac cycle was quantified using five indices: stiffness ratio, rates of relaxation and contraction and time constants of relaxation and contraction. The yield of ARFI acquisitions was evaluated based on metrics of signal strength and tracking fidelity such as displacement signal-to-noise ratio, signal-to-clutter level, temporal coherence of speckle and spatial similarity within the region of excitation. These were quantified using the mean ARF-induced displacements over the cardiac cycle, the contrast between the myocardium and the cardiac chambers, the minimum correlation coefficients of radiofrequency signals and the correlation between displacement traces across simultaneously acquired azimuthal beams, respectively. Forty-one percent of ARFI acquisitions were determined to be “successful” using a mean ARF-induced displacement threshold of 1.5 μm. “Successful” acquisitions were found to have higher (i) signal-to-clutter levels, (ii) temporal coherence and (iii) spatial similarity compared with “unsuccessful” acquisitions. Median values of these three metrics, between the two groups, were measured to be 13.42dB versus 5.42dB, 0.988 versus 0.976 and 0.984 versus 0.849, respectively. Signal-to-clutter level, temporal coherence and spatial similarity were also found to correlate with each other. Across the cohort of healthy volunteers, the stiffness ratio measured was 2.74 ± 0.86; the rate of relaxation, 7.82 ± 4.69/s; and the rate of contraction, –7.31±3.79 /s. The time constant of relaxation was 35.90 ± 20.04ms, and that of contraction was 37.24 ± 19.85ms. ARFI-derived indices of myocardial stiffness were found to be similar in both views. These results indicate the feasibility of using ARFI to measure dynamic myocardial stiffness trends in a non-invasive manner and also highlightthe technical challenges of implementing this method in the transthoracic imaging environment.     

Acoustic Radiation Force Impulse Imaging of Human Prostates Ex Vivo

It has been challenging for clinicians using current imaging modalities to visualize internal structures and detect lesions inside human prostates. Lack of contrast among prostatic tissues and high false positive or negative detection rates of prostate lesions have limited the use of current imaging modalities in the diagnosis of prostate cancer. In this study, acoustic radiation force impulse (ARFI) imaging is introduced to visualize the anatomical and abnormal structures in freshly excised human prostates. A modified Siemens Antares ultrasound scanner (Siemens Medical Solutions USA Inc., Malvern, PA) and a Siemens VF10-5 linear array were used to acquire ARFI images. The transducer was attached to a three-dimensional (3-D) translation stage, which was programmed to automate volumetric data acquisition. A depth dependent gain (DDG) method was developed and applied to 3-D ARFI datasets to compensate for the displacement gradients associated with spatially varying radiation force magnitudes as a function of depth. Nine human prostate specimens were collected and imaged immediately after surgical excision. Prostate anatomical structures such as seminal vesicles, ejaculatory ducts, peripheral zone, central zone, transition zone and verumontanum were visualized with high spatial resolution and in good agreement with McNeal's zonal anatomy. The characteristic appearance of prostate pathologies, such as prostate cancerous lesions, benign prostatic hyperplasia, calcified tissues and atrophy were identified in ARFI images based upon correlation with the corresponding histologic slides. This study demonstrates that ARFI imaging can be used to visualize internal structures and detecting suspicious lesions in the prostate and appears promising for image guidance of prostate biopsy. (E-mail:liang.zhai@duke.edu)     

Quantification of Pediatric Burn Scar Stiffness Using Acoustic Radiation Force Impulse Ultrasound Elastography

The purpose of this study was to quantify the stiffness of hypertrophic scars using acoustic radiation force impulse ultrasound elastography. Sixteen pediatric patients with hypertrophic scars resulting from burn injuries participated in this study (mean age: 5.13, standard deviation: 3.20). Values for the elastic modulus (E) of scar and control sites were obtained. Scarred areas were found to be almost four times stiffer than control sites (scar E_mean = 39.29 kPa compared with control E_mean = 10.19 kPa) (p = 0.0004). Correlations between scar stiffness and clinician-reported subjective scar scale scores were not observed (r_s = 0.30, p = 0.27 and r_s = 0.25, p = 0.35 respectively). We found that acoustic radiation force impulse imaging can discriminate between hypertrophic scars and normal skin and should be considered a potentially valuable tool in the armamentarium of objective scar measures. Future research should focus on evaluating the technology's ability to detect scar change over time in order to determine responsiveness to treatment.     

声脉冲辐射力成像技术与肝癌术后并发症的相关性分析

目的 探讨声脉冲辐射力成像技术(Acoustic Radiation Force Impulse,ARFI)与肝纤维化的关系,以降低肝癌患者术后并发症的可能。 方法 纳入我院150例行肝癌手术切除的患者,对其手术前后的临床资料进行分析。依据肝纤维化分期标准,将肝纤维化S0、S1、S2、S3、S4分别对应的剪切波值进行单因素方差分析,再分析剪切波值与肝纤维化的相关性;进一步利用剪切波值构建ROC曲线分析肝纤维化的鉴别能力;最后通过剪切波值与病理结果检验肝癌术后并发症的敏感度、特异度对比,反应ARFI的应用的价值。 结果 S0、S1、S2、S3、S4分别对应的剪切波值显著升高,差异有统计学意义 (F=54.678,P﹤0.05)。剪切波值与肝纤维化程度呈正相关关系(r=0.76,P=0.000); ROC曲线得到ARFI鉴别判断肝纤维化的AUC为0.885,最佳临界值为1.315,敏感度94.6%以及特异度为64.5%。进一步的分析发现,ARFI判断术后并发症敏感度和特异度与病理结果近似(ARFI：敏感度94.4%、特异度92.7%;病理：敏感度98.1%、特异度94.8%)。结论 ARFI有助于提高术前判断肝癌患者肝纤维化准确度,为今后肝癌患者减少术后并发症的发生提供参考依据。