Study of ultrasound stiffness imaging methods using tissue mimicking phantoms

The purpose of this study was to assess the value of acoustic radiation force impulse (ARFI) for evaluating portal hypertension by correlating the elasticity of liver cirrhosis, as measured by ARFI, with haemodynamic indices measured by Doppler ultrasound. We evaluated the data of a total of 154 prospectively enrolled patients who underwent both duplex Doppler ultrasound and ARFI imaging. The duplex Doppler ultrasound indices, including the mean portal vein velocity, splenic index (SI) and splenoportal index (SPI) were evaluated to determine the statistical correlation with shear wave velocity (SWV) of ARFI. We also analysed the differences in the correlations between the SI, SPI and SWV of the group who had varices. The correlations were assessed with Spearman's rank correlation coefficients. There was an increase of SWV in parallel with the increase of the SI (ρ=0.409, p<0.01) and SPI (ρ=0.451, p<0.01). In the patient group who did not have varices (n=74), the Doppler indices were found to be more correlated with the SWV (SI: ρ=0.447, SPI: ρ=0.552, p<0.01). However, the group with varices showed no correlation between the SWV and the Doppler parameters. SWV of ARFI was well correlated statistically with Doppler parameters, but is of limited value in predicting portal hypertension directly owing to great variability of Doppler parameters. By evaluating the correlation between ARFI and Doppler ultrasound, we suggest that the SWV might be a non-invasive supplementary tool for predicting portal hypertension.

The purpose of the study was to assess the diagnostic utility of acoustic radiation force impulse (ARFI) imaging in primary Sjögren's syndrome (pSS). One hundred fifty-seven patients with sicca symptoms and/or salivary gland swelling were included. Sicca symptoms, Schirmer test, unstimulated whole saliva (UWS), SS-A/B antibodies, and histology were assessed according to American-European Consensus group (AECG) criteria. All patients underwent high-resolution ultrasound and ARFI imaging of the parotid (PG) and submandibular glands (SMG). Seventy patients were classified as having pSS. The remaining 87 patients suffered from idiopathic sicca (n = 24), rheumatoid arthritis (n = 12), sarcoidosis (n = 9), cutaneous/systemic lupus erythematosus (n = 7), scleroderma (n = 2), dermatomyositis (n = 1), HBV/HCV (n = 2), and panarteritis nodosa (n = 1), and disorders in 29 patients were classified as not otherwise specified. ARFI values of the PG were significantly higher in the pSS versus non-pSS groups (2.86 ± 0.07 m/s vs. 2.15 ± 0.11 m/s, p < 0.0001). ARFI imaging demonstrated diagnostic sensitivity and specificity of 81 % and 67 %, respectively. In addition to histology, ARFI imaging was the most important diagnostic tool for identifying early pSS. • Early stages in Sjögren's syndrome become apparent with major salivary gland enlargements. • Schirmer and unstimulated whole saliva tests demonstrated insufficient sensitivity/specificity for early-stage diagnosis. • Acoustic radiation force impulse imaging is a reliable tool for diagnosing early disease stages.

The acoustic radiation force impulse (ARFI) technology is a novel ultrasound method that provides information about the local elasticity of tissue in real-time. ARFI is integrated in a conventional ultrasound system. The aim of this exploratory study was to evaluate this new technique in the assessment of liver fibrosis in a cohort with chronic viral hepatitis B and C and to ascertain the most reliable hepatic segment for measurements. 57 patients (27 female, 30 male, mean age 54 years) with chronic viral hepatitis B and C underwent ARFI imaging and consecutively liver biopsy. The results were compared to the histological fibrosis degree (F), which served as the reference. 20 healthy volunteers received ARFI quantification of different segments of the liver. The best ARFI assessments with the lowest rate of invalid measurements were carried out by an intercostal approach to segment VII/VIII of the liver. The ARFI velocities of the healthy group had a mean of 1.09 m/s (range 0.79 - 1.32 m/s), the means of the patient group ranged from 0.83 to 4.19 m/s. ARFI quantification correlated significantly with the histological fibrosis stage (p < 0.001). The area under the receiver operating characteristic (ROC) curves for the accuracy of ARFI imaging was 85 %, 92 % and 87 % for the diagnosis of moderate fibrosis (>or= F2), severe fibrosis (>or= F3) and cirrhosis ( = F 4), respectively. This study underscores the usefulness of ARFI as a quick method for assessing liver fibrosis or cirrhosis in patients with HBV or HCV. ARFI measurements of the liver should be performed via an intercostal access. Increasing ARFI velocities correlate with higher degree of hepatic fibrosis.

Background/Objectives: Acoustic radiation force impulse (ARFI) is a novel non-invasive technology for the assessment of stages of liver fibrosis in chronic hepatic disease. Some studies previously reported that ARFI is a promising method for assessing liver fibrosis in patients with NAFLD/NASH. This study aimed to validate the diagnostic usefulness of ARFI for prediction of staging of liver fibrosis in patients with NASH. Patients and Methods: The study was carried out on 51 patients with NASH. All of patients underwent a liver biopsy for histological assessment of liver fibrosis and ARFI elastography. Cut-off values were determined using receiver-operating characteristic (ROC) curves. Results: Histological liver fibrosis was evaluated by Metavir scoring; F0: 8 cases, F1: 29 cases, F2: 10 cases and F3: 4 cases. ARFI quantification correlated significantly with the fibrosis stage (Spearman rho: 0.44, p &lt;0.05). The areas under the ROC curves (AUROC) were 0.75 (95% confidence intervals: 0.60-0.90) for ≥F2 and 0.78 (0.53-0.99) for F3. The cut-off values of the shear wave velocity (SWV) were as follows: ≥1.29 m/s for ≥F2 (sensitivity 64.3%, specificity 83.8%, PPV 60% and NPV 86.1%), ≥ 1.38 m/s for F3 (sensitivity 75%, specificity 89.4%, PPV 57.5%, NPV 97.7%). Conclusions: Increasing ARFI velocities correlate with high degree of liver fibrosis. ARFI has quite good accuracy and high specificity, NPV for prediction of significant and advanced fibrosis in patients with NASH. The method should be employed routinely in the workup of patients with NASH to exclude the presence of significant and advanced liver fibrosis. Key words: liver fibrosis, liver stiffness, non-alcoholic fatty liver disease (NAFLD), nonalcoholic steatohepatitis (NASH), acoustic radiation force impulse imaging (ARFI).

Intracardiac acoustic radiation force impulse imaging: a novel imaging method for intraprocedural evaluation of radiofrequency ablation lesions.

Acoustic Radiation Force Impulse (ARFI) shear wave imaging is a noninvasive method of assessment of the liver to detect fibrosis in patients with chronic hepatitis and nonalcoholic fatty liver disease (NAFLD). The aim of this retrospective study was to investigate whether noninvasive measurement of shear wave velocity (SWV) by ARFI shear wave imaging has a potential usefulness for detection of fibrosis secondary to NAFLD in patients with morbid obesity. Twenty-eight morbidly obese patients were included in this study. NAFLD and fibrosis were classified according to the nonalcoholic steatohepatitis (NASH) Clinical Research Network NAFLD activity score. SWV was quantified by ARFI imaging. Component steatosis, inflammation and ballooning scores, and fibrosis staging were correlated with SWV, and diagnostic accuracy of ARFI for fibrosis was assessed. There was a decrease in mean SWV with increasing hepatic steatosis (P = .057). The SWV showed a significant negative correlation (r = -0.417, P = .011) with steatosis grade. The mean SWV was neither significantly different nor correlating with the obesity classes based on body mass index (BMI), steatosis grades, inflammation grades, ballooning grades, and fibrosis stages of NAFLD. Receiver operating characteristic analysis showed no significant area under curve for diagnosis of fibrosis using SWV. Valid SWV could be acquired in all subjects; however, only 21.42% fulfilled the interquartile range criterion. ARFI SWV values do not correlate with fibrosis on liver biopsy in morbidly obese patients and lack accuracy for diagnosis. Discordant values may be related to higher BMI and increasing hepatic steatosis.

The aim of this study was to investigate the feasibility of using acoustic radiation force impulse (ARFI) imaging to diagnose acute appendicitis. Abdominal ultrasonography (US) and ARFI imaging were performed in 53 patients that presented with right lower quadrant pain, and the results were compared with those obtained in 52 healthy subjects. Qualitative evaluation of the patients was conducted by Virtual Touch™ tissue imaging (VTI), while quantitative evaluation was performed by Virtual Touch™ tissue quantification (VTQ) measuring the shear wave velocity (SWV). The severity of appendix inflammation was observed and rated using ARFI imaging in patients diagnosed with acute appendicitis. Alvarado scores were determined for all patients presenting with right lower quadrant pain. All patients diagnosed with appendicitis received appendectomies. The sensitivity and specificity of ARFI imaging relative to US was determined upon confirming the diagnosis of acute appendicitis via histopathological analysis. The Alvarado score had a sensitivity and specificity of 70.8% and 20%, respectively, in detecting acute appendicitis. Abdominal US had 83.3% sensitivity and 80% specificity, while ARFI imaging had 100% sensitivity and 98% specificity, in diagnosing acute appendicitis. The median SWV value was 1.11 m/s (range, 0.6-1.56 m/s) for healthy appendix and 3.07 m/s (range, 1.37-4.78 m/s) for acute appendicitis. ARFI imaging may be useful in guiding the clinical management of acute appendicitis, by helping its diagnosis and determining the severity of appendix inflammation.

Sclerotic skin diseases are associated with inflammation and fibrosis in the dermis, and these changes in collagen content with disease progression make this pathology amenable to being characterized with Acoustic Radiation Force Impulse (ARFI) and Shear Wave Elasticity Imaging (SWEI) methods. We characterized skin stiffness in healthy individuals at repeated three month intervals and compared sclerotic to healthy skin stiffness. ARFI and SWEI were implemented using a Siemens 14L5 linear array on an ACUSON S2000™ scanner. A single dermatologist performed all imaging in twenty-two patients. Normal and sclerotic skin stiffnesses were characterized by (1) mean ARFI displacement magnitude, and (2) group shear wave speed estimated using a Radon sum of shear wave velocity data. Imaging was performed at different anatomic sites, including the upper and lower back, arm, forearm, abdomen, thigh and calf. Five repeat data acquisitions were performed in each anatomic location. ARFI displacement and SWEI shear wave speeds were reconstructed in 96% of all acquisitions when the region of interest was exclusively contained in the dermis. Overall, ARFI and SWEI metrics showed no significant difference between contralateral imaging locations across different anatomic sites in healthy skin (p 200% greater in sclerotic lesions than in contralateral healthy skin in patients with graft-versus-host disease (GVHD) (p < 0.01), and 25% greater in patients with morphea. ARFI displacements exhibited greater variability than shear wave speed in characterizing sclerotic skin, showing a 61% decrease compared to healthy skin in GVHD patients (p < 0.05) and a 19% decrease in morphea patients (p < 0.05). ARFI and SWEI are able differentiate sclerotic skin lesions from healthy skin, and studies are underway to evaluate their utility in longitudinally-monitoring disease progression and response to therapy. Additional study details, data and conclusions can be found in the full-length manuscript describing this work [1].

Children receiving multiple blood cell transfusions are prone to iron overload and successive tissue damage in liver parenchyma, making noninvasive screening options desirable. Ultrasound (US) elastography using acoustic radiation force impulse (ARFI) imaging enables evaluation of liver parenchyma stiffness, and MRI allows for quantification of liver iron concentration. The objective was to correlate US elastography with MRI in children who had undergone bone marrow transplantation and to evaluate the modification of liver tissue with US in combination with clinical parameters at follow-up. ARFI, T2*-weighted MRI and a clinical score (HepScore, based on parameters of liver function) were performed in 45 patients (24 male; mean age 9.7years) before and 100days and 365days after transplantation. All received multiple blood transfusions (mean number 22.2 up until 1year after transplantation). We correlated US findings and HepScore with MRI findings. We observed signs of iron accumulation in 29/45 (64.4%) patients on MRI (T2*<10ms) and 15/45 (33.3%) showed increased tissue stiffness (ARFI>5.5kPa). Correlation of elastography and MRI was not significant (P=0.57; n=51 matched measurements). Comparing US elastography with HepScore in receiver operating characteristic (ROC) curve analysis indicated a cut-off for affected parenchyma if HepScore was >5 points (sensitivity 67%, specificity 68%). Simultaneous increases of both indicated tissue alteration. Combining US and HepScore enabled detection of liver tissue alteration through iron overload, but we found no direct significant effect of estimated iron from MRI on ARFI imaging.

PD4-12 3D ACOUSTIC RADIATION FORCE IMPULSE (ARFI) ELASTICITY IMAGING OF PROSTATE CANCER: CORRELATION BETWEEN IN VIVO IMAGING AND WHOLE MOUNT HISTOLOGY

Objective To investigate the value of acoustic radiation force impulse (ARFI) and color Doppler flow imaging (CDFI) in the diagnostic of acute rejection (AR) after liver transplantation. Methods B mode ultrasound, CDFI and ARFI exams were performed on fifty-eight patients who was diagnosed with AR through liver biopsy in our hospital. The liver allograft size, mean velocity of portal vein, hepatic vein spectrum waveform and shear-wave velocity were obtained and compared with the results of 30 healthy subjects as control group. Results Compare to control group, the AR group had a significant increase in liver allograft, decrease in mean velocity of portal vein, the elimination of triphasic wave of hepatic vein, and a significant increase in shear-wave velocity (P=0.000, 0.000, 0.007, 0.000, respectively). The correlation coefficient between four criteria and grouping was 0.478, 0.557, 0.286, 0.483, respectively. The area under ROC curves for diagnosing AR using the four criterias mentioned above was 0.914. Conclusions Combination of CDFI and ARFI in diagnosing of AR after liver transplantation has higher sensitivity and accuracy. Key words: Ultrasonography; Liver transplantation; Transplant rejection; Acoustic radiation force impulse technique

Evaluation of Myocardial Stiffness in Cardiac Amyloidosis Using Acoustic Radiation Force Impulse and Natural Shear Wave Imaging.

Four pigs, three with focal infarctions in the apical intraventricular septum (IVS) and/or left ventricular free wall (LVFW), were imaged with an intracardiac echocardiography (ICE) transducer. Custom beam sequences were used to excite the myocardium with focused acoustic radiation force (ARF) impulses and image the subsequent tissue response. Tissue displacement in response to the ARF excitation was calculated with a phase-based estimator, and transverse wave magnitude and velocity were each estimated at every depth. The excitation sequence was repeated rapidly, either in the same location to generate 40 Hz M-modes at a single steering angle, or with a modulated steering angle to synthesize 2-D displacement magnitude and shear wave velocity images at 17 points in the cardiac cycle. Both types of images were acquired from various views in the right and left ventricles, in and out of infarcted regions. In all animals, acoustic radiation force impulse (ARFI) and shear wave elasticity imaging (SWEI) estimates indicated diastolic relaxation and systolic contraction in noninfarcted tissues. The M-mode sequences showed high beat-to-beat spatio-temporal repeatability of the measurements for each imaging plane. In views of noninfarcted tissue in the diseased animals, no significant elastic remodeling was indicated when compared with the control. Where available, views of infarcted tissue were compared with similar views from the control animal. In views of the LVFW, the infarcted tissue presented as stiff and non-contractile compared with the control. In a view of the IVS, no significant difference was seen between infarcted and healthy tissue, whereas in another view, a heterogeneous infarction was seen to be presenting itself as non-contractile in systole.

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

We present results of a pilot study of ex vivo and in vivo acoustic radiation force impulse (ARFI) imaging demonstrating measurements of the mechanical properties of the medial and adventitial layers in the carotid, and popliteal arteries. The data was obtained on a commercial scanner, providing co-registered B-mode and Color Doppler images. A real-time ARFI imaging system capable of achieving frame rates of 0.75 Hz was developed. The 2-D and 1-D images of the tissue's response to brief and localized applications of radiation force show good correlation with B-mode and pathology based characterization of vessel geometry and plaque stiffness. Measurements of arterial response during both systole and diastole are presented. We address implementation issues and discuss the potential applications of this new vascular imaging method.