Showing papers on "Elastography published in 2010"

Breast Lesions: Quantitative Elastography with Supersonic Shear Imaging—Preliminary Results

Abstract: Malignant lesions were significantly different from benign solid ones with regard to lesion elasticity quantitative value; because no shear wave propagation occurs in liquid areas, cystic lesions were diagnosed, regardless of their B-mode appearance.

Quantitative shear wave ultrasound elastography: initial experience in solid breast masses

Abstract: Shear wave elastography is a new method of obtaining quantitative tissue elasticity data during breast ultrasound examinations. The aims of this study were (1) to determine the reproducibility of shear wave elastography (2) to correlate the elasticity values of a series of solid breast masses with histological findings and (3) to compare shear wave elastography with greyscale ultrasound for benign/malignant classification. Using the Aixplorer® ultrasound system (SuperSonic Imagine, Aix en Provence, France), 53 solid breast lesions were identified in 52 consecutive patients. Two orthogonal elastography images were obtained of each lesion. Observers noted the mean elasticity values in regions of interest (ROI) placed over the stiffest areas on the two elastography images and a mean value was calculated for each lesion. A sub-set of 15 patients had two elastography images obtained by an additional operator. Reproducibility of observations was assessed between (1) two observers analysing the same pair of images and (2) findings from two pairs of images of the same lesion taken by two different operators. All lesions were subjected to percutaneous biopsy. Elastography measurements were correlated with histology results. After preliminary experience with 10 patients a mean elasticity cut off value of 50 kilopascals (kPa) was selected for benign/malignant differentiation. Greyscale images were classified according to the American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS). BI-RADS categories 1-3 were taken as benign while BI-RADS categories 4 and 5 were classified as malignant. Twenty-three benign lesions and 30 cancers were diagnosed on histology. Measurement of mean elasticity yielded an intraclass correlation coefficient of 0.99 for two observers assessing the same pairs of elastography images. Analysis of images taken by two independent operators gave an intraclass correlation coefficient of 0.80. Shear wave elastography versus greyscale BI-RADS performance figures were sensitivity: 97% vs 87%, specificity: 83% vs 78%, positive predictive value (PPV): 88% vs 84%, negative predictive value (NPV): 95% vs 82% and accuracy: 91% vs 83% respectively. These differences were not statistically significant. Shear wave elastography gives quantitative and reproducible information on solid breast lesions with diagnostic accuracy at least as good as greyscale ultrasound with BI-RADS classification.

Biomechanical Properties of In Vivo Human Skin From Dynamic Optical Coherence Elastography

Abstract: Dynamic optical coherence elastography is used to determine in vivo skin biomechanical properties based on mechanical surface wave propagation. Quantitative Young's moduli are measured on human skin from different sites, orientations, and frequencies. Skin thicknesses, including measurements from different layers, are also measured simultaneously. Experimental results show significant differences among measurements from different skin sites, between directions parallel and orthogonal to Langer's lines, and under different skin hydration states. Results also suggest surface waves with different driving frequencies represent skin biomechanical properties from different layers in depth. With features such as micrometer-scale resolution, noninvasive imaging, and real-time processing from the optical coherence tomography technology, this optical measurement technique has great potential for measuring skin biomechanical properties in dermatology.

Shear Wave Elastography: A New Ultrasound Imaging Mode for the Differential Diagnosis of Benign and Malignant Thyroid Nodules

Abstract: Context: Elastography uses ultrasound (US) to assess elasticity. Shear wave elastography (SWE) is a new technique that estimates tissue stiffness in real time and is quantitative and user independent. Objectives: The aim of the study was to assess the efficiency of SWE in predicting malignancy and to compare SWE with US. Design: Ninety-three patients and 39 control subjects were included in the study. Predictive value of SWE was assessed by correlation between elasticity, US parameters, and histology. Elasticity index (EI) was first analyzed alone. Scores have been constructed with echographic parameters, i.e. vascularity, hypoechogenicity, and microcalcifications (Score 1 = US Score), and with the same parameters plus EI (Score 2 = US+SWE Score). For statistical analysis, univariate and multivariate analysis and receiver operating characteristic curves were used. Results: A total of 146 nodules from 93 patients were analyzed. Twenty-nine nodules (19.9%) were malignant. Mean (±sd) EI was 150 ± 95 kPa (ran...

Nonalcoholic Fatty Liver Disease: US-based Acoustic Radiation Force Impulse Elastography

Abstract: US-based acoustic radiation force impulse elastography could be used as a noninvasive method for assessing liver fibrosis in patients with nonalcoholic fatty liver disease.

Quantitative Assessment of Arterial Wall Biomechanical Properties Using Shear Wave Imaging

Abstract: A new ultrasound-based technique is proposed to assess the arterial stiffness: the radiation force of an ultrasonic beam focused on the arterial wall induces a transient shear wave (� 10 ms) whose propagation is tracked by ultrafast imaging. The large and high-frequency content (100 to 1500 Hz) of the induced wave enables studying the wave dispersion, which is shown experimentally in vitro and numerically to be linked to arterial wall stiffness and geometry.The proposedmethod isappliedinvivo.Byrepeatingtheacquisition upto 10timesper second(theo- retical maximal frame rate is � 100 Hz), it is possible to assess in vivo the arterial wall elasticity dynamics: shear modulus of a healthy volunteer carotid wall is shown to vary strongly during the cardiac cycle and measured to be 130 ± 15 kPa in systole and 80 ± 10 kPa in diastole. (E-mail: mathieu.couade@gmail.com) 2010 World Feder- ation for Ultrasound in Medicine & Biology.

Evaluation of acoustic radiation force impulse elastography for fibrosis staging of chronic liver disease: a pilot study

Abstract: Background: Acoustic radiation force impulse (ARFI) is a new technology integrated into conventional B-mode ultrasonography. ARFI is used to evaluate tissue stiffness in several organs, but this method has not been applied for liver fibrosis. Aim: The aim of this study was to determine whether ARFI elastography is useful for the evaluation of liver fibrosis. Methods: This study enrolled 55 consecutive patients with chronic liver disease who underwent a liver biopsy for histological assessment of liver fibrosis by the Metavir scoring system. Liver stiffness of the 55 patients and 25 healthy volunteers was evaluated by ARFI elastography and was expressed as the shear wave velocity. Cut-off values were determined using receiver-operating characteristic (ROC) curves. Results: Histological liver fibrosis was evaluated by Metavir scoring; F0: six cases, F1: 14 cases, F2: nine cases, F3: nine cases and F4: 17 cases. Liver stiffness determined by ARFI elastography was correlated with histological liver fibrosis (Po0.0001). The areas under the ROC curves were 0.94 (95% confidence intervals, 0.87‐0.99) for F2‐F4, 0.94 (0.88‐0.99) for F3‐F4 and 0.96 (0.91‐1.01) for F4. The cut-off values of the shear wave velocity were as follows: 41.34m/s for F2‐F4 (sensitivity 91.4%, specificity 80%); 41.44m/ s for F3‐F4 (sensitivity 96.2%, specificity 79.3%); and 41.80m/s for F4 (sensitivity 94.1%, specificity 86.8%). Conclusions: Ultrasonic ARFI elastography is a novel, non-invasive and reliable method for the assessment of liver fibrosis in patients with chronic liver disease.

Real‐time visualization of muscle stiffness distribution with ultrasound shear wave imaging during muscle contraction

Abstract: A stand-alone ultrasound shear wave imaging technology has been developed to quantify and visualize Young's modulus distribution by remotely applying ultrasound radiation force and tracking the resulting microvibrations in soft tissues with ultrafast ultrasound imaging. We report the first preliminary data that detected the distribution of local muscle stiffness within and between resting and contracting muscles at different muscle lengths with this technology. This technique may assist clinicians in characterizing muscle injuries or neuromuscular disorders.

Muscle shear elastic modulus measured using supersonic shear imaging is highly related to muscle activity level.

Abstract: This pilot study was designed to determine whether the shear elastic modulus measured using supersonic shear imaging can be used to accurately estimate muscle activity level. Using direct visual fe...

Viscoelasticity-based staging of hepatic fibrosis with multifrequency MR elastography.

Abstract: The overall high sensitivity and specificity in distinguishing early from advanced hepatic fibrosis is a strong argument that liver biopsy can be replaced by MR elastography for assigning a score to fibrosis

Real-Time 2-D Temperature Imaging Using Ultrasound

Abstract: We have previously introduced methods for noninvasive estimation of temperature change using diagnostic ultrasound. The basic principle was validated both in vitro and in vivo by several groups worldwide. Some limitations remain, however, that have prevented these methods from being adopted in monitoring and guidance of minimally invasive thermal therapies, e.g., RF ablation and high-intensity-focused ultrasound (HIFU). In this letter, we present first results from a real-time system for 2-D imaging of temperature change using pulse-echo ultrasound. The front end of the system is a commercially available scanner equipped with a research interface, which allows the control of imaging sequence and access to the RF data in real time. A high-frame-rate 2-D RF acquisition mode, M2D, is used to capture the transients of tissue motion/deformations in response to pulsed HIFU. The M2D RF data is streamlined to the back end of the system, where a 2-D temperature imaging algorithm based on speckle tracking is implemented on a graphics processing unit. The real-time images of temperature change are computed on the same spatial and temporal grid of the M2D RF data, i.e., no decimation. Verification of the algorithm was performed by monitoring localized HIFU-induced heating of a tissue-mimicking elastography phantom. These results clearly demonstrate the repeatability and sensitivity of the algorithm. Furthermore, we present in vitro results demonstrating the possible use of this algorithm for imaging changes in tissue parameters due to HIFU-induced lesions. These results clearly demonstrate the value of the real-time data streaming and processing in monitoring, and guidance of minimally invasive thermotherapy.

Acoustic radiation force impulse elastography as compared to transient elastography and liver biopsy in patients with chronic hepatopathies.

Abstract: Purpose To compare two methods of noninvasive assessment: transient elastography (TE) and acoustic radiation force impulse elastography (ARFI) Patients and methods Our study included 114 subjects: 38 healthy volunteers, (considered to have no fibrosis - F 0) and 76 patients with chronic liver disease: 53 who had undergone liver biopsy (LB) (7 with F 1, 24 with F 2, 22 with F 3 Metavir) and 23 previously diagnosed with cirrhosis (F4 Metavir) In each patient we performed a liver stiffness measurement by means of TE and ARFI ARFI (shear wave velocity quantification) was performed at 3 points: at 0 - 1 cm, at 1 - 2 cm and at 2 - 3 cm under the capsule For each depth, 5 valid measurements were made, and a median value was calculated, measured in m/sec Results A direct, strong, linear correlation (Spearman rho = 0848) was found between TE and the stage of fibrosis (p 0), TE had the best predictive value: optimized cut-off 565 kPa (AUROC -0898) For ARFI, the cut-offs were: 14 m/sec, AUROC -0747 (1 - 2 cm), and 126 m/sec AUROC -0721 (2 - 3 cm) For predicting cirrhosis (F = 4 Metavir), the optimized cut-offs were: TE -129 kPa (AUROC -0994); ARFI - 178 m/sec for measurements made 2 - 3 cm below the capsule, AUROC - 0951 Conclusion At present, liver elasticity evaluation by means of ARFI is not superior to TE for the assessment of liver fibrosis For ARFI, the most reliable results are obtained if measurements are made 1 - 2 and 2 - 3 cm below the liver capsule ARFI is an accurate test for the diagnosis of cirrhosis

Tomography-Based and MRI-Based Imaging Systems

Abstract: Tomography limitations in vivo due to incomplete, inconsistent and intricate measurements require solution of inverse problems. The new strategies disclosed in this application are capable of providing faster data acquisition, higher image quality, lower radiation dose, greater flexibility, and lower system cost. Such benefits can be used to advance research in cardiovascular diseases, regenerative medicine, inflammation, and nanotechnology. The present invention relates to the field of medical imaging. More particularly, embodiments of the invention relate to methods, systems, and devices for imaging, including tomography-based and MRI-based applications. For example, included in embodiments of the invention are compressive sampling based tomosynthesis methods, which have great potential to reduce the overall x-ray radiation dose for a patient. To name a few, compressive sensing based carbon nano-tube based interior tomosynthesis systems, tomography-based dynamic cardiac elastography systems, cardiac elastodynamic biomarkers from interior MR imaging, exact and stable interior ROI reconstructions for radial MRI, and interior reconstruction based ultrafast tomography systems are provided.

Utility of elastography for differential diagnosis of benign and malignant thyroid nodules.

Abstract: Objective 1) To classify the appearance of thyroid nodules displayed on ultrasound elastography; 2) to explore the sensitivity and specificity of this examination for differentiating benign and malignant nodules, with histopathologic analysis as the reference standard; and 3) to evaluate its utility for avoiding unnecessary procedures. Study Design Diagnostic test assessment. Setting Community hospital. Subjects and Methods Forty-seven thyroid nodules in 44 consecutive patients were examined with ultrasound elastography. The images we obtained were classified into four patterns. In addition, the mean strain index of the thyroid nodule and that of the sternocleidomastoid muscle were measured, and the nodule-to-muscle strain ratio was calculated. As the reference findings, the presence or absence of calcification, irregular margins, and hypoechogenicity of the thyroid nodules were examined using B-mode ultrasound. Results Elastography patterns 3 and 4 were predictive of malignancy, with 73 percent sensitivity (95% confidence interval [CI]: 39%-94%) and 64 percent specificity (95% CI: 46%-79%). Additionally, all nodules without calcification and those that presented with patterns 1 or 2 were benign. A strain ratio greater than 1.5 was set as the predictor of thyroid malignancy. This criterion showed 90 percent sensitivity (95% CI: 59%-100%) and 50 percent specificity (95% CI: 33%-67%). Conclusion Although elastography can assist in the differential diagnosis of thyroid nodules, its diagnostic performance is not ideal at present. Further improvements in the technique and the diagnostic criteria are necessary for this examination to provide a useful contribution to diagnosis.

Spectroscopic optical coherence elastography

Abstract: We present an optical technique to image the frequency-dependent complex mechanical response of a viscoelastic sample. Three-dimensional hyperspectral data, comprising two-dimensional B-mode images and a third dimension corresponding to vibration frequency, were acquired from samples undergoing external mechanical excitation in the audio-frequency range. We describe the optical coherence tomography (OCT) signal when vibration is applied to a sample and detail the processing and acquisition techniques used to extract the local complex mechanical response from three-dimensional data that, due to a wide range of vibration frequencies, possess a wide range of sample velocities. We demonstrate frequency-dependent contrast of the displacement amplitude and phase of a silicone phantom containing inclusions of higher stiffness. Measurements of an ex vivo tumor margin demonstrate distinct spectra between adipose and tumor regions, and images of displacement amplitude and phase demonstrated spatially-resolved contrast. Contrast was also observed in displacement amplitude and phase images of a rat muscle sample. These results represent the first demonstration of mechanical spectroscopy based on B-mode OCT imaging. Spectroscopic optical coherence elastography (S-OCE) provides a high-resolution imaging capability for the detection of tissue pathologies that are characterized by a frequency-dependent viscoelastic response.

Differential Diagnosis of Small Single Solid Thyroid Nodules using Real-Time Ultrasound Elastography

Abstract: In this prospective study, the diagnostic value of real-time ultrasound elastography (USE) was evaluated in 51 consecutive patients referred for surgical treatment with single solid thyroid nodules < 10 mm in maximum diameter with an indeterminate result on B-mode and colour Doppler ultrasonography. Ultrasonographic results were compared with histopathological data. Nineteen follicular adenomas and 32 papillary thyroid microcarcinomas (PTMCs) were observed. A real-time USE score of 4 - 5 diagnosed PTMCs with a sensitivity of 90.63%, a specificity of 89.47% and an accuracy of 90.20%. The positive and negative predictive values were 93.55% and 85.00%, respectively. It is concluded that real-time USE is a promising imaging technique that could assist in the differential diagnosis of single solid thyroid nodules < 10 mm in maximum diameter that give indeterminate results on conventional ultrasound.

Developments in musculoskeletal ultrasound and clinical applications

Abstract: Ultrasound (US) technologies are rapidly advancing, offering several refined transducer technologies as well as soft and hardware facilities. The aim of this article is to outline US developments, from B-mode technologies over Doppler advances to more sophisticated technologies, and their potential clinical impact in the field of musculoskeletal (MSK) imaging. When using B-mode ultrasound, compound imaging and beam-steering are of help to decrease anisotropy in tendons and ligaments, that are less well depicted due to their oblique course. Doppler imaging has become sensitive in the detection of flow in small vessels, which is of particular value in rheumatologic conditions, tumour and overuse assessment. The use of US microbubble contrast agents improves detection of low-volume blood flow in smaller vessels by increasing the signal-to-noise ratio and thereby facilitating detection of angiogenetic vessels in inflammatory conditions or tumours. The use of US blood pool contrast agents enables molecular imaging in real-time, and thus the diagnostic potential of US is expanded, opening up a new field of US applications. Objective quantification of altered tissue (e.g., synovial proliferation, tumours) is still demanding and might be improved by the use of three-dimensional imaging and software tools as parametric evaluation. Real-time sonoelastography (EUS) is a new development for visualization of tissue elasticity by measurement of tissue displacement in terms of tissue stiffness changes, promising new insights into tendon disorders. Image fusion is an exciting development that enables superimposition of CT/MRI data sets on real-time US scanning. This technique might be helpful in guiding injections under real-time conditions even in regions less easily accessible by US as, for instance, the axial skeleton, and can additionally provide an interesting tool for teaching MSK imaging and ways to guide interventions. In summary, exciting developments are expanding the applications of US in the MSK field, offering the advantages of real-time performance, high tissue resolution and relative speed at a reasonable cost.

Assessment of liver fibrosis and steatosis in PBC with FibroScan, MRI, MR-spectroscopy, and serum markers.

Abstract: BackgroundIn recent years noninvasive methods have been evaluated for the assessment of liver fibrosis predominantly in patients with viral hepatitis. In this study, transient elastography (FibroScan), magnetic resonance imaging (MRI), magnetic resonance (MR)-spectroscopy, and serum markers were com

Magnetic resonance imaging, ultrasound and real-time ultrasound elastography of the thigh muscles in congenital muscle dystrophy.

Abstract: Congenital muscle dystrophy includes a range of genetic disorders characterized by muscle weakness and contractures. We report the magnetic resonance (MR), ultrasound (US) and real-time sonoelastography (RTE) imaging findings of the thigh muscles of a 15-year-old boy with Bethlem myopathy diagnosed with clinical, electromyographic and histopathological criteria. Ultrasound and MR showed hyperechoic appearance and high signal intensity on T1- and T2-weighted sequences respectively at the periphery of the vastus lateralis and the long head of the biceps femoris muscles, and at a central area within the rectus femoris muscles. RTE was employed to examine the elastic properties of the muscle. The elastograms were presented as colour-coded maps superimposed on the B-mode images and revealed that the elastographic pattern correlated with the MR and US pattern of involvement. The abnormal muscle areas were stiffer (blue) than the normal-appearing areas (green), a finding that probably correlates with the presence of dystrophic collagen at the affected areas. This report suggests that RTE could be used as an additional imaging tool to evaluate the pattern of muscle changes in congenital myopathy. Further studies are needed to investigate the specificity and clinical value of RTE in the diagnosis and monitoring of neuromuscular disease.

Dynamic spectral-domain optical coherence elastography for tissue characterization

Abstract: A dynamic spectral-domain optical coherence elastography (OCE) imaging technique is reported. In this technique, audio-frequency compressive vibrations are generated by a piezoelectric stack as external excitation, and strain rates in the sample are calculated and mapped quantitatively using phase-sensitive spectral-domain optical coherence tomography. At different driving frequencies, this technique provides contrast between sample regions with different mechanical properties, and thus is used to mechanically characterize tissue. We present images of a three-layer silicone tissue phantom and rat tumor tissue ex vivo, based on quantitative strain rate. Both acquisition speed and processing speed are improved dramatically compared with previous OCE imaging techniques. With high resolution, high acquisition speed, and the ability to characterize the mechanical properties of tissue, this OCE technique has potential use in non-destructive volumetric imaging and clinical applications.

A Method for Characterization of Tissue Elastic Properties Combining Ultrasonic Computed Tomography With Elastography

Abstract: Objective. The correlation between various diseases and the change in the local mechanical properties of soft tissues has been long known. Over the past 20 years, there have been increasing research efforts to characterize mechanical properties of biological tissues using ultrasonic elastography. However, most of these works were based on characterization of only 1 type of waves (longitudinal or shear). The goal of this work was to devise a comprehensive ultrasound-based imaging method capable of measuring elastic parameters by combining both backscattered elastography and throughtransmitted ultrasonic computed tomography. Methods. Our suggested technique provides measurements of both longitudinal and shear wave velocities. This enables the noninvasive computation of several tissue elasticity parameters such as Young’s and shear moduli, Poisson’s ratio, and, more importantly, the bulk modulus, the determination of which requires both wave velocities. Four different phantom types were examined: agar-gelatin–based phantoms and porcine fat tissue, turkey breast tissue, and bovine liver tissue in vitro specimens. The values of Young’s modulus, the shear modulus, and Poisson’s ratio were estimated and were consistent with values published in the literature. Results. The average bulk modulus values of the phantoms ± SD were 2.83 ± 0.001, 2.25 ± 0.01, 2.48 ± 0.01, and 2.53 ± 0.02 GPa, respectively. A statistically significant difference (P < .001) in the values of the bulk modulus of the different phantoms was found. Conclusions. The bulk modulus is suitable for differentiation between different tissue types. The obtained results show the feasibility of using a comprehensive ultrasonic imaging technique for noninvasive quantitative tissue characterization. Key words: bulk modulus; computed tomography; elastic parameters; elastography; tissue characterization; wave velocity.

Elastography for the Characterization of Breast Lesions: Initial Clinical Experience:

Abstract: BackgroundWhile breast biopsy remains the gold standard for diagnosis of suspicious lesions, a large proportion of biopsy specimens reveal a benign result. Therefore, a noninvasive and reliable method to identify low-risk lesions would be a valuable tool.MethodsWe assessed the application and diagnostic performance of elastography for the characterization of breast lesions in patients referred for biopsy. Subjects referred for ultrasound-guided biopsy of sonographically apparent breast lesions were included in this study. The Hitachi Hi-Vision 900 ultrasound was used to generate index test results for elastography scoring (ES) and for strain ratio (SR) measurement. Sensitivity, specificity, and positive and negative predictive values were determined using pathologic results from 14-gauge core needle biopsy as the reference standard.ResultsA total of 310 lesions in 288 patients were included in this series. Of these 310 lesions, 223 (72%) were benign and 87 (28%) were malignant. Sensitivity was 0.76 for ES...

Real-time qualitative ultrasound elastography of cervical lymph nodes in routine clinical practice: interobserver agreement and correlation with malignancy.

Abstract: To evaluate real-time qualitative ultrasound (US) elastography for cervical lymphadenopathy in routine clinical practice, 74 nodes (37 malignant, 37 benign) in 74 patients undergoing sonography underwent US elastography prior to fine needle aspiration for cytology. Dynamic cine loops of elasticity imaging displayed using a chromatic-scale were qualitatively scored by three independent observers for the proportion of stiff areas from ES1-4 (soft to stiff). There was fair to good interobserver agreement as indicated by weighted kappa (κ) statistic from 0.374 to 0.738. Median ES for benign and malignant nodes were 2 and 3 respectively. ES was higher in malignant nodes (p = 0.0003-0.0049, Mann Whitney U tests) although areas under receiver operating characteristic curves (0.68-0.74) indicated suboptimal discrimination. The optimal discriminatory cut-off, ES > 2, achieved only 62.2% sensitivity, 83.8% specificity and 73% accuracy for malignancy. Improvements in reliability and accuracy of real-time qualitative ultrasound elastography are required for it to be adopted into routine clinical practice.