Ultrasound Elastography Techniques Research Articles

Effect of proteinuria at relapse on shear wave velocity assessed using ultrasound elastography in children with idiopathic nephrotic syndrome.

Shear wave velocity (SWV) is an ultrasound elastography technique that provides much information for kidney disease assessment. However, the factors that alter SWV are not fully understood; it is unclear whether the variation in SWV seen in proteinuria associated with disease progression is due to tissue or proteinuria. This study investigated the effect of proteinuria on SWV. This prospective observational study compared SWV at remission with SWV at relapse in children treated for idiopathic nephrotic syndrome (INS) between April 2020 and December 2023. All relapses without oral steroids during the observation period were measured. SWV at remission was defined as the date closest to relapse during which repeated measurements were taken approximately every 3months after steroid discontinuation. Eight patients were treated for INS with a median observation period of 21.9months (11.8-27.1). Of the 15 relapses, five that met the definition were considered for the study. The median interval between the measurement at relapse and remission was 40days (11-55). SWV was significantly lower at relapse than remission (2.40 ± 0.20m/s vs. 2.14 ± 0.15m/s, P < 0.01). SWV decreased in the presence of severe proteinuria at relapse compared to the remission measurements. Although more cases need to be studied, the decrease in SWV may reflect the mechanism by which protein leaks into the urine, not just a direct change caused by the presence of proteinuria.

Ultrasound elastography to quantify average percent pressure-normalized strain reduction associated with different aortic endografts in 3D-printed hydrogel phantoms

ObjectiveStrain has become a viable index for evaluating abdominal aortic aneurysm stability after endovascular aneurysm repair (EVAR). In addition, literature has shown that healthy aortic tissue requires a degree of strain to maintain homeostasis. This has led to the hypothesis that too much strain reduction conferred by a high degree of graft oversizing is detrimental to the aneurysm neck in the seal zone of abdominal aortic aneurysms after EVAR. We investigated this in a laboratory experiment by examining the effects that graft oversizing has on the pressure-normalized strain (ερ+¯/pulse pressure [PP]) reduction using four different infrarenal EVAR endografts and our ultrasound elastography technique. Approximate graft oversizing percentages were 20% (30 mm phantom-graft combinations), 30% (28 mm phantom-graft combinations), and 50% (24 mm phantom-graft combinations). MethodsAxisymmetric, 10% by mass polyvinyl alcohol phantoms were connected to a flow simulator. Ultrasound elastography was performed before and after implantation with the four different endografts: (1) 36 mm polyester/stainless steel, (2) 36 mm polyester/electropolished nitinol, (3) 35 mm polytetrafluoroethylene (PTFE)/nitinol, and (4) 36 mm nitinol/polyester/platinum-iridium. Five ultrasound cine loops were taken of each phantom-graft combination. They were analyzed over two different cardiac cycles (end-diastole to end-diastole), yielding a total of 10 maximum mean principal strain (ερ+¯) values. ερ+¯ was divided by pulse pressure to yield pressure-normalized strain (ερ+¯/PP). An analysis of variance was performed for graft comparisons. We calculated the average percent ερ+¯/PP reduction by manufacturer and percent oversizing. These values were used for linear regression analysis. ResultsResults from one-way analysis of variance showed a significant difference in ερ+¯/PP between the empty phantom condition and all oversizing conditions for all graft manufacturers (F(3, 56) = 106.7 [graft A], 132.7 [graft B], 106.5 [graft C], 105.7 [graft D], P < .0001 for grafts A-D). There was a significant difference when comparing the 50% condition with the 30% and 20% conditions across all manufacturers by post hoc analysis (P < .0001). No significant difference was found when comparing the 20% and 30% oversizing conditions for any of the manufacturers or when comparing ερ+¯/PP values across the manufacturers according to percent oversize. Linear regression demonstrated a significant positive correlation between the percent graft oversize and the all-graft average percent ερ+¯/PP reduction (R2 = 0.84, P < .0001). ConclusionsThis brief report suggests that a 10% increase in graft oversizing leads to an approximate 5.9% reduction in ερ+¯/PP on average. Applied clinically, this increase may result in increased stiffness in axisymmetric vessels after EVAR. Further research is needed to determine if this is clinically significant.

Optimization of the Tracking Beam Sequence in Harmonic Motion Imaging.

Harmonic motion imaging (HMI) is an ultrasound elastography technique that estimates the viscoelastic properties of tissues by inducing localized oscillatory motion using focused ultrasound (FUS). The resulting displacement, assumed to be inversely proportional to the tissue local stiffness, is estimated using an imaging array based on RF speckle tracking. In conventional HMI, this is accomplished with plane-wave (PW) imaging, which inherently suffers from low lateral resolution. Coherent PW compounding (PWC) leverages spatial and temporal resolution using synthetic focusing in transmit. In this study, we introduced focused imaging with parallel tracking in HMI and compared parallel tracking of various transmit F-numbers (F/2.6, 3, 4, and 5) qualitatively and quantitatively with PW and PWC imaging at various compounded angle ranges (6°, 12°, and 18°). An in silico model of a 56-kPa spherical inclusion (diameter: 3.6 mm) embedded in a 5.3-kPa background and a 5.3-kPa elastic phantom with cylindrical inclusions (Young's moduli: 22-56 kPa, diameters: 2.0-8.6 mm) were imaged to assess different tracking beam sequences. Speckle biasing in displacement estimation associated with parallel tracking was also investigated and concluded to be negligible in HMI. Parallel tracking in receive (Rx) resulted in 2%-7% and 8%-12% increase compared to PW imaging ( ) in HMI contrast and contrast-to-noise ratio in silico and phantoms. Focused imaging with parallel tracking in Rx was concluded to be most robust among PW and PWC imaging for displacement estimation, and its preclinical feasibility was demonstrated in postsurgical human cancerous breast tissue specimens and in vivo murine models of breast cancer.

The role of shear wave elastography in predicting endometrial cancer in patients presenting with abnormal uterine bleeding.

Shear Wave Elastography (SWE) is an objective quantitative ultrasound elastography technique that can demonstrate the stiffness of anatomical structures to aid in their detection and characterization. We aimed to evaluate the role of shear wave elastography in differentiating endometrial carcinoma from benign uterine pathologies in women with abnormal uterine bleeding. This prospective study was conducted at our institution from January 2020 to April 2020. A hundred patients with endometrial sampling planned and SWE due to abnormal uterine bleeding were included in the study. According to the histopathological results of the patients, those with normal and atrophic endometrium results were defined as group I (control group), those with benign results such as polyps and endometrial hyperplasia were defined as group II, and those with endometrial cancers were defined as group III. After adjustment for age, a statistically significant difference was found in Emean (mean and adjusted mean) value between the study groups (F2.96=86.37, p<.001, η2=0.64). The post-hoc analysis was performed with a Bonferroni adjustment. The mean Emean value was found to be statistically significantly higher in group III (17.14±0.40) compared to group I (10.39±0.26) and group II (11.49±0.32) (p<0.001). In addition, a statistically significant difference was found between the benign and normal groups. As a new diagnostic technique in gynecology, elastography appears to be a valuable tool in differentiating malign endometrial pathologies from normal or benign endometrial pathologies in females with abnormal uterine bleeding.

Assessment of spinal cord injury using ultrasound elastography in a rabbit model in vivo

The effect of the mechanical micro-environment on spinal cord injury (SCI) and treatment effectiveness remains unclear. Currently, there are limited imaging methods that can directly assess the localized mechanical behavior of spinal cords in vivo. In this study, we apply new ultrasound elastography (USE) techniques to assess SCI in vivo at the site of the injury and at the time of one week post injury, in a rabbit animal model. Eleven rabbits underwent laminectomy procedures. Among them, spinal cords of five rabbits were injured during the procedure. The other six rabbits were used as control. Two neurological statuses were achieved: non-paralysis and paralysis. Ultrasound data were collected one week post-surgery and processed to compute strain ratios. Histologic analysis, mechanical testing, magnetic resonance imaging (MRI), computerized tomography and MRI diffusion tensor imaging (DTI) were performed to validate USE results. Strain ratios computed via USE were found to be significantly different in paralyzed versus non-paralyzed rabbits. The myelomalacia histologic score and spinal cord Young’s modulus evaluated in selected animals were in good qualitative agreement with USE assessment. It is feasible to use USE to assess changes in the spinal cord of the presented animal model. In the future, with more experimental data available, USE may provide new quantitative tools for improving SCI diagnosis and prognosis.

Noncontact longitudinal shear wave imaging for the evaluation of heterogeneous porcine brain biomechanical properties using optical coherence elastography.

High-resolution quantification of heterogeneous brain biomechanical properties has long been an important topic. Longitudinal shear waves (LSWs) can be used to assess the longitudinal Young's modulus, but contact excitation methods have been used in most previous studies. We propose an air-coupled ultrasound transducer-based optical coherence elastography (AcUT-OCE) technique for noncontact excitation and detection of LSWs in samples and assessment of the nonuniformity of the brain's biomechanical properties. The air-coupled ultrasonic transducer (AcUT) for noncontact excitation of LSWs in the sample has a center frequency of 250 kHz. Phase-resolved Doppler optical coherence tomography (OCT) was used to image and reconstruct the propagation behavior of LSWs and surface ultrasound waves at high resolution. An agar phantom model was used to verify the feasibility of the experimental protocol, and experiments with ex vivo porcine brain samples were used to assess the nonuniformity of the brain biomechanical properties. LSWs with velocities of 0.83 ± 0.11 m/s were successfully excited in the agar phantom model. The perivascular elastography results in the prefrontal cortex (PFC) of the ex vivo porcine brains showed that the Young's modulus was significantly higher in the longitudinal and transverse directions on the left side of the cerebral vessels than on the right side and that the Young's modulus of the PFC decreased with increasing depth. The AcUT-OCE technique, as a new scheme for LSW applications in in vivo elastography, can be used for noncontact excitation of LSWs in brain tissue and high-resolution detection of heterogeneous brain biomechanical properties.

Intermediate pressure-normalized principal wall strain values are associated with increased abdominal aortic aneurysmal growth rates.

Current abdominal aortic aneurysm (AAA) assessment relies on analysis of AAA diameter and growth rate. However, evidence demonstrates that AAA pathology varies among patients and morphometric analysis alone is insufficient to precisely predict individual rupture risk. Biomechanical parameters, such as pressure-normalized AAA principal wall strain (/PP, %/mmHg), can provide useful information for AAA assessment. Therefore, this study utilized a previously validated ultrasound elastography (USE) technique to correlate /PP with the current AAA assessment methods of maximal diameter and growth rate. Our USE algorithm utilizes a finite element mesh, overlaid a 2D cross-sectional view of the user-defined AAA wall, at the location of maximum diameter, to track two-dimensional, frame-to-frame displacements over a full cardiac cycle, using a custom image registration algorithm to produce /PP. This metric was compared between patients with healthy aortas and AAAs (≥3 cm) and compared between small and large AAAs (≥5 cm). AAAs were then separated into terciles based on /PP values to further assess differences in our metric across maximal diameter and prospective growth rate. Non-parametric tests of hypotheses were used to assess statistical significance as appropriate. USE analysis was conducted on 129 patients, 16 healthy aortas and 113 AAAs, of which 86 were classified as small AAAs and 27 as large. Non-aneurysmal aortas showed higher /PP compared to AAAs (0.044 ± 0.015 vs. 0.034 ± 0.017%/mmHg, p = 0.01) indicating AAA walls to be stiffer. Small and large AAAs showed no difference in /PP. When divided into terciles based on /PP cutoffs of 0.0251 and 0.038%/mmHg, there was no difference in AAA diameter. There was a statistically significant difference in prospective growth rate between the intermediate tercile and the outer two terciles (1.46 ± 2.48 vs. 3.59 ± 3.83 vs. 1.78 ± 1.64 mm/yr, p = 0.014). There was no correlation between AAA diameter and /PP, indicating biomechanical markers of AAA pathology are likely independent of diameter. AAAs in the intermediate tercile of /PP values were found to have nearly double the growth rates than the highest or lowest tercile, indicating an intermediate range of /PP values for which patients are at risk for increased AAA expansion, likely necessitating more frequent imaging follow-up.

Chinese expert consensus on the diagnosis of cirrhotic portal hypertension by ultrasound elastography (2023 version)

The population with cirrhosis in China is about 7 million, and portal hypertension is an important factor affecting the prognosis of these patients. The severity of portal hypertension determines the occurrence and development of liver related complications, such as ascites, variceal bleeding, and hepatic encephalopathy. In recent years, ultrasound elastography technology has been rapidly developed and widely applied in the field of liver diseases. Transient elastography, point shear wave elastography, and two-dimensional shear-wave elastography are all of great value for non-invasive evaluation of portal hypertension. However, there is currently no unified operating standard and reference threshold for evaluating cirrhotic portal hypertension using ultrasound elastography. Therefore, Ultrasonic Medicine Branch of the Chinese Medical Association and Chinese Portal Hypertension Alliance (CHESS) initialed and convened domestic experts from multiple disciplines, including ultrasound medicine, hepatology, gastroenterology, to form a consensus based on the latest domestic and international guidelines, medical evidence, and Chinese clinical practice. The aim is to standardize the examination process of different ultrasound elastography techniques, and standardize the application of liver stiffness and spleen stiffness in compensated advanced chronic liver disease, clinically significant portal hypertension, avoidance of endoscopic screening, risk stratification of portal hypertension, and personalized clinical management.

Multisample Ultrasound Point Shear Wave Elastography of the Liver: Repeatability and Agreement With Conventional Point Shear Wave Elastography.

To characterize the technical performance of a multisample ultrasound point shear wave elastography (pSWE) technique that allows 15 individual measurements of liver stiffness in a single acquisition. In 56 overweight and obese adults, research ultrasound examinations were performed using conventional pSWE and multisample pSWE (Sequoia; Siemens Healthineers). Five independent measurements were acquired with the conventional technique over five consecutive breath holds (5C1 and DAX transducers). A single multisample acquisition (DAX transducer) of up to 15 unique measurements was acquired during a single breath hold. All imaging was performed before (baseline) and after a "coffee break" (repeat). Median liver stiffness measurements between techniques and between baseline and repeat imaging were compared using Pearson correlation (r) and intra-class correlation (ICC) coefficients. Mean participant age was 33.7 ± 11.4 years; 40 participants were female. There was high correlation between conventional pSWE measurements obtained using the 5C1 and DAX transducers at baseline (r = .75 [95% CI: 0.61-0.85], P < .0001) and repeat (r = .88 [95% CI: 0.78-0.92], P < .0001). There was moderate agreement between conventional pSWE measurements obtained using the 5C1 and DAX transducers at baseline (ICC = 0.69 [95% CI: 0.52-0.81]), and good agreement at repeat (ICC = 0.81 [95% CI: 0.65-0.90]). There was moderate correlation (r = .59 [95% CI: 0.39-0.74], P < .0001) and moderate agreement (ICC = 0.58 [95% CI: 0.38-0.73]) between baseline conventional and multisample pSWE measurements acquired using the DAX transducer; there was high correlation (r = .73 [95% CI: 0.57-0.83], P < .0001) and moderate agreement (ICC = 0.72 [95% CI: 0.56-0.82] between techniques at repeat. There was moderate correlation (r = .65 [95% CI: 0.46-0.78], P < .0001) and moderate agreement (ICC = 0.64 [95% CI: 0.45-0.77]) between baseline and repeat multisample pSWE measurements. Multisample pSWE, allowing up to 15 measurements in a single breath hold, showed moderate to high correlation and moderate agreement with conventional pSWE.

Stiffness pulsation of the human brain detected by non-invasive time-harmonic elastography.

Introduction: Cerebral pulsation is a vital aspect of cerebral hemodynamics. Changes in arterial pressure in response to cardiac pulsation cause cerebral pulsation, which is related to cerebrovascular compliance and cerebral blood perfusion. Cerebrovascular compliance and blood perfusion influence the mechanical properties of the brain, causing pulsation-induced changes in cerebral stiffness. However, there is currently no imaging technique available that can directly quantify the pulsation of brain stiffness in real time. Methods: Therefore, we developed non-invasive ultrasound time-harmonic elastography (THE) technique for the real-time detection of brain stiffness pulsation. We used state-of-the-art plane-wave imaging for interleaved acquisitions of shear waves at a frequency of 60Hz to measure stiffness and color flow imaging to measure cerebral blood flow within the middle cerebral artery. In the second experiment, we used cost-effective lineby-line B-mode imaging to measure the same mechanical parameters without flow imaging to facilitate future translation to the clinic. Results: In 10 healthy volunteers, stiffness increased during the passage of the arterial pulse wave from 4.8% ± 1.8% in the temporal parenchyma to 11% ± 5% in the basal cisterns and 13% ± 9% in the brain stem. Brain stiffness peaked in synchrony with cerebral blood flow at approximately 180 ± 30ms after the cardiac R-wave. Line-by-line THE provided the same stiffness values with similar time resolution as high-end plane-wave THE, demonstrating the robustness of brain stiffness pulsation as an imaging marker. Discussion: Overall, this study sets the background and provides reference values for time-resolved THE in the human brain as a cost-efficient and easy-touse mechanical biomarker associated with cerebrovascular compliance.

Enhanced full-inversion-based ultrasound elastography for evaluating tumor response to neoadjuvant chemotherapy in patients with locally advanced breast cancer

PurposeAn enhanced ultrasound elastography technique is proposed for early assessment of locally advanced breast cancer (LABC) response to neoadjuvant chemotherapy (NAC). MethodsThe proposed elastography technique inputs ultrasound radiofrequency data obtained through tissue quasi-static stimulation and adapts a strain refinement algorithm formulated based on fundamental principles of continuum mechanics, coupled with an iterative inverse finite element method to reconstruct the breast Young’s modulus (E) images. The technique was explored for therapy response assessment using data acquired from 25 LABC patients before and at weeks 1, 2, and 4 after the NAC initiation (100 scans). The E ratio of tumor to the surrounding tissue was calculated at different scans and compared to the baseline for each patient. Patients’ response to NAC was determined many months later using standard clinical and histopathological criteria. ResultsReconstructed E ratio changes obtained as early as one week after the NAC onset demonstrate very good separation between the two cohorts of responders and non-responders to NAC. Statistically significant differences were observed in the E ratio changes between the two patient cohorts at weeks 1 to 4 after treatment (p-value < 0.001; statistical power greater than 97%). A significant difference in axial strain ratio changes was observed only at week 4 (p-value = 0.01; statistical power = 76%). No significant difference was observed in tumor size changes at weeks 1, 2 or 4. ConclusionThe proposed elastography technique demonstrates a high potential for chemotherapy response monitoring in LABC patients and superior performance compared to strain imaging.

Intermediate Pressure-Normalized Strain Values Are Associated With Increased Abdominal Aortic Aneurysmal Growth Rates

Current abdominal aortic aneurysm (AAA) assessment methods rely on simple morphometric analysis of the AAA diameter and growth rate. However, evidence has shown that AAA pathology varies among patients, and morphometric analysis alone is insufficient to predict individual risk of growth. Biomechanical parameters, such as pressure-normalized aortic wall strain (εp+/PP), can provide a surrogate to vessel wall stiffness. We aimed to use our novel ultrasound elastography (USE) technique to measure ερ+/PP and correlate ερ+/PP with maximal AAA diameter and growth rate in the largest clinical trial to date. Our USE algorithm uses a finite element mesh overlayed on a 2D axial view of the user-defined AAA wall at the point of maximum diameter to track frame-to-frame displacements over a full cardiac cycle to measure ερ+/PP. ερ+/PP and growth rate were assessed between small and large AAAs based on a diameter of ≥5 cm. Patients with AAA were then separated into terciles based on ερ+/PP values of 0.0251 and 0.038 to assess differences in the AAA diameter and growth rate. Mann-Whitney U and Kruskal-Wallis tests were used to assess differences as appropriate. USE analysis was conducted on 127 patients, 16 normal aortas and 111 AAAs. A total of 79 patients had at least one follow-up clinical scan used to calculate growth rate. Of the 111 aortas, 85 were classified as small and 26 as large. AAAs showed lower ερ+/PP (stiffer) compared with nonaneurysmal aortas (0.034 ± 0.017 vs 0.044 ± 0.015 %/kPa; P = .006). There was no difference in ερ+/PP or growth rate between small and large AAAs. When divided into terciles based on ερ+/PP, there was no difference in the AAA diameter. There was a statistically significant difference in growth rate between the intermediate tercile and the outer terciles (1.46 ± 2.48 vs 3.59 ± 3.83 vs 1.78 ± 1.64 mm/y; P = .014) (Fig). Our validated USE algorithm shows that AAAs are stiffer than nonaneurysmal aortas, similar to previous reports. There was no correlation between AAA diameter and ερ+/PP, indicating that AAA stiffness is independent of diameter, and diameter thresholds alone may not accurately assess future risk of growth. AAAs in the intermediate tercile of ερ+/PP values were found to have greater growth rates than the outer tercile, indicating that an intermediate range of ερ+/PP values, regardless of diameter, place patients at increased risk for AAA growth. These findings also suggest that AAA growth may be related to a failure of collagen remodeling and may be the underlying event that leads to AAA rupture.

Different Ultrasound Shear Wave Elastography Techniques as Novel Imaging-Based Approaches for Quantitative Evaluation of Hepatic Steatosis—Preliminary Findings

Modern ultrasound (US) shear-wave dispersion (SWD) and attenuation imaging (ATI) can be used to quantify changes in the viscosity and signal attenuation of the liver parenchyma, which are altered in hepatic steatosis. We aimed to evaluate modern shear-wave elastography (SWE), SWD and ATI for the assessment of hepatic steatosis. We retrospectively analyzed the US data of 15 patients who underwent liver USs and MRIs for the evaluation of parenchymal disease/liver lesions. The USs were performed using a multifrequency convex probe (1-8 MHz). The quantitative US measurements for the SWE (m/s/kPa), the SWD (kPa-m/s/kHz) and the ATI (dB/cm/MHz) were acquired after the mean value of five regions of interest (ROIs) was calculated. The liver MRI (3T) quantification of hepatic steatosis was performed by acquiring proton density fat fraction (PDFF) mapping sequences and placing five ROIs in artifact-free areas of the PDFF scan, measuring the fat-signal fraction. We correlated the SWE, SWD and ATI measurements to the PDFF results. Three patients showed mild steatosis, one showed moderate steatosis and eleven showed no steatosis in the PDFF sequences. The calculated SWE cut-off (2.5 m/s, 20.4 kPa) value identified 3/4 of patients correctly (AUC = 0.73, p > 0.05). The SWD cut-off of 18.5 m/s/kHz, which had a significant correlation (r = 0.55, p = 0.034) with the PDFF results (AUC = 0.73), identified four patients correctly (p < 0.001). The ideal ATI (AUC = 0.53 (p < 0.05)) cut-off was 0.59 dB/cm/MHz, which showed a significantly good correlation with the PDFF results (p = 0.024). Hepatic steatosis can be accurately detected using all the US-elastography techniques applied in this study, although the SWD and the SWE showed to be more sensitive than the PDFF.

Transient elastography with focused shear wave beams

Transient elastography (TE) is a clinically available ultrasound elastography technique in which mechanical vibration of a small piston at the tissue surface generates a short shear wave pulse that propagates into the body. The piston doubles as an ultrasonic transducer; thus, the shear wave propagation is measured with pulse-echo ultrasound along the beam axis, yielding the wave speed and tissue stiffness. The long shear wavelength compared to piston diameter used in current devices results in low shear wave signal that decays rapidly on axis as the shear wave spreads in all directions, thus limiting the signal-to-noise ratio and imaging depth in practice. We present an overview of our new technology of focused shear wave beams, which aims to overcome these limitations by concentrating shear wave energy in TE near to the beam axis with vibration of a concave circular piston. Analytical modeling of focused shear wave generation and propagation is validated against measurements in gelatin phantoms. Results indicate that focused shear wave beams have relatively larger amplitudes and penetration depths compared to unfocused shear wave beams. Ongoing modeling and experimental efforts towards the measurement of elastic anisotropy, such as of skeletal muscle, using focused shear wave beams will be discussed.

Value of cervical strain in ultrasound elastography as a predictor of spontaneous preterm delivery

BackgroundCervical incompetence is a failure of the cervix to retain the products of conception throughout pregnancy, which results into cervical dilatation and preterm delivery. Many methods are conducted for early detection of cervical shortening, ripening and eventually dilatation to lessen the incidence of the preterm delivery, which is responsible for about 75% of neonatal comorbidities. Ultrasound plays an important role in the diagnosis and early detection of cervical incompetence. Elastography is a relatively new technique, which investigates into another important factor for cervical insufficiency which is “tissue stiffness”. The process of early cervical ripening, which is an important and main step in spontaneous preterm delivery, precedes cervical shortening and renders the human cervix soft which can be diagnosed through the color-coding method of the sonoelastography technique. The aim of this study is to determine the value of cervical elastography as a predictor of spontaneous preterm labor and validate the role of strain ratio in such technique.ResultsIn our study, we examined the pregnant females by transvaginal conventional B-mode ultrasound and complementary elastography technique and recorded the elastography index of their cervix, internal os and external os together with measuring the amount of strain and strain ratio at internal and external os.ConclusionsWe concluded that women who had preterm delivery did have higher strain and elastography index as their cervices were softer than those who had full-term deliveries. Elastography therefore can be a reliable method for the prediction of preterm delivery.

How to Identify Advanced Fibrosis in Adult Patients with Non-Alcoholic Fatty Liver Disease (NAFLD) and Non-Alcoholic Steatohepatitis (NASH) Using Ultrasound Elastography—A Review of the Literature and Proposed Multistep Approach

Non-alcoholic fatty liver disease (NAFLD), and its progressive form, non-alcoholic steatohepatitis (NASH), represent, nowadays, real challenges for the healthcare system. Liver fibrosis is the most important prognostic factor for NAFLD, and advanced fibrosis is associated with higher liver-related mortality rates. Therefore, the key issues in NAFLD are the differentiation of NASH from simple steatosis and identification of advanced hepatic fibrosis. We critically reviewed the ultrasound (US) elastography techniques for the quantitative characterization of fibrosis, steatosis, and inflammation in NAFLD and NASH, with a specific focus on how to differentiate advanced fibrosis in adult patients. Vibration-controlled transient elastography (VCTE) is still the most utilized and validated elastography method for liver fibrosis assessment. The recently developed point shear wave elastography (pSWE) and two-dimensional shear wave elastography (2D-SWE) techniques that use multiparametric approaches could bring essential improvements to diagnosis and risk stratification.

Use of Sound Touch Elastography and Sound Touch Quantification for the Noninvasive Evaluation of Portal Hypertension in a Rat Model.

In this study, we used the recently developed ultrasound elastography techniques sound touch elastography (STE) and sound touch quantification (STQ) to quantify portal hypertension (PHT) severity in a rat model of carbon tetrachloride (CCl4 )-induced cirrhotic PHT. In total, 60 rats were used. Various degrees of PHT were established. Liver and spleen stiffness were measured by STE (L-STE and S-STE, respectively) and STQ (L-STQ and S-STQ, respectively). We measured portal pressure (PP) after ultrasonographic examination. The performance of the STE and STQ parameters in the identification of PHT was evaluated using receiver operating characteristic (ROC) analyses. Liver and spleen stiffness measurements obtained with STE and STQ correlated positively with the PP (r=0.566-0.882, all P < .001). The areas under ROC curves for L-STE, S-STE, L-STQ, and S-STQ values were 0.931 (95% confidence interval [CI], 0.847-1.000), 0.982 (95% CI, 0.956-1.000), 0.796 (95% CI, 0.680-0.912), and 0.925 (95% CI, 0.858-0.993), respectively, for PP ≥5 mmHg; 0.937 (95% CI, 0.865-1.000), 0.938 (95% CI, 0.864-1.000), 0.967 (95% CI, 0.923-1.000), and 0.960 (95% CI, 0.897-1.000), respectively, for PP ≥10 mmHg; and 0.954 (95% CI, 0.897-1.000), 0.790 (95% CI, 0.652-0.928), 0.808 (95% CI, 0.680-0.935), and 0.740 (95% CI, 0.595-0.885), respectively, for PP ≥12 mmHg. STE and STQ are reliable noninvasive tools for the assessment of PHT severity, especially for PP ≥10 mmHg, in a rat model of CCl4 -induced cirrhotic PHT.

Two-dimensional shear wave elastography utilized in patients with ascites: a more reliable method than transient elastography for noninvasively detecting the liver stiffness-an original study with 170 patients.

Two dimensional shear wave elastography (2D-SWE) is an ultrasound elastography technique based on shear waves implemented on a diagnostic ultrasound system. Transient elastography (TE) uses an ultrasound displacement M-mode and A-mode image produced by the system. So, TE mechanically induced impulse at tissue surface and difficultly across water. This paper compared the reliability and reproducibility of 2D-SWE with that of TE in patients with chronic hepatic disease. Comparisons were made in terms of the success rate, reliability, reproducibility, operation time, and influence of operator experience. A total of 170 patients were included in this study. Participants underwent 2D-SWE and TE performed by 2 different operators (a novice and veteran) on the same day. Nonparametric statistical tests were used to compare the technical success rate and reliable measurement rate, and inter-operator reproducibility was evaluated using intra-class correlation coefficients (ICCs). The 2D-SWE technique showed a higher technical success rate than TE. Either 2D-SWE or TE can be utilized in patients with ascites lamella of less than 10 mm or ascites lamella plus skin-capsular distance of less than 25 mm. However, although the reliability rate of liver stiffness measurement with 2D-SWE did not significantly differ between the novice and veteran operators, for TE, there was a significant difference when body mass index (BMI) ≤25 kg/m2. When performed by the novice and veteran operators, 2D-SWE and TE both showed excellent inter-operator agreement, with ICCs of 0.968 and 0.973, respectively. Both 2D-SWE and TE displayed reliable measurement and excellent reproducibility in patients with chronic liver disease, were minimally influenced by operator experience. 2D-SWE may be a more reliable method for clinical application in noninvasive detecting the liver stiffness.

Changes in intraoperative aortic strain as detected by ultrasound elastography in patients following abdominal endovascular aneurysm repair.

Predicting success after endovascular aneurysm repair (EVAR) of abdominal aortic aneurysms (AAAs) relies on measurements of aneurysm sac regression. However, in the absence of regression, morphometric analysis alone is insufficient to reliably predict the successful remodeling of AAAs after EVAR. Biomechanical parameters, such as pressure-normalized principal strain, might provide useful information in the post-EVAR AAA assessment. Our objective was to assess the feasibility of our novel ultrasound elastography (USE) technique to detect changes in the aortic wall principal strain in patients who had undergone EVAR and determine the temporal nature of the biomechanical changes in the aorta. USE images were obtained from patients undergoing elective EVAR intraoperatively, immediately before and after endograft implantation, and at their 30-day follow-up. The maximal mean principal strain ( ) for each scan was assessed using our novel technique, which uses a finite element mesh to track the frame-to-frame displacements of the aortic wall over one cardiac cycle. The in the user-defined aortic wall was then divided by the pulse pressure at the time of the scan to produce a pressure-normalized strain measurement ( /PP), a surrogate for tissue stiffness. Paired t tests were used to compare the pre- and postoperative /PP and the postoperative and 30-day /PP. Patient 30-day sac regression and endoleak data were collected by a review of 30-day follow-up computed tomography scans. USE analysis of the data from 12 patients demonstrated a significant reduction in aortic wall /PP (average, 0.191%± 0.09%/kPa vs 0.087%± 0.04%/kPa; P= .002) immediately after graft implantation, with a nonsignificant change in the /PP (0.091%± 0.04%/kPa vs 0.102%± 0.05%/kPa; P= .47) from postoperatively to 30-day follow-up. This represents an average 46.5% reduction after stent placement, with a nonsignificant 18.1% increase at 30-day follow-up. All the patients showed sac stability, except for two patients who had demonstrated 7.3-mm and 6.8-mm sac regressions. Our analysis has demonstrated that the presented USE technique is a feasible method for detecting significant reductions in aortic /PP intraoperatively after EVAR. We found that patients undergoing EVAR will experience large reductions in the /PP intraoperatively after graft implantation, with stabilization found at their 30-day follow-up. These preliminary data have shown that an intraoperative /PP reduction could be a promising correlate of post-EVAR aneurysm remodeling. Our results have also suggested that endograft design likely plays a large role in determining the aneurysm biomechanical changes immediately after implantation.

High-Frequency Ultrasound Elastography to Assess the Nonlinear Elastic Properties of the Cornea and Ciliary Body.

Mechanical properties of the anterior anatomical structures of the eye, such as the cornea and ciliary body, play a key role in the ocular function and homeostasis. However, measuring the biomechanical properties of the anterior ocular structures, especially deeper structures, such as the ciliary body, remains a challenge due to the lack of high-resolution imaging tools. Herein, we implement a mechanical shaker-based high-frequency ultrasound elastography technique that can track the induced elastic wave propagation to assess the linear and nonlinear elastic properties of anterior ocular structures. The findings of this study advance our understanding of the role of anterior ocular structures in the pathogenesis of different ocular disorders, such as glaucoma.