Ultrasound Elastography: Review of Techniques and Clinical Applications

Clinical practice of the transrectal shear-wave elastography in benign prostatic hyperplasia

OBJECTIVE

To investigate the practical value of the transrectal two-dimensional shear-wave elastography (SWE) in benign prostatic hyperplasia (BPH).

METHODS

Consecutive male participants with and without BPH constituted the BPH and control group respectively were enrolled prospectively between March and December 2022. Transrectal conventional ultrasound and SWE examinations for the prostate were performed on these participants. Data of quantitative stiffness of the transitional zone (TZ) and peripheral zone (PZ) of prostate, volume of prostate (VP) and volume of TZ (VTZ) and prostate specific androgen (PSA), etc., were collected. Linear regression analyses were used to investigate the associations between quantitative stiffness data and other clinical parameters.

RESULTS

There were 200 participants evaluated, including 100 healthy participants and 100 BPH patients. For every one-year increment in age, it was correlated with 0.50 kPa increasement of TZ stiffness. VP and VTZ were correlated with TZ stiffness. Higher TZ stiffness was associated with higher free prostate specific antigen (PSA) and total PSA.

CONCLUSIONS

The prostate is stiffer and larger in BPH group compared to control group. Quantitative stiffness of the TZ was related with age, VP, VTZ and PSA.

3D vector MR elastography applications in small organs

BACKGROUND

Magnetic resonance elastography (MRE) is a rapidly developing medical imaging technique that allows for quantitative assessment of the biomechanical properties of the tissue. MRE is now regarded as the most accurate noninvasive test for detecting and staging liver fibrosis. A two-dimensional (2D MRE) acquisition version is currently deployed at >2000 locations worldwide. 2D MRE allows for the evaluation of the magnitude of the complex shear modulus, also referred to as stiffness. The development of 3D vector MRE has enabled researchers to assess the biomechanical properties of small organs where wave propagation cannot be adequately analyzed with the 2D MRE imaging approach used in the liver. In 3D vector MRE, the shear waves are imaged and processed throughout a 3D volume and processed with an algorithm that accounts for wave propagation in any direction. Additionally, the motion is also imaged in x, y, and z directions at each voxel, allowing for more advanced processing to be applied.

PURPOSE

This review describes the technical principles of 3D vector MRE, surveys its clinical applications in small organs, and discusses potential clinical significance of 3D vector MRE.

CONCLUSION

3D vector MRE is a promising tool for characterizing the biomechanical properties of small organs such as the uterus, pancreas, thyroid, prostate, and salivary glands. However, its potential has not yet been fully explored.

3D Ultrasound Shear Wave Elastography for Musculoskeletal Tissue Assessment Under Compressive Load: A Feasibility Study

Given its real-time capability to quantify mechanical tissue properties, ultrasound shear wave elastography holds significant promise in clinical musculoskeletal imaging. However, existing shear wave elastography methods fall short in enabling full-limb analysis of 3D anatomical structures under diverse loading conditions, and may introduce measurement bias due to sonographer-applied force on the transducer. These limitations pose numerous challenges, particularly for 3D computational biomechanical tissue modeling in areas like prosthetic socket design. In this feasibility study, a clinical linear ultrasound transducer system with integrated shear wave elastography capabilities was utilized to scan both a calibrated phantom and human limbs in a water tank imaging setup. By conducting 2D and 3D scans under varying compressive loads, this study demonstrates the feasibility of volumetric ultrasound shear wave elastography of human limbs. Our preliminary results showcase a potential method for evaluating 3D spatially varying tissue properties, offering future extensions to computational biomechanical modeling of tissue for various clinical scenarios.

Combined gray scale ultrasonography and doppler diagnostic tools with strain elastography in assessment of inflammatory bowel disease in pediatrics patients

BACKGROUND

Intestinal changes in inflammatory bowel disease (IBD) are frequently observed on ultrasound. Invasive diagnostic procedures are often employed to differentiate between the main types of IBD and detect complications. Ultrasound Strain Elastography (SE) is a promising non-invasive technique for detecting intestinal changes and assessing inflammatory activity in pediatric IBD.

AIM OF THE STUDY

This research aims to evaluate the diagnostic performance of conventional ultrasound, color Doppler, and SE in assessing inflammatory bowel disease in pediatric patients, both separately and in combination as additional tools.

PATIENTS AND METHODS

Forty patients (18 females and 22 males) initially diagnosed with IBD through clinical and endoscopic biopsy, along with 20 healthy controls, underwent conventional ultrasound, color Doppler, SE, and laboratory evaluations, including CBC, ESR, CRP, Fecal calprotectin, and assessment of IBD activity using PIBDAI.

RESULTS

Conventional ultrasound, color Doppler, and SE significantly contributed to detecting disease activity and intestinal changes in IBD (p < 0.001; 95% CI 0.79-1.100), demonstrating better sensitivity in combination compared to each method individually. The combined approach showed 100% sensitivity, 84% specificity, 78.6% precision (Positive Predictive Value), 100% Negative Predictive Value, and an overall accuracy of 92%.

CONCLUSION

The addition of Color Doppler and SE parameters to grayscale ultrasound provides diagnostic value comparable to endoscopy, histopathology, and laboratory markers in detecting inflammatory activity and intestinal changes in IBD. This combined approach can help avoid unnecessary invasive techniques for follow-up.

Role of artificial intelligence in Crohn's disease intestinal strictures and fibrosis

Crohn's disease (CD) is a chronic inflammatory disorder of the gastrointestinal tract. Intestinal fibrosis or stricture is one of the most prevalent complications in CD with a high recurrence rate. Manual examination of intestinal fibrosis or stricture by physicians may be biased or inefficient. A rapid development of artificial intelligence (AI) technique in recent years facilitates the detection of existing or possible intestinal fibrosis and stricture in CD through various modalities, including endoscopy, imaging examination, and serological biomarkers. We reviewed the articles on AI application in diagnosing intestinal fibrosis and stricture in CD during the past decade and categorized them into three aspects based on the detection methods, and found that AI helps accurate and expedient identification and prediction of intestinal fibrosis and stenosis in CD.

Shear Wave Elastography of the Skin following Radial Forearm Free Flap Surgery in Transgender Patients: Observational Study

Background: Ultrasound shear wave elastography (SWE) noninvasively measures the stiffness of tissue by producing and measuring tissue deformation. Scar formation, a crucial aspect of wound healing, can lead to functional and aesthetic complications when pathological. While SWE has shown promise in dermatological evaluations, its role in surgical scar assessment remains underestimated. Our study aims to investigate SWE in evaluating surgical scars at the donor site after forearm free flap surgery in transgender patients. Methods: After radial forearm free flap harvesting, the donor site was grafted with a split-thickness skin graft with or without interposition of Matriderm. Eleven patients were evaluated more than one year after surgery, using SWE alongside scar characteristics, sensory outcomes, and patient satisfaction surveys. Results: Our study revealed no significant difference in stiffness (p > 0.15), pigmentation (p = 0.32), or erythema (p = 0.06) between operated and non-operated sides. The interposition of Matriderm did not influence the stiffness. Patients significantly (p < 0.0001) reported a loss of discrimination. Patients' subjective scar evaluation appeared in line with our quantitative and objective results. Conclusions: This study contributes to the evolving understanding of SWE's role in scar assessment, highlighting its feasibility in evaluating surgical scars. However, continued research efforts are necessary to establish SWE as a reliable and objective method for surgical scar evaluation and management.

Clinical Diagnostic Value of Shear-Wave Elastography in Detecting Malignant Nipple Retraction

OBJECTIVES

In recent years, the use of shear-wave elastography (SWE) as a diagnostic tool for detecting malignant breast lesions has shown promising results. This study aims to determine the clinical diagnostic value of SWE in detecting malignant nipple retraction.

METHODS

Both US and SWE (Philips EPIQ7 system) were performed for 41 consecutive patients with nipple retraction (56 nipples). The mean, median, and maximum tissue elasticity values (in kilopascals) were determined for each nipple by using SWE. The sensitivity, specificity, and overall accuracy of each measurement was determined by using the surgical pathology results or clinical diagnosis as the gold standard.

RESULTS

Of the 56 retracted nipples, 32 were due to benign lesions, and 24 were due to malignant lesions. No significant differences in dimensions or echo features were found between the benign and malignant groups. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the color Doppler flow imaging (CDFI) pattern were 63.89% (23/36), 95% (19/20), 95.83 (23/24), 59.38 (19/32), and 75% (42/56), respectively; the corresponding values for median elasticity on SWE were 88.46% (23/26), 96.67% (29/30), 95.83 (23/24), 90.63 (29/32), and 92.85 (52/56), respectively.

CONCLUSIONS

The addition of SWE to conventional US could help differentiate benign from malignant lesions associated with nipple retraction.

Shear-wave elastography as a supplementary tool for axillary staging in patients undergoing breast cancer diagnosis

BACKGROUND

Preoperative evaluation of axillary lymph node status is crucial for the selection of both systemic and surgical treatment in early breast cancer. This study assessed the particular role of additional shear wave elastography (SWE) in axillary staging in patients undergoing initial breast cancer diagnostics.

METHODS

One hundred patients undergoing axillary lymph node biopsy due to a sonographically suspicious axillary lymph node were prospectively evaluated with SWE using virtual touch tissue imaging quantification (VTIQ). Mean values of tissue stiffness for axillary tissue and lymph node tissue were measured prior to core-cut biopsy of the lymph node. All lymph nodes were clip-marked during the biopsy. Cut-off values to differentiate between malignant and benign lymph nodes were defined using Youden's index.

RESULTS

Lymph nodes with evidence of malignant tumor cells in the final pathological examination showed a significantly higher velocity as measured by SWE, with a mean velocity of 3.48 ± 1.58 m/s compared to 2.33 ± 0.62 m/s of benign lymph nodes (p < 0.0001). The statistically optimal cutoff to differentiate between malignant and benign lymph nodes was 2.66 m/s with a sensitivity of 69.8% and a specificity of 87.5%.

CONCLUSIONS

Lymph node metastases assessed with SWE showed significantly higher elasticity values compared to benign lymph nodes. Thus, SWE provides an additional useful and quantifiable parameter for the sonographic assessment of suspicious axillary lymph nodes in the context of pre-therapeutic axillary staging in order to differentiate between benign and metastatic processes and support the guidance of definitive biopsy work-up.

CRITICAL RELEVANCE STATEMENT

Shear-wave elastography provides an additional useful and quantifiable parameter for the assessment of suspicious axillary lymph nodes in the context of pre-therapeutic axillary staging in order to differentiate between benign and metastatic processes and support guiding the definitive biopsy work-up.

KEY POINTS

SWE is a quantifiable ultrasound parameter in breast cancer diagnosis. SWE shows a significantly higher velocity in malignant lymph nodes. SWE is useful in improving the sensitivity and specificity of axillary staging.

Post-Chemotherapy Canine Lymphomatous Lymph Node Observations on B-Mode and Strain Elastographic Ultrasound

Canine multicentric lymphoma (CML) is a prevalent hematopoietic neoplasm that initially responds well to treatment but often relapses due to chemotherapy resistance. Evaluation of treatment response is essential for effective management. Ultrasound (US) can differentiate between benign and lymphomatous lymph nodes (LLNs). However, its utility in monitoring LLNs post chemotherapy is limited. This study aimed to compare US parameters of LLNs during the first 3 weeks post treatment and evaluate their diagnostic performance compared with the conventional method for assessing treatment response. This study included 95 LLNs from 15 dogs with CML and 60 normal lymph nodes (NLNs) from 15 healthy dogs. US, including B-mode and elastography, was performed pre-treatment and weekly for 3 weeks post treatment, and compared with the results of NLNs. LLNs were categorized into partial response and stable disease groups using the conventional method. US scores were established by combining B-mode and elastography parameters. The results showed significantly higher values of LLNs in the short-to-long axis ratio, elastographic scales, and blue-to-green color histogram compared with NLNs. Additionally, LLNs at pre-treatment had significantly higher values than LLNs post treatment. US scores significantly differed among the healthy, partial response, and stable disease groups. In conclusion, B-mode US, elastography, and US scores demonstrated changes during chemotherapy consistent with the conventional method and can be used in conjunction with the conventional method to evaluate the treatment response of CML.

The Networking Brain: How Extracellular Matrix, Cellular Networks, and Vasculature Shape the In Vivo Mechanical Properties of the Brain

Mechanically, the brain is characterized by both solid and fluid properties. The resulting unique material behavior fosters proliferation, differentiation, and repair of cellular and vascular networks, and optimally protects them from damaging shear forces. Magnetic resonance elastography (MRE) is a noninvasive imaging technique that maps the mechanical properties of the brain in vivo. MRE studies have shown that abnormal processes such as neuronal degeneration, demyelination, inflammation, and vascular leakage lead to tissue softening. In contrast, neuronal proliferation, cellular network formation, and higher vascular pressure result in brain stiffening. In addition, brain viscosity has been reported to change with normal blood perfusion variability and brain maturation as well as disease conditions such as tumor invasion. In this article, the contributions of the neuronal, glial, extracellular, and vascular networks are discussed to the coarse-grained parameters determined by MRE. This reductionist multi-network model of brain mechanics helps to explain many MRE observations in terms of microanatomical changes and suggests that cerebral viscoelasticity is a suitable imaging marker for brain disease.

Combining Potential Strain Elastography and Radiomics for Diagnosing Breast Lesions in BI-RADS 4: Construction and Validation a Predictive Nomogram

RATIONALE AND OBJECTIVES

To develop a nomogram by integrating B-mode ultrasound (US), strain ratio (SR), and radiomics signature (RS) effectively differentiating between benign and malignant lesions in the Breast Imaging Reporting and Data System (BI-RADS) 4.

MATERIALS AND METHODS

We retrospectively recruited 709 consecutive patients who were assigned a BI-RADS 4 and underwent curative resection or biopsy between 2017 and 2022. US images were collected before surgery. A RS was developed through a multistep feature selection and construction process. Histology findings served as the gold standard. Univariate and multivariate regression analysis were employed to analyze the clinical and US characteristics and identify variables for developing a nomogram. The calibration and discrimination of the nomogram were conducted to evaluate its performance.

RESULTS

The study included a total of 709 patients, with 497 in the training set and 212 in the validation set. In the training set, the B-mode US had an AUC of 0.84 (95% confidence interval [CI], 0.80, 0.87). The SR demonstrated an AUC of 0.78 (95% CI, 0.74, 0.82), while the RS showed an AUC of 0.85 (95% CI, 0.81, 0.88). Notably, the nomogram exhibited superior performance compared to the conventional US, SR, and RS (AUC=0.93, both p < 0.05, as per the Delong test). The clinical usefulness of the nomogram was favorable.

CONCLUSION

The calibrated nomogram can be specifically designed to predict the malignancy of breast lesions in the BI-RADS 4 category.

Noninvasive liver fibrosis markers are independently associated with carotid atherosclerosis risk in patients with nonalcoholic fatty liver disease

OBJECTIVE

Nonalcoholic fatty liver disease (NAFLD) is considered an independent risk factor for cardiovascular disease (CVD). The overall morbidity and mortality of CVD increase with higher fibrosis stage in NAFLD. Carotid atherosclerosis (CAS) is an important predictor of cardiovascular events. However, the relationship between liver fibrosis degree and the risk of CAS in NAFLD patients remains uncertain. We aimed to investigate the relationship between noninvasive liver fibrosis markers and CAS risk in patients with NAFLD.

MATERIALS AND METHODS

This study included 3,302 participants with NAFLD. Participants were divided into a CAS group and a non-CAS group based on carotid artery ultrasound results. They were then stratified into quartiles using various noninvasive liver fibrosis markers (fibrosis-4 (FIB-4), modified FIB-4 (mFIB-4), aminotransferase to platelet ratio index (APRI), aminotransferase to alanine aminotransferase ratio (AAR), AAR-to-platelet ratio index (AARPRI), and Forns index) to assess the associations between these markers and the risk of CAS.

RESULTS

In the NAFLD population, individuals with CAS exhibited elevated levels of blood pressure, glucose, lipids, and noninvasive liver fibrosis markers (p < 0.001). The higher quartiles of noninvasive liver fibrosis markers, including FIB-4, mFIB-4, AAR, AARPRI, and Forns index, were significantly associated with increased risks of CAS, even after adjusting for multiple CVD risk factors.

CONCLUSIONS

In individuals with NAFLD, increased noninvasive liver fibrosis markers were independently associated with elevated CAS risk, which may be beneficial in assessing the risk of CVD in individuals with NAFLD.

In silico analysis reveals the prospects of renal anisotropy in improving chronic kidney disease detection using ultrasound shear wave elastography

Renal anisotropy is a complex property of the kidney and often poses a challenge in obtaining consistent measurements when using shear wave elastography to detect chronic kidney disease. To circumvent the challenge posed by renal anisotropy in clinical settings, a dimensionless biomarker termed the 'anisotropic ratio' was introduced to establish a correlation between changes in degree of renal anisotropy and progression of chronic kidney disease through an in silico perspective. To achieve this, an efficient model reduction approach was developed to model the anisotropic property of kidneys. Good agreement between the numerical and experimental data were obtained, as percentage errors of less than 5.5% were reported when compared against experimental phantom measurement from the literature. To demonstrate the applicability of the model to clinical measurements, the anisotropic ratio of sheep kidneys was quantified, with both numerical and derived experimental results reporting a value of .667. Analysis of the anisotropic ratio with progression of chronic kidney disease demonstrated that patients with normal kidneys would have a lower anisotropic ratio of .872 as opposed to patients suffering from renal impairment, in which the anisotropic ratio may increase to .904, as determined from this study. The findings demonstrate the potential of the anisotropic ratio in improving the detection of chronic kidney disease using shear wave elastography.

The Relationship between Placental Shear Wave Elastography and Fetal Weight-A Prospective Study

Background/Objectives: The utility of shear wave elastography (SWE) as an adjunct to ultrasound biometry and Doppler velocimetry for the examination of placental dysfunction and suboptimal fetal growth is unclear. To date, limited data exist correlating the mechanical properties of placentae with fetal growth. This study aimed to investigate the relationship between placental shear wave velocity (SWV) and ultrasound estimated fetal weight (EFW), and to ascertain if placental SWV is a suitable proxy measure of placental function in the surveillance of small-for-gestational-age (SGA) pregnancies. Methods: This prospective, observational cohort study compared the difference in placental SWV between SGA and appropriate-for-gestational-age (AGA) pregnancies. There were 221 women with singleton pregnancies in the study cohort-136 (61.5%) AGA and 85 (38.5%) SGA. Fetal biometry, Doppler velocimetry, the deepest vertical pocket of amniotic fluid, and mean SWV were measured at 2-4-weekly intervals from recruitment to birth. Results: There was no difference in mean placental SWV in SGA pregnancies compared to AGA pregnancies, nor was there any relationship to EFW. Conclusions: Although other studies have shown some correlation between increased placental stiffness and SGA pregnancies, our investigation did not support this. The mechanical properties of placental tissue in SGA pregnancies do not result in placental SWVs that are apparently different from those of AGA controls. As this study did not differentiate between constitutionally or pathologically small fetuses, further studies in growth-restricted cohorts would be of benefit.

Ultrasonic Imaging of Deeper Bone Defect Using Virtual Source Synthetic Aperture with Phased Shift Migration: A Phantom Study

Ultrasound imaging for bone is a difficult task in the field of medical ultrasound. Compared with other phase array techniques, the synthetic aperture (SA) has a better lateral resolution but a limited imaging depth due to the limited ultrasonic energy emitted by the single emitter in each transmission. In contrast, the virtual source (VS) synthetic aperture allows a simultaneous multi-element emission and could provide a higher ultrasonic incident energy in each transmission. Therefore, the VS might achieve a high imaging quality at a deeper depth for bone imaging than the traditional SA. In this study, we proposed the virtual source phase shift migration (VS-PSM) method to achieve ultrasonic imaging of the deeper bone defect featured in the multilayer structure. The proposed VS-PSM method was validated using standard soft tissue phantom and printed bone phantom with artificial defects. The image quality was evaluated in terms of contrast-to-noise ratios (CNR) and amplitudes of scatters and defects at different imaging depths. The results showed that the VS-PSM method could achieve a high imaging quality of the soft tissues with a significant improvement in the scattering amplitude and without a significant sacrifice of the lateral and axial resolution. The PSM was superior to the DAS in suppressing the background noise in the images. Compared with the traditional SA-PSM, the VS-PSM method could image deeper bone defects at different ultrasonic frequencies, with an average improvement of 50% in CNR. In conclusion, this study demonstrated that the proposed VS-PSM method could image deeper bone defects and might help the diagnosis of bone disease using ultrasonic imaging.

Beyond stiffness: deciphering the role of viscoelasticity in cancer evolution and treatment response

There is increasing evidence that cancer progression is linked to tissue viscoelasticity, which challenges the commonly accepted notion that stiffness is the main mechanical hallmark of cancer. However, this new insight has not reached widespread clinical use, as most clinical trials focus on the application of tissue elasticity and stiffness in diagnostic, therapeutic, and surgical planning. Therefore, there is a need to advance the fundamental understanding of the effect of viscoelasticity on cancer progression, to develop novel mechanical biomarkers of clinical significance. Tissue viscoelasticity is largely determined by the extracellular matrix (ECM), which can be simulatedin vitrousing hydrogel-based platforms. Since the mechanical properties of hydrogels can be easily adjusted by changing parameters such as molecular weight and crosslinking type, they provide a platform to systematically study the relationship between ECM viscoelasticity and cancer progression. This review begins with an overview of cancer viscoelasticity, describing how tumor cells interact with biophysical signals in their environment, how they contribute to tumor viscoelasticity, and how this translates into cancer progression. Next, an overview of clinical trials focused on measuring biomechanical properties of tumors is presented, highlighting the biomechanical properties utilized for cancer diagnosis and monitoring. Finally, this review examines the use of biofabricated tumor models for studying the impact of ECM viscoelasticity on cancer behavior and progression and it explores potential avenues for future research on the production of more sophisticated and biomimetic tumor models, as well as their mechanical evaluation.

Reliability and robustness of a novel preclinical torsional wave-based device for stiffness evaluation

In this work, we present a novel preclinical device utilizing Torsional Wave Elastography (TWE). It comprises a rotational actuator element and a piezoceramic receiver ring circumferentially aligned. Both allow the transmission of shear waves that interact with the tissue before being received. Our main objective is to demonstrate and characterize the reliability, robustness, and accuracy of the device for characterizing the stiffness of elastic materials and soft tissues. Experimental tests are performed using two sets of tissue mimicking phantoms. The first set consists of calibrated CIRS gels with known stiffness value, while the second test uses non-calibrated manufactured phantoms. Our experimental observations show that the proposed device consistently and repeatably quantifies the stiffness of elastic materials with high accuracy. Furthermore, comparison with established techniques demonstrates a very high correlation (> 95%), supporting the potential medical application of this technology. The results obtained pave the way for a cross-sectional study aiming to investigate the correlation between gestational age and cervical elastic properties during pregnancy.

DFA-UNet: dual-stream feature-fusion attention U-Net for lymph node segmentation in lung cancer diagnosis

In bronchial ultrasound elastography, accurately segmenting mediastinal lymph nodes is of great significance for diagnosing whether lung cancer has metastasized. However, due to the ill-defined margin of ultrasound images and the complexity of lymph node structure, accurate segmentation of fine contours is still challenging. Therefore, we propose a dual-stream feature-fusion attention U-Net (DFA-UNet). Firstly, a dual-stream encoder (DSE) is designed by combining ConvNext with a lightweight vision transformer (ViT) to extract the local information and global information of images; Secondly, we propose a hybrid attention module (HAM) at the bottleneck, which incorporates spatial and channel attention to optimize the features transmission process by optimizing high-dimensional features at the bottom of the network. Finally, the feature-enhanced residual decoder (FRD) is developed to improve the fusion of features obtained from the encoder and decoder, ensuring a more comprehensive integration. Extensive experiments on the ultrasound elasticity image dataset show the superiority of our DFA-UNet over 9 state-of-the-art image segmentation models. Additionally, visual analysis, ablation studies, and generalization assessments highlight the significant enhancement effects of DFA-UNet. Comprehensive experiments confirm the excellent segmentation effectiveness of the DFA-UNet combined attention mechanism for ultrasound images, underscoring its important significance for future research on medical images.

Evolution of Natural Myocardial Shear Wave Behavior in Young Hearts: Determinant Factors and Reproducibility Analysis

BACKGROUND

Myocardial diastolic function assessment in children by conventional echocardiography is challenging. High-frame rate echocardiography facilitates the assessment of myocardial stiffness, a key factor in diastolic function, by measuring the propagation velocities of myocardial shear waves (SWs). However, normal values of natural SWs in children are currently lacking. The aim of this study was to explore the behavior of natural SWs among children and adolescents, their reproducibility, and the factors affecting SW velocities from childhood into adulthood.

METHODS

One hundred six healthy children (2-18 years of age) and 62 adults (19-80 years of age) were recruited. High-frame rate images were acquired using a modified commercial scanner. An anatomic M-mode line was drawn along the ventricular septum, and propagation velocities of natural SWs after mitral valve closure were measured in the tissue acceleration-coded M-mode display.

RESULTS

Throughout life, SW velocities after mitral valve closure exhibited pronounced age dependency (r = 0.73; P < .001). Among the pediatric population, SW velocities correlated significantly with measures of cardiac geometry (septal thickness and left ventricular end-diastolic dimension), local hemodynamics (systolic blood pressure), and echocardiographic parameters of systolic and diastolic function (global longitudinal strain, mitral E/e' ratio, isovolumic relaxation time, and mitral deceleration time) (P < .001). In a multivariate analysis including all these factors, the predictors of SW velocities were age, mitral E/e', and global longitudinal strain (r = 0.81).

CONCLUSIONS

Natural myocardial SW velocities in children can be detected and measured. SW velocities showed significant dependence on age and diastolic function. Natural SWs could be a promising additive tool for the assessment of diastolic function among children.

Viscoelasticity in 3D Cell Culture and Regenerative Medicine: Measurement Techniques and Biological Relevance

The field of mechanobiology is gaining prominence due to recent findings that show cells sense and respond to the mechanical properties of their environment through a process called mechanotransduction. The mechanical properties of cells, cell organelles, and the extracellular matrix are understood to be viscoelastic. Various technologies have been researched and developed for measuring the viscoelasticity of biological materials, which may provide insight into both the cellular mechanisms and the biological functions of mechanotransduction. Here, we explain the concept of viscoelasticity and introduce the major techniques that have been used to measure the viscoelasticity of various soft materials in different length- and timescale frames. The topology of the material undergoing testing, the geometry of the probe, the magnitude of the exerted stress, and the resulting deformation should be carefully considered to choose a proper technique for each application. Lastly, we discuss several applications of viscoelasticity in 3D cell culture and tissue models for regenerative medicine, including organoids, organ-on-a-chip systems, engineered tissue constructs, and tunable viscoelastic hydrogels for 3D bioprinting and cell-based therapies.

Association between different obesity patterns and the risk of NAFLD detected by transient elastography: a cross-sectional study

BACKGROUND

Obesity has become a major global public health challenge. Studies examining the associations between different obesity patterns and the risk of nonalcoholic fatty liver disease (NAFLD) are limited. This study aimed to investigate the relationships between different obesity patterns and the risk of NAFLD in a large male population in the US.

METHODS

Data from the 2017 to March 2020 National Health and Nutrition Examination Survey (NHANES) were utilized. Liver steatosis and fibrosis were assessed with FibroScan using the controlled attenuation parameter (CAP) and liver stiffness measurements (LSM). Steatosis was identified with a CAP value of 248 dB/m or higher. Abdominal obesity was defined by a waist circumference (WC) of 102 cm or more for males and 88 cm or more for females. Overweight was defined as a body mass index (BMI) of 24.0 kg/m2 and above. General obesity was identified with a BMI of 28.0 kg/m2 or higher. Obesity status was categorized into four types: overweight, general obesity, abdominal obesity, and combined obesity. Multivariate logistic regression, adjusting for potential confounders, was used to examine the link between obesity patterns and NAFLD risk. Subgroup analysis further explored these associations.

RESULTS

A total of 5,858 adults were included. After multivariable adjustment, compared to the normal weight group, the odds ratios (ORs) [95% confidence interval (CI)] for NAFLD in individuals with overweight, general obesity, abdominal obesity, and combined obesity were 6.90 [3.74-12.70], 2.84 [2.38-3.39], 3.02 [2.02-4.51], and 9.53 [7.79-11.64], respectively. Subgroup analysis showed the effect of different obesity patterns on NAFLD risk was stable among individuals with different clinical conditions. In the fully adjusted multivariate logistic regression model, WC was positively associated with NAFLD risk (OR: 1.48; 95% CI: 1.42-1.53; P < 0.001). WC also demonstrated strong discriminatory ability for NAFLD in Receiver Operating Characteristic (ROC) analysis, achieving an Area Under the Curve (AUC) of 0.802.

CONCLUSIONS

Different patterns of obesity are risk factors for NAFLD. An increase in WC significantly increased NAFLD risk. More attention should be paid to preventing different patterns of obesity among adults.

Usefulness of Body Fat and Visceral Fat Determined by Bioimpedanciometry versus Body Mass Index and Waist Circumference in Predicting Elevated Values of Different Risk Scales for Non-Alcoholic Fatty Liver Disease

BACKGROUND

Obesity constitutes a public health problem worldwide and causes non-alcoholic fatty liver disease (MALFD), the leading cause of liver disease in developed countries, which progresses to liver cirrhosis and liver cancer. MAFLD is associated with obesity and can be evaluated by validated formulas to assess MAFLD risk using different parameters such as the body mass index (BMI) and waist circumference (WC). However, these parameters do not accurately measure body fat. As MAFLD is strongly associated with obesity, we hypothesize that measuring body and visceral fat by electrical bioimpedance is an efficient method to predict the risk of MAFLD. The objective of our work was to demonstrate that electrical bioimpedance is a more efficient method than the BMI or WC to predict an elevated risk of MAFLD.

METHODS

A cross-sectional, descriptive study involving 8590 Spanish workers in the Balearic Islands was carried out. The study's sample of employees was drawn from those who underwent occupational medicine examinations between January 2019 and December 2020. Five MAFLD risk scales were determined for evaluating very high levels of body fat and visceral fat. The determination of body and visceral fat was performed using bioimpedanciometry. Student's t-test was employed to ascertain the mean and standard deviation of quantitative data. The chi-square test was used to find prevalences for qualitative variables, while ROC curves were used to define the cut-off points for body and visceral fat. The calculations included the area under the curve (AUC), the cut-off points along with their Youden index, sensitivity, and specificity. Correlation and concordance between the various scales were determined using Pearson's correlation index and Cohen's kappa, respectively.

RESULTS

As both total body fat and visceral fat increase, the risk of MAFLD increases with a statistically significant result (p < 0.001), presenting a higher risk in men. The areas under the curve (AUC) of the five scales that assess overweight and obesity to determine the occurrence of high values of the different MAFLD risk scales were very high, most of them exceeding 0.9. These AUC values were higher for visceral and body fat than for the BMI or waist circumference. FLD-high presented the best results in men and women with the AUC at around 0.97, both for visceral fat and total body fat, with a high Youden index in all cases (women body fat = 0.830, visceral fat = 0.892; men body fat = 0.780, visceral fat = 0.881).

CONCLUSIONS

In our study, all the overweight and obesity scales show a very good association with the scales assessing the risk of MAFLD. These values are higher for visceral and body fat than for waist circumference and the BMI. Both visceral fat and body fat are better associated than the BMI and waist circumference with MAFLD risk scales.

Radiology of fibrosis part III: genitourinary system

Fibrosis is a pathological process involving the abnormal deposition of connective tissue, resulting from improper tissue repair in response to sustained injury caused by hypoxia, infection, or physical damage. It can impact any organ, leading to their dysfunction and eventual failure. Additionally, tissue fibrosis plays an important role in carcinogenesis and the progression of cancer.Early and accurate diagnosis of organ fibrosis, coupled with regular surveillance, is essential for timely disease-modifying interventions, ultimately reducing mortality and enhancing quality of life. While extensive research has already been carried out on the topics of aberrant wound healing and fibrogenesis, we lack a thorough understanding of how their relationship reveals itself through modern imaging techniques.This paper focuses on fibrosis of the genito-urinary system, detailing relevant imaging technologies used for its detection and exploring future directions.

Current evidence for lung ultrasound elastography in the field of pneumology: a systematic review

Background and objectives

Elastography is a technology that has strongly impacted several medical specialties; however, it is not yet applied as part of standard clinical practice in the field of pulmonology. The objective of this systematic review is to analyse the evidence available to date in relation to pleuropulmonary ultrasound elastography, focusing on the three pathologies with the most publications: subpleural consolidations, interstitial lung diseases and pleural effusion.

Methods

Original in vivo studies published up until 12 August 2023 in the Embase, MEDLINE or Web of Science databases were included. The QUADAS-2 tool was applied to analyse bias.

Results

We found 613 records in database search. After duplicates removal, we screened 246 records and finally included 18 papers. The average cohort sample size was 109 patients. The elastography modes most frequently used were strain (22.2%), transient elastography (22.2%), point shear-wave elastography (38.9%) and two-dimensional shear-wave elastography (22.2%). The possibility of a meta-analysis was ruled out because of the heterogeneity of the studies included.

Discussion

The currently available literature indicates that pleuropulmonary ultrasound elastography produces promising and consistent results, although the lack of standardisation in the use of the technique and in the elastography modes employed still impedes its use in daily clinical pneumology practice. The development of a clinical guideline establishing a common nomenclature and standardised techniques for pleuropulmonary elastography will be imperative to generate quality scientific evidence in this field.

Diagnostic value of Achilles tendon shear wave elastography in patients with ankylosing spondylitis: A case-control study

OBJECTIVES

Ankylosing spondylitis (AS) can cause peripheral arthritis, tendinitis, enthesitis, and axial skeletal involvement. This study aims to determine early tendon damage by shear wave elastography (SWE) for the Achilles tendon in AS patients.

METHODS

48 AS patients and 48 asymptomatic individuals were included in the study. Participants were systematically examined with B-mode, power Doppler, and SWE using a high-resolution linear 6-15 MHz probe. Bilateral Achilles tendon stiffness, thickness, and vascularity were evaluated. Measurements were taken from the middle third of the Achilles tendon in the sagittal plane. Difference between the two groups was evaluated with statistical methods. Receiver operating characteristic analysis was performed to test the diagnostic performance of Achilles tendon stiffness. Additionally, the Spearman correlation test examined the relationship between Achilles tendon stiffness and disease duration.

RESULTS

The difference between the two groups regarding Achilles tendon stiffness was statistically significant (p < 0.05). It was observed that Achilles tendon stiffness decreased in the patient group compared with the control group. The diagnostic value of Achilles tendon stiffness measured by SWE was found to be high. A negative correlation was detected between disease duration and tendon stiffness (p < 0.05).

CONCLUSION

In patients diagnosed with AS, deterioration in the Achilles tendon structure was observed, and a significant decrease in tendon stiffness compared with the healthy population. It has been determined that these changes in the Achilles tendon are related to the duration of the disease.

Point-shear wave elastography generated by acoustic radiation force impulse in chronic pancreatitis

BACKGROUND

Transcutaneous point-shear wave elastography (p-SWE) performed using an acoustic radiation force impulse can be used to quantify pancreatic stiffness in chronic pancreatitis (CP). We aimed to evaluate its usefulness to diagnose and monitor CP.

METHODS

175 participants were included in this prospective study including patients with CP (n = 65), liver cirrhosis (LC; n = 60), alcohol abuse (n = 10) and healthy controls (n = 40). Point-shear wave elastography of the pancreas was performed and quantified as median shear wave velocity (SWV). In the same way, p-SWE of the spleen served as a marker of portal hypertension. The M-ANNHEIM Severity score was used as global marker for disease activity in CP.

RESULTS

Compared to healthy controls, pancreatic SWV was significantly elevated in CP (1.38 vs. 0.96 m/s; p < 0.0001, MWU-test). Pancreatic SWV was increased in alcoholic CP but not in hereditary CP. Receiver operating characteristic analysis revealed 1.2 m/s as the optimal cut-off to identify non-heredity-CP subjects (90% specificity; 81% sensitivity; 92% positive predictive value). Pancreatic SWV correlated significantly with the M-ANNHEIM Severity score, severity of CP-typical complications (both p < 0.05, linear regression analysis), morphological changes of the pancreas and need for hospital treatment (both p < 0.05, MWU-test) but not with exocrine or endocrine insufficiency. Pancreatic SWV >1.7 m/s was identified to predict M-ANNHEIM Severity score ≥11 points. Pancreatic SWV was also elevated in LC (1.42 m/s; p < 0.001), correlating with increased splenic SWV.

CONCLUSION

Transcutaneous pancreatic p-SWE represents a bedside, cost-effective and non-invasive tool which adds valuable information to the process of diagnosing and monitoring CP. By portal hypertension, an increased pancreatic SWV must be expected.

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

PURPOSE

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.

METHODS

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 3 months after steroid discontinuation.

RESULTS

Eight patients were treated for INS with a median observation period of 21.9 months (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 40 days (11-55). SWV was significantly lower at relapse than remission (2.40 ± 0.20 m/s vs. 2.14 ± 0.15 m/s, P < 0.01).

CONCLUSIONS

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.

Shear Wave Elastography for Assessment of Changes in Abdominal Soft Tissues after Lipoabdominoplasty

BACKGROUND

The changes in the elasticity of the abdominal skin, subcutaneous tissues and muscles after lipoabdominoplasty are still unknown. The aim of this study was to provide an objective assessment of tissue elasticity after lipoabdominoplasty using ultrasound elastography.

METHODS

A total of 21 female patients (31-41 years old) who underwent lipoabdominoplasty from Oct 2019 to Mar 2022 were included in this retrospective study. The elastography values of the skin, subcutaneous tissues and abdominal muscles were obtained with the ultrasound shear wave elasticity imaging system pre-operation (Pre) and 6 months post-operation (Post) at four different points.

RESULTS

Twenty-one female patients were included. The elasticity of the abdominal skin, subcutaneous tissues, rectus abdominis and external oblique abdominis significantly increased at 6 months post-operation. The improvements in abdominal soft tissue elasticity were not uniform across the examined points.

CONCLUSIONS

Significant changes in the elasticity of the abdominal skin, subcutaneous tissues and muscles were observed after lipoabdominoplasty. Ultrasound elastographic assessment was objective and feasible for evaluating the effect of lipoabdominoplasty on abdominal soft tissue.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Advances in Noninvasive Molecular Imaging Probes for Liver Fibrosis Diagnosis

Liver fibrosis is a wound-healing response to chronic liver injury, which may lead to cirrhosis and cancer. Early-stage fibrosis is reversible, and it is difficult to precisely diagnose with conventional imaging modalities such as magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography, and ultrasound imaging. In contrast, probe-assisted molecular imaging offers a promising noninvasive approach to visualize early fibrosis changes in vivo, thus facilitating early diagnosis and staging liver fibrosis, and even monitoring of the treatment response. Here, the most recent progress in molecular imaging technologies for liver fibrosis is updated. We start by illustrating pathogenesis for liver fibrosis, which includes capillarization of liver sinusoidal endothelial cells, cellular and molecular processes involved in inflammation and fibrogenesis, as well as processes of collagen synthesis, oxidation, and cross-linking. Furthermore, the biological targets used in molecular imaging of liver fibrosis are summarized, which are composed of receptors on hepatic stellate cells, macrophages, and even liver collagen. Notably, the focus is on insights into the advances in imaging modalities developed for liver fibrosis diagnosis and the update in the corresponding contrast agents. In addition, challenges and opportunities for future research and clinical translation of the molecular imaging modalities and the contrast agents are pointed out. We hope that this review would serve as a guide for scientists and students who are interested in liver fibrosis imaging and treatment, and as well expedite the translation of molecular imaging technologies from bench to bedside.

Liver stiffness is associated with right heart dysfunction, cardiohepatic syndrome, and prognosis in pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) can lead to congestive hepatopathy, known as cardiohepatic syndrome (CHS). Hepatic congestion is associated with increased liver stiffness, which can be quantified using shear wave elastography. We aimed to investigate whether hepatic shear wave elastography detects patients at risk in the early stages of PH.

METHODS

Sixty-three prospectively enrolled patients undergoing right heart catheterization (52 diagnosed with PH and 11 with invasive exclusion of PH) and 52 healthy volunteers underwent assessments including echocardiography and hepatic shear wave elastography. CHS was defined as increased levels of ≥2 of the following: gamma-glutamyl transferase, alkaline phosphatase, and bilirubin. Liver stiffness was defined as normal (≤5.0 kPa) or high (>5.0 kPa).

RESULTS

Compared with normal liver stiffness, high liver stiffness was associated with impaired right ventricular (RV) and right atrial (RA) function (median [interquartile range] RV ejection fraction: 54 [49; 57]% vs 45 [34; 51]%, p < 0.001; RA reservoir strain: 49 [41; 54]% vs 33 [22; 41]%, p < 0.001), more severe tricuspid insufficiency (p < 0.001), and higher prevalence of hepatovenous backflow (2% vs 29%, p < 0.001) and CHS (2% vs 10%, p = 0.038). In the patient subgroup with precapillary PH (n = 48), CHS and high liver stiffness were associated with increased European Society of Cardiology/European Respiratory Society 2022 risk scores (p = 0.003).

CONCLUSIONS

Shear wave liver elastography yields important information regarding right heart function and may complement risk assessment in patients with (suspected) PH.

Collagen in hepatocellular carcinoma: A novel biomarker and therapeutic target

HCC is globally recognized as a major health threat. Despite significant progress in the development of treatment strategies for liver cancer, recurrence, metastasis, and drug resistance remain key factors leading to a poor prognosis for the majority of liver cancer patients. Thus, there is an urgent need to develop effective biomarkers and therapeutic targets for HCC. Collagen, the most abundant and diverse protein in the tumor microenvironment, is highly expressed in various solid tumors and plays a crucial role in the initiation and progression of tumors. Recent studies have shown that abnormal expression of collagen in the tumor microenvironment is closely related to the occurrence, development, invasion, metastasis, drug resistance, and treatment of liver cancer, making it a potential therapeutic target and a possible diagnostic and prognostic biomarker for HCC. This article provides a comprehensive review of the structure, classification, and origin of collagen, as well as its role in the progression and treatment of HCC and its potential clinical value, offering new insights into the diagnosis, treatment, and prognosis assessment of liver cancer.

Learning-based distortion correction enables proximal-scanning endoscopic OCT elastography

Proximal rotary scanning is predominantly used in the clinical practice of endoscopic and intravascular OCT, mainly because of the much lower manufacturing cost of the probe compared to distal scanning. However, proximal scanning causes severe beam stability issues (also known as non-uniform rotational distortion, NURD), which hinders the extension of its applications to functional imaging, such as OCT elastography (OCE). In this work, we demonstrate the abilities of learning-based NURD correction methods to enable the imaging stability required for intensity-based OCE. Compared with the previous learning-based NURD correction methods that use pseudo distortion vectors for model training, we propose a method to extract real distortion vectors from a specific endoscopic OCT system, and validate its superiority in accuracy under both convolutional-neural-network- and transformer-based learning architectures. We further verify its effectiveness in elastography calculations (digital image correlation and optical flow) and the advantages of our method over other NURD correction methods. Using the air pressure of a balloon catheter as a mechanical stimulus, our proximal-scanning endoscopic OCE could effectively differentiate between areas of varying stiffness of atherosclerotic vascular phantoms. Compared with the existing endoscopic OCE methods that measure only in the radial direction, our method could achieve 2D displacement/strain distribution in both radial and circumferential directions.

Flexible Ultrasonic Transducers for Wearable Biomedical Applications: A Review on Advanced Materials, Structural Designs, and Future Prospects

Due to the rapid developments in materials science and fabrication techniques, wearable devices have recently received increased attention for biomedical applications, particularly in medical ultrasound (US) imaging, sensing, and therapy. US is ubiquitous in biomedical applications because of its noninvasive nature, nonionic radiating, high precision, and real-time capabilities. While conventional US transducers are rigid and bulky, flexible transducers can be conformed to curved body areas for continuous sensing without restricting tissue movement or transducer shifting. This article comprehensively reviews the application of flexible US transducers in the field of biomedical imaging, sensing, and therapy. First, we review the background of flexible US transducers. Following that, we discuss advanced materials and fabrication techniques for flexible US transducers and their enabling technology status. Finally, we highlight and summarize some promising preliminary data with recent applications of flexible US transducers in biomedical imaging, sensing, and therapy. We also provide technical barriers, challenges, and future perspectives for further research and development.

Shear Wave Elastography in Breast Cancer: Unveiling Correlations With Histopathological Grades and Subtypes

Objective This study explores the correlation between shear wave elastography (SWE) features and histopathological grades and subtypes in breast cancer, aiming to enhance diagnostic accuracy and personalized treatment strategies. Methods The study retrospectively analyzed 59 consecutive women with breast cancer who underwent breast ultrasound with SWE. SWE parameters and histopathologic information, including histological type and grade, were recorded. Qualitative and quantitative SWE findings were analyzed, and B-mode findings were evaluated. Sociodemographic and clinical factors and B-mode findings were assessed as predictors of elastography stiffness using logistic regression analysis. Results Of the 59 participants diagnosed with breast cancer, invasive ductal carcinoma of no special type (IDC-NST) was predominantly found in 50 (84.7%) cases, followed by invasive medullary carcinoma in 5 (8.5%) cases. The majority of participants belonged to the 50-59 age group, comprising 19 (32.2%) patients. Histopathological grading revealed grade II tumors in 27 (45.8%) cases and grade III tumors in 24 (40.7%) cases. Notably, grade III tumors exhibited higher tissue stiffness compared to grade II tumors. Out of 36 stiff lesions, 30 (83.3%%) were IDC-NST while 3 (8.3%) were invasive medullary carcinoma. A significant association was observed between higher histopathological grade (grade III) and increased tissue stiffness (p < 0.05). Furthermore, among participants with stiff lesions, 21 (58.3%) exhibited color defects while 4 (23.5%) cases with soft lesions also displayed color defects Conclusion The correlation between SWE findings and histopathological grades and subtypes underscores the potential of SWE as a valuable tool for predicting tumor aggressiveness and characterizing specific subtypes. SWE enhances diagnostic accuracy and complements traditional imaging modalities, holding promise for personalized treatment strategies.

Nomogram for predicting the risk of central lymph node metastasis in papillary thyroid microcarcinoma: a combination of sonographic findings and clinical factors

Background

A considerable controversy over performing thyroidectomy and central lymph node dissection in patients with papillary thyroid microcarcinoma (PTMC) remained. However, accurate prediction of central lymph node metastasis (CLNM) is crucial for surgical extent and proper management. The aim of this study was to develop and validate a practical nomogram for predicting CLNM in patients with PTMC.

Methods

A total of 1,029 patients with PTMC who underwent thyroidectomy and central lymph node dissection at Tangdu Hospital (the Second Affiliated Hospital of Air Force Medical University) and Xijing Hospital (the First Affiliated Hospital of Air Force Medical University) were selected. Seven hundred and nine patients were assigned to the training set and 320 patients to the validation set. Data encompassing demographic characteristics, ultrasonography results, and biochemical indicators were obtained. Stepwise backward selection and multiple logistic regression were used to screen the variables and establish the nomogram. Concordance index (C-index), receiver operating characteristic (ROC) curve analysis, and decision curve analysis (DCA) were employed to evaluate the nomogram's distinguishability, accuracy, and clinical utility.

Results

Young age, multifocality, bigger tumor, presence of microcalcification, aspect ratio (height divided by width) ≥1, loss of fatty hilum, high free thyroxine (FT4), and lower anti-thyroid peroxidase antibody (TPOAb) were significantly associated with CLNM. The nomogram showed strong predictive capacity, with a C-index and accuracy of 0.784 and 0.713 in the training set and 0.779 and 0.703 in the external validation set, respectively. DCA indicated that the nomogram demonstrated strong clinical applicability.

Conclusions

We established a reliable, cost-effective, reproducible, and noninvasive nomogram for predicting CLNM in patients with PTMC. This tool could be a valuable guidance for deciding on management in PTMC.

Inspiring a convergent engineering approach to measure and model the tissue microenvironment

Understanding the molecular and physical complexity of the tissue microenvironment (TiME) in the context of its spatiotemporal organization has remained an enduring challenge. Recent advances in engineering and data science are now promising the ability to study the structure, functions, and dynamics of the TiME in unprecedented detail; however, many advances still occur in silos that rarely integrate information to study the TiME in its full detail. This review provides an integrative overview of the engineering principles underlying chemical, optical, electrical, mechanical, and computational science to probe, sense, model, and fabricate the TiME. In individual sections, we first summarize the underlying principles, capabilities, and scope of emerging technologies, the breakthrough discoveries enabled by each technology and recent, promising innovations. We provide perspectives on the potential of these advances in answering critical questions about the TiME and its role in various disease and developmental processes. Finally, we present an integrative view that appreciates the major scientific and educational aspects in the study of the TiME.

Development and Characterization of Hemoglobin Microbubbles for Acoustic Blood Oxygen Level Dependent Imaging

Oxygen levels in tissues and organs are crucial for their normal functioning, and approaches to monitor them non-invasively have wide biological and clinical applications. In this study, we developed a method of acoustically detecting oxygenation using contrast-enhanced ultrasound (CEUS) imaging. Our approach involved the use of specially designed hemoglobin-based microbubbles (HbMBs) that reversibly bind to oxygen and alter the state-dependent acoustic response. We confirmed that the bioactivity of hemoglobin remained intact after the microbubble shell was formed, and we did not observe any significant loss of heme. We conducted passive cavitation detection (PCD) experiments to confirm whether the acoustic properties of HbMBs vary based on the level of oxygen present. The experiments involved driving the HbMBs with a 1.1 MHz focused ultrasound transducer. Through the PCD data collected, we observed significant differences in the subharmonic and harmonic responses of the HbMBs when exposed to an oxygen-rich environment versus an oxygen-depleted one. We used a programmable ultrasound system to capture high-frame rate B mode videos of HbMBs in both oxy and deoxy conditions at the same time in a two-chambered flow phantom and observed that the mean pixel intensity of deoxygenated HbMB was greater than in the oxygenated state using B-mode imaging. Finally, we demonstrated that HbMBs can circulate in vivo and are detectable by a clinical ultrasound scanner. To summarize, our results indicate that CEUS imaging with HbMB has the potential to detect changes in tissue oxygenation and could be a valuable tool for clinical purposes in monitoring regional blood oxygen levels.

Effectiveness of two-dimensional shear-wave sonoelastography in the diagnosis and follow-up of infantile hypertrophic pyloric stenosis

INTRODUCTION

We sought to determine the effectiveness and utility of two-dimensional shear-wave sonoelastography (2D-SW-SE) in the diagnosis and postoperative follow-up of infantile hypertrophic pyloric stenosis (IHPS).

MATERIALS AND METHODS

Twenty-three infants were included in the study, 13 in the IHPS group and 10 in the control group (CG). Preoperative B-mode ultrasonography measurements (longitudinal length and single-wall thickness of the pylorus) and 2D-SW-SE measurements (pylorus tissue stiffness and shear-wave propagation speed) were compared between the groups. The infants with IHPS then underwent Ramstedt pyloromyotomy and were invited for follow-ups on the tenth day and the first, third, and sixth months postoperatively. Measurements taken at the follow-ups were compared with the preoperative values.

RESULTS

No differences were found between the groups regarding age, gender, body weight, or week of birth. The pyloric lengths in the IHPS group were longer than in the CG (p < 0.001), and the single-wall thicknesses were thicker (p < 0.001). The pylorus in the IHPS group was four times stiffer than in the CG (27.4 kPa versus 7.66 kPa), and the shear-wave propagation speed in the tissue was higher (1.34 m/s versus 2.69 m/s; p < 0.001). Both values decreased over time in the IHPS group and were normal by the third postoperative month.

CONCLUSIONS

2D-SW-SE can be used as an assistive imaging tool alongside B-mode ultrasound for diagnosing IHPS. It can also be used to identify inadequate surgery by detecting whether the pyloric tissue has softened at follow-up.

Intraoral Ultrasonography for the Exploration of Periodontal Tissues: A Technological Leap for Oral Diagnosis

INTRODUCTION

Periodontal disease is an infectious syndrome presenting inflammatory aspects. Radiographic evaluation is an essential complement to clinical assessment but has limitations such as the impossibility of assessing tissue inflammation. It seems essential to consider new exploration methods in clinical practice. Ultrasound of periodontal tissues could make it possible to visualize periodontal structures and detect periodontal diseases (periodontal pocket measurement and the presence of intra-tissue inflammation). Clinical Innovation Report: An ultrasound probe has been specially developed to explore periodontal tissues. The objective of this clinical innovation report is to present this device and expose its potential.

DISCUSSION

Various immediate advantages favor using ultrasound: no pain, no bleeding, faster execution time, and an image recording that can be replayed without having to probe the patient again. Ultrasound measurements of pocket depth appear to be as reliable and reproducible as those obtained by manual probing, as do tissue thickness measurements and the detection of intra-tissue inflammation.

CONCLUSIONS

Ultrasound seems to have a broad spectrum of indications. Given the major advances offered by ultrasound imaging as a complementary aid to diagnosis, additional studies are necessary to validate these elements and clarify the potential field of application of ultrasound imaging in dentistry.

Clinical experience with shear wave elastography (SWE) for assessing healthy uterus in a transabdominal approach

Aim of the study was to evaluate the diagnostic performance and feasibility of transabdominal ultrasound shear wave elastography (SWE) in assessing sonoelastographic features of the uterus. Twenty-seven premenopausal women were enrolled between 2021 and 2022. Transabdominal SWE measured myometrial stiffness in various uterine segments. Additionally, tissue stiffness of the quadriceps femoris muscle and autochthonous back muscle was measured. Statistical analysis employed non-parametric tests, t test, and a robust mixed linear model. Stiffness values of the uterus and the two investigated muscle types exhibited a similar spectrum: 6.38 ± 2.59 kPa (median 5.61 kPa; range 2.76-11.31 kPa) for the uterine myometrium, 7.22 ± 1.24 kPa (6.82 kPa; 5.11-9.39 kPa) for the quadriceps femoris musle, and 7.43 ± 2.73 kPa (7.41 kPa; 3.10-13.73 kPa) for the autochthonous back muscle. A tendency for significant differences in myometrial stiffness was observed concerning the type of labor mode (mean stiffness of 9.17 ± 1.35 kPa after vaginal birth vs. 3.83 ± 1.35 kPa after Caesarian section, p = 0.01). No significant differences in myometrial stiffness were observed concerning age, BMI, previous pregnancies, uterine flexion and menstrual cycle phase. Transabdominal SWE of uterine stiffness seems to be a fast and practicable method in a clinical setting. Uterine stiffness appears to be largely independent of various factors, except for the mode of delivery. However, further studies are needed to validate these results.

The Biomechanics of Musculoskeletal Tissues during Activities of Daily Living: Dynamic Assessment Using Quantitative Transmission-Mode Ultrasound Techniques

The measurement of musculoskeletal tissue properties and loading patterns during physical activity is important for understanding the adaptation mechanisms of tissues such as bone, tendon, and muscle tissues, particularly with injury and repair. Although the properties and loading of these connective tissues have been quantified using direct measurement techniques, these methods are highly invasive and often prevent or interfere with normal activity patterns. Indirect biomechanical methods, such as estimates based on electromyography, ultrasound, and inverse dynamics, are used more widely but are known to yield different parameter values than direct measurements. Through a series of literature searches of electronic databases, including Pubmed, Embase, Web of Science, and IEEE Explore, this paper reviews current methods used for the in vivo measurement of human musculoskeletal tissue and describes the operating principals, application, and emerging research findings gained from the use of quantitative transmission-mode ultrasound measurement techniques to non-invasively characterize human bone, tendon, and muscle properties at rest and during activities of daily living. In contrast to standard ultrasound imaging approaches, these techniques assess the interaction between ultrasound compression waves and connective tissues to provide quantifiable parameters associated with the structure, instantaneous elastic modulus, and density of tissues. By taking advantage of the physical relationship between the axial velocity of ultrasound compression waves and the instantaneous modulus of the propagation material, these techniques can also be used to estimate the in vivo loading environment of relatively superficial soft connective tissues during sports and activities of daily living. This paper highlights key findings from clinical studies in which quantitative transmission-mode ultrasound has been used to measure the properties and loading of bone, tendon, and muscle tissue during common physical activities in healthy and pathological populations.

Ultrasound Shear Wave Elastography Evaluation of the Liver and Implications for Perioperative Medicine

Ultrasound shear wave elastography (SWE) is a non-invasive, low risk technology allowing the assessment of tissue stiffness. Used clinically for nearly two decades to diagnose and stage liver fibrosis and cirrhosis, it has recently been appreciated for its ability to differentiate between more subtle forms of liver dysfunction. In this review, we will discuss the principle of ultrasound shear wave elastography, its traditional utilization in grading liver cirrhosis, as well as its evolving role in identifying more subtle degrees of liver injury. Finally, we will show how this capacity to distinguish nuanced changes may provide an opportunity for its use in perioperative risk stratification.

Sonodynamic and sonomechanical effect on cellular stemness and extracellular physicochemical environment to potentiate chemotherapy

BACKGROUND

Hypoxia-activated prodrug (HAP) is a promising candidate for highly tumor-specific chemotherapy. However, the oxygenation heterogeneity and dense extracellular matrix (ECM) of tumor, as well as the potential resistance to chemotherapy, have severely impeded the resulting overall efficacy of HAP.

RESULTS

A HAP potentiating strategy is proposed based on ultrasound responsive nanodroplets (PTP@PLGA), which is composed of protoporphyrin (PpIX), perfluoropropane (PFP) and a typical HAP, tirapazamine (TPZ). The intense vaporization of PFP upon ultrasound irradiation can magnify the sonomechanical effect, which loosens the ECM to promote the penetration of TPZ into the deep hypoxic region. Meanwhile, the PpIX enabled sonodynamic effect can further reduce the oxygen level, thus activating the TPZ in the relatively normoxic region as well. Surprisingly, abovementioned ultrasound effect also results in the downregulation of the stemness of cancer cells, which is highly associated with drug-refractoriness.

CONCLUSIONS

This work manifests an ideal example of ultrasound-based nanotechnology for potentiating HAP and also reveals the potential acoustic effect of intervening cancer stem-like cells.

Application of strain elastography ultrasound to the endometrium of normal women

BACKGROUND

While there is a scarcity of studies utilizing strain elastography (SE) for the endometrium, commonly used gynecologic ultrasound instruments are equipped with built-in elastography modalities, primarily SE. With the objective of facilitating comprehensive examinations for gynecologic patients on a single ultrasound instrument, we undertook this study. Therefore, our aim was to study the value of SE ultrasonography in the assessment of endometrial elasticity in normal women.

METHODS

Three hundred and twenty normal women were recruited at our hospitals from November 2021 to December 2022. Each volunteer underwent a transvaginal two-dimensional (2D) and SE ultrasound during either the endometrial proliferative or secretory phase. The 2D ultrasound indices obtained included endometrial thickness, echo type (type A, B, and C), and blood flow grading (grades 0, 1, 2, and 3). SE indices obtained included endometrial strain values, myometrial strain values, and endometrial strain ratios. Differences in endometrial ultrasound indices between different menstrual cycles and different age groups were compared.

RESULTS

Comparison of 2D ultrasound parameters revealed that endometrial thickness in the proliferative phase endometrium group was smaller than that in the secretory phase endometrium group, with a statistically significant difference. Additionally, there was a statistically significant difference in endometrial echo types between the two groups, while the disparity in endometrial blood flow grading was not significant. Regarding SE parameters, the median and mean values of endometrial strain ratio in the proliferative phase endometrium group were smaller than those in the secretory phase endometrium group, showing a statistically significant difference. However, there were no significant differences observed between the two groups in endometrial strain and myometrial strain in the fundus. Furthermore, there were no significant differences in any of the endometrial ultrasound indices among the different age groups.

CONCLUSIONS

SE can reflect changes in endometrial stiffness in different menstrual cycles and is an important tool for assessing endometrial softness.

Revisiting the standards of cancer detection and therapy alongside their comparison to modern methods

In accordance with the World Health Organization data, cancer remains at the forefront of fatal diseases. An upward trend in cancer incidence and mortality has been observed globally, emphasizing that efforts in developing detection and treatment methods should continue. The diagnostic path typically begins with learning the medical history of a patient; this is followed by basic blood tests and imaging tests to indicate where cancer may be located to schedule a needle biopsy. Prompt initiation of diagnosis is crucial since delayed cancer detection entails higher costs of treatment and hospitalization. Thus, there is a need for novel cancer detection methods such as liquid biopsy, elastography, synthetic biosensors, fluorescence imaging, and reflectance confocal microscopy. Conventional therapeutic methods, although still common in clinical practice, pose many limitations and are unsatisfactory. Nowadays, there is a dynamic advancement of clinical research and the development of more precise and effective methods such as oncolytic virotherapy, exosome-based therapy, nanotechnology, dendritic cells, chimeric antigen receptors, immune checkpoint inhibitors, natural product-based therapy, tumor-treating fields, and photodynamic therapy. The present paper compares available data on conventional and modern methods of cancer detection and therapy to facilitate an understanding of this rapidly advancing field and its future directions. As evidenced, modern methods are not without drawbacks; there is still a need to develop new detection strategies and therapeutic approaches to improve sensitivity, specificity, safety, and efficacy. Nevertheless, an appropriate route has been taken, as confirmed by the approval of some modern methods by the Food and Drug Administration.

Tissue-Mimicking Material Fabrication and Properties for Multiparametric Ultrasound Phantoms: A Systematic Review

Medical imaging has allowed for significant advancements in the field of ultrasound procedures over the years. However, each imaging modality exhibits distinct limitations that differently affect their accuracy. It is imperative to ensure the quality of each modality to identify and eliminate these limitations. To achieve this, a tissue-mimicking material (TMM) phantom is utilised for validation. This study aims to perform a systematic analysis of tissue-mimicking materials used for creating ultrasound phantoms. We reviewed 234 studies on the use of TMM phantoms in ultrasound that were published from 2013 to 2023 from two research databases. Our focus was on studies that discussed TMMs' properties and fabrication for ultrasound, elastography, and flow phantoms. The screening process led to the selection of 16 out of 234 studies to include in the analysis. The TMM ultrasound phantoms were categorised into three groups based on the solvent used; each group offers a broad range of physical properties. The water-based material most closely aligns with the properties of ultrasound. This study provides important information about the materials used for ultrasound phantoms. We also compared these materials to real human tissues and found that PVA matches most of the human tissues the best.

Photoacoustic method for measuring the elasticity of polydimethylsiloxane at various mixing ratios

Measuring elasticity without physical contact is challenging, as current methods often require deconstruction of the test sample. This study addresses this challenge by proposing and testing a photoacoustic effect-based method for measuring the elasticity of polydimethylsiloxane (PDMS) at various mixing ratios, which may be applied on the wide range of applications such as biomedical and optical fields. A dual-light laser source of the photoacoustic (PA) system is designed, employing cross-correlation signal processing techniques. The platform systems and a mathematical model for performing PDMS elasticity measurements are constructed. During elasticity detection, photoacoustic signal features, influenced by hardness and shapes, are analyzed using cross-correlation calculations and phase difference detection. Results from phantom tests demonstrate the potential of predicting Young's modulus using the cross-correlation method, aligning with the American Society for Testing and Materials (ASTM) standard samples. However, accuracy may be affected by mixed materials and short tubes. Normalization or calibration of signals is suggested for aligning with Young's coefficient.

Magneto-Acoustic Theranostic Approach: Integration of Magnetomotive Ultrasound Shear Wave Elastography and Magnetic Hyperthermia

OBJECTIVES

Although magnetically induced hyperthermia has shown great efficiency in the treatment of solid tumors, it is still a challenge to avoid incomplete ablation or overtreatment. In this study, we applied magnetomotive ultrasound shear wave elastography (MMUS-SWE) as a tool for real-time image guidance and feedback in the magnetic hyperthermia (MH) process. We called this new method as magneto-acoustic theranostic approach (MATA).

METHODS

In MATA, a ferromagnetic particle (fMP) was simultaneously used as a thermoseed for MH and a shear wave source for MMUS-SWE. The fMP was excited by a high-frequency magnetic field to induce the heating effect for MH. Meanwhile, the fMP was stimulated by a pulsed magnetic field to generate shear wave propagation for MMUS-SWE. Thus, the changes in elastic modulus surrounding fMP can be used to estimate the therapy effect of MH.

RESULTS

The phantom and in vitro experiments were conducted to verify the feasibility of MATA, which has good performance in magnetothermal conversion and treatment efficacy feedback. The shear wave speed of the isolated pork liver changed significantly after the MH process, which varied from about 1.36 to 4.85 m/s.

CONCLUSIONS

Preliminary results proved that changes in elastic modulus could be useful to estimate the therapy effect of MH. We expect that MATA, which is the integration of MMUS-SWE and MH, will be a novel theranostic method for clinical translation.