Soft tissue elasticity in total knee arthroplasty: An in vivo quantitative analysis.

BACKGROUND: Soft tissue balance is essential for total knee arthroplasty success. The elastic properties of soft tissues affect knee-joint stability and flexibility. This study proposed a novel methodology for in vivo quantitative analysis of soft tissue elasticity during total knee arthroplasty. In this study, we aimed to (1) establish a mathematical model to depict medial and lateral soft tissue elasticity, (2) report the individual differences and interindividual commonalities in soft tissue elasticity. METHODS: A specifically designed knee tensor was used to evaluate soft tissue elasticity by dynamically applying sequential tensions to medial and lateral compartments while measuring knee joint gaps in both compartments. Measurements were performed on ten knees of six cadavers. Bivariate polynomial regression was used for analysis, and the equivalent elastic coefficient (N/mm) was calculated. FINDINGS: Soft-tissue elasticity showed high individual differences. The equivalent elastic coefficient was larger in the medial compartment than in the lateral compartment, and the equivalent elastic coefficient of the lateral compartment gradually decreased while the medial equivalent elastic coefficient remained constant when the knee was flexed. The lateral gaps increased from 0.1 to 3.9 mm, and the medial gaps increased from 0 to 1.5 mm when the tension increased from 60 to 90 N. The shapes and distributions of the silkworm-like lattices in elasticity and balance evaluations are clinically relevant to knee balance. INTERPRETATION: Soft-tissue balance in total knee arthroplasty is significantly affected by soft-tissue elasticity. An intraoperative quantitative analysis of elasticity helps to tail an individualized balancing target for total knee arthroplasty.

Multiparametric liver assessment in patients successfully treated for hepatitis C: a 4-year follow-up.

BACKGROUND: Hepatitis C virus (HCV) is a major cause of chronic liver disease, in which liver stiffness increases. Liver stiffness measurements (LSM) are therefore essential in diagnosing liver diseases and predicting disease development. The study objective was to perform a comprehensive prospective assessment of the liver before, after and 4 years after treatment for HCV, including an assessment of the long-term outcome of fibrosis, steatosis and inflammation. METHODS AND FINDINGS: Patients eligible for HCV treatment were included prospectively in 2018 (n = 47). Liver stiffness was measured using transient elastography and 2D shear-wave elastography (SWE). Blood tests, B-mode ultrasound (US) and SWE, were performed before, after (end of treatment [EOT]), 3 months after (EOT3) and 4 years after treatment (4Y). At the final visit, we added attenuation imaging and shear-wave dispersion slope (SWDS) measurements to assess steatosis and inflammation. Three months after treatment, the sustained virologic response rate was 93%. The median liver stiffness for baseline, EOT, EOT3 and 4Y was 8.1, 5.9, 5.6 and 6.3 kPa, respectively. There was a significant reduction in liver stiffness from baseline to EOT, and from EOT to EOT3. After 4 years, the mean attenuation coefficient (AC) was 0.58 dB/cm/MHz, and the mean SWDS value was 14.3 (m/s)/kHz. CONCLUSION: The treatment for HCV was highly effective. Measurements of liver stiffness decreased significantly after treatment and remained low after 4 years. AC measurements indicated low levels of liver steatosis. Shear-wave dispersion values indicated inflammation of the liver, but the clinical implication is undetermined and should be explored in larger studies.Clinicaltrials.gov: NCT03434470. ABBREVIATIONS: AC: attenuation coefficient; APRI: aspartate aminotransferase to platelet ratio index; ATI: attenuation imaging; cACLD: compensated advanced chronic liver disease; CAP: controlled attenuation parameter; FIB-4: Fibrosis-4 Index for liver fibrosis; HCC: hepatocellular carcinoma; LSM: liver stiffness measurement; NAFLD: non-alcoholic fatty liver disease; NASH: non-alcoholic steatohepatitis; SWDS: shear-wave dispersion slope; SWE: shear-wave elastography; US: ultrasound.

Lesion Classification by Model-Based Feature Extraction: A Differential Affine Invariant Model of Soft Tissue Elasticity in CT Images.

The elasticity of soft tissues has been widely considered a characteristic property for differentiation of healthy and lesions and, therefore, motivated the development of several elasticity imaging modalities, for example, ultrasound elastography, magnetic resonance elastography, and optical coherence elastography to directly measure the tissue elasticity. This paper proposes an alternative approach of modeling the elasticity for prior knowledge-based extraction of tissue elastic characteristic features for machine learning (ML) lesion classification using computed tomography (CT) imaging modality. The model describes a dynamic non-rigid (or elastic) soft tissue deformation in differential manifold to mimic the tissues' elasticity under wave fluctuation in vivo. Based on the model, a local deformation invariant is formulated using the 1st and 2nd order derivatives of the lesion volumetric CT image and used to generate elastic feature map of the lesion volume. From the feature map, tissue elastic features are extracted and fed to ML to perform lesion classification. Two pathologically proven image datasets of colon polyps and lung nodules were used to test the modeling strategy. The outcomes reached the score of area under the curve of receiver operating characteristics of 94.2% for the polyps and 87.4% for the nodules, resulting in an average gain of 5 to 20% over several existing state-of-the-art image feature-based lesion classification methods. The gain demonstrates the importance of extracting tissue characteristic features for lesion classification, instead of extracting image features, which can include various image artifacts and may vary for different protocols in image acquisition and different imaging modalities.

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.

Biomechanical Integrity Score of the Female Pelvic Floor for Stress Urinary Incontinence.

INTRODUCTION AND HYPOTHESIS: This study is aimed at developing and validating a new integral parameter, the Biomechanical Integrity score (BI-score) of the female pelvic floor for stress urinary incontinence conditions. METHODS: A total of 130 subjects were included in the observational cohort study; 70 subjects had normal pelvic floor conditions, and 60 subjects had stress urinary incontinence (SUI). A Vaginal Tactile Imager (VTI) was used to acquire and automatically calculate 52 biomechanical parameters for eight VTI test procedures (probe insertion, elevation, rotation, Valsalva maneuver, voluntary muscle contractions in two planes, relaxation, and reflex contraction). Statistical methods were applied (t test, correlation) to identify the VTI parameters sensitive to the pelvic SUI conditions. RESULTS: Twenty-seven parameters were identified as statistically sensitive to SUI development. They were subdivided into five groups to characterize tissue elasticity (group 1), pelvic support (group 2), pelvic muscle contraction (group 3), involuntary muscle relaxation (group 4), and pelvic muscle mobility (group 5). Every parameter was transformed to its standard deviation units using the dataset for normal pelvic conditions, similar to the T-score for bone density. Linear combinations with specified weights led to the composition of five component parameters for groups 1-5 and to the BI-score in standard deviation units. The p value for the BI-score has p = 4.0 × 10-28 for SUI versus normal conditions. CONCLUSIONS: Quantitative transformations of the pelvic tissues, support structures, and functions under diseased conditions may be studied with the SUI BI-score in future research and clinical applications.

Continuous Shear Wave Elastography for Liver Using Frame-to-Frame Equalization of Complex Amplitude.

This study addresses a crucial necessity in the field of noninvasive liver fibrosis diagnosis by introducing the concept of continuous shear wave elastography (C-SWE), utilizing an external vibration source and color Doppler imaging. However, an application of C-SWE to assess liver elasticity, a deep region within the human body, arises an issue of signal instability in the obtained data. To tackle this challenge, this work proposes a method involving the acquisition of multiple frames of datasets, which are subsequently compressed. Furthermore, the proposed frame-to-frame equalization method compensates discrepancies in the initial phase that might exist among multiple-frame datasets, thereby significantly enhancing signal stability. The experimental validation of this approach encompasses both phantom tests and in vivo experiments. In the phantom tests, the proposed technique is validated through a comparison with the established shear wave elastography (SWE) technique. The results demonstrate a remarkable agreement, with an error in shear wave velocity of less than 4.2%. Additionally, the efficacy of the proposed method is confirmed through in vivo tests. As a result, the stabilization of observed shear waves using the frame-to-frame equalization technique exhibits promising potential for accurately assessing human liver elasticity. These findings collectively underscore the viability of C-SWE as a potential diagnostic instrument for liver fibrosis.

Liver Elastography in Acute Liver Failure: A Pilot Study.

OBJECTIVES: We aimed to assess the feasibility and reliability of sequential ultrasonographic and elastographic monitoring in acute liver failure (ALF). DESIGN: Observational study. SETTING: ALF is a rare, life-threatening disease that requires intensive care admission and often liver transplant, where the accurate selection of patients is crucial. Liver elastography is a noninvasive tool that can measure hepatic stiffness, but previous results have been inconclusive in ALF. PATIENTS: Patients admitted between October 2021 and March 2023 to the Liver Intensive Therapy Unit at King's College Hospital with ALF were recruited, with healthy control (HC) individuals and acute-on-chronic liver failure (ACLF) used as controls. INTERVENTION: None. MEASUREMENTS: Average shear wave velocity was recorded with ElastPQ on the right and left liver lobes and the spleen. Portal vein flow, hepatic artery resistive index, and peak systolic velocity were also recorded. Physiologic and histologic data were used for comparison. MAIN RESULTS: Forty patients with ALF, 22 patients with ACLF, and 9 HC individuals were included in the study. At admission, liver stiffness measurement (LSM) of the right lobe was statistically different between HC individuals (5.6 ± 2 kPa), ALF (31.7 ± 17 kPa), and ACLF (76.3 ± 71 kPa) patients (ALF vs. ACLF, p = 0.0301). Spleen size and stiffness discriminated between ALF (10.4 ± 2 cm and 21.4 ± 16.6 kPa) and ACLF (14 ± 2.3 cm and 42.6 ± 26 kPa). At admission, LSM was not different between ALF patients who spontaneously survived versus patients who died or were transplanted in the following 90 days. However, the trend over the first 10 days of admission was different with a peak of LSM at day 5 in spontaneous survivors followed by reduction during the recovery phase. ALF patients with poor prognosis showed a persistently increased LSM. CONCLUSIONS: In ALF stiffness peaks at day 5 of admission with subsequent reduction in patients spontaneously surviving, showing significant difference according to the prognosis at day 7 of admission. LSM might be useful in distinguishing acute from acute-on-chronic liver failure together with spleen volume and stiffness.

Evaluation of skeletal muscle elasticity using color Doppler shear wave imaging.

PURPOSE: This study aimed to (1) assess the precision and reproducibility of color Doppler shear wave imaging (CD SWI) by comparing it with shear wave elastography (SWE) via elasticity phantom measurements, and (2) investigate the potential clinical applications of CD SWI in the upper limb muscles by assessing the reproducibility of skeletal muscle elasticity evaluations. METHODS: Four elastography phantoms of different stiffness (6.0-7.5 wt%) were used to assess the precision and reproducibility of CD SWI (compared with SWE) at depths. Typical upper limb muscles of 24 men were also assessed for this comparison. RESULTS: At superficial depths (0-2 cm), the phantom measurements obtained using CD SWI and SWE were similar at all levels of stiffness. Furthermore, both methods were highly reliable, with almost perfect intra- and inter-operator reliabilities. At greater depths (2-4 cm), measurements obtained using both methods were similar at all stiffness levels. Although standard deviations (SDs) of the phantom measurements obtained using both methods at lower stiffness were similar, those at higher stiffness were different. The SD of the CD SWI measurements was < 50% of that of the SWE measurements. However, both methods were highly reliable in the phantom test, with almost perfect intra- and inter-operator reliabilities. The intra- and inter-operator reliabilities of the shear wave velocity measurements for typical muscles of the upper limbs were also substantial in clinical settings. CONCLUSION: CD SWI is a valid method for measuring elasticity, with precision and reliability as high as those of SWE.

Variability of Transrectal Shear Wave Elastography in a Phantom Model.

Purpose: This study aimed to assess the variability of transrectal shear wave elastography (SWE) using a designed phantom. Materials and Methods: In a phantom, the SWE values were examined by two radiologists using agarose and emulsion silicone of different sizes (1, 2, and 3 cm) and shapes (round, cubic) at three depths (1, 2, and 3 cm), two region of interest (ROI) and locations (central, peripheral) using two ultrasound machines (A, B from different vendors). Variability was evaluated using the coefficient of variation (CV). Results: The CVs decreased with increasing phantom size. Significant changes in SWE values included; agarose phantom at 3 cm depth (p < 0.001; machine A), 1 cm depth (p = 0.01; machine B), emulsion silicone at 2 cm depth (p = 0.047, p = 0.020; both machines). The CVs increased with increasing depth. Significant changes in SWE values included; 1 cm agarose (p = 0.037, p = 0.021; both machines) and 2 cm agarose phantom (p = 0.047; machine A). Significant differences in SWE values were observed between the shapes for emulsion silicone phantom (p = 0.032; machines A) and between ROI locations on machine B (p ≤ 0.001). The SWE values differed significantly between the two machines (p < 0.05). The intra-/inter-operator agreements were excellent (intraclass correlation coefficient > 0.9). Conclusion: The phantom size, depth, and different machines affected the variability of transrectal SWE.

Corrigendum: Hippocampus of the APPNL-G-F mouse model of Alzheimer's disease exhibits region-specific tissue softening concomitant with elevated astrogliosis.

[This corrects the article DOI: 10.3389/fnagi.2023.1212212.].

Hippocampus of the APPNL-G-F mouse model of Alzheimer's disease exhibits region-specific tissue softening concomitant with elevated astrogliosis.

Widespread neurodegeneration, enlargement of cerebral ventricles, and atrophy of cortical and hippocampal brain structures are classic hallmarks of Alzheimer's disease (AD). Prominent macroscopic disturbances to the cytoarchitecture of the AD brain occur alongside changes in the mechanical properties of brain tissue, as reported in recent magnetic resonance elastography (MRE) measurements of human brain mechanics. Whilst MRE has many advantages, a significant shortcoming is its spatial resolution. Higher resolution "cellular scale" assessment of the mechanical alterations to brain regions involved in memory formation, such as the hippocampus, could provide fresh new insight into the etiology of AD. Characterization of brain tissue mechanics at the cellular length scale is the first stepping-stone to understanding how mechanosensitive neurons and glia are impacted by neurodegenerative disease-associated changes in their microenvironment. To provide insight into the microscale mechanics of aging brain tissue, we measured spatiotemporal changes in the mechanical properties of the hippocampus using high resolution atomic force microscopy (AFM) indentation tests on acute brain slices from young and aged wild-type mice and the APPNL-G-F mouse model. Several hippocampal regions in APPNL-G-F mice are significantly softer than age-matched wild-types, notably the dentate granule cell layer and the CA1 pyramidal cell layer. Interestingly, regional softening coincides with an increase in astrocyte reactivity, suggesting that amyloid pathology-mediated alterations to the mechanical properties of brain tissue may impact the function of mechanosensitive astrocytes. Our data also raise questions as to whether aberrant mechanotransduction signaling could impact the susceptibility of neurons to cellular stressors in their microenvironment.

Origins of brain tissue elasticity under multiple loading modes by analyzing the microstructure-based models.

Constitutive behaviors and material properties of brain tissue play an essential role in accurately modeling its mechanical responses. However, the measured mechanical behaviors of brain tissue exhibit a large variability, and the reported elastic modulus can differ by orders of magnitude. Here we develop the micromechanical models based on the actual microstructure of the longitudinally anisotropic plane of brain tissue to investigate the microstructural origins of the large variability. Specifically, axonal fiber bundles with the specified configurations are distributed in an equivalent matrix. All micromechanical models are subjected to multiple loading modes, such as tensile, compressive, and shear loading, under periodic boundary conditions. The predicted results agree well with the experimental results. Furthermore, we investigate how brain tissue elasticity varies with its microstructural features. It is revealed that the large variability in brain tissue elasticity stems from the volume fraction of axonal fiber, the aspect ratio of axonal fiber, and the distribution of axonal fiber orientation. The volume fraction has the greatest impact on the mechanical behaviors of brain tissue, followed by the distribution of axonal fiber orientation, then the aspect ratio. This study provides critical insights for understanding the microstructural origins of the large variability in brain tissue elasticity.

Axial stress determines the velocity of shear wave propagation in passive but not active muscles in vivo.

Ultrasound shear wave elastography can be used to characterize mechanical properties of unstressed tissue by measuring shear wave velocity (SWV), which increases with increasing tissue stiffness. Measurements of SWV have often been assumed to be directly related to the stiffness of muscle. Some have also used measures of SWV to estimate stress, since muscle stiffness and stress covary during active contractions, but few have considered the direct influence of muscle stress on SWV. Rather, it is often assumed that stress alters the material properties of muscle, and in turn, shear wave propagation. The objective of this study was to determine how well the theoretical dependency of SWV on stress can account for measured changes of SWV in passive and active muscles. Data were collected from six isoflurane-anesthetized cats; three soleus muscles and three medial gastrocnemius muscles. Muscle stress and stiffness were measured directly along with SWV. Measurements were made across a range of passively and actively generated stresses, obtained by varying muscle length and activation, which was controlled by stimulating the sciatic nerve. Our results show that SWV depends primarily on the stress in a passively stretched muscle. In contrast, the SWV in active muscle is higher than would be predicted by considering only stress, presumably due to activation-dependent changes in muscle stiffness. Our results demonstrate that while SWV is sensitive to changes in muscle stress and activation, there is not a unique relationship between SWV and either of these quantities when considered in isolation.NEW & NOTEWORTHY Ultrasound shear wave elastography may be an inexpensive way to measure muscle stress in passive muscle. Here, using a cat model we directly measured shear wave velocity (SWV), muscle stress, and muscle stiffness. Our results show that SWV depends primarily on the stress in a passively stretched muscle. In contrast, the SWV in active muscle is higher than would be predicted by considering only stress, presumably due to activation-dependent changes in muscle stiffness.

Measuring Shear Wave Velocity in Adult Skeletal Muscle with Ultrasound 2-D Shear Wave Elastography: A Scoping Review.

Ultrasound 2-D shear wave elastography (US 2D-SWE) is a non-invasive, cost-effective tool for quantifying tissue stiffness. Amidst growing interest in US 2D-SWE for musculoskeletal research, it has been recommended that shear wave velocity (SWV) should be reported instead of elastic moduli to avoid introducing unwanted error into the data. This scoping review examined the evolving use of US 2D-SWE to measure SWV in skeletal muscle and identified strengths and weaknesses to guide future research. We searched electronic databases and key review reference lists to identify articles published between January 2000 and May 2021. Two reviewers assessed the eligibility of records during title/abstract and full-text screening, and one reviewer extracted and coded the data. Sixty-six studies met the eligibility criteria, of which 58 were published in 2017 or later. We found a striking lack of consensus regarding the effects of age and sex on skeletal muscle SWV, and widely variable reliability values. Substantial differences in methodology between studies suggest a pressing need for developing standardized, validated scanning protocols. This scoping review illustrates the breadth of application for US 2D-SWE in musculoskeletal research, and the data synthesis exposed several notable inconsistencies and gaps in current literature that warrant consideration in future studies.

Clinical correlation of 2D shear wave elastography findings in children with type 1 diabetes mellitus without autoimmune thyroiditis.

OBJECTIVES: The aim of study was to evaluate the 2D shear wave sonoelastography (SWE) findings of the thyroid gland in children with type 1 diabetes mellitus (T1DM) with normal gray-scale findings and without thyroid autoimmunity (AIT) and obtain data that will be useful for the early detection of glandular involvement. METHODS: The study included 46 T1DM patients (mean age: 11.28 ± 3.3 years) and 46 healthy children (mean age: 12.01 ± 3.8 years) as the control group. The thyroid gland mean elasticity value was obtained as kPa and compared in groups. A correlation was investigated between elasticity values and age at diabetes, serum free T4, thyroid stimulating hormone (TSH), anti-thyroglobulin, anti-tissue peroxidase, and hemoglobin A1c values. RESULTS: No difference was found between T1DM patients and the control group in the thyroid 2D SWE evaluation (the median kPa value: 17.1 (10.2) in the study group and 16.8 (7.0) in the control group) (p=0.15). No significant correlation was found between 2D SWE kPa values and age at diagnosis, serum free T4, TSH, anti-thyroglobulin, anti-tissue peroxidase, and hemoglobin A1c levels in T1DM patients. CONCLUSIONS: Our study showed that the elasticity of the thyroid gland in T1DM patients without AIT was not affected differently from that of the normal population. If 2D SWE is used in routine follow-up in T1DM patients before the development of AIT, we think that it will be useful in the early detection of thyroid gland affections and AIT, and long-term comprehensive studies in this direction will contribute to the literature.

Magnetic Resonance Acoustic Radiation Force Imaging (MR-ARFI) for the monitoring of High Intensity Focused Ultrasound (HIFU) ablation in anisotropic tissue.

OBJECTIVE: We introduce a non-invasive MR-Acoustic Radiation Force Imaging (ARFI)-based elastography method that provides both the local shear modulus and temperature maps for the monitoring of High Intensity Focused Ultrasound (HIFU) therapy. MATERIALS AND METHODS: To take tissue anisotropy into account, the local shear modulus µ is determined in selected radial directions around the focal spot by fitting the phase profiles to a linear viscoelastic model, including tissue-specific mechanical relaxation time τ. MR-ARFI was evaluated on a calibrated phantom, then applied to the monitoring of HIFU in a gel phantom, ex vivo and in vivo porcine muscle tissue, in parallel with MR-thermometry. RESULTS: As expected, the shear modulus polar maps reflected the isotropy of phantoms and the anisotropy of muscle. In the HIFU monitoring experiments, both the shear modulus polar map and the thermometry map were updated with every pair of MR-ARFI phase images acquired with opposite MR-ARFI-encoding. The shear modulus was found to decrease (phantom and ex vivo) or increase (in vivo) during heating, before remaining steady during the cooling phase. The mechanical relaxation time, estimated pre- and post-HIFU, was found to vary in muscle tissue. DISCUSSION: MR-ARFI allowed for monitoring of viscoelasticity changes around the HIFU focal spot even in anisotropic muscle tissue.

Virtual magnetic resonance elastography predicts the intraoperative consistency of meningiomas.

BACKGROUND AND PURPOSE: Virtual magnetic resonance elastography (vMRE) is an experimental imaging modality designed to non-invasively predict the haptic properties of tissues. The modality is sensitive to tissue stiffness and fibrosis. Information about meningioma consistency prior to resection is of great interest in neurological surgery as the surgical plan and outcome may be affected by the tumor's stiffness. In this study, we assessed the ability of vMRE to predict the intraoperative consistency and mechanical heterogeneity of intracranial meningiomas. MATERIALS AND METHODS: We included 12 patients scheduled for meningioma resection, of which one patient was found to have a solitary fibrous tumor on histological examination. All participants underwent preoperative vMRE and intraoperative consistency grading. RESULTS AND CONCLUSIONS: Intraoperative qualitative consistency correlated positively with vMRE-based consistency assessment (odds ratio 5.63, 95% CI 1.12-28.30, p = 0.04) at b1000. Mechanically homogenous tumors had significantly lower ∆ mean stiffness than heterogeneous tumors (8.13 vs 18.07 kPa, p = 0.01). This study thus demonstrates a possible clinical application of vMRE in predicting the intraoperative consistency and mechanical heterogeneity of meningiomas.

Predicting Progression of Kidney Injury Based on Elastography Ultrasound and Radiomics Signatures.

Background: Shear wave elastography ultrasound (SWE) is an emerging non-invasive candidate for assessing kidney stiffness. However, its prognostic value regarding kidney injury is unclear. Methods: A prospective cohort was created from kidney biopsy patients in our hospital from May 2019 to June 2020. The primary outcome was the initiation of renal replacement therapy or death, while the secondary outcome was eGFR < 60 mL/min/1.73 m2. Ultrasound, biochemical, and biopsy examinations were performed on the same day. Radiomics signatures were extracted from the SWE images. Results: In total, 187 patients were included and followed up for 24.57 ± 5.52 months. The median SWE value of the left kidney cortex (L_C_median) is an independent risk factor for kidney prognosis for stage 3 or over (HR 0.890 (0.796−0.994), p < 0.05). The inclusion of 9 out of 2511 extracted radiomics signatures improved the prognostic performance of the Cox regression models containing the SWE and the traditional index (chi-square test, p < 0.001). The traditional Cox regression model had a c-index of 0.9051 (0.8460−0.9196), which was no worse than the machine learning models, Support Vector Machine (SVM), SurvivalTree, Random survival forest (RSF), Coxboost, and Deepsurv. Conclusions: SWE can predict kidney injury progression with an improved performance by radiomics and Cox regression modeling.

Do deep inspiration breath-holds and free-breathing affect pancreatic tissue stiffness in shear wave elastography?

PURPOSE: The use of ultrasound (US) elastography to assess the pancreas is subject to serious limitations, and it is not easy to perform US elastography for the pancreas with satisfactory and reproducible accuracy. The aim of our study was to show the normal pancreatic stiffness values with shear wave elastography (SWE) and to evaluate the pancreatic tissue stiffness at two different respiratory phases. METHODS: Sixty-three subjects were included in the study. Median values of pancreatic stiffness were recorded. Values during deep inspiration and free breathing were compared. RESULTS: The stiffness values of the pancreatic tissue measured during deep inspiration breath holds and during free breathing were 5.70 ± 1.74 kPa and 4.15 ± 1.70 kPa, respectively. It was found that the values of pancreatic tissue stiffness measured during deep inspiration were statistically significantly higher than those measured during physiological breathing (p < 0.001). CONCLUSIONS: Because of the reference value differences between different ultrasound elastography devices, it is important to know the reference ranges of normal pancreatic stiffness according to the device, in order to distinguish possible pathologies. In addition, the variability of pancreatic stiffness measurements with respiratory phases should be considered in clinical applications.

Biomechanical integrity score of the female pelvic floor.

INTRODUCTION AND HYPOTHESIS: The aim of this study is to develop and validate a new integral parameter, the Biomechanical Integrity score (BI-score), for the characterization of the female pelvic floor. METHODS: A total of 253 subjects with normal and pelvic organ prolapse (POP) conditions were included in the multi-site observational, case-control study; 125 subjects had normal pelvic floor conditions, and 128 subjects had POP stage II or higher. A Vaginal Tactile Imager (VTI) was used to acquire and automatically calculate 52 biomechanical parameters for eight VTI test procedures (probe insertion, elevation, rotation, Valsalva maneuver, voluntary muscle contractions in two planes, relaxation, and reflex contraction). Statistical methods were applied (t-test, correlation) to identify the VTI parameters sensitive to the pelvic conditions. RESULTS: Twenty-six parameters were identified as statistically sensitive to POP development. They were subdivided into five groups to characterize (1) tissue elasticity, (2) pelvic support, (3) pelvic muscle contraction, (4) involuntary muscle relaxation, and (5) pelvic muscle mobility. Every parameter was transformed to its standard deviation units against the patient age similar to T-score for bone density. Linear combinations with specified weights led to the composition of five component parameters for groups (1)-(5) and the BI-score in standard deviation units. The p-value for the BI-score has p = 4.3 × 10-31 for POP versus normal conditions. A reference BI-score curve against age for normal pelvic floor conditions was defined. CONCLUSIONS: Quantitative transformations of the pelvic tissues, support structures, and functions under diseased conditions may be studied with the BI-score in future research and practical applications.