Dispersion Slope Research Articles

Clinical applications of shear wave dispersion imaging for breast lesions: a pictorial essay.

Shear wave dispersion (SWD) imaging is a newly developed ultrasound technology designed to evaluate the dispersion slope of shear waves, which is related to tissue viscosity. This advanced imaging technique holds potential for distinguishing malignant lesions from benign lesions and normal breast tissue. The SWD slope, as determined by shear wave elastography (SWE), could offer crucial insights into the characterization of breast lesions. This article presents SWE and SWD images of both malignant and benign breast lesions, in addition to normal breast tissue.

Trench-assisted multi-ring-core fiber for orbital angular momentum modes

Orbital angular momentum (OAM) multiplexing technology has attracted significant interest due to its ability to increase the data transmission capacity in optical communications. By combining OAM-based mode division multiplexing (MDM) and wavelength division multiplexing (WDM) techniques in multi-core fiber (MCF), the transmission rate and spectral efficiency of the optical communication systems can be greatly enhanced. In this paper, we present a design of a multi-ring air-core trench-assisted fiber that supports transmission over the entire C + L (1530–1625 nm) band with low inter-ring crosstalk. The high-contrast ring and trench design can effectively suppress the inter-modal crosstalk. The effects of the ring spacing, wavelength range and doping concentration on the crosstalk suppression are also systematically investigated. Furthermore, the complexity of the MIMO processing system is greatly reduced with a fewer-optical-core structure while keeping low inter-ring crosstalk. The results demonstrate that our designed fiber can support 140 OAM modes at 1550 nm with < −79.4 dB inter-ring crosstalk at low Ge-doped concentration (12.5 mol%), and it can keep the inter-ring crosstalk below −66.56 dB across the C + L band, which features lower inter-ring crosstalk than the other reports while supporting more OAM modes. Furthermore, to support more OAM modes with lower inter-ring crosstalk and intra-modal crosstalk, we further provide a second low-doping-concentration (12.5 mol%) fiber design, which can support 196 OAM modes with < −35.74 dB inter-ring crosstalk and Δneff > 5.39 × 10−4. Additionally, our designed fiber can support 224 OAM modes (37.5 mol% Ge-doped) and < −63 dB inter-ring crosstalk with low intra-modal crosstalk (Δneff > 5.45 × 10−4) and flat dispersion distribution (chromatic dispersion slope lower than 0.171 ps/nm2/km) across the C + L band.

Influence of Measurement Depth and Acquisition Parameters on Shear Wave Speed and Shear Wave Dispersion in Certified Phantoms Using a Canon Aplio Clinical Ultrasound Scanner.

The aim of the work described here was to investigate the relative contribution of confounding factors on liver shear wave speed (SWS) and shear wave dispersion slope (SWDS) measurements in three certified phantoms using a Canon Aplio clinical ultrasound scanner. A Canon Aplio i800 i-series ultrasound system (Canon Medical Systems Corporation, Otawara, Tochigi, Japan) with i8CX1 convex array (center frequency=4 MHz) was used to examine dependencies caused by the depth, width and height of the acquisition box (AQB), the depth and size of the region of interest (ROI), the AQB angle and the pressure of the ultrasound probe on the surface of the phantom. Results revealed that depth is the most significant confounder in both SWS and SWDS measurements. AQB angle, height and width and ROI size exhibited minimal confounding effects on measurements. For SWS, the most consistent measurement depth is when the top of the AQB is placed between 2 and 4 cm, and the ROI is located between 3 and 7 cm deep. For SWDS, results indicate that measurement values significantly decrease with depth from the surface of the phantom until approximately 7 cm deep, and consequently no stable area of AQB placement or ROI depth exists. In contrast to SWS, the same ideal acquisition depth range cannot necessarily be applied to SWDS measurements because of a significant depth dependency.

Diagnostic Performance of Quantitative Ultrasound Parameters in Non-alcoholic Fatty Liver Disease

Marked liver steatosis, steatohepatitis, and significant fibrosis are risk factors for unfavorable outcomes in non-alcoholic fatty liver disease (NAFLD). In this study, the diagnostic performance ofattenuation coefficient(AC), liver stiffness(LS), and dispersion slope (DS) was evaluated separately and combined in the diagnosis of liver steatosis and fibrosis in NAFLD suspects using biopsy or magnetic resonance imaging (MRI) as a reference standard. Seventy-four NAFLD suspects were prospectively imaged with an Aplio i800 ultrasound scanner (Canon Medical Systems, Tustin, CA). AC, LS, and DS measurements were obtained from the right liver lobe. Thirty-four patients underwent liver biopsy, and 40 had MRI. There were 32 patients (43%) with liver steatosis and fibrosis (S+F), 22(30%) with steatosis (S), 5 (7%) with fibrosis (F), and 15 (20%) with normal liver (N). Mean ACs were significantly higher in steatotic livers (n=54) than in non-steatotic livers (n=20) (P<0.0001). LS and DS were significantly higher in patients with liver fibrosis (n=37) compared tonon-fibrotic livers (n=37) (P=0.0004 and P=0.0002, respectively). In detecting (S+F), the area under the receiver operating characteristic curve (AUROCC) was 0.87 for combined ultrasound parameters of LS and AC (negative predictive value [NPV]: 75%, positive predictive value [PPV]: 77%, P<0.0001). In detecting patients with liver steatosis and fibrosis stage ≥2, LS had an AUROCC of 0.93 (NPV: 87%, PPV: 82%, P<0.0001). In the biopsy group, 32% (11/34) were diagnosed with non-alcoholic steatohepatitis (NASH). DS values showed a significant difference among patients with (n=23) or without (n=11) hepatocellular ballooning (P=0.02). AUROCC was 0.87 for combined ultrasound parameters of AC, LS, and DS with body mass index (BMI) in detecting NASH (NPV: 80%, PPV: 87%, P=0.0006). AC and LS showed high diagnostic value in detecting liver steatosis and fibrosis, respectively. The combined AC and LS values further improved the diagnostic accuracy in detecting NAFLD and high-risk NAFLD patients.

Shear Wave Dispersion in Chronic Liver Disease: From Physical Principles to Clinical Usefulness.

The development of new applications in ultrasound (US) imaging in recent years has strengthened the role of this imaging technique in the management of different pathologies, particularly in the setting of liver disease. Improved B-mode imaging (3D and 4D), contrast-enhanced US (CEUS) and especially US-based elastography techniques have created the concept of multiparametric ultrasound (MP-US), a term borrowed from radiological sectional imaging. Among the new elastography techniques, shear wave dispersion is a newly developed imaging technology which enables the assessment of the shear waves' dispersion slope. The analysis of the dispersion qualities of shear waves might be indirectly related to the tissue viscosity, thus providing biomechanical information concerning the pathologic state of the liver such as necroinflammation. Some of the most recent US devices have been embedded with software that evaluate the dispersion of shear waves/liver viscosity. In this review, the feasibility and the clinical applications of liver viscosity are reviewed based on the preliminary findings of both animal and human studies.

Role of Multiparametric Ultrasound in Evaluating Hepatic Acute Graft-versus-Host Disease: An Animal Study.

Hepatic acute graft-versus-host disease (aGVHD) is a serious complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and is one of the leading causes of early non-recurrent death. The current diagnosis is based mainly based on clinical diagnosis, and there is a lack of non-invasive quantitative diagnosis methods. We propose a multiparametric ultrasound (MPUS) imaging method and explore its effectiveness in evaluating hepatic aGVHD. In this study, 48 female Wistar rats were used as receptors and 12 male Fischer 344 rats were used as donors for allo-HSCT to establish aGVHD models. After transplantation, 8 rats were randomly selected for ultrasonic examination weekly, including color Doppler ultrasound, contrast-enhanced ultrasound (CEUS) and shear wave dispersion (SWD) imaging. The values of nine ultrasonic parameters were obtained. Hepatic aGVHD was subsequently diagnosed by histopathological analysis. A classification model for predicting hepatic aGVHD was established using principal component analysis and support vector machines. According to the pathological results, the transplanted rats were categorized into the hepatic aGVHD and non-GVHD (nGVHD) groups. All parameters obtained by MPUS differed statistically between the two groups. The first three contributing percentages of principal component analysis results were resistivity index, peak intensity and shear wave dispersion slope, respectively. The accuracy of classifying aGVHD and nGVHD using support vector machines reached 100%. The accuracy of the multiparameter classifier was significantly higher than that of the single parameter. The MPUS imaging method has proven to be useful in detecting hepatic aGVHD.

Tailoring Group Delay Dispersion of Spatial Phaser using Anisotropic Metasurface and Polarized Incident Waves

AbstractMetasurface‐based spatial phaser, exhibiting dispersive group delay responses, is able to perform real‐time analogue signal processing on the temporal spectrum of spatial electromagnetic waves, e.g., Fourier transformation, pulse chirping, pulse spread, and compression. The functionality of a spatial phaser is closely related to its group delay dispersion slope. For instance, for an up‐chirped incident pulse, the positive‐slope‐dispersion phaser spreads the pulse whereas the negative‐slope‐dispersion one compresses the pulse. Most reported spatial phasers exhibit fixed dispersion slopes and hence perform single functionality only, which cannot meet the demand of multifunctional systems in communication and sensing applications. In this paper, a new way is proposed to control and tune the dispersion slope of spatial phasers using polarization of incident waves, which is simpler and more efficient than conventional approaches based on tunable circuits. To verify the proposed method, a first‐order spatial phaser is designed and experimentally demonstrated within 9.4–10.6 GHz. It is able to generate negative‐slope, positive‐slope, and zero‐slope group delay dispersions, in case of x‐, y‐, and ±45°‐polarized waves. Such a reconfigurable phaser may find wide applications in integrated communication and sensing.

Measurements of the dispersion, the dispersion slope and nonlinear coefficients of photonic crystal fibers based on degenerate four-wave mixing (FWM)

Abstract A simple and accurate method based on degenerate four-wave mixing (FWM) to evaluate optical fiber dispersion and nonlinearity is presented. We investigated the continuous wave degenerate FWM characteristics of two photonic crystal fibers (PCFs) and a SMF28 fiber. Simply by measuring and analyzing the continuous wave degenerate FWM conversion efficiency as a function of the wavelength difference between pump and signal waves, fitting between experimental data and analytical FWM conversion efficiency expression is carried out to determine the dispersion, dispersion slope and nonlinear coefficient of the fiber. The fiber parameters simultaneously obtained from a single set of FWM measurement for Single Mode Fiber 28 (SMF28) are found to be agreement with the manufacturer specifications for this fiber, thus validating the PCF results and, more generally, the acceptable accuracy of the simple method proposed here.

Shear Wave Dispersion Slope of the Liver Can Predict Adverse Outcomes in Patients with Pulmonary Hypertension

Pulmonary hypertension (PH) often causes right-sided heart failure (HF), inducing organ damage. Shear wave elastography (SWE) is a novel ultrasound technique for characterizing tissue. Some studies have reported that shear wave dispersion slope (SWDS) enables the assessment of early hepatic damage in HF. This study aimed to evaluate the prognostic impact of SWDS in patients with PH.This single-center cohort study enrolled 36 patients with PH who underwent SWE at Okayama University Hospital between March 2018 and April 2021. Patients were divided into 2 groups on the basis of the median value of SWDS: low SWDS group (SWDS < 12.4 m/second/kHz, n = 18) and high SWDS group (SWDS ≥ 12.4 m/second/kHz, n = 18). The primary endpoint was the complex of all-cause death or hospitalization for HF. During the follow-up of 391 ± 288 days, all-cause death or hospitalization for HF occurred in 8 patients. One patient died in the low SWDS group. Three patients died and 4 patients were hospitalized for HF in the high group. Kaplan-Meier analysis revealed that the event-free survival rate was significantly worse in the high SWDS group than in the low SWDS group (log-rank, P = 0.01). In univariate Cox proportional hazards analysis, high SWDS was associated with the events (hazard ratio 10.8; 95% confidence interval 1.89-202, P = 0.005).An elevated SWDS was associated with a high rate of events in patients with PH. SWDS has the potential to predict adverse outcomes in patients with PH.

Match Zehnder interferometry and Laguerre–Gaussian fields dependent photon drag in atomic medium

The absorption, dispersion and transmission are controlled and modified with the intensities of Laguerre–Gaussian control fields in a four level cesium atomic medium. The normal and anomalous slope of dispersion are investigated for subluminal and superluminal propagation. The maximum measured value of positive/negative group index is n g =±1×107, at which, the group velocity is ±30 ms−1. The maximum delay time between the two beams at the detector without dragging is 0.414 ns and in the presence of dragging is measured to 0.44 ns. The fractional change in delay time without and in the presence of dragging Δt F is measured to ±2%. The maximum phase shift without dragging is reported to 2.6 micro radian and in the presence of dragging is investigated to ±4 micro radian. The fractional change in phase shift is reported from −200% to 50% and may be used for gravitational waves detection and other signals identification.

Clinical significance of dispersion imaging by shear wave elastography in the treatment and diagnosis of pancreatic cancer.

Recently, dispersion imaging by shear wave elastography has been developed to visualize a tissue viscosity-related factor by measuring the dispersion slope. However, clinical significance of dispersion imaging in the field of pancreatic cancer is unknown. This study aimed to investigate the clinical significance of dispersion imaging in the treatment and diagnosis of pancreatic cancer. We measured shear wave dispersion slope (SWD) (m/s/kHz) and shear wave elasticity (SWE) (kPa) in patients with pancreatic ductal adenocarcinoma (PDA). The primary endpoint was the relationship between the changes in SWD and SWE values before and after chemotherapy and the response to chemotherapy. Secondary endpoints included SWD and SWE values in relation to differences between PDA and non-PDA sites and histopathological scores of stroma, inflammation, fibrosis, and necrosis in endoscopic ultrasound-guided fine-needle aspiration specimens. Fifty-six patients were included, 30 of whom underwent chemotherapy. There was no relationship between the changes of SWD and SWE values and chemotherapy responses. In 56 patients, the median SWD value was 12.20m/s/kHz (interquartile range [IQR]: 10.88-13.61) at PDA sites and 13.57m/s/kHz (IQR: 12.28-16.20) at non-PDA sites (P=0.005). The median SWE value was 8.18kPa (IQR: 7.00-9.74) at PDA sites and 6.14kPa (IQR: 5.40-6.77) at non-PDA sites (P<0.001). Histopathological evaluation revealed that inflammation scores were correlated with SWD values (rs =0.42, P<0.001). Dispersion imaging in pancreatic cancer would be useful for diagnosis and assessing inflammation.

Complete beam optics analysis along the Muon Campus External Beamline

The Fermilab Mu2e experiment aims to measure the event ratio of the neutrinoless coherent conversion of muons to electrons in the field of an aluminum nucleus to ordinary capture as a means to probe the possibility of charged lepton flavor violation. Since the number of muons at the Mu2e production target is highly correlated to the upstream beam Twiss parameters, knowledge of these parameters is critical. Such measurement is not trivial since the accelerator line contains several bending magnets which can induce non-negligible dispersion. We discuss a methodology that in addition to the Twiss parameters can extract dispersion, slope of dispersion and momentum spread using only a set of beam profiles. We then apply this technique along the Fermilab Muon Campus and show it can play a significant role in maximizing the muon flux of the Mu2e Experiment.

Comparison between splenic dispersion slope and splenic shear wave speed on ultrasound elastography for predicting esophageal varices

Comparison between splenic dispersion slope and splenic shear wave speed on ultrasound elastography for predicting esophageal varices

Generation of supercontinuum covering 520 nm to [formula omitted] by noise-like laser pulses in an integrated all-fiber system

Supercontinuum (SC) is generated in an integrated all-fiber system, starting with a fiber laser. High-power laser pulses at the 1.56μm center wavelength are pumped into a hybrid nonlinear fiber, which consists of a highly nonlinear fiber (HNLF) fusion-spliced with a photonic crystal fiber (PCF). After the laser pulses propagate through an HNLF with a small dispersion slope of 0.0071 ps/nm2/km at 1.56μm wavelength, a supercontinuum covering a spectral range from 875 nm to 2.2μm is generated. Subsequently, a photonic crystal fiber (PCF) with a zero-dispersion wavelength (ZDW) at 1.04μm is used to expand the SC spectrum to the visible region. The relation between the center wavelength of the pulses and the ZDW of the nonlinear fibers matches the condition that is possible to induce strong soliton-related dynamics. In this study, it is experimentally found that noise-like pulses (NLPs) are more effective to generate ultra-broadband SC spectra than well-defined pulses (WDPs). The SC generated by pumping NLPs into a hybrid nonlinear fiber of an 8 cm HNLF and a 2 m PCF has an average power of 1.9 W and a spectrum covering a wavelength range from 520 nm to 2.25μm. The SC generated by pumping WDPs into the same hybrid nonlinear fiber has an average power of 1.85 W and a spectrum covering a wavelength range from 680 nm to 2.25μm.

Dispersive waves generation in photonic crystal fibers: The role on supercontinuum generation and rogue waves manipulation

Based on photonic crystal fiber, the generation and behavior of dispersive waves in optical fiber system are presented. The individual soliton induced dispersive waves and collision-induced dispersive waves generation are introduced and compared, and the ways of dispersion wave generation are also given in terms of pumping conditions and fiber properties. The dispersion slope affects soliton trapping of dispersive waves and the role of soliton trapping of dispersive waves on supercontinuum is different in photonic crystal fibers with different zero dispersion wavelengths. From the point of view of the number of zero dispersion wavelength, we reveal the effect of dispersive waves on supercontinuum generation and the relationship between dispersive wave and zero dispersion wavelength. Rogue waves induced by dispersive waves are also discussed and how to control rogue waves by using dispersive waves is shown.

Improving MDM–WDM optical network performance via optimized power allocation using Gaussian noise model

The few-mode fiber nonlinearity has been well modeled by an additive Gaussian Noise (GN) source. The available GN models in Mode Division Multiplexing–Wavelength Division Multiplexing (MDM–WDM) systems are incoherent and neglect the dispersion slope. The incoherent GN model assumes that the Nonlinear Interference (NLI) noise created at each span is summed up in power incoherently at the receiver and leads to underestimating the NLI noise power. In the first part of this paper, a coherent GN model is derived by taking into account the dispersion slope and verified through Split-Step Fourier Method (SSFM) simulations. In the second part of this paper, the total capacity maximization, as well as the minimum Signal to Noise Ratio (SNR) margin maximization problems are presented and solved based on the obtained GN model. MDM–WDM multi-node nonlinear network under different scenarios including Equal/Non-Equal Required SNR (ERS/NERS), and Flat/Non-Flat Amplifier Gain (FG/NFG) are considered in the numerical simulations. Considering 200 different sets of randomized traffic demands (random channel-mode distributions) the cumulative distribution function of minimum SNR margin improvement in optimized power allocation compared with the best flat power allocation is in 99% more than 1 dB, 1.2 dB, 2.4 dB, and 2.8 dB, for ERS-FG, ERS-NFG, NERS-FG, and NERS-NFG scenarios, respectively.

Stratifying Non-alcoholic Steatohepatitis With the Non-invasive Ultrasound Markers Shear Wave Dispersion Slope and Shear Wave Velocity: An Animal Study.

We evaluated the significance of the ultrasound (US) markers shear wave dispersion slope (SWDS) and shear wave velocity (SWV) for identification of non-alcoholic steatohepatitis (NASH) and high-risk NASH; the latter was defined as the presence of steatohepatitis, a non-alcoholic fatty liver disease activity score (NAS) ≥4 or a fibrosis stage ≥2. Thirty-six male Sprague-Dawley (SD) rats were assigned to two groups: the study (n=30) and control (n=6) groups. To initiate non-alcoholic steatohepatitis, study group rats were fed a diet deficient in methionine and choline. All rats were examined using ultrasonography to obtain the SWDS and SWV parameters of the liver at the same time points. Fatty liver pathological grades were determined after euthanasia; the livers were categorized in the normal (n=6), NAFL (non-alcoholic fatty liver) (n=10) and NASH (n=20) subgroups based on the NAS scoring system. They were also categorized into subgroups F0 (n=22), F1 (n=3), F2 (n=7) and F3 (n=4) on the basis of the METAVIR (Meta-analysis of Histological Data in Viral Hepatitis) scoring system. Measurement differences between various grades were evaluated by analysis of variance (ANOVA) or the Mann-Whitney U-test. We used logistic regression to calculate a combination of the two parameters for combined assessment of parameters. The diagnostic value of SWDS, SWV and the two-variable model was determined by receiver operating characteristic (ROC) curve analysis. This analysis revealed stepwise increases in SWDS and SWV with increasing NAFLD severity. The accuracy of SWDS in diagnosing NASH was good (area under the ROC curve [AUC]: 0.88) and was superior to that of SWV (AUC: 0.76). The combination of SWV and SWDS exhibited higher performance (AUC: 0.90). SWV was higher than SWDS in participants with a fibrosis grade ≥2 (high-risk NASH). For identification of high-risk NASH, SWV exhibited the best diagnostic performance (AUC: 0.89), which was equivalent to that of the two-variable model (AUC: 0.88) and slightly higher than that of SWDS (AUC: 0.85). This study indicates that of the US-based markers, SWDS outperforms SWV in identifying NASH in rats and that combining the two markers may increase their clinical utility in guiding NAFLD and NASH treatment.

Shear Wave Dispersion Slope Measured with Shear Wave Dispersion Imaging Is Associated with Variceal Hemorrhage in Cirrhotic Patients.

Portal hypertension (PH), as the main consequence of cirrhosis, leads to the development of gastroesophageal varices (GEVs). Variceal hemorrhage (VH) caused by the rupture of GEVs is a life-threatening emergency. Thus, the prediction of VH risk is considerably important. Our pilot study aimed to identify the risk factors of variceal hemorrhage (VH) in cirrhosis. Cirrhotic patients were prospectively included and divided into two groups according to the presence or absence of VH. Conventional ultrasound and shear wave dispersion (SWD) imaging were conducted to detect the portal vein diameter, spleen diameter, ascites, liver stiffness (LS) and shear wave dispersion slope (SWDS). The laboratory tests were recorded, including platelets (PLT), alanine transaminase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL) and albumin (ALB). The risk factors of VH were screened using univariate analyses and identified using multivariate logistic regression. The ROC curves were used to assess diagnostic accuracy. Comparisons between AUCs were performed using the Delong method. Sixty-five patients with 22 VHs were finally included. The SWDS, spleen diameter and ascites were identified as independent risk factors for VH. The SWDS showed good performance for diagnosing VH (AUC = 0.768, 95% CI: 0.647-0.864), and sensitively identified 95.5% (95% CI: 77.2%-99.9%) of patients with VH. Including the three risk factors in multivariate logistic regression, we obtained a formula for diagnosing VH: -20.749 + 0.804 × SWDS + 0.449 × spleen diameter + 1.803 × ascites (no ascites = 0, ascites = 1). Comparison of AUCs revealed that the formula (AUC = 0.900, 95% CI: 0.800-0.961) performed better than LS, SWDS, and spleen diameter in diagnosing VH (p &lt; 0.001; p &lt; 0.05; p &lt; 0.05). SWDS is a sensitive parameter for assessing the risk of VH. Combining the SWDS, spleen diameter and ascites resulted in good diagnostic accuracy.

Low crosstalk and large effective mode field area heterogeneous 13-core 6-mode fiber with double high refractive index rings

We propose a heterogeneous thirteen-core few-mode fiber, which has the excellent characteristics of low crosstalk (XT), large effective mode field area (Aeff) and low dispersion slope (Dslope). The double high refractive index ring can precisely control the effective refractive index difference between the LP mode in the core and reduce intra-core XT. The relative spatial efficiency (RSE) of the 13-core 6-mode fiber reaches 33.84, and the number of spatial channels is as high as 130. The inter-core crosstalk is less than −60 dB/km at 1550 nm. The results show that the proposed fiber with low crosstalk and large Aeff is sufficient to satisfy the requirements of long-distance transmission in the future.

Failure mode and genesis of bare dispersive soil slope in the cold dry region: insights from Southwest Songnen Plain, China

Failure mode and genesis of bare dispersive soil slope in the cold dry region: insights from Southwest Songnen Plain, China