Real-time ultrasound attenuation imaging of diffuse fatty liver disease

Pulse-echo ultrasound attenuation tomography

Objective.We present the first fully two-dimensional attenuation imaging technique developed for pulse-echo ultrasound systems. Unlike state-of-the-art techniques, which use line-by-line acquisitions, our method uses steered emissions to constrain attenuation values at each location with multiple crossing wave paths, essential to resolve the spatial variations of this tissue property.Approach.At every location, we compute normalized cross-correlations between the beamformed images that are obtained from emissions at different steering angles. We demonstrate that their log-amplitudes provide the changes between attenuation-induced amplitude losses undergone by the different incident waves. This allows us to formulate a linear tomographic problem, which we efficiently solve via a Tikhonov-regularized least-squares approach.Main results.The performance of our tomography technique is first validated in numerical examples and then experimentally demonstrated in custom-made tissue-mimicking phantoms with inclusions of varying size, echogenicity, and attenuation. We show that this technique is particularly good at resolving lateral variations in tissue attenuation and remains accurate in media with varying echogenicity.Significance.Based on a similar principle, this method can be easily combined with computed ultrasound tomography in echo mode for speed-of-sound imaging, paving the way towards a multi-modal ultrasound tomography framework characterizing multiple acoustic tissue properties simultaneously.

Relationship between transmission/reception conditions of high-frequency plane wave compounding and evaluation accuracy of extended amplitude envelope statistics

The double-Nakagami (DN) model provides a method for analyzing the amplitude envelope statistics of quantitative ultrasound (QUS). In this study, the relationship between the sound field characteristics and the robustness of QUS evaluation was evaluated using five HF linear array probes and tissue-mimicking phantoms. Compound plane-wave imaging (CPWI) was used to acquire echo data. Five phantoms containing two types of scatterers were used to mimic fatty liver tissue. After clarifying the relationship between the sound field characteristics of the probes and QUS parameters, DN QUS parameters in 10 rat livers with different lipidification were evaluated using one HF linear array probe. For both phantom and in situ liver analyses, correlations between fat content and multiple QUS parameters were confirmed, suggesting that the combination of CPWI using a HF linear array probe with the DN model is a robust method for quantifying fatty liver and has potential clinical diagnostic applications.

Modified multi-Rayleigh model-based statistical analysis of ultrasound envelope for quantification of liver steatosis and fibrosis

PURPOSE

Quantitative diagnosis of the degree of fibrosis progression is currently a focus of attention for fatty liver in nonalcoholic steatohepatitis (NASH). However, previous studies have focused on either lipid droplets or fibrotic tissue, and few have reported the evaluation of both in patients whose livers contain adipose and fibrous features. Our aim was to evaluate fibrosis tissue and lipid droplets in the liver.

METHODS

We used an analytical method combining the multi-Rayleigh (MRA) model and a healthy liver structure filter (HLSF) as a technique for statistical analysis of the amplitude envelope to estimate fat and fibrotic volumes in clinical datasets with different degrees of fat and fibrosis progression.

RESULTS

Fat mass was estimated based on the non-MRA fraction corresponding to the signal characteristics of aggregated lipid droplets. Non-MRA fraction has a positive correlation with fat mass and is effective for detecting moderate and severe fatty livers. Progression of fibrosis was estimated using MRA parameters in combination with the HLSF. The proposed method was used to extract non-healthy areas with characteristics of fibrotic tissue. Fibrosis in early fatty liver suggested the possibility of evaluation. On the other hand, fat was identified as a factor that reduced the accuracy of estimating fibrosis progression in moderate and severe fatty livers.

CONCLUSION

The proposed method was used to simultaneously evaluate fat mass and fibrosis progression in early fatty liver, suggesting the possibility of quantitative evaluation for discriminating between lipid droplets and fibrous tissue in the early fatty liver.

Reverberation clutter signal suppression in ultrasound attenuation estimation using wavelet-based robust principal component analysis

Objective. Ultrasound attenuation coefficient estimation (ACE) has diagnostic potential for clinical applications such as quantifying fat content in the liver. Previously, we have proposed a system-independent ACE technique based on spectral normalization of different frequencies, called the reference frequency method (RFM). This technique does not require a well-calibrated reference phantom for normalization. However, this method may be vulnerable to severe reverberation clutter introduced by the body wall. The clutter superimposed on liver echoes may bias the estimation. Approach. We proposed to use robust principal component analysis, combined with wavelet-based sparsity promotion, to suppress the severe reverberation clutters. The capability to mitigate the reverberation clutters was validated through phantom and in vivo studies. Main Results. In the phantom studies with added reverberation clutters, higher normalized cross-correlation and smaller mean absolute errors were attained as compared to RFM results without the proposed method, demonstrating the capability to reconstruct tissue signals from reverberations. In a pilot patient study, the correlation between ACE and proton density fat fraction (PDFF), a measurement of liver fat by MRI as a reference standard, was investigated. The proposed method showed an improvement of the correlation (coefficient of determination, R = 0.82) as compared with the counterpart without the proposed method (R = 0.69). Significance: The proposed method showed the feasibility of suppressing the reverberation clutters, providing an important basis for the development of a robust ACE with large reverberation clutters.

Quantitative Ultrasound Assessment of Hepatic Steatosis

BACKGROUND/AIMS

Non-alcoholic fatty liver disease (NAFLD) is widespread chronic disease of the live in humans with the prevalence of 30% of the United States population.^1,2 The goal of the study is to validate the performance of quantitative ultrasound algorithms in the assessment of hepatic steatosis in patients with suspected NAFLD.

METHODS

This prospective study enrolled a total of 31 patients with clinical suspicion of NAFLD to receive liver fat measurements by quantitative ultrasound and reference MRI measurements (proton density fat-fraction, PDFF). The following ultrasound (US) parameters based on both raw ultrasound RF (Radio Frequency) data and 2D B-mode images of the liver were analyzed with subsequent correlation with MRI-PDFF: hepatorenal index, acoustic attenuation coefficient, Nakagami coefficient parameter, shear wave viscosity, shear wave dispersion and shear wave elasticity. Ultrasound parameters were also correlated with the presence of hypertension and diabetes.

RESULTS

The mean (± SD) age and body mass index of the patients were 49.03 (± 12.49) and 30.12 (± 6.15), respectively. Of the aforementioned ultrasound parameters, the hepatorenal index and acoustic attenuation coefficient showed a strong correlation with MRI-PDFF derivations of hepatic steatosis, with r-values of 0.829 and 0.765, respectively. None of the remaining US parameters showed strong correlations with PDFF. Significant differences in Nakagami parameters and acoustic attenuation coefficients were found in those patients with and without hypertension.

CONCLUSIONS

Hepatorenal index and acoustic attenuation coefficient correlate well with MRI-PDFF-derived measurements of hepatic steatosis. Quantitative ultrasound is a promising tool for the diagnosis and assessment of patients with NAFLD.

Improved Ultrasound Attenuation Measurement Method for the Non-invasive Evaluation of Hepatic Steatosis Using FibroScan

Controlled attenuation parameter (CAP) is a measurement of ultrasound attenuation used to assess liver steatosis non-invasively. However, the standard method has some limitations. This study assessed the performance of a new CAP method by ex vivo and in vivo assessments. The major difference with the new method is that it uses ultrasound data continuously acquired during the imaging phase of the FibroScan examination. Seven reference tissue-mimicking phantoms were used to test the performance. In vivo performance was assessed in two cohorts (in total 195 patients) of patients using magnetic resonance imaging proton density fat fraction (MRI-PDFF) as a reference. The precision of CAP was improved by more than 50% on tissue-mimicking phantoms and 22%-41% in the in vivo cohort studies. The agreement between both methods was excellent, and the correlation between CAP and MRI-PDFF improved in both studies (0.71 to 0.74; 0.70 to 0.76). Using MRI-PDFF as a reference, the diagnostic performance of the new method was at least equal or superior (area under the receiver operating curve 0.889-0.900, 0.835-0.873). This study suggests that the new continuous CAP method can significantly improve the precision of CAP measurements ex vivo and in vivo.

A multiparametric volumetric quantitative ultrasound imaging technique for soft tissue characterization

Quantitative ultrasound (QUS) offers a non-invasive and objective way to quantify tissue health. We recently presented a spatially adaptive regularization method for reconstruction of a single QUS parameter, limited to a two dimensional region. That proof-of-concept study showed that regularization using homogeneity prior improves the fundamental precision-resolution trade-off in QUS estimation. Based on the weighted regularization scheme, we now present a multiparametric 3D weighted QUS (3D QUS) method, involving the reconstruction of three QUS parameters: attenuation coefficient estimate (ACE), integrated backscatter coefficient (IBC) and effective scatterer diameter (ESD). With the phantom studies, we demonstrate that our proposed method accurately reconstructs QUS parameters, resulting in high reconstruction contrast and therefore improved diagnostic utility. Additionally, the proposed method offers the ability to analyze the spatial distribution of QUS parameters in 3D, which allows for superior tissue characterization. We apply a three-dimensional total variation regularization method for the volumetric QUS reconstruction. The 3D regularization involving N planes results in a high QUS estimation precision, with an improvement of standard deviation over the theoretical 1/N rate achievable by compounding N independent realizations. In the in vivo liver study, we demonstrate the advantage of adopting a multiparametric approach over the single parametric counterpart, where a simple quadratic discriminant classifier using feature combination of three QUS parameters was able to attain a perfect classification performance to distinguish between normal and fatty liver cases.

Noise Suppression for Ultrasound Attenuation Coefficient Estimation Based on Spectrum Normalization

Ultrasound attenuation coefficient estimation (ACE) has great diagnostic potential for fatty liver detection and assessment. In a previous study, we proposed a reference phantom-free ACE method, called reference frequency method (RFM), which does not require a calibrated phantom for normalization. The power of each frequency component can be normalized by the power of an adjacent frequency component in the spectrum to cancel system-dependent effects such as focusing and time gain compensation (TGC). RFM demonstrated accurate ACE in both phantom and in in-vivo liver studies. However, our study also showed that the robustness and penetration of RFM were affected by noise in the ACE signals. Here we propose a noise suppression (NS) and a signal-to-noise ratio (SNR) quality control method to reduce the influence of noise on ACE-RFM performance. The proposed methods were tested in harmonic ACE because harmonic imaging is a more frequently used mode than fundamental imaging for abdominal applications. After applying the NS and SNR control methods, the noise-induced bias for attenuation estimation in harmonic ACE was effectively reduced, leading to significantly improved effective penetration depth. The proposed methods directly measure the noise spectrum of the ultrasound system, which can also be adapted to other spectrum-based ACE methods, such as the reference phantom method and the spectra shift method.

Diagnostic Value of Ultrasound in Fatty Liver Disease

Hepatic steatosis is a commonly seen phenomenon in clinical practice and is the result of the accumulation of lipids in the hepatocytes. In most cases steatosis refers to nonalcoholic fatty liver disease (NAFLD), but it also occurs in other diseases of the liver parenchyma of a different etiology and is the result of the dysregulation of metabolic processes. Consequently, inflammatory processes can induce progressive fibrosis. Due to the high prevalence of fatty liver disease, a further increase in metabolic liver cirrhosis with corresponding complications can be expected in the near future. Due to its broad availability, ultrasound is particularly important, especially for the management of NAFLD. In addition to diagnosis and risk stratification, the monitoring of high-risk patients in NAFLD is becoming increasingly clinically important. Multimodality ultrasound includes B-mode and duplex methods, analysis of tissue stiffness (elastography), contrast-enhanced imaging (CEUS), and steatosis quantification. When using ultrasound in fatty liver disease, a standardized approach that takes into account the limitations of the method is essential.

Reproducibility of ultrasound attenuation imaging for the noninvasive evaluation of hepatic steatosis

PURPOSE

The purpose of this study was to evaluate the intra-observer reproducibility of ultrasound attenuation imaging (ATI) for the noninvasive assessment of hepatic steatosis in patients with suspected hepatic steatosis and the inter-observer reproducibility in asymptomatic volunteers.

METHODS

This prospective study was approved by our institutional review board and informed consent was obtained from all patients. In group 1, composed of patients with suspected hepatic steatosis (n=143), one abdominal radiologist performed gray-scale ultrasonography and two sessions of ATI. In group 2, composed of healthy volunteers (n=18), three independent sessions of ATI were performed by three abdominal radiologists. The visual degree of hepatic steatosis in all study subjects was graded on a 4-point scale by two independent reviewers using gray-scale ultrasonography. Thereafter, the attenuation coefficient (AC) was correlated with the degree of hepatic steatosis using Spearman rank correlation analysis. Intra-class correlation coefficients (ICCs) were used to assess the intra-observer (group 1) and inter-observer reproducibility (group 2) of ATI measurements.

RESULTS

For the intra-observer reproducibility of ATI, the ICC was 0.929 (95% confidence interval [CI], 0.901 to 0.949), and the coefficient of variation was 7.1%. Inter-observer reproducibility of ATI measurements showed an ICC of 0.792 (95% CI, 0.549 to 0.916). The AC showed a significant correlation with the visual grade of hepatic steatosis for both reviewers (rho, 0.780 and 0.695; P<0.001, respectively).

CONCLUSION

ATI showed high intra- and inter-observer reproducibility in the assessment of hepatic steatosis.

Metabolic Syndrome Is Associated With Advanced Liver Fibrosis Among Pediatric Patients With Non-alcoholic Fatty Liver Disease

Background: Non-alcoholic fatty liver disease (NAFLD) among children is a growing concern with potential significant outcome. This study aims to investigate the relationship between hepatic steatosis, metabolic syndrome, and liver fibrosis among children with obesity and diabetes mellitus. Methodology: Children aged 6-18 years old were recruited from pediatric obesity and diabetes clinic in University Malaya Medical Center (UMMC) between year 2016 and 2019. Data on basic demographics, anthropometric measurements and clinical components of metabolic syndrome were collected. Transient elastography was performed with hepatic steatosis and liver fibrosis assessed by controlled attenuation parameter (CAP) and liver stiffness measurement (LSM) respectively. Mild, moderate and severe steatosis were defined as >248, >268, and >280 dB/m respectively, and LSM above 7.0 kPa for fibrosis stage F ≥ 2, 8.7 kPa for F ≥ 3, and 10.3 kPa for F4 (cirrhosis). Results: A total of 57 children (60% male) with median age of 13 years old were recruited. Fifty (87.7%) of the children are obese and 27 (54%) out of 50 are morbidly obese. Among 44 (77.2%) patients with steatosis, 40 (70.2%) had severe steatosis and 18 (40.9%) had developed liver fibrosis of stage 2 and above. Advanced fibrosis or cirrhosis was detected in 8 (18.2%) children with presence of steatosis. Twenty-three out of 57 (40.4%) was diagnosed with metabolic syndrome. Fibrosis is three times more likely to occur in the presence of metabolic syndrome (OR = 3.545, 95% CI: 1.135-11.075, p = 0.026). Waist circumference is a significant predictor of fibrosis after multiple regression analysis. Conclusion: Obese children with metabolic syndrome are more likely to have advanced liver fibrosis compared to those without metabolic syndrome. Waist circumference predicts development of liver fibrosis.

Flash Imaging Used in the Post-vascular Phase of Contrast-Enhanced Ultrasonography is Useful for Assessing the Progression in Patients with Hepatitis C Virus-Related Liver Disease

Sonazoid is a commonly used contrast agent for characterizing liver tumors in ultrasonography (US). We performed flash imaging in the post-vascular phase of contrast-enhanced US (CEUS) to investigate associations between collapse of Sonazoid microbubbles (MB) and progression of liver disease. This study enrolled 409 patients (205 men, 204 women) with hepatitis C virus-related liver disease (CLD) between 2007 and 2017 (mean age 60 ± 14 y; range 20-90 y). In the post-vascular phase, 10 min after administering Sonazoid, flash imaging was performed to burst MB in the liver parenchyma; the range of bubble destruction was measured from the surface of the liver. The range of bubble destruction, stage of fibrosis, shear wave velocity (Vs), serologic markers and fibrosis-4 (FIB4) index were analyzed in 259 patients who underwent liver biopsy. Fibrosis stage was F0-1 in 108 patients, F2 in 73, F3 in 38 and F4 in 40. In 150 patients with cirrhosis, diagnosis was made based on imaging findings. The range of bubble destruction was 42.0 ± 10.4 mm in F0-1 patients, 42.9 ± 13.2 mm in F2, 51.5 ± 15.9 mm in F3 and 55.4 ± 17.3 mm in F4 and was significantly increased according to progression of fibrosis staging. The range of bubble destruction was positively correlated with Vs (r = 0.34; p < 0.01), total bilirubin (r = 0.25; p < 0.01) and FIB4 index (r = 0.38; p < 0.01). In contrast, the range of bubble destruction was negatively correlated with serum levels of albumin (r = -0.34; p < 0.01), platelet count (r = -0.35; p < 0.01) and prothrombin time (r = -0.36; p < 0.01). The results indicated that flash imaging in the post-vascular phase of CEUS was a non-invasive assessment and could predict disease progression in patients with CLD.

Metabolic Characteristics of a Novel Ultrasound Quantitative Diagnostic Index for Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is an emerging epidemic worldwide and is regarded as a hepatic manifestation of metabolic syndrome (MetS). Only a few studies have discussed the biological features associated with quantitative assessment of ultrasound for characterizing NAFLD. Our aim was to delineate relevant metabolic characteristics using a new quantitative tool, the ultrasound quantitative diagnostic index (QDI). A total of 394 ultrasound data were analyzed to extract texture-feature parameters, the signal-to-noise ratio (SNR), and the slope of the center frequency downshift (CFDS) for determining the QDI. The texture index, SNR, and CFDS slope were all negatively correlated with high-density lipoprotein and positively correlated with other anthropometric indices and metabolic factors (all P < 0.05). The SNR had the greatest contribution to anthropometric and biochemical factors, followed by the texture index and CFDS slope. An increase in 1 unit of QDI score engendered a 9% higher risk of MetS, reflecting that the tool is feasible for use in identifying MetS (area under the receiver operating characteristic curve: 0.89). The QDI was correlated with metabolic factors and an independent predictor for MetS. Thus, this QDI might be a feasible method for use in clinical surveillance, epidemiology research, and metabolic function evaluations in patients with NAFLD.

Attenuation Coefficient Estimation of Normal Placentas

Attenuation coefficient estimation has the potential to be a useful tool for placental tissue characterization. A current challenge is the presence of inhomogeneities in biological tissue that result in a large variance in the attenuation coefficient estimate (ACE), restricting its clinical utility. In this work, we propose a new Attenuation Estimation Region Of Interest (AEROI) selection method for computing the ACE based on the (i) envelope signal-to-noise ratio deviation and (ii) coefficient of variation of the transmit pulse bandwidth. The method was first validated on a tissue-mimicking phantom, for which an 18%-21% reduction in the standard deviation of ACE and a 14%-24% reduction in the ACE error, expressed as a percentage of reported ACE, were obtained. A study on 59 post-delivery clinically normal placentas was then performed. The proposed AEROI selection method reduced the intra-subject standard deviation of ACE from 0.72 to 0.39 dB/cm/MHz. The measured ACE of 59 placentas was 0.77 ± 0.37 dB/cm/MHz, which establishes a baseline for future studies on placental tissue characterization.

System-Independent Ultrasound Attenuation Coefficient Estimation Using Spectra Normalization

Ultrasound attenuation coefficient estimation (ACE) has diagnostic potential for clinical applications such as differentiating tumors and quantifying fat content in the liver. The two commonly used ACE methods in the ultrasound array imaging system are the spectral shift method and the reference-phantom-based methods. The spectra shift method estimates the central frequency downshift along depth, whereas the reference-phantom-based methods use a well-calibrated phantom to cancel system dependent effects in attenuation estimation. In this study, we propose a novel system-independent ACE technique based on spectra normalization of different frequencies. This technique does not require a reference phantom for normalization. The power of each frequency component is normalized by the power of an adjacent frequency component in the spectrum to cancel system-dependent effects, such as focusing and time gain compensation (TGC). This method is referred to as the reference frequency method (RFM), and its performance has been evaluated in phantoms and in vivo liver studies. The RFM technique can be applied to various transducer geometries (e.g., linear or curved arrays) with different beam patterns (e.g., focused or unfocused).

Instantaneous frequency as a new approach for evaluating the clinical severity of Duchenne muscular dystrophy through ultrasound imaging

Duchenne muscular dystrophy (DMD) results in loss of ambulation for the patients. Ultrasound attenuation correlates with fat content in muscles, resulting in changes in signal frequency. The Hilbert-Huang transform (HHT) allows time-frequency analysis with high time-frequency resolution. This study explored the feasibility of using the instantaneous frequency (IF) obtained from the HHT to diagnose the walking function of patients with DMD. Eighty-five participants (12 control and 73 patients with DMD) underwent a standard-care ultrasound examination of the gastrocnemius to acquire raw image data for ultrasound B-mode and IF calculations, which were compared with the DMD stage using Pearson correlation and receiver operating characteristic (ROC) curve analyses. With increasing DMD stage, the median IF decreased from 7.25 to 7.01 MHz (the correlation coefficient r = -0.73; the probability value p < 0.0001). The area under the ROC curve was 0.97 when using ultrasound IF to discriminate between ambulatory and nonambulatory patients (accuracy: 91.76%; sensitivity: 93.75%; and specificity: 90.57%). The study reveals that ultrasound IF has great potential in DMD evaluation and management.

Multiparametric QUS Analysis for Placental Tissue Characterization

Multiparametric Quantitative Ultrasound (QUS) holds promise for characterizing placental tissue and detecting placental disorders. In this study, we simultaneously extract two qualitatively different QUS parameters, namely attenuation coefficient estimate (ACE) and shear wave speed from ultrasound radio frequency data acquired using a shear wave vibro elastography (SWAVE) method. The study comprised data from 59 post-delivery clinically normal placentas. The shear wave speed was found to be equal to 1.74 ± 0.13 m/s whereas the attenuation coefficient estimate was 0.57 ± 0.48 dB/cm-MHz. This provides a baseline for future studies of placental disorders.

The B-Mode Image-Guided Ultrasound Attenuation Parameter Accurately Detects Hepatic Steatosis in Chronic Liver Disease

The purpose of our study was to evaluate the diagnostic accuracy of the ultrasound-guided attenuation parameter (UGAP) for the detection of hepatic steatosis in comparison with the controlled attenuation parameter (CAP), using histopathology as the reference standard. We prospectively analyzed 163 consecutive chronic liver disease patients who underwent UGAP, CAP, computed tomography and a liver biopsy on the same day between April 2016 and July 2017. Radiofrequency signals corresponding to the images were compensated by the reference signal previously measured from the uniform phantom with known attenuation (0.44 dB/cm/MHz). The attenuation coefficient was calculated from the signals' decay slope. The median attenuation coefficient values in patients with S0 (n = 62), S1 (n = 63), S2 (n = 23) and S3 grade (n = 15) were 0.485, 0.560, 0.660 and 0.720, respectively. Significant correlations were found between attenuation coefficient and percentage steatosis, CAP values and liver-to-spleen computed tomography attenuation ratio (p < 0.001). The areas under the receiver operating characteristic curve of UGAP for identifying ≥S1, ≥S2 and ≥S3 were 0.900, 0.953 and 0.959, respectively, which were significantly better than the results obtained with CAP for identifying ≥S2 and ≥S3. In conclusion, UGAP had high diagnostic accuracy for detecting hepatic steatosis in patients with chronic liver disease.

Hepatic Steatosis Assessment with Ultrasound Small-Window Entropy Imaging

Nonalcoholic fatty liver disease is a type of hepatic steatosis that is not only associated with critical metabolic risk factors but can also result in advanced liver diseases. Ultrasound parametric imaging, which is based on statistical models, assesses fatty liver changes, using quantitative visualization of hepatic-steatosis-caused variations in the statistical properties of backscattered signals. One constraint with using statistical models in ultrasound imaging is that ultrasound data must conform to the distribution employed. Small-window entropy imaging was recently proposed as a non-model-based parametric imaging technique with physical meanings of backscattered statistics. In this study, we explored the feasibility of using small-window entropy imaging in the assessment of fatty liver disease and evaluated its performance through comparisons with parametric imaging based on the Nakagami distribution model (currently the most frequently used statistical model). Liver donors (n = 53) and patients (n = 142) were recruited to evaluate hepatic fat fractions (HFFs), using magnetic resonance spectroscopy and to evaluate the stages of fatty liver disease (normal, mild, moderate and severe), using liver biopsy with histopathology. Livers were scanned using a 3-MHz ultrasound to construct B-mode, small-window entropy and Nakagami images to correlate with HFF analyses and fatty liver stages. The diagnostic values of the imaging methods were evaluated using receiver operating characteristic curves. The results demonstrated that the entropy value obtained using small-window entropy imaging correlated well with log₁₀(HFF), with a correlation coefficient r = 0.74, which was higher than those obtained for the B-scan and Nakagami images. Moreover, small-window entropy imaging also resulted in the highest area under the receiver operating characteristic curve (0.80 for stages equal to or more severe than mild; 0.90 for equal to or more severe than moderate; 0.89 for severe), which indicated that non-model-based entropy imaging-using the small-window technique-performs more favorably than other techniques in fatty liver assessment.

Teleconsultation ultrasonography: a new weapon to combat cholangiocarcinoma

Although cholangiocarcinoma (CCA) is usually a rare cancer, in northeast Thailand it kills 20 000 or more people every year. The prognosis is very poor owing to late stage diagnosis, with palliative treatment often representing the only option. In this area of predominantly rural Thailand, CCA is associated with infection with the liver fluke, Opisthorchis viverrini, which is classified as a group 1 carcinogen. Up to 6 million Thais are infected with this fluke. The Cholangiocarcinoma Screening and Care Program (CASCAP) was initiated in 2014 with the aim of detecting early stage CCA, allowing curative surgery, by using ultrasound (US) screening of prospectively 500 000 at risk individuals. In order to assess the massive number of radiological images, a teleconsultation system was set-up. This allows US images to be sent to a dedicated server where they can be viewed by an expert radiologist who then provides a provisional diagnosis, recommending more advanced diagnostic techniques (CT and MRI) for suspected cases. To date, 250 000 people have been screened, and 2000 cases of CCA diagnosed. This innovative information transfer procedure will also be made available to Laos, Cambodia and Vietnam, where O. viverrini infection is also common.

Multifeature analysis of an ultrasound quantitative diagnostic index for classifying nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease related to metabolic syndrome. This study applied an integrated analysis based on texture, backscattering, and attenuation features in ultrasound imaging with the aim of assessing the severity of NAFLD. Ultrasound radiofrequency data obtained from 394 clinical cases were analyzed to extract three texture features (autocorrelation, sum average, and sum variance), the signal-to-noise ratio (SNR), and the slope of the center-frequency downshift (CFDS slope). The texture, SNR, and CFDS slope were combined to produce a quantitative diagnostic index (QDI) that ranged from 0 to 6. We trained the QDI using training data and then applied it to test data to assess its utility. In training data, the areas (AUCs) under the receiver operating characteristic curves for NAFLD and severe NAFLD were 0.81 and 0.84, respectively. In test data, the AUCs were 0.73 and 0.81 for NAFLD and severe NAFLD, respectively. The QDI was able to distinguish severe NAFLD and a normal liver from mild NAFLD, and it was significantly correlated with metabolic factors. This study explored the potential of using the QDI to supply information on different physical characteristics of liver tissues for advancing the ability to grade NAFLD.

Hepatic artery resistive index (HARI) and non-alcoholic fatty liver disease (NAFLD) fibrosis score in NAFLD patients: cut-off suggestive of non-alcoholic steatohepatitis (NASH) evolution

PURPOSE OF THE STUDY

Conventional ultrasound (US) is reliable to reveal the presence of non-alcoholic fatty liver disease (NAFLD), but it is neither sensitive nor specific to reveal fibrosis clues, except in advanced stages where signs of cirrhosis are evident. NALFD fibrosis score is a non-invasive parameter that predicts well the presence of significant fibrosis, but correlations with US parameters are lacking. The aim of this study was, therefore, to compare resistive index of hepatic artery (HARI) of NAFLD patients with different severity degrees of diffuse fatty liver disease vs HARI of controls, and to compare HARI of NAFLD patients with different NAFLD fibrosis scores vs HARI of controls.

METHODS

This was a spontaneous, no-profit observational study conducted in our US department between December 2013 and July 2014. Patients with NAFLD with different severity of disease and healthy controls were included. Echogenicity and size of liver and spleen, maximum portal vein velocity, RI, peak systolic velocity (PSV), and end diastolic velocity (EDV) of splenic artery, PSV, EDV, and RI of hepatic artery, and NAFLD fibrosis score were acquired and compared between groups.

RESULTS

HARI was significantly lower in NAFLD patients than controls (p < 0.0001). A significant difference was also found between the groups of NAFLD severity (p < 0.0001). There was also a difference between HARI of NAFLD patients with different NAFLD fibrosis scores vs HARI of controls (p < 0.0001) with a positive correlation between HARI and NAFLD fibrosis score.

CONCLUSION AND DISCUSSION

Conventional Doppler US can be helpful to detect NAFLD patients with the risk of fibrous tissue accumulation. HARI tends to exceed the range of controls for patients with NAFLD fibrosis score greater than 0.675. The detection of HARI greater than 0.9 in NAFLD patients, regardless of the US degree of severity of steatosis, might suggest the execution of biopsy to predict the risk of progression to steatohepatitis and fibrous tissue accumulation. Low values of HARI may be expression of lower risk, which does not necessitate any biopsy.

Effects of fatty infiltration in human livers on the backscattered statistics of ultrasound imaging

Ultrasound imaging has been widely applied to screen fatty liver disease. Fatty liver disease is a condition where large vacuoles of triglyceride fat accumulate in liver cells, thereby altering the arrangement of scatterers and the corresponding backscattered statistics. In this study, we used ultrasound Nakagami imaging to explore the effects of fatty infiltration in human livers on the statistical distribution of backscattered signals. A total of 107 patients volunteered to participate in the experiments. The livers were scanned using a clinical ultrasound scanner to obtain the raw backscattered signals for ultrasound B-mode and Nakagami imaging. Clinical scores of fatty liver disease for each patient were determined according to a well-accepted sonographic scoring system. The results showed that the Nakagami image can visualize the local backscattering properties of liver tissues. The Nakagami parameter increased from 0.62 ± 0.11 to 1.02 ± 0.07 as the fatty liver disease stage increased from normal to severe, indicating that the backscattered statistics vary from pre-Rayleigh to Rayleigh distributions. A significant positive correlation (correlation coefficient ρ = 0.84; probability value (p value) < 0.0001) exists between the degree of fatty infiltration and the Nakagami parameter, suggesting that ultrasound Nakagami imaging has potentials in future applications in fatty liver disease diagnosis.

Separation of hepatic iron and fat by dual-source dual-energy computed tomography based on material decomposition: an animal study

Objective

To explore the feasibility of dual-source dual-energy computed tomography (DSDECT) for hepatic iron and fat separation in vivo.

Materials and Methods

All of the procedures in this study were approved by the Research Animal Resource Center of Shanghai Ruijin Hospital. Sixty rats that underwent DECT scanning were divided into the normal group, fatty liver group, liver iron group, and coexisting liver iron and fat group, according to Prussian blue and HE staining. The data for each group were reconstructed and post-processed by an iron-specific, three-material decomposition algorithm. The iron enhancement value and the virtual non-iron contrast value, which indicated overloaded liver iron and residual liver tissue, respectively, were measured. Spearman's correlation and one-way analysis of variance (ANOVA) were performed, respectively, to analyze statistically the correlations with the histopathological results and differences among groups.

Results

The iron enhancement values were positively correlated with the iron pathology grading (r = 0.729, p<0.001). Virtual non-iron contrast (VNC) values were negatively correlated with the fat pathology grading (r = −0.642,p<0.0001). Different groups showed significantly different iron enhancement values and VNC values (F = 25.308,p<0.001; F = 10.911, p<0.001, respectively). Among the groups, significant differences in iron enhancement values were only observed between the iron-present and iron-absent groups, and differences in VNC values were only observed between the fat-present and fat-absent groups.

Conclusion

Separation of hepatic iron and fat by dual energy material decomposition in vivo was feasible, even when they coexisted.

Window-modulated compounding Nakagami imaging for ultrasound tissue characterization

Ultrasound Nakagami parametric imaging is a useful tool for tissue characterization. Previous literature has suggested using a square with side lengths corresponding to 3 times the transducer pulse length as the minimum window for constructing the Nakagami image. This criterion does not produce sufficiently smooth images for the Nakagami image to characterize homogeneous tissues. To improve image smoothness, we proposed window-modulated compounding (WMC) Nakagami imaging based on summing and averaging the Nakagami images formed using sliding windows with varying window side lengths from 1 to N times the transducer pulse length in 1 pulse length step. Simulations (the number densities of scatterers: 2-16 scatterers/mm(2)) and experiments on fully developed speckle phantoms (the scatterer diameters: 20-106 μm) were conducted to suggest an appropriate number of frames N and to evaluate the image smoothness and resolution by analyzing the full width at half maximum (FWHM) of the parameter distribution and the widths of the image autocorrelation function (ACF), respectively. In vivo ultrasound measurements on rat livers without and with cirrhosis were performed to validate the practical performance of the WMC Nakagami image in tissue characterization. The simulation results showed that using a range of N from 7 to 10 as the number of frames for image compounding reduces the estimation error to less than 5%. Based on this criterion, the Nakagami parameter obtained from the WMC Nakagami image increased from 0.45 to 0.95 after increasing the number densities of scatterers from 2 to 16 scatterers/mm(2). The FWHM of the parameter distribution (bins=40) was 13.5±1.4 for the Nakagami image and 9.1±1.43 for the WMC Nakagami image, respectively (p-value<.05). The widths of the ACF for the Nakagami and WMC Nakagami images were 454±5.36 and 458±4.33, respectively (p-value>.05). In the phantom experiments, we also found that the FWHM of the parameter distribution for the WMC Nakagami image was smaller than that of the conventional Nakagami image (p-value<.05), and there was no significant difference of the ACF width between the Nakagami and WMC Nakagami images (p-value>.05). In the animal experiments, the Nakagami parameters obtained from the WMC Nakagami image for normal and cirrhotic rat livers were 0.62±0.08 and 0.92±0.07, respectively (p-value<.05). The results demonstrated that the WMC technique significantly improved the image smoothness of Nakagami imaging without resolution degradation, giving Nakagami model-based imaging the ability to visualize scatterer properties with enhanced image quality.

Measurement of ultrasonic attenuation in diabetic neuropathic sciatic nerves for diagnostic and therapeutic applications

Measurements of ultrasonic attenuation in the sciatic nerves of rats were performed to verify the feasibility of ultrasound diagnosis of peripheral neuropathy and to avoid damage to the nerves caused by overheating in pain management applications. A rat model of diabetic peripheral neuropathy was established. The proximal-segment and middle-segment sciatic nerves of control and neuropathic rats were dissected for the attenuation measurement. Two commercial ultrasound transducers and a self-developed experimental platform were used in the measurements. Using H&E staining and transmission electron (TE) microscopy, morphological analysis of the control and neuropathic nerves was performed to determine the relationship between attenuation and the histology of the nerves. The experimental results showed that the attenuation coefficients of the control, second-week, fourth-week, and eighth-week neuropathic nerves were -6.68 ± 0.50, -5.61 ± 0.34, -6.27 ± 0.40, and -7.10 ± 0.35 dB/cm at 2.68 MHz, respectively. The respective values at 7.50 MHz were -14.96 ± 0.79, -12.65 ± 0.28, -13.98 ± 1.07, and -16.00 ± 0.54 dB/cm. The changes in the attenuation coefficients were significantly different among the second-week, fourth-week, and eighth-week DN nerves. Additionally, the ultrasonic attenuation coefficient of the rat sciatic nerve was fourfold that of the cat brain and cow liver and twofold that of human muscle.

No correlation between PNPLA3 rs738409 genotype and fatty liver and hepatic cirrhosis in Japanese patients with HCV

Background

Hepatitis C virus (HCV) infection is associated with the development of cirrhosis and hepatocellular carcinoma and is also related to fatty change of the liver. Variation in patatin-like phospholipase domain-containing 3 (PNPLA3) gene is associated with disease progression in nonalcoholic fatty liver disease (NAFLD). Recent reports have suggested that PNPLA3, IL28B and TLR4-associated single nucleotide polymorphisms (SNPs) may have an impact on hepatic steatosis or fibrosis in patients with chronic HCV infection.

Methods and Findings

Four SNPs (PNPLA3 rs738409, TLR4 rs4986790, TLR4 rs4986791, IL28B rs8099917) were identified in Japanese patients infected with HCV. We examined the association between the distribution of these SNP alleles and fatty change of the liver or existence of hepatic cirrhosis diagnosed by ultrasonography, one of the widely accessible and easy-to-use methods. PNPLA3 rs738409 G-allele and IL28B rs 8099917 minor allele were found in 70.0% and 31.1%, respectively. These two TLR4 SNPs were uniform in Japanese. Fatty change of the liver developed independent of the abscence of hepatic cirrhosis on sonographic findings and younger age. Hepatic cirrhosis was associated with a higher aspartate aminotransferase/platelet ratio index (APRI), no fatty change of the liver, higher BMI and higher AFP levels. No association between PNPLA3 rs738409/IL28B rs8099917 genotypes and hepatic steatosis or liver fibrosis was observed.

Conclusions

According to ultrasound examinations, no association between PNPLA3 rs738409 genotype and fatty change of the liver or hepatic cirrhosis was found in Japanese patients infected with HCV. Together, our results suggested that the mechanism of hepatic steatosis underlying HCV infection might differ from that of NAFLD and should be explored.

No correlation between PNPLA3 rs738409 genotype and fatty liver and hepatic cirrhosis in Japanese patients with HCV

BACKGROUND

Hepatitis C virus (HCV) infection is associated with the development of cirrhosis and hepatocellular carcinoma and is also related to fatty change of the liver. Variation in patatin-like phospholipase domain-containing 3 (PNPLA3) gene is associated with disease progression in nonalcoholic fatty liver disease (NAFLD). Recent reports have suggested that PNPLA3, IL28B and TLR4-associated single nucleotide polymorphisms (SNPs) may have an impact on hepatic steatosis or fibrosis in patients with chronic HCV infection.

METHODS AND FINDINGS

Four SNPs (PNPLA3 rs738409, TLR4 rs4986790, TLR4 rs4986791, IL28B rs8099917) were identified in Japanese patients infected with HCV. We examined the association between the distribution of these SNP alleles and fatty change of the liver or existence of hepatic cirrhosis diagnosed by ultrasonography, one of the widely accessible and easy-to-use methods. PNPLA3 rs738409 G-allele and IL28B rs 8099917 minor allele were found in 70.0% and 31.1%, respectively. These two TLR4 SNPs were uniform in Japanese. Fatty change of the liver developed independent of the abscence of hepatic cirrhosis on sonographic findings and younger age. Hepatic cirrhosis was associated with a higher aspartate aminotransferase/platelet ratio index (APRI), no fatty change of the liver, higher BMI and higher AFP levels. No association between PNPLA3 rs738409/IL28B rs8099917 genotypes and hepatic steatosis or liver fibrosis was observed.

CONCLUSIONS

According to ultrasound examinations, no association between PNPLA3 rs738409 genotype and fatty change of the liver or hepatic cirrhosis was found in Japanese patients infected with HCV. Together, our results suggested that the mechanism of hepatic steatosis underlying HCV infection might differ from that of NAFLD and should be explored.