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.

Deep learning approach for discrimination of liver lesions using nine time-phase images of contrast-enhanced ultrasound

PURPOSE

Contrast-enhanced ultrasound (CEUS) shows different enhancement patterns depending on the time after administration of the contrast agent. The aim of this study was to evaluate the diagnostic performance of liver nodule characterization using our proposed deep learning model with input of nine CEUS images.

METHODS

A total of 181 liver lesions (48 benign, 78 hepatocellular carcinoma (HCC), and 55 non-HCC malignant) were included in this prospective study. CEUS were performed using the contrast agent Sonazoid, and in addition to B-mode images before injection, image clips were stored every minute up to 10 min. A deep learning model was developed by arranging three ResNet50 transfer learning models in parallel. This proposed model allowed inputting up to nine datasets of different phases of CEUS and performing image augmentation of nine images synchronously. Using the results, the correct prediction rate, sensitivity, and specificity between "benign" and "malignant" cases were analyzed for each combination of the time phase. These accuracy values were also compared with the washout score judged by a human.

RESULTS

The proposed model showed performance superior to the referential standard model when the dataset from B-mode to the 10-min images were used (sensitivity: 93.2%, specificity: 65.3%, average correct answer rate: 60.1%). It also maintained 90.2% sensitivity and 61.2% specificity even when the dataset was limited to 2 min after injection, and this accuracy was equivalent to or better than human scoring by experts.

CONCLUSION

Our proposed model has the potential to identify tumor types earlier than the Kupffer phase, but at the same time, machine learning confirmed that Kupffer-phase Sonazoid images contain essential information for the classification of liver nodules.

Multivariable Quantitative US Parameters for Assessing Hepatic Steatosis

Background Because of the global increase in the incidence of nonalcoholic fatty liver disease, the development of noninvasive, widely available, and highly accurate methods for assessing hepatic steatosis is necessary. Purpose To evaluate the performance of models with different combinations of quantitative US parameters for their ability to predict at least 5% steatosis in patients with chronic liver disease (CLD) as defined using MRI proton density fat fraction (PDFF). Materials and Methods Patients with CLD were enrolled in this prospective multicenter study between February 2020 and April 2021. Integrated backscatter coefficient (IBSC), signal-to-noise ratio (SNR), and US-guided attenuation parameter (UGAP) were measured in all participants. Participant MRI PDFF value was used to define at least 5% steatosis. Four models based on different combinations of US parameters were created: model 1 (UGAP alone), model 2 (UGAP with IBSC), model 3 (UGAP with SNR), and model 4 (UGAP with IBSC and SNR). Diagnostic performance of all models was assessed using area under the receiver operating characteristic curve (AUC). The model was internally validated using 1000 bootstrap samples. Results A total of 582 participants were included in this study (median age, 64 years; IQR, 52-72 years; 274 female participants). There were 364 participants in the steatosis group and 218 in the nonsteatosis group. The AUC values for steatosis diagnosis in models 1-4 were 0.92, 0.93, 0.95, and 0.96, respectively. The C-indexes of models adjusted by the bootstrap method were 0.92, 0.93, 0.95, and 0.96, respectively. Compared with other models, models 3 and 4 demonstrated improved discrimination of at least 5% steatosis (P < .01). Conclusion A model built using the quantitative US parameters UGAP, IBSC, and SNR could accurately discriminate at least 5% steatosis in patients with CLD. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Han in this issue.

Modified CEUS LI-RADS using Sonazoid for the diagnosis of hepatocellular carcinoma

This review outlines several modified versions of the contrast-enhanced ultrasonography Liver Imaging Reporting and Data System (CEUS LI-RADS) that utilize Sonazoid. Furthermore, it discusses the advantages and challenges of diagnosing hepatocellular carcinoma using these guidelines, as well as the authors' expectations and opinions regarding the next CEUS LI-RADS version. It is possible that Sonazoid could be incorporated into the next version of CEUS LI-RADS.

The effect of attenuation inside the acoustic traps on the configuration of vertical artifacts in lung ultrasound: an experimental study with simple models

Purpose

Using simple experimental models for lung ultrasound, we evaluated the relationship of the attenuation inside the sources of vertical artifacts to the echo intensity and attenuation of artifacts.

Methods

As sources of artifacts, we made 10 different hemispherical gel objects with two different mediums (pure agar or agar containing graphite with an attenuation coefficient of 0.5 dB/cm · MHz) and five different diameters (3.6, 5.6, 7.5, 9.5, or 11.4 mm). Ten of each hemispherical gel object were prepared for the statistical analyses. Each object was placed onto a chest wall phantom as the plane of the hemisphere was placed in an upward position. The echo intensity and attenuation of the artifact generated from each object was measured and compared.

Results

For all sizes, the intensity and attenuation of the artifacts in the objects made of agar containing graphite were significantly lower and larger, respectively, than those in the objects made of pure agar. In the objects containing graphite, the intensity decreased when the frequency was changed from 5 to 9 MHz.

Conclusion

Based on this experiment, assessing the intensity and attenuation of vertical artifacts may help estimate the physical composition of sources of vertical artifacts in lung ultrasound.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10396-022-01244-0.

Comparison of modified CEUS LI-RADS with sonazoid and CT/MRI LI-RADS for diagnosis of hepatocellular carcinoma

AIM

To compare the diagnostic performance based on the modified CEUS Liver Imaging Reporting and Data System (LI-RADS), which includes Kupffer-phase findings as a major imaging feature, with that of CT and MRI (CT/MRI) LI-RADS for liver nodules in patients at high risk of HCC.

METHODS

A total of 120 patients with 120 nodules were included in this retrospective study. The median size of the lesions was 20.0 mm (interquartile range, 14.0-30.8 mm). Of these lesions, 90.0% (108 of 120) were confirmed as HCCs, 6.7% (8 of 120) were intrahepatic cholangiocarcinomas, 1.7% (2 of 120) were metastases, and 1.7% (2 of 120) were dysplastic nodules. All nodules were diagnosed histopathologically. Each nodule was categorized according to the modified CEUS LI-RADS and CT/MRI LI-RADS version 2018. The diagnostic performance and inter-modality agreement of each criterion was compared.

RESULTS

The inter-modality agreement for the modified CEUS LI-RADS and CT/MRI LI-RADS was slight agreement (kappa = 0.139, p = 0.015). The diagnostic accuracies of HCCs for the modified CEUS LR-5 and CT/MRI LR-5 were 70.0% (95% confidence interval [CI]: 61.0%, 78.0%) versus 70.8% (95% CI: 61.8%, 78.8%) (p = 0.876), respectively. The diagnostic accuracies of non-HCC malignancies for the modified CEUS LR-M and CT/MRI LR-M were 84.2% (95% CI: 76.4%, 90.2%) versus 96.7% (95% CI: 91.7%, 99.1%) (p = 0.002), respectively.

CONCLUSIONS

The diagnostic performance for HCCs on the modified CEUS LR-5 and CT/MRI LR-5 are comparable. In contrast, CT/MRI LR-M has better diagnostic performance for non-HCC malignancy than that of the modified CEUS LR-M.

Attenuation Coefficient Measurement Using a High-Frequency (2-9 MHz) Convex Transducer for Children Including Fatty Liver

We evaluated the measurement feasibility and diagnostic ability of an ultrasound-guided attenuation parameter (UGAP) using a high-frequency convex transducer in children. This retrospective study included all consecutive children who underwent abdomen ultrasonography from July to December 2020. Attenuation coefficients (ACs) of the liver were measured using both 1- to 6-MHz (AC1-6) and 2- to 9-MHz (AC2-9) probes of the LOGIQ E10 system (GE Healthcare). t-Tests and Pearson's or partial correlation analyses were performed, and AC cutoff values for diagnosing fatty liver were obtained from receiver operating characteristic curve analyses. Finally, 118 patients (M:F = 83:35, mean age: 10.2 ± 4.1 y) were evaluated, and the measurement success rate was 98.3% (116/118) for AC2-9. AC1-6 was available in children with a liver depth greater than 9 cm. The ratio of interquartile range to median of the AC2-9 was lower than that of the AC1-6 (4.3 vs. 8.5, p < 0.001). In the normal group (n = 41), the AC2-9 values were not associated with age, sex or body mass index. For the evaluation of steatosis, the AC2-9 values exhibited a positive correlation with the MR fat fraction (coefficient = 0.498, p < 0.001). The cutoff value of 0.699 dB/cm/MHz had 90.2% sensitivity and 100% specificity for diagnosing fatty liver. In conclusion, measurements of ACs using a high-frequency convex transducer are feasible even in small children, with lower measurement variability. The AC2-9 values also had good diagnostic performance for pediatric fatty liver.

Noninvasive Diagnosis of Hepatocellular Carcinoma on Sonazoid-Enhanced US: Value of the Kupffer Phase

The aim of this study was to compare the diagnostic performance of Contrast-Enhanced US Liver Imaging Reporting and Data System (CEUS LI-RADS) version 2017, which includes portal- and late-phase washout as a major imaging feature, with that of modified CEUS LI-RADS, which includes Kupffer-phase findings as a major imaging feature. Participants at risk of hepatocellular carcinoma (HCC) with treatment-naïve hepatic lesions (≥1 cm) were recruited and underwent Sonazoid-enhanced US. Arterial phase hyperenhancement (APHE), washout time, and echogenicity in the Kupffer phase were evaluated using both criteria. The diagnostic performance of both criteria was analyzed using the McNemar test. The evaluation was performed on 102 participants with 102 lesions (HCCs (n = 52), non-HCC malignancies (n = 36), and benign (n = 14)). Among 52 HCCs, non-rim APHE was observed in 92.3% (48 of 52). By 5 min, 73.1% (38 of 52) of HCCs showed mild washout, while by 10 min or in the Kupffer phase, 90.4% (47 of 52) of HCCs showed hypoenhancement. The sensitivity (67.3%; 35 of 52; 95% CI: 52.9%, 79.7%) of modified CEUS LI-RADS criteria was higher than that of CEUS LI-RADS criteria (51.9%; 27 of 52; 95% CI: 37.6%, 66.0%) (p = 0.0047). In conclusion, non-rim APHE with hypoenhancement in the Kupffer phase on Sonazoid-enhanced US is a feasible criterion for diagnosing HCC.

Simple Experimental Models for Elucidating the Mechanism Underlying Vertical Artifacts in Lung Ultrasound: Tools for Revisiting B-Lines

Using simple experimental models, we evaluated the generation, configuration and echo intensity of vertical artifacts by varying the point or plane of contact and height of objects that correspond to sources of vertical artifacts in the subpleural space. We used an ultrasound gel spot to imitate the source and a block of bacon as a chest wall phantom. As the size of the point of contact between the gel spot on the polypropylene sheet and the phantom decreased by peeling the sheet, a vertical artifact measuring ≤1 cm was generated and/or extended deeper, finally reaching 10 cm in depth. Next, objects of different shapes made using gel balls were used to observe the generation of artifacts and measure and compare the echo intensity. For a given shape, the intensity was markedly higher in one model with the point of contact than in the other model with the plane of contact. With the same point or plane of contact, the echo intensity was higher in the taller model. The size of the point or plane of contact and height of the source were observed to be key factors in the generation, length and echo intensity of the artifacts.

Two-dimensional shear wave elastography and ultrasound-guided attenuation parameter for progressive non-alcoholic steatohepatitis

Background and aims

We investigated the usefulness of combining two-dimensional shear wave elastography and the ultrasound-guided attenuation parameter for assessing the risk of progressive non-alcoholic steatohepatitis, defined as non-alcoholic steatohepatitis with a non-alcoholic fatty liver disease activity score of ≥4 and a fibrosis stage of ≥2.

Methods

This prospective study included 202 patients with non-alcoholic fatty liver disease who underwent two-dimensional shear wave elastography, ultrasound-guided attenuation parameter, vibration-controlled transient elastography, the controlled attenuation parameter, and liver biopsy on the same day. Patients were grouped according to liver stiffness measurement using two-dimensional shear wave elastography and the attenuation coefficient, assessed using the ultrasound-guided attenuation parameter: A, low liver stiffness measurement/low attenuation coefficient; B, low liver stiffness measurement/high attenuation coefficient; C, high liver stiffness measurement/low attenuation coefficient; and D, high liver stiffness measurement/high attenuation coefficient.

Results

Two-dimensional shear wave elastography and vibration-controlled transient elastography had equivalent diagnostic performance for fibrosis. The areas under the curve of the ultrasound-guided attenuation parameter for identifying steatosis grades ≥S1, ≥S2, and S3 were 0.89, 0.91, and 0.92, respectively, which were significantly better than those of the controlled attenuation parameter (P<0.05). The percentages of progressive non-alcoholic steatohepatitis in Groups A, B, C, and D were 0.0%, 7.7%, 35.7%, and 50.0%, respectively (P<0.001). The prediction model was established as logit (p) = 0.5414 × liver stiffness measurement (kPa) + 7.791 × attenuation coefficient (dB/cm/MHz)—8.401, with area under the receiver operating characteristic curve, sensitivity, and specificity values of 0.832, 80.9%, and 74.6%, respectively; there was no significant difference from the FibroScan-aspartate aminotransferase score.

Conclusion

Combined assessment by two-dimensional shear wave elastography and the ultrasound-guided attenuation parameter is useful for risk stratification of progressive non-alcoholic steatohepatitis and may be convenient for evaluating the necessity of specialist referral and liver biopsy.

Liver stiffness does not affect ultrasound-guided attenuation coefficient measurement in the evaluation of hepatic steatosis

AIM

Recently, a new method has been developed to diagnose hepatic steatosis with attenuation coefficients based on the ultrasound-guided attenuation parameter (UGAP). We investigated whether fibrosis identified by hepatic stiffness measurements based on magnetic resonance elastography (MRE) affects attenuation coefficient measurement using UGAP for the evaluation of hepatic steatosis.

METHODS

A total of 608 patients with chronic liver disease were analyzed. Correlations between magnetic resonance imaging-determined proton density fat fraction (PDFF) or MRE value and attenuation coefficients were evaluated. In addition, the interaction between hepatic fibrosis and the attenuation coefficient was analyzed.

RESULTS

The correlation coefficient (r) between PDFF values and attenuation coefficient values was 0.724, indicating a strong relationship. Conversely, the r between MRE values and attenuation coefficient values was -0.187, indicating almost no relationship. In the multiple regression assessment of the effect of PDFF and MRE on the attenuation coefficient based on UGAP, the P-values for PDFF, MRE, and PDFF × MRE were < 0.001, 0.277, and 0.903, respectively. In patients with non-alcoholic fatty liver disease (n = 169), the r between PDFF values and attenuation coefficient values was 0.695, indicating a moderate relationship. Conversely, the r between MRE values and attenuation coefficient values was -0.068, indicating almost no relationship. In the multiple regression assessment of the effect of PDFF and MRE on the attenuation coefficient based on UGAP, the P-values for PDFF, MRE, and PDFF × MRE were <0.001, 0.948, and 0.706, respectively.

CONCLUSION

UGAP-determined attenuation coefficient was weakly affected by liver stiffness, an indicator of hepatic fibrosis.

P6453Activation of necroptotic pathway by downregulated caspase-8 expression is associated with progression of left ventricular remodeling in nonischemic dilated cardiomyopathy

Background

Necroptosis, a form of programmed necrosis, has been suggested to be involved in the pathogenesis of various pathological conditions including heart failure. Protein expression of caspase-8, an endogenous inhibitor of necroptosis, is reported to be downregulated in human failing hearts, but its clinical significance remains unclear.

Methods

Endomyocardial biopsy specimens were obtained from patients with nonischemic dilated cardiomyopathy (n=57, 56.2±14.5 years old, 70% male). The area stained with antibodies against caspase-8 and phospho-MLKL-Ser358 was calculated using an image analyzer, and fibrotic and cardiomyocyte areas were determined by Masson's Trichrome staining. Using a level of median caspase-8 expression (6.04% of the area of the myocardium with caspase-8 signal), patients were classified into a high caspase-8 expression group (H-cas8) and a low caspase-8 expression group (L-cas8).

Results

Caspase-8 signals were detected in cytoplasm and intercalated disks of cardiomyocytes. Patients in the L-cas8 group was younger (51.3±13.1 vs. 61.2±14.3 years old) and had larger left ventricular end-diastolic volume (LVEDV: 174±49 vs. 131±41 ml), larger left ventricular end-systolic volume (LVESV: 123±51 vs. 87±39 ml), and higher ratio of mitral peak velocity of early filling to late diastolic filling (E/A: 1.94±1.48 vs. 1.12±0.66) compared with the H-cas8 group. Caspase-8 expression level was positively correlated with age (r=0.34, p=0.01) and negatively correlated with LVEDV (r=−0.47, p<0.01), LVESV (r=−0.40, p<0.01), and E/A (r=−0.39, p<0.01) in simple linear regression analysis. The extent of myocardial fibrosis was not correlated with caspase-8 expression level. Multiple regression analysis indicated that LVEDV, LVESV, and E/A were independent explanatory factors of caspase-8 expression level after adjusting age and sex. Phospho-MLKL signals, an index of activation of necroptotic pathway, were frequently observed in cytoplasm, intercalated disks, and nuclei in the L-cas8 group but not in the H-cas8 group.

Conclusion

Lower caspase-8 expression in cardiomyocytes was associated with increased phosphorylation of MLKL and larger left ventricular volume, suggesting that downregulated caspase-8 may contribute to progression of myocardial remodeling via activation of MLKL in human dilated cardiomyopathy.

A New Method to Quantify Concentration of Microbubbles in Attenuating Media Using Bubble Destruction Curve Analysis of the Contrast-Enhanced Ultrasound

It is known that the microbubbles of Sonazoid are accumulated in the liver parenchyma due to the phagocytosis of Kupffer cells in the sinusoid. Because this phagocytic function decreases due to the progression of fibrosis in chronic liver disease, the deterioration of the liver function may be quantified by measuring the concentration of the accumulated Sonazoid microbubbles. In this article, a new method to quantify the concentration of microbubbles accumulated in attenuating media is proposed. This method utilizes the contrast-enhanced imaging with high mechanical index, measures the depth of the bubble destruction for each frame and analyze the shape of the destruction curve to estimate the concentration of the bubbles. A phantom experiment was performed with various concentrations of the contrast agent Sonazoid solution as well as various attenuation coefficients of the viscous media. Because of the theoretical model proposed, the estimated attenuation indexes, related to the concentration of Sonazoid microbubbles, were independent of the background attenuation of the propagating medium. The result suggest it has a potential to quantify Sonazoid concentration in the liver parenchyma more precisely against different liver attenuation conditions.

Ultrasonic B-Line-Like Artifacts Generated with Simple Experimental Models Provide Clues to Solve Key Issues in B-Lines

We evaluated the influence of settings on an ultrasound machine on the configuration of a single B-line in a healthy model and analyzed the frequency spectrum. We also devised simple experimental models that generated B-line-like artifacts and evaluated the influence of the machine settings on the configuration. Visualization of B-lines was affected by the spatial compound imaging, the focal zone and the frequency. The spectra of both the B-line and non-B-line region at the same depth had the same center frequency and bandwidth. B-line-like artifact was generated by a spindle-shaped juice sac of a mandarin orange, an edible string-shaped glucomannan gel, glass beads and glass plates. Visualization of B-line-like artifacts was also affected by these machine settings. Our study indicated that the physical basis of some B-lines is multiple reverberations. B-line-like artifacts provide clues for solving key issues, such as the physical basis of B-lines, the sonographic-pathologic correlation in B-lines and the effects of machine settings.

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.

Accuracy of 2D shear wave elastography in the diagnosis of liver fibrosis in patients with chronic hepatitis C

PURPOSE

This prospective study was conducted to assess the diagnostic accuracy of two-dimensional shear wave elastography (2D SWE) in the diagnosis of liver fibrosis in patients with chronic liver disease and hepatitis C virus (HCV) compared with the serum liver fibrosis biomarkers using the results of liver biopsy as the reference standard.

METHODS

We analyzed 233 consecutive HCV patients. On the same day, 2D SWE m, biochemical tests, and liver biopsy were performed. We used the METAVIR staging system and receiver operating characteristic curves for the analysis.

RESULTS

The success rate of 2D-SWE was 98.7%. The median shear wave velocities (SWVs) of patients in the F0, F1, F2, F3, and F4 stages were 1.35 m/s, 1.42 m/s, 1.58 m/s, 1.83 m/s, and 2.13 m/s, respectively, demonstrating a stepwise increase (P < .0001). The accuracy of 2D-SWE in the prediction of ≥F1, ≥F2, ≥F3, and F4 was .888 (95% CI: .85-.93), .915 (95% CI: .88-095), .940 (95% CI: .91-.97), and .949 (95% CI: .92-.97), respectively. 2D-SWE was significantly superior to serum liver fibrosis biomarkers.

CONCLUSION

2D-SWE was positively correlated with the severity of liver fibrosis and was more useful for to predict all liver fibrosis grades in HCV patients than liver fibrosis biomarkers.

Investigation of SO3 absorption line for in situ gas detection inside combustion plants using a 4-μm-band laser source

We have investigated 4-μm-band SO₃ absorption lines for in situSO₃ detection using a mid-infrared laser source based on difference frequency generation in a quasi-phase-matched LiNbO₃ waveguide. In the wavelength range of 4.09400-4.10600 μm, there were strong SO₃ absorption lines. The maximum absorption coefficient at a concentration of 170 ppmv was estimated to be about 3.2×10^-5  cm^-1 at a gas temperature of 190°C. In coexistence with H₂O, the reduction of the SO₃ absorption peak height was observed, which was caused by sulfuric acid formation. We discuss a method of using an SO₃ equilibrium curve to derive the total SO₃ molecule concentration.

Acoustic characterization and pharmacokinetic analyses of new nanobubble ultrasound contrast agents

In contrast to the clinically used microbubble ultrasound contrast agents, nanoscale bubbles (or nanobubbles) may potentially extravasate into tumors that exhibit more permeable vasculature, facilitating targeted molecular imaging and drug delivery. Our group recently presented a simple strategy using the non-ionic surfactant Pluronic as a size control excipient to produce nanobubbles with a mean diameter of 200 nm that exhibited stability and echogenicity on par with microbubbles. The objective of this study was to carry out an in-depth characterization of nanobubble properties as compared with Definity microbubbles, both in vitro and in vivo. Through use of a tissue-mimicking phantom, in vitro experiments measured the echogenicity of the contrast agent solutions and the contrast agent dissolution rate over time. Nanobubbles were found to be more echogenic than Definity microbubbles at three different harmonic frequencies (8, 6.2 and 3.5 MHz). Definity microbubbles also dissolved 1.67 times faster than nanobubbles. Pharmacokinetic studies were then performed in vivo in a subcutaneous human colorectal adenocarcinoma (LS174T) in mice. The peak enhancement and decay rates of contrast agents after bolus injection in the liver, kidney and tumor were analyzed. No significant differences were observed in peak enhancement between the nanobubble and Definity groups in the three tested regions (tumor, liver and kidney). However, the decay rates of nanobubbles in tumor and kidney were significantly slower than those of Definity in the first 200-s fast initial phase. There were no significant differences in the decay rates in the liver in the initial phase or in three regions of interest in the terminal phase. Our results suggest that the stability and acoustic properties of the new nanobubble contrast agents are superior to those of the clinically used Definity microbubbles. The slower washout of nanobubbles in tumors suggests potential entrapment of the bubbles within the tumor parenchyma.

Arrival time parametric imaging of the hemodynamic balance changes between the hepatic artery and the portal vein during deep inspiration, using Sonazoid-enhanced ultrasonography: A case of Budd-Chiari syndrome

This case report concerns a 40-year-old male who had previously been treated for an esophageal varix rupture, at the age of 30 years. The medical examination at that time revealed occlusion of the inferior vena cava in the proximity of the liver, leading to the diagnosis of the patient with Budd-Chiari syndrome. The progress of the patient was therefore monitored in an outpatient clinic. The patient had no history of drinking or smoking, but had suffered an epileptic seizure in 2004. The patient's family history revealed nothing of note. In February 2012, color Doppler ultrasonography (US) revealed a change in the blood flow in the right portal vein branch, from hepatopetal to hepatofugal, during deep inspiration. Arrival time parametric imaging (At-PI), using Sonazoid-enhanced US, was subsequently performed to examine the deep respiration-induced changes observed in the hepatic parenchymal perfusion. US images captured during deep inspiration demonstrated hepatic parenchymal perfusion predominantly in red, indicating that the major blood supply was the hepatic artery. During deep expiration, the portal venous blood flow remained hepatopetal, and hepatic parenchymal perfusion was displayed predominantly in yellow, indicating that the portal vein was the major source of the blood flow. The original diagnostic imaging results were reproduced one month subsequently by an identical procedure. At-PI enabled an investigation into the changes that were induced in the hepatic parenchymal perfusion by a compensatory mechanism involving the hepatic artery. These changes occurred in response to a reduction in the portal venous blood flow, as is observed in the arterialization of hepatic blood flow that is correlated with the progression of chronic hepatitis C. It has been established that the peribiliary capillary plexus is important in the regulation of hepatic arterial blood flow. However, this case demonstrated that the peribiliary capillary plexus also regulates acute changes in portal venous blood flow, in addition to the chronic reduction in blood flow that is observed in patients with chronic hepatitis C.

Arrival time parametric imaging using Sonazoid-enhanced ultrasonography is useful for the detection of spoke-wheel patterns of focal nodular hyperplasia smaller than 3 cm

It is considered difficult to make a definitive diagnosis of focal nodular hyperplasia (FNH) of <3 cm when using conventional diagnostic imaging modalities. Typical FNH imaging findings are: i) central scar formation, ii) nutrient vessels extending radially from the center and iii) the presence of Kupffer cells. In a clinical setting, identification of a spoke-wheel pattern formed by nutrient vessels extending radially is a key feature in the diagnosis of FNH. In this study, we investigated the detection rate of spoke-wheel patterns of FNH <3 cm using arrival time parametric imaging (At-PI) technology with Sonazoid-enhanced ultrasonography (US). Five patients with FNH <3 cm who had undergone Sonazoid-enhanced US at the Toho University Omori Medical Center between February 2008 and March 2009 were included in the study. The mean tumor diameter was 20.2±7.2 mm. Lesions were enhanced with 0.5 ml Sonazoid US contrast agent and a video of the procedure was saved and used for At-PI analysis of contrast agent dynamics in FNH. Three ultrasonographic specialists examined the images and made a diagnosis of FNH based on the findings of spoke-wheel patterns. Similarly, micro-flow imaging (MFI) was performed to evaluate the contrast agent dynamics in FNH. Using MFI, FNH was diagnosed in 3 of the 5 cases by the three specialists, whereas At-PI enabled the identification of spoke-wheel patterns in all 5 cases. At-PI using Sonazoid-enhanced US is superior for detecting spoke-wheel patterns of FNH <3 cm.

Hepatocellular carcinoma treated with sorafenib: early detection of treatment response and major adverse events by contrast-enhanced US

BACKGROUND & AIMS

Early prediction of tumour response and major adverse events (AEs), especially liver failure, in patients with hepatocellular carcinoma (HCC) is essential for maximizing the clinical benefits of sorafenib. To evaluate the usefulness of dynamic contrast-enhanced ultrasound (DCE-US) for the early prediction of tumour response and major AEs in HCC patients.

METHODS

Thirty-seven HCC patients were started on a reduced dosage of sorafenib, subsequently increased to the standard dosage. Tumour response at 1 month was assessed by CT using the Response Evaluation Criteria in Solid Tumors (RECIST). Major AEs were defined as grade 3 or higher. DCE-US was performed before treatment (day 0) and on days 7, 14 and 28. Changes in perfusion parameters in the tumour and liver parenchyma between day 0 and later time points were compared between treatment responders and nonresponders based on RECIST and between patients who experienced major AEs and those who did not. Tumour results were also compared with progression-free survival (PFS) and overall survival (OS).

RESULTS

Tumour perfusion parameters based on the area under the time-intensity curve (AUC) were statistically significant, with AUC during washin on day 14, the most relevant for tumour response (P = 0.0016) and AUC during washin on day 7, the most relevant for both PFS (P = 0.009) and OS (P = 0.037). A decrease in total AUC between days 0 and 7 in the liver parenchyma was strongly correlated with major AEs (P = 0.0002).

CONCLUSION

DCE-US may be useful for the early prediction of tumour response and major AEs in patients with HCC.

Real-time ultrasound attenuation imaging of diffuse fatty liver disease

A method for real-time ultrasound attenuation imaging and quantification is proposed in this paper. We employed a simple algorithm for comparing two signal intensities of different frequencies to extract attenuation quantitatively. The usefulness of this method was verified by numerical simulation of the acoustic field and validated by phantom experiments. The accuracy of the results was reduced by noise in areas with a low signal-to-noise ratio, but we found that the effects of noise could be reduced by applying our noise cancellation technique or simply setting a sufficiently high gain. The estimated attenuation coefficients for clinical liver images showed acceptable correlation with the liver-to-spleen ratio of computed tomography numbers. These findings suggest that real-time attenuation parametric imaging may be able to replace CT for quantifying the degree of fatty infiltration of the liver. However, further development is needed to obtain the local attenuation distribution in cross sections with sufficient reliability.

Contrast-enhanced ultrasonography using Sonazoid(®) is useful for diagnosis of malignant ovarian tumors: comparison with Doppler ultrasound

PURPOSE

The purpose of this study was to assess the usefulness of Sonazoid(®)-enhanced ultrasonography (US) in the diagnosis of ovarian cancer in comparison with Doppler US.

METHODS

Twenty-five ovarian tumor patients who were scheduled to undergo surgery were recruited for this study. The day before the operation, each patient was evaluated with color and power Doppler and baseline US during intravenous infusion of Sonazoid. Each lesion was classified as "benign" or "malignant" on the basis of specific criteria for a Doppler signal or Sonazoid-enhanced pattern. The reference standard was the histology of surgically removed adnexal tumors.

RESULTS

Twenty patients were diagnosed with malignant tumors (invasive cancer, n = 15; metastatic cancer, n = 1; borderline tumor, n = 4), and the remaining five were diagnosed with benign tumors. Sonazoid-enhanced US correctly depicted the presence or absence of intratumoral blood flow in all patients with an accuracy of 92 %. Color Doppler ultrasound depicted the malignancies with an accuracy of 64 %, and power Doppler ultrasound depicted them with an accuracy of 76 %.

CONCLUSION

Our study suggests that Sonazoid-enhanced US is superior to conventional color Doppler US for the diagnosis of malignant ovarian tumors, but not to power Doppler US. The data and their interpretation in our study should be taken with some degree of caution because of the small number of subjects. Further studies involving a larger sample size would be needed to confirm these findings.

Non-invasive determination of hepatic steatosis by acoustic structure quantification from ultrasound echo amplitude

AIM: To use leptin-deficient (ob/ob) mice with demonstrated differences in steatosis levels to test a new diagnostic method using the acoustical structure quantification (ASQ) mode and the associated analytical parameter, “focal disturbance ratio” (FD-ratio).

METHODS: Nine ob/ob mice, at 5, 8, and 12 wk of age (n = 3 in each age group), were used as models for hepatic steatosis. Echo signals obtained from ultrasonography in the mice were analyzed by ASQ, which uses a statistical analysis of echo amplitude to estimate inhomogeneity in the diagnostic region. FD-ratio, as calculated from this analysis, was the focus of the present study. FD-ratio and fat droplet areas and sizes were compared between age groups.

RESULTS: No fibrosis or inflammation was observed in any of the groups. The fat droplet area significantly (P < 0.01) increased with age from 1.25% ± 0.28% at 5 wk to 31.07% ± 0.48% at 8 wk to 51.69% ± 3.19% at 12 wk. The median fat droplet size also significantly (P < 0.01) increased with age, from 1.33 (0.55-10.52) μm at 5 wk, 2.82 (0.61-44.13) μm at 8 wk and 6.34 (0.66-81.83) μm at 12 wk. The mean FD-ratio was 0.42 ± 0.11 at 5 wk, 0.11 ± 0.05 at 8 wk, and 0.03 ± 0.02 at 12 wk. The FD-ratio was significantly lower at 12 wk than at 5 wk and 8 wk (P < 0.01). A significant negative correlation was observed between the FD-ratio and either the fat droplet area (r = -0.7211, P = 0.0017) or fat droplet size (r = -0.9811, P = 0.0052).

CONCLUSION: This tool for statistical analysis of signals from ultrasonography using the FD-ratio can be used to accurately quantify fat in vivo in an animal model of hepatic steatosis, and may serve as a quantitative biomarker of hepatic steatosis.

Usefulness of arrival time parametric imaging in evaluating the degree of liver disease progression in chronic hepatitis C infection

OBJECTIVE

To determine whether the degree of liver disease progression in chronic hepatitis C infection can be evaluated by arrival time parametric imaging using contrast-enhanced sonography with Sonazoid (perfluorobutane; GE Healthcare, Oslo, Norway).

METHODS

In this study, 60 patients with liver disease in chronic hepatitis C infection were examined and compared with 10 healthy volunteers who served as controls. A recommended dose of the sonographic contrast agent Sonazoid was intravenously infused, and the S5 or S6 region of the liver and right kidney were observed concurrently while movies of the procedure were saved. Arrival time parametric images of liver parenchymal blood flow were created, with red pixels to indicate an arrival time of 0 to 5 seconds and yellow pixels to indicate an arrival time of 5 to 10 seconds. From the obtained images, the ratio of the red area to the entire enhanced area of the liver was calculated using image-processing software. Each participant was subsequently subjected to liver biopsy for liver fibrosis staging according to Metavir scores, and the determined fibrosis stage was compared with the ratio of red. The serum albumin level, platelet count, and prothrombin time were also compared with the ratio of red for each participant.

RESULTS

The ratio of red increased significantly as liver fibrosis stage advanced (P < .01 for F1 versus F2; P < .01 for F1 versus F3; P < .01 for F1 versus F4; and P < .01 for F2 versus F4). As the ratio of red increased, significant decreases were observed in the serum albumin level (r = -0.29; P = .027), platelet count (r = -0.46; P = .0003), and prothrombin time (r = -0.46; P = .0002).

CONCLUSIONS

Arrival time parametric imaging using Sonazoid-enhanced sonography enables noninvasive evaluation of the degree of progression of liver disease in chronic hepatitis C infection and is thus considered clinically useful.

Diagnosis of hepatic hemangioma by parametric imaging using sonazoid-enhanced US

BACKGROUND/AIMS

Comparison of Parametric Imaging (PI) using Sonazoid-enhanced ultrasonography (US) and microflow imaging (MFI) to determine the possibility of hepatic hemangioma diagnosis using PI.

METHODOLOGY

Twenty-two hepatic hemangioma nodules (mean±SD diameter: 31.6±19.1mm) undergoing Sonazoid-enhanced US between February 2008 and March 2009. After Sonazoid-enhanced US, COMMUNE ultrasonographic image analysis software was used for analysis of tumor imaging dynamics in the vascular phase using PI and MFI. In PI, 0s was set as the time contrast agent reached the tumor. Imaging within the tumor after 0s was color-coded according to time, and the images were displayed in color. In MFI, 0s was set as the time contrast agent reached the tumor. The path of microbubbles as it flowed through blood vessels was superimposed on the original B-mode images. Three trained physicians used these methods to analyze tumor imaging dynamics.

RESULTS

All physicians concluded all cases were hepatic hemangioma regardless of method used. However, compared to MFI, PI allowed determination of more detailed blood flow dynamics in high-flow hepatic hemangioma, where blood flow speed was faster than in normal hepatic hemangioma.

CONCLUSIONS

It is possible to diagnose hepatic hemangioma using PI using sonazoid-enhanced US.

Drinking status of heavy drinkers detected by arrival time parametric imaging using sonazoid-enhanced ultrasonography: study of two cases

Chronic heavy consumption of alcohol is associated with increased risks of developing liver cirrhosis, hepatocellular carcinoma, and esophageal varices. Cessation of alcohol consumption is the most important requirement in treating these diseases. However, judging whether patients have actually maintained abstinence from alcohol requires reliance on their reports, which vary substantially across individuals using the test methods currently available. Arrival time parametric imaging (At-PI) using Sonazoid-enhanced ultrasonography is regarded as a useful approach for assessing the progression of lesions that have developed in liver parenchyma. In this study, we report two cases for whom this approach was successfully applied to indicate the drinking status of a heavy drinker. At-PI enables approximate and objective assessment of the drinking status of patients, independent of their reports; therefore, it is a promising method for providing information about drinking status.

Transplanting normal vascular proangiogenic cells to tumor-bearing mice triggers vascular remodeling and reduces hypoxia in tumors

Blood vessels deliver oxygen and nutrients to tissues, and vascular networks are spatially organized to meet the metabolic needs for maintaining homeostasis. In contrast, the vasculature of tumors is immature and leaky, resulting in insufficient delivery of nutrients and oxygen. Vasculogenic processes occur normally in adult tissues to repair "injured" blood vessels, leading us to hypothesize that bone marrow mononuclear cells (BMMNC) may be able to restore appropriate vessel function in the tumor vasculature. Culturing BMMNCs in endothelial growth medium resulted in the early outgrowth of spindle-shaped attached cells expressing CD11b/Flt1/Tie2/c-Kit/CXCR4 with proangiogenic activity. Intravenous administration of these cultured vascular proangiogenic cells (VPC) into nude mice bearing pancreatic cancer xenografts and Pdx1-Cre;LSL-Kras(G12D);p53(lox/+) genetically engineered mice that develop pancreatic ductal adenocarcinoma significantly reduced areas of hypoxia without enhancing tumor growth. The resulting vasculature structurally mimicked normal vessels with intensive pericyte coverage. Increases in vascularized areas within VPC-injected xenografts were visualized with an ultrasound diagnostic system during injection of a microbubble-based contrast agent (Sonazoid), indicating a functional "normalization" of the tumor vasculature. In addition, gene expression profiles in the VPC-transplanted xenografts revealed a marked reduction in major factors involved in drug resistance and "stemness" of cancer cells. Together, our findings identify a novel alternate approach to regulate abnormal tumor vessels, offering the potential to improve the delivery and efficacy of anticancer drugs to hypoxic tumors.

Effects of nonlinear propagation in ultrasound contrast agent imaging

This paper investigates two types of nonlinear propagation and their effects on image intensity and contrast-to-tissue ratio (CTR) in contrast ultrasound images. Previous studies have shown that nonlinear propagation can occur when ultrasound travels through tissue and microbubble clouds, making tissue farther down the acoustic path appear brighter in pulse inversion (PI) images, thus reducing CTR. In this study, the effect of nonlinear propagation through tissue or microbubbles on PI image intensity and CTR are compared at low mechanical index. A combination of simulation and experiment with SonoVue microbubbles were performed using a microbubble dynamics model, a laboratory ultrasound system and a clinical prototype scanner. The results show that, close to the bubble resonance frequency, nonlinear propagation through a bubble cloud of a few centimeter thickness with a modest concentration (1:10000 dilution of SonoVue microbubbles) is much more significant than through tissue-mimicking material. Consequently, CTR in regions distal to the imaging probe is greatly reduced for nonlinear propagation through the bubble cloud, with as much as a 12-dB reduction compared with nonlinear propagation through tissue-mimicking material. Both types of nonlinear propagation cause only a small change in bubble PI signals at the bubble resonance frequency. When the driving frequency increases beyond bubble resonance, nonlinear propagation through bubbles is greatly reduced in absolute values. However because of a greater reduction in nonlinear scattering from bubbles at higher frequencies, the corresponding CTR is much lower than that at bubble resonance frequency.

Parametric imaging using contrast-enhanced ultrasound with Sonazoid for hepatocellular carcinoma

PURPOSE

To clarify the usefulness of parametric imaging using contrast-enhanced ultrasound (CE-US) with Sonazoid by comparing parametric images of hepatocellular carcinoma (HCC) with histopathological findings.

METHODS

Two patients with HCCs underwent CE-US with Sonazoid before surgical resection. A single focus point was set at the lower margin of the tumor, and a bolus intravenous injection of Sonazoid (0.5 ml) was administered. Images of the ideal scanning plane were displayed in real-time mode for the early vascular phase. We analyzed these images using prototype PC software. The software watches, pixel by pixel, the increase in the intensity due to the inflow of the microbubbles, and displays colors if the intensity becomes larger than a certain threshold. Parametric images were compared with histopathological findings.

RESULTS

The level of blood flow in the tumor could be visually evaluated using a single image by expressing the detailed hemodynamics of the tumor in terms of differences in color using a time axis appropriate for each case.

CONCLUSIONS

Parametric imaging is a very useful way of facilitating straightforward visualization of the level of blood flow within HCC and the distribution of histopathological findings in single static images.

How to characterize non-hypervascular hepatic nodules on contrast-enhanced computed tomography in chronic liver disease: feasibility of contrast-enhanced ultrasound with a microbubble contrast agent

BACKGROUND AND AIM

Although hypervascular appearance is characteristic in hepatocellular carcinoma (HCC), hepatic nodules without hypervascular appearance are sometimes found in patients with chronic liver disease (CLD). The aim of the present study was to clarify the efficacy of contrast-enhanced ultrasound (CEUS) with Levovist to characterize small, non-hypervascular hepatic nodules on contrast-enhanced computed tomography (CECT) in patients with CLD.

METHODS

The subject was 41 hepatic nodules (<30 mm, 18.5 +/- 5.6 mm) which showed non-hypervascular appearance on CECT in 35 patients with CLD; their histological results were 31 HCC (15 well, 14 moderate, and two poor) and 10 regenerative nodules (RN). CEUS with Levovist was performed under intermittent scanning (1-s interval) using APLIO at the early phase and the liver-specific phase, and the contrast enhancement of the nodule was assessed in comparison to that of the surrounding liver parenchyma. The contrast-enhanced findings with the time-intensity analysis were compared with the histological results.

RESULTS

Twelve nodules with weak enhancement in the liver-specific phase were HCC, regardless of their early-phase appearances. The other 29 nodules with equivalent or weak enhancement in the early phase and equivalent enhancement in the liver-specific phase were 19 HCC and 10 RN. Among them, the maximum-intensity ratio of tumor to non-tumor in the early phase was significantly higher in HCC than in RN (P < 0.01, n = 16), and the receiver-operating characteristic analysis showed a sensitivity of 1.0 and a specificity of 0.83 for their characterization.

CONCLUSION

CEUS with Levovist may be an alternative to biopsy to characterize small, non-hypervascular hepatic nodules on CECT in patients with CLD.

Analysis of morphological vascular changes of hepatocellular carcinoma by microflow imaging using contrast-enhanced sonography

AIM

To determine whether the findings of microflow imaging (MFI), composed of a flash replenishment and a maximum intensity holding sequence, using contrast-enhanced sonography, correlate with the degree of histological differentiation of hepatocellular carcinoma (HCC).

METHODS

This study was approved by the institutional review board; patients gave informed consent. The samples comprised of 61 nodules histologically diagnosed as HCC: 20 well-differentiated, 26 moderately-differentiated, and 15 poorly-differentiated HCC. SonoVue was used as the ultrasound (US) contrast agent. The US equipment used was a SSA-770 A with the imaging mode set at MFI. MFI is an imaging method combining flash replenishment imaging and maximum intensity holding. Two independent readers (readers 1 and 2) classified the microflow images into four patterns: (i) normal pattern; (ii) cotton pattern; (iii) vascular pattern; and (iv) dead wood pattern. The results were compared with the degree of histopathological differentiation of the HCC.

RESULTS

In each of the 61 HCC, blood vessels in the tumor were clearly resolved down to their fine branches. With regard to the relationship between imaging patterns and thehistological findings, it was found (with high percentages) that the normal and cotton patterns were associated with well-differentiated HCC, that the vascular pattern was associated with moderately-differentiated HCC, and that the dead wood pattern was associated with poorly-differentiated HCC. If HCC with the normal and cotton patterns were assessed as well differentiated and those with the vascular or dead wood pattern were assessed as moderately or poorly differentiated, the sensitivity, specificity, and accuracy of these assessments were found to be 85%, 92.7%, and 90%, respectively, for reader 1, and 85%, 82.9%, and 83.6%, respectively, for reader 2.

CONCLUSION

The angioarchitecture and hemodynamics of HCC could be evaluated in detail using MFI. The results of this study demonstrate the feasibility of a non-invasive preoperative diagnosis of the histological differentiation of HCC using MFI.

Computer-aided diagnosis for the classification of focal liver lesions by use of contrast-enhanced ultrasonography

The authors developed a computer-aided diagnostic (CAD) scheme for classifying focal liver lesions (FLLs) as liver metastasis, hemangioma, and three histologic differentiation types of hepatocellular carcinoma (HCC), by use of microflow imaging (MFI) of contrast-enhanced ultrasonography. One hundred and three FLLs obtained from 97 cases used in this study consisted of 26 metastases (15 hyper- and 11 hypovascularity types), 16 hemangiomas (five hyper- and 11 hypovascularity types) and 61 HCCs: 24 well differentiated (w-HCC), 28 moderately differentiated (m-HCC), and nine poorly differentiated (p-HCC). Pathologies of all cases were determined based on biopsy or surgical specimens. Locations and contours of FLLs on contrast-enhanced images were determined manually by an experienced physician. MFI was obtained with contrast-enhanced low-mechanical-index (MI) pulse subtraction imaging at a fixed plane which included a distinctive cross section of the FLL. In MFI, the inflow high signals in the plane, which were due to the vascular patterns and the contrast agent, were accumulated following flash scanning with a high-MI ultrasound exposure. In the initial step of our computerized scheme, a series of the MFI images was extracted from the original cine clip (AVI format). We applied a smoothing filter and time-sequential running average techniques in order to reduce signal noise on the single MFI image and cyclic noise on the sequential MFI images, respectively. A kidney, vessels, and a liver parenchyma region were segmented automatically by use of the last image of a series of MFI images. The authors estimated time-intensity curves for an FLL by use of a series of the temporally averaged MFI images in order to determine temporal features such as estimated replenishment times at early and delayed phases, flow rates, and peak times. In addition, they extracted morphologic and gray-level image features which were determined based on the physicians' knowledge of the diagnosis of the FLL, such as the size of lesion, vascular patterns, and the presence of hypoechoic regions. They employed a cascade of six independent artificial neural networks (ANNs) by use of extracted temporal and image features for classifying five types of liver diseases. A total of 16 temporal and image features, which were selected from 43 initially extracted features, were used for six different ANNs for making decisions at each decision in the cascade. The ANNs were trained and tested with a leave-one-lesion-out test method. The classification accuracies for the 103 FLLs were 88.5% for metastasis, 93.8% for hemangioma, and 86.9% for all HCCs. In addition, the classification accuracies for histologic differentiation types of HCCs were 79.2% for w-HCC, 50.0% for m-HCC, and 77.8% for p-HCC. The CAD scheme for classifying FLLs by use of the MFI on contrast-enhanced ultrasonography has the potential to improve the diagnostic accuracy in the histologic diagnosis of HCCs and the other liver diseases.

Correlation between parametric imaging using contrast ultrasound and the histological differentiation of hepatocellular carcinoma

AIM

To determine whether parametric imaging correlates with the degree of histological differentiation of hepatocellular carcinoma (HCC).

METHODS

The samples comprised 49 nodules diagnosed histologically as HCC: 19 well differentiated (w-HCC), 22 moderately differentiated (m-HCC), and eight poorly differentiated (p-HCC). The ultrasound (US) equipment used was SSA-770 A (Toshiba Medical Systems, Otawara, Japan) and the contrast agent was SonoVue (Bracco, Milan, Italy). After 1.5 mL of SonoVue was injected intravenously and staining of the tumors and parenchyma was confirmed, microbubbles in the scanned volume were eliminated using high mechanical index (MI) scanning frames. The "arrival time (T(A)) images," reflecting beta-values, were displayed with color codes at the phase after reperfusion. Images at the phase when the staining reached a plateau (90-180 s) were used as "A images," reflecting A values. These images were compared between each histological grade of differentiation.

RESULTS

Analysis of T(A) images indicated that beta-values in m-HCC were higher than those in the adjacent non-tumor parenchyma in all 22 samples and also were significantly higher than in the other HCCs (P < 0.001 for w-HCC; P < 0.05 for p-HCC). Furthermore, beta-values in p-HCC samples had significantly larger variations in terms of time and space than in the other HCCs (P < 0.001 for w-HCC; P < 0.01 for m-HCC). Analysis of A images indicated that the A value for w-HCC was significantly higher than those for either m-HCC or p-HCC (P < 0.001).

CONCLUSION

Both T(A) and A images were useful for diagnosing the histological differentiation of HCC.

Quantitative measurement of thyroid blood flow for differentiation of painless thyroiditis from Graves' disease

OBJECTIVE

Differentiation between destruction-induced thyrotoxicosis and Graves' thyrotoxicosis is important for selection of proper therapy. It is, however, often difficult to make this distinction without measurement of radioactive iodine uptake. We investigated the possibility that assessment of thyroid blood flow would allow differentiation between the two entities.

PATIENTS AND MEASUREMENTS

One hundred and fourteen untreated patients with thyrotoxicosis (56 Graves' disease, 28 painless thyroiditis, 30 subacute thyroiditis) and 25 normal controls were examined. Serum levels of freeT4 (FT4), freeT3 (FT3) and TSH were measured by chemiluminescent immunoassay, and anti-TSH receptor antibodies (TSH-binding inhibitory immunoglobulin, TBII) were measured by enzyme-linked immunosorbent assay. Thyroid volume and blood flow (TBF) were measured quantitatively by ultrasonography.

RESULTS

TBF was significantly higher in Graves' disease (mean +/- 1SD: 14.9 +/- 6.4%, P < 0.0001) than in painless thyroiditis (0.8 +/- 0.5%), subacute thyroiditis (0.9 +/- 0.7%) and in normal controls (0.8 +/- 0.5%). All patients with Graves' disease had TBF values of more than 4% and all patients with painless thyroiditis and subacute thyroiditis had TBF values less than 4%. TBF values significantly correlated with values of radioactive iodine uptake (RAIU) either at 3 h (r = 0.492, P < 0.01) or 24 h (r = 0.762, P < 0.001) within the Graves' disease and painless thyroiditis groups. There was no relationship between TBF values and thyroid volumes or values of TBII in the Graves' disease group. All patients with Graves' disease had positive TBII of 15% or more. Three of 28 patients with painless thyroiditis and one of 30 patients with subacute thyroiditis had positive TBII.

CONCLUSION

TBF was quantitatively measured by power Doppler ultrasonography and was more effective than TBII for differentiation between destruction-induced thyrotoxicosis (painless or subacute thyroiditis) and Graves' thyrotoxicosis. TBF values of less than 4% in untreated thyrotoxic patients are laboratory signals of destruction-induced thyrotoxicosis and if these are determined, the radioactive iodine uptake test can be omitted for differential diagnosis of these two types of thyrotoxicosis.

Parametric imaging of contrast ultrasound for the evaluation of neovascularization in liver tumors

AIM

To assess the efficacy of parametric imaging for the diagnosis of neovascularization in liver tumors.

METHODS

The subjects were 17 rabbits (five with normal liver and 12 with VX2 tumor implanted in the liver). The contrast agents used were SonoVue (Bracco, Milan, Italy). A diagnostic ultrasound system was used with a programmable replenishment sequence. The images obtained between the initial frame after the high mechanical index (MI) scan, which diminishes microbubbles in the scan volume, and the current frame were coded in color according to the arrival and peak times. After the experiment, the tumors were excised and sectioned. Sections were prepared for light microscopy with hematoxylin-eosin (HE) staining and CD31 staining to evaluate vascular density.

RESULTS

Arrival time imaging (ATI) delineated the fine blood vessels (100-200 mum in diameter) in all of the rabbits. Tortuous and meandering tumor vessels were visualized in the VX2 tumors. Differences of perfusion velocity between tumor tissue and tumor-free areas were shown in peak time imaging (PTI). Vascularity evaluated on the ATI and perfusion speed recognized on the ATI and PTI were related to the vascular density measured by pathological investigation.

CONCLUSION

Parametric imaging is a promising new method for the visualization of perfusion and the estimation of tumor blood vessels.

Quantification of hepatic parenchymal blood flow by contrast ultrasonography with flash-replenishment imaging

Flash-replenishment (FR) utilizes destruction of microbubbles in the scan volume by high-power ultrasound and enables to observe reperfusion at a low acoustic power. In this paper, we introduced theoretic equation between probability density function (PDF) of the transit time in the scan volume and time intensity curve (TIC) measured by FR method. From the equations, it was explained that the mean transit time (MTT) through the scan volume was calculated from the plateau level and tangent of the initial slope. Animal experiments were also performed to measure TIC in the parenchymal region of the liver using FR method. From the result of the TIC, the variant of the PDF for the transit time was found to be small and the average MTT was 11.1 s. Hepatic blood flow by an ultrasonic transit time flowmeter was also measured in the same experiment, and adequate correlation was obtained from between the two methods. The results suggested that the FR method, which is a noninvasive measurement, can predict the blood flow of the liver.

Sonographic shift of hypervascular liver tumor on blood pool harmonic images with definity: time-related changes of contrast-enhanced appearance in rabbit VX2 tumor under extra-low acoustic power

We elucidated the features of the time-related contrast-enhanced ultrasound appearance of hypervascular liver tumor using Definity, which has no accumulation activity in the liver. Ten rabbits with VX2 tumors broadcast into the liver were used. Changes in contrast-enhanced sonograms were evaluated by real-time observation (FR 15 Hz) of harmonic imaging under extra-low MI (MI 0.065) with Definity, and their intensity changes were analyzed. Hepatic angiography (4/10) and histopathological examination (10/10) were performed to investigate the tumor vascularity. VX2 tumors were hypervascular on angiogram (4/10) and histology (10/10). They showed time-related sonographic appearance changes from hyperechoic to hypoechoic, which were confirmed by quantitative intensity analysis. Hypervascular VX2 tumors showed characteristic time-related shift on contrast-enhanced sonograms in real-time and extra-low MI harmonic images with Definity. These findings may be useful for the ultrasound diagnosis of human hypervascular liver tumor like hepatocellular carcinoma with blood-pool contrast agent.

Real-time blood-pool images of contrast enhanced ultrasound with Definity in the detection of tumour nodules in the liver

Lower mechanical index (MI) technique with newer microbubble agents has been introduced into clinical practice as a newer ultrasound (US) imaging. However, the efficacy in detecting tumour nodules has not been proven scientifically. The aim of this study was to elucidate the efficacy of a blood-pool image of real-time contrast-enhanced US under low MI in detecting liver tumours. 15 rabbits with VX-2 tumour were used; the number of implantations was none in two rabbits, one in four, two in five and three in four. US equipment was APLIO (Toshiba) with linear probe (3.5/7.0 MHz). The number, location and size of tumour nodules were examined by non-contrast tissue harmonic imaging (NC-US) or contrast-enhanced pulse subtraction harmonic imaging (C-US) under extra-low MI (MI 0.065) with the injection of Definity (30 microl kg(-1)). The number of tumour nodules detected by both NC-US and C-US were consistent with the histopathological results in five rabbits - two with none, two with one nodule and one with two nodules. In the other 10 rabbits, C-US showed all the implanted tumours and small daughter nodules around them that were confirmed by histopathology. However, NC-US failed to demonstrate two implanted nodules and all the daughter nodules. On the basis of the histopathological results, detectability of implanted tumour was not significantly different between NC-US (24/26, 92.3%) and C-US (26/26, 100%). However C-US was superior to NC-US in delineating the nodules and in detecting small daughter nodules. The sizes of the implanted tumour nodules measured by histopathology correlated closely with those measured by C-US. Real-time blood-pool images by pulse subtraction harmonic imaging under extra-low MI with Definity will contribute to the improvement of the ultrasound delineation and detection of liver tumours.

[Thrombus entrapped in a patent foramen ovale of the atrial septum]

A 59-year-old women was referred to our hospital due to severe dyspnea and shock status 12 days after intracranial hematoma evacuation for the hypertensive right putaminal hemorrhage. Transthoracic echocardiography revealed right ventricular dilatation and floating structures in the right atrium. Transesophageal echocardiography demonstrated a large, snake-like structure crossing her foramen ovale of the interatrial septum, and impending paradoxical embolism was diagnosed. She did not receive any anticoagulation and surgery due to recent cerebral hemorrhage. Follow-up TEE showed complete disappearance of the thrombus in the atrium two weeks after the onset. Phlebogram of deep vein demonstrated several thrombus in her leg. She underwent placement of inferior vena cava filter and was discharged from our hospital without any symptom of paradoxical embolism.

Noninvasive detection of total occlusion of the left anterior descending coronary artery with transthoracic Doppler echocardiography

OBJECTIVES

The purpose of this study was to evaluate the value of transthoracic Doppler echocardiography (TTDE) for the noninvasive detection of total left anterior descending coronary artery (LAD) occlusion.

BACKGROUND

Total coronary occlusion is associated with an adverse long-term prognosis, and mechanical revascularization may be required for the patient with total coronary occlusion. However, a noninvasive diagnosis of total coronary occlusion before coronary angiography (CAG) has been difficult, especially in patients without clinical signs.

METHODS

We studied 103 consecutive patients who underwent CAG for the evaluation of coronary artery disease. The study group consisted of 16 patients with total LAD occlusion (group A) and 87 patients without total LAD occlusion (group B). Coronary flow velocity in the mid-portion of the LAD was recorded by TTDE.

RESULTS

Adequate spectral Doppler recordings of diastolic flow in the LAD were obtained in 98 study patients (95%; 15 patients in group A and 83 patients in group B). In group A, retrograde LAD flow was obtained in 14 (93%) of 15 patients. The mean diastolic velocity of the retrograde flow was 21.0 +/- 6.1 cm/s. In group B, antegrade LAD flow was obtained in all 83 patients (100%). The mean diastolic velocity of the antegrade flow was 21.5 +/- 7.1 cm/s. Retrograde LAD flow by TTDE had a sensitivity of 93% and a specificity of 100% for the detection of total LAD occlusion.

CONCLUSIONS

Retrograde flow in the LAD by TTDE is a highly sensitive and specific finding that can be used to noninvasively diagnose total LAD occlusion.

Grey-scale contrast enhancement in rabbit liver with DMP115 at different acoustic power levels

The contrast enhancement effect of ultrasound (US) contrast agent DMP-115 (YM454, Definity) in rabbit liver at two acoustic transmit power levels was studied. A total of 12 rabbits with healthy livers and 7 rabbits with VX-2 tumors were used. Grey-scale ultrasonograms in both fundamental (3.75 MHz) and harmonic (2.5/5.0 MHz) imaging modes were performed at a frame rate of 26 Hz under baseline acoustic power (MI = 0.6) or lower acoustic power (MI = 0.2). The contrast enhancement depended on the contrast agent dose and the acoustic power. The video intensity change was higher in the portal vein under the baseline acoustic power and higher in the liver parenchyma under the lower acoustic power. The contrast-enhanced US observation of the VX-2 tumor in the arterial phase correlated well with the angiographic and histopathological appearance of the tumor. In the parenchymal phase, the borderline of the tumor could be clearly delineated from the surrounding liver parenchyma. Continuous fundamental and harmonic grey-scale imaging with DMP115 has the capability of making peripheral circulation images of liver parenchyma and tumors.

Pulse dispersion due to atrial fibrillation causes arterial thrombosis in a rabbit experimental model

Thrombosis associated with atrial fibrillation (AF) is usually caused by a left atrial (LA) thrombus, but it is not always detected. The present study was based on the hypothesis that abnormalities in peripheral artery are responsible for the ischemic stroke associated with AF. Peripheral arterial coagulability was investigated in a rabbit experimental model in which AF was induced by high-frequency stimulation of the right atrium, creating stenosis of the carotid artery together with endothelial damage. The rabbits were classified into 4 groups: (i) sinus rhythm only (group 1), (ii) sinus rhythm after 6 h of pacing (group 2), (iii) short AF (continuous pacing for 5 min; group 3) and (iv) long AF (continuous pacing for 6 h: group 4). The carotid blood flow developed a typical pattern, called cyclic flow reductions (CFRs), the frequency of which (CFRF) was 18.59+/-2.85 in AF (group 3+4) compared with 14.46+/-2.1 in sinus rhythm (group 1+2) (p<0.0005). Among the groups with AF, correlation analysis showed an association between CFRF and pulse dispersion (p<0.02, r=0.58). This study suggests that the distinctive hemodynamic effects with AF, in particular pulse dispersion, substantively influence thrombus formation on injured vascular endothelium.

In vivo kinetics of microbubbles of SH U 508 A (Levovist): comparison with indocyanine green in rabbits

The aim of this study was to evaluate in vivo kinetics of microbubbles of SH U 508 A, in comparison with Indocyanine Green, a dye used as an indicator of blood flow. Microbubble kinetics were evaluated in various vessels (i.e., vena cava, aorta, renal artery, renal vein and portal vein) in rabbits after injection of SH U 508 A by measuring Doppler signals (n = 5). The kinetics of Indocyanine Green were evaluated by measuring absorbance using a photodiode (n = 5). Test substances (SH U 508 A 300 mg/mL and Indocyanine Green 1.25 mg/mL) were injected IV at a dose of 0.1 mL/kg B.W. Peak signal intensity was observed immediately after injection of SH U 508 A, followed by biphasic decay. The rates of biphasic decay were similar in all vessels. A second peak of the signal, which indicated recirculation of the microbubbles, was observed in the vena cava. The circulation and recirculation times of the microbubbles after injection of SH U 508 A were similar to that of Indocyanine Green. These findings suggest that the majority of SH U 508 A microbubbles circulate through the body similarly to blood flow, without retention, in the vasculature.

Analysis of flash echo from contrast agent for designing optimal ultrasound diagnostic systems

Microbubble-based contrast agents can enhance echoes in areas of low blood flow, but the bubbles are extremely sensitive and collapse easily when exposed to ultrasound (US) irradiation. An experimental study of bubble collapse was carried out to design new functions for US diagnostic systems to detect echoes from microbubbles more efficiently. For contrast agent (Levovist) solution, a high-intensity, but momentary, echo (flash echo), was observed in the first frame image after a several-second suspension of transmission, but was not seen in the second frame image. These "flash echo" signals were analyzed and categorized based on microscopic observation, and the results showed that the longevity of the microbubbles was reduced by conditions such as B-mode imaging. Next, a numerical simulation of the bubbles in liquid was performed under the same conditions as in the in vitro experiment. The results showed that even bubbles less than 1 microm in diameter expand and collapse within one pulse drive, which would generate flash echoes. The flash echo imaging system described here permits flexible intermittent scanning with variable intervals, with a variable number of frames at the trigger, and with simultaneous monitoring at low power output. Animal experiments were also conducted to evaluate the system. As the interval between frames was increased, the flash echoes gradually increased, and perfusion in the parenchyma was clearly observed with an interval of 4 s.