Acoustic Radiation Force Impulse (ARFI) ultrasound imaging of solid focal liver lesions

B-Mode Ultrasonography and Acoustic Radiation Force Impulse Elastography in Evaluation of Urothelial Carcinoma in Dogs

Bladder tumors in dogs represent approximately 2% of all malignant lesions recorded, with urothelial carcinoma being the most common and aggressive form. This study aimed to characterize the elastographic properties of canine urothelial carcinoma using ARFI (Acoustic Radiation Force Impulse) elastography and to evaluate its diagnostic capacity. Seven dogs with urothelial carcinoma and nine healthy dogs were evaluated, comparing shear wave velocity (SWV) and bladder wall thickness between the groups. The results showed that SWV was significantly higher in dogs with urothelial carcinoma (median of 2.53 m/s) compared with healthy dogs (median of 1.41 m/s) (p = 0.0045). Bladder wall thickness was also greater in dogs with carcinoma (0.28 ± 0.05 cm) compared to healthy dogs (0.14 ± 0.26 cm) (p = 0.0003). Receiver operating characteristic (ROC) curve analysis revealed a high sensitivity (100%) and specificity (88.9%) for SWV in differentiating healthy and neoplastic tissues. These findings suggest that ARFI elastography is a promising tool for diagnosing urothelial carcinoma in dogs, offering a noninvasive and quantitative approach that can complement traditional diagnostic methods. ARFI elastography may aid in early diagnosis and clinical management, improving the prognosis of patients with bladder neoplasia.

The Clinical Value of Multimodal Ultrasound for the Differential Diagnosis of Hepatocellular Carcinoma from Other Liver Tumors in Relation to Histopathology

Recent advances in the field of ultrasonography offer promising tools for the evaluation of liver tumors. We aim to assess the value of multimodal ultrasound in differentiating hepatocellular carcinomas (HCCs) from other liver lesions. We prospectively included 66 patients with 72 liver tumors. The histological analysis was the reference standard for the diagnosis of malignant liver lesions, and partially for benign tumors. All liver lesions were assessed by multiparametric ultrasound: standard ultrasound, contrast-enhanced ultrasound (CEUS), the point shear wave elastography (pSWE) using shear wave measurement (SWM) method and real-time tissue elastography (RTE). To diagnose HCCs, CEUS achieved a sensitivity, specificity, accuracy and positive predictive value (PPV) of 69.05%, 92.86%, 78.57% and 93.55%, respectively. The mean shear-wave velocity (Vs) value in HCCs was 1.59 ± 0.29 m/s, which was lower than non-HCC malignancies (p < 0.05). Using a cut-off value of 1.58 m/s, SWM achieved a sensitivity of 54.76%, and 82.35% specificity, for differentiating HCCs from other malignant lesions. The combination of SWM and CEUS showed higher sensitivity (79.55%) compared with each technique alone, while maintaining a high specificity (89.29%). In RTE, most HCCs (61.53%) had a mosaic pattern with dominant blue areas corresponding to type "c" elasticity. Elasticity type "c" was 70.59% predictive for HCCs. In conclusion, combining B-mode ultrasound, CEUS, pSWE and RTE can provide complementary diagnostic information and potentially decrease the requirements for other imaging modalities.

Ultrasound Elastography for Characterization of Focal Liver Lesions

Focal liver lesions (FLL) are typically detected by conventional ultrasound or other imaging modalities. After the detection of FLL, further characterization is essential, and this can be done by contrast-enhanced imaging techniques, e.g., contrast-enhanced ultrasound (CEUS) and magnetic resonance imaging (MRI) or by means of biopsy with histological evaluation. Elastographic techniques are nowadays integrated into high-end ultrasound systems and their value for the detection of severe liver fibrosis and cirrhosis has been shown in studies and meta-analyses. The use of an ultrasound elastographic technique for the differentiation of malignant and benign liver tumors is less well-established. This review summarizes the current data on utility and performance of ultrasound elastography for the characterization of FLL.

Hepatocellular carcinoma in the non-cirrhotic liver

Liver cirrhosis is an established high-risk factor for HCC and the majority of patients diagnosed with HCC have cirrhosis. However, HCC also arises in non-cirrhotic livers in approximately 20 %of all cases. HCC in non-cirrhotic patients is often clinically silent and surveillance is usually not recommended. HCC is often diagnosed at an advanced stage in these patients. Current information about HCC in patients with non-cirrhotic liver is limited. Here we review the current knowledge on epidemiology, clinical features and imaging features of those patiens.

Elastography for characterization of focal liver lesions: current evidence and future perspectives

Focal liver lesions (FLLs) are a common finding during routine abdominal ultrasound (US). The differential diagnosis between diverse types of FLLs, especially between benign and malignant ones, is extremely important and can often be particularly challenging. Radiological techniques with contrast administration and/or liver biopsy are mostly necessary for establishing diagnosis, but they have several contraindications or complications. Due to limitations of these tools, there is urgent and still unmet need to develop a first line, non-invasive and simple method to diagnose FLLs. Elastography is an US-based imaging modality that provides information about the physical parameter corresponding to the tissue stiffness and can be considered a virtual biopsy. Several elastographic approaches have been developed, such as transient elastography, strain imaging and share wave imaging, which include point shear wave elastography and 2D shear wave elastography. These tools are already in use for evaluating liver fibrosis and in the assessment of focal lesions in other organs, like breast and thyroid gland. This review aims to assess the current evidence of different techniques based on elastography in the setting of FLLs, in order to evaluate accuracy, limitations and future perspectives. In particular, we focused on two contexts: the ability of discriminating between benign and malignant lesions, especially hepatocellular carcinoma and liver metastasis, and the surveillance after percutaneous therapy. This could have a high clinical impact making elastography crucial to identify the appropriate management of FLLs.

Is There a Place for Elastography in the Diagnosis of Hepatocellular Carcinoma?

BACKGROUND AND AIMS

Elastography can provide information regarding tissue stiffness (TS). This study aimed to analyze the elastographic features of hepatocellular carcinoma (HCC) and the factors that influence intratumoral elastographic variability in patients with liver cirrhosis.

METHODS

This prospective study included 115 patients with liver cirrhosis and hepatocellular carcinoma evaluated between June 2016-November 2019. A total of 88 HCC nodules visualized in conventional abdominal ultrasound (US) met the inclusion criteria and underwent elastographic evaluation. Elastographic measurements (EM) were performed in HCC and liver parenchyma using VTQ (Virtual Touch Quantification), a point shear wave elastography (pSWE) technique. In all patients, we performed contrast-enhanced ultrasound (CEUS), and the final diagnosis of HCC was established by contrast-enhanced-CT or contrast-enhanced-MRI.

RESULTS

The mean VTQ values in HCCs were 2.16 ± 0.75 m/s. TS was significantly lower in HCCs than in the surrounding liver parenchyma 2.16 ± 0.75 m/s vs. 2.78 ± 0.92 (p < 0.001). We did not find significant differences between the first five and the last five EM, and the intra-observer reproducibility was excellent ICC: 0.902 (95% CI: 0.87-0.950). However, the tumor size, heterogeneity, and depth correlated with higher intralesional stiffness variability (p < 0.001).

CONCLUSIONS

VTQ brings additional information for HCC characterization. Intra-observer reproducibility for both HCC and liver parenchyma was excellent. Knowing the stiffness of HCC's might endorse an algorithm-based approach towards focal liver lesions (FLLs) in liver cirrhosis.

Role of real-time shear-wave elastogarphy in differentiating hepatocellular carcinoma from other hepatic focal lesions

BACKGROUND

Hepatocellular carcinoma (HCC) has an increasing incidence worldwide, and is considered the second cause of cancer-related death.

AIM

The aim of the study is to assess the usefulness of real-time shear-wave elastography in differentiating HCC from other hepatic focal lesions.

PATIENTS AND METHODS

The current study was conducted on 110 patients in addition to 10 healthy subjects, divided into four groups as follows: liver cirrhosis, HCC, hepatic focal lesions other than HCC, and control. Demographic, laboratory and imaging data were collected and then elastographic assessment of the hepatic focal lesions and the surrounding liver parenchyma using elastograph point quantification (ElastPQ) (iU22x MATRIX, Philips) was done.

RESULTS

ElastPQ (iU22x MATRIX, Philips) has shown its ability to differentiate between HCC and cystic focal lesions, HCC and cholangiocarcinoma, and HCC and focal nodular hyperplasia (FNH). Cystic lesions demonstrated lower stiffness in comparison to HCC; however, cholangiocarcinoma and FNH demonstrated higher stiffness in comparison to HCC. ElastPQ was unable to differentiate between stiffness in both 'HCC and hemangioma' and 'HCC and metastatic focal lesions'. ElastPQ showed that HCC, cystic focal lesions, and cholangiocarcinoma had lower stiffness in comparison to their surrounding liver parenchyma, whereas FNH had higher stiffness in comparison to the surrounding liver parenchyma. ElastPQ showed that the surrounding liver parenchyma of the HCC group has the highest stiffness amongst all studied hepatic focal lesions surrounding liver parenchyma.

CONCLUSION

'Point' shear-waves elastography (ElastPQ; Philips iU22x MATRIX, Philips) is a noninvasive, quantitative and nonradiating method for evaluation of tissue elasticity, and is helpful in differentiating HCC from other hepatic focal lesions.

Role of shear wave sono-elastography (SWE) in characterization of hepatic focal lesions

Background

Focal liver lesions are considered a major problem during abdominal examinations. Shear wave sono-elastography (SWE) has been demonstrated to be helpful in assessment of liver fibrosis degree.

The purpose of this study was to evaluate the role of SWE in characterization of benign and malignant hepatic focal lesions.

Results

Seventy-five (75) patients with variable focal liver lesions (52 malignant and 23 benign) were analyzed by SWE. The stiffness values of surrounding hepatic parenchyma were also measured as a reference for readings of the focal lesion stiffness values. Final diagnosis was achieved by core needle biopsy (in 1 benign and 38 malignant cases) and contrast enhanced CT and MRI (in all cases).

Cholangiocarcinoma (CCC) was the stiffest malignant lesion with median stiffness value (35.9 kPa). Focal nodular hyperplasia (FNH) was the stiffest benign lesion (26.7 kPa).

The median stiffness value of malignant focal lesions (20.22 kPa) was significantly higher than that of benign focal lesions (10.68 kPa) (P value < 0.001).

ROC curve of SWE median stiffness values for differentiation of benign from malignant hepatic focal lesions had AUC = 0.834, and using cut of value 14.165 kPa, yielding 98.1% sensitivity, 78.3% specificity, and 92% accuracy.

Conclusion

SWE has high accuracy in differentiating benign form malignant liver focal lesions with promising results in individual characterization of some malignant (HCC and CCC) and benign hepatic focal lesion (FNH from other benign lesions).

Role of shear wave elastography in characterization of hepatic focal lesions

Background

Elastography is a recently developed diagnostic method that aims to evaluate tissue stiffness. Its utility is based on the fact that pathological tissues are generally stiffer than surrounding healthy tissues which often show up as a hard lesion. Shear wave elastography (SWE) is a new technique based on shear waves that has been implemented in diagnostic ultrasound (US) systems. The aim of this study is to study the role of shear wave elastography in differentiation between benign and malignant hepatic focal lesions.

Results

The study was conducted on 110 patients (92 males, 18 females) with a mean age of 51.7 years. Age range was from 30 to 70 years; 28 patients were diagnosed with benign lesions, and 82 with malignant lesions. SWE shows that there is a significant difference in stiffness between malignant and benign lesions with p value = 0.002 and with mean ± SD of 10.3 ± 6.31 kPa for the benign lesions and 16.2 ± 9.32 kPa for the malignant group. A cutoff value of 13.24 was selected to differentiate between benign and malignant lesions using the SWE mean providing sensitivity 78.04%, specificity 71.42%, and accuracy 64.2%.

Conclusion

SWE is a good tool in the differentiation of benign and malignant hepatic focal lesions.

Hepatocellular Carcinoma and Non-Alcoholic Fatty Liver Disease: A Step Forward for Better Evaluation Using Ultrasound Elastography

Simple Summary

Non-alcoholic fatty liver disease (NAFLD) attracts a lot of attention, due to the increasing prevalence and progression to fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Consequently, new non-invasive, cost-effective diagnostic methods are needed. This review aims to explore the diagnostic performance of ultrasound (US) elastography in NAFLD and NAFLD-related HCC, adding a new dimension to the conventional US examination—the liver stiffness quantification. The vibration controlled transient elastography (VCTE), and 2D-Shear wave elastography (2D-SWE) are effective in staging liver fibrosis in NAFLD. VCTE presents the upside of assessing steatosis through the controlled attenuation parameter. Hereby, we critically reviewed the elastography techniques for the quantitative characterization of focal liver lesions (FLLs), focusing on HCC: Point shear wave elastography and 2D-SWE. 2D-SWE presents a great potential to differentiate malignant from benign FLLs, guiding the clinician towards the next diagnostic steps. As a disease-specific surveillance tool, US elastography presents prognostic capability, improving the NAFLD-related HCC monitoring.

Abstract

The increasing prevalence of non-alcoholic fatty liver disease (NAFLD) in the general population prompts for a quick response from physicians. As NAFLD can progress to liver fibrosis, cirrhosis, and even hepatocellular carcinoma (HCC), new non-invasive, rapid, cost-effective diagnostic methods are needed. In this review, we explore the diagnostic performance of ultrasound elastography for non-invasive assessment of NAFLD and NAFLD-related HCC. Elastography provides a new dimension to the conventional ultrasound examination, by adding the liver stiffness quantification in the diagnostic algorithm. Whilst the most efficient elastographic techniques in staging liver fibrosis in NAFLD are vibration controlled transient elastography (VCTE) and 2D-Shear wave elastography (2D-SWE), VCTE presents the upside of assessing steatosis through the controlled attenuation parameter (CAP). Hereby, we have also critically reviewed the most important elastographic techniques for the quantitative characterization of focal liver lesions (FLLs), focusing on HCC: Point shear wave elastography (pSWE) and 2D-SWE. As our paper shows, elastography should not be considered as a substitute for FLL biopsy because of the stiffness values overlap. Furthermore, by using non-invasive, disease-specific surveillance tools, such as US elastography, a subset of the non-cirrhotic NAFLD patients at risk for developing HCC can be detected early, leading to a better outcome. A recent ultrasomics study exemplified the wide potential of 2D-SWE to differentiate benign FLLs from malignant ones, guiding the clinician towards the next steps of diagnosis and contributing to better long-term disease surveillance.

ACR Appropriateness Criteria® Chronic Liver Disease

The liver fibrosis stage is the most important clinical determinate of morbidity and mortality in patients with chronic liver diseases. With newer therapies, liver fibrosis can be stabilized and possibly reversed, thus accurate diagnosis and staging of liver fibrosis are clinically important. Ultrasound, CT, and conventional MRI can be used to establish the diagnosis of advanced fibrosis/cirrhosis but have limited utility for assessing earlier stages of fibrosis. Elastography-based ultrasound and MRI techniques are more useful for assessment of precirrhotic hepatic fibrosis. In patients with advanced fibrosis at risk for hepatocellular carcinoma (HCC), ultrasound is the surveillance modality recommended by international guidelines in nearly all circumstances. However, in patients in whom ultrasound does not assess the liver well, including those with severe steatosis or obesity, multiphase CT or MRI may have a role in surveillance for HCC. Both multiphase CT and MRI can be used for continued surveillance in patients with a history of HCC, and contrast-enhanced ultrasound may have an emerging role in this setting. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Performance of Shear Wave Elastography in Delineating the Radiofrequency Ablation Boundary: An in Vivo experiment

This study was aimed at exploring the cutoff value of Young's modulus of ablated tissue and the optimal scale at which shear wave elastography (SWE) can delineate the ablation boundary. The livers of 30 rabbits were radiofrequency (RF) ablated, and ultrasonic imaging, including SWE and contrast-enhanced ultrasound (CEUS), was performed. The ablation boundary in the SWE image was located using CEUS, and the SWE parameters of the boundary were measured to calculate the cutoff value of Young's modulus. The cutoff value of the ablated tissue was 48-50 kPa 2 h to 28 d post-ablation. The regions of increased stiffness in SWE images at a scale of 0-50 kPa overlapped well with the non-enhanced regions of CEUS images in 88% of specimens. Therefore, elasticity values differed significantly between ablated and non-ablated tissues, and the cutoff value for Young's modulus differentiated these tissues. SWE delineated the ablation boundary well at the optimal SWE scale with respect to the cutoff value.

Diagnostic effect of shear wave elastography imaging for differentiation of malignant liver lesions: a meta-analysis

Background

Shear wave elastography (SWE) imaging have been proposed for characterization of focal liver lesions. We conducted a meta-analysis to evaluate the accuracy and clinical utility of SWE imaging for differentiation of malignant and benign hepatic lesions.

Methods

PubMed, Embase, Web of Science, and the Cochrane Library were systematically reviewed to search for studies published between January 1, 1990, and November 30, 2018. The studies published in English relating to the evaluation the diagnostic accuracy of SWE imaging for distinguishing malignant and benign liver lesions were retrieved and examined for pooled sensitivity, specificity, likelihood ratios, and diagnostic odds ratios, using bivariate random-effects models. The hierarchical summary receiver operating characteristic (HSROC) curve was estimated to assess the SWE imaging accuracy. The clinical utility of SWE imaging for differentiation of malignant liver lesions was evaluated by Fagan plot.

Results

A total of 15 studies, involving 1894 liver lesions in 1728 patients, were eligible for the meta-analysis. The pooled sensitivity and specificity for identification of malignant liver lesions were 0.82 (95% CI: 0.77–0.86) and 0.82 (95% CI: 0.76–0.87), respectively. The AUC was 0.89 (95% CI: 0.86–0.91). When the pre-test probability was 50%, after SWE imaging measurement over the cut-off value (positive result), the corresponding post-test probability for the presence of malignant liver lesions was 82%; the post-test probability was 18% after negative measurement.

Conclusions

SWE imaging showed high sensitivity and specificity in differentiating malignant and benign liver lesions and may be promising for noninvasive evaluation of liver lesions.

Trial registration

The review was registered in the International Prospective Register of Systematic Reviews (PROSPERO): CRD42018104510.

Electronic supplementary material

The online version of this article (10.1186/s12876-019-0976-2) contains supplementary material, which is available to authorized users.

The role of acoustic radiation force impulse elastography in the differentiation of benign and malignant focal liver masses

BACKGROUND/AIMS

The aim of this study was to evaluate elasticity of benign and malign focal liver lesions and surrounding parenchyma as measured by acoustic radiation force impulse (ARFI).

MATERIALS AND METHODS

34 hemangiomas, 4 focal nodular hyperplasia (FNH), 10 hepatocellular carcinoma (HCC) and 22 metastatic lesions from a total of 62 patients were examined with ARFI elastography. ARFI measurements for each tumor type were expressed as mean ± standard deviation for liver mass and surrounding parenchyma. ARFI values were compared between tumor types and surrounding parencyhma.

RESULTS

The mean stiffness values were 2.15±0.73 m/s for hemangiomas (n=34), 3.22±0.18 m/s for FNH (n=4), 2.75±0.53 m/s for HCC (n=10) and 3.59±0.51 m/s for metastasis (n=22). Although there was not a significant difference between hemangiomas and HCC lesions in ARFI values (p>0.05), hemangiomas showed significantly different ARFI values from FNH and metastases (p<0.05). Also, there were significant differences in ARFI values between malignant and benign masses. The area under the receiver-operating characteristics curves for discriminating the malignant from benign liver masses was 0.826 (p<0.001). An ARFI value of 2.32 m/s was selected as cut-off value to differentiate malignant liver masses from benign ones (sensitivity: 0.93, specificity: 0.60).

CONCLUSION

Although currently ARFI is not a definitive method for the primary diagnosis of focal solid liver lesions, it provides additional important information non-invasively for differential diagnosis.

Correlation of the Stiffness of Hepatocellular Carcinoma and Surrounding Liver Parenchyma by Point Shear Wave Elastography

The purpose of this study was to assess the correlation between hepatocellular carcinoma (HCC) and surrounding liver parenchyma stiffness using point shear wave elastography (pSWE). HCC was diagnosed using the criteria of the American Association for the Study of Liver Diseases. Liver fibrosis was classified into three groups (nonsignificant fibrosis, significant fibrosis, and cirrhosis). pSWE was performed on the HCC and the adjacent hepatic parenchyma and was expressed as kilopascal (kPa). A total of 59 HCC patients with 64 tumors were included in the study. The mean stiffnesses of HCC and liver background were 9.25 ± 3.76 and 10.84 ± 4.81 kPa, respectively. There was no statistical significance in HCC stiffness in any stage of liver fibrosis. Low HCC/liver background stiffness ratio was noted in the cirrhotic group and statistically significant in two comparison groups (cirrhosis vs significant fibrosis and cirrhosis vs nonsignificant fibrosis), with P < .001. In this cohort, HCC stiffness alone demonstrated no statistically significant difference in various stages of liver fibrosis.

Can point shear wave elastography differentiate focal nodular hyperplasia from hepatocellular adenoma

PURPOSE

Focal nodular hyperplasia (FNH) and hepatocellular adenoma (HCA) are liver tumors that require different management. We assessed the potential of point shear wave elastography (pSWE) to differentiate FNH from HCA and the interobserver and intraobserver reliability of pSWE in the examination of these lesions and of native liver tissue (NLT).

METHODS

The study included 88 patients (65 FNH, 23 HCA). pSWE was performed by two experienced liver sonographers (observers 1 [O1] and 2 [O2]) and acquired within the lesion of interest and NLT. Group differences, optimal cutoff for characterization and interobserver reliability was assessed with Mann-Whitney-U, area under the ROC curce (AUROC) and intraclass correlation coefficient (ICC). Intraobserver reliability in NLT was assessed in 20 healthy subjects using ICC.

RESULTS

Median stiffness was significantly higher in FNH than in HCA (7.01 kPa vs 4.98 kPa for O1 (P = 0.017) and 7.68 kPa vs 6.00 kPa for O2 (P = 0.031)). A cutoff point for differentiation between the two entities could not be determined with an AUROC of 0.67 (O1) and 0.69 (O2). Interobserver reliability was good for lesion- stiffness (ICC = 0.86) and poor for NLT stiffness (ICC = 0.09). In healthy subjects, intraobserver reliability for NLT-stiffness was poor for O1 (ICC = 0.23) and moderate for O2 (ICC = 0.62).

CONCLUSION

This study shows that pSWE cannot reliably differentiate FNH from HCA. Interobserver and intraobserver reliability for pSWE in NLT were insufficient. Interpretation of results gained with this method should be done with great caution.

Role of acoustic radiation force impulse and shear wave velocity in prediction of preterm birth: a prospective study

Background Preterm birth is one of the important causes of neonatal morbidity where we rely on subjective criteria such as modified Bishop's scoring and contemporary sonographic measurement of cervical length. Acoustic radiation force impulse (ARFI) is a technological advancement in elastography that can be employed in prediction of cervical softening and preterm labor. Purpose To evaluate the role of ARFI technique and shear wave velocity (SWV) estimates as a predictor of preterm birth and its comparison with other clinical and sono-elastographic measures. Material and Methods Thirty-four pregnant women (gestation age = 28-37 weeks age) showing features suggestive of preterm labor were included and evaluated with modified Bishop's score, cervical length by ultrasound (US), ARFI to derive Elastography index (EI), and SWV of the cervix. The patients were later divided into two groups, using the clinical outcome of preterm or term delivery. Results Twenty patients delivered at term (gestational age > 37 weeks) and 14 were preterm. Receiver operating characteristics (ROC) curves showed SWV with highest sensitivity and specificity (93% and 90%, respectively) for the prediction of preterm birth at a cutoff value of 2.83 m/s. EI and modified Bishop's score were comparable to each other, but were less sensitive techniques. Conclusion Elastographic assessment of antenatal cervix is a novel technique of virtual palpation of internal os and can be utilized as an objective criterion for preterm birth prediction.

Role of Acoustic Radiation Force Impulse Elastography in the Characterization of Focal Solid Hepatic Lesions

Objective:

The purpose of the study is to investigate the usefulness of acoustic radiation force impulse (ARFI) elastography in the characterization of focal solid liver lesions as benign, malignant, or metastatic using ARFI two-dimensional (2D) imaging and ARFI quantification (shear wave velocities [SWVs]).

Materials and Methods:

Sixty lesions were included in this study. The lesions were classified into three groups: Group I included benign lesions (n = 25), Group II included malignant lesions (n = 27), and Group III included metastatic lesions (n = 8). ARFI elastography was performed in all these patients using a Siemens ACUSON S 2000™ ultrasound machine. Stiffness and size of the lesions were assessed on ARFI 2D images in correlation with B-mode ultrasound images. SWVs were obtained in these lesions for the quantification of stiffness.

Results:

In ARFI 2D images, malignant lesions were predominantly stiffer and larger, while benign lesions were softer and similar in size (P < 0.05). The mean SWVs in benign, malignant, and metastatic lesions were 1.30 ± 0.35 m/s, 2.93 ± 0.75 m/s, and 2.77 ± 0.90 m/s, respectively. The area under receiver operating characteristic curve of SWV for differentiating benign from malignant lesions was 0.877, suggesting fair accuracy (95% confidence interval: 0.777–0.976); with a cutoff value of 2 m/s, showing sensitivity: 92%; specificity: 96%; positive predictive value: 96%; negative predictive value: 93% (P < 0.05). Statistically significant difference exists in SWV of benign and malignant or metastatic lesions.

Conclusion:

ARFI elastography with 2D imaging and quantification might be useful in the characterization of benign and malignant liver lesions.

Novel ultrasound-based methods to assess liver disease: The game has just begun

In the last 10 years the availability of ultrasound elastography allowed to diagnose and stage liver fibrosis in a non-invasive way and changed the clinical practice of hepatology. Newer ultrasound-based techniques to evaluate properties of the liver tissue other than fibrosis are emerging and will lead to a more complete characterization of the full spectrum of diffuse and focal liver disease. Since these methods are currently undergoing validation and go beyond elastography for liver tissue evaluation, they were not included in the recent guidelines regarding elastography issued by the European Federation of Societies in Ultrasound in Medicine and Biology. In this review paper, we outline the major advances in the field of ultrasound for liver applications, with special emphasis on techniques that could soon be part of the future armamentarium of ultrasound specialists devoted to the assessment of liver disease. Specifically, we discuss current and future ultrasound assessment of steatosis, spleen stiffness for portal hypertension, and elastography for the evaluation of focal liver lesions; we also provide a short glimpse into the next generation of ultrasound diagnostic methods.

Utility of point shear wave elastography in characterisation of focal liver lesions

BACKGROUND

The present study aimed at evaluation of the usefulness of point shear wave elastography (pSWE) in characterization of FLL(s) by quantifying their stiffness.

METHODS

In total, 197 patients (mean age was 56.57 years) with FLL(s) on conventional ultrasound were included. Final diagnoses, confirmed by imaging and/or biopsy whenever possible, included hepatocellular carcinoma (HCC) (n = 143), metastasis (n = 36), hemangioma (n = 16), and focal nodular hyperplasia (n = 2). Stiffness evaluation was performed by pSWE. Stiffness ratio (lesion to background liver) was calculated. ROC analysis was performed to evaluate the diagnostic accuracy of the stiffness value and stiffness ratio and to extract the optimal cutoff values for characterisation of FLL(s).

RESULTS

HCC was significantly softer than its surrounding liver parenchyma [5.43 (3.03) vs. 17.05 (8.53) kPa, p <0.001]. However, the stiffness values for the other examined FLLs were comparable to their surrounding liver parenchyma. No significant difference was detected across different types of metastases or between metastases and surrounding liver (p>0.05). Stiffness ratio was superior to stiffness value in discrimination of HCC from metastasis (AUROC, 0.91 vs. 0.51 respectively).

CONCLUSION

pSWE could provide a complementary information about FLLs especially in differentiation between HCCs from metastases.

Can ultrasound elastography identify mass-like focal fatty change (FFC) from liver mass?

Focal fatty change (FFC) may mimic liver mass on conventional B-mode ultrasound. Clinical differentiation of mass-like FFC and liver mass is important due to different clinical interventions. Contrast-enhanced imaging (CEI) or biopsy is reliable for this differentiation, but is expensive and invasive. This study aimed to explore utilities of ultrasound elastography for this differentiation.This study enrolled 79 patients with focal liver lesions (FLLs), of which 26 were mass-like FFC confirmed by at least 2 CEI modalities. The other 53 were liver masses, confirmed by pathology (n = 28) or at least 2 CEI modalities (n = 25). Lesion stiffness value (SV), absolute stiffness difference (ASD), and stiffness ratio (SR) of lesion to background were obtained using point shear-wave elastography (pSWE) and compared between FFC group and liver mass group. The performance of SV, ASD, and SR for identifying FFC from liver mass was evaluated.SV was 5.6 ± 2.4 versus 16 ± 12 kPa, ASD was 2.0 ± 1.9 versus 11 ± 12 kPa, and SR was 1.4 ± 0.6 versus 3.0 ± 1.9 for FFC and liver mass group, respectively (P < .0001). The area under the receiver operating characteristic curve of SV, ASD, and SR for discriminating mass-like FFC and liver mass was 0.840, 0.842, and 0.791, respectively (P < .05). Particularly, with cut-off ASD < 1.0 kPa, positive predictive value was 100%, specificity was 100%, and accuracy was 82% for diagnosing FFC.pSWE may be a potential useful modality for identifying mass-like FFC from liver mass, which might help reduce the necessity for further CEI or biopsy for diagnosing mass-like FFC.

Combination of acoustic radiation force impulse imaging, serological indexes and contrast-enhanced ultrasound for diagnosis of liver lesions

AIM

To assess the value of combined acoustic radiation force impulse (ARFI) imaging, serological indexes and contrast-enhanced ultrasound (CEUS) in distinguishing between benign and malignant liver lesions.

METHODS

Patients with liver lesions treated at our hospital were included in this study. The lesions were divided into either a malignant tumor group or a benign tumor group according to pathological or radiological findings. ARFI quantitative detection, serological testing and CEUS quantitative detection were performed and compared. A comparative analysis of the measured indexes was performed between these groups. Receiver operating characteristic (ROC) curves were constructed to compare the diagnostic accuracy of ARFI imaging, serological indexes and CEUS, alone or in different combinations, in identifying benign and malignant liver lesions.

RESULTS

A total of 112 liver lesions in 43 patients were included, of which 78 were malignant and 34 were benign. Shear wave velocity (SWV) value, serum alpha-fetoprotein (AFP) content and enhancement rate were significantly higher in the malignant tumor group than in the benign tumor group (2.39 ± 1.20 m/s vs 1.50 ± 0.49 m/s, 18.02 ± 5.01 ng/mL vs 15.96 ± 4.33 ng/mL, 2.14 ± 0.21 dB/s vs 2.01 ± 0.31 dB/s; P < 0.05). The ROC curve analysis revealed that the areas under the curves (AUCs) of SWV value alone, AFP content alone, enhancement rate alone, SWV value + AFP content, SWV value + enhancement rate, AFP content + enhancement rate and SWV value + AFP content + enhancement rate were 85.1%, 72.1%, 74.5%, 88.3%, 90.4%, 82.0% and 92.3%, respectively. The AUC of SWV value + AFP content + enhancement rate was higher than those of SWV value + AFP content and SWV value + enhancement rate, and significantly higher than those of any single parameter or the combination of any two of parameters.

CONCLUSION

The combination of SWV, AFP and enhancement rate had better diagnostic performance in distinguishing between benign and malignant liver lesions than the use of any single parameter or the combination of any two of parameters. It is expected that this would provide a tool for the differential diagnosis of benign and malignant liver lesions.

Comparison between acoustic radiation force impulse quantification data and perfusion-CT parameters in hepatocellular carcinoma

OBJECTIVE

To find out, if ultrasound elastography of hepatocellular carcinoma (HCC) can predict patterns of tumor perfusion in volume perfusion computed tomography (VPCT).

MATERIAL AND METHODS

25 consecutive patients (mean age, 68.9; range, 51-85 years) with liver cirrhosis suspected of HCC underwent VPCT and acoustic radiation force impulse (ARFI) elastography the same day. Quantitative elasticity values were registered, while blood flow (BF), blood volume (BV) and hepatic perfusion index (HPI) of the HCC lesions were calculated. Additionally, we identified histologic WHO grading, lesion size and localization. The Siemens Acuson S 3000 HELX-System with Virtual Touch™-Software and Siemens Somatom Definition Flash with Syngo^® software were used.

RESULTS

A total of 43 HCC lesions were assessed. Mean shear wave velocity was 2.6m/s (range, 1.1-4.3m/s). There was no significant linear correlation between the elasticity values and BF (p=0.751), BV (p=0.426) and HPI (p=0.437). However, elasticity values were higher, the larger the tumor was (p=0.008). Shear wave velocity declined with increasing distance of the HCC to the skin surface (p=0.028) and depending on liver segment. In addition, elasticity values were higher in less differentiated HCCs. This trend was not statistically significant (p=0.842).

CONCLUSION

Tissue elasticity in HCC does not correlate with the degree of tumor vascularization, but calculated values are influenced both by the tumor size and localization inside the liver.

Utility of virtual touch quantification in the diagnosis of pancreatic ductal adenocarcinoma

This study aimed to compare the tissue stiffness of pancreatic ductal adenocarcinoma (PDAC) with that of pancreatic parenchyma using virtual touch quantification (VTQ). SWV was measured in 34 PDAC lesions and in pancreatic parenchyma of both controls and patients. SWVs in PDAC lesions were significantly higher than in pancreatic parenchyma in both healthy controls and in patients with PDAC. The area under the ROC for diagnosis of PDAC was 0.94 for pancreatic parenchyma in healthy controls, and 0.85 for pancreatic parenchyma in patients with PDAC. VTQ can provide a useful and additional information for diagnosis of PDAC.

Shear Wave Elastography of Focal Liver Lesion: Intraobserver Reproducibility and Elasticity Characterization

PURPOSE

The aim of the study was to evaluate the intraobserver reproducibility and to determine the elasticity characteristics of focal liver lesions (FLLs) by shear wave elastography (SWE).

METHODS

One hundred thirty-six FLLs in 118 patients were examined with SWE for quantitative and qualitative assessment of stiffness. Three SWE images were obtained for each lesion and liver parenchyma by 1 radiologist. Intraobserver reproducibility was assessed by intraclass correlation coefficients (ICCs). Patient and lesion factors that can affect the reproducibility were evaluated. For characterization of the lesion elasticity, the difference in stiffness between the groups of lesions was evaluated.

RESULTS

The mean (SD) diameter and depth of the lesions were 3.98 (2.07) and 4.4 (1.59) cm, respectively. The ICC of intraobserver reproducibility was 0.763. Deep-seated lesions (≥6 cm; ICC, 0.621) showed significantly lower intraobserver reproducibility compared with superficial lesions (ICC, 0.793; P = 0.047). Stiffness values of malignant lesions (n = 85, 60.41 [47.81] kPa) were significantly higher than those of benign lesions (n = 51, 22.05 [17.24] kPa, P < 0.0001). Mean (SD) stiffness of hepatocellular carcinoma (45.72 [35.65] kPa) was significantly lower than that of metastasis (67.43 [43.39] kPa) and was significantly higher than benign FLLs (22.05 [17.24] kPa). However, mean (SD) lesion-parenchyma ratio of hepatocellular carcinoma (3.76 [4]) was not significantly different from that of benign FLLs (3.7 [3.77]).

CONCLUSIONS

Overall, intraobserver reproducibility of SWE in evaluation of FLLs was excellent, but it can be affected by lesion depth. In addition, SWE is helpful in elasticity characterization of FLLs.

Functional imaging of hepatocellular carcinoma

Imaging plays a key role in the clinical management of hepatocellular carcinoma (HCC), but conventional imaging techniques have limited sensitivity in visualizing small tumors and assessing response to locoregional treatments and sorafenib. Functional imaging techniques allow visualization of organ and tumor physiology. Assessment of functional characteristics of tissue, such as metabolism, proliferation and stiffness, may overcome some of the limitations of structural imaging. In particular, novel molecular imaging agents offer a potential tool for early diagnosis of HCC, and radiomics may aid in response assessment and generate prognostic models. Further prospective research is warranted to evaluate emerging techniques and their cost-effectiveness in the context of HCC in order to improve detection and response assessment.

Ultrasound elastographic techniques in focal liver lesions

Elastographic techniques are new ultrasound-based imaging techniques developed to estimate tissue deformability/stiffness. Several ultrasound elastographic approaches have been developed, such as static elastography, transient elastography and acoustic radiation force imaging methods, which include point shear wave and shear wave imaging elastography. The application of these methods in clinical practice aims at estimating the mechanical tissues properties. One of the main settings for the application of these tools has been liver stiffness assessment in chronic liver disease, which has been studied mainly using transient elastography. Another field of application for these techniques is the assessment of focal lesions, detected by ultrasound in organs such as pancreas, prostate, breast, thyroid, lymph nodes. Considering the frequency and importance of the detection of focal liver lesions through routine ultrasound, some studies have also aimed to assess the role that elestography can play in studying the stiffness of different types of liver lesions, in order to predict their nature and thus offer valuable non-invasive methods for the diagnosis of liver masses.

Ultrasound elastography: liver

Ultrasound elastography, also termed sonoelastography, is being used increasingly in clinical practice to aid the diagnosis and management of diffuse liver disease. Elastography has been shown to be capable of differentiating advanced and early-stage liver fibrosis, and consequently a major application in clinical liver care includes progression to cirrhosis risk stratification through (1) assessment of liver fibrosis stage in HCV and HBV patients, (2) distinguishing non-alcoholic steatohepatitis from simple steatosis in non-alcoholic fatty liver disease patients, and (3) prognostic evaluation of liver disease is autoimmune liver disease. In addition, elastographic characterization of focal liver lesions and evaluation of clinically significant portal hypertension have the potential to be clinically useful and are areas of active clinical research.

Acoustic radiation force impulse with shear wave speed quantification of pancreatic masses: A prospective study

BACKGROUND

Acoustic Radiation Force Impulse (ARFI) is a new ultrasound technique that evaluates mechanical properties of tissues. To evaluate the use of ARFI with shear waves speed quantification for pancreatic masses characterization during the ultrasound examination.

METHODS

123 pancreatic lesions were prospectively evaluated. Median shear waves speeds were compared with Mann-Whitney U test. Two reading methods were applied for the characterization of adenocarcinoma: more than one measurement above the top shear waves speed (SWS) value. Two reading methods were applied to diagnose mucinous lesion: at least 2 (method 1) or 3 (method 2) numerical measurements. Sensitivity, specificity, positive and negative predictive values and accuracy of each reading method were calculated. Forty volunteers were included for normal ARFI values.

RESULTS

In the adenocarcinoma group median SWS value was 2.74 m/s. In the volunteers group the median SWS value was 1.17 m/s. Significant difference between SWS median values of adenocarcinoma and normal pancreas was found (P < 0.05). For the diagnosis of pancreatic solid masses if more than one measurement is above the top SWS value of 4.00 m/s results in the study, the diagnosis of ductal adenocarcinoma is highly specific with specificity and PPV of 100%. Good sensitivity (73.3%) and specificity (83.3%) were obtained for the characterization of mucinous cystic lesions.

CONCLUSIONS

Acoustic Radiation Force Impulse imaging could help in the non-invasive characterization of solid and cystic lesions of the pancreas during a conventional US examination.

Ultrasound Elasticity Imaging System with Chirp-Coded Excitation for Assessing Biomechanical Properties of Elasticity Phantom

The biomechanical properties of soft tissues vary with pathological phenomenon. Ultrasound elasticity imaging is a noninvasive method used to analyze the local biomechanical properties of soft tissues in clinical diagnosis. However, the echo signal-to-noise ratio (eSNR) is diminished because of the attenuation of ultrasonic energy by soft tissues. Therefore, to improve the quality of elastography, the eSNR and depth of ultrasound penetration must be increased using chirp-coded excitation. Moreover, the low axial resolution of ultrasound images generated by a chirp-coded pulse must be increased using an appropriate compression filter. The main aim of this study is to develop an ultrasound elasticity imaging system with chirp-coded excitation using a Tukey window for assessing the biomechanical properties of soft tissues. In this study, we propose an ultrasound elasticity imaging system equipped with a 7.5-MHz single-element transducer and polymethylpentene compression plate to measure strains in soft tissues. Soft tissue strains were analyzed using cross correlation (CC) and absolution difference (AD) algorithms. The optimal parameters of CC and AD algorithms used for the ultrasound elasticity imaging system with chirp-coded excitation were determined by measuring the elastographic signal-to-noise ratio (SNRe) of a homogeneous phantom. Moreover, chirp-coded excitation and short pulse excitation were used to measure the elasticity properties of the phantom. The elastographic qualities of the tissue-mimicking phantom were assessed in terms of Young's modulus and elastographic contrast-to-noise ratio (CNRe). The results show that the developed ultrasound elasticity imaging system with chirp-coded excitation modulated by a Tukey window can acquire accurate, high-quality elastography images.

The Role of Acoustic Radiation Force Impulse Elastography in the Differentiation of Infectious and Neoplastic Liver Lesions

We aimed to evaluate the effectiveness of acoustic radiation force impulse (ARFI) elastography in differentiating between hepatic lesions. The prospective study included 117 patients with liver masses. Shear wave velocity (SWV) values for lesions were determined by ARFI imaging and compared statistically. The difference between SWV values for benign and malignant hepatic masses was significant (p < 0.01). The threshold SWV value for malignant hepatic lesions was established at 2.52 m/s, and the sensitivity and specificity of this cut-off value were 97% and 66%, respectively. We concluded that ARFI elastography provides supplementary data that aid in the differential diagnosis of liver masses.

Liver reserve function assessment by acoustic radiation force impulse imaging

AIM: To evaluate the utility of liver reserve function by acoustic radiation force impulse (ARFI) imaging in patients with liver tumors.

METHODS: Seventy-six patients with liver tumors were enrolled in this study. Serum biochemical indexes, such as aminotransferase (ALT), aspartate aminotransferase (AST), serum albumin (ALB), total bilirubin (T-Bil), and other indicators were observed. Liver stiffness (LS) was measured by ARFI imaging, measurements were repeated 10 times, and the average value of the results was taken as the final LS value. Indocyanine green (ICG) retention was performed, and ICG-K and ICG-R15 were recorded. Child-Pugh (CP) scores were carried out based on patient’s preoperative biochemical tests and physical condition. Correlations among CP scores, ICG-R15, ICG-K and LS values were observed and analyzed using either the Pearson correlation coefficient or the Spearman rank correlation coefficient. Kruskal-Wallis test was used to compare LS values of CP scores, and the receiver-operator characteristic (ROC) curve was used to analyze liver reserve function assessment accuracy.

RESULTS: LS in the ICG-R15 10%-20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.19 ± 0.27 vs 1.59 ± 0.32, P < 0.01). LS in the ICG-R15 > 20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.92 ± 0.29 vs 1.59 ± 0.32, P < 0.01). The LS value in patients with CP class A was lower than in patients with CP class B (1.57 ± 0.34 vs 1.86 ± 0.27, P < 0.05), while the LS value in patients with CP class B was lower than in patients with CP class C (1.86 ± 0.27 vs 2.47 ± 0.33, P < 0.01). LS was positively correlated with ICG-R15 (r = 0.617, P < 0.01) and CP score (r = 0.772, P < 0.01). Meanwhile, LS was negatively correlated with ICG-K (r = -0.673, P < 0.01). AST, ALT and T-Bil were positively correlated with LS, while ALB was negatively correlated with LS (P < 0.05). The ROC curve revealed that the when the LS value was 2.34 m/s, the Youden index was at its highest point, sensitivity was 69.2% and specificity was 92.1%.

CONCLUSION: For patients with liver tumors, ARFI imaging is a useful tool for assessing liver reserve function.

Focal nodular hyperplasia and hepatocellular adenoma: The value of shear wave elastography for differential diagnosis

OBJECTIVE

This study assessed the clinical usefulness of shear wave elastography (SWE) during ultrasound for differentiating between focal nodular hyperplasias (FNHs) and hepatocellular adenomas (HAs).

MATERIALS AND METHODS

SWE was performed on 56 patients presenting with 76 liver lesions (57 FNHs and 19HAs) that were confirmed by MRI and contrast-enhanced ultrasound (CEUS) (n=55) or by histology (n=21). A mean elasticity value was obtained for each lesion. The ratios of the elasticity of the lesions to the elasticity of the surrounding liver were determined. The optimal elasticity cut-off value for distinguishing between the two lesion types was determined using ROC analysis. All lesions that were classified as "undetermined" after CEUS were reclassified using the elasticity values.

RESULTS

The mean elasticity value was 46.99 ± 31.15 kPa for FNHs and 12.08 ± 10.68 kPa for HAs (p<0.0001). The mean relative elasticity ratio values were 7.94 ± 6.43 and 1.91 ± 1.70, respectively (p<0.0001). The ROC analysis showed a maximal accuracy of 95% for identification with a cut-off of 18.8 kPa for lesion elasticity (accuracy of 96% with a cut-off of 1.98 for the relative elasticity ratio). A total of 68 CEUS were performed, and 17 lesions (25%) were classified as "undetermined" after CEUS. With these cut-off values 16 lesions (94.1%) were correctly reclassified as FNHs.

CONCLUSION

SWE is a useful adjunctive tool for differentiation between FNH and HA during ultrasound examination.

Hepatocellular carcinoma: stiffness value and ratio to discriminate malignant from benign focal liver lesions

PURPOSE

To investigate the use of stiffness value and stiffness ratio (ratio of lesion to background liver parenchyma values) to discriminate malignant from benign focal liver lesions by using histologic results as the reference standard.

MATERIALS AND METHODS

This study was approved by the institutional review board, and written informed consent was obtained. Three hundred seventy-three patients with focal liver lesions proven at histologic examination underwent measurement of liver stiffness with elastography point quantification. First, stiffness values in two regions of the background liver parenchyma (at 0.5-2 cm and >2 cm from the lesion periphery) near 163 hepatocellular carcinomas were analyzed to determine a reference background liver for calculating the stiffness ratio. Second, the use of the lesion stiffness value and the stiffness ratio for prediction of liver malignancy was investigated in a cohort of patients with 58 benign and 201 malignant lesions. Results were validated in another independent cohort of patients with 25 benign and 89 malignant lesions by using analysis of the area under the receiver operating characteristic (AUC) curve.

RESULTS

The coefficient of variation for the background liver at 0.5-2 cm from the lesion was higher (196%) than that at greater than 2 cm from the lesion (66%). In the development phase, diagnostic accuracy with use of the stiffness value was significantly higher than that with use of the stiffness ratio for discrimination of malignant from benign lesions (AUC, 0.86 vs 0.66, respectively; P < .001). Diagnostic performance with the stiffness value was lower than that with the stiffness ratio (AUC, 0.53 vs 0.86, respectively; P < .001) for discrimination of cirrhotic nodules from other benign lesions. Diagnostic performance with the stiffness value was significantly lower than that with the stiffness ratio (AUC, 0.58 vs 0.71 respectively; P = .007) for discrimination of metastasis from primary liver cancers. In the validation phase, similar findings were revealed for the discrimination of malignant from benign lesions (AUC, 0.87 vs 0.67; P < .001) and discrimination between metastasis and primary liver cancers (AUC, 0.49 vs 0.73; P < .001).

CONCLUSION

Use of stiffness values measured in the liver parenchyma at more than 2 cm from the lesion allowed better diagnostic performance than did values measured in a region closer to the tumor. Stiffness value was more accurate than stiffness ratio for differentiation of malignant from benign focal liver lesions, but the stiffness ratio might be useful for subclassification of benign and malignant lesions. Online supplemental material is available for this article.

Reliability analysis of acoustic radiation force impulse ultrasound imaging with virtual touch tissue quantification: ex vivo ox liver

The effect of scanning angle and region of interest (ROI) depth on shear-wave velocity (SWV) was investigated in this study. Shear-wave velocity of ox liver ex vivo was measured with different approaches. Region of interest was set underneath the liver capsule at depths of 1, 2, 3, 4, and 5 cm. Three groups of measurements were performed at different scanning angles. One group of measurement was conducted with a scanning angle of 0 to 15 degrees from the midline, and the other 2 groups were performed with scanning angles of 15 to 30 degrees and 30 to 45 degrees. The data on SWV from different scan angles and ROI depths were analyzed statistically. Scanning angle and ROI depth were found to be the 2 factors that affect SWV. Interaction was observed between the scan angle and ROI depth. The data at different depths within 0- to 15-degree scanning angles exhibited no significant difference. However, the reliability of SWV decreased with the increase in ROI depth. In the groups of 15 to 30 degrees and 30 to 45 degrees, a significant difference was found between the 2 different measured depths. Scanning angle and ROI depth affected the reliability of SWV measurement. The scanning angle should be confined within 15 degrees from the midline. Therefore, SWV from shallow ROI is more reliable than that at deep ROI.

Differentiation of metastatic cervical lymph nodes with ultrasound elastography by virtual touch tissue imaging: preliminary study

OBJECTIVES

The purpose of this study was to investigate the clinical usefulness of acoustic radiation force impulse elastography for the differential diagnosis of cervical lymph nodes.

METHODS

Virtual touch tissue imaging (Siemens Medical Solutions, Mountain View, CA) was analyzed in 81 patients (mean age, 46.6 years; range, 5-82 years) with 81 lymph nodes (45 metastatic nodes and 36 benign nodes).

RESULTS

Most benign lymph nodes were slightly darker or the same in brightness compared with surrounding tissue, whereas most metastatic nodes were obviously darker. The mean area ratio of benign lymph nodes ± SD (1.05 ± 0.15) was statistically lower than the mean area ratio of metastatic lymph nodes (1.39 ± 0.20; P < 0.001). The area ration cutoff level for metastatic lymph nodes was estimated to be 1.16. With the use of a receiver operating characteristic curve with this cutoff value, the area ratio predicted malignancy with sensitivity of 91.1%, specificity of 83.3%, and an area under the curve of 0.925.

CONCLUSIONS

Acoustic radiation force impulse imaging is feasible for cervical lymph nodes. The Virtual Touch tissue imaging technique can complement conventional sonography, thereby making it easier to diagnose cervical lymph nodes.

Imaging of benign hepatocellular lesions: current concepts and recent updates

Focal nodular hyperplasia (FNH) and hepatocellular adenoma (HCA) are a variety of solid lesions mostly found in the absence of underlying chronic liver disease in young patients. HCA is no longer to be considered as a unique lesion but as a recollection of different entities sharing common points but most of all separated by different typical morphological aspects. Accurate diagnosis is of clinical importance as the management is most of the time conservative for FNH, whereas HCAs expose patients to hemorrhage and malignant transformation, and may lead to a more invasive treatment, mainly surgical resection. Moreover, the different HCA subtypes expose to different risks of complication. The best imaging techniques for the differentiation between FNH and HCAs and for the subtyping of HCAs are contrast-enhanced ultrasound (CEUS) and magnetic resonance imaging (MRI), as specific combinations of imaging features have been associated with the different lesions. They should be considered as complementary examinations. Atypical or multiple lesions, lesions containing fat or presence of an associated steatosis represent diagnostic challenges. Recently, MR hepatospecific contrast agents have been shown to be useful. Emergent elastography techniques might also be helpful in the near future. Biopsy should always be performed in case of uncertain diagnosis to reach a final diagnosis and avoid unnecessary invasive treatment.

Characterization of fortuitously discovered focal liver lesions: additional information provided by shearwave elastography

OBJECTIVES

To prospectively assess the stiffness of incidentally discovered focal liver lesions (FLL) with no history of chronic liver disease or extrahepatic cancer using shearwave elastography (SWE).

METHODS

Between June 2011 and May 2012, all FLL fortuitously discovered on ultrasound examination were prospectively included. For each lesion, stiffness was measured (kPa). Characterization of the lesion relied on magnetic resonance imaging (MRI) and/or contrast-enhanced ultrasound, or biopsy. Tumour stiffness was analysed using ANOVA and non-parametric Mann-Whitney tests.

RESULTS

105 lesions were successfully evaluated in 73 patients (61 women, 84%) with a mean age of 44.8 (range: 20‒75). The mean stiffness was 33.3 ± 12.7 kPa for the 60 focal nodular hyperplasia (FNH), 19.7 ± 9.8 k Pa for the 17 hepatocellular adenomas (HCA), 17.1 ± 7 kPa for the 20 haemangiomas, 11.3 ± 4.3 kPa for the five focal fatty sparing, 34.1 ± 7.3 kPa for the two cholangiocarcinomas, and 19.6 kPa for one hepatocellular carcinoma (p < 0.0001). There was no difference between the benign and the malignant groups (p = 0.64). FNHs were significantly stiffer than HCAs (p < 0.0001). Telangiectatic/inflammatory HCAs were significantly stiffer than the steatotic HCAs (p = 0.014). The area under the ROC curve (AUROC) for differentiating FNH from other lesions was 0.86 ± 0.04.

CONCLUSION

SWE may provide additional information for the characterization of FFL, and may help in differentiating FNH from HCAs, and in subtyping HCAs.

KEY POINTS

• SWE might be helpful for the characterization of solid focal liver lesions • SWE cannot differentiate benign from malignant liver lesions • FNHs are significantly stiffer than other benign lesions • Telangiectatic/inflammatory HCA are significantly stiffer than steatotic ones.

Liver masses: a clinical, radiologic, and pathologic perspective

Liver masses present a relatively common clinical dilemma, particularly with the increasing use of various imaging modalities in the diagnosis of abdominal and other symptoms. The accurate and reliable determination of the nature of the liver mass is critical, not only to reassure individuals with benign lesions but also, and perhaps more importantly, to ensure that malignant lesions are diagnosed correctly. This avoids the devastating consequences of missed diagnosis and the delayed treatment of malignancy or the unnecessary treatment of benign lesions. With appropriate interpretation of the clinical history and physical examination, and the judicious use of laboratory and imaging studies, the majority of liver masses can be characterized noninvasively. Accurate characterization of liver masses by cross-sectional imaging is particularly dependent on an understanding of the unique phasic vascular perfusion of the liver and the characteristic behaviors of different lesions during multiphasic contrast imaging. When noninvasive characterization is indeterminate, a liver biopsy may be necessary for definitive diagnosis. Standard histologic examination usually is complemented by immunohistochemical analysis of protein biomarkers. Accurate diagnosis allows the appropriate selection of optimal management, which is frequently reassurance or intermittent follow-up evaluations for benign masses. For malignant lesions or those at risk of malignant transformation, management depends on the tumor staging, the functional status of the uninvolved liver, and technical surgical considerations. Unresectable metastatic masses require oncologic consultation and therapy. The efficient characterization and management of liver masses therefore requires a multidisciplinary collaboration between the gastroenterologist/hepatologist, radiologist, pathologist, hepatobiliary or transplant surgeon, and medical oncologist.

The impact of share wave elastography in differentiation of hepatic hemangioma from malignant liver tumors in pediatric population

OBJECTIVE

In children it is crucial to differentiate malignant liver tumors from the most common benign tumor, hepatic hemangiomas since the treatment strategies are quite different. We aimed to evaluate the efficiency of shear wave elastography (SWE) technique in differentiation of malignant hepatic tumors and hepatic hemangiomas.

METHODS

Twenty patients with hepatic tumor were included in our study. Two radiologists performed SWE for 13 patients with malignant hepatic tumors including hepatoblastoma (n=7), hepatocellular carcinoma (n=3), metastasis (n=2), embryonal sarcoma (n=1) and 7 patients with hepatic hemangioma. All of our patients were between the age of 1 and 192 months (mean age: 56.88 months). Receiver operating characteristic analysis was achieved to evaluate the diagnostic accuracy of SWE and to determine the optimal cut-off value in differentiation hepatic hemangioma from malignant hepatic tumors.

RESULTS

The mean SWE values (in kPa) for the first observer were 46.94 (13.8-145) and 22.38 (6.6-49.6) and those for the second observer were 57.91 (11-237) and 23.87 (6.4-57.5), respectively for malignant hepatic tumors and hepatic hemangiomas. The SWE values of malignant hepatic tumors were significantly higher than those of hepatic hemangioma (p=0.02). The inter-observer agreement was almost perfect (0.81). The area under the receiver operating characteristic curve of SWE for differentiating the hepatic hemangioma from malignant hepatic tumors was 0.77 with a sensitivity of 72.7% and a specificity of 66.7% at a cutoff value of 23.62 with 95% confidence interval.

CONCLUSION

Shear wave elastography can be helpful in differentiation of malignant hepatic tumors and hepatic hemangioma.

Effects of vascularity and differentiation of hepatocellular carcinoma on tumor and liver stiffness: in vivo and in vitro studies

Tissue stiffness has been found to be a useful predictor of malignancy in various cancers. However, data on the stiffness of hepatocellular carcinomas (HCCs) and their background livers are contradictory. The aim of this study was to investigate the effects of vascularity and histologic differentiation on HCC stiffness. Elastography point quantification (ElastPQ), a new shear wave-based elastography method, was used to measure liver stiffness in vivo in 99 patients with pathology-proven HCC. Lesion vascularity was assessed using contrast-enhanced ultrasound, computed tomography and/or magnetic resonance imaging. The association of HCC vascularity and differentiation with liver stiffness was determined. In addition, in vitro stiffness of 20 of the 99 surgical HCC specimens was mechanically measured and compared with in vivo measurements. We found that in vivo stiffness was significantly higher than in vitro stiffness in both HCCs and their background livers (p < 0.0001). Moreover, significantly higher stiffness was observed in hyper-vascular and poorly differentiated lesions than in hypo-vascular (p = 0.0352) and moderately to well-differentiated lesions (p = 0.0139). These in vivo and in vitro studies reveal that shear wave-based ultrasound elasticity quantification can effectively measure in vivo liver stiffness.

Relationship between the liver tissue shear modulus and histopathologic findings analyzed by intraoperative shear wave elastography and digital microscopically assisted morphometry in patients with hepatocellular carcinoma

OBJECTIVES

Shear wave elastography is a novel noninvasive method for assessing liver fibrosis by measuring liver stiffness. This study was conducted to evaluate how pathologic changes could have an impact on measured elasticity values in both resected hepatocellular carcinomas and adjacent liver tissue.

METHODS

Intraoperative shear wave elastography was performed in 7 patients who underwent liver resection at our institution; 7 hepatocellular carcinomas and adjacent liver tissue were subjected to elastographic measurements. A total of 48 circular regions of interest (ROIs; 3-8 mm in diameter) were located in the hepatocellular carcinomas (n = 37) and adjacent liver tissue (n = 11), and mean stiffness values were obtained from each ROI. All of the histologic images corresponding to the 48 ROIs after surgery were transformed into digital microscopic images by a scanning system, and histologic parameters, such as the proportions of nuclear areas, fatty areas, fibrous areas, and vessel areas, were quantitatively assessed. Relationships between the mean stiffness and the histologic parameters were investigated by the mixed effects model.

RESULTS

By univariate analysis, the proportions of collagen fiber areas (P = .039), fibrous areas (P = .045), hepatocellular nuclear areas (P = .045), and nuclear areas other than hepatocellular and lymphoplasmacytic areas (P = .039) showed statistically positive associations with mean stiffness values. Multivariate analysis indicated that the proportion of collagen fiber areas was the strongest pathologic determinant of mean stiffness (P = .008), with hepatocellular nuclear areas also having a significant effect (P = .010).

CONCLUSIONS

Fibrosis predictably affects elastographic estimation, but hepatocellular density (ie, hepatocellular nuclear areas) also alters elastographic assessment.

Liver elastography, comments on EFSUMB elastography guidelines 2013

Recently the European Federation of Societies for Ultrasound in Medicine and Biology Guidelines and Recommendations have been published assessing the clinical use of ultrasound elastography. The document is intended to form a reference and to guide clinical users in a practical way. They give practical advice for the use and interpretation. Liver disease forms the largest section, reflecting published experience to date including evidence from meta-analyses with shear wave and strain elastography. In this review comments and illustrations on the guidelines are given.

Acoustic radiation force impulse elastography for focal hepatic tumors: usefulness for differentiating hemangiomas from malignant tumors

Objective

The purpose of this study is to investigate whether acoustic radiation force impulse (ARFI) elastography with ARFI quantification and ARFI 2-dimensional (2D) imaging is useful for differentiating hepatic hemangiomas from malignant hepatic tumors.

Materials and Methods

One-hundred-and-one tumors in 74 patients were included in this study: 28 hemangiomas, 26 hepatocellular carcinomas (HCCs), three cholangiocarcinomas (CCCs), 20 colon cancer metastases and 24 other metastases. B-mode ultrasound, ARFI 2D imaging, and ARFI quantification were performed in all tumors. Shear wave velocities (SWVs) of the tumors and the adjacent liver and their SWV differences were compared among the tumor groups. The ARFI 2D images were compared with B-mode images regarding the stiffness, conspicuity and size of the tumors.

Results

The mean SWV of the hemangiomas was significantly lower than the malignant hepatic tumor groups: hemangiomas, 1.80 ± 0.57 m/sec; HCCs, 2.66 ± 0.94 m/sec; CCCs, 3.27 ± 0.64 m/sec; colon cancer metastases, 3.70 ± 0.61 m/sec; and other metastases, 2.82 ± 0.96 m/sec (p < 0.05). The area under the receiver operating characteristics curve of SWV for differentiating hemangiomas from malignant tumors was 0.86, with a sensitivity of 96.4% and a specificity of 65.8% at a cut-off value of 2.73 m/sec (p < 0.05). In the ARFI 2D images, the malignant tumors except HCCs were stiffer and more conspicuous as compared with the hemangiomas (p < 0.05).

Conclusion

ARFI elastography with ARFI quantification and ARFI 2D imaging may be useful for differentiating hepatic hemangiomas from malignant hepatic tumors.

Acoustic radiation force impulse of the liver

Acoustic radiation force impulse (ARFI) imaging is a new and promising ultrasound-based diagnostic technique that, evaluating the wave propagation speed, allows the assessment of the tissue stiffness. ARFI is implemented in the ultrasound scanner. By short-duration acoustic radiation forces (less than 1 ms), localized displacements are generated in a selected region of interest not requiring any external compression so reducing the operator dependency. The generated wave scan provides qualitative or quantitative (wave velocity values) responses. Several non-invasive methods for assessing the staging of fibrosis are used, in order to avoid liver biopsy. Liver function tests and transient elastography are non-invasive, sensitive and accurate tools for the assessment of liver fibrosis and for the discrimination between cirrhotic and non-cirrhotic liver. Many published studies analyse ARFI performance and feasibility in studying diffuse liver diseases and compare them to other diagnostic imaging modalities such as conventional ultrasonography and transient elastography. Solid focal liver lesions, both benign and malignant, are common findings during abdominal examinations. The accurate characterization and differential diagnosis are important aims of all the imaging modalities available today. Only few papers describe the application of ARFI technology in the study of solid focal liver lesions, with different results. In the present study, the existing literature, to the best of our knowledge, about ARFI application on diffuse and focal liver pathology has been evaluated and results and statistical analyses have been compared, bringing to the conclusion that ARFI can be used in the study of the liver with similar accuracy as transient elastography in diagnosing significant fibrosis or cirrhosis and has got some advantages in respect to transient elastography since it does not require separate equipment, better displays anatomical structures and measurements can be successfully carried out almost in every patient.