American Institute ofUltrasound in Medicine recommendations for contrast-enhanced liver ultrasound imaging clinical trials

Mechanical properties of human hepatic tissues to develop liver-mimicking phantoms for medical applications

Using liver phantoms for mimicking human tissue in clinical training, disease diagnosis, and treatment planning is a common practice. The fabrication material of the liver phantom should exhibit mechanical properties similar to those of the real liver organ in the human body. This tissue-equivalent material is essential for qualitative and quantitative investigation of the liver mechanisms in producing nutrients, excretion of waste metabolites, and tissue deformity at mechanical stimulus. This paper reviews the mechanical properties of human hepatic tissues to develop liver-mimicking phantoms. These properties include viscosity, elasticity, acoustic impedance, sound speed, and attenuation. The advantages and disadvantages of the most common fabrication materials for developing liver tissue-mimicking phantoms are also highlighted. Such phantoms will give a better insight into the real tissue damage during the disease progression and preservation for transplantation. The liver tissue-mimicking phantom will raise the quality assurance of patient diagnostic and treatment precision and offer a definitive clinical trial data collection.

Targeted Contrast-Enhanced Ultrasound for Inflammation Detection

Molecular imaging is a form of nanotechnology that enables the noninvasive examination of biological processes in vivo. Radiopharmaceutical agents are used to target biochemical markers, permitting their detection and evaluation. Early visualization of molecular variations indicative of pathophysiological processes can aid in patient diagnoses and management decisions. Molecular imaging is performed by introducing into the body molecular probes, which are often contrast agents that have been nanoengineered to target and tether to molecules, thus enabling their radiologic identification. Through a nanoengineering process, ultrasound contrast agents can be targeted to specific molecules, extending ultrasound’s capabilities from the tissue to molecular level. Molecular ultrasound, or targeted contrast-enhanced ultrasound (TCEUS), has recently emerged as a popular molecular imaging technique due to its ability to provide real-time anatomic and functional information without ionizing radiation. However, molecular ultrasound represents a novel form of molecular imaging and consequently remains largely preclinical. This review explores the commonalities of TCEUS across several molecular targets and points to the need for standardization of kinetic behavior analysis. The literature underscores evidence gaps and the need for additional research. The application of TCEUS is unlimited but needs further standardization to ensure that future research studies are comparable.

Imaging Techniques for the Diagnosis of Hepatocellular Carcinoma: A Systematic Review and Meta-analysis

BACKGROUND

Several imaging modalities are available for diagnosis of hepatocellular carcinoma (HCC).

PURPOSE

To evaluate the test performance of imaging modalities for HCC.

DATA SOURCES

MEDLINE (1998 to December 2014), the Cochrane Library Database, Scopus, and reference lists.

STUDY SELECTION

Studies on test performance of ultrasonography, computed tomography (CT), or magnetic resonance imaging (MRI).

DATA EXTRACTION

One investigator abstracted data, and a second investigator confirmed them; 2 investigators independently assessed study quality and strength of evidence.

DATA SYNTHESIS

Few studies have evaluated imaging for HCC in surveillance settings. In nonsurveillance settings, sensitivity for detection of HCC lesions was lower for ultrasonography without contrast than for CT or MRI (pooled difference based on direct comparisons, 0.11 to 0.22), and MRI was associated with higher sensitivity than CT (pooled difference, 0.09 [95% CI, 0.07 to 12]). For evaluation of focal liver lesions, there were no clear differences in sensitivity among ultrasonography with contrast, CT, and MRI. Specificity was generally 0.85 or higher across imaging modalities, but this item was not reported in many studies. Factors associated with lower sensitivity included use of an explanted liver reference standard, and smaller or more well-differentiated HCC lesions. For MRI, sensitivity was slightly higher for hepatic-specific than nonspecific contrast agents.

LIMITATIONS

Only English-language articles were included, there was statistical heterogeneity in pooled analyses, and costs were not assessed. Most studies were conducted in Asia and had methodological limitations.

CONCLUSION

CT and MRI are associated with higher sensitivity than ultrasonography without contrast for detection of HCC; sensitivity was higher for MRI than CT. For evaluation of focal liver lesions, the sensitivities of ultrasonography with contrast, CT, and MRI for HCC are similar.

PRIMARY FUNDING SOURCE

Agency for Healthcare Research and Quality. (

PROSPERO

CRD42014007016).

Efficacy of contrast enhanced grey scale ultrasound in characterisation of hepatic focal lesions: A pilot study

BACKGROUND

Contrast enhanced ultrasound (CEUS) has recently gained widespread acceptance as an adjunct to conventional grey scale ultrasound. The present pilot study was undertaken to evaluate the efficacy of this technique in characterisation of hepatic focal lesions.

METHODS

Adult patients who had at least one focal liver lesion underwent ultrasound evaluation in regular and contrast mode before and after intravenous administration of sulphur hexafluoride. The diagnoses were confirmed by comparison with a reference standard (multidetector CT), response to treatment or pathological correlation.

RESULTS

The rate of correct diagnosis for unenhanced ultrasound was 54%, CEUS was 72% and multidetector CT (MDCT) was 92%. A comparison of unenhanced ultrasound versus CEUS using the McNemar test yielded a p value of 0.0704 (>0.05). However, comparison of CEUS versus MDCT using the McNemar test yielded a p value of 0.0265 (<0.05). Additionally, comparison of unenhanced ultrasound versus MDCT using the McNemar test yielded a p value of <0.0001.

CONCLUSION

CEUS increases diagnostic efficacy over unenhanced ultrasound but does not have any significant advantages over MDCT. Currently it may be used as a problem solving tool in atypical haemangiomas, echogenic focal liver lesions, contrast sensitivity and to avoid multiple studies utilising ionising radiation.

Translational imaging endpoints to predict treatment response to novel targeted anticancer agents

Response Evaluation Criteria in Solid Tumors (RECIST) and World Health Organization (WHO) Criteria have been traditionally used for the evaluation of therapeutic response to chemotherapeutic treatment regimens. They determine anatomic criteria for patients response to anti-cancer therapy based on morphological measurements of each target lesion. While this assessment is justified for cytotoxic (chemotherapeutic) drugs, it is now recognized that morphological imaging protocols are poorly suited to the evaluation of the efficacy of novel signal transduction inhibitors (STIs) which exhibit cytostatic rather than cytotoxic properties. New imaging technologies are now designed to evaluate, in a functional manner, modifications in tumor metabolic activity, cellularity, and vascularization before a reduction in tumor volume can be detected. Introduction of physiological imaging end-points, derived from dynamic contrast-enhanced (DCE) imaging protocols--including magnetic resonance imaging (MRI), computed tomography (CT) and ultrasound (US)--allow for early assessment of disruption in tumor perfusion and permeability for targeted anti-angiogenic agents. Diffusion-weighted MRI (DWI) provides another physiological imaging end-point since tumor necrosis and cellularity are seen early in response to anti-angiogenic treatment. Changes in glucose and phospholipid turnover, based on metabolic MRI and positron emission tomography (PET), provide reliable markers for therapeutic response to novel receptor-targeting agents. Finally, novel molecular imaging techniques of protein and gene expression have been developed in animal models followed by a successful human application for gene therapy-based protocols.

Voiding urosonography with US contrast agent for the diagnosis of vesicoureteric reflux in children: an update

Voiding urosonography (VUS) entails the intravesical administration of US contrast agent (USCA) for the diagnosis of vesicoureteric reflux (VUR). VUS is now recognized as a practical, safe, radiation-free modality with comparable or higher sensitivity than direct radionuclide cystography (DRNC) and voiding cystourethrography (VCUG), respectively. An extensive review of the literature regarding both the procedural aspects and comparative diagnostic values of VUS has been published (Darge Pediatr Radiol 38:40-63, 2008a, b). The aim of this review is to provide an update on various facets of VUS that have taken place since the publication of the above-mentioned two reviews.

Microbubble Compositions, Properties and Biomedical Applications

Over the last decade, there has been significant progress towards the development of microbubbles as theranostics for a wide variety of biomedical applications. The unique ability of microbubbles to respond to ultrasound makes them useful agents for contrast ultrasound imaging, molecular imaging, and targeted drug and gene delivery. The general composition of a microbubble is a gas core stabilized by a shell comprised of proteins, lipids or polymers. Each type of microbubble has its own unique advantages and can be tailored for specialized functions. In this review, different microbubbles compositions and physiochemical properties are discussed in the context of current progress towards developing novel constructs for biomedical applications, with specific emphasis on molecular imaging and targeted drug/gene delivery.

Contrast-enhanced ultrasound: what is the evidence and what are the obstacles?

OBJECTIVE

Although ultrasound contrast agents (UCAs) are popular and widely used in Europe and Asia, the U.S. Food and Drug Administration (FDA) has not approved a microbubble agent for radiology imaging in the United States. Herein, we discuss the evidence for and the obstacles to using UCAs for contrast-enhanced ultrasound (CEUS).

CONCLUSION

Despite the obstacles to the use of UCAs for CEUS including regulatory and practice patterns, the evidence indicates that radiologists and patients will be missing an effectual imaging option if we do not encourage the use of CEUS and strongly support the approval of UCAs by the FDA. The evidence outweighs the obstacles: CEUS is cost-effective; can be performed at the bedside; uses no ionizing radiation; has no nephrotoxicity; and, most importantly, can provide accurate diagnostic information comparable to CT and MRI.

Frequency dependence of kidney injury induced by contrast-aided diagnostic ultrasound in rats

This study was performed to examine the frequency dependence of glomerular capillary hemorrhage (GCH) induced by contrast-aided diagnostic ultrasound (DUS) in rats. Diagnostic ultrasound scanners were used for exposure at 3.2, 5.0 and 7.4 MHz, and previously published data at 1.5 and 2.5 MHz was also included. A laboratory exposure system was used to simulate DUS exposure at 1.0, 1.5, 2.25, 3.5, 5.0 and 7.5 MHz, with higher peak rarefactional pressure amplitudes (PRPAs) than were available from our DUS systems. The right kidneys of rats mounted in a water bath were exposed to intermittent image pulse sequences at 1 s intervals during infusion of diluted ultrasound contrast agent. The percentage of GCH was zero for low PRPAs, and then rapidly increased with increasing PRPAs above an apparent threshold, p(t). The values of p(t) were approximately proportional to the ultrasound frequency, f, such that p(t) /f was approximately 0.5 MPa/MHz for DUS and 0.6 MPa/MHz for laboratory system exposures. The increasing thresholds with increasing frequency limited the GCH effect for contrast-aided DUS, and no GCH was seen for DUS at 5.0 or 7.4 MHz for the highest available PRPAs.

Impact of contrast-enhanced ultrasonography in a tertiary clinical practice

OBJECTIVE

The purpose of this study was to assess the impact of contrast-enhanced ultrasonography (CEUS) of the liver in a tertiary clinical practice.

METHODS

One thousand forty consecutive CEUS examinations performed over 30 months for mass characterization were reviewed to determine their source, accuracy, and clinical impact.

RESULTS

Two hundred seventy-five (26.4%) of 1040 examinations were motivated by incidental detection of a mass at routine ultrasonography; 765 (73.6%) were clinical referrals, most often for characterization of a mass in a high-risk patient scanned for hepatoma surveillance or characterization of an indeterminate mass after prior imaging. Clinician referrals increased from 57 in the first 6 months after CEUS introduction to 158 in the last 6 months of the study. Surveillance scans yielded 78 confirmed hepatocellular carcinomas characterized on CEUS at the time of identification. Contrast-enhanced ultrasonography was accurate in 233 (89.2%) of 261 with histologic proof, including 208 malignant lesions. Clinical impact included reduced referrals for other imaging in 226 (21.7%) of 1040 patients, decreased time to diagnosis in 390 (37.5%), and successful guidance for ablation therapy in 26 (2.5%). A positive change in management occurred in 182 (17.5%) of 1040, including alteration of a previous diagnosis, a diagnosis made by CEUS after indeterminate prior imaging, and a diagnosis upstaged by CEUS. Negative impacts included delayed management in 8 (0.8%) small hepatocellular carcinomas misdiagnosed as benign lesions and wrong management of a solitary sclerotic hemangioma, in a high-risk patient for hepatoma, misdiagnosed as a malignant tumor on CEUS, computed tomography, and magnetic resonance imaging, leading to its surgical removal.

CONCLUSIONS

Contrast-enhanced ultrasonography has a positive impact on clinical management, providing rapid, accurate diagnosis of incidentally detected masses and resolving nodules on surveillance scans and indeterminate masses on other imaging.