Contrast-enhanced ultrasonography: advance and current status in abdominal imaging

Clinical applications of Doppler ultrasonography for thyroid disease: consensus statement by the Korean Society of Thyroid Radiology

Doppler ultrasonography (US) is widely used for the differential diagnosis of thyroid nodules, metastatic cervical lymph nodes in patients with thyroid cancer, and diffuse parenchymal disease, as well as for guidance in various US-guided procedures, including biopsy and ablation. However, controversies remain regarding the appropriate use and interpretation of Doppler US. Therefore, the Korean Society of Thyroid Radiology organized a taskforce to develop a consensus statement on the clinical use of Doppler US for thyroid disease. The review and recommendations in this article are based on a comprehensive analysis of the current literature and the consensus of experts.

Contrast-Enhanced Ultrasound is a Useful Adjunct to Doppler Ultrasound in the Initial Assessment of Patients Suspected of Budd Chiari Syndrome

BACKGROUND

Doppler is the screening modality of choice for assessment of patients suspected of Budd Chiari syndrome (BCS). The aim of this study was to compare the diagnostic value of contrast enhanced ultrasound (CEUS) with Doppler in the initial evaluation of patients with BCS.

METHODS

This was a retrospective study of patients with suspicion of BCS who underwent CEUS of the hepatic veins and inferior vena cava between July 2017 and April 2019. CEUS was performed using Sonovue. All patients underwent Doppler evaluation of the hepatic veins and inferior vena cava. The final diagnosis of BCS was based on transvenous or percutaneous digital subtraction venography. The diagnostic accuracy of CEUS was compared with Doppler.

RESULTS

A total of 19 patients (median age, 30 years; 11 males) were evaluated with CEUS and Doppler. A final diagnosis of BCS was established on digital subtraction venography in 15 patients. CEUS was found to have a 100% sensitivity and 75% specificity. The sensitivity and specificity of Doppler was 100% and 25%. The diagnostic accuracies of CEUS and Doppler were 94.74% and 84.29%, respectively.

CONCLUSION

CEUS is a useful adjunct to the Doppler in the initial assessment of patients with BCS. However, further prospective studies must confirm our preliminary observations.

Contrast imaging ultrasound for the detection and characterization of carotid vulnerable plaque

Not only the degree of luminal narrowing but also the plaque morphology and composition play an important role in risk stratification of carotid atherosclerotic lesions. During the last few years, carotid contrast-enhanced ultrasound (CEUS) has emerged as a valuable imaging tool to assess such vulnerable carotid plaques. This review article discussed the use of CEUS for the detection of carotid plaque irregularities and ulcerations as well as the quantification of intraplaque neovascularization and its correlation with histology and inflammatory biomarkers. Apart from evaluating for markers of vulnerable carotid plaques, CEUS enhancement is directly associated with past cerebrovascular events. More importantly, preliminary evidence has shown that CEUS could be used to predict future cerebrovascular and cardiovascular events. Despite the progress in CEUS imaging for carotid atherosclerotic disease, past studies still suffer from the retrospective nature, small sample size, and a lack of matched, well controlled prospective studies. In the future, large multi-center prospective studies addressing the relationship between CEUS findings and patient clinical outcomes in carotid atherosclerotic disease are warranted.

Benign gallbladder diseases: Imaging techniques and tips for differentiating with malignant gallbladder diseases

Benign gallbladder diseases usually present with intraluminal lesions and localized or diffuse wall thickening. Intraluminal lesions of the gallbladder include gallstones, cholesterol polyps, adenomas, or sludge and polypoid type of gallbladder cancer must subsequently be excluded. Polyp size, stalk width, and enhancement intensity on contrast-enhanced ultrasound and degree of diffusion restriction may help differentiate cholesterol polyps and adenomas from gallbladder cancer. Localized gallbladder wall thickening is largely due to segmental or focal gallbladder adenomyomatosis, although infiltrative cancer may present similarly. Identification of Rokitansky-Aschoff sinuses is pivotal in diagnosing adenomyomatosis. The layered pattern, degree of enhancement, and integrity of the wall are imaging clues that help discriminate innocuous thickening from gallbladder cancer. High-resolution ultrasound is especially useful for analyzing the layering of gallbladder wall. A diffusely thickened wall is frequently seen in inflammatory processes of the gallbladder. Nevertheless, it is important to check for coexistent cancer in instances of acute cholecystitis. Ultrasound used alone is limited in evaluating complicated cholecystitis and often requires complementary computed tomography. In chronic cholecystitis, preservation of a two-layered wall and weak wall enhancement are diagnostic clues for excluding malignancy. Magnetic resonance imaging in conjunction with diffusion-weighted imaging helps to differentiate xathogranulomatous cholecystitis from gallbladder cancer by identifying the presence of fat and degree of diffusion restriction. Such distinctions require a familiarity with typical imaging features of various gallbladder diseases and an understanding of the roles that assorted imaging modalities play in gallbladder evaluations.

Understanding the Role of Gadoxetic Acid in MRI

Background:

Radiological imaging methods used at a large scale in the assessment of hepatic lesions include: Ultrasound, computed tomography and magnetic resonance. To further characterize these lesions, specific contrast agents may be added, thus revealing the vascularity of the lesions.

Discussion:

This review focuses on gadoxetic acid, which is a hepatospecific contrast agent used in MRI. The aim of the review is to briefly explain the mechanism of GA enhancement, describe the enhancement patterns of some benign and malignant hepatic lesions and discuss possible advantages of GA over standard contrast agents.

Conclusion:

The role of GA in functional MR cholangiography and the idea of accessing liver function by measuring parenchymal enhancement will also be explained.

Perfluorobutane contrast-enhanced ultrasonography: a new standard for ultrasonography-guided thermal ablation of sonographically occult liver tumours?

INTRODUCTION

Image-guided thermal ablation, preferably with ultrasonography (US), is increasingly used for treatment of small liver tumours. Perfluorobutane-contrast enhanced US (pCEUS) is a promising tool that may allow for targeting of tumours that are otherwise imperceptible on greyscale US. Although pCEUS has been reported to be effective, the literature has been limited outside of Japan and South Korea. We aimed to provide data that supports the use of pCEUS in thermal ablation of sonographically occult liver tumours.

METHODS

We conducted a retrospective single-centre study of 35 consecutive patients who underwent pCEUS-guided ablation of 48 liver tumours with a median size of 1.2 cm. Periprocedural, one-month post-treatment, and relevant follow-up imaging studies were reviewed. Electronic records were also obtained, with long-term follow-up data of 12-28 months being available for 32 patients.

RESULTS

36 (75%) of tumours that were imperceptible on greyscale US became visible with pCEUS. Overall, complete tumour ablation at one month was 89%. 1 (3%) patient developed a major complication following treatment, while 6 (17%) had minor post-treatment complaints. The local tumour progression rate was 17% with a median time of 14 months.

CONCLUSION

pCEUS has a role in US-guided thermal ablation of liver tumours, offering a high technical success rate that is comparable to reported data. Additional benefits may include improved procedural time and freedom from ionising radiation.

Differentiation of atypical hepatic hemangioma from liver metastases: Diagnostic performance of a novel type of color contrast enhanced ultrasound

BACKGROUND

In clinical practice, the diagnosis is sometimes difficult with contrast-enhanced ultrasound (CEUS) when the case has an atypical perfusion pattern. Color parametric imaging (CPI) is an analysis software for CEUS with better detection of temporal differences in CEUS imaging using arbitrary colors. It measures the differences in arrival time of the contrast agent in lesions so that the perfusion features of atypical hemangioma and colorectal cancer (CRC) liver metastasis can be distinguished.

AIM

To evaluate the role of a novel type of CPI of CEUS in the differential diagnosis of atypical hemangioma from liver metastases in patients with a history of CRC.

METHODS

From January 2016 to July 2018, 42 patients including 20 cases of atypical hemangioma and 22 cases of liver metastases from CRC were enrolled. These patients had a mean age of 60.5 ± 9.3 years (range: 39-75 years). All patients received ultrasound, CEUS and CPI examinations. Resident and staff radiologists independently and retrospectively reviewed CEUS and CPI images. Two sets of criteria were assigned: (1) Routine CEUS alone; and (2) CEUS and CPI. The diagnostic sensitivity, specificity, accuracy and receiver operating characteristic (ROC) curve of resident and staff radiologists were analyzed.

RESULTS

The following CPI features were significantly different between liver hemangioma and liver metastases analyzed by staff and resident radiologists: Peripheral nodular enhancement (65%-70.0% vs 4.5%-13.6%, P < 0.001, P = 0.001), mosaic/chaotic enhancement (5%-10% vs 68.2%-63.6%, P < 0.001, P < 0.001) and feeding artery (20% vs 59.1%-54.5%, P = 0.010, P = 0.021). CPI imaging offered significant improvements in detection rates compared with routine CEUS in both resident and staff groups. By resident radiologists, the specificity and accuracy of CEUS+CPI were significantly increased compared with that of CEUS (77.3% vs 45.5%, P = 0.030; 78.6% vs 50.0%, P = 0.006). In addition, the area under the curve (AUC) of CEUS+CPI was significantly higher than that of CEUS (0.803 vs 0.757, P = 0.036). By staff radiologists, accuracy was improved in CEUS+CPI (81.0% vs 54.8%, P = 0.010), whereas no significant differences in specificity and sensitivity were found (P = 0.144, P = 0.112). The AUC of CEUS+CPI was significantly higher than that of CEUS (0.890 vs 0.825, P = 0.013) by staff radiologists.

CONCLUSION

Compared with routine CEUS, CPI could provide specific information on the hemodynamic features of liver lesions and help to differentiate atypical hemangioma from liver metastases in patients with CRC, even for senior radiologists.

Application of new ultrasound techniques for focal liver lesions

Ultrasonography (US) has the overwhelming advantages of not entailing radiation exposure and being a noninvasive, real-time, convenient, easy-to-perform, and relatively inexpensive imaging modality. It is used as the first-line imaging modality for screening, detection, and diagnosis of focal liver lesions (FLLs) [small hepatocellular carcinomas (HCCs), in particular]. However, with the increasing demand for accurate and early diagnosis of small HCCs, newer radiologic methods need to be explored to overcome certain limitations of US. For example, the imaging is easily negatively affected by the presence of gas, rib cage, and subcutaneous fat, and is insensitive for capturing the subtle but vital information on the blood flow. It was in response to this need that new promising technologies such as contrast-enhanced ultrasound and fusion imaging were introduced for the detection of liver lesions. This paper presents an overview of the epidemiology and mechanisms of the development of HCCs, with an emphasis on the application of US in the diagnosis and treatment of FLLs. The aim of this article is to provide the state-of-the-art developments in the imaging diagnosis of FLLs and evaluation of ablation treatment of early HCCs. By keeping abreast of these recent advances, we hope that doctors and researchers working in the field of diagnosis/treatment of liver diseases will be able to discriminate benign FLLs such as regenerative nodules and focal nodular hyperplasia from HCCs, so as to avoid unnecessary repeated tumor biopsies and overtreatment. In particular, we expect that small HCCs or precancerous nodules (such as dysplastic nodules) can be accurately diagnosed and appropriately treated even at an early stage.

A Prospective Study on the Value of Ultrasound Microflow Assessment to Distinguish Malignant from Benign Solid Breast Masses: Association between Ultrasound Parameters and Histologic Microvessel Densities

OBJECTIVE

To investigate the value of ultrasound (US) microflow assessment in distinguishing malignant from benign solid breast masses as well as the association between US parameters and histologic microvessel density (MVD).

MATERIALS AND METHODS

Ninety-eight breast masses (57 benign and 41 malignant) were examined using Superb Microvascular Imaging (SMI) and contrast-enhanced US (CEUS) before biopsy. Two radiologists evaluated the quantitative and qualitative vascular parameters on SMI (vascular index, morphology, distribution, and penetration) and CEUS (time-intensity curve analysis and enhancement characteristics). US parameters were compared between benign and malignant masses and the diagnostic performance was compared between SMI and CEUS. Subgroup analysis was performed according to lesion size. The effect of vascular parameters on downgrading Breast Imaging Reporting and Data System (BI-RADS) category 4A masses was evaluated. The association between histologic MVD and US parameters was analyzed.

RESULTS

Malignant masses were associated with a higher vascular index (15.1 ± 7.3 vs. 5.9 ± 5.6), complex vessel morphology (82.9% vs. 42.1%), central vascularity (95.1% vs. 59.6%), penetrating vessels (80.5% vs. 31.6%) on SMI (all, p < 0.001), as well as higher peak intensity (37.1 ± 25.7 vs. 17.0 ± 15.8, p < 0.001), slope (10.6 ± 11.2 vs. 3.9 ± 4.2, p = 0.001), area (1035.7 ± 726.9 vs. 458.2 ± 410.2, p < 0.001), hyperenhancement (95.1% vs. 70.2%, p = 0.005), centripetal enhancement (70.7% vs. 45.6%, p = 0.023), penetrating vessels (65.9% vs. 22.8%, p < 0.001), and perfusion defects (31.7% vs. 3.5%, p < 0.001) on CEUS (p ≤ 0.023). The areas under the receiver operating characteristic curve (AUCs) of SMI and CEUS were 0.853 and 0.841, respectively (p = 0.803). In 19 masses measuring < 10 mm, central vascularity on SMI was associated with malignancy (100% vs. 38.5%, p = 0.018). Considering all benign SMI parameters on the BI-RADS assessment, unnecessary biopsies could be avoided in 12 category 4A masses with improved AUCs (0.500 vs. 0.605, p < 0.001). US vascular parameters associated with malignancy showed higher MVD (p ≤ 0.016). MVD was higher in malignant masses than in benign masses, and malignant masses negative for estrogen receptor or positive for Ki67 had higher MVD (p < 0.05).

CONCLUSION

US microflow assessment using SMI and CEUS is valuable in distinguishing malignant from benign solid breast masses, and US vascular parameters are associated with histologic MVD.

Additional value of contrast-enhanced ultrasound (CEUS) on arterial phase non-hyperenhancement observations (≥ 2 cm) of CT/MRI for high-risk patients: focusing on the CT/MRI LI-RADS categories LR-3 and LR-4

PURPOSE

To determine the added value of CEUS on arterial phase non-hyperenhancement (APNHE) observations (LR-3 and LR-4) of CT/MRI in high-risk patients.

METHODS

Forty-three patients with APNHE observations (≥ 2 cm) from CT/MRI were prospectively enrolled in this IRB-approved study and underwent CEUS. All observations were assessed by LI-RADS for CT/MRI and CEUS. The hemodynamic findings were compared. The mean follow-up period was 11.8 ± 2.1 months. Reference standard was made on 34-APNHE observations based on biopsy (n = 2), surgery (n = 2), and follow-up image (n = 30).

RESULTS

The median of observation size was 2.3 cm (IQR 2.0-2.5 cm). Among the 43-APNHE observations, 12-observations (27.9%) were further presented as arterial phase hyperenhancement (APHE) in CEUS with early (n = 1, CEUS LR-M), late (n = 10, CEUS LR-5), or no (n = 1, CEUS LR-4) washout. Compared to CT, CEUS presented concordant enhancement patterns in 16 (44.4%) in AP and 20 (55.6%) in PVP, respectively. Similarly, 13 (59.1%) and 14 (63.6%) observations showed concordant enhancement patterns between CEUS and MRI in AP and PVP, respectively. Of the 34-APNHE observations with final diagnosis (hepatocellular carcinoma [HCC] n = 12; intrahepatic cholangiocarcinoma [IHCC], n = 1; non-malignancy, n = 21), 4 HCCs (33.3%) and 1 IHCC (100%) were additionally diagnosed by CEUS, while 1 non-malignant lesion (4.5%) was misdiagnosed as HCC by CEUS.

CONCLUSION

Adding CEUS to APNHE observations from CT/MRI would be useful not only for definitely diagnosing HCC (CEUS LR-5) but also for other malignancies (CEUS LR-M). The discordance of dynamic features between the LI-RADS for CEUS and CT/MRI may reflect the different properties of contrast media, although the systems are not interchangeable.

Untargeted Contrast-Enhanced Ultrasound Versus Contrast-Enhanced Computed Tomography: A Differential Diagnostic Performance (DDP) Study for Kidney Lesions

OBJECTIVES

Histopathology is the 'gold standard' for diagnosing renal cell carcinoma but is limited by sample size. Contrast-enhanced ultrasound can differentiate malignant and benign lesions, but the Chinese guidelines on the management of renal cell carcinoma do not include this method. The purpose of this study was to compare the diagnostic parameters of contrast-enhanced ultrasound against those of contrast-enhanced computed tomography for detecting kidney lesions, with histopathology considered the reference standard.

METHODS

Patients with suspected kidney lesions from prior grayscale ultrasonography and computed tomography were included in the analysis (n=191). The contrast-enhanced ultrasound, contrast-enhanced computed tomography, and histopathology data were collected and analyzed. A solid, enhanced mass was considered a malignant lesion, and an unenhanced mass or cyst was considered a benign lesion. The Bosniak criteria were used to characterize the lesions.

RESULTS

Contrast-enhanced ultrasound and contrast-enhanced computed tomography both detected that 151 patients had malignant tumors and 40 patients had benign tumors. No significant differences in the tumors and their subtypes were reported between contrast-enhanced ultrasound and histopathology (p=0.804). Chromophobe renal cell carcinoma was detected through contrast-enhanced computed tomography (n=1), but no such finding was reported by contrast-enhanced ultrasound. A total of 35 cases of papillary renal cell carcinoma were reported through contrast-enhanced ultrasound while 32 were reported through histopathology.

CONCLUSIONS

Contrast-enhanced ultrasound might be safe and as accurate as histopathology in diagnosing kidney lesions, especially renal cell carcinoma. Additionally, this study provides additional information over histopathology and has an excellent safety profile.

LEVEL OF EVIDENCE

III.

Resolution of indeterminate MRI with CEUS in patients at high risk for hepatocellular carcinoma

PURPOSE

To show the contribution of CEUS to characterization of indeterminate MRI observations in high-risk patients for hepatocellular carcinoma (HCC).

METHODS

From July to December 2015, 42 consecutive patients referred to CEUS with indeterminate MRI scans comprise our study cohort. There are 50 indeterminate nodule-like observations and 10 arterial phase hyperenhancing foci, suggesting pseudolesions/arterio-portal shunts. MRI and CEUS lesions are classified according to their enhancement features in all phases and Liver Imaging and Reporting Data System (LI-RADS) in a blind read format. Clinical pathologic correlation and 24 months follow-up are performed.

RESULTS

A majority, 37/50 (74%), of indeterminate nodule-like observations have arterial phase enhancement without washout on MRI. CEUS further characterizes enhancement and shows washout in 14/37 (38%). In total, CEUS diagnoses 16 malignant lesions in 14 patients including 14 HCC and 2 ICC. 12/16 (75%) malignant lesions are confirmed by biopsy or follow-up. Ultrasound identification of a nodule differentiates real nodules from pseudolesions. Of the ten suspected arterial-portal shunts on MRI, two show a real nodule on ultrasound, confirmed as an HCC and a regenerative nodule. 15/42 (36%) patients have LI-RADS escalated from LR-3 or 4 on MRI to LR-4 or 5 on CEUS. Overall, the sensitivity of CEUS is (13/16) 81.3% and specificity is (37/37) 100% for malignant diagnosis.

CONCLUSION

Grayscale ultrasound detects true nodules. Dynamic CEUS detects and characterizes washout, correctly predicting HCC. CEUS is complimentary to MRI and can serve as a problem-solving tool when MRI is indeterminate.

Contrast enhanced ultrasound: A review of radiology applications

Ultrasound contrast agents have been used for decades in Europe and Asia for cardiac and abdominal imaging and are now being more commonly utilized in the United States for radiology applications. Our article reviews the basics of contrast-enhanced ultrasound including how the contrast agent works, advantages and disadvantages, as well as pearls and pitfalls to help the radiologist efficiently integrate this technology into day-to-day clinical practice. We also discuss the diagnosis of focal hepatic lesions as well as off-label applications such as evaluation of renal masses.

Rates of success and failure of biopsies of hollow abdominal organs: descriptive analysis

Abstract Objective: To evaluate the rates of success and failure of ultrasound-guided percutaneous biopsy of lesions in hollow abdominal organs, as well as the influence of contrast enhancement on those rates. Materials and Methods: This was a retrospective, single-center study evaluating patients submitted to ultrasound-guided percutaneous biopsy of abdominal lesions in hollow organs between January 2017 and June 2018. Patient records were reviewed using a standardized data collection form. Results: We included 49 procedures performed in 48 patients, of whom 18 (38%) had a prior diagnosis of cancer. Malignancy was suspected in 44 cases (90%). Among those 44 cases, the suspicion was of a new neoplasm in 28 (64%), of relapse in 11 (25%), and of a metastatic lesion in 5 (11%). The histopathological findings were sufficient to make the diagnosis in all 44 of those cases, 33 (75%) of which were found to be malignant. The diagnosis was consistent with the clinical suspicion in 33 (75%) of the cases in which there was a definitive histological result. There were no complications resulting from the procedure. Conclusion: Ultrasound-guided percutaneous biopsy is a safe procedure that demonstrates high efficacy in providing a sufficient sample for the diagnosis. The main reason to perform such a biopsy is suspicion of a new neoplasm, followed by suspicion of a metastatic lesion. The histopathological results were concordant with the suspicion in the majority of the cases evaluated here.

Technological Advances in Diagnostic Imaging in Exotic Pet Medicine

Diagnostic imaging relies on interpretation of interactions between the body tissue and various energies, such as x-rays, ultrasound, and magnetic or nuclear energies, to differentiate normal from abnormal tissues. Major technological improvements regarding emission and detection of the energetic waves, as well as reconstruction and interpretation of the images, have occurred. These advances made possible visualization of smaller structures, quantitative evaluation of functional processes, and development of unique imaging-guided procedures. This article reviews the technological advances that allowed development of cone beam computed tomography, dual-energy x-ray absorptiometry, and contrast-enhanced ultrasonography, which all could have applications in exotic pet medicine.

Effect of catheter diameter and injection rate of flush solution on renal contrast-enhanced ultrasonography with perfluorobutane in dogs

OBJECTIVE

To assess effects of catheter diameter and injection rate of flush solution (saline [0.9% NaCl] solution) on renal contrast-enhanced ultrasonography (CEUS) with perfluorobutane in dogs.

ANIMALS

5 healthy Beagles.

PROCEDURES

CEUS of the kidneys was performed by IV injection of contrast medium (0.0125 mL/kg) followed by injection of 5 mL of saline solution at rates of 1, 3, and 5 mL/s through a 20-gauge or 24-gauge catheter; thus, CEUS was repeated 3 times for each catheter diameter. Time-intensity curves were created for regions of interest drawn in the renal cortex and medulla. Repeatability was determined by calculating the coefficient of variation (CV). Statistical analysis was used to assess whether perfusion variables or CV of the perfusion variables was associated with catheter diameter or injection rate.

RESULTS

Perfusion variables did not differ significantly between catheter diameters. Time to peak enhancement (TTP) in the renal cortex was affected by injection rate, and there were significantly lower values for TTP at higher injection rates. The CEUS variables with the lowest CVs among injection rates were TTP for the renal cortex; the CV for TTP of the renal cortex was the lowest at an injection rate of 5 mL/s.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of a 24-gauge catheter did not alter CEUS with perfluorobutane; therefore, such catheters could be used for CEUS of the kidneys of small dogs. Moreover, a rate of 5 mL/s is recommended for injection of flush solution to obtain greater accuracy for renal CEUS in Beagles.

Contrast-Enhanced Ultrasound Guidance for Interventional Procedures

Since its introduction, contrast-enhanced ultrasound (CEUS) has gained an important role in the diagnosis and management of abdominal and pelvic diseases. Contrast-enhanced ultrasound can improve lesion detection rates as well as success rates of interventional procedures when compared to conventional ultrasound alone. Additionally, CEUS enables the interventionalist to assess the dynamic enhancement of different tissues and lesions, without the adverse effects of contrast-enhanced computed tomography, such as exposure to ionizing radiation and nephrotoxicity from iodinated contrast material. This review article describes the various applications and advantages of the use of CEUS to enhance performance of ultrasound-guided interventions in the abdomen and pelvis.

Automatic Respiratory Gating Hepatic DCEUS-based Dual-phase Multi-parametric Functional Perfusion Imaging using a Derivative Principal Component Analysis

Purpose: Angiogenesis in liver cancers can be characterized by hepatic functional perfusion imaging (FPI) on the basis of dynamic contrast-enhanced ultrasound (DCEUS). However, accuracy is limited by breathing motion which results in out-of-plane image artifacts. Current hepatic FPI studies do not correct for these artifacts and lack the evaluation of correction accuracy. Thus, a hepatic DCEUS-based dual-phase multi-parametric FPI (DM-FPI) scheme using a derivative principal component analysis (PCA) respiratory gating is proposed to overcome these limitations.

Materials and Methods: By considering severe 3D out-of-plane respiratory motions, the proposed scheme's accuracy was verified with in vitro DCEUS experiments in a flow model mimicking a hepatic vein. The feasibility was further demonstrated by considering in vivo DCEUS measurements in normal rabbit livers, and hepatic cavernous hemangioma and hepatocellular carcinoma in patients. After respiratory kinetics was extracted through PCA of DCEUS sequences under free-breathing condition, dual-phase respiratory gating microbubble kinetics was identified by using a derivative PCA zero-crossing dual-phase detection, respectively. Six dual-phase hemodynamic parameters were estimated from the dual-phase microbubble kinetics and DM-FPI was then reconstructed via color-coding to quantify 2.5D angiogenic hemodynamic distribution for live tumors.

Results: Compared with no respiratory gating, the mean square error of respiratory gating DM-FPI decreased by 1893.9 ± 965.4 (p < 0.05), and mean noise coefficients decreased by 17.5 ± 7.1 (p < 0.05), whereas correlation coefficients improved by 0.4 ± 0.2 (p < 0.01). DM-FPI observably removed severe respiratory motion artifacts on PFI and markedly enhanced the accuracy and robustness both in vitro and in vivo.

Conclusions: DM-FPI precisely characterized and distinguished the heterogeneous angiogenic hemodynamics about perfusion volume, blood flow and flow rate within two anatomical sections in the normal liver, and in benign and malignant hepatic tumors. DCEUS-based DM-FPI scheme might be a useful tool to help clinicians diagnose and provide suitable therapies for liver tumors.

Biomedical applications of acoustically responsive phase shift nanodroplets: Current status and future directions

The evolution of ultrasonic contrast agents to enhance the reflectivity of structures in the human body has consolidated ultrasound's stance as a reliable diagnostic imaging modality. A significant development within this field includes the advent of liquid nanodroplets that are capable of vaporising into gaseous microbubbles upon ultrasonic irradiation. This literature review will therefore appraise and summarise the available literature on the generation of phase-shift nanodroplets, their formulations, applications, safety issues, future developments and any implications that may inhibit their clinical implementation. The main findings of this review affirm that phase change nanodroplets do indeed demonstrate functionality in drug delivery and targeting and characterisation of tumours. Its bioeffects however, have not yet been extensively researched, prompting further exploration into how bubble size can be controlled once it has vaporised into microbubbles and the resulting complications. As such, future research should be directed towards determining the safety, longevity and suitability of phase-shift nanodroplets over contrast agents in current clinical use.

Super-Resolution Contrast-Enhanced Ultrasound Methodology for the Identification of In Vivo Vascular Dynamics in 2D

OBJECTIVES

The aim of this study was to provide an ultrasound-based super-resolution methodology that can be implemented using clinical 2-dimensional ultrasound equipment and standard contrast-enhanced ultrasound modes. In addition, the aim is to achieve this for true-to-life patient imaging conditions, including realistic examination times of a few minutes and adequate image penetration depths that can be used to scan entire organs without sacrificing current super-resolution ultrasound imaging performance.

METHODS

Standard contrast-enhanced ultrasound was used along with bolus or infusion injections of SonoVue (Bracco, Geneva, Switzerland) microbubble (MB) suspensions. An image analysis methodology, translated from light microscopy algorithms, was developed for use with ultrasound contrast imaging video data. New features that are tailored for ultrasound contrast image data were developed for MB detection and segmentation, so that the algorithm can deal with single and overlapping MBs. The method was tested initially on synthetic data, then with a simple microvessel phantom, and then with in vivo ultrasound contrast video loops from sheep ovaries. Tracks detailing the vascular structure and corresponding velocity map of the sheep ovary were reconstructed. Images acquired from light microscopy, optical projection tomography, and optical coherence tomography were compared with the vasculature network that was revealed in the ultrasound contrast data. The final method was applied to clinical prostate data as a proof of principle.

RESULTS

Features of the ovary identified in optical modalities mentioned previously were also identified in the ultrasound super-resolution density maps. Follicular areas, follicle wall, vessel diameter, and tissue dimensions were very similar. An approximately 8.5-fold resolution gain was demonstrated in vessel width, as vessels of width down to 60 μm were detected and verified (λ = 514 μm). Best agreement was found between ultrasound measurements and optical coherence tomography with 10% difference in the measured vessel widths, whereas ex vivo microscopy measurements were significantly lower by 43% on average. The results were mostly achieved using video loops of under 2-minute duration that included respiratory motion. A feasibility study on a human prostate showed good agreement between density and velocity ultrasound maps with the histological evaluation of the location of a tumor.

CONCLUSIONS

The feasibility of a 2-dimensional contrast-enhanced ultrasound-based super-resolution method was demonstrated using in vitro, synthetic and in vivo animal data. The method reduces the examination times to a few minutes using state-of-the-art ultrasound equipment and can provide super-resolution maps for an entire prostate with similar resolution to that achieved in other studies.

A novel method to determine hepatic segments using Sonazoid, an ultrasound contrast agent

The conventional radiologic method for liver segmentation is based on the position of the hepatic and portal veins. However, during surgery, liver segments are resected based on the distribution of hepatic portal blood flow. This discrepancy can lead to a number of problems, such as miscommunication among clinicians, missing the location of the segment with the hepatic mass, and the risk of extended hepatic resection. We suggest a novel method to determine hepatic segments based on portal blood flow, as in the surgical approach, but by using high and low mechanical indexes in contrast-enhanced ultrasonography with Sonazoid. This approach is helpful for preoperatively determining hepatic segments and reducing the risk of missing the location of a hepatic tumor or extended hepatic resection.

General principles and overview of vascular contrast-enhanced ultrasonography

Ultrasonography (US) is the first-line modality for the evaluation of vascular pathology. Although well-established for many diseases, US has inherent limitations that can occasionally hinder an accurate diagnosis. The value of US was improved by the introduction of microbubbles as ultrasonographic contrast agents (UCAs) and the emergence of contrast-enhanced ultrasonography (CEUS), following the introduction of second-generation UCAs and the emergence of modern contrast-specific techniques. CEUS offers valuable information about vascular disease, both on a macrovascular and a microvascular level, with well-established applications for carotid disease, post-interventional follow-up of abdominal aortic aneurysms, and the assessment of portal vein thrombosis. The purpose of this review is to discuss the principles of CEUS and to present an overview of its vascular applications.

Abdominal ultrasound and alpha‐fetoprotein for the diagnosis of hepatocellular carcinoma

This is a protocol for a Cochrane Review (Diagnostic test accuracy). The objectives are as follows:

To assess the diagnostic accuracy of abdominal ultrasound and alpha‐fetoprotein (AFP), alone or in combination, for the diagnosis of hepatocellular carcinoma (HCC) of any size and at any stage in people with chronic advanced liver disease, either in a surveillance programme or in a clinical setting.

Contrast-enhanced ultrasound of hepatocellular carcinoma: where do we stand?

Contrast-enhanced ultrasound (CEUS) represents a significant breakthrough in ultrasonography (US), and it is being increasingly used for the evaluation of focal liver lesions (FLLs). CEUS is unique in that it allows non-invasive assessment of liver perfusion in real time throughout the vascular phase, which has led to dramatic improvements in the diagnostic accuracy of US in the detection and characterization of FLLs, the choice of therapeutic procedures, and the evaluation of response. Currently, CEUS is included as a part of the suggested diagnostic work-up of FLLs, including in cirrhotic patients with hepatocellular carcinoma, resulting in better patient management and cost-effective delivery of therapy.

Transmission-reflection optoacoustic ultrasound (TROPUS) computed tomography of small animals

Rapid progress in the development of multispectral optoacoustic tomography techniques has enabled unprecedented insights into biological dynamics and molecular processes in vivo and noninvasively at penetration and spatiotemporal scales not covered by modern optical microscopy methods. Ultrasound imaging provides highly complementary information on elastic and functional tissue properties and further aids in enhancing optoacoustic image quality. We devised the first hybrid transmission-reflection optoacoustic ultrasound (TROPUS) small animal imaging platform that combines optoacoustic tomography with both reflection- and transmission-mode ultrasound computed tomography. The system features full-view cross-sectional tomographic imaging geometry for concomitant noninvasive mapping of the absorbed optical energy, acoustic reflectivity, speed of sound, and acoustic attenuation in whole live mice with submillimeter resolution and unrivaled image quality. Graphics-processing unit (GPU)-based algorithms employing spatial compounding and bent-ray-tracing iterative reconstruction were further developed to attain real-time rendering of ultrasound tomography images in the full-ring acquisition geometry. In vivo mouse imaging experiments revealed fine details on the organ parenchyma, vascularization, tissue reflectivity, density, and stiffness. We further used the speed of sound maps retrieved by the transmission ultrasound tomography to improve optoacoustic reconstructions via two-compartment modeling. The newly developed synergistic multimodal combination offers unmatched capabilities for imaging multiple tissue properties and biomarkers with high resolution, penetration, and contrast.

Tunable Nonlinear Acoustic Reporters Using Micro- and Nanosized Air Bubbles with Porous Polymeric Hard Shells

The ability to tailor acoustic cavitation of contrast agents is pivotal for ultrasound applications in enhanced imaging, drug delivery, and cancer therapy, etc. A biopolymer-based system of microbubbles and nanobubbles was developed as acoustic reporters that consist of extremely porous hard shells. Despite the existence of an incompressible shell, these porous contrast agents exhibited strong nonlinear acoustic response under very low acoustic pressure, e.g, harmonics, characteristic of free gas bubbles. The large air/water surface area within the transmural capillaries are believed to facilitate oscillation of the inner gas core. Furthermore, the acoustic cavitation can be tailored by variation in polymer structures. This synthetically based platform offers insight for the rational design of advanced acoustic biomaterials.

Healing Response of a Structural Hamstring Injury: Perfusion Imaging 8-Week Follow-Up

CONTEXT

Hamstring injuries are frequently observed in various sports disciplines both in elite and recreational sport.

OBJECTIVE

To quantify intramuscular tissue perfusion via contrast-enhanced ultrasound in the acute phase and during the healing of a structural muscle injury confirmed by high-resolution magnetic resonance imaging.

DESIGN

Case study.

SETTING

Laboratory environment.

PATIENT

A 32-year-old wakeboarder (height = 176 cm, body weight = 76 kg, and body mass index = 24.5 kg/m2) with an acute indirect muscle injury of the semimembranosus muscle.

MAIN OUTCOME MEASURES

Average values of quantifiable contrast-enhanced ultrasound, represented as peak enhancement and wash-in area under the curve, as well as conventional ultrasound, 1.5T magnetic resonance imaging were assessed at 48-hour, 3-week, and 8-week postinjury.

RESULTS

Average values of the quantitative perfusion analysis at 48-hour and 8-week postinjury revealed an approximate 5-fold increase in peak enhancement, and the wash-in area under the curve increased more than 3-fold in the center of the lesion. Magnetic resonance imaging, performed 48 hours after the injury to gather reference data as gold standard, revealed a grade III structural muscle tear.

CONCLUSIONS

The authors are able to demonstrate significant changes in intramuscular tissue perfusion in the center of the structural lesion as well as in the adjacent tissue. Quantifiable contrast-enhanced ultrasound seems to be able to gather relevant data for the assessment and monitoring of muscle injuries and could be established as a valuable tool for further studies focusing on healing processes or therapeutic interventions.

Usefulness of real-time contrast-enhanced ultrasound guided coaxial needle biopsy for focal liver lesions

PURPOSE

To evaluate the utility of real-time contrast-enhanced ultrasound (CEUS)-guided coaxial needle biopsies for focal liver lesions (FLL) that were inconspicuous or could not be accurately identified the active site on B-mode ultrasound (US).

MATERIALS AND METHODS

This prospective study included 76 patients who had CEUS-guided coaxial needle biopsies for FLL between December 2015 and June 2017. We recorded characteristics of target lesions. We evaluated conspicuity of target lesions and accuracy of identifying the active site of target lesions on B-mode US and CEUS using a 5-point scale. Patients were divided into three groups, and analyzed according to body mass index (BMI). Based on the final diagnosis, the diagnostic performance was evaluated.

RESULTS

The mean size and depth of target lesions were 41.5 ± 28.5 and 47.9 ± 18.9 mm on CEUS, respectively. In arterial phase, the enhanced pattern of target lesions varied. The conspicuity of target lesions and accuracy of identifying the active site of target lesions was significantly improved on CEUS compared to B-mode US (p < 0.05). The three BMI groups had significant differences in conspicuity of target lesions after using CEUS (p < 0.05). The high BMI group had a greater change in conspicuity of lesions compared to the normal BMI group or the low BMI group (p < 0.05). The sensitivity, specificity, and accuracy of this technique for the diagnosis of FLL were 92.8%, 100%, and 93.4%, respectively.

CONCLUSION

Real-time CEUS-guided coaxial needle biopsy can be very useful for FLL that are inconspicuous or cannot be accurately identified the active site on B-mode US.

Effect of Compression Garments on the Development of Delayed-Onset Muscle Soreness: A Multimodal Approach Using Contrast-Enhanced Ultrasound and Acoustic Radiation Force Impulse Elastography

BACKGROUND

Delayed-onset muscle soreness (DOMS) is one of the most common reasons for impaired muscle performance in sports. However, little consensus exists regarding which treatments may be most effective, and the underlying mechanisms are poorly understood.

OBJECTIVES

To investigate the influence of compression garments on the development of DOMS, focusing on changes in muscle perfusion and muscle stiffness.

METHODS

In this controlled laboratory study with repeated measures, muscle perfusion and stiffness, calf circumference, muscle soreness, passive ankle dorsiflexion, and creatine kinase levels were assessed in participants before (baseline) a DOMS-inducing eccentric calf exercise intervention and 60 hours later (follow-up). After DOMS induction, a sports compression garment (18-21 mmHg) was worn on 1 randomly selected calf until follow-up, while the contralateral calf served as an internal control. Muscle perfusion was assessed using contrast-enhanced ultrasound (peak enhancement and wash-in area under the curve), while muscle stiffness was assessed using acoustic radiation force impulse (shear-wave velocities). A magnetic resonance imaging scan of both lower legs was also performed during the follow-up testing session to characterize the extent of exercise-induced muscle damage. Comparisons were made between limbs and over time.

RESULTS

Shear-wave velocity values of the medial gastrocnemius showed a significant interaction between time and treatment (P = .006), with the noncompressed muscle demonstrating lower muscle stiffness values at follow-up compared to baseline or to the compressed muscle. No significant differences in soleus muscle stiffness were noted between limbs or over time, as was the case for muscle perfusion metrics (peak enhancement and wash-in area under the curve) for the medial gastrocnemius and soleus muscles. Further, compression had no significant effect on passive ankle dorsiflexion, muscle soreness, calf circumference, or injury severity, per magnetic resonance imaging.

CONCLUSION

Continuous wearing of compression garments during the inflammation phase of DOMS may play an important role in regulating muscle stiffness; however, compression garments have no significant effects on intramuscular perfusion or other common clinical assessments. J Orthop Sports Phys Ther 2018;48(11):887-894. Epub12 Jun 2018. doi:10.2519/jospt.2018.8038.

Sonoporation by microbubbles as gene therapy approach against liver cancer

INTRODUCTION

An innovative method, known as sonoporation, was used to induce the expression of silenced genes, such as (but not restricted to) TRAIL and p53, in liver cancer cells (HepG2). The principal aim of the present study was the re-activation of silenced apoptotic pathways in liver cancer models, by using diagnostic synovial microbubble as plasmid gene delivery tools in combination with epigenetic treatments.

MATERIAL AND METHODS

HepG2 cells were used as a liver cancer model. Microbubbles (Sonovue®) were chosen as gene deliver system in combination with the sonoporation approach. Plasmid pEGFP-TRAIL and pEGFP-p53 were selected and propagated in Escherichia coli grown in LB broth, in order to obtain the necessary amount.

RESULTS

Sonoporation was induced by using transducer (Sonitron 2000) and, among the several conditions tested, 3 MHz, 51% Duty Cycle, and 5 W/cm2, 30 s resulted as the best parameters. Data collected showed a dose dependent effect in terms of output energy. A transfection efficacy of 30 - 50% was achieved and recombinant gene expression induced apoptotic effects. In order to increase efficacy, we used the histone deacetylase inhibitor (HDACi, entinostat) MS-275, able to activate TRAIL and thus inducing a stronger pro-apoptotic effect in combination with TRAIL-gene re-expression.

CONCLUSION

For the first time, it was shown the possibility to induce the exogenous expression of the pro-apoptotic gene TRAIL and p53 in a liver cancer HepG2 cells via a sonoporation procedure. The epigenetic treatment using HDACi was able to increase the pro-apoptotic effects of the gene therapy.

Quantitative evaluation of renal parenchymal perfusion using contrast-enhanced ultrasonography in renal ischemia-reperfusion injury in dogs

This study evaluated whether renal perfusion changes can be noninvasively estimated by using contrast-enhanced ultrasonography (CEUS) in renal ischemia-reperfusion injury and investigated the correlation between renal perfusion measured by CEUS and necrosis and apoptosis of renal tubular epithelial cells. In six dogs with experimentally induced renal ischemia-reperfusion injury, changes in time to peak intensity, peak intensity, and area under the curve were measured on CEUS. Peak intensity and area under the curve of the renal cortex began to decrease on day 1 (about 20% lower than baseline) and reached the lowest levels (about 50% of baseline) on day 4. They then gradually increased until day 10, at which time peak intensity was about 87% and area under the curve was about 95% of baseline; neither fully recovered. Both parameters were strongly correlated with the necrosis scores on histopathologic examination on day 4 (r = −0.810 of peak intensity and r = −0.886 of area under the curve). CEUS allowed quantitative evaluation of perfusion changes in acute renal ischemia-reperfusion injury, and CEUS results were correlated with renal tubular damage on histopathologic examination. Thus, CEUS could be a noninvasive, quantitative diagnostic method for determining progress of renal ischemia-reperfusion injury.

Contrast-Enhanced Ultrasound as a New Investigative Tool in Diagnostic Imaging of Muscle Injuries-A Pilot Study Evaluating Conventional Ultrasound, CEUS, and Findings in MRI

OBJECTIVE

To emphasize the diagnostic value of contrast-enhanced ultrasound (CEUS) in the imaging of muscle injuries with different degrees of severity by comparing findings to established imaging modalities such as conventional ultrasound and magnetic resonance imaging (MRI).

DESIGN

Case series.

SETTING

Institutional study. Conventional ultrasound and CEUS were performed in the Department of Internal Medicine. Magnetic resonance imaging was carried out in the Department of Radiology within the Magnetom Avanto 1.5T and Magnetom Skyra fit 3T (Siemens Healthineers, Erlangen, Germany) and in the Institution of Imaging Diagnostics and Therapy (Magnetom Avanto 1.5T; Siemens, Erlangen, Germany).

PATIENTS

Fifteen patients who underwent an acute muscle injury were recruited.

MAIN OUTCOME MEASURES

The appearance and detectable size of muscle injuries were compared between each imaging modality. The injuries were assessed by 3 independent observers and blinded between imaging modalities.

RESULTS

All 15 injuries were identified on MRI and CEUS, whereas 10 injuries showed abnormalities in conventional ultrasound. The determination and measurement revealed significant differences between conventional ultrasound and CEUS depending on injury severity. Contrast-enhanced ultrasound revealed an impairment of microcirculation in grade I lesions (corresponding to intramuscular edema observed in MRI), which was not detectable using conventional ultrasound.

CONCLUSIONS

Our results indicate that performing CEUS seems to be a sensitive additional diagnostic modality in the early assessment of muscle injuries. Our results highlight the advantages of CEUS in the imaging of low-grade lesions when compared with conventional ultrasound, as this was the more accurate modality for identifying intramuscular edema.

Differentiating Cystic Liver Lesions: A Review of Imaging Modalities, Diagnosis and Management

Hepatic cysts (HCs) are frequently discovered incidentally on abdominal imaging. The prevalence of HCs has been reported as high as 15-18% in the United States. Although most cysts are benign, some are malignant or premalignant. It is important to diagnose cystic lesions in order to properly manage them. Imaging with conventional ultrasound, computed tomography, magnetic resonance imaging, or contrast-enhanced ultrasound can be used to further characterize and diagnose HCs. Ultrasound is typically the first-line imaging modality, whereas more advanced imaging can help narrow down the specific lesion. Contrast-enhanced ultrasound is a newer modality, recently approved in the United States, which offers non-invasive evaluation in real-time. The first step in diagnosis is stratifying risk by differentiating simple and complex cysts. There are several features that can help identify HCs, including septae, mural consistency, calcifications, and quality of cystic fluid. Simple cysts are mainly congenital cysts, but also occur in polycystic liver disease. Complex cysts include mucinous neoplasms, echinococcal cysts, hemorrhagic cysts, cystic hepatocellular carcinoma and other rare lesions. Treatment is indicated in symptomatic cysts or those suspicious for malignant or premalignant features. Treatment modalities include fenestration, aspiration sclerotherapy, or surgical resection.

Contrast-enhanced ultrasound measurement of pancreatic blood flow dynamics predicts type 1 diabetes progression in preclinical models

In type 1 diabetes (T1D), immune-cell infiltration into the islets of Langerhans (insulitis) and β-cell decline occurs many years before diabetes clinically presents. Non-invasively detecting insulitis and β-cell decline would allow the diagnosis of eventual diabetes, and provide a means to monitor therapeutic intervention. However, there is a lack of validated clinical approaches for specifically and non-invasively imaging disease progression leading to T1D. Islets have a denser microvasculature that reorganizes during diabetes. Here we apply contrast-enhanced ultrasound measurements of pancreatic blood-flow dynamics to non-invasively and predictively assess disease progression in T1D pre-clinical models. STZ-treated mice, NOD mice, and adoptive-transfer mice demonstrate altered islet blood-flow dynamics prior to diabetes onset, consistent with islet microvasculature reorganization. These assessments predict both time to diabetes onset and future responders to antiCD4-mediated disease prevention. Thus contrast-enhanced ultrasound measurements of pancreas blood-flow dynamics may provide a clinically deployable predictive marker for disease progression in pre-symptomatic T1D and therapeutic reversal.

Emergency and critical care applications for contrast-enhanced ultrasound

INTRODUCTION

Contrast-enhanced ultrasound (CEUS) using intravascular microbubbles has potential to revolutionize point-of-care ultrasonography by expanding the use of ultrasonography into clinical scenarios previously reserved for computed tomography (CT), magnetic resonance imaging, or angiography.

METHODS

We performed a literature search and report clinical experience to provide an introduction to CEUS and describe its current applications for point-of-care indications.

RESULTS

The uses of CEUS include several applications highly relevant for emergency medicine, such as solid-organ injuries, actively bleeding hematomas, or abdominal aortic aneurysms. Compared with CT as the preeminent advanced imaging modality in the emergency department, CEUS is low cost, radiation sparing, repeatable, and readily available. It does not require sedation, preprocedural laboratory assessment, or transportation to the radiology suite.

CONCLUSIONS

CEUS is a promising imaging technique for point-of-care applications in pediatric and adult patients and can be applied for patients with allergy to CT contrast medium or with impaired renal function. More high-quality CEUS research focusing on accuracy, patient safety, health care costs, and throughput times is needed to validate its use in emergency and critical care settings.

Practical advantages of contrast-enhanced ultrasound in abdominopelvic radiology

Computed tomography (CT) and magnetic resonance imaging (MRI) are two of the workhorse modalities of abdominopelvic radiology. However, these modalities are not without patient- and technique-specific limitations that may prevent a timely and accurate diagnosis. Contrast-enhanced ultrasound (CEUS) is an effective, rapid, and cost-effective imaging modality with expanding clinical utility in the United States. In this pictorial essay, we provide a case-based discussion demonstrating the practical advantages of CEUS in evaluating a variety of pathologies in which CT or MRI was precluded or insufficient. Through these advantages, CEUS can serve a complementary role with CT and MRI in comprehensive abdominopelvic radiology.

Axillary Nodal Staging with Contrast-Enhanced Ultrasound

Purpose of Review

Axillary staging in the context of breast cancer is a contentious topic due to the varied practices across UK, Europe, and America. The ACOSOG Z0011 trial has questioned the role of axillary ultrasound in women with breast cancer. Published data has shown that women with ultrasound-positive lymph nodes have a worse prognosis than those with ultrasound-negative lymph nodes. Axillary ultrasound is limited as the sentinel lymph node (SLN) cannot be identified using B-mode ultrasound; however, with the advent of contrast-enhanced ultrasound (CEUS), this has now changed.

Recent Findings

The published literature has shown that the sentinel lymph node can be identified using CEUS. The rates are equivalent to blue dye alone but currently inferior to the dual technique of sentinel lymph node biopsy. There are several different contrast agents that can be used and the agents that remain in the sentinel lymph node for longer can identify areas of poor enhancement, allowing for targeted biopsy.

Summary

CEUS has the potential to revolutionize the way we manage the axilla in the future and may even replace surgical staging.

Up-to-date Doppler techniques for breast tumor vascularity: superb microvascular imaging and contrast-enhanced ultrasound

Ultrasonographic Doppler techniques have improved greatly over the years, allowing more sophisticated evaluation of breast tumor vascularity. Superb microvascular imaging (SMI) and contrast-enhanced ultrasound (CEUS) with second-generation contrast agents are two representative up-to-date techniques. SMI is a sensitive Doppler technique that adopts an intelligent filter system to separate low-flow signals from artifacts. With the development of second-generation contrast agents, CEUS has also emerged as a useful Doppler technique for evaluating tumor microcirculation. Both techniques can improve the diagnostic performance of gray-scale ultrasonography by providing vascular information useful not only for the morphologic assessment of microvessels, but also for the quantitative analysis of perfusion. In this review, we explain the imaging principles and previous research underlying these two vascular techniques, and describe our clinical experiences.

Two patterns of contrast-enhanced ultrasonography with Sonazoid® in spontaneous rupture of hepatocellular carcinoma: a report of four cases

Spontaneous rupture is a life-threatening complication of hepatocellular carcinoma (HCC). Detecting active bleeding is critical. Color Doppler and contrast-enhanced ultrasonography (CEUS) with Levovist^® are reported to be useful for detecting active bleeding. A few reports have described using Sonazoid^® to detect bleeding in ruptured HCC. This report describes two distinctive patterns of bleeding from ruptured HCC observed in CEUS with Sonazoid^®. Four patients with suspected HCC rupture were examined by gray-scale ultrasonography (US) and then CEUS with Sonazoid^®. Two patterns of bleeding were observed with CEUS: jet-like extravasation (n = 2) and bubble leakage (n = 2). While contrast-enhanced computed tomography and angiography revealed active bleeding in only one patient, CEUS detected active bleeding and enabled the bleeding site to be estimated in all patients. Transcatheter arterial embolization was performed based on the findings of CEUS, and hemostasis was achieved in all patients. CEUS using Sonazoid^® could demonstrate active bleeding as two patterns, and these findings enabled us to detect the rupture site of HCC more confidently than with other modalities.

Measuring Absolute Blood Perfusion in Mice Using Dynamic Contrast-Enhanced Ultrasound

We investigated the feasibility of estimating absolute tissue blood perfusion using dynamic contrast-enhanced ultrasound (CEUS) imaging in mice. We developed a novel method of microbubble administration and a model-free approach to estimate absolute kidney perfusion, and explored the kidney as a reference organ to estimate absolute perfusion of a neuroblastoma tumor. We performed CEUS on the kidneys of CD1 nude mice using the VisualSonics VEVO 2100 imaging system. We estimated individual kidney blood perfusion using the burst-replenishment (BR) technique. We repeated the kidney imaging on the mice after a week. We performed CEUS imaging of a neuroblastoma mouse xenograft tumor along with its right kidney using two sets of microbubble administration parameters to estimate absolute tumor blood perfusion. We performed statistical tests at a significance level of 0.05. Our estimated absolute kidney perfusion (425 ± 123 mL/min/100 g) was within the range of previously reported values. There was no statistical difference between the estimated absolute kidney blood perfusions from the 2 wk of imaging (paired t-test, p = 0.09). We estimated the absolute blood perfusion in the neuroblastoma tumor to be 16.49 and 16.9 mL/min/100 g for the two sets of microbubble administration parameters (Wilcoxon rank-sum test, p = 0.6). We have established the kidney as a reliable reference organ in which to estimate absolute perfusion of other tissues. Using a neuroblastoma tumor, we have determined the feasibility of estimating absolute blood perfusion in tissues using contrast-enhanced ultrasound imaging.

Recent advances in ultrasound-based diagnosis and therapy with micro- and nanometer-sized formulations

Ultrasound (US) is one of the most frequently used imaging methods in the clinic. The broad spectrum of its applications can be increased by the use of gas-filled microbubbles (MB) as ultrasound contrast agents (UCA). In recent years, also nanoscale UCA like nanobubbles (NB), echogenic liposomes (ELIP) and nanodroplets have been developed, which in contrast to MB, are able to extravasate from the vessels into the tissue. New disease-specific UCA have been designed for the assessment of tissue biomarkers and advanced US to a molecular imaging modality. For this purpose, specific binding moieties were coupled to the UCA surface. The vascular endothelial growth factor receptor-2 (VEGFR-2) and P-/E-selectin are prominent examples of molecular US targets to visualize tumor blood vessels and inflammatory diseases, respectively. Besides their application in contrast-enhanced imaging, MB can also be employed for drug delivery to tumors and across the blood-brain barrier (BBB). This review summarizes the development of micro- and nanoscaled UCA and highlights recent advances in diagnostic and therapeutic applications, which are ready for translation into the clinic.

Contrast-Enhanced Ultrasound Using Perfluorobutane-Containing Microbubbles in the Assessment of Liver Allograft Damage: An Exploratory Prospective Study

This prospective study investigated the usefulness of contrast (perfluorobutane-containing microbubbles)-enhanced ultrasound in the non-invasive assessment of liver allograft damage. Forty-one liver recipients underwent contrast-enhanced ultrasound followed by a liver biopsy. The hepatic filling rate (time between the arrival of contrast agent in the right hepatic artery and the maximum intensity of hepatic parenchyma) and parenchymal intensity difference before and after instantaneous high-power emission in the Kupffer phase were measured. Patients with allograft damage had higher hepatic filling rates and lower parenchymal intensity differences than those without damage (42.0 ± 16.9 vs. 30.5 ± 7.7 s, p = 0.005; 6.1 ± 7.4 vs. 16.6 ± 16.1 dB, p = 0.047, respectively). In the diagnosis of liver allograft damage, hepatic filling rate and parenchymal intensity difference had sensitivities of 61.5% and 90.9% and specificities of 92.6% and 63.6% using cutoffs of >38.5 s and ≤10.3 dB, respectively. In conclusion, contrast-enhanced ultrasound may be a promising tool in the detection of liver allograft damage.

Safety of Sulfur Hexafluoride Microbubbles in Sonography of Abdominal and Superficial Organs: Retrospective Analysis of 30,222 Cases

OBJECTIVES

The purpose of this study was to investigate the safety of the sulfur hexafluoride microbubble contrast agent SonoVue (Bracco SpA, Milan, Italy) and to implement precautions with the intent of further improving the safety of this contrast agent.

METHODS

A total of 30,222 patients undergoing contrast-enhanced sonography of abdominal and superficial organs in our hospital from January 2005 to December 2014 were retrospectively investigated. SonoVue was used as the ultrasound contrast agent. The symptoms and treatments of adverse reactions occurring during the contrast-enhanced sonographic examinations were reviewed and analyzed.

RESULTS

No patient died as a result of any adverse reaction. Six patients (0.020%) had adverse reactions of varying degrees, including 2 patients (0.007%) who had signs of early anaphylactic shock (chest tightness, palpitations, sweating, and rapid and weak pulse, followed by cyanosis, a disappearing pulse, and a drop in blood pressure) that improved after active rescue. The remaining 4 patients developed the following: redness and a rash on the arm above the injection site, nasal bleeding and nausea, nausea and vomiting, and back pain with numbness of the lips and limbs. Symptoms in these 4 patients self-resolved after a period of rest.

CONCLUSIONS

Contrast-enhanced sonography with sulfur hexafluoride microbubbles had good clinical safety, but rare adverse reactions were observed. A comprehensive emergency plan and rescue measures for adverse reactions should be prepared and made available to minimize the occurrence of negative clinical outcomes.

Added Value of Contrast-Enhanced Ultrasound on Biopsies of Focal Hepatic Lesions Invisible on Fusion Imaging Guidance

Objective

To assess whether contrast-enhanced ultrasonography (CEUS) with Sonazoid can improve the lesion conspicuity and feasibility of percutaneous biopsies for focal hepatic lesions invisible on fusion imaging of real-time ultrasonography (US) with computed tomography/magnetic resonance images, and evaluate its impact on clinical decision making.

Materials and Methods

The Institutional Review Board approved this retrospective study. Between June 2013 and January 2015, 711 US-guided percutaneous biopsies were performed for focal hepatic lesions. Biopsies were performed using CEUS for guidance if lesions were invisible on fusion imaging. We retrospectively evaluated the number of target lesions initially invisible on fusion imaging that became visible after applying CEUS, using a 4-point scale. Technical success rates of biopsies were evaluated based on histopathological results. In addition, the occurrence of changes in clinical decision making was assessed.

Results

Among 711 patients, 16 patients (2.3%) were included in the study. The median size of target lesions was 1.1 cm (range, 0.5–1.9 cm) in pre-procedural imaging. After CEUS, 15 of 16 (93.8%) focal hepatic lesions were visualized. The conspicuity score was significantly increased after adding CEUS, as compared to that on fusion imaging (p < 0.001). The technical success rate of biopsy was 87.6% (14/16). After biopsy, there were changes in clinical decision making for 11 of 16 patients (68.8%).

Conclusion

The addition of CEUS could improve the conspicuity of focal hepatic lesions invisible on fusion imaging. This dual guidance using CEUS and fusion imaging may affect patient management via changes in clinical decision-making.

Contrast-Enhanced Ultrasound in Focal Liver Lesions: Where Do We Stand?

Contrast-enhanced ultrasound (CEUS) represents a significant breakthrough in sonography, and it is being increasingly used for the evaluation of focal liver lesions (FLLs). Currently, CEUS is included as a part of the suggested diagnostic workup of FLLs, resulting in a better patient management and delivering cost-effective therapy. After a brief technical note, contrast-enhancement patterns of different types of benign and malignant FLLs, along with hepatic pseudolesions, are described and discussed based on our experience and literature data. At the same time, the most recent concepts and the use of CEUS in different clinical settings are presented.