LI-RADS CEUS Nonradiation TRA Version 2024: Application on HCC Patients Treated With Ablation Treatment

OBJECTIVE

To evaluate the performance of Liver Imaging Reporting and Data System (LI-RADS) contrast-enhanced ultrasound (CEUS) Nonradiation treatment response assessment (TRA) categorization v2024 for detecting viable tumors of ablated hepatocellular carcinoma (HCC).

METHODS

Between June 2020 and December 2022, standardized CEUS data of HCC patients were prospectively collected. A retrospective analysis of LI-RADS CEUS Nonradiation TRA v2024 evaluation on HCCs was conducted by 2 independent radiologists assigning per-lesion TRA (TR-nonviable, TR-equivocal, or TR-viable) categorizations. Inter-reader agreement between the 2 readers and inter-modality agreement between LI-RADS CEUS and CT/MRI LI-RADS TRA were assessed. The diagnostic performance of imaging criteria was explored. The potential influencing factors of LI-RADS TRA categorization across modalities were further analyzed.

RESULTS

A total of 101 CEUS-LI-RADS TRA category evaluations of 88 lesions in 83 patients were included. Inter-reader agreement for the 2 readers were substantial to almost perfect (intralesional tumor viability: κ = 0.92, 95% CI: 0.76-1.0; perilesional tumor viability: κ = 0.72, 95% CI: 0.57-0.87; CEUS LR-TR: κ = 0.71, 95% CI: 0.55-0.88). Inter-modality agreements between CEUS and CT/MRI LI-RADS TRA categorizations were excellent (ICC = 0.90). CEUS LR-TRA categorization demonstrated good diagnostic performance, particularly in specificity (88.1%-100 %) and negative predictive value (NPV: 93.9%-97.9 %). Time period and abstract shape were identified as significant factors influencing reader evaluations (p < 0.05).

CONCLUSION

LI-RADS CEUS Nonradiation TRA v2024 demonstrates fine inter-reader and inter-modality agreement, with outstanding diagnostic performance, supporting its potential for clinical application in assessing treatment response for ablated HCC.

Ultrasound innovations in abdominal radiology: evaluation of focal liver lesions

Focal liver lesions (FLLs) are common and are often first identified on abdominal ultrasound examinations. Although CT and MRI were historically required to noninvasively characterize many FLLs, introduction of microbubble contrast agents produced a groundbreaking change as contrast enhanced ultrasound (CEUS) showed vascularity to the capillary level for the first time. CEUS shows specific arterial phase enhancement patterns in benign lesions and accurately differentiates malignant lesions based on the timing and intensity of washout. Parametric time of arrival and microvascular imaging techniques can demonstrate vascularity in FLLs with significantly improved sensitivity compared with conventional Doppler techniques. Shear-wave elastography and quantitative ultrasound are generally used to evaluate diffuse liver disease but show promise in evaluation of FLLs.

The Association Between the Thickness of the Hypoechoic Halo of Thyroid Nodules and Thyroid Cancer: A Retrospective Study

RATIONALE AND OBJECTIVES

The association between hypoechoic halos and thyroid cancer in patients with thyroid nodules remains a contentious issue. The objective of this study was to examine the potential correlation between the thickness of hypoechoic halos and the presence of thyroid cancer in individuals with thyroid nodules.

METHODS

The study retrospectively analyzed a cohort of 320 patients with thyroid nodules presenting hypoechoic halos from January 2019 to December 2022. Logistic regression models, both univariate and multivariate, were applied to investigate the association between hypoechoic halo thickness and thyroid cancer, with adjustments for potential confounding variables. Interaction and stratified analyses were conducted to assess the influence of demographic and tumor-specific characteristics, such as age, sex, halo thickness, tumor size, and tumor location, on the relationship between halo thickness and thyroid cancer risk.

RESULTS

After adjusting for multiple covariates, the odds ratios (ORs) (95% confidence intervals (CIs)) of thyroid cancer for participants with a halo thickness ≥1 mm were 3.99 (2.4-6.62), 3.73 (2.09-6.67), and 3.16 (1.61-6.19), compared to those with a thickness <1 mm. The association between thyroid cancer and the thickness of the halo remained stable across different subgroups (all P for interaction > 0.05). The area under the curve (AUC) for the hypoechoic halo in nodules for diagnosing thyroid cancer was 0.821 (95% CI: 0.774-0.868), with the highest sensitivity and specificity observed at a thickness cutoff value of 1.29 mm.

CONCLUSION

Our single-center study on adults reveals a positive correlation between halo thickness and thyroid cancer risk, indicating that halo thickness may potentially serve as a valuable predictor for thyroid cancer incidence.

Occult liver nodules: their detection and characterization with CEUS

OBJECTIVES

Contrast enhanced ultrasound (CEUS) now joins the ranks of CT and MRI for noninvasive diagnosis of hepatocellular carcinoma (HCC). CEUS LI-RADS provides greater than 95% specificity for diagnosis within LR-5. Unlike CT/MRI, CEUS is nodule based. Currently, LI-RADS does not recommend CEUS of nodules occult or invisible on pre-contrast ultrasound except by experts. This study addresses our ability to find occult nodules using CEUS and to characterize them with CEUS LI-RADS.

METHODS

100 patients at risk for HCC, 81 with cirrhosis, with occult lesions were retrospectively identified from our archived patient logs. All patients had CEUS examination. Three specialized CEUS techniques (blindshot injection, portal venous (PVP) sweep of the liver, and on-top injection) are used to evaluate nodules.

RESULTS

There were 114 occult lesions in 100 patients. The origin of 78(68%) lesions was an MRI (n = 69) or CT scan (n = 9) with an observation of abnormal enhancement, generally arterial phase hyperenhancement (APHE). All these patients had blindshot CEUS injection looking for a correlate with APHE. The remainder of occult lesions (n = 36)(32%) were first detected during CEUS, generally as washout foci on PVP sweeps or incidental APHE or washout nearby other targets. All washout areas had subsequent on-top injection to assess for APHE. Application of CEUS LI-RADS algorithm categorized 26 LR-5, 34 LR-4, and 5 LR-M. CEUS upgraded LI-RADS category of 24/50(48%) occult lesions reported on CT/MRI. 29(25%) occult lesions were offered treatment and from categories LR-5 and LR-M, 5 had biopsy confirmation and 15 were treated. From both sources, MR/CT and CEUS, there were 12 occult lesions scanned for treatment response, categorized as 7 LR-TR viable, 1 LR-TR nonviable, and 4 LR-TR equivocal on CEUS.

CONCLUSION

Our study shows we can find and characterize occult nodules using CEUS techniques and CEUS LI-RADS algorithm, with positive impact on clinical management.

Unraveling distinctions between contrast-enhanced ultrasound and CT/MRI for liver mass diagnosis

Contrast-enhanced ultrasound (CEUS) offers a distinctive approach to liver mass diagnosis by utilizing intravenous contrast agents for enhanced visualization of vascular structures and tissue characterization. This review highlights the unique advantages of CEUS compared to computed tomography (CT) and magnetic resonance imaging (MRI), particularly focusing on the Liver Imaging Reporting and Data System framework. Key differences include CEUS's realtime imaging capability, which minimizes arterial phase mistiming and improves detection of hyperenhancing lesions, and its ability to provide detailed washout patterns. Also, CEUS's intravascular nature and lower risk of adverse reactions make it a safer alternative for patients with renal impairment or those contraindicated for CT/MRI.

Contrast-Enhanced Ultrasound Compared With Hepatobiliary Agent MRI for Differentiation of Focal Nodular Hyperplasia and Hepatic Adenoma: A Prospective Trial

ABSTRACT

Magnetic resonance imaging (MRI) may be time-consuming, expensive, or poorly tolerated by patients with liver lesions. This is a prospective clinical trial designed to evaluate if contrast-enhanced ultrasound (CEUS) can be used to differentiate focal nodular hyperplasia (FNH) from hepatocellular adenoma (HCA) with similar accuracy compared with hepatobiliary agent MRI.Institutional review board approval was obtained (1805450097), and the trial was registered with ClinicalTrials.gov (NCT03652636). From 2018 through 2023, 40 patients who had lesions consistent with FNH or HCA on HBA-MRI underwent 1-time prospective CEUS of up to 2 hepatic lesions. Sonographic images obtained before and after intravenous administration of 2 mL sulfur hexafluoride lipid-type A microspheres (Lumason) per lesion totaling 59 lesions (27 FNHs/32 HCAs). Two blinded radiologists provided a diagnosis of FNH or HCA.Thirty-eight female and 2 male patients (age 36.7 ± 9.9) were scanned. Radiologists provided diagnosis of FNH or HCA with respective sensitivity (66.7/64.0%), specificity (71.9/90.6%), and accuracy (69.5/78.0%). For 38 lesions greater than or equal to 2 cm in size (17 FNHs/21 HCAs), readers had sensitivity (70.6/84.2%), specificity (70.6/84.2%), and accuracy (81.5/86.8%). Interobserver agreement for all lesions was fair (κ = 0.34), whereas agreement for lesions 2 cm or larger was substantial (κ = 0.67).Contrast-enhanced ultrasound can differentiate FNH from HCA with accuracy approaching that of hepatobiliary agent MRI for lesions 2 cm or greater. Interobserver agreement is improved with larger lesions. CEUS may have utility as an alternate diagnostic tool for FNH/HCA, especially in patients who cannot or do not desire to undergo MRI.

Contrast-enhanced ultrasound fundamentals: the pharmacodynamics and pharmacokinetics of contrast. Basics of contrast-enhanced ultrasound imaging

Contrast-enhanced ultrasound (CEUS) is a medical imaging technique that offers multiple advantages over other modalities such as computed tomography (CT) and magnetic resonance imaging (MRI). These advantages include portability, no ionising radiation and no renal toxicity, with the great advantage of real-time imaging. CEUS has numerous established applications for the study of different pathologies, both intravenous and intracavitary administration. The contrast used is different in composition and function from CT or MRI contrast. It is a purely intravascular contrast and, therefore, the enhancement of the lesions may have some differences with respect to CT or MRI in the equilibrium phase. Ultrasound contrast has a very good safety profile, with infrequent, generally mild and immediate adverse reactions in intravascular use and no adverse reactions reported in intracavitary use. It is important to know the basics of contrast-enhanced ultrasound, the different ways to optimise the image and the different artefacts.

Synoptic Reporting of Focal Liver Masses in at Risk Patients: Algorithmic Diagnosis and CEUS LI-RADS

OBJECTIVES

Reporting contrast-enhanced ultrasound (CEUS) for focal liver masses in at risk patients is a challenging task. Traditionally used prose reporting (PR) is inconsistent and lacks standardization. We propose synoptic reporting (SR), encompassing algorithmic interpretation and liver imaging and reporting data system (LI-RADS) categorization.

METHODS

A software worksheet from Kailo Medical (Melbourne, AU), incorporates the CEUS algorithm for liver interpretation and CEUS LI-RADS categorization. Part 1. Feasibility of SR: twenty participants of varying experience were presented a brief lecture on SR, algorithmic approach to liver mass interpretation, and CEUS LI-RADS categorization. Ten representative liver masses were shown as unknown cases. Participants inputted data into SR worksheets. Results and LI-RADS category were generated solely by SR. Data were categorized as "correct" or "incorrect." Part 2. Prospective Analysis: Ninety-one patients for SR and 56 for PR, all were tested for completeness, efficiency, and user satisfaction.

RESULTS

Part 1: Junior participants, pass rate 81.6%, and senior participants, pass rate 83.3% showed no difference in performance. Part 2: Completeness: SR 98.4% and PR 87.0%. Efficiency: Average total time to completion: SR 11 minutes and PR 20 minutes. User satisfaction: Ultrasound technologists, all referring physicians, and six out of seven radiologists preferred SR over PR. Major benefits cited were total time saved, consistency and accuracy in documentation, and report completeness.

CONCLUSIONS

SR is a reliable and useful tool in clinical practice to report liver masses on ultrasound and assign an appropriate LI-RADS categorization and management pathway. This ultimately improves communication with referring clinicians and leads to better patient outcomes.

Unique portal venous phase imaging discordance between CEUS and MRI: a valuable predictor of intrahepatic cholangiocarcinoma?

PURPOSE

We have long noted unique portal venous phase (PVP) imaging discordance of focal liver masses between CEUS, showing rapid marked washout, and MRI, showing progressive or sustained enhancement. We postulate association of this unique discordance with intrahepatic cholangiocarcinoma (ICC) and causal relationship to different contrast agent behavior. We investigate this unique discordance, propose its clinical significance for ICC diagnosis, and confirm further histologic associations.

METHODS

Cases were collected within our CEUS department and from pathology records over a ten-year interval. This retrospective review includes 99 patients, 73 with confirmed ICC and 26 other diagnoses, showing unique PVP discordance. The CEUS and MRI enhancement characteristics were compared for all patients.

RESULTS

Unique discordance is identified in 67/73 (92%) ICC and difference between the PVP appearance on MRI and CEUS is statistically significant (p <  0.0001). Arterial phase enhancement did not show statistically significant difference between CEUS and MRI, p >  0.05. Other diagnoses showing unique discordance include especially lymphoma (n = 7), sclerosed hemangioma (n = 6), HCC (n = 4), metastases (n = 2), and other rare entities.

CONCLUSION

ICC shows this discrepant intermodality enhancement pattern in a statistically significant number of cases and should be considered along with other LR-M features in at-risk patients. Discordance is also rarely seen in a number of other liver lesions.

A Novel Technology for Resolution of CEUS Imaging Problems in Patients With High BMI and Fatty Liver

OBJECTIVES

In high-BMI patients with and without fatty liver, we evaluate performance of a commercially available specially designed ultrasound probe (SDP) for scanning at depth. Greyscale and contrast-enhanced ultrasound (CEUS) capability of SDP for parenchymal assessment and liver mass characterization, emphasizing HCC, is compared with standard curvilinear probes.

METHODS

This retrospective study included 60 patients. Fifty-five with measured BMI included 46/55 (84%) overweight or obese, and 9/55(16%) in the normal range with severe fatty liver. Fifty-six patients with focal liver abnormality included 37 with a mass and 19 with post-ablative treatment site. Masses included 23 confirmed malignancies, 15 HCC, 4 ICC, and 4 metastases. SDP followed suboptimal ultrasound using a standard probe. Images with varying fat content were compared for depth of penetration on greyscale and ability of CEUS to diagnose tumors.

RESULTS

SDP showed statistically significant improvement P = <.05 in CEUS penetration for all degrees of fatty liver (mild, moderate, and severe). In malignant tumors, SDP improved detection of lesion washout in the portal venous/late phase (PVP/LP) at depth >10 cm, and in all malignant masses (P < .05). Fifteen confirmed deep HCC showed arterial phase hyperenhancement on standard probe in 10/15 (67%) and 15/15 (100%) on SDP. PVP/LP washout on standard probe was shown in 4/15 (26%) and on SDP, 14/15, (93%). Therefore, 93% of LR-5 tumors were diagnosed with SDP. Removing necessity for biopsy.

CONCLUSIONS

Metabolic syndrome and obesity challenge ultrasound, especially CEUS. SDP overcame limitations of standard probes for CEUS penetration especially in fatty liver. SDP was optimal for the liver mass characterization by detecting washout.

Imaging of Hepatobiliary Cancer

The liver and biliary tree are common sites of primary and secondary malignancies. MRI followed by CT is the mainstay for the imaging characterization of these malignancies with the dynamically acquired contrast enhanced phases being the most important for diagnosis. The liver imaging reporting and data system classification provides a useful framework for reporting lesions in patents with underlying cirrhosis or who are at high risk for developing hepatocellular carcinoma. Detection of metastases is improved with the use of liver specific MRI contrast agents and diffusion weighted sequences. Aside from hepatocellular carcinoma, which is often diagnosed noninvasively, other primary hepatobiliary tumors may require biopsy for definite diagnosis, especially when presenting with nonclassic imaging findings. In this review, we examine the imaging findings of common and less common hepatobiliary tumors.

Hepatocellular Adenomas: Molecular Basis and Multimodality Imaging Update

Hepatocellular adenomas (HCAs) are a family of liver tumors that are associated with variable prognoses. Since the initial description of these tumors, the classification of HCAs has expanded and now includes eight distinct genotypic subtypes based on molecular analysis findings. These genotypic subtypes have unique derangements in their cellular biologic makeup that determine their clinical course and may allow noninvasive identification of certain subtypes. Multiphasic MRI performed with hepatobiliary contrast agents remains the best method to noninvasively detect, characterize, and monitor HCAs. HCAs are generally hypointense during the hepatobiliary phase; the β-catenin-mutated exon 3 subtype and up to a third of inflammatory HCAs are the exception to this characterization. It is important to understand the appearances of HCAs beyond their depictions at MRI, as these tumors are typically identified with other imaging modalities first. The two most feared related complications are bleeding and malignant transformation to hepatocellular carcinoma, although the risk of these complications depends on tumor size, subtype, and clinical factors. Elective surgical resection is recommended for HCAs that are persistently larger than 5 cm, adenomas of any size in men, and all β-catenin-mutated exon 3 HCAs. Thermal ablation and transarterial embolization are potential alternatives to surgical resection. In the acute setting of a ruptured HCA, patients typically undergo transarterial embolization with or without delayed surgical resection. This update on HCAs includes a review of radiologic-pathologic correlations by subtype and imaging modality, related complications, and management recommendations. ^© RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Artifacts and Technical Considerations at Contrast-enhanced US

Contrast-enhanced US (CEUS), similar to other radiologic modalities, requires specific technical considerations and is subject to image artifacts. These artifacts may affect examination quality, negatively impact diagnostic accuracy, and decrease user comfort when using this emerging technique. Some artifacts are related to commonly known gray-scale US artifacts that can also appear on the contrast-only image (tissue-subtracted image obtained with the linear responses from background tissues nulled). These may include acoustic shadowing and enhancement; reverberation, refraction, and reflection; and poor penetration. Other artifacts are exclusive to CEUS owing to the techniques used for contrast mode image generation and the unique properties of the microbubbles that constitute ultrasound-specific contrast agents (UCAs). UCA-related artifacts may appear on the contrast-only image, the gray-scale image, or various Doppler mode images. Artifacts related to CEUS may include nonlinear artifacts and unintentional microbubble destruction resulting in pseudowashout. The microbubbles themselves may result in specific artifacts such as pseudoenhancement, signal saturation, and attenuation and shadowing and can confound the use of color and spectral Doppler US. Identifying and understanding these artifacts and knowing how to mitigate them may improve the quality of the imaging study, increase user confidence, and improve patient care. The authors review the principles of UCAs and the sound-microbubble interaction, as well as the technical aspects of image generation. Technical considerations, including patient positioning, depth, acoustic window, and contrast agent dose, also are discussed. Specific artifacts are described, with tips on how to identify and, if necessary, apply corrective measures, with the goal of improving examination quality. ^© RSNA, 2022 Online supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.

A Comprehensive Motion Compensation Method for In-Plane and Out-of-Plane Motion in Dynamic Contrast-Enhanced Ultrasound of Focal Liver Lesions

Contrast-enhanced ultrasound (CEUS) acquisitions of focal liver lesions are affected by motion, which has an impact on contrast signal quantification. We therefore developed and tested, in a large patient cohort, a motion compensation algorithm called the Iterative Local Search Algorithm (ILSA), which can correct for both periodic and non-periodic in-plane motion and can reject frames with out-of-plane motion. CEUS cines of 183 focal liver lesions in 155 patients from three hospitals were used to develop and test ILSA. Performance was evaluated through quantitative metrics, including the root mean square error and R2 in fitting time-intensity curves and standard deviation value of B-mode intensities, computed across cine frames), and qualitative evaluation, including B-mode mean intensity projection images and parametric perfusion imaging. The median root mean square error significantly decreased from 0.032 to 0.024 (p < 0.001). Median R2 significantly increased from 0.88 to 0.93 (p < 0.001). The median standard deviation value of B-mode intensities significantly decreased from 6.2 to 5.0 (p < 0.001). B-Mode mean intensity projection images revealed improved spatial resolution. Parametric perfusion imaging also exhibited improved spatial detail and better differentiation between lesion and background liver parenchyma. ILSA can compensate for all types of motion encountered during liver CEUS, potentially improving contrast signal quantification of focal liver lesions.

When Benign Behaves Badly: Atypical Hemangiomas on Contrast-Enhanced Ultrasonography

ABSTRACT

Hemangioma is the most common benign liver tumor and is frequently encountered as an incidental finding on imaging. The classic enhancement pattern of hemangioma is diagnostic on contrast-enhanced ultrasound (CEUS), and it follows the same pattern of enhancement on computed tomography and magnetic resonance imaging. However, there is a subset of hemangiomas that demonstrate atypical enhancement patterns on CEUS. The ability to recognize the different enhancement patterns and discern when additional imaging or biopsy may be necessary is essential to accurately interpret an atypical hemangioma on CEUS. This article reviews various enhancement patterns of hemangioma on CEUS to avoid pitfalls in characterization of focal liver lesions on CEUS.

Loco-regional treatment of hepatocellular carcinoma: Role of contrast-enhanced ultrasonography

Hepatocellular carcinoma (HCC) is one of the few cancers for which locoregional treatments (LRTs) are included in international guidelines and are considered as a valid alternative to conventional surgery. According to Barcelona Clinic Liver Cancer classification, percutaneous treatments such as percutaneous ethanol injection, radiofrequency ablation and microwave ablation are the therapy of choice among curative treatments in patients categorized as very early and early stage, while transcatheter arterial chemoembolization is considered the better option for intermediate stage HCC. A precise assessment of treatment efficacy and surveillance is essential to optimize survival rate, whereas residual tumor requires additional treatment. Imaging modalities play a key role in this task. Currently, contrast-enhanced computed tomography/magnetic resonance imaging are considered the standard imaging modalities for this purpose. Contrast enhanced ultrasound (CEUS), using second generation contrast agents, plays an increasingly important role in detecting residual disease after LRTs. CEUS is a straightforward to perform, repeatable and cost-effective imaging modality for patients with renal failure or iodine allergies. Due to the ability to focus on single regions, CEUS can also provide high temporal resolution. Moreover, several studies have reported the same or better diagnostic accuracy as contrast-enhanced computed tomography for assessing tumor vascularity 1 mo after LRTs, and recently three-dimensional (3D)-CEUS has been reported as a promising technique to improve the evaluation of tumor response to therapy. Furthermore, CEUS could be used early after procedures in monitoring HCC treatments, but nowadays this indication is still debated, and data from literature are conflicting, especially after transcatheter arterial chemoembolization procedure.

Characterization of Focal Liver Masses: A Multicenter Comparison of Contrast-Enhanced Ultrasound, Computed Tomography, and Magnetic Resonance Imaging

OBJECTIVES

To demonstrate the usefulness of contrast-enhanced ultrasound (CEUS) for the evaluation of focal liver masses via a direct comparison to standard ultrasound and computed tomography/magnetic resonance imaging (CT/MRI).

METHODS

A cohort of 214 patients with previously undiagnosed focal liver masses were included from 5 different centers. Each patient was imaged using CEUS and CT and/or MRI. Anonymized and randomized images were interpreted by 4 separate blind readers from 3 of the participating centers (2 readers for CEUS and 2 readers for CT/MRI). Readers were blinded to patient demographics and past medical history. Readers were asked to decide if the lesion was benign or malignant, provide a final diagnosis for the lesion, and provide a confidence interval. Results were compared to truth standard from pathology or expert consensus.

RESULTS

In determination of malignancy, CEUS had a sensitivity of 95%, specificity of 82%, PPV of 82%, NPV of 95%, statistically better than standard ultrasound (sensitivity 82%, specificity 56%, PPV 60%, NPV 78%) with P < .01 and not statistically different from CT (sensitivity 90%, specificity 73% PPV 81%, NPV 86%) or MRI (sensitivity 85%, specificity 79%, PPV 68%, NPV 91%) with P ≥ .01. In assigning a final diagnosis, CEUS had an accuracy of 78% statistically better than standard ultrasound (46%) with P < .01 and not statistically different from CT (68%) or MRI (71%) with P > .01.

CONCLUSIONS

In the evaluation of focal liver lesions, both for determination of malignancy and in accuracy of final diagnosis, CEUS performs better than standard ultrasound and at least equivalent to both CT and MRI.

Super-Resolution Ultrasound Localization Microscopy on a Rabbit Liver VX2 Tumor Model: An Initial Feasibility Study

Ultrasound localization microscopy can image microvasculature in vivo without sacrificing imaging penetration depth. However, the reliance on super-resolution inference limits the applicability of the technique because subpixel tissue motion can corrupt microvascular reconstruction. Consequently, the majority of previous pre-clinical research on this super-resolution procedure has been restricted to low-motion experimental models with ample motion correction or data rejection, which precludes the imaging of organ sites that exhibit a high degree of respiratory and other motion. In this article, we present a novel anesthesia protocol in rabbits that induces safe, controllable periods of apnea to enable the long image-acquisition times required for ultrasound localization microscopy. We apply this protocol to a VX2 liver tumor model undergoing sorafenib therapy and compare the results to super-resolution images from conventional high-dose isoflurane anesthesia. We find that the apneic protocol was necessary to correctly identify the poorly vascularized tumor cores, as verified by immunohistochemistry, and to reveal the tumoral microvascular architecture.

Contrast-Enhanced Ultrasound in Chronic Liver Diseases

Contrast-enhanced ultrasound (CEUS) is a safe adjunct tool for liver imaging and can be an alternative to computed tomography or MR imaging. CEUS has a proven track record in guiding management for patients with chronic liver disease who need further evaluation of focal liver lesions. CEUS is a dynamic examination with high temporal and spatial resolution. CEUS uses a pure blood pool contrast agent that allows for a unique evaluation of the perfusion kinetics of a region of interest.

Quantitative analysis of in-vivo microbubble distribution in the human brain

Microbubbles (MB) are widely used as contrast agents to perform contrast-enhanced ultrasound (CEUS) imaging and as acoustic amplifiers of mechanical bioeffects incited by therapeutic-level ultrasound. The distribution of MBs in the brain is not yet fully understood, thereby limiting intra-operative CEUS guidance or MB-based FUS treatments. In this paper we describe a robust platform for quantification of MB distribution in the human brain, allowing to quantitatively discriminate between tumoral and normal brain tissues and we provide new information regarding real-time cerebral MBs distribution. Intraoperative CEUS imaging was performed during surgical tumor resection using an ultrasound machine (MyLab Twice, Esaote, Italy) equipped with a multifrequency (3-11 MHz) linear array probe (LA332) and a specific low mechanical index (MI < 0.4) CEUS algorithm (CnTi, Esaote, Italy; section thickness, 0.245 cm) for non-destructive continuous MBs imaging. CEUS acquisition is started by enabling the CnTI PEN-M algorithm automatically setting the MI at 0.4 with a center frequency of 2.94 MHz-10 Hz frame rate at 80 mm-allowing for continuous non-destructive MBs imaging. 19 ultrasound image sets of adequate length were selected and retrospectively analyzed using a custom image processing software for quantitative analysis of echo power. Regions of interest (ROIs) were drawn on key structures (artery-tumor-white matter) by a blinded neurosurgeon, following which peak enhancement and time intensity curves (TICs) were quantified. CEUS images revealed clear qualitative differences in MB distribution: arteries showed the earliest and highest enhancement among all structures, followed by tumor and white matter regions, respectively. The custom software built for quantitative analysis effectively captured these differences. Quantified peak intensities showed regions containing artery, tumor or white matter structures having an average MB intensity of 0.584, 0.436 and 0.175 units, respectively. Moreover, the normalized area under TICs revealed the time of flight for MB to be significantly lower in brain tissue as compared with tumor tissue. Significant heterogeneities in TICs were also observed within different regions of the same brain lesion. In this study, we provide the most comprehensive strategy for accurate quantitative analysis of MBs distribution in the human brain by means of CEUS intraoperative imaging. Furthermore our results demonstrate that CEUS imaging quantitative analysis enables discernment between different types of brain tumors as well as regions and structures within the brain. Similar considerations will be important for the planning and implementation of MB-based imaging or treatments in the future.

Use of Contrast-Enhanced Ultrasound in Ablation Therapy of HCC: Planning, Guiding, and Assessing Treatment Response

Contrast-enhanced ultrasonography (CEUS) plays an important role in the management of patients treated with ablation therapies, in the diagnostic, therapeutic and monitoring phases. Compared to contrast-enhanced computed tomography and contrast-enhanced magnetic resonance imaging, CEUS presents several advantages in imaging HCC, including real time imaging capability, high sensitivity for tumor vascularity, absence of renal toxicity, no ionizing radiation, repeatability of injections, good compliance by the patient and low cost. The purpose of this review is to evaluate the role of CEUS in the management of the patients with HCC treated with ablation therapies and describe how in our protocol CEUS is integrated with the other imaging modalities such as contrast-enhanced computed tomography and contrast-enhanced magnetic resonance imaging.

Contrast-Enhanced Ultrasound in Children: Implementation and Key Diagnostic Applications

Contrast-enhanced ultrasound (CEUS) utilization is expanding rapidly, particularly in children, in whom the modality offers important advantages of dynamic evaluation of the vasculature, portability, lack of ionizing radiation, and lack of need for sedation. Accumulating data establish an excellent safety profile of ultrasound contrast agents in children. Although only FDA-approved for IV use in children for characterizing focal liver lesions and for use during echocardiography, growing off-label applications are expanding the diagnostic potential of ultrasound. Focal liver lesion evaluation is the most common use of CEUS, and the American College of Radiology Pediatric LI-RADS Working Group recommends including CEUS for evaluation of a newly discovered focal liver lesion in many circumstances. Data also support the role of CEUS in hemodynamically stable children with blunt abdominal trauma, and CEUS is becoming a potential alternative to CT in this setting. Additional potential applications that require further study include evaluation of pathology in the lung, spleen, brain, pancreas, bowel, kidney, female pelvis, and scrotum. This review explores the implementation of CEUS in children, describing basic principles of ultrasound contrast agents and CEUS technique and summarizing current and potential IV diagnostic applications based on pediatric-specific supporting evidence.

Contrast-enhanced US for the Interventional Radiologist: Current and Emerging Applications

US is a powerful and nearly ubiquitous tool in the practice of interventional radiology. Use of contrast-enhanced US (CEUS) has gained traction in diagnostic imaging given the recent approval by the U.S. Food and Drug Administration (FDA) of microbubble contrast agents for use in the liver, such as sulfur hexafluoride lipid-type A microspheres. Adoption of CEUS by interventional radiologists can enhance not only procedure guidance but also preprocedure patient evaluation and assessment of treatment response across a wide spectrum of oncologic, vascular, and nonvascular procedures. In addition, the unique physical properties of microbubble contrast agents make them amenable as therapeutic vehicles in themselves, which can lay a foundation for future therapeutic innovations in the field in drug delivery, thrombolysis, and vascular flow augmentation. The purpose of this article is to provide an introduction to and overview of CEUS aimed at the interventional radiologist, highlighting its role before, during, and after frequently practiced oncologic and vascular interventions such as biopsy, ablation, transarterial chemoembolization, detection and control of hemorrhage, evaluation of transjugular intrahepatic portosystemic shunts (TIPS), detection of aortic endograft endoleak, thrombus detection and evaluation, evaluation of vascular malformations, lymphangiography, and percutaneous drain placement. Basic physical principles of CEUS, injection and scanning protocols, and logistics for practice implementation are also discussed. Early adoption of CEUS by the interventional radiology community will ensure rapid innovation of the field and development of future novel procedures. Online supplemental material is available for this article. ^©RSNA, 2020.

Contrast-enhanced ultrasound can guide the therapeutic strategy by improving the detection of colorectal liver metastases

BACKGROUND & AIMS

CT may miss up to 30% of cases of colorectal liver metastases (CRLMs). We assessed the impact of contrast-enhanced ultrasound (CEUS) on the detection of CRLMs and on changes to the therapeutic strategy; additionally, we assessed the accuracy of CEUS in differentiating unclear focal liver lesions (FLLs) compared to staging-CT.

METHODS

We prospectively analyzed all patients with newly diagnosed and histologically confirmed colorectal cancer (CRC) at our tertiary gastroenterological center between December 2015 and May 2019. CEUS was performed in a total of 296 patients without CRLMs after staging-CT using the contrast agent (SonoVue®). Standard of reference was obtained by MRI or histology to diagnose CRLMs missed by CT. Benign FLLs were confirmed by MRI or follow-up CT (mean follow-up interval: 18 months).

RESULTS

Eight additional CRLMs were detected by CEUS (overall 2.7%; sensitivity 88.9%, specificity 99.0%, positive predictive value 100%, negative predictive value 99.6%). All patients with CRLMs detected only by CEUS were in tumor stage T3/T4 (4.0% additionally detected CRLMs). The number needed to screen to detect 1 additional CRLM by CEUS was 37 in all patients and 24.5 in T3/T4-patients. When results were reviewed by a board-certified radiologist and oncologist, the therapeutic strategy changed in 6 of these 8 patients. Among the 62 patients (20.9%) with unclear FLLs after staging-CT, CEUS determined the dignity (malignant vs. benign) of 98.4% of the FLLs.

CONCLUSION

Overall, CEUS detected 2.7% additional CRLMs (including 4.0% in tumor stage T3/T4) with a significant impact on the oncological therapeutic strategy for 75% of these patients. Patients with tumor stage T3/T4 would particularly benefit from CEUS. We propose CEUS as the first imaging modality for CT-detected lesions of unknown dignity.

LAY SUMMARY

In patients with newly diagnosed colorectal cancer, contrast-enhanced ultrasound (CEUS) detected additional liver metastases after computed tomography (CT). In the majority of these patients, the oncological therapy was changed after obtaining the CEUS results. After staging-CT, 21% of hepatic lesions remained unclear. In these cases, CEUS was accurate to either reveal or exclude liver metastasis in nearly all patients and could reduce costs (e.g., number of MRI scans).

Contrast-Enhanced Ultrasound for Focal Hepatic Lesions: When to Use and How to Differentiate Lesions?

Contrast-enhanced ultrasound can be used effectively to evaluate focal hepatic lesions and offers unique advantages over computed tomography and magnetic resonance imaging. Serial vascular filling patterns of focal hepatic lesions during arterial, portal, and late phases can provide unique information on lesion characterization and differentiation. Sensitive depiction of arterial hypervascularity and analysis of washout pattern are clues for differentiation of several indeterminate hepatic nodules on conventional ultrasound and computed tomography/magnetic resonance. In this report, we present cases demonstrating clinical applications of contrast-enhanced ultrasound in the diagnosis and management of focal hepatic lesions.

Multimodal VEGF-Targeted Contrast-Enhanced Ultrasound and Photoacoustic Imaging of Rats with Inflammatory Arthritis: Using Dye-VEGF-Antibody-Loaded Microbubbles

Owing to the heavy health burdens from rheumatoid arthritis, a sensitive and objective imaging method is needed for early diagnosis and accurate evaluation of the disease. We aimed to fabricate vascular epithelial growth factor (VEGF)-targeted microbubbles (MBs) to evaluate the expression levels of VEGF within the inflammatory lesions of rats with adjuvant-induced arthritis (AIA) using a multimodal photoacoustic (PA)/ultrasound (US) imaging system. Fluorescein isothiocyanate-biotin double-labeled vascular endothelial growth factor receptor 2 antibodies and Cy5.5-biotin double-labeled VEGF2 antibodies were added to the avidin-labeled MBs to synthesize VEGF-targeted MBs. The antibodies could specifically bind to the MBs according to the flow cytometry and fluorescence imaging. In vitro experiments on the cellular uptake of the target MBs also validated the interaction of the VEGF antibodies and the MBs. Multimodal contrast-enhanced US (CEUS)/PA imaging was performed in sequence on the inflamed paws of the AIA rats with a single PA/US imaging system after the injection of the targeted MBs. The CEUS and PA signals were then quantified and verified by the pathologic results. A CEUS pattern of fast wash in and slow washout was observed in the AIA rats after injection of targeted MBs. Compared with AIA rats injected with unconnected VEGF antibodies and naked MBs, AIA rats injected with targeted MBs presented a higher peak intensity (p = 0.0079 and 0.0079 respectively) and a longer time to peak (p = 0.0117 and 0.0117, respectively). The PA signals were also significantly enhanced after injection of targeted MBs (p = 0.0112 and 0.0119, respectively), which was in accordance with the pathologic and immunohistochemical results. In conclusion, VEGF-targeted MBs can be used as agents for multimodal CEUS/PA imaging and to detect VEGF expression in the inflammatory lesions of AIA rats in vivo. This strategy may be useful in imaging evaluation of arthritis by identifying inflammation-related molecules in different imaging modes.

Contrast-Enhanced Ultrasonography for Screening and Diagnosis of Hepatocellular Carcinoma: A Case Series and Review of the Literature

Background: Contrast-enhanced ultrasound (CEUS) is a safe and noninvasive imaging technique that can characterize and evaluate liver lesions, and has been approved for this use in the Unites States since 2016. CEUS has been shown to be similar in accuracy to computed tomography (CT) and magnetic resonance imaging (MRI) for noninvasive diagnosis of hepatocellular carcinoma (HCC) and offers several advantages in certain patient populations who have contraindications for CT or MRI. However, CEUS has inherent limitations and has not been widely employed for evaluation of HCC. Methods: We present three retrospective cases of liver lesions in patients with cirrhosis, who underwent screening for HCC using concurrent, well-timed CT and CEUS. Results: In these cases, the liver lesions were better visualized and then diagnosed as malignancy via CEUS, whereas the lesions were best appreciated on CT only in retrospect. Conclusions: In some cirrhotic patients, a focal lesion may be more easily identifiable via CEUS than on CT and thus accurately characterized, suggesting an important and complementary role of CEUS with CT or MRI. Further studies are indicated to support the use of CEUS for the diagnosis and characterization of liver lesions in screening patients at risk for developing HCC.

The role of imaging in surgical planning for liver resection: what the radiologist need to know

The management of patients undergoing surgical resection for liver malignancies requires a multidisciplinary team, including a dedicated radiologist. In the preoperative workup, the radiologist has to provide precise, relevant information to the surgeon. This requires the radiologist to know the basics of surgical techniques as well as liver surgical anatomy in order to help to avoid unexpected surgical scenarios and complications. Moreover, virtual resections and volumetries on radiological images will be discussed, and basic concepts of postoperative liver failure, regeneration, and methods for hypertrophy induction will be provided.

Use of contrast ultrasound in differentiating thrombosed pseudoaneurysm from sarcoma, prior to surgery

We describe a case of a 69-year-old male with a right-sided popliteal mass following a motor vehicle accident 15 years ago. The mass was indeterminate via multiple modalities (magnetic resonance imaging, digital subtraction angiography, and vascular ultrasound) with biopsy requested prior to surgical removal to determine the appropriate surgical team – vascular versus sarcoma oncologic surgery. Contrast ultrasound was utilized to determine if biopsy was indicated and if so, to determine the most appropriate target. Contrast ultrasound showed no areas of enhancement, therefore biopsy was not performed and the patient safely proceeded to vascular surgery. Pathology confirmed the mass to be a thrombosed pseudoaneurysm of the popliteal artery. We present the benefits of using contrast ultrasound in the work up and diagnosis of a popliteal neoplasm versus suspected vascular complication.

RadioGraphics Update: Contrast-enhanced US Approach to the Diagnosis of Focal Liver Masses

Editor's Note.-Articles in the RadioGraphics Update section provide current knowledge to supplement or update information found in full-length articles previously published in RadioGraphics. Authors of the previously published article provide a brief synopsis that emphasizes important new information such as technological advances, revised imaging protocols, new clinical guidelines involving imaging, or updated classification schemes. Articles in this section are published solely online and are linked to the original article.

Characterization of Indeterminate Liver Lesions on CT and MRI With Contrast-Enhanced Ultrasound: What Is the Evidence?

OBJECTIVE. CT or MRI is most commonly used for characterizing focal hepatic lesions. However, findings on CT and MRI are occasionally indeterminate. Contrast-enhanced ultrasound (CEUS), with its unique characteristics as a purely intravascular contrast agent and real-time evaluation of enhancement, is a useful next step. The purpose of this article is to review the evidence for performing CEUS in the assessment of indeterminate hepatic lesions seen on CT and MRI. CONCLUSION. CEUS is a useful problem-solving tool in the evaluation of liver lesions that are indeterminate on CT and MRI. Uses include detection of arterial phase hyperenhancement; differentiation between hepatocellular carcinoma and intrahepatic cholangiocarcinoma; determination of benign versus malignant tumor thrombus, benign versus neoplastic cystic hepatic lesions, and hepatocellular adenoma versus focal nodular hyperplasia; and monitoring for recurrence in postablative therapies. CEUS can help establish a confident diagnosis and determine the need for further invasive diagnosis or treatment.

Hepatic hemangioma supplied by abnormal portal vein: A case report

Hepatic hemangioma is the most common hepatic tumor with a prevalence of approximately 3%. It is typically supplied by the hepatic artery as evident from findings of abdominal angiography, contrast-enhanced ultrasonography (CEUS), contrast-enhanced computed tomography (CT), and contrast-enhanced magnetic resonance imaging. However, few cases of hepatic hemangioma supplied by the portal vein have been reported. In this paper, we report a rare case of hepatic hemangioma supplied by the portal vein as shown on CEUS and CT arterioportography.

Contrast-Enhanced Ultrasound of Focal Liver Masses: A Success Story

The epidemic of increasing fatty liver disease and liver cancer worldwide, and especially in Western society, has given new importance to non-invasive liver imaging. Contrast-enhanced ultrasound (CEUS) using microbubble contrast agents provides unique advantages over computed tomography (CT) and magnetic resonance imaging (MRI), the currently established methods. CEUS provides determination of malignancy and allows excellent differential diagnosis of a focal liver mass, based on arterial phase enhancement patterns and assessment of the timing and intensity of washout. Today, increased use of CEUS has provided safe and rapid diagnosis of incidentally detected liver masses, improved multidisciplinary management of nodules in a cirrhotic liver, facilitated ablative therapy for liver tumors and allowed diagnosis of hepatocellular carcinoma without biopsy. Benefits of CEUS include the dynamic real-time depiction of tumor perfusion and the fact that it is a purely intravascular agent, accurately reflecting tumoral and inflammatory blood flow. CEUS has many similarities to contrast-enhanced CT and MRI but also unique differences, which are described. The integration of CEUS into a multimodality imaging setting optimizes patient care.

Advances in Diagnostic Imaging in Pediatric Gastroenterology

PURPOSE OF REVIEW

The purpose is to provide a review of cross-sectional imaging updates in the assessment of gastrointestinal diseases, relevant to clinical practice and research.

RECENT FINDINGS

New magnetic resonance imaging contrast agents (Eovist) are taken up by hepatocytes and excreted via the biliary tree. As such, a lesion will retain contrast only if hepatocytes are present, which aids in refining the differential diagnosis. Magnetic resonance enterography is a method for non-invasively diagnosing and following various GI conditions, predominantly inflammatory bowel disease. Contrast-enhanced ultrasound uses gas-filled microbubbles providing superb temporal resolution most notably in the arterial phase, which aids in differentiating lesions. Elastography is a new technique which assesses stiffness of liver for evaluating fibrosis. These new techniques provide more accurate diagnoses and information, often limiting ionizing radiation exposure from other modalities. While ultrasound will still remain the initial imaging modality, familiarity with these other options is valuable for appropriate pathology workup.

Liver contrast-enhanced sonography: computer-assisted differentiation between focal nodular hyperplasia and inflammatory hepatocellular adenoma by reference to microbubble transport patterns

OBJECTIVE

A new computer tool is proposed to distinguish between focal nodular hyperplasia (FNH) and an inflammatory hepatocellular adenoma (I-HCA) using contrast-enhanced ultrasound (CEUS). The new method was compared with the usual qualitative analysis.

METHODS

The proposed tool embeds an "optical flow" algorithm, designed to mimic the human visual perception of object transport in image series, to quantitatively analyse apparent microbubble transport parameters visible on CEUS. Qualitative (visual) and quantitative (computer-assisted) CEUS data were compared in a cohort of adult patients with either FNH or I-HCA based on pathological and radiological results. For quantitative analysis, several computer-assisted classification models were tested and subjected to cross-validation. The accuracies, area under the receiver-operating characteristic curve (AUROC), sensitivity and specificity, positive predictive values (PPVs), negative predictive values (NPVs), false predictive rate (FPRs) and false negative rate (FNRs) were recorded.

RESULTS

Forty-six patients with FNH (n = 29) or I-HCA (n = 17) with 47 tumours (one patient with 2 I-HCA) were analysed. The qualitative diagnostic parameters were accuracy = 93.6%, AUROC = 0.94, sensitivity = 94.4%, specificity = 93.1%, PPV = 89.5%, NPV = 96.4%, FPR = 6.9% and FNR = 5.6%. The quantitative diagnostic parameters were accuracy = 95.9%, AUROC = 0.97, sensitivity = 93.4%, specificity = 97.6%, PPV = 95.3%, NPV = 96.7%, FPR = 2.4% and FNR = 6.6%.

CONCLUSIONS

Microbubble transport patterns evident on CEUS are valuable diagnostic indicators. Machine-learning algorithms analysing such data facilitate the diagnosis of FNH and I-HCA tumours.

KEY POINTS

• Distinguishing between focal nodular hyperplasia and an inflammatory hepatocellular adenoma using dynamic contrast-enhanced ultrasound is sometimes difficult. • Microbubble transport patterns evident on contrast-enhanced sonography are valuable diagnostic indicators. • Machine-learning algorithms analysing microbubble transport patterns facilitate the diagnosis of FNH and I-HCA.

Contrast-Enhanced Ultrasound of Congenital and Infantile Hemangiomas: Preliminary Results From a Case Series

OBJECTIVE. The contrast-enhanced ultrasound (CEUS) imaging features of hepatic vascular tumors in infants, including infantile hemangioma (IH) and congenital hemangioma (CH), are not well reported. Frequent inaccurate use of lesion terminology in the literature has created diagnostic confusion. The purpose of this study is to describe the CEUS features of IH and CH. MATERIALS AND METHODS. Ten patients, ranging in age from 8 days to 16 months, with hepatic vascular tumors were included for retrospective analysis. Gray-scale ultrasound, color Doppler ultrasound, and CEUS features were reviewed, and interobserver kappa coefficients were calculated. Final diagnoses were clinically determined by a pediatrician with expertise in vascular anomalies except in one patient who underwent surgical excision. RESULTS. Of the 10 patients, five had CHs and five had IHs. All 10 lesions were hyperenhancing in the early arterial phase. In the portal venous phase, four of five (80%) CHs showed hyperenhancement relative to normal liver parenchyma, whereas four of five (80%) IHs showed isoenhancement. In the late phase, washout of contrast material was seen in three of five (60%) IHs, whereas one IH remained isoenhancing and one IH was hyperenhancing. None of the CHs showed late washout. Interobserver kappa coefficients for CEUS features ranged from 0.60 to 1.00. CONCLUSION. Except for the CEUS feature portal venous phase enhancement (κ = 0.60), good to excellent (κ = 0.74-1.00) agreement about CEUS features of IHs and CHs was observed. A significant proportion of IHs (60%) showed washout at delayed phase imaging, which has also been reported with malignancies. Recognition of the overlap in imaging appearance of these two entities is vital to preventing misdiagnosis of malignancy.