Effects of Needle and Catheter Size on Commercially Available Ultrasound Contrast Agents

Image-guided focused ultrasound-mediated molecular delivery to breast cancer in an animal model

Tumors become inoperable due to their size or location, making neoadjuvant chemotherapy the primary treatment. However, target tissue accumulation of anticancer agents is limited by the physical barriers of the tumor microenvironment. Low-intensity focused ultrasound (FUS) in combination with microbubble (MB) contrast agents can increase microvascular permeability and improve drug delivery to the target tissue after systemic administration. The goal of this research was to investigate image-guided FUS-mediated molecular delivery in volume space. Three-dimensional (3-D) FUS therapy functionality was implemented on a programmable ultrasound scanner (Vantage 256, Verasonics Inc.) equipped with a linear array for image guidance and a 128-element therapy transducer (HIFUPlex-06, Sonic Concepts). FUS treatment was performed on breast cancer-bearing female mice (N= 25). Animals were randomly divided into three groups, namely, 3-D FUS therapy, two-dimensional (2-D) FUS therapy, or sham (control) therapy. Immediately prior to the application of FUS therapy, animals received a slow bolus injection of MBs (Definity, Lantheus Medical Imaging Inc.) and near-infrared dye (IR-780, surrogate drug) for optical reporting and quantification of molecular delivery. Dye accumulation was monitored viain vivooptical imaging at 0, 1, 24, and 48 h (Pearl Trilogy, LI-COR). Following the 48 h time point, animals were humanely euthanized and tumors excised forex vivoanalyzes. Optical imaging results revealed that 3-D FUS therapy improved delivery of the IR-780 dye by 66.4% and 168.1% at 48 h compared to 2-D FUS (p= 0.18) and sham (p= 0.047) therapeutic strategies, respectively.Ex vivoanalysis revealed similar trends. Overall, 3-D FUS therapy can improve accumulation of a surrogate drug throughout the entire target tumor burden after systemic administration.

Microbubbles in the belly: optimizing the protocol for contrast-enhanced ultrasound of the pediatric abdomen

Intravenous contrast-enhanced ultrasound (CEUS) can serve as a diagnostic or problem-solving tool in pediatric imaging. CEUS of abdominal solid organs has been reported for a number of indications. The approach to the examination broadly falls into two categories: evaluation of a focal lesion or surveillance of an organ or organs for lesions or perfusion abnormalities. A consistent, technical imaging protocol for both of these clinical scenarios facilitates integration of routine use of CEUS in an imaging department. Here we review the CEUS imaging protocols for abdominal organs in children, including technical and solid-organ-specific considerations.

Contrast-enhanced ultrasound of the neonatal brain

Cranial US is an integral component of evaluating the neonatal brain, especially in the setting of critically ill infants and in the emergency setting, because cranial US can be performed portably at the bedside, is safe, and can be repeated whenever needed. Contrast-enhanced ultrasound (CEUS) involves intravenously injecting microbubbles to allow for improved visibility of large and small vessels to assess vascularity and is becoming a widespread technique to improve diagnostic performance of US across a broad spectrum of applications. CEUS has the potential to add value to routine brain US and become a useful adjunct to MRI in infants in need of bedside imaging. In this review we describe the basics of US contrast agents and CEUS technique, including safety considerations, and detail the potential clinical uses of brain CEUS.

Advanced Ultrasound Techniques for Neuroimaging in Pediatric Critical Care: A Review

Because of its portability, safety profile, and accessibility, ultrasound has been integral in pediatric neuroimaging. While conventional B-mode and Doppler ultrasound provide anatomic and limited flow information, new and developing advanced ultrasound techniques are facilitating real-time visualization of brain perfusion, microvascular flow, and changes in tissue stiffness in the brain. These techniques, which include contrast-enhanced ultrasound, microvascular imaging, and elastography, are providing new insights into and new methods of evaluating pathologies affecting children requiring critical care, including hypoxic-ischemic encephalopathy, stroke, and hydrocephalus. This review introduces advanced neurosonography techniques and their clinical applications in pediatric neurocritical care.

Contrast-enhanced ultrasound of the kidneys and adrenals in children

Pediatric applications of contrast-enhanced ultrasound (CEUS) are growing. Evaluation of the kidneys and adrenal glands in children using intravenous administration of US contrast agents, however, is still an off-label indication. Pediatric CEUS applications for kidneys are similar to those in adults, including ischemic disorders, pseudo- versus real tumors, indeterminate lesions, complex cystic lesions, complicated pyelonephritis, and abscesses. CEUS applications for evaluation of adrenal glands in children are limited, mainly focusing on the assessment and follow-up of adrenal trauma and the differentiation between an adrenal hemorrhage and a mass. This review addresses the current experience in pediatric CEUS of the kidneys and adrenal glands. By extrapolating the established knowledge for US contrast evaluations in the adult kidney to the pediatric context we can note opportunities for CEUS clinical use in children.

Pediatric contrast-enhanced ultrasound: optimization of techniques and dosing

When performing contrast-enhanced ultrasound (CEUS), ultrasound (US) scanner settings, examination technique, and contrast agent dose and administration must be optimized to ensure that high-quality, diagnostic and reproducible images are acquired for qualitative and quantitative interpretations. When carrying out CEUS in children, examination settings should be tailored to their body size and specific indications, similar to B-mode US. This review article details the basic background knowledge that is needed to perform CEUS optimally in children, including considerations related to US scanner settings and US contrast agent dose selection and administration techniques.

Contrast-enhanced ultrasound of transplant organs - liver and kidney - in children

Ultrasound (US) is the first-line imaging tool for evaluating liver and kidney transplants during and after the surgical procedures. In most patients after organ transplantation, gray-scale US coupled with color/power and spectral Doppler techniques is used to evaluate the transplant organs, assess the patency of vascular structures, and identify potential complications. In technically difficult or inconclusive cases, however, contrast-enhanced ultrasound (CEUS) can provide prompt and accurate diagnostic information that is essential for management decisions. CEUS is indicated to evaluate for vascular complications including vascular stenosis or thrombosis, active bleeding, pseudoaneurysms and arteriovenous fistulas. Parenchymal indications for CEUS include evaluation for perfusion defects and focal inflammatory and non-inflammatory lesions. When transplant rejection is suspected, CEUS can assist with prompt intervention by excluding potential underlying causes for organ dysfunction. Intracavitary CEUS applications can evaluate the biliary tract of a liver transplant (e.g., for biliary strictures, bile leak or intraductal stones) or the urinary tract of a renal transplant (e.g., for urinary obstruction, urine leak or vesicoureteral reflux) as well as the position and patency of hepatic, biliary and renal drains and catheters. The aim of this review is to present current experience regarding the use of CEUS to evaluate liver and renal transplants, focusing on the examination technique and interpretation of the main imaging findings, predominantly those related to vascular complications.

Contrast-enhanced ultrasound of the pediatric brain

Brain contrast-enhanced ultrasound (CEUS) is an emerging application that can complement gray-scale US and yield additional insights into cerebral flow dynamics. CEUS uses intravenous injection of ultrasound contrast agents (UCAs) to highlight tissue perfusion and thus more clearly delineate cerebral pathologies including stroke, hypoxic-ischemic injury and focal lesions such as tumors and vascular malformations. It can be applied not only in infants with open fontanelles but also in older children and adults via a transtemporal window or surgically created acoustic window. Advancements in CEUS technology and post-processing methods for quantitative analysis of UCA kinetics further elucidate cerebral microcirculation. In this review article we discuss the CEUS examination protocol for brain imaging in children, current clinical applications and future directions for research and clinical uses of brain CEUS.

How to Perform Intra-Operative Contrast-Enhanced Ultrasound of the Brain-A WFUMB Position Paper

Intra-operative ultrasound has become a relevant imaging modality in neurosurgical procedures. While B-mode, with its intrinsic limitations, is still considered the primary ultrasound modality, intra-operative contrast-enhanced ultrasound (ioCEUS) has more recently emerged as a powerful tool in neurosurgery. Though still not used on a large scale, ioCEUS has proven its utility in defining tumor boundaries, identifying lesion vascular supply and mapping neurovascular architecture. Here we propose a step-by-step procedure for performing ioCEUS analysis of the brain, highlighting its neurosurgical applications. Moreover, we provide practical advice on the use of ultrasound contrast agents and review technical ultrasound parameters influencing ioCEUS 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.

Cavitation Emissions Nucleated by Definity Infused through an EkoSonic Catheter in a Flow Phantom

The EkoSonic endovascular system has been cleared by the U.S. Food and Drug Administration for the controlled and selective infusion of physician specified fluids, including thrombolytics, into the peripheral vasculature and the pulmonary arteries. The objective of this study was to explore whether this catheter technology could sustain cavitation nucleated by infused Definity, to support subsequent studies of ultrasound-mediated drug delivery to diseased arteries. The concentration and attenuation spectroscopy of Definity were assayed before and after infusion at 0.3, 2.0 and 4.0 mL/min through the EkoSonic catheter. PCI was used to map and quantify stable and inertial cavitation as a function of Definity concentration in a flow phantom mimicking the porcine femoral artery. The 2.0 mL/min infusion rate yielded the highest surviving Definity concentration and acoustic attenuation. Cavitation was sustained throughout each 15 ms ultrasound pulse, as well as throughout the 3 min infusion. These results demonstrate a potential pathway to use cavitation nucleation to promote drug delivery with the EkoSonic endovascular system.

Contrast-enhanced ultrasound applications in liver transplant imaging

Contrast-enhanced ultrasound (CEUS) is gaining ever-increasing acceptance in the preoperative and postoperative evaluation of liver-transplanted patients. While indications are still a matter of research, CEUS is used in tertiary centers to supplement ultrasound (US) and Color Doppler US examination, with the potential of providing a comprehensive first-line ultrasound-based diagnosis. Alternatively, CEUS is used as a problem-solving tool when previous cross-sectional or US imaging was inconclusive, especially in assessing hepatocellular carcinoma, parenchymal perfusion abnormalities, the vascular status, and even the biliary tree. This review describes the potential use for CEUS in the setting of orthotopic liver transplantation (OLT).

Contrast-Enhanced Subharmonic Aided Pressure Estimation (SHAPE) using Ultrasound Imaging with a Focus on Identifying Portal Hypertension

Noninvasive, accurate measurement of pressures within the human body has long been an important but elusive clinical goal. Contrast agents for ultrasound imaging are gas-filled, encapsulated microbubbles (diameter < 10 μm) that traverse the entire vasculature and enhance signals by up to 30 dB. These microbubbles also produce nonlinear oscillations at frequencies ranging from the subharmonic (half of the transmit frequency) to higher harmonics. The subharmonic amplitude has an inverse linear relationship with the ambient hydrostatic pressure. Here an ultrasound system capable of performing real-time, subharmonic aided pressure estimation (SHAPE) is presented. During ultrasound contrast agent infusion, an algorithm for optimizing acoustic outputs is activated. Following this calibration, subharmonic microbubble signals (i.e., SHAPE) have the highest sensitivity to pressure changes and can be used to noninvasively quantify pressure. The utility of the SHAPE procedure for identifying portal hypertension in the liver is the emphasis here, but the technique has applicability across many clinical scenarios.

Point-of-care echocardiography for the evaluation of right-to-left cardiopulmonary shunts: a narrative review

Right-to-left pulmonary and cardiac shunts (RLS) are important causes of refractory hypoxia in the critically-ill perioperative patient. Using a point-of-care ultrasound (POCUS) agitated saline bubble study for an early diagnosis allows patients with clinically significant RLSs to receive expedited therapy. This narrative review discusses the principles of agitated saline ultrasonography as well as the role of POCUS in detecting the most common RLS types seen in the intensive care unit, including patent foramen ovale, atrial septal defects, and pulmonary arterio-venous malformations. An illustrated discussion of the procedure, as well as shunt-enhancing maneuvers (Valsalva or lung recruitment maneuver with subsequent rapid release) is provided. With the wide dissemination of bedside ultrasound within the perioperative and critical care arena, POCUS practitioners should be knowledgeable of the potential pitfalls leading to both false-positive and false-negative studies. False-positive studies may be due to congenital abnormalities, mischaracterization of intrapulmonary shunts as intracardiac shunts (and vice versa), or evidence of the Valsalva effect. False negatives are typically due to respiratory-phasic variation, performing an inadequate shunt-enhancing maneuver, inadequate injection of agitated saline, or pathophysiologic states of elevated left atrial pressure. Finally, alternative POCUS methods for determining presence of an RLS in patients with poor echocardiographic windows are discussed, with a focus on pulsed-wave Doppler interrogation of arterial signals.

Characterizing Breast Lesions Using Quantitative Parametric 3D Subharmonic Imaging: A Multicenter Study

RATIONALE AND OBJECTIVES

Breast cancer is the leading type of cancer among women. Visualization and characterization of breast lesions based on vascularity kinetics was evaluated using three-dimensional (3D) contrast-enhanced ultrasound imaging in a clinical study.

MATERIALS AND METHODS

Breast lesions (n = 219) were imaged using power Doppler imaging (PDI), 3D contrast-enhanced harmonic imaging (HI), and 3D contrast-enhanced subharmonic imaging (SHI) with a modified Logiq 9 ultrasound scanner using a 4D10L transducer. Quantitative metrics of vascularity derived from 3D parametric volumes (based on contrast perfusion; PER and area under the curve; AUC) were generated by off-line processing of contrast wash-in and wash-out. Diagnostic accuracy of these quantitative vascular parameters was assessed with biopsy results as the reference standard.

RESULTS

Vascularity was observed with PDI in 93 lesions (69 benign and 24 malignant), 3D HI in 8 lesions (5 benign and 3 malignant), and 3D SHI in 83 lesions (58 benign and 25 malignant). Diagnostic accuracy for vascular heterogeneity, PER, and AUC ranged from 0.52 to 0.75, while the best logistical regression model (vascular heterogeneity ratio, central PER, and central AUC) reached 0.90.

CONCLUSION

3D SHI successfully detects contrast agent flow in breast lesions and characterization of these lesions based on quantitative measures of vascular heterogeneity and 3D parametric volumes is promising.

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.

Novel contrast agent Visphere™ is feasible for contrast-enhanced ultrasonography in dogs

Contrast-enhanced ultrasonography provides a more functional diagnostic image than conventional ultrasonography. This prospective exploratory study compared the novel contrast agent, Visphere^™ , with commercial contrast agents in five healthy Beagle dogs. Visphere^™ has the smallest diameter and highest concentration compared with Sonazoid^® and SonoVue^® . Each dog received an intravenous injection of Visphere^™ , Sonazoid^® , or SonoVue^® . Images were recorded for 300, 600, and 60 s in the heart, liver, and left kidney, respectively. The mean pixel values of the regions of interest for each organ were expressed as time intensity curves (TIC). The agents all improved the visualization of left ventricular endocardial border delineation in the heart, and had similar TICs and clinical useful durations. In contrast, Visphere^™ expressed the highest mean pixel value in the liver parenchyma at an early observation time and maintained the intensity until 600 s, like Sonazoid^® . The renal evaluation results indicated there were no statistically significant differences in time-to-peak for the renal cortex or medulla among the agents. Compared with the other two agents, SonoVue^® had the lowest peak enhancement for the renal cortex and medulla. No dogs had any adverse reactions during or after the study. All three agents provided adequate results for left ventricular endocardial border delineation, and Visphere^™ may have the same potential as Sonazoid^® to detect and characterize hepatic lesions. Visphere^™ and Sonazoid^® may offer better visualization quality to evaluate renal function. In conclusion, the novel contrast agent, Visphere^™ , is comparable with commercial agents and could be applied in different major organs in dogs.

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.

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.

Introduction to contrast-enhanced ultrasound of the brain in neonates and infants: current understanding and future potential

Contrast-enhanced ultrasound (CEUS) is a valuable bedside imaging technique that enables both qualitative and quantitative assessment of cerebral perfusion. In neonates and infants whose fontanelles remain open, the technique is particularly useful as it delineates cerebral pathology with high soft-tissue contrast. The technique has the potential to be a valuable alternative to computed tomography (CT) or magnetic resonance imaging (MRI) in critically ill neonates and infants in need of bedside imaging. While further studies are needed to validate the technique, preliminary data in this regard appear promising. This review introduces the current understanding and future potential of brain CEUS.

Evolving clinical applications of contrast-enhanced ultrasound (CEUS) in the abdominal aorta

Ultrasound (US) represents the initial modality in the workup of abdominal aortic pathology based on the plethora of advantages including widespread availability, low cost, safety profile and repeatability. However, US has inherent limitations including limited spatial information of pathologic processes to neighboring structures, lower sensitivity to slow blood flow and aortic luminal irregularities. For evaluation of aortic pathology angiography has long been considered the gold standard. Non-invasive cross-sectional imaging techniques like computed tomography angiography (CTA) and magnetic resonance angiography (MRA) have gradually replaced interventional angiography for the evaluation of aorta, currently being regarded as the diagnostic imaging modalities of choice for diagnosis of virtually every aortic disease. Interventional angiography is currently primarily performed for treatment purposes of aortic pathology. The introduction of microbubbles as ultrasonographic contrast agents has rendered contrast-enhanced ultrasound (CEUS) an evolving valuable complementary technique with markedly increased diagnostic accuracy for certain aortic applications. CEUS is characterized by the potential to be performed in patients with impaired renal function. Due to its superior spatial and temporal resolution, ability for prolonged scanning and dynamic and real-time imaging, it provides clinically significant additional information compared to the standard Duplex US. The purpose of this paper is to discuss the currently available literature regarding abdominal aortic applications of CEUS, briefly elaborate on CEUS technique and safety and present cases in order to illustrate the added value in aortic pathologies. Conditions discussed include abdominal aortic aneurysm (AAA), aneurysm rupture, aneurysm surveillance after endovascular repair, dissection and aortitis.

How to perform Contrast-Enhanced Ultrasound (CEUS)

"How to perform contrast-enhanced ultrasound (CEUS)" provides general advice on the use of ultrasound contrast agents (UCAs) for clinical decision-making and reviews technical parameters for optimal CEUS performance. CEUS techniques vary between centers, therefore, experts from EFSUMB, WFUMB and from the CEUS LI-RADS working group created a discussion forum to standardize the CEUS examination technique according to published evidence and best personal experience. The goal is to standardise the use and administration of UCAs to facilitate correct diagnoses and ultimately to improve the management and outcomes of patients.

Influence of contrast-enhanced ultrasound administration setups on microbubble enhancement: a focus on pediatric applications

BACKGROUND

In pediatrics, contrast-enhanced ultrasound offers high-quality imaging with an excellent safety profile.

OBJECTIVE

To investigate the effects of varying intravenous administration setups on in vitro enhancement and concentration of two commercially available ultrasound contrast agents, taking into consideration potential pediatric applications.

MATERIALS AND METHODS

We quantified in vitro enhancement using a flow phantom (ATS Laboratories, Bridgeport, CT) and Acuson S3000 ultrasound system (Siemens Healthineers, Mountain View, CA) with a 9L4 probe in Cadence pulse sequencing mode. We determined microbubble concentration with an LSRII flow cytometer (BD Biosciences, San Jose, CA). We investigated Optison (GE Healthcare, Princeton, NJ) and Lumason (Bracco, Geneva, Switzerland) ultrasound contrast agents. The ultrasound (US) contrast agent was injected via a 1 mL syringe and flushed with 5 mL of saline through a 22-gauge diffusion catheter (BD Medical, Franklin Lakes, NJ) with the following variations: in-line injection through a 3-way stopcock with and without a neutral displacement connector (ICU Medical, San Clemente, CA), perpendicular through a 3-way stopcock with and without a connector, and without a 3-way stopcock. We also conducted injections through a 22-gauge standard angiocatheter.

RESULTS

Injection through the connector and perpendicular injection via the 3-way stopcock resulted in significant decreases in enhancement for both ultrasound contrast agents (P<0.0001). Injection through the connector resulted in significant decrease in concentration for Optison (P<0.05). Neither addition of the 3-way stopcock (P>0.24) nor use of a pediatric diffusion catheter (P>0.28) affected the enhancement.

CONCLUSION

Ultrasound contrast agent enhancement depends on the administration route, although some effects appear to be specific to the ultrasound contrast agent used. To avoid loss of enhancement, neutral displacement connectors and perpendicular injection should be avoided.

Quantitative Three-Dimensional Dynamic Contrast-Enhanced Ultrasound Imaging: First-In-Human Pilot Study in Patients with Liver Metastases

Purpose: To perform a clinical assessment of quantitative three-dimensional (3D) dynamic contrast-enhanced ultrasound (DCE-US) feasibility and repeatability in patients with liver metastasis, and to evaluate the extent of quantitative perfusion parameter sampling errors in 2D compared to 3D DCE-US imaging.

Materials and Methods: Twenty consecutive 3D DCE-US scans of liver metastases were performed in 11 patients (45% women; mean age, 54.5 years; range, 48-60 years; 55% men; mean age, 57.6 years; range, 47-68 years). Pairs of repeated disruption-replenishment and bolus DCE-US images were acquired to determine repeatability of parameters. Disruption-replenishment was carried out by infusing 0.9 mL of microbubbles (Definity; Latheus Medical Imaging) diluted in 35.1 mL of saline over 8 min. Bolus consisted of intravenous injection of 0.2 mL microbubbles. Volumes-of-interest (VOI) and regions-or-interest (ROI) were segmented by two different readers in images to extract 3D and 2D perfusion parameters, respectively. Disruption-replenishment parameters were: relative blood volume (rBV), relative blood flow (rBF). Bolus parameters included: time-to-peak (TP), peak enhancement (PE), area-under-the-curve (AUC), and mean-transit-time (MTT).

Results: Clinical feasibility and repeatability of 3D DCE-US using both the destruction-replenishment and bolus technique was demonstrated. The repeatability of 3D measurements between pairs of repeated acquisitions was assessed with the concordance correlation coefficient (CCC), and found to be excellent for all parameters (CCC > 0.80), except for the TP (0.74) and MTT (0.30) parameters. The CCC between readers was found to be excellent (CCC > 0.80) for all parameters except for TP (0.71) and MTT (0.52). There was a large Coefficient of Variation (COV) in intra-tumor measurements for 2D parameters (0.18-0.52). Same-tumor measurements made in 3D were significantly different (P = 0.001) than measurements made in 2D; a percent difference of up to 86% was observed between measurements made in 2D compared to 3D in the same tumor.

Conclusions: 3D DCE-US imaging of liver metastases with a matrix array transducer is feasible and repeatable in the clinic. Results support 3D instead of 2D DCE US imaging to minimize sampling errors due to tumor heterogeneity.

Enhancing the role of paediatric ultrasound with microbubbles: a review of intravenous applications

Contrast-enhanced ultrasound (CEUS) represents a complementary technique to greyscale and colour Doppler ultrasonography which allows for real-time visualization and characterization of tissue perfusion. Its inherent advantages in the child makes ultrasonography an ideal imaging modality; repeatability and good tolerance along with the avoidance of CT, a source of ionizing radiation, renders ultrasonography imaging desirable. Although currently paediatric CEUS is principally used in an "off-label" manner, ultrasonography contrast agents have received regulatory approval for assessment of paediatric focal liver lesions (FLL) in the USA. The safety of ultrasound contrast-agents is well documented in adults, as safe as or even surpassing the safety profile of CT and MR contrast agents. Except for the established intracavitary use of CEUS in voiding urosonography, i.v. paediatric applications have been introduced with promising results in the abdominal trauma initial diagnosis and follow-up, characterization and differential diagnosis of FLL and characterization of lung, pleura, renal and splenic pathology. CEUS has also been used to detect complications after paediatric transplantation, evaluate inflammatory bowel disease activity and assess tumour response to antiangiogenic therapy. The purpose of this review was to present these novel i.v. paediatric applications of CEUS and discuss their value.