Recommendations on the safe use of ultrasound contrast agents

In Vivo Temperature Rise Measurements of Rabbit Liver and Femur Bone Surface Exposed to an Acoustic Radiation Force Impulse

Acoustic radiation force impulse (ARFI) imaging and shear wave elastography use a "push pulse." The push pulse, which is referenced as an ARFI in this study, has a longer duration than that of conventional diagnostic pulses (several microseconds). Therefore, there are concerns regarding thermal safety in vivo. However, few in vivo studies have been conducted using living animals. In this study, to suggest a concept for deciding an ARFI output and cooling time while considering thermal safety, the liver (with and without an ultrasound contrast agent) and femur bone surface of living rabbits were exposed to an ARFI, and the maximum temperature rise, temperature rise for 5-min duration, and cooling time were measured via a thermocouple. While testing within the regulation limits of diagnostic ultrasound outputs, a maximum temperature rise on the femur bone surface exceeded the allowable temperature rise (1.5°C) in the British Medical Ultrasound Society (BMUS) statement. However, using the linear relationships between the pulse intensity integral (PII) of a single pulse and the above three temperature parameters, PII may be determined so that the maximum temperature rise is within the allowable temperature rise in the BMUS statement. The cooling time can be estimated from the PII.

Experiência inicial com ultrassom Doppler com contraste por microbolhas em adição ao ultrassom Doppler convencional para seguimento de correção endovascular de aneurisma de aorta abdominal

Background

Microbubble contrast enhanced ultrasound (CEUS) is an accurate diagnostic method for follow-up after endovascular abdominal aortic aneurysm repair (EVAR) that has been well-established in international studies. However, there are no Brazilian studies that focus on this follow-up method.

Objectives

The objective of this study was to report initial experience with CEUS at a tertiary hospital, comparing the findings of CEUS with those of conventional Doppler ultrasound (DUS), with the aim of determining whether addition of contrast to the standard ultrasonographic control protocol resulted in different findings.

Methods

From 2015 to 2017, 21 patients in follow-up after EVAR underwent DUS followed by CEUS. The findings of these examinations were analyzed in terms of identification of complications and their capacity to identify the origin of endoleaks.

Results

There was evidence of complications in 10 of the 21 cases examined: seven patients exhibited endoleaks (33.3%); two patients exhibited stenosis of a branch of the endograft (9.52%); and one patient exhibited a dissection involving the external iliac artery (4.76%). In the 21 patients assessed, combined use of both methods identified 10 cases of post-EVAR complications. In six of the seven cases of endoleaks (85.71%), use of the methods in combination was capable of identifying the origin of endoleakage. DUS alone failed to identify endoleaks in two cases (28.5%) and identified doubtful findings in another two cases (28.5%), in which diagnostic definition was achieved after employing CEUS.

Conclusions

CEUS is a technique that is easy to perform and provides additional support for follow-up of infrarenal EVAR.

The AFSUMB Consensus Statements and Recommendations for the Clinical Practice of Contrast-Enhanced Ultrasound using Sonazoid

The first edition of the guidelines for the use of ultrasound contrast agents was published in 2004, dealing with liver applications. The second edition of the guidelines in 2008 reflected changes in the available contrast agents and updated the guidelines for the liver, as well as implementing some nonliver applications. The third edition of the contrast-enhanced ultrasound (CEUS) guidelines was the joint World Federation for Ultrasound in Medicine and Biology-European Federation of Societies for Ultrasound in Medicine and Biology (WFUMB-EFSUMB) venture in conjunction with other regional US societies such as Asian Federation of Societies for Ultrasound in Medicine and Biology, resulting in a simultaneous duplicate on liver CEUS in the official journals of both WFUMB and EFSUMB in 2013. However, no guidelines were described mainly for Sonazoid due to limited clinical experience only in Japan and Korea. The new proposed consensus statements and recommendations provide general advice on the use of Sonazoid and are intended to create standard protocols for the use and administration of Sonazoid in hepatic and pancreatobiliary applications in Asian patients and to improve patient management.

The AFSUMB Consensus Statements and Recommendations for the Clinical Practice of Contrast-Enhanced Ultrasound using Sonazoid

The first edition of the guidelines for the use of ultrasound contrast agents was published in 2004, dealing with liver applications. The second edition of the guidelines in 2008 reflected changes in the available contrast agents and updated the guidelines for the liver, as well as implementing some nonliver applications. The third edition of the contrast-enhanced ultrasound (CEUS) guidelines was the joint World Federation for Ultrasound in Medicine and Biology-European Federation of Societies for Ultrasound in Medicine and Biology (WFUMB-EFSUMB) venture in conjunction with other regional US societies such as Asian Federation of Societies for Ultrasound in Medicine and Biology, resulting in a simultaneous duplicate on liver CEUS in the official journals of both WFUMB and EFSUMB in 2013. However, no guidelines were described mainly for Sonazoid due to limited clinical experience only in Japan and Korea. The new proposed consensus statements and recommendations provide general advice on the use of Sonazoid and are intended to create standard protocols for the use and administration of Sonazoid in hepatic and pancreatobiliary applications in Asian patients and to improve patient management.

Safety of Perfluorobutane (Sonazoid) in Characterizing Focal Liver Lesions

Background:

The purpose of this study was to report the safety of perfluorobutane (Sonazoid) as a vascular-phase imaging agent in characterizing focal liver lesions (FLLs).

Materials and Methods:

From May 2014 to April 2015, a total of 54 individuals who received Sonazoid contrast-enhanced ultrasound (CEUS) were enrolled at 5 hospitals of 4 medical centers. All individuals were included in safety evaluation. A prospective study to evaluate the adverse effect (AE) incidences after intravenous administration of Sonazoid.

Results:

Sonazoid was well tolerated. Treatment-emergent adverse events (TEAEs) representing AE were recorded for 13 (24.1%) patients. The most common AE was abdominal pain (9.3%), followed by heart rate irregularity (5.6%). The majority of these patients (69.2%) experienced TEAEs that were mild in intensity. Sonazoid causes no significant AEs after intravenous injection. The only noteworthy AEs are related to tolerable myalgia (3.7%), abdominal pain (1.9%), and headache (1.9%). None of the 54 patients showed serious adverse effects.

Conclusion:

Sonazoid shows good safety and tolerance of intravenous use during CEUS of the liver for evaluation of FLLs.

Contrast-Enhanced Ultrasound of the Liver: Optimizing Technique and Clinical Applications

OBJECTIVE

The purpose of this article is to review the general principles, technique, and clinical applications of contrast-enhanced ultrasound of the liver.

CONCLUSION

Proper technique and optimization of contrast-enhanced ultrasound require a balance between maintaining the integrity of the microbubble contrast agent and preserving the ultrasound signal. Established and emerging applications in the liver include diagnosis of focal lesions, aiding ultrasound-guided intervention, monitoring of therapy, and aiding surgical management.

Ultrasound localization microscopy to image and assess microvasculature in a rat kidney

The recent development of ultrasound localization microscopy, where individual microbubbles (contrast agents) are detected and tracked within the vasculature, provides new opportunities for imaging the vasculature of entire organs with a spatial resolution below the diffraction limit. In stationary tissue, recent studies have demonstrated a theoretical resolution on the order of microns. In this work, single microbubbles were localized in vivo in a rat kidney using a dedicated high frame rate imaging sequence. Organ motion was tracked by assuming rigid motion (translation and rotation) and appropriate correction was applied. In contrast to previous work, coherence-based non-linear phase inversion processing was used to reject tissue echoes while maintaining echoes from very slowly moving microbubbles. Blood velocity in the small vessels was estimated by tracking microbubbles, demonstrating the potential of this technique to improve vascular characterization. Previous optical studies of microbubbles in vessels of approximately 20 microns have shown that expansion is constrained, suggesting that microbubble echoes would be difficult to detect in such regions. We therefore utilized the echoes from individual MBs as microscopic sensors of slow flow associated with such vessels and demonstrate that highly correlated, wideband echoes are detected from individual microbubbles in vessels with flow rates below 2 mm/s.

Measurement of sound pressure and temperature in tissue-mimicking material using an optical fiber Bragg grating sensor

PURPOSE

The experimental investigation of an optical fiber Bragg grating (FBG) sensor for biomedical application is described. The FBG sensor can be used to measure sound pressure and temperature rise simultaneously in biological tissues exposed to ultrasound. The theoretical maximum values that can be measured with the FBG sensor are 73.0 MPa and 30 °C.

METHODS

In this study, measurement of sound pressure up to 5 MPa was performed at an ultrasound frequency of 2 MHz. A maximum temperature change of 6 °C was measured in a tissue-mimicking material.

RESULTS

Values yielded by the FBG sensor agreed with those measured using a thermocouple and a hydrophone.

CONCLUSION

Since this sensor is used to monitor the sound pressure and temperature simultaneously, it can also be used for industrial applications, such as ultrasonic cleaning of semiconductors under controlled temperatures.

Role of US Contrast Agents in the Assessment of Indeterminate Solid and Cystic Lesions in Native and Transplant Kidneys

Ultrasonography (US) is often the initial imaging modality employed in the evaluation of renal diseases. Despite improvements in B-mode and Doppler imaging, US still faces limitations in the assessment of focal renal masses and complex cysts as well as the microcirculation. The applications of contrast-enhanced US (CEUS) in the kidneys have dramatically increased to overcome these shortcomings with guidelines underlining their importance. This article describes microbubble contrast agents and their role in renal imaging. Microbubble contrast agents consist of a low solubility complex gas surrounded by a phospholipid shell. Microbubbles are extremely safe and well-tolerated pure intravascular agents that can be used in renal failure and obstruction, where computed tomographic (CT) and magnetic resonance (MR) imaging contrast agents may have deleterious effects. Their intravascular distribution allows for quantitative perfusion analysis of the microcirculation, diagnosis of vascular problems, and qualitative assessment of tumor vascularity and enhancement patterns. Low acoustic power real-time prolonged imaging can be performed without exposure to ionizing radiation and at lower cost than CT or MR imaging. CEUS can accurately distinguish pseudotumors from true tumors. CEUS has been shown to be more accurate than unenhanced US and rivals contrast material-enhanced CT in the diagnosis of malignancy in complex cystic renal lesions and can upstage the Bosniak category. CEUS can demonstrate specific enhancement patterns allowing the differentiation of benign and malignant solid tumors as well as focal inflammatory lesions. In conclusion, CEUS is useful in the characterization of indeterminate renal masses and cysts.

Can contrast-enhanced ultrasound with second-generation contrast agents replace computed tomography angiography for distinguishing between occlusion and pseudo-occlusion of the internal carotid artery?

OBJECTIVE

The purpose of this study was to evaluate the effectiveness of contrast-enhanced ultrasound with a second-generation contrast agent in distinguishing between occlusion and pseudo-occlusion of the cervical internal carotid artery, comparing it with that of conventional Doppler ultrasound and the gold standard, computed tomography angiography.

METHOD

Between June 2006 and June 2012, we screened 72 symptomatic vascular surgery outpatients at a public hospital. Among those patients, 78 cervical internal carotid arteries were previously classified as occluded by Doppler ultrasound (without contrast). The patients were examined again with Doppler ultrasound, as well as with contrast-enhanced ultrasound and computed tomography angiography. The diagnosis was based on the presence or absence of flow.

RESULTS

Among the 78 cervical internal carotid arteries identified as occluded by Doppler ultrasound, occlusion was confirmed by computed tomography angiography in only 57 (73.1%), compared with 59 (77.5%) for which occlusion was confirmed by contrast-enhanced ultrasound (p>0.5 vs. computed tomography angiography). Comparing contrast-enhanced ultrasound with Doppler ultrasound, we found that the proportion of cervical internal carotid arteries classified as occluded was 24.4% higher when the latter was used (p<0.001).

CONCLUSIONS

We conclude that, in making the differential diagnosis between occlusion and pseudo-occlusion of the cervical internal carotid artery, contrast-enhanced ultrasound with a second-generation contrast agent is significantly more effective than conventional Doppler ultrasound and is equally as effective as the gold standard (computed tomography angiography). Our findings suggest that contrast-enhanced ultrasound could replace computed tomography angiography in this regard.

JSUM ultrasound elastography practice guidelines: pancreas

Ultrasound elastography is a relatively new diagnostic technique for measuring the elasticity (hardness) of tissue. Eleven years have passed since the debut of elastography. Various elastography devices are currently being marketed by manufacturers under different names. Pancreatic elastography can be used not only with transabdominal ultrasonography but also with endoscopic ultrasonography, but some types of elastography are difficult to perform for the pancreas. These guidelines aim to classify the various types of elastography into two major categories depending on the differences in the physical quantity (strain, shear wave), and to present the evidence for pancreatic elastography and how to use pancreatic elastography in the present day. But the number of reports on ultrasound elastography for the pancreas is still small, and there are no reports on some elastography devices for the pancreas. Therefore, these guidelines do not recommend methods of imaging and analysis by elastography device.

Prenatal ultrasound heating impacts on fluctuations in haematological analysis of Oryctolagus cuniculus

Prenatal Ultrasound (US) is commonly used as a routine procedure on pregnant women. It is generally perceived as a safe procedure due to the use of non-ionizing radiation. However, the neurotoxicity of diagnostic prenatal US was detected to have a correlation with high susceptibility to early developing fetus. This research involved in vivo experimental model by using 3(rd) trimester pregnant Oryctolagus cuniculus and exposing them to US exposures for 30, 60, and 90 minutes at their gestational day (GD) 28-29. The output power and intensities, spatial peak temporal average intensity (ISPTA) of US were varied from 0.4 to 0.7 W and 0.13 to 0.19 W/cm(2) respectively were tested initially in free-field, water. Haematological analysis was carried out to detect any changes in blood constituents. Statistically significant differences were detected in red blood cell (RBC) count (P<0.001), haemoglobin (Hb) concentration (P<0.001) and also platelet (PLT) count (P<0.001) in newborn of Oryctolagus cuniculus. These findings indicate the possibility of US heating in causing defects on studied animal.

Double contrast-enhanced ultrasonography in preoperative Borrmann classification of advanced gastric carcinoma: comparison with histopathology

The purpose of this study was to investigate the accuracy of double contrast-enhanced ultrasonography (DCEUS) for assessing the Borrmann classification of advanced gastric carcinoma (AGC) preoperatively. Three hundred twenty nine patients with proved AGC were enrolled. DCEUS (intravenous microbubbles combined with combined with oral contrast-enhanced ultrasound) was performed preoperatively. The diagnostic accuracy of DCEUS in determining Borrmann classification was compared with postoperative pathological findings. The reliability of DCEUS was analyzed. The accuracy of DCEUS in determining the Borrmann classification of AGC was 91.49%. The intra- and inter-observer reproducibility was both almost perfect for assessing the Borrmann classification of AGC by DCEUS. DCEUS could be considered as an accurate, non-invasive, and reliable diagnostic method for preoperative Borrmann classification of advanced gastric carcinoma.

JSUM ultrasound elastography practice guidelines: basics and terminology

Ten years have passed since the first commercial equipment for elastography was released; since then clinical utility has been demonstrated. Nowadays, most manufacturers offer an elastography option. The most widely available commercial elastography methods are based on strain imaging, which uses external tissue compression and generates images of the resulting tissue strain. However, imaging methods differ slightly among manufacturers, which results in different image characteristics, for example, spatial and temporal resolution, and different recommended measurement conditions. In addition, many manufacturers have recently provided a shear wave-based method, providing stiffness images based on shear wave propagation speed. Each method of elastography is designed on the basis of assumptions of measurement conditions and tissue properties. Thus, we need to know the basic principles of elastography methods and the physics of tissue elastic properties to enable appropriate use of each piece of equipment and to obtain more precise diagnostic information from elastography. From this perspective, the basic section of this guideline aims to support practice of ultrasound elastography.

Changes in hemocoagulation in acute stroke patients after one-hour sono-thrombolysis using a diagnostic probe

The aim was to monitor the changes in hemocoagulation parameters in acute ischemic stroke (AIS) patients after sono-thrombolysis of the occluded middle cerebral artery using a duplex transcranial probe with 2.0-MHz frequency in Doppler mode. Sixteen AIS patients indicated for intravenous thrombolysis (IVT) (8 males; mean age 68.3 +/- 7.1 y) and 16 AIS patients contraindicated for IVT (11 males; mean age 67.9 +/- 7.9 y) were randomized for sono-thrombolysis (8 + 8 patients) or standard treatment (control group) (8 + 8 patients). The significant decrease of plasminogen activator inhibitor-1, plasminogen and alpha-2-antiplasmin activity by a mean of 60, 32 and 24%, respectively, and the increase of tissue plasminogen activator by a mean of 56% was found after sono-thrombolysis when compared with control group (p < 0.0125); these changes were more evident in patients treated with a combination of sono-thrombolysis and IVT (79, 38, 50 and 82%, respectively) than in patients treated by sono-thrombolysis alone (34, 13, 17 and 30%, respectively).

First experience using intraoperative contrast-enhanced ultrasound during endovascular aneurysm repair for infrarenal aortic aneurysms

BACKGROUND

Endovascular aortic repair (EVAR) has become an additional treatment option for patients with infrarenal aortic aneurysms and suitable aortic morphology. However, endoleaks are commonly encountered and represent a relevant risk for secondary treatment failure. In addition, impaired renal function or allergic reactions to intravascular iodine application might represent exclusion criteria for conventional infrarenal endovascular aortic repair using intraoperative angiography with iodine contrast media. Real-time contrast-enhanced ultrasound (CEUS) with a low mechanical index (MI) is a promising method recently introduced for follow up after endovascular infrarenal aortic repair.

METHODS

In this study, intraoperative CEUS using SonoVue as ultrasound contrast agent was evaluated in 17 patients for localization of the proximal infrarenal landing zone, the distal iliac fixation area, and identification of endoleaks in patients suitable for endovascular aortic repair with an infrarenal aortic neck > or =10 mm and non-aneurysmal common iliac arteries. For comparison, 20 patients were treated by conventional EVAR using intraoperative fluoroscopy and iodine contrast media.

RESULTS

Intraoperative application of contrast-enhanced ultrasound (iCEUS) for identification of the infrarenal landing zone and proximal stent graft release was achieved in 14 out of 17 patients (82.4%), as verified by intraoperative angiography or postinterventional imaging. Intraoperative CEUS-assisted visualization of the distal fixation area proximal to the level of the iliac bifurcation was achieved in 89.3% (25 out of 28 iliac arteries examined) in comparison to intraoperative angiography or postinterventional CEUS, computed tomography (CT), or magnetic resonance (MR) angiography. Three selected patients having contraindications for iodine-based contrast media were treated by iCEUS-assisted EVAR without the use of any iodine contrast during fluoroscopy. Time for exposure to intraoperative radiation, volume of contrast medium used, and the number of intraoperative angiographies and postinterventional CT or MR angiographies were significantly reduced in the iCEUS-assisted EVAR group in comparison to conventional endovascular aortic treatment (P < .002 or less for all parameters). Intraoperative application of CEUS detected more endoleaks than conventional EVAR (8/17 vs 4/20; P = .08) treated by proximal stent graft extension in one symptomatic patient with a type Ia endoleak.

CONCLUSIONS

Intraoperative CEUS-assisted EVAR in patients with infrarenal aortic aneurysms represents a new option for intraoperative visualization of aortoiliac segments required as proximal or distal fixation zones and identification of endoleaks, especially in those patients with contraindications for usage of iodine-containing contrast agents, in association with a reduction of iodine contrast media used and radiation exposure during fluoroscopy.

Knowledge of the bio-effects of ultrasound among physicians performing clinical ultrasonography: Results of a survey conducted by the Italian Society for Ultrasound in Medicine and Biology (SIUMB)

INTRODUCTION

Safety issues should always be kept in mind when using diagnostic ultrasound, which is associated with potentially hazardous bio-effects, especially with the introduction of new technologies.

AIM

To assess the level of awareness and knowledge of safety issues related to the clinical use of ultrasound among physician-members of the Italian National Society for Ultrasound.

MATERIALS AND METHODS

A questionnaire with 11 multiple-choice questions was sent to members of the Italian Society for Ultrasound in Medicine and Biology. The answers were forwarded from the Society's Secretariat to the investigators, who statistically analyzed the data.

RESULTS

The mean age of the 105 respondents was 44 years. The most frequent kind of ultrasound examinations (in addition to conventional B-mode) were: Doppler (74%), contrast-enhanced US (43%), and pediatric studies (43%). Only 50-60% of the responders knew the correct definitions of the terms thermal index and mechanical index. Almost all respondents understood the bio-effects reflected by the thermal index, but only a minority knew the most likely organ target of bio-effects related to the mechanical index and what do indicate the units in which the thermal index is expressed. The majority knew that fetuses are at higher risk of damage. Few respondents were able to identify the correct safety statements included in the recommendations of the International Ultrasound Societies.

CONCLUSION

In conclusion, the present findings indicate that greater efforts of National Ultrasound Societies are warranted in disseminating knowledge of the bio-effects of diagnostic ultrasound modalities among operators.

[Ultrasound contrast agents. Pharmaceutical drug safety and bioeffects]

In this overview safety aspects of ultrasound contrast agents (USCA) are described and discussed. In general USCA are very safe drugs. However, allergic adverse reactions can rarely occur, particularly due to the colloidal structure of USCA. In addition, the use of USCA could reduce the threshold for acoustically induced bioeffects and has the potential to increase these effects. In in vitro studies and animal trials USCA caused petechial hemorrhages, vascular damage, and the formation of free radicals. Even DNA damage with single strand breaks could be demonstrated. In human studies and clinical practice none of these bioeffects could be observed. In contrast-enhanced echocardiography a higher rate of premature ventricular contractions has been reported when imaging was triggered at the end systole. Compared with other contrast agents contrast-enhanced ultrasound showed no nephrotoxic effects and could prove to be an alternative diagnostic method for patients with renal failure.