Coherent Contrast Imaging Research Articles

Evaluation of non-critical coronary stenosis by coherent contrast imaging

Objective To investigate whether non-critical coronary stenosis can be detected by coherent contrast imaging(CCI) at rest without stress.Methods Three degrees of stenosis were made in left anterior descending of 12 dogs.Myocardial contrast echocardiography(MCE) was performed with CCI and the correlation among the variables of MCE curve and the degrees of stenosis were analyzed by cubic regression.Results The time to peak was significantly prolonged with progressive coronary stenosis (P＜0.01) and related to the degree of stenosis (R~2=0.991,P＜0.001).Conclusions CCI could be used to detected non-critical coronary stenosis at rest without stress. Key words: Echocardiography; Microbubbles; Coronary stenosis

Standardize and Compare Contrast-enhanced Ultrasonographic Digital Images Obtained with Different Technologies: How to Overcome the Subjectivity

This study was conducted to compare digital images obtained with cadence contrast pulse sequencing (CPS) and coherent contrast imaging (CCI) technologies for contrast-enhanced ultrasonography (CEUS). A CEUS study on 17 focal liver lesions was performed using CPS and CCI technologies with a second-generation contrast media. The lesion/liver ratio and conspicuity index were then calculated and compared with Adobe Photoshop 6.0. Lesion/liver ratio and conspicuity index using CCI ranged from 1.3 to 7.1 (mean value, 3) and 19 to 127 (mean value, 58), respectively; by using CPS, we obtained results ranging from 2 to 19.1 (mean value, 8.9) and 57 to 164 (mean value, 109.2). Lesion/liver ratio and the conspicuity index for the lesions using CPS showed significantly (p < 0.0001) superior results than those obtained using CCI. The computed analysis with standardization allows an objective evaluation of digital images of CEUS. CPS technology resulted in better lesion conspicuity compared to CCI during CEUS study on focal liver lesions.

Differential Diagnosis of Focal Liver Lesions in Signal-Enhanced Ultrasound Using BR 1, a Second-Generation Ultrasound Signal Enhancer

Aim: The aim was to evaluate the diagnostic value of contrast-enhanced ultrasound in the differential diagnosis of focal liver lesions, in a blinded experiment. In clinical routine the examiner can generally be influenced by the patient’s history. Method: 62 patients with focal liver lesions, which could not be clearly differentiated and diagnosed by conventional ultrasound, were examined with contrast-enhanced (BR1, SonoVue^®, Bracco) ultrasound and included in a blinded prospective and randomized study. The examinations performed on a Sequoia 512 (Acuson) in a coherent contrast imaging method were recorded by an S-VHS recorder and afterwards analyzed by an examiner who did not know the patient’s history. The basis of the diagnosis was the dynamic appearance and enhancement of the ultrasound contrast enhancer in different phases of liver perfusion. The conformation of the diagnoses was made by corresponding reference methods, as computer tomography, magnetic resonance imaging, biopsy and clinical follow-up. Results: The following diagnoses were confirmed by reference methods: 18 patients with metastases, 4 hepatocellular carcinomas, 19 haemangiomas, 6 focal nodular hyperplasias, 13 patients with focal fatty infiltration and 2 patients with focal fatty sparing. 59 out of 62 patients with one or more liver lesions were correctly diagnosed by contrast-enhanced ultrasound. Conclusion: Second-generation ultrasound contrast enhancers improve the differential diagnosis of benign and malignant liver lesions considerably, especially in a blinded study.

Case Report: Microbubble Contrast-Enhanced Ultrasound Characteristics of Multiple Biliary Hamartomas (von Meyenberg Complexes)

Multiple biliary hamartomas (von Meyenberg complexes) are an uncommon benign biliary neoplasm detected incidentally on imaging. To our knowledge the appearances of multiple biliary hamartomas on microbubble contrast-enhanced ultrasound have not been previously described. We report a case using Coherent Contrast Imaging® and Agent Detection Imaging® techniques with the contrast agents Sonovue®and Levovist®. While both methodologies failed to differentiate these focal liver lesions from malignant neoplasms, they enhanced the conspicuity of the hamartomas. Radiologically-guided biopsy and histological analysis remain the reference standard in the diagnosis of multiple biliary hamartomas.

Evaluation of hepatocellular carcinoma using SonoVue, a second generation ultrasound contrast agent: correlation with cellular differentiation

The appearance of hepatocellular carcinoma (HCC) with contrast-enhanced ultrasound (CEUS) in the vascular phase is described and evaluated as to whether the enhancement pattern correlates with the degree of cellular differentiation. One hundred four HCCs were prospectively evaluated with CEUS using coherent-contrast imaging (CCI) and SonoVue with a low mechanical index (<0.2). The enhancement of HCCs in the vascular phase was analyzed according to the degree of pathological differentiation obtained by fine-needle biopsy. In the arterial phase, all HCCs except for four well differentiated ones (96.2%) showed enhancement ( P<0.05). Histological differentiation of hypoechoic lesions in the early portal phase (7 HCCs; 16%) significantly differed from hyperechoic (1 HCC; 1%) or isoechoic lesions (87 HCCs; 83.6%) ( P<0.05), with a significant probability of a worse differentiation in hypoechoic lesions. Histological differentiation of isoechoic lesions in the late phase (30 HCCs; 28.8%) significantly differed from hypoechoic lesions (74 HCCs; 71.2%) ( P<0.05), with a significant probability of a better differentiation in isoechoic lesions. CEUS using CCI and SonoVue revealed enhancement in the arterial phase in >95% of HCCs, with a few well-differentiated cases not being diagnosed due to the absence of enhancement. Echogenicity in the portal and late phases correlated with cellular differentiation.

Imaging of macro and microcirculation of focal liver lesions (FLL) using a second-generation ultrasound contrast agent and gray scale harmonic imaging (coherent contrast imaging, CCI) combined with color Doppler (CD)

Imaging of macro and microcirculation of focal liver lesions (FLL) using a second-generation ultrasound contrast agent and gray scale harmonic imaging (coherent contrast imaging, CCI) combined with color Doppler (CD)

Comparison of real-time coherent contrast imaging to dipyridamole thallium-201 single-photon emission computed tomography for assessment of myocardial perfusion and left ventricular wall motion

Real-time coherent contrast imaging (CCI) echocardiography has the ability to evaluate wall motion and myocardial perfusion simultaneously, but its clinical applicability in the diagnosis of coronary artery disease (CAD) remains to be determined. This study examines the level of agreement between real-time CCI echocardiography and thallium-201 single-photon emission computed tomography (SPECT) following stress vasodilation. Forty-two patients with known or suspected CAD underwent real-time CCI using octafluoropropane-filled microspheres infusion before and after dipyridamole and thallium-201 injections. The apical 4- and 2-chamber views were each divided into 6 segments to assess wall motion and perfusion. Real-time CCI and SPECT were interpreted independently. Thirty-eight patients successfully completed tests, and 4 had suboptimal contrast images. Each vascular territory was classified as normal or abnormal by CCI perfusion, wall motion, and SPECT at baseline and at stress. Of the 114 territories (3 in each of the 38 patients), 3 (3.5%) were not analyzed; however, all territories corresponding to the left anterior descending artery were suitable for analysis. Concordance between CCI echocardiography and thallium-201 SPECT perfusion for left anterior descending, left circumflex, and right coronary artery territories were 91%, 86%, and 69%, respectively; between CCI perfusion and wall motion, the correlations were 93%, 93%, and 91%, respectively. When CCI perfusion and wall motion analysis were combined, their concordance to thallium-201 SPECT uptake improved to 94%, 89%, and 79%, respectively. In conclusion, real-time CCI echocardiography agrees very closely with thallium-201 SPECT in assessing myocardial perfusion following vasodilatory stress. Assessment of myocardial perfusion, in addition to segmental wall motion analysis, during stress echocardiography may be a significant contribution to the noninvasive evaluation of patients with ischemic heart disease.

Bubbles in echocardiography: climbing the learning curve

The past few years have seen the rapid development of novel imaging modes tuned to the specific detection of microbubbles; these include harmonic 13-mode, phase or pulse inversion, power modulation, coherent contrast imaging, and recently power pulse inversion. These contrast-specific imaging modes, combined with insonation at low incident pressure, result in greatly enhanced contrast between the vessels that contain the ultrasound contrast agent and the surrounding tissues, rendering perfusion defects highly visible. SonoVue (Bracco, Milan, Italy) is a new echocontrast agent with outstanding stability. Thanks to their very flexible shell, the SonoVue microbubbles are able to generate strong harmonics even when insonated at extremely low mechanical index (MI). The present review illustrates the different modalities of contrast bubble insonation (at high and low MI), which allow visualization of fixed defects and ischaemic or infarcted areas of the myocardium in real-time.

Ultrasound Imaging with SonoVue: Low Mechanical Index Real-Time Imaging

Ultrasound contrast specific imaging was improved in the last years by the introduction of a wealth of novel techniques, exploiting the nonlinear response of microbubble contrast agents. This included a number of techniques based on transmission of alternately phased positive and negative pulses ( 1 Bauer A Hauff P Lazenby J et al. Wideband harmonic imaging: a novel contrast ultrasound imaging technique. Eur Radiol. 1999; 9: S364-S367 Crossref PubMed Google Scholar , 3 Burns PN Wilson SR Simpson DH Pulse inversion imaging of liver blood flow: improved method for characterizing focal masses with microbubble contrast. Invest Radiol. 2000; 35: 58-71 Crossref PubMed Scopus (326) Google Scholar ) (Phase Inversion, Pulse Inversion, Power Pulse Inversion, Wideband harmonic, Coherent Contrast Imaging) as well as techniques based on alternating transmit power (Power Modulation, B Flow) and using higher harmonics ( 2 Bouakaz A Frigstad S Ten Cate FJ de Jong N Super harmonic imaging: a new imaging technique for improved contrast detection. Ultrasound Med Biol. 2002; 28: 59-68 Abstract Full Text Full Text PDF PubMed Scopus (192) Google Scholar ) (Ultraharmonic Imaging). Other techniques are based on the destruction of microbubbles (Agent Destruction Imaging) or can be used to image microbubbles in this way (power/Color Doppler -Loss of correlation) ( 6 Schlachetzki F Hoelscher T Dorenbeck U et al. Sonographic parenchymal and brain perfusion imaging: preliminary results in four patients following decompressive surgery for malignant middle cerebral artery infarct. Ultrasound Med Biol. 2001; 27: 21-31 Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar ) and therefore are limited to a relatively high mechanical index. The destructive techniques are further limited to low framerate or triggered imaging ( 5 Masugata H Lafitte S Peters B Strachan GM DeMaria AN Comparison of real-time and intermittent triggered myocardial contrast echocardiography for quantification of coronary stenosis severity and transmural perfusion gradient. Circulation. 2001; 104: 1550-1556 Crossref PubMed Scopus (63) Google Scholar ), thereby losing one of the key advantages of ultrasound: its realtime capability.

Bubbles and microcirculatory disorders.

Doppler methods are in daily clinical use for the assessment of blood flow in various vessels. With the adjunct of an ultrasound (US) contrast agent, weaker signals, for instance in smaller vessels, can be detected. However, even in the presence of an US contrast agent, colour, spectral or even power Doppler can only detect blood flow in vessels exceeding 200‐300 µm. The microvasculature is not detectable because the flow velocity in capillaries, at approximately 1 mm/s, is actually lower than the tissue motion velocity and is therefore filtered out by the equipment. It was recently demonstrated that using US contrast agents, together with novel bubble-specific imaging modes, allows the blood flow detection threshold to be lowered and the presence of microbubbles even in very small vessels to be detected. Detection of flow in such smaller vessels increases considerably the clinical utility of US, in particular for the detection of reductions in vascularity, for instance in ischaemic or infarcted tissues, or increases in vascularity, for instance in tumor angiogenesis. These bubble-specific methods, which have emerged from extensive research carried out on US contrast agents during the last decade, make use of the nonlinear properties of bubbles. Harmonic B-mode, harmonic power Doppler, phase or pulse inversion, power pulse inversion, coherent contrast imaging, and power modulation are some of the most popular of these novel imaging methods. By detecting specifically bubble signals and reducing the background signals from the surrounding structures, these methods dramatically enhance the image contrast-to-tissue ratio. Studies making use of contrast agents in combination with harmonic power Doppler have shown that vessels of approximately 40 µm in diameter can be detected in the kidney [1]. Pulse inversion imaging provides an even better resolution than harmonic imaging. Moreover, it allows the use of low-power pulses, thus preventing bubble destruction. In the following article, the new opportunities offered by the combination of new US contrast agents and novel imaging modes will be illustrated by a number of studies carried out with SonoVue, a novel ultrasound contrast medium constituted by phospholipid-stabilized microbubbles of sulfur hexafluoride (SF6) [2].

Future directions in ultrasound contrast agent research

Since the introduction of Levovist® in Europe and Albunex® in the United States, interest in ultrasound contrast agents has increased enormously. This change is reflected in the ensuing rapid pace of technical development, and the depth of the discussions during this topical meeting. Before Albunex®, it was essentially impossible to convince an equipment manufacturer to devote time to the development of contrast-specific imaging modalities. After Albunex®, harmonic gray-scale imaging was in the clinic within the year, followed by harmonic color Doppler imaging, power Doppler, pulse inversion gray scale, pulse inversion Doppler, power modulation, coherent contrast imaging, and so on. The trend continues today as old techniques are improved, new techniques (e.g., subharmonic imaging) are tested and new approaches (e.g., phase-shift imaging) are conceived. Similarly, rapid advances have occurred in other areas, with models now including the details of shell viscoelasticity, in vitro studies now imaging single bubble dynamics to microsecond resolution, and specially designed microbubbles being used for targeted imaging, drug delivery, and gene therapy. Even bioeffects research has ‘‘advanced’’ with the discovery of imaging-modality-dependent contrast agent effects such as induction of premature ventricular contractions. Selected aspects of each of these areas will be discussed.