SHU 508, a transpulmonary echocontrast agent: initial experience

Efficacy of Contrast-Enhanced Endoscopic Ultrasonography for the Diagnosis of Pancreatic Tumors

Endoscopic ultrasound can be useful for obtaining detailed diagnostic images for pancreatic disease. Contrast-enhanced harmonic endoscopic ultrasound has allowed to demonstrate not only microvasculature but also real perfusion imaging using second-generation contrast agents. Furthermore, endoscopic ultrasound fine-needle aspiration cytology and histology have become more ubiquitous; however, the risk of dissemination caused by paracentesis has yet to be resolved, and the application of less invasive contrast-enhanced endoscopic ultrasound for the differential diagnosis of pancreatic tumors has been anticipated. Contrast-enhanced harmonic endoscopic ultrasound can contribute to the differential diagnosis of pancreatic tumors.

Safety of ultrasound contrast agents in patients with known or suspected cardiac shunts

Contrast-enhanced ultrasound imaging is a radiation-free diagnostic tool that uses biocompatible ultrasound contrast agents (UCAs) to improve image clarity. UCAs, which do not contain dye, often salvage "technically difficult" ultrasound scans, increasing the accuracy and reliability of a front-line ultrasound diagnosis, reducing unnecessary downstream testing, lowering overall health care costs, changing therapy, and improving patient care. Two UCAs currently are approved and regulated by the US Food and Drug Administration. They have favorable safety profiles and risk/benefit ratios in adult and pediatric populations, including compromised patients with severe cardiovascular diseases. Nevertheless, these UCAs are contraindicated in patients with known or suspected right-to-left, bidirectional, or transient right-to-left cardiac shunts. These patients, who constitute 10% to 35% of the general population, typically receive no UCAs when they undergo echocardiography. If their echocardiographic images are suboptimal, they may receive inappropriate diagnosis and treatment, or they may be referred for additional diagnostic testing, including radiation-based procedures that increase their lifetime risk for cancer or procedures that use contrast agents containing dye, which may increase the risk for kidney damage. An exhaustive review of current peer-reviewed research demonstrated no scientific basis for the UCA contraindication in patients with known or suspected cardiac shunts. Initial safety concerns were based on limited rodent data and speculation related to macroaggregated albumin microspheres, a radioactive nuclear imaging agent with different physical and chemical properties and no relation to UCAs. Radioactive macroaggregated albumin is not contraindicated in adult or pediatric patients with cardiac shunts and is routinely used in these populations. In conclusion, the International Contrast Ultrasound Society Board recommends removal of the contraindication to further the public interest in safe, reliable, radiation-free diagnostic imaging options for patients with known or suspected cardiac shunts and to reduce their need for unnecessary downstream testing.

Surgical resection for small hepatocellular carcinoma in cirrhosis: the Eastern experience

Detection of small Hepatocarcinoma (HCC) by screening of high-risk populations is important to increase the percentage of patients suitable for curative treatment, which would lead to prolongation of the mean survival of patients with HCC. It should be remembered that small HCC is not always necessarily equivalent to early HCC as defined histologically. With recent advances in diagnostic imaging modalities, including contrast-enhanced ultrasonography and magnetic resonance imaging with liver-specific contrast enhancement, accurate differential diagnosis of early HCCs from dysplastic nodules has become possible. Because a certain proportion of small HCCs is known to show microscopic vascular invasion, surgical resection would be the treatment of first choice. To minimize potential microscopic invasion, anatomic resection and/or resection with a wide margin should be performed, while preserving liver function to the maximum extent possible. Surgical resection, however, cannot prevent multicentric occurrence of HCC, which remains a major issue precluding curative treatment of HCC.

Vascularisation pattern of chronic pancreatitis compared with pancreatic carcinoma: results from contrast-enhanced endoscopic ultrasound

Discriminating between focal chronic pancreatitis and pancreatic cancer is always a challenge in clinical medicine. Contrast-enhanced endoscopic ultrasound using Doppler techniques can uniquely reveal different vascularisation patterns in pancreatic tissue alterated by chronic inflammatory processes and even allows a discrimination from pancreatic cancer. This paper will describe the basics of contrast-enhanced high mechanical index endoscopic ultrasound (CEHMI EUS) and contrast enhanced low mechanical index endoscopic ultrasound (CELMI EUS) and explain the pathophysiological differences of the vascularisation of chronic pancreatitis and pancreatic carcinoma. Furthermore it will discuss how to use these techniques in daily clinical practice.

Ultrasound microbubble contrast agents: application to therapy for peripheral vascular disease

Ultrasound contrast agents are not only effective in ultrasonic imaging but are also important tools for drug or gene delivery. Ultrasound beams can disrupt microbubbles and cell membranes, offering the opportunity to locally deliver drugs or genes. Liposome-shelled microbubbles have many advantages and are widely used in many applications, while Lipofectamine (Invitrogen, Life Technologies, Carlsbad, CA, USA), as a material of microbubble membranes, has been used to enhance the effects of gene delivery. Ultrasound contrast agents that have therapeutic effects can be used for treating peripheral vascular diseases, particularly in thrombotic and angiogenic diseases. A combination of targeted contrast agent and drug-carrying contrast agent may be safer and more effective in treating thrombosis. Vascular endothelial growth factor-loaded microbubbles are expected to treat a variety of neovascular diseases such as severe limb ischemia and other diseases. Although there are several limitations in the application of therapeutic ultrasound microbubble contrast agents, it will offer a new hope for the treatment of peripheral vascular disease.

Stable polymeric microballoons as multifunctional device for biomedical uses: synthesis and characterization

Gas filled hollow microparticles, i.e., microbubbles and microballoons, are soft matter devices used in a number of diverse applications ranging from protein separation and purification in food science to drilling technology and ultrasound imaging. Aqueous dispersions of these mesoscopic systems are characterized by the stabilization of the air/water interface by a thin shell of phospholipid bilayer or multilayers or by a denatured and cross-linked proteic matrix. We present a study of a type of microballoons based on modified poly(vinyl alcohol), PVA, a synthetic biocompatible polymer, with new structural features. A cross-linking reaction carried out at the air/water interface provides polymeric air-filled microbubbles with average dimensions depending on the reaction temperature. Characterization of diameters and shell thicknesses for microbubbles obtained at different temperatures has been carried out. Conversion to solvent-filled hollow microcapsules is possible by soaking microbubbles in dimethyl sulfoxide. Microcapsules permeability to fluorescent labeled dextran molecular weight standards was correlated to the mesh size of the polymer network of the shell. Microbubbles were covalently grafted under very mild conditions with beta-cyclodextrin and poly-l-lysine with a view to assay the capability of the device for delivery of hydrophobic drugs or DNA. PVA based microballoons show a remarkable shelf life of several months, their external surface can be decorated with many biologically relevant molecules. These features, together with a tested biocompatibility, make them attractive candidates for use as multifunctional device for diagnosis and therapeutic purposes, i.e., as ultrasound reflectors in ecographic investigation and as drug platforms for in situ sonoporation.

Sonovue improves endocardial border detection and variability in assessing wall motion score and ejection fraction during stress echocardiography

BACKGROUND

Stress echocardiography is useful for assessing patients with coronary artery disease unable to undergo formal exercise testing. Considerable skill is required to avoid large intra- and inter-observer variability due to poor endocardial definition. Intravenous ultrasound contrast agents are now available which may improve this variability.

AIM

To study intravenous Sonovue in assessing wall motion score and ejection fraction (EF) during stress echocardiography.

METHODS

Thirty-eight patients undergoing arbutamine stress echocardiography for known or suspected coronary artery disease were studied. Echocardiographic analysis of wall motion score index, endocardial border detection (EBD) and EF was performed at rest and at peak stress before and after intravenous injection of Sonovue, by experienced and inexperienced observers.

RESULTS

All three observers noted an improvement in endocardial border definition following Sonovue (p=<0.001). At baseline, there was a significant difference in wall motion score index between experienced and inexperienced observers at rest (p=0.01) and at peak stress (p=0.001). Following Sonovue administration this was no longer significant (p=0.07, p=0.114). Intra-observer variability of end diastolic, end systolic volumes (ESV) and EF improved following contrast (p<0.05) at rest and during stress.

CONCLUSION

Sonovue significantly improved EBD and reduced intra-observer variability of EF at rest and during peak arbutamine infusion.

Contrast-enhanced power Doppler harmonic imaging--influence on visualization of renal vasculature

To compare contrast-enhanced power Doppler (PD) harmonic imaging (CHI) with contrast-enhanced power Doppler fundamental imaging (CPD) in the depiction of renal cortical vessels, 20 healthy volunteers were subjected to PD imaging and HI assessment of the kidney after bolus injection of Levovist(R) (SH U 508A). System settings were standardized and the pulse-repetition frequencies (PRF) systematically toggled from 750 to 500 and 250. Videotapes were independently reviewed by three readers with regard to the presence of artefacts, the degree of Doppler signal enhancement, demarcation of vessels and the extent of visualization. The assessments were graded separately for each PRF in accordance with a multistage scoring system. In comparison to contrast-enhanced PD, artefacts were significantly lower with CHI for all PRF (p = 0.0001). Vessels were better visualized (p = 0.002) and less blurred (p = 0.006) with CHI than with CPD. There was no significant difference in the extent of Doppler signal increase between CPD and the contrast-enhanced harmonic mode. Combination of the contrast-enhanced harmonic method and PD allows the PRF to be lowered and, by balancing the greater susceptibility of PD to interference from clutter, increases the likelihood of detection of flow in small vessels.

Hepatocellular carcinoma treated with chemoembolization: assessment with contrast-enhanced doppler ultrasonography

PURPOSE

To report our preliminary experience concerning the use of Doppler ultrasonography (DUS) techniques after intravenous injection of the galactose-based contrast agent Levovist in the assessment of hepatocellular carcinoma (HCC) treated with transcatheter arterial chemoembolization (TACE). The sonographic findings are correlated with those obtained using iodized oil (Lipiodol) helical computed tomography (CT).

METHODS

For 7 months we studied 28 patients with cirrhosis and HCC (a total of 43 nodules) who had undergone TACE between 18 and 30 days previously. The lesions were investigated with color Doppler ultrasonography (CDUS) and power Doppler ultrasonography (PDUS), before and after infusion of the echo-contrast agent (300 mg/ml, maximum 1 injection for each nodule, administered at constant velocity within 60-90 sec), and with helical Lipiodol-CT (0-7 days after DUS). In the retrospective analysis, special attention was given to the Doppler signals related to pulsatile intra- and perinodular flow and to the detection of new vessels after contrast agent injection. The signal intensity was graded as 0 (absent), 1 (low), 2 (medium), or 3 (high), while its distribution was classified as peripheral, central, or diffuse. Oily agent retention on CT scans was assessed as 0 (absent), I (<10%), II (<50%), III (>50%), or IV (homogeneous). These scores were awarded separately, without knowledge of the other judgments.

RESULTS

An hepatic global echo-enhancing effect was identified in all cases and always lasted long enough to allow an accurate analysis of all parenchymal lesions (at least 8 min). The signal scores could be evaluated in 39 of 43 HCCs, as follows: basal CDUS: grade 0 in 17 lesions, grade 1 in 16, grade 2 in 6; contrast-enhanced CDUS: grade 0 in 12 lesions, grade 1 in 10, grade 2 in 14, grade 3 in 3; basal PDUS: grade 0 in 15 lesions, grade 1 in 13, grade 2 in 9, grade 3 in 2; contrast-enhanced PDUS: grade 0 in 11 lesions, grade 1 in 9, grade 2 in 15, grade 3 in 6. Lipiodol-CT scoring was: grade 0 in 1 lesion, grade I in 7, grade II in 11, grade III in 9, grade IV in 11. In all but one nodule the difference between CDUS and PDUS scores, compared both with each other and with nonenhanced and contrast-enhanced examinations, was never greater than one grade.

CONCLUSIONS

Contrast-enhanced DUS is a simple and fast procedure allowing a valuable, constant echo-enhancing effect of sufficient duration. DUS techniques, especially contrast-enhanced PDUS, offer an effective and realistic analysis of HCC nodules treated with TACE and show more evident agreement with Lipiodol-CT findings than baseline studies.

Use of intravenous contrast material in transcranial sonography

RATIONALE AND OBJECTIVES

The appearance of the intracranial vasculature was compared on power and color Doppler ultrasound (US) scans obtained with and without a microbubble contrast agent.

MATERIALS AND METHODS

Nine patients (three men, six women) aged 42-70 years (mean age, 53 years) participated in the study. Seven patients underwent both color Doppler US and power Doppler US before and after intravenous administration of contrast agent, and two underwent only color Doppler US. All patients had previously undergone cerebral angiography.

RESULTS

Before contrast material was administered, power Doppler US was more sensitive than color Doppler US in the detection of intracranial vessels (P < .05); neither technique depicted the entire circle of Willis in eight of nine patients. Postcontrast power Doppler US depicted more vascular segments than postcontrast color Doppler US (P < .01) or precontrast power Doppler US (P < .01). Use of intravenous contrast material enabled the entire circle of Willis to be evaluated from a single temporal bone acoustic window with both power Doppler US and color Doppler US in all patients. Contrast-enhanced power Doppler US depicted vessels not shown by enhanced color Doppler US.

CONCLUSION

Contrast-enhanced power Doppler US depicted more vessels, better demonstrated specific vascular segments, and provided better vascular definition of the intracranial vasculature than contrast-enhanced color Doppler US or unenhanced power Doppler US.

Human biodistribution of an ultrasound contrast agent (Quantison) by radiolabelling and gamma scintigraphy

The biodistribution and kinetics of an air filled human serum albumin microcapsule formulation (Quantison) intended for use as an intravenous ultrasound contrast agent have been examined. 12 healthy subjects were administered with approximately 50 million microcapsules per kilogram body weight, radiolabelled with 50 MBq 123I. Imaging was performed over a period of 58 h using a large field-of-view gamma camera and the amount of labelled material present in the blood, urine and faeces measured. Imaging demonstrated that the liver was the organ with the highest uptake, with a mean uptake of 41.8% (SD 10.4%) of the administered dose 1 h following administration. The maximum uptake of the agent in the lungs was low, mean 4.0% (SD 3.4%). A small amount of uptake was visible in the bone marrow; however, this was not quantifiable. There was also evidence of minimal myocardial activity within 5 min of administration. No adverse events were observed and there were no changes in any of the individual post-study indices. The present study demonstrates the safety of Quantison. Gamma scintigraphy played a useful role in confirming the biodistribution of the agent with little lung uptake, high liver uptake and evidence of myocardial uptake.

Possibility of differentiating small hyperechoic liver tumours using contrast-enhanced colour Doppler ultrasonography: a preliminary study

We performed a preliminary study to investigate the possibility of differentiating small hyperechoic liver tumours, including hepatocellular carcinomas (HCCs), haemangiomas and focal fatty lesions, by administering a galactose-based contrast agent (SH/TA-508 (Levovist)) during colour Doppler ultrasonography (US). Ten patients (age range: 48-81 years) with small liver tumours (four HCCs, four hemangiomas and two focal fatty lesions) of less than 20 mm in diameter presented with hyperechoic masses with no intratumoural colour signals on conventional colour Doppler US. All patients subsequently underwent colour Doppler US with this contrast agent. Colour Doppler images of the tumours were assessed before and after the intravenous injection of 8 ml of the contrast agent at a concentration of 400 mg/ml. Prior to injection of the contrast agent, no intratumoural colour signals were observed in any cases. After injection, intratumoural colour signals appeared in all HCCs and in two haemangiomas with tumour-margin enhancement. The enhanced colour signals appeared to be related to cardiac contraction in the HCCs, but not in the haemangiomas. In the remaining two haemangiomas, only tumour-margin enhancement was observed. In the focal fatty lesions, neither intratumoural nor tumour-margin enhancement was observed. These results, although preliminary, suggest that the detection of colour Doppler signals is improved by using a contrast agent and the differences between enhanced colour signals from HCCs and haemangiomas may help differentiate hyperechoic HCCs from other hyperechoic tumours, including haemangiomas and focal fatty lesions.

New technology in echocardiography II: imaging techniques

Images

Myocardial contrast echo effect: the dilemma of coronary blood flow and volume

Despite the useful information provided by myocardial contrast echocardiography, the meaning of myocardial contrast intensity remains elusive. This review is meant to define the contribution of physical and biologic factors in producing myocardial contrast and to elucidate the relative roles of coronary blood flow and intramyocardial blood volume in determining contrast effect. The main physical factors influencing the contrast echo effect include the properties of microbubbles as scattering elements (mainly their radius, compressibility, stability and concentration), electronic signal processing, instrument setting and contrast-induced signal attenuation. The effect of these factors can be limited by an appropriate experimental or clinical setup. Biologic factors are less easily controllable, and changes in coronary blood flow and alterations in myocardial blood volume appear to be the main determinants of myocardial contrast intensity. Moreover, these factors influence contrast intensity in opposite directions. Both the area under the time-intensity curve and the mean transit time of myocardial contrast are inversely related to coronary blood flow but directly related to myocardial vascularity and blood volume. Therefore, an increase in coronary flow not accompanied by an increase in myocardial vascularity and volume is accompanied by a decrease in the area under the curve and mean transit time of contrast. Conversely, an increase in coronary flow mediated by augmented myocardial vascularity and volume will produce an increase in the area under the curve and mean transit time. A better understanding of the physical and biologic determinants of contrast echo intensity will be fundamental in the clinical application of new agents and technologies.

First experience with a new echographic contrast agent

The intravenous injection of an ultrasound contrast agent can enhance signals from blood flow. Broad toxicological and pharmaceutical studies in animals confirmed the safety and efficacy of an ultrasound contrast agent made of microparticles of galactose with stabilised microbubbles in watery suspension (SH U 508 A). In this paper 10 patients with different malignant orbital and ocular tumours have been evaluated with an echo colour Doppler machine before and after the injection of SH U 508 A. An enhancement of the Doppler signals in the lesions in different degrees has been detected. This echographic contrast agent seems to be very important not only in the evaluation of vascular lesions, but also in evaluating the effectiveness of radiotherapy in malignant tumours and could spread the echographic indications in several other ophthalmic fields.

Increased sensitivity of flow detection in the left coronary artery by transesophageal echocardiography after intravenous administration of transpulmonary stable echocontrast agent

Transesophageal echocardiography (TEE) combined with color and pulsed Doppler allows a noninvasive assessment of flow in the proximal anterior descending coronary artery (LAD). The aim of this study was to assess whether the peripheral administration of a transpulmonary stable echocontrast agent with prolonged in vivo stability may improve the feasibility and accuracy of coronary flow detection by TEE Doppler. In 12 out of 14 consecutive patients undergoing routine diagnostic TEE examination, color-coded images of left main coronary artery (LM) and the origin of the LAD and circumflex artery (CXA), as well as spectral Doppler signals from the LAD, were evaluated before and after intravenous injection of SHU 508 A. After administration of echocontrast material, the coronary Doppler signal (both color-coded and spectral) was enhanced for approximately 100 seconds. The length and diameter of color-coded flow increased significantly in the LM, LAD, and CXA. (The length of color-coded flow before and after injection of contrast material were the following: in LM 0.94 +/- 0.44 versus 1.39 +/- 0.52 cm, p < 0.001; in LAD 0.68 +/- 0.36 versus 1.20 +/- 0.41 cm, p < 0.001; and in CXA 0.54 +/- 0.20 versus 1.06 +/- 0.86 cm; in this artery, color-coded flow was visualized only in six patients before and 11 patients after injection of contrast material. The corresponding values for the diameters of color-coded flow in LM were 0.36 +/- 0.08 versus 0.46 +/- 0.09 cm, p < 0.001; in LAD 0.29 +/- 0.07 versus 0.41 +/- 0.1 cm, p < 0.002; and in CXA 0.26 +/- 0.05 versus 0.40 +/- 0.04 cm.) By pulsed Doppler, significant increments in peak diastolic (47.8 +/- 21.3 versus 37.2 +/- 14.5 cm/sec, p < 0.05), mean diastolic (37.4 +/- 14.7 versus 27.9 +/- 8.4 cm/sec, p < 0.005), mean systolic flow velocity (23.2 +/- 6.8 versus 19.0 +/- 4.7 cm/sec, p < 0.005), and diastolic (11.0 +/- 3.9 versus 7.7 +/- 3.0 cm, p < 0.001) and total flow integral (16.8 +/- 5.3 versus 10.5 +/- 4.6 cm, p < 0.001) were observed. By contrast, peak systolic velocity did not increase. However, the systolic component of coronary flow, detectable in 7 out of 12 patients before injection of contrast material, became detectable in all 12 patients after injection of contrast material.(ABSTRACT TRUNCATED AT 400 WORDS)

Improved Doppler signal intensity in coronary arteries after intravenous peripheral injection of a lung-crossing contrast agent (SHU 508A)

OBJECTIVES

We tested the hypothesis that SHU 508A, a new lung-crossing contrast agent capable of increasing the Doppler signal to noise ratio in the right heart as well as left heart cavities after intravenous injection, could increase Doppler signal intensity in coronary arteries, thus improving the feasibility and quality of transesophageal Doppler echocardiographic evaluation of coronary blood flow velocity.

BACKGROUND

Coronary blood flow velocity can be evaluated by transesophageal Doppler echocardiography. However, an adequate Doppler tracing is obtainable in a relatively low percent of patients.

METHODS

Transesophageal Doppler echocardiography of coronary arteries was performed in 35 patients before and after SHU 508A injection at four different dosages (200 mg/ml in 5 ml, 200 mg/ml in 10 ml, 300 mg/ml in 5 ml and 300 mg/ml in 10 ml). Color Doppler mapping of coronary flow and pulsed wave Doppler measurement of coronary blood flow velocity were attempted in all patients.

RESULTS

Color Doppler flow mapping of 105 evaluated coronary segments (left main, left anterior descending and circumflex in 35 patients) was not detectable or was weak in 88% of patients before and 33% of patients after echo contrast injection (p < 0.0001); it was optimal (that is, well delineated with complete flow mapping of the explored vessel) in only 11% of patients before and 67% after echo contrast injection (p < 0.0001). In addition, pulsed wave Doppler signal quality improved after echo contrast injection: Pulsed wave Doppler recording of coronary blood flow velocity was not obtainable or was weak in 78% of cases before and 34% after echo contrast injection (p < 0.0001); pulsed wave Doppler recording of coronary blood flow velocity was optimal (that is, there was a complete and well defined outline of diastolic coronary blood flow velocity in 23% of cases before and 66% after echo contrast injection [p < 0.0001]. Both length and width of color Doppler mapping in the left anterior descending coronary artery increased after SHU 508A injection (from 5.75 +/- 5.32 and 1.51 +/- 1.17 to 17.04 +/- 8.76 and 4.21 +/- 1.78 mm, respectively, mean +/- SD, p < 0.0001).

CONCLUSIONS

The feasibility and quality of recording coronary blood flow velocity by transesophageal Doppler echocardiography are considerably improved by intravenous injection of SHU 508A. The improved feasibility of this new semi-invasive method for evaluating coronary blood flow velocity and flow reserve can considerably increase its research and clinical utilization.

Contrast echocardiography

Myocardial contrast echocardiography (MCE) is an ultrasound imaging technique which promises to provide a safe, noninvasive means of assessing myocardial perfusion. A contrast agent, consisting of a suspension of air-filled microspheres, serves as an ultrasound tracer. When these microspheres are injected intravascularly, the acoustic interface created between the blood and the microspheres enhances the reflected ultrasound signals. Thus, the flow pattern of the microspheres represent the actual blood flow patterns. This paper will review the field of contrast echocardiography, its background and history, the development of ultrasound contrast agents, and a variety of experimental as well as clinical uses. Contrast echocardiography has been utilized in the cardiac catheterization laboratory for the assessment of "risk area," assessment of collateral blood flow and assessment of coronary blood reserve. In the operating room, contrast echo is utilized for the determination of cardioplegic perfusion, assessment of graft patency and evaluation of valvular regurgitation. In the future, with the technical advancement in ultrasound imaging and the active interest and growth in the field of myocardial perfusion imaging using contrast echocardiography, the ability to provide routine real-time perfusion imaging may become a reality.

Pitfalls in quantitative contrast echocardiography: the steps to quantitation of perfusion

Current methods used clinically to assess myocardial perfusion are invasive and expensive. As the technology of ultrasound imaging improves, CE may provide a relatively inexpensive, noninvasive means of quantitating myocardial perfusion. Issues regarding stability of microbubble contrast agents must be studied more closely under physiologic conditions. As such, encapsulated microbubbles may provide more stability under physiologic pressures than free gas microbubbles. Introducing high concentrations of contrast, either by hyperconcentrating the contrast agent or by increasing the injection rate, may provide greater stability under physiologic conditions. Further, before quantitative statement of tissue perfusion can be made, the relationship between tracer concentration and system response must be established. Further, a "linear" postprocessing ultrasound setting does not eliminate this requirement as data must still undergo nonlinear transformation during log compression and time-gain compensation. Additionally, issues regarding "electronic thresholding" must be explored more extensively in vivo. Commercial ultrasound scanners, in their present form, may not offer adequate sensitivity for absolute quantitative studies. Further development of modified ultrasound systems may provide sufficient sensitivity for quantitative perfusion imaging. CE offers a potentially powerful tool in the clinical management of patients with ischemic heart disease. Conventional coronary angiography provides information on the size of a lesion, but accompanying tissue perfusion distal to the lesion cannot be determined. Doppler ultrasonography determines velocity of blood flow in large vessels but does not offer the potential to quantitate tissue perfusion. Clearly, CE has a place in the future of diagnostic imaging. The recent work of Ito et al. demonstrated the qualitative potential of CE in the identification of "areas at risk" in patients who had undergone thrombolysis or percutaneous transluminal coronary angioplasty after an acute myocardial infarction. With further improvement in the ultrasound imaging techniques and microbubble stability, CE may offer an inexpensive, noninvasive means of assessing myocardial perfusion.

Contrast-enhanced transcranial color-coded real-time sonography. Results of a phase-two study

BACKGROUND AND PURPOSE

Transcranial color-coded real-time sonography has been developed as a promising new bedside procedure to monitor central nervous system parenchymal and vascular pathology; the present study was designed to investigate the potential role of galactose microparticles (SH U 508 A) as a new ultrasound contrast-enhancing agent for transcranial sonography.

METHODS

Ten patients (four women and six men, 24-63 years of age) with a broad spectrum of central nervous system pathology were investigated by transcranial color-coded real-time sonography in a phase-two clinical study. After conventional ultrasound examination, all patients received a maximum of six injections of 10 ml with 200, 300, or 400 mg/mL SH U 508 A. The intracranial vessels were scanned by color flow imaging in the axial and coronal planes through a transtemporal acoustic bone window; in addition, the vertebrobasilar system was followed through the foramen magnum.

RESULTS

SH U 508 A was well tolerated without side effects. In axial and coronal scans, the application of SH U 508 A resulted in detection of peripheral branches of the anterior, middle, and posterior cerebral arteries, as well as the posterior communicating and superior cerebellar arteries. In addition, the deep cerebral veins (i.e., inferior sagittal sinus, internal cerebral veins, great cerebral vein of Galen, straight sinus, and the confluence sinuum) were revealed. The transforaminal approach led to detection of the main infratentorial branches (anterior inferior, posterior inferior, and superior cerebellar arteries). One patient could not be insonated without contrast, but after SH U 508 A the trunks of the large intracranial arteries were detected. No obvious changes in the ultrasound pattern of the central nervous system parenchyma were observed.

CONCLUSIONS

These preliminary data indicate that the use of a transpulmonary ultrasound contrast agent (SH U 508 A) may substantially broaden the spectrum and potential diagnostic utility of transcranial ultrasound by allowing detection of supratentorial peripheral central nervous system arteries, deep cerebral veins, and (through the foramen magnum) the entire vertebrobasilar system, including the cerebellar arteries.