Low Mechanical Index Research Articles

2310 USEFULNESS OF CONTRAST-ENHANCED ULTRASOUND USING A TIME- INTENSITY CURVE FOR THE DIAGNOSIS OF CYSTIC RENAL CELL CARCINOMA

You have accessJournal of UrologyImaging/Radiology: Uroradiology1 Apr 20112310 USEFULNESS OF CONTRAST-ENHANCED ULTRASOUND USING A TIME- INTENSITY CURVE FOR THE DIAGNOSIS OF CYSTIC RENAL CELL CARCINOMA Shigeyuki Aoki, Genya Nishikawa, Takahiko Yoshizawa, Yoshiharu Kato, Kenji Zennami, Motoi Tobiume, Kogenta Nakamura, Yoshiaki Yamada, Nobuaki Honda, Tokunori Yamamoto, Rhohei Hattori, and Momokazu Gotoh Shigeyuki AokiShigeyuki Aoki Aichi, Japan More articles by this author , Genya NishikawaGenya Nishikawa Aichi, Japan More articles by this author , Takahiko YoshizawaTakahiko Yoshizawa Aichi, Japan More articles by this author , Yoshiharu KatoYoshiharu Kato Aichi, Japan More articles by this author , Kenji ZennamiKenji Zennami Aichi, Japan More articles by this author , Motoi TobiumeMotoi Tobiume Aichi, Japan More articles by this author , Kogenta NakamuraKogenta Nakamura Aichi, Japan More articles by this author , Yoshiaki YamadaYoshiaki Yamada Aichi, Japan More articles by this author , Nobuaki HondaNobuaki Honda Aichi, Japan More articles by this author , Tokunori YamamotoTokunori Yamamoto Nagoya, Japan More articles by this author , Rhohei HattoriRhohei Hattori Nagoya, Japan More articles by this author , and Momokazu GotohMomokazu Gotoh Nagoya, Japan More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.2556AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES On imaging differentiation, cystic renal cell carcinoma remains a common and difficult diagnostic problem. We assessed the usefulness of contrast-enhanced ultrasound (CEUS) for the diagnosis of cystic renal cell carcinoma by using a time-intensity curve. METHODS CEUS was performed in 30 patients, who had renal masses detected by ultrasound (US) or computed tomography (CT). In all, 10 of the 30 patients had cystic renal masses. The CT images were assessed using the Bosniak classification. The 10 cystic renal masses were categorized by CT as follows: Bosniak category IIF (n=2), category III (n=3) and category IV (n=5). The final diagnosis of all patients was pathologically confirmed using tissue specimens obtained from radical or partial nephrectomy. CEUS was performed prior to surgery using high-resolution US units (LOGIQ 7 [GE Medical Systems; Milwaukee, WI, USA]) equipped with hybrid contrast imaging. The US contrast agent perflubutane (Sonazoid®,Daiichi-Sankyo, Tokyo, Japan) was intravenously administered by bolus injection (0.015ml/kg). To reduce microbubble destruction, a low mechanical index (0.4) was used. Real-time scanning commenced immediately after the injection of the contrast agent. Contrast enhancement as a function of time was measured in two (tumor or solid component of cystic lesions and normal parenchyma) circular regions of interest (ROI) and time-intensity curves were obtained. The time to the contrast enhancement peak (TTP), intensity change from the baseline to peak (ΔI), and ΔI / TTP of the tumor and the normal parenchyma were measured from the time-intensity curve and compared statistically. RESULTS The pathologic diagnosis were renal cell carcinoma in 30 patients. In subgroups of patients with solid and cystic tumors, the TTP of the tumor was significantly shorter than that of the normal parenchyma in all cases (mean seconds [s] ±SD: 5.8±1.6 vs. 10.0±2.9; p<0.0001). There was no ΔI difference between the tumor and normal parenchyma (mean decibels [db] ±SD: 22.3±6.0 vs. 20.5±7.2; p=0.68); the ΔI / TTP of the tumor was significantly higher than that of the normal parenchyma (mean db/s±SD: 4.1±1.4 vs. 2.2±1.1; p<0.0001). The time-intensity curve patterns of solid and cystic cancers were very similar. CEUS demonstrated a well-enhancing mural nodule within the lesion in two cystic tumors diagnosed as Bosniak category IIF. CONCLUSIONS Contrast-enhanced ultrasound using a time-intensity curve is a promising tool in the diagnosis of cystic renal cell carcinoma. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e926 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Shigeyuki Aoki Aichi, Japan More articles by this author Genya Nishikawa Aichi, Japan More articles by this author Takahiko Yoshizawa Aichi, Japan More articles by this author Yoshiharu Kato Aichi, Japan More articles by this author Kenji Zennami Aichi, Japan More articles by this author Motoi Tobiume Aichi, Japan More articles by this author Kogenta Nakamura Aichi, Japan More articles by this author Yoshiaki Yamada Aichi, Japan More articles by this author Nobuaki Honda Aichi, Japan More articles by this author Tokunori Yamamoto Nagoya, Japan More articles by this author Rhohei Hattori Nagoya, Japan More articles by this author Momokazu Gotoh Nagoya, Japan More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Real-Time Ultrasound Brain Perfusion Imaging with Analysis of Microbubble Replenishment in Acute MCA Stroke

Real-time ultrasound perfusion imaging (rt-UPI) allows visualization of microbubbles flowing through the cerebral microvasculature. We hypothesized that analysis of microbubble tissue replenishment would enable for characterization of perfusion deficits in acute middle cerebral artery (MCA) territory stroke. Twenty-three patients (mean age 70.2 ± 13.2 years, 9 weeks) were included. Sequential images of bubble replenishment were acquired by transcranial rt-UPI at low mechanical index immediately after microbubble destruction. Different parameters were calculated from regions of interest (ROIs): real-time time to peak (rt-TTP), rise rate (β), and plateau (A) of acoustic intensity, and A × β was used as an index of blood flow. Results were compared with diffusion-weighted and perfusion magnetic resonance imaging. Parameters of rt-UPI had lower values in ROIs of ischemic as compared with normal tissue (β=0.58 ± 0.40 versus 1.25 ± 0.83; P=0.001; A=1.44 ± 1.75 versus 2.63 ± 2.31; P=0.05; A × β=1.14 ± 2.25 versus 2.98 ± 2.70; P=0.01). Real-time time to peak was delayed in ischemic tissue (11.43 ± 2.67 versus 8.88 ± 1.66 seconds; P<0.001). From the analysis of receiver operating characteristic curves, β and A × β had the largest areas under the curve with optimal cutoff values of β<0.76 and A × β<1.91. We conclude that rt-UPI with analysis of microbubble replenishment correctly identifies ischemic brain tissue in acute MCA stroke.

Qualitative and Quantitative Real Time Myocardial Contrast Echocardiography for Detecting Hibernating Myocardium

Real time myocardial contrast echocardiography (RTMCE) is an emerging imaging modality for assessing myocardial perfusion that allows for noninvasive quantification of regional myocardial blood flow (MBF). We sought to assess the value of qualitative analysis of myocardial perfusion and quantitative assessment of myocardial blood flow (MBF) by RTMCE for predicting regional function recovery in patients with ischemic heart disease who underwent coronary artery bypass grafting (CABG). Twenty-four patients with coronary disease and left ventricular systolic dysfunction (ejection fraction <45%) underwent RTMCE before and 3 months after CABG. RTMCE was performed using continuous intravenous infusion of commercially available contrast agent with low mechanical index power modulation imaging. Viability was defined by qualitative assessment of myocardial perfusion as homogenous opacification at rest in ≥2 segments of anterior or ≥1 segment of posterior territory. Viability by quantitative assessment of MBF was determined by receiver-operating characteristics curve analysis. Regional function recovery was observed in 74% of territories considered viable by qualitative analysis of myocardial perfusion and 40% of nonviable (P = 0.03). Sensitivity, specificity, positive and negative predictive values of qualitative RTMCE for detecting regional function recovery were 74%, 60%, 77%, and 56%, respectively. Cutoff value of MBF for predicting regional function recovery was 1.76 (AUC = 0.77; 95% CI = 0.62-0.92). MBF obtained by RTMCE had sensitivity of 91%, specificity of 50%, positive predictive value of 75%, and negative predictive value of 78%. Qualitative and quantitative RTMCE provide good accuracy for predicting regional function recovery after CABG. Determination of MBF increases the sensitivity for detecting hibernating myocardium.

Imaging of carotid arterial diseases with contrast-enhanced ultrasound (CEUS)

Carotid duplex ultrasound is the standard of care for the initial diagnosis of carotid artery bifurcation diseases. But in difficult examinations, carotid abnormalities are commonly encountered and may represent a diagnostic challenge in patients with clinical symptoms as well as in the follow up after carotid endarterectomy or carotid artery stenting. Contrast enhanced ultrasound (CEUS) with low mechanical index (low MI) is a promising new method in the diagnosis and follow up of pathological carotid diseases. Unlike most contrast agents used for magnetic resonance imaging or computed tomography, the microbubbles used in CEUS with SonoVue ® remain within the vascular space and hence can be used to study vascular disease. In addition to improving current carotid structural scans, CEUS has potential to improve or add extra information on carotid arterial diseases. This review describes the current carotid duplex ultrasound examination and compares the pathological findings with CEUS.

Contrast-Enhanced Ultrasound With Perflubutane Microbubble Agent: Evaluation of Differentiation of Hepatocellular Carcinoma

The aim of this study was to evaluate the effectiveness of contrast-enhanced ultrasound with a perflubutane microbubble agent in the assessment of cellular differentiation of hepatocellular carcinoma (HCC). Continuous harmonic imaging with a low mechanical index (0.21-0.30) was performed 1, 5, and 10 minutes after i.v. contrast injection (0.0075 mL/kg). Tumor enhancement was evaluated by both subjective reading and objective intensity analysis based on the signal distribution in the nontumor parenchyma. Tumor vascularity was assessed with CT during hepatic arteriography. Sixty-four patients with 77 histologically proved HCCs (mean greatest dimension, 19.1 ± 5.3 mm)--six poorly differentiated HCCs, 45 moderately differentiated HCCs, and 26 well-differentiated HCCs--were enrolled in this prospective study. Among 64 hyperenhancing lesions on peak enhancement sonograms, four poorly differentiated HCCs and eight moderately differentiated HCCs exhibited washout within 1 minute. In addition to these 12 lesions, 36 lesions exhibited washout 5 minutes after injection, resulting in a total of 48 washout lesions. Fifty-four lesions exhibited washout 10 minutes after contrast injection (six poorly differentiated, 38 moderately differentiated, and 10 well-differentiated HCCs). Washout was more frequent in poorly than in moderately differentiated HCC (p = 0.0117) and well-differentiated HCC (p = 0.0003) in the 1-minute phase and was more frequent in moderately differentiated than in well-differentiated HCC in the 5-minute (p = 0.0026) and 10-minute (p = 0.0117) phases. Thirteen lesions were isoenhancing or hypoenhancing on peak enhancement sonograms (three moderately differentiated and 10 well-differentiated HCCs). Contrast-enhanced ultrasound and CT during hepatic arteriography did not differ significantly with respect to rate of detection of hyperenhancing lesions. The findings at contrast-enhanced ultrasound with the perflubutane microbubble agent may be predictive of cellular differentiation of HCC without needle biopsy.

Carotid Plaque Vulnerability: Quantification of Neovascularization on Contrast-Enhanced Ultrasound With Histopathologic Correlation

The purpose of this research is to develop a computerized method to quantify carotid plaque neovascularization on contrast-enhanced ultrasound images and to compare the results with the histopathologic analysis of the plaque. Twenty-seven patients (age range, 48-84 years; mean [± SD] age, 68.4 ± 9.72 years) were recruited before endarterectomy. Contrast-enhanced ultrasound examination of the carotid artery was performed by applying low mechanical index and harmonics with pulse inversion. An algorithm was developed that implemented several image processing methods to automatically quantify neovascularization and reconstruct the vascular tree in the atheromatous plaque. Neovascularization and the number of inflammatory cells seen on histopathologic analysis of the plaque after endarterectomy were compared with neovascularization determined by the computerized method. The mean (± SD) ratios of the ultrasound and histopathologic measurements were calculated. In five patients, heavy calcification of the plaque prevented visualization of plaque texture. Intraplaque neovascularization on contrast-enhanced ultrasound images was significant in 19 patients and low in three patients. The ratio of the neovascularization area to the total plaque area on contrast-enhanced ultrasound images was well correlated with the same histopathologic ratio (R(2) = 0.7905) and with the number of inflammatory cells present in the plaque (R(2) = 0.6109). The histopathologic ratio and the number of intraplaque inflammatory cells also were well correlated (R(2) = 0.7034). The newly developed method allowed quantification of the intraplaque neovascularization as a feature of vulnerability in the carotid plaque and proved to be highly correlated with histopathologic results.

Phantom study for quantitative measurement of tissue perfusion using perflubutane dynamic contrast-enhanced ultrasonography with low mechanical-index

Phantom study for quantitative measurement of tissue perfusion using perflubutane dynamic contrast-enhanced ultrasonography with low mechanical-index

Contrast Agent Manipulation with Medical Ultrasound Imaging

Contrast agents are manipulated with acoustic radiation force while ultrasound imaging. Continuous waves for acoustic radiation force are transmitted. Substantially simultaneously, pulsed waves for imaging are transmitted. Low mechanical index continuous and pulsed waves may be used to increase binding efficiency of drug containing contrast agents with the tissue for treatment. Various techniques may be used to minimize the effect of the continuous waves on imaging with the pulsed waves. The acoustic radiation force may be transmitted with an amplitude profile and/or unfocused or defocused.

State-of-the-art imaging techniques in endoscopic ultrasound

Endoscopic ultrasound (EUS) has recently evolved through technological improvement of equipment, with a major clinical impact in digestive and mediastinal diseases. State-of-the-art EUS equipment now includes real-time sono-elastography, which might be useful for a better characterization of lesions and increased accuracy of differential diagnosis (for e.g. lymph nodes or focal pancreatic lesions). Contrast-enhanced EUS imaging is also available, and is already being used for the differential diagnosis of focal pancreatic masses. The recent development of low mechanical index contrast harmonic EUS imaging offers hope for improved diagnosis, staging and monitoring of anti-angiogenic treatment. Tridimensional EUS (3D-EUS) techniques can be applied to enhance the spatial understanding of EUS anatomy, especially for improved staging of tumors, obtained through a better assessment of the relationship with major surrounding vessels. Despite the progress gained through all these imaging techniques, they cannot replace cytological or histological diagnosis. However, real-time optical histological diagnosis can be achieved through the use of single-fiber confocal laser endomicroscopy techniques placed under real-time EUS-guidance through a 22G needle. Last, but not least, EUS-assisted natural orifice transluminal endoscopic surgery (NOTES) procedures offer a whole new area of imaging applications, used either for combination of NOTES peritoneoscopy and intraperitoneal EUS, but also for access of retroperitoneal organs through posterior EUS guidance.

Quantitative Contrast-Enhanced Harmonic Endoscopic Ultrasonography for the Discrimination of Solid Pancreatic Masses

Contrast-enhanced harmonic endoscopic ultrasonography (CEH-EUS) for the assessment of microcirculation and the delineation of pancreatic tumors in order to characterize and stage them has only recently become available for commercial use, and few reports have been published. The purpose of the study was the qualitative and quantitative digital image analysis of pancreatic adenocarcinomas using conventional endoscopic ultrasonography (EUS) and CEH-EUS and the evaluation of whether contrast medium injection modified adenocarcinoma staging and patient management. In each of 30 prospectively examined patients with suspected pancreatic solid lesions, CEH-EUS was performed using the same quantity of the contrast agent SonoVue and a low mechanical index (0.3 - 0.4), followed by EUS-FNA. The histology, based on EUS-FNA or surgery and 9 months of follow-up, was: pancreatic adenocarcinoma (n = 15), pseudotumoral chronic pancreatitis (n = 12), neuroendocrine tumor (n = 1), common bile duct tumor (n = 1), lymph node metastases of gastric cancer (n = 1). The quantitative analysis was based on histograms obtained from each CEH-EUS video recording. CEH-EUS showed a hypoenhanced pattern in 14 cases of adenocarcinoma and in 10 cases of chronic pancreatitis. The index of the contrast uptake ratio was significantly lower in adenocarcinoma than in mass-forming chronic pancreatitis. A cut-off uptake ratio index value of 0.17 for diagnosing adenocarcinoma corresponded to an AUC (CI 95%) of 0.86 (0.67 - 1.00) with a sensitivity of 80%, a specificity of 91.7%, a positive predictive value of 92.8%, and a negative predictive value of 78%. The size of the pancreatic mass was assessed significantly more effectively by CEH-EUS but adenocarcinoma staging was not modified. The majority of cases of both pancreatic adenocarcinoma and chronic pancreatitis were hypoenhanced and visual discrimination was not possible. This is the first study about CEH-EUS for the quantitative assessment of uptake after contrast injection which has shown that it can aid differentiation between benign and malignant masses but cannot replace EUS-FNA. Neither tumor stage nor therapeutic management have changed after contrast medium injection during CEH-EUS.

Diagnostic accuracy of contrast‐enhanced ultrasound in differentiating benign and malignant focal liver lesions: A retrospective study

The purpose of this study was to assess the diagnostic accuracy of our early experience with contrast-enhanced ultrasound (CEUS) in the characterisation of focal liver lesions (FLLs) using histopathology, contrast-enhanced computed tomography (CT), magnetic resonance imaging (MRI) or other imaging follow-up as the standard of reference. Seventy-three patients with 82 FLLs who underwent liver CEUS from January 2006 to December 2008 were retrospectively reviewed. CEUS was performed with up to 4.8 mL of SonoVue® (Bracco, Milan, Italy) using a low mechanical index mode. The CEUS findings were compared with histopathology, or where histopathology was not available, clinical and imaging follow-up over at least 12 months was used as the standard of reference. Of the 82 FLLs, 50 were malignant and 32 were benign at final diagnosis. CEUS correctly identified 43 malignant FLLs, with final diagnosis confirmed by histopathology in 13 lesions and clinico-radiological follow-up in 30 lesions. Twenty-nine lesions were correctly identified as benign on CEUS, with all these lesions confirmed on clinico-radiological follow-up. CEUS demonstrated a sensitivity of 86.0% and a specificity of 90.6% in the characterisation of liver lesions as malignant, with an overall accuracy of 87.8% (P < 0.05). Our early experience has shown that CEUS can be accurate in differentiating malignant from benign FLLs and may become a useful first-line imaging tool where CT or MRI are not available or contra-indicated.

Unenhanced and Contrast-Enhanced Ultrasonography During Hepatic Transarterial Embolization and Chemoembolization With Drug-Eluting Beads

The purpose of this study was to describe and evaluate the findings of unenhanced ultrasonography (US) and contrast-enhanced ultrasonography (CEUS) when these modalities are applied during transarterial embolization (TAE) or transarterial chemoembolization (TACE) of liver tumors. Sixteen tumors (9 hepatocellular carcinomas, 5 metastases from colorectal cancer, and 2 hemangiomas) were treated with TAE with microspheres and/or TACE with drug-eluting beads. All of these lesions were studied with intraprocedural unenhanced US and 12 were studied with intraprocedural CEUS. For the latter, a second-generation echo-enhancer (SonoVue; Bracco, Milan, Italy) and a low mechanical index technique were used. Intraprocedural findings were classified according to an arbitrary scale and were compared with pretreatment imaging (CEUS and computed tomography or CEUS and magnetic resonance imaging), with postembolization angiography, and with follow-up results. On unenhanced intraprocedural US, 13 of 16 tumors demonstrated intralesional high-level echoes of varying extent. These feature correlated poorly (r = 0.33, p = 0.097) with and generally underestimated the actual extent of necrosis. Exceptionally, high-level echoes that occupied the largest part of the treated lesions were associated with >50% tumor necrosis. Intraprocedural CEUS clearly depicted immediate partial or complete disappearance of tumor enhancement as a result of TAE/TACE. Three of 6 tumors with complete devascularization on postembolization angiogram showed residual enhancement on intraprocedural CEUS. Intraprocedural CEUS findings correlated closely (r = 0.91, p = 0.002) with follow-up findings. Intraprocedural sonography, particularly with echo-enhancers, could be used for intraprocedural monitoring in selected cases of liver tumors that undergo TAE or TACE.

Role of Low-Mechanical Index CEUS in the Differentiation between Low and High Grade Bladder Carcinoma: a Pilot Study

To assess the efficacy of low-mechanical index contrast-enhanced ultrasonography (CEUS) in the differentiation of a series of histologically proven bladder lesions identified via conventional cystoscopy and biopsied. 36 patients (mean age: 62 years; range 45 - 72 years) with bladder lesions previously detected by color power Doppler ultrasonography (CDUS) were prospectively examined with low-mechanical index contrast-enhanced US after bolus administration of 2.4 ml of Sonovue (Bracco, Milan, Italy). All lesions were evaluated in real-time continuous scanning for 2 minutes and the videos were registered. Two ultrasound (US) experts evaluated the videos by consensus and assigned a score to the enhancement pattern. Subsequently, a specific sonographic quantification software (Qontrast, Bracco, Milan, Italy) based on pixel by pixel signal intensity over time was used to obtain contrast-enhanced sonographic perfusion maps for each lesion. Time-intensity curves (TICs) of each lesion were then extracted from the region of interest positioned within the lesion and in the closest bladder wall. The sensitivity and specificity of CDUS and CEUS were compared using McNemar's test. All patients subsequently underwent conventional cystoscopy with biopsy or transurethral resection. 22 high-grade and 14 low-grade transitional cell carcinomas (TCCs) were histologically diagnosed (mean diameter 2.1 cm; range: 1 - 4.5 cm). The sensitivity and specificity of CDUS were 86.4% (19 / 22; 95% CI = 66.7 - 95.3%) and 42.9% (6 / 14; 95% CI = 21.4 - 67.4%), respectively. The sensitivity and specificity of CEUS were 90.9% (20 / 22; 95% CI = 72.2 - 97.5%) and 85.7% (12 / 14; 95% CI = 60.1 - 95.9%), respectively. The sensitivity and specificity of CEUS using TICs were 95.4% (21 / 22; 95% CI = 78.2 - 99.2%) and 85.7% (12 / 14; 95% CI = 60.1 - 95.9%), respectively. There was no significant difference between the sensitivity of CDUS versus CEUS, CDUS versus TIC, and CEUS versus TIC (p > 0.05; McNemar's test). The specificity of CEUS and TIC was significantly higher than that of CDUS (p < 0.05; McNemar test). CEUS is a reliable noninvasive method for differentiating low- and high-grade bladder carcinomas since it provides typical enhancement patterns as well as specific contrast-sonographic perfusion curves. However, further studies involving larger patient populations is mandatory to confirm these promising results.

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

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. 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. 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. 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.

Transcranial Perfusion Sonography Using a Low Mechanical Index and Pulse Inversion Harmonic Imaging: Reliability, Inter-/Intraobserver Variability

Transcranial perfusion sonography (TPS) is an emerging noninvasive bedside method for evaluating brain perfusion. The purpose was to assess the feasibility of a low MI/almost real-time frame rate approach and to test its intra-/interobserver variability. 10 healthy volunteers were investigated 3 times with TPS at a low MI (1.0) and a high frame rate (8.3 Hz). Investigations were performed by 2 sonographers in a cross-over design: 1.) twofold measurements each with 5 volunteers (intraobserver test), and 2.) single measurements of the other 5 volunteers (interobserver test). From 8 established regions of interest (ROI), time-intensity curves (TIC) with the following parameters were calculated: peak intensity (PI), time-to-PI (TTP), area-under-curve (AUC), and cerebral transit time (CTT). The TIC quality was described by the coefficient of determination. TIC parameters were presented descriptively. Intra- and interobserver variability was tested by Spearman's correlation. The overall quality of the TIC was very good (mean r(2) = 0.92, 0.87 - 0.97). TTP (25.7 - 28.1 sec; mean 26.8 sec) and CTT (8.2 - 10.7 sec; mean 9.9 sec) were the most robust parameters. The intraobserver variability was lower with the more experienced sonographer (r = 0.70 vs. r = 0.29). The interobserver reliability was r = 0.34 (p < 0.05). Low MI TPS allows for nearly real-time imaging facilitating probe control. Sound sonographer experience allows for a high reliability and makes TPS an interesting tool for the diagnosis and follow-up of perfusion changes, e. g. in stroke or anti-angiogenic brain tumor therapy.

The current status of contrast-enhanced ultrasound in China.

This review article provides an overview of the use of contrast-enhanced ultrasound (CEUS) in China. Currently, the only licensed contrast agent is SonoVue, a sulfur hexafluoride-filled microbubble contrast agent. In combination with a low mechanical index contrast-specific imaging mode, SonoVue-enhanced CEUS can be used to visualize the micro and macro-vasculature continuously. Since 2004, CEUS has been widely used in China in various clinical scenarios. The authors compared CEUS with baseline ultrasound or contrast-enhanced computed tomography with regard to characterization of focal liver lesions (FLLs). On CEUS, heterogeneous or homogeneous hyperenhancement during the arterial phase and washout in the portal/late phase are typical findings for hepatocellular carcinoma. The enhancement features of intrahepatic cholangiocarcinoma, infected FLLs, focal fatty infiltration, focal fatty sparing, complex cystic FLLs, and uncommon benign FLLs were carefully depicted. CEUS was also used for patient selection in ablation therapy and evaluation of response to ablation for liver cancer. The utility of three-dimensional CEUS of the liver was also explored. In non-liver use, CEUS in hilar cholangiocarcinoma, gallbladder, breast, and prostate was initially investigated. In addition, CEUS was used in interventional procedures such as CEUS-guided hemostatic injection, intraoperative CEUS in neurosurgery, and evaluation of response to high-intensity focused ultrasound ablation of uterine fibroids. The Chinese experience has resulted in increased use of CEUS.

Detection of Hepatic Metastases from Colorectal Cancer: Prospective Evaluation of Gray Scale US Versus SonoVue® Low Mechanical Index Real Time-Enhanced US as Compared with Multidetector-CT or Gd-BOPTA-MRI

To compare ultrasound (US), low-mechanical index contrast enhanced US (CEUS) and multidetector-CT (MDCT) for the detection of hepatic metastases from colorectal cancer. From January to June 2006, 110 patients (65 males, 45 females; mean age 62 years; range 39-78) with suspected hepatic lesions from colorectal cancer were prospectively evaluated with US, CEUS and MDCT by two independent readers. Intraoperative ultrasonography (IOUS, n = 45) or a follow-up up for at least 6 months by using MDCT or Gd-BOPTA-enhanced MRI was considered the gold standard. McNemar test was employed. Reference standards revealed 430 metastases in 110 patients. On a patient-by-patients analysis, CEUS improved US sensitivity from 67.4-71.6% to 93.4-95.8% (p < 0.05). On a lesion-by-lesion analysis, CEUS improved the sensitivity of US from 60.9-64.9% to 85.3-92.8% (p < 0.001). The specificity increased from 50-60% to 76.7-83.3%. No significant differences in sensitivity or specificity between CEUS and MDCT were found. Contrast-enhanced US was significantly more sensitive than baseline US in the detection of metastases smaller than 1 cm (p < 0.001) with an increase in sensitivity from 29.1-35% to 63.3-76.6% no significant statistical difference was identified when compared with MDCT (sensitivity of 73.3-75.8%). CEUS is significantly more accurate than US and highly comparable with MDCT in the detection of liver metastases from colorectal cancer. Therefore, in the evaluation of patients with suspected hepatic metastases from colorectal tumour, US examination must be performed after contrast administration.

Contras-enhanced ultrasound features of ovarian tumor torsion

Objective To investigate the contrast enhanced ultrasound(CEUS)features of ovarian tumor torsion(OTT).Methods Seventeen cases with OTT were evaluated using CEUS.CEUS was performed with low mechanical index and the contrast agent of Sono Vue.Results Thirteen cases with total torsion of ovarian tumor appeared as no enhancement.Four cases with partial torsion showecl hyperechoic enhancement in the early phase and hypoechogenicity in the late phase.Conclusions The enhancement of OTT has characteristic,which would be helpful for the diagnosis and differential diagnosis of OTT. Key words: Ultrasonography; Microbubbles; Ovarian neoplasms; Torsion

Contrast-enhanced ultrasonography in evaluating hepatic metastases from neuroendocrine tumours

Objectives At presentation, gastroenteropancreatic neuroendocrine tumours (GEP NETs) frequently show prognostically negative hepatic involvement. The aim of this study was to characterise hepatic metastases of GEP NETs as revealed by contrast-enhanced ultrasonography (CEUS), which allows the fine definition of the microvascular system, and to correlate these findings to the biological behaviour of the tumour. Methods Eighteen out of 62 GEP NET patients examined between January 2007 and September 2008 had histologically proven hepatic metastases from primary ileal (#6), gastric (#1) or rectal (#1) carcinoids, pancreatic tumours (#7), or primary duodenal (#2) or occult gastrinomas (#1), and all underwent low mechanical index real-time CEUS with SonoVue ® injection. Results Strong early enhancement in the arterial phase was observed in 15 cases (83%), and a rapid wash-out in the portal venous phase in 14 (78%). In the late venous phase, the lesions were hypoechoic in 12 cases (67%), isoechoic in five (28%), and hyperechoic in one (0.05%). The time of arterial enhancement correlated with the Ki-67 proliferative index ( r s = 0.516; p = 0.028). Conclusions Most of the neuroendocrine liver metastases showed increased arterial enhancement at CEUS, a behaviour that is similar to that of hepatocellular carcinomas and the opposite of that of other metastases. CEUS can be a useful diagnostic means of characterising such metastases.

Effects of Nonlinear Propagation in Ultrasound Contrast Agent Imaging

This paper investigates two types of nonlinear propagation and their effects on image intensity and contrast-to-tissue ratio (CTR) in contrast ultrasound images. Previous studies have shown that nonlinear propagation can occur when ultrasound travels through tissue and microbubble clouds, making tissue farther down the acoustic path appear brighter in pulse inversion (PI) images, thus reducing CTR. In this study, the effect of nonlinear propagation through tissue or microbubbles on PI image intensity and CTR are compared at low mechanical index. A combination of simulation and experiment with SonoVue microbubbles were performed using a microbubble dynamics model, a laboratory ultrasound system and a clinical prototype scanner. The results show that, close to the bubble resonance frequency, nonlinear propagation through a bubble cloud of a few centimeter thickness with a modest concentration (1:10000 dilution of SonoVue microbubbles) is much more significant than through tissue-mimicking material. Consequently, CTR in regions distal to the imaging probe is greatly reduced for nonlinear propagation through the bubble cloud, with as much as a 12-dB reduction compared with nonlinear propagation through tissue-mimicking material. Both types of nonlinear propagation cause only a small change in bubble PI signals at the bubble resonance frequency. When the driving frequency increases beyond bubble resonance, nonlinear propagation through bubbles is greatly reduced in absolute values. However because of a greater reduction in nonlinear scattering from bubbles at higher frequencies, the corresponding CTR is much lower than that at bubble resonance frequency. (E-mail: mengxing.tang@imperial.ac.uk)