Contrast Harmonic Imaging Research Articles

Characterization of intra-abdominal lesions of undetermined origin by contrast-enhanced harmonic EUS (with videos)

The diagnosis of intra-abdominal lesions of undetermined origin is often a challenge for endoscopists and radiologists. To evaluate the microvasculature of benign and malignant intra-abdominal lesions by contrast-enhanced harmonic EUS (CEH-EUS) and to investigate its usefulness for discriminating between malignant and benign lesions. The vascularity of intra-abdominal lesions of undetermined origin was observed by using CEH-EUS. The lesions were classified according to their vascular patterns. The effectiveness of CEH-EUS in differentiating malignant from benign lesions was evaluated. Kinki University School of Medicine, Osaka, Japan. Forty-three patients, each with a lesion of undetermined origin, were evaluated prospectively by CEH-EUS between March 2007 and March 2009. CEH-EUS was performed by using a prototype echoendoscope and the extended pure harmonic detection mode (a specific mode for contrast harmonic imaging). The lesions were categorized by 2 physicians as having no, homogeneous, or heterogeneous enhancement. A consensus was reached for each case offline. How the benign and malignant groups differed in terms of their enhancement patterns was examined. The kappa coefficient of the interobserver agreement test was 0.953 (P < .001). Of the 27 malignant lesions, 26 (96.3%) exhibited heterogeneous enhancement. The 1 remaining malignant lesion (3.7%) showed homogeneous enhancement. Of the 16 benign lesions, none displayed heterogeneous enhancement, and 12 (75%) and 4 (25%) exhibited homogeneous and no enhancement, respectively. The malignant and benign lesion groups differed significantly in terms of homogeneous and heterogeneous enhancement (P < .001). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy with which CEH-EUS differentiated malignant from benign lesions were 96.3%, 100%, 100%, 94.1%, and 97.6%, respectively. A single medical unit with a limited number of patients. CEH-EUS depicted the microvasculature of intra-abdominal lesions of undetermined origin very clearly and may be useful for characterizing such lesions.

Characterization of microvascularization of liver tumor lesions with high resolution linear ultrasound and contrast enhanced ultrasound (CEUS) during surgery: First results

Evaluation of high resolution linear ultrasound and intra-operative linear contrast enhanced ultrasound (CEUS) and its benefit for the detection and characterization of tumor lesions. Twenty patients were investigated preoperatively regarding tumor detection using CT (n = 8) or MRI (n = 12) and image fusion (VNav) (n = 3). All patients had surgery for their hepatic tumor (hepatocellular carcinoma (HCC), cholangiocellular carcinoma (CCC), metastasis, and adenoma). Ultrasound was performed intra-operatively first with B-scan using a convex probe. Than multifrequency linear transmitters (6-9 MHz, 6-15 MHz, LOGIQ E9, GE) were applied for B-scan, coulor coded Doppler sonography (CCDS) and Power Doppler followed by dynamic CEUS with Contrast Harmonic Imaging (CHI) after bolus injection of a maximum of 15 mL SonoVue®. In 9 cases with the use of intra-operative CEUS additional tumor lesions (diameter 4-15 mm) could be detected and were histologically confirmed after surgical resection (7 cases) or intra-operative biopsy (2 cases). Using intraoperative CEUS 64 tumor lesions could be detected compared to 51 tumor lesions detected by preoperative CT or MRI (p < 0.05). Using the 6-15 MHz multifrequency linear transducer with CHI, arterial perfusion of adenomas, neuroendocrine metastases and HCC lesions was detectable. In 3 cases a resection was not achievable. Two of these cases were treated with radio frequency ablation (RFA). The other case had no curable option due to multifocal tumor manifestation. The intra-operative use of high-resolution linear transducer techniques with CEUS offers new diagnostic perspectives for an effective liver surgery.

Image fusion with volume navigation of contrast enhanced ultrasound (CEUS) with computed tomography (CT) or magnetic resonance imaging (MRI) for post-interventional follow-up after transcatheter arterial chemoembolization (TACE) of hepatocellular carcinomas (HCC): Preliminary results

The assessment of the immediate post-interventional microcirculation and perfusion following transcatheter arterial chemoembolization (TACE) with new real time imaging fusion technique (VNav) of computed tomography (CT) or magnetic resonance imaging (MRI) with contrast enhanced ultrasound (CEUS) compared to follow-up. Following TACE an image fusion of CEUS with CT or MRI of the liver was performed in 20 patients (18 men, 2 women; age 29-75 years) with confirmed hepatocelluar carcinoma (HCC) to evaluate the post-interventional tumor vascularization and perfusion of HCC tumor lesions. Image fusion with CEUS performed immediately was compared with the result at the end of TACE (DSA), with post TACE CT (non-enhanced CT within 24 hours) and with follow up CT (enhanced CT after 6 weeks) after embolization. Ultrasound was performed using a 1-5 MHz multifrequency SonoVue transducer (LOGIQ 9/GE) after a bolus injection of 2-4ml SonoVue® with contrast harmonic imaging (CHI). Thirteen examinations were fused with a contrast enhanced CT, 7 with a MRI performed before TACE. The post-interventional volume navigation image fusion of CT or MRI with CEUS showed differences regarding the residual tumor perfusion compared to other modalities. The correlation (Spearman-test) between the perfusion result at the end of TACE, non-enhanced CT after TACE and image fusion with CEUS was 0.42 and 0.50. The difference between the result at the end of TACE and the fusion with CEUS was significant (p < 0.05, Wilcoxon-test). The correlation between fusion of CEUS with CT/MRI and follow-up CT (after 6 weeks) was 0.64, the difference was not significant (p > 0.05). The differences between native CT within 24 hours after TACE and follow up CT after 6 weeks or fusion of CEUS and CT/MRI were significant (p < 0.05). The inter-observer variability was 0.61 at the end of TACE, 0.58 at non-enhanced CT (within 24 hours), 0.87 at fusion CEUS with CT/MRI and 0.74 at follow up CT after 6 weeks (Cohens Kappa test). Image fusion with volume navigation (VNav) of CEUS with CT or MRI allows an accurate localisation of foci in patients with HCC. This exact mapping permits an easier control and evaluation of the results after TACE. The fusion of CEUS and CT or MRI allows a better evaluation of the microcirculation and the residual tumor perfusion at an earlier point of time than usual modalities of therapy control like non-enhanced CT. This might lead to a more differentiated monitoring of therapy.

Application of image fusion for ultrasound contrast harmonic imaging

Application of image fusion for ultrasound contrast harmonic imaging

Evaluation of Malignant Liver Tumors: Biphasic MS-CT versus Quantitative Contrast Harmonic Imaging Ultrasound

It was the aim of our study to establish the extent to which contrast enhancement with SonoVue(R) in combination with quantitative evaluation of contrast-medium dynamics facilitates the detection of malignant hepatic tumors. One hundred patients with histologically confirmed malignant or benign hepatic tumors (maximum size 5 cm) were analyzed. We used a high-end ultrasound machine (Logic 9, GE Healthcare, Milwaukee, WI, USA), with a multifrequency curved array transducer (2.5 - 4 MHz), Contrast-enhanced ultrasound (bolus injection 2.4 mL SonoVue(R)) was carried out with the intermittent breath-holding technique. Native vascularization was analyzed with power Doppler sonography. The contrast-enhanced dynamic ultrasound investigation was carried out with contrast harmonic imaging in the true detection mode during the arterial, portal venous and late phases. The mechanical index was set at 0.15. Perfusion analysis was performed by post-processing of the raw data (time intensity curve [TIC] analysis). Biphasic 16- or 64-slice multislice computed tomography served as reference method in nearly all cases. One hundred patients with 59 malignant (43 colon, 5 breast, 2 endocrine metastases, 7 hepatocellular carcinomas and 2 kidney cancers) and 41 benign (12 circumscribed fatty changes, 2 abscesses, 7 focal nodular hyperplasias, 5 complicated cysts and 15 hemangiomas) tumors were included. The CT classification was true positive in 71 of 92 patients, false negative in 8 cases, and in 13 cases no final diagnosis was possible; sensitivity was 96.7 % and specificity was 71.4 % for CT. The quantitative contrast harmonic imaging ultrasound classification was true positive in 98 of 100 patients and false negative in 2 cases; the sensitivity was 98.6 % and the specificity was 96.6 %. The Fisher test showed a significant difference at p < 0.05. No investigator-dependency was noted. In our study contrast-enhanced ultrasound was more accurate than multislice computed tomography in the prediction of malignancy and benignity of liver tumors.

Exploitation of capacitive micromachined transducers for nonlinear ultrasound imaging

Capacitive micromachined ultrasonic transducers (CMUTs) present advantages such as wide frequency bandwidth, which could be further developed for nonlinear imaging. However, the driving electrostatic force induces a nonlinear behavior of the CMUT, thus generating undesirable harmonic components in the generated acoustic signal. Consequently, the use of CMUT for harmonic imaging (with or without contrast agents) becomes challenging. This paper suggests 2 compensation approaches, linear and nonlinear methods, to cancel unwanted nonlinear components. Furthermore, nonlinear responses from contrast agent were evaluated using CMUT in transmit before and after compensation. The results were compared with those obtained using a PZT transducer in transmit. Results showed that CMUT nonlinear behavior is highly influenced by the excitation to bias voltage ratio. Measurements of output pressure very close to the CMUT surface allow the estimation of optimal parameters for each compensation approach. Both methods showed a harmonic reduction higher than 20 dB when one element or several elements are excited. In addition, the study demonstrates that nonlinear approach seems to be more efficient because it is shown to be less sensitive to interelement variability and further avoids fundamental component deterioration. The results from contrast agent measurements showed that the responses obtained using CMUT elements in transmit with compensation were similar to those from PZT transducer excitation. This experimental study demonstrates the opportunity to use CMUT with traditional harmonic contrast imaging techniques.

Testicular Contrast Harmonic Imaging to Evaluate Intratesticular Perfusion Alterations in Patients With Varicocele

To determine whether changes in intratesticular microcirculation perfusion affect spermatogenesis in patients with left varicocele we performed testicular contrast harmonic imaging. A total of 90 patients with left varicocele (oligospermia in 50 and normozoospermia in 40) and 36 controls without varicocele (oligospermia in 16 and normozoospermia in 20) were enrolled in the study. Before contrast harmonic imaging all participants were evaluated by clinical examination, hormonal analysis, semen sample and scrotal ultrasound. We calculated contrast material arrival time in the arteriolar circulation (wash-in), time to peak in arterial circulation, arrival time in the venular circulation (washout) and mean transit time in each testis on contrast harmonic imaging. We found no difference in the distribution rate of varicocele grade in patients with vs without oligospermia. All contrast harmonic imaging parameters were significantly higher in patients with varicocele plus normozoospermia or oligospermia and controls. We found no significant differences in contrast harmonic imaging parameters in patients with lower varicocele grading with respect to the higher grades. In patients with varicocele we found a negative linear correlation between total sperm count and left mean transit time (r = -0.29). In a multivariate model left mean transit time was the only independent predicting parameter of oligospermia (p <0.05). Mean transit time greater than 36 seconds predicted oligospermia in patients with left varicocele with 78% sensitivity and 58% specificity. To our knowledge we report for the first time that testicular contrast harmonic imaging may be a new diagnostic tool able to improve our knowledge about the influence of varicocele on intratesticular microcirculation.

Detection and Characterization of Endoleaks Following Endovascular Treatment of Abdominal Aortic Aneurysms using Contrast Harmonic Imaging (CHI) with Quantitative Perfusion Analysis (TIC) Compared to CT Angiography (CTA)

To show the feasibility of the detection of endoleaks following endovascular treatment of aortic aneurysms using contrast harmonic imaging (CHI) in comparison to computed tomography angiography (CTA). 51 patients with suspected endoleaks, who underwent previous endovascular treatment for abdominal aortic aneurysm, were examined using CTA and vascular ultrasound. Biphasic CTA in all cases and digital subtraction angiography (DSA) in 8 patients were evaluated by two radiologists in consensus and served as the standard of reference. Ultrasound was performed by an experienced examiner with a multi-frequency linear transducer (2 - 4 MHz) using CHI following bolus injection of 2.4 ml of SonoVue® IV (maximum 5 ml). All images were evaluated by two observers in consensus regarding the reperfusion of the abdominal aneurysm using time intensity curve (TIC) analysis. In 30 of 51 patients, endoleaks were detected concordantly in CHI and CTA. In 20 of 51 patients, no endoleak was found in CHI and CTA/DSA. In one patient, a type II endoleak could initially only be detected in CHI and was later confirmed in follow-up examinations by CTA (sens. 99%, spec. 93%, NPV 99 %, PPV 95%). TIC analysis allowed evaluation of the perfusion dynamics of endoleaks in all patients. Significant differences were found (p < 0.05, Mann Whitney U Test) regarding the perfusion within the aneurysm when an endoleak was present (10.39 ± 4.29 dB) or not present (6.42 ± 2.86 dB). CHI with perfusion analysis allows definite detection of endoleaks, especially if contraindications for CTA are present. CHI presents an alternative for follow-up monitoring.

Bolus compared with continuous infusion of microbubble contrast agent using real-time contrast harmonic imaging ultrasound in breast tumors

Contrast-enhanced ultrasound (CEUS) has gained interest because of its ability to gather vascular information in various organs. There is still a matter of debate concerning its value in breast lesions. The method of choice on how to administer the contrast agent varies depending on the organ to be studied. Infusion of microbubbles is used in echocardiography, while bolus administration is the preferred technique for abdominal organs. To compare-in equal doses-bolus versus continuous infusion of microbubbles, using real-time contrast harmonic imaging in breast tumors. A total of 29 female patients (mean age 54 years) with either clear malignant or benign findings in the breast or axilla were included. Contrast harmonic imaging (CHI US) was performed with a Philips iU22 using an L9-3 MHz linear probe, especially designed for this purpose. A low mechanical index (0.06-0.07) was used to avoid massive destruction of the microbubbles. A dose of 2.4 ml of Sono Vue was first infused intravenously over 1 min with an infusion pump. After 10 min, the same dose was injected as a bolus over 2 s, followed by a flush of 10 ml of saline solution. Contrast uptakes by the tumors were recorded 2 min from the moment of injection, with both methods for each patient. Bolus administration of contrast agent provided a sharply demarcated enhancement and wash-out pattern for all lesions. The continuous infusion of the same contrast agent failed to show any wash-in/wash-out or time-to-peak/peak intensity phenomena in all cases. CEUS using real-time harmonic imaging in order to evaluate breast tumors should be performed with bolus administration of contrast agent in order to achieve better intensity/time curve outcomes.

Contrast-enhanced endoscopic ultrasound and elastosonoendoscopy

Until recently, there was no contrast harmonic imaging technique available for EUS examination. Second-generation US contrast agents produce harmonic signals at lower acoustic powers and, therefore, are suitable for EUS imaging at low acoustic powers. CE-EUS could provide a contribution to the differential diagnosis between a primary pancreatic carcinoma, chronic pancreatitis and a pancreatic metastasis, and therefore can have a decisive influence on the selection of appropriate therapeutic strategies (follow-up, chemotherapy or surgery, for example). However, histology remains the standard in the differential diagnosis of pancreatic tumours. Regarding lymph nodes, CE-EUS cannot replace EUS-guided fine-needle aspiration. Elastography examines the elastic properties of tissues by applying a slight compression to the tissue and comparing an image obtained before and after this compression. EUS elastography is a new application in the field of endosonography and seems to be able to differentiate fibrous and benign tissue from malignant lesions. While our results are very encouraging, further research will be needed to further define the place of this new technique and should be aimed at further defining criteria for accurate elastography as well as subsequently assessing the technique using multiple operators in a blinded setting. EUS-guided sonoelastography has the potential for further guiding the diagnosis and therapy of gastrointestinal-related tumours.

1466: Low-MI Contrast Harmonic Imaging of Breast Tumor by Perflubutane

1466: Low-MI Contrast Harmonic Imaging of Breast Tumor by Perflubutane

1081: Basic Research on Safety Assessment of Medical Ultrasound - The Problems in the Estimation of Safety Indexes

New type ultrasound diagnostic equipments with new functions like color Doppler imaging, harmonic imaging, 3 dimensional imaging etc. tend to irradiate higher intensity ultrasound with high frequency. Therefore the safety became important topic in medical ultrasound field. We measured the irradiated ultrasound pulse waveform, acoustic field and -12 dB output beam dimensions. The mechanical index MI, soft-tissue thermal index TIS and cranial-bone thermal index TIC were calculated from the results. The mechanical index can be calculated from attenuated peak-rarefactional acoustic pressure Pr,α divided by the square root of acoustic working frequency fawf. And they were divided by CMI. The soft-tissue thermal index can be calculated from the output power P multiplied by acoustic working frequency. And they were divided by CTIS1. In this case, CMI is defined as 1 MPa MHz-1/2 and CTIS1 is defined as 210 mW MHz in JIS T 0601-2-37: 2005 and IEC 62359 Ed. 1.0: 2005. Harmonic components with many different frequencies are generated by propagation of ultrasound in water and tissues or nonlinear behavior of micro bubble in the ultrasound diagnosis like tissue harmonic imaging or contrast harmonic imaging methods. These frequency components are different from the transmitting frequency and the fundamental frequency. Therefore it is difficult to determine the acoustic working frequency in the measured frequency spectrum for calculation of safety indexes by conventional definition. We will report about this important problem. New type ultrasound diagnostic equipments with new functions like color Doppler imaging, harmonic imaging, 3 dimensional imaging etc. tend to irradiate higher intensity ultrasound with high frequency. Therefore the safety became important topic in medical ultrasound field. We measured the irradiated ultrasound pulse waveform, acoustic field and -12 dB output beam dimensions. The mechanical index MI, soft-tissue thermal index TIS and cranial-bone thermal index TIC were calculated from the results. The mechanical index can be calculated from attenuated peak-rarefactional acoustic pressure Pr,α divided by the square root of acoustic working frequency fawf. And they were divided by CMI. The soft-tissue thermal index can be calculated from the output power P multiplied by acoustic working frequency. And they were divided by CTIS1. In this case, CMI is defined as 1 MPa MHz-1/2 and CTIS1 is defined as 210 mW MHz in JIS T 0601-2-37: 2005 and IEC 62359 Ed. 1.0: 2005. Harmonic components with many different frequencies are generated by propagation of ultrasound in water and tissues or nonlinear behavior of micro bubble in the ultrasound diagnosis like tissue harmonic imaging or contrast harmonic imaging methods. These frequency components are different from the transmitting frequency and the fundamental frequency. Therefore it is difficult to determine the acoustic working frequency in the measured frequency spectrum for calculation of safety indexes by conventional definition. We will report about this important problem.

Recent advances and future directions in ophthalmologic neuroimaging

Advances in neuroimaging over the past 5–10 years have offered opportunities to address challenging and previously unanswered clinical questions in ophthalmologic neuroimaging. Among these advances are diffusion-weighted imaging, diffusion-tensor imaging (DTI), perfusion MRI (PWI), functional MRI (fMRI) as well as single-photon emission tomography, PET scanning and high-frequency contrast harmonic ultrasound imaging. The MRI techniques are based on imaging the static or dynamic changes of the hydrogen proton in a controlled magnetic field. Diffusion-weighted imaging, for instance, offers temporal characterization of acute infarction and differentiation of neoplasm from bacterial abscess, or differentiation between certain types of neoplasms that may present with visual symptoms. The addition of PWI allows rapid assessment of tissue at risk (penumbra) beyond the core (umbra) in the setting of acute stroke. PWI, computed tomography perfusion and high-frequency contrast harmonic imaging are used to study the perfusion characteristics of the ocular tumors for determination of their prognosis. PWI is also being studied for its utility in histopathologic grading of intracranial tumors. DTI and fMRI offer new insights into presurgical planning of the brain tumor resection. DTI helps to identify the retrochiasmatic optic pathways. Importantly, such fibertracking by DTI enables the differentiation of invasive from displacing lesions. fMRI is also being studied for its utility to identify retinotopic borders, motion processing, visual attention and patients with visual defects. Furthermore, the combination of both fiber tracking and fMRI offers the opportunity to demonstrate not only spatial networks within the brain but also temporal activation and recruitment of components of such networks. Single-photon emission tomography and PET scanning are helpful for the noninvasive estimation of the cerebral visual function, as well as the evaluation of functional recovery in patients. With these advancements, neuroradiology continues to lead the transition of diagnostic imaging from anatomic to physiologic and molecular imaging.

744 Ultrasound-Guided Treatments Under Low Acoustic Power Contrast Harmonic Imaging with Sonazoid Is Effective for Hepatocellular Carcinomas Undetected By B-Mode Ultrasonography

744 Ultrasound-Guided Treatments Under Low Acoustic Power Contrast Harmonic Imaging with Sonazoid Is Effective for Hepatocellular Carcinomas Undetected By B-Mode Ultrasonography

The preparation of sulfur hexafluoride lipid-coated microbubbles

Objective To prepare phospholipid-based sulfur hexafluoride gas-filled microbubbles, which were designed for targeting microbubbles. Methods The microbubbles composed of DSPC and mPEG2000-PE were produced by film-sonication method,and were compared with SonoVue. In the physical chemistry characteristics studies, the morphology, particle diameter, concentration, pH value and osmotic pressure were investigated. In the echogenicity studies, contrast harmonic imaging technique was used to investigate the enhancement of vitro water sac and normal rabbit kidney parenchyma. Results The lipid microbubbles were well-distributed, round with air holes. The average diameter of self-made microbubbles and SonoVue were 2.25 μm and 2.50μm respectively. The average diameter of self-made microbubbles and SonoVue distributed from 0.4 μm to 10 μm and 0.2 μm to 10 μm,and 90% were under 6 μm and 8 μm respectively,the concentration were 5 x 108～10 x 108/ml and 1 x I08～5 x 108/ml respectively with a stability of 6 hours. In vitro water sac, the gray scale of self-made lipid microbubbles and SonoVue were 121.67±6.76 and 122.33 ± 4.53 respectively( P>0.05). In normal rabbit kidney parenchyma, the peak video intensity of normal rabbit kidney parenchyma of self-made lipid microbubbles and SonoVue were 72.00 ± 7.21 and 74. 65± 10.93 respectively(P>0.05). Conclusions The lipid microbubbles have satisfactory physical chemistry characteristics and echogenicity. Key words: Ultrasonography; Microbubbles

Ultrasound‐guided treatments under low acoustic power contrast harmonic imaging for hepatocellular carcinomas undetected by B‐mode ultrasonography

The aim was to examine the efficacy of contrast-enhanced ultrasound (US) with Sonazoid to demonstrate ultrasonically unrecognizable hypervascular hepatocellular carcinoma (HCC) and apply percutaneous US-guided treatments. The subjects of this prospective study were 44 cirrhotic patients with 55 hypervascular lesions (12.7+/-4.5 mm) found by contrast-enhanced computed tomography but unrecognized by non-contrast US. Contrast-enhanced US was performed to demonstrate these hepatic lesions after an intravenous injection of Sonazoid (0.0075 ml/kg). The sonograms in both the early phase (for 1 min after injection) and the late phase (5-10 min after) were taken in the harmonic imaging mode under a low mechanical index (0.24-0.3). Fifty-three lesions were demonstrated by contrast-enhanced US, 52 with positive enhancement in the early phase and 44 with negative enhancement in the late phase. Percutaneous US-guided treatments were successfully performed for 42 lesions (ethanol injection in 20 and radiofrequency ablation in 22) in 32 patients with reference to contrast-enhanced US findings. Six patients were treated by transarterial chemoembolization alone because they had more than three lesions in the liver. In the remaining seven lesions in six patients, six were diagnosed as non-HCC lesions: five with vascular abnormalities such as arterioportal or arteriovenous communication and the other one with benign lesion in alcoholic liver disease. These six lesions and one HCC lesion with severe liver damage were followed up without any treatment. As the detectability of ultrasonically unrecognizable hypervascular HCC improved by contrast-enhanced US with Sonazoid, a wider application of percutaneous US-guided treatments may be possible.

Contrast harmonic imaging ultrasound and perfusion imaging for surveillance after endovascular abdominal aneurysm repair regarding detection and characterization of suspected endoleaks

Is Contrast Harmonic Imaging (CHI) comparable to computed tomography angiography (CTA) scan in detecting and characterizing suspected endoleaks after endovascular abdominal aneurysm repair in a non-selected group including reintervention procedure and branched endografts in daily practice? In a prospective study computed tomography angiography (CTA) and contrast-enhanced ultrasound (CEUS) were performed in 30 consecutive patients (26 males, 4 females, mean age: 72 years, range: 38-87) with suspected endoleaks in follow-up (mean 13 months, range: 1-95) after endovascular abdominal aneurysm repair or procedure in dissection or penetrated ulcer of the aorta (25 infrarenal, 5 suprarenal stent grafts, mean aortic diameter 56 mm, range: 27-98). CTA was supposed to be gold standard for determining the presence of endoleaks (multislice CT, collimation 16 x 0.75 mm, 100 ml of iodized contrast agent bolus). Ultrasonography used a multi-frequency probe (1-4 MHz) with the modalities of colour coded Doppler sonography (CCDS), power Doppler (PD) combined with contrast enhancement and the technique of contrast harmonic imaging (CHI) and low mechanical index (MI < 0.2). 2.4 ml of SonoVue (Bracco, Altana Pharma GmbH, Italy) were administered to each patient intravenously as a bolus injection. Out of 30 patients, 21 endoleaks were identified in CTA (6 type I or III, 15 type II), 22 in CHI. Thus, sensitivity for CHI was therefore 99%, its specificity 85% (Spearman correlation coefficient (CC) 0.92). In follow-up the localizations of endoleak type I or III exclusively detected by CHI were confirmed as true positive by angiography. Due to its dynamic characteristic CHI seemed to be more helpful in characterization of endoleaks than CTA. In case of a rupture after reintervention a type III endoleak leads to prompt intervention before receiving the result of the CT scan. Altogether, CHI failed to identify 1 combined type I and II endoleak (sensitivity 0.99). Both, CCDS and PD were positive only in 6/30 patients (CC 0.33 and 0.39). Interestingly the application of contrast agent doubles the detection rate of endoleaks (12/30) in CCDS and PD (CC 0.39). Contrast harmonic imaging (CHI) compared to computed tomography angiography (CTA) accurately depicts endoleaks after endovascular abdominal aneurysm repair and stent-graft procedure in dissected and ulcerated aorta. It seems to be superior in characterization of the type of endoleaks and can be established in order to reduce iodized contrast agent and radiation exposure in follow-up. In contrast to CTA scan CHI can be offered to patients with chronic renal insufficiency and allows a dynamic examination and a perfusion analysis.

Contrast-enhanced ultrasound in liver transplant: First results and potential for complications in the postoperative period

This study compared the efficacy of contrast-enhanced ultrasound (CEUS) using a second generation contrast medium versus CT or MRA in the assessment of vascular and biliary complications in postoperative follow-up of liver transplantation. The study group consisted of 36 consecutive liver transplant recipients who underwent post-transplantation CEUS examination after developing ascites and/or unclear liver function tests. Real time CEUS was performed after a bolus injection of SonoVue (1.6-2.4 ml, Bracco, Imaging Germany) followed by 10 ml of saline solution. Using contrast harmonic imaging (CHI) technique (Logiq 9, GE) with a 2.5-4-MHz transducer, a low mechanical index was chosen to avoid early destruction of the microbubbles (MI 0.1-0.2). In order to confirm the results, the patients underwent contrast-enhanced MRI or CT. Complications were identified in 16 of 36 patients (44.4%). Five transplants (14%) had hepatic artery thrombosis (n=2) or significant stenosis (n=3). Six transplants (16%) developed portal vein stenosis (n=4) or portal vein thrombosis (n=2). MRI or CT confirmed the findings of the CEUS in all 11 cases. Biliary stricture at the anastomotic site was detected in 5 patients. MR-CP confirmed the findings of all strictures. Due to advances in contrast-enhanced US, vascular and biliary complications in the postoperative period following liver transplantation can be reliably diagnosed non-invasively on the intensive care unit. CEUS shows vascular as well as biliary complications in the postoperative patient with a high degree of accuracy.

Contrast-enhanced ultrasound in diagnosing liver malignancy

The use of contrast enhancers has widened the possibilities of sonographic imaging, and allows the differentiation of characteristic enhancement patterns leading to diagnosis in focal liver lesions. The aim of our study was to evaluate contrast ultrasound signs in diagnosing malignant liver lesions. 86 patients with 100 solid liver lesions were enrolled. A baseline gray-scale sonogram was obtained with a multifrequency 4 C convex array probe, followed by contrast-enhanced sonography with a low mechanical index (<0.2) over 300 seconds. Final diagnosis was confirmed by histology or in case of haemangioma by CT/NMR and quantitative contrast harmonic imaging (CHI) with perfusion analysis (contrast). 55 malignant (6 HCC, 46 secondary malignant lesions - 3 of them lymphoma, 3 cholangiocarcinoma), and 45 benign lesions (8 FNH, 1 von Meyenburg complex, 1 granuloma, 3 adenoma, 21 hemangioma, 2 focal fat storage imbalances, 7 abscesses, one scar, and in one case normal liver) were found. 51/55 malignant (all but one filia and three HCC), but also 17/45 benign lesions showed hypoperfusion in the late phase. The ultrasound pattern in the arterial phase differed in malignant lesions: 22 lesions were initially hypervascular, 20 had rim enhancement and in 13 lesions there was a non-specific vascularisation. In all but one malignant lesion a diminishing of contrast agent in the late phase compared to the arterial phase with respect to the surrounding liver tissue was observed. Only three benign lesions with this later sign were falsely diagnosed as malignant: one adenoma, one epitheloid granuloma, and a scar. Quantitative perfusion pattern was analyzed exemplary. Diminishing of contrast agent in the late phase compared to the arterial phase with respect to the surrounding liver tissue as a sign for malignancy had a positive predictive value of 95%, a sensitivity of 98%, a negative predictive value of 98%, and a specificity of 93%. Diminishing of contrast agent in the late phase compared to the arterial phase with respect to the surrounding liver tissue is a helpful sign in contrast enhanced ultrasound to diagnose malignancies.

New real-time image fusion technique for characterization of tumor vascularisation and tumor perfusion of liver tumors with contrast-enhanced ultrasound, spiral CT or MRI: First results

Evaluation and characterization of the vascularisation and perfusion of liver tumors by means of image fusion of dynamic contrast-enhanced ultrasound (CEUS), multidetector-CT (MD-CT) or magnetic resonance imaging (MRI) with the ultrasound navigation technique. For interventional planning a real-time image fusion involving CEUS (LOGIQ E9, GE) was performed in 20 patients (12 men, 8 women, age 43-69 years, median 54) with histologically confirmed malignant liver tumors (9 x hepatocellular carcinoma (HCC), 5 x metastases, 2 x hemangiomas, 1 x cholangiocellular carcinoma (CCC), 1 x lymphoma, 1 x neuroendocrine tumor, 1 x focal nodular hypoplasia (FNH)). In 17 patients the real-time CEUS was fused with contrast-enhanced MD-CT and in three patients with contrast-enhanced MRI (Gd-DTPA and liver-specific contrast medium Resovist. All of the ultrasound examinations were performed by an experienced examiner with a multi-frequency probe (2-5 MHz, LOGIQ E9, GE); dynamic image sequences up to 3 minutes in true agent detection mode of contrast harmonic imaging (CHI) were documented. An evaluation of the tumor was performed by the characterization of the dynamics of the contrast medium and microperfusion with CEUS, fused with MD-CT or MRI. In 18/20 cases there was an accurate agreement with respect to the segmental localization of the tumor lesion. In 2/20 cases the localization was comparable with the image fusion of CEUS and reference imaging (a total of at least 65 lesions: 3 x 1 lesion, 5 x 2 lesions, 8 x 3 lesions, 2 x 5 lesions, 1 x 8 lesions, 1 x at least 10 lesions (multifocal)). With image fusion a certain characterization was attained in 17/20 cases. In 3/20 cases (lymphoma after liver transplantation, multifocal CCC, metastases of a neuroendocrine tumor) the diagnosis was at first doubtful and had to be confirmed histologically. In patients with HCC an evaluation of the tumor perfusion was feasible in all 9 cases (8/9 after local trans-arterial chemoembolization (TACE), 1/9 after radio frequency ablation (RFA)). A tendency toward the identification of more lesions with image fusion of CEUS and CT than with contrast-enhanced CT alone could be recognized (p=0.059). Applying a new real-time fusion technique of MD-CT or MRI with CEUS new possibilities for the evaluation, intervention and monitoring of the therapy of liver lesions were made possible, since the method also comprised the dynamic microperfusion.