Vascularity of hepatocellular carcinoma: assessment with contrast-enhanced second-harmonic versus conventional power Doppler US

Morphometric analysis of tumor microvessels for detection of hepatocellular carcinoma using contrast-free ultrasound imaging: A feasibility study

Introduction

A contrast-free ultrasound microvasculature imaging technique was evaluated in this study to determine whether extracting morphological features of the vascular networks in hepatic lesions can be beneficial in differentiating benign and malignant tumors (hepatocellular carcinoma (HCC) in particular).

Methods

A total of 29 lesions from 22 patients were included in this work. A post-processing algorithm consisting of clutter filtering, denoising, and vessel enhancement steps was implemented on ultrasound data to visualize microvessel structures. These structures were then further characterized and quantified through additional image processing. A total of nine morphological metrics were examined to compare different groups of lesions. A two-sided Wilcoxon rank sum test was used for statistical analysis.

Results

In the malignant versus benign comparison, six of the metrics manifested statistical significance. Comparing only HCC cases with the benign, only three of the metrics were significantly different. No statistically significant distinction was observed between different malignancies (HCC versus cholangiocarcinoma and metastatic adenocarcinoma) for any of the metrics.

Discussion

Obtained results suggest that designing predictive models based on such morphological characteristics on a larger sample size may prove helpful in differentiating benign from malignant liver masses.

Assessment of neovascularization during bone healing using contrast-enhanced ultrasonography in a canine tibial osteotomy model: a preliminary study

Blood perfusion of skeletal muscle and callus was evaluated using contrast-enhanced ultrasonography (CEUS) in a canine osteotomy model to determine the applicability of CEUS in the assessment of neovascularization during fracture healing and to compare the vascular signals on CEUS between external skeletal fixation and cast-applied dogs. In 6 Beagle dogs, a simple transverse osteotomy was performed at the left tibial shaft and external skeletal fixation (n = 3) or a cast (n = 3) was applied. Radiography, power Doppler ultrasonography (power Doppler), and CEUS were performed until complete union was achieved. On CEUS, vascular changes were quantitatively evaluated by measuring peak intensity (PI) and time to PI in the soft tissue and callus and by counting the vascular signals. Vascular signals from the soft tissue were detected on power Doppler and CEUS on day 2. Significantly more vascular signals were detected by CEUS than by power Doppler. On CEUS, PI in the surrounding soft tissue was markedly increased after the fracture line appeared indistinctively changed on radiography in all dogs. In the cast-applied dogs, vascular signals from the periosteal and endosteal callus were detected on CEUS before mineralized callus was observed on radiography. CEUS was useful in assessing the vascularity of soft tissue and callus, particularly in indirect fracture healing, and provided indications of a normally healing fracture.

Comparison of MicroFlow Imaging with color and power Doppler imaging for detecting and characterizing blood flow signals in hepatocellular carcinoma

PURPOSE

The purpose of this study was to compare the sensitivity of MicroFlow Imaging (MFI) with that of color and power Doppler imaging (CDI and PDI, respectively) in detecting the vascularity of hepatocellular carcinomas (HCCs).

METHODS

This prospective study enrolled 51 patients diagnosed with HCC between August 2018 and December 2018. CDI, PDI, MFI, and contrast-enhanced ultrasound (CEUS) were performed. Two radiologists evaluated the presence and pattern of tumoral vascularity on CDI, PDI, and MFI. Vascular presence was graded on a 5-point scale (0, absent; 4, >50% of the tumor). The vascular pattern was chosen from following categories: basket, vessels in tumor, spot, detouring, mixed, or others. Two additional radiologists assessed CEUS images for the presence and pattern of tumoral vascularity, which served as the reference standard. If the tumoral vascular pattern on each examination matched that of the CEUS images, the Wilcoxon test and McNemar test, respectively, were used to compare the sensitivity for detecting tumoral vascularity between MFI and CDI, and between MFI and PDI. Logistic regression analysis was performed to identify factors associated with MFI detectability of tumoral vascularity.

RESULTS

CEUS demonstrated tumoral vascularity in 98.0% (50 of 51) of patients. MFI (58.0%, 29 of 50) demonstrated a higher sensitivity than CDI (14.0%, 7 of 50) or PDI (14.0%, 7 of 50) (P<0.001 for both) in detecting tumoral vascularity, provided that the vascular pattern was correctly depicted. Only tumor depth was associated with the MFI detectability of tumoral vascularity.

CONCLUSION

The sensitivity of MFI was higher than that of CDI or PDI in detecting the vascularity of HCCs when the vascular pattern was considered. MFI better detected the vascularity of shallow tumors.

Evaluation of transcatheter arterial embolization therapy on hepatocellular carcinomas using contrast-enhanced harmonic power Doppler sonography: comparison with CT, power Doppler sonography, and dynamic MRI

PURPOSE

The aim of this study was to assess and compare the sensitivity of power Doppler sonography, contrast-enhanced sonography, plain computed tomography (CT), and dynamic magnetic resonance imaging (MRI) for detecting hepatocellular carcinoma (HCC) nodules incompletely treated with transcatheter arterial embolization (TAE).

METHODS

A total of 63 unresectable HCC nodules were examined in this study. The HCCs were treated with TAE. All patients underwent plain CT, power Doppler sonography, contrast-enhanced harmonic power Doppler sonography, and dynamic MRI 1 week after TAE. The sensitivity of each modality to incompletely treated HCC nodules was compared. Detection of the residual viable HCC on angiography or tumor biopsy was regarded as the gold standard for the diagnosis of incomplete treatment.

RESULTS

Twenty-four nodules (38%) were diagnosed as incompletely treated. The sensitivities of plain CT, power Doppler sonography, contrast-enhanced harmonic power Doppler sonography, and dynamic MRI to these incompletely treated nodules were 42% (10/24), 46% (11/24), 88% (21/24), and 79% (19/24), respectively. Eighty percent (19 nodules) of the 24 incompletely treated nodules were located within a depth of less than 8 cm. The sensitivities of plain CT, power Doppler sonography, contrast-enhanced harmonic power Doppler sonography, and dynamic MRI to these superficial incompletely treated nodules were 37% (7/19), 53% (10/19), 100% (19/19), and 74% (14/19), respectively. In contrast, the sensitivities of each modality to deeply located nodules were 60% (3/5), 20% (1/5), 40% (2/5), and 100% (5/5), respectively.

CONCLUSION

Plain CT and power Doppler sonography had a low sensitivity to HCC nodules incompletely treated with TAE. Except for those that were deeply located, contrast-enhanced harmonic sonography showed the highest sensitivity in detecting incompletely treated HCC nodules.

Detection of tumor vascularity in hepatocellular carcinoma with contrast-enhanced Dynamic Flow imaging: Comparison with contrast-enhanced power Doppler imaging

OBJECTIVE

To compare the effectiveness of contrast-enhanced Dynamic Flow imaging and contrast-enhanced power Doppler imaging using Levovist(®) as a microbubble contrast agent in evaluating intratumoral vascularity in hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Twenty-nine patients with 54 hepatocellular carcinoma nodules (before treatment, 31; after treatment, 23) were studied with both Dynamic Flow and power Doppler imaging with intravenous injection of Levovist(®). Tumor vascularity was categorized as 0, no blood flow signals within the tumor; 1, dotlike blood flow signals within the tumor; 2, moderate blood flow signals within the tumor; and 3, abundant blood flow signals within the tumor. Detectability of intratumoral vascularity of hepatocellular carcinoma in three groups based on tumor depth, blooming and noise artifacts on contrast-enhanced Dynamic Flow and contrast-enhanced power Doppler imaging were also compared with results obtained using dynamic CT as a the gold standard. The effectiveness of contrast-enhanced Dynamic Flow and contrast-enhanced power Doppler imaging in assessing therapeutic effect were compared at the same time.

RESULTS

The ability of contrast-enhanced Dynamic Flow Doppler imaging to detect tumor vascularity in the superficial and intermediate hepatocellular carcinoma groups was close to that of contrast-enhanced power Doppler imaging (p>0.05). However, contrast-enhanced Dynamic Flow imaging demonstrated tumor parenchymal stain in 28 hepatocellular carcinoma nodules (61%), which was not detected by contrast-enhanced power Doppler imaging. Further, significantly fewer artifacts appeared in contrast-enhanced Dynamic Flow imaging than in contrast-enhanced power Doppler imaging (p<0.001). In assessing therapeutic response, the sensitivity of contrast-enhanced Dynamic Flow imaging was similar to that of dynamic CT. In deep areas, however, those more than 6 cm below the surface of the body, contrast-enhanced Dynamic Flow imaging was less sensitivity than contrast-enhanced power Doppler imaging (p=0.005).

CONCLUSION

Contrast-enhanced Dynamic Flow imaging provides an effective approach to assessing intratumoral vascularity and therapeutic response in HCC lesions situated less than 6 cm from the surface of the body. It is superior to contrast-enhanced power Doppler imaging in its ability to detect tumor parenchymal stain and production of fewer artifacts.

Controlling the size distribution of lipid-coated bubbles via fluidity regulation

Lipid-coated bubbles exhibit oscillation responses capable of enhancing the sensitivity of ultrasound imaging by improving contrast. Further improvements in performance enhancement require control of the size distribution of bubbles to promote correspondence between their resonance frequency and the frequency of the ultrasound. Here we describe a size-controlling technique that can shift the size distribution using a currently available agitation method. This technique is based on regulating the membrane dynamic fluidity of lipid mixtures and provides a general size-controlling variable that could also be applied in other fabrication methods. Three materials (1,2-dihexadecanoyl-sn-glycero-3-phosphocholine, 1,2-dioctadecanoyl-sn-glycero-3-phospho-(1'-rac-glycerol) and polyethylene glycol 40 stearate) with distinct initial fluidities and phase behaviors were used to demonstrate the use of fluidity regulation to control bubble sizes. Bubble size distributions of different formulations were determined by electrical impedance sensing, and bubble volumes and surface areas were calculated. To confirm the relationship between regulated fluidity and mean bubble size, the membrane fluidity of each composition was determined by fluorescence anisotropy, with the results indicating linear relations in the compositions with similar main transition temperatures. Compositions with a higher molar proportion of polyethylene glycol 40 stearate showed higher fluidities and larger bubbles. B-mode ultrasound imaging was performed to investigate the echogenicity and lifetime of the fabricated bubbles, with the results indicating that co-mixing a high-transition-temperature charged lipid (i.e., 1,2-dioctadecanoyl-sn-glycero-3-phospho-(1'-rac-glycerol)) extends the tailoring range of this fluidity regulation technique, allowing refined and continuous changes in mean bubble size (from 0.93 to 2.86 μm in steps of ∼0.5 μm), and also prolongs bubble lifetime. The polydispersity of each composition was also determined to evaluate practicality in particular applications. Our study demonstrates a feasible approach to naturally controling bubble size distribution and provides a practical reference for other fabrication systems and ultrasound imaging applications.

Evaluation of finger joint synovial vascularity in patients with rheumatoid arthritis using contrast-enhanced ultrasound with water immersion and a stabilized probe

PURPOSE.: To assess synovial microvascularity in finger joints with rheumatoid arthritis (RA) by contrast-enhanced ultrasound (CEUS), distinguishing between cases of active disease and those in remission; to standardize the technique for software analysis. METHODS.: Fifty-two finger joints of RA patients (26 with active disease and 26 in remission) were immersed in water and examined by CEUS using a fixed probe. Signal intensity curves were calculated with the software. RESULTS.: Contrast enhancement was detectable in all 26 patients with active RA (100%), but not in 25 of 26 patients in remission (96%); one of the latter patients (4%) showed minimal enhancement. The method's sensitivity and specificity in distinguishing active disease from remission were 100% and 96%. The grades of synovial enhancement correlated with clinical disease activity and software flow parameters. The peak contrast levels correlated with clinical activity, a peak of 9% representing the cutoff between remission and active disease. CONCLUSIONS.: CEUS with a fixed probe on finger joints immersed in water detected synovial vascularization in RA, producing results suitable for standardized software analysis and avoiding artifacts.

Assessment of hepatocellular carcinoma by contrast-enhanced ultrasound with perfluorobutane microbubbles: comparison with dynamic CT

OBJECTIVE

The aim of this study was to evaluate tumour vascularity and Kupffer cell imaging in hepatocellular carcinoma (HCC) using contrast-enhanced ultrasonography (CEUS) with Sonazoid (perfluorobutane) and to compare performance with dynamic CT.

METHODS

We studied 118 nodules in 88 patients with HCC. HCC was diagnosed as a hyperenhancement lesion in the arterial phase with washout in the portal phase on dynamic CT or by percutaneous biopsy. We observed tumour vascularity at the early vascular phase (10-30 s after contrast injection) and Kupffer imaging at the post-vascular phase (after 10 min).

RESULTS

Detection of vascularity at the early vascular phase was 88% in nodules that were found to be hypervascular on dynamic CT and 28% in hypo-/isovascular nodules; the detection of local recurrence nodules was 92%. The detection of vascularity was significantly lower in nodules >9 cm deep than in those ≤9 cm deep, but was not affected by tumour size. The detection of tumours at the post-vascular phase on CEUS was 83% in nodules with low density in the portal phase on dynamic CT and 82% in nodules with isodensity. The rate did not depend on the severity of underlying liver disease; rates decreased in nodules deeper than 9 cm, those smaller than 2 cm in diameter and in iso-enhancing nodules at the early vascular phase of CEUS.

CONCLUSION

CEUS with Sonazoid is a useful tool for assessing the vascularity of HCC and is equal to that of dynamic CT; however, the detectability of HCC vascularity is affected by location.

Analysis of morphological vascular changes of hepatocellular carcinoma by microflow imaging using contrast-enhanced sonography

AIM

To determine whether the findings of microflow imaging (MFI), composed of a flash replenishment and a maximum intensity holding sequence, using contrast-enhanced sonography, correlate with the degree of histological differentiation of hepatocellular carcinoma (HCC).

METHODS

This study was approved by the institutional review board; patients gave informed consent. The samples comprised of 61 nodules histologically diagnosed as HCC: 20 well-differentiated, 26 moderately-differentiated, and 15 poorly-differentiated HCC. SonoVue was used as the ultrasound (US) contrast agent. The US equipment used was a SSA-770 A with the imaging mode set at MFI. MFI is an imaging method combining flash replenishment imaging and maximum intensity holding. Two independent readers (readers 1 and 2) classified the microflow images into four patterns: (i) normal pattern; (ii) cotton pattern; (iii) vascular pattern; and (iv) dead wood pattern. The results were compared with the degree of histopathological differentiation of the HCC.

RESULTS

In each of the 61 HCC, blood vessels in the tumor were clearly resolved down to their fine branches. With regard to the relationship between imaging patterns and thehistological findings, it was found (with high percentages) that the normal and cotton patterns were associated with well-differentiated HCC, that the vascular pattern was associated with moderately-differentiated HCC, and that the dead wood pattern was associated with poorly-differentiated HCC. If HCC with the normal and cotton patterns were assessed as well differentiated and those with the vascular or dead wood pattern were assessed as moderately or poorly differentiated, the sensitivity, specificity, and accuracy of these assessments were found to be 85%, 92.7%, and 90%, respectively, for reader 1, and 85%, 82.9%, and 83.6%, respectively, for reader 2.

CONCLUSION

The angioarchitecture and hemodynamics of HCC could be evaluated in detail using MFI. The results of this study demonstrate the feasibility of a non-invasive preoperative diagnosis of the histological differentiation of HCC using MFI.

Computer-aided diagnosis for the classification of focal liver lesions by use of contrast-enhanced ultrasonography

The authors developed a computer-aided diagnostic (CAD) scheme for classifying focal liver lesions (FLLs) as liver metastasis, hemangioma, and three histologic differentiation types of hepatocellular carcinoma (HCC), by use of microflow imaging (MFI) of contrast-enhanced ultrasonography. One hundred and three FLLs obtained from 97 cases used in this study consisted of 26 metastases (15 hyper- and 11 hypovascularity types), 16 hemangiomas (five hyper- and 11 hypovascularity types) and 61 HCCs: 24 well differentiated (w-HCC), 28 moderately differentiated (m-HCC), and nine poorly differentiated (p-HCC). Pathologies of all cases were determined based on biopsy or surgical specimens. Locations and contours of FLLs on contrast-enhanced images were determined manually by an experienced physician. MFI was obtained with contrast-enhanced low-mechanical-index (MI) pulse subtraction imaging at a fixed plane which included a distinctive cross section of the FLL. In MFI, the inflow high signals in the plane, which were due to the vascular patterns and the contrast agent, were accumulated following flash scanning with a high-MI ultrasound exposure. In the initial step of our computerized scheme, a series of the MFI images was extracted from the original cine clip (AVI format). We applied a smoothing filter and time-sequential running average techniques in order to reduce signal noise on the single MFI image and cyclic noise on the sequential MFI images, respectively. A kidney, vessels, and a liver parenchyma region were segmented automatically by use of the last image of a series of MFI images. The authors estimated time-intensity curves for an FLL by use of a series of the temporally averaged MFI images in order to determine temporal features such as estimated replenishment times at early and delayed phases, flow rates, and peak times. In addition, they extracted morphologic and gray-level image features which were determined based on the physicians' knowledge of the diagnosis of the FLL, such as the size of lesion, vascular patterns, and the presence of hypoechoic regions. They employed a cascade of six independent artificial neural networks (ANNs) by use of extracted temporal and image features for classifying five types of liver diseases. A total of 16 temporal and image features, which were selected from 43 initially extracted features, were used for six different ANNs for making decisions at each decision in the cascade. The ANNs were trained and tested with a leave-one-lesion-out test method. The classification accuracies for the 103 FLLs were 88.5% for metastasis, 93.8% for hemangioma, and 86.9% for all HCCs. In addition, the classification accuracies for histologic differentiation types of HCCs were 79.2% for w-HCC, 50.0% for m-HCC, and 77.8% for p-HCC. The CAD scheme for classifying FLLs by use of the MFI on contrast-enhanced ultrasonography has the potential to improve the diagnostic accuracy in the histologic diagnosis of HCCs and the other liver diseases.

Correlation between parametric imaging using contrast ultrasound and the histological differentiation of hepatocellular carcinoma

AIM

To determine whether parametric imaging correlates with the degree of histological differentiation of hepatocellular carcinoma (HCC).

METHODS

The samples comprised 49 nodules diagnosed histologically as HCC: 19 well differentiated (w-HCC), 22 moderately differentiated (m-HCC), and eight poorly differentiated (p-HCC). The ultrasound (US) equipment used was SSA-770 A (Toshiba Medical Systems, Otawara, Japan) and the contrast agent was SonoVue (Bracco, Milan, Italy). After 1.5 mL of SonoVue was injected intravenously and staining of the tumors and parenchyma was confirmed, microbubbles in the scanned volume were eliminated using high mechanical index (MI) scanning frames. The "arrival time (T(A)) images," reflecting beta-values, were displayed with color codes at the phase after reperfusion. Images at the phase when the staining reached a plateau (90-180 s) were used as "A images," reflecting A values. These images were compared between each histological grade of differentiation.

RESULTS

Analysis of T(A) images indicated that beta-values in m-HCC were higher than those in the adjacent non-tumor parenchyma in all 22 samples and also were significantly higher than in the other HCCs (P < 0.001 for w-HCC; P < 0.05 for p-HCC). Furthermore, beta-values in p-HCC samples had significantly larger variations in terms of time and space than in the other HCCs (P < 0.001 for w-HCC; P < 0.01 for m-HCC). Analysis of A images indicated that the A value for w-HCC was significantly higher than those for either m-HCC or p-HCC (P < 0.001).

CONCLUSION

Both T(A) and A images were useful for diagnosing the histological differentiation of HCC.

Decrease in accumulation of ultrasound contrast microbubbles in non-alcoholic steatohepatitis

AIM

Non-alcoholic steatohepatitis (NASH) is one of the representative liver diseases in developed countries. Diagnosis of NASH is dependent on histological findings from liver biopsy.

METHODS

The usefulness of contrast ultrasound with Levovist for diagnosis of NASH is described. 2.5 g of ultrasound contrast agent Levovist was injected intravenously. The liver was scanned at 5, 10, 15, 20, 30, 40 and 50 min and changes in microbubble accumulation were evaluated. The signal intensity from regions of interest (ROI) on the contrast images was measured and estimated using time intensity curves (TICs). Twenty-one patients with NASH, 33 with non-alcoholic fatty liver disease (NAFLD) and 10 healthy volunteers (HV) were studied. The signal intensity was measured quantitatively at 5 and 20 min after injection.

RESULTS

There was a statistically significant decrease in NASH, when compared with NAFLD and HV groups. These changes in signal intensity were not correlated to the degree of fibrosis and steatosis in histological study. The sensitivity, specificity and overall accuracy obtained from the receiver operating characteristic (ROC) curve were 100% when the cut-off value was set at 43.6 of signal intensity at 20 min.

CONCLUSION

The Levovist contrast study is a useful screening examination which picks up NASH among fatty liver patients.

Doppler and harmonic ultrasound for hepatocellular carcinoma

Ultrasound (US) is the imaging method most frequently used for the detection and diagnosis of hepatocellular carcinoma (HCC). US image quality has greatly improved in recent years, with advances in transducer, beam-former technology and sophisticated image processing. In addition, the recent availability of US contrast agents including first- and second-generation contrast agents and the remarkable advances in US technology have led to the rapid development of new imaging methods such as low and high mechanical index (MI) imaging technology for the vascular phase and parenchymal phase of the liver. In terms of contrast agent, most reported studies in Asian countries have used a very fragile, first-generation microbubble agent. Nowadays, more stable,second-generation contrast agents are developing and used in clinical application to the liver. In the future, better results can be obtained in the diagnosis of HCC, decision of treatment method and assessment of therapeutic response if more durable contrast agents are used with advanced US techniques. In this article, the principles, methods, imaging findings and potential roles of new diagnostic US techniques with contrast agents in the diagnosis of HCC are discussed.

Recent advances in the diagnosis of hepatocellular carcinoma

In the last decade, new imaging techniques have become available, offering the possibility of investigating contrast perfusion of liver nodules in cirrhosis. It is now accepted that a non-invasive diagnosis of hepatocellular carcinoma (HCC) can be established based on the vascular pattern, obtained with pure blood pool contrast agents. The diagnostic pattern includes: hypervascularity in the arterial phase (15-35 s after contrast injection), consisting in a contrast signal in the nodule greater than in the surrounding parenchyma, followed by contrast wash out, which leads the nodule to show the same, or, more specifically, a lower contrast signal, than the surrounding parenchyma in the portal and late phases (>40 s after injection). Such a pattern can be obtained not only by computed tomography or magnetic resonance imaging, but also by contrast-enhanced ultrasonography, most simply with real-time low mechanical index harmonic imaging ultrasound equipment with second-generation ultrasound contrast agents. The risk of false-positive diagnosis of malignancy isnearly abolished when the functional vascular pattern is not the only feature, but is superimposed on a nodule visible also without contrast. One single contrast imaging technique may suffice to make a diagnosis of HCC if the nodule is >1 cm in diameter and has developed during a surveillance program. Other types of contrast agents, such as those taken up by the reticular-endothelial system cells, may offer additional diagnostic clues, but definitive evidence of their efficacy is still to be produced. In conclusion, contrast-enhanced imaging techniques now offer the possibility of a non-invasive diagnosis of HCC in a large number of cases, reducing the need of invasive investigations, such as ultrasound-guided biopsy or angiography.

Small hepatic nodules (< or =2 cm) in cirrhosis patients: characterization with contrast-enhanced ultrasonography

AIM

We evaluated the efficacy of contrast-enhanced ultrasonography (CEUS) for the characterization of small hepatic nodules (< or =2 cm) in cirrhosis patients.

PATIENTS AND METHODS

Thirty cirrhosis patients with 30 hepatic nodules (1-2 cm) were enrolled in this study. Eighteen hepatic nodules were hepatocellular carcinomas (HCC) and 12 were benign lesions. CEUS was performed using microbubble contrast (Levovist). With surrounding hepatic parenchyma as a reference, two characteristics of hepatic nodules, including arterial phase enhancement (AE) and the absence of delayed phase enhancement (ADE), were evaluated as criteria for the diagnosis of HCC. A radiologist independently reviewed the dynamic computed tomographies (CT) of 26 hepatic nodules.

RESULTS

CEUS showed AE in 15 nodules (13 HCC and two benign) and ADE in 17 lesions (14 HCC and three benign). For HCC, the coincidental AE of both CEUS and dynamic CT was 40%. Using both AE and ADE for HCC diagnosis, the sensitivity, specificity, accuracy, positive predictive value and negative predictive values were 55.6%, 91.7%, 70%, 90.9% and 57.9%, respectively. When using either AE or ADE for HCC diagnosis, the same parameters were 94.4%, 66.7%, 83.3%, 81% and 88.9%, respectively. One benign hepatic nodule with both AE and ADE was diagnosed as HCC 29 months after the CEUS study.

CONCLUSIONS

A combination of characteristics of AE and ADE as determined by CEUS was highly specific for small HCCs in cirrhosis patients. Concurrent delayed phase imaging is useful in the diagnosis of small hypovascular HCCs.

Ultrasound contrast agents: an overview

With the introduction of microbubble contrast agents, diagnostic ultrasound has entered a new era that allows the dynamic detection of tissue flow of both the macro and microvasculature. Underpinning this development is the fact that gases are compressible, and thus the microbubbles expand and contract in the alternating pressure waves of the ultrasound beam, while tissue is almost incompressible. Special software using multiple pulse sequences separates these signals from those of tissue and displays them as an overlay or on a split screen. This can be done at low acoustic pressures (MI<0.3) so that the microbubbles are not destroyed and scanning can continue in real time. The clinical roles of contrast enhanced ultrasound scanning are expanding rapidly. They are established in echocardiography to improve endocardial border detection and are being developed for myocardial perfusion. In radiology, the most important application is the liver, especially for focal disease. The approach parallels that of dynamic CT or MRI but ultrasound has the advantages of high spatial and temporal resolution. Thus, small lesions that can be indeterminate on CT can often be studied with ultrasound, and situations where the flow is very rapid (e.g., focal nodular hyperplasia where the first few seconds of arterial perfusion may be critical to making the diagnosis) are readily studied. Microbubbles linger in the extensive sinusoidal space of normal liver for several minutes whereas they wash out rapidly from metastases, which have a low vascular volume and thus appear as filling defects. The method has been shown to be as sensitive as three-phase CT. Microbubbles have clinical uses in many other applications where knowledge of the microcirculation is important (the macrocirculation can usually be assessed adequately using conventional Doppler though there are a few important situations where the signal boost given by microbubbles is useful, e.g., transcranial Doppler for evaluating vasospasm after subarachnoid haemorrhage). An important situation where demonstrating tissue devitalisation is important is in interstitial ablation of focal liver lesions: using microbubble contrast agents at the end of a procedure allows immediate evaluation of the adequacy of the ablation which can be extended if needed; this is much more convenient and cost-saving than moving the patient to CT and perhaps needing an additional ablation session at a later date. Similar considerations suggest that contrast-enhanced ultrasound might have a role in abdominal trauma: injury to the liver, spleen and kidneys can be assessed rapidly and repeatedly if necessary. Its role here alongside dynamic CT remains to be evaluated. Infarcts or ischaemia and regions of abnormal vascularity, especially in malignancies, in the kidneys and spleen seem to be useful and improved detection of the neovascularisation of ovarian carcinomas is promising. Similar benefits in the head-and-neck and in the skin while the demonstration of the neovascularisation of atheromatous plaques and of aggressive joint inflammation offer interesting potentials.

CT Evaluation of the Progression of Hypoattenuating Nodular Lesions in Virus-Related Chronic Liver Disease

OBJECTIVE

The purpose of this study was to clarify the natural outcomes of hypoattenuating nodular lesions in patients with virus-related chronic liver disease depicted on dynamic CT.

MATERIALS AND METHODS

Sixty lesions (mean size, 1.3 cm) exhibiting hypoattenuation or isoattenuation in the arterial and delayed phases of dynamic CT were retrospectively evaluated with additional CT (mean, six examinations) for a mean period of 838 days. The primary end point was emergence of hyperattenuating areas within hypoattenuating lesions, a phenomenon called attenuation conversion. Cumulative attenuation conversion rates suggesting rates of malignant transformation were calculated with the Kaplan-Meier method, and factors affecting attenuation conversion rate were analyzed with the Cox proportional hazard model.

RESULTS

Thirty-six (60%) of 60 hypoattenuating lesions developed to hyperattenuating lesions, 21 were unchanged, and three disappeared spontaneously. The 36 lesions that became hyperattenuating were divided into two subgroups according to lesion enhancement pattern: hyper-in-hypoattenuating (n = 25) and entirely hyperattenuating (n = 11). The cumulative attenuation conversion rates for the 60 hypoattenuating lesions were 15.8%, 44.3%, and 58.7% at 1, 2, and 3 years. The hyper-in-hypoattenuating lesions showed more rapid progression to entirely enhanced lesions. Positive results for hepatitis C viral antibody (p = 0.028) and initial lesion size (p = 0.007) showed a positive correlation with attenuation conversion rate.

CONCLUSION

Hypoattenuating hepatic nodular lesions in chronic liver disease depicted on dynamic CT have high malignant potential and should be followed with special attention to conversion from hypoattenuation to hyperattenuation to determine the optimal timing of treatment.

State-of-the-art ultrasonography of hepatocellular carcinoma

Over the last few decades sonographic techniques have progressed remarkably. Recent advances in ultrasonography include harmonics, real-time spatial compound imaging, adaptive image processing, 3D power Doppler imaging and contrast-enhanced gray-scale harmonic ultrasonography. These advances have had positive effects on the diagnosis of hepatocellular carcinomas and on the evaluation of their responses to therapy. In this article, we review recent sonographic advances for the diagnosis and treatment of hepatocellular carcinomas and its typical imaging features.

Evaluation of pathological features of hepatocellular carcinoma by contrast-enhanced ultrasonography: comparison with pathology on resected specimen

Features of hepatocellular carcinoma (HCC) observed by contrast-enhanced ultrasonography (CEUS) were compared to pathological features of corresponding resected HCC specimens, to evaluate the ability of CEUS to depict the pathological features of HCC. We investigated 50 HCC nodules that were treated by surgical resection. All nodules had been examined by CEUS with intravenous contrast agent (Levovist) before surgery. CEUS findings were divided into three phases for evaluation and classification of enhancement patterns: two vascular phases (arterial phase and portal venous phase) and the delayed phase. Pathological examination focused on differentiation and on the presence or absence of a tumor capsule, intratumoral septum, and intratumoral necrosis. All 21 nodules that showed a linear or annular vessel around the tumor margin in the arterial phase had capsular formation. Of the 27 nodules that showed heterogeneous perfusion in the portal venous phase, 21 (77.8%) had an intratumoral septum and 23 (85.2%) showed intratumoral necrosis. All nodules that were depicted as a defect with an unclear margin in the delayed phase were well-differentiated HCCs, whereas all nodules that were depicted as a defect with a clear margin were moderately or poorly differentiated HCCs. From our observations, the arterial, portal venous, and delayed phases of CEUS could reflect different pathological aspects of HCC. Some pathological characteristics of HCC might be evaluated preoperatively and non-invasively, by means of combined analysis of three phases of CEUS findings.

1.5 Harmonic Imaging Sonography with microbubble contrast agent improves characterization of hepatocellular carcinoma

AIM: To investigate the usefulness of 1.5 Harmonic Imaging Sonography with the use of the contrast agent Levovist for the diagnosis of hepatocellular carcinoma (HCC) and for the evaluation of therapeutic response.

METHODS: Phantom experiments were performed to compare the contrast effects of 2^nd harmonic imaging and 1.5 Harmonic Imaging Sonography. 1.5 Harmonic Imaging Sonography was employed to examine 36 patients with HCC (42 nodules) before and after the treatment and to compare against the findings obtained using other diagnostic imaging modalities.

RESULTS: In 1.5 Harmonic Imaging Sonography, the tumor vessels of HCCs were clearly identified during the early phase, and late-phase images clearly demonstrated the differences in contrast enhancement between the tumor and surrounding hepatic parenchyma. Blood flow within the tumor was detected in 36 nodules (85.7%) during the early phase and in all 42 nodules (100%) during the late phase using 1.5 Harmonic Imaging Sonography, in 38 nodules (90.5%) using contrast-enhanced CT, in 34 nodules (81.0%) using digital subtraction angiography (DSA), and in 42 nodules (100%) using US CO₂ angiography. Following transcatheter arterial embolization, 1.5 Harmonic Imaging Sonography detected blood flow and contrast enhancement within the tumors that were judged to contain viable tissue in 20 of 42 nodules (47.6%). However, 6 of these 20 cases were not judged in contrast-enhanced CT. 1.5 Harmonic Imaging Sonography was compared with the US CO2 angiography findings as the gold standard, and the sensitivity and specificity of these images for discerning viable and nonviable HCC after transcatheter arterial embolization were 100% and 100%, respectively.

CONCLUSION: 1.5 Harmonic Imaging Sonography permits the vascular structures of HCCs to be identified and blood flow within the tumor to be clearly demonstrated. Furthermore, 1.5 Harmonic Imaging Sonography is potentially useful for evaluating the therapeutic effects of transcatheter arterial embolization on HCC.

Comparison of contrast-enhanced power Doppler ultrasound (Levovist) and computed tomography in alveolar echinococcosis

BACKGROUND

To date, no study has compared unenhanced and contrast-enhanced (Levovist) power Doppler ultrasound with three-phase helical computed tomography (CT) for the analysis of the vascularization of hepatic lesions in patients who have alveolar echinococcosis.

METHODS

Fifteen patients (11 female and four male; average age, 45.8 years) with confirmed Echinococcus multilocularis infection underwent unenhanced and contrast-enhanced (Levovist) power Doppler ultrasound (2- to 5-MHz transducer head) and three-phase helical CT. The largest identified lesion in each patient was studied.

RESULTS

CT visualized vascularization peripheral or central to the largest echinococcal lesions in 11 of 15 patients. Vascularization in the area of the echinococcal lesions was not visualized by unenhanced or contrast-enhanced power Doppler ultrasound in any of the 15 patients studied.

CONCLUSION

Three-phase helical CT visualizes the vascularization associated with Echinococcus multilocularis lesions in the liver. Neither unenhanced nor contrast-enhanced ultrasound in power mode is suitable for this application.

An ultrasonic microbubble semi-intermodulated imaging technique

The performance of contrast imaging technique is critically influenced by some factors, such as spatial resolution, agent-to-tissue ratio, lifetime of contrast agents and attenuation effect. By using a transducer with higher frequency and higher bandwidth of transmitted signals, the spatial resolution can be improved. Similarly, a better signal-to-interference ratio (SIR) can improve the agent-to-tissue ratio, a lower transmission pressure can prolong the lifetime of contrast agents and a lower center frequency can diminish the attenuation effect. We extend the two-frequency analytic solutions of to approximate the short-pulse responses of microbubbles in a low-amplitude field. Based on their results, there is an expected component near 0 Hz in the spectrum of bubble echoes excited by a short pulse of ultrasound. Here, this component is called the low-frequency response; and it is shown to have a special bandwidth-dependent property and to have potential applications in imaging. We have established the procedure of semi-intermodulated (low-frequency) imaging and the effects of the attenuation effect on imaging resolution, SIR, and signal-to-noise ratio are also analyzed. The obtained experimental images demonstrate that the SIR in semi-intermodulated imaging is better than that in fundamental imaging under various attenuation conditions.

Contrast-enhanced ultrasonographic imaging diagnosis on assessment of vascularity in liver metastatic lesions

AIM: To investigate the vasculature of rabbit liver metastatic lesions by color Doppler imaging and power Doppler imaging (PDI) techniques.

METHODS: Eight New Zealand rabbits with implanted VX2 liver tumors were used. All ultrasound examinations were performed with a HP 5500 color Doppler ultrasound scanner. Before and after the injection of contrast agent, the changes of gray scale and the periphery and intralesional blood flow of the liver metastatic lesion were carefully observed by B mode ultrasound, color Doppler flow imaging (CDFI) and PDI.

RESULTS: Twelve lesions were found in the eight rabbits with implanted VX2 liver tumors, whose diameter ranged from 1.6 to 4.8 cm. Echoes of these lesions were not characterized and has lack of specificity. After the injection of contrast agent, the numbers of dot or strip-like flow messages increased both at the periphery and inside of these lesions under the mode of CDFI and PDI, and were more pronounced under PDI. Morphology of intralesional vessels extended, even branched and some signals were clearly found encircling the lesion. And some vessels were found penetrating into the center of the lesion.

CONCLUSION: PDI after injection of self-made echo contrast agent can show a pronounced sensitivity than that of B mode ultrasound and CDFI in diagnosis of vascularity of a metastatic lesion.

Effect of thalidomide in hepatocellular carcinoma: assessment with power doppler US and analysis of circulating angiogenic factors

PURPOSE

To prospectively evaluate the feasibility of using power Doppler ultrasonography (US) and measurement of circulating angiogenic factors to assess the antiangiogenic effect of thalidomide in hepatocellular carcinoma.

MATERIALS AND METHODS

The Ethics Committee of the National Taiwan University Hospital approved the study, and all patients gave prior written informed consent. Evaluation of response to thalidomide treatment was based on findings at computed tomography (CT) and change in serum alpha-fetoprotein level. Tumor vascularity index was evaluated with power Doppler US in patients with advanced hepatocellular carcinoma treated with 200-300 mg/d thalidomide. Serum levels of vascular endothelial growth factor, basic fibroblast growth factor, and placental growth factor were measured with enzyme-linked immunoassay. The chi(2) test or Fisher exact test was used for categorical variables, and the nonparametric Mann-Whitney test was used for numeric variables. A P value of less than .05 was considered to indicate a statistically significant difference.

RESULTS

Of 47 patients enrolled in the study who had disease that was bidimensionally assessable on CT scans, 44 were assessable for tumor response. Of the 44 evaluated, five were classified as showing objective response (responders): One each showed a complete and a partial response according to World Health Organization criteria, and three had a decrease in alpha-fetoprotein level by more than 50% and stable disease for 10.4, 5.3, or 3.5 months. The pretreatment vascularity index was significantly higher in responders (median, 7.42; range, 2.99-13.90) than in nonresponders (median, 2.15; range, 0-25.36) (P = .03). Four of five responders had a significant decrease in vascularity index with thalidomide. Serum levels of angiogenic factors did not differ significantly between responders and nonresponders.

CONCLUSION

Higher vascularity index may be associated with a better chance of response to thalidomide in patients with advanced hepatocellular carcinoma. Serum levels of circulating angiogenic factors do not appear to be clinically useful as an indicator of response.

Imaging diagnosis of hepatocellular carcinoma with differentiation from other pathology

Recent advances in liver imaging techniques and better understanding of imaging findings have facilitated the detection and characterization of hepatocellular nodules in a cirrhotic liver. It is important to recognize that various types of benign nodules and pseudolesions are identified on all imaging scans performed for the diagnosis of hepatocellular carcinoma. An accurate differentiation between them is critical for adequate management of cirrhotic patients. Unfortunately, any of the imaging tests and even percutaneous biopsy are not diagnostic for borderline lesions. Intimate collaboration of hepatologists, pathologists, surgeons, and radiologists with reasonable imaging and clinical criteria estimating the degree of malignancy is imperative.

Evaluation using contrast-enhanced harmonic gray scale sonography after radio frequency ablation of small hepatocellular carcinoma: sonographic-histopathologic correlation

OBJECTIVE

To evaluate the usefulness of contrast-enhanced harmonic wideband gray scale sonographic images obtained after radio frequency-induced coagulation necrosis, we compared the morphologic and histopathologic characteristics of the ablated tumors with sonographic images of the tumors.

METHODS

Forty-eight patients with 72 hepatocellular carcinomas with a maximal diameter of 3 cm or less were treated percutaneously using radio frequency ablation. Six treated tumors in 4 patients were resected 1 month after ablation; the remaining 66 treated tumors were evaluated by a biopsy procedure performed with an 18-gauge fine needle 1 month after ablation. The excised tumors and biopsy specimens were then examined by histopathologic methods, and the findings were compared with those obtained on contrast-enhanced harmonic wideband gray scale sonography. Hematoxylin-eosin-stained specimens were inconclusive as to whether cellular viability remained; therefore, cell viability was determined by a positive result after histochemical (lactate dehydrogenase and nicotinamide adenine dinucleotide phosphate-diaphorase) staining.

RESULTS

Contrast-enhanced harmonic wideband gray scale sonography after radio frequency ablation showed residual tumor enhancement in 5 (6.9%) of the 72 tumors; the histopathologic results for these 5 tumors were also positive for tumor residue. The remaining 67 tumors (93.1%) did not show any residual tumor enhancement when examined by sonography; however, only 66 tumors did not reveal tumor residue when examined histopathologically. Contrast-enhanced harmonic wideband sonographic imaging provided results that were comparable with histopathologic findings, the criterion standard for diagnosis; the sensitivity and specificity of the sonographic images for the detection of residual tumor tissue in ablated tumors were 83.3% (5 of 6) and 100% (66 of 66), respectively.

CONCLUSIONS

Contrast-enhanced harmonic wideband gray scale sonography is a potentially useful technique for evaluating the therapeutic effects of radio frequency ablation on hepatocellular carcinoma.

Imaging of focal liver lesions: low-mechanical-index real-time ultrasonography with SonoVue

OBJECTIVE

The purpose of this study was to evaluate the usefulness of a contrast-enhanced contrast-specific ultrasonographic technique with a low mechanical index for characterization of focal liver lesions.

METHODS

Contrast-specific ultrasonography was used to assess 144 patients with 147 focal liver lesions: 87 primary liver carcinomas, 27 hemangiomas, 16 focal nodular hyperplasias, 5 hepatic abscesses, 3 inflammatory pseudotumors of the liver, and 9 metastases. A sulfur hexafluoride gas-based contrast agent was used with a mechanical index of 0.08 to 0.11.

RESULTS

On contrast-enhanced ultrasonography, the typical hemodynamic pattern of primary liver carcinoma was the whole-lesion enhancement or mosaic enhancement in the arterial phase with an enhancement defect in the late phase (sensitivity, 92.0%; specificity, 86.7%). The most common enhancement pattern of hemangioma was that enhancement appeared in the periphery first and progressively filled into the lesion center (sensitivity, 96.3%; specificity, 97.5%). The enhancement pattern of focal nodular hyperplasia was that the whole lesion enhanced early and rapidly in the arterial phase with a centrifugal radiating configuration and appeared isoechoic or hyperechoic until the late phase (sensitivity, 87.6%; specificity, 94.5%). The central scar was detected in 31.3% of cases in the late phase. The specific enhancement of a hepatic abscess was the honeycomblike enhancement in all phases (sensitivity, 80.0%; specificity, 100%). No enhancement of a lesion in all phases was specific for an inflammatory pseudotumor of the liver.

CONCLUSIONS

Contrast-enhanced real-time ultrasonography is a promising approach in the noninvasive characterization of focal liver lesions and can be useful as a first-line imaging technique clinically when a focal liver lesion is detectable on ultrasonography.

[Contrast ultrasound imaging in focal liver lesions: diagnostic value and guidelines]

The recent introduction of high quality scanners and contrast agents for ultrasound deeply modifies diagnosis strategy in focal liver lesions by using validated criteria. Non-linear imaging methods using low mechanical index (MI<0.2) and second generation contrast agents allow real-time continuous imaging with concomitant limitation in background tIssue signal and also in agent collapse for a high quality contrast imaging giving dramatic improvement in detection and characterization of lesions. Interpretation is based on the presence of contrast agent within the lesion or not (hyper-, hypo- or isosignal) and the delay after injection (arterial, portal or parenchymal or late phase) as previously used by non-ultrasound methods. This allows an easy differentiation of benign from malignant lesions. Moreover, this allows complete characterization in 85 to 95% of all focal liver lesions and 75% in hepatocellular carcinomas. Those results markedly improve ultrasound accuracy compared to conventional sonography and so put contrast-enhanced sonography among recommended non-invasive imaging methods for focal liver lesions with changes in diagnostic strategy according to the lesion type and actual place of US methods. It is recommended to use contrast ultrasound methods in cancer staging for an optimal detection of liver metastases as well as in characterization of lesions detected during conventional sonography with a consecutive decrease of cost-diagnosis ratio.

Advanced dynamic flow imaging with contrast-enhanced ultrasonography for the evaluation of tumor vascularity in liver tumors

To examine the usefulness of advanced dynamic flow imaging in diagnosing hepatic tumor and in assessing therapeutic effects in patients with hepatocellular carcinoma (HCC) and metastatic hepatic tumor, we performed contrast-enhanced ultrasonography (US) with Levovist, a microbubble contrast agent. Twenty-two patients of 35 HCC nodules infected with hepatitis C virus (HCV) and six patients with metastatic liver nodules were studied. They were diagnosed as having HCC or metastasis with helical dynamic computed tomography (CT) and/or celiac angiography. Tumor vascularities in the early arterial and postvascular phases were assessed by real-time scanning of advanced dynamic flow imaging and intermittent interval-delay scanning of contrast pulse subtraction imaging with a wide-band power Doppler technology. All patients showed hypervascular enhancement of HCC on contrast-enhanced US and/or dynamic CT. The advanced dynamic flow could be obtained as vascular and perfusion images of hepatic tumors. Tumor vascularities, including tumor vessels and parenchymal flow, were able to demonstrate in 27 of 29 nodules including 17 patients with 27 HCC nodules and 2 patients with 2 metastatic nodules before radiofrequency ablation (RFA) treatment by the advanced dynamic flow on contrast-enhanced harmonic US. Two nodules gave insufficient dynamic flow which were located approximately 12 cm in depth from the body surface. The advanced dynamic flow, which was done 7-10 days after RFA, indicated disappearance of the tumor vessels in 27 of visible 27 nodules. The study on early phase of helical dynamic CT revealed the same results as noted in early vascular phase of dynamic flow US. No major complication of RFA procedure was noted. The results indicated that contrast-enhanced advanced dynamic flow imaging on US clearly depicted intratumoral vascularity in real time and thus it is useful to diagnose and assess therapeutic efficacy in patients with HCC and metastatic liver tumor.

CONTRAST HARMONIC ULTRASOUND OF SPONTANEOUS LIVER NODULES IN 32 DOGS

Thirty-two dogs with spontaneous hepatic nodules were given intravenous ultrasound contrast medium (Definity or Sonovue) and imaged with contrast harmonic software on a conventional ultrasound machine system. Digital video images were initially reviewed to describe the perfusion pattern of malignant nodules. The images were reviewed again to test this pattern against all individual nodules. Subjectively, there was improved conspicuity of malignant nodules after contrast enhancement compared with conventional imaging and increased numbers of malignant nodules were often noted. There was decreased conspicuity of benign nodules and no additional nodules were seen after contrast enhancement. There was a highly significant (P < 0.0001) association of malignancy with a hypoechoic nodule at surrounding normal liver peak contrast enhancement. Benign nodules were isoechoic to the surrounding normal liver at peak contrast enhancement. Only one benign nodule (hepatoma) had regions of hypoechogenicity compared with the surrounding normal liver at peak liver contrast enhancement. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were highly significant (P < 0.0001) (100%, 94.1%, 93.8%, 100%, and 96.9%, respectively). No complications or morbidity was noted throughout the course of the study. Contrast harmonic ultrasound appears to be accurate at discriminating between naturally occurring benign and malignant nodules in the liver of dogs.

Usefulness of contrast-enhanced wide-band Doppler ultrasonograpy to diagnose alveolar echinococcosis of the liver and evaluate the effect of the treatment

Alveolar echinococcosis is a rare parasitic disease caused by Echinococcus multicularis and most commonly involves the liver. Early diagnosis and accurate evaluation of the effect of the treatment are essential to improve the prognosis of patients with alveolar echinococcosis of the liver (AEL). The aim of this study was to demonstrate the characteristic imaging of AEL by contrast-enhanced Dynamic Flow (CE-DF) employing a wide-band Doppler technique for the diagnosis and the accurate evaluation of the effect of the treatment. Four patients with five AEL lesions before treatment or during medication were examined by CE-DF. All of the five AEL lesions examined by CE-DF revealed a defect with an irregular and distinct margin like a worm-eaten defect appearance, which was never observed on other hepatic lesions, in liver perfusion image during post-vascular phase. In addition, CE-DF made it possible to measure the size of AEL lesions accurately because the margin was detected distinctly. These data suggest that CE-DF is clinically useful for the diagnosis of AEL and the evaluation of the effect of the treatment.

Contrast-enhanced ultrasound assessment of tissue response to high-intensity focused ultrasound

We report the use of contrast-enhanced ultrasonography as an immediate means of assessing the clinical response to high-intensity focused ultrasound (US) or HIFU treatment of liver tumours. HIFU is a noninvasive transcutaneous technique for the ablation of tumours that has been shown to destroy tumour vasculature, as well as to cause coagulative necrosis of tumour cells. As a dynamic indicator of tissue perfusion, microbubble contrast agents have already been reported to increase the diagnostic sensitivity of ultrasonography in the detection of liver tumours. This report documents the ability of one i.v. microbubble contrast agent (SonoVue, Bracco, Italy) to delineate the extent of HIFU ablation by comparison of pre- and immediately posttreatment perfusion within the target tumour. Observed changes were seen to correlate well with the ablated volume on histologic evaluation of the treated volume. This is the first time that this imaging technique has been reported in this setting.

Contrast-enhanced power Doppler sonography of ductal pancreatic adenocarcinomas: correlation with digital subtraction angiography findings

PURPOSE

The purpose of this prospective study was to utilize contrast-enhanced power Doppler sonography to evaluate the enhancement characteristics of ductal pancreatic adenocarcinomas and correlate them with the tumor vascularity observed on digital subtraction angiography (DSA).

METHODS

Twenty consecutive patients with ductal pancreatic adenocarcinoma underwent power Doppler sonography and DSA. Tumor vascularity was assessed using unenhanced and contrast-enhanced power Doppler sonography. The contrast agent Levovist was administered intravenously by bolus injection of a dose of 2.5 g at a concentration of 350 mg/mL; saline was administered immediately thereafter. The patients were asked to hold their breath for 30 seconds (for the period 15-45 seconds after saline injection) while the early phase of enhancement was studied; the delayed phase of enhancement was observed between 60 and 120 seconds after saline administration, while patients breathed gently.

RESULTS

None of the 20 pancreatic carcinomas showed any color signals on power Doppler sonography before administration of the contrast medium. Seventeen (85%) of the 20 pancreatic carcinomas also showed no enhancement in the early and delayed phases of contrast-enhanced power Doppler sonography. However, in the early phase of contrast-enhanced power Doppler sonography; 1 lesion showed pronounced enhancement and 2 showed mild enhancement. On DSA, the 17 carcinomas showing no enhancement on power Doppler sonography were found to be hypovascular, whereas the remaining 3 carcinomas with contrast enhancement on power Doppler sonography were found to be hypervascular.

CONCLUSIONS

The enhancement characteristics of the ductal pancreatic adenocarcinomas correlated well with the tumor vascularity observed on DSA. However, further study is needed to determine the accuracy of contrast-enhanced sonography in the diagnosis of pancreatic masses.

[The role of contrast-enhanced ultrasonography for the detection of hepatocellular carcinoma]

The incidence of the hepatocellular carcinoma (HCC) is increasing in Occident, as well as in France. Primary prevention is the only solution for early detection. The combination of ultrasound (US) and alphaFP each 4 to 6 Months dosage has many limitations. The sensitivity of US examination is rather poor (less than 70% for lesions below 2 cm in diameter) and serum alphaFP values remain normal in almost 50% of HCC. US contrast agents (USCAs) with perfluorocarbon gases increase the backscattered signals during all phases of the liver transit, including arterial, portal and delayed phases. Hepatocellular lesions exhibit a specific kinetics with strong enhancement during arterial phase, and rapid wash-out during portal and delayed phases. USCAs increase the detection of HCCs and allow characterization of additional focal lesions found in cirrhotic livers (regenerative and dysplastic nodules, haemangiomas.). Indeed, regenerative nodules contrast uptake is synchronous to the surrounding parenchyma, and usually disappear during portal and delayed phases. However, US in cirrhosis remains a difficult examination, with limitations due to limited access to sub-diaphragmatic localization, attenuation of the ultrasound beam and shortness of the arterial phase.

Evaluation of blood flow in pancreatic ductal carcinoma using contrast-enhanced, wide-band Doppler ultrasonography: correlation with tumor characteristics and vascular endothelial growth factor

BACKGROUND AND AIMS

Tumor vascularization has been attracting attention. However, there have been only a few reports on tumor vascularization in pancreatic ductal carcinoma, especially on vascularization depicted by imaging modalities. We investigated the relationship among wide-band Doppler signals, clinicopathological factors, and vascular endothelial growth factor (VEGF) expression.

METHODS

Sixty-nine patients with pancreatic ductal carcinoma were investigated. The vascular signals from carcinoma lesions were assessed by contrast-enhanced, wide-band Doppler ultrasonography (dynamic flow). VEGF expression was quantitated by enzyme immunoassay for 28 patients. Depending on the intensity of the signals, the patients were classified into type A (definite vascular signal) or type B (almost no vascular signal).

RESULTS

Type A patients and type B patients accounted for 65% and 35% of patients, respectively. According to multivariate analysis of vascular signal type and clinicopathological factors, liver metastasis occurred significantly more frequently in the type A group. VEGF expression was also significantly higher in the type A group than in the type B group.

CONCLUSIONS

Dynamic flow has very high sensitivity for detecting the vascular signals from pancreatic ductal carcinoma. The quantity of vascular signals correlated with tumor characteristics and VEGF.

Factor analysis in both spatial and temporal domains of color blooming artifacts in ultrasound investigations utilizing contrast agents

Color blooming artifacts can cause misinterpretations of normal and pathological structures during color Doppler flow imaging with ultrasound contrast agents (USCAs). These artifacts are characterized in both the spatial and temporal domains: in the spatial domain, artifacts result from wave propagation and the ultrasound system; and in the temporal domain, the color blooming time (CBT) is used to denote the duration of artifacts. In our experiments, CBT decreased from 86.7 to 46.8 s when the transmitting pressure was decreased from 370 to 180 kPa. From this, we conclude that an adaptive mechanical index can significantly shorten the CBT, which may in turn prolong the optimal viewing time during in vivo ultrasound investigations utilizing USCAs.

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

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

The current status of imaging diagnosis of hepatocellular carcinoma

Early detection of hepatocellular carcinoma (HCC) is important, since the most effective treatment for HCC is surgical resection or local ablation therapy when the tumor is small. Fortunately, recent advances in liver imaging techniques have facilitated the detection of small HCCs. Recent progression of noninvasive imaging technology includes various techniques of harmonic ultrasound (US) imaging with several kinds of US contrast agents, multislice helical computed tomography (CT), and rapid high-quality magnetic resonance (MR) technique with new, tissue-specific contrast agents. These techniques seem to have a strong potential to improve detection and characterization of HCC. In this review, the technique and efficacy of new imaging methods including contrast enhanced US, multislice CT, and recent MR techniques with new contrast agents for detecting and diagnosing HCC will be described.

Evaluation of hepatic focal nodular hyperplasia with contrast-enhanced gray scale harmonic sonography: initial experience

OBJECTIVE

To assess the potential of contrast-enhanced gray scale harmonic sonography in the evaluation of the typical vascular and enhancement patterns of hepatic focal nodular hyperplasia.

METHODS

Thirteen patients with 13 lesions of hepatic focal nodular hyperplasia underwent contrast-enhanced gray scale harmonic sonography. After the injection of a microbubble contrast agent (SH U 508A), gray scale harmonic sonographic studies using a Coded Harmonic Angio technique were performed with a combination of a period of continuous scanning to assess the vascular pattern (vascular imaging) and interval delay scanning to determine the sequential enhancement pattern (acoustic emission imaging). Each imaging pattern was categorized and analyzed by consensus of 2 experienced radiologists.

RESULTS

In 12 (92%) of 13 lesions, vascular imaging during the arterial phase showed central arteries of a spoked wheel pattern, whereas the remaining lesion had stippled vascularity. On acoustic emission imaging, 11 (85%) of 13 lesions were hyperechoic during the early phase, and the remaining 2 (15%) were isoechoic compared with surrounding parenchyma. Ten (77%) of 13 lesions remained either hyperechoic (5 of 13) or isoechoic (5 of 13) during the delay phase, whereas the remaining 3 lesions (23%) were hypoechoic.

CONCLUSIONS

Contrast-enhanced gray scale harmonic sonography showed the typical vascularity of a spoked wheel pattern during the vascular phase and persistent enhancement on serial acoustic emission imaging in most cases of hepatic focal nodular hyperplasia, and thereby it can be a promising technique in noninvasive diagnosis of this entity.

Qualitative assessment of tumor vascularity in hepatocellular carcinoma by contrast-enhanced coded ultrasound: comparison with arterial phase of dynamic CT and conventional color/power Doppler ultrasound

The purpose of this study was to evaluate the detection rate of tumor vessels and vascularity in hepatocellular carcinoma (HCC) by contrast-enhanced coded US using Levovist, and to compare with conventional color/power Doppler US (CDUS) and dynamic CT. Ninety nodules (72 hypo/isoechoic nodules, 18 hyperechoic nodules) in 61 patients were studied. We observed tumor vessels by continuous transmission at the early vascular phase (40 s following administration of Levovist) and vascularity by intermittent transmission (intervals of 2-3 s) at the late vascular phase (40 to approximately 120 s). The detection rate of tumor vessels at the early vascular phase was 97% in hypo/isoechoic nodules and 70% in hyperechoic nodules with high density in dynamic CT being higher than that by CDUS. Tumor vascularity at the late vascular phase in hypo/isoechoic and hyperechoic nodules was hyper-enhancement in 78 and 40%, iso-enhancement in 19 and 40%, and hypo-enhancement in 3 and 0%, respectively. The detection rates of tumor vessels and vascularity in hyperechoic nodules were similar to those by CDUS. The detection rates of tumor vessels and vascularity were not affected by the tumor size in HCC tumors with high density in dynamic CT. Contrast-enhanced US with Levovist was superior to CDUS and equal to dynamic CT to assess tumor vessels in hypo/isoechoic nodules. Although it was equal to CDUS for hyperechoic nodules, this modality is useful in evaluating tumor hemodynamics.

Flash-echo gray-scale imaging in the subtraction mode for assessing perfusion of small hepatocellular carcinoma

PURPOSE

The aim of this study was to evaluate the effectiveness of using flash-echo imaging (FEI) in the subtraction mode to assess the vascularity of small hepatocellular carcinomas (HCCs) that had been unsatisfactorily assessed with power Doppler sonography.

METHODS

Between May 2000 and April 2001, we prospectively assessed nodular small HCCs using FEI in the subtraction mode after power Doppler sonography resulted in unsatisfactory images. After microbubble contrast was injected, we used the FEI technique to assess tumor perfusion in the arterial, portal, and delayed phases.

RESULTS

Our study population comprised 14 patients (10 men and 4 women) whose ages ranged from 31 to 79 years (mean, 61 +/- 13.7 years) and whose tumors ranged in size from 0.8 to 3 cm (mean, 1.8 +/- 0.5 cm). Power Doppler sonography was unable to assess tumor vascularity in 6 cases because of interference by heart pulsation, and it failed to detect a color signal in the other 8 cases. All tumors were enhanced with FEI. In the arterial phase, 7 of the 14 tumors (50%) showed hyperperfusion relative to liver parenchyma enhancement, 5 of 14 (36%) showed isoperfusion, and 2 of 14 (14%) showed hypoperfusion. In the portal phase, 3 of the 14 tumors (21%) showed isoperfusion, and the other 11 (79%) showed hypoperfusion. In the delayed phase, all 14 tumors showed hypoperfusion.

CONCLUSIONS

Despite heart pulsation and slow vascular flow, FEI in the subtraction mode was sensitive and effective in assessing the perfusion of small HCCs.

Hepatocellular carcinoma: assessment of vascularity with single-level dynamic ultrasonography during the arterial phase

OBJECTIVE

To evaluate the hemodynamic features of hepatocellular carcinoma on single-level dynamic ultrasonography during the arterial phase.

METHODS

Twenty-two hepatocellular carcinomas were examined by single-level dynamic ultrasonography with high transmit intensity and SH U 508A. The scans were performed for 40 seconds with a 1-second interval between each ultrasound transmission and with individual optimization of the scan delay time. The times of initiation of enhancement for both the hepatic artery and the tumor and the time of maximal enhancement for the tumor were recorded, and the mean echo values at every second for the tumor and hepatic parenchyma were measured.

RESULTS

Twelve tumors showed hyperechoic enhancement compared with hepatic parenchyma throughout the scans. The other 10 showed hyperechoic enhancement during some segments (range, 8-34 seconds) and either isoechoic (n = 5) or hypoechoic (n = 5) enhancement during the remaining parts; the hyperechoic segments were often short (< 20 seconds, 14%). Although the times for initiation of enhancement for the hepatic artery and hepatocellular carcinoma and the time of maximal enhancement for the tumor varied, the tumor usually initiated enhancement immediately after the hepatic artery (r = 0.986; P = .000001). The interval between the time of initiation of enhancement for the tumor or hepatic artery and that of maximal enhancement for the tumor was significantly correlated with the tumor size (r = 0.700; P = .008; and r = 0.780; P = .002).

CONCLUSIONS

With individual optimization of the scan delay time, single-level dynamic ultrasonography is useful for depicting the hypervascularity of hepatocellular carcinoma during the arterial phase.