Hepatocellular carcinoma: contrast enhancement with Levovist

Management of an incidental liver mass

The increased use of sensitive imaging modalities has led to increased identification of the incidental liver mass (ILM). A combination of careful consideration of patient factors and imaging characteristics of the ILM enables clinicians to recommend a safe and efficient course of action. Using an algorithmic approach, this article includes pertinent clinical factors and the specific radiologic criteria of ILMs and discusses the indications for potential procedures. It is the aim of this article to assist with the development of an individualized strategy for each patient with an ILM.

Computer-aided image analysis of focal hepatic lesions in ultrasonography: preliminary results

PURPOSE

To develop a computer-aided image analysis (CAIA) algorithm for analyzing US features of focal hepatic lesions and to correlate the feature values of CAIA with radiologists' grading.

MATERIALS AND METHODS

Two abdominal radiologists, blinded to the final diagnosis, independently evaluated sonographic images of 51 focal hepatic lesions in 47 patients: hemangiomas (n = 19), hepatic simple cysts or cystic lesions (n = 14), hepatocellular carcinoma (n = 11), metastases (n = 6), and focal fat deposition (n = 1). All images were graded using a 3- to 5-point scale, in terms of border (roundness, sharpness, and the presence of peripheral rim), texture (echogenicity, homogeneity, and internal artifact), posterior enhancement, and lesion conspicuity. Using a CAIA, texture and morphological parameters representing radiologists' subjective evaluations were extracted. Correlations between the radiologists and the CAIA for assessing parameters in corresponding categories were computed by means of weighted kappa statistics and Spearman correlation test.

RESULTS

A good agreement was achieved between CAIA and radiologists for grading echogenicity (weighted kappa = 0.675) and the presence of hyper- or hypoechoic rim (weighted kappa = 0.743). Several CAIA-derived features representing homogeneity of the lesions showed good correlations (correlation coefficient (gamma) = 0.603 approximately 0.641) with radiologists' grading (P < 0.05). For internal artifact (gamma = 0.469-0.490) and posterior enhancement (gamma = -0.516) of the cyst and lesion conspicuity (gamma = 0.410), a fair correlation between CAIA and radiologists was obtained (P < 0.05). However, parameters representing lesions' border such as sharpness (gamma = 0.252-0.299) and roundness (gamma = -0.134-0.163) showed no significant correlation (P > 0.05).

CONCLUSION

As a preliminary step in US computer-aided diagnosis for focal hepatic lesions, a CAIA algorithm was constructed with a good agreement and correlation with human observers in most US features. In addition, these features should be weighted highly when a computer-aided diagnosis for characterizing focal liver lesions on US is designed and developed.

Recent advances in ultrasound technology

Technical improvements have made profound changes in diagnostic ultrasound imaging. Some of these changes, such as encoded pulses and receive focusing, occur in the background and are essentially nonadjustable. Others, including harmonics and compounding, are real-time options and are adjustable by the imager. New technologies that offer great promise for improved characterization of lesions include contrast ultrasound and elastography. This article will attempt to update the small animal imager on the clinical applications of these newer technologies.

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.

Enhancement pattern of hepatocellular carcinoma: comparison of real-time contrast-enhanced ultrasound and contrast-enhanced computed tomography

We compared the enhancement pattern of 98 hepatocellular carcinoma nodules in 92 patients on contrast-enhanced ultrasound (CEUS) and contrast-enhanced computed tomography (CECT). Contrast-enhanced ultrasound was performed with SonoVue and a low mechanical index method. In arterial phase, 98 nodules were hyperenhancing on CEUS and 94 on CECT. In portal phase, 82 nodules were hypoenhancing on CEUS and 83 on CECT. Peripheral thin-rim-like enhancement was exhibited in 30 nodules on CEUS and 31 on CECT. Intratumoral vessels were visualized in 94 nodules on CEUS and 36 on CECT.

Prospective multicenter trial evaluating a novel method of characterizing focal liver lesions using contrast-enhanced sonography

OBJECTIVE

The purpose of this study was to assess the clinical value and potential impact of SonoVue-enhanced sonography in the characterization of focal liver lesions.

SUBJECTS AND METHODS

This study included 127 patients with 82 malignant and 52 benign lesions in the liver. Contrast-enhanced sonography was performed using nonlinear imaging modes at low mechanical index (0.1-0.3) to enable real-time visualization of arterial, portal, and late-phase enhancement. Digital recordings of unenhanced sonography and contrast-enhanced sonography were reviewed by on-site investigators and two off-site blinded interpreters. The final diagnosis was based on consensus interpreting of all examinations by another two expert observers with access to CT, MRI, and histologic data; the diagnostic accuracy of contrast-enhanced sonography in identifying the lesion as benign, malignant, or indeterminate and as actual tumor type was compared with baseline sonography.

RESULTS

For on-site investigators, contrast-enhanced sonography reduced the number of indeterminate diagnoses by 67% and improved the sensitivity and specificity to 90.2% and 80.8%, respectively (p < 0.001). For off-site interpreters, contrast-enhanced sonography reduced the number of indeterminate diagnoses by 51-56% (p < 0.001); significantly improved sensitivity and specificity to 90.8-95.4% and 83.7-89.8%, respectively (p < 0.001); eliminated observers' variability (kappa coefficient: 0.66-0.77); and showed no significant difference in all comparisons in the analysis of lesions measuring less than 1.5 cm, 1.5-2.5 cm, and all sizes combined. Contrast-enhanced sonography did not rely on availability of clinical history to enable the diagnoses, and it reduced the need for further imaging investigations 23.7% to 90.4%.

CONCLUSION

Contrast-enhanced sonography improves the characterization of focal liver lesions and may limit the need for further investigations.

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.

An Algorithm for the Diagnosis of Focal Liver Masses Using Microbubble Contrast-Enhanced Pulse-Inversion Sonography

OBJECTIVE

The objective of this study was to develop an algorithm for liver mass diagnosis using microbubble contrast-enhanced pulse-inversion sonography.

SUBJECTS AND METHODS

Ninety-six lesions in 92 patients were evaluated with DMP 115 (Definity)-enhanced pulse-inversion sonography, comprising 44 malignancies (29 hepatocellular carcinomas, 12 metastases, two peripheral cholangiocarcinomas, and one hepatic lymphoma) and 52 benign lesions (26 hemangiomas, 20 focal nodular hyperplasias, and six others). All had continuous low-mechanical-index imaging through the arterial and portal venous phase. A three-person blind review evaluated single images at baseline, early and peak arterial phases, and through the extended portal phases with a movie showing arterial phase wash-in. Reviewers assessed lesional vascularity and enhancement blindly but did not make a diagnosis. Combinations of answers were compared with independently determined final diagnoses to develop an algorithm for liver mass diagnosis.

RESULTS

Portal phase enhancement comprises the first step of the algorithm, with positive or sustained enhancement identifying 48 (92%) of 52 benign lesions and negative enhancement or washout present in 41 (93%) of 44 malignancies. Sustained portal phase enhancement with arterial phase peripheral nodularity and centripetal progression predicted 24 (92%) of 26 of the hemangiomas; diffuse arterial phase enhancement greater than the liver identified 19 (95%) of 20 of the focal nodular hyperplasias. With negative portal phase enhancement, arterial phase information was less effective at differentiating hepatocellular carcinoma (25 [86%] of 29 cases) from another hepatic malignancy (11 [73%] of 15 cases).

CONCLUSION

A simple diagnostic algorithm for interpretation of microbubble-enhanced sonography provides sensitive and accurate diagnosis of commonly encountered liver masses.

Comparison of fundamental sonography, tissue-harmonic sonography, fundamental compound sonography, and tissue-harmonic compound sonography for focal hepatic lesions

Image qualities of fundamental, tissue-harmonic, fundamental compound, and tissue-harmonic compound sonography for evaluating focal hepatic lesions were compared. Two radiologists, blinded to the type of techniques and to the final diagnosis, independently evaluated 384 images of 96 hepatic lesions: hemangiomas (n=35), hepatic cystic lesions (n=28), cirrhosis-related nodules (n=22), focal nodular hyperplasia (n=1), and metastases (n=10). All images were graded in terms of lesion conspicuity, margin sharpness, and overall image quality using a 4- or 5-point scale. In the cases of cystic lesions, posterior acoustic enhancement and internal artifacts were also analyzed. A Friedman test was used for multiple statistical comparisons of the four techniques for all parameters. Compound imaging was significantly superior to fundamental imaging regarding lesion conspicuity, margin sharpness, and overall quality (P<0.05). For posterior enhancement and internal artifacts within the cyst, harmonic ultrasonography (US) was significantly better than fundamental US (P<0.05). For evaluating focal hepatic lesions on US, compound imaging provided better lesion conspicuity, better margin sharpness, and better overall image quality than fundamental imaging did. Tissue harmonic imaging also provided better posterior enhancement and fewer internal artifacts of the cyst than fundamental imaging.

CHARACTERIZATION OF LYMPHOMATOUS LYMPH NODES IN DOGS USING CONTRAST HARMONIC AND POWER DOPPLER ULTRASOUND

Doppler ultrasound has been used in humans to determine angioarchitecture of lymph nodes as the criterion for the determination of malignancy. We hypothesized that the vascular and perfusion patterns of a canine malignant lymph node could be characterized with intravenous microbubble ultrasound contrast media and that contrast harmonic ultrasound could provide better conspicuity of the angioarchitecture when compared with Power Doppler ultrasound. In this study, 11 peripheral lymph nodes in dogs with histologically verified malignant lymphoma were imaged with fundamental ultrasound, Power Doppler ultrasound, and three contrast harmonic pulse sequences to characterize the vascular pattern and perfusion. Vascular imaging was greatly enhanced in these nodes with 2.13 times more vessels seen with contrast harmonic ultrasound compared with Power Doppler ultrasound (P < 0.01). The angioarchitecture of lymphomatous lymph nodes of dogs in this study were similar to those previously described in malignant superficial lymph nodes in human patients; 45.5% of the nodes had displacement of the central hilar vessel, 45.5% had aberrant vessels, 63.6% had pericapsular vessels, 36.4% had subcapsular vessels, and 81.8% had loss of the central hyperechoic band in fundamental sonography. Poor perfusion, indicated by a lower mean pixel intensity increase between pre- and postcontrast administration images, was seen in 36.4% of the lymph nodes while 63.6% had fair to good perfusion. The perfusion patterns in nine of the 11 lymph nodes were homogenous and two showed focal hypoperfused regions. We conclude that Power Doppler and contrast harmonic ultrasound are beneficial in accurately depicting angioarchitechture and can provide additional information in determining the presence of malignant vascular characteristics within lymphomatous nodes in dogs.

Radiofrequency ablation of liver cancer: early evaluation of therapeutic response with contrast-enhanced ultrasonography

The early assessment of the therapeutic response after percutaneous radiofrequency (RF) ablation is important, in order to correctly decide whether further treatment is necessary. The residual unablated tumor is usually depicted on contrast-enhanced multiphase helical computed tomography (CT) as a focal enhancing structure during the arterial and portal venous phases. Contrast-enhanced color Doppler and power Doppler ultrasonography (US) have also been used to detect residual tumors. Contrast-enhanced gray-scale US, using a harmonic technology which has recently been introduced, allows for the detection of residual tumors after ablation, without any of the blooming or motion artifacts usually seen on contrast-enhanced color or power Doppler US. Based on our experience and reports in the literature, we consider that contrast-enhanced gray-scale harmonic US constitutes a reliable alternative to contrast-enhanced multiphase CT for the early evaluation of the therapeutic response to RF ablation for liver cancer. This technique was also useful in targeting any residual unablated tumors encountered during additional ablation.

Diagnosis of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is responsible for a large proportion of cancer deaths worldwide. HCC is frequently diagnosed after the development of clinical deterioration at which time survival is measured in months. Long-term survival requires detection of small tumors, often present in asymptomatic individuals, which may be more amenable to invasive therapeutic options. Surveillance of high-risk individuals for HCC is commonly performed using the serum marker alpha-fetoprotein (AFP) often in combination with ultrasonography. Various other serologic markers are currently being tested to help improve surveillance accuracy. Diagnosis of HCC often requires more sophisticated imaging modalities such as CT scan and MRI, which have multiphasic contrast enhancement capabilities. Serum AFP used alone can be helpful if levels are markedly elevated, which occurs in fewer than half of cases at time of diagnosis. Confirmation by liver biopsy can be performed under circumstances when the diagnosis of HCC remains unclear.

Noninvasive assessment of tumor vascularity by contrast-enhanced ultrasonography and the prognosis of patients with nonresectable pancreatic carcinoma

BACKGROUND

Studies have shown that angiogenesis is one of the factors that influences the prognosis of patients with solid tumors, including pancreatic carcinomas. However, none have assessed noninvasively the relation between angiogenesis and prognosis in patients with pancreatic carcinoma. Contrast-enhanced ultrasonography (US) not only is a convenient, harmless, and noninvasive imaging modality, but it also provides detailed information on tumor vascularity. The objectives of this study were to assess the vascularity of pancreatic carcinoma noninvasively by contrast-enhanced US and to clarify the prognostic value of tumor vascularity in patients with nonresectable pancreatic carcinoma.

METHODS

Thirty-five consecutive patients with pathologically confirmed, nonresectable pancreatic carcinoma were examined with contrast-enhanced US before systemic chemotherapy. The correlations among tumor vascularity, clinicopathologic factors, and clinical outcomes then were analyzed statistically to investigate prognostic indicators.

RESULTS

The median time to progression (TTP) was longer in patients who had avascular tumors compared with patients who had vascular tumors (110 days vs. 28 days, respectively; P=0.0072; log-rank test). The median survival also was longer in patients who had avascular tumors (267 days vs. 115 days, respectively; P=0.0034; log-rank test). A multivariate analysis using a Cox proportional hazards model revealed that tumor vascularity was a significant, independent factor that influenced TTP (P <0.001) and survival (P=0.022) along with primary tumor size and serum lactate dehydrogenase (LDH) level, which are well known as prognostic factors in patients with pancreatic carcinoma.

CONCLUSIONS

The current results indicated that contrast-enhanced US may be useful in assessing the prognosis of patients with nonresectable pancreatic carcinoma who receive systemic chemotherapy.

Ultrasound detection of spontaneous hepato-cellular carcinomas in X/myc bitransgenic mice

AIMS

To evaluate trans-abdominal ultrasound for the detection of Hepatocellular carcinoma (HCC) in a bitrasgenic murine (X/myc) model using a commercially available high-frequency ultrasound unit.

METHODS

Sixty-one female animals were included in this study. These animals were submitted to a single ultrasound examination of the liver under general anesthesia (isoflurane), and then euthanized. Results of ultrasound were compared with necropsy and histopathology.

RESULTS

The lesions demonstrated a fairly consistent aspect (oval- or round-shaped, well-defined hypoechoic homogeneous lesions), and lesions as small as 2 mm were identified. For detection of hepatic nodules per mouse the sensitivity was 75%, the specificity was 100% and the accuracy was 88.5%. For detection of hepatic focal lesions per lesions the overall sensitivity was 60%, the specificity was 97%, and the accuracy was 75.9%. Contrast-enhanced harmonic ultrasound imaging did not improve the identification of the lesions in our experimental conditions.

CONCLUSION

High-frequency ultrasound appears to be an efficient tool allowing new possibilities to use this animal model and evaluate new therapies in longitudinal studies, which are much more powerful.

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.

Contrast-enhanced sonographic appearance of hepatocellular carcinoma in patients with cirrhosis: comparison with contrast-enhanced helical CT appearance

OBJECTIVE

We sought to investigate the efficacy of contrast-enhanced sonography using a second-generation contrast agent for the evaluation of hepatocellular carcinoma in patients with cirrhosis by comparing the results to those obtained with contrast-enhanced helical CT.

SUBJECTS AND METHODS

Between October 2002 and March 2003, 74 patients with cirrhosis (60 men and 14 women; age range, 47-80 years; mean age, 67 years) who had a single nodule of hepatocellular carcinoma were selected to be studied from a cohort of 437 patients with cirrhosis. The size range of the 74 nodules was 9-65 mm (mean, 28.2 mm). Twenty-eight (38%) were 20 mm smaller (range, 9-20 mm; mean, 16.6 mm), and 46 (62%) were larger than 20 mm (range, 21-65 mm; mean, 35.2 mm). Contrast-enhanced sonography was performed at a low mechanical index after IV administration of the contrast agent SonoVue. CT scans were obtained in all patients. The enhancement pattern related to tumor hypervascularity was analyzed. The chi-square test was used for statistical analysis.

RESULTS

For the 28 hepatocellular carcinomas 20 mm or smaller, contrast-enhanced sonography showed 15 (53.6%) as hypervascular and 10 (35.7%) as avascular; three (10.7%) carcinomas were missed. On CT, 12 (42.9%) of the 28 hepatocellular carcinomas appeared hypervascular, 13 (46.4%) appeared hypovascular, and three (10.7%) were missed. For the 46 hepatocellular carcinomas larger than 20 mm, contrast-enhanced sonography showed 42 (91.3%) as hypervascular and four (8.7%) as avascular. On CT, 35 (76.1%) hepatocellular carcinomas appeared hypervascular, eight (17.4%) appeared hypovascular, and three (6.5%) were missed. Differences between CT appearance of hepatocellular carcinomas and contrast-enhanced sonographic appearance of the carcinomas were not statistically significant. Concordance between contrast-enhanced sonographic and CT appearances was observed in 61 (82.4%) of 74 cases.

CONCLUSION

Contrast-enhanced sonography is similar to CT for detecting hepatocellular carcinoma hypervascularity. It could be complementary to conventional unenhanced sonography for evaluation of liver nodules.

Modern hepatic imaging

This article provides a brief overview of the current status of commonly employed diagnostic techniques--US, CT, MR, and PET--for the evaluation of liver metastases and HCC as well as a description of imaging in RF ablation and liver transplantation. The various advantages and limitations of the techniques have been outlined. At the present time, at our center, MRI is used most often to evaluate these liver pathologies, due to its high accuracy for lesion detection and characterization.

Evaluation of esophageal varices using contrast-enhanced coded harmonic ultrasonography

AIM

To investigate if esophageal varices can be evaluated using external contrast-enhanced ultrasonography with Levovist and coded harmonic angio (CHA).

METHODS

Subjects were six healthy adult volunteers and 23 patients with liver cirrhosis. After identification of the lower esophagus under B-mode scanning, 300 mg/mL of Levovist was intravenously injected into the cubital vein at a rate of 1 mL/s under observation by CHA-mode scanning. Approximately 30 s after intravenous administration, interval-delay scanning was performed every second to visualize the area around the lower esophageal lumen. The degree of ultrasonographic enhancement was assessed as either no enhancement (negative); linear enhancement along the esophageal wall (weak) or full enhancement of the esophageal lumen (strong). Endoscopic evaluation of esophageal varices was also performed.

RESULTS

The CHA enhancement around the lower esophageal lumen was identified in 21 of the 23 patients. Of these 21 patients, endoscopic assessments of varices were as follows: F0 in four patients, F1 in seven patients, F2 in three patients, and F3 in seven patients. Nine patients were red color sign (RCS)-positive. Regarding the relationship between ultrasonographic enhancement and endoscopic assessment, enhancement was identified as negative in all four F0 patients, negative in three and weak in three and strong in one of the seven F1 patients, weak in one and strong in two of the three F2 patients, and weak in two and strong in five of the seven F3 patients, respectively. Furthermore, of the nine RCS-positive patients, enhancement was recognized as strong in seven and weak in two patients. Ultrasonographic enhancement was identified as negative in all six healthy volunteers.

CONCLUSIONS

By performing contrast-enhanced CHA ultrasonography using Levovist, ultrasonographic enhancement was detectable in all patients with varices categorized as F2 or above. Because the present method is easy to perform and causes less pain to patients compared to endoscopy, it is useful for following and assessing esophageal varices in patients with liver cirrhosis.

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.

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.

Therapeutic response evaluation of malignant hepatic masses treated by interventional procedures with contrast-enhanced agent detection imaging

OBJECTIVE

To assess the usefulness of microbubble contrast-enhanced agent detection imaging in evaluating the therapeutic response of malignant hepatic masses to treatment with interventional procedures.

METHODS

Fifty-eight patients with 68 hepatocellular carcinomas and 6 metastases who were treated with interventional procedures were evaluated with SH U 508A-enhanced agent detection imaging and helical computed tomography. Helical computed tomography was also performed to help establish the outcome of therapy with unenhanced computed tomography 2 weeks after transcatheter arterial chemoembolization and with dynamic contrast-enhanced computed tomography 1 day after radio frequency ablation or percutaneous ethanol injection. The studies were reviewed separately and randomly, and the sensitivity and specificity of agent detection imaging for detection of viable tumor residue were determined by follow-up imaging performed at least 3 months later.

RESULTS

Follow-up computed tomography or magnetic resonance imaging revealed complete tumor responses in 44 (59.5%) of 74 cases after the therapeutic procedures. The sensitivity of agent detection imaging was 94.7% after transcatheter arterial chemoembolization and 72.7% after radio frequency ablation and percutaneous ethanol injection. The specificity of agent detection imaging for the detection of residual tumors was 80% after transcatheter arterial chemoembolization and 79.2% after radio frequency ablation and percutaneous ethanol injection. The false-positive rate for agent detection imaging in cases of radio frequency ablation or percutaneous ethanol injection was 20.8% (5 of 24), resulting from reactive hyperemia or vascularity within the safety margin. In the assessment of the therapeutic effects, the concordance of contrast-enhanced agent detection imaging with helical computed tomography was statistically significant after transcatheter arterial chemoembolization (P < .00001) and radio frequency ablation or percutaneous ethanol injection (P < .02).

CONCLUSIONS

Contrast-enhanced agent detection imaging proved useful and as effective as helical computed tomography for evaluating the therapeutic effects of interventional therapeutic procedures for malignant hepatic masses.

Evaluation of contrast enhancement patterns in pancreatic tumors by coded harmonic sonographic imaging with a microbubble contrast agent

OBJECTIVE

The purpose of the study was to assess patterns of primary pancreatic lesions by contrast-enhanced sonography for differentiating ductal carcinomas from other pancreatic tumors.

METHODS

One hundred six consecutive patients with pancreatic masses, consisting of 83 ductal carcinomas, 7 endocrine carcinomas, 5 intraductal papillary mucinous tumors, 3 cases of autoimmune-related pancreatitis, 3 solid pseudopapillary tumors, 2 cases of chronic pancreatitis, 1 serous cystadenoma, 1 osteoclastoid giant cell tumor, and 1 follicular lymphoma, were examined by contrast-enhanced sonography with coded harmonic imaging in a phase inversion harmonic technique. The contrast enhancement patterns were assessed, and specimens removed during pancreatectomy were subjected to pathologic examination.

RESULTS

Internal tumoral vascularity was detected in 47 (56.6%) of the 83 ductal carcinomas. Vascular image spreading and homogeneous staining throughout the tumors were observed in all endocrine carcinomas. Two of the 5 intraductal papillary mucinous tumors were positive for enhancement effects. Enhancement effects were observed in all 3 cases of autoimmune-related pancreatitis, but the degree varied. There was a significant correlation between the intensity of enhancement effects and the ratio of patent vessels in the tumors (P < .05).

CONCLUSIONS

Vascularity was detected by contrast-enhanced sonography in only about half of the ductal carcinomas, confirming the difficulty in distinguishing those tumors from other pancreatic tumors. There was a correlation between the patency of the vessels in the tumors and their vascularity.

Small hepatocellular carcinomas in patients with liver cirrhosis: potentials and limitations of contrast-enhanced power Doppler sonography

Detection and characterization of focal liver lesions are critical for patients with liver cirrhosis. The potential of contrast-enhanced sonography in the characterization of focal liver lesions is well established in the literature. However, prospective studies in the assessment of patients with suspected hepatocellular carcinoma (HCC) in liver cirrhosis are rare. B-mode imaging often cannot differentiate small focal lesions in cirrhotic livers. Also, power Doppler is not capable of characterizing small focal lesions in cirrhosis. Contrast-enhanced sonography with a first-generation enhancer seems to improve the accuracy of diagnosis of small HCC. The differentiation of HCC and dysplastic nodules is notoriously difficult. In addition, other arterial hypervascularized liver lesions should be considered, depending on the clinical background. The limitations and drawbacks of contrast-enhanced sonography should be considered. All imaging methods are of limited value in the detection of solid liver lesions smaller than 1 cm.

Use of contrast harmonic ultrasound for the diagnosis of congenital portosystemic shunts in three dogs

Contrast harmonic ultrasound was used to determine macrovascular and perfusion patterns in three dogs with congenital extrahepatic solitary portosystemic shunts (PSS). With coded harmonic angiographic ultrasound, the size and tortuosity of the hepatic arteries were subjectively increased. Single pulse intermittent low-amplitude harmonic perfusion imaging provided contrast enhancement time-intensity curves from regions of interest in the liver. Mean (+/- standard deviation) peak perfusion times of dogs with PSS were significantly shorter (p = 0.01; 7.0 +/- 2.0 s) than reported in normal dogs (22.8 +/- 6.8 s). The contrast inflow slope for the dogs with PSS (14.6 +/- 3.7 pixel intensity units [PIU] was significantly (p = 0.05) larger than reported for normal dogs (3.6 +/- 1.4 PIU/s). These results indicate that combined coded harmonic angiographic and contrast harmonic perfusion sonography can be used to detect increased hepatic arterial blood flow as an indicator of PSS in dogs.

Harmonic ultrasound: a review

Harmonic ultrasound is a technique based on the principle of transmitting at frequency f and receiving at frequency 2f (or 1/2f). This technology has become available through the development of wide-bandwidth transducers. Microbubble contrast media produce a large amount of harmonic signal. Contrast harmonic ultrasound provides the opportunity to image patterns of high flow vasculature and overall perfusion. Regions of poor perfusion, including necrosis or infarction, can be identified with contrast harmonic ultrasound. While proportionately lower, tissues also produce harmonic signals. Tissue harmonic ultrasound sequences often improve subjective image quality compared to fundamental ultrasound in echocardiographic and abdominal examinations. This review will discuss the physical principles of harmonic ultrasound signal generation, medical and animal research applications, and an overview of current veterinary experiences.