[Evaluation of early response to antiangiogenic treatment with dynamic contrast enhanced ultrasound]

Contrast-enhanced ultrasound of malignant liver lesions

Contrast-enhanced ultrasound (CEUS) is a safe, relatively inexpensive, and widely available imaging technique using dedicated imaging ultrasound sequences and FDA-approved contrast microbubbles that allow detection and characterization of malignant focal liver lesions with high diagnostic accuracy. CEUS provides dynamic real-time imaging with high spatial and temporal capability, allowing for unique contributions to the already established protocols for diagnosing focal liver lesions using CT and MR imaging. In patients with lesions indeterminate on CT and MRI, CEUS is a helpful problem-solving complementary tool that improves patient management. Furthermore, CEUS assists guidance of liver biopsies and local treatment. Variations of CEUS such as DCE-US and ultrasound molecular imaging are emerging for quantitative monitoring of treatment effects and possible earlier detection of cancer. In this review, basic principles of CEUS techniques and ultrasound contrast agents along with a description of the enhancement patterns of malignant liver lesions are summarized. Also, a discussion of the role of CEUS for treatment guidance and monitoring, intraoperative CEUS, and an outlook on emerging applications is provided.

Dynamic contrast-enhanced ultrasound for quantification of tissue perfusion

Dynamic contrast-enhanced ultrasound (US) imaging, a technique that uses microbubble contrast agents with diagnostic US, has recently been technically summarized and reviewed by a European Federation of Societies for Ultrasound in Medicine and Biology position paper. However, the practical applications of this imaging technique were not included. This article reviews and discusses the published literature on the clinical use of dynamic contrast-enhanced US. This review finds that dynamic contrast-enhanced US imaging is the most sensitive cross-sectional real-time method for measuring the perfusion of parenchymatous organs noninvasively. It can measure parenchymal perfusion and therefore can differentiate between benign and malignant tumors. The most important routine clinical role of dynamic contrast-enhanced US is the prediction of tumor responses to chemotherapy within a very short time, shorter than using Response Evaluation Criteria in Solid Tumors criteria. Other applications found include quantifying the hepatic transit time, diabetic kidneys, transplant grafts, and Crohn disease. In addition, the problems involved in using dynamic contrast-enhanced US are discussed.

Recent developments in dynamic contrast-enhanced ultrasound imaging of tumor angiogenesis

Angiogenesis is a critical process for tumor growth and metastatic dissemination. There is tremendous interest in the development of noninvasive methods for imaging tumor angiogenesis, and ultrasound (US) is an emerging platform technology to address this challenge. The introduction of intravascular microbubble contrast agents not only allows real-time visualization of tumor perfusion during an US examination, but they can be functionalized with specific ligands to permit molecular US imaging of angiogenic biomarkers that are overexpressed on the tumor endothelium. In this article, we will review current concepts and developing trends for US imaging of tumor angiogenesis, including relevant preclinical and clinicsal findings.

Tumours and pseudotumours of the soft tissue in adults: perspectives and current role of sonography

Soft tissue tumours of the musculoskeletal system are reported relatively frequently. The quality of the information gained from different imaging modalities (Doppler sonography, multislice CT, MRI spectroscopy, and diffusion MRI) means that in a growing number of situations, we can envisage determining with great accuracy not only the usual information of tumour size and topography, but often the exact nature of the tissue, almost always identifying whether a lesion is aggressive or not. Of all these techniques, Doppler sonography has become the most widely used due to the striking improvements in its sensors, especially for superficial applications. Some other recent developments are: panoramic imaging, elastography (although its current contribution is still to be determined but it seems to offer promising potential), and, most importantly, specific contrast agents. These techniques have considerably refined the quality of the information obtained, and have particularly enhanced the degree of sensitivity with which lesion progression can be assessed. Ultrasonography is the very first investigation in our protocol. It is also very often used to close investigations, as it accurately guides core needle biopsy from these generally accessible lesions. The purpose of this article is to bring together updated information on the various collections of sonographic features seen in soft tissue tumours and pseudotumours and to emphasise the considerable contributions of these new technological developments, in particular contrast-enhanced sonography. The discussion will follow the World Health Organisation's anatomical pathology classifications of soft tissue tumours. We will close with a synthesis that summarises the main steps in our diagnostic process.

Time-intensity curve parameters in colorectal tumours measured using double contrast-enhanced ultrasound: correlations with tumour angiogenesis

AIM

The aim of the study was to assess the correlation between time-intensity curve (TIC) parameters and colorectal tumour angiogenesis using double contrast-enhanced ultrasound (DCEUS), in which an intraluminal contrast agent was used in combination with an intravascular contrast agent.

METHOD

Thirty nine patients with colorectal tumours were examined preoperatively. During hydrocolonal examination with the intraluminal contrast agent, an intravascular contrast agent, SonoVue, was used to perform the DCEUS. The parameter arrival time (AT), time to peak (TTP), peak intensity (PI) and area under the curve (AUC) were measured. Postoperative specimens were assessed for microvessel density (MVD) and vascular endothelial growth factor (VEGF). The correlation between TIC parameters and the expression of VEGF or MVD was studied.

RESULTS

The mean values of AT, TTP, PI and AUC of the colorectal tumours were 14.32 ± 11.36 s, 30.61 ± 18.65 s, 20.38 ± 17.45 dB and 221.10 ± 156.09 dB.s, respectively. Both AUC and MVD were significantly higher in colorectal adenocarcinomas than in adenomas (all P < 0.05). A positive linear correlation was found between the AUC and MVD in colorectal tumours (r = 0.686, P = 0.0019). No correlation was found between VEGF and any TIC parameter.

CONCLUSION

DCEUS is a valuable method for evaluating angiogenesis in colorectal tumours in vivo. The AUC has a positive linear correlation with MVD and could form a new index for assessing angiogenesis and the biological behaviour of colorectal tumours.

Contrast-enhanced ultrasonography of peripheral soft-tissue tumors: Feasibility study and preliminary results

OBJECTIVES

To determine the diagnostic value of contrast-enhanced ultrasonography, to differentiate benign and malignant soft-tissue tumors and to assess the feasibility and interest of modelling enhancement curves.

PATIENTS AND METHODS

This retrospective study includes 118 patients with soft-tissue tumors, examined with ultrasound after injection of SonoVue(®), a contrast product. The raw data were treated with CHI-Q acquisition software to model the enhancement curves. We analyzed tumor uptake of the contrast product visually and studied the enhancement curves, characterized by five parameters: peak intensity, time to peak, mean transit time, initial slope, and area under the curve.

RESULTS

There were 81 benign and 37 malignant tumors. For a diagnosis of benign tumor, the absence of contrast uptake had a sensitivity of 60%, a specificity of 68%, a positive predictive value of 50% and a negative predictive of 83%. Study of the 70 curves obtained (48 benign and 22 malignant tumors) showed that the parameters of area under the curve (Chi(2)=8.6 and P<0.005), slope (Chi(2)=8.12 and P=0.004), and peak intensity (Chi(2)=7.55, P=0.005) differed significantly between the two populations.

CONCLUSION

Absence of contrast uptake suggests a benign lesion. The study of enhancement curves showed significant differences between the different tumor populations.

Molecular ultrasound imaging and its potential for paediatric radiology

US is a low-cost, real-time imaging modality that is the most used diagnostic tool in paediatric radiology. Reasons include the improved US image quality in children as compared to adults and the demand for avoiding X-rays as much as possible because children are more sensitive to radiation than adults. Stabilized microbubbles have been approved as US contrast agents for adults and show great potential in improving the diagnostic accuracy for many diseases. Initial studies show that in paediatric radiology contrast-enhanced US could also be beneficial for more than just the diagnosis of vesicoureteral reflux, if US contrast agents were approved for children. Molecular US imaging utilizes microbubbles conjugated to biomolecules that target intravascular disease-specific molecules. Many preclinical studies show that molecular US imaging is a highly sensitive tool to detect neovascularisation, inflammation and cardiovascular diseases. Its main advantages are the higher informative value, the longer persistence of the label at the target lesion and the chance to work with lower contrast agent dosages. Now, clinical translation of molecular US appears at the horizon. This review article reports on the current status of molecular US imaging and discusses its potential for paediatric radiology.

Contrast-enhanced and targeted ultrasound

Ultrasonic imaging is becoming the most popular medical imaging modality, owing to the low price per examination and its safety. However, blood is a poor scatterer of ultrasound waves at clinical diagnostic transmit frequencies. For perfusion imaging, markers have been designed to enhance the contrast in B-mode imaging. These so-called ultrasound contrast agents consist of microscopically small gas bubbles encapsulated in biodegradable shells. In this review, the physical principles of ultrasound contrast agent microbubble behavior and their adjustment for drug delivery including sonoporation are described. Furthermore, an outline of clinical imaging applications of contrast-enhanced ultrasound is given. It is a challenging task to quantify and predict which bubble phenomenon occurs under which acoustic condition, and how these phenomena may be utilized in ultrasonic imaging. Aided by high-speed photography, our improved understanding of encapsulated microbubble behavior will lead to more sophisticated detection and delivery techniques. More sophisticated methods use quantitative approaches to measure the amount and the time course of bolus or reperfusion curves, and have shown great promise in revealing effective tumor responses to anti-angiogenic drugs in humans before tumor shrinkage occurs. These are beginning to be accepted into clinical practice. In the long term, targeted microbubbles for molecular imaging and eventually for directed anti-tumor therapy are expected to be tested.

Hybrid ultrasound imaging techniques (fusion imaging)

Visualization of tumor angiogenesis can facilitate non-invasive evaluation of tumor vascular characteristics to supplement the conventional diagnostic imaging goals of depicting tumor location, size, and morphology. Hybrid imaging techniques combine anatomic [ultrasound, computed tomography (CT), and/or magnetic resonance imaging (MRI)] and molecular (single photon emission CT and positron emission tomography) imaging modalities. One example is real-time virtual sonography, which combines ultrasound (grayscale, colour Doppler, or dynamic contrast harmonic imaging) with contrast-enhanced CT/MRI. The benefits of fusion imaging include an increased diagnostic confidence, direct comparison of the lesions using different imaging modalities, more precise monitoring of interventional procedures, and reduced radiation exposure.

Contrast-enhanced endoscopic ultrasonography

Contrast agents are increasingly being used to characterize the vasculature in an organ of interest, to better delineate benign from malignant pathology and to aid in staging and directing therapeutic procedures. We review the mechanisms of action of first, second and third generation contrast agents and their use in various endoscopic procedures in the gastrointestinal tract. Various applications of contrast-enhanced endoscopic ultrasonography include differentiating benign from malignant mediastinal lymphadenopathy, assessment of depth of invasion of esophageal, gastric and gall bladder cancers and visualization of the portal venous system and esophageal varices. In addition, contrast agents can be used to differentiate pancreatic lesions. The use of color Doppler further increases the ability to diagnose and differentiate various pancreatic malignancies. The sensitivity of power Doppler sonography to depict tumor neovascularization can be increased by contrast agents. Contrast-enhanced harmonic imaging is a useful aid in identifying the tumor vasculature and studying pancreatic microperfusion. In the future, these techniques could potentially be used to quantify tumor perfusion, to assess and monitor the efficacy of antiangiogenic agents, to assist targeted drug delivery and allow molecular imaging.

Quantitative functional imaging by dynamic contrast enhanced ultrasonography (DCE-US) in GIST patients treated with masatinib

OBJECTIVES

To determine the quantitative parameters of DCE-US for predicting early functional response of patients with metastatic gastrointestinal stromal tumors (GIST).

MATERIALS AND METHODS

Phase II multicentre clinical trial in patients with metastatic GIST treated with masatinib mesylate (7.5 mg/kg daily by oral route) Patients followed using three different imaging techniques: 1) DCE-US before treatment and on days 1, 7, 15 and after 1, 2, 4, 6 months and every 3 months. 2) CT assessments, using RECIST criteria, before treatment, after 2, 4, 6 months and then every 3 months. 3) FDG PET before treatment and after 1 month.

RESULTS

Twenty patients included and followed-up for up to 36 months, with 269 DCE-US examinations performed. No significant changes in the 7 selected DCE-US variables on day 1 and 7 vs baseline. On day 15, significant reductions in all the variables related to blood volume recorded: area under the curve (AUC) (p = 0. 004), area under the wash-in (AUWI) (p = 0.002), area under the wash-out (AUWO) (p = 0.002) and Peak Intensity (p = 0.005). Also slope of wash-in changed significantly (p = 0.003). An important reduction in Standard Uptake Values (SUV) recorded in 7/11 patients (PFS >18 months). Decrease in DCE-US AUC, AUWI and AUWO values on day 7 were predictive of PET-CT results.

CONCLUSIONS

AUC AUWI, AUWO are the DCE-US parameters related to blood volume that at D 15 can predict the response of GISTs to treatment with masatinib. Additional studies are ongoing.

Preoperative cervical lymph node size evaluation in patients with malignant head/neck tumors: comparison between ultrasound and computer tomography

PURPOSE

The spread of malignant lymph nodes due to malignancies of the head and neck is systematically observed. However, sentinel lymph nodes in the cervical region, such as in the axillary or supraclavicular regions, are not described. Therefore, precise preoperative lymph node screening of all neck compartments is required.

MATERIALS AND METHODS

Forty-five patients with a primary malignant tumor in the head and neck area underwent lymph node staging of the head by means of both CT and ultrasound as a preoperative evaluation. The lymph nodes were classified on the origin of the level system proposed by Som et al. (174:837-844, 2000), which is based on the recommendation of the American College of Radiology introduced in 1990. According to the manual measurement of World Health Organization and the Revised Response Evaluation Criteria in Solid Tumors, the longest transversal and longitudinal diameters were measured by ultrasound, while only the two longest transversal diameters were recorded by CT. The study was conducted by two independent observers. These results were compared with the histopathological results as references.

RESULTS

Six hundred and twenty-four lymph nodes were detected, 64 of which were malignant. Most of the transformed lymph nodes were found in level IIa, II b and III. A more precise measurement was given using ultrasound. The correct positive rate of sonographically detected malignant lymph nodes was significantly higher compared to the CT reading.

CONCLUSION

Cervical lymph node staging can be performed safely by ultrasound. It is a cheap, easy-to-handle and cost-effective diagnostic method. However, only the uppermost regions of the neck are accessible with a linear transducer. Despite this restriction, ultrasound is a reliable and valuable tool for screening lymph nodes in the case of a head or neck malignancy.