Monitoring of liver metastases after stereotactic radiotherapy using low-MI contrast-enhanced ultrasound--initial results

Point of care ultrasound in thoracic malignancy

Ultrasonography is a safe, efficient and cost-effective mode of imaging that can assist clinicians with important treatment decisions and provide procedural guidance. Today, point of care ultrasound plays an essential role in the assessment of benign and malignant conditions of chest, both in the outpatient and inpatient setting. Small, ultra-portable, affordable units can now be carried in the coat pocket. Advanced lung cancer, metastatic diseases to the lungs or thoracic malignancies can present with pleural effusion, pulmonary edema, post-obstructive pneumonia, or ascites that can be assessed by the clinician with ultrasound. It can be used to evaluate the extent of thoracic tumors beyond the parenchyma to the parietal pleura or chest wall, assess cervical, supraclavicular lymphadenopathy prior to fine needle aspiration or to determine venous thromboembolism (VTE) associated with malignancy. Thoracic ultrasound is currently being practiced by the pulmonologists, thoracic surgeons and intensivists to provide guidance during placement of pleural catheters, chest tubes or to evaluate the pleural cavity before thoracoscopy. Point of care ultrasound can improve efficiency in procedures by decreasing complications, increasing success and reducing financial strain on the health care system.

Review of ultrasound image guidance in external beam radiotherapy part II: intra-fraction motion management and novel applications

Imaging has become an essential tool in modern radiotherapy (RT), being used to plan dose delivery prior to treatment and verify target position before and during treatment. Ultrasound (US) imaging is cost-effective in providing excellent contrast at high resolution for depicting soft tissue targets apart from those shielded by the lungs or cranium. As a result, it is increasingly used in RT setup verification for the measurement of inter-fraction motion, the subject of Part I of this review (Fontanarosa et al 2015 Phys. Med. Biol. 60 R77-114). The combination of rapid imaging and zero ionising radiation dose makes US highly suitable for estimating intra-fraction motion. The current paper (Part II of the review) covers this topic. The basic technology for US motion estimation, and its current clinical application to the prostate, is described here, along with recent developments in robust motion-estimation algorithms, and three dimensional (3D) imaging. Together, these are likely to drive an increase in the number of future clinical studies and the range of cancer sites in which US motion management is applied. Also reviewed are selections of existing and proposed novel applications of US imaging to RT. These are driven by exciting developments in structural, functional and molecular US imaging and analytical techniques such as backscatter tissue analysis, elastography, photoacoustography, contrast-specific imaging, dynamic contrast analysis, microvascular and super-resolution imaging, and targeted microbubbles. Such techniques show promise for predicting and measuring the outcome of RT, quantifying normal tissue toxicity, improving tumour definition and defining a biological target volume that describes radiation sensitive regions of the tumour. US offers easy, low cost and efficient integration of these techniques into the RT workflow. US contrast technology also has potential to be used actively to assist RT by manipulating the tumour cell environment and by improving the delivery of radiosensitising agents. Finally, US imaging offers various ways to measure dose in 3D. If technical problems can be overcome, these hold potential for wide-dissemination of cost-effective pre-treatment dose verification and in vivo dose monitoring methods. It is concluded that US imaging could eventually contribute to all aspects of the RT workflow.

Evaluation of contrast-enhanced ultrasonography for hepatocellular carcinoma prior to and following stereotactic body radiation therapy using the CyberKnife® system: A preliminary report

The CyberKnife® is expected to be a novel local treatment for hepatocellular carcinoma (HCC), however, a long-term follow-up using dynamic computed tomography and magnetic resonance imaging is required to determine the effect of treatment in a number of the affected patients. Therefore, there is a requirement to evaluate procedures for early determination of the effect of CyberKnife treatment. The present study aimed to evaluate the changes in the hemodynamics of the tumors and the hepatic parenchyma surrounding the tumor prior to and following CyberKnife treatment for HCC. A total of 4 HCC patients were enrolled in this study. These patients underwent CyberKnife treatment and were evaluated by image analysis prior to and following treatment using contrast-enhanced ultrasonography (CEUS) with Sonazoid. CEUS was performed prior to treatment, at 2 and 4 weeks post-treatment, and every 4 weeks thereafter for as long as possible. The dynamics of the enhancement of the tumor and the hepatic parenchyma surrounding the tumor in the vascular phase, and the presence or absence of a hypoechoic area in the hepatic parenchyma surrounding the tumor in the post-vascular phase were assessed. Results showed that: i) In the patient with earlier changes, hemodynamic changes were evident in the tumor at 4 weeks and in the hepatic parenchyma surrounding the tumor at 2 weeks post-treatment, respectively; ii) the tumor showed hypoenhancement in all patients; and iii) with regard to findings in the hepatic parenchyma surrounding the tumor, strong hyperenhancement appeared in the vascular phase initially, followed by a hypoechoic area in the post-vascular phase. Evaluation of the hemodynamics of tumors and hepatic parenchyma surrounding the tumor using CEUS with Sonazoid may be therapeutically applicable, as it is less invasive than dynamic computed tomography (CT) and provides an early evaluation of the effectiveness of CyberKnife treatment.

Contrast enhancement ultrasound application in focal liver lesions characterization: a retrospective study about guidelines application (SOCEUS-CEUS survey)

INTRODUCTION

The SOCEUS survey aims to evaluate how contrast-enhanced ultrasound (CEUS) is effectively used in the focal liver lesions characterization.

MATERIALS AND METHODS

In the survey were involved Verona, Brescia and Trieste Radiological Centers and Arezzo and Bologna Non-radiological Centers. Inclusion criteria were liver focal lesion detection at conventional ultrasound and studied by means of CEUS, with or without CT or MRI examinations, done previous or subsequent to CEUS.

RESULTS

1069 forms were collected. Patients with benign lesions, who did not undergo any other studies, were 255/561 (45.5 %). Among patients with diagnosis of hemangioma at CEUS, those who had no other investigations were 129/267 (48.3 %). Patients with malignant lesions who had studies pre-CEUS (CT and/or MRI) were 328/508 (65 %), whereas those who had examinations post-CEUS (CT and/or MRI) were 218/508 (42.9 %). Concordance rate between CEUS and CT investigations pre- and post-CEUS was, respectively, 66 and 89 %. Concordance rate between CEUS and MRI studies pre- and post-CEUS was, respectively, 87.5 and 81.5 %.

CONCLUSION

This study proves contrast-enhanced ultrasound correct application in the involved centers.

Application of Combined Two-Dimensional and Three-Dimensional Transvaginal Contrast Enhanced Ultrasound in the Diagnosis of Endometrial Carcinoma

Objective. The goal of this study was to explore the clinical value of combining two-dimensional (2D) and three-dimensional (3D) transvaginal contrast-enhanced ultrasounds (CEUS) in diagnosis of endometrial carcinoma (EC). Methods. In this prospective diagnostic study, transvaginal 2D and 3D CEUS were performed on 68 patients with suspected EC, and the results of the obtained 2D-CEUS and 3D-CEUS images were compared with the gold standard for statistical analysis. Results. 2D-CEUS benign endometrial lesions showed the normal uterine perfusion phase while EC cases showed early arrival and early washout of the contrast agent and nonuniform enhancement. The 3D-CEUS images differed in central blood vessel manifestation, blood vessel shape, and vascular pattern between benign and malignant endometrial lesions (P < 0.05). Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of transvaginal 2D-CEUS and 2D-CEUS combined with 3D-CEUS for diagnosis of benign and malignant endometrial lesions were 76.9%, 73.8%, 64.5%, 83.8%, and 75.0% and 84.6%, 83.3%, 75.9%, 89.7%, and 83.8%, respectively. Conclusion. 3D-CEUS is a useful supplement to 2D-CEUS and can clearly reveal the angioarchitecture spatial relationships between vessels and depth of myometrial invasion in EC. The combined use of 2D and 3D-CEUS can offer direct, accurate, and comprehensive diagnosis of early EC.

[Evaluation of the therapeutic response after stereotactic body radiation therapy for liver tumors]

Stereotactic body radiation therapy takes more and more an important place in the therapeutic arsenal of primitive and secondary liver tumours. The administration of ablative radiation doses can result in specific changes to both the tumour and the healthy hepatic parenchyma, relative to conventional radiation therapy, making the assessment of local changes after stereotactic body radiation therapy, in terms of local control and reaction of healthy tissue, often difficult. It is mandatory to standardize and simplify our evaluation criteria to benefit from a better understanding of the effectiveness of this new treatment modality and allow better reproducibility of available imaging exams. This article presents a literature review of the various radiological changes observed after stereotactic body radiation therapy for liver tumours according to the multiple assessment methods used to determine local control. From the data available, we recommend using modified RECIST criteria proposed by the American Association for the Study of Liver Diseases (AASLD), as objective and relevant criteria of local control after stereotactic body radiation therapy for liver tumours.

Visualization, imaging and new preclinical diagnostics in radiation oncology

Innovative strategies in cancer radiotherapy are stimulated by the growing knowledge on cellular and molecular tumor biology, tumor pathophysiology, and tumor microenvironment. In terms of tumor diagnostics and therapy monitoring, the reliable delineation of tumor boundaries and the assessment of tumor heterogeneity are increasingly complemented by the non-invasive characterization of functional and molecular processes, moving preclinical and clinical imaging from solely assessing tumor morphology towards the visualization of physiological and pathophysiological processes. Functional and molecular imaging techniques allow for the non-invasive characterization of tissues in vivo, using different modalities, including computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, positron emission tomography (PET) and optical imaging (OI). With novel therapeutic concepts combining optimized radiotherapy with molecularly targeted agents focusing on tumor cell proliferation, angiogenesis, and cell death, the non-invasive assessment of tumor microcirculation and tissue water diffusion, together with strategies for imaging the mechanisms of cellular injury and repair is of particular interest. Characterizing the tumor microenvironment prior to and in response to irradiation will help to optimize the outcome of radiotherapy. These novel concepts of personalized multi-modal cancer therapy require careful pre-treatment stratification as well as a timely and efficient therapy monitoring to maximize patient benefit on an individual basis. Functional and molecular imaging techniques are key in this regard to open novel opportunities for exploring and understanding the underlying mechanisms with the perspective to optimize therapeutic concepts and translate them into a personalized form of radiotherapy in the near future.

Contrast-enhanced ultrasound after devascularisation of neuroendocrine liver metastases: functional and morphological evaluation

OBJECTIVE

To evaluate morphological and perfusion changes in liver metastases of neuroendocrine tumours by contrast-enhanced ultrasound (CEUS) after transarterial embolisation with bead block (TAE) or trans-arterial chemoembolisation with doxorubicin-eluting beads (DEB-TACE).

METHODS

In this retrospective study, seven patients underwent TAE, and ten underwent DEB-TACE using beads of the same size. At 1 day before embolisation, 2 days, 1 month and 3 months after the procedure, a destruction-replenishment study using CEUS was performed with a microbubble-enhancing contrast material on a reference tumour. Relative blood flow (rBF) and relative blood volume (rBV) were obtained from the ratio of values obtained in the tumour and in adjacent liver parenchyma. Morphological parameters such as the tumour's major diameter and the viable tumour's major diameter were also measured. A parameter combining functional and morphological data, the tumour vitality index (TVI), was studied. The Wilcoxon rank-sum test and Fisher's test were used to compare treatment groups.

RESULTS

At 3 months rBF, rBV and TVI were significantly lower (P = 0.005, P = 0.04 and P = 0.03) for the group with doxorubicin. No difference in morphological parameters was found throughout the follow-up.

CONCLUSIONS

One parameter, TVI, could evaluate the morphological and functional response to treatments.

Molecular and clinical aspects of targeting the VEGF pathway in tumors

Tumor angiogenesis is a complex process resulting from many signals from the tumor microenvironment. From preclinical animal models to clinical trials and practice, targeting tumors with antiangiogenic therapy remains an exciting area of study. Although many scientific advances have been achieved, leading to the development and clinical use of antiangiogenic drugs such as bevacizumab, sorafenib, and sunitinib, these therapies fall short of their anticipated benefits and leave many questions unanswered. Continued research into the complex signaling cascades that promote tumor angiogenesis may yield new targets or improve upon current therapies. In addition, the development of reliable tools to track tumor responses to antiangiogenic therapy will enable a better understanding of current therapeutic efficacy and may elucidate mechanisms to predict patient response to therapy.

Undetectable late hepatic sequelae after hypofractionated stereotactic radiotherapy for liver tumors

Hypofractionated liver stereotactic radiotherapy has produced long-term survival, but the hepatobiliary system is radiosensitive and may be severely damaged by the treatment. We have evaluated long-term radiation effects on hepatobiliary functions in the first long-term survivors reported after radiotherapy to the hepatobiliary system for liver tumors. Eleven patients were followed for up to 13 years after treatment of tumors≤9 cm in size. Conventional blood chemistry, clearance of indocyanine green and segmental uptake and excretion of radiolabeled mebrofenin were assayed. Slightly abnormal routine blood chemistry was found during the first 2 years in some patients with pre-existing liver damage. Other parameters were seemingly unaffected, and liver segments which received differing mean doses did not differ measurably with regard to parenchymal or ductal function. Late liver functions were therefore not demonstrably affected by the radiotherapy in most patients even in the presence of mild cirrhosis, after previous exposure to liver toxic agents, or after resection. However, slight to moderate late dysfunction occurred in one patient after three courses of irradiation, and in a cirrhotic patient after two major liver resections following radiotherapy. Our previous doses for irradiation of liver tumors gave no measurable chronic side effects and may be increased in order to control tumors more effectively. In selected patients, irradiation is possible even in the presence of liver dysfunction, and previous irradiation or resection does not absolutely contraindicate salvage treatment by re-irradiation or resection.

Semi-automated quantification of hepatic lesions in a phantom

PURPOSE

Accurate measurement is crucial for the assessment of tumor dimensions to allow accurate evaluation of tumor response. Thus, the purpose of our study was to assess the accuracy of semi-automated RECIST and volumetric measurements of liver lesions in a liver phantom with different CT acquisition parameters.

MATERIALS AND METHODS

A phantom of the upper abdomen with 14 hepatic lesions of different sizes (diameter: 12.0-40.0 mm), densities (45/180 HU at 120 kV), or alignment (vertical/transverse) was scanned with a 16-slice multidetector row computed tomography using varying tube currents (40/60/80/100/120/165mAs eff), reconstruction kernels (Siemens B20/30/40/50/70s), or slice thicknesses (1/2/3/4/5 mm). Longest axial diameter and volume of the 14 lesions were quantified using a semi-automated software tool (SyngoOncology, Siemens Medical Solutions, Forchheim, Germany) and compared with the known real longest axial diameter and volume values of the lesions. Absolute percentage errors (APE) were calculated. Degree of agreement in longest axial diameter and volume between software and real measurements was represented graphically in Bland-Altman plots and by corresponding concordance correlation coefficient.

RESULTS

At standard soft tissue reconstruction kernel (Siemens B30s) and slice thickness (3 mm) mean absolute percentage error APE (concordance correlation coefficients) ranged between 6.93 and 14.27 (0.96 and 0.99) for longest axial diameter and between 4.98 and 10.85 (0.99 and 1.00) for volume. At varying reconstruction kernels, APE values (concordance correlation coefficients) ranged between 7.92 and 8.31 (0.98 and 0.99) for longest axial diameter and between 4.95 and 6.93 (1.00) for volume. Applying different slice sections APE values (concordance correlation coefficients) differed from 6.54 to 11.82 (0.97 and 0.99) for longest axial diameter and from 6.93 to 9.17 (1.00) for volume.

CONCLUSIONS

Software quantification of longest axial diameter and volume of hepatic lesions in a phantom demonstrated a high correlation and accuracy under varying multidetector row computed tomography parameter.

Hepatocellular cancer response to radiofrequency tumor ablation: contrast-enhanced ultrasound

Radiofrequency ablation (RFA) is increasingly being used as percutaneous treatment of choice for patients with early stage hepatocellular carcinoma (HCC). An accurate assessment of the RFA therapeutic response is of crucial importance, considering that a complete tumor ablation significantly increases patient survival, whereas residual unablated tumor calls for additional treatment. Imaging modalities play a pivotal role in accomplishing this task, but ultrasound (US) is not considered a reliable modality for the evaluation of the real extent of necrosis, even when color/power Doppler techniques are used. Recently, newer microbubble-based US contrast agents used in combination with grey-scale US techniques, which are very sensitive to non-linear behavior of microbubbles, have been introduced. These features have opened new prospects in liver ultrasound and may have a great impact on daily practice, including cost-effective assessment of therapeutic response of percutaneous ablative therapies. Technical evolution of CEUS focusing on findings after RFA are illustrated. These latter are detailed, cross-referenced with the literature and discussed on the basis of our personal experience. Timing of CEUS posttreatment assessment among with advantages and limitations of CEUS are also described with a perspective on further technologic refinement.

Evaluation of quantitative contrast harmonic imaging to assess malignancy of liver tumors: A prospective controlled two-center study

AIM: To establish the extent to which contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics facilitates the detection of hepatic tumors.

METHODS: One hundred patients with histologically confirmed malignant or benign hepatic tumor (maximum size 5 cm) were analyzed. Contrast-enhanced ultrasound (bolus injection 2.5 mL SonoVue) was carried out with intermittent breath-holding technique using a multifrequency transducer (2.5-4 MHz). Native vascularization was analyzed with power Doppler. The contrast-enhanced dynamic ultrasound investigation was carried out with contrast harmonic imaging in true detection mode during the arterial, portal venous and late phases. Mechanical index was set at 0.15. Perfusion analysis was performed by post-processing of the raw data [time intensity curve (TIC) analysis]. The cut-off of the gray value differences between tumor and normal liver tissue was established using Receiver Operating Characteristic (ROC) analysis 64-line multi-slice computed tomography served as reference method in all cases. Magnetic resonance tomography was used additionally in 19 cases.

RESULTS: One hundred patients with 59 malignant (43 colon, 5 breast, 2 endocrine metastases, 7 hepatocellular carcinomas and 2 kidney cancers) and 41 benign (15 hemangiomas, 7 focal nodular hyperplasias, 5 complicated cysts, 2 abscesses and 12 circumscribed fatty changes) tumors were included. The late venous phase proved to be the most sensitive for classification of the tumor type. Fifty-eight of the 59 malignant tumors were classified as true positive, and one as false negative. This resulted in a sensitivity of 98.3%. Of the 41 benign tumors, 37 were classified as true negative and 4 as false negative, which corresponds to a specificity of 90.2%. Altogether, 95.0% of the diagnoses were classified as correct on the basis of the histological classification. No investigator-dependency (P = 0.23) was noted.

CONCLUSION: The results show the possibility of accurate prediction of malignancy of hepatic tumors with a positive prognostic value of 93.5% using advanced contrast-enhanced ultrasound. Contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics is a valuable tool to discriminate hepatic tumors.

Comparison of contrast enhanced ultrasound and contrast enhanced CT or MRI in monitoring percutaneous thermal ablation procedure in patients with hepatocellular carcinoma: a multi-center study in China

To evaluate the ability of contrast enhanced ultrasound (CEUS) in monitoring percutaneous thermal ablation procedure in patients with hepatocellular carcinoma (HCC) in comparison with contrast enhanced computed tomography (CECT) and/or magnetic resonance imaging (CEMRI). A total of 151 patients were enrolled in the study. Before the radio-frequency (RF) or microwave ablation treatment, tumor vascularity was assessed in 139 patients with three imaging modalities i.e., US (139 exams), CEUS (139 exams) and CECT (103 exams)/CEMR (36 exams). CEUS examination was performed using a sulphur hexafluoride-filled microbubble contrast agent (SonoVue((R)), Bracco, Milan, Italy) and real-time contrast-specific imaging techniques. Within 30 +/- 7 d after the ablation procedure, 118/139 patients were monitored to assess the tumor response to treatment. Before ablation, contrast enhancement within tumor was observed in 129/139 (92.8%) patients with CEUS and 133/139 (95.7%) patients with CECT/CEMRI. Compared with CECT/CEMRI, CEUS sensitivity and accuracy in detecting tumor vascularity were 97.0% and 94.2%, respectively. One month after treatment, no enhancement was seen in 110/118 (93.2%) both on CEUS and CECT/CEMRI. Concordance between CEUS and CECT/CEMR on the presence of residual vascularization was obtained in four patients (true positive). The specificity and accuracy of CEUS in detecting tumor vascularity were 98.2% and 96.6%, respectively. The periprocedural impact of SonoVue administration on the assessment of treatment extent was also evaluated in a subgroup of patients and CEUS showed its superiority compared with baseline US in defining treatment outcome. In conclusion, in the detection of HCC tumor vascularity and assessment of response to thermal ablation after 1 month, real time CEUS provided results comparable to those obtained with CECT/CEMRI. CEUS examination proved to be a safe and easy to access procedure, with potential for diagnostic impact in the clinical practice.

Dynamic MRI signals in the second week of radiotherapy relate to treatment outcomes of hepatocellular carcinoma: a preliminary result

AIM

Radiotherapy (RT) has been used to treat hepatocellular carcinoma (HCC) in recent years. Despite its good local control, slow tumoral shrinkage and rapid recurrence compromise treatment outcomes. We evaluated the signal intensity of the hepatic parenchyma and tumours by using dynamic contrast enhanced magnetic resonance imaging (MRI) and correlated the findings with clinical outcomes. Nineteen patients with advanced HCC received 50 Gy in 25 fractions. They underwent a dynamic contrast-enhanced, turbo fast low-angle shot MR sequence at 1.5 T before therapy, at 2 weeks of therapy, and 1 month (week 9) later. Initial first-pass enhancement slopes (slope) and peak enhancement ratios (peak) were measured.

RESULTS

Initial signal intensities were not associated with RT outcomes. An increased slope and peak of the tumour at week 2 was associated with an improved local response (P<0.05). In the parenchyma, an increased slope at week 2 was associated with recurrence outside the radiation fields or with progression over distant sites (P<0.05). The differences in signal changes at week 2 during RT were not persistent at a statistically significant level at 1 month after RT.

CONCLUSION

Dynamic contrast-enhanced MRI signals may act as biomarkers for early prediction of responses to RT in patients with HCC. Signal intensities at week 2 are important in evaluating treatment outcomes.

Microbubble ultrasound contrast agents: an update

Microbubble contrast agents for ultrasound (US) have gained increasing interest in recent years, and contrast-enhanced US (CEUS) is a rapidly evolving field with applications now extending far beyond the initial improvements achieved in Doppler US. This has been achieved as a result of the safe profile and the increased stability of microbubbles persisting in the bloodstream for several minutes, and also by the availability of specialized contrast-specific US techniques, which allow a definite improvement in the contrast resolution and suppression of signal from stationary tissues. CEUS with low transmit power allows real-time scanning with the possibility of prolonged organ insonation. Several reports have described the effectiveness of microbubble contrast agents in many clinical applications and particularly in the liver, spleen, and kidneys. CEUS allows the assessment of the macrovasculature and microvasculature in different parenchymas, the identification and characterization of hepatic and splenic lesions, the depiction of septal enhancement in cystic renal masses, and the quantification of organ perfusion by the quantitative analysis of the echo-signal intensity. Other fields of application include the assessment of abdominal organs after traumas and the assessment of vesico-ureteral reflux in children. Finally, tumor-targeted microbubbles make possible the depiction of specific biologic processes.

Transient hepatic echogenicity difference on contrast-enhanced ultrasonography: sonographic sign and pitfall

OBJECTIVE

The purpose of this study was to report and analyze a new contrast-enhanced ultrasonographic (CEUS) imaging finding, the transient hepatic echogenicity difference due to perfusion changes, using computed tomography (CT) as a reference standard.

METHODS

We retrospectively investigated the records of patients evaluated in a 2-year period, selecting those who had undergone both CT and CEUS within 15 days, who had CT evidence of a perfusion abnormality, and who had had a CEUS study that included the malperfused parenchymal area.

RESULTS

There were 30 patients with 44 hepatic perfusion changes on CT scans (28 around liver focal lesions and 16 unrelated to focal lesions). Retrospectively, CEUS allowed recognition of 21 of 28 perifocal transient hepatic attenuation differences (THADs), 6 of 10 subsegmental THADs, 2 of 3 segmental THADs, and 1 of 3 lobar THADs. Only some of these abnormalities had been identified at the original CEUS examinations: 0 of 3 lobar THADs, 1 of 3 segmental THADs, 2 of 10 subsegmental THADs, and 16 of 28 perifocal THADs.

CONCLUSIONS

Contrast-enhanced ultrasonography can show hepatic perfusion abnormalities similar to those well known from CT literature, although with a lower sensitivity. Knowledge of this transient hepatic echogenicity difference phenomenon may be relevant for avoiding incorrect image interpretation or incorrect tumor size measurement and for eventually identifying occult vascular disorders such as venous thrombosis or fistulas.

Preoperative imaging staging of rectal cancer

Carcinomas of the rectum are associated with a significant local and distant recurrence rate. Not all patients are appropriate candidates for preoperative radiation therapy. Preoperative identification of those most likely to benefit from neoadjuvant therapy is important. There is no general consensus on the role of endorectal ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI) in staging patients with rectal cancer. Although the tumor stage is an important prognostic factor, preoperative assessment is associated with prediction of the circumferential resection margin. Newer developments such as coils, sequences and gradients in MRI, evolution of multidetector CT and new contrast media, allow for an algorithm selection aiming at the best diagnostic options for patients. The present review will discuss the current role of the various imaging modalities in staging carcinomas of the rectum.

Detection of colorectal cancer hepatic metastases with contrast-enhanced ultrasound: comparison with conventional B-mode ultrasound

The aim of this study was to assess whether contrast-enhanced ultrasound (CE-US) could provide improved diagnostic information in detecting liver metastases from colorectal cancer as compared to B-mode non-enhanced ultrasound (B-US). 32 patients (M/F 23/9, age range 48-82 years, mean 58.2 years) under chemotherapy for colorectal cancer were examined with B-US and CE-US using a second-generation ultrasound contrast agent and a dedicated protocol for contrast detection. The presence of focal liver lesions along with the number, size, pre- and post-contrast sonographic features were recorded digitally. Lesion conspicuity with a three-grade scoring scale was performed on both techniques and contrast intensity measurements were calculated for each focal lesion. CE-US detected 17% more metastases in patient-by-patient and lesion-by-lesion analysis. A statistically significant difference was found between the scoring mean values with regard to conspicuity of the lesions. Accurate characterization of the liver lesions was achievable only with contrast-enhanced technique. A quantitative contrast intensity measurement method confirmed the invariably washing-out vascular pattern in all metastases at sinusoidal-parenchymal liver phase. In conclusion, CE-US is superior to B-US and provides an effective tool in the investigation of colorectal cancer liver metastases.

Contrast-enhanced ultrasound for examining tumor biology

This paper reviews the potential of ultrasound for assessing the viability and biological behavior of tumors. Unlike color Doppler sonography, modern techniques for contrast-enhanced ultrasound permit the measurement of tissue perfusion irrespective of vessel size or flow velocity. Perfusion can also be assessed quantitatively, using replenishment kinetics or derivates thereof. The perfusion of tumors is a surrogate parameter of their viability and may mirror their response to therapy. Furthermore, the degree of vascularity in a tumor may express its aggressiveness and help to predict its response to treatment. In animal models, a decrease in blood flow has been shown to precede a shrinkage of tumors treated with anti-angiogenic compounds. In liver metastases, arterial and portal blood supply can be assessed separately, and a response to stereotactic radiotherapy was found to go along with a decrease in arterial perfusion. Moreover, a relatively high arterial perfusion of liver metastases may predict a response to chemotherapy. Contrast-enhanced ultrasound may be a potent tool for assessing the effects of anti-angiogenic treatment in patients.

Is microbubble-enhanced ultrasonography sufficient for assessment of response to percutaneous treatment in patients with early hepatocellular carcinoma?

The objective of this study was to assess the efficacy of contrast-enhanced ultrasonography (CEUS) with SonoVue to evaluate the response to percutaneous treatment (ethanol injection/radiofrequency) of hepatocellular carcinoma in comparison with spiral computed tomography (CT) immediately and 1 month after treatment. Forty-one consecutive cirrhotic patients with early stage tumor (not suitable for resection) were included. Spiral CT and CEUS were performed in all patients before treatment, in the following 24 h, and 1 month later. The results of each examination were compared with the 1-month spiral CT, considered the gold standard technique. The 24-h CEUS and the 24-h spiral CT sensitivity to detect residual disease were 27% and 20%, respectively. The 24-h CEUS and the 24-h spiral CT positive predictive value of persistent vascularization detection were 75% and 66%, respectively. The 1-month CEUS detected partial responses in ten out of 11 cases (91% sensitivity, 97% specificity, 95% accuracy). Spiral CT and CEUS performed in the 24 h following treatment are slightly useful to evaluate therapeutic efficacy. The 1-month CEUS has a high diagnostic accuracy compared with spiral-CT in the usual assessment of percutaneous treatment response.

Extracranial Radiosurgery (Stereotactic Body Radiation Therapy) for Oligometastases

Extracranial radiosurgery, also known as stereotactic body radiation therapy (SBRT), is an increasingly used method of treatment of limited cancer metastases located in a variety of organs/sites including the spine, lungs, liver, and other areas in the abdomen and pelvis. The techniques used to perform SBRT were initially modeled after intracranial radiosurgery, although considerable evolution in technique and conduct has occurred for extracranial applications. Unlike intracranial radiosurgery, SBRT requires characterization and accounting for inherent organ movement including breathing motion. Potent dose hypofractionation schedules have been used with SBRT such that the treatment is generally both ablative and convenient. Because the treatment is severely damaging to tissues within and about the target, the volume of adjacent normal tissue must be strictly minimized to avoid toxic late effects. Outcomes in various sites show very high rates of local control with toxicity mostly related to tubular tissues like the airways and bowels. With proper conduct though, SBRT can be an extremely effective treatment option for oligometastases.

Comparison of contrast-enhanced ultrasonography versus baseline ultrasound and contrast-enhanced computed tomography in metastatic disease of the liver: diagnostic performance and confidence

AIM

The aim of this study was to compare contrast-enhanced ultrasonography (CEUS) to baseline US and contrast-enhanced computed tomography (CT) in metastatic disease of the liver diagnosed or suspected by US during presurgical staging or postsurgical follow-up for primary malignancies.

MATERIALS AND METHODS

Two hundred-fifty-three patients considered suitable for US due to the complete explorability of the liver and with one to five proven or suspected liver metastases at baseline US were included. All patients underwent US before and after microbubble injection, and multiphase contrast-enhanced CT. Independent panels of readers reviewed US and CT scans and recorded liver metastases according to a 5-grade scale of diagnostic confidence. Sensitivity, specificity (diagnostic performance) and area under the receiver operating characteristics (ROC) curve (diagnostic confidence) were calculated.

RESULTS

Reference standards revealed no metastases in 57/253, more than five in 59/253, and one to five in 137/253 patients. In patients with one to five metastases, CEUS versus baseline US revealed more metastases in 64/137 and the same number in 73/137 patients while CEUS versus CT revealed more metastases in 10/137, the same number in 99/137, and lower number in 28/137. Sensitivity, specificity, and area under ROC curve of CEUS (83%, 84%, 0.929, respectively) differed from baseline US (40%, 63%, 0.579, respectively; P<0.01) while did not differ from CT (89%, 89%, 0.945, respectively; P>0.05).

CONCLUSION

CEUS improved liver metastases diagnosis in comparison with baseline US while it revealed similar diagnostic performance and confidence to contrast-enhanced CT in patients considered suitable for US and with proven or suspected liver metastases at baseline US.

[Possible target specific molecular imaging with ultrasound contrast agents]

Non-invasive molecular imaging technologies provide researchers with the opportunity to study cellular and molecular processes. Among different imaging technologies, ultrasound based molecular imaging methods are also of interest, since the use of ultrasound contrast agents allows specific and sensitive depiction of molecular targets. Recent studies are encouraging and have demonstrated the feasibility of ultrasound based molecular imaging. This review summarizes current experiences and recent preclinical studies with target-specific ultrasound contrast agents.