Angiogenesis inhibitors in a murine neuroblastoma model: quantitative assessment of intratumoral blood flow with contrast-enhanced gray-scale US

Translational research in pediatric contrast-enhanced ultrasound

The role of contrast-enhanced ultrasound (CEUS) imaging is being widely explored by various groups for its use in the pediatric population. Clinical implementation of new diagnostic or therapeutic techniques requires extensive and meticulous preclinical testing and evaluation. The impact of CEUS will be determined in part by the extent to which studies are oriented specifically toward a pediatric population. Rather than simply applying principles and techniques used in the adult population, these studies are expected to advance and augment preexisting knowledge with pediatric-specific information. To further develop this imaging modality for use in children, pediatric-focused preclinical research is essential. In this paper we describe the development and implementation of the pediatric-specific preclinical animal and phantom models that are being used to evaluate CEUS with the goal of clinical translation to children.

Noninvasive Imaging for Assessment of the Efficacy of Therapeutic Agents for Hepatocellular Carcinoma

Morphological imaging techniques are typically used in the anti-cancer drug efficacy evaluation process. However, these techniques can evaluate the therapeutic efficacy only when the tumor shows anatomic changes-usually at later stages, when the therapeutic effects are poor. In contrast, molecular imaging allows noninvasive monitoring of tumor growth, assessment of drug metabolism, and evaluation of therapeutic efficacy at the molecular and cellular levels. Multimodality molecular imaging, which combines the advantages of various imaging modalities, provides even more comprehensive therapeutic efficacy assessment in preclinical and clinical studies. This review provides an overview of molecular imaging evaluation of therapeutic efficacy of the anti-tumor drugs in hepatocellular carcinoma (HCC) both in preclinical and clinical research, which holds great promise in guiding HCC treatment into the era of precision medicine.

Comparison of Contrast-Enhanced Ultrasound and Positron Emission Tomography/Computed Tomography (PET/CT) in Lymphoma

Background

This study aimed to assess the value of contrast-enhanced ultrasound (CEUS) in the diagnosis and prognosis of lymphoma based on PET-CT.

Material/Methods

Our study included 88 superficial lymph nodes and 63 patients who underwent ultrasound-guided biopsy or surgery for pathology from October 2015 to March 2017. All lymph nodes were assessed by CEUS and PET-CT. CEUS and PET-CT parameters were recorded, including arrive time (AT), time to peak (TTP), base intensity (BI), peak intensity (PI), ascending slope (AS), descending slope (DS), area under the TIC curve (AUC), maximum standardized uptake value (SUVmax), and mean standardized uptake value (SUVmean). Pearson’s correlation was used to assess the associations of CEUS and PET-CT parameters.

Results

Of the 88 lymph nodes examined,12 were Hodgkin’s lymphoma (HL) and76 were non-Hodgkin’s lymphoma (NHL). The variations of CEUS dose parameters (ΔI, AUC, and AS) were positively correlated with PET-CT results (SUVmax and TLG). Correlation coefficients were 0.609, 0.518, 0.456, 0.630, 0.593, and 0. 532, respectively. The remaining time values (AT, TP, and ΔT) were negatively associated with PET-CT results. Correlation coefficients were −0.239, −0.272, −0.284and −0.377, −0.391, and −0.320, respectively.

Conclusions

Quantitative CEUS data were correlated with PET-CT values, with potential use in the diagnosis of lymphoma.

Contrast-enhanced ultrasonography of cervical carcinoma: perfusion pattern and relationship with tumour angiogenesis

OBJECTIVE

This study aimed to investigate the use of contrast-enhanced ultrasonography (CEUS) and time-intensity curves to assess angiogenesis in cervical cancer.

METHODS

60 patients who were scheduled to undergo radical surgery for biopsy-proven cervical cancers underwent CEUS. Surgical tissue sections from 32 patients who did not receive neoadjuvant chemotherapy were analyzed with CD34 staining to estimate intratumoral microvessel density (MVD). CEUS images were analyzed for maximum intensity (IMAX), rise time (RT), time to peak (TTP) and mean transit time.

RESULTS

Cervical lesions had a higher IMAX and shorter RT and TTP (p < 0.001) than reference regions. There was a linear association between the IMAX of the cervical lesion and the mean intratumoral MVD (r = 0.624, p < 0.001). There were no significant differences in CEUS variables according to histological type, grade and stage.

CONCLUSION

Quantitative CEUS variables have potential use for monitoring perfusion changes in tumours after non-surgical therapy for advanced cervical cancer.

ADVANCES IN KNOWLEDGE

The article demonstrates the capability and value of quantitative CEUS as a non-invasive strategy for detecting the perfusion and angiogenic status of cervical cancer. Quantitative CEUS variables have potential use for monitoring tumour response to non-surgical therapy.

Use of Quantitative Dynamic Contrast-Enhanced Ultrasound to Assess Response to Antiangiogenic Therapy in Children and Adolescents With Solid Malignancies: A Pilot Study

OBJECTIVE

The purpose of this study was to investigate contrast-enhanced ultrasound assessment of tumor response to antiangiogenic therapy in children and adolescents with solid malignancies.

SUBJECTS AND METHODS

Children with recurrent solid tumors who were enrolled in an institutional phase 1 study of antiangiogenic therapy underwent contrast-enhanced ultrasound of target lesions before therapy, on therapy days 3 and 7, and at the end of course 1. Acoustic data from target lesion ROIs were used to measure peak enhancement, time to peak, rate of enhancement, total AUC, AUC during wash-in (AUC1), and AUC during washout (AUC2). The Cox regression model was used to assess the association between changes in parameters from baseline to follow-up time points and time to tumor progression. Values of p ≤ 0.050 were considered significant.

RESULTS

Target lesion sites included liver (n = 3), pleura (n = 2), and supraclavicular mass, soft-tissue component of bone metastasis, lung, retroperitoneum, peritoneum, lymph node, muscle mass, and perineum (n = 1 each). Hazard ratios for changes from baseline to end of course 1 for peak enhancement (1.17, p = 0.034), rate of enhancement (3.25, p = 0.029), and AUC1 (1.02, p = 0.040) were significantly associated with time to progression. Greater decreases in these parameters correlated with longer time to progression.

CONCLUSION

Contrast-enhanced ultrasound measurements of tumor peak enhancement, rate of enhancement, and AUC1 were early predictors of time to progression in a cohort of children and adolescents with recurrent solid tumors treated with antiangiogenic therapy. Further investigation of these findings in a larger population is warranted.

Reducing tumor growth and angiogenesis using a triple therapy measured with Contrast-enhanced ultrasound (CEUS)

Background

To evaluate the in vivo response by detecting the anti-angiogenic and invasion-inhibiting effects of a triple-combination-therapy in an experimental-small-animal-squamous-cell-carcinoma-model using the “flash-replenishment” (FR) method to assess tissue hemodynamics via contrast-enhanced-ultrasound (CEUS).

Methods

Human hypopharynx-carcinoma-cells were subcutaneously injected into the left flank of 22-female-athymic-nude-rats. After seven days of subcutaneous tumor growth, FR-measurements were performed on each rat. Treatment-group and control-group were treated every day for a period of one week, with the treatment-group receiving solvents containing a triple therapy of Upamostat®, Celecoxib® and Ilomastat® and the control-group solvents only. On day seven, follow-up measurements were performed using the same measurement protocol to assess the effects of the triple therapy. VueBox® was used to quantify the kinetic parameters and additional immunohistochemistry analyses were performed for comparison with and validation of the CEUS results against established methods (Proliferation/Ki-67, vascularization/CD31, apoptosis/caspase3).

Results

Compared to the control-group, the treatment-group that received the triple-therapy resulted in a reduction of tumor growth by 48.6% in size. Likewise, the immunohistochemistry results showed significant decreases in tumor proliferation and vascularization in the treatment-group in comparison to the control-group of 26%(p≤0.05) and 32.2%(p≤0.05) respectively. Correspondingly, between the baseline and follow-up measurements, the therapy-group was associated with a significant(p ≤ 0.01) decrease in the relative-Blood-Volume(rBV) in both the whole tumor(wt) and hypervascular tumor(ht) areas (p≤0.01), while the control-group was associated with a significant (p≤0.01) increase of the rBV in the wt area and a non-significant increase (p≤0.16) in the ht area. The mean-transit-time (mTT) of the wt and the ht areas showed a significant increase (p≤0.01) in the follow-up measurements in the therapy group.

Conclusion

The triple-therapy is feasible and effective in reducing both tumor growth and vascularization. In particular, compared with the placebo-group, the triple-therapy-group resulted in a reduction in tumor growth of 48.6% in size when assessed by CEUS and a significant reduction in the number of vessels in the tumor of 32% as assessed by immunohistochemistry. As the immunohistochemistry supports the CEUS findings, CEUS using the “flash replenishment”(FR) method appears to provide a useful assessment of the anti-angiogenic and invasion-inhibiting effects of a triple combination therapy.

Perfusion estimation using contrast-enhanced 3-dimensional subharmonic ultrasound imaging: an in vivo study

OBJECTIVES

The ability to estimate tissue perfusion (in milliliter per minute per gram) in vivo using contrast-enhanced 3-dimensional (3D) harmonic and subharmonic ultrasound imaging was investigated.

MATERIALS AND METHODS

A LOGIQ™ 9 scanner (GE Healthcare, Milwaukee, WI) equipped with a 4D10L probe was modified to perform 3D harmonic imaging (HI; f(transmit), 5 MHz and f(receive), 10 MHz) and subharmonic imaging (SHI; f(transmit), 5.8 MHz and f(receive), 2.9 MHz). In vivo imaging was performed in the lower pole of both kidneys in 5 open-abdomen canines after injection of the ultrasound contrast agent (UCA) Definity (Lantheus Medical Imaging, N Billerica, MA). The canines received a 5-μL/kg bolus injection of Definity for HI and a 20-μL/kg bolus for SHI in triplicate for each kidney. Ultrasound data acquisition was started just before the injection of UCA (to capture the wash-in) and continued until washout. A microvascular staining technique based on stable (nonradioactive) isotope-labeled microspheres (Biophysics Assay Laboratory, Inc, Worcester, MA) was used to quantify the degree of perfusion in each kidney (the reference standard). Ligating a surgically exposed branch of the renal arteries induced lower perfusion rates. This was followed by additional contrast-enhanced imaging and microsphere injections to measure post-ligation perfusion. Slice data were extracted from the 3D ultrasound volumes and used to generate time-intensity curves offline in the regions corresponding to the tissue samples used for microvascular staining. The midline plane was also selected from the 3D volume (as a quasi-2-dimensional [2D] image) and compared with the 3D imaging modes. Perfusion was estimated from the initial slope of the fractional blood volume uptake (for both HI and SHI) and compared with the reference standard using linear regression analysis.

RESULTS

Both 3D HI and SHI were able to provide visualization of flow and, thus, perfusion in the kidneys. However, SHI provided near-complete tissue suppression and improved visualization of the UCA flow. Microsphere perfusion data were available for 4 canines (1 was excluded because of an error with the reference blood sample) and showed a mean (SD) perfusion of 9.30 (6.60) and 5.15 (3.42) mL/min per gram before and after the ligation, respectively. The reference standard showed significant correlation with the overall 3D HI perfusion estimates (r = 0.38; P = 0.007), but it correlated more strongly with 3D SHI (r = 0.62; P < 0.001). In addition, these results showed an improvement over the quasi-2D HI and SHI perfusion estimates (r = -0.05 and r = 0.14) and 2D SHI perfusion estimates previously reported by our group (r = 0.57).

CONCLUSIONS

In this preliminary study, 3D contrast-enhanced nonlinear ultrasound was able to quantify perfusion in vivo. Three-dimensional SHI resulted in better overall agreement with the reference standard than 3D HI did and was superior to previously reported 2D SHI results. Three-dimensional SHI outperforms the other methods for estimating blood perfusion because of the improved visualization of the complete perfused vascular networks.

Safety of contrast-enhanced ultrasound in children for non-cardiac applications: a review by the Society for Pediatric Radiology (SPR) and the International Contrast Ultrasound Society (ICUS)

The practice of contrast-enhanced ultrasound in children is in the setting of off-label use or research. The widespread practice of pediatric contrast-enhanced US is primarily in Europe. There is ongoing effort by the Society for Pediatric Radiology (SPR) and International Contrast Ultrasound Society (ICUS) to push for pediatric contrast-enhanced US in the United States. With this in mind, the main objective of this review is to describe the status of US contrast agent safety in non-cardiac applications in children. The five published studies using pediatric intravenous contrast-enhanced US comprise 110 children. There is no mention of adverse events in these studies. From a European survey 948 children can be added. In that survey six minor adverse events were reported in five children. The intravesical administration of US contrast agents for diagnosis of vesicoureteric reflux entails the use of a bladder catheter. Fifteen studies encompassing 2,951 children have evaluated the safety of intravesical US contrast agents in children. A European survey adds 4,131 children to this group. No adverse events could be attributed to the contrast agent. They were most likely related to the bladder catheterization. The existing data on US contrast agent safety in children are encouraging in promoting the widespread use of contrast-enhanced US.

Regions of interest and parameters for the quantitative analysis of contrast-enhanced ultrasound to evaluate the anti-angiogenic effects of bevacizumab

The aim of the present study was to identify effective regions of interest (ROIs) and parameters for the quantitative analysis of contrast-enhanced ultrasound (CEUS) to evaluate the anti-angiogenic effects of bevacizumab. Thirty mice were subcutaneously injected with CT26 cells and randomly divided into a bevacizumab‑treated (Bev) group and a control group (normal saline-treated). CEUS and quantitative analysis were performed on days 7, 11, 14 and 21 following tumor establishment. ROItotal, which included the whole tumor, and ROIsmall, which included the most enhanced part of the tumor, were selected and outlined. Parameters including time to peak (TTP), maximum intensity (Imax) and area under the curve (AUC; in addition to rates of AUC1, AUC2, AUCfast and AUCslow) were recorded. The tumors were resected on day 21 for microvessel density (MVD) counting. Our results showed that the MVD in the Bev group was significantly lower compared with that in the control group (4.09 vs. 6.41; P=0.001). Additional parameters of ROIsmall were identified to be significantly different between the two groups, compared with those of ROItotal. No significant differences in TTP and Imax were observed between the two groups at the four time‑points examined (P>0.05). For the AUC parameters in ROIsmall, AUC and the rates of AUC2, AUCfast and AUCslow were lower in the Bev group compared with those in the control group on days 7 and 11 (P<0.05). These findings indicate that ROIsmall and AUC parameters in the quantitative analysis of CEUS may be useful for the evaluation of changes in tumor angiogenesis following bevacizumab treatment.

Contrast-enhanced ultrasonography assessment of gastric cancer response to neoadjuvant chemotherapy

AIM: To quantitatively assess the ability of double contrast-enhanced ultrasound (DCUS) to detect tumor early response to pre-operative chemotherapy.

METHODS: Forty-three patients with gastric cancer treated with neoadjuvant chemotherapy followed by curative resection between September 2011 and February 2012 were analyzed. Pre-operative chemotherapy regimens of fluorouracil + oxaliplatin or S-1 + oxaliplatin were administered in 2-4 cycles over 6-12 wk periods. All patients underwent contrast-enhanced computed tomography (CT) scan and DCUS before and after two courses of pre-operative chemotherapy. The therapeutic response was assessed by CT using the response evaluation criteria in solid tumors (RECIST 1.1) criteria. Tumor area was assessed by DCUS as enhanced appearance of gastric carcinoma due to tumor vascularity during the contrast phase as compared to the normal gastric wall. Histopathologic analysis was carried out according to the Mandard tumor regression grade criteria and used as the reference standard. Receiver operating characteristic (ROC) analysis was used to evaluate the efficacy of DCUS parameters in differentiating histopathological responders from non-responders.

RESULTS: The study population consisted of 32 men and 11 women, with mean age of 59.7 ± 11.4 years. Neither age, sex, histologic type, tumor site, T stage, nor N stage was associated with pathological response. The responders had significantly smaller mean tumor size than the non-responders (15.7 ± 7.4 cm vs 33.3 ± 14.1 cm, P < 0.01). According to Mandard’s criteria, 27 patients were classified as responders, with 11 (40.7%) showing decreased tumor size by DCUS. In contrast, only three (18.8%) of the 16 non-responders showed decreased tumor size by DCUS (P < 0.01). The area under the ROC curve was 0.64, with a 95%CI of 0.46-0.81. The effects of several cut-off points on diagnostic parameters were calculated in the ROC curve analysis. By maximizing Youden’s index (sensitivity + specificity - 1), the best cut-off point for distinguishing responders from non-responders was determined, which had optimal sensitivity of 62.9% and specificity of 56.3%. Using this cut-off point, the positive and negative predictive values of DCUS for distinguishing responders from non-responders were 70.8% and 47.4%, respectively. The overall accuracy of DCUS for therapeutic response assessment was 60.5%, slightly higher than the 53.5% for CT response assessment with RECIST criteria (P = 0.663). Although the advantage was not statistically significant, likely due to the small number of cases assessed. DCUS was able to identify decreased perfusion in responders who showed no morphological change by CT imaging, which can be occluded by such treatment effects as fibrosis and edema.

CONCLUSION: DCUS may represent an innovative tool for more accurately predicting histopathological response to neoadjuvant chemotherapy before surgical resection in patients with locally-advanced gastric cancer.

Application of a second-generation US contrast agent in infants and children--a European questionnaire-based survey

BACKGROUND

No US contrast agent (US-CA) is currently licensed for use in children.

OBJECTIVE

To survey the off-label use in children of a second-generation US-CA.

MATERIALS AND METHODS

Questionnaires were e-mailed to European paediatric radiologists, who were asked about their experience with the second-generation US-CA Sonovue® (Bracco, Milan, Italy). Number of examinations per indication and adverse effects were recorded. Examinations were categorised by intravenous or intracavitary use of US-CA.

RESULTS

Out of 146 respondents, 88 stated that they did not perform contrast-enhanced US in children, but 36 of these (44%) would appreciate paediatric approval. Forty-five centres reported 5,079 examinations in children (age mean: 2.9 years; range: birth-18 years, M/F: 1/ 2.8). The majority (4,131 [81%] in 29 centres) were intravesical applications. The minority (948 [19%] in 30 centres) were intravenous applications. No adverse effects had been recorded from intravesical use. Six minor adverse effects (skin reaction, unusual taste, hyperventilation) had been recorded after five intravenous studies (0.52%).

CONCLUSION

Responses suggest a favourable safety profile of this second-generation US-CA in children. It also demonstrates a demand for such US-CA from paediatric radiologists.

Phase I and clinical pharmacology study of bevacizumab, sorafenib, and low-dose cyclophosphamide in children and young adults with refractory/recurrent solid tumors

PURPOSE

To determine the maximum-tolerated dose (MTD), dose-limiting toxicities (DLT), pharmacokinetics, and pharmacodynamics of sorafenib, bevacizumab, and low-dose oral cyclophosphamide in children and young adults with recurrent/refractory solid tumors.

EXPERIMENTAL DESIGN

Sorafenib dose was escalated from 90 to 110 mg/m(2) twice daily with fixed doses of bevacizumab at 5 mg/kg every 3 weeks and cyclophosphamide at 50 mg/m(2) daily. Once sorafenib's MTD was established, bevacizumab dose was escalated. Each course was of 21 days. Pharmacokinetics and pharmacodynamics studies were conducted during the first course.

RESULTS

Nineteen patients (11 males; median age, 9.2 years) received a median of four courses (range, 1-23). DLTs during course 1 included grade 3 rash (two), increased lipase (one), anorexia (one), and thrombus (one). With an additional 71 courses of therapy, the most common toxicities ≥ grade 3 included neutropenia (nine), lymphopenia (nine), and rashes (four). Five of 17 evaluable patients had partial tumor responses, and five had disease stabilization (>2 courses). Median day 1 cyclophosphamide apparent oral clearance was 3.13 L/h/m(2). Median day 1 sorafenib apparent oral clearance was 44 and 39 mL/min/m(2) at the 2 dose levels evaluated, and steady-state concentrations ranged from 1.64 to 4.8 mg/L. Inhibition of serum VEGF receptor 2 (VEGFR2) was inversely correlated with sorafenib steady-state concentrations (P = 0.019).

CONCLUSION

The recommended phase II doses are sorafenib, 90 mg/m(2) twice daily; bevacizumab, 15 mg/kg q3 weeks; and cyclophosphamide, 50 mg/m(2) once daily. This regimen is feasible with promising evidence of antitumor activity that warrants further investigation.

Contrast-enhanced sonography of malignant pediatric abdominal and pelvic solid tumors: preliminary safety and feasibility data

BACKGROUND

Little information exists regarding pediatric contrast-enhanced US.

OBJECTIVE

To assess the safety and feasibility of contrast-enhanced US of pediatric abdominal and pelvic tumors.

MATERIALS AND METHODS

This prospective study included eight boys and five girls (mean age, 10.8 years) with abdominal or pelvic tumors. Cohorts of three subjects underwent US with perflutren contrast agent at escalating dose levels. Neurological and funduscopic examination, electrocardiography and continuous pulse oximetry were performed before and after contrast administration. Three radiologists independently scored six imaging parameters on pre- and postcontrast sonography. Inter-reviewer agreement was measured by the Kappa statistic.

RESULTS

No neurological, retinal, electrocardiographical or pulse oximetry changes were attributable to the contrast agent. Two subjects reported minor, transient symptoms. Postcontrast US parameter scores improved slightly in 8 of 12 subjects. Postcontrast ultrasound inter-reviewer agreement improved slightly for detection of tumor margins (precontrast = 0.20, postcontrast = 0.26), local tumor invasion (precontrast = -0.01, postcontrast = 0.10) and adenopathy (precontrast = 0.35, postcontrast = 0.44).

CONCLUSIONS

Although our sample size is small, perflutren contrast agents appear to be safe and well tolerated in children. Contrast-enhanced sonography of pediatric abdominal and pelvic tumors is feasible, but larger studies are needed to define their safety and efficacy in children.

Quantitative mapping of tumor vascularity using volumetric contrast-enhanced ultrasound

OBJECTIVE

The goal of this research project was to develop a volumetric strategy for real-time monitoring and characterization of tumor blood flow using microbubble contrast agents and ultrasound (US) imaging.

MATERIALS AND METHODS

Volumetric contrast-enhanced US (VCEUS) imaging was implemented on a SONIX RP US system (Ultrasonix Medical Corp, Richmond, BC) equipped with a broadband 4DL14-5/38 probe. Using a microbubble-sensitive harmonic imaging mode (transducer transmits at 5 MHz and receives at 10 MHz), acquisition of postscan-converted VCEUS data was achieved at a volume rate of 1 Hz. After microbubble infusion, custom data processing software was used to derive microbubble time-intensity curve-specific parameters, namely, blood volume (IPK), transit time (T1/2PK), flow rate (SPK), and tumor perfusion (AUC).

RESULTS

Using a preclinical breast cancer animal model, it is shown that millimeter-sized deviations in transducer positioning can have profound implications on US-based blood flow estimators, with errors ranging from 6.4% to 40.3% and dependent on both degree of misalignment (offset) and particular blood flow estimator. These errors indicate that VCEUS imaging should be considered in tumor analyses, because they incorporate the entire mass and not just a representative planar cross-section. After administration of an antiangiogenic therapeutic drug (bevacizumab), tumor growth was significantly retarded compared with control tumors (P > 0.03) and reflects observed changes in VCEUS-based blood flow measurements. Analysis of immunohistologic data revealed no differences in intratumoral necrosis levels (P = 0.70), but a significant difference was found when comparing microvessel density counts in control with therapy group tumors (P = 0.05).

CONCLUSIONS

VCEUS imaging was shown to be a promising modality for monitoring changes in tumor blood flow. Preliminary experimental results are encouraging, and this imaging modality may prove clinically feasible for detecting and monitoring the early antitumor effects in response to cancer drug therapy.

Correlation and agreement between contrast-enhanced ultrasonography and perfusion computed tomography for assessment of liver metastases from endocrine tumors: normalization enhances correlation

We studied correlation and agreement between perfusion parameters derived from contrast-enhanced ultrasonography (CEUS) and computed tomography (CT). Both techniques were performed in 16 patients with proven liver metastases from endocrine tumor. Replenishment study after ultrasound-induced destruction of microbubbles was used for CEUS quantification. CEUS-derived relative values of blood flow, blood volume and mean transit time were compared with perfusion CT-derived parameters measured in the same tumors. Significant correlation was observed between CEUS normalized values and CT absolute tumor values for blood flow (r = 0.58; p = 0.018), blood volume (r = 0.61; p = 0.012) and mean transit time (r = 0.52; p = 0.037). Correlation was not significant for non-normalized values. Agreement between CEUS normalized values and perfusion CT relative values was significant (p < 0.04). Estimated bias between CEUS and CT for relative perfusion values was -1.38 (-5.02; 2.27) for blood flow, +0.26 (-0.79; 1.31) for blood volume and +0.21 (-0.46; 0.87) for mean transit time. We conclude that normalization markedly increased correlation between CEUS- and CT-derived perfusion values and allowed agreement assessment.

[Contrast-enhanced ultrasound in animal models]

In the past the detection of tumor perfusion was achieved solely via invasive procedures, such as intravital microscopy or with the help of costly modalities, such as multidetector computed tomography (MDCT), magnetic resonance tomography (MRT) or the combined use of positron emission tomography and computed tomography (PET/CT). Ultrasound offers the non-invasive display of organs without usage of ionizing radiation and it is widely available. However, colour-coded ultrasound and power Doppler do not allow the detection of tumor microcirculation. The introduction of contrast-enhanced ultrasound (CEUS) as well as new high-frequency ultrasound probes made it possible to detect and quantify tumor microcirculation with high resolution. CEUS has been used clinically on human beings for more than 10 years. During the last years different tumor models in experimental animals were used for the establishment of this new technique, e.g. in rats, hamsters and mice. CEUS allows the detection of functional parameters, such as the angiogenetic metabolic status of tissue pretreatment and posttreatment. Further research is required to solve the problems of absolute quantification of these perfusion parameters to allow the comparison of CEUS with other modalities (e.g. MRT and CT).

Rapamycin-induced tumor vasculature remodeling in rhabdomyosarcoma xenografts increases the effectiveness of adjuvant ionizing radiation

PURPOSE

Rapamycin inhibits vascular endothelial growth factor expression. Vascular endothelial growth factor is a tumor-elaborated protein that stimulates neovascularization. This inhibition can cause transient "normalization" of the generally dysfunctional tumor vasculature, resulting in improved tumor perfusion and oxygenation. We hypothesized that this may potentiate the antitumor effects of adjuvant ionizing radiation.

METHODS

Mice bearing orthotopic Rh30 alveolar rhabdomyosarcomas were treated with rapamycin (5 mg/kg intraperitoneally daily ×5). Tumors were then evaluated for changes in intratumoral oxygenation, perfusion, vessel permeability, and microvessel density. Additional tumor-bearing mice were treated with 5 doses of rapamycin, irradiation (4 Gy), or 5 doses of rapamycin with irradiation administered on the first or sixth day of rapamycin treatment.

RESULTS

Although tumor vessel permeability changed only minimally, microvessel density decreased (3153 ± 932 vs 20,477 ± 3717.9 pixels per high-power field), whereas intratumoral oxygenation increased significantly (0.0385 ± 0.0141 vs 0.0043 ± 0.0023 mm Hg/mm(3)) after 5 doses of rapamycin. Contrast-enhanced ultrasound demonstrated a significantly increased rate of change of signal intensity after 5 days of rapamycin, suggesting improved intratumoral perfusion. Tumor volume 14 days after treatment was smallest in mice treated with the combination of rapamycin given before irradiation.

CONCLUSION

Combination therapy with rapamycin given before irradiation to normalize the tumor vasculature, thereby improving tumor oxygenation, increased the sensitivity of alveolar rhabdomyosarcoma xenografts to adjuvant irradiation.

Quantitative evaluation of viable tissue perfusion changes with contrast-enhanced greyscale ultrasound in a mouse hepatoma model following treatment with different doses of thalidomide

OBJECTIVE

This study aimed to quantify intratumoural viable tissue perfusion with contrast-enhanced greyscale ultrasound to evaluate tumour response to anti-angiogenic treatment.

METHODS

H22 hepatoma-bearing mice were treated with low-dose thalidomide (Group B), high-dose thalidomide (Group C) or 0.5% carboxylmethylcellulose (Group A). Contrast-enhanced greyscale ultrasound was performed after 7 days of treatments to evaluate the percentage of non-enhanced area for each tumour; regions of interest within the enhanced area were analysed offline to determine the area under the curve (AUC), maximum intensity (IMAX), perfusion index (PI), mean transit time (MTT), time to peak (TTP) and quality of fit (QOF). Immunohistochemical analysis was performed for evaluation of microvascular density (MVD).

RESULTS

The percentage of non-enhanced area was significantly larger in Group C than in Groups A and B (p<0.05); however, there was no significant difference between Groups A and B. Treatment with thalidomide resulted in a significant decrease in AUC, PI and IMAX compared with Group A (p<0.05). Immunohistochemistry showed significant decreases in MVD in Groups B and C compared with Group A (p<0.05); however, there was no significant difference in MVD between Groups B and C. MVD was positively correlated with IMAX (r = 0.419, p = 0.023) and PI (r = 0.455, p = 0.013).

CONCLUSION

Quantitatively analysing intratumoural viable tissue perfusion enables early evaluation of tumour response to anti-angiogenic therapy before apparent changes in tumour necrosis.

An automatic respiratory gating method for the improvement of microcirculation evaluation: application to contrast-enhanced ultrasound studies of focal liver lesions

Contrast-enhanced ultrasound (CEUS), with the recent development of both contrast-specific imaging modalities and microbubble-based contrast agents, allows noninvasive quantification of microcirculation in vivo. Nevertheless, functional parameters obtained by modeling contrast uptake kinetics could be impaired by respiratory motion. Accordingly, we developed an automatic respiratory gating method and tested it on 35 CEUS hepatic datasets with focal lesions. Each dataset included fundamental mode and cadence contrast pulse sequencing (CPS) mode sequences acquired simultaneously. The developed method consisted in (1) the estimation of the respiratory kinetics as a linear combination of the first components provided by a principal components analysis constrained by a prior knowledge on the respiratory rate in the frequency domain, (2) the automated generation of two respiratory-gated subsequences from the CPS mode sequence by detecting end-of-inspiration and end-of-expiration phases from the respiratory kinetics. The fundamental mode enabled a more reliable estimation of the respiratory kinetics than the CPS mode. The k-means algorithm was applied on both the original CPS mode sequences and the respiratory-gated subsequences resulting in clustering maps and associated mean kinetics. Our respiratory gating process allowed better superimposition of manually drawn lesion contours on k-means clustering maps as well as substantial improvement of the quality of contrast uptake kinetics. While the quality of maps and kinetics was satisfactory in only 11/35 datasets before gating, it was satisfactory in 34/35 datasets after gating. Moreover, noise amplitude estimated within the delineated lesions was reduced from 62 ± 21 to 40 ± 10 (p < 0.01) after gating. These findings were supported by the low residual horizontal (0.44 ± 0.29 mm) and vertical (0.15 ± 0.16 mm) shifts found during manual motion correction of each respiratory-gated subsequence. The developed technique could be used as a basis for accurate quantification of perfusion parameters for the evaluation and follow-up of patients under antiangiogenic therapies.

The morphology and haemodynamics of the rabbit renal artery: evaluation by conventional and contrast-enhanced ultrasonography

The purpose of this study was to test the morphology and haemodynamics of the renal artery in the rabbit as evaluated by conventional and contrast-enhanced ultrasonography (CEUS). The morphology and haemodynamics of the rabbit renal artery, including the diameter, which were measured using B-mode ultrasonography (US), colour Doppler US and CEUS, and systolic velocity, diastolic velocity and resistive index (RI) were measured using pulsed wave Doppler US. CEUS was used to measure the renal artery diameter: 0.21 ± 0.04 cm (right) and 0.21 ± 0.03 cm (left). Values of the main renal artery diameter obtained from CEUS significantly correlated with those of digital subtraction angiography. The blood flow velocity of the right main renal artery was 44.20 ± 8.71/18.92 ± 6.26 cm/s (systolic/diastolic) and 36.30 ± 6.89/17.64 ± 5.58 cm/s (systolic/diastolic), at its origin from the aorta and at the renal hilus, respectively. The blood flow velocity of the left main renal artery was 45.10 ± 8.49/19.00 ± 6.80 cm/s (systolic/diastolic) and 41.70 ± 10.25/19.55 ± 7.90 cm/s (systolic/diastolic), at its origin from the aorta and at the renal hilus, respectively. Conventional US provides a more feasible modality for measuring the morphology and haemodynamics of the rabbit renal artery. CEUS is a more accurate method for measuring diameter. This information on the morphology and haemodynamics of the rabbit renal artery might be helpful for researchers.

Contrast-enhanced sonography in pediatrics

Microbubble US contrast agents are composed of an outer shell of protein, phospholipid or polymer that encase air or perfluorocarbon gas. These contrast agents have been widely used in adult cardiology patients to improve endocardial border delineation and have been proved safe and well tolerated in this patient population. There is also a growing body of literature elucidating the value of contrast-enhanced sonography to distinguish benign from malignant liver lesions in adults and to characterize non-hepatic adult malignancies. Because these agents have not been approved for pediatric use in many countries, less is known of the value of contrast-enhanced sonography in children. In this review I will discuss several proven and potential pediatric applications of contrast-enhanced sonography.

Contrast-enhanced ultrasonography of hepatocellular carcinoma: correlation between quantitative parameters and arteries in neoangiogenesis or sinusoidal capillarization

OBJECTIVE

The quantitative parameters in contrast-enhanced ultrasonography-time-intensity curve of hepatocellular carcinoma (HCC) were studied to explore their potential importance in monitoring the effects of anti-angiogenic therapy for HCC.

METHODS

115 HCC patients were studied with contrast-enhanced ultrasonography-time-intensity curve (CEUS-TIC) and with immunohistochemical analysis of tissue sections. The CEUS images were analyzed off-line to obtained quantitative parameters including maximum of intensity (IMAX), rise time (RT), time to peak (TTP), mean transit time (mTT), rise slope (RS), and washout time (WT). Monoclonal antibodies specific for smooth muscle actin and anti-CD34 were used to observe unpaired arteries (UAs) and microvessel area (MVA) of sinusoidal capillarization, respectively. The UAs and MVA of 82 HCC cases were successfully stained.

RESULTS

The number of UAs had moderate correlation with RT (r=-0.446), TTP (r=-0.432), and RS (r=0.431) (P<0.05), and it had mild correlation with IMAX (r=0.303) and WT (r=0.285) (P<0.05). MVA of sinusoidal capillarization had no correlation with perfusion parameters.

CONCLUSION

Quantitative CEUS-TIC parameters reflecting hemodynamics of tumors are correlated with UAs, but not with MVA, and they might be used to monitor the effects of anti-angiogenic therapy on HCC.

Contrast-enhanced gray-scale ultrasound for quantitative evaluation of tumor response to chemotherapy: preliminary results with a mouse hepatoma model

OBJECTIVE

The purpose of this study was to quantify tumor blood perfusion with contrast-enhanced gray-scale ultrasound in the evaluation of tumor response to chemotherapy.

MATERIALS AND METHODS

Mice bearing H22 hepatoma were treated with cisplatin or placebo by intraperitoneal injection. Contrast-enhanced gray-scale ultrasound was performed on day 8 after bolus injection of a lipid-based ultrasound contrast agent. Regions of interest within the tumor were analyzed offline to determine area under the curve, maximum intensity, perfusion index, mean transit time, time to peak, and quality of fit. Immediately after imaging, mice were euthanized, and tumor tissue was removed for fixation in 10% formalin solution. Microvascular density was measured after anti-CD34 staining.

RESULTS

The volume of treated tumors was significantly smaller than that of control tumors (p < 0.001). Treatment with cisplatin resulted in a significant decrease in perfusion index and maximum intensity compared with control tumors (p < 0.05). There were no significant differences between control and treated tumors (p > 0.05) with respect to area under the curve, mean transit time, and time to peak. The microvascular density of treated tumors was significantly lower than that of control tumors (p < 0.001).

CONCLUSION

Quantitative analysis of tumor blood perfusion with contrast-enhanced ultrasound can be used for noninvasive assessment of functional changes in tumors after chemotherapy.

Antiangiogenic effects of pazopanib in xenograft hepatocellular carcinoma models: evaluation by quantitative contrast-enhanced ultrasonography

Background

Antiangiogenesis is a promising therapy for advanced hepatocellular carcinoma (HCC), but the effects are difficult to be evaluated. Pazopanib (GW786034B) is a pan-vascular endothelial growth factor receptor inhibitor, the antitumor effects or antiangiogenic effects haven't been investigated in HCC.

Methods

In vitro direct effects of pazopanib on human HCC cell lines and endothelial cells were evaluated. In vivo antitumor effects were evaluated in three xenograft nude mice models. In the subcutaneous HCCLM3 model, intratumoral blood perfusion was detected by contrast-enhanced ultrasonography (CEUS), and serial quantitative parameters were profiled from the time-intensity curves of ultrasonograms.

Results

In vitro proliferation of various HCC cell lines were not inhibited by pazopanib. Pazopanib inhibited migration and invasion and induced apoptosis significantly in two HCC cell lines, HCCLM3 and PLC/PRF/5. Proliferation, migration, and tubule formation of human umbilical vein endothelial cells were inhibited by pazopanib in a dose-dependent manner. In vivo tumor growth was significantly inhibited by pazopanib in HCCLM3, HepG2, and PLC/PRF/5 xenograft models. Various intratumoral perfusion parameters changed over time, and the signal intensity was significantly impaired in the treated tumors before the treatment efficacy on tumor size could be observed. Mean transit time of the contrast media in hotspot areas of the tumors was reversely correlated with intratumoral microvessel density.

Conclusions

Antitumor effects of pazopanib in HCC xenografts may owe to its antiangiogenic effects, and the in vivo antiangiogenic effects could be evaluated by quantitative CEUS.

Antiangiogenic effects of pazopanib in xenograft hepatocellular carcinoma models: evaluation by quantitative contrast-enhanced ultrasonography

BACKGROUND

Antiangiogenesis is a promising therapy for advanced hepatocellular carcinoma (HCC), but the effects are difficult to be evaluated. Pazopanib (GW786034B) is a pan-vascular endothelial growth factor receptor inhibitor, the antitumor effects or antiangiogenic effects haven't been investigated in HCC.

METHODS

In vitro direct effects of pazopanib on human HCC cell lines and endothelial cells were evaluated. In vivo antitumor effects were evaluated in three xenograft nude mice models. In the subcutaneous HCCLM3 model, intratumoral blood perfusion was detected by contrast-enhanced ultrasonography (CEUS), and serial quantitative parameters were profiled from the time-intensity curves of ultrasonograms.

RESULTS

In vitro proliferation of various HCC cell lines were not inhibited by pazopanib. Pazopanib inhibited migration and invasion and induced apoptosis significantly in two HCC cell lines, HCCLM3 and PLC/PRF/5. Proliferation, migration, and tubule formation of human umbilical vein endothelial cells were inhibited by pazopanib in a dose-dependent manner. In vivo tumor growth was significantly inhibited by pazopanib in HCCLM3, HepG2, and PLC/PRF/5 xenograft models. Various intratumoral perfusion parameters changed over time, and the signal intensity was significantly impaired in the treated tumors before the treatment efficacy on tumor size could be observed. Mean transit time of the contrast media in hotspot areas of the tumors was reversely correlated with intratumoral microvessel density.

CONCLUSIONS

Antitumor effects of pazopanib in HCC xenografts may owe to its antiangiogenic effects, and the in vivo antiangiogenic effects could be evaluated by quantitative CEUS.

Assessment of tissue perfusion by contrast-enhanced ultrasound

Contrast-enhanced ultrasound (CEUS) with microbubble contrast agents is a new imaging technique for quantifying tissue perfusion. CEUS presents several advantages over other imaging techniques in assessing tissue perfusion, including the use of microbubbles as blood-pool agents, portability, availability and absence of exposure to radiation or nuclear tracers. Dedicated software packages are necessary to quantify the echo-signal intensity and allow the calculation of the degree of tissue contrast enhancement based on the accurate distinction between microbubble backscatter signals and native tissue background. The measurement of organ transit time after microbubble injection and the analysis of tissue reperfusion kinetics represent the two fundamental methods for the assessment of tissue perfusion by CEUS. Transit time measurement has been shown to be feasible and has started to become accepted as a clinical tool, especially in the liver. The loudness of audio signals from spectral Doppler analysis is used to generate time-intensity curves to follow the wash-in and wash-out of the microbubble bolus. Tissue perfusion may be quantified also by analysing the replenishment kinetics of the volume of microbubbles after their destruction in the imaged slice. This allows to obtain semiquantitative parameters related to local tissue perfusion, especially in the heart, brain, and kidneys.

Perfusion CT and US of colorectal cancer liver metastases: a correlative study of two dynamic imaging modalities

The purpose of this study was to evaluate the correlation between dynamic-contrast-enhanced computed tomography (DCE-CT) and first-pass dynamic-contrast-enhanced ultrasound (DCE-US) of normal appearing liver parenchyma and of colorectal cancer liver metastases. Thirty patients with hepatic metastases from colorectal cancer underwent DCE-CT and DCE-US. To obtain DCE-US reproducibility measurements, double contrast-passages (2 × 2.4 mL SonoVue intravenous) were acquired. From several DCE-US-derived perfusion indices, the slope-value scored best with a reproducibility concordance correlation coefficient ranging from 0.75-0.93 and overall highest correlation to DCE-CT-derived variables (r = 0.52 to 0.73). The DCE-US-based tumor-to-liver perfusion gradient also showed a low test-retest variability and moderately correlated to DCE-CT (concordance correlation coefficient 0.87-0.92; r = 0.57 to 0.59). To conclude, DCE-US-based slope-value and tumor-to-liver perfusion gradient correlate best with DCE-CT perfusion values. However, both techniques cannot be used interchangeably. DCE-US should be restricted for studies in which a considerable change in perfusion is expected and for patients with a relatively high tumor blood flow at baseline.

A screening platform for glioma growth and invasion using bioluminescence imaging

Object

The study of tumor cell growth and invasion in cancer biology is often limited by the inability to visualize tumor cell behavior in real time in animal models. The authors provide evidence that glioma cells are heterogeneous, with a subset responsible for increased invasiveness. The use of bioluminescence (BL) imaging to investigate dynamic aspects of glioma progression are discussed.

Methods

Glioblastoma multiforme–initiating cells were generated under conditions typically used to sustain neural stem cells. The invasiveness potential was determined using a Matrigel chamber. The presence of an “invasiveness gene signature” that correlated with patient survival outcome was ascertained through microarray gene expression analysis. To measure invasiveness, the authors devised a method focussed on BL imaging and tested it in vitro and in vivo using a zebrafish xenograft model. Bioluminescence imaging signals were verified using known inhibitors of glioma growth: AEE788, N-[(3,5-Difluorophenyl)acetyl]-L-alanyl-2-phenylglycine-1,1-dimethylethyl ester, and compound E.

Results

The authors' data support the idea that glioblastoma multiforme–initiating cells are heterogeneous and possess an invasive subset; BL imaging was used as a readout method to assess this invasive subset. The in vitro data obtained using a known glioma growth inhibitor, AEE788, showed that BL imaging could detect cellular movement and invasion even before overall cell death was detectable on conventional viability assays. Further work using a zebrafish tumor xenograft model supported the efficacy of BL imaging in monitoring changes in tumor load.

Conclusions

The authors used optically transparent zebrafish and high-resolution confocal imaging to track tumor growth in vivo and demonstrate the efficacy of this model for screening antitumor and antiangiogenic compounds. The integration of zebrafish transgenic technology into human cancer biological studies may aid in the development of cancer models targeting specific organs, tissues, or cell types within tumors. Zebrafish could also provide a cost-effective means for the rapid development of therapeutic agents directed at blocking tumor growth and invasion.

Contrast-enhanced Coded Phase-inversion Harmonic Sonography of Knee Synovitis Correlates with Histological Vessel Density: 2 Automated Digital Quantifications

Objective.

To use contrast-enhanced coded phase-inversion harmonic B-mode sonography to assess the acoustic enhancement of the synovial area of the knee; and to compare the data with the histological vessel density.

Methods.

Eleven patients eligible for a knee arthroscopy were studied. Acoustic quantification was carried out by a digital image analysis program that detects the time-dependent increase [intensity (time) = k × time + C] of gray-level intensity in all the pixels of a specific region of interest (ROI) following intravenous injection of the microbubble contrast agent sulfur hexafluoride. Echo-guided synovial biopsies were carried out in the same ROI. Synovial vessel areas were quantified after Factor VIII immunostaining of synovial biopsies using an automated digital image analysis.

Results.

Significant (p < 0.05) correlations were observed between histological vessel density and percentage of the synovial area with a k value > 0.01 (r = 0.93) and kmaxvalues (r = 0.79), as well as between the 2 latter parameters (r = 0.72). The histological vessel density and the 2 acoustic parameters were also significantly correlated with the logarithm of erythrocyte sedimentation rate (r = 0.77, r = 0.87, r = 0.67, respectively) and with log C-reactive protein serum concentration (r = 0.69, r = 0.83, r = 0.62, respectively).

Conclusion.

Contrast-enhanced coded phase-inversion harmonic B-mode sonography coupled with an appropriate data analysis method is a new tool to identify and quantify vessel density in knee synovitis.

PET Imaging of Angiogenesis

Angiogenesis is a highly-controlled process that is dependent on the intricate balance of both promoting and inhibiting factors, involved in various physiological and pathological processes. A comprehensive understanding of the molecular mechanisms that regulate angiogenesis has resulted in the design of new and more effective therapeutic strategies. Due to insufficient sensitivity to detect therapeutic effects by using standard clinical endpoints or by looking for physiological improvement, a multitude of imaging techniques have been developed to assess tissue vasculature on the structural, functional and molecular level. Imaging is expected to provide a novel approach to noninvasively monitor angiogenesis, to optimize the dose of new antiangiogenic agents and to assess the efficacy of therapies directed at modulation of the angiogenic process. All these methods have been successfully used preclinically and will hopefully aid in antiangiogenic drug development in animal studies. In this review article, the application of PET in angiogenesis imaging at both functional and molecular level will be discussed. For PET imaging of angiogenesis related molecular markers, we emphasize integrin alpha(v)beta(3), VEGF/VEGFR, and MMPs.

Morphologic changes of mammary carcinomas in mice over time as monitored by flat-panel detector volume computed tomography

Noninvasive methods are strongly needed to detect and quantify not only tumor growth in murine tumor models but also the development of vascularization and necrosis within tumors. This study investigates the use of a new imaging technique, flat-panel detector volume computed tomography (fpVCT), to monitor in vivo tumor progression and structural changes within tumors of two murine carcinoma models. After tumor cell inoculation, single fpVCT scans of the entire mice were performed at different time points. The acquired isotropic, high-resolution volume data sets enable an accurate real-time assessment and precise measurements of tumor volumes. Spreading of contrast agent-containing blood vessels around and within the tumors was clearly visible over time. Furthermore, fpVCT permits the identification of differences in the uptake of contrast media within tumors, thus delineating necrosis, tumor tissues, and blood vessels. Classification of tumor tissues based on the decomposition of the underlying mixture distribution of tissue-related Hounsfield units allowed the quantitative acquisition of necrotic tissues at each time point. Morphologic alterations of the tumor depicted by fpVCT were confirmed by histopathologic examination. Concluding, our data show that fpVCT may be highly suitable for the noninvasive evaluation of tumor responses to anticancer therapies during the course of the disease.

Neural progenitor cell-mediated delivery of interferon beta improves neuroblastoma response to cyclophosphamide

BACKGROUND

We have shown that continuous systemic delivery of interferon beta (IFN-beta) remodels dysfunctional tumor vasculature, thereby improving tumor perfusion and enhancing delivery and efficacy of chemotherapeutic drugs. We hypothesized that because of their inherent tumor tropism, neural progenitor cells (NPCs) engineered to express IFN-beta could also effect maturation of tumor vasculature without generating high systemic levels of IFN-beta.

METHODS

Mice with luciferase-expressing disseminated human neuroblastoma were divided into four groups of equal tumor burden by bioluminescence imaging: (1) untreated controls; (2) NPC-IFN-beta only; (3) cyclophosphamide (CTX) only; and (4) NPC-IFN-beta in combination with CTX. Two million NPC-IFN-beta cells were administered twice, 7 days apart, starting 21 days after tail vein administration of tumor cells. CTX was administered every 6 days for three doses. Mice were killed at 6 weeks, livers and kidneys weighed, and tumor removed for immunohistochemical staining for endothelial cells (CD34), pericytes (alpha-SMA), apoptosis (TUNEL [terminal deoxynucleotidyl transferase dUTP nick-end labeling]), and diI-labeled NPCs.

RESULTS

Fluorescent-labeled NPCs confirmed localization of these cells to tumors. The alpha-SMA/CD34 ratio, a marker for vascular maturation, greatly increased in NPC-IFN-beta-treated tumors compared with controls. Bioluminescent signal from luciferase-expressing tumor cells, reflecting tumor burden, was lower with combination therapy than control or either monotherapy, and combination therapy resulted in far less tumor burden by weight in the kidneys and liver.

CONCLUSIONS

Targeted delivery of IFN-beta with NPCs produced low circulating levels of IFN-beta, yet the maturing effect on the tumor vasculature and the enhanced efficacy of adjuvant therapy was maintained. Thus, combination therapy of NPC-IFN-beta with CTX warrants further investigation for the treatment of high-risk neuroblastoma patients.

Assessment of hepatic VX2 tumors with combined percutaneous transhepatic lymphosonography and contrast-enhanced ultrasonographic imaging

AIM: To evaluate the feasibility and efficacy of percutaneous transhepatic lymphosonography (PTL) as a novel method for the detection of tumor lymphangiogenesis in hepatic VX₂ of rabbits and to evaluate combined PTL and routine contrast-enhanced ultrasonographic imaging for the diagnosis of liver cancer.

METHODS: Ten rabbits with VX₂ tumor were included in this study. SonoVue (0.1 mL/kg) was injected into each rabbit via an ear vein for contrast-enhanced ultrasonographic imaging, and 0.5 mL SonoVue was injected into the normal liver parenchyma near the VX₂ tumor for PTL. Images and/or movie clips were stored for further analysis.

RESULTS: Ultrasonographic imaging showed VX₂ tumors ranging 5-19 mm in the liver of rabbits. The VX₂ tumor was hyperechoic and hypoechoic to liver parenchyma at the early and later phase, respectively. The hepatic lymph vessels were visualized immediately after injection of contrast medium and continuously visualized with SonoVue^® during PTL. The boundaries of VX₂ tumors were hyperechoic to liver parenchyma and the tumors. There was a significant difference in the values for the boundaries of VX₂ tumors after injection compared with the liver normal parenchyma and the tumor parenchyma during PTL.

CONCLUSION: PTL is a novel method for the detection of tumor lymphangiogenesis in hepatic VX₂ of rabbits. Combined PTL and contrast-enhanced ultrasonographic imaging can improve the diagnosis of liver cancer.

Simplified contrast ultrasound accurately reveals muscle perfusion deficits and reflects collateralization in PAD

BACKGROUND

Simplified contrast-enhanced ultrasound (CEUS) can be used to evaluate muscle perfusion in peripheral arterial disease (PAD). Here, we report its diagnostic accuracy for detecting symptomatic PAD. Additionally, we hypothesize that the extent of collateral formation is reflected by CEUS.

METHODS

Ultrasound contrast agent was injected into an antecubital vein of 58 control subjects and 52 symptomatic PAD patients and its appearance in the calf muscle was evaluated. Interreader variability was tested using 118 raw data films. Arterial collateralization of PAD patients was assessed by angiographic imaging.

RESULTS

PAD patients showed a significantly longer median time to peak intensity (TTP, 36.9s) than control subjects (19.4s, p<0.001) with longer TTPs in advanced PAD stages. The area under the receiver operating characteristic curve was 0.942 and the mean TTP difference between two blinded readers was 0.28s. A TTP cut off at 30.5s was associated with 91% positive predictive value. PAD patients with good collateralization showed a significantly shorter TTP (34.1s) than patients with poor collateralization (44.0 s, p=0.008) but not a higher ankle-brachial index (ABI).

CONCLUSIONS

CEUS accurately displays perfusion deficits of the calf muscle in symptomatic PAD patients. The degree of arterial collateralization is reflected by CEUS and not by ABI.

Dynamic contrast-enhanced ultrasonography (DCE-US) with quantification of tumor perfusion: a new diagnostic tool to evaluate the early effects of antiangiogenic treatment

Dynamic contrast-enhanced ultrasonography (DCE-US) using the contrast agent Sonovue and vascular recognition imaging software is a novel technique that enables the detection of microvessels and quantitative assessment of solid tumor perfusion using raw linear data. Clinical trials have shown that DCE-US can be used to assess the anticancer efficacy of antiangiogenic treatment, for which conventional efficacy criteria based on size are unsuitable. Reduction in tumor vascularization can easily be detected in responders after 1-2 weeks and is correlated with progression-free survival and overall survival. DCE-US is supported by the French Cancer National Institut. This program is currently studying the technique in metastatic breast cancer, melanoma, colon cancer, gastrointestinal stromal tumor, and renal cell carcinoma, as well as in primary hepatocellular carcinoma, to establish the optimal perfusion parameters and timing for quantitative anticancer efficacy assessments.

New frontiers in pediatric oncologic imaging

As imaging technologies advance, a paradigm shift is emerging in the assessment of tumor response to therapy. The traditional method of measuring tumor size may not reflect changes in tumor viability induced by chemotherapy and radiation therapy. Today's oncologists and radiologists seek objective methods for assessing tumor metabolism and blood flow, measures that provide earlier, more accurate information about treatment effects. Pediatric imaging presents unique challenges not encountered in adult imaging, including the need for sedation and consideration of the long-term effects of radiation exposure in a growing child. Therefore, the potential risks and benefits of new imaging approaches for monitoring anticancer treatment in children require careful consideration. Several new imaging techniques are currently under investigation for use in pediatric oncology. These include dynamic enhanced magnetic resonance imaging and quantitative contrast-enhanced ultrasonography for assessment of blood flow in solid tumors such as osteosarcoma and neuroblastoma, and nuclear imaging, including positron emission tomography–computed tomography, for assessment of pediatric musculoskeletal tumors and neuroblastoma. The potential value, relative advantages, and limitations of these new methods in monitoring anticancer therapy in children are discussed.

Early quantitative evaluation of a tumor vasculature disruptive agent AVE8062 using dynamic contrast-enhanced ultrasonography

OBJECTIVES

To evaluate the early tumor vasculature disrupting effects of the AVE8062 molecule and the feasibility of dynamic contrast-enhanced ultrasonography (DCE-US) in the quantitative assessment of these effects.

MATERIAL AND METHODS

AVE8062 was administered at a single dose (41 mg/kg) to 40 melanoma-bearing nude mice, which were all imaged before and after drug administration (5 + 15 minutes, 1, 6, and 24 hours). Using an ultrasound scanner (Aplio, Toshiba), intratumor vessels were counted in power Doppler mode and tumor microvasculature was assessed in a specific harmonic mode associated with a perfusion and quantification software for contrast-uptake quantification (Sonovue, Bracco). The peak intensity (PI), time-to-PI (T PI), and full-width at half maximum (FWHM) were extracted from the time-intensity curves expressed as linear raw data. Histologic analysis evaluated microvessel density (MVD) and necrosis at each time point studied. Statistical significance was estimated (paired sum rank and Mann-Whitney tests) to evaluate drug activity and to compare its efficacy at the different time points.

RESULTS

In power Doppler mode, intratumoral vessels depletion started 15 minutes postinjection (32%, P = 0.004) and the decrease was maximal at 6 hours (51%, P = 0.002). PI decreased by 3.5- and 45.7-fold at 1 and 6 hours, respectively, compared with preinjection values (P = 0.016 and P = 0.008). The decrease at 6 hours was significantly different from the variation at 1 hour (P = 0.0012) and at 24 hours (P = 0.0008). T PI and FWHM showed a significant increase exclusively at 6 hours (P = 0.0034, P = 0.0039). Histology revealed significantly decreased MVD and increased necrosis at 24 hours (P < 0.01).

CONCLUSION

DCE-US allowed quantitative in vivo evaluation of the functional effects of AVE8062, which was found most effective on tumoral microvasculature 6 hours after its administration. A clinical phase-1 study of AVE8062 is ongoing using the same ultrasonography methodology before and 6 and 24 hours postadministration.

Bevacizumab-induced transient remodeling of the vasculature in neuroblastoma xenografts results in improved delivery and efficacy of systemically administered chemotherapy

PURPOSE

Dysfunctional tumor vessels can be a significant barrier to effective cancer therapy. However, increasing evidence suggests that vascular endothelial growth factor (VEGF) inhibition can effect transient "normalization" of the tumor vasculature, thereby improving tumor perfusion and, consequently, delivery of systemic chemotherapy. We sought to examine temporal changes in tumor vascular function in response to the anti-VEGF antibody, bevacizumab.

EXPERIMENTAL DESIGN

Established orthotopic neuroblastoma xenografts treated with bevacizumab were evaluated at serial time points for treatment-associated changes in intratumoral vascular physiology, penetration of systemically administered chemotherapy, and efficacy of combination therapy.

RESULTS

After a single bevacizumab dose, a progressive decrease in tumor microvessel density to <30% of control was observed within 7 days. Assessment of the tumor microenvironment revealed a rapid, sustained decrease in both tumor vessel permeability and tumor interstitial fluid pressure, whereas intratumoral perfusion, as assessed by contrast-enhanced ultrasonography, was improved, although this latter change abated by 1 week. Intratumoral drug delivery mirrored these changes; penetration of chemotherapy was improved by as much as 81% when given 1 to 3 days after bevacizumab, compared with when both drugs were given concomitantly, or 7 days apart. Finally, administering topotecan to tumor-bearing mice 3 days after bevacizumab resulted in greater tumor growth inhibition (36% of control size) than with monotherapy (88% bevacizumab, 54% topotecan) or concomitant administration of the two drugs (44%).

CONCLUSIONS

Bevacizumab-mediated VEGF blockade effects alterations in tumor vessel physiology that allow improved delivery and efficacy of chemotherapy, although careful consideration of drug scheduling is required to optimize antitumor activity.

Continuous delivery of IFN-beta promotes sustained maturation of intratumoral vasculature

IFNs have pleiotropic antitumor mechanisms of action. The purpose of this study was to further investigate the effects of IFN-beta on the vasculature of human xenografts in immunodeficient mice. We found that continuous, systemic IFN-beta delivery, established with liver-targeted adeno-associated virus vectors, led to sustained morphologic and functional changes of the tumor vasculature that were consistent with vessel maturation. These changes included increased smooth muscle cell coverage of tumor vessels, improved intratumoral blood flow, and decreased vessel permeability, tumor interstitial pressure, and intratumoral hypoxia. Although these changes in the tumor vasculature resulted in more efficient tumor perfusion, further tumor growth was restricted, as the mature vasculature seemed to be unable to expand to support further tumor growth. In addition, maturation of the intratumoral vasculature resulted in increased intratumoral penetration of systemically administered chemotherapy. Finally, molecular analysis revealed increased expression by treated tumors of angiopoietin-1, a cytokine known to promote vessel stabilization. Induction of angiopoietin-1 expression in response to IFN-beta was broadly observed in different tumor lines but not in those with defects in IFN signaling. In addition, IFN-beta-mediated vascular changes were prevented when angiopoietin signaling was blocked with a decoy receptor. Thus, we have identified an alternative approach for achieving sustained vascular remodeling-continuous delivery of IFN-beta. In addition to restricting tumor growth by inhibiting further angiogenesis, maturation of the tumor vasculature also improved the efficiency of delivery of adjuvant therapy. These results have significant implications for the planning of combination anticancer therapy.

In vivo bioluminescence imaging for early detection and monitoring of disease progression in a murine model of neuroblastoma

BACKGROUND

We evaluated the potential of bioluminescence imaging (BLI) for early tumor detection, demonstrating occult sites of disseminated disease and assessing disease progression in a murine model of neuroblastoma.

METHODS

Neuroblastoma cells engineered to express the enzyme firefly luciferase were used to establish localized tumors and disseminated disease in SCID mice. Bioluminescent signal intensity was measured at serial time points, and compared with traditional methods of evaluating tumor growth.

RESULTS

Bioluminescence imaging detected subcutaneous and retroperitoneal tumors weeks before they were palpable or appreciable by ultrasound. Bioluminescent signal intensity at both sites then paralleled tumor growth. After intravenous administration of tumor cells, BLI revealed disseminated disease in the liver, lungs, and bone marrow, again weeks before any gross disease was present. The presence of tumor within these sites at early time points was confirmed by reverse transcriptase-polymerase chain reaction. Finally, BLI permitted a real-time, noninvasive, quantitative method for following response to therapy in a model of minimal residual disease.

CONCLUSION

Bioluminescence imaging detects tumor much earlier than traditional methods. In addition, it can detect, quantify, and follow micrometastasis in real-time during disease progression. This methodology is extremely valuable for studying tumor tissue tropism, mechanisms of metastasis, and response to therapy in murine tumor models.

In vivo mouse imaging and spectroscopy in drug discovery

Imaging modalities such as micro-computed tomography (micro-CT), micro-positron emission tomography (micro-PET), high-resolution MRI, optical imaging, and high-resolution ultrasound have become invaluable tools in preclinical pharmaceutical research. They can be used to non-invasively investigate, in vivo, rodent biology and metabolism, disease models, and pharmacokinetics and pharmacodynamics of drugs. The advantages and limitations of each approach usually determine its application, and therefore a small-rodent imaging laboratory in a pharmaceutical environment should ideally provide access to several techniques. In this paper we aim to illustrate how these techniques may be used to obtain meaningful information for the phenotyping of transgenic mice and for the analysis of compounds in murine models of disease.

Functional imaging of colorectal cancer angiogenesis

Angiogenesis is a key factor in the growth and dissemination of colorectal cancer, with significant implications for its clinical management. Previous trials have provided proof-of-principle that inhibition of angiogenesis has the potential to enhance the effectiveness of treatment for this disease. Characterisation of the angiogenic status of the tumour on an individual patient basis could allow for a more targeted approach to treatment. In vivo imaging techniques that assess tumour microvessel function have the potential to improve the management of treatment for patients with colorectal cancer. This review focuses on MRI and CT assessment of colorectal cancer angiogenesis. We discuss the effects that these two techniques have had in the assessment of this disease, including tumour staging and therapeutic assessment. Their comparability with other imaging techniques, in particular ultrasound, and their limitations are also addressed.