Functional computed tomographic quantification of angiogenesis in rabbit VX2 soft-tissue tumor before and after interventional therapy. J Comput Assist Tomogr. 2008;32:697-705. [PMID: 18830097 DOI: 10.1097/rct.0b013e31815b7dcf]

Photoacoustic imaging for the evaluation of early tumor response to antivascular treatment

Background

Photoacoustic imaging (PAI) provides real-time noninvasive and contrast agent-free monitoring of the concentrations of some endogenous compounds related to tumor vascularization and oxygenation. In this study, we used PAI to noninvasively evaluate tumor responses to antiangiogenic therapy.

Methods

In vivo studies were performed with the approval of our institutional animal ethics committee. We used a xenograft mouse model of 4T1 breast cancer treated with different doses of bevacizumab or vehicle. Seven days after implantation, tumor-bearing mice (with tumors ~5-8 mm diameter) were randomly divided into low-dose (10 mg/kg), high-dose (20 mg/kg) and vehicle groups (same dose of saline). Each experimental group was administered bevacizumab intraperitoneally only once. Before and after treatment, acoustic resolution-photoacoustic microscopy (AR-PAM), a type of PAI, was conducted in vivo consecutively from day 1 to day 5. PAI-derived quantitative parameters were calculated at each time point. Additional cohorts of mice were used to quantify CD31 and hypoxia by immunohistochemical assays.

Results

The values of the PAI parameters were not significantly different among the experimental and control groups at the same time point before treatment (all P>0.05). The total hemoglobin (HbT) levels in the treatment group gradually decreased from day 1 to day 2 (relative to those in the control group, P>0.05) and decreased significantly relative to those in the control group from day 3 to day 5 (P<0.05). The deoxyhemoglobin (HbR) levels in the treatment group decreased from day 1 to 5 after treatment. The high-dose group had significantly decreased HbR levels relative to the control group from day 1 to 5 (P<0.05). The low-dose group also showed a gradual and significant decrease in HbR levels on day 3 (P<0.05). CD31 was decreased in the low-dose group relative to the control group on day 1 (decreased by 34.05%, P=0.067) and day 3 (decreased by 45.27%, P=0.180), and the decrease in CD31 persisted on day 5 (decreased by 71.41%, P=0.000). CD31 decreased to a greater extent in the high-dose group than in the low-dose group. Tumor hypoxia was significantly increased on day 1 from day 0 in the treatment groups (P<0.05), especially in the high-dose group. Hypoxia was decreased on days 3 and 5 in the low-dose group (10.92±0.92 and 8.17±1.9, P=0.317) but continuously increased over time in the high-dose group. Significantly greater hypoxia was observed in the high-dose group than in the low-dose group (17.60±1.20 and 20.33±0.47, P<0.05).

Conclusions

PAI can be used to evaluate both vessel regression and hypoxia in response to anti-vascular treatment.

Differential diagnostic value of computed tomography perfusion combined with vascular endothelial growth factor expression in head and neck lesions

There are numerous types of head and neck lesions (HNLs), and conventional computed tomography (CT) has low specificity and sensitivity in the definitive and differential diagnosis of HNLs. The aim of the present study was to evaluate the value of perfusion CT (CTP) combined with vascular endothelial growth factor (VEGF) expression in the differentiation between malignant and benign HNLs. In total, 41 HNLs, which were pathologically confirmed, underwent CTP and VEGF expression analysis. All lesions were divided into three groups: Group A, benign hypovascular lesions; Group B, benign hypervascular lesions; and Group C, malignant lesions. Time density curve (TDC) and CTP parameters [maximum intensity projection (MIP), blood volume (BV), blood flow (BF), mean transit time and capillary permeability] were analyzed. The association between perfusion measurements and VEGF was assessed using Pearson's correlation. TDCs were classified into three types, and type I was more frequently identified in benign tumors (Groups A and B) compared with malignant tumors (Group C) (P=0.003). Malignant tumors primarily had a TDC of type II and III. MIP, BF and BV were all significantly higher in Groups B and C compared to Group A (P<0.01). VEGF expression of malignant tumors was significantly higher than benign tumors (P=0.007). No correlation was identified between VEGF and any CTP parameter. The present findings suggest that CTP combined with VEGF may differentiate between malignant and benign HNLs, and between benign hypovascular and hypervascular lesions.

Perfusion computed tomography in renal cell carcinoma

Various imaging modalities are available for the diagnosis, staging and response evaluation of patients with renal cell carcinoma (RCC). While contrast enhanced computed tomography (CT) is used as the standard of imaging for size, morphological evaluation and response assessment in RCC, a new functional imaging technique like perfusion CT (pCT), goes down to the molecular level and provides new perspectives in imaging of RCC. pCT depicts regional tumor perfusion and vascular permeability which are indirect parameters of tumor angiogenesis and thereby provides vital information regarding tumor microenvironment. Also response evaluation using pCT may predate the size criteria used in Response Evaluation Criteria in Solid Tumors, as changes in the perfusion occurs earlier following tissue kinase inhibitors before any actual change in size. This may potentially help in predicting prognosis, better selection of therapy and more accurate and better response evaluation in patients with RCC. This article describes the techniques and role of pCT in staging and response assessment in patients with RCCs.

Dynamic contrast-enhanced magnetic resonance imaging for pancreatic ductal adenocarcinoma at 3.0-T magnetic resonance: correlation with histopathology

PURPOSE

The aim of this study was to discuss the correlation of quantitative dynamic contrast-enhanced magnetic resonance imaging (QDCE-MRI) at 3.0-T magnetic resonance and histopathology for pancreatic ductal adenocarcinoma (PDA).

METHODS

Twenty-three patients with histopathologically proven PDA were included in this study after 75 cases of suspected pancreatic tumors had been performed by QDCE-MRI. The quantitative kinetic parameters analyzed by 2-compartment and 3-compartment models were calculated automatically, which included the volume transfer constant of the contrast agent, the rate constant (Kep), the volume as a percentage of the extravascular extracellular leakage space, the time of arrival of contrast agent, the time of peaking of contrast agent, the maximum slope of signal intensity ascent, and the contrast enhancement ratio. According to magnetic resonance images, tissue section were selected and stained for evaluating tumor differentiation, tumor fibrosis, tumor microvessel density, the expression of tumor vascular endothelial growth factor (VEGF) and Ki67. Subsequently, the relationship between the parameters of QDCE-MRI and histopathology of PDA was analyzed.

RESULTS

The tumor Kep and extravascular extracellular leakage space showed a statistically significant correlation with tumor fibrosis; the tumor volume transfer constant of the contrast agent 2-compartment showed a statistically significant correlation with the expressions of tumor VEGF; and the tumor Kep, maximum slope of signal intensity ascent, and contrast enhancement ratio showed a statistically significant correlation with the expression of tumor Ki67.

CONCLUSIONS

The parameters of QDCE-MRI of PDA can be used to evaluate the degrees of tumor fibrosis and the expressions of VEGF and Ki67.

Inhibition of growth in a rabbit VX2 thigh tumor model with intraarterial infusion of carbon dioxide-saturated solution

PURPOSE

To evaluate the efficacy of intraarterial infusion of CO2-saturated solution in rabbit VX2 thigh tumors.

MATERIALS AND METHODS

Fourteen Japanese white rabbits had VX2 tumors implanted in the right femoral muscle 3 weeks before intraarterial infusion. Rabbits were divided into control and CO2 groups (n = 7 each). Fifty milliliters of solution (saline solution and CO2-saturated solution for the control and CO2 groups, respectively) was administered via a 24-gauge catheter in the ipsilateral iliac artery close to the feeding artery of the VX2 tumor. All rabbits were killed for tumor harvest on day 3 after the procedure. Tumor volume was evaluated with in vivo direct caliper measurement and contrast-enhanced computed tomography (CT). Tumor apoptotic changes were examined by DNA fragmentation assay and immunoblot analysis. The tumor growth ratio and apoptotic cell rate were analyzed.

RESULTS

Body weight was equally increased in both groups, but the mean tumor growth ratio was significantly decreased in the CO2 group compared with the control group (-9.5% ± 7.9 vs 27.2% ± 6.6 and 4.1% ± 4.4 vs 35.7% ± 4.5 measured by calipers and contrast-enhanced CT, respectively; P < .01). Apoptotic activity in the CO2 group was higher than in the control group (number of apoptotic cells per area, 215.0 ± 58.7 vs 21.8 ± 5.4; adjusted relative density of cleaved caspase-3, 0.23 ± 0.07 vs 0.04 ± 0.01; P < .01).

CONCLUSIONS

Intraarterial infusion of CO2-saturated solution inhibits rabbit VX2 thigh tumor growth by activation of apoptotic cell death through cleaved caspase-3 upregulation.

Comparing CT perfusion with oxygen partial pressure in a rabbit VX2 soft-tissue tumor model

The aim of this study was to evaluate the oxygen partial pressure of the rabbit model of the VX2 tumor using a 64-slice perfusion CT and to compare the results with that obtained using the oxygen microelectrode method. Perfusion CT was performed for 45 successfully constructed rabbit models of a VX2 brain tumor. The perfusion values of the brain tumor region of interest, the blood volume (BV), the time to peak (TTP) and the peak enhancement intensity (PEI) were measured. The results were compared with the partial pressure of oxygen (PO2) of that region of interest obtained using the oxygen microelectrode method. The perfusion values of the brain tumor region of interest in 45 successfully constructed rabbit models of a VX2 brain tumor ranged from 1.3-127.0 (average, 21.1 ± 26.7 ml/min/ml); BV ranged from 1.2-53.5 ml/100g (average, 22.2 ± 13.7 ml/100g); PEI ranged from 8.7-124.6 HU (average, 43.5 ± 28.7 HU); and TTP ranged from 8.2-62.3 s (average, 38.8 ± 14.8 s). The PO2 in the corresponding region ranged from 0.14-47 mmHg (average, 16 ± 14.8 mmHg). The perfusion CT positively correlated with the tumor PO2, which can be used for evaluating the tumor hypoxia in clinical practice.

Imaging tumor angiogenesis: the road to clinical utility

OBJECTIVE

Tumor growth and progression require the formation of new blood vessels from preexisting vasculature, a process called angiogenesis. The ability to noninvasively visualize angiogenesis may provide new opportunities to more appropriately select patients for antiangiogenesis treatment and to monitor treatment efficacy.

CONCLUSION

The superior molecular sensitivity of PET and the lack of radiation from MRI and contrast-enhanced ultrasound put these techniques at the forefront of clinical translation.

In vivo assessment of intratumoral aspirin injection to treat hepatic tumors

AIM: To study the antineoplastic efficacy of 10% aspirin intralesional injection on VX2 hepatic tumors in a rabbit model.

METHODS: Thirty-two male rabbits (age: 6-9 wk; body weight: 1700-2500 g) were inoculated with VX2 hepatic tumor cells (10⁴ cells/rabbit) via supra-umbilical median laparotomy. On day 4 post-implantation, when the tumors were about 1 cm in diameter, the rabbits were randomly divided into the following groups (n = 8 each group) to assess early (24 h) and late (7 d) antineoplastic effects of intratumoral injection of 10% bicarbonate aspirin solution (experimental groups) in comparison to intratumoral injection of physiological saline solution (control groups): group 1, 24 h control; group 2, 24 h experimental; group 3, 7 d control; group 4, 7 d experimental. The serum biochemistry profile (measurements of glycemia, alkaline phosphatase, gamma-glutamyl transferase, aspartate aminotransferase, and alanine aminotransferase) and body weight measurements were obtained for all animals at the following time points: D0, before tumor implant; D4, day of treatment; D5, day of sacrifice for groups 1 and 2; D11, day of sacrifice for groups 3 and 4. Gross assessments of the abdominal and thoracic cavities were carried out upon sacrifice. The resected liver tissues, including hepatic tumors, were qualitatively (general morphology, signs of necrosis) and quantitatively (tumor area) assessed by histopathological analysis.

RESULTS: Gross examination showed no alterations, besides the left hepatic lobe tumors, had occurred in the thoracic and abdominal cavities of any animal at any time point evaluated. However, the features of the tumor foci were distinctive between the groups. Compared to the control groups, which showed normal unabated tumor progression, the aspirin-treated groups showed imprecise but limited tumor boundaries and a general red-white coloration (indicating hemorrhaging) at 24 h post-treatment, and development of yellow-white areas of a cicatricial aspect at 7 d after treatment. At all time points evaluated, all except one biochemical parameters tested within the reference range (P > 0.05); a significant increase was detected in the alkaline phosphatase level of the control group 3 on D11 (P < 0.05). At 24 h post-treatment, the aspirin-treated groups showed extensive coagulation necrosis accompanied by a remarkable absence of viable tumor foci; at 7 d after treatment, the tumors had completely disappeared in these animals and fibrous necrotic nodules had developed. In contrast, throughout the study course, the tumors of the control groups remained unchanged, showing tumor nodules without necrosis at the time point corresponding to 24 h post-treatment and increased amounts of tumor nodules at the time point corresponding to 7 d post-treatment. Quantitative analysis of the remaining tumor area revealed that the aspirin-treated groups had significantly smaller tumor foci at 24 h post-treatment (8.5% ± 0.7%) and at 7 d after treatment (11.0% ± 4.2%), compared to those in the control groups (24 h: 98.5% ± 1.5% and 7 d: 94.0% ± 2.7%; both, P < 0.005).

CONCLUSION: Intralesional injection of a 10% aspirin solution causes destruction of VX2 hepatic tumors in rabbits without evidence of relapse at 7 d after treatment administration.

The role of perfusion CT as a follow-up modality after transcatheter arterial chemoembolization: an experimental study in a rabbit model

OBJECTIVES

To prospectively evaluate the feasibility of perfusion CT as a follow-up modality after transcatheter arterial chemoembolization (TACE) and to compare these findings with those of histopathology as the reference standard in a VX2 tumor rabbit model.

MATERIALS AND METHODS

VX2 carcinoma tumors were implanted into the liver of 20 rabbits 3 weeks prior to TACE. Perfusion CT was performed prior to TACE and 1- and 4-week after TACE. After obtaining perfusion index maps on perfusion CT, 2 radiologists measured the parametric perfusion indices of blood flow (BF), blood volume (BV), mean transit time (MTT), permeability of the capillary vessel surface (PS), and hepatic arterial fraction (HAF) of primary tumors on pre-TACE perfusion CT, chemoembolized primary tumors on 1-week perfusion CT, and recurred tumors on 4-week perfusion CT. The normal liver parenchyma indices were also recorded. In addition, the radiologists investigated the presence of a recurred tumor adjacent to the chemoembolized area on perfusion index maps of 4-week CT images. The areas of higher hepatic blood flow (HBF), hepatic blood volume (HBV), PS, and HAF, and lower MTT on 4-week perfusion CT than the normal liver parenchyma and the identical area on 1-week perfusion CT were considered as recurred tumors. Histopathology revealed the presence of a recurred tumor, and mean vessel density (MVD) was determined by immunochemical staining for CD31. CT perfusion indices were compared by use of the t test. Comparisons were made for the primary tumor versus normal liver parenchyma on pre-TACE CT, the primary tumor on pre-TACE CT versus the chemoembolized tumor on 1-week CT, the recurred tumor on 4-week CT versus the identical area on 1-week CT, and the primary tumor on pre-TACE CT versus the recurred tumor on 4-week CT. For the detection of recurred tumors, the sensitivity and specificity for 4-week perfusion CT were calculated. Correlation analysis between the recurred tumor perfusion indices and the MVD of the corresponding tumor region was performed. Among 20 rabbits, 6 were excluded from the analysis, and results were based on 14 rabbits.

RESULTS

Recurred tumors were histologically proven in 8 of 14 rabbits (57.1%). The BF, BV, PS, and HAF indices of primary tumors were significantly higher, whereas the MTT was significantly lower than that of the normal liver parenchyma on pre-TACE perfusion CT and that of chemoembolized areas on 1-week perfusion CT (P < 0.05). In addition, recurred tumors also showed significantly higher BF, BV, PS, and HAF, and lower MTT indices than the identical areas on 1-week perfusion CT (P < 0.05). The perfusion indices of recurred tumors were not significantly different from the indices of primary tumors (P > 0.05). Both sensitivity and specificity were 100% for 4-week perfusion CT. There were significant positive correlations between BF (r = 0.947), BV (r = 0.758), PS (r = 0.759), HAF (r = 0.955), and MVD in recurred tumors, and a significant inverse correlation between MTT (r = -0.782) and MVD was observed (P < 0.05).

CONCLUSIONS

We believe that perfusion CT is a feasible alternative modality for the successful early response assessment and early detection of a marginally recurred tumor after TACE. However, perfusion CT has limitations for the prediction of tumor recurrence after TACE.

Angiogenesis of renal cell carcinoma: perfusion CT findings

OBJECTIVE

To observe the perfusion CT findings of renal cell carcinoma (RCC) and prospectively correlate perfusion CT parameters with tumor MVD and VEGF expression.

METHODS

Dynamic contrast-enhanced multislice spiral CT was performed prospectively in 73 cases with histologically proven RCC (65 clear cell, 3 papillary, and 5 chromophobe). Blood flow (BF), blood volume (BV), mean transit time (MTT), and permeability surface-area product (PS) of RCC and normal renal cortex were measured, respectively. The tumor MVD count and VEGF expression level were determined by immunohistochemistry with specific monoclonal antibodies.

RESULTS

There was significant difference between BF, BV, MTT, and PS of normal renal cortex (454.32 ± 110.90 mL/min/100 g, 23.53 ± 5.71 mL/100 g, 3.62 ± 1.38 s, 63.95 ± 18.85 mL/min/100 g) and RCC (261.96 ± 175.86 mL/min/100 g, 17.17 ± 8.34 mL/100 g, 7.08 ± 3.42 s, 25.07 ± 13.20 mL/min/100 g) (P < 0.01). BF and BV among RCC histologic subtypes were significantly different (P < 0.05), MTT and PS were not (P > 0.05). MVD (42.29 ± 21.00) of RCC is positively correlated with BF, BV, and PS (P < 0.01), not with MTT (P > 0.05). No relationship was found between the expression levels of VEGF and any perfusion CT parameter.

CONCLUSIONS

Perfusion CT is a feasible technique to assess tissue perfusion in patients with RCC. BV, BF, and PS correlate positively with MVD and may reflect angiogenesis of RCC.