Ovarian volume measurements in mice with high-resolution ultrasonography

Ultrasound Molecular Imaging of Angiogenesis Using Vascular Endothelial Growth Factor-Conjugated Microbubbles

Imaging of angiogenesis receptors could provide a sensitive and clinically useful method for detecting neovascularization such as occurs in malignant tumors, and responses to antiangiogenic therapies for such tumors. We tested the hypothesis that microbubbles (MB) tagged with human VEGF₁₂₁ (MB_VEGF) bind to the kinase insert domain receptor (KDR) in vitro and angiogenic endothelium in vivo, and that this specific binding can be imaged on a clinical ultrasound system. In this work, targeted adhesion of MB_VEGF was evaluated in vitro using a parallel plate flow system containing adsorbed recombinant human KDR. There was more adhesion of MB_VEGF to KDR-coated plates when the amount of VEGF₁₂₁ on each MB or KDR density on the plate was increased. MB_VEGF adhesion to KDR-coated plates decreased with increasing wall shear rate. On intravital microscopic imaging of bFGF-stimulated rat cremaster muscle, there was greater microvascular adhesion of MB_VEGF compared to that of isotype IgG-conjugated control MB (MB_CTL). To determine if MB_VEGF could be used to ultrasonically image angiogenesis, ultrasound imaging was performed in mice bearing squamous cell carcinoma after intravenous injection of MB_VEGF. Ultrasound videointensity enhancement in tumor was significantly higher for MB_VEGF (17.3 ± 9.7 dB) compared to MB_CTL (3.8 ± 4.4 dB, n = 6, p < 0.05). This work demonstrates the feasibility of targeted ultrasound imaging of an angiogenic marker using MB_VEGF. This approach offers a noninvasive bedside method for detecting tumor angiogenesis and could be extended to other applications such as molecular monitoring of therapeutic angiogenesis or antiangiogenic therapies in cardiovascular disease or cancer.

Complementarity of ultrasound and fluorescence imaging in an orthotopic mouse model of pancreatic cancer

BACKGROUND

Pancreatic cancer is a devastating disease characterized by dismal 5-year survival rates and limited treatment options. In an effort to provide useful models for preclinical evaluation of new experimental therapeutics, we and others have developed orthotopic mouse models of pancreatic cancer. The utility of these models for pre-clinical testing is dependent upon quantitative, noninvasive methods for monitoring in vivo tumor progression in real time. Toward this goal, we performed whole-body fluorescence imaging and ultrasound imaging to evaluate and to compare these noninvasive imaging modalities for assessing tumor burden and tumor progression in an orthotopic mouse model of pancreatic cancer.

METHODS

The human pancreatic cancer cell line XPA-1, engineered for stable, high-level expression of red fluorescent protein (RFP), was implanted into the pancreas of nude mice using orthotopic implantation. The tumors were allowed to grow over a period of one to several weeks during which time the mice were imaged using both fluorescence imaging and ultrasound imaging to measure tumor burden and to monitor tumor growth.

RESULTS

Whole-body fluorescence imaging and ultrasound imaging both allowed for the visualization and measurement of orthotopic pancreatic tumor implants in vivo. The imaging sessions were well-tolerated by the mice and yielded data which correlated well in the quantitative assessment of tumor burden. Whole-body fluorescence and two-dimensional ultrasound imaging showed a strong correlation for measurement of tumor size over a range of tumor sizes (R(2) = 0.6627, P = 0.003 for an exposure time of 67 msec and R(2) = 0.6553, P = 0.003 for an exposure time of 120 msec).

CONCLUSION

Our findings suggest a complementary role for fluorescence imaging and ultrasound imaging in assessing tumor burden and tumor progression in orthotopic mouse models of human cancer.

In vitro ultrasound biomicroscopic imaging of colitis in rats

OBJECTIVE

The purpose of this study was to show the feasibility of 50-MHz ultrasound biomicroscopy (UBM) to image the rat colon.

METHODS

B-mode images were obtained from ex vivo colon samples (n = 4) collected from Rattus norvegicus (Berkenhout, 1769) rats, with 2,4,6-trinitrobenzene sulfonic acid-induced colitis in 3 of them. Left colon rectangular fragments (5 x 5 mm) were obtained after necropsy, and UBM images were acquired with the samples immersed in saline at 37 degrees C. All layers of the normal intestinal wall were analyzed according to their thickness and the presence of uneven bowel mucosa (ulcers). The folds and layers detected by UBM were correlated with histopathologic analysis.

RESULTS

The 4 layers of the normal colon were identified on the UBM images: the mucosa (hyperechoic), muscularis mucosae (hypoechoic), submucosa (hyperechoic), and muscularis externa (hypoechoic). On 2 UBM images, superficial ulcers were detected, approximately 0.5 mm in size, with intestinal involvement limited to the mucosa. The histopathologic analysis verified enlargement of submucosa layers due to an edema associated with sub-mucosa leukocyte infiltration. On 1 UBM image, it was possible to detect a deep ulcer, which was confirmed by the light microscopic analysis.

CONCLUSIONS

An ultrasound imaging system was scaled and optimized to visualize the rat colon. Ultrasound biomicroscopy provided axial and lateral resolutions close to 25 and 45 mum, respectively, and adequate penetration depth to visualize the whole thickness of an inflamed colon. The system identified the colon layers and was able to detect mural changes and superficial ulcers on the order of 500 mum.