Compact Laser Doppler Flowmeter (LDF) Fundus Camera for the Assessment of Retinal Blood Perfusion in Small Animals.

PURPOSE: Noninvasive techniques for ocular blood perfusion assessment are of crucial importance for exploring microvascular alterations related to systemic and ocular diseases. However, few techniques adapted to rodents are available and most are invasive or not specifically focused on the optic nerve head (ONH), choroid or retinal circulation. Here we present the results obtained with a new rodent-adapted compact fundus camera based on laser Doppler flowmetry (LDF). METHODS: A confocal miniature flowmeter was fixed to a specially designed 3D rotating mechanical arm and adjusted on a rodent stereotaxic table in order to accurately point the laser beam at the retinal region of interest. The linearity of the LDF measurements was assessed using a rotating Teflon wheel and a flow of microspheres in a glass capillary. In vivo reproducibility was assessed in Wistar rats with repeated measurements (inter-session and inter-day) of retinal arteries and ONH blood velocity in six and ten rats, respectively. These parameters were also recorded during an acute intraocular pressure increase to 150 mmHg and after heart arrest (n = 5 rats). RESULTS: The perfusion measurements showed perfect linearity between LDF velocity and Teflon wheel or microsphere speed. Intraclass correlation coefficients for retinal arteries and ONH velocity (0.82 and 0.86, respectively) indicated strong inter-session repeatability and stability. Inter-day reproducibility was good (0.79 and 0.7, respectively). Upon ocular blood flow cessation, the retinal artery velocity signal substantially decreased, whereas the ONH signal did not significantly vary, suggesting that it could mostly be attributed to tissue light scattering. CONCLUSION: We have demonstrated that, while not adapted for ONH blood perfusion assessment, this device allows pertinent, stable and repeatable measurements of retinal blood perfusion in rats.

Dynamic contrast-enhanced (DCE) MRI assessment of microvascular characteristics in the murine orthotopic pancreatic cancer model.

OBJECT: The aim of this study was to assess the dynamic contrast enhanced magnetic resonance imaging (DCE-MRI)-derived pharmacokinetic parameters between two contrast agents in a murine orthotopic pancreatic cancer model and to evaluate the tumor heterogeneity and the potential association between kinetic parameters and angiogenic markers such as the microvessel density (MVD) and vascular endothelial growth factor (VEGF) expression by immunohistochemistry. MATERIALS AND METHODS: Human pancreatic adenocarcinoma cell line MIAPaCa-2 was injected into the pancreas of BALB/C nu/nu mice. DCE-MRI was performed using Gd-DTPA and Gd-EOB-DTPA. Quantitative and semi-quantitative vascular parameters (K(trans), Kep, Ve and AUC) were calculated by using a dedicated postprocessing software program. Values were compared with tumor rim, tumor core and the entire tumor. The MVD and VEGF expressions between tumor rim and tumor core were also compared. RESULTS: There were no significant differences in K(trans), Kep, Ve, and AUC values of the three groups when using Gd-DTPA. However there were significant differences in K(trans), Kep, and AUC values of the three groups when using Gd-EOB-DTPA (P=0.014, 0.022, 0.007, respectively), in addition, the K(trans) and Kep values of tumor core were significantly lower than those of the entire tumor (adjusted P=0.014 and 0.027, respectively), the AUC values of core were significantly lower than those of the entire tumor and rim (adjusted P=0.039 and 0.009, respectively). Immunohistology results revealed that MVD and VEGF expression in the tumor rim was significantly higher than that in the core. There was positive correlation between AUC and MVD, VEGF. CONCLUSION: The murine orthotopic pancreatic cancer model provides an ideal animal model to study human pancreatic cancer. It can more sensitively semi-quantitatively and quantitatively analyze tumor angiogenesis through selecting the albumin-binding contrast agent.

Perfusion heterogeneity in breast tumors for assessment of angiogenesis.

OBJECTIVES: The purpose of this study was to investigate the perfusion heterogeneity of malignant and benign breast tumors and assay their vascular architecture changes and molecular expression, thereby evaluating the relevance between imaging and histologic characteristics of angiogenesis. METHODS: Real-time grayscale contrast-enhanced sonography was performed in 310 women with 317 breast tumors. The enhancement patterns and perfusion parameters for malignant and benign tumors were analyzed by contrast-enhanced sonography with microvascular imaging and quantitative time-intensity curve analysis. Structural characteristics were observed by light and electron microscopy. The microvessel density, vascular endothelial growth factor (VEGF) expression, and human kinase insert domain-containing receptor (KDR) expression for all tumors were assessed by immunohistochemical staining of CD31, KDR, and VEGF. RESULTS: Surgical pathologic analysis showed 163 malignant and 154 benign tumors. Significant morphologic differences, including perfusion defects, vessel distortion, vessel dilatation, and heterogeneous enhancement, were observed between the malignant and benign groups (P < .05). The mean perfusion parameters (peak intensity, ascending slope, area under the curve, and wash-out time) were greater in the malignant tumors (P < .05). There were significant differences in the peak intensity, ascending slope, area under the curve, and wash-out time between peripheral and central regions of the malignant tumors (P < .05) but none in the benign tumors. Vessels had various morphologic and distributional characteristics in the peripheral and central regions of the malignant tumors. The microvessel density and VEGF and KDR expression were significantly higher in the malignant group (P < .05), especially in the peripheral regions. CONCLUSIONS: Perfusion heterogeneity was closely associated with the tumor microvascular architecture and molecular expression. Perfusion features, especially regional morphologic and hemodynamic features, can provide valuable information for differentiating malignant from benign breast tumors.