Magnetic Resonance Angiography Visualization of Abnormal Tumor Vasculature in Genetically Engineered Mice

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Abstract
Previous research on the vasculature of tumor-bearing animals has focused upon the microvasculature. Magnetic resonance angiography (MRA) offers a noninvasive, complementary approach that provides information about larger vessels. Quantitative analysis of MRA images of spontaneous preclinical tumor models has not been previously reported. Eleven TgT121;p53+/− mice, which invariably develop choroid plexus carcinoma (CPC), and nine age-matched healthy controls were imaged using T1, T2, and a high-resolution three-dimensional time-of-flight MRA sequences at 3 T. Tumors and vessels were segmented to determine tumor volume and vascular attributes, including number of terminal branches, vessel count, and the average vessel radii of MRA-visible vessels within the tumor. Differences in the vasculature between tumor-bearing animals and healthy controls were analyzed statistically. Although the spatial resolution of MRA prohibits visualization of capillaries, a high density of intratumor blood vessels was visualized in CPC mice. A significant increase in terminal branch count and vessel count, but not average vessel radius, was observed in CPCs when compared with normal controls. Both terminal branch count and vessel count were highly correlated with tumor volume. This study represents the first MRA analysis of a spontaneous preclinical brain tumor model. Although the spatial resolution of MRA is less than histologic analysis, MRA-obtained vascular attributes provide useful information with full brain coverage. We show that consistent tumor vasculature properties can be determined by MRA. Such methods are critical for developing preclinical therapeutic testing and will help guide the development of human brain tumor analyses.