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M.J. Rondeau, L. Leung, R.H. Silverman, A. Chabi, F.L. Lizzi, R. Folberg, D. Coleman; Uveal Melanoma Imaging With Echogenic Liposomes . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3647.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: In an increasing number of tumors (melanoma, breast, prostate) the presence of clusters of tumor cells surrounded by extravascular matrix (EVM) has been found to be a strong prognostic indicator. This study explores the use of echogenic liposome and echogenic immunoliposome ultrasonic contrast agents to enhance detection of these patterns in a human tumor xenograft model. Methods: Echogenic liposomes with and without a fluorchrome lipid component, and with and without antibody decoration (anti-vitronectin, anti-elastin) were produced and maintained in the fluffy-cake lyophilized state prior to rehydration immediately before use. Human tumor xenografts (C918 human uveal melanoma model) in the BALB/c nu/nu mouse were grown to an approximate volume of 1200 mm3. Mice were tail vein catheterized, anesthetized, depilitated and placed in a high frequency (37 MHz center frequency, 10-60 -15db bandwidth) multi-axis immersion scanning system. Serial digital RF scans were acquired before during and after bolus injection of liposomes. Typical scan parameters were 512 lines of 2048 samples at 250 MHz. Calibrated ensemble-averaged power spectrum parameters (cq2, size, and mid-band fit) were obtained. Results: Bolus liposome injection in the murine xenograft model produces a persistent increase of ~ 2db in mid-band fit amplitude and was spatially localized in vessels detectable by slow flow techniques and in other tumor regions in the late detection phase. Conclusions: Echogenic liposomes can enhance ultrasonic detection and localization of tumor vasculature and associated EVM structure. While the murine xenograft model lacks a realistic EVM pattern microarchitecture due to the lack of environmental modulators, the results suggest that echogenic liposomes could be used to detect the presence of these patterns in a clinical setting.
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