Magnetic Resonance Imaging of Uveal Melanoma in Mice

Abstract

Purpose: : Uveal melanoma is the primary intraocular malignancy. More tumor-specific treatments are needed to reduce the incidence of ocular complications during treatment of uveal melanoma, but current methods do not allow for determination of the effects of treatments on the physiology of the tumor and its circulation. In cancer, diffusion MRI changes due to cell swelling and apoptosis are measurable at an earlier stage than subsequent conventional radiological response indicator. It is not yet known if diffusion MRI is useful in uveal melanoma. In the present study, longitudinal diffusion MRI was employed to localize and characterize uveal melanoma followed by the contrast enhanced MRI on day 7 to assess tumor vasculature in mice.

Methods: : Adult male C57BL/6 mice underwent intraocular choroidal inoculation of 50 10³ B16F10 cells in 1.0µL medium. Diffusion MRI was performed to determine the apparent diffusion coefficient (ADC) on day 4 (n = 6), 7 (n = 3), and 10 (n = 3) after cell inoculation. T1-weighted MRI after i.p. administration of Gd-DTPA was performed on day 7 to assess tumor vasculature.

Results: : On day 4, uveal melanoma ADC was 0.65 10^-3 mm²/s, significantly higher than 0.36 10^-3 mm²/s of remote intact retina (p < 0.05) , a value not changed with tumor mass increase on days 7 and 10. Thus, the uveal melanoma was clearly differentiated from the retina on the ADC map (Fig 1A & B). At day 7, the tumor vasculature was delineated based on the regional signal enhancement after the administration of Gd-DTPA (Fig. 1C & D).

Conclusions: : ADC changes appear as an early marker for uveal melanoma. These preliminary findings suggest that MRI may be useful to monitor the temporal evolution of uveal melanoma and detect tumor vasculature in vivo.

Keywords: oncology • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • melanoma