9.4T and 17.6T MRI of Retinoblastoma: Ex Vivo evaluation of microstructural anatomy and disease extent compared with histopathology

Background Retinoblastoma is the most common intraocular tumor in childhood with a good prognosis in terms of mortality, but detailed information about tumor morphology and disease extent in retinoblastoma is important for treatment decision making. Purpose To demonstrate ultrahigh‐field MRI tumor morphology and tumor extent in retinoblastoma correlating with in and ex vivo images with histopathology. Study Type Prospective case series. Population Six retinoblastoma patients (median age 5.5 months, range 2–14) were prospectively included in this study. Median time between diagnosis and enucleation was 8 days (range 7–19). Field Strength/Sequence In vivo pre‐enucleation at 1.5T MRI with a circular surface coil. Ex vivo imaging (FLASH T1‐weighted and RARE T2‐weighted) was performed at field strengths of 9.4T and 17.6T. Assessment After ex vivo imaging, the eyes were histopathologically analyzed and morphologically matched with MRI findings by three authors (two with respectively 14 and 4 years of experience in ocular MRI and one with 16 years of experience in ophthalmopathology). Results Small submillimeter morphological aspects of intraocular retinoblastoma were successfully depicted with higher‐resolution MRI and matched with histopathology images. With ex vivo MRI a small subretinal tumor seed (300 μm) adjacent to the choroid was morphologically matched with histopathology. Also, a characteristic geographical pattern of vital tumor tissue (400 μm) surrounding a central vessel interspersed with necrotic areas correlated with histopathology images. Tumor invasion into the optic nerve showed a higher signal intensity on T1‐weighted higher‐resolution MRI. Data Conclusion Higher‐resolution MRI allows for small morphological aspects of intraocular retinoblastoma and extraocular disease extent not visible on currently used clinical in vivo MRI to be depicted. Level of Evidence: 4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1487–1497.