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S. M. Barb, M. W. Wilson, C. Rodriguez-Galindo, N. S. Phillips, P. Zou, B. G. Haik, R. J. Ogg; Characterization of Visual System Development in Children With Retinoblastoma Using Functional Neuroimaging. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3305.
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© ARVO (1962-2015); The Authors (2016-present)
To use functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) to characterize visual system development of children with retinoblastoma.
Subjects: So far, 42 patients (median age 23 months, range 1 month-8.5 years) have been enrolled in our IRB-approved protocol: 26 with unilateral and 16 with bilateral disease. All subjects were imaged (under anesthesia) at diagnosis and will be imaged every ~6 months after diagnosis until 5 years post-diagnosis. MRI: 1.5T Siemens Symphony scanner acquired sagittal 3D T1-weighted images for anatomical reference. fMRI: 23-slice volume every 2.058s during flashing light stimulus through closed eyelids. fMRI analysis: SPM2 (www.fil.ion.ucl.ac.uk/spm): 5 voxel extent threshold with p=.001 (uncorrected). DTI: Double-spin echo EPI, b=0 and six gradient directions with b=1000s/mm2, 4 repetitions. DTI Analysis: SPM2 using the DTI Toolkit (http://sourceforge.net/projects/spmtools). ROI’s were manually drawn to calculate diffusion parameters (FA and ADC) in the genu and splenium (of the corpus callosum) and periventricular optic radiations.
Functional activation in the visual cortex was asymmetric between hemispheres and reproducibly located in the anterior portion of the visual cortex. Nasal hemiretina dominance has been shown in unilateral patients with single-eye enucleation using fMRI. Blood oxygen level dependant (BOLD) signal was negative in all studies except one (>3 months). FA and ADC values followed a normal developmental trajectory in the genu but developed slower than expected in the splenium for both unilateral patients and bilateral patients. FA and ADC in the optic radiations were laterally symmetric and had values comparable to normal peripheral white matter.
Functional MRI and DTI are feasible in this challenging patient population. Inter-hemispherical asymmetry of activation in the visual cortex likely reflects the effects of tumor and/or loss of an eye. DTI results showed evidence of altered development of white matter in the posterior brain. This longitudinal study will document the development of neural systems for vision in patients with retinoblastoma and changes with therapy, and may help to clarify unresolved questions regarding developmental changes in the BOLD signal.
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