High-Resolution Diffusion-Weighted Imaging of the Orbits Using Readout-Segmented EPI

Introduction: Diffusion-weighted MRI (DWI) has demonstrated great value for the diagnostic workup of acute ischemic stroke and other abnormalities of the neurocranium, such as abscesses, CJD, etc. Similar diagnostic benefits could be anticipated from using DWI on orbital pathologies. High on the list of interesting pathologies are certainly periorbital dermoids/epidermois, fungal and pyogenic infections, and ischemic changes to the optic nerve. Moreover, DWI might be of value for evaluating cellular orbital and periorbital tumors (e.g. lymphomas, PNET, leukemic chloromas, and neuroblastoma mets) as well as other orbital tumors (e.g. optical gliomas, melanomas of the globe, mets, meningiomas, and lacrimal gland tumors). Sadly, anatomic structures within and adjacent to the orbits, such as the nasal cavities, perturb the magnetic field homogeneity, and lead to profound signal loss and distortions on conventional single-shot EPI-based DWI scans. This in turn often renders DWI of these regions meaningless. Recently, readout-segmented (RS)-EPI [1,2] has been suggested as a promising variant of EPI that can significantly reduce EPI-distortions and increase spatial resolution. In a prospectively designed study, a comparative evaluation was performed between standard accelerated (ASSET) EPI DWI and GRAPPA-accelerated RS-EPI DWI on a cohort of 35 pediatric patients at 3T. Incidentally, we found that diffusion-weighted RS-EPI of the orbits was of remarkable diagnostic quality. These findings will be reported here.