Visualization of orbital flow by means of phase contrast MRI.

Magnetic Resonance Imaging (MRI) is a high resolution medical imaging technique to image internal anatomical structures. Phase contrast MRI (pcMRI) technique is an add-on specification of MRI devices in order to quantify flow. Although different attempts have been introduced to measure orbital flows, a relationship between different ophthalmic physiological structures including superior ophthalmic vein, ophthalmic artery and optic nerve sheath (containing cerebrospinal fluid) using phase contrast MRI has not been established. In this study we investigate orbital flow in 5 normal subjects using a 3 tesla MRI device. pcMRI technique has been applied to extract flow in the superior ophthalmic vein and optic nerve sheath. Electrocardiogram of each subject was monitored and gated to the MRI in order to extract flow waveforms. Results show multiple peaks when assessing orbital flow waveforms, suggesting possible reflection of flow from back of the eye. These peaks have been characterized and a possible explanation to this phenomenon has been provided. This study enhances understanding of interaction between physiological structures at the retrolaminar portion of the eye which may be responsible for different ophthalmic abnormalities.