A low-cost telescope for enhanced stimulus visual field coverage in functional MRI.

A common limitation of typical projection systems used for visual fMRI is the limited field of view that can be presented to the observer within the scanner. A wide field of view over which stimuli can be presented is critical when investigating peripheral visual function, in particular visual disorders or diseases that lead to the loss of peripheral vision.

We present a relatively low-cost Galilean telescopic device that can be used in most MRI scanners to double the effective visual field being presented. The system described is non-ferromagnetic, and compatible with most standard methods of visual presentation in MRI environments. The increase in area of visual cortex activation was quantified by comparing the extent of visual activity evoked by observing flickering checkerboards with and without the telescope in place.

In all three observers that reported image fusion from the telescope, the extent of cortical activation was greater with the telescope, while in the fourth observer there was no difference between the two methods due to a lack of fusion.

The telescope is a low cost, easy to implement solution in situations where changes to the existing equipment or setup are not feasible.