MRI setup change - Mirror for visual stimuli

Dear users TAKE HOME MESSAGE: A FRONT-SILVERED MIRROR HAS NOW BEEN MOUNTED IN MRI IMPROVING IMAGE QUALITY Many of you will be aware that the visual stimulus delivery setup in MRI relies on back-projection onto a screen which the participant then views via a mirror mounted in front of their face. We have always been aware that standard mirrors are sub-optimal for this type of setup: as soon as a standard mirror is tilted internal reflection and refraction of light causes slight blurring of the image .. sometimes this is perceived as a 'double edge' when viewing object binocularly. This effect can be minimised by using a minimum glass thickness in front of the reflective surface of the mirror. Thus, to date, we have used a 2mm thick mirror to aid image quality. Unfortuantely many of you have expressed concerns that this is still not as good as you would like. We have thus decided to fit a custom cut front-silvered mirror in place of the previous setup. These mirrors have effectively no glass thickness since it is the front surface of the mirror that is the reflective one. This (for the money) is as close as we can get to perfect reflection and should resolve your problems. Unlike standard mirrors, front-silvered ones have no protection of the reflective surface and are highly sensitive to scratching and marking. The mirror can only be cleaned of dust with special products and oily stains may be impossible to remove. As such all users / operators must avoid handling the mirror surface directly and should place the mirror array in place / store with care to avoid scratching of the mirror surface by other objects. We hope the improved quality will benefit us all. Contact me if you have any queries. Kind regards, Andre' -- ************************************************************************ Andre Gouws User Support Manager York Neuroimaging Centre The Biocentre York Science Park Heslington YO10 5DG Tel: +44 (0) 1904 435328 Fax: +44 (0) 1904 435356