Education, tips and tricks to help you conduct better fMRI experiments.
Sure, you can try to fix it during data processing, but you're usually better off fixing the acquisition!

Friday, February 5, 2016

Corrective lenses for tight head coils


Most labs have plastic goggles for correcting a subject's vision in the MRI. Here's our box of tricks:



These goggles work pretty well for a standard sized head coil, such as the 12-channel TIM coil on my Siemens Trio. But for a tighter fitting coil, such as the 32-channel head coil, there is simply no way to cram a subject wearing goggles into the space available. For a start the goggles' frame prevents the subject's nose from penetrating the appropriate gap in the front of the coil.

A simple solution is to relocate the corrective lenses on the outer surface of the head coil. All that's required is a different way to hold the lenses in place. My ace engineer, Rick, made this pair of holders for our 32-channel coil:



The plastic strip with the label on it is actually optional, it's a way to keep the otherwise independent lens holders together in the store cupboard. Here's what one of the holders looks like with lens inserted:



The plastic mounts into the gap in the RF coil with moderate friction to hold it in place. In the above photo you can also see the black velcro strips that can be used to hold the pair of holders together, but as mentioned above the holders actually mount independently.

Below are a few more quick pix of a holder showing its basic construction: a block cut to the right size to fit snugly into the socket on the coil, and a smooth groove to hold the lens in place. I have no idea if there is a company making these things but they are basic enough that you could fashion some yourself in an afternoon.





9 comments:

  1. This is a fantastic idea! I'm definitely going to make a set of these for our scanners too. Thanks!

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  2. Hello, I am looking for fMRI solution for this tight 32ch coil, since my nordic goggle is not compatible with this headcoil. Would you let me know which setting (goggle or projection) and brand you are using?

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    1. Hi June, we use a rear projection system, the projector is from Avotec and the screen and mirrors are custom. More info here: http://technicalfmri.blogspot.co.uk/search/label/projector

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  3. Hello. This appears to have been 3D printed? Do you happen to have the 3D model files available? We are using the same glasses and head coil.

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    1. Ah, I'm afraid it was machined by my expert shop guy. I'll be out of the lab for the next ten days, but when I get back I'll find out if it's possible for us to scan them and send you a digital file. Will be back in touch in a couple of weeks.

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    2. Any follow up on the scanning? We’d love to 3D print a pair. Thanks!

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    3. My colleague is working on a 3D scan now. Keep an eye on the TechniCal fMRI blog for an update! I'll try to remember to cross post a link here.

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    4. Blog post is now live! You should be able to download the files from the Dropbox link at the bottom of the post. Let me know how they work out for you :-)

      https://technicalfmri.blogspot.com/2018/10/designing-and-3d-printing-custom-lens.html

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