Science Fail Monday: Not All Brass is Created Equal

Posted: 05 11, 2015

Before undergoing an MRI scan, the patient must answer a laundry list of safety questions.  For example, the MRI technician will ask about any metal that you may have on (or in) your body. That’s because some metals are strongly magnetic, and may present a safety hazard or simply interfere with the scan image quality. My research uses MRI on small animals, and we have to be equally cautious of the metals we introduce to the scanner. For brain stimulation experiments, I use electrodes made from tungsten- a material safe for MRI that interferes minimally with image quality. To keep these electrodes in place on the animal’s head, I use another metal-containing piece – small brass screws drilled into the skull. In my experience, brass had always been a great material, essentially invisible in MRI scans. Recently, I purchased brass screws from a new vendor. At this point, I’d like to draw your attention to the picture below. The image on the left is a rat brain, scanned using MRI. This is the image I expect when I first place the animal in the scanner. Now, look to the right; this brain scan was taken of a rat with my new brass screws. No, I didn’t take a scoop out of the rat’s brain. That’s called a distortion artifact, and can be caused by certain metals interfering with the MRI scanning process. Apparently, these brass screws have some metal impurity that distorts my images. If anyone is interested, I have a few packs of small “brass” screws up for grabs, although I wouldn’t recommend them for MRI.

brass screws mr scan

by Dan Albaugh

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This article by Dan Albaugh was co-published on the SWAC Blog, The Pipettepen: http://swac.web.unc.edu/thepipettepen/

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