Surgical removal of implanted microchips to correct MRI susceptibility artifacts in mice

Implanted microchips are becoming increasingly common in research for animal identification and have been adopted by commercial vendors for some mouse strains. However, they often contain metal components, which generate magnetic susceptibility artifacts on MR images. Despite this, some microchips are marketed as MR-compatible, even though they are likely to affect image quality.

We assessed the impact of a radiofrequency identification microchip on MR images of the mouse brain and present a method for precise surgical removal. A handheld magnet was used to locate and stabilize the microchips during removal. Mice were imaged before and after microchip removal.

Although marketed as MR-compatible, implanted microchips caused magnetic susceptibility artifacts in all imaged mice, despite variation in the location of the microchip. Surgical removal corrected these artifacts, allowing for high-resolution imaging without interference. All subjects recovered well from the procedure.

The discrepancy in the use of the term "MR-compatible" highlights a disconnect between researchers and some manufacturers. Microchips should be carefully evaluated for experiments involving MRI. In the event that microchips require removal before imaging, surgical removal using a handheld magnet to precisely locate the microchips is effective.