I came here with a similar thought. Given that we don't have a really precise definition of that transition from living to dead, I wonder if this could be it.

Some parts of the dead mice still emit in that spectrum. There won't be a clear and distinct "the lights went out" moment but a gradual fading, so you'll have to define some threshold to translate from radiation distribution and intensity do dead/alive. I don't think an image of photon emission will help pronounce someone dead.