[I'm "promoting" this comment left by "Cerebrocrat" in the Terri Schiavo News thread. --Amp]
But there’s something being lost in this discussion of brain imaging methods. The fact that an MRI would give a better structural picture of Terri Schiavo’s brain does not at all mean that the existing CAT scan isn’t good enough for present purposes. I see much serious armchair scan-reading in this thread that signals ignorance of the subject. Let me tell you: if you are sufficiently familiar with brains and brain images, you do not need an MRI to tell you how severely the brain in the pictured CAT scan is damaged, nor do you need to see more slices than the one depicted here. This single image shows a very severely damaged brain. The large “blue blobs” in the middle are ventricles, also present in healthy brains (you can see the two little dark crescent shapes in the brain on the right) that have expanded to such a large size because the overall brain volume is so low. Cranial space that would otherwize have been filled by gray matter is now filled with cerebrospinal fluid. And yes, that’s what the blue space is: cerebrospinal fluid that is filling up space left behind by necrotic brain tissue that has been scavenged and removed by the body. The white squiggly things are white matter – connective tracts that have the loose, uncoiled look about them that they do because, again, the grey matter that once compressed them is no longer there, so they “float” loosely in CSF. The gigantic ventricles, expanded white matter, and undifferentiated blue space in that scan all point to the same thing: massive loss of grey matter in the cerebral cortex. You don’t need an MRI to tell you that, it’s clearly visible in the CAT scan.
It is true that given the poor resolution of this image, it’s possible that some cortical tissue has been spared. But that doesn’t matter. Whatever wisps of cortex we might be missing in this image are not enough to sustain behaviors that could differentiate Terri Schiavo from any other vertebrate. All the neural equipment you need to do ocular following and emotional responses is subcortical. All the neural equipment you need to be a self-aware, reasoning, behaving human being is cortical. And since i gather this image was made some time ago, the present condition of the brain can only be worse.
There is no way any qualified brain doctor or scientist could look at this image and suggest that significant recovery of function is possible. The fact that we could have all this discussion on the subject is a triumph of politics over science. Tragic for Terri Schiavo, and really for us all.
(Please see the comments for Cerebrocrat’s description of his background).