Sharon wrote:I believe the difference is between focal and diffuse brain damage. MRI is great for focal imaging, but the SPECT shows diffuse damage more distinctly. I will be imaged by a triple head SPECT which is more precise than the single. Diffuse damage is more prevalent in secondary progressive - focal in relapsing remitting.
Blood flow is imaged - I am unsure about blood volume. So much to learn...
Flow, if it's volumetric flow, adds the dimension of time to volume: if not for it being volume per
second, it would be linear only, that is, velocity, or rate of movement of, say, a single blood cell. You could have a volume of blood that is not moving at all, for instance in a donation bag. I think volume is often a characteristic of the container, i.e., blood vessels, where flow often describes the thing contained, i.e., blood.
I think flow rate is even more important if oxygen is being exchanged, as it is in blood flow that is diffuse, that is, taking place spread out over a large, fine group of parallel vessels (capillaries). Oxygen is needed also by larger vessels, to nourish the endothelium and energize the smooth muscles.
The endothelium is like capillaries in that it is a single layer of cells, while capillaries often are only large enough for allow passage of a single cell. The scales are similar.
differentiated cells do proliferate in vivo, generally via mitosis. Cancerous cells proliferate excessively, with no control from the cell cycle. Due to these facts stem cells aren't the only cell type to proliferate. With regards to the potency of the cells, zygotic cells are totipotent - meaning they can differentiate into any of the somatic cells of the organism. Adult stem cells however have lost some of their potency and are Pluripotent- They can only differentiate into the three germ layers, Ectoderm, mesoderm (if present) and Endoderm.
...which, if true, means that anyone trying to rely on adult stem cells to undo the ravages of "MS", may be barking up a dead tree, or flogging the wrong horse, or something....