We perform it in all three directions and it is critical when we are reading diffusion-weighted sequences. We become used to wanting to look in all three directions. ADC maps are helpful as well. But we become sensitized to having to look at a whole host of different images in order to appreciate the changes taking place. This is a sensitive indicator of early ischemia.
Diffusion decreases as early as three minutes after onset.
The hypothesis is that it is related to movement of water from the extracellular space into the more restricted intracellular space. Again, I think that if we are not using diffusion imaging now, we will be using diffusion imaging tomorrow. And, in fact, I would say that it so much improves the reading of ischemic disease that we really need to use it now. We have some loss of gray and white. I think the big difference with diffusion is old from new or acute from subacute.