comparing MRAs

comparing MRAs

Dear radiology professionals,
here is my problem, I would appreciate any thoughts on it:

I have a group of 6 patients.
For each patient I have 3 MRAs for the arteries of the brain, done on
the same day, at 3 different times:
MRA1 - before any treatment
MRA2 - after false treatment
MRA3 - after treatment

They have been done using Inflow (Time of Flight) methodology.

My hypothesis is that the treatment results in a significant
difference in the the blood circulation in the brain.
The radiologist I worked with said he saw significant difference when
he looks at the 3D reconstruction,
because he can see significantly more arteries on the MRA1 and 2 than
in MRA3.

According to your experience:
1) What could this mean (seeing more arteries)?
2) Can this difference be reliably proven numerically and how ?
3) If I do an ROI on each of MRAs and show that the Mean Intensity in
that area is higher in MRA1 and 2 than in MRA 3, does that prove there
is also a difference in the blood circulation in the brain after
treatment ? (Basically, are intensities on 2 different MRAs comparable
- if they were done at different times, but on the same volume and
with the same settings on the machine)

Thank you very much,

p.s. I am also trying to do a similar analysis for Cerebro-Spinal
Fluid. Any thoughts on that would also be appreciated.