negative number for CBF

[tayebeh ebrahimi]

Dear  Dr. Jan Petr,

I have analyzed pulsed ASL images using ExploreASLV1.3.0. I have used Harvard-Oxford as the atlas. Also, I have selected only 12 ROIs in which CBF showed no n/a values. But I have two problems with the results:

1- some ROIs showed a negative value for qCBF (in the stats folder).

2- total gray matter CBF was far less than the mean CBF values of these ROIs.

It is kind of you to tell me the probable reasons for these results.

Best,

Tayebe

[Jan Petr]

Dear Tayebeh,

The Harvard-Oxford atlas has both larger and smaller regions. It can happen that some smaller ROIs have negative values due to certain issues with the acquisition (background suppression, vascular signal). You would have to send me the file (part of it) to see what could be wrong.

best,

Jan