perfusion imaging CT multivolume and sequence frame

Hi there,
I’ve been using the Slicer software for a few months now. I have several CT perfusion images that I need to analyze for changes in intensity over time, in different areas and across different frames. Initially, in Slicer 4, I drew regions of interest and converted them to binary before plotting them using the Multivolume Explorer. This gave me reasonable results.
However, as the project progressed, I needed to perform motion correction on the images. Therefore, I converted the multivolume to sequence frames and used sequence registration to correct for the motion. Now, I’m having trouble analyzing the intensity of different regions over time after converting the sequence frames back to multivolume.
Additionally, the segment statistics are providing me with strange numbers, and I’m not sure if it’s the sum of frames intensity or something else.
Thank you in advance for your assistance.

I can also switch the question?
How can I get intensity over time for multiple segments based on sequence nrrd.
Also what unit is the that? In multivolume it was hu but the number seems much higher in the sequence nrrd?