SPECT subtraction analysis and SPM

Hi specialists,

This is a follow up question for a problem that I first asked at the NITRC forum. I am posting here as this forum seems to be covered by specialists from several areas within neurosciences, not only neuroimagers.

I want to analyse inter-intra epileptic SPECTS of patients that have been diagnosed with non-epileptic seisures. The sample size is seven.

During my investigations of the methods, I noticed that most of publications use the subtraction of these images, instead of comparing them using a paired t-test in SPM. The next step was then to find a way of performing these subtractions.

I noticed that each researcher uses his own formula to acquire the subtraction and, in the interest of reproducibility, decided to use an older, but open tool to do this. I used ISAS Bioimage Suite to acquire the subtractions, which were later realigned, centered to the anterior comissure, and coregistered to the T1 MNI template (provided by ISAS) in SPM. Some significant clusters were found in a one sample t-test.

Now to the question:

  • Can I determine the direction of these clusters? Are these hyper or hypoperfusion? Is there some way of assess the direction of these using SPM?

The use of subtraction precludes determining the direction of these clusters?