Inverting ROI

regina

Hi 
I have chosen a ROI on the left hemisphere of the brain and then cropped that region. Now I want to invert the ROI to get the right hemisphere, this seems to work well for measurements, but when I try to crop it I get the left side (represented as a black hole) as well. How can I avoid this?

CraigW

Here is a  screen capture of the three images referred to by Regina.

What I'm seeing here is that the actual ROI for each hemisphere is not critical (that is, it is OK to have some of the image outside of the tissue included in the ROI), but you do want the entire brain to be in one or the other of the right or left ROIs.  Furthermore, there appears to be no simple algorithm that would automatically partition the image properly, so the operator needs to draw the ROI for one side or the other.  Thus the inverted Right Hemisphere ROI is OK as the Left Hemisphere ROI except that it is too big and has an unnecessary hole in it.  So I'm going to suggest a simple extra step to clean things up: after you have cropped the image with the inverted Right Hemisphere ROI (giving you the image with the big hole), rather than saving it then, just delete that ROI and draw a new rectangular ROI around the section of the image you want to keep.  Then you can save that image as the Left Hemisphere cropped image.  I've illustrated this two-step cropping approach below:

YuriG

There is Invert ROIs button in the ROI options dropdown:



Yuri

CraigW

If I understand your question correctly, you don't really want to invert the ROI, but rather you want to reflect the left hemisphere ROI across the midline of the brain image in order to get a right hemisphere ROI.

There is no built in way to do this, but it can be done with a macro.  Maybe you could post a screen capture showing your image with the left-hemisphere ROI drawn, so we could see exactly what sort of situation we are working with (e.g., is the ROI always a rectangle or is it a polygon).

regina

Thanks for your help. CraigW could I please have an email address to send the images. I am happy to have them posted on the forum, but I am having trouble getting the images to paste.