Working between datasets/slices and reanalyzing saved data

Hey everyone!
I am a student from Rush University and we are working on a project which analyzes muscle area and hounsefield units on CT scans of the L3 region in hospitalized patients.

The major issues that occur are in regard to working between images and trying to figure out if we can reanalyze/correct saved work. When I work on a slice I set a threshold to mark up the muscle area (-30 to 150) but for some reason the brush does not work when loading a new image into the slicer program. Currently, I have to close and reopen the program and redo every step to successfully paint the muscle area in the new image. Is there a way how to use the threshold brush for every image that I load into the program without reselecting threshold parameters?

My next question is about the possibility to reload/reanalyze a slice that has been measured with the software and saved. For example, when I save the image with the measured data, is it possible to reopen that image because a part of the image was brushed/selected wrongly to be corrected?