hi Kris,
I can't speak to brain imaging regarding reversibility, but in my experience with young adults who quit gaming they see pretty dramatic differences in mood, attention, impulse control, sleep, etc within months (if not weeks, depending on the level of addiction). Tech addiction that starts at an early age (esp before puberty) is going to affect the brain more severely. Some changes may be permanent, hence the concern, but I suspect much of it is reversible especially with longer periods of abstinence.