I am struggling for a while to figure out a way to detect changes that have been applied to a frame since last “view” 

I found recently that a request to REST api getImage (https://www.figma.com/developers/api#get-images-endpoint) will generate a image and the response is cached. 

From what I see, the file is regenerated if I do any sort of change in the frame. 

Is it safe to assume that I can use the cached image key as an way to detect changes? 

Is there any other “official” way to trach changes to a frame? 

Thanks