My understanding is that “tree in bud”describes the small damaged bronchial airways that indicate bronchiectasis. (They may indicate other things but I don’t know since I am not a medical expert.) My pulmonologist pointed this out to me on my CT scans when I was first diagnosed with bronchiectasis. You must have had a knowledgeable radiologist that read your CT. My report just came back from the radiologist saying lesions. The pulmonologist referred to these “lesions “ as “tree in bud”.