@thumperguy Here is the explanation from my ID doc about the CT findings - the CT shows signs of the infection in the form of lesions, cavities and other damage. It also shows the extent and severity of the underlying bronchiectasis. The culture confirms the presence of a specific organism such as MAC, and can be further tested to see which drugs it is susceptible to. The repeat CT is used to determine if the signs of infection are improving, and may be used in conjunction with repeat sputum culture.
In my case, the lung CT clearly showed improvement, with the cavities and clouded areas gone. My cough was better, and my sputum clear so even though there is still MAC in my culture, the doc decided 18 months was enough of an antibiotic assault on my body.
So now I am in wait and watch mode, nebbing 7% saline in hopes of keeping the remaining MAC from growing. The CT will likely be repeated after a year of if my symptoms return.