Shooie, originally, it was the opinion to have a 5 yr interval between ct scans because they are very powerful and can disrupt and damage cells. From what I have heard from others is that ct radiation levels have been lowered and now there is a 2 yr interval. I have not looked it up yet to see if that is true, but I will. Your dr may be thinking that a regular sputem test is unessessary because mac is a slow grower. I think it is important to get a sputem test every yr or sooner if you have a bad exacerbation. Reason being; you may have pseudomonas growing in your lungs or some other bad organism. We are at risk to other 'bugs' infecting us due to having bronchiectasis. I would stay on top of your lung health. I chose not to treat mine back in 2005 and have permanently lost a lot of lung function I think as a result of my decision.