Drug resistant TB ?

I was in my 3rd month of inh therapy for latent tb. For 20 yrs I have had a PPD for employment. In May 09 my PPD was possibly pos, chest x-ray was neg and no further treatment was given. In May 10 a QuantiFERON gold was pos & infectious disease dr requested a chest cat scan. At first it was read neg but then was questioned by my dr and refered to pulmonary dr. Pulm dr read it as abn but "I do not think it is significant pathology". All drs agreed to start inh therapy. At the time (and now)I felt great,had no symptoms of active tb, walked 3 mi a day 5 times a wk, went to the gym & ran 3 mi on the treadmill 3 times a wk. Baseline ast/alt was 29/21. Bloodwork at 4 wk, 8 wk, & 10 wk showed 45/41, 290/274, & 443/343 and inh was stopped. Questions: Do you think the tb has become drug resistant after 10 wks? How often is it necessary to have chest xrays/cat scans?(I am very concerned about the amounts of radiation I am receiving)