Is the use of PET worthwhile?

Differentiating benign tumor from malignancy,diagnosing the metastasis and recurrence of cancer and coronary artery disease (CAD),PET possesses high specificity and sensitivity,and the high accuracy. But the check methods being used aren't replaced by it.Because the cost of PET is too expensive.Is there no feasibility in using PET like that? The analyses for the cost-effectiveness of PET to expatiat on wich PET is economical and accurate. So it will substitute for the present check methods.