Which modality is better for detecting or confirming metastasis pet scan or bone scan? !

PET scan: I do believe that pet is better in the early stages especially for detecting bone marrow metastatic disease and osteoplastic bone changes.

PET scan: Pet scan involves injection of f18 fdg, isotope attached to metabolite of glucose. Tumors usually have high metabolism of glucose.Pet scan can detect very small active foci of metatastatic disease(5mm or less). Bone scan positive if metastatic disease is in skeleton and the host bone is reacting to the disease. Some metastases form bone and are seen. Soft tissue disease. Nodes, lung, not seen.

Depends on cancer: Each cancer type has an optimum way to image it, especially with techniques that image physiology, like pet and bone scan, as opposed to techniques that image anatomy, like ct and mri. Pet is best for cancers that use a lot of glucose as an energy source, like lung cancer. Bone scans are best for cancers that disrupt bone, like prostate cancer.