Question: Medicare covers NaF-18 PET to identify bone metastasis only for patients in a clinical study. How can I prove trial participation on the claim? Ohio Subscriber Answer: Append modifier Q0 (Investigational clinical service provided in a clinical research study that is in an approved clinical research study) to indicate that patient is in an approved study. Wait, there's more: The claim must include all of the following: 1. A PET or PET/CT code: 78608 -- Brain imaging, positron emission tomography (PET); metabolic evaluation 78811-78813 -- Positron emission tomography (PET) imaging ... 78814-78816 -- Positron emission tomography (PET) with concurrently acquired computed tomography (CT) ... 2. Modifier Q0 3. Either modifier PI (Positron emission tomography [PET] or PET/computed tomography [CT] to inform the initial treatment strategy of tumors ...) OR modifier PS (Positron emission tomography [PET] or PET/computed tomography [CT] to inform the subsequent treatment strategy of cancerous ...). 4. A9580 -- Sodium fluoride F-18, diagnostic, per study dose, up to 30 millicuries 5. A cancer ICD-9 code (such as 198.5, Secondary malignant neoplasm of other specified sites; bone and bone marrow, depending on documentation). NCD: Note: