What is the preferred imaging modality for assessing tumor response after palliative radiation to the bone?

In some cases of palliative radiation, particularly for oligometastases, assessing response by imaging after radiation is helpful to determine whether ongoing systemic therapy is needed. Would MRI or PET/CT be more accurate at 1-2 months after treatment? Is there a role for DW-MRI for distinguishing between inflammation of the bone or active tumor? How long after radiation can you adequately see response? Does this depend on the dose used?