I agree with all of the previous comments. In addition, I'd like to add my own anecdotal experience. I saw a patient with widely metastatic melanoma who underwent head CT instead of an MRI brain due to the presence of pacemaker. There was a nodular enhancing focus read as suspicious for metastasis, ...

On occasion, I have treated patients with SRS using CT (with contrast) alone. This was reserved for the rare patient who was unable to undergo MRI, had excellent functional status, wanted to avoid WBRT, and had more factors favoring oligometastatic disease (controlled primary, long intracranial dise...

Reasonable to do. I usually do a 2 mm margin (as opposed to my usual 1 mm) as the exact end of the lesion is less difficult to visualize compared to the CT head with contrast. There is an inherent risk of not catching smaller lesions with MRI, but to me, it is not enough reason to remove it as a tre...

I would be reluctant to treat with SRS alone and would favor whole brain RT with or without an SRS boost, as a CT scan can underestimate the extent of disease and number of lesions. If treated with SRS alone, there may be an increased risk of neuro deficits from progression ...

Assuming that radiation is the only modality felt appropriate at the time (for example, the patient is not felt to be a resection candidate by neurosurgery), yes. One could either treat with whole brain now and potentially treat at progression later with SRS, or one could treat with SRS now and pot...