After going through treatment for primary brain tumor is there a way to tell if there are any live cancer cells?

No: Imaging with MRI will give the best evaluation to see if there is any remaining tumor. Often the changes from surgery and radiation might leave abnormal scan. Evaluating the symptoms and any growth in repeat scans determines any activity. Using dedicated brain pet or spect scans may give a better idea of live or active cells but this is not done often since the treatment was just accomplished.

May be Difficult: Mri with contrast and ct scans can show residual tumor but it is often difficult to differentiate from normal post-operative changes. Repeat studies may show growth, if this occurs. Pet scans and spect images can show active or live tumor cells, but again, in the first few months after surgery it can be difficult to differentiate from normal postoperative changes.