- Evaluation of tumor extent with magnetic resonance imaging (MRI) of the nasopharynx and neck within 28 days prior to registration; if MRI is medically contraindicated, obtain computed tomography (CT) scan with =< 3 mm contiguous slices with contrast and bone windows (to evaluate base of skull involvement); Note: If a treatment planning CT scan is used, it must be with =< 3 mm contiguous slices with contrast and be read by a radiologist