- GTR must be confirmed on post-operative imaging following the most recent surgery; submission of both pre-operative and post-operative MRIs is required for patients; if a second surgery is performed, submission of post-operative MRI is required and pre-operative MRI is required only if obtained; all sequences obtained in the pre- and post-operative MR imaging are to be submitted to National Radiology Group (NRG) Oncology for study registration; imaging subsequent to enrollment must include pre and post gadolinium contrast-enhanced three-dimensional spoiled gradient (SPGR), magnetization-prepared rapid gradient echo (MP-RAGE), or turbo field echo (TFE) MRI scan and an axial T2 fluid attenuated inversion recovery (FLAIR) sequence; to yield acceptable image quality, the gadolinium contrast-enhanced three-dimensional SPGR, MP-RAGE, or TFE axial MRI scan should use the smallest possible axial slice thickness not exceeding 1.5 mm; the post-operative MRI must be completed within sufficient time to permit step 1 registration within 180 days of the initial resection; these same conditions apply in the setting of a second surgical procedure, although if a second surgery is completed, step 1 registration must still occur with 180 days of initial surgery; computed tomography (CT) imaging is not required, but may be obtained if desired clinically, for instance to assess calcifications or hyperostosis