18F-FLT Positron Emission Tomography and Diffusion-Weighted Magnetic Resonance Imaging in Planning Surgery and Radiation Therapy and Measuring Response in Patients With Newly Diagnosed Ewing Sarcoma

Inclusion Criteria: * Histological confirmation of newly diagnosed localized or newly diagnosed with metastatic Ewing sarcoma (ES) or primitive neuroectodermal tumor (PNET) of bone or soft tissue * Planning to receive definitive RT or surgery with or without adjuvant RT * Willing to sign release of information for any follow-up records * Provide informed written consent if \>= 18 years; if \< 18 years, provide informed written assent and parent or legal guardian provide informed written consent * Patients must have measurable disease * Willingness to participate in mandatory imaging studies * Willingness to provide mandatory pathology samples for correlative research Exclusion Criteria: * Unable to undergo MRI scans with contrast (e.g. cardiac pacemaker, defibrillator, kidney failure) * Unable to undergo 18F-FLT PET scan * Any of the following: * Pregnant women * Nursing women * Men or women of childbearing potential who are unwilling to employ adequate contraception