 Outline: This study will examine the feasibility of MRF in children and AYA and determine whether quantitative measures of T1 and T2 relaxation times can be derived in subjects 35 years of age. Approximately 80 subjects will be evaluated and include subgroups where MRF may be of particular utility, including children and AYA subjects with brain tumors and subjects with neurofibromatosis type 1 NF1. Additional aims will investigate the utility of MRF in these groups. 