Pediatric cancer imaging stands to benefit from higher tumor detection sensitivity without ionizing radiation exposure. A prospective protocol compared diagnostic I-metaiodobenzylguanidine (I-mIBG) with whole-body diffusion-weighted MRI (DWI) to validate adjunctive methods of identifying small-volume oligometastatic neuroblastoma tumor deposits. Dual-modality imaging (I-mIBG and DWI) was obtained within a 3- and 25-day window at baseline and again at one year in the first enrolled patient. MRI was able to define the full extent of metastatic disease foci with improved resolution. These findings may provide critical information for definitive locoregional surgery and radiotherapy for high-risk neuroblastoma treatment.