Objective: Neuroblastoma is the most common extracranial solid tumor in children. In disseminated disease, total body irradiation (TBI) is used as part of myeloablative conditioning regimens prior to autologous stem cell transplantation (ASCT); however, it is associated with severe long-term sequelae including microcephaly, neurocognitive impairment, and skeletal growth arrest. Lu-177-DOTATATE is not proposed as a substitute for TBI in the conditioning setting, but rather is being evaluated as a targeted tumour therapy for relapsed or refractory SSTR2-positive high-risk neuroblastoma. This study aims to perform a dosimetric comparison of TBI and Lu-177-DOTATATE with respect to radiation doses delivered to developmentally critical organs, in order to quantify the differential organ-dose burden of each modality within its respective clinical indication. Methods: Pediatric patients undergoing TBI as part of myeloablative conditioning and patients receiving Lu-177-DOTATATE for relapsed or refractory high-risk neuroblastoma will be enrolled following ethical approval. Dosimetric evaluation will include organ-absorbed dose calculations for the brain, growth plates, bone marrow, kidneys, and liver. TBI dosimetry will be assessed using thermoluminescent dosimeters (TLDs), and Lu-177 dosimetry will be performed using SPECT/CT-based quantification with the MIRD schema. Expected Results: We hypothesize that Lu-177-DOTATATE delivers significantly lower absorbed doses to developmentally sensitive organs compared to TBI, while maintaining comparable anti-tumor efficacy in somatostatin receptor-positive neuroblastoma. Quantitative dosimetric data will be presented per organ and compared between the two modalities. Conclusion: This dosimetric analysis is intended to provide radiobiological evidence supporting the integration of Lu-177-DOTATATE into standard pediatric oncology protocols as a safer alternative to TBI, particularly for patients with disseminated neuroblastoma expressing somatostatin receptor type 2.