Inter-tissue implantation of radioactive particles: The radioactive particles (e.g. 125I) are implanted into malignant tumors in a precise location, and the radiation source emits continuous low-energy rays to kill the tumor to a high degree of conformality. Due to the short radiation distance of radioactive particles (1.7-2.0cm), only the dose in the target area of the tumor is increased, while the dose in the surrounding normal tissues is steeply decreased, thus greatly improving the therapeutic efficacy and reducing the radiation damage to the surrounding normal tissues. Inter-tissue implantation of radioactive particles provides a new effective adjuvant treatment for oral and maxillofacial malignant tumors and head and neck. Currently, it is mainly used for: (1) malignant tumors of the oral and maxillofacial region and head and neck that cannot be surgically resected or radically resected; (2) sarcomas and malignant tumors of glandular origin that are insensitive to chemotherapy and external radiation therapy.