In children with acute lymphomatic leukemia (ALL) and in myelodysplastic syndrome (MDS) with older patients it is extremely important to measure the minimal residual disease (MRD) to monitor the progress of chemotherapy at early stages Such measurements determine the prognosis, efficacy, and levels of the treatment. The normal method for detection and monitoring is through bone marrow biopsies. Unfortunately, this method requires multiple biopsies to obtain sufficient samples and these must be made at periodic intervals to monitor the treatment. It is possible to substantially improve the efficiency of biopsies through the use of appropriately labeled magnetic nanoparticles and using magnetic collection methods. These antibody-labeled magnetic nanoparticles seek out, and attach themselves to, cancer cells, which can then be collected magnetically. This grant application describes the methodology behind this biopsy technique using a }smart} magnetic biopsy needle making it possible to substantially increase the efficiency of the biopsy as well as the specificity for particular leukemia cancer types but also including the sampling of metastatic rare cancer cells in the marrow. By using magnetic nanoparticles coated with anti-cancer agents and magnetically concentrated, direct therapeutic intervention at the cancer site is possible. PUBLIC HEALTH RELEVANCE: Nanotechnology for Disease Detection, Magnetic Nanoparticles for targeting Disease, Magnetic Needle for Bone Marrow Biopsy