The present invention relates to myeloid derived suppressor cells (MDSCs) and using these cells in conjunction with nuclear medicine imaging methods to image cancer tumors. The MDSC cells are separated from blood and either radiolabeled with nuclear medicine agents or pretargeting agents and reinjected in patient. The cells preferentially concentrate in tumors allowing imaging of cancer tumors. The imaging technique can be used to image tumors for diagnosis and/or assessment of treatment response for cancer patients undergoing cancer treatments.
