Ex vivo distribution analysis revealed that, in addition to the tumor, the signal concentrated in the liver, kidney, spleen, stomach, intestine, and submandibular gland upon initial injection of CXCR4-IR-783, but the signal intensity decreased over time, suggesting that, within proper window, this probe could be used to detect osteosarcoma with relative high signal-to-noise ratio. The gene discussed is CXCR4; the disease is neoplasm.