Non-invasive methods and systems for detection of cancer or arterial vascular disorder involving administering to an individual a composition comprising noble metal nanoparticles that accumulate in a cancerous or injured vascular tissue; optically irradiating an area of a tissue suspected of being a cancerous or injured vascular tissue with a light source outputting an optical signal of at least one wavelength; and measuring diffusion reflection of the area of the irradiated tissue using at least one detector, whereby detection from the measured diffusion reflection of accumulation of the noble metal nanoparticles in this area indicates that the irradiated tissue is a cancerous or injured vascular tissue.