text: A clinical application of DCS is for use in diagnosis of cancers. An example of this is measuring red blood cell flow in breast tumors. In this experiment, both healthy patients and patients with breast tumors were recruited. Researchers scanned the tumor with a hand-held optical probe with 4 sources and detectors 2.5 cm apart from each other.   Then, the resultant correlation functions were fit to the solution of the correlation diffusion equation to obtain the blood flow index. The average relative blood flow was reported at each position. Blood flow increased in both horizontal and vertical scans as the probe crossed over the tumor. These findings were consistent with previous Doppler ultrasound and PET results.