High-speed detection of occult tumor cells in peripheral blood

Although detection of tumor cells in peripheral blood using imitiunocytochemistry and optical scanning is a promising method for screening and monitoring cancer, it poses a major technical challenge due to the extremely low tumor cell concentration in blood. The preferred detection method - digital microscopy - is far too slow for analysis of the large numbers of cells required for statistical validity. We describe here a novel prescan instrument that rapidly identifies a small number of candidates for subsequent examination by digital microscopy to determine if they are genuine tumor cells. The prescan is 500 times faster than digital microscopy and yet has a similar sensitivity. The high prescan speed is accomplished by trading resolution for field of view. The resolution of the prescan is determined by the laser spot size of about 10 microns. While this resolution is much coarser than the submicron resolution of microscopes, it is still sufficient for detecting fluorescent cells because it matches the size of a typical cell. The wide field of view and high scan rate are enabled by a novel application of fiber optics.