An optical 
examination technique employs an optical 
system (15, 45, 100, 150, 200, 260 or 300) for 
in vivo, non-invasive examination of internal tissue of a subject. The optical 
system includes an 
optical module (12 or 14), a controller and a processor. The 
optical module is arranged for placement on the exterior of the 
abdomen or chest. The module includes an array of optical input ports and optical detection ports located in a selected geometrical pattern to provide a multiplicity of 
photon migration paths targeted to examine a selected tissue region, such as an internal organ or an 
in utero fetus. Each optical input port is constructed to introduce into the examined tissue visible or 
infrared light emitted from a 
light source. Each optical detection port is constructed to provide light from the tissue to a 
light detector. The controller is constructed and arranged to activate one or several light sources and light detectors so that the 
light detector detects light that has migrated over at least one of the 
photon migration paths. The processor receives signals corresponding to the detected light and forms at least one 
data set used for tissue examination.