A tissue oximeter device comprising: a probe (108) for performing oximeter measurements； a panel connector for interconnecting a connection interface (112) to a unit (104)； the connection interface (112) to couple the probe (108) to the unit (104) and allow the probe (108) to connect to a first source (116) of radiation, a second source (through the panel connector) 120) of radiation, a first photodetector (136), and a second photodetector (136), wherein the first radiation source, second radiation source, first photodetector and second photodetector are external to the probe (108)； and a sensor head (128) comprising a first source structure and a second source structure for emitting light and a first detector structure and a second detector structure for detecting light, the first and second source structures being arranged to be coupled to the first and second sources (116,120) of radiation through the connection interface (112), and the first and second detector structures being arranged to engage the first and second photodetectors through the interface (112) of connection, where the first and second structures are arranged to define a first axis (214) that passes through the central point of each detector structure (208a, 208b), a distance from a central line (216) that passes through from a central point of the first source structure (204a) to the first axis (214) defines a first line segment, a distance from a central line (218) that passes through a ce ntral of the second structure (204b) source up to the first axis (214) defines a second line segment, which is parallel to the first line segment, where each of the central lines and the first axis are approximately parallel to an axis x (212a) and where the central line (216) of the first source structure (204a) is parallel to, but does not match, the central line (218) of the second source structure (204b) and the lengths of the segments of first and second line along an axis and (212b) are not equal, and wh
