Transcranial optical spectroscopy--A comparison of the TOS 96 and INVOS 3100 cerebral oximeters.

We evaluated two user-friendly, commercially available transcranial cerebral oximeters (TOS 96, Tostec, Tokyo, Japan and INVOS 3100, Somanetics, Troy, USA) for use in adults. We compared the absolute values (%) of regional cerebral oxygen saturation (rSO2) from 108 measurements in 54 healthy volunteers (31 women, mean age 35.8 +/- 16.3 years and 23 men, mean age 35.4 +/- 9.2 years). The mean rSO2 values obtained by the TOS 96 and INVOS 3100 systems were 72.3 +/- 8.4 % and 72.6 +/- 7.2% respectively. Significant differences (p < 0.01) were found between females and males with the INVOS equipment. The study shows that anatomical (thickness of the skull) and technical (calibration) aspects have to be taken into consideration when interpreting absolute rSO2 values.