Either Rhodamine B (RhB) (Sigma Aldrich Fluka, Saint-Quentin Fallavier, France) or Fluorescein (FITC) acide libre, (Sigma Aldrich Fluka, Saint-Quentin Fallavier, France), each diluted in water, are also added to provide fluorescence in the phantom. Even if it is far off their absorption maximum, both absorb light at 405 nm. Moreover, RhB emits light at around 580 nm, similar to Lipopigments, and FITC emission is around 515 nm, right in the Flavin range. A typical fluorophore concentration used for our phantoms is . The absorption spectra of these molecules were measured by an absorption spectrometer (UVICON 932, Bio-Tek, Kontron Instrument, Milan, Italy). The values of absorption coefficients of FITC and RhB at a 405-nm excitation wavelength, for a concentration of are 0.13 and , respectively. These are very weak compared with absorption coefficients of cerebral tissues. Thus it is not necessary to make an additional correction to the definition of the ink concentration of the phantoms.