[Homer-users] MBLL Missing ln(10)

[alexis machado]

HiI am a PhD student in NIRS.I have a doubt on the definition of the Modified Beer Lambert Law as used in the sofware HOMER version1. Indeed HOmer uses a natural logarithm to define the absorbance  ( also known as optical density) whereas the extinction coefficients values provided were calculated with a log base 10 definition of  the absorbance. Let me explain much: Let see the definition : REF  HomER: a review of time-series analysis methods for near-infrared  spectroscopy of the brain  Theodore J. Huppert  Solomon G. Diamond Maria A. Franceschini and David A. Boas you define the delta optical density or delta absorbance as equation: 1bDOD=-ln(I/Io)=eps_1*D[HbO] +eps_2*D[HbR] *L   % it is a natural logarithm definition where D stands for variation from a baseline period, and OD the absorbancewhere I is the detected fluence and Io the detected baseline fluencewhere eps_1 is the molar extinction coeff of HbO and eps_2 the molar extinction coeff of HbR and L is the mean total optical pathlengthBecause the beer lamber law states that I/Io=exp(-mua*L)  equation 1.b implies that  Dmua the absorption coeff  variation= eps_1*D[HbO] +eps_2*D[HbR] However according to the  header explanation of the GetExtinctions.m function located in /HOMER/GeneralSubs/   the provided eps where measured using a different definition of the absorbance which is DOD=-log10(I/Io) . Indeed  they say clearly that  mua =ln(10)*( eps_1*[HbO] +eps_2*[HbR])Therefore, I think the equation 1.b should be corrected as in REF  A review on continuous wave functional near-infrared spectroscopy and imaging instrumentation and methodology Scholkmann F, Kleiser S, Metz AJ, Zimmermann R, Mata Pavia J, Wolf U, Wolf M.equation 1DOD=-log10(I/Io) = eps_1*D[HbO] +eps_2*D[HbR] *LPlease correct me if i am wrong !!best regardsAlexis 		 	   		  
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