[Homer-users] HomER question regarding units on dConc

[thuppert]

Greetings:

Someone asked a question about the units on dConc in HomER.

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"Could do you tell me what  the unit of dConc time course is?
It's mM*mm , mM or others? If it's mM, could do you tell me what the
default of DPF in Homer is?"


The answer is that by default the units on delta-Concentration are Molar*cm.
Or, its the solution of the Beer-Lambert equation with L=1cm.  The reason
for this is because we did not want to assume a default DPF.

If the DPF is specified, which can be done by the fields under "Advanced
Filtering Options", then the units of dConc will be Molar (i.e. a couple of
microMolar change would be expected).  Otherwise, the units are Molar*Cm.


With this unit of dConc, the relative changes in HbO2 and dHb are comparable
(except of course for any cross-talk effects that might come about because
you haven't specified the DFP for each wavelegth).  If DPF is the same for
each wavelength, then this is just a scaling factor and you can change the
dConc values to Molar by simply dividing the values by (CM*DPF).



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Ted Huppert, M.Sc.

PhD student-Harvard Univ.
Dept of Biophysics
Photon Migration Imaging lab
Mass General Hospital/CNY

Tele: (617)726-1223
Cell: (617) 869-1205

thuppert at nmr.mgh.harvard.edu