[Homer-users] Units of HbO, HbR and HbT

[David Boas]

Homer2 gives it in units of micro Molar.
I don’t know what Shimadzu does.

I like the convention of presenting the concentration changes in units of [concentration length],  [mM mm] is often used in the literature (milliMolar millimeter). This convention is used in recognition that the partial path length of light through the region of brain activation needs to be approximated and thus is not necessarily accurately known.

Homer uses assumed path lengths or path lengths provided by the users in the hmrOD2Conc function. The default path length factors are 6 for each wavelength and this is multiplied by the source-detector separation in converting from OD to concentration units.

If I had to guess, I would assume that Shimadzu is using the [mM mm] units. If you divide Shimadzu’s 0.1 by a path length of 30mm x 6 where 30 mm is a typical separation and 6 a typical path length factor, then you get ~1 microMolar which is of the same order of magnitude as Homer.






On Sep 25, 2014, at 3:26 AM, Pankaj Gupta <beckman16 at gmail.com> wrote:

> Hi,
> I have NIRS device provided by Shimadzu corp. and it gives me Oxygenated Hb(HbO), deoxygenated Hb(HbR) and Total Hb(HbT) apart from raw intensity values.
> 
> I use the raw intensity values along with Homer toolkit to obtain optical density and then HbO, HbR and HbT values. But these HbO values have way much smaller range [-5e-6 5e-6] as compared to [-1e-1 1e-1] of the ones that Shimadzu device already gives me.
> 
> Does anyone know the unit of HbO, HbR and HbT that Homer toolkit gives ?
> Apologies if its a naive question.
> 
> Regards
> Pankaj
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