[BioC] Limma package question

[V.C.L. de Jager]

I am using the Limma package 1.6.1 to normalize Imagene files.

Reading the source code I was wondering if there is a particular reason to
take the 'Signal Mean' signal values and the 'Background Median' background
values from the Imagene files. Why not for instance use the 'Signal Median'
column for the signal values?

I hope someone can shed a light on these choices so I can explain them to
some of my colleagues

regards

	Victor de Jager