>>>>> On Tue, 8 Feb 2005 19:19:48 +0100, Karsten Specht <[log in to unmask]> said:
Karsten> The scaling on the second level is only useful, if your are
Karsten> going to analyses other images than con_images; MRI-Perfusion
Karsten> images or PET images, for example. Here, it is necessary,
Karsten> that the global mean is the same across subjects. In case of
Karsten> a 'classical' second level analysis, you are analysing the
Karsten> con-images, which are already appropriately scaled,
Karsten> i.e. positive values are reflecting a signal increase,
Karsten> negative values a decrease and the value itself represents
Karsten> somewhat like the strength of the effect.
Dear Karsten,
I'm trying to compare fractional anisotropy map of a patient with
control database created from 26 normal volunteers to detect lesions
after normalization and smoothing of all of them. What do you
recommend in this kind of study (one patient compared with multiple
controls), use global scaling & grand mean or skip them?
I would really appreciate any help in advance.
--
Kohkichi Hosoda M.D.
Department of Neurosurgery,
Hyogo Emergency Medical Center/Kobe Red Cross Hospital,
1-3-1 Wakinohama-Kaigan-Dori, Chuo-ku, Kobe, 651-0073, JAPAN
Telephone 078-241-3131
Fax 078-241-2772
e-mail address : [log in to unmask]
