Dear Bing Fang
> I have several questions and statement here related to your E-mail.
> 1). Our NM physicians use the 7% based on ' plenty of NM literature '
> that the range of asymmetry in SPEC scans of normal population is from
> 5% to 10%. They call 7-9 % in borderline and > 9 % as abnormal with
> traditional RIO method; I did some phantom studies using
> Hoffman Brain Phantom and found there is 5% asymmetry with optimum setting
of
> acquisition; CERETEC has a 5-10% asymmetry on normal scan according to
> Amersham (ECD?). It's almost impossible to get a actual
> normal pediatric subject scan and they all come in with some kind of
diagnosis.
> So Iselected these less than 7 % asymmetry as a control group not a normal
> baseline.
On the basis of your observation with Ceretec, these thresholds sound
reasonable
and certainly consistent with observations I've made and with phantom
studies
using the JB003 brain phantom with Tc99m, but imaged with the Strichman
Neuro 900,
12-detector system.
Routinely clinicians (in Edinburgh) would look for asymmetry of around 20%
to be
deemed pathological, but opinions vary. *** ISAK PROHOVNIK ***, if you're
out there,
can you provide some input on this? (Apologies for shouting, but it's a
personal
"heads up" call...copyright Darren Gitelman)
> Do you think that 'no major differences between a custom SPECT and
> supplied PET template for normalization results' can be extended to
> pediatric patient (assuming supplied PET made from adult)?
I'm not sure but it may be prudent to consider making a paediatric template
as
it's bound to be more unlike the adult (PET) template than an "elderly"
adult
brain.
> 3). When I learnt the SPM from a local spmer, I have been instructed
> that I had to do at least Coregister and reslice and Spatial
> Normalization (Smooth as an option) on an object image to create a
> snr---.img file for Statistics. I have been suggested to use supplied
> PET as template then. But I have a impression from your
> E-mails that the Coregister step might not be necessary in the process
(?).
Routinely, one would not normally coregister and reslice a SPECT image
in a separate stage from normalisation against (whatever) template image, so
I think you may be referring to the issue of "piggy-back" spatial
transformations
where MRI derived parameters are applied to the SPECT image from the same
subject. In theory this should work, but my experience (and of others) has
shown
it's better to treat these images separately for spatial normalisation. My
guess
is that errors arise due to poor co-registration between SPECT and MRI
images - again
the reason is probably that our Neuro 900 have low spatial resolution in the
z-plane, with 12-14 slices of 8 - 10 mm slice thickness. If you have a gamma
camera
which acquires a more complete data set, this may not be an issue.
see:
"Assessing spatial transformation options in a SPECT and MRI study of
elderly
depression and dementia using SPM'96". Glabus, M & Ebmeier, K.P., 1999,
Neuroimage,9:6:Pt 2 of 2:S149.
Regards - Mike
--
---------------------------------------------
Mike Glabus, PhD
Visiting Fellow in Functional Neuroimaging
Unit on Integrative Neuroimaging,
Clinical Brain Disorders Branch, NIMH, NIH
Building 10, Rm 4C101, 9000 Rockville Pike
Bethesda, MD, 20892-1365, USA
Tel: + 301 496 7864 FAX: + 301 496 7437
[log in to unmask]
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|