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Subject:

RE:"Normal" assymetry

From:

"Chris Gottschalk, MD" <[log in to unmask]>

Reply-To:

Chris Gottschalk, MD

Date:

Tue, 27 Jun 2000 15:23:07 -0400

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (114 lines)

Drs Glabus and Fang [and I eagerly await Isak's input as well; if he
doesn't chime in, I will go find him...]

	I am fascinated by this interchange regarding assymtery in *phantom* data
as opposed to *human beings* deemed "normal". the data from a phantom
define, I think, what the MINIMUM range of assymetry you should accept for
your scans, given that a phantom is uniform, by definition. However, whose
data are we using to define what the normal range of assymetry is in
[presumably] resting images of people in a gamma camera? Certainly, those
values will vary according to which structures you are identifying with
ROIs to define assymetry. 
	Perhaps I envision the wrong thing: are you both referring to percent
differences between [whole] hemispheric values? 



>> 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]
> 

********************************************************
Christopher Gottschalk, MD			*
Assistant Professor of Neurology & Psychiatry	*
Yale School of Medicine			*
						*
Mailing Adress:				*
VAMC [116-A]		tel [203] 932-5711 x4329*
950 Campbell Avenue		    FAX 937-4791*
West Haven, CT 06516			*
********************************************************


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