[Mristudio-users] DTI & clinical featues of Lewy Body Spectrum Disease Grant

Wed Nov 6 05:52:23 EST 2013

Hi Sussanne,

Our software is not supporting HARDI type image analysis. We have been
carefully following the non-tensor type analysis methods and some members
in our lab do use them for ex vivo high-resolution brain imaging, but for
live human, we don't use them and thus haven't supported them. So, we use
"regular" DTI protocols, just like you mentioned except for using only one
b-value at around 700-1000. b=700 is my favorite but for multi-center
study, I use more conventional b=1,000.

Anyway, here is my thoughts about non-tensor type diffusion study;

First, let me list up downside of non-tensor approaches, which are all
immediate and tangible issues;
> The image parameter dimension and analysis methods have too many
variables and each of them could have profound impacts on the results.
Difficult to standardize and compare results across studies.
> Requirement of high b has detrimental issues; loss of SNR, more motion
artifacts, difficult post-processing QC (due to low SNR).
> Low SNR usually means longer scan time to achieve similar SNR or lower
resolution. I believe your 64-orientation x 2 b-value take almost 20 min?
The longer the scan, more registration issues arise.
> Some say b=3,000 is enough, some simulation shows b=3,000 is not enough.
Some says 30-orientation can do and some say at least 60 is needed.
> Above all, what are actually the image contrasts (pixel intensity) you
can obtain that carry anatomical information substantially different from
FA/MD? The number of fibers in each voxel? The crossing angles in each
voxel?

The advantages are;
> more information can be obtained from each voxels (DTI gives 6), such as
crossing angles, the number of crossing fibers. You can say the DTI's 6
parameter including fiber angles are "WRONG" or "first-order
approximation", depending on how you see it.
> The fiber orientation information could be more accurate.
> The tractography could be more accurate.

 I do believe the non-tensor type diffusion imaging has quite a potential
to explore human brain anatomy (therefore we use it for our ex vivo
studies). For live human study, our image protocols are always a product of
practical compromise.  I usually use scan times to do conventional DTI with
short TE, good SNR, and optimum resolution (usually 2-2.2mm) within 10 min,
followed by good QC. Non-tensor approaches remain as an exploratory
approach, but of course it is my personal opinion.

By the way, I want to add one more comment about "DTI information is
wrong". Yes, it is proven. For example, the principal eigenvector may not
represent the true axonal orientation if there are more than one
orientation. However, MRI is based on physical and chemical properties of
water molecules, while we want to know cellular architecture. They can't
have one-to-one relationship. Even for the cortical thickness based on T1
imaging, I can give you thin cortex or thick cortex at will by tweaking
imaging parameters. MRI is a tool to downsample the entire brain anatomy to
a mere 10 MB file. That is the point of MRI and if some say "it doesn't
accurately reflect the anatomy", of course, it doesn't. We just have to
know this downsampling, while it provide us with a mean to quantify and
compare anatomy readily, makes the interpretation of the results difficult
because a huge amount of cellular-level anatomical information is already
degenerated.

On Tue, Nov 5, 2013 at 8:00 AM, susanne steinberg <
susanne.steinberg45 at gmail.com> wrote:

> Dear Dr. Mori and Experts
>
> I am applying for two pilot grants on the subject of the association of
> white matter integrity, neuropsychiatric symptoms and  mild neurocognitive
> impairment in Lewy Body Dementia and Parkinson’s Disease. There has been
> much debate whether these diseases are separate entities or whether they
> are the actually one disease with variable clinical presentation. This has
> prevented us from finding the best biomarker for early diagnosis and
> treatment.  I have reviewed the literature on DTI in Lewy Body Spectrum
> Diseases, there are some interesting results but there is much more to
> learn to answer my research question.
>
> I need help to set up the DTI protocol which could be run at UPenn. I have
> been to the MRIStudio but have had no reason to use what I learnt but now I
> do. I am also interested in adding a protocol for high angular resolution
> imaging. Have you been using that at all? We have wonderful neuroimaging
> experts on Aging but not in DTI or HARDI. I think the answers lie in
> multimodal approach to imaging (ASL, volumetric MRI and DTI/HARDI)
>
>
>
> Thanks for considering this request.
>
> Susanne
>
>
>
> Susanne Inez Steinberg MD, MBA, MSCE
> Director of Geriatric Psychiatrist & Senior Research Associate
> Crozer Chester Medical Center & Children's Hospital Of Pennsylvania
> One Medical Center Blvd
> Philadelphia, PA 19013
> Crozer Telephone: 610-874-5257
>
> CHOP Telephone: 267-426-6047
>
> Cell: 215-287-2961
> Email: susanne.steinberg at crozer.org
>
> Emai:l susanne.steinberg45 at gmail.com
>
> Email: steinbergs1 at email.chop.edu
>
>
>
>
>
> *From:* mristudio-users-bounces at mristudio.org [mailto:
> mristudio-users-bounces at mristudio.org] *On Behalf Of *susumu mori
> *Sent:* Wednesday, December 14, 2011 7:38 AM
> *To:* DTI Studio, ROI Editor, DiffeoMap Questions/Support
> *Subject:* Re: [Mristudio-users] g value
>
>
>
> Do you mean b-value?
>
> Many simulation studies point 800-1,200 are good numbers.
>
> I prefer a bit lower side like 700. It's personal preference. I like it
> because of less motion artifacts and short TE. I came up with this number
> based on my subjective experience, but I would say it's safer to use 1,000.
>
> On Wed, Dec 14, 2011 at 2:44 AM, Santosh Yadav <
> santoshyadav20076 at gmail.com> wrote:
>
> Hi DTI experts,
>
>
>
> I was just wondering that what g value (optimum) should be used for making
> the bet images in adult population.
>
>
>
> With regards
>
>
>
> Santosh
>
>
>
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