<div dir="ltr">Hi Sussanne,<div><br></div><div>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. </div>
<div><br></div><div>Anyway, here is my thoughts about non-tensor type diffusion study;</div><div><br></div><div>First, let me list up downside of non-tensor approaches, which are all immediate and tangible issues;</div><div>
> 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.</div><div>> Requirement of high b has detrimental issues; loss of SNR, more motion artifacts, difficult post-processing QC (due to low SNR).</div>
<div>> 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.</div><div>> 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.</div>
<div>> 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?</div>
<div><br></div><div>The advantages are;</div><div>> 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.</div>
<div>> The fiber orientation information could be more accurate.</div><div>> The tractography could be more accurate.</div><div><br></div><div> 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.<br>
</div><div><br></div><div>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. </div>
<div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Nov 5, 2013 at 8:00 AM, susanne steinberg <span dir="ltr"><<a href="mailto:susanne.steinberg45@gmail.com" target="_blank">susanne.steinberg45@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div lang="EN-US" link="blue" vlink="purple"><div><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Dear Dr. Mori and Experts<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">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.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">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)<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Thanks for considering this request.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Susanne <u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d">Susanne Inez Steinberg MD, MBA, MSCE<br>Director of Geriatric Psychiatrist & Senior Research Associate<br>Crozer Chester Medical Center & Children's Hospital Of Pennsylvania<br>
One Medical Center Blvd<br>Philadelphia, PA 19013<br>Crozer Telephone: <a href="tel:610-874-5257" value="+16108745257" target="_blank">610-874-5257</a><u></u><u></u></span></p><p class="MsoNormal"><span style="color:#1f497d">CHOP Telephone: <a href="tel:267-426-6047" value="+12674266047" target="_blank">267-426-6047</a><u></u><u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d">Cell: <a href="tel:215-287-2961" value="+12152872961" target="_blank">215-287-2961</a><br>Email: <a href="mailto:susanne.steinberg@crozer.org" target="_blank">susanne.steinberg@crozer.org</a><u></u><u></u></span></p>
<p class="MsoNormal"><span style="color:#1f497d">Emai:l <a href="mailto:susanne.steinberg45@gmail.com" target="_blank"><span style="color:#1f497d">susanne.steinberg45@gmail.com</span></a><u></u><u></u></span></p><p class="MsoNormal">
<span style="color:#1f497d">Email: <a href="mailto:steinbergs1@email.chop.edu" target="_blank">steinbergs1@email.chop.edu</a><u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p><div style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <a href="mailto:mristudio-users-bounces@mristudio.org" target="_blank">mristudio-users-bounces@mristudio.org</a> [mailto:<a href="mailto:mristudio-users-bounces@mristudio.org" target="_blank">mristudio-users-bounces@mristudio.org</a>] <b>On Behalf Of </b>susumu mori<br>
<b>Sent:</b> Wednesday, December 14, 2011 7:38 AM<br><b>To:</b> DTI Studio, ROI Editor, DiffeoMap Questions/Support<br><b>Subject:</b> Re: [Mristudio-users] g value<u></u><u></u></span></p></div><p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Do you mean b-value?<u></u><u></u></p><div><p class="MsoNormal">Many simulation studies point 800-1,200 are good numbers.<u></u><u></u></p></div><div><p class="MsoNormal" style="margin-bottom:12.0pt">
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.<u></u><u></u></p>
<div><p class="MsoNormal">On Wed, Dec 14, 2011 at 2:44 AM, Santosh Yadav <<a href="mailto:santoshyadav20076@gmail.com" target="_blank">santoshyadav20076@gmail.com</a>> wrote:<u></u><u></u></p><p class="MsoNormal">Hi DTI experts,<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">I was just wondering that what g value (optimum) should be used for making the bet images in adult population.<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">With regards<u></u><u></u></p><div><p class="MsoNormal"><u></u> <u></u></p></div><div><p class="MsoNormal"><span style="color:#888888">Santosh<u></u><u></u></span></p></div><p class="MsoNormal" style="margin-bottom:12.0pt">
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