Thanks Dr Greve for your reply. I understand it can be taken into account if study group is the same and different scanner is used on the same group. So does it mean there is a differential change in volume depending on the field strength?<div><br></div><div>Appreciate your help.</div><div><br></div><div>Kind regards,</div><div><br></div><div>Sam<br><br>On Tuesday, May 30, 2017, Douglas Greve &lt;<a href="javascript:_e(%7B%7D,&#39;cvml&#39;,&#39;greve@nmr.mgh.harvard.edu&#39;);" target="_blank">greve@nmr.mgh.harvard.edu</a>&gt; wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
  
    
  
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    <p>You do need to take it into account, but you cannot if one group
      is 1.5T and the other is 3T.</p>
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    <div>On 5/28/17 10:41 AM, Dr Sampada Sinha
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        <div class="gmail_default" style="font-family:verdana,sans-serif">Dear freesurfer
          experts,</div>
        <div class="gmail_default" style="font-family:verdana,sans-serif"><br>
        </div>
        <div class="gmail_default" style="font-family:verdana,sans-serif">I am presently trying
          to calculate hippocampal volume for two different study
          groups. One study group images (MDD) was acquired on 1.5T and
          the other age-matched study group (Healthy controls) on 3T
          MRI. On doing the statistics I have significant differences in
          the hippocampal volume correlating with their cognitive scores
          between the two study groups. Do I need to take into
          consideration different scanner parameters when doing the
          statistics? How do I go about it?</div>
        <div class="gmail_default" style="font-family:verdana,sans-serif"><br>
        </div>
        <div class="gmail_default" style="font-family:verdana,sans-serif">Thanks for your help.</div>
        <div class="gmail_default" style="font-family:verdana,sans-serif"><br>
        </div>
        <div class="gmail_default" style="font-family:verdana,sans-serif">Kind regards,</div>
        <div class="gmail_default" style="font-family:verdana,sans-serif"><br>
        </div>
        <div class="gmail_default" style="font-family:verdana,sans-serif">Sam </div>
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                                                  <div dir="ltr"><span style="font-family:verdana,sans-serif;font-size:small">Dr
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                                                      <div>​Research
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                                                    <div style="font-size:small;font-family:verdana,sans-serif">Department
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                                                    <div style="font-size:small;font-family:verdana,sans-serif">King
                                                      George Medical
                                                      University</div>
                                                    <div style="font-size:small;font-family:verdana,sans-serif">Lucknow-226003
                                                      <div style="display:inline">​,
                                                        Uttar Pradesh​</div>
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                                                    <div style="font-size:small;font-family:verdana,sans-serif">India</div>
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      <pre>______________________________<wbr>_________________
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</div><br><br>-- <br><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><span style="font-family:verdana,sans-serif;font-size:small">Dr Sampada Sinha</span><br></div><div><div style="font-size:small;font-family:verdana,sans-serif"><div>​Research medical scientist (B)​</div></div><div style="font-size:small;font-family:verdana,sans-serif">Department of Geriatric Mental Health (DGMH)</div><div style="font-size:small;font-family:verdana,sans-serif">King George Medical University</div><div style="font-size:small;font-family:verdana,sans-serif">Lucknow-226003<div style="display:inline">​, Uttar Pradesh​</div></div><div style="font-size:small;font-family:verdana,sans-serif">India</div></div></div><div dir="ltr"><div><font face="verdana, sans-serif"><br></font></div><div><font face="verdana, sans-serif"><br></font></div><div><font face="verdana, sans-serif"><br></font></div><div><font face="verdana, sans-serif"><br></font></div><div><font face="verdana, sans-serif"><br></font></div><div><br></div><div><b><i><font face="garamond, serif" size="4"><font color="#0000ff"><br></font></font></i></b></div><div><br></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div><br>