<div dir="ltr">Thank you Dr. Mori,<div><br></div><div style>You were right. Setting up "Rotate gradients if applicable" and closing-opening again the window showed the same gradients calculated from par/rec. It was a bit tricky because I thought "rotate gradients" would show the correct table in the textbox. Instead, the gradients in the box are wrong, they are corrected on the fly when the software loads the images. The only way to see them is to close and open the window again.</div>
<div style><br></div><div style>About my second question, I agree to your advice, 16x2 should be more useful. Can you tell me which study said 32x1 is better than 16x2?</div><div style><br></div><div style>Again thank you.</div>
<div style>Dorian</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">2013/4/12 susumu mori <span dir="ltr"><<a href="mailto:susumu@mri.jhu.edu" target="_blank">susumu@mri.jhu.edu</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">Answering your second question, simulation study says 32-orientation x 1 gives better SNR.<div>I always use 2 repetition. In your case, 16x2 because the subtraction of the two sets gives good idea about existence of motion and quality of image registration. You can find corrupted images easier too.<br>
<div class="gmail_extra"><br><br><div class="gmail_quote"><div><div class="h5">On Fri, Apr 12, 2013 at 10:41 AM, Dorian P. <span dir="ltr"><<a href="mailto:alb.net@gmail.com" target="_blank">alb.net@gmail.com</a>></span> wrote:<br>
</div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5">
<div dir="ltr">Hi everybody, and thank you for previous answers.<div><br></div><div>I have two questions today. First, I am comparing the gradient table obtained by PAR/REC and DICOM files. They are very different, I can't find similar lines. However, the final statistics on fiber tracking look similar. Below you can find the two gradient tables and the fiber statistics. Can you please tell me whether the difference in gradient tables is normal, and if one is more precise than the other (the PAR/REC table was calculated by a Matlab script developed at the John Hopkins).</div>
<div><br></div><div>Second question: Given a fixed time is available on a 1.5T, is it better to obtain 2 scans of 16 directions or one scan of 32 directions? I can imagine the SNR is much better with two, but not sure whether more directions compensate for SNR too.</div>
<div><br></div><div>Thank you.</div><div>Dorian</div><div><br></div><div><br></div><div><div>Gradient table calculated from Philips PAR file:</div><div><br></div><div>0: -0.44136, -0.57117, -0.69207</div>
<div>1: -0.56394, -0.42335, 0.70905</div><div>2: 0.69797, -0.70323, 0.13526</div><div>3: -0.59198, -0.34304, -0.72931</div><div>4: -0.15274, -0.74584, -0.64838</div><div>5: 0.074435, -0.77687, -0.62525</div><div>6: 0.47574, -0.63875, -0.60471</div>
<div>7: 0.74718, -0.22799, -0.62429</div><div>8: -0.5922, -0.34308, -0.7291</div><div>9: -0.24242, -0.7705, -0.58954</div><div>10: 0.34275, -0.76982, -0.53843</div><div>11: 0.56981, -0.55721, -0.60402</div><div>12: 0.75753, -0.35855, -0.54552</div>
<div>13: -0.66312, -0.52489, -0.53364</div><div>14: -0.43153, -0.75822, -0.48876</div><div>15: 0.59311, -0.69541, -0.40574</div><div>16: 0.74571, -0.52489, -0.41038</div><div>17: -0.71084, -0.70326, 0.011793</div><div>18: -0.75432, -0.41491, 0.50878</div>
<div>19: 0.65451, -0.41491, 0.63204</div><div>20: 0.41865, -0.64824, 0.63602</div><div>21: -0.71152, -0.70239, 0.019779</div><div>22: -0.69363, -0.35558, 0.62645</div><div>23: -0.71454, -0.69646, 0.066208</div><div>24: -0.354, -0.63595, 0.68575</div>
<div>25: 0.22954, -0.63595, 0.7368</div><div>26: 0.69727, -0.70239, 0.14303</div><div>27: 0.64596, -0.224, 0.72977</div><div>28: -0.71425, -0.69728, 0.060467</div><div>29: -0.033138, -0.62847, 0.77712</div><div>30: 0.69693, -0.70198, 0.14667</div>
<div>31: 0.64313, 0.073913, 0.76219</div><div>32: 0, 0, 0</div><div>33: 100, 100, 100</div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div>Gradient table obtined by DICOM file:</div><div><br>
</div><div>0: 0.000000, 0.000000, 0.000000, 0.000000</div><div>1: -0.499998, -0.499998, -0.707110, 850.000000</div><div>2: -0.499998, -0.499998, 0.707110, 850.000000</div><div>3: 0.707107, -0.707107, 0.000000, 850.000000</div>
<div>4: -0.653288, -0.270606, -0.707098, 850.000000</div><div>5: -0.208664, -0.675630, -0.707095, 850.000000</div><div>6: 0.019658, -0.706829, -0.707112, 850.000000</div><div>7: 0.421225, -0.567950, -0.707109, 850.000000</div>
<div>8: 0.689925, -0.154927, -0.707108, 850.000000</div><div>9: -0.653495, -0.270675, -0.706880, 850.000000</div><div>10: -0.292882, -0.707102, -0.643604, 850.000000</div><div>11: 0.294515, -0.706411, -0.643619, 850.000000</div>
<div>12: 0.514993, -0.486072, -0.706056, 850.000000</div><div>13: 0.707102, -0.292882, -0.643604, 850.000000</div><div>14: -0.707102, -0.472486, -0.526084, 850.000000</div><div>15: -0.472486, -0.707102, -0.526084, 850.000000</div>
<div>16: 0.555492, -0.643950, -0.526077, 850.000000</div><div>17: 0.707102, -0.472486, -0.526084, 850.000000</div><div>18: -0.707107, -0.707107, -0.000212, 850.000000</div><div>19: -0.707102, -0.472486, 0.526084, 850.000000</div>
<div>20: 0.707102, -0.472486, 0.526084, 850.000000</div><div>21: 0.472486, -0.707102, 0.526084, 850.000000</div><div>22: -0.707085, -0.707085, 0.007849, 850.000000</div><div>23: -0.636392, -0.425181, 0.643604, 850.000000</div>
<div>24: -0.706047, -0.706047, 0.054730, 850.000000</div><div>25: -0.292882, -0.707102, 0.643604, 850.000000</div><div>26: 0.292882, -0.707102, 0.643604, 850.000000</div><div>27: 0.707085, -0.707085, 0.007849, 850.000000</div>
<div>28: 0.707102, -0.292882, 0.643604, 850.000000</div><div>29: -0.706260, -0.706260, 0.048932, 850.000000</div><div>30: 0.034719, -0.706256, 0.707105, 850.000000</div><div>31: 0.707060, -0.707060, 0.011526, 850.000000</div>
<div>32: 0.707107, -0.000000, 0.707107, 850.000000</div><div>33: 100.000000, 100.000000, 100.000000, 850.000000</div><div><br></div><div>Fiber statistics for each:</div><div><a href="http://img580.imageshack.us/img580/2887/capturenbh.jpg" target="_blank">http://img580.imageshack.us/img580/2887/capturenbh.jpg</a><br>
</div></div></div>
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