[Mristudio-users] 2 questions

Fri Apr 12 13:42:48 EDT 2013

Thank you Dr. Mori,

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.

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?

Again thank you.
Dorian

2013/4/12 susumu mori <susumu at mri.jhu.edu>

> Answering your second question, simulation study says 32-orientation x 1
> gives better SNR.
> 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.
>
>
> On Fri, Apr 12, 2013 at 10:41 AM, Dorian P. <alb.net at gmail.com> wrote:
>
>> Hi everybody, and thank you for previous answers.
>>
>> 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).
>>
>> 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.
>>
>> Thank you.
>> Dorian
>>
>>
>> Gradient table calculated from Philips PAR file:
>>
>> 0: -0.44136, -0.57117, -0.69207
>> 1: -0.56394, -0.42335, 0.70905
>> 2: 0.69797, -0.70323, 0.13526
>> 3: -0.59198, -0.34304, -0.72931
>> 4: -0.15274, -0.74584, -0.64838
>> 5: 0.074435, -0.77687, -0.62525
>> 6: 0.47574, -0.63875, -0.60471
>> 7: 0.74718, -0.22799, -0.62429
>> 8: -0.5922, -0.34308, -0.7291
>> 9: -0.24242, -0.7705, -0.58954
>> 10: 0.34275, -0.76982, -0.53843
>> 11: 0.56981, -0.55721, -0.60402
>> 12: 0.75753, -0.35855, -0.54552
>> 13: -0.66312, -0.52489, -0.53364
>> 14: -0.43153, -0.75822, -0.48876
>> 15: 0.59311, -0.69541, -0.40574
>> 16: 0.74571, -0.52489, -0.41038
>> 17: -0.71084, -0.70326, 0.011793
>> 18: -0.75432, -0.41491, 0.50878
>> 19: 0.65451, -0.41491, 0.63204
>> 20: 0.41865, -0.64824, 0.63602
>> 21: -0.71152, -0.70239, 0.019779
>> 22: -0.69363, -0.35558, 0.62645
>> 23: -0.71454, -0.69646, 0.066208
>> 24: -0.354, -0.63595, 0.68575
>> 25: 0.22954, -0.63595, 0.7368
>> 26: 0.69727, -0.70239, 0.14303
>> 27: 0.64596, -0.224, 0.72977
>> 28: -0.71425, -0.69728, 0.060467
>> 29: -0.033138, -0.62847, 0.77712
>> 30: 0.69693, -0.70198, 0.14667
>> 31: 0.64313, 0.073913, 0.76219
>> 32: 0, 0, 0
>> 33: 100, 100, 100
>>
>>
>>
>>
>>
>> Gradient table obtined by DICOM file:
>>
>> 0: 0.000000, 0.000000, 0.000000, 0.000000
>> 1: -0.499998, -0.499998, -0.707110, 850.000000
>> 2: -0.499998, -0.499998, 0.707110, 850.000000
>> 3: 0.707107, -0.707107, 0.000000, 850.000000
>> 4: -0.653288, -0.270606, -0.707098, 850.000000
>> 5: -0.208664, -0.675630, -0.707095, 850.000000
>> 6: 0.019658, -0.706829, -0.707112, 850.000000
>> 7: 0.421225, -0.567950, -0.707109, 850.000000
>> 8: 0.689925, -0.154927, -0.707108, 850.000000
>> 9: -0.653495, -0.270675, -0.706880, 850.000000
>> 10: -0.292882, -0.707102, -0.643604, 850.000000
>> 11: 0.294515, -0.706411, -0.643619, 850.000000
>> 12: 0.514993, -0.486072, -0.706056, 850.000000
>> 13: 0.707102, -0.292882, -0.643604, 850.000000
>> 14: -0.707102, -0.472486, -0.526084, 850.000000
>> 15: -0.472486, -0.707102, -0.526084, 850.000000
>> 16: 0.555492, -0.643950, -0.526077, 850.000000
>> 17: 0.707102, -0.472486, -0.526084, 850.000000
>> 18: -0.707107, -0.707107, -0.000212, 850.000000
>> 19: -0.707102, -0.472486, 0.526084, 850.000000
>> 20: 0.707102, -0.472486, 0.526084, 850.000000
>> 21: 0.472486, -0.707102, 0.526084, 850.000000
>> 22: -0.707085, -0.707085, 0.007849, 850.000000
>> 23: -0.636392, -0.425181, 0.643604, 850.000000
>> 24: -0.706047, -0.706047, 0.054730, 850.000000
>> 25: -0.292882, -0.707102, 0.643604, 850.000000
>> 26: 0.292882, -0.707102, 0.643604, 850.000000
>> 27: 0.707085, -0.707085, 0.007849, 850.000000
>> 28: 0.707102, -0.292882, 0.643604, 850.000000
>> 29: -0.706260, -0.706260, 0.048932, 850.000000
>> 30: 0.034719, -0.706256, 0.707105, 850.000000
>> 31: 0.707060, -0.707060, 0.011526, 850.000000
>> 32: 0.707107, -0.000000, 0.707107, 850.000000
>> 33: 100.000000, 100.000000, 100.000000, 850.000000
>>
>> Fiber statistics for each:
>> http://img580.imageshack.us/img580/2887/capturenbh.jpg
>>
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