[Mristudio-users] Philips gradient tables

Fri Jul 25 07:12:32 EDT 2008

Seongjin,

In Philips, there are 3 types (low: 6, medium: 15, high: 32) x 2 (overplus
on/off) = 6 gradient tables.

The "gradient overplus = on" always use at least two gradients to enhance b
efficiency and therefore gaining several millisecond of echo time. In your
example, the low and high is "overplus = off" and the medium is "overplus =
on". You can see "1, 0, 0" in the first two but not in the medium. 

The medium with "overplus = off" should look like;

            0:   0,    0,    0

            1:   1,    0,    0

            2:   0,    1,    0

            3:   0,    0,    1

            4:   -0.0424,-0.1146,-0.9925  

            5:  0.1749,-0.2005,-0.9639

            6:  0.2323,-0.1626,-0.9590

            7:  0.3675,0.0261,-0.9296     

            8: 0.1902,0.3744,-0.9076

            9: -0.1168,0.8334,-0.5402           

            10: -0.2005,0.2527,-0.9466

            11: -0.4958,0.1345,-0.8580

            12: -0.0141,-0.6281,-0.7780

            13: -0.7445,-0.1477,-0.6511

            14: -0.7609,0.3204,-0.5643

            15: -0.1809,0.9247,-0.33510

            16: -0.6796,-0.4224,-0.5997

            17: 0.7771,0.4707,-0.4178

            18: 0.9242,-0.1036,-0.3677

            19: 0.4685,-0.7674,-0.4378

            20: 0.8817,-0.1893,-0.4322

            21: 0.6904,0.7062,-0.1569

            22: 0.2391,0.7571,-0.6080

            23: -0.0578,0.9837,0.1703

            24: -0.5368,0.8361,-0.1135

            25: -0.9918,-0.1207,-0.0423

            26: -0.9968,0.0709,-0.0379

            27: -0.8724,0.4781,-0.1014

            28: -0.2487,0.9335,0.2581

            29: 0.1183,0.9919,-0.0471

            30: 0.3376,0.8415,0.4218

            31: 0.5286,0.8409,0.1163

            32: 0.9969,0.0550,-0.0571

In general, I do not recommend to user "overplus = on", because tensor
calculation get complicated when oblique planes are used. You have to
recalculate the table based on the image angles.

Also, please note that the "0, 0, 0" could be the first or the last image
depending on how you specify the output files.

Susumu

  _____  

From: mristudio-users-bounces at mristudio.org
[mailto:mristudio-users-bounces at mristudio.org] On Behalf Of [Seongjin]
Sent: Wednesday, July 23, 2008 3:47 PM
To: DTI Studio, ROI Editor, Landmarker Questions/Support
Subject: [Mristudio-users] Philips gradient tables

Dear DTIstudio users,

I wonder if you have gradient tables for Philips Achieva system.

>From a source I have a gradient table for low resolution as follows:

0:1.0000, 0.0000, 0.0000
1:0.0000, 1.0000, 0.0000
2:0.0000, 0.0000, 1.0000
3:-0.7044, -0.0881, -0.7044
4:0.7044, 0.7044, 0.0881
5:0.0881, 0.7044, 0.7044
6:0.0000, 0.0000, 0.0000

For medium,

0: 0.7071 -0.7071 1.00
1: 0.7071 -0.7071 -1.00
2: 1.0000 1.0000 0.0000
3: 0.9999 -0.1561 0.9879
4: 0.9894 0.4091 0.9240
5: 0.4674 0.8874 0.9970
6: 0.3866 0.9297 0.9930
7: 0.7667 -0.9511 0.7124
8: 0.6945 0.9954 -0.7295
9: 0.3580 -0.9800 -0.9547
10: 1.0000 -0.9992 -0.0392
11: 0.9999 -0.3989 -0.9171
12: 0.9923 0.4082 -0.9213
13: 0.9989 0.9982 -0.0759
14: 0.2899 0.9919 -0.9655
15: 0.0000 0.0000 0.0000

For high,

 0: 1.000, 0.000, 0.000
 1: 0.000, 1.000, 0.000
 2: 0.000, 0.000, 1.000
 3: -0.042, -0.115, -0.993
 4: 0.175, -0.200, -0.964
 5: 0.232, -0.163, -0.959
 6: 0.368, 0.026, -0.930
 7: 0.190, 0.374, -0.908
 8: -0.117, 0.833, -0.540
 9: -0.200, 0.253, -0.947
 10: -0.496, 0.134, -0.858
 11: -0.014, -0.628, -0.778
 12: -0.744, -0.148, -0.651
 13: -0.761, 0.320, -0.564
 14: -0.181, 0.925, -0.335
 15: -0.680, -0.422, -0.600
 16: 0.777, 0.471, -0.418
 17: 0.924, -0.104, -0.368
 18: 0.468, -0.767, -0.438
 19: 0.882, -0.189, -0.432
 20: 0.690, 0.706, -0.157
 21: 0.239, 0.757, -0.608
 22: -0.058, 0.984, 0.170
 23: -0.537, 0.836, -0.113
 24: -0.992, -0.121, -0.042
 25: -0.997, 0.071, -0.038
 26: -0.872, 0.478, -0.101
 27: -0.249, 0.933, 0.258
 28: 0.118, 0.992, -0.047
 29: 0.338, 0.841, 0.422
 30: 0.529, 0.841, 0.116
 31: 0.997, 0.055, -0.057
 32: 0.000, 0.000, 0.000

I wonder if the tables above are correct or not. Is there anything incorrect
or partially incomplete, please let me know.
Thanks in advance.

Sincerely,
Seongjin 

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