Dear Thais,
> Dear Jesper,
>
> Thank you for your reply. I have 64 diffusion directions sampled on the whole brain. I used a Philips machine, so as it happens, I will need help to design my acqp file.
64 directions on the whole sphere is definitely enough.
>
> 1- On the protocol attached below, it says that the direction was AP, but the item 'user defined direction' is coded as 0 1 0 rather than 0 -1 0. Which of those 2 should I use? (the images look pretty good)
If you only have a single EP direction the sign will be of no consequence at all. Just pick one.
> 2- based on the other parameters, how can I calculate my echo spacing?
Getting the echo-spacing right is only important if you have different acquisitions with different echo spacings, OR if you want the estimated fieldmaps to be quantitative (in Hz). I suspect that on one but me has ever looked at one of those maps, so probably not of interest to you.
So, my suggestion is you use
0 1 0 0.1
as your acqp file, and that will work perfectly fine.
Jesper
>
> Regards,
>
> Thais Minett
>
>
> Nucleus = "H1";
> Coil selection = "SENSE-Head-8";
> element selection = "SENSE";
> connection = "d";
> Dual coil = "no";
> CLEAR = "yes";
> body tuned = "no";
> FOV RL (mm) = 270;
> AP (mm) = 270;
> FH (mm) = 124.48999;
> Voxel size RL (mm) = 2.20000005;
> AP (mm) = 2.20338988;
> Slice thickness (mm) = 2.1099999;
> Recon voxel size (mm) = 2.109375;
> Fold-over suppression = "no";
> Reconstruction matrix = 128;
> SENSE = "yes";
> P reduction (AP) = 2;
> P os factor = 1;
> Stacks = 1;
> type = "parallel";
> slices = 59;
> slice gap = "user defined";
> gap (mm) = 0;
> slice orientation = "transverse";
> fold-over direction = "AP";
> fat shift direction = "P";
> Stack Offc. AP (P=+mm) = 0;
> RL (L=+mm) = 0;
> FH (H=+mm) = 0;
> Ang. AP (deg) = 0;
> RL (deg) = 0;
> FH (deg) = 0;
> Minimum number of packages = 1;
> Slice scan order = "default";
> Large table movement = "no";
> PlanAlign = "no";
> REST slabs = 0;
> Interactive positioning = "no";
> Patient position = "head first";
> orientation = "supine";
> Scan type = "Imaging";
> Scan mode = "MS";
> technique = "SE";
> Modified SE = "no";
> Acquisition mode = "cartesian";
> Fast Imaging mode = "EPI";
> shot mode = "single-shot";
> Echoes = 1;
> partial echo = "no";
> TE = "shortest";
> Flip angle (deg) = 90;
> TR = "shortest";
> Halfscan = "yes";
> factor = 0.680851042;
> Water-fat shift = "minimum";
> Shim = "auto";
> Fat suppression = "SPIR";
> strength = "strong";
> frequency offset = "default";
> Water suppression = "no";
> BB pulse = "no";
> MTC = "no";
> Research prepulse = "no";
> Diffusion mode = "DTI";
> sequence = "SE";
> gradient duration = "maximum";
> gradient overplus = "no";
> directional resolution = "user defined";
> nr of directions = 64;
> user defined dirs = 1,
> (3) 0, 1, 0, (3) 0.579999983,
> (2) 0, 1, 0.819999993, (2) -0.409999996,
> 0, 0.709999979, -0.709999979,
> (2) 0.579999983, -0.579999983,
> 0.819999993, -0.409999996,
> 0.409999996, 0, (2) 0.709999979,
> 0.439999998, -0.670000017,
> -0.600000024, 0.649999976,
> 0.170000002, -0.74000001,
> -0.600000024, -0.620000005,
> 0.5, -0.25999999, 0.879999995,
> -0.400000006, 0.430000007,
> -0.0900000036, (2) 0.899999976,
> -0.439999998, 0, 0.610000014,
> -0.779999971, -0.159999996,
> 0.100000001, -0.430000007,
> 0.899999976, -0.159999996,
> 0.310000002, -0.939999998,
> 0.560000002, 0.800000012,
> 0.200000003, -0.219999999,
> -0.680000007, 0.699999988,
> -0.829999983, 0.25, -0.5,
> -0.699999988, 0.639999986,
> -0.300000012, 0.569999993,
> -0.270000011, -0.769999981,
> 0.119999997, -0.469999999,
> -0.879999995, -0.810000002,
> -0.519999981, -0.25999999,
> -0.0700000003, -0.779999971,
> -0.620000005, 0.899999976,
> 0.0199999996, -0.430000007,
> -0.49000001, -0.75, -0.430000007,
> -0.589999974, -0.800000012,
> 0.0599999987, 0.209999993,
> -0.930000007, -0.300000012,
> 0.689999998, 0.180000007,
> 0.709999979, -0.560000002,
> 0.100000001, -0.829999983,
> -0.939999998, 0.349999994,
> -0.0399999991, -0.209999993,
> -0.970000029, -0.150000006,
> 0.239999995, -0.0199999996,
> -0.970000029, -0.74000001,
> -0.25, -0.620000005, -0.730000019,
> 0.639999986, 0.239999995,
> 0.200000003, -0.790000021,
> 0.579999983, -0.230000004,
> -0.920000017, 0.319999993,
> -0.970000029, -0.0199999996,
> 0.219999999, -0.400000006,
> -0.479999989, -0.779999971,
> -0.5, 0.579999983, 0.639999986,
> -0.540000021, 0.119999997,
> 0.829999983, 0.879999995,
> 0.419999987, -0.230000004,
> 0.569999993, -0.769999981,
> 0.289999992, -0.200000003,
> -0.150000006, -0.970000029,
> -0.460000008, 0.889999986,
> -0.00999999978, -0.270000011,
> 0.879999995, 0.389999986,
> -0.469999999, 0.550000012,
> -0.689999998, 0.280000001,
> 0.419999987, -0.860000014,
> -0.370000005, -0.289999992,
> 0.879999995, -0.879999995,
> -0.449999988, 0.180000007,
> 0.529999971, -0.469999999,
> 0.709999979, 0.189999998,
> -0.970000029, 0.140000001,
> -0.819999993, 0.280000001,
> 0.5, -0.189999998, 0.370000005,
> (2) 0.910000026, 0.00999999978,
> 0.419999987, 0.209999993,
> 0.899999976, 0.379999995,
> -0.769999981, -0.219999999,
> 0.610000014, 0.230000004,
> 0.899999976, -0.370000005,
> 0.870000005, 0.439999998,
> 0.219999999, 0.589999974,
> 0.779999971, -0.189999998,
> -0.970000029, -0.0900000036,
> -0.230000004, 0.289999992,
> 0.389999986, 0.870000005,
> (192) 0;
> nr of b-factors = 2;
> b-factor order = "ascending";
> max b-factor = 1000;
> average high b = "user defined";
> b-factor averages = 6,
> (15) 1;
> SAR mode = "high";
> B1 mode = "default";
> PNS mode = "high";
> Gradient mode = "maximum";
> SofTone mode = "no";
> Cardiac synchronization = "no";
> Respiratory compensation = "no";
> Navigator respiratory comp = "no";
> Flow compensation = "no";
> Temporal slice spacing = "default";
> NSA = 1;
> Manual start = "no";
> Dynamic study = "no";
> dyn stabilization = "no";
> Arterial Spin labeling = "no";
> Preparation phases = "auto";
> Manual Offset Freq. = "no";
> B0 field map/Dixon = "no";
> B1 field map = "no";
> MIP/MPR = "no";
> Images = " M", (3) " no";
> Autoview image = " M";
> Calculated images = (4) " no";
> Reference tissue = "Grey matter";
> EPI 2D phase correction = "no";
> Preset window contrast = "soft";
> Reconstruction mode = "on the fly";
> Save raw data = "no";
> Hardcopy protocol = "no";
> Ringing filtering = "rectangular";
> Geometry correction = "default";
> IF_info_seperator = 0;
> Total scan duration = "07:19.4";
> Rel. signal level (%) = 100;
> Act. TR (ms) = "6103";
> Act. TE (ms) = "70";
> ACQ matrix M x P = "124 x 120";
> ACQ voxel MPS (mm) = "2.18 / 2.25 / 2.11";
> REC voxel MPS (mm) = "2.11 / 2.11 / 2.11";
> Scan percentage (%) = 96.9230804;
> Packages = 1;
> Min. slice gap (mm) = 0;
> Diffusion gradient timing DELTA / delta (ms) =
> "34.8 / 23.3";
> EPI factor = 63;
> WFS (pix) / BW (Hz) = "14.628 / 29.7";
> BW in EPI freq. dir. (Hz) = "2653.0";
> SAR / head = "< 36 % / 1.1 W/kg";
> Whole body / level = "< 0.1 W/kg / normal";
> B1 rms [uT] = 1.39387262;
> PNS / level = "100 % / 1st level";
> Sound Pressure Level (dB) = 24.6646099;
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