<div dir="ltr"><div><div><div><div>Hi,<br><br></div>I have downloaded a few DTI dataset
from ADNI. I would like to use Runge-Kutta method (rk4) to track the
fibers. But I got errors when the tensor data were interpolated.
However, this didn't happen when I used the "euler" option, even the
same interpolation method was used. Here is the error message:<br>
<br>"Processing ROI 1 of 1<br>Processing seed 1 of 61660Exception in thread "main" java.lang.NullPointerException<br> at tractography.EightNeighbourLinearInterpolator.interpolateVectorElements(EightNeighbourLinearInterpolator.java:80)<br>
at tractography.VectorLinearInterpolator.getTrackingDirection(VectorLinearInterpolator.java:87)<br> at tractography.RK4FibreTracker.getNextStep(RK4FibreTracker.java:94)<br> at tractography.RK4FibreTracker.getFirstStep(RK4FibreTracker.java:56)<br>
at tractography.FibreTracker.trackFromSeed(FibreTracker.java:303)<br> at tractography.FibreTracker.trackFromSeed(FibreTracker.java:230)<br> at apps.StreamlineTractography.execute(StreamlineTractography.java:946)<br>
at apps.EntryPoint.main(EntryPoint.java:284)"<br><br></div>The commands I used:<br>1. image2voxel -4dimage adni.nii.gz -outputfile adni.Bfloat<br>2. dtfit adni.Bfloat adni.scheme -bgmask adni_brain_mask.nii.gz >adni_dwi.Bdouble<br>
3. track -inputfile adni_dwi.Bdouble -inputmodel dt -seedfile
adni_seed.nii -curvethresh 40 -anisthresh 0.2 -anisfile adni_FA.nii
-tracker rk4 -interpolator linear -stepsize 1>adni_rk4_tract.Bfloat<br><br></div>Have you used the "rk4" option and encountered the same error?<br>
<br></div>Thanks,<br>Yan</div>