[Camino-users] Runge-Kutta error message in the Track command (r1218)

[Yan Jin]

Hi,

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:

"Processing ROI 1 of 1
Processing seed 1 of 61660Exception in thread "main"
java.lang.NullPointerException
        at
tractography.EightNeighbourLinearInterpolator.interpolateVectorElements(EightNeighbourLinearInterpolator.java:80)
        at
tractography.VectorLinearInterpolator.getTrackingDirection(VectorLinearInterpolator.java:87)
        at tractography.RK4FibreTracker.getNextStep(RK4FibreTracker.java:94)
        at
tractography.RK4FibreTracker.getFirstStep(RK4FibreTracker.java:56)
        at tractography.FibreTracker.trackFromSeed(FibreTracker.java:303)
        at tractography.FibreTracker.trackFromSeed(FibreTracker.java:230)
        at
apps.StreamlineTractography.execute(StreamlineTractography.java:946)
        at apps.EntryPoint.main(EntryPoint.java:284)"

The commands I used:
1. image2voxel -4dimage adni.nii.gz  -outputfile adni.Bfloat
2. dtfit  adni.Bfloat adni.scheme -bgmask adni_brain_mask.nii.gz
>adni_dwi.Bdouble
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

Have you used the "rk4" option and encountered the same error?

Thanks,
Yan
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