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questions > RE: Voxel values 500 times higher with dcm2niix
Feb 9, 2017 09:02 PM | Felix Navarro Guirado - Hospital Regional Universitario de Málaga
RE: Voxel values 500 times higher with dcm2niix
Dear Chris,
Using your tool to convert a Philips ADC map from dicom to nifti (Chris Rorden's dcm2niiX version 10oct2016 (32-bit Windows)) I get this:
Philips Precise RS:RI:SS = 3.01783:0:0.0042949 (see PMC3998685)
Looking into PMC3998685 I can find that the final equation used to transform stored values (PV) into the final values (FP) is:
FP = PV ·(1/SS) + RI/(RS·SS) = PV · scl_slope + scl_intercept.
The scl_slope (1/SS) and the scl_intercept (RI/(RS·SS)) values written in the nifti file by your tool agree with that definition, but if I get the FP values using the PV values written in the raster I don't get the FP values obtained with other tools (DWIConvert and mcverter, which perform this operation and save a nifti file with scl_slope=1, scl_intercept = 0 and FP values in the raster). In order to make your nifti agree with the other two I need to use FP = PV · 1/scl_slope.
I'm pretty sure that the correct values are the other two because I'm working with an ADC map and those are which make sense.
Am I missing something?
Thanks for sharing your tool.
Using your tool to convert a Philips ADC map from dicom to nifti (Chris Rorden's dcm2niiX version 10oct2016 (32-bit Windows)) I get this:
Philips Precise RS:RI:SS = 3.01783:0:0.0042949 (see PMC3998685)
Looking into PMC3998685 I can find that the final equation used to transform stored values (PV) into the final values (FP) is:
FP = PV ·(1/SS) + RI/(RS·SS) = PV · scl_slope + scl_intercept.
The scl_slope (1/SS) and the scl_intercept (RI/(RS·SS)) values written in the nifti file by your tool agree with that definition, but if I get the FP values using the PV values written in the raster I don't get the FP values obtained with other tools (DWIConvert and mcverter, which perform this operation and save a nifti file with scl_slope=1, scl_intercept = 0 and FP values in the raster). In order to make your nifti agree with the other two I need to use FP = PV · 1/scl_slope.
I'm pretty sure that the correct values are the other two because I'm working with an ADC map and those are which make sense.
Am I missing something?
Thanks for sharing your tool.
Threaded View
Title | Author | Date |
---|---|---|
Pascal Pas | Oct 23, 2016 | |
Chris Rorden | Feb 19, 2017 | |
Chris Rorden | Oct 26, 2016 | |
Felix Navarro Guirado | Feb 9, 2017 | |
Chris Rorden | Feb 9, 2017 | |
Felix Navarro Guirado | Feb 10, 2017 | |
Pascal Pas | Oct 26, 2016 | |
Chris Rorden | Oct 25, 2016 | |
Pascal Pas | Oct 25, 2016 | |