I just found the log of the error. It is weird that I can display the file with matplotlib in python through Nipype and that Slicer says the file does not exist. Please see below :
vtkITKArchetypeImageSeriesReader::ExecuteInformation: Archetype file /Users/quentinfrancois/Documents/Robeaut�/brain_imaging/results/registrationT1Scan/result.0.nii does not exist.
Algorithm vtkITKArchetypeDiffusionTensorImageReaderFile(0x7fa6150ec7e0) returned failure for request: vtkInformation (0x600001400240)
Debug: Off
Modified Time: 2787208
Reference Count: 1
Registered Events: (none)
Request: REQUEST_INFORMATION
ALGORITHM_AFTER_FORWARD: 1
FORWARD_DIRECTION: 0
vtkITKArchetypeImageSeriesReader::ExecuteInformation: Archetype file /Users/quentinfrancois/Documents/Robeaut�/brain_imaging/results/registrationT1Scan/result.0.nii does not exist.
Algorithm vtkITKArchetypeImageSeriesVectorReaderSeries(0x7fa6150e9070) returned failure for request: vtkInformation (0x6000017fce40)
Debug: Off
Modified Time: 2788701
Reference Count: 1
Registered Events: (none)
Request: REQUEST_INFORMATION
ALGORITHM_AFTER_FORWARD: 1
FORWARD_DIRECTION: 0
vtkITKArchetypeImageSeriesReader::ExecuteInformation: Archetype file /Users/quentinfrancois/Documents/Robeaut�/brain_imaging/results/registrationT1Scan/result.0.nii does not exist.
Algorithm vtkITKArchetypeImageSeriesScalarReader(0x7fa6150e6c50) returned failure for request: vtkInformation (0x6000017fee00)
Debug: Off
Modified Time: 2789484
Reference Count: 1
Registered Events: (none)
Request: REQUEST_INFORMATION
ALGORITHM_AFTER_FORWARD: 1
FORWARD_DIRECTION: 0
ReadData: This is not a nrrd file
ReadData: Cannot read file as a volume of type DiffusionTensorVolume[fullName = /Users/quentinfrancois/Documents/Robeaut�/brain_imaging/results/registrationT1Scan/result.0.nii]
Number of files listed in the node = 0.
File reader says it was able to read 0 files.
File reader used the archetype file name of /Users/quentinfrancois/Documents/Robeaut�/brain_imaging/results/registrationT1Scan/result.0.nii []
FileNotFoundError
ReadData: This is not a nrrd file
ReadData: Failed to instantiate a file reader
ReadData: Cannot read file as a volume of type Volume[fullName = /Users/quentinfrancois/Documents/Robeaut�/brain_imaging/results/registrationT1Scan/result.0.nii]
Number of files listed in the node = 0.
File reader says it was able to read 0 files.
File reader used the archetype file name of /Users/quentinfrancois/Documents/Robeaut�/brain_imaging/results/registrationT1Scan/result.0.nii []
FileNotFoundError
Quentin FRANCOIS
quentinfrancois0@gmail.com