读取文件夹及其文件，计算nii文件平均值和标准差，并将结果保存为nii文件(Read the folder and its files, calculate the average value and standard deviation of the NII file, and save the result as a NII file)

对nii文件进行Z变换，并保存成nii文件(Z transform to the NII file and save it as a NII file)