Table 1.

An overview of techniques for pre-processing based on MRI.

References	Pre-processing	Tool
Al-Saffar and Yildirim (40)	Skull stripping based on threshold,	MATLAB
	Median filtering for noise reduction
Gutta et al. (41)	Skull stripping	Brainsuite software
KV et al. (42)	Skull stripping	Brainsuite software
Chen et al. (43)	Bias correction, Z-score normalization	SPM12
Siakallis et al. (44)	Logarithmic transformation, normalization,
	Offset field correction, strength matching
Kandemirli et al. (45)	Grayscale normalization, Discretization