3D MRI sequences have many advantages over 2D sequences. Images acquired by 3D sequences have isotropic voxel dimensions and absence of inter-slice gap so it can be easily reformatted without degrading the image quality; in addition, it allows time acceleration using compressed sensing . Another good factor in 3D images is decreased slice thickness that also leads to increased number of detected lesions .
Early studies showed that 3D-FLAIR is more superior than routinely used 2D sequences (T2 and 2D-FLAIR) in detection of MS lesions [12, 13]; however, in early trials, 3D sequences took long acquisition times as it were multi-slab mode, and that disadvantage was adjusted by using single-slab mode .
In this study, although 3D-FLAIR sequence has longer time 5:40 min compared to 1:32 min in T2 sequence and 1:12 min in 2D FLAIR sequence, it is not considered a drawback as it is 3D volume images by which axial, coronal, and sagittal reformate images could be obtained.
3D-FLAIR sequence is one of 3D sequences that have advantage of good signal with small voxels and by turn high SNRs [9, 15]. Another advantage seen in 3D-FLAIR sequences is better CSF suppression than T2 and 2D FLAIR sequences and by turn absence of CSF flow artifacts that occurs because large volume excited using 3D technique; these advantages improve MS lesion detection .
In current study, 3D-FLAIR sequence significantly detected more overall number of lesions comparing to standard used 2D-FLAIR and T2 sequences.
In current study, the detected lesions were mainly in supratentorial region (periventricular, deep WM and juxta-cortical), and in all three locations, 3D-FLAIR sequence showed significantly more lesions than 2D-FLAIR and T2 sequences. We found that in juxta-cortical region, much more lesions were depicted by 3D-FLAIR sequence than 2D-FLAIR and T2 sequences with more significance and high-percentage ratio than in periventricular WM and deep WM. The major number of that higher count of lesions was due to depiction of new smaller lesions not seen by 2D-FLAIR and T2 sequences, in addition to many lesions that appeared as single confluenting lesion on both sequences were found to be multiple distinct lesions adjacent to each other by 3D-FLAIR.
Recently, juxta-cortical lesions more frequently occur and have found to be related to more clinical disability [17,18,19].
Few lesions seen in infratentorial region in this study is probably due to limited number of patients, that is keeping with Patzig M et al.  that reported few infratentorial lesions found in brain stem and cerebellum probably due to limited number of patients that was also seen in our study.
In current present study, 3D-FLAIR sequence was superior to T2 sequence in depicting the infratentorial lesions and also much more superior to 2D-FLAIR sequence.
It have been found that 2D-FLAIR sequences are not ideal in the depiction of infratentorial lesion due to CSF flow artifact and lower contrast seen between lesion and white matter [21, 22].
This study results are in keeping with Moraal B et al.  who reported that 3D-FLAIR sequence provided the highest sensitivity for depiction of hyperintense MS plaque in all anatomical locations including supra-tentorial and infratentorial lesions compared to any other 2D sequences, in particular 2D-T2SE, that could lead to earlier diagnosis of the disease.
In MS, there is associated changes white matter diffusion seen in diffusion-weighted images (DWI), and it index apparent diffusion coefficient (ADC) by primary inflammatory changes consisting of the cytotoxic edema followed by vasogenic edema, and active plaques may demonstrate high or low ADC (increased or decreased diffusion) .
Larsson HB et al.  declares the role of DWI in early depiction of acute MS lesions, and few other studies have discussed the role of diffusion as good diagnostic method as comparable to conventional MRI with conflicting results [24, 25]
Many studies have been done and examined the role of 3D DIR sequences in diagnosis of MS; in DIR sequences, there is using of additional inversion pulse that increase attenuation of white matter and CSF, and in turn, increase lesion hyperintensity and its depiction; 3D-FLAIR sequences stimulates similar effect and white matter lesions become more hyperintense [9, 26, 27].
Further studies are needed to compare results of 3D-FLAIR and 3D-DIR in depiction of MS lesions.
Acknowledgement of study limitation due to limited number of MS patients is included in the study, but statistical analysis from this work was based on large total number of MS lesions which was considered sufficient.