Figure 3: SNR computed with method 4 for images obtained with two repetitions of 12 DTI gradient directions. DTI-A ( -value = 900 s/mm2, 50 slices) (red) is compared with DTI-B ( -value = 1000 s/mm2, 40 slices) (blue). Note that DTI-B has been obtained with the last slice ( direction from feet to head) positioned as the last slice of DTI-A slice group.