SNR has been higher in the SD group compared to the HD group even though not statistically significant at any time-point for both IM ( SD vs. HD : 87.7 73 vs. 65 66 ; 0.15 < p < 0.38 ) and N-IM ( SD vs. HD : 22 61 vs. 9.9 6.5 ; 0.09 < p < 0.43 ) .