Objective To compare the value of standard deviation(SD)method and root mean square(RMS)method for measuring signal-to-noise ratio(SNR)of MRI of American College of Radiology(ACR)phantom based on phased array coils.Methods ACR phantom was scanned with head coil(Head),abdominal coil(Anterior),dual piece flexible coil(Flex L)and abdominal coil+flexible coil(Anterior+Flex L)each for 6 times,respectively,with sequences of axial T 1W-spin echo(SE)and T2W-SE.And the scanning schemes were divided into 8 groups based on 4 types of coils and 2 sequences.SNR of 8 groups were measured with standard deviation method and root mean square method,respectively,and the differences between the above 2 methods were observed.Results For T1W-SE sequence,SNRsD of MRI based on Head,Anterior,Flex L and Anterior+Flex L was 1.25±0.07,0.56±0.02,1.15±0.10 and 1.04±0.11,respectively,while SNRRMs was 1.10±0.07,0.58±0.03,1.01±0.13 and 1.31±0.15,respectively.For T2W-SE sequence,SNRsD was 1.40±0.08,0.48±0.02,1.04±0.07 and 1.08±0.06,respectively,while SNRRMs was 1.29±0.09,0.53±0.03,0.84±0.08 and 1.35±0.12,respectively.Compared pairwise,significant difference of SNRsD was found in 9 pairs(all P＜0.05),while of SNRRMs was detected in 10 pairs(all P＜0.05).Conclusion Compared with standard deviation method,root mean square method was more suitable for measuring SNR of MRI of ACR phantom based on phased array coils.

Objective To compare the value of standard deviation(SD)method and root mean square(RMS)method for measuring signal-to-noise ratio(SNR)of MRI of American College of Radiology(ACR)phantom based on phased array coils.Methods ACR phantom was scanned with head coil(Head),abdominal coil(Anterior),dual piece flexible coil(Flex L)and abdominal coil+flexible coil(Anterior+Flex L)each for 6 times,respectively,with sequences of axial T 1W-spin echo(SE)and T2W-SE.And the scanning schemes were divided into 8 groups based on 4 types of coils and 2 sequences.SNR of 8 groups were measured with standard deviation method and root mean square method,respectively,and the differences between the above 2 methods were observed.Results For T1W-SE sequence,SNRsD of MRI based on Head,Anterior,Flex L and Anterior+Flex L was 1.25±0.07,0.56±0.02,1.15±0.10 and 1.04±0.11,respectively,while SNRRMs was 1.10±0.07,0.58±0.03,1.01±0.13 and 1.31±0.15,respectively.For T2W-SE sequence,SNRsD was 1.40±0.08,0.48±0.02,1.04±0.07 and 1.08±0.06,respectively,while SNRRMs was 1.29±0.09,0.53±0.03,0.84±0.08 and 1.35±0.12,respectively.Compared pairwise,significant difference of SNRsD was found in 9 pairs(all P＜0.05),while of SNRRMs was detected in 10 pairs(all P＜0.05).Conclusion Compared with standard deviation method,root mean square method was more suitable for measuring SNR of MRI of ACR phantom based on phased array coils.