Analysis and comparison of the signal difference to noise ratio (SDNR), signal difference (SD), and the signal to noise ratio (SNR): evaluating the suitability of the SD and SDNR as MRI quality control parameters

The SDNR value is a display independent parameter that quantitatively measures the contrast-generating ability of a MR protocol. The intent of this research effort was to investigate the performance and suitability of the SDNR and SD measurements as possible MRI quality control parameters to augment the SNR currently employed, Six clinical MRI units were surveyed daily for a 5-week period. A quality control phantom was imaged at the start of each day and the SDNR, SD, and SNR values were calculated and recorded. In addition to daily measurements, performance testing investigated the following seven factors; (1) slice thickness, (2) TR, (3) TE, (4) FOV, (5) NEX, (6) flip angle, and (7) RF nonuniformity. The SDNR performance was similar to SNR performance in the tests conducted. The SD performance was similar to both the SNR and SDNR; however, the sensitivity of the SD measurement was greater in the RF non-uniformity performance tests. Testing results confirm the capability of the SDNR parameter to be used as a QC indicator. Based on the results of the RF nonuniformity test there is a notable and significant difference in sensitivity of the SD and SDNR parameters when compared to the SNR and SDNR measurements. The study results indicate that the SDNR and SD measures could be used to augment the SNR quality control parameter, thereby providing additional quality control capability. Both parameters are easily automated and can be incorporated to augment existing quality control parameters.