Background:  The number of signal averages (NSA) parameters is one of the parameters that can affect the quality of the MRI image making the selection of accurate parameters is necessary to produce an optimal image produced and a short imaging time. 

Objectives: The purpose of this study was to determine the effect of variations in the value of the NSA to scan time and get a lumbar MRI anatomical image on sagittal STIR sequences and NSA that generate value anatomic information with an optimal scan time on lumbar MRI sagittal STIR sequences.

Method: This research is a quantitative research experiment conducted with a 1.5 Tesla MRI at the Kasih Ibu Hospitals Denpasar. Data are in the form of 50 image sagittal STIR sequences MRI lumbar of the 10 volunteers with five NSA variations (1, 2, 3, 4 and 5).  The assessment is performed by 3 people regarding information generated imagery and data were analyzed by using Friedman test.

Result: The results showed that there was the influence of variations in the value of the NSA to scan time and a lumbar MRI anatomical image slices sagittal with STIR sequences with a significance level of p value <0.05. Based on an assessment of the respondents, the value of the NSA which produce good anatomical information at the lumbar spine MRI sagittal slice with STIR sequences is NSA 5. And the NSA optimal value is based on the standard of NSA 2 relative value of SNR and scan time.

Conclusion: there was the influence of variations in the value of the NSA to scan time and get a lumbar MRI anatomical image slices sagittal with  STIR sequences with a significance level of p value <0.05. The value of the NSA which produced good anatomical information at the lumbar spine MRI sagittal slice with STIR sequences is NSA 5. And the NSA optimal value is based on the standard  of NSA 2 relative value of SNR and scan time

Keyword: NSA, Information Anatomy, STIR.