Table 6 Description of QC measures of BOLD data.
From: Cognitive tasks, anatomical MRI, and functional MRI data evaluating the construct of self-regulation
Image Quality Metric (Label) | Description | Range across all functional scans (Median) |
|---|---|---|
Ghost to Signal Ratio (gsr_y) | Measure of signal intensity in areas along encoding direction, subtract the signal intensity in areas not along the encoding direction, and then divide the resultant value by the signal intensity in the brain37. Lower values are better. | 0.011–0.199 (0.036) |
DVARS (dvars_vstd) | Measure of signal changes from volume to volume. Lower values are better. | 0.777–1.503 (0.984) |
Framewise displacement (fd_mean) | Measure of motion throughout the scan measured in millimeters. Lower values are better. | 0.030–0.595 (0.089) |
Foreground-background energy ratio (fber) | Average value of energy within the head compared to regions outside of the head36. Higher values are better. | 574.653–46811.020 (10483.188) |
Temporal SNR (tsnr) | Relative measure of background noise across time course. tsnr value is the median value of \(\frac{{average\; BOLD\; signal}({across\; time})}{{temporal\; standard}-{deviation\; map}}\) that is calculated for each timepoint of the image. Higher values are better. | 12.884–54.966 (37.324) |
Signal-to-noise ratio (snr) | Relative measure of background noise. Calculated as \(\frac{{\mu }_{F}}{{\sigma }_{F}\sqrt{n/(n-1)}}\) where \({\mu }_{F}\) is the mean intensity of tissues, \({\sigma }_{F}\) is the standard deviation of tissues and \(n\) is the number of voxels in the tissue mask. Higher values are better. | 2.111–4.304 (3.266) |
