# A Systematic Literature Review on Applications of GAN-Synthesized Images for Brain MRI
## 3 Results
### Comparative Study of Evaluation Metric (RQ 4)  
The success of a GAN depends upon the quality of the synthesized image. The evaluation metric that can quantitatively characterize the synthesis accuracy is necessary to comment on the quality of the synthetic image. There are two types of metrics; the first is Full-Reference (FR) Quality Metrics, where the quality of a synthetic image is measured to the quality of a ground-truth image. The second is No-Reference (NR) Quality Metrics, where the quality scores of the synthetic image are based on expected image statistics. Two commonly used evaluation metrics are discussed below. Table 10 presents the comparative study of existing evaluation metrics. Some of the metrics from the table assess the quality of the synthesized image as a whole, while others asses the image on patch-wise and are thus suitable for the segmentation task [69].  
Figure 10: Format conversion of ground truth brain MRI.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Preprocessing Software** & **URL** & **Use** & **Ref. No.** \\ \hline \multirow{3}{*}{Freesurfer} & [[http://surfer.nmr.mgh.harvard.edu](http://surfer.nmr.mgh.harvard.edu)]([http://surfer.nmr.mgh.harvard.edu](http://surfer.nmr.mgh.harvard.edu)) & Skull-stripping, Registration, & [114; 162] \\  & (accessed on 26 August 2022) & fMRI Analysis & [114; 162] \\ \cline{1-1} \cline{2-4} \multirow{3}{*}{Functional magnetic resonance imaging} & [[http://fsl.fmrib.ox.ac.uk/](http://fsl.fmrib.ox.ac.uk/)]([http://fsl.fmrib.ox.ac.uk/](http://fsl.fmrib.ox.ac.uk/)) (accessed on & Registration, alignment, & [115; 162] \\ \cline{1-1} \cline{2-4} \multirow{3}{*}{Advanced Normalization Tool (ANT)} & 26 August 2022) & Skull-stripping & [115; 162] \\ \cline{1-1} \cline{2-4}  & [[http://stnava.github.io/ANTs/](http://stnava.github.io/ANTs/)]([http://stnava.github.io/ANTs/](http://stnava.github.io/ANTs/)) (accessed on 26 August 2022) & Registration & [5; 49; 163; 164] \\ \cline{1-1} \cline{2-4} \multirow{3}{*}{Statistical Parameter Mapping (SPM)} & [[http://www.filion.ucl.ac.uk/spm](http://www.filion.ucl.ac.uk/spm)]([http://www.filion.ucl.ac.uk/spm](http://www.filion.ucl.ac.uk/spm)) (accessed on 26 August 2022) & Skull-stripping & [74; 121] \\ \cline{1-1} \cline{2-4} \multirow{3}{*}{Velocity (Varian)} & [[https://www.varian.com/](https://www.varian.com/)]([https://www.varian.com/](https://www.varian.com/)) (accessed on 26 August 2022) & Registration & [25; 27; 165] \\ \cline{1-1} \cline{2-4} \multirow{3}{*}{Data Processing Assistant for Resting-State fMRI (DPARSF)} & [[http://www.restim.net](http://www.restim.net)]([http://www.restim.net](http://www.restim.net)) (accessed on 26 August 2022) & Data processing of fMRI & [166] \\ \cline{1-1} \cline{2-4} \multirow{3}{*}{Elastic} & [[https://elastic.lumc.nl/](https://elastic.lumc.nl/)]([https://elastic.lumc.nl/](https://elastic.lumc.nl/)) (accessed on 26 August 2022) & Registration & [68; 167] \\ \cline{1-1} \cline{2-4} \multirow{3}{*}{BrainSuite} & [[http://brainsuite.org/](http://brainsuite.org/)]([http://brainsuite.org/](http://brainsuite.org/)) (accessed on 26 August 2022) & Skull-stripping & [162] \\ \hline \hline \end{tabular}
\end{table}
Table 9: Summary of preprocessing software packages commonly used for brain MRI.  
Figure 9: Distribution of preprocessing operations performed on ground truth brain MRI.