# [PERSON] Coding-Based Medical Image Data Hiding Method against Salt and Pepper Noise
## 4 Experimental Results
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Stego Image** & **PSNR (dB)** & **MSE** & **SSIM** & **Stego Image** & **PSNR (dB)** & **MSE** & **SSIM** \\ \hline CT(1) & 48.49 & 0.842 & 0.981 & US(1) & 48.97 & 0.527 & 0.991 \\ CT(2) & 46.76 & 1.370 & 0.958 & US(2) & 47.82 & 0.926 & 0.974 \\ CT(3) & 48.39 & 0.938 & 0.974 & US(3) & 47.15 & 1.177 &  
In Table 4, quality comparison results are given for the different stego image with 0.33 bpp or less embedding capacity. If the embedding capacity of the other methods is equal to the proposed method, all values of these methods will decrease. Considering this situation, stego images offer better visual qualities than existing methods in terms of both PSNR and SSIM. After data hiding, the stego image is transmitted to the receiver side through the communication channel that noiseless or contains different densities of salt and pepper noise. Secret data was extracted from the stego image in the receiver and the results were evaluated. Another data hiding (called no-RS) method was used to compare the performance of the proposed RS-based method. In this method, the secret logo is hidden directly on medical images without the RS method. Namely, the message sequence of the secret logo, which is converted into bits as a result of pre-processing, is divided into triple symbol groups and converted into decimal numbers. These elements are hidden directly to the units digit of the medical image by a similar method. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Method** & **PSNR (dB)** & **SSIM** & **Capacity (bpp)** & **Image Type** \\ \hline Proposed RS-based & 46.26 & 0.9858 & 0.33 & X-ray \\ [3] & 37.86 & 0.9830 & 0.30 & MRI \\ [4] & 41.19 & 0.9905 & 0.10 & X-ray \\ [13] & 40.26 & 0.9627 & 0.01 & CT \\ [29] & 46.22 & 0.9406 & 0.01 & CT \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Stego image quality comparison with existing methods (Capacity \(\leq\) 0.33 bpp). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Stego Image Type** & **Capacity (bpp)** & **Avg. PSNR (dB)** & **Avg. MSE** & **Avg. SSIM** \\ \hline CT & & & 50.80 & 0.519 & 0.985 \\ MRI & 0.083 & & 52.17 & 0.375 & 0.989 \\ US & & & 50.81 & 0.464 & 0.987 \\ X-ray & & & 51.73 & 0.326 & 0.991 \\ \hline CT & & & 47.72 & 1.040 & 0.971 \\ MRI & 0.164 & & 49.08 & 0.743 & 0.979 \\ US & & & 47.79 & 0.935 & 0.975 \\ X-ray & & & 48.79 & 0.650 & 0.983 \\ \hline CT & & & 44.55 & 2.135 & 0.945 \\ MRI & 0.332 & & 45.87 & 1.471 & 0.964 \\ US & & & 44.56 & 1.991 & 0.950 \\ X-ray & & & 45.61 & 1.373 & 0.967 \\ \hline CT & & & 41.74 & 3.905 & 0.910 \\ MRI & 0.656 & & 42.87 & 3.905 & 0.945 \\ US & & & 41.63 & 3.833 & 0.913 \\ X-ray & & & 42.77 & 2.478 & 0.950 \\ \hline CT & & & 35.21 & 16.89 & 0.681 \\ MRI & & & 36.16 & 11.71 & 0.823 \\ US & & & 35.23 & 16.10 & 0.704 \\ X-ray & & & 36.35 & 10.432 & 0.842 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Average quality parameters of the proposed method under different capacity conditions. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Method** & **PSNR (dB)** & **SSIM** & **Capacity (bpp)** & **Image Type** \\ \hline Proposed RS-based & 41.85 & 0.9335 & 0.794 & MRI \\ [14] & 38.31 & 0.8992 & 0.789 & MRI \\ [3] & 37.27 & 0.9777 & 0.600 & MRI \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Stego image quality comparison with existing methods (Capacity \(\leq\) 0.79 bpp). The abbreviations in the tables are as follows:  
* Proposed RS-based: the proposed method of this paper that used RS-based data hiding. * No-RS: similar to the proposed method, but without RS coding secret data embedded directly. Figure 4 shows the logos extracted from stego images exposed to salt and pepper noise at a density of 1%. Thanks to the proposed RS-based method, the logo is exactly retrieved in the same quality in all medical image types. Figure 5 shows the logos extracted from MRI stego images that were exposed to salt and pepper noise of different densities.