Limits...
Simultaneous storage of medical images in the spatial and frequency domain: a comparative study.

Nayak J, Bhat PS, Acharya U R, Uc N - Biomed Eng Online (2004)

Bottom Line: It can be seen from results, the process does not affect the picture quality.Spatial and DFT domain interleaving gave very less %NRMSE as compared to DCT and DWT domain.Among the frequency domain interleaving methods, DFT was found to be very efficient.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of E & C Engg, Manipal Institute Of Technology, Manipal, India 576104. jag.nayak@mit.manapal.edu

ABSTRACT

Background: Digital watermarking is a technique of hiding specific identification data for copyright authentication. This technique is adapted here for interleaving patient information with medical images, to reduce storage and transmission overheads.

Methods: The patient information is encrypted before interleaving with images to ensure greater security. The bio-signals are compressed and subsequently interleaved with the image. This interleaving is carried out in the spatial domain and Frequency domain. The performance of interleaving in the spatial, Discrete Fourier Transform (DFT), Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) coefficients is studied. Differential pulse code modulation (DPCM) is employed for data compression as well as encryption and results are tabulated for a specific example.

Results: It can be seen from results, the process does not affect the picture quality. This is attributed to the fact that the change in LSB of a pixel changes its brightness by 1 part in 256. Spatial and DFT domain interleaving gave very less %NRMSE as compared to DCT and DWT domain.

Conclusion: The Results show that spatial domain the interleaving, the %NRMSE was less than 0.25% for 8-bit encoded pixel intensity. Among the frequency domain interleaving methods, DFT was found to be very efficient.

Show MeSH

Related in: MedlinePlus

Scheme for Interleaving in DCT Domain
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC425593&req=5

Figure 5: Scheme for Interleaving in DCT Domain

Mentions: Blocks of 8 × 8 pixels are selected in a raster fashion from the image to be compressed. This forms the input to the encoder. Applying DCT to these blocks transforms the image from spatial domain to frequency domain. The DCT contains the DC coefficient, which measures the zero frequency, and 63 AC coefficients. The DCT coefficients are quantized according to perceptual criteria. For interleaving the LSB of each DCT coefficient is replaced by the text data (after the quantization and zigzag encoding). The eight bits of ASCII code in the text file will replace the LSB of eight consecutive DCT coefficients of the image from the middle frequency range onwards (from 32 to 63 coefficients). If the data file is a graphic signal having 16-bit word, 16 consecutive DCT coefficients are used for interleaving a single word. The LSB is chosen for data interleaving because, the resulting degradation of image is minimal. In the decoding side, the interleaved text or graphical signal can be obtained by de-interleaving i.e., extracting the LSBs and concatenating the same, before, inverse quantization, zigzag coding and inverse DCT. The Interleaving procedure implemented in DCT domain is shown in figure 5.


Simultaneous storage of medical images in the spatial and frequency domain: a comparative study.

Nayak J, Bhat PS, Acharya U R, Uc N - Biomed Eng Online (2004)

Scheme for Interleaving in DCT Domain
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC425593&req=5

Figure 5: Scheme for Interleaving in DCT Domain
Mentions: Blocks of 8 × 8 pixels are selected in a raster fashion from the image to be compressed. This forms the input to the encoder. Applying DCT to these blocks transforms the image from spatial domain to frequency domain. The DCT contains the DC coefficient, which measures the zero frequency, and 63 AC coefficients. The DCT coefficients are quantized according to perceptual criteria. For interleaving the LSB of each DCT coefficient is replaced by the text data (after the quantization and zigzag encoding). The eight bits of ASCII code in the text file will replace the LSB of eight consecutive DCT coefficients of the image from the middle frequency range onwards (from 32 to 63 coefficients). If the data file is a graphic signal having 16-bit word, 16 consecutive DCT coefficients are used for interleaving a single word. The LSB is chosen for data interleaving because, the resulting degradation of image is minimal. In the decoding side, the interleaved text or graphical signal can be obtained by de-interleaving i.e., extracting the LSBs and concatenating the same, before, inverse quantization, zigzag coding and inverse DCT. The Interleaving procedure implemented in DCT domain is shown in figure 5.

Bottom Line: It can be seen from results, the process does not affect the picture quality.Spatial and DFT domain interleaving gave very less %NRMSE as compared to DCT and DWT domain.Among the frequency domain interleaving methods, DFT was found to be very efficient.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of E & C Engg, Manipal Institute Of Technology, Manipal, India 576104. jag.nayak@mit.manapal.edu

ABSTRACT

Background: Digital watermarking is a technique of hiding specific identification data for copyright authentication. This technique is adapted here for interleaving patient information with medical images, to reduce storage and transmission overheads.

Methods: The patient information is encrypted before interleaving with images to ensure greater security. The bio-signals are compressed and subsequently interleaved with the image. This interleaving is carried out in the spatial domain and Frequency domain. The performance of interleaving in the spatial, Discrete Fourier Transform (DFT), Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) coefficients is studied. Differential pulse code modulation (DPCM) is employed for data compression as well as encryption and results are tabulated for a specific example.

Results: It can be seen from results, the process does not affect the picture quality. This is attributed to the fact that the change in LSB of a pixel changes its brightness by 1 part in 256. Spatial and DFT domain interleaving gave very less %NRMSE as compared to DCT and DWT domain.

Conclusion: The Results show that spatial domain the interleaving, the %NRMSE was less than 0.25% for 8-bit encoded pixel intensity. Among the frequency domain interleaving methods, DFT was found to be very efficient.

Show MeSH
Related in: MedlinePlus