Norazeani Abdul Rahman
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Norazeani Abdul Rahman
Official Name
Norazeani, Abdul Rahman
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Rahman, Norazeani Abdul
Rahman, N. A.
Rahman, Norazeani A.
Rahman, N. A.Z.
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16833887100

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Fractal compression using hierarchical clustered peer adjacent domain and multiclass SVM for computed radiography images

2022 , Norazeani Abdul Rahman

The volume of data from medical imaging is growing and consumes high costs of digital data storage. A method that can reduce the image size, fast retrieving and preserving the critical medical details of the image is a highlight in the research. Therefore, fractal image compression (FIC) is essential to obtain a substantially higher compression ratio (C ratio) without perceptible image degradation, which is clinically essential for effective diagnostic performance. The encoding phase in full-search FIC is time-intensive as a sequential search must be performed through a massive domain pool to find the best-matched domain for each block of ranges. This study proposes an improved FIC method based on hierarchical clustered peer adjacent domain and unsupervised multiclass support vector machine (SVM) mapping for computed radiography (CR). The optimal fractal parameters were proposed to increase FIC encoding efficiency using this approach. Combining the peer-adjacent domain with the Pearson correlation coefficient (PCC) is designed to reduce computations, reducing the number of domain blocks in a domain pool. The PCC being used for domain block classification based on correlation value speeds up the encoding. The unsupervised multiclass SVM and K-means clustering are developed in the study to improve the mapping process. The novelty of the proposed approach lies in the use of hierarchical clustered peer adjacent domains with multiclass SVM for accurate domain-range mapping, resulting in a high compression ratio with reduced storage, fast retrieving time, and high reconstructed image quality. The proposed method was tested using various standard test image and two sets database of medical images from The Cancer Imaging Archive (TCIA) and the Japanese Society of Radiological Technology (JSRT). The performance of the proposed optimal fractal parameters is evaluated using the Society of Motion Picture and Television Engineers (SMPTE) image and computed radiography lung images. The results show that the optimal factual parameters for increasing encoding efficiency are quadtree threshold (QTH) equal to 0.2, range size is (4,8), and three decoding iterations. The proposed method shows good performance in the encoding time reduction evaluation for the standard test image in terms of peak signal-to-noise ratio (PSNR), compression time, and compression ratio, with 27.27 dB, 6.88 s, and 16.13, respectively. Eva;uation of various medical image modalities and sizes from TCIA images demonstrates that the proposed method can compress larger images better than small images. For the 16.3 MB 4096 x 4096 mammography image, the proposed method retrieves the compressed image less than a minute with 39.5 dB. The implementation of multiclass SVM and K-means clustering has further improved the compressed image quality. The results for the proposed method evaluation executed using 360 CR images with and without chest lung nodules showed the high quality of reconstructed images with a PSNR equal to 41 dB for a range size of (4,8) and encoded less than a minute. The proposed method saved the storage about 95.6 percent with stored only 358 kB out of 8193 kB original size image. The finding demonstrates that the proposed method obtained high quality reconstructed images with more extensive storage and adequate encoding time.

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Peer adjacent mapping with optimum parameters for fractal image compression on medical images

2020 , Norazeani Abdul Rahman , Rizalafande Che Ismail , Ahmad Husni Mohd Shapri , Mohd Nazrin Md Isa

In order to reduce fractal image compression (FIC) computational complexity, this paper presents a novel approach based on peer adjacent and mean difference method in mapping the domain and range blocks. It allows the substitution of the costly process of the domain and range mapping with straight-forward peer adjacent schemes. The optimum parameters are suggested in terms of quadtree threshold, range sizes and number of iterations to fine-tune the output. Simulations on real computed radiography images show that the proposed method with optimum parameters yields a considerable peak signal-to-noise ratio (PSNR) value above 48 dB, reducing the runtime by as much as 19.32 s with the highest compression ratio is 20.03. Comparison with the standard FIC method confirms that our method not only accelerated the domain-range mapping procedure but also provided a high compression ratio with remarkable visual quality.

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An Improved Irreversible Fractal Scheme for Medical Image Compression

2020-12-18 , Norazeani Abdul Rahman , Rizalafande Che Ismail , Ahmad Husni Mohd Shapri

In this paper, an improved fractal image compression (FIC) based on peer adjacent scheme and domain classification was proposed. The proposed method has low computation cost since it contains no search operations, thus becoming fast irreversible fractal scheme. Comprehensive experiments on a standard test image and several types of digital radiology images revealed that the proposed method is competitive when compared to established quadtree-based FIC techniques. The novelty of the proposed method lies in the use of this improved domain classification and mapping strategy for accurate and more precise FIC encoding. The empirical result of standard test image suggests that the proposed method is more competitive compared to the established schemes and achieves better performance in terms the peak signal-to-noise ratio (PSNR) and compression time averaging at 27.27 dB and 6.88 s, respectively. Also, the proposed method obtains an efficient compression ratio with 16.13 compared to others. Additionally, experiments involving various medical image modalities confirmed the superiority of the proposed method for practical applications of medical image compression.

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Enhancing fractal image compression speed using peer adjacent mapping with sum of absolute difference for computed radiography images

2020 , Norazeani Abdul Rahman , Rizalafande Che Ismail , Ahmad Husni Mohd Shapri , Mohd Nazrin Md Isa

The encoding phase in full-search fractal image compression (FIC) is time-intensive as a sequential search must be performed through a massive domain pool to find the best-matched domain for each block of ranges. In this paper, a peer adjacent with the sum of absolute difference (SAD) mapping has been suggested to enhance the FIC speed while retaining the reconstructed image quality. The SAD similarity measure applied in searching the most matching domain between domain pool for a range before transformation in order to shorten the mapping process. Therefore, instead of performing a complete search in the next level, one requires to only search a close neighbourhood of the region computed from the previous search. The efficiency of the proposed method is evaluated using standard test image, SMPTE test pattern and standard computed radiography digital images from JSRT database, from which the peak signal-to-noise ratio (PSNR), compression time and compression ratio are calculated. The experimental results validate the effectiveness of the proposed method. © 2020 Author(s).

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