以移動估測與JPEG-LS編碼進行無失真醫學影像壓縮

近幾年來，隨著龐大的醫學影像被數位化，壓縮醫學影像已成為重要的研究課題。以目前每秒拍攝兩張的商用膠囊內視鏡為例，其8小時所拍攝的資料量為10.5 GB，更別提其最新的每秒4張膠囊內視鏡所拍攝的資料量。且隨著科技的進步，預期膠囊內視鏡的檢查費用將不再如此昂貴，因此會有越來越多的病患選擇膠囊內視鏡，要解決儲存這類影像的問題也會愈來愈重要。然而為了避免醫療糾紛，壓縮醫學影像最好使用無失真壓縮。雖然無失真JPEG-LS壓縮在膠囊內視鏡影像上有不錯的壓縮率，但是JPEG-LS是以單張影像作為處理，並無使用膠囊影像時間上的資訊。因此，本論文針對膠囊內視鏡影像提出一套結合移動向量與JPEG-LS壓縮提升無失真膠囊內視鏡影像序列編碼效能的壓縮方法。在實驗中，我們使用6種不同影像內容且各為100張的膠囊內視鏡影像作為測試影像。實驗結果顯示，我們所提出的方法可提升直接使用JPEG-LS壓縮時的壓縮效能從4% ~ 31.6%不等。此外，我們也壓縮MRI醫學影像以及自然連續影像，結果顯示我們的方法在MRI影像上也有極佳的壓縮效能，但對於提升自然影像的壓縮效能則不明顯。

關鍵字

無失真壓縮；醫學影像；移動向量； JPEG-LS

並列摘要

As enormous amount of medical images is under digitization recently, medical image compression has become a hot topic for study. One of the digitized sources is from the commercially available capsule endoscopy, which takes two pictures per second. These images occupy 10.5 GB of data space in eight hours. If the latest capsule endoscopy, which takes four pictures per second, is used the required storage space is even larger. With the advancement of technology development, the charge for the capsule endoscopy treatment is expected to be less expensive, and more and more patients can afford it. Consequently a good resolution to the issue of storing such images is more and more important. To avoid the lawsuit in medical disputes, compression of medical images is better performed losslessly. Although lossless JPEG-LS has good performance on compressing capsule endoscope images, it only compresses a single picture with intra coding and does not utilize the temporal information in adjacent pictures. Therefore, this thesis proposes a method that combines motion vectors and JPEG-LS to enhance the compression performance of basic JPEG-LS. In the experiment, we have six capsule endoscope image sequences for testing, and each sequence consists of 100 images. Experiment results show that the proposed scheme achieves a compression gain from 4% to 31.6% than the method of using JPEG-LS directly. A further experiment attempts to compress the MRI and natural images. The compression results also show very good performance for MRI images, but no obvious improvement for natural images.

並列關鍵字

medical image ； JPEG-LS ； motion vector ； lossless compression

參考文獻

[2] R. C. Gonzalez and R. E. Woods, Digital Image Processing, 2nd ed., Prentice-Hall, 2002.

[3] K. Sayood, Introduction to Data Compression, 2nd ed, Morgan Kaufmann, 2000.

[6] FCD 14495, Lossless and near-lossless coding of continuous tone still images (JPEG-LS), ISO/IEC JTC 1/SC 29/WG 1, 1997.

[7] M. J. Weinberger, G. Seroussi, and G. Sapiro, “The LOCO-I lossless image compression algorithm: principles and standardization into JPEG-LS,” IEEE Trans. Image Processing, vol. 9, pp. 1309-1324, Aug. 2000.

[9] S. David and W. Michael, JPEG2000—Image Compression Fundamentals, Standard and Practice, Kluwer Academic Publishers, Taubman Marcellin, 2002.

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以移動估測與JPEG-LS編碼進行無失真醫學影像壓縮

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