以模型影像為基礎之金屬假影矯正法

電腦斷層（computed tomography, CT）攝影可提供相當豐富的診斷資訊，對於現今的臨床醫療帶來相當大的幫助及便利性，然而，當病人體內有金屬植入物時，該部位之影像便會產生大量的金屬假影，嚴重的影響影像品質。本研究提出一個以模型影像為基礎的金屬假影校正法，首先藉由k-means分叢產生初始模型影像，對於初始模型影像中因金屬假影造成分叢錯誤的部分則利用空間資訊計算及影像修復法消除，便完成模型影像的建立，接著將原始影像與模型影像相減求出差異影像，並將此差異影像取絕對值常態化到1後，利用指數形式之加權函數求得加權因子，對原始及模型的投影資料加權，最後利用濾波反投影即可獲得矯正後影像。我們挑選四種含有金屬假影的影像作為研究案例，分別為圓柱形水假體、骨盆腔、口腔及髖關節之CT影像，結果顯示本方法在不同案例中皆可有效移除影像中之金屬假影，使各區域的CT值在矯正後皆能有所改善，並提升影像的灰階均勻度，除此之外，口腔及髖關節CT影像之表面呈像或體素呈像重建結果亦獲得改善。因此我們認為，本研究提出之金屬假影矯正法能夠有效消除金屬假影對影像的損害。

關鍵字

k-means分叢；金屬假影；電腦斷層攝影

並列摘要

Computed tomography (CT) provides various diagnosis information which are beneficial and convenient for clinical medicine today. However, high-density metal implants in the CT scans induce metal artifact and compromise image quality. In this study, we proposed a model-based metal artifact correction method. First, we built a model image using k-means clustering technique and removed the errors within the clustering results by local statistics of spatial information and image inpainting. The difference between the original image and model image were then calculated, and the projection data of the original image and model image were then combined together by a weighting factor estimated from an exponential weighting function. At last, the corrected image was reconstructed using the filtered back-projection method. Four case images which form the scan results of cylindrical water phantom, pelvic, oral cavity and hip joint were used to test the correction ability of our algorithm. All of the correction results show that our algorithm can effectively removed the metal artifact arising from metal objects and significant improved the image continuity and image uniformity. Furthermore, the results of surface rendering and volume rendering of oral CT image and pelvic CT image were also recovered. We conclude that metal artifact correction method proposed in this study is useful for reducing the metal artifact.

並列關鍵字

k-means clustering ； Computed tomography ； Metal artifact

參考文獻

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國際替代計量

以模型影像為基礎之金屬假影矯正法

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