以影像為基礎的電腦斷層金屬假影矯正法（金屬假影矯正法）

Image-based Metal Artifact Correction for Computed Tomography (Running Title: Metal Artifact Correction)

吳杰(Jay Wu) ； 張哲堯(James Chang) ； 莊克士(Keh-Shih Chuang) ； 黃英明(Ing-Ming Hwang) ； 蔡忠宏(Chung-Hung Tsai) ； 季匡華(Kwan-Hwa Chi)

《中華放射線技術學雜誌》 30卷2期 (2006/12) Pp. 79-86

https://doi.org/10.30045/CJRT.200612.0001

摘要

電腦斷層(computed tomography, CT)影像在頭部與腹部的病變診斷上，已大量取代傳統的X光影像，成為放射診斷中不可或缺的一環。然而，使用電腦斷層造影的同時，金屬假影(metal artifact)卻可能嚴重的影響影像品質。本研究提出一個以影像為基礎的金屬假影矯正法，首先根據金屬假影的灰階值設定閾值(threshold)並尋找放射中心(radial center)，透過放射中心對整張CT影像做360度的切割，以計算每個區塊的加權因子，並利用此加權因子分別對每個區塊中的亮紋與暗紋做矯正。我們將Rando假體的頭部植入一顆直徑4公釐的鋼球，並利用所提出的金屬假影矯正法進行影像的修正。矯正結果成功的將金屬假影亮紋部份的CT值(CT number)降低，並且有效提升暗紋的CT值，進而減少金屬假影的對比。在治療劑量上，金屬假影的矯正對於有興趣區域的劑量體積直方圖的影響相當有限。我們認為所提出的以影像為基礎的金屬假影矯正法確實可以減少金屬假影的影響，進而改善影像品質。

關鍵字

金屬假影 ； 電腦斷層 ； 影像品質

並列摘要

Computed tomography (CT) has been successfully used in clinical imaging applications recently. However, the metal artifact seriously degrades image quality, particularly near the metal surfaces. In this research, we proposed an image-based correction method for the metal artifact. Radial centers were selected, by which the CT image was divided into 360 parts. Weighting factor for each region was then calculated and applied to the streak artifacts. A metal sphere was inserted in the head of the Rando phantom. The affected image was achieved and corrected by the proposed method. The results indicate that the correction method effectively reduced the CT number of the bright streaks and increased the CT number of the dark lines simultaneously. In the treatment planning system, using this metal artifact correction method has limited effect in the ROI's dose volume histogram. We conclude that the proposed correction method could reduce the metal artifacts and improve the image quality significantly.

並列關鍵字

Metal artifact ； Computed tomography ； Image quality