- 學位論文
醫學影像之切割與隱藏技術之研究
The Study of Segmentation and Hiding Techniques for Medical Images
摘要
影像切割技術能有效地切割出影像中有感興趣的物件，且常被應用於影像識別與醫學影像等應用中。Otsu 門檻植方法為最常被廣泛使用的影像切割方法之一。不幸地，當某一群組其資料量較大或者是標準差較大時，Otsu門檻植方法無法決定一適合地門檻植。本論文提出一個可適應性門檻值偵測法來解決Otsu門檻值的缺點。其方法考慮了群組的標準差、資料量、以及組距等因素來決定一合適的門檻植。 子宮頸癌為婦女十大死亡癌症之一，為了有效提升子宮頸影像切割準確率，以及降低人力成本，本論文提出一子宮頸影像細胞核與細胞質輪廓偵測法。此方法首先利用可適應性門檻值偵測出子宮頸影像的細胞質輪廓，接著使用最大灰階顏色-梯度差異法描繪出子宮頸影像中細胞核的輪廓。 透過網路傳送資料至他人或醫學影像資訊至護理專業人員、醫療供應商、以及醫療組織，已經變成一種普遍管道。然而，非法人士透過公開的網路頻道容易擷取、複製或者竄改資料。可逆影像隱藏技術是一種將秘密資訊藏入負載影像當中，藉以保護秘密資訊被非法攻擊者所擷取。此外，當秘密資訊被取出時，該技術可以將負載影像完全恢復。本論文提出一個植基於高頻的高容量可逆影像隱藏法。此方法，將秘密資訊隱藏至Harr小波轉換後的高頻頻帶係數值中。 醫學影像中，有感興趣區域記綠醫學影像中重要的資訊，故必須無失真的將其儲存。因此，本論文提出一植基於有感興趣區域的影像隱藏技術。該方法，利用可適應性門檻值偵測法自動切割出影像中有感興趣區域。接下來，將祕密資訊利用不可逆影像隱藏技術藏入非有感興趣區域，和利用可逆影像隱藏技術藏入有感興趣區域以增加資訊隱藏量。
並列摘要
Image segmentation can effectively segment the interested objects from the image, and it often was used in pattern reorganization and medical image processing etc. Otsu’s thresholding (OTM) method is one of widely used image segmentation methods. However, OTM cannot successfully give a proper threshold when the standard deviations or the numbers of data in different classes are quite different from each other. In this thesis, “adaptable threshold detector” (ATD) is proposed to overcome the drawbacks of OTM. The ATD minimizes “within-class standard deviation” (WCSD) as the criterion, which considers the standard deviation of group, the quantity of data, and the group interval within a group to be factors in deciding the optimal thresholds. The cervical cancer is one of women’s common diseases and its incidence and mortality rates are ranked prior top in the woman’s common diseases. In order to effectively improve the accuracy and reduce the cost of image segmentation, this thesis proposes a nucleus and cytoplasm contour detector for cervical smear image, which is called “nucleus and cytoplasm contour” (NCC) detector. First, the NCC detector adopts ATD to detect the contour of cytoplasm on a cervical smear image. After that, the NCC detector employs the maximal gray-level-gradient-difference method to extract the contour of nucleus from the extracted cytoplasm region. Transmitting data to people or medical image among health care professionals, providers, and organizations has become popular via the Internet. However, the illegal attackers or hackers can easily grab, duplicate, or revise the data on the Internet. The reversible image hiding method can embed the secret data into cover image for protecting the secret data that be stolen by the illegal attacker. However, reversible image hiding method can recover the original cover image without any distortion while extracting the secret data. In the thesis, a high payload frequency-based reversible image hiding method is proposed. In the proposed method, the secret data are embedded into the coefficients in a high-frequency band in frequency domain. In a medical image, “region of interest” (ROI) is a region which contains important information and must be stored without any distortion. This thesis hence proposes an ROI-based image hiding method. In this method, the ATD is applied to automatically segment ROI. Next, the secret data embeds in non-ROI by an irreversible image hiding method and in ROIs by a reversible image hiding method to increase embedding capacity.
參考文獻
延伸閱讀
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