本論文提出了基於掌骨X光影像中骨骺/幹骺切割技術以及其對電腦化骨齡群集估測之相關研究。主要貢獻如下︰(1)基於X光片中複雜及不規則的背景及不論手掌在X光片中是否定位，提出一個全自動且有效的骨骺/幹骺特徵區域擷取方法。(2)提出一個以空間統計為基礎的distance approach adaptive two-means影像切割方法，其骨骺/幹骺區域的切割結果之準確度遠高於基於機率分佈的adaptive two-mean方法，同時亦大幅地降低了整個演算法的迭代次數及運算時間。(3)進一步地，我們考量不論是何種adaptive two-means的方法，其最終分類結果往往取決於初始分類的好壞，而初始分類又受到不同指節的特徵區域影像特性之影響。因此，為了更精進整個演算法對於的骨骺/幹骺區域切割的精準度及效率，我們針對不同指節提出兩個影像切割方法。針對遠端及中間指節，提出一個不考慮背景的影像切割方法，克服了在大部分影像切割分法如Sobel, two-means, Canny edge-detection 及 watershed中，因含背景導致所得到初始分類之精確度將嚴重影響最終切割結果的問題。針對近端指節，提出一個基於α-gamma equalization enhanced的影像切割方法，解決了在近端指節特徵區域影像中，因骨組織及軟組織之灰度階對比低而影響初始分類的問題。實驗結果顯示，上述我們提出的兩個方法，其最終得到之骨骺/幹骺區域切割的準確度均遠高於影像切割常用到之GVF的方法。(4)依據上述方法所得到的切割結果，萃取出各指節骨骺/幹骺區域之直徑比值作為特徵，提出一個基於模糊類神經網路系統之掌骨X光影像骨齡群集之估測系統，並重新定義出不同於傳統骨骼發展階段(前期及後期)的四個階段，以及建議各階段所對應的ROI處理及特徵選取方法。本系統最主要解決了以往骨齡估測必須依賴先驗知識(a priori knowledge)預先決定骨骼發展階段，據以作為選擇適當特徵項目及分類器的問題。實驗結果證明，我們提出的系統除了可以說明上述四個新定義骨骼發展階段之合理性之外，並可準確地估測掌骨X光影像之骨齡群集，使得整個電腦化骨齡估測系統更具彈性與可靠度。This dissertation is focused on the study of segmentation for epiphyseal/metaphyseal regions of interest (EMROI) and bone age cluster assessment system using fuzzy neural network (FNN) based on phalangeal image segmentation. The contributions are illustrated as follows. (1)An automated ROI extraction with normalization is proposed to automatically select ROIs no matter whether the hand position is in upright or not. (2)A distance approach adaptive two-means clustering scheme is proposed to get a more precise segmentation on ROI and greatly reduce the processing time by comparing the probability approach adaptive two-means clustering method. (3) Furthermore, the performance of any above-mentioned segmentation techniques relies on the precisian of a given initial segmentation. In general, the initial segmentation is given by random or manual choices. Thus, two modification methods for optimum reliability, robustness and computational efficiency according to the properties of phalangeal ROIs are presented. For the distal and middle phalange, an excluding background initial segmentation method is proposed to overcome the initial segmentation problem for the bony structure segmentation. Experimental results verify that using this method can provide a better initial segmentation than other methods, such as Sobel, two-means, Canny edge-detection and watershed. An α-gamma equalization enhanced image segmentation scheme for proximal phalange is given to solve the problem of poor intensity contrast between soft tissues and bony tissues. The comparative experimental results show that these two methods really promote the performance and achieve a more accurate and robust epiphyseal/metaphyseal segmentation against GVF snake. (4) A bone age cluster assessment system using fuzzy neural network (FNN) based on phalangeal image segmentation is presented. This could avoid taking an a priori knowledge for bone age stage and provide a more flexible and reliable BAA system. Experimental results reveal that the presented FNN system provides a very well ability to assign the hand radiograph to an appropriate bone age cluster. The rationality of our four new defined stages which are different from the traditional skeletal development stages (the early and later stage). Furthermore, the related feature clustering analysis for various stages is discussed to obtain an accurate quantitative evaluation of specific features for the final BAA. Finally, it can provide a more flexible and reliable BAA system.摘 要 I
Abstract II
List of Figures VI
List of Tables IX
Chapter 1 Introduction 1
1.1 Motivation 1
1.2 Review of Segmentation Methods for Epiphyseal/Metaphyseal Regions 3
1.3 Review of CABAA system 5
1.4 Dissertation Organization 7
Chapter 2 Preliminaries 8
2.1 Finding Maximum Connected Component 8
2.2 Bilinear Interpolation 9
2.3 Adaptive Lee Filter 10
2.4 Some Image Segmentation and Edge Detection Methods 11
2.5 Measure of Errors (MOE) for image Segmentation 19
2.6 Some Classification Methods 21
Chapter 3 26
Automated ROI Extraction with Normalization 26
3.1 Background Removal 27
3.2 Hand Object Extraction 28
3.3 Hand Normalization 30
3.4 Finger Normalization and EMROI Extraction 34
Chapter 4 38
Distance Approach Adaptive Two-means Clustering Scheme 38
4.1 The Image Preprocessing 39
4.2 The Distance Approach Adaptive Two-means Clustering Algorithm 41
4.3 The Comparison of Probability Approach and Distance Approach Scheme 47
4.4 Experimental Results 49
Chapter 5 57
Two Segmentation Schemes Based on the Property of Different EMROIs 57
5.1 Excluding Background Initial Segmentation Scheme 57
5.2 An α-Gamma Equalization Enhanced Image Segmentation Scheme 63
Chapter 6 74
Bone Age Cluster Assessment and Feature Clustering Analysis 74
6.1 Stage and Feature Analysis 76
6.2 The Bone Age Cluster Assessment Using the Fuzzy Neural Network 83
6.3 Performance Analysis 91
Chapter 7 96
Conclusions and Further Researches 96
7.1 Conclusions 96
7.2 Further Researches 99
Bibliography 10
