(34.237.124.210) 您好!臺灣時間:2021/02/25 19:29
字體大小: 字級放大   字級縮小   預設字形  
回查詢結果

詳目顯示:::

我願授權國圖
: 
twitterline
研究生:劉文山
研究生(外文):Wen-Shan Liu
論文名稱:放射治療照野片的影像增強與客觀評估
論文名稱(外文):The Image Enhancement and Objective Evaluation of Portal Film Used in Radiotherapy
指導教授:鄭國順鄭國順引用關係
指導教授(外文):Kuo-shang Chang
學位類別:碩士
校院名稱:國立成功大學
系所名稱:醫學工程研究所
學門:工程學門
學類:綜合工程學類
論文種類:學術論文
論文出版年:2000
畢業學年度:87
語文別:英文
論文頁數:36
中文關鍵詞:放射治療照野片
相關次數:
  • 被引用被引用:0
  • 點閱點閱:141
  • 評分評分:系統版面圖檔系統版面圖檔系統版面圖檔系統版面圖檔系統版面圖檔
  • 下載下載:0
  • 收藏至我的研究室書目清單書目收藏:0
研究目的:改善照野片的影像品質,以使臨床應用時更容易辨識照野片中的物體。同時也要發展一套系統,作為客觀性評估不同的影像增強方法。
簡介:一般而言,大多數學者都同意在放射治療過程中拍攝照野片,仍然是最主要的校正和確保幾何學上準確性的步驟。很不幸的是,因為照野片的影像品質不佳而使肉眼直接閱片是非常困難的。我們相信要解決此問題最方便的方式就是應用數位影像技術來增強照野片的影像品質。
材料與方法:照野片的材料是Konica MG X光片,此片子再置入Kodak X-Omatic "PORTAL VERIFICATION" 片夾。此片夾放在細微對比假體的下方,以直線加速器產生的六百萬電子伏特X光大約7MU單位來照射。當片子顯像出來後,再以掃瞄器數位化成為800  686 畫素(8-bit灰階解析度)的數位影像。本研究所採用的影像增強方法包括有灰階值柱狀圖平均法(histogram equalization),限制對比適應化灰階值柱狀圖平均法(contrast-limited adaptive histogram equalization, CLAHE),頻率域高斯濾波器加上限制對比適應化灰階值柱狀圖平均法(frequency Gaussian filter plus contrast-limited adaptive histogram equalization),以及複雜方法(頻率域高斯濾波器,柱狀圖平均法,空間域高斯濾波器,及適應化灰階值柱狀圖平均法)等四方式。客觀評估系統是跟據統計學上t檢定的方法。此方法比較前景與背景的畫素灰階值有無統計學上的差異。前景畫素的定義是假體上圓孔所構成的畫素群,背景畫素的定義是包圍此圓孔所構成的正方畫素群(除去此圓孔所構成的畫素)。統計學上有意義(視同可辨識)的分割值為5.0。
結果:主觀判斷上,四種影像增強方法的影像均優於原始的照野影像。原始影像、灰階值柱狀圖平均法、限制對比適應化灰階值柱狀圖平均法、頻率域高斯濾波器加上限制對比適應化灰階值柱狀圖平均法、與複雜方法的圓孔辨識率分別為23.2%、21.4%、25.0%、51.8%、以及42.8%。
結論:包括頻率域高斯濾波器加上限制對比適應化柱狀圖平均法與複雜方法等兩種影像方式增強後的的影像,是明顯優於原始的影像。T檢定是一種有效的客觀評估方法,可用以判斷不同影像增強方式的優劣。

Purpose: To improve the image quality of portal films in order to make the interpretation more easily. We also aim to develop a system for evaluation of various enhancement methods objectively.
Introduction: It is generally admitted that took a portal film remains the most important procedures of assuring geometric accuracy during radiotherapy. Unfortunately, it is difficult to interpret a portal film due to the poor image quality of these films. The most convenient method is to apply digital processing technique in order to improve quality of portal films.
Material and Methods: This study used Konica MG x-rays films and Kodak X-Omatic "PORTAL VERIFICATION" cassette as portal film preparation. A contrast-detail phantom was put ahead of above cassette and exposed with 6-MV x-rays at 7 MU. After film development, these portal films were digitized with scanner into a 800  686 pixels with 8-bit grayscale images. The enhancement methods in this study included histogram equalization, contrast-limited adaptive histogram equalization (CLAHE), frequency Gaussian filter plus contrast-limited adaptive histogram equalization (CLAHE), and complex methods (frequency Gaussian filter, spatial histogram equalization, spatial Gaussian filter, and AHE in series) four methods. The objective evaluation system was based on t-test statistical analysis. This method compared the statistical difference of grayscales compositions between foreground and background groups of pixels. The foreground group was defined as the pixels of the holes on phantom and the background group was defined as the pixels of the square surrounding these testing holes. The statistical cut-off level is defined as 5.0.
Results: The subjective image qualities of enhanced images, including all above four methods, were superior to the original image. The ratio of successful identification of holes on phantom for original, HE, CLAHE, frequency Gaussian filter plus CLAHE, and complex method were 23.2%, 21.4%, 25.0%, 51.8%, and 42.8%, respectively.
Conclusion: The enhancement methods including CLAHE with frequency Gaussian filtering and complex enhancement methods are obviously better than the original image. The t-test method is an effective way for objective evaluation of the enhancement results.

CONTENTS
AcknowledgementI
Abstract (Chinese)II
Abstract (English) III
ContentsIV
Contents of FiguresVI
Contents of TablesVII
CHAPTER ONEINTRODUCTION1
1.1Motivation and Purpose1
1.2Literatures Review2
1.3The Principle of Radiotherapy6
1.3.1Biological Consideration6
1.3.2Physical Consideration9
CHAPTER TWOENHANCEMENT OF PORTAL IMAGE11
2.1Introduction11
2.2Image acquisition14
2.3 Enhancement in Frequency Domain17
CHAPTER THREEOBJECTIVE METHOD FOR EVALUATION 20
OF PORTAL IMAGE
3.1 Phantom Selection and Construction20
3.2Objective Evaluation Method22
CHAPTER FOURRESULTS AND DISCUSSION25
4.1Results25
4.2Discussion30
CHAPTER FIVECONCLUSION AND FUTURE ASPECT31
REFERENCE32
自傳36

REFERENCES
1. Motz and Danos: Image information content and patient
exposure. Med. Phys. 5, 8-22, 1978
2. Boyer AL: A review of electronic portal imaging devices.
Med. Phys. 19(1):1-16, 1992
3. Leong J: “A digital image processing system for high energy
x-ray portal images.” Phys. Med. Biol. 29(12): 1527-1535,
1984.
4. Rosenman J, Roe CA, Cromartie R, Muller KE, and Pizer SM:
Portal film enhancement: technique and clinical utility.
Int. J. Radiat. Oncol. Biol. Phys. V25 (2): 333-338, 1993.
5. Pizer SM, Amburn EP, and Austin JD et al: Adaptive histogram
equalization and its variations. Comp. Vision, Graph. Image
Proc. 39:355-368, 1987.
6. Hummel RA: Image enhancement by histogram transformation.
Comput. Graphics Image Process. 6: 184-195, 1977.
7. Perona P, Malik J: Scale space and edge detection using
anisotropic diffusion. IEEE Trans PAMI 12: 629-639; 1990.
8. Kreuder F, Schreiber B, Kausch C, and Dossel O. A structure-
based method for on-line matching of portal images for an
optimal patient set-up in radiotherapy. Philips J Res. 51
(2): 317-337; 1998.
9. Rajapakshe R and Shalev S: Noise analysis in real-time
portal imaging. I. Quantization noise. Med. Phys. 21(8):
1263-1268; 1994.
10. Lutz WR and Bjarngard BE: A test object for evaluation of
portal films. Int. J. Radiat. Oncol. Biol. Phys. 11(3): 631-
634, 1985.
11. Dong L and Boyer AL: An objective method for evaluating
electronic portal imaging devices. Med. Phys. 21(6): 755-
760; 1994.
12. Quastler H: The nature of intestinal radiation death.
Radiat. Res. 4: 303; 1956.
13. Hall EJ and Cox JD. Physical and Biologic Basis of
Radiation Therapy. In: Cox JD ed. Moss’ Radiation Oncology,
rationale, technique, and results. Mosby-Year Book Inc.
1994: 13-17.
14. Ellis F.: Dose time and fractionation; a clinical
hypothesis. Clin. Radio. 41: 450-466; 1969.
15. Strandqvist M.: Studien uber die kumulative Wirkung der
Rontgenstrahlen bei Fraktionierung. Acta Radiologica. 55
(Suppl.): 1-300; 1944.
16. Orton CG and Ellis F.: A simplification in the use of the
NSD concept in practical radiotherapy. British J Radio. 46:
529-537; 1973.
17. Douglas BG and Fowler JF. : The effect of multiple small
doses of X-rays on skin reactions in the mouse and a basic
interpretation. Radia. Research. 96: 603-610; 1976.
18. Perez CA and Brady LW. Overview. In: Perez CA and Brady LW
ed. Principles and practice of radiation oncology. J.B.
Lippincott Company, 1992: 10-11.
19. American Association of Physicists in Medicine (AAPM).
Physical Aspects of Quality Assurance in Radiation Therapy,
Report 13. AAPM, Now York, 1984.
20. Khan FM. Interactions of X and  Radiations. In: Khan FM.
The physics of radiation therapy. Williams and Wilkins.
1984: 74-77; 153-155.
21. Siedband MP. Medical imaging systems. In: Webster JG ed.
Medical Instrumentation, application and design. John Wiley
& Sons Inc. 1995: 641-644.
22. Gonzalez RC. Image enhancement. In: Gonzalez RC ed. Digital
Image Processing. Addison-Wesley Publishing Company, Inc.
1992: 161:249.
23. Meertens H.: Digital processing of high-energy photon beam
images. Med. Phys. 12(1): 111-113; 1984.
24. 楊志良. 等距變項的統計. 楊志良著. 生物統計學新論. 增修版. 巨
流圖書公司. 1987: 111-137.
25. Abildgaard A and Notthellen JA: Increasing contrast when
viewing radiographic images. Radiology 185(2):475-8; 1992.
26. Droege RT, Bjarngard BE: Influence of metal screens on
contrast in megavoltage x-ray imaging. Med Phys 6(6):487-93;
1979.

QRCODE
 
 
 
 
 
                                                                                                                                                                                                                                                                                                                                                                                                               
第一頁 上一頁 下一頁 最後一頁 top
系統版面圖檔 系統版面圖檔