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Digital Subtraction Bowel Cleansing for CT Colonography Using

Morphological and Linear Filtration Methods

作者 : Michael E. Zalis*, James Perumpillichira,

Peter F. Hahn

出處 : IEEE TRANSACTIONS ON MEDICAL IMAGING

VOL. 23, NO. 11, NOVEMBER 2004 pp.1335-1343學生 :林上智指導老師 :張顧耀

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Outline

Introduction Methods Experiment Conclusions

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Introduction(1/3) First description in 1994

Computed Tomography Colonography What is CTC?

Noninvasive Consist of Low X ray does CT Preparation

Cleansing colon Air insufflation

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Introduction(3/3) Traditional

Patients undergo a rigorous purgation cleansing of the colon

Feeling Discomfort and inconvenience

Digital Subtraction Bowel Cleansing (DSBC) Not require to

take any bowel cathartic change eating habits

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Hounsfield Unit(1/2) Definition

X Ray attenuation unit used in CT Scan interpretation

Characterizes the relative density of a substance

Each pixel is assigned a value between -1k to 1k

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Hounsfield Unit(2/2) Substance densities in Hounsfield Unit

s Air: -1000 Fat: -50 Water: 0 Soft tissue such as muscle: +40 Calculus: +100 to +400 Bone: +1000

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Outline

Introduction Methods Experiment Conclusions

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Threshold

來源 : 灰階圖片 作法 : 影像依其灰階予以分群處理，灰階分

劃將影像分成兩種灰階值 , 設定 >= , 保留點 , 設成 1 < , 移除點 , 設成 0

目的 : 處理的主體和不需要存在的背景分離 ( 雜訊 )

圖形邊緣處會有明顯不連續的現象

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Artifact

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Morphology

Dilation

Erosion

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Artifact

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Outline

Introduction Methods Experiment Conclusions

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Phantom

Colon phantom specifically designed to resemble the human

colon in terms of CT density colon contour

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Exam

The approach is Use DSBC ,dilation, detection algorithm CT

Range From

Soft tissue of the colon wall To

Colon lumen

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Exam 1

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Exam 1

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Exam 2

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Exam 2

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Exam 3

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Exam 3

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Outline

Introduction Method Experiment Conclusions

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Conclusion

DSBC offers the possibility of improving patient comfort for colon.

Compared to traditionally cleansed datasets in human subjects ,readers rated electronically cleansed exams favorably.