Automatic Segmentation and Detection of Joints

in X-Ray Images

Institute of Mathematics, Mechanics and Computer ScienceSouthern Federal University

Alexey Mikhaylichenko, Yana Demyanenko, Elena Grushko

AIST, 2016

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The problem

a)

⇒

b)

(a) Initial image; (b) result of contours detecting (of knee joint)

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Algorithm scheme

a)

⇒

b)

⇒

c)

⇒

⇒

d)

⇒

e)

⇒

f)

(a) Computation of edge map of image; (b) computation of top binarizationthreshold; (c) edge thinning; (d) computation of optimal binarization threshold;

(e) binarization; (f) chaining process

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Edge map

a) b) c)

(a) Sobel operator; (b) gradient vector flow field 1; (c) result of element-wisemultiplication (gamma correction applied to images)

1Xu C., Prince J. L. Snakes, Shapes, and Gradient Vector Flow

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Edge thinning

a) b)

(a) Result of applying non-maximum suppression; (b) result of binarizing withone of threshold

binarization is performed for each of thresholds

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Discontinuity points

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Chaining

Violation of condition «does not intersect already existing fragments of boundson image» (left) and example of removing a discontinuity (right)

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Chaining

Chaining algorithm for unpaired point of discontinuity

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Threshold computation

Process of threshold finding, T0 < .. < Ti < .. < Tn ≤ T

E* = max{Ei}i=0,n,T* — optimal threshold

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Comparison with Canny edge detector

a) b)

(a) Proposed method; (b) Canny edge detector with manually selectedthresholds, some of best results

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Experimental results

Results of applying the method to coronal and lateral projection of joint(success — 74%)

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Performance

Average time a single-threaded version (top); average time a multi-threadedversion (bottom)

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Minuses

a) b) c)

Problems: (a), (b) false border detection (14, 2%); (c) etc. (11, 8%)

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Conclusion

We propose an approach for automatic bone contours detection whichdoes not require homogeneity of regions. The main issues are:

I accurate edge fragments detection and elimination of discontinuitiesbetween them;

I the criteria for calculating numerical characteristics of the quality ofimage contours detection;

I the algorithm for tracing contours.

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