Active contour models for knee cartilage and meniscus ultrasound image segmentation / Amir Faisal
Quantification of the cartilage degeneration as well as the meniscus degeneration and displacement requires segmentation of various parts of the knee joints in the twodimensional ultrasound images in order to provide a direct measurement of the cartilage thickness and the meniscus area and positi...
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Format: | Thesis |
Published: |
2017
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Online Access: | http://studentsrepo.um.edu.my/7900/2/All.pdf http://studentsrepo.um.edu.my/7900/4/faisal.pdf http://studentsrepo.um.edu.my/7900/ |
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Summary: | Quantification of the cartilage degeneration as well as the meniscus degeneration
and displacement requires segmentation of various parts of the knee joints in the twodimensional
ultrasound images in order to provide a direct measurement of the cartilage
thickness and the meniscus area and position, respectively. The goal in the knee cartilage
ultrasound image segmentation is to locate the boundaries of a monotonous hypoechoic
band between hyperechoic lines of the soft tissue-cartilage interface and of the cartilagebone
interface. Hence, the true thickness between the two interfaces can be computed
based on the segmented images. Meanwhile, the goal in segmenting the meniscus ultrasound
image is to locate the femoral condyle, the meniscus, and the tibial plateau simultaneously.
This thesis presents active contour models for knee cartilage and meniscus
ultrasound image segmentation. Cartilage boundary segmentation using locally statistical
level setmethod (LSLSM) and cartilage thickness estimation using the normal distance are
presented. In addition, multiple active contours using scalable local regional information
on expandable kernel (MLREK) have been proposed to capture multiple, separate objects
of the femoral condyle, the meniscus, and the tibial plateau. Segmentation performance
is then validated using Dice coefficient and Hausdorff distance metrics. Segmentation
results of the presented methods are compared to the existing active contour methods in
the attempt of segmenting the knee cartilage andmeniscus in the ultrasound images, which
show an improvement on the segmentation performance offered by the proposed methods.
The choice of various parameters in MLREK in response to the segmentation outcome
is then investigated. A demonstration on how to choose the threshold value to adapt the
kernel size in order to successfully reach the boundary concavity is given. The ability
of multiple contours in preventing merging and overlapping in the shared boundaries of separate regions is shown. A flexibility in setting each contour with different parameter
values for multiple structure segmentation is also illustrated. MLREK has shown to perform
multiple object segmentation all at once in an ultrasound image. Application of the
presented methods to segment a set of the knee cartilage and meniscus ultrasound images
illustrates a good and consistent segmentation performance. The reproducibility of the
ultrasound-based cartilage thicknessmeasurements using intraclass correlation coefficient
and agreement between pairs of the measurements by the normal distance and the manual
measurement using Bland-Altman analysis are determined. The cartilage segmentation
possiblewith LSLSMhas allowed the obtained segmentation results to be used formaking
the cartilage thickness computation. The robustness of themethods described against various
thickness of the cartilage and various shapes and areas of themultiple objects indicates
a potential of the methods to be applied for the assessment of the cartilage degeneration
as well as the meniscus degeneration and displacement. The cartilage degeneration and
the meniscus degeneration and displacement typically seen as changes in the cartilage
thickness and the meniscus area and position can be quantified over time by comparing
the cartilage thickness and the meniscus area and position at a certain time interval. |
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