Biomedical subjects

Yan Kang

Publications and source records attributed to Yan Kang.

3 recordsLinked to original sources

PubMed2004

Interactive 3D editing tools for image segmentation.

Segmentation is an important part of image processing, which often has a large impact on quantitative image analysis results. Fully automated operator independent segmentation procedures that successfully work in a population with a larger biological variation are extremely difficult to design and usually some kind of operator intervention is required, at least in pathological cases. We developed a variety of 3D editing tools that can be used to correct or improve results of initial automatic segmentation procedures. Specifically we will discuss and show examples for three types of editing tools that we termed: hole-filling (tool 1), point-bridging (tool 2), and surface-dragging (tool 3). Each tool comes in a number of flavors, all of which are implemented in a truly 3D manner. We describe the principles, evaluate efficiency and flexibility, and discuss advantages and disadvantages of each tool. We further demonstrate the superiority of the 3D approach over the time-consuming slice-by-slice editing of 3D datasets, which is still widely used in medical image processing today. We conclude that performance criteria for automatic segmentation algorithms may be eased significantly by including 3D editing tools early in the design process.

Algorithms↗

PubMed2003

A new accurate and precise 3-D segmentation method for skeletal structures in volumetric CT data.

We developed a highly automated three-dimensionally based method for the segmentation of bone in volumetric computed tomography (CT) datasets. The multistep approach starts with three-dimensional (3-D) region-growing using local adaptive thresholds followed by procedures to correct for remaining boundary discontinuities and a subsequent anatomically oriented boundary adjustment using local values of cortical bone density. We describe the details of our approach and show applications in the proximal femur, the knee, and the skull. The accuracy of the determination of geometrical parameters was analyzed using CT scans of the semi-anthropomorphic European spine phantom. Depending on the settings of the segmentation parameters cortical thickness could be determined with an accuracy corresponding to the side length of 1 to 2.5 voxels. The impact of noise on the segmentation was investigated by artificially adding noise to the CT data. An increase in noise by factors of two and five changed cortical thickness corresponding to the side length of one voxel. Intraoperator and interoperator precision was analyzed by repeated analysis of nine pelvic CT scans. Precision errors were smaller than 1% for trabecular and total volumes and smaller than 2% for cortical thickness. Intraoperator and interoperator precision errors were not significantly different. Our segmentation approach shows: 1) high accuracy and precision and is 2) robust to noise, 3) insensitive to user-defined thresholds, 4) highly automated and fast, and 5) easy to initialize.

Algorithms↗

PubMed2002

[Therapeutic effect of high-density lipoprotein of human plasma on rat endotoxemia].

OBJECTIVE: To investigate the therapeutic effect of high-density lipoprotein (HDL) of human plasma on rat endotoxemia. METHODS: Rats were divided into 2 groups randomly, the treated group received bolus intravenous endotoxin (500 EU/kg), then followed by a bolus HDL (75 mg/kg) intravenously as their blood pressure decreased obviously. The control group just received bolus intravenously endotoxin (500 EU/kg) without HDL. Blood pressure, survival time, the concentration of TNF and the levels of endotoxin in plasma were determined using radioimmunoassay and limulus lysate test. RESULTS: The decrease of blood pressure was obviously attenuated (P < 0.01), the survival time was significantly increased (P < 0.01) and the concentration of plasma TNF was decreased (P < 0.05) in the treated group, compared with those in the control group. The levels of endotoxin were of no significant difference between the two groups (P > 0.05). CONCLUSION: HDL of human plasma has obvious therapeutic effect on rat endotoxemia it could enhance the resistance of rats to endotoxemia, and the mechanism therein may be related to the inhibition of the release of TNF.

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