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Biomedical subjects

Ya-zhu Chen

Publications and source records attributed to Ya-zhu Chen.

5 recordsLinked to original sources

SVM for density estimation and application to medical image segmentation.

A method of medical image segmentation based on support vector machine (SVM) for density estimation is presented. We used this estimator to construct a prior model of the image intensity and curvature profile of the structure from training images. When segmenting a novel image similar to the training images, the technique of narrow level set method is used. The higher dimensional surface evolution metric is defined by the prior model instead of by energy minimization function. This method offers several advantages. First, SVM for density estimation is consistent and its solution is sparse. Second, compared to the traditional level set methods, this method incorporates shape information on the object to be segmented into the segmentation process. Segmentation results are demonstrated on synthetic images, MR images and ultrasonic images.

Humans↗

Correlation dimension and the largest Lyapunov exponent characterization of RR interval.

OBJECTIVE: To search for evidence of deterministic chaos and to characterise it quantitatively in RR intervals of different subjects. METHOD: An improved Grassberger-Procaccia (GP) algorithm was proposed for computing the correlation dimensions (CD) of RR intervals in ten healthy young men, ten healthy old men, and ten atrial fibrillation (AF) patients. Analysis was also performed by calculating the largest Lyapunov exponents. RESULT: It was found that the cardiac systems of healthy young men are some 7-8 dimensional complex dynamic systems, while those of healthy old men are 6-6.5 dimensional, and those of AF patients had dimensions of about 4-4.5. The young men had the largest Lyapunov exponents of about 0.019-0.23, the largest Lyapunov exponents of old men was 0.12-0.16, and that of AF patients was 0.083-0.123. CONCLUSION: The above results demonstrated that the RR intervals could be chaotic. The decrease in the CDs and the largest Lyapunov exponents as we move from the young to the old and then to the AF patients reflects the loss of complexity as the heart becomes less healthy. Therefore, correlation dimension and the largest Lyapunov exponent could be used as some novel non-invasive analysis tools for clinical cardiology.

Adult↗

[Development of the combined tumor therapeutic equipment].

This paper describes the development of the combined tumor therapeutic equipment based on the theory of 1 + 1 = 3 or 1 + 1 > 3 tumor combined treatment synergism. It has become a promising and valuable method dealing with cancer tumors for its good adaptability, better effectiveness and convenience. The therapeutic equipment is combined with PC and MS windows operation system, and adopts intellectual temperature control device, which realizes homogeneous and smooth heating to intracavity tumor focus and automatic processing and statistical management of all case data. The equipment works stably and is of great value in clinical applications.

Algorithms↗

[The development of 3D US system for treating target localization in focused ultrasound surgery].

Focused Ultrasound Surgery (FUS) is a promising minimally invasive technique in tissue ablation. Because of the high intensity at the ultrasound focus, a precise 3D-localization system is required to determine the site of the treating target in order to increase the efficiency and security of FUS. This paper represents a three dimensional ultrasound (3D US) localization system developed and its workflow. The system is mainly composed of imaging and image processing system, movement device and its controlling circuits, and position feedback device. The system has a maximum scan range of +/- 30 degrees with a resolution of 8 levels from 0.54' to 0.36 degrees. For a spherical shape like target, in theory, the maximum diameter is 160 mm the system can treat. The system can be used to localize precisely the treatment targets with general sizes in the suitable parts of the body in FUS.

Algorithms↗

[Development of RF ablation therapeutic instrument based on improved PID algorithm].

The development of a RF ablation therapeutic instrument based on improved PID algorithm is introduced here. It is based on the theory of radio frequency local destruction. By adopting the improved PID temperature control algorithm, the problem of the temperature control precision reduction due to tumor tissue characteristic changing by heating has been solved, thus ensuring homogeneous and smooth radio frequency heating to tumor foci. Experiments demonstrate that the new algorithm has strong adaptability and anti-disturbance capability, the equipment works stably and reliably, and can control therapeutic temperature precisely (+/- 2 degrees C), which indicates a good clinical application value.

Algorithms↗