Catálogo de publicaciones - libros

In this paper, important virtual medicine research related to visible human data sets would be outlined. In particular, latest visible human related research carried out in the Visualization, Virtual Reality and Imaging Research Centre of the Chinese University of Hong Kong (CUHK) will be discussed in detail, while related applications such as virtual acupuncture, virtual anatomy, and virtual orthopedics training briefly shaped our current and future research and development on visible human-related virtual medicine. Our latest advancement in segmentation, imaging, user-interface design as well as surgical education and training will be discussed.

It is significant to detect and analyze its mechanical property for the design of the artificial knee joint, especially for the design of an osseointegrated prosthetic limb.Since normal six-component force sensors are unsuitable for detecting the mechanical property of the lower limb prosthesis, a novel sensor is presented in this paper. It can be easily fixed between the artificial knee joint and the stump of the patient to detect the load condition during walking. The mathematic model of the sensor is analyzed, and strength check, stiffness design and the linearity of the sensor were studied with FEA. Finally, the Transmission Matrix is calculated. This kind of sensor can help us to get academic foundations for the designment and the evaluation of the limb prosthesis and its performance.

In order to access the effects of shoe-heel height on knee muscle activity for transtibial amputees during standing, five male subjects volunteered for the study. Three pairs of shoes with zero, 20 mm and 40 mm heel height were used during normal standing. Surface EMG of 10 muscles was recorded by the Noraxon surface EMG collection system. EMG-MAV of the medial and lateral gastrocnemius of the sound leg almost change double with increase in heel height from zero to 40 mm, and EMG-MAV of the rectus fomris, vastus lateralis and vastus medialis of prosthetic side became larger to different extent. The finding in this paper suggested that an alignment change was necessary to accommodate the heel height change and the prostheses users should be cautious to choose shoes in daily life.

Coronary artery diseases are usually revealed using X-ray angiographies. Such images are complex to analyze because they provide a 2D projection of a 3D object. Medical diagnosis suffers from inter- and intra-clinician variability. Therefore, reliable software for the 3D modeling of the coronary tree is strongly desired. This paper focuses on the automatic 3D modeling of the vessels from X-ray angiography. Our approach is based on a 3D model of standard vessels. The model is projected because it is difficult to suitably transform standard into individual vessels on 3D space. The modeling process is carried out in two steps. The first step consists of selecting automatically two sets of corresponding control points between standard and individual vessels. In the second step, 3D model of individual vessels is performed by warping with corresponding control points. Accurate descriptions of 3D model would be useful for quantitative diagnosis of atherosclerosis, for surgical or treatment planning, for monitoring disease progress or remission, and for comparing efficacies of treatments.

Coronary Angiography, Control point, Image Transformation, 3D Modeling.

The direct anchorage of a lower-limb prosthesis to the bone has been shown to be an excellent alternative for amputees experiencing complications in using a conventional prosthetic socket. After surgical implantation, amputees have to go through a weight bearing exercise program to prepare the bone to tolerate forces and promote bone-remodeling. Currently, the load magnitude prescribed by the clinician is measured by a weight scale which reports only the axial force in the limb. Previous study using a load transducer revealed that in addition to the axial force there were other forces and moments. This study develops a FE model and utilizes our load data to investigate the stress distribution at the bone-implant interface. The model shows that the stress distribution could be highly non-uniform during the exercise. Bone-implant interface stress has certain implications in pain adaptation and bone-remodeling, and a good understanding of it can assist in future attempts to refine and shorten the period of rehabilitation exercise.

Atrial fibrillation (AF) is one of the most common cardiac diseases that cause morbidity and mortality. One of the most frequently used clinical treatments of AF is to use a large and brief external electrical shock to reset atrial tissue from a disordered fibrillation state to a quiescent state, then the pacemaker of the heart resumes its control of atrial excitation rhythm and thus a defibrillation is achieved. Though widely used in practice, the mechanisms underlying the success of an electrical shock in defibrillation is incompletely understood. In this study, we developed a computer model of human atrial tissue to investigate the actions of an external electrical shock on atrial excitations. Using the model, we computed the defibrillation threshold of the human atrium. We found that due to the supernormal excitability of human atrium, the computed successful defibrillation threshold is much less than the excitation threshold of human atrium in resting state. This study provides some new insights to understand the mechanisms underlying AF defibrillation.

In medical imaging, many applications require visualization and analysis of three-dimensional (3D) objects. Visualization is the process of exploring, transforming, and view data as images to gain understanding and insight into the data, which requires fast interactive speed and high image quality. In this paper, we describe the key techniques in medical image visualization. In order to improve ray casting rendering speed, a synthetically accelerated algorithm is proposed. Firstly, rendering algorithms are fully studied and compared. Secondly, proximity clouds algorithm has been selected and extended to continuous ray casting. Finally, the accelerated algorithm based on ray coherence has been realized. The experimental results on 3D medical image reconstruction are given, which show the medical image visualization technology has provided a powerful technology base for computer-aided diagnosis, virtual surgery and e-learning in medicine field.

With growth of sequenced genome, a number of algorithms for gene identification were created. These algorithms use fixed gene features which are chosen based on observation or experience. These features may not be major features of a genome. In this paper, we illustrate several candidate features and propose a dynamic feature choosing algorithm to determine the major features. We describe nucleotide sequence by feature vector and use Discriminant analysis to them to make decision on coding/non-coding. To test the algorithm, we apply the algorithm to the S.cerevisiae genome and achieve accuracy of above 98%.

We describe the latest development of a computer-based virtual reality environment for training interventional neuroradiology procedures. The system, Neuroradiology Catheterization Simulator), includes extraction and construction of a vascular model from different imaging modalities that represents the anatomy of patient in a computationally efficient manner, and a finite element method (FEM) based physical model that simulates the interaction between the devices and neuro-vasculature. A realistic visual interface with multiple, synchronized windows and plenty of video control functions are developed. The latest version is also equipped with haptic feedback module that gives the sense of touch in real-time, and customizable vascular model so that trainer can understand the importance of vascular variations and practice. According to the validation in several clinical centers, 70%-75% of training features have been realized which makes the system well suitable for training of interventional neuroradiologists.

Computer Simulations of cardiac wave propagation may be used as a tool towards understanding the mechanisms of cardiac conduction, the nature of various heart diseases, as well as the effect of drugs in cardiac function. Such simulations depend on the ionuc current model adopted, and various such models have been proposed. The exact propagation wavefront thus depends on the ionic model and the tissue properties, being homogeneous or heterogeneous. The latter case, which corresponds to infracted cardiac tissue, is the focus in this work. The ionic current properties and the sodium kinetics on a two-dimensional grid where wavefront rotations around barriers at bifurcation sites take place, are examined in detail and differences in propagation characteristics elicited by using fast or slow fast inward current kinetics such as can be found in the Beeler-Reuter, Luo-Rudy and Ebihara-Johnson models are elaborated.