Temporal-spatial Pulse Signals Detection

The pulse is an important human physiological process, which can affect the whole body, and originates from the heart. As an important basis for the evaluation of health and the diagnosis of disease for the body, the pulse contains a plethora of physiological information, and its value cannot be replaced by other physiological signals. Owing to the advantage of easy detection, the pulse signal of the radial artery has always been a hot academic research topic. Although the traditional method used detects the time domain pulse signal, this way we can only obtain limited information. With the expansion of research and innovation on traditional pulse signals, temporal-spatial pulse signals have drawn increasing public at tention. The temporal-spatial pulse signal contains not only time-domain characteristics, but also physiological information on the elasticity and compliance of the artery, and blood flow pattern. In a word, the temporal-spatial pulse signal has broad research prospects and great research value. The main contents of this thesis are composed of four parts, and the main results of this thesis are as following:(1) A detection system for temporal-spatial pulse signals based on a flexible airbag probe was developed using binocular stereo vision measurements. The detection system was generally a leveraged mechanical structure with the ability of pneumatic regulation balance. The contact pressure between the probe and the wrist can be regulated through controlling the internal pressure of the small cylinder. The bottom of the probe, which comes in contact with the wrist, is a nitrile film, with properties similar to finger pulp. At the time of the detection, the contact film undergoes periodic deformation with the change of the pulse, and this deformation contains temporal-spatial pulse signals.(2) The detection method for temporal-spatial pulse signals is divided into four steps. First, the Zhang Zheng-you method is used for calibration of the camera system. Second, the intersection points of the structural lines printed on the contact films are used as identification points in binocular stereo vision measurements, and a new identification points’ extraction method is proposed based on image segmentation and ridge line fitting. The experimental results show that the proposed method possesses high accuracy, and the intersection point obtained by this method is located in the centre of the intersection area of the grid line. Thirdly, a matrix data structure is proposed, and the fast matching of the intersection point of right-and-left images can be realized using the matrices’ subscripts. Finally, the 3D coordinates of the intersection points of the grid lines can be calculated based on the principle of binocular stereo vision, and the 3D pulse signals can then be acquired by surface fitting on these sets of spatial points.(3) The research was based on the finite element model of radial artery pulses under the action of the probe. This finite element model include s the geometric model, material model, boundary conditions, load, analysis step and unit partition. According to medical image data and samples, the structure of the wrist’s anatomy was simplified reasonably, the geometric model of the wrist’s anatomy was set up, and the geometric model of the probe was built at a realistic size. The research results of Holzapfel and Haut were employed as the material model of blood vessel walls and cutaneous soft-tissue. A tensile test was conducted for the contact film, the results show that a second order Mooney-Rivlin hyperelastic material model can be adopted to express the mechanical properties of the contact membrane. The loading of the model included blood pressure, contact pressure and the internal pressure of pr obe. The deformation regularity of the contact film was studied under the combined action of the three loads. The model was verified and optimized using a high precision laser displacement sensor; the simulation results and binocular stereo vision measure ment results matched each other very well.(4) Based on the results of finite element simulation, the research showed that the bottom of the contact film is almost level, but there is a tiny hump at the centre of the film, and the area of hump was of near ly elliptical shape. This area is called the key area. The geometrical features of the key area are closely related to the intensity of pulse. A more intense pulse led to a larger aspect ratio of the key area, and a larger curvature ratio of central point of the key area, which indicated that the global geometrical features of the key area can be used instead of the local geometrical features of the central point for describing temporal-spatial pulse signals to some extent. We formulated a non-linear relationship between the amplitude at the central point on the contact film and blood pressure, contact pressure, internal pressure of probe, and the coefficients of the relationship were obtained by multivariate regression and genetic algorithms. Then, the ma thematical models for measurement of continuous blood pressure were proposed. The temporal-spatial pulse signals follow similar principles with the finger sensation of TCM pulse palpation, so seven quantified indicators of the pulse condition based on the temporal-spatial pulse signals were presented. These indicators serve as the effective tools for research on the objectivity of pulse diagnosis.