Two simulated phosphene models were proposed in this paper. Model I was based on uniform or Gaussian round or square spots which arranged in rectangle or hexagonal arrays. Model II was based on partial clinical experiment data of one optic nerve prosthesis research. Numbers, letters and Chinese characters were pixelated by these models. The feasibility of using Model II to perform simulation experiments was discussed and confirmed.

The evaluation of phosphene is one of the most important things after the electrode array's implantation. Some experiments have been used to study the basic rules on people using their tactile perception in describing the characteristics of simulated phosphenes, such as the dispersion, accuracy, and response time. In order to describe the simulated phosphenes more systematically and scientifically, an improved phosphene-positioning method using tactile board was designed in this study. Using tactile board to guide the tactile perception, the dispersion was limited to less than 6 mm, while the largest mean error was 8.1 mm, which was nearly equal to the minimal resolution of tactile board (8 mm). The response time greatly increased because of the standard processes in using tactile board. Moreover, the long-term experiment to repeat the procedure could improve and sustain the subjects' performance in good results.

The influence of complexity and minimum resolution necessary for recognition of pixelized Chinese characters (CCs) was investigated by using simulated prosthetic vision. An image-processing method was used to evaluate the complexity of CCs, which is defined as the frequency of black pixels and analyzed by black pixel statistic complexity algorithm. A total of 631 most commonly used CCs that can deliver 80% of the information in Chinese daily reading were chosen as the testing database in order to avoid the negative effect due to illegibility and incognizance. CCs in Hei font style were captured as images and pixelized as 6 x 6, 8 x 8, 10 x 10, and 12 x 12 pixel arrays with square dots. Recognition accuracy of CCs with different complexity and different numbers of pixel arrays was tested by using simulated prosthetic vision. The results indicate that both pixel array number and complexity have significant impact on pixelized reading of CCs. Recognition accuracy of pixelized CCs drops with the increase of complexity and the decrease of pixel number. More than 80% of CCs with any complexity can be recognized correctly; 10 x 10 pixel array can sufficiently provide pixelized reading of CCs for visual prosthesis. Pixelized reading of CCs with low resolution is possible only for characters with low complexity (complexity less than 0.16 for a 6 x 6 pixel array and less than 0.24 for an 8 x 8 pixel array).

In recent years, as stimulation electrodes have been implanted in the visual cortex, optic nerve, and retina to generate visual perceptions (phosphenes), the research on prosthetic vision has become a popular topic. After implantation, it is crucial to evaluate the characteristics of the stimulated phosphenes. Until now, several methods using tactile perception are proposed to describe the phosphene position, but no systematic study of the perceptional behavior has been performed. Here, an experimental study of tactile perception based on phosphene positioning was proposed using simulated prosthetic vision. Results show that the dispersion was smaller and the response time was less when phosphenes are generated in near visual field compared to the far visual field. The dispersion, the accuracy, and the response speed were better when using the visual guide. Moreover, the widely used method of using the left hand as reference and the right hand to point the phosphene may cause geographic error.

Different to conventional water-proton MRI, the signal source of optical pumping hyperpolarized noble gas (HPNG) MRI is hyperpolarized noble gas. A set of phantom was designed to evaluate the performance of HPNG MRI system. In order to keep the polarizations of HPNG, all of sections of phantom were manufactured by nonmetal materials such as methacrylic resin or glass. All interfaces of phantom which contact with hyperpolarized noble gas were coated with paraffin to reduce the spin-lattice relaxation of HPNG caused by collisions between HPNG and phantom walls. The phantom was used to establish absolutely performance standards. The magnetic resonance imaging of phantom provides information of HPNG MRI system including: image uniformity, slice position, spatial linearity, slice thickness, spatial resolution, phase related image artifacts. The phantom system includes resolution section, slice thickness section, uniformity and linearity section. All of these sections were placed inside of a rectangular box with vacuum valve.

Objective To investigate the simulation and optimization of birdcage coil in the 0.3T Permanent Magnet MRI system. Methods The Biot-Savart's law was applied, a high-pass 8-leg birdcage coil, whose resonant frequency was consistent with ~3H and ~ 129 Xe , was designed through some related calculations and simulations. IDL was used to calculate and simulate our scheme. Results The results showed the uniformity and symmetry of magnetic filed produced by the high-pass 8-leg birdcage coil in a low field. When the legs were reduced to 6 and 4, the uniformity and symmetry fell largely. Conclusion The precision of simulation was good. The uniformity and symmetry of B_1 filed would be damaged when the number of the coil legs decreased.