No abstract

No abstract

The conventional P300 Bel system for character spelling is typically composed of a paradigm that displays flashing characters and a classifier which identifies target characters. Typically a user has to type each character of a word at a time: this spelling process is slow and it can take several minutes to type an entire word. In this work, we propose a new word typing scheme by integrating a word suggestion mechanism via a dictionary search into the conventional P300-based speller. Our new P300-based word typing system consists of an initial character spelling paradigm, a smart dictionary unit to give suggestions of possible words, and the final word selection paradigm to select a word out of the suggestions. Our proposed methodology reduces typing time significantly and makes word typing more convenient. We have tested our system with four subjects and our results demonstrate an average words typing time of 1.66 minute, whereas the conventional took 2.9 minute for the same words.

Dual high and low energy images of Dual Energy X-ray Absorptiometry (DEXA) suffer from noises due to the use of weak amount of X-rays. Denoising these DEXA images could be a key process to enhance and improve a Bone Mineral Density (BMD) map which is derived from a pair of high and low energy images. This could further improve the accuracy of diagnosis of bone fractures, osteoporosis, and etc. In this paper, we present a denoising technique for dual high and low energy images of DEXA via non-local means filter (NLMF). The noise of dual DEXA images is modeled based on both source and detector noises of a DEXA system. Then, the parameters of the proposed NLMF are optimized for denoising utilizing the experimental data from uniform phantoms. The optimized NLMF is tested and verified with the DEXA images of the uniform phantoms and real human spine. The quantitative evaluation shows the improvement of Signal-to-Noise Ratio (SNR) for the high and low phantom images on the order of 30.36% and 27.02% and for the high and low real spine images on the order of 22.28% and 33.43%, respectively. Our work suggests that denoising via NLMF could be a key preprocessing process for clinical DEXA imaging.

Transcranial Direct Current Stimulation (tDCS) is considered as one of the promising techniques for noninvasive brain stimulation and brain disease therapy. In this study, we have investigated the effect of skull and white matter (WM) anisotropy on the induced electric field (EF) by tDCS in two different montages; one using a pair of clinically used rectangular pad electrodes and the other 4(cathodes)+1(anode) ring electrodes. Using a gyri-specific finite element (FE) head model, we simulated tDCS and investigated the radial and tangential components of the induced EF in terms of their distribution over the cortical surface besides the distribution of the transverse and longitudinal components within WM. The results show that the tangential component of the EF on the cortical surface seems to be the main cause of the cortical stimulation of tDCS. Also WM anisotropy seems to increase the dispersion of the transverse component of the EF that affects the dispersion of the EF magnitude within the WM region.