Biomedical Engineering: Applications, Basis and Communications

Quantitative positron emission tomography (PET) using statistical techniques requires: (a) a system geometric model that represents the probability of detecting an emission from each image pixel at each detector-pair, and (b) an iterative algorithm that reconstructs image as quantitative measurements of radiotracer distribution in vivo. Conventional implementations of iterative reconstruction use system geometric models based either on linear interpolation or on computing the volume of intersection of detection tubes with each voxel, but these simple models ignore many important physical system factors, like depth dependent geometric sensitivity and spatially variant detector pair resolution. In this paper, we evaluate a more accurate system geometric model that includes these physical factors. In addition, implementation variation among different iterative algorithms is another factor that limits the performance. Here, we compare performance of filtered backprojection (FBP) with the ordered subsets expectation maximization (OSEM) algorithm and a maximum a posteriori (MAP) method using a Gibbs prior with convex potential functions. Using the contrast recovery coefficient (CRC) as a performance measurement, we conducted various phantom experiments to investigate how the choices of algorithm and system matrix affect reconstruction accuracy. The results of these studies show that all of the iterative methods tested produce superior CRCs than FBP at matched background variance. And the combination of the accurate system geometric model and MAP reconstruction algorithm outperforms the other statistical methods.

In this paper, we present a noise reduction technique for hearing-aid systems. The proposed algorithm adopted adaptive beamformer with combination of subband filtering technique. The structure of conventional hearing aids is relatively simple. They amplify ambient sounds that include speech signal as well as noise. Because noise and human speech signal are amplified at the same time, hearing-aid users can't clearly hear speech signal in noisy environment. The direction of sound can be used to discriminate speech signal from noise by combining adaptive noise canceller and adaptive beamformer. We have developed a system that based on the constrained adaptive noise canceller to preserve speech signal from straight ahead and minimize background noise arriving from other directions. This system also uses subband filtering technique to reduce the requirement for computation and enhance the flexibility of the system. The performance of this system is illustrated using simulated and real-world noises. The results show that the developed system can reserve the right ahead speech signal and substantially reject noises from other directions.

During pregnancy, a woman changes obviously in body weight, body shape, and endocrine system. Those changes make the posture and gait pattern of the pregnant women different from those of the non-pregnant women. At the same time, activities of daily living become more difficult. But there was still no published paper discussing the posture and gait changes of the pregnant women in details and in a whole.

In this study, we used the optimization method to define the hip joint center of the pregnant women. The optimization method could compensate the lack of the anthropometric data of the pregnant women. Due to the variations of physiological changes in the pregnant women, it was difficulty to standardize the gait analysis of pregnant women, even in the same gestational age. The results revealed that there really was some correlation between the significant finding of gait analysis and sacroiliac pain of the pregnant women. The sacroiliac pain often occurred in the following conditions of gait analysis: (1) when the hip extension moment increased; (2) when the knee extension moment decreased; (3) when the angle of ankle plantar-flexion decreased; and (4) when the sacroiliac ajoint torsion increased. The gait analysis of the pregnant is a feasible, but complicated method for study. The data of gait analysis were also compare with questionnaires for further analysis.

The main sequence relations of saccades stated that the duration was linearly correlated to the saccadic amplitude for a wide range, whereas the peak velocity correlated exponentially to the amplitude with saturation occurred at 30°-40°. Skewness was used efficiently in delineating the asymmetry between the acceleration and deceleration phases of the saccadic velocity profiles. It can be estimated from the shape parameter obtained by applying gamma function to the velocity profile. The relationship between peak velocity and skewness was derived according to the following observations. (1) At the same target amplitude and under the similar test conditions, data from previous investigations showed that great intra- and inter-subject variation of the peak velocity and the skewness were always observed. (2) Although the velocity was substantially decreased and the duration greatly increased, accuracy was not affected with the saccadic amplitude was almost unchanged for the subjects after diazepam had been taken. (3) The duration of acceleration phase is almost unchanged for different amplitudes.

Fifteen normal subjects (range 21 to 26 years with mean of 23.6) without history of neurological disease were recruited and tested in this study. Electro-oculograph (EOG) was used for recording the eye movements with amplitudes ranging from 10° to 60°. The results show that the data were highly correlated to the derived peak velocity and skewness relation with correlation coefficient (R) as high as 0.66-0.92 for great amplitudes (>30°). This study provides an alternative method in quantitative analysis of saccadic dynamics

The available guide tools of the orientation and mobility for a blind are the cane, guide dog and electronic guide devices. A cane is easy to detect the hindrance that is in front of the user but not for the hindrance above the user waist. That's why a cane user of a blind sometimes will be hit by the upper hindrance. Guide dog is a very powerful mobility guider but expensive and the training and living care for the dogs are difficult. Hence, guide dog is not popular in many countries. The electronic devices for blind guide tools such as laser cane; sonic glasses, sonic guide etc. can only detect a single point at a time and not for a whole view. In our system, a machine vision blind guide system is proposed. A CCD grabbed the image of front view and divided the image into nine blocks. Each block is calculated to get the distance message, which is multipoint data to guide the blind by the converted voice signal.

This review focuses both on the basic formulations of bioheat equation in the living tissue and on the determination of thermal dose during thermal therapy. The temperature distributions inside the heated tissues, generally controlled by heating modalities, are obtained by solving the bioheat transfer equation. However, the major criticism for the Pennes' model focused on the assumption that the heat transfer by blood flow occurs in a non-directional, heat sink- or source-like term. Several bioheat transfer models have been introduced to compare their convective and perfusive effects in vascular tissues. The present review also elucidates thermal dose equivalence that represents the extent of thermal damage or destruction of tissue in the clinical treatment of tumor with local hyperthermia. In addition, this study uses the porous medium concept to describe the heat transfer in the living tissue with the directional effect of blood flow, and the polynomial expression of thermal dose in terms of the curve fitting of the experimental isosurvival curve data by Dewey et al. Results show that the values of factor R is a function of the heating temperature instead of the two different constants suggested by Sapareto and Dewey.