Biomedical Engineering: Applications, Basis and Communications

Determining the sensitivity of the patient (SOP) during the induction stage is important because it is related to the confidence of the anaesthetist in controlling this system. Not only does this stage involve no surgical disturbances or artifacts, it is also fast and dynamic and very suitable for identifying the response of the patient to the drug. Eight patients underwent major abdominal surgery during intravenous anaesthesia and were all classified as ASA physical status category 1 or 2. A personal computer was connected via the RS232 ports for the Dinamap (i.e., Critikon, Inc., USA) and the Graseby 3400 syringe pump (i.e., Graseby Medical Limited, UK). All the trials measured patients' systolic arterial pressure (SAP) and heart rate (HR) using a Dinamap instrument. The clinical signs (i.e., sweating (SW), lacrimation (LA), and pupil response (PR)) were observed and input regularly about 5 min by the anaesthetist. A Graseby 3400 syringe pump which can pump from 0.1 to 1200 ml/hr was used to infuse propofol. Fentanyl was injected manually by syringe according to the rule-base. Also, a hierarchical fuzzy logic monitoring and rule-based control advisory system is tested in this paper to assess the determining the patient's sensitivity in the induction stage. The patient sensitivity of the elicited rule-base from anaesthetists' experience has been tested with the 8 patients during induction stage. Therefore, the good recovery time between acceptable and fast was 75 % in 8 patients. And, the mean (SD) of recovery time was 8.13 ± 5.94 min. Furthermore, the monitoring depth of anaesthesia (DOA) in terms of deciding of the confidence of depth of anaesthesia (CDOA) has also been tested with the 8 patients during maintenance stage. The mean (SD) of the mean CDOA in 8 patients was 93.55 ± 5.80 %. We conclude that determining the SOP in the induction stage is important because it is related to the confidence of the anaesthetist in controlling this advisory system. But a longer series of patients is needed to refine the rule-bases of the SOP, and to see how widely they are applicable.

The coherence mapping was used in frequency analysis of atrial fibrillation (AF). Unipolar electrograms were recorded at AF and during infusion of antiarrhythmic drug, using a 120-electrode array (electrode spacing is 3 mm) placed on the right atrial free wall of canine. We used magnitude-squared coherence in frequency (MSCF) maps to show the frequency distribution during AF. The spectra were limited to 2-15 Hz for AF signals. We chose each site as a reference and established its MSC spectra with other sites in the array. Dominant frequency (DF) was defined by maximum power of spectrum from reference. MSC spectrum was calculated for every point in the array relative to the reference site. If the MSC value of DF is greater than or equal to 0.5, the frequency at this site is set to DF, otherwise it is set to zero. The majority of these values was assigned as the DF of that position. The spatial distribution of DFs was presented as a map, MSCF map. The dominant area (DA) was chosen from the isochronal maps. We developed the MSCF maps for four episodes: (1) normal sinus rhythm: (2) AF without drug infusion: (3) just before AF termination by drug infusion: (4) sinus rhythm following termination. The results show that MSCF map in DA just before AF termination has a uniform pattern. The signals in DA have lower frequencies and longer cycle lengths compared with those in other areas (P < 0.05). In conclusion, this mapping study of the epicardial surface during induced atrial fibrillation in canine right atrial wall has demonstrated that a dominant area near SA node may have an important role for drug-induced AF termination.

A highly accurate Binary Amplitude-Shift-Keyed (BASK) ultrasonic tremor measurement system for use in isothermal air is developed. In this paper, we present a simple but efficient algorithm based upon phase shifts generated by three ultrasonic waves of different frequencies. By the proposed method, we can conduct larger range measurement than the phase-shift method and also get higher accuracy compared with the time-of-flight (TOF) method. Our microcomputer-based system includes two important parts. One of which is BASK modulation signal generator. The other is a phase meter designed to record and compute the phase shifts of the three different frequencies and the result motion is then sent to either an LCD for display or a PC for calibration. Experiments are done in the laboratory using BASK modulation for the frequencies of 200 Hz and 1 kHz with a 40 kHz carrier. The measurement accuracy of this measurement system in the reported experiments is within +/- 0.98 mm. The main advantages of this ultrasonic tremor measurement system are high resolution, narrow bandwidth requirement, low cost, and easy to be implemented.

The clinical images of an ultrasound system are normally obtained by analyzing the ultrasonic echoes from the discontinuities in a patient. Information such as wave speed, acoustic impedance, and the attenuation coefficient computed from the ultrasonic echoes are the primary parameters used in constructing an ultrasonic image. However, the traditional medical imaging is insensitive to identify the abnormal regions of small stiff change. It often fails to reveal the extent or existence of tumors, which are found to be more stiff than surrounding normal tissues.

To overcome these problems, this research proposes an ultrasonic imaging method based on tissue elasticity through the harmonic filter to construct a strain-harmonic image. This technique is formed by a process involving two steps. First, the phantom is compressed externally to generate an internal strain field. Second, ultrasonic transmitting signals before and after compression are acquired and processed by harmonic filter. The strain profiles of a soft sample are converted into two-dimensional gray images using MATLAB software. Experiments were conducted for the comparison between the strain and strain-harmonic image. It is observed that the strain-harmonic images can illustrate layer location of the phantoms better than those plotted in the strain images.

Custom fitted seat cushions work to improve posture, alleviate fatigue and prevent bedsores by evenly distributing body mass and relieving single or multiple points of pressure. Existing commercially-available bedding and seating is unsatisfactory to patients and professionals alike. Three-dimensional anthropometric measurement technology is employed to establish a database of hip-form profiles. This database includes 400 individuals grouped into five categories based on the shapes and measurements of 3-D hip-forms analogous to women's brassiere cup sizes. Each class is matched within a range of a anthropomtric values such as height, weight, hip-circumference and thigh-diameter. With such human factor engineering considerations, the preliminary 3-D hip-form database has created practical distinctions between the five hip-form classes that could help to design patient specific seating that is both comfortable and healthy.

This paper presents results from using a 3-dimensional finite element model to assess the stress distribution in the bone, in the implant and in the abutment as a function of the implant's diameter and length. Increasing implant diameter and length increases the stability of the implant system. By using a finite element analysis, we show that implant length does not decrease the stress distribution of either the implant or the bone. Alternatively, however implant diameter increases reduce the stresses. For the latter case, the contact area between implant and bone is increased thus the stress concentration effect is decreased. Also, with increased implant diameter the bone loss is decreased and as a consequence the success rate is improved.