IEEE transactions on bio-medical engineering
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IEEE Trans Biomed Eng · Apr 2005
Comparative StudyEffects of radiofrequency energy on human chondromalacic cartilage: an assessment of insulation material properties.
The objective of this study was to establish guidelines for the selection of an insulation material used to surround the electrode of radiofrequency energy (RFE) probes used for thermal chondroplasty. These guidelines were established by identifying which insulation materials resulted in the least amount of chondrocyte death while smoothing the surface of chondromalacic cartilage. RFE causes electrolyte oscillation and molecular friction in the tissue to heat it and subsequently smooth the surface. ⋯ Prototype probes made with Macor, 99.5% alumina, and ZTA had TC < or = 30 W/mol x K and resulted in a mean of 35% less cell death (176+/-56 microm, 130+/-48 microm, and 114+/-33 microm, respectively) than aluminum nitride, PTFE, and YTZP (246+/-68 microm, 231+/-108 microm, and 195+/-89 microm, respectively). Macor, 99.5% alumina, and ZTA prototype probes all had VR > or = 1 x 10(14) ohm x cm and resulted in a mean 37% less cell death than aluminum nitride or YTZP. There was no apparent relationship between CTE and the depth of chondrocyte death.
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Some additions/corrections are offered to Geddes, 2004. Stimulation is initiated by the second spatial derivative of the voltage along the nerve (activating function) rather than current density. Chronaxie values change with distance from the electrode. Anodic stimulation can excite via anodic break excitation, or via virtual cathodes around the anode.
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IEEE Trans Biomed Eng · Apr 2005
A technique to track individual motor unit action potentials in surface EMG by monitoring their conduction velocities and amplitudes.
The speed of propagation of an action potential along a muscle fiber, its conduction velocity (CV), can be used as an indication of the physiological or pathological state of the muscle fiber membrane. The motor unit action potential (MUAP), the waveform resulting from the spatial and temporal summation of the individual muscle fiber action potentials of that motor unit (MU), propagates with a speed referred to as the motor unit conduction velocity (MUCV). ⋯ An assessment of the performance of the algorithm has been achieved using simulated SEMG signals. It is concluded that this analysis technique enhances the suitability of SEMG for clinical applications and points toward a future of noninvasive diagnosis and assessment of neuromuscular disorders.
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IEEE Trans Biomed Eng · Mar 2005
Comparative StudyA clinical water-coated antenna applicator for MR-controlled deep-body hyperthermia: a comparison of calculated and measured 3-D temperature data sets.
A magnetic resonance (MR)-compatible three-dimensional (3-D) hyperthermia applicator was developed and evaluated in the magnetic resonance (MR) tomograph Siemens MAGNETOM Symphony 1.5 T. Radiating elements of this applicator are 12 so-called water coated antenna (WACOA) modules, which are designed as specially shaped and adjustable dipole structures in hermetically closed cassettes that are filled by deionized water. The WACOA modules are arranged in the applicator frame in two transversal antenna subarrays, six antennas per subarray. ⋯ The applicator's design and the E-field calculations were performed using the finite-difference time-domain (FDTD) method. The calculation and optimization of temperature patterns was obtained using the finite element method (FEM). For MR temperature measurements the proton resonance frequency (PRF) method was used.
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IEEE Trans Biomed Eng · Mar 2005
Comparative StudyWavelet-based lossy-to-lossless ECG compression in a unified vector quantization framework.
In a prior work, a wavelet-based vector quantization (VQ) approach was proposed to perform lossy compression of electrocardiogram (ECG) signals. In this paper, we investigate and fix its coding inefficiency problem in lossless compression and extend it to allow both lossy and lossless compression in a unified coding framework. The well-known 9/7 filters and 5/3 integer filters are used to implement the wavelet transform (WT) for lossy and lossless compression, respectively. ⋯ In addition, a new and cost-effective coding strategy is proposed to enhance the coding efficiency of set partitioning in hierarchical tree (SPIHT) at the less significant bit representation of a WT coefficient. ECG records from the MIT/BIH Arrhythmia and European ST-T Databases are selected as test data. In terms of the coding efficiency for lossless compression, experimental results show that the proposed codec improves the direct SPIHT approach and the prior work by about 33% and 26%, respectively.