Ultrasound speed and impedance microscopy for in vivo imaging.

Ultrasound speed and impedance microscopy was developed in order to develop in vivo imaging system. The sound speed mode realized non-contact high resolution imaging of cultured cells. This mode can be applied for assessment of biomechanics of the cells and thinly sliced tissues. The impedance mode visualized fine structures of the surface of the rat's brain. This mode can be applied for intra-operative pathological examination because it does not require slicing or staining.

Modified scaled Fourier linear combiner in thoracic impedance cardiography.

New filtering algorithms; a modified scaled Fourier linear combiner (mSFLC) and a modified ensemble averaging (mEA) are proposed to remove the phase distortion of the impedance waveform caused by SFLC. Performance of the filters is assessed from the shape of the filtered waveform and the estimation of systolic time intervals. It was found that the mSFLC and mEA could compensate for drawbacks of the SFLC and precisely reproduce the impedance waveforms; however, misinterpretation and attenuation in the cardiac variables may be caused when abrupt changes or irregularities occur in the source waveform.

Beat-to-beat evaluation of systolic time intervals during bicycle exercise using impedance cardiography.

In order to elucidate the beat-to-beat changes of the systolic time intervals (STI) during exercise, we proposed new techniques relating to an adaptive filter and detection algorithms for B- and X-points in the impedance cardiograph (ICG). Six male subjects underwent a ramp bicycle exercise up to maximum intensity during which an ECG, ICG and phonocardiogram (PCG) were continuously measured. Following the application of an adaptive filter, the scaled Fourier linear combiner (SFLC), to the first derivative (dZ/dt) of the base impedance (deltaZ) and PCG waveforms, the B- and X-points were automatically determined. For the B-point detection we used three criteria: the zero-crossing point (B(zero)), the 15% response point (B15%) of the negative peak of the dZ/dt (dZ/dt(min)) and a new algorithm (B(new)). The X-point was separately determined by using the ICG and PCG waveforms. It was found that the shape of the dZ/dt waveform directly affected the determination of the B- and X-points. The B-points determined using B(zero) and B15%, criteria were sometimes unstable caused by the location of a notch preceding the dZ/dt(min) compared to the B(new). The time difference between the X-points measured by the ICG and PCG was mostly within +/- 20 milliseconds but statistically significant. Although a wide variation was seen in R-R intervals, the STI were more stable. The relationships between HR and STI from rest to maximal exercise showed a gentle curvilinear relationship. It is suggested that the STI can be obtained precisely on a beat-to-beat basis by using the adaptive filter and detection algorithms for the inflection points of the ICG even during maximum exercise.