Behavior of right atrial strain in high systolic pulmonary artery pressure.

Aims: Evaluate the ability of right atrial (RA) strain to predict systolic pulmonary artery pressure (SPAP).

Methods And Results: A total of 102 patients were prospectively enrolled. Conventional echocardiographic measures were performed.

A conceptual experiment on single-beam coincidence detection with pseudothermal light.

Ghost imaging produced by pseudothermal light is commonly obtained by correlating the intensities of two separate beams, neither of which conveys information about the shape of the object to be imaged. The single-beam experiment discussed here, while not exploitable for the practical purpose of reconstructing the shape of a real mask, uses the same mathematical machinery as two-beam experiments; it also suggests that image retrieval by classical light ghost imaging is only a product of normal signal processing and does not involve any "ghost". In addition, the singlebeam setup allows simpler calibration procedures in systematic investigations of the efficiency of coincidence imaging.

Use of an intensity threshold to improve the visibility of ghost images produced by incoherent light.

In thermal light ghost imaging, the transparent mask, located in the object arm of the optical setup, is numerically reconstructed by correlating the speckle patterns acquired by the video camera with the output of a bucket detector placed behind the mask. We show that the visibility of images can be significantly improved by discarding every speckle pattern whose bucket output falls below a certain threshold. We also demonstrate that the efficiency of the conventional method strongly decreases when the speckle statistics deviate from the negative exponential, whereas the threshold method is more robust against changes in the statistical distribution of the speckle intensity.

Complete destructive interference of partially coherent sources of acoustic waves.

Theoretical analysis has recently shown that the optical fields from several point sources may exhibit complete destructive interference even if the sources are not fully coherent with respect to each other. The experimental verification of this statement in the optical domain is not easy. In this Letter we demonstrate the effect using acoustical waves instead of light waves.

Spatial and temporal coherence of filtered thermal light.

When a filter is placed in front of a double slit illuminated by a primary source of finite extent, the theory of partial coherence predicts that in general the interference fringes do not acquire unit visibility even as the passband of the filter is made arbitrarily narrow. The effect of reducing the filter bandwidth is that the visibility of the fringes tends to the modulus of the spectral degree of coherence and that more interference fringes become visible. A systematic experimental verification of these theoretical predictions is lacking so far and is provided here from the use of a highly sensitive CCD camera.

Pulsatile electrical impedance response from cerebrally dead adult patients is not a reliable tool for detecting cerebral perfusion changes.

The original objective of this work was to verify the possibility of using electrical pulsatile cerebral impedance measurements as a diagnostic aid for assessing the brain-death condition in adults; a subordinate target was to validate a simple method for detecting perfusional changes in the brain. To this end, impedance signals were recorded, for a comparative study, from both live subjects and brain-dead patients, using a simple four-electrode arrangement. Rather unexpectedly, pulsatile transcephalic impedance waveforms exhibiting a temporal dependance similar to those of live subjects were detected in artificially ventilated, cerebrally dead, adult subjects; distributions of the time delays between impedance peaks and ECG peaks were also recorded for the two groups (dead and live subjects).

Cerebral blood-flow monitor for use in neonatal intensive care units.

The implementation of a real-time multichannel system for monitoring cerebral blood-flow is described. The instrument relies on a completely modular architecture and is based on the principle of measuring the electrical impedance between a number of periodically sensed electrode pairs positioned around the subject's head. The whole setup is controlled by a host computer that performs several functions, such as real-time acquisition, analysis, display and data logging.

Real-time spectral analysis of HRV signals: an interactive and user-friendly PC system.

We present a real-time system, built around a PC and a low-cost data acquisition board, for the spectral analysis of the heart rate variability signal. The Windows-like operating environment on which it is based makes the computer program very user-friendly even for non-specialized personnel. The Power Spectral Density is computed through the use of a hybrid method, in which a classical FFT analysis follows an autoregressive finite-extension of data; the stationarity of the sequence is continuously checked.

Measurements of surface roughness: use of a CCD camera to correlate doubly scattered speckle patterns.

We describe an instrument, built around a commercial CCD camera and some fast image-processing boards, that evaluates roughness height by measuring the average size of doubly scattered speckle patterns. The device is a variant of a recent proposal that was based on the use of a spatial modulator to perform the Fourier transform of a speckle image. In the present setup, the Fourier transform is replaced by the direct evaluation of a second-order correlation function.

An instrument for real-time spectral estimation of heart rate variability signals.

A Digital Signal Processor (DSP)-based instrument is proposed for estimating and displaying the Heart Rate Variability (HRV) spectrum in real-time. It consists of an intelligent module which is properly interfaced to an IBM PC and whose operations are independent from the computer's other tasks. In this way, the simultaneous recording of the ECG sequence, needed for the more complete off-line analysis, can be performed by the same host.

Multipurpose analyzers for photoelectron statistics: implementation and use.

The statistical properties of variously scattered laser light can be derived from photocount data through the estimate of different functions. Even if the second-order correlation usually plays the main role, other function (e.g.

Edge-detection schemes highly suitable for hardware implementation.

Two schemes for edge detection of real images based on gradient maxima are presented. Images are filtered with narrow filters to increase localization. Experimental results and theoretical considerations suggest that the exact shape of the filter is not critical for good performance of the algorithm.

Triggering techniques in triggered photon-counting.

In the measurement of triggered photon-counting distributions (TPCDs) the triggering pulse which starts a collecting interval may be picked up according to different random procedures. We investigate, both theoretically and experimentally, the extent to which TPCDs are affected by the choice of the triggering pulses. It turns out that in ordinary conditions the measured distribution may be significantly influenced by the triggering procedure.

Measurement of zero-count probability in photoelectron statistics.

The probability of zero-count P(0)(T) (as a function of the counting interval T) is one of the most interesting functions characterizing a light field. Experimentally, P(0)(T) is usually obtained by measuring successively the zero-count probability for a set of different intervals. This procedure exposes the measurement of P(0)(T) to errors imputable to drift.