Gloria Cosoli

A novel approach for features extraction in physiological signals

The authors have investigated a novel processing technique, which allows to measure possibly relevant features in the ECG (Electrocardiogram) signal according to the morphology of its waveform. The aim of this work is to prove its efficacy in the assessment of the subjects Heart Rate (HR) and to broaden its use to signals coming from different biomedical sensors (based on optical, acoustical and mechanical principles) for the computation of HR. The analysis technique proposed for the identification of the main feature (R-peak) in ECG signal provides results that are comparable to those obtained with traditional approaches. The approach has also been applied to other signals related to blood flow, such as PCG (Phonocardiography), PPG (Photoplethysmography) and VCG (Vibrocardiography), where standard algorithms (i.e. Pan & Tompkins) could not be widely applied. HR results from a measurement campaign on 8 healthy subjects have shown, respect to ECG, a deviation (calculated as 2σ) of ±3.3 bpm, ±2.3 bpm and ±1.5 bpm for PCG, PPG and VCG. Future work will involve the extraction of additional features from the previous signals, with the aim of a deeper characterization of them to better describe the subjects health status.

Evaluation of Heart Rate Variability by means of Laser Doppler Vibrometry measurements

Heart Rate Variability (HRV) analysis aims to study the physiological variability of the Heart Rate (HR), which is related to the health conditions of the subject. HRV is assessed measuring heart periods (HP) on a time window of >5 minutes (1)-(2). HPs are determined from signals of different nature: electrocardiogram (ECG), photoplethysmogram (PPG), phonocardiogram (PCG) or vibrocardiogram (VCG) (3)-(4)-(5). The fundamental aspect is the identification of a feature in each heartbeat that allows to accurately compute cardiac periods (such as R peaks in ECG), in order to make possible the measurement of all the typical HRV evaluations on those intervals. VCG is a non-contact technique (4), very favourable in medicine, which detects the vibrations on the skin surface (e.g. on the carotid artery) resulting from vascular blood motion consequent to electrical signal (ECG).In this paper, we propose the use of VCG for the measurement of a signal related to HRV and the use of a novel algorithm based on signal geometry (7) to detect signal peaks, in order to accurately determine cardiac periods and the Poincare plot (9)-(10). The results reported are comparable to the ones reached with the gold standard (ECG) and in literature (3)-(5). We report mean values of HP of 832±54 ms and 832±55 ms by means of ECG and VCG, respectively. Moreover, this algorithm allow us to identify particular features of ECG and VCG signals, so that in the future we will be able to evaluate specific correlations between the two.

The non-contact measure of the heart rate variability by laser Doppler vibrometry: comparison with electrocardiography

The assessment of the heart rate variability (HRV) is of utmost importance, being one of the most promising markers of the activity of the autonomic nervous system and associated to cardiovascular mortality. Different signals can be used to perform HRV, primarily electrocardiography (ECG), photoplethysmography (PPG), phonocardiography (PCG) or vibrocardiography (VCG), since the fundamental aspect is the individuation of a periodic feature strictly correlated with cardiac activity (i.e. R-peak in ECG or the first sound in PCG). In this work, the authors demonstrate that the VCG performances in HRV analysis are sufficiently accurate if compared to the ones measured by ECG (i.e. standard methodology); moreover, the authors want to prove the feasibility of such measurement in correspondence of different measurement points (i.e. carotid artery—which is the typical VCG measurement point—and the radial artery on the wrist)1. Results show that VCG has a mean deviation of <1 bpm with respect to ECG in heart rate (HR) measurement; carotid artery is the most accurate site for the assessment, but also the radial artery is a valid site, even if with a reduced SNR. With regards to HRV parameters, the mean percentage deviation is <10% in correspondence of carotid artery, and ≈16% for the radial artery. So, VCG allows for non-contact monitoring of the cardiac activity.

Heart Rate assessment by means of a novel approach applied to signals of different nature

Electrocardiographic (ECG) signal presents many clinically relevant features (e.g. QT-interval, that is the duration of the ventricular depolarization). A novel processing technique has been demonstrated to be capable to measure some important characteristics according to the morphology of the waveform. Basing on that, the aim of this work is to propose an improved algorithm and to prove its efficacy in the assessment of the subjects Heart Rate (HR) in comparison to standard algorithms (i.e. Pan & Tompkins). Results obtained in experimentally collected ECG signals for the identification of the main feature (R-peak) are comparable to those obtained with the traditional approach (sensitivity of 99.55% and 99.95%, respectively). Moreover, the use of this algorithm has been broaden to signals coming from different biomedical sensors (based on optical, acoustical and mechanical principles), all related to blood flow, for the computation of HR. In particular, it has been employed to PCG (Phonocardiography), PPG (Photoplethysmography) and VCG (Vibrocardiography), where standard algorithms could not be widely applied. HR results from a measurement campaign on 8 healthy subjects have shown, with respect to ECG, deviations (calculated as 2σ) of ±3.3 bpm, ±2.3 bpm and ±1.5 bpm for PCG, PPG and VCG, respectively. In conclusion, it is possible to state that the adopted algorithm is able to measure HR accurately from different biosignals. Future work will involve the extraction of additional morphological features in order to characterise the waveforms more deeply and to better describe the subjects health status.

An innovative therapy for peri-implantitis based on radio frequency electric current: Numerical simulation results and clinical evidence

Peri-implantitis is a severe inflammatory pathology that affects soit and hard tissues surrounding dental implants. Nowadays, only prevention is effective to contrast peri-implantitis, but, in recent years, there is the clinical evidence of the efficiency of a therapy based on the application of radio frequency electric current, reporting that 81% of the cases (66 implants, 46 patients) were successfully treated. The aim of this paper is to present the therapy mechanism, exploring the distribution of the electric currents in normal and pathologic tissues. A 3D numerical FEM model of tooth root with a dental implant screwed in the alveolar bone has been realized and the therapy has been simulated in COMSOL Multiphysics® environment. Results show that the electric current is focused in the inflamed zone around the implant, due to the fact that its conductivity is higher than the healthy tissue one. Moreover, by means of a movable return electrode, the electric current and field lines can be guided in the most inflamed area, limiting the interference on healthy tissues and improving the therapy in the area of interest. In conclusion, it can be stated that this innovative therapy would make a personalized therapy for peri-implantitis possible, also through impedance measurements, allowing the clinician to evaluate the tissue inflammation state.Peri-implantitis is a severe inflammatory pathology that affects soit and hard tissues surrounding dental implants. Nowadays, only prevention is effective to contrast peri-implantitis, but, in recent years, there is the clinical evidence of the efficiency of a therapy based on the application of radio frequency electric current, reporting that 81% of the cases (66 implants, 46 patients) were successfully treated. The aim of this paper is to present the therapy mechanism, exploring the distribution of the electric currents in normal and pathologic tissues. A 3D numerical FEM model of tooth root with a dental implant screwed in the alveolar bone has been realized and the therapy has been simulated in COMSOL Multiphysics® environment. Results show that the electric current is focused in the inflamed zone around the implant, due to the fact that its conductivity is higher than the healthy tissue one. Moreover, by means of a movable return electrode, the electric current and field lines can be guided in the most inflamed area, limiting the interference on healthy tissues and improving the therapy in the area of interest. In conclusion, it can be stated that this innovative therapy would make a personalized therapy for peri-implantitis possible, also through impedance measurements, allowing the clinician to evaluate the tissue inflammation state.

Indirect measurement of the carotid arterial pressure from vibrocardiographic signal: Calibration of the waveform and comparison with photoplethysmographic signal

The detection of arterial Blood Pressure waveform provides important information about the subject health status. Laser Doppler Vibrometry (LDV) is a non-contact technique with high sensitivity able to detect mechanical movements of the arterial wall; several previous studies have shown that LDV is able to characterize cardiac activity. Photoplethysmogram (PPG) quantifies the digital volume artery pulse, which has been demonstrated to be closely related to the pressure signal measured by an arterial tonometer. In this paper, an indirect measurement of carotid arterial pressure by means of LDV is presented. Moreover, a comparison between LDV and PPG is conducted in order to estimate the time interval between opening and closing of the aortic valve, that is the Left Ventricular Ejection Time (LVET). Results show an average reduction of around 20% of the systolic pressure derived from LDV signal measured over the carotid artery with respect to the systolic pressure measured at brachial level (i.e. peripheral pressure value). Finally, the comparison between LDV and PPG in the estimation of LVET shows a mean percentage deviation <;10%. So, in conclusion, it can be stated that LDV technique has the potential of providing a displacement waveform that, adequately calibrated, can furnish significant information about pressure waveform.The detection of arterial Blood Pressure waveform provides important information about the subject health status. Laser Doppler Vibrometry (LDV) is a non-contact technique with high sensitivity able to detect mechanical movements of the arterial wall; several previous studies have shown that LDV is able to characterize cardiac activity. Photoplethysmogram (PPG) quantifies the digital volume artery pulse, which has been demonstrated to be closely related to the pressure signal measured by an arterial tonometer. In this paper, an indirect measurement of carotid arterial pressure by means of LDV is presented. Moreover, a comparison between LDV and PPG is conducted in order to estimate the time interval between opening and closing of the aortic valve, that is the Left Ventricular Ejection Time (LVET). Results show an average reduction of around 20% of the systolic pressure derived from LDV signal measured over the carotid artery with respect to the systolic pressure measured at brachial level (i.e. peripheral pressure value). Finally, the comparison between LDV and PPG in the estimation of LVET shows a mean percentage deviation <;10%. So, in conclusion, it can be stated that LDV technique has the potential of providing a displacement waveform that, adequately calibrated, can furnish significant information about pressure waveform.

Bioimpedance Measurement in Dentistry: Detection of Inflamed Tissues

This work aims at determining if bioimpedance measurements are able to provide information about the inflammatory state of the tissues; if the presence of an inflamed tissue can be located by means of bioimpedance measure, it would be possible to focus a potential treatment in this site. Different numerical 3D models have been realized to simulate the measurement conditions present in the event of inflamed gingiva around a dental implant. A premolar has been represented and different inflammation volumes have been considered; both geometric and electrical properties have been taken from the literature. In addition, some preliminary measurements have been conducted in three patients with dental implants in different conditions: healthy tissues, inflammation and peri-implantitis. The percentage difference of impedance (∆Z) between healthy and inflamed tissues has been considered. In addition, also three numerical models of healthy teeth have been realized (i.e. incisor, canine and premolar roots), in order to evaluate the normal range of teeth bioimpedance values. The results obtained from the numerical simulations show ∆Z values of 6–20% for the dental implant, depending on the inflamed volume. The bioimpedance values experimentally measured are in agreement with the ones obtained from the simulations and ∆Z values are also more marked (34% for inflammation, 55% for peri-implantitis), suggesting that in real inflamed tissues not only electrical properties but also dimensions are different with respect to the normal case. As regards the healthy teeth, the modulus of the measured impedance is higher than that of the implant; this was predictable and is due to the presence of bone instead of the implant. In conclusion, it is possible to state that bioimpedance measurements allow the clinician to detect inflamed tissues, so that the therapy can be focused on the impaired zone, limiting the influence in the surrounding healthy tissues and personalizing the therapy according to the inflammation severity.

Measurement of the 100 MHz EMF radiation in vivo effects on zebrafish D. rerio embryonic development: A multidisciplinary study

The augmented exposure of both environment and human being to electromagnetic waves and the concomitant lack of an unequivocal knowledge about biological consequences of these radiations, raised public interest on electromagnetic pollution. In this context, the present study aims to evaluate the biological effects on zebrafish (ZF) embryos of 100 MHz radiofrequency electromagnetic field (RF-EMF) exposure through a multidisciplinary protocol. Because of the shared synteny between human and ZF genomes that validated its use in biomedical research, toxicology and developmental biology studies, ZF was here selected as experimental model and a measurement protocol and biological analyses have been set up to clearly discriminate between RF-EMF biological and thermal effects. The results showed that a 100 MHz EMF was able to affect ZF embryonic development, from 24 to 72 h post fertilization (hpf) in all the analyzed pathways. Particularly, at the 48 hpf stage, a reduced growth, an increased transcription of oxidative stress genes, the onset of apoptotic/autophagic processes and a modification in cholesterol metabolism were detected. ZF embryos faced stress induced by EMF radiation by triggering detoxification mechanisms and at 72 hpf they partially recovered from stress reaching the hatching time in a comparable way respect to the control group. Data here obtained showed unequivocally the in vivo effects of RF-EMF on an animal model, excluding thermal outcomes and thus represents the starting point for more comprehensive studies on dose response effects of electromagnetic fields radiations consequences.

The measurement of blood pressure without contact: An LDV-based technique

This work is aiming to demonstrate the possibility to assess arterial blood pressure without the need to put any element in physical contact with the subject (except for the signal calibration). The authors have developed a measurement technique for the non contact measurement of blood pressure (BP) as manifest in the carotid artery, based on the use of a laser Doppler vibrometer (LDV). The LDV produces a signal that can be related to the continuous pressure pulse waveform. As such, the signal supports the calculation of some physiologically important time intervals. In this paper, we provide a comparison with the pressure waveform recorded using conventional applanation tonometry: the waveform has an analogous shape and, overall, provides the same characteristics in the time axis. More in details, results show that the systolic blood pressure have a mean deviation of 8% with respect to the reference value (obtained from tonometric data). Fundamental aspects to be considered are the precise laser pointing perpendicularly to the measurement site (to optimize the signal-to-noise ratio), the measurement conditions (e.g. the subject has to remain as still as possible) and also the reflective properties of the subjects skin, which can be improved by applying a proper reflective lotion or tape. The major factors contributing to uncertainty of the LDV measures have been evaluated, in order to identify ways to enhance performance. The current uncertainty value of 15% is not negligible, but does not greatly exceed that of the standard BP measuring devices.

Bioimpedance measurements in dentistry to detect inflammation: numerical modelling and experimental results

Bioimpedance measurements represent an advantageous method to evaluate the physio-pathological conditions of biological tissues and their use is spreading in different application fields, from the evaluation of body composition to the vital signs monitoring, passing through the individuation of cancer tissues and the detection of different substances (e.g. glucose measurements in people affected by diabetes). In fact, tissues electric properties vary with their conditions; for example, electrical conductivity increases when there is an inflammatory process, because of the presence of oedema, hyperaemia and infiltration. Inflammatory phenomena are frequent in dentistry, in diseases like periodontitis and peri-implantitis; however, at present the diagnosis is mainly done with the naked eye, by observing the gingiva redness and swelling. OBJECTIVE The aim of this work is to prove the feasibility of the inflammation detection by means of bioimpedance measurements. APPROACH Both numerical simulations and preliminary experimental measurements provide significant outcomes in differentiating between healthy and inflamed tissues. MAIN RESULTS Percentage differences in the impedance modulus equal to 4-20% (numerical simulations) and 35-56% (experimental measurements), respectively, depending on the considered conditions (e.g. electrodes characteristics and inflammation severity), were found. SIGNIFICANCE Such a measure could be integrated in electromedical devices designed, for example, for the therapy of peri-implantitis, in order to personalise the therapeutic dose in terms of intensity and duration and focusing it on the impaired area, minimising the effects on the surrounding tissues.