L. Spinelli - Academia.edu (original) (raw)

Papers by L. Spinelli

Research paper thumbnail of Cardiac performance during exercise in patients with Fabry's disease

European Journal of Clinical Investigation, 2008

Background Fatigability and dyspnoea on effort are present in many patients with Fabry's disease.... more Background Fatigability and dyspnoea on effort are present in many patients with Fabry's disease. We assessed the determinants of cardiac performance during exercise in patients with Fabry's disease and preserved left ventricular ejection fraction at rest. Materials and methods Sixteen patients with Fabry's disease and 16 control subjects underwent radionuclide angiography at rest and during exercise, tissue Doppler echocardiography and magnetic resonance imaging at rest. Results The exercise-induced change in stroke volume was +25 ± 14% in controls and +5•8 ± 19% in patients with Fabry's disease (P < 0•001). In 10 patients (group 1), the stroke volume increased (+19 ± 10%), and in 6 patients (group 2) it decreased (-16 ± 9%) with exercise. Patients of group 2 were older, had worse renal function, higher left ventricular mass and impaired diastolic function compared to group 1. The abnormal stroke volume response to exercise in group 2 was associated with a decrease in end-diastolic volume (P < 0•001) and a lack of reduction of end-systolic volume (P < 0•01) compared with both controls and group 1. The ratio of peak earlydiastolic velocity from mitral filling to peak early-diastolic mitral annulus velocity was the only independent predictor of exercise-induced change in stroke volume (B-0•44; SE 0•119; β-0•70; P < 0•005). Conclusions The majority of patients with Fabry's disease were able to augment stroke volume during exercise by increasing end-diastolic volume, whereas patients with more advanced cardiac involvement may experience the inability to increase cardiac output by the Frank Starling mechanism.

Research paper thumbnail of Usefulness of Satisfactory Control of Low-Density Lipoprotein Cholesterol to Predict Left Ventricular Remodeling After a First ST-Elevation Myocardial Infarction Successfully Reperfused

The American Journal of Cardiology, 2011

Research paper thumbnail of Prognostic value of dobutamine stress echocardiography in patients with terminal renal insufficiency undergoing hemodialysis: A 5-year follow up

Research paper thumbnail of Abstracts of Presentations at the International Conference

Research paper thumbnail of Mapping Cerebral Hemodynamics in Brain Cortex by Multi-Channel Time-Resolved Near-Infrared Spectroscopy

Biomedical Optics, 2006

1. Introduction Mapping functional activation in the human brain by optical radiation is a challe... more 1. Introduction Mapping functional activation in the human brain by optical radiation is a challenging task [1]. The diffusive nature of biological tissues prevents in fact the discrimination of absorption and scattering contributions by simple continuous wave (CW) techniques. Therefore, CW techniques measure changes in the absorption coefficient and consequently derive changes, rather than absolute values, in the hemodynamic parameters (ie concentration of oxyhemoglobin and deoxy-hemoglobin) [2]. For a majority of applications this approach is nonetheless ...

Research paper thumbnail of Heuristic Analytical Solution of the Time Dependent Radiative Transfer Equation for a Semi-Infinite Medium

Research paper thumbnail of Monitoring Muscle Hemodynamics by Time-Domain Near Infrared Spectroscopy during Muscle Contractions Induced by Functional Electrical Stimulation

Biomedical Optics, 2008

Abstract A time-domain NIRS multichannel system was used to monitor hemodynamic changes in the mu... more Abstract A time-domain NIRS multichannel system was used to monitor hemodynamic changes in the muscle of 6 healthy volunteers and 4 hemiplegic patients during knee flex-extension induced by functional electrical stimulation for rehabilitation purposes.

Research paper thumbnail of Reconstruction in Diffuse Optical Tomography Using Genetic Algorithm

Biomedical Optics and 3-D Imaging, 2010

Diffuse optical tomography can be solved by global optimization method (genetic algorithm). For n... more Diffuse optical tomography can be solved by global optimization method (genetic algorithm). For noise-free data, GA can find exact solutions with a probability of 80%. For noisy data, GA has better performance than Tikhonov regularization.

Research paper thumbnail of Effects of tissue heterogeneity on the optical estimate of breast density

Breast density is a recognized strong and independent risk factor for developing breast cancer. A... more Breast density is a recognized strong and independent risk factor for developing breast cancer. At present, breast density is assessed based on the radiological appearance of breast tissue, thus relying on the use of ionizing radiation. We have previously obtained encouraging preliminary results with our portable instrument for time domain optical mammography performed at 7 wavelengths (635-1060 nm). In that case, information was averaged over four images (cranio-caudal and oblique views of both breasts) available for each subject. In the present work, we tested the effectiveness of just one or few point measurements, to investigate if tissue heterogeneity significantly affects the correlation between optically derived parameters and mammographic density. Data show that parameters estimated through a single optical measurement correlate strongly with mammographic density estimated by using BIRADS categories. A central position is optimal for the measurement, but its exact location is not critical.

Research paper thumbnail of Cerebral cortex activation mapping upon electrical muscle stimulation by 32-channel time-domain functional near-infrared spectroscopy

The application of different EMS current thresholds on muscle activates not only the muscle but a... more The application of different EMS current thresholds on muscle activates not only the muscle but also peripheral sensory axons that send proprioceptive and pain signals to the cerebral cortex. A 32-channel time-domain fNIRS instrument was employed to map regional cortical activities under varied EMS current intensities applied on the right wrist extensor muscle. Eight healthy volunteers underwent four EMS at different current thresholds based on their individual maximal tolerated intensity (MTI), i.e., 10 % < 50 % < 100 % < over 100 % MTI. Time courses of the

Research paper thumbnail of Bone tissue phantoms for optical flowmeters at large interoptode spacing generated by 3D-stereolithography

Research paper thumbnail of Optical mammography: Characterization of malignant and benign breast lesions by a perturbative model

Benign and malignant breast lesions were characterized in terms of both absorption properties and... more Benign and malignant breast lesions were characterized in terms of both absorption properties and constituent concentration by the use of a perturbative model. Differences between lesions and healthy tissue were observed.

Research paper thumbnail of Optical properties of developing pip and stone fruit reveal underlying structural changes

Analyzing the optical properties of fruits represents a powerful approach for non-destructive obs... more Analyzing the optical properties of fruits represents a powerful approach for non-destructive observations of fruit development. With classical spectroscopy in the visible and near-infrared wavelength ranges, the apparent attenuation of light results from its absorption or scattering. In horticultural applications, frequently, the normalized difference vegetation index (NDVI) is employed to reduce the effects of varying scattering properties on the apparent signal. However, this simple approach appears to be limited. In the laboratory, with time-resolved reflectance spectroscopy, the absorption coefficient, μa , and the reduced scattering coefficient, μs &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;, can be analyzed separately. In this study, these differentiated optical properties were recorded (540-940 nm), probing fruit tissue from the skin up to 2 cm depth in apple (Malus × domestica &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;Elstar&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;) and plum (Prunus domestica &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;Tophit plus&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;) harvested four times (65-145 days after full bloom). The μa spectra showed typical peak at 670 nm of the chlorophyll absorption. The μs &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; at 670 nm in apple changed by 14.7% (18.2-15.5 cm(-1) ), while in plum differences of 41.5% (8.5-5.0 cm(-1) ) were found. The scattering power, the relative change of μs &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;, was zero in apple, but enhanced in plum over the fruit development period. This mirrors more isotropic and constant structures in apple compared with plum. For horticultural applications, the larger variability in scattering properties of plum explains the discrepancy between commercially assessed NDVI values or similar indices and the absolute μa values in plum (R &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05), while the NDVI approach appeared reasonable in apple (R ≥ 0.80).

Research paper thumbnail of Tomography of brain activation using a time-gated camera

Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 2009

The mean penetration depth of diffusely reflected photons is dependent on the arrival time t of p... more The mean penetration depth of diffusely reflected photons is dependent on the arrival time t of photons, but not on the source-detector distance. Thus, all photons collected at the same t have the same depth sensitivity, and can be used for the reconstruction.

Research paper thumbnail of Measurement of the local muscular metabolism by time-domain near infrared spectroscopy during knee flex-extension induced by functional electrical stimulation

Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 2009

We present a preliminary study that combines functional electrical stimulation and time-domain ne... more We present a preliminary study that combines functional electrical stimulation and time-domain near infrared spectroscopy for a quantitative measurement of the local muscular metabolism during rehabilitation of post-acute stroke patients. Seven healthy subjects and nine post-acute stroke patients underwent a protocol of knee flex-extension of the quadriceps induced by functional electrical stimulation. During the protocol time-domain near infrared spectroscopy measurement were performed on both left and right muscle. Hemodynamic parameters (concentration of oxy-and deoxy-genated hemoglobin) during baseline did not show any significant differences between healthy subject and patients, while functional performances (knee angle amplitude) were distinctly different. Nevertheless, even if their clinical histories were noticeably different, there was no differentiation among functional performances of patients. On the basis of the hemodynamic parameters measured during the recovery phase, instead, it was possible to identify two classes of patients showing a metabolic trend similar or very different to the one obtained by healthy subjects. The presented results suggest that the combination of functional and metabolic information can give an additional tool to the clinicians in the evaluation of the rehabilitation in post-acute stroke patients.

Research paper thumbnail of Functional tomography using a time-gated ICCD camera

Biomedical Optics Express, 2011

We present a system for near infrared functional tomography based on a single pulsed source and a... more We present a system for near infrared functional tomography based on a single pulsed source and a time-gated camera, for non-contact collection over a large area. The mean penetration depth of diffusely reflected photons is dependent on the arrival time of photons, but not on the source-detector distance. Thus, time-encoded data can be used to recover depth information while photon exiting point is exploited for lateral localization. This approach was tested against simulations, demonstrating both detection and localization capabilities. Preliminary measurements on inhomogeneous phantoms showed good detection sensibility, even for a low optical perturbation, and localization capabilities, yet with decreasing spatial resolution for increasing depths. Potential application of this method to in vivo functional studies on the brain is discussed.

Research paper thumbnail of Functional near-infrared spectroscopy at small source-detector distance by means of high dynamic-range fast-gated SPAD acquisitions: first in-vivo measurements

Neurophotonics, 2013

ABSTRACT In this article, we show experimental results of time-resolved optical spectroscopy perf... more ABSTRACT In this article, we show experimental results of time-resolved optical spectroscopy performed with small distance between launching and detecting fibers. It was already demonstrated that depth discrimination is independent of source-detector separation and that measurements at small sourcedetector distance provide better contrast and spatial resolution. The main disadvantage is represent by the huge increase in early photons (scarcely diffused by tissue) peak that can saturate the dynamic range of most detectors, hiding information carried by late photons. Thanks to a fast-gated Single- Photon Avalanche Diode (SPAD) module, we are able to reject the peak of early photons and to obtain high-dynamic range acquisitions. We exploit fast-gated SPAD module to perform for the first time functional near-infrared spectroscopy (fNIRS) at small source-detector distance for in vivo measurements and we demonstrate the possibility to detect non-invasively the dynamics of oxygenated and deoxygenated haemoglobin occurring in the motor cortex during a motor task. We also show the improvement in terms of signal amplitude and Signal-to-Noise Ratio (SNR) obtained exploiting fastgated SPAD performances with respect to “non-gated” measurements.

Research paper thumbnail of A method for discriminating systemic and cortical hemodynamic changes by time domain fNIRS

Neurophotonics, 2013

ABSTRACT Functional near-infrared spectroscopy (fNIRS) is a non-invasive optical technique able t... more ABSTRACT Functional near-infrared spectroscopy (fNIRS) is a non-invasive optical technique able to measure hemodynamic response in the brain cortex. Among the different approaches the fNIRS can be based on, the time resolved one allows a straightforward relationship between the photon detection time and its path within the medium, improving the discrimination of the information content relative to the different layers the tissues are composed of. Thus absorption and scattering properties of the probed tissue can be estimated, and from them the oxy- and deoxy-hemoglobin concentration. However, an open issue in the optical imaging studies is still the accuracy in separating the superficial hemodynamic changes from those happening in deeper regions of the head and more likely involving the cerebral cortex. In fact a crucial point is the precise estimate of the time dependent pathlength spent by photons within the perturbed medium. A novel method for the calculus of the absorption properties in time domain fNIRS, based on a refined computation of photon pathlength in multilayered media, is proposed. The method takes into account the non-ideality of the measurement system (its instrument response function) and the heterogeneous structure of the head. The better accuracy in computing the optical pathlength can improve the NIRS data analysis, especially for the deeper layer. Simulations and preliminary analysis on in vivo data have been performed to validate the method and are here presented.

Research paper thumbnail of Anatomical Brain Atlas for NIRS Measurements of Brain Activation

Diffuse Optical Imaging III, 2011

Abstract Anatomical brain atlases have been introduced in the analysis NIRS data of brain activat... more Abstract Anatomical brain atlases have been introduced in the analysis NIRS data of brain activation and good spatial activation localization has been proved. We applied this method to visualize NIRS data from different protocols.

Research paper thumbnail of <title>Frontal brain activation during a working memory task: a time-domain fNIRS study</title>

Photonic Therapeutics and Diagnostics V, 2009

We evaluated frontal brain activation during a working memory task with graded levels of difficul... more We evaluated frontal brain activation during a working memory task with graded levels of difficulty in a group of 19 healthy subjects, by means of time-resolved fNIRS technique. Brain activation was computed, and was then separated into a &amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;block-related&amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; and a &amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;tonic&amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; components. Load-related increases of blood oxygenation were studied for the four different levels of task difficulty. Generalized Linear

Research paper thumbnail of Cardiac performance during exercise in patients with Fabry's disease

European Journal of Clinical Investigation, 2008

Background Fatigability and dyspnoea on effort are present in many patients with Fabry's disease.... more Background Fatigability and dyspnoea on effort are present in many patients with Fabry's disease. We assessed the determinants of cardiac performance during exercise in patients with Fabry's disease and preserved left ventricular ejection fraction at rest. Materials and methods Sixteen patients with Fabry's disease and 16 control subjects underwent radionuclide angiography at rest and during exercise, tissue Doppler echocardiography and magnetic resonance imaging at rest. Results The exercise-induced change in stroke volume was +25 ± 14% in controls and +5•8 ± 19% in patients with Fabry's disease (P < 0•001). In 10 patients (group 1), the stroke volume increased (+19 ± 10%), and in 6 patients (group 2) it decreased (-16 ± 9%) with exercise. Patients of group 2 were older, had worse renal function, higher left ventricular mass and impaired diastolic function compared to group 1. The abnormal stroke volume response to exercise in group 2 was associated with a decrease in end-diastolic volume (P < 0•001) and a lack of reduction of end-systolic volume (P < 0•01) compared with both controls and group 1. The ratio of peak earlydiastolic velocity from mitral filling to peak early-diastolic mitral annulus velocity was the only independent predictor of exercise-induced change in stroke volume (B-0•44; SE 0•119; β-0•70; P < 0•005). Conclusions The majority of patients with Fabry's disease were able to augment stroke volume during exercise by increasing end-diastolic volume, whereas patients with more advanced cardiac involvement may experience the inability to increase cardiac output by the Frank Starling mechanism.

Research paper thumbnail of Usefulness of Satisfactory Control of Low-Density Lipoprotein Cholesterol to Predict Left Ventricular Remodeling After a First ST-Elevation Myocardial Infarction Successfully Reperfused

The American Journal of Cardiology, 2011

Research paper thumbnail of Prognostic value of dobutamine stress echocardiography in patients with terminal renal insufficiency undergoing hemodialysis: A 5-year follow up

Research paper thumbnail of Abstracts of Presentations at the International Conference

Research paper thumbnail of Mapping Cerebral Hemodynamics in Brain Cortex by Multi-Channel Time-Resolved Near-Infrared Spectroscopy

Biomedical Optics, 2006

1. Introduction Mapping functional activation in the human brain by optical radiation is a challe... more 1. Introduction Mapping functional activation in the human brain by optical radiation is a challenging task [1]. The diffusive nature of biological tissues prevents in fact the discrimination of absorption and scattering contributions by simple continuous wave (CW) techniques. Therefore, CW techniques measure changes in the absorption coefficient and consequently derive changes, rather than absolute values, in the hemodynamic parameters (ie concentration of oxyhemoglobin and deoxy-hemoglobin) [2]. For a majority of applications this approach is nonetheless ...

Research paper thumbnail of Heuristic Analytical Solution of the Time Dependent Radiative Transfer Equation for a Semi-Infinite Medium

Research paper thumbnail of Monitoring Muscle Hemodynamics by Time-Domain Near Infrared Spectroscopy during Muscle Contractions Induced by Functional Electrical Stimulation

Biomedical Optics, 2008

Abstract A time-domain NIRS multichannel system was used to monitor hemodynamic changes in the mu... more Abstract A time-domain NIRS multichannel system was used to monitor hemodynamic changes in the muscle of 6 healthy volunteers and 4 hemiplegic patients during knee flex-extension induced by functional electrical stimulation for rehabilitation purposes.

Research paper thumbnail of Reconstruction in Diffuse Optical Tomography Using Genetic Algorithm

Biomedical Optics and 3-D Imaging, 2010

Diffuse optical tomography can be solved by global optimization method (genetic algorithm). For n... more Diffuse optical tomography can be solved by global optimization method (genetic algorithm). For noise-free data, GA can find exact solutions with a probability of 80%. For noisy data, GA has better performance than Tikhonov regularization.

Research paper thumbnail of Effects of tissue heterogeneity on the optical estimate of breast density

Breast density is a recognized strong and independent risk factor for developing breast cancer. A... more Breast density is a recognized strong and independent risk factor for developing breast cancer. At present, breast density is assessed based on the radiological appearance of breast tissue, thus relying on the use of ionizing radiation. We have previously obtained encouraging preliminary results with our portable instrument for time domain optical mammography performed at 7 wavelengths (635-1060 nm). In that case, information was averaged over four images (cranio-caudal and oblique views of both breasts) available for each subject. In the present work, we tested the effectiveness of just one or few point measurements, to investigate if tissue heterogeneity significantly affects the correlation between optically derived parameters and mammographic density. Data show that parameters estimated through a single optical measurement correlate strongly with mammographic density estimated by using BIRADS categories. A central position is optimal for the measurement, but its exact location is not critical.

Research paper thumbnail of Cerebral cortex activation mapping upon electrical muscle stimulation by 32-channel time-domain functional near-infrared spectroscopy

The application of different EMS current thresholds on muscle activates not only the muscle but a... more The application of different EMS current thresholds on muscle activates not only the muscle but also peripheral sensory axons that send proprioceptive and pain signals to the cerebral cortex. A 32-channel time-domain fNIRS instrument was employed to map regional cortical activities under varied EMS current intensities applied on the right wrist extensor muscle. Eight healthy volunteers underwent four EMS at different current thresholds based on their individual maximal tolerated intensity (MTI), i.e., 10 % < 50 % < 100 % < over 100 % MTI. Time courses of the

Research paper thumbnail of Bone tissue phantoms for optical flowmeters at large interoptode spacing generated by 3D-stereolithography

Research paper thumbnail of Optical mammography: Characterization of malignant and benign breast lesions by a perturbative model

Benign and malignant breast lesions were characterized in terms of both absorption properties and... more Benign and malignant breast lesions were characterized in terms of both absorption properties and constituent concentration by the use of a perturbative model. Differences between lesions and healthy tissue were observed.

Research paper thumbnail of Optical properties of developing pip and stone fruit reveal underlying structural changes

Analyzing the optical properties of fruits represents a powerful approach for non-destructive obs... more Analyzing the optical properties of fruits represents a powerful approach for non-destructive observations of fruit development. With classical spectroscopy in the visible and near-infrared wavelength ranges, the apparent attenuation of light results from its absorption or scattering. In horticultural applications, frequently, the normalized difference vegetation index (NDVI) is employed to reduce the effects of varying scattering properties on the apparent signal. However, this simple approach appears to be limited. In the laboratory, with time-resolved reflectance spectroscopy, the absorption coefficient, μa , and the reduced scattering coefficient, μs &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;, can be analyzed separately. In this study, these differentiated optical properties were recorded (540-940 nm), probing fruit tissue from the skin up to 2 cm depth in apple (Malus × domestica &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;Elstar&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;) and plum (Prunus domestica &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;Tophit plus&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;) harvested four times (65-145 days after full bloom). The μa spectra showed typical peak at 670 nm of the chlorophyll absorption. The μs &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; at 670 nm in apple changed by 14.7% (18.2-15.5 cm(-1) ), while in plum differences of 41.5% (8.5-5.0 cm(-1) ) were found. The scattering power, the relative change of μs &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;, was zero in apple, but enhanced in plum over the fruit development period. This mirrors more isotropic and constant structures in apple compared with plum. For horticultural applications, the larger variability in scattering properties of plum explains the discrepancy between commercially assessed NDVI values or similar indices and the absolute μa values in plum (R &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05), while the NDVI approach appeared reasonable in apple (R ≥ 0.80).

Research paper thumbnail of Tomography of brain activation using a time-gated camera

Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 2009

The mean penetration depth of diffusely reflected photons is dependent on the arrival time t of p... more The mean penetration depth of diffusely reflected photons is dependent on the arrival time t of photons, but not on the source-detector distance. Thus, all photons collected at the same t have the same depth sensitivity, and can be used for the reconstruction.

Research paper thumbnail of Measurement of the local muscular metabolism by time-domain near infrared spectroscopy during knee flex-extension induced by functional electrical stimulation

Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 2009

We present a preliminary study that combines functional electrical stimulation and time-domain ne... more We present a preliminary study that combines functional electrical stimulation and time-domain near infrared spectroscopy for a quantitative measurement of the local muscular metabolism during rehabilitation of post-acute stroke patients. Seven healthy subjects and nine post-acute stroke patients underwent a protocol of knee flex-extension of the quadriceps induced by functional electrical stimulation. During the protocol time-domain near infrared spectroscopy measurement were performed on both left and right muscle. Hemodynamic parameters (concentration of oxy-and deoxy-genated hemoglobin) during baseline did not show any significant differences between healthy subject and patients, while functional performances (knee angle amplitude) were distinctly different. Nevertheless, even if their clinical histories were noticeably different, there was no differentiation among functional performances of patients. On the basis of the hemodynamic parameters measured during the recovery phase, instead, it was possible to identify two classes of patients showing a metabolic trend similar or very different to the one obtained by healthy subjects. The presented results suggest that the combination of functional and metabolic information can give an additional tool to the clinicians in the evaluation of the rehabilitation in post-acute stroke patients.

Research paper thumbnail of Functional tomography using a time-gated ICCD camera

Biomedical Optics Express, 2011

We present a system for near infrared functional tomography based on a single pulsed source and a... more We present a system for near infrared functional tomography based on a single pulsed source and a time-gated camera, for non-contact collection over a large area. The mean penetration depth of diffusely reflected photons is dependent on the arrival time of photons, but not on the source-detector distance. Thus, time-encoded data can be used to recover depth information while photon exiting point is exploited for lateral localization. This approach was tested against simulations, demonstrating both detection and localization capabilities. Preliminary measurements on inhomogeneous phantoms showed good detection sensibility, even for a low optical perturbation, and localization capabilities, yet with decreasing spatial resolution for increasing depths. Potential application of this method to in vivo functional studies on the brain is discussed.

Research paper thumbnail of Functional near-infrared spectroscopy at small source-detector distance by means of high dynamic-range fast-gated SPAD acquisitions: first in-vivo measurements

Neurophotonics, 2013

ABSTRACT In this article, we show experimental results of time-resolved optical spectroscopy perf... more ABSTRACT In this article, we show experimental results of time-resolved optical spectroscopy performed with small distance between launching and detecting fibers. It was already demonstrated that depth discrimination is independent of source-detector separation and that measurements at small sourcedetector distance provide better contrast and spatial resolution. The main disadvantage is represent by the huge increase in early photons (scarcely diffused by tissue) peak that can saturate the dynamic range of most detectors, hiding information carried by late photons. Thanks to a fast-gated Single- Photon Avalanche Diode (SPAD) module, we are able to reject the peak of early photons and to obtain high-dynamic range acquisitions. We exploit fast-gated SPAD module to perform for the first time functional near-infrared spectroscopy (fNIRS) at small source-detector distance for in vivo measurements and we demonstrate the possibility to detect non-invasively the dynamics of oxygenated and deoxygenated haemoglobin occurring in the motor cortex during a motor task. We also show the improvement in terms of signal amplitude and Signal-to-Noise Ratio (SNR) obtained exploiting fastgated SPAD performances with respect to “non-gated” measurements.

Research paper thumbnail of A method for discriminating systemic and cortical hemodynamic changes by time domain fNIRS

Neurophotonics, 2013

ABSTRACT Functional near-infrared spectroscopy (fNIRS) is a non-invasive optical technique able t... more ABSTRACT Functional near-infrared spectroscopy (fNIRS) is a non-invasive optical technique able to measure hemodynamic response in the brain cortex. Among the different approaches the fNIRS can be based on, the time resolved one allows a straightforward relationship between the photon detection time and its path within the medium, improving the discrimination of the information content relative to the different layers the tissues are composed of. Thus absorption and scattering properties of the probed tissue can be estimated, and from them the oxy- and deoxy-hemoglobin concentration. However, an open issue in the optical imaging studies is still the accuracy in separating the superficial hemodynamic changes from those happening in deeper regions of the head and more likely involving the cerebral cortex. In fact a crucial point is the precise estimate of the time dependent pathlength spent by photons within the perturbed medium. A novel method for the calculus of the absorption properties in time domain fNIRS, based on a refined computation of photon pathlength in multilayered media, is proposed. The method takes into account the non-ideality of the measurement system (its instrument response function) and the heterogeneous structure of the head. The better accuracy in computing the optical pathlength can improve the NIRS data analysis, especially for the deeper layer. Simulations and preliminary analysis on in vivo data have been performed to validate the method and are here presented.

Research paper thumbnail of Anatomical Brain Atlas for NIRS Measurements of Brain Activation

Diffuse Optical Imaging III, 2011

Abstract Anatomical brain atlases have been introduced in the analysis NIRS data of brain activat... more Abstract Anatomical brain atlases have been introduced in the analysis NIRS data of brain activation and good spatial activation localization has been proved. We applied this method to visualize NIRS data from different protocols.

Research paper thumbnail of <title>Frontal brain activation during a working memory task: a time-domain fNIRS study</title>

Photonic Therapeutics and Diagnostics V, 2009

We evaluated frontal brain activation during a working memory task with graded levels of difficul... more We evaluated frontal brain activation during a working memory task with graded levels of difficulty in a group of 19 healthy subjects, by means of time-resolved fNIRS technique. Brain activation was computed, and was then separated into a &amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;block-related&amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; and a &amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;tonic&amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; components. Load-related increases of blood oxygenation were studied for the four different levels of task difficulty. Generalized Linear