Giuseppe Baselli

Politecnico di Milano

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S. Cerutti

Politecnico di Milano

117

Maria Marcella Laganà

Don Carlo Gnocchi Foundation

Alberto Porta

University of Milan

Francesca Baglio

Don Carlo Gnocchi Foundation

Alberto Malliani

Istituto Nazionale per le Ricerche Cardiovascolari

Anna Maria Bianchi

Politecnico di Milano

Federico Aletti

Vita-Salute San Raffaele University

Federico Lombardi

University of Milan

M. Pagani

Centro Universitário Cesumar

Elisabetta De Bernardi

University of Milano-Bicocca

Cooperative Institutions

University of Milan

210

Politecnico di Milano

184

Istituti di Ricovero e Cura a Carattere Scientifico

139

Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico

Luigi Sacco Hospital

Don Carlo Gnocchi Foundation

Ospedale Maggiore

Fondazione IRCCS Istituto Neurologico Carlo Besta

University of Brescia

National Research Council

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Evaluation of Frequency-Distance Relation Validity for FORE Optimization in 3-D PET

IEEE Transactions on Nuclear Science (2007)

Elisabetta De Bernardi Marco Mazzoli Felicia Zito Giuseppe Baselli

Fourier rebinning (FORE) is the most widely used rebinning algorithm to reorganize 3-D PET data into 2-D sinograms. In Fourier transform (FT) domain, data from oblique sinograms are assigned to transaxial ones at a proper axial displacement given by the frequency-distance relation. Approximation accuracy falls at low frequencies, where only low-copolar angles can be exploited by means of single slice rebinning (SSRB). Usually, an abrupt partition by a square region centered on DC is applied, which does not weight accuracy in the sinogram FT domain and copolar angle dependence, and can introduce artifacts due to the sharp transition. In this work we propose a simple index which maps the frequency-distance relation validity in the sinogram FT domain. Two new criteria were tested on this basis: 1) an abrupt transition based on validity map contours and 2) a gradual transition following the monotonical validity increase with frequency. In both criteria copolar angle dependence was introduced. Standard, abrupt, and gradual partitions were compared on different phantoms acquired with ECAT EXACT HR+ scanner, characterized by a large span = 9 (saved sinograms group 4 or 5 acquired sinograms, by averaging) and by a low maximum copolar angle (6deg). In this condition the methods provided similar tradeoffs of SNR optimization against blur and artifact appearance, thus confirming the validity of the frequency-distance relation at low copolar angles. A simulation study emulating an hypothetical scanner with span = 3 and larger acceptance copolar angle (25.5deg) conversely showed more clear improvements.

10.1109/tns.2007.905175

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Cardiac and Respiratory Influences on Intracranial and Neck Venous Flow, Estimated Using Real-Time Phase-Contrast MRI

Biosensors (2022)

Maria Marcella Laganà Alice Pirastru Francesca Ferrari Sonia Di Tella Marta Cazzoli

The study of brain venous drainage has gained attention due to its hypothesized link with various neurological conditions. Intracranial and neck venous flow rate may be estimated using cardiac-gated cine phase-contrast (PC)-MRI. Although previous studies showed that breathing influences the neck's venous flow, this aspect could not be studied using the conventional segmented PC-MRI since it reconstructs a single cardiac cycle. The advent of real-time PC-MRI has overcome these limitations. Using this technique, we measured the internal jugular veins and superior sagittal sinus flow rates in a group of 16 healthy subjects (12 females, median age of 23 years). Comparing forced-breathing and free-breathing, the average flow rate decreased and the respiratory modulation increased. The flow rate decrement may be due to a vasoreactive response to deep breathing. The respiratory modulation increment is due to the thoracic pump's greater effect during forced breathing compared to free breathing. These results showed that the breathing mode influences the average blood flow and its pulsations. Since effective drainage is fundamental for brain health, rehabilitative studies might use the current setup to investigate if respiratory exercises positively affect clinical variables and venous drainage.

10.3390/bios12080612

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Optimization of rapid acquisition with relaxation enhancement (RARE) pulse sequence parameters for ¹⁹F‐MRI studies

Journal of Magnetic Resonance Imaging (2013)

Alfonso Mastropietro Elisabetta De Bernardi Gian Luca Breschi Ileana Zucca Massimo Cametti

Purpose To optimize signal‐to‐noise ratio (SNR) in fast spin echo (rapid acquisition with relaxation enhancement [RARE]) sequences and to improve sensitivity in 19 F magnetic resonance imaging (MRI) on a 7T preclinical MRI system, based on a previous experimental evaluation of T 1 and T 2 actual relaxation times. Materials and Methods Relative SNR changes were theoretically calculated at given relaxation times (T 1 , T 2 ) and mapped in RARE parameter space (TR, number of echoes, flip back pulse), at fixed acquisition times. T 1 and T 2 of KPF 6 phantom samples (solution, agar mixtures, ex vivo perfused brain) were measured and experimental SNR values were compared with simulations, at optimal and suboptimal RARE parameter values. Results The optimized setting largely depended on T 1 , T 2 times and the use of flip back pulse improved SNR up to 30% in case of low T 1 /T 2 ratios. Relaxation times in different conditions showed negligible changes in T 1 (below 14%) and more evident changes in T 2 (−95% from water solution to ex vivo brain). Experimental data confirmed theoretical forecasts, within an error margin always below 4.1% at SNR losses of ∼20% and below 8.8% at SNR losses of ∼40%. The optimized settings permitted a detection threshold at a concentration of 0.5 mM, corresponding to 6.22 × 10 16 fluorine atoms per voxel. Conclusion Optimal settings according to measured relaxation times can significantly improve the sensitivity threshold in 19 F MRI studies. They were provided in a wide range of (T 1 , T 2 ) values and experimentally validated showing good agreement. J. Magn. Reson. Imaging 2014;40:162–170 . © 2013 Wiley Periodicals, Inc .

Flip angle

Pulse sequence

T2 relaxation

10.1002/jmri.24347

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A Novel Approach of Groupwise fMRI-Guided Tractography Allowing to Characterize the Clinical Evolution of Alzheimer's Disease

PLoS ONE (2014)

Maria Giulia Preti Nikos Makris George Papadimitriou Maria Marcella Laganà Ludovica Griffanti

Guiding diffusion tract-based anatomy by functional magnetic resonance imaging (fMRI), we aim to investigate the relationship between structural connectivity and functional activity in the human brain. To this purpose, we introduced a novel groupwise fMRI-guided tractographic approach, that was applied on a population ranging between prodromic and moderate stages of Alzheimer's disease (AD). The study comprised of 15 subjects affected by amnestic mild cognitive impairment (aMCI), 14 diagnosed with AD and 14 elderly healthy adults who were used as controls. By creating representative (ensemble) functionally guided tracts within each group of participants, our methodology highlighted the white matter fiber connections involved in verbal fluency functions for a specific population, and hypothesized on brain compensation mechanisms that potentially counteract or reduce cognitive impairment symptoms in prodromic AD. Our hope is that this fMRI-guided tractographic approach could have potential impact in various clinical studies, while investigating white/gray matter connectivity, in both health and disease.

Verbal fluency test

10.1371/journal.pone.0092026

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Citations (21)

Model based lesion segmentation in FDG-PET from raw data and clinical images

Giuseppe Baselli Elisabetta De Bernardi Chiara Soffientini Chiara Gianoli Elena Faggiano

A review of recent works by our group in the segmentation and quantification of oncological lesions in 18-fluoro-deoxy-glucose (FDG) positron emission tomography (PET) images is given, stressing the underlying model assumption. In a first approach, a targeted reconstruction strategy was set in the framework of linear space variant (LSV) reconstruction from projections. Resolution recovery by ordered subset expectation maximization (OSEM) from raw emission data was based on the Poissonian description of errors and on a parametric model of PET scanner space variant blurring. The targeted strategy estimates and refines lesion basis functions while freezing the rest of background in a single one, thus providing an estimate of lesion borders and uptake. In a second approach lesions are segmented on standard clinical images. Reconstructed images lose the original Poissonian features and are well fitted by Gaussian mixture models (GMM). However, this popular clustering method required a specific adaptation to lesion segmentation: constraint of the warm background based on GMM modeling of healthy tissue; proximity priors in the voxel-wise classification to extract connected object and increase noise robustness. In both approaches, the spill-out of high uptake organs in the lesion area was removed by means of appropriate models relying on the CT anatomy. Results obtained on digital and physical phantoms and on clinical datasets will be recalled.

Robustness

10.1109/rtsi.2016.7740585

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Interaction between peripheral blood flow and low frequency components in cardiovascular variability signals

Alberto Porta Giuseppe Baselli S. Cerutti Daniela Lucini L. Della Vecchia

The contribution of vasomotion to low frequency (LF, 0.03-0.14 Hz) waves in arterial pressure (AP, finger pletismography) and RR variabilities is addressed by comparing the spectra of RR, systolic AP (SAP), diastolic AP (DAP), and peripheral resistances (RES, mean AP over mean flow by laser Doppler) in the palmar region. In 22 normal volunteers, recordings were performed at rest (R) in clinostatic position and during mild exercise (EXEl, 10% maximum effort) cycling in the same position. LF predominance over the high frequency (HF, respiratory frequency) component was higher in SAP and even more in DAP than in RR; HF was virtually absent in RES. The LF central frequency shifted from 0.100 Hz for RR to 0.091 for SAP, 0.085 for DAP, and 0.073 for RES. EXEl activated LF and inhibited HF in RR; but power and frequency relationships in vascular parameters were not significantly changed.

Vasomotion

10.1109/cic.1999.826051

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Cardiovascular variability signals: towards the identification of a closed-loop model of the neural control mechanisms

IEEE Transactions on Biomedical Engineering (1988)

Giuseppe Baselli S. Cerutti Silvia Civardi Alberto Malliani M. Pagani

The authors consider parametric methods for processing cardiovascular signals and try to provide a global, although indirect evaluation of some neural regulatory activities. In particular, the variability signals of the heart rate (under the form of interval tachogram) and arterial blood pressure (systogram) together with respiratory movement signal (respirogram) are considered as inputs to a closed-loop model which describes a few aspects of the physiological interactions among the signals themselves. The identifiability of the transfer function of the model is demonstrated from the joint process black-box description of the signals. A direct identification procedure is proposed dividing the system into two dynamic adjustment models. A few suggestions are deduced on how and where the respirogram enters the model and on the genesis of the 10-s rhythm, parameters relevant to the Starling effect, Windkessel model, and the gain of baroreceptor mechanisms. The approach presented is intended also to provide a general frame for closed-loop identification in different pathophysiological conditions.< >

Identifiability

Identification

SIGNAL (programming language)

Internal model

10.1109/10.8688

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Citations (243)

Model study of the effects of interactions between systemic and peripheral circulation on interstitial fluid balance.

Federico Aletti Giuseppe Baselli

Interstitial fluid balance is severely altered in microgravity, but the mechanisms underlying the fluid shift from lower to upper body are still partially unclear. A lumped parameter model of the arterial tree with active and non linear modulation of peripheral resistances and capillary fluid exchange was adopted to simulate the response of microcirculation to pulsatility and edema. Results suggest that myogenic regulation not only impinges on arteriolar radius, but it also indirectly affects interstitial fluid balance. Non linear dynamics of blood pressure (BP) and flow in capillary beds are influenced by systemic pulsatility, hinting that local activity is involved in the response to peripheral edema as well.

Interstitial fluid

Interstitial space

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Opening the black box of machine learning in radiology: can the proximity of annotated cases be a way?

European Radiology Experimental (2020)

Giuseppe Baselli Marina Codari Francesco Sardanelli

Abstract Machine learning (ML) and deep learning (DL) systems, currently employed in medical image analysis, are data-driven models often considered as black boxes . However, improved transparency is needed to translate automated decision-making to clinical practice. To this aim, we propose a strategy to open the black box by presenting to the radiologist the annotated cases (ACs) proximal to the current case (CC), making decision rationale and uncertainty more explicit. The ACs, used for training, validation, and testing in supervised methods and for validation and testing in the unsupervised ones, could be provided as support of the ML/DL tool. If the CC is localised in a classification space and proximal ACs are selected by proper metrics, the latter ones could be shown in their original form of images, enriched with annotation to radiologists, thus allowing immediate interpretation of the CC classification. Moreover, the density of ACs in the CC neighbourhood, their image saliency maps, classification confidence, demographics, and clinical information would be available to radiologists. Thus, encrypted information could be transmitted to radiologists, who will know model output (what) and salient image regions (where) enriched by ACs, providing classification rationale (why). Summarising, if a classifier is data-driven, let us make its interpretation data-driven too.

Black box

10.1186/s41747-020-00159-0

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Citations (41)

Simultaneous Measures of Kinematics and fMRI

Claudia Casellato Simona Ferrante Nicola Volonterio Giancarlo Ferrigno Giuseppe Baselli

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