Papers by Marco Castellaro
ABSTRACT Questo lavoro ha avuto lo scopo di caratterizzare l'emodinamica cerebrale in paz... more ABSTRACT Questo lavoro ha avuto lo scopo di caratterizzare l'emodinamica cerebrale in pazienti affetti da sclerosi multipla a partire dalla definizione di un protocollo di acquisizione ottimizzato per questo tipo di indagini per poi proseguire nella quantificazione della perfusione cerebrale e nella sua analisi. é stato quindi definito, testato e validato un protocollo di acquisizione Dynamic Susceptibility Contrast (DSC-MRI), che è entrato a far parte della sequenza di esami standard che viene effettuata nei soggetti affetti da sclerosi multipla. In seguito si è adattato e migliorato un software preesistente per la quantificazione dei parametri emodinamici per il protocollo DSC-MRI. Inoltre si è messo a punto un metodo per l'analisi delle lesioni corticali tra soggetti diversi, confrontandole con l'andamento nelle zone apparentemente normali della materia grigia. é stato quindi possibile individuare una diminuzione significativa del flusso e del volume ematico (CBF e CBV) ed un aumento significativo del tempo medio di transito (MTT)
ABSTRACT Questo lavoro ha avuto lo scopo di caratterizzare l'emodinamica cerebrale in paz... more ABSTRACT Questo lavoro ha avuto lo scopo di caratterizzare l'emodinamica cerebrale in pazienti affetti da sclerosi multipla a partire dalla definizione di un protocollo di acquisizione ottimizzato per questo tipo di indagini per poi proseguire nella quantificazione della perfusione cerebrale e nella sua analisi. é stato quindi definito, testato e validato un protocollo di acquisizione Dynamic Susceptibility Contrast (DSC-MRI), che è entrato a far parte della sequenza di esami standard che viene effettuata nei soggetti affetti da sclerosi multipla. In seguito si è adattato e migliorato un software preesistente per la quantificazione dei parametri emodinamici per il protocollo DSC-MRI. Inoltre si è messo a punto un metodo per l'analisi delle lesioni corticali tra soggetti diversi, confrontandole con l'andamento nelle zone apparentemente normali della materia grigia. é stato quindi possibile individuare una diminuzione significativa del flusso e del volume ematico (CBF e CBV) ed un aumento significativo del tempo medio di transito (MTT)
Journal of Cognitive Neuroscience, 2016
A consolidated practice in cognitive neuroscience is to explore the properties of human visual wo... more A consolidated practice in cognitive neuroscience is to explore the properties of human visual working memory through the analysis of electromagnetic signals using cued change detection tasks. Under these conditions, EEG/MEG activity increments in the posterior parietal cortex scaling with the number of memoranda are often reported in the hemisphere contralateral to the objects' position in the memory array. This highly replicable finding clashes with several reported failures to observe compatible hemodynamic activity modulations using fMRI or fNIRS in comparable tasks. Here, we reconcile this apparent discrepancy by acquiring fMRI data on healthy participants and employing a cluster analysis to group voxels in the posterior parietal cortex based on their functional response. The analysis identified two distinct subpopulations of voxels in the intraparietal sulcus (IPS) showing a consistent functional response among participants. One subpopulation, located in the superior IPS, showed a bilateral response to the number of objects coded in visual working memory. A different subpopulation, located in the inferior IPS, showed an increased unilateral response when the objects were displayed contralaterally. The results suggest that a cluster of neurons in the inferior IPS is a candidate source of electromagnetic contralateral responses to working memory load in cued change detection tasks.
Multiple sclerosis (Houndmills, Basingstoke, England), Jan 3, 2016
Although temporal lobe pathology may explain some of the symptoms of multiple sclerosis (MS), its... more Although temporal lobe pathology may explain some of the symptoms of multiple sclerosis (MS), its role in the pathogenesis of seizures has not been clarified yet. To investigate the role of temporal lobe damage in MS patients suffering from epilepsy, by the application of advanced multimodal 3T magnetic resonance imaging (MRI) analysis. A total of 23 relapsing remitting MS patients who had epileptic seizures (RRMS/E) and 23 disease duration matched RRMS patients without any history of seizures were enrolled. Each patient underwent advanced 3T MRI protocol specifically conceived to evaluate grey matter (GM) damage. This includes grey matter lesions (GMLs) identification, evaluation of regional cortical thickness and indices derived from the Neurite Orientation Dispersion and Density Imaging model. Regional analysis revealed that in RRMS/E, the regions most affected by GMLs were the hippocampus (14.2%), the lateral temporal lobe (13.5%), the cingulate (10.0%) and the insula (8.4%). Co...
PLOS ONE, 2015
Both gray-matter (GM) atrophy and lesions occur from the earliest stages of Multiple Sclerosis (M... more Both gray-matter (GM) atrophy and lesions occur from the earliest stages of Multiple Sclerosis (MS) and are one of the major determinants of long-term clinical outcomes. Nevertheless, the relationship between focal and diffuse GM damage has not been clarified yet. Here we investigate the regional distribution and temporal evolution of cortical thinning and how it is influenced by the local appearance of new GM lesions at different stages of the disease in different populations of MS patients. We studied twenty MS patients with clinically isolated syndrome (CIS), 27 with early relapsing-remitting MS (RRMS, disease duration <5 years), 29 with late RRMS (disease duration ≥ 5 years) and 20 with secondary-progressive MS (SPMS). The distribution and evolution of regional cortical thickness and GM lesions were assessed during 5-year follow-up. The results showed that new lesions appeared more frequently in hippocampus and parahippocampal gyri (9.1%), insula (8.9%), cingulate cortex (8.3%), superior frontal gyrus (8.1%), and cerebellum (6.5%). The aforementioned regions showed the greatest reduction in thickness/volume, although (several) differences were observed across subgroups. The correlation between the appearance of new cortical lesions and cortical thinning was stronger in CIS (r2 = 50.0, p<0.001) and in early RRMS (r2 = 52.3, p<0.001), compared to late RRMS (r2 = 25.5, p<0.001) and SPMS (r2 = 6.3, p = 0.133). We conclude that GM atrophy and lesions appear to be different signatures of cortical disease in MS having in common overlapping spatio-temporal distribution patterns. However, the correlation between focal and diffuse damage is only moderate and more evident in the early phase of the disease.
Medical Imaging 2015: Biomedical Applications in Molecular, Structural, and Functional Imaging, 2015
ABSTRACT Motion correction in Arterial Spin Labeling (ASL) is essential to accurately assess brai... more ABSTRACT Motion correction in Arterial Spin Labeling (ASL) is essential to accurately assess brain perfusion. Motion correction techniques are usually based on intensity-related information, which might be unreliable in ASL due to local intensity differences between control and labeled acquisitions and to non-uniform volume magnetization caused by background-suppressed acquisition protocols. Accordingly, a novel motion correction technique based only on brain contour points is presented and tested against a widely used intensity-based technique (MCFLIRT). The proposed Contour-Based Motion Correction (CBCM) technique relies on image segmentation (to extract brain contour point clouds) and on Iterative Closest Point algorithm (to estimate the roto-translation required to align them). At variance with other approaches based on point clouds alignment, the local 3D curvature is also computed for each contour point and used as an additional coordinate to increase the accuracy of the alignment. The technique has been tested along with MCFLIRT on a database of randomly roto-translated brain volumes. Several error metrics have been computed and compared between the two techniques. The results show that the proposed technique is able to achieve a higher accuracy than MCFLIRT without any intensity-dependent information.
2014 IEEE 11th International Symposium on Biomedical Imaging (ISBI), 2014
In order to assess brain perfusion, one of the available methods is the estimation of parameters ... more In order to assess brain perfusion, one of the available methods is the estimation of parameters such as cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) from Dynamic Susceptibility Contrast MRI (DSC-MRI). This estimation requires both high temporal and spatial resolution to capture the rapid tracer kinetic and detect small impairments and reliably discriminate boundaries. With this in mind, we propose a compressed sensing approach to decrease the acquisition time without sacrificing the reconstruction, especially in the region affected by the tracer. Within the framework of a TV-L1-L2 minimization for solving the reconstruction from partial Fourier data, we introduce a novel baseline-constraining term weighting the difference of the reconstructed volume from the baseline in all regions where no perfusion is apparent. We show that the proposed reconstruction scheme is able to provide accurate estimation of the tracer kinetics (the necessary step for estimating CBF, CBV and MTT) in the volume even at high acceleration (x16), with a RMSE of 11, a third of what achievable without the baseline constraint.
Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine, Jan 26, 2014
QUASAR arterial spin labeling (ASL) permits the application of deconvolution approaches for the a... more QUASAR arterial spin labeling (ASL) permits the application of deconvolution approaches for the absolute quantification of cerebral perfusion. Currently, oscillation index regularized singular value decomposition (oSVD) combined with edge-detection (ED) is the most commonly used method. Its major drawbacks are nonphysiological oscillations in the impulse response function and underestimation of perfusion. The aim of this work is to introduce a novel method to overcome these limitations. A system identification method, stable spline (SS), was extended to address ASL peculiarities such as the delay in arrival of the arterial blood in the tissue. The proposed framework was compared with oSVD + ED in both simulated and real data. SS was used to investigate the validity of using a voxel-wise tissue T1 value instead of using a single global value (of blood T1 ). SS outperformed oSVD + ED in 79.9% of simulations. When applied to real data, SS exhibited a physiologically realistic range for...
ABSTRACT Hemodynamics of the human brain may be studied with Dynamic Susceptibility Contrast MRI ... more ABSTRACT Hemodynamics of the human brain may be studied with Dynamic Susceptibility Contrast MRI (DSC-MRI) imaging. The sequence of volumes obtained exhibits a strong spatiotemporal correlation, that can be exploited to predict which measurements will bring mostly the new information contained in the next frames. In general, the sampling speed is an important issue in many applications of the MRI, so that the focus of many current researches is to study methods to reduce the number of measurement samples needed for each frame without degrading the image quality. For the DSC-MRI, the frequency under-sampling of single frame can be exploited to make more frequent space or time acquisitions, thus increasing the time resolution and allowing the analysis of fast dynamics not yet observed. Generally (and also for MRI), the recovery of sparse signals has been achieved by Compressed Sensing (CS) techniques, which are based on statistical properties rather than deterministic ones.. By studying analytically the compound Fourier+Wavelet transform, involved in the processes of reconstruction and sparsification of MR images, we propose a deterministic technique for a rapid-MRI, exploiting the relations between the wavelet sparse representation of the recovered and the frequency samples. We give results on real images and on artificial phantoms with added noise, showing the superiority of the methods both with respect to classical Iterative Hard Thresholding (IHT) and to Location Constraint Approximate Message Passing (LCAMP) reconstruction algorithms.
ABSTRACT In order to asses brain perfusion, one of the available methods is the estimation of par... more ABSTRACT In order to asses brain perfusion, one of the available methods is the estimation of parameters such as cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) from Dynamic Susceptibility Contrast-MRI (DSC-MRI). This estimation requires both high temporal resolution to capture the rapid tracer kinetic, and high spatial resolution to detect small impairments and reliably discriminate boundaries.With this inmind, we propose a compressed sensing approach to decrease the acquisition time without sacrificing the reconstruction, especially in the region affected by tracer passage. To this end we propose the utilization of an available TVL1- L2 minimization scheme with a novel additional term that introduce the information on the volume at baseline (no tracer). We show on simulated data the benefit of such a scheme, that is able to achieve an accurate reconstruction even at high acceleration (x16), with a RMSE of 2.8, 10 times lower than the error obtained with the original reconstruction.
Journal of Cerebral Blood Flow & Metabolism, 2013
In this study, dynamic susceptibility contrast-magnetic resonance imaging (DSC-MRI) was used to q... more In this study, dynamic susceptibility contrast-magnetic resonance imaging (DSC-MRI) was used to quantify the cerebral blood flow (CBF), the cerebral blood volume (CBV), and the mean transit time (MTT) and to analyze the changes in cerebral perfusion associated with the cortical lesions in 44 patients with relapsing-remitting multiple sclerosis. The cortical lesions showed a statistically significant reduction in CBF and CBV compared with the normal-appearing gray matter, whereas there were no significant changes in the MTT. The reduced perfusion suggests a reduction of metabolism because of the loss of cortical neurons. A small population of outliers showing an increased CBF and/or CBV has also been detected. The presence of hyperperfused outliers may imply that perfusion could evolve during inflammation. These findings show that perfusion is altered in cortical lesions and that DSC-MRI can be a useful tool to investigate more deeply the evolution of cortical lesions in multiple sclerosis.
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Papers by Marco Castellaro