Maria Filomena Santarelli

National Research Council, Roma, Latium, Italy

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Publications (133)226.7 Total impact

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    ABSTRACT: Magnetic resonance spectroscopy (MRS) of hyperpolarized 13C pyruvate and its metabolites in large animal models is a powerful tool for assessing cardiac metabolism in patho-physiological conditions. In 13C studies, a high signal-to-noise ratio (SNR) is crucial to overcome the intrinsic data quality limitation due to the low molar concentration of certain metabolites as well as the low flux of conversion. Since 13C-MRS is essentially a semi-quantitative technique, the SNR of the spectra acquired in different myocardial segments should be homogeneous. MRS coil design plays an important role in achieving both targets. In this study, a 16-channel receive surface coil was designed for 13C hyperpolarized studies of the pig heart with a clinical 3-T scanner. The coil performance was characterized by phantom experiments and compared with that of a birdcage coil used in transmit/receive mode. Segmental signal distribution in the left ventricle (LV) was assessed by experiments on six healthy mini pigs. The proposed coil showed a significant increase in SNR for the LV wall close to the coil surface with respect to that for the birdcage but also significant segmental inhomogeneity. Hence, the use of the 16-channel coil is recommended for studies of septal and anterior LV walls.
    Full-text · Article · Jan 2016 · Journal of Medical and Biological Engineering
  • M F Santarelli · V Positano · N Martini · G Valvano · L Landini
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    ABSTRACT: Most recent technical innovations in cardiovascular MR imaging (CMRI) are presented in this review. They include hardware and software developments, and novelties in parametric mapping. All these recent improvements lead to high spatial and temporal resolution and quantitative information on the heart structure and function. They make it achievable ambitious goals in the field of magnetic resonance, such as the early detection of cardiovascular pathologies. In this review article, we present recent innovations in CMRI, emphasizing the progresses performed and the solutions proposed to some yet opened technical problems.
    No preview · Article · Nov 2015 · Current pharmaceutical design
  • Giuseppe Valvano · Nicola Martini · Luigi Landini · Maria Filomena Santarelli
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    ABSTRACT: To develop a 3D sampling strategy based on a stack of variable density spirals for compressive sensing MRI. A random sampling pattern was obtained by rotating each spiral by a random angle and by delaying for few time steps the gradient waveforms of the different interleaves. A three-dimensional (3D) variable sampling density was obtained by designing different variable density spirals for each slice encoding. The proposed approach was tested with phantom simulations up to a five-fold undersampling factor. Fully sampled 3D dataset of a human knee, and of a human brain, were obtained from a healthy volunteer. The proposed approach was tested with off-line reconstructions of the knee dataset up to a four-fold acceleration and compared with other noncoherent trajectories. The proposed approach outperformed the standard stack of spirals for various undersampling factors. The level of coherence and the reconstruction quality of the proposed approach were similar to those of other trajectories that, however, require 3D gridding for the reconstruction. The variable density randomized stack of spirals (VDR-SoS) is an easily implementable trajectory that could represent a valid sampling strategy for 3D compressive sensing MRI. It guarantees low levels of coherence without requiring 3D gridding. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
    No preview · Article · Jul 2015 · Magnetic Resonance in Medicine
  • Valentina Hartwig · Nicola Vanello · Giulio Giovannetti · Luigi Landini · Maria Filomena Santarelli
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    ABSTRACT: The purpose of this work is to estimate the induced electric field E due to movements of magnetic resonance (MR) workers in static magnetic field. Different operator walking speeds and paths are taken into account, based on real-world scenarios for a 3T MR scanner. The spectral components of magnetic field gradient are estimated to verify the compliance with the specific International Commission on Non-Ionizing Radiation Protection safety guidelines for MR workers. The induced electric fields on the chosen paths are estimated using a previously described software tool based on an analytical model. Finally, a real situation is considered in which an operator performs the patient preparation for a brain MR examination. From the spectral components of the motion-induced magnetic field gradient, it is possible to see that the highest values are concentrated on frequencies below 1 Hz. For the basic paths considered, the worst-case scenario is a walking perpendicular to the magnet cylinder along the x-axis. For the example of a real path, the critical zone where the worker exposure is highest is highlighted. The results of this study could be used for training MR workers to follow correct behavior in the scanner room to avoid high-exposure scenarios. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering), 2015
    No preview · Article · Mar 2015 · Concepts in Magnetic Resonance Part B Magnetic Resonance Engineering
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    ABSTRACT: Hyperpolarized 13C Magnetic Resonance represents a promising modality for in vivo spectroscopy since it provides a unique opportunity for the non-invasive assessment of regional cardiac metabolism. Although it represents a powerful tool for the study of the heart physiology in pig models, by permitting metabolic activity mapping, a number of technological problems still limit this technology and need innovative solutions such as the design of suitable radiofrequency (RF) coils, capable to provide a large sensitivity region.
    No preview · Article · Jan 2015 · Measurement
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    ABSTRACT: Magnetic resonance (MRI) with hyperpolarized 13C-pyruvate is a new technique for the assessment of myocardial metabolism.
    Full-text · Article · Jan 2015 · IJC Metabolic and Endocrine
  • M.F. Santarelli · V. Positano · L. Landini
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    ABSTRACT: In the present work, a dynamic PET data generation and analysis tool is described. It allows to analyze several factors influencing the data SNR and the consequent correctness of the pharmacokinetic parameters estimation.
    No preview · Article · Jan 2015 · IFMBE proceedings
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    ABSTRACT: T2(⁎) maps obtained by the processing of multiecho MR sequences can be useful in several clinical applications. T2(⁎) map generation procedures should join a processing time compatible with on-line image analysis with a good precision in the entire T2(⁎) range of clinical interest. Fast generation of T2(⁎) maps can be achieved by the estimation of the T2(⁎) values by the weighted linear fitting of the logarithm of the signal (WLSL) method. This approach fails if the signal decay diverges from a pure exponential decay, as happens at low T2((⁎)) values where the rapid decay in the signal intensity leads to a plateau in the later echo times (TE). The proposed method implements the automatic truncation of the signal decay curves to be fitted in order to compensate for the signal collapse at low T2(⁎) values, allowing the extension of the WLSL method through the entire clinical range of T2(⁎) values. Validation was performed on synthetic images and on 60 thalassemia major patients with different levels of myocardial iron overload. Phantom experiments showed that a 5% fitting error threshold represented the best compromise between T2(⁎) value measurement precision and processing time. A good agreement was found between T2(⁎) map pixel-wise measurements and ROI-based measurements performed by expert readers (CoV=1.84% in global heart T2(⁎), CoV=5.8% in segmental analysis). In conclusion, the developed procedure was effective in generating correct T2(⁎) maps for the entire T2(⁎) clinical range. Copyright © 2014 Elsevier Ltd. All rights reserved.
    No preview · Article · Nov 2014 · Computers in Biology and Medicine
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    ABSTRACT: Dissolution-dynamic nuclear polarization (dissolution-DNP) for magnetic resonance (MR) spectroscopic imaging has recently emerged as a novel technique for noninvasive studies of the metabolic fate of biomolecules in vivo. Since acetate is the most abundant extra- and intracellular short-chain fatty acid, we focused on [1-13C]acetate as a promising candidate for a chemical probe to study the myocardial metabolism of a beating heart. The dissolution-DNP procedure of Na[1-13C]acetate for in vivo cardiac applications with a 3 T MR scanner was optimized in pigs during bolus injection of doses of up to 3 mmol. The Na[1-13C]acetate formulation was characterized by a liquid-state polarization of 14.2% and a T1Effin vivo of 17.6 ± 1.7 s. In vivo Na[1-13C]acetate kinetics displayed a bimodal shape: [1-13C]acetyl carnitine (AcC) was detected in a slice covering the cardiac volume, and the signal of 13C-acetate and 13C-AcC was modeled using the total area under the curve (AUC) for kinetic analysis. A good correlation was found between the ratio AUC(AcC)/AUC(acetate) and the apparent kinetic constant of metabolic conversion, from [1-13C]acetate to [1-13C]AcC (kAcC), divided by the AcC longitudinal relaxation rate (r1). Our study proved the feasibility and the limitations of administration of large doses of hyperpolarized [1-13C]acetate to study the myocardial conversion of [1-13C]acetate in [1-13C]acetyl-carnitine generated by acetyltransferase in healthy pigs. Copyright © 2014 John Wiley & Sons, Ltd.
    Full-text · Article · Sep 2014 · Contrast Media & Molecular Imaging
  • Santarelli M.F. · Martini N. · Positano P. · Landini L.
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    ABSTRACT: Cardiac health depends on the heart's ability to utilize different substrates to support overall oxidative metabolism. To characterize a variety of cardiac diseases, there is an ever-growing demand for an accurate non-invasive approach to evaluating myocardial substrate metabolism. Data obtained from quantitative metabolic imaging modalities add functional information to the anatomic imaging modalities and can aid patient management. The goal of this review is to emphasize the role of non-invasive imaging techniques (such as PET, SPECT, MR spectroscopy and spectroscopic imaging) to detect the metabolic footprints of heart disease. The advancement of models and methods to estimate kinetic parameters of dynamic processes using data acquired from cardiac imaging modalities is discussed.
    No preview · Article · Apr 2014 · Current pharmaceutical design
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    ABSTRACT: Sodium MRI is a powerful tool for providing biochemical information on the tissue viability, cell integrity and function in quantitative and noninvasive manner and it has already been applied in vivo in most human tissues. Although it could provide useful and new information not available with classic proton MRI, the low detectable sodium signal gives rise to technological limitations in terms of data quality when using clinical scanners. The design of dedicated coils capable of providing large field of view with high Signal-to-Noise Ratio (SNR) data is of fundamental importance. This work presents magnetostatic simulation, test and application of a transmit/receive circular coil designed for 23Na MR experiments in phantoms and humans with a clinical 3T scanner. In particular, the paper provides details of the design, modeling and construction of the coil. Such coil prototype was tested at workbench by using a dual-loop probe and a network analyzer, for quality factors and Q ratios measurements. Finally, the coil was employed in MR experiments to acquire phantom and in vivo data on different human organs (heart, kidney, calf and brain).
    No preview · Article · Apr 2014 · Measurement
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    ABSTRACT: Reconstruction methods for Non-Cartesian magnetic resonance imaging have often been analyzed using the root mean square error (RMSE). However, RMSE is not able to measure the level of structured error associated with the reconstruction process. An index for geometric information loss was presented using the 2D autocorrelation function. The performances of Least Squares Non Uniform Fast Fourier Transform (LS-NUFFT) and gridding reconstruction (GR) methods were compared. The Direct Summation method (DS) was used as reference. For both methods, RMSE and the loss in geometric information were calculated using a digital phantom and a hyperpolarized (13)C dataset. The performance of the geometric information loss index was analyzed in the presence of noise. Comparing to GR, LS-NUFFT obtained a lower RMSE, but its error image appeared more structured. This was observed in both phantom and in vivo experiments. The evaluation of geometric information loss together with the reconstruction error was important for an appropriate performance analysis of the reconstruction methods. The use of geometric information loss was helpful to determine that LS-NUFFT loses relevant information in the reconstruction process, despite the low RMSE.
    No preview · Article · Dec 2013 · Computers in Biology and Medicine
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    ABSTRACT: Magnetic resonance imaging (MRI) using high static field (>3T) generates high-quality images, thanks to high homogeneity in transmission as well as high signal-to-noise ratio (SNR) in reception. On the other hand, biological effects are proportional to the magnetic field strength and moreover the diagnostic accuracy is not always linked to high-quality imaging. For these reasons, the interest in low-field imaging becomes greater, also because of cheaper setting, greater patients comfort and more safety profile. In simple cases, as for surface coil, the coil performance is evaluated using classical electromagnetic theory, but for more complex geometry and in presence of a sample, is more difficult to evaluate the solution and often is necessary to follow a trial-and-error approach. Numerical methods represent a solution to this problem. In this work, we performed numerical simulation on a two-channel knee coil for low-field (0.5 T) MRI scanner. We are interested in seeing the effect of a sample placed inside the coil on the sample-induced resistance and decoupling between channels. In particular, we observe how the position of the sample inside the channel influences the resistance value and for performing this we compared an innovative method based on the exponential fitting on voltage oscillation damping with a validated method (estimation using quality factor). Finally, for the complete coil, the scatter parameters were calculated in loaded and unloaded conditions.
    No preview · Article · Dec 2013 · Applied Magnetic Resonance
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    ABSTRACT: Hyperpolarized C-13 magnetic resonance spectroscopy in pig models enables cardiac metabolism assessment and provides a powerful tool for heart physiology studies, although the low molar concentration of derivate metabolites gives rise to technological limitations in terms of data quality. The design of dedicated coils capable of providing large field of view with high Signal-to-Noise Ratio (SNR) data is of fundamental importance. This work presents magnetostatic simulations and tests of two butterfly coils with different geometries, both designed for C-13 hyperpolarized studies of pig heart with a clinical 3T scanner. In particular, the paper provides details of the design, modeling, construction and application of the butterfly style coils. While both coils could be successfully employed in single configuration (linear mode), the second prototype was used to design a quadrature surface coil constituted by the butterfly and a circular loop both in receive (RX) mode while using a birdcage coil as transmitter (TX). The performance of this coils configuration was compared with the single TX/RX birdcage coil, in order to verify the advantage of the proposed configuration over the volume coil throughout the volume of interest for cardiac imaging in pig. Experimental SNR-vs-depth profiles, extracted from the [1-C-13] acetate phantom chemical shift image (CSI), permitted to highlight the performance of the proposed coils configuration.
    No preview · Article · Nov 2013 · Measurement
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    ABSTRACT: Hyperpolarized 13C magnetic resonance spectroscopy in pig models enables metabolic activity mapping, providing a powerful tool for the study of the heart physiology, but requires the development of dedicated radiofrequency coils, capable of providing large field of view with high signal-to-noise ratio (SNR) data. This work describes the simulations and the tests of a transmit-only (TX) volume coil/receive-only (RX) surface coil both designed for hyperpolarized studies of pig heart with a clinical 3T scanner. The coil characterization is performed by developing an SNR model for coil performance in terms of coil resistance, sample-induced resistance and magnetic field pattern. In particular, coil resistances were calculated from Ohm’s law, while magnetic field patterns and sample-induced resistances were calculated using a numerical finite-difference time-domain algorithm. Experimental phantom chemical shift image, showed good agreement with the theoretical SNR-vs-depth profiles and highlighted the advantage of the novel configuration over the single transmit–receive coils throughout the volume of interest for cardiac imaging in pig. Finally, the TX-birdcage/RX-circular configuration was tested by acquiring metabolic maps with hyperpolarized [1-13C] pyruvate injected i.v. in a pig. The results of the phantom and pig experiments show the ability of the coil configuration to image well the metabolites distribution.
    No preview · Article · Oct 2013 · Applied Magnetic Resonance
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    ABSTRACT: Purpose: Myocardial iron overload assessment by multislice multiecho T2* technique is used in the clinical management of thalassemia major (TM) patients. Signal decay curves are extracted from the 16 left ventricular (LV) segments and the fitting of these curves to a mono-exponential model provides the corresponding T2* values. In patients with severe cardiac iron overload, where signal will decay quickly becoming comparable to image noise, manual truncation of signal decay curves excluding later echo times (TEs) is adopted. In this study an automatic truncation method avoiding the variability associated with the manual selection of the truncation point is introduced and validated. Methods: Twenty patients (13 males, age 33±7 years) enrolled in the MIOT Network and diagnosed for severe iron overload (T2*<10 ms) were considered. Using a previously validated software the segmental T2* values were evaluated by the standard methodology (i.e. manual truncation). Images were independently analysed by the developed automated approach. The percentage fitting error (e) was computed as the root mean square error between the signal decay curve and the mono-exponential model normalized to the mean value of the signal. If e was > 5%, the algorithm cut-off the last TE and performed again the fitting. The procedure was iterated until the error become <5% or the number of TEs become equal to three. To assess the inter-operator variability, the dataset was processed by a second operator. Results: The Coefficient of Variability (CoV) for inter-observer variability was 6.82±4.01%. The CoV between automated and manual analysis was 6.15±3.92%, not significantly different from inter-observer variability (P=0.332). No significant difference was detected between mid-septum and global T2* values evaluated with manual and automated procedure (P=0.26 and P=0.91, respectively). The mean fitting error was not significantly different in manual and automated analysis (4.10±2.11 vs. 4.52±2.12, P=0.53). In segmental analysis, no significant differences were found between manual and automatic procedure (P>0.01 for all segments). Conclusions: Truncation of signal decay curve needed to compensate for low signal in later echoes in patients with severe iron overload can be effectively automatized avoiding operator induced variability.
    Full-text · Article · Sep 2013 · Journal of Cardiovascular Magnetic Resonance
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    ABSTRACT: Radiofrequency coils in Magnetic Resonance systems are used to produce a homogeneous B1 field for exciting the nuclei and to pick up the signals emitted by the nuclei with high signal-to-noise ratio. Accordingly, coil performance affects strongly the quality of the obtained data and images.Coil efficiency, defined as the B1 magnetic field induced at a given point on the square root of supplied power P, is an important parameter that characterizes coil performance, since by maximizing efficiency will also maximize the signal-to-noise ratio.This work describes and compares four methods for coil efficiency estimation, based on different theoretical approaches. Three methods allow efficiency measurement by using “probe techniques” (perturbing loop, perturbing sphere and pick-up coil), which can be used both on the bench and inside the scanner, while an “NMR technique” has been employed for comparison purpose.Methods were tested on a 13C birdcage coil tuned at 32.13 MHz.
    No preview · Article · Aug 2013 · Measurement

  • No preview · Article · Jun 2013 · JACC. Cardiovascular imaging
  • Fabio Gibiino · Vincenzo Positano · Luigi Landini · Maria Filomena Santarelli
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    ABSTRACT: Non-Cartesian acquisition strategies are widely used in MRI to dramatically reduce the acquisition time while at the same time preserving the image quality. Among non-Cartesian reconstruction methods, the least squares non-uniform fast Fourier transform (LS_NUFFT) is a gridding method based on a local data interpolation kernel that minimizes the worst-case approximation error. The interpolator is chosen using a pseudoinverse matrix. As the size of the interpolation kernel increases, the inversion problem may become ill-conditioned. Regularization methods can be adopted to solve this issue. In this study, we compared three regularization methods applied to LS_NUFFT. We used truncated singular value decomposition (TSVD), Tikhonov regularization and L(1) -regularization. Reconstruction performance was evaluated using the direct summation method as reference on both simulated and experimental data. We also evaluated the processing time required to calculate the interpolator. First, we defined the value of the interpolator size after which regularization is needed. Above this value, TSVD obtained the best reconstruction. However, for large interpolator size, the processing time becomes an important constraint, so an appropriate compromise between processing time and reconstruction quality should be adopted.Copyright © 2013 John Wiley & Sons, Ltd.
    No preview · Article · May 2013
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    ABSTRACT: This work describes the design of a quadrature surface coil constituted by a circular loop and a butterfly coil, employed in transmit/receive (TX/RX) mode for hyperpolarized 13C studies of pig heart with a clinical 3T scanner. The coil characterization is performed by developing an SNR model for coil performance evaluation in terms of coil resistance, sample-induced resistance and magnetic field pattern. Experimental SNR-vs.-depth profiles, extracted from the [1–13C]acetate phantom chemical shift image (CSI), showed good agreement with the theoretical SNR-vs.-depth profiles. Moreover, the performance of the quadrature coil was compared with the single TX/RX circular and TX/RX butterfly coil, in order to verify the advantage of the proposed configuration over the single coils throughout the volume of interest for cardiac imaging in pig. Finally, the quadrature surface coil was tested by acquiring metabolic maps with hyperpolarized [1–13C]pyruvate injected i.v. in a pig. © 2013 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 43B: 69–77, 2013
    No preview · Article · Mar 2013 · Concepts in Magnetic Resonance Part B Magnetic Resonance Engineering

Publication Stats

1k Citations
226.70 Total Impact Points


  • 2000-2015
    • National Research Council
      • Institute of Clinical Physiology IFC
      Roma, Latium, Italy
  • 2008-2014
    • Fondazione Toscana Gabriele Monasterio
      Pisa, Tuscany, Italy
    • INO - Istituto Nazionale di Ottica
      Florens, Tuscany, Italy
    • Clinical and Experimental Center for Functional Magnetic Resonance Imaging
      Torino, Piedmont, Italy
  • 1993-2009
    • Università di Pisa
      • • Department of Information Engineering
      • • Department of Clinical and Experimental Medicine
      Pisa, Tuscany, Italy