Optimization of the energy for Breast monochromatic absorption X-ray Computed Tomography

The limits of mammography have led to an increasing interest on possible alternatives such as the breast Computed Tomography (bCT). The common goal of all X-ray imaging techniques is to achieve the optimal contrast resolution, measured through the Contrast to Noise Ratio (CNR), while minimizing the radiological risks, quantified by the dose. Both dose and CNR depend on the energy and the intensity of the X-rays employed for the specific imaging technique. Some attempts to determine an optimal energy for bCT have suggested the range 22keV\u201334keV, some others instead suggested the range 50keV\u201360keV depending on the parameters considered in the study. Recent experimental works, based on the use of monochromatic radiation and breast specimens, show that energies around 32keV give better image quality respect to setups based on higher energies. In this paper we report a systematic study aiming at defining the range of energies that maximizes the CNR at fixed dose in bCT. The study evaluates several compositions and diameters of the breast and includes various reconstruction algorithms as well as different dose levels. The results show that a good compromise between CNR and dose is obtained using energies around 28keV

Generation of primary photons through inverse Compton scattering using a Monte Carlo simulation code

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Characterization of breast tissues in density and effective atomic number basis via spectral X-ray computed tomography

Differentiation of breast tissues is challenging in X-ray imaging because tissues might share similar or even the same linear attenuation coefficients $\mu$. Spectral computed tomography (CT) allows for more quantitative characterization in terms of tissue density and effective atomic number by exploiting the energy dependence of $\mu$. In this work, 5 mastectomy samples and a phantom with inserts mimicking breast soft tissues were evaluated in a retrospective study. The samples were imaged at three monochromatic energy levels in the range of 24 - 38 keV at 5 mGy per scan using a propagation-based phase-contrast setup at SYRMEP beamline at the Italian national synchrotron Elettra. A custom-made algorithm incorporating CT reconstructions of an arbitrary number of spectral energy channels was developed to extract the density and effective atomic number of adipose, fibro-glandular, pure glandular, tumor, and skin from regions selected by a radiologist. Preliminary results suggest that, via spectral CT, it is possible to enhance tissue differentiation. It was found that adipose, fibro-glandular and tumorous tissues have average effective atomic numbers (5.94 $\pm$ 0.09, 7.03 $\pm$ 0.012, and 7.40 $\pm$ 0.10) and densities (0.90 $\pm$ 0.02, 0.96 $\pm$ 0.02, and 1.07 $\pm$ 0.03 g/cm$^{3}$) and can be better distinguished if both quantitative values are observed together.Comment: 26 pages, 7 figures, submitted to Physics in Medicine and Biolog

Plethysmography system to monitor the jugular venous pulse: A feasibility study

Cerebral venous outflow is investigated in the diagnosis of heart failure through the monitoring of jugular venous pulse, an indicator to assess cardiovascular diseases. The jugular venous pulse is a weak signal stemming from the lying internal jugular vein and often invasive methodologies requiring surgery are mandatory to detect it. Jugular venous pulse can also be extrapolated via the ultrasound technique, but it requires a qualified healthcare operator to perform the examination. In this work, a wireless, user-friendly, wearable device for plethysmography is developed to investigate the possibility of monitoring the jugular venous pulse non-invasively. The proposed device can monitor the jugular venous pulse and the electrocardiogram synchronously. To study the feasibility of using the proposed device to detect physiological variables, several measurements were carried out on healthy subjects by considering three different postures: supine, sitting, and upright. Data acquired in the experiment were properly filtered to highlight the cardiac oscillation and remove the breathing contribution, which causes a considerable shift in the amplitude of signals. To evaluate the proper functioning of the wearable device for plethysmography, a comparison with the ultrasound technique was carried out. As a satisfactory result, the acquired signals resemble the typical jugular venous pulse waveforms found in literature.Web of Science1112art. no. 239

A Cationic Contrast Agent in X-ray Imaging of Articular Cartilage: Pre-Clinical Evaluation of Diffusion and Attenuation Properties

The aim of this study was the preliminary assessment of a new cationic contrast agent, the CA4+, via the analysis of spatial distribution in cartilage of ex vivo bovine samples, at micrometer and millimeter scale. Osteochondral plugs (n = 18) extracted from bovine stifle joints (n = 2) were immersed in CA4+ solution up to 26 h. Planar images were acquired at different time points, using a microCT apparatus. The CA4+ distribution in cartilage and saturation time were evaluated. Tibial plates from bovine stifle joints (n = 3) were imaged with CT, before and after 24 h-CA4+ bath immersion, at different concentrations. Afterward, potential CA4+ washout from cartilage was investigated. From microCT acquisitions, the CA4+ distribution differentiated into three distinct layers inside the cartilage, reflecting the spatial distribution of proteoglycans. After 24 h of diffusion, the iodine concentration reached in cartilage was approximately seven times that of the CA4+ bath. The resulting saturation time was 1.9 ± 0.9 h and 2.6 ± 2.9 h for femoral and tibial samples, respectively. Analysis of clinical CT acquisitions confirmed overall contrast enhancement of cartilage after 24 h immersion, observed for each CA4+ concentration. Distinct contrast enhancement was reached in different cartilage regions, depending on tissue's local features. Incomplete but remarkable washout of cartilage was observed. CA4+ significantly improved cartilage visualization and its qualitative analysis

Drain Brain: monitorare il drenaggio cerebrale negli astronauti per prevenire problemi cardiovascolari

Un importante obbiettivo della ricerca spaziale internazionale, in preparazione all'esplorazione umana della Luna e di Marte, è quello di tutelare la salute degli astronauti. Il volo spaziale induce importanti alterazioni a carico di diversi sistemi fisiologici e queste risposte adattative inducono un generale decondizionamento dell'organismo. I programmi di ricerca medica hanno lo scopo di assicurare la salute degli astronauti che affronteranno viaggi spaziali oltre l'orbita bassa, permetterne la pronta operatività una volta arrivati a destinazione e consentirne un sicuro recupero al rientro sulla Terra. Fra i programmi messi in campo dall'Agenzia Spaziale Italiana (ASI), gli esperimenti denominati Drain Brain, svolti in collaborazione con l'Università di Ferrara, sono particolarmente esemplificativi da questo punto di vista. Il progetto, iniziato con la collaborazione di Samantha Cristoforetti nel 2014, ha permesso di dimostrare il funzionamento di un pletismografo per lo studio del circolo cerebrale ed il ritorno venoso dall'encefalo al cuore in condizioni di microgravità. Nei prossimi due anni, grazie al progetto Drain Brain 2.0, gli equipaggi della Stazione Spaziale Internazionale verranno studiati con una nuova versione del sensore pletismografico, sincronizzato con l'elettrocardiogramma, per valutare l'efficienza cardiaca ed il drenaggio cerebrale in rapporto a sintomi come vista offuscata, intorpidimento, annebbiamento o il temuto insorgere di una trombosi giugulare, legata al rallentamento del flusso per assenza del gradiente gravitazionale. Drain Brain 2.0 genererà anche importanti ritorni a Terra, chiudendo il circolo virtuoso dell'applicazione terrestre della ricerca condotta nello Spazio. La nuova strumentazione è di fatto ideale per un uso in telemedicina su pazienti cardiopatici o con problemi cognitivi

X-ray topographic determination of the granular structure in a graphite mosaic crystal : a three-dimensional reconstruction

Section topographs recorded at different spatial locations and at different rocking angles of a highly oriented pyrolytic graphite (HOPG) crystal allow three-dimensional maps of the local angular-dependent scattering power to be obtained. This is performed with a direct reconstruction from the intensity distribution on such topographs. The maps allow the extraction of information on local structural parameters such as size, form and internal mosaic spread of crystalline domains. This data analysis leads to a new method for the characterization of mosaic crystals. Perspectives and limits of applicability of this method are discussed

Drain Brain: monitorare il drenaggio cerebrale negli astronauti per prevenire problemi cardiovascolari

Un importante obbiettivo della ricerca spaziale internazionale, in preparazione all'esplorazione umana della Luna e di Marte, è quello di tutelare la salute degli astronauti. Il volo spaziale induce importanti alterazioni a carico di diversi sistemi fisiologici e queste risposte adattative inducono un generale decondizionamento dell'organismo. I programmi di ricerca medica hanno lo scopo di assicurare la salute degli astronauti che affronteranno viaggi spaziali oltre l'orbita bassa, permetterne la pronta operatività una volta arrivati a destinazione e consentirne un sicuro recupero al rientro sulla Terra. Fra i programmi messi in campo dall'Agenzia Spaziale Italiana (ASI), gli esperimenti denominati Drain Brain, svolti in collaborazione con l'Università di Ferrara, sono particolarmente esemplificativi da questo punto di vista. Il progetto, iniziato con la collaborazione di Samantha Cristoforetti nel 2014, ha permesso di dimostrare il funzionamento di un pletismografo per lo studio del circolo cerebrale ed il ritorno venoso dall'encefalo al cuore in condizioni di microgravità. Nei prossimi due anni, grazie al progetto Drain Brain 2.0, gli equipaggi della Stazione Spaziale Internazionale verranno studiati con una nuova versione del sensore pletismografico, sincronizzato con l'elettrocardiogramma, per valutare l'efficienza cardiaca ed il drenaggio cerebrale in rapporto a sintomi come vista offuscata, intorpidimento, annebbiamento o il temuto insorgere di una trombosi giugulare, legata al rallentamento del flusso per assenza del gradiente gravitazionale. Drain Brain 2.0 genererà anche importanti ritorni a Terra, chiudendo il circolo virtuoso dell'applicazione terrestre della ricerca condotta nello Spazio. La nuova strumentazione è di fatto ideale per un uso in telemedicina su pazienti cardiopatici o con problemi cognitivi

Phase-contrast breast CT: the effect of propagation distance

X-ray phase imaging has the potential to dramatically improve soft tissue contrast sensitivity, which is a crucial requirement in many diagnostic applications such as breast imaging. In this context, a program devoted to perform in-vivo phase-contrast synchrotron radiation breast computed tomography is ongoing at the Elettra facility (Trieste, Italy). The used phase-contrast technique is the propagation-based configuration, which requires a spatially coherent source and a sufficient object-to-detector distance. In this work the effect of this distance on image quality is quantitatively investigated scanning a large breast surgical specimen at 3 object-to-detector distances (1.6, 3, 9 m) and comparing the images both before and after applying the phase-retrieval procedure. The sample is imaged at 30 keV with a 60 \ub5m pixel pitch CdTe single-photon-counting detector, positioned at a fixed distance of 31.6~m from the source. The detector fluence is kept constant for all acquisitions. The study shows that, at the largest distance, a 20-fold SNR increase can be obtained by applying the phase-retrieval procedure. Moreover, it is shown that, for phase-retrieved images, changing the object-to-detector distance does not affect spatial resolution while boosting SNR (4-fold increase going from the shortest to the largest distance). The experimental results are supported by a theoretical model proposed by other authors, whose salient results are presented in this paper

A proposal for a quality control protocol in breast CT with synchrotron radiation

The SYRMA-3D collaboration is setting up the first clinical trial of phase-contrast breast CT with synchrotron radiation at the Elettra synchrotron facility in Trieste, Italy. In this communication, a quality control protocol for breast CT is proposed, and a first test of image quality measurements is performed by means of a custom-made radiographic phantom. Materials and methods A set of projections is acquired and used to perform a CT reconstruction of two selected portions of the phantom. Such portions contain a uniform layer of water and a set of radiographic inserts, respectively. Together, they allow to perform several image quality measurements, namely CT number linearity, reconstruction accuracy, uniformity, noise, and low contrast resolution. All measurements are repeated at different beam energies in the range of interest, and at two different dose values. Results Measurements show a good linearity in the soft tissue range, paired to a high accuracy of the CT number reconstruction. Uniformity and noise measurements show that reconstruction inhomogeneities are bound to a few percent of the average pixel values. However, low contrast detectability is limited to the higher portion of the explored energy range. Conclusions The results of the measurements are satisfactory in terms of their quality, feasibility and reproducibility. With minimal modifications, the phantom is promising to allow a set of image quality measurements to be used in the upcoming clinical trial