1,721,000 research outputs found
A New Sandpile Model with Smoothness Assumptions
No full textWe consider two new granular dynamical systems obtained from the Sand Pile Model SPM(n) by adding a smoothness condition. First, we define the Smooth Sand Pile Model SmSPM(n) and we provide a characterization of the reachable states, together with some interesting properties of the resulting lattice. Then we extend it to SmSPM∗(n), a related dynamical system with a more complex lattice structure
Extension to fat X-rays of uniqueness results for the grid model in discrete tomography
No full textIn some circumstances it is preferable, instead of modeling the real world as a continuous space, facing directly the discrete problem. It may happen in the framework of Tomography, where we can employ several tools relying on discrete models: this is Discrete Tomography.
In this work we start our investigation from a limit case of the discretization process, namely the grid model, and then show how we can extend our approach to a more general framework. It turns out that, if we employ X-rays in the strip model whose width is under a given threshold, uniqueness of reconstruction, which came from exploiting the line structure of X-rays in the grid model, is still achieved. Moreover, we wrote a program which enumerates all possible sets of four valid directions which ensure uniqueness of reconstruction in a given lattice grid
Reconstruction of convex polyominoes with a blocking component
No full textSeveral papers in the available literature tackled problems concerning convex polyominoes in discrete tomography. An interesting subclass consists of L-convex polyominoes, since the related reconstruction problem can have only a unique solution. On the other hand, recent studies have modeled an approach to reconstruct objects even in the case that some of the projections are unavailable, due to a particularly dense part of the scanned object, that we refer to as a blocking component. In this work we merge the two problems in order to obtain efficient reconstruction algorithms for convex and L-convex polyominoes, in case a blocking component is included
Conservative treatment and radiological follow-up in a case of pneumatosis intestinalis associated with enteral tube feeding
No full textPneumatosis Intestinalis (PI) is a rare radiological finding and is defined as the presence of extra- luminal gas within the intestinal wall. PI can be distinguished in a benign form and a life-threatening form, burdened with high mortality. The correct management of PI must always take into account patient's history, his clinical context, laboratory test results and radiological findings, in order to administrate a proper therapy and avoid unnecessary surgical intervention. The pathogenesis of primary PI is still unknown and several theories have been proposed. Here, we report the case of a man with a previous severe traumatic brain injury who developed a transitory PI secondary to the enteral nutrition through a tube feeding, conservatively treated and underwent a radiological follow- up. Our report strengthens the relationship with enteral tube feeding and PI suggesting that any disaccharide used as pharmacological excipient or sweetener in the formulations for enteral tube feeding can potentially promote PI development, especially if administered in large quantities and in particular predisposing conditions. For this reason, the correct management of PI must always take into account patient's history, his clinical context, laboratory test results and radiological findings, in order to achieve a clear comprehension of its aetiology and administrate a proper therapy, avoiding unnecessary and potentially harmful surgery
Morphological, dynamic and functional characteristics of liver pseudolesions and benign lesions
No full textHepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide and one of the most common causes of death among patients with cirrhosis, developing in 1-8% of them every year, regardless of their cirrhotic stage. The radiological features of HCC are almost always sufficient for reaching the diagnosis; thus, histological confirmation is rarely needed. However, the study of cirrhotic livers remains a challenge for radiologists due to the developing of fibrous and regenerative tissue that cause the distortion of normal liver parenchyma, changing the typical appearances of benign lesions and pseudolesions, which therefore may be misinterpreted as malignancies. In addition, a correct distinction between pseudolesions and malignancy is crucial to allow appropriate targeted therapy and avoid treatment delays.The present review encompasses technical pitfalls and describes focal benign lesions and pseudolesions that may be misinterpreted as HCC in cirrhotic livers, providing the imaging features of regenerative nodules, large regenerative nodules, siderotic nodules, hepatic hemangiomas (including rapidly filling and sclerosed hemangiomas), segmental hyperplasia, arterioportal shunts, focal confluent fibrosis and focal fatty changes. Lastly, the present review explores the most promising new imaging techniques that are emerging and that could help radiologists differentiate benign lesions and pseudolesions from overt HCC
Optimization of pineapple juice amount used as a negative oral contrast agent in magnetic resonance cholangiopancreatography
Full text linkTo evaluate the potential variability of Manganese (Mn2+) in commercial pineapple juice (PJ) produced
in diferent years and to identify the optimal Mn2+ concentration in the correct amount of PJ to be
administered prior to Magnetic Resonance Cholangiopancreatography (MRCP) in order to suppress
the gastroduodenal (GD) liquid signal. The Mn2+ concentration in PJ produced in diferent years was
defned using Atomic Absorption Spectrometry. The optimal Mn2+ concentration and the amount
of PJ, were estimated in an in-vitro analysis, and were then prospectively tested in a population of
patients who underwent MRCP. The results were compared with those achieved with the previous
standard amount of PJ used in a similar population. The concentrations of Mn2+ in commercial PJ
produced in diferent years did not difer. A total amount of 150 ml (one glass) of PJ having a high Mn2+
content (2.37 mg/dl) was sufcient for the suppression of the GD liquid signal, despite the additional
dilution caused by GD liquids since it led to a fnal concentration of Mn2+ of 0.5–1.00 mg/dl. The
optimized single-dose oral administration of 150 ml (approximately one glass) of PJ having a high Mn2+
concentration prior to MRCP was adequate to guarantee the correct amount of Mn2+ to suppress the
GD signa
A New Quantitative Classification of the Extrahepatic Biliary Tract Related to Cystic Duct Implantation
No full textBackground: Knowledge regarding biliary anatomy and its variations, including the cystic duct (CD), is important in the pre-surgical setting and for predicting biliary diseases. However, no large series has focused on CD evaluation using a quantitative analysis. The primary aim of this prospective study was to create a ‘taxonomic’ classification of CD anatomy in a large cohort of subjects who underwent magnetic resonance cholangiopancreatography (MRCP). The secondary aim was to evaluate the correlations between extrahepatic bile duct (EHBD) variants and biliary diseases. Methods: We enrolled patients who underwent MRCP for different clinical indications from January 2017 to May 2019. Demographical, anatomical and clinical data were evaluated using statistical analyses, as appropriate. The anatomical assessment of EHBD was performed using the standard classification for CD in low, medium, and high insertions, and the lengths of CD to the duodenal papilla (DP), and EHBD was determined to conduct a new quantitative analysis. Results: The final study population comprised 1004 subjects. A new classification for EHBD as per the percentile distribution of the ratio CDDP/EHBD was designed, and the following categories were obtained: type 1 (below the 25th percentile) for CDDP/EHBD ratio ≤ 50%; type 2 (25th to 75th percentile) for CDDP/EHBD ratio 51–75% and type 3 (above the 75th percentiles) for CDDP/EHBD ratio > 75%. Type 1 of the new classification of CD implantation was significantly superior in terms of the detection of low, medial and intra-pancreatic CD that was significantly correlated with a high risk of choledochal lithiasis in comparison with the standard classification (P < 0.001). Conclusions: The new classification of CD implantation enables identification of the vast majority of intra-pancreatic CDs that are correlated with a high risk of choledochal lithiasis in a single category (type 1) that is easy to identify using imaging
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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