DIAGNOSTIC AND THERAPEUTIC PROBLEMS OF ACUTE RENAL FAILURE IN CHILDHOOD

Acute renal failure (ACR) is a clinical-biological syndrome of sudden rapidly advancing, commonly reversible damage of renal function when a normal body homeostasis cannot be maintained. In the Department of Paediatrics, Medical University of Varna, 18 children with ACR were treated. The most common reasons for the ACR were the following: acute glomerulonephritis, haemolytic-uraemic syndrome, and severe malformations of the urinary tract. Blood urea, creatinine, ionogram,acid-base balance, and diuresis were dynamically monitored in all the children. Therapeutic behaviour was directed towards the correction of the dyselectrolytaemia and acid-alkaline profile. The elevated lethality rate still persisted. Three patients deceased

THE NEW FACE OF VITAMIN K - MORE THAN BLOOD CLOTTING FACTOR

Introduction: Twenty years ago, the metabolism of vitamin K was connected with its role in hemostasis. Since that time, it has been shown that vitamin K exerts multiple functions mediated by the Gla-proteins, having vitamin K as a cofactor. Numerous publications affirm that these Gla-proteins are related to physiological processes beyond coagulations, such as bone metabolism, vascular health and energy homeostasis.Aim: The aim of this research is to provide new data for the role of vitamin K in a myriad of physiological processes beyond blood clotting. Additionally, it aims to assess the potential new applications of vitamin K as a supplement for the prevention of bone and vascular diseases.Materials and Methods: Using the online databases Scopus, PubMed and Google Scholar, a search with the keywords: `vitamin K2`, `bone metabolism`, `cardiovascular diseases`, `osteocalcin` and `MGP` was conducted. Information regarding the effects of vitamin K on bone and vascular health was referred to in this work.Results: Vitamin K and vitamin K-dependent proteins play pivotal roles in the physiology of bone mineralization and in preventing ectopic calcification. Osteocalcin, a Gla protein located in bone and dentin, is important for bone mineralization. Following the posttranslational carboxylation of Glu-residues with a cofactor vitamin K2 (menaquinone), rather than vitamin K1 (phylloquinone), osteocalcin shows increased affinity for calcium. Osteocalcin is believed to be involved in osteoblast regulation and hydroxyapatite crystal growth. Matrix GLa-protein (MGP), sharing some sequences with osteocalcin, is a local inhibitor of arterial calcification. Vitamin K deficiency impairs the function of osteocalcin and MGP and, therefore, presumably contributes to bone demineralization and vascular calcification, the so-called calcium paradox.Conclusions: Vitamin K deficiencies, traditionally regarded as a cause for internal hemorrhages and blood clotting disorders, apparently can be linked to cardiovascular calcification and abnormal bone modelling. Appropriate treatment of vitamin K deficiency may improve bone and arterial health

Comparisons of glandular breast dose between digital mammography, tomosynthesis and breast CT based on anthropomorphic patient-derived breast phantoms

Purpose: To evaluate the bias to the mean glandular dose (MGD) estimates introduced by the homogeneous breast models in digital breast tomosynthesis (DBT) and to have an insight into the glandular dose distributions in 2D (digital mammography, DM) and 3D (DBT and breast dedicated CT, BCT) x-ray breast imaging by employing breast models with realistic glandular tissue distribution and organ silhouette. Methods: A Monte Carlo software for DM, DBT and BCT simulations was adopted for the evaluation of glandular dose distribution in 60 computational anthropomorphic phantoms. These computational phantoms were derived from 3D breast images acquired via a clinical BCT scanner. Results: g·c·s·T conversion coefficients based on homogeneous breast model led to a MGD overestimate of 18% in DBT when compared to MGD estimated via anthropomorphic phantoms; this overestimate increased up to 21% for recently computed DgNDBT conversion coefficients. The standard deviation of the glandular dose distribution in BCT resulted 60% lower than in DM and 55% lower than in DBT. The glandular dose peak – evaluated as the average value over the 5% of the gland receiving the highest dose – is 2.8 times the MGD in DM, this factor reducing to 2.6 and 1.6 in DBT and BCT, respectively. Conclusions: Conventional conversion coefficients for MGD estimates based on homogeneous breast models overestimate MGD by 18%, when compared to MGD estimated via anthropomorphic phantoms. The ratio between the peak glandular dose and the MGD is 2.8 in DM. This ratio is 8% and 75% higher than in DBT and BCT, respectively

Normalized glandular dose coefficients in mammography, digital breast tomosynthesis and dedicated breast CT

Purpose To provide mean glandular dose (MGD) estimates via Monte Carlo (MC) simulations as a function of the breast models and scan parameters in mammography, digital breast tomosynthesis (DBT) and dedicated breast CT (BCT). Methods The MC code was based on GEANT4 toolkit. The simulated compressed breast was either a cylinder with a semi-circular section or ad hoc shaped for oblique view (MLO). In DBT we studied the influence of breast models and exam parameters on the T-factors (i.e. the conversion factor for the calculation of the MGD in DBT from that for a 0-degree projection), and in BCT we investigated the influence on the MGD estimates of the ion chamber volume used for the air kerma measurements. Results In mammography, a model representative of a breast undergoing an MLO view exam did not produce substantial differences (0.4%) in MGD estimates, when compared to a conventional cranio-caudal (CC) view breast model. The beam half value layer did not present a significant influence on T-factors in DBT (<0.8%), while the skin model presented significant influence on MGD estimates (up to 3.3% at 30 degrees scan angle), increasing for larger scan angles. We derived a correction factor for taking into account the different ion chamber volume used in MGD estimates in BCT. Conclusions A series of MC code modules for MGD estimates in 2D and 3D breast imaging have been developed in order to take into account the most recent advances in breast models

GEANT4 Monte Carlo simulations for virtual clinical trials in breast X-ray imaging: Proof of concept

Virtual clinical trials (VCT) are in-silico reproductions of medical examinations, which adopt digital models ofpatients and simulated devices. They are intended to produce clinically equivalent outcome data avoiding long execution times, ethical issues related to radiation induced risks and huge costs related to real clinical trials with a patient population. In this work, we present a platform for VCT in 2D and 3D X-ray breast imaging. The VCT platform uses Monte Carlo simulations based on the Geant4 toolkit and patient breast models derived from a cohort of high resolution dedicated breast CT (BCT) volume data sets. Projection images of the breast and three-dimensional glandular dose maps are generated for a given breast model, by simulating both 2D full-field digital mammography (DM) and 3D BCT examinations. Uncompressed voxelized breast models were derived from segmented patient images. Compressed versions of the digital breast phantoms for DM were generated using apreviously published digital compression algorithm. The Monte Carlo simulation framework has the capability of generating and tracking ~10^5 photons/s using a server equipped with 16-cores and 3.0 GHz clock speed. The VCT platform will provide a framework for scanner design optimization, comparison between different scanner designs and between different modalities or protocols on computational breast models, without the need for scanning actual patients as in conventional clinical trials

The Napoli-Varna-Davis project for virtual clinical trials in X-ray breast imaging

Virtual clinical trials (VCTs) have been proposed to overcome the limitations of clinical trials using a patient population. VCTs are in-silico reproductions of medical examinations using digital models of the patients and simulated imaging devices. In this work, we present a VCT framework for imaging and dosimetry in breast computed tomography (BCT), digital breast tomosynthesis (DBT) and 2D digital mammography (DM), realized by Univ. Napoli Federico II in collaboration with the medical physics teams at Univ. California Davis and the Medical University of Varna, Bulgaria. Computational phantoms of the uncompressed (pendant) breast were generated by clinical BCT scans acquired at UC Davis. A dataset of digital breast phantoms was produced by means of voxel classification of the uncompressed breast CT images. The voxels were classified as air, skin, adipose and glandular tissue using a semi-automatic algorithm. A software compression algorithm (developed at U. Varna) applied to the 3D phantoms produces compressed breast digital phantoms for virtual DM and DBT investigations using a clinical scanners' technical specifications and geometry as inputs. Monte Carlo simulations, based on Geant4, were used to provide in-silico reproductions of real scans of a given patient breast model. The software permits the estimation of mean glandular dose (MGD) in 2D and 3D imaging as well as the 3D dose distribution. The platform produces breast projection images which are then reconstructed using analytical or iterative algorithms. Patient-specific MGD estimations, as well as simulated BCT volume data sets were compared with the clinical BCT scans. The VCT platform reported herein will be used for scanner optimization and for virtual trials comparing BCT against mammography and DBT, in terms of image quality and glandular dose distributions. In addition to in-silico evaluation, 3D printing methods were used to produce compressed and uncompressed anthropomorphic breast phantoms from the patient image-derived digital breast phantoms for the purpose of experimental validation

OD130 - AGATA: advanced Geant4-based application for in-silico clinical trial in x-ray breast imaging

Purpose: New 3D breast x-ray imaging techniques, such as digital breast tomosynthesis (DBT) and breast dedicated CT (BCT), are being evaluated in specific clinical trials to study potential benefits in comparison to conventional 2D digital mammography (DM). These studies involve large patient cohorts for several years with the study ongoing in USA (TMIST) for the comparison of DBT and DM with a target enrollment of 160,000 patients. Virtual clinical trials represent an alternative solution to large scale human trials, with the prospect of reducing costs, time and issues related to the patient exposure to ionizing radiation. These are in-silico models of clinical trials with simulated devices and digital patient models. In this context, the INFN AGATA project aims at developing a platform for virtual clinical trials in breast x-ray imaging by means of digital models of patients obtained from high-resolution 3D breast images and a Monte Carlo simulation software. Materials and Methods: The digital breast phantoms were derived from 300 3D breast images acquired at UC Davis during clinical trials involving a BCT scanner. Each of the image voxels was classified as air, glandular tissue, adipose tissue or skin by means of a semi-automatic procedure. A mechanical model of the tissues permitted accurate compression to be applied in order to simulate DM or DBT examinations. The devices were simulated using Monte Carlo software based on the Geant4 toolkit. On the basis of the input exam specifications and modality, the software simulates the glandular dose distribution within the organ and the breast image projections. Results: The AGATA platform computed the dose distribution assuming ideal detectors for the image acquisition in DM, BCT or DBT, relying on digital breast phantoms. The developed software tracked up to 7×10 4 photons/s on a 16-core Dual-CPU AMD Opteron(tm) Processor4284. An ad-hoc cluster of servers reduces the computational times down to practical levels. Conclusions: The developed platform represents an alternative strategy for testing and developing devices in the field of 2D and 3D breast x-ray imaging. It permits access to patient-like data to a broad range of researchers and for comparing many technical solutions and imaging modalities by avoiding patient exposure to ionizing radiation