Numerical simulations of the blood flow in the patient-specific arterial cerebral circle region

The Cerebral Circle Region, also known as the Circle of Willis (CoW), is a loop of arteries that form arterial connections between supply arteries to distribute blood throughout the cerebral mass. Among the population, only 25% to 50% have a complete system of arteries forming the CoW. 3D time-varying simulations for three different patient-specific artery anatomies of CoW were performed in order to gain a better insight into the phenomena existing in the cerebral blood flow. The models reconstructed on the basis of computer tomography images start from the aorta and include the largest arteries that supply the CoW and the arteries of CoW. Velocity values measured during the ultrasound examination have been compared with the results of simulations. It is shown that the flow in the right anterior artery in some cases may be supplied from the left internal carotid artery via the anterior communicating artery. The investigations conducted show that the computational fluid dynamic tool, which provides high resolution in both time and space domains, can be used to support physicians in diagnosing patients of different ages and various anatomical arterial structures.     

Parameter set for computer-assisted texture analysis of fetal brain

Background

Magnetic resonance data were collected from a diverse population of gravid women to objectively compare the quality of 1.5-tesla (1.5 T) versus 3-T magnetic resonance imaging of the developing human brain. MaZda and B11 computational-visual cognition tools were used to process 2D images. We proposed a wavelet-based parameter and two novel histogram-based parameters for Fisher texture analysis in three-dimensional space.

Results

Wavenhl, focus index, and dispersion index revealed better quality for 3 T. Though both 1.5 and 3 T images were 16-bit DICOM encoded, nearly 16 and 12 usable bits were measured in 3 and 1.5 T images, respectively. The four-bit padding observed in 1.5 T K-space encoding mimics noise by adding illusionistic details, which are not really part of the image. In contrast, zero-bit padding in 3 T provides space for storing more details and increases the likelihood of noise but as well as edges, which in turn are very crucial for differentiation of closely related anatomical structures.

Conclusions

Both encoding modes are possible with both units, but higher 3 T resolution is the main difference. It contributes to higher perceived and available dynamic range. Apart from surprisingly larger Fisher coefficient, no significant difference was observed when testing was conducted with down-converted 8-bit BMP images.

     

A Novel Attempt to Standardize Results of CFD Simulations Basing on Spatial Configuration of Aortic Stent-Grafts

Currently, studies connected with Computational Fluid Dynamic (CFD) techniques focus on assessing hemodynamic of blood flow in vessels in different conditions e.g. after stent-graft’s placement. The paper propose a novel method of standardization of results obtained from calculations of stent-grafts'' “pushing forces” (cumulative WSS—Wall Shear Stress), and describes its usefulness in diagnostic process. AngioCT data from 27 patients were used to reconstruct 3D geometries of stent-grafts which next were used to create respective reference cylinders. We made an assumption that both the side surface and the height of a stent-graft and a reference cylinder were equal. The proposed algorithm in conjunction with a stent-graft “pushing forces” on an implant wall, allowed us to determine which spatial configuration of a stent-graft predispose to the higher risk of its migration. For stent-grafts close to cylindrical shape (shape factor φ close to 1) WSS value was about 267Pa, while for stent-grafts different from cylindrical shape (φ close to 2) WSS value was about 635Pa. It was also noticed that deformation in the stent-graft’s bifurcation part impaired blood flow hemodynamic. Concluding the proposed algorithm of standardization proved its usefulness in estimating the WSS values that may be useful in diagnostic process. Angular bends or tortuosity in bifurcations of an aortic implant should be considered in further studies of estimation of the risk of implantation failure.     

3H-oestradiol-17β counter current transfer from the ovarian vein into the ovarian artery in cows

During laparatomy the ovary in the luteal phase with the ovarian pedicle was isolated and transferred under stereomicroscope. The ovary was supplied with blood flowing out of the facial artery through a cannula. ³H-oestradiol-17β or ⁵¹Cr-labelled red blood cells (⁵¹Cr-RBC) were infused for 30 min through the cannula inserted into the ovarian vein 3 cm below the ovary. During and 30 min after the ³H-oestradiol-17β infusion, radioactivity was found both in the ovarian arterial blood near the ovary and in ovarian tissue. When ⁵¹Cr-RBC were infused in the same way as ³H-oestradiol, there was no radioactivity in the arterial blood or ovarian tissue. These experiments indicate the existence of a counter current transfer of ³H-oestradiol-17β from the ovarian vein into the ovarian artery in a cow's ovarian pedicle.     

Assessment of intraorbital structure volume using a numerical segmentation image technique (NSI): the fatty tissue and the eyeball

INTRODUCTION: Measurement of the degree of exophthalmos is one of the main methods used in the assessment of pathological processes that occur in the orbital space and is widely used. However, this only provides initial information about the volume relations between the intraorbital structures. The aims of our work were as follows: to draw up a new computer application, namely the numerical segmentation image (NSI) technique, for the automatic calculation of the volume of the intraorbital structures on the basis of magnetic resonance imaging (MRI) images, to determine its usefulness in the segmentation of fatty tissue and the eyeball and to estimate their volume in relation to the degree of exophthalmos. MATERIAL AND METHODS: A total of 45 patients (90 orbits) were included in the study. All the patients underwent MRI examination of the orbits by a 1.5 T scanner using a head coil. The degree of exophthalmos was determined clinically and radiologically in relation to the interzygomatic line. Quantitative assessment of the eyeball and fatty tissue was made using an NSI application. RESULTS: The influence of fatty tissue volume on the degree of exophthalmos was determined as being statistically significant (r = 0.367, p = 0.000374) but was smaller in comparison with the relationship between total eye muscle volume and degree of exophthalmos; eyeball volume was found to have the least influence (r = 0.344, p = 0.000374). Two eyeballs of significantly smaller volume were found in the group of 90 orbits analysed. CONCLUSIONS: The NSI technique is a clinically useful application, providing objective data calculated individually for each orbit. A credible protocol for estimating the degree of exophthalmos on the basis of the NSI technique should include the eye muscle volume, fatty tissue volume and, in cases where eyeball pathologies coexist, the eyeball volume as well.     

Assessment of the volume of intraorbital structures using the numerical segmentation image technique (NSI): the extraocular muscles

INTRODUCTION: In recent years the use of computer systems has allowed numerical analysis of medical images to be introduced and has speeded up the conversion of numerical data into clinically valuable information. The creation of a software application that could almost automatically calculate the volume of anatomical structures imaged by MRI has seemed possible. The aim of our study was to determine the clinical usefulness of an numerical segmentation image technique (NSI) software application in estimating the volume of extraocular muscles. MATERIAL AND METHODS: The study group was formed of 45 patients (90 orbits). All the patients underwent MRI examinations of the orbits by a 1.5 T scanner using a head coil. The degree of exophthalmos was determined clinically and radiologically in relation to the interzygomatic line. The quantitative assessment of all eye muscles was carried out using the NSI application, a new software program introduced by the authors. RESULTS: A close correlation between muscle volume and the degree of exophthalmos was revealed and confirmed by statistical analysis (r = 0.543, p = 3.13396E-08) in agreement with other papers. CONCLUSIONS: The NSI software program is an application which offers a reliable and precise estimation of eye muscle volume. It is therefore useful in the diagnosis of the pathological processes leading to exophthalmos. It has special clinical value for monitoring discrete volume changes of muscles during treatment.