Evaluating the accuracy of geometrical distortion correction of magnetic resonance images for use in intracranial brain tumor radiotherapy

AimDetermine the 1) effectiveness of correction for gradient-non-linearity and susceptibility effects on both QUASAR GRID3D and CIRS phantoms; and 2) the magnitude and location of regions of residual distortion before and after correction.BackgroundUsing magnetic resonance imaging (MRI) as a primary dataset for radiotherapy planning requires correction for geometrical distortion and non-uniform intensity.Materials and MethodsPhantom Study: MRI, computed tomography (CT) and cone beam CT images of QUASAR GRID3D and CIRS head phantoms were acquired. Patient Study: Ten patients were MRI-scanned for stereotactic radiosurgery treatment. Correction algorithm: Two magnitude and one phase difference image were acquired to create a field map. A MATLAB program was used to calculate geometrical distortion in the frequency encoding direction, and 3D interpolation was applied to resize it to match 3D T1-weighted magnetization-prepared rapid gradient-echo (MPRAGE) images. MPRAGE images were warped according to the interpolated field map in the frequency encoding direction. The corrected and uncorrected MRI images were fused, deformable registered, and a difference distortion map generated.ResultsMaximum deviation improvements: GRID3D, 0.27mm y-direction, 0.07mm z-direction, 0.23mm x-direction. CIRS, 0.34mm, 0.1mm and 0.09mm at 20-, 40- and 60-mm diameters from the isocenter. Patient data show corrections from 0.2 to 1.2mm, based on location. The most-distorted areas are around air cavities, e.g. sinuses.ConclusionsThe phantom data show the validity of our fast distortion correction algorithm. Patient-specific data are acquired i

MoNuSAC2020:A Multi-Organ Nuclei Segmentation and Classification Challenge

Detecting various types of cells in and around the tumor matrix holds a special significance in characterizing the tumor micro-environment for cancer prognostication and research. Automating the tasks of detecting, segmenting, and classifying nuclei can free up the pathologists' time for higher value tasks and reduce errors due to fatigue and subjectivity. To encourage the computer vision research community to develop and test algorithms for these tasks, we prepared a large and diverse dataset of nucleus boundary annotations and class labels. The dataset has over 46,000 nuclei from 37 hospitals, 71 patients, four organs, and four nucleus types. We also organized a challenge around this dataset as a satellite event at the International Symposium on Biomedical Imaging (ISBI) in April 2020. The challenge saw a wide participation from across the world, and the top methods were able to match inter-human concordance for the challenge metric. In this paper, we summarize the dataset and the key findings of the challenge, including the commonalities and differences between the methods developed by various participants. We have released the MoNuSAC2020 dataset to the public

EXPERIMENTAL SURVEY OF THE EFFECT OF SPOILER HEIGHT AND DIFFUSER ON AERODYNAMIC COEFFICIENTS OF A GENERIC CAR

In recent years, aerodynamic analysis of automobiles has became one of the most important issue which affect the competition of the companies present in the world markets. Therefore it can be considered as one of the most important factor in aerodynamic design of the vehicles. This paper investigates the effect of aerodynamic devices on how to reduce the aerodynamic forces in the rear of a car model. The study was conducted experimentally at speeds of 0 to 60 m/s and a constant speed of 60 m/s. In these experiments aerodynamic forces, lift and drag coefficients were measured and the effect of the spoiler with three different heights along with diffuser were compared. The most important result of these experiments was the effective reduction of lift and drag coefficients with the presence of a spoiler and diffuser on the mode

Women’s clothing in Ancient Iran(Case Study: Achaemenid Period)

This paper, adopting a historical-descriptive approach, aims at studying women’s clothing in Achaemenid Period. Therefore all of the sources in which there is some information about women’s clothing are studied critically in this research. At first, the way Achaemenid ascended the throne is studied and Iranians’ and Greeks’ different attitudes on Achaemenid women’s life are presented, then women’s representation in Achaemenid archeological evidences is investigated and a precise description of women’s clothing and costume is given. The findings of this research, which are based on historical resources and the representation of women in Achaemenid archeological evidences such as seals and reliefs over stones/engraves, clearly reveal that despite of political and economic activities and considerable freedom women had in Achaemenid Period, they used a kind of clothing that covered all over their bodies. Using this kind/style of clothing was based on this attitude that in fact Iranian women in Achaemenid Period considered nudity and bareness obscence/dirty and inappropriate so they wore a kind of costumes that covered all over their bodies

Accept or reject a ride? This is the problem

Online ride-hailing platforms match drivers with passengers by receiving ride requests from passengers and forwarding them to the nearest driver. In this context, the low acceptance rate of offers by drivers leads to friction in the process of driver and passenger matching. What policies by the platform may increase the acceptance rate and by how much? What factors influence drivers' decisions to accept or reject offers and how much? Are drivers more likely to turn down a ride offer because they know that by rejecting it, they can quickly receive another offer, or do they reject offers due to the availability of outside options? This paper aims to answer such questions using a novel dataset from Tapsi, a ride-hailing platform located in Iran

Fatigue and Fracture of Additively Manufactured Metallic Materials

Design of critical load carrying components utilizing additive manufacturing (AM) processes is still at its infancy. This is due to the fact that most of the load carrying components made by AM processes are subjected to cyclic loads, and fatigue behavior of AM metals is far less understood as compared with those made by conventional methods. To better understand the fatigue behavior of AM metals, a wide range of issues that affect the behavior in a synergistic manner must be considered. These include the effects of defects, residual stresses, surface finish, geometry and size, layer orientation, heat treatment, stress concentrations, and stress states. In this article, these features are reviewed and illustrated by reference to data from several AM metals

Fatigue assessment of 17-4 PH stainless steel notched specimens made by direct metal laser sintering

Direct metal laser sintering (DMLS) offers economical production of customized components with complex geometries in a shorter design-to-manufacture cycle. Similar to other additive manufacturing (AM) techniques, this method is used for the production of complex geometries that include various kinds of notch geometries. The basic understanding of the fatigue behavior of the notched specimens produced with AM techniques, however, must be substantially improved before the unique features of this rapidly developing technology can be used in critical load bearing applications. The axial and torsional fatigue behavior of severely notched components made of additively manufactured 17-4 PH stainless steel was studied in the present paper. The experimental fatigue tests were performed under axial- and torsional-loading conditions. Cylindrical specimens with notch tip radius of 0.1 mm were employed to evaluate the fatigue behavior of the specimens under different loading conditions