Biomedical Imaging / Medical Imaging
Elham Mohammadi; Abbas Nasiraei Moghaddam
Volume 16, Issue 1 , May 2022, , Pages 63-74
Abstract
Real-time MRI using highly undersampled radial acquisition can be used for dynamic assessments of the heart. The main challenges, however, are the presence of severe undersampling artifacts in the periphery of the images. In this study, to improve the visual quality of the final real-time images, a new ...
Read More
Real-time MRI using highly undersampled radial acquisition can be used for dynamic assessments of the heart. The main challenges, however, are the presence of severe undersampling artifacts in the periphery of the images. In this study, to improve the visual quality of the final real-time images, a new method for the acquisition of successive frames based on a radial trajectory with the turned arrangement is presented. Accordingly, by combining the information obtained from successive frames, it is possible to reconstruct images with high and low spatial resolution. In the proposed method, specifically due to the use of the Polar Fourier Transform reconstruction method, reconstructed images with two different resolutions can be combined to reduce the visual effects of undersampling artifacts. In this paper, the proposed method has been used especially for the real-time radially tagged images to increase the efficiency and accuracy of measuring left ventricular rotation motion. According to the simulation results, the structural similarity measure is improved from 0.6 to 0.8. Real-time imaging with a time resolution of 46 ms of healthy individuals also shows that while the temporal resolution of the rotational information is well preserved, the visual quality of images is improved.
Biomedical Imaging / Medical Imaging
Farzaneh Keyvanfard; Alireza Rahiminasab; Abbas Nasiraei Moghaddam
Volume 15, Issue 3 , December 2021, , Pages 211-220
Abstract
In brain disorders, both the brain structural and functional connectivity are altered and cause different behavioral symptoms. Recognizing these variations can help us to diagnose, treat, and control its progression. Schizophrenia is one of these mental disorders that widely affects the brain structure ...
Read More
In brain disorders, both the brain structural and functional connectivity are altered and cause different behavioral symptoms. Recognizing these variations can help us to diagnose, treat, and control its progression. Schizophrenia is one of these mental disorders that widely affects the brain structure and function. Investigation of brain variations in this disease has commonly been based on voxel-wise analysis or region-based studies. The aim of this study is to evaluate brain structure and function alterations in schizophrenia patients comparing to healthy control from the brain connectivity perspective. For this purpose, using the statistical test method, a comparison was made between all the structural and functional connections in the brain of 92 healthy individuals and 37 schizophrenia patients obtained from diffusion tensor imaging (DTI) and functional Magnetic Resonance Imaging (fMRI) respectively. The findings of this study indicate that the number of altered edges in the brain functional network of patients is about 4 times more than the number of varied structural connections, which indicates the high impact of this disorder on brain function. Also, examination of the number of altered edges connected to each node, the affected areas in this disease were identified and it was shown that the schizophrenia patients’ brain has changed in parts of the brain subnetworks related to the default mode network (DMN), attention, somatomotor and vision networks. It was also shown that the altered brain structural connections of patients are involved in the areas of the superior frontal gyrus, temporal gyrus and part of the occipital cortex which are mostly shown relative increasing of the structural connectivity weights. The results of this study indicate the widespread effect of this disorder on the brain and suggest that the occurrence of some abnormal behaviors in schizophrenia patients may be due to some increased structural connectivity weights.
Biomedical Imaging / Medical Imaging
Neda Sardaripour; Alireza Sedghi; Ali Yoonessi; Ali Khadem; Hamid Abrishami Moghaddam
Volume 12, Issue 4 , January 2019, , Pages 299-315
Abstract
During vision process, the information produced by rod and cone photoreceptors is compressed in retina and then is transmitted by three separated pathways of ganglion cells, Magno, Parvo and Konio, to the upper level processing centers. There are electrophysiological and psychophysical evidences that ...
Read More
During vision process, the information produced by rod and cone photoreceptors is compressed in retina and then is transmitted by three separated pathways of ganglion cells, Magno, Parvo and Konio, to the upper level processing centers. There are electrophysiological and psychophysical evidences that these three pathways show characteristic patterns of malfunction in multiple sclerosis (MS) patients. Although fMRI can provide accurate localization of the neural activities in these pathways, there is no fMRI study on malfunctions of these pathwyas in MS yet. So by employing the differences in structure and function of these cells, we generated three different visual stimuli with different spatial and temporal frequencies to stimulate each pathway separately. These stimuli were shown to the subject inside MRI scanner by a calibrated projector located outside of scanner room. The fMRI data were acquired from two groups of normal and MS subjects (each including 5 subjects) by using a standard protocol. Finally, the activation results in visual lobe and LGN were analyzed in within-group and between-group levels. The group analysis of fMRI data was performed by using general linear modeling (GLM) and fixed-effect method via FSL software and results showed patterns of malfunctions in visual cortex and LGN in MS group. Also, among Magno, Parvo, and Konio cellular pathways in LGN, just the activation of Magno cellular pathway showed significant malfunction in MS group.
