scholarly journals Model-based physiological noise removal in fast fMRI

NeuroImage ◽  
2020 ◽  
Vol 205 ◽  
pp. 116231 ◽  
Author(s):  
Uday Agrawal ◽  
Emery N. Brown ◽  
Laura D. Lewis
2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Gang Dong ◽  
Boying Wu

AbstractThis paper focuses on the problem of noise removal. First, we propose a new convex–nonconvex variation model for noise removal and consider the nonexistence of solutions of the variation model. Based on the new variation method, we propose a class of singular diffusion equations and prove the of solutions and comparison rule for the new equations. Finally, experimental results illustrate the effectiveness of the model in noise reduction.


2017 ◽  
Vol 137 ◽  
pp. 160-176 ◽  
Author(s):  
Jing Dong ◽  
Zifa Han ◽  
Yuxin Zhao ◽  
Wenwu Wang ◽  
Ales Prochazka ◽  
...  

2016 ◽  
Vol 32 ◽  
pp. 131-132
Author(s):  
F. Pennarola ◽  
M. Fanfoni ◽  
V. Cannata' ◽  
B. Bernardi ◽  
A. Napolitano

2015 ◽  
Vol 24 (1) ◽  
pp. 249-260 ◽  
Author(s):  
Zhenyu Zhou ◽  
Zhichang Guo ◽  
Gang Dong ◽  
Jiebao Sun ◽  
Dazhi Zhang ◽  
...  

Optical character recognition (OCR) is a strategy to perceive character from optically checked and digitized pages. OCR plays an important role for Indian script research. The official language of the state Odisha is Odia. OCR face an incredible difficulties to recognize Odia language due to similar shape characters, their complex nature, the complicated way in which they combine form to compound character, use of Matra etc. Each character and numbers are passed through several modules like binarization, noise removal, segmentation, line segmentation, word segmentation, skeletonization, deskewing, thinning, thickening. The input picture is standardized to a size of 50 x 50 2D pictures. HMM is a stochastic process which has utilized in various applications for example speech recognition, Handwriting recognition, Gesture recognition. In this paper we utilized HMM to recognize the Odia character and numbers. Hidden Markov Model have many advantages such as resistant to noise, handle contrast recorded as a hard copy and the HMM devices are effectively accessible. In our proposed method we have developed an efficient recognition algorithm using Hidden Markov model based on moment based and structural feature to recognize Odia characters and numerals.


Author(s):  
Michalis Kassinopoulos ◽  
Georgios D. Mitsis

AbstractThe blood oxygenation level-dependent (BOLD) contrast mechanism allows the noninvasive monitoring of changes in deoxyhemoglobin content. As such, it is commonly used in functional magnetic resonance imaging (fMRI) to study brain activity since levels of deoxyhemoglobin are indirectly related to local neuronal activity through neurovascular coupling mechanisms. However, the BOLD signal is severely affected by physiological processes as well as motion. Due to this, several noise correction techniques have been developed to correct for the associated confounds. The present study focuses on cardiac pulsatility fMRI confounds, aiming to refine model-based techniques that utilize the photoplethysmograph (PPG) signal. Specifically, we propose a new technique based on convolution filtering, termed cardiac pulsatility model (CPM) and compare its performance with RETROICOR, which is a technique commonly used to model fMRI fluctuations due to cardiac pulsatility. Further, we investigate whether variations in the amplitude of the PPG pulses (PPG-Amp) covary with variations in amplitude of pulse-related fMRI fluctuations, as well as with the systemic low frequency oscillations (SLFOs) component of the fMRI global signal (GS – defined as the mean signal across all gray matter voxels). Capitalizing on 3T fMRI data from the Human Connectome Project, CPM was found to explain a significantly larger fraction of the fMRI signal variance compared to RETROICOR, particularly for subjects with larger heart rate variability during the scan. The amplitude of the fMRI pulse-related fluctuations did not covary with PPG-Amp; however, PPG-Amp explained significant variance in the GS that was not attributed to variations in heart rate or breathing patterns. Our results suggest that the proposed approach can model high-frequency fluctuations due to pulsation as well as low-frequency physiological fluctuations more accurately compared to model-based techniques commonly employed in fMRI studies.


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