Optimization of parameter values for complex pulse sequences by simulated annealing: Application to 3D MP-RAGE imaging of the brain

1994 ◽  
Vol 31 (2) ◽  
pp. 164-177 ◽  
Author(s):  
Frederick H. Epstein ◽  
John P. Mugler ◽  
James R. Brookeman
Keyword(s):  
Simulated Annealing ◽  
Pulse Sequences ◽  
Parameter Values ◽  
The Brain

Experimental intracerebral and subarachnoid/intraventricular haemorrhages: MR detectability at 0.5 T and 1.5 T

2002 ◽  
Vol 43 (5) ◽  
pp. 464-473
Author(s):  
M. Alemany Ripoll ◽  
R. Raininko
Keyword(s):  
Cerebrospinal Fluid ◽  
Mr Imaging ◽  
Spin Echo ◽  
Autologous Blood ◽  
Pulse Sequences ◽  
Proton Density ◽  
Gradient Echo ◽  
The Brain ◽  
Formalin Fixed

Purpose: To compare the detectability of small experimental intracranial haemorrhages on MR imaging at 0.5 T and 1.5 T, from hyperacute to subacute stages. Material and Methods: 1 ml of autologous blood was injected into the brain of 15 rabbits to create intraparenchymal haematomas. Since the blood partially escaped into the cerebrospinal fluid (CSF) spaces, detectability of subarachnoid and intraventricular blood was also evaluated. MR imaging at 0.5 T and at 1.5 T was repeated up to 14 days, including T1-, proton density- and T2-weighted (w) spin-echo (SE), FLAIR and T2*-w gradient echo (GE) pulse sequences. The last MR investigation was compared to the formalin-fixed brain sections in 7 animals. Results: The intraparenchymal haematomas were best revealed with T2*-w GE sequences, with 100% of sensitivity at 1.5 T and 90–95% at 0.5 T. Blood in the CSF spaces was significantly ( p < 0.05) better detected at 1.5 T with T2*-w GE sequences and detected best during the first 2 days. The next most sensitive sequence for intracranial blood was FLAIR. SE sequences were rather insensitive. Conclusion: 1.5 T equipment is superior to 0.5 T in the detection of intracranial haemorrhages from acute to subacute stages. T2*-w GE sequences account for this result but other sequences are also needed for a complete examination.

Comparison of T1-weighted spin-echo and 3D T1-weighted multi-shot echo planar pulse sequences in imaging the brain at IT

1999 ◽  
Vol 17 (5) ◽  
pp. 663-668 ◽  
Author(s):  
A.H Karantanas ◽  
N Papanikolaou ◽  
K Vasiou ◽  
E Lavdas
Keyword(s):  
Spin Echo ◽  
Pulse Sequences ◽  
Echo Planar ◽  
The Brain

scholarly journals Magnetic Nanoparticles as In Vivo Tracers for Alzheimer’s Disease

2020 ◽  
Vol 6 (1) ◽  
pp. 13
Author(s):  
Bhargy Sharma ◽  
Konstantin Pervushin
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Early Diagnosis ◽  
Contrast Agents ◽  
Neurological Diseases ◽  
Pulse Sequences ◽  
Experimental Conditions ◽  
Magnetic Resonance Imaging Mri ◽  
The Brain

Drug formulations and suitable methods for their detection play a very crucial role in the development of therapeutics towards degenerative neurological diseases. For diseases such as Alzheimer’s disease, magnetic resonance imaging (MRI) is a non-invasive clinical technique suitable for early diagnosis. In this review, we will discuss the different experimental conditions which can push MRI as the technique of choice and the gold standard for early diagnosis of Alzheimer’s disease. Here, we describe and compare various techniques for administration of nanoparticles targeted to the brain and suitable formulations of nanoparticles for use as magnetically active therapeutic probes in drug delivery targeting the brain. We explore different physiological pathways involved in the transport of such nanoparticles for successful entry in the brain. In our lab, we have used different formulations of iron oxide nanoparticles (IONPs) and protein nanocages as contrast agents in anatomical MRI of an Alzheimer’s disease (AD) brain. We compare these coatings and their benefits to provide the best contrast in addition to biocompatibility properties to be used as sustainable drug-release systems. In the later sections, the contrast enhancement techniques in MRI studies are discussed. Examples of contrast-enhanced imaging using advanced pulse sequences are discussed with the main focus on important studies in the field of neurological diseases. In addition, T1 contrast agents such as gadolinium chelates are compared with the T2 contrast agents mainly made of superparamagnetic inorganic metal nanoparticles.

scholarly journals Quantitative Radiomics: Impact of Pulse Sequence Parameter Selection on MRI-Based Textural Features of the Brain

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
John Ford ◽  
Nesrin Dogan ◽  
Lori Young ◽  
Fei Yang
Keyword(s):  
Pulse Sequence ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Parameter Selection ◽  
Inversion Recovery ◽  
Textural Features ◽  
Imaging Data ◽  
Gradient Echo ◽  
The Impact ◽  
The Brain

Objectives. Radiomic features extracted from diverse MRI modalities have been investigated regarding their predictive and/or prognostic value in a variety of cancers. With the aid of a 3D realistic digital MRI phantom of the brain, the aim of this study was to examine the impact of pulse sequence parameter selection on MRI-based textural parameters of the brain. Methods. MR images of the employed digital phantom were realized with SimuBloch, a simulation package made for fast generation of image sequences based on the Bloch equations. Pulse sequences being investigated consisted of spin echo (SE), gradient echo (GRE), spoiled gradient echo (SP-GRE), inversion recovery spin echo (IR-SE), and inversion recovery gradient echo (IR-GRE). Twenty-nine radiomic textural features related, respectively, to gray-level intensity histograms (GLIH), cooccurrence matrices (GLCOM), zone size matrices (GLZSM), and neighborhood difference matrices (GLNDM) were evaluated for the obtained MR realizations, and differences were identified. Results. It was found that radiomic features vary considerably among images generated by the five different T1-weighted pulse sequences, and the deviations from those measured on the T1 map vary among features, from a few percent to over 100%. Radiomic features extracted from T1-weighted spin-echo images with TR varying from 360 ms to 620 ms and TE = 3.4 ms showed coefficients of variation (CV) up to 45%, while up to 70%, for T2-weighted spin-echo images with TE varying over the range 60–120 ms and TR = 6400 ms. Conclusion. Variability of radiologic textural appearance on MR realizations with respect to the choice of pulse sequence and imaging parameters is feature-dependent and can be substantial. It calls for caution in employing MRI-derived radiomic features especially when pooling imaging data from multiple institutions with intention of correlating with clinical endpoints.

scholarly journals TPA: A Two-Phase Approach Using Simulated Annealing for the Optimization of Census Taker Routes in Mexico

2015 ◽  
Vol 2015 ◽  
pp. 1-9
Author(s):  
Silvia Gaona ◽  
David Romero
Keyword(s):  
Simulated Annealing ◽  
Shortest Path ◽  
Travel Distance ◽  
Visibility Graph ◽  
Second Phase ◽  
Two Phase ◽  
Phase Approach ◽  
Dijkstra's Algorithm ◽  
Average Improvement ◽  
Parameter Values

Censuses in Mexico are taken by the National Institute of Statistics and Geography (INEGI). In this paper a Two-Phase Approach (TPA) to optimize the routes of INEGI’s census takers is presented. For each pollster, in the first phase, a route is produced by means of the Simulated Annealing (SA) heuristic, which attempts to minimize the travel distance subject to particular constraints. Whenever the route is unrealizable, it is made realizable in the second phase by constructing a visibility graph for each obstacle and applying Dijkstra’s algorithm to determine the shortest path in this graph. A tuning methodology based on theiracepackage was used to determine the parameter values for TPA on a subset of 150 instances provided by INEGI. The practical effectiveness of TPA was assessed on another subset of 1962 instances, comparing its performance with that of the in-use heuristic (INEGIH). The results show that TPA clearly outperformsINEGIH. The average improvement is of 47.11%.

B1 mapping for bias-correction in quantitative T 1 imaging of the brain at 3T using standard pulse sequences

2017 ◽  
Vol 46 (6) ◽  
pp. 1673-1682 ◽  
Author(s):  
Mathieu Boudreau ◽  
Christine L. Tardif ◽  
Nikola Stikov ◽  
John G. Sled ◽  
Wayne Lee ◽  
...  
Keyword(s):  
Bias Correction ◽  
Pulse Sequences ◽  
B1 Mapping ◽  
Standard Pulse ◽  
The Brain

scholarly journals Optimal Scaling Approaches for Perfusion MRI with Distorted Arterial Input Function (AIF) in Patients with Ischemic Stroke

2022 ◽  
Vol 12 (1) ◽  
pp. 77
Author(s):  
Sukhdeep Singh Bal ◽  
Fan Pei Gloria Yang ◽  
Yueh-Feng Sung ◽  
Ke Chen ◽  
Jiu-Haw Yin ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Arterial Input Function ◽  
Input Function ◽  
Peak Height ◽  
Perfusion Mri ◽  
Mri Imaging ◽  
Inaccurate Estimation ◽  
Parameter Values ◽  
The Brain ◽  
Accurate Quantification

Background: Diagnosis and timely treatment of ischemic stroke depends on the fast and accurate quantification of perfusion parameters. Arterial input function (AIF) describes contrast agent concentration over time as it enters the brain through the brain feeding artery. AIF is the central quantity required to estimate perfusion parameters. Inaccurate and distorted AIF, due to partial volume effects (PVE), would lead to inaccurate quantification of perfusion parameters. Methods: Fifteen patients suffering from stroke underwent perfusion MRI imaging at the Tri-Service General Hospital, Taipei. Various degrees of the PVE were induced on the AIF and subsequently corrected using rescaling methods. Results: Rescaled AIFs match the exact reference AIF curve either at peak height or at tail. Inaccurate estimation of CBF values estimated from non-rescaled AIFs increase with increasing PVE. Rescaling of the AIF using all three approaches resulted in reduced deviation of CBF values from the reference CBF values. In most cases, CBF map generated by rescaled AIF approaches show increased CBF and Tmax values on the slices in the left and right hemispheres. Conclusion: Rescaling AIF by VOF approach seems to be a robust and adaptable approach for correction of the PVE-affected multivoxel AIF. Utilizing an AIF scaling approach leads to more reasonable absolute perfusion parameter values, represented by the increased mean CBF/Tmax values and CBF/Tmax images.

scholarly journals Modeling the Effect of Binding Kinetics in Spatial Drug Distribution in the Brain

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Nelson Kashaju ◽  
Mark Kimathi ◽  
Verdiana G. Masanja
Keyword(s):  
Specific Binding ◽  
Extracellular Fluid ◽  
Drug Distribution ◽  
Drug Binding ◽  
Binding Kinetics ◽  
Binding Parameter ◽  
Specific Binding Sites ◽  
Distribution Process ◽  
Parameter Values ◽  
The Brain

A 3-dimensional mathematical model is developed to determine the effect of drug binding kinetics on the spatial distribution of a drug within the brain. The key components, namely, transport across the blood-brain barrier (BBB), drug distribution in the brain extracellular fluid (ECF), and drug binding kinetics are coupled with the bidirectional bulk flow of the brain ECF to enhance the visualization of drug concentration in the brain. The model is developed based on the cubical volume of a brain unit, which is a union of three subdomains: the brain ECF, the BBB, and the blood plasma. The model is a set of partial differential equations and the associated initial and boundary conditions through which the drug distribution process in the mentioned subdomains is described. Effects of drug binding kinetics are investigated by varying the binding parameter values for both nonspecific and specific binding sites. All variations of binding parameter values are discussed, and the results show the improved visualization of the effect of binding kinetics in the drug distribution within the brain. For more realistic visualization, we suggest incorporating more brain components that make up the large volume of the brain tissue.

Optimization of a novel Nakagami-m Fading Affected Multiuser Cognitive Radio System Using a New Hybrid DE/BBO/SA

2020 ◽  
Vol 10 ◽  
Author(s):  
Kiranjot Kaur ◽  
Munish Rattan ◽  
Manjeet Singh Patterh
Keyword(s):  
Simulated Annealing ◽  
Cognitive Radio ◽  
Statistical Test ◽  
Radio System ◽  
Fitness Functions ◽  
Transmission Parameters ◽  
Cr System ◽  
Parametric Statistical Test ◽  
Parameter Values ◽  
General Communication

Background and Objective: This communication introduces a multiple secondary user (SU) cognitive radio (CR) system in a dynamic fading environment, specifically Nakagami-m fading. The transmission parameters of CR system are optimized to turn it into an optimal design. Method: For this purpose, a new hybrid of differential evolution, biogeography-based optimization with simulated annealing, namely DE/BBO/SA is proposed. The suggested method searches the best CR parameter values while accomplishing general communication objectives. Fitness functions of these objectives are modified to include fading as well as to accommodate multiple carriers. Results and Conclusion: DE/BBO/SA generated results in terms of optimized parameters, fitness core and values of the objectives are compared with the ones acquired by other available techniques in literature to show efficacy of DE/BBO/SA in cognitive radio optimization. The performances are further validated by conducting a non-parametric statistical test to prove the use of proposed technique for solving CR problem.

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