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Α Β Γ Δ Ε Ζ Η Θ Ι Κ Λ Μ Ν Ξ Ο Π Ρ Σ Τ Υ Φ Χ Ψ Ω α β γ δ ε ζ η θ ι κ λ μ ν ξ ο π ρ σ τ υ φ χ ψ ω
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      저자 : Goh Junghwan (검색결과 2 건)
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        Simulation of microvascular signal changes used on a gadolinium-chelated contrast agent at 3 T MRI in the presence of amyloid-beta plaques

        Yoo Chang Hyun,Goh Junghwan,Jahng Geon-Ho,Jin Seokha,Lee DongKyu,Cho HyungJoon 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.11

        It is important to understand microvascular alterations in the brain of Alzheimer disease (AD) patients which usually has amyloid-beta plaques in an imaging voxel, causing a phase dispersion in an MRI signal. The objective of this study was to simulate the changes of transverse relaxation rates and microvascular indexes with and without the presence of amyloid-beta plaques in an imaging voxel with using a clinically available contrast agent. The Monte Carlo simulations with the fnite perturber method were used to calculate microvascular indices of mean vessel diameter (mVD), vessel size index (VSI), mean vessel density (Q), blood volume fraction (BVf), and microvessel-weighted imaging (MvWI) with and without the presence of amyloid-beta plaques in an imaging voxel. The simulation was performed with the conditions of three diferent magnetic feld strengths (1.5 T, 3 T and 7 T), several diferent echo times for gradient-echo (15, 40, and 60 ms) and spin-echo (20, 80, and 100 ms) images, and two diferent contrast agents (gadolinium (Gd)-chelated and superparamagnetic iron oxide nanoparticles (SPION)-based contrast agents). The changes of relaxation rates and microvascular indexes were evaluated with increasing the microvascular vessel sizes and with increasing the amyloid plaque loads. In the microvascular structures without amyloid plaques, ΔR2* and ΔR2 increased as the B0 feld became stronger, the susceptibility diference of the contrast agent became larger, and the echo time was increased. Both mVD and VSI increased with increasing microvessel sizes, but Q decreased with increasing microvessel sizes. In the microvascular structures with amyloid plaques, ΔR2* and ΔR2 were not varied with increasing the vessel radius, but higher in the 3.81% concentration of amyloid plaque than 1.83% of that. BVf and MvWI were increased with increasing the plaque load. The BVf and MvWI indices were sensitive to evaluate the integrity of the microvascular in the AD brain since those values were increased with increasing the plaque load. Therefore, it is worthwhile to evaluate microvascular structure changes in the AD human brain using 3 T MRI with a Gd contrast agent.

      • KCI등재

        Contribution of Microbleeds on Microvascular Magnetic Resonance Imaging Signal

        Chang Hyun Yoo,Junghwan Goh,Geon-Ho Jahng Korean Society of Medical Physics 2022 의학물리 Vol.33 No.4

        Purpose: Cerebral microbleeds are more susceptible than surrounding tissues and have been associated with a variety of neurological and neurodegenerative disorders that are indicative of an underlying vascular pathology. We investigated relaxivity changes and microvascular indices in the presence of microbleeds in an imaging voxel by evaluating those before and after contrast agent injection. Methods: Monte Carlo simulations were run with a variety of conditions, including different magnetic field strengths (B<sub>0</sub>), different echo times, and different contrast agents. ΔR2<sup>*</sup> and ΔR2 and microvascular indices were calculated with varying microvascular vessel sizes and microbleed loads. Results: As B<sub>0</sub> and the concentration of microbleeds increased, 𝜟R2<sup>*</sup> and 𝜟R2 increased. 𝜟R2<sup>*</sup> increased, but 𝜟R2 decreased slightly as the vessel radius increased. When the vessel radius was increased, the vessel size index (VSI) and mean vessel diameter (mVD) increased, and all other microvascular indices except mean vessel density (Q) increased when the concentration of microbleeds was increased. Conclusions: Because patients with neurodegenerative diseases often have microbleeds in their brains and VSI and mVD increase with increasing microbleeds, microbleeds can be altered microvascular signals in a voxel in the brain of a neurodegenerative disease at 3T magnetic resonance imaging.

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