apparent diffusion coefficient

• 見かけの拡散定数

関

ADC

WordNet

1. appearing as such but not necessarily so; "for all his apparent wealth he had no money to pay the rent"; "the committee investigated some apparent discrepancies"; "the ostensible truth of their theories"; "his seeming honesty" (同)ostensible, seeming
2. clearly revealed to the mind or the senses or judgment; "the effects of the drought are apparent to anyone who sees the parched fields"; "evident hostility"; "manifest disapproval"; "patent advantages"; "made his meaning plain"; "it is plain that he is no reactionary"; "in plain view" (同)evident, manifest, patent, plain, unmistakable
3. (physics) the process in which there is movement of a substance from an area of high concentration of that substance to an area of lower concentration
4. the spread of social institutions (and myths and skills) from one society to another
5. a constant number that serves as a measure of some property or characteristic

PrepTutorEJDIC

1. 『明白な』,はっきりした / 『外見上の』,見かけの,うわべの
2. 放散,発散,拡散[作用] / 普及,流布 / (文体などの)散漫,冗漫
3. (数学で)係数,(物理で)係数,率

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/11/08 15:56:59」(JST)

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[Wiki en表示]

The effective diffusion coefficient (also referred to as the apparent diffusion coefficient) of a diffusant in atomic diffusion of solid polycrystalline materials like metal alloys is often represented as a weighted average of the grain boundary diffusion coefficient and the lattice diffusion coefficient. Diffusion along both the grain boundary and in the lattice may be modeled with an Arrhenius equation. The ratio of the grain boundary diffusion activation energy over the lattice diffusion activation energy is usually 0.4 - 0.6, so as temperature is lowered, the grain boundary diffusion component increases. Increasing temperature often allows for increased grain size, and the lattice diffusion component increases with increasing temperature, so often at 0.8T_melt (of an alloy), the grain boundary component can be neglected.

Modeling

The effective diffusion coefficient can be modeled using Hart's equation when only grain boundary and lattice diffusion are dominant:

D_gb D_l.

where

effective diffusion coefficient.

D_gb = grain boundary diffusion coefficient.

D_l = lattice diffusion coefficient.

.δ

value based on grain shape, 1 for parallel grains, 3 for square grains.

average grain size.

δ grain boundary width,often assumed to be 0.5 nm.

Grain boundary diffusion is significant in face centered cubic metals below about 0.8 T_melt (Absolute). Line dislocations and other crystalline defects can become significant below ~0.4 T_melt in FCC metals.

References

See also

• Kirkendall effect
• Phase transformations in solids
• Mass diffusivity

UpToDate Contents

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• Cornea.Cornea.2013 Feb;32(2):179-84. doi: 10.1097/ICO.0b013e31825646de.
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• PMID 22868628

• Does positron emission tomography data acquisition impact simultaneous diffusion-weighted imaging in a whole-body PET/MRI system?

• Buchbender C, Hartung-Knemeyer V, Heusch P, Heusner TA, Beiderwellen K, Wittsack HJ, Kühl H, Forsting M, Bockisch A, Antoch G, Lanzman RS.SourceUniv Dusseldorf, Medical Faculty, Department of Diagnostic and Interventional Radiology, D-40225 Dusseldorf, Germany; Univ Duisburg-Essen, Medical Faculty, Department of Diagnostic and Interventional Radiology and Neuroradiology, D-45147 Essen, Germany.
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• OBJECTIVES: The purpose of this study was to test whether the acquisition of positron emission tomography (PET) does interfere with simultaneous diffusion weighted imaging (DWI) in an integrated whole-body PET/MRI system.MATERIAL AND METHODS: Fourteen consecutive oncological patients (9 men, 5 women
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• Locally advanced rectal cancer: Value of ADC mapping in prediction of tumor response to radiochemotherapy.

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• European journal of radiology.Eur J Radiol.2013 Feb;82(2):234-40. doi: 10.1016/j.ejrad.2012.09.027. Epub 2012 Nov 1.
• PURPOSE: To evaluate the diagnostic performance of quantitative apparent diffusion coefficient (ADC) measurements, in the assessment of the therapeutic response to chemo-radiation therapy (CRT) in patients with locally advanced rectal cancer, by analyzing post CRT values of ADC, in relation to tumor
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Japanese Journal

• 坐骨神経痛診断における拡散強調MRIの可能性

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• NAID 40020241492

• 子宮頸癌における拡散強調画像とADC値の検討

• 松浦 基樹,玉手 雅人,真里谷 奨 [他]
• 産科と婦人科 81(6), 773-777, 2014-06
• NAID 40020104736

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Related Links

• 拡散強調画像 - Wikipedia

また、スピンエコー法のパルス系列において、傾斜磁場の強さや印加時間を変えること によりディフェージングの効果を付けて得られた複数の画像から、見かけ上の拡散係数 ( apparent diffusion coefficient, ADC) を求めて画像化することができ、これを拡散（ ...

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リンク元	「ADC」「見かけの拡散定数」
関連記事	「apparent」「diffusion」「coefficient」

「ADC」

　　[★]

• 見かけの拡散定数

関

apparent diffusion coefficient

「見かけの拡散定数」

　　[★]

英

apparent diffusion coefficient、ADC

「apparent」

　　[★]

• adj.

• 見かけ上の、明らかな、明白な

関

apparently、clear、clearly、evident、evidently、indisputable、obvious、obviously、overt、overtly、palpable、plain、pronounced、unambiguous、unambiguously、unequivocal、visibly

　 　 　

「diffusion」

　　[★]

• n.

• 拡散、放散、流布、普及、伝播

　 　 　

「coefficient」

　　[★]

• n.

• 係数

関

moduli、modulus