Estimation of brain iron concentration in vivo using a linear relationship between regional iron and apparent transverse relaxation rate of the tissue water at 4.7T

Mitsumori, Fumiyuki; Watanabe, Hidehiro; Takaya, Nobuhiro

doi:10.1002/mrm.22097

Cited by 58 publications

(63 citation statements)

References 16 publications

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“…In fact, several studies report a linear relationship between iron content and T 2 in brain tissue. [23][24][25] …”

Section: Endogenous T 2 Contrastmentioning

confidence: 99%

“…63 Most iron is chelated and stored in the protein ferritin as Fe 3+ , 23,63 which shortens water proton T 1 and T 2 relaxation times. 23,64 Accordingly, several studies reported T 1 and T 2 effects as a function of iron content 10,[23][24][25]65 in the human brain, with concentration in the globus pallidus (GP) among the highest. Though T 2 W MR imaging shows a similar pattern of signal reduction around the GP (white arrows in Fig.…”

Section: Nerve Cellsmentioning

confidence: 99%

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<i>In Vivo</i> Brain MR Imaging at Subnanoliter Resolution: Contrast and Histology

2016

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This article provides an overview of in vivo magnetic resonance (MR) imaging contrasts obtained for mammalian brain in relation to histological knowledge. Emphasis is paid to the (1) significance of high spatial resolution for the optimization of T 1 , T 2 , and magnetization transfer contrast, (2) use of exogenous extra-and intracellular contrast agents for validating endogenous contrast sources, and (3) histological structures and biochemical compounds underlying these contrasts and (4) their relevance to neuroradiology. Comparisons between MR imaging at subnanoliter resolution and histological data indicate that (a) myelin sheaths, (b) nerve cells, and (c) the neuropil are most responsible for observed MR imaging contrasts, while (a) diamagnetic macromolecules, (b) intracellular paramagnetic ions, and (c) extracellular free water, respectively, emerge as the dominant factors. Enhanced relaxation rates due to paramagnetic ions, such as iron and manganese, have been observed for oligodendrocytes, astrocytes, microglia, and blood cells in the brain as well as for nerve cells. Taken together, a plethora of observations suggests that the delineation of specific structures in high-resolution MR imaging of mammalian brain and the absence of corresponding contrasts in MR imaging of the human brain do not necessarily indicate differences between species but may be explained by partial volume effects. Second, paramagnetic ions are required in active cells in vivo which may reduce the magnetization transfer ratio in the brain through accelerated T 1 recovery. Third, reductions of the magnetization transfer ratio may be more sensitive to a particular pathological condition, such as astrocytosis, microglial activation, inflammation, and demyelination, than changes in relaxation. This is because the simultaneous occurrence of increased paramagnetic ions (i.e., shorter relaxation times) and increased free water (i.e., longer relaxation times) may cancel T 1 or T 2 effects, whereas both processes reduce the magnetization transfer ratio.

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“…In fact, several studies report a linear relationship between iron content and T 2 in brain tissue. [23][24][25] …”

Section: Endogenous T 2 Contrastmentioning

confidence: 99%

Section: Nerve Cellsmentioning

confidence: 99%

<i>In Vivo</i> Brain MR Imaging at Subnanoliter Resolution: Contrast and Histology

2016

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“…These imaging methods have been used for quantifying iron changes in deep grey matter (Haacke et al, 2009a;Ogg et al, 1999) and qualitatively for enhancing image contrast, particularly between MS lesions and normal tissue (Eissa et al, 2009;Haacke et al, 2009b;Hammond et al, 2008b). While transverse relaxation rate (R2 or R2*) mapping is sensitive to iron in normal individuals (Bermel et al, 2005), phase imaging should be both more sensitive to iron because it depends on subtle phase shifts rather than significant dephasing, and more specific since phase is not significantly affected by water content, which could be a confound in cases of neurodegeneration (Mitsumori et al, 2009).…”

Section: Introductionmentioning

confidence: 98%

Susceptibility phase imaging with comparison to R2* mapping of iron-rich deep grey matter

Walsh

Wilman

2011

NeuroImage

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“…27 Specifically, adiabatic T1ρ can detect changes in neuronal cellular density, 24, 28 whereas adiabatic T2ρ has been shown to be sensitive to iron, 24 and even capable of quantifying iron levels in the brain. 29 …”

Section: Introductionmentioning

confidence: 99%

Magnetization transfer and adiabatic T1ρ MRI reveal abnormalities in normal-appearing white matter of subjects with multiple sclerosis

et al. 2013

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Background Diffuse abnormalities are known to occur within the brain tissue of multiple sclerosis (MS) patients which is ‘normal appearing’ on T1-weighted and T2-weighted magnetic resonance images. Objectives With the goal of exploring the sensitivity of novel MRI parameters to detect such abnormalities, we implemented an inversion-prepared magnetization transfer (MT) protocol and adiabatic T1ρ and T2ρ rotating frame relaxation methods. Methods Nine relapsing-remitting MS patients and seven healthy controls were recruited. Relaxation parameters were measured in a single slice just above the lateral ventricles and approximately parallel to AC-PC line. Results The MT ratio of regions encompassing the normal appearing white matter (NAWM) was different in MS patients as compared with controls (p=0.043); however the T1 measured during off-resonance irradiation (T1sat) was substantially more sensitive than the MT ratio for detecting differences between groups (p=0.0006). Adiabatic T1ρ was significantly prolonged in the NAWM of MS patents as compared to controls (by 6%, p=0.026), while no differences were found among groups for T2ρ. No differences among groups were observed in the cortical grey matter for any relaxation parameter. Conclusions The results suggest degenerative processes occurring in the NAWM of MS, likely not accompanied by significant abnormalities in iron content.

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Estimation of brain iron concentration in vivo using a linear relationship between regional iron and apparent transverse relaxation rate of the tissue water at 4.7T

Abstract: Maps of the apparent transverse relaxation time (T 2 † ) were collected on a transaxial plane across the basal ganglia in 54 healthy subjects at 4.7T using a multiecho adiabatic spinecho (MASE) imaging sequence. We attempted to quantify the nonhemin iron concentration (

Cited by 58 publications

References 16 publications

<i>In Vivo</i> Brain MR Imaging at Subnanoliter Resolution: Contrast and Histology

<i>In Vivo</i> Brain MR Imaging at Subnanoliter Resolution: Contrast and Histology

Susceptibility phase imaging with comparison to R2* mapping of iron-rich deep grey matter

Magnetization transfer and adiabatic T1ρ MRI reveal abnormalities in normal-appearing white matter of subjects with multiple sclerosis

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