Comparison of t2 relaxation in blood, brain, and ferritin

Brooks, Rodney A.; Vymazal, Josef; Baumgarner, Charles D.; Vu, Tran Anh; Bulte, Jeff W.M.

doi:10.1002/jmri.1880050414

Cited by 73 publications

(91 citation statements)

References 27 publications

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“…Theoretical reasons (25) suggest a range of possibilities from constant to quadratic dependence. A linear relationship has been found in postmortem blood-free monkey brain specimens (24) and is assumed in the present study, although the limitations of such a transfer are understood. The difference between the GE and SE relaxation rates in blood is neglected.…”

Section: Numerical Values Of Parametersmentioning

confidence: 75%

“…This resulted in R 2a0 ϭ 2.76 s Ϫ1 and R 2v0 ϭ 5.97 s Ϫ1 . For blood the validity of such a conversion follows from many reports (23,24), and from the quadratic dependence of the relaxation rate on the blood oxygenation level observed in Ref. 12.…”

Section: Numerical Values Of Parametersmentioning

confidence: 87%

“…Then Eq. [5] takes the form c app ͑⌬t͒ ϭ f app ͑0͒c a ͑⌬t͒⌬t [24] c app ͑2⌬t͒ ϭ ͓f app ͑0͒c a ͑2⌬t͒ ϩ f app ͑⌬t͒c a ͑⌬t͔͒⌬t [25] and so on. The initial value f app (0) is defined from Eq.…”

Section: Apparent Blood Flow and Residue Functionmentioning

confidence: 99%

“…The initial value f app (0) is defined from Eq. [24], and then f app (⌬t) is found from Eq. [25], etc.…”

Section: Apparent Blood Flow and Residue Functionmentioning

confidence: 99%

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On the theoretical basis of perfusion measurements by dynamic susceptibility contrast MRI

Kiselev

2001

Magnetic Resonance in Med

170

199

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A quantitative analysis was undertaken to calibrate the perfusion quantification technique based on tracking the first pass of a bolus of a blood pool contrast agent. A complete simulation of the bolus passage, of the associated changes in the T 2 and T* 2 signals, and of the data processing was performed using the tracer dilution theory, an analytical theory of the MR signal from living tissues and numerical simulations. Magnetic resonance imaging (MRI) of the first passage of a bolus of a blood pool contrast agent is a promising method for assessment of regional perfusion (1,2). This method implies a measurement of the contrast agent concentration time course in both a volume of interest (VOI) and a feeding artery. The quantification of the perfusion is achieved by comparison of these data sets. The underlying theory rests on two basic assumptions. First, it is assumed that the measured MR signal is proportional to the concentration of the contrast agent, with a universal proportionality coefficient for both the VOI and a reference voxel in the artery. Second, the kinetic of the contrast agent is described in terms of a linear model. The aim of this work is to demonstrate that the former assumption is invalid in proton MRI: the relationship between the MRI signal and the concentration of the contrast agent in the VOI significantly differs from that in the reference voxel. It depends on the MRI pulse sequence and the vascular composition of the investigated tissue.The reason for such variability in the MRI signal is the contribution of the extravascular protons. These parenchymal protons are dephased by the blood pool contrast agent through the inhomogeneous, long-ranged, susceptibilityinduced magnetic field. Thus, their contribution to the MR signal follows the time course of the contrast agent concentration with a specific functional dependence that significantly differs from the relaxation effect of the contrast agent in blood. This peculiarity is not accounted for in the present theory (1,3).Until now, theoretical interest has been focused on the so-called deconvolution procedure in the presence of noise. This issue is well understood (3) and is not considered here. The presented results were obtained for a noisefree simulation. This allows analysis of the inherent accuracy of the method. The obtained theoretical predictions are compared with published experimental data (4 -6). METHODS Tracer Dilution TheoryLet us start with a brief review of the tracer dilution theory (7). Consider a VOI and a voxel inside a properly chosen supplying artery. Let us denote as c a (t) and c(t) the concentrations of the contrast agent in the artery and in blood in the studied tissue, respectively. The concentration c(t) linearly depends on the history of c a (t). This is expressed as a convolution with a kernel h(t) which describes the blood transport:[1]In practical calculations the lower limit in this integral can be replaced with the moment of bolus injection. The function h(t) possesses a propertywhich reflects the fact t...

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Section: Numerical Values Of Parametersmentioning

confidence: 75%

Section: Numerical Values Of Parametersmentioning

confidence: 87%

Section: Apparent Blood Flow and Residue Functionmentioning

confidence: 99%

“…The initial value f app (0) is defined from Eq. [24], and then f app (⌬t) is found from Eq. [25], etc.…”

Section: Apparent Blood Flow and Residue Functionmentioning

confidence: 99%

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On the theoretical basis of perfusion measurements by dynamic susceptibility contrast MRI

Kiselev

2001

Magnetic Resonance in Med

170

199

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“…In contrast, the (1, 3)-GMA with the three lowest low and the first high frequency moment approximates the long time limit significantly better than the short time limit. An application to biological tissue is provided in Figure 4C where mono-and bi-exponential approximations in the GMA of the correlation function are visualized for values that are typical for susceptibility gradients based on nonheme ironstorage in brain tissue (through iron-rich oligodendrocytes in the Globus pallidus that approximately have radii R i of 3-4 µm, a frequency shift of δω = 184 s −1 , a tissue density of η = 0.04 and D = 0.76 · 10 −9 m 2 s −1 , leading to τ = 16.12 ms; see [50,51] for more details). It can be seen that the biexponential approximations K (1,3) (t) and K (2,2) (t) are in excellent agreement with the actual correlation function K(t), while the monoexponential functions K i (t) only approximate K(t) sufficiently for t 30 ms.…”

Section: Spheresmentioning

confidence: 99%

Generalized Moment Analysis of Magnetic Field Correlations for Accumulations of Spherical and Cylindrical Magnetic Perturbers

et al. 2016

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In biological tissue, an accumulation of similarly shaped objects with a susceptibility difference to the surrounding tissue generates a local distortion of the external magnetic field in magnetic resonance imaging. It induces stochastic field fluctuations that characteristically influence proton spin dephasing in the vicinity of these magnetic perturbers. The magnetic field correlation that is associated with such local magnetic field inhomogeneities can be expressed in the form of a dynamic frequency autocorrelation function that is related to the time evolution of the measured magnetization. Here, an eigenfunction expansion for two simple magnetic perturber shapes, that of spheres and cylinders, is considered for restricted spin diffusion in a simple model geometry. Then, the concept of generalized moment analysis, an approximation technique that is applied in the study of (non-)reactive processes that involve Brownian motion, allows deriving analytical expressions of the correlation function for different exponential decay forms. Results for the biexponential decay for both spherical and cylindrical magnetized objects are derived and compared with the frequently used (less accurate) monoexponential decay forms. They are in asymptotic agreement with the numerically exact value of the correlation function for long and short times.

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Relaxation induced by ferritin and ferritin-like magnetic particles: The role of proton exchange

Gossuin¹,

Roch²,

Müller³

et al. 2000

Magn. Reson. Med.

111

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Comparison of t2 relaxation in blood, brain, and ferritin

Cited by 73 publications

References 27 publications

On the theoretical basis of perfusion measurements by dynamic susceptibility contrast MRI

On the theoretical basis of perfusion measurements by dynamic susceptibility contrast MRI

Generalized Moment Analysis of Magnetic Field Correlations for Accumulations of Spherical and Cylindrical Magnetic Perturbers

Relaxation induced by ferritin and ferritin-like magnetic particles: The role of proton exchange

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