<i>T</i>
            <sub>1</sub>
            : The Longitudinal Relaxation Time

Gowland, Penny; Stevenson, Valerie

doi:10.1002/0470869526.ch5

Cited by 33 publications

(26 citation statements)

References 72 publications

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“…Similarly, mean T 1 values for the core region were initially elevated, lowest at 1 week, increased continuously to 6 months and thereafter appeared to level off. The small decrease of T 1 values at 1 week compared to the value at 1 day may be associated with a decline in tissue water content due to reduction of edema (Ewing et al, 1999) and/or an increase in the concentration of paramagnetic compounds (Gowland and Stevenson, 2003) in the tissue due to vascular degradation. Mean T 1sat values in the core regions at 1 day and 1 week after MCAO were almost the same and were significantly higher than the corresponding contralateral regions (Fig.…”

Section: Discussionmentioning

confidence: 99%

Chronic brain tissue remodeling after stroke in rat: A 1-year multiparametric magnetic resonance imaging study

et al. 2010

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Rats subjected to 2 hours of transient middle cerebral artery occlusion were studied temporally over 1 year by magnetic resonance imaging (MRI) and behavioral testing. Multiparameter MRI measures of T 2 , T 1 , T 1 in the presence of off-resonance saturation of the bound proton signal (T 1sat ), apparent diffusion coefficient (ADC) and susceptibility-weighted imaging (SWI) were obtained at 1 day, 1, 2, 3 and 4 weeks, and 3, 6, 9 and 12 months post-ischemia. Regions of interest included: ischemic core (damaged both at 1 day and later); new lesion (normal at 1 day, but damaged later); and recovery (damaged at 1 day, but normal later) areas. Hematoxylin and eosin, Prussian blue and ED-1, a monoclonal antibody murine macrophage marker, stainings were performed for histological assessment. Core area T 2 and ADC values increased until ~6 months, and T 1 and T 1sat until ~12 months. New lesion area MRI parameter values increased until ~6 months (T 2 , T 1 and ADC), or ~1 year (T 1sat ). Lesion area was largest at 1 day (mean±SD: 37.0±13.7 mm 2 ) and smallest at 1 year (18.1±10.5 mm 2 ). Recovery area was largest at 3 weeks (8.9±3.8 mm 2 ) and smallest at 1 year (6.4±3.3 mm 2 ). The ipsilateral/contralateral ventricle area ratio was 0.7±0.2 at 1 day and increased significantly at 1 year (2.4±0.7). Iron-laden macrophages, histologically confirmed at 1 year, were detected in the lesion borders by SWI at 3, 6, 9 and 12 months. Our data indicate that MRI detectable changes of ischemia-damaged brain tissue continue for at least 1 year post-ischemia.

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Section: Discussionmentioning

confidence: 99%

Chronic brain tissue remodeling after stroke in rat: A 1-year multiparametric magnetic resonance imaging study

et al. 2010

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“…The phase contrast data were analyzed using standard methods (30) and the flow velocity was obtained from a region of interest (ROI) that covered the inside of the tube in which the water was flowing. The reference T 1 was found from a three parameter fit to a model of the SEIR signal (31). The CA relaxivity r 1 was subsequently found from a linear regression to in which C is the CA concentration and T 10 is T 1 at C = 0 mM.…”

Section: Methodsmentioning

confidence: 99%

Effects of inflow and radiofrequency spoiling on the arterial input function in dynamic contrast‐enhanced MRI: A combined phantom and simulation study

Garpebring

Wirestam

Östlund

et al. 2011

Magnetic Resonance in Med

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The arterial input function is crucial in pharmacokinetic analysis of dynamic contrast-enhanced MRI data. Among other artifacts in arterial input function quantification, the blood inflow effect and nonideal radiofrequency spoiling can induce large measurement errors with subsequent reduction of accuracy in the pharmacokinetic parameters. These errors were investigated for a 3D spoiled gradient-echo sequence using a pulsatile flow phantom and a total of 144 typical imaging settings. In the presence of large inflow effects, results showed poor average accuracy and large spread between imaging settings, when the standard spoiled gradient-echo signal equation was used in the analysis. For example, one of the investigated inflow conditions resulted in a mean error of about 40% and a spread, given by the coefficient of variation, of 20% for K trans . Minimizing inflow effects by appropriate slice placement, combined with compensation for nonideal radiofrequency spoiling, significantly improved the results, but they remained poorer than without flow (e.g., 3-4 times larger coefficient of variation for K trans ). It was concluded that the 3D spoiled gradient-echo sequence is not optimal for accurate arterial input function quantification and that correction for nonideal radiofrequency spoiling in combination with inflow minimizing slice placement should be used to reduce the errors. Magn Reson Med 65:1670-1679, 2011. V C 2011 Wiley-Liss, Inc.Key words: dynamic contrast-enhanced MRI; arterial input function; blood flow effects; RF spoiling Dynamic contrast-enhanced MRI (DCE-MRI) is a technique based on the acquisition of a series of images before, during, and after intravenous administration of contrast agent (CA). CA concentration curves can be derived from the images, and tissue specific quantitative pharmacokinetic parameters can subsequently be obtained by appropriate modeling (1).This technique has many applications, for example, in clinical oncology. Biomarkers for drug efficacy and clinical outcome, derived from DCE-MRI, can potentially increase cost efficiency and thus facilitate early phase clinical trials of antiangiogenic and vascular disrupting agents. In the clinical setting, DCE-MRI can provide noninvasive tumor grading as well as predict treatment outcome (2,3).In general, the data acquisition of quantitative DCE-MRI consists of two steps. First, baseline T 1 is quantified, typically by using a gradient echo (GRE) variable flip angle (FA) method (4). After that, a dynamic scan is performed in which the first few images are acquired before the injection of CA (i.e., the baseline signal), and the remaining images are acquired during and up to several minutes after the injection. Then, the T 1 relaxation time is estimated from baseline and dynamic scan images. Under the assumption of the fast exchange limit (5), one can estimate the concentration of CA from a linear relationship between the concentration and the T 1 relaxation rate provided that the relaxivity of the CA is known. The relaxivity is typically ...

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“…An inversion-recovery EPI sequence was used to quantify the T 1 values. 24 A global adiabatic inversion pulse (flip angle 5 1808, duration 5 2 ms) was applied followed by 10 inversion times exponentially spaced from 8.1 ms to 7.5 seconds (Supporting Information Table S3). Other parameters were as follows: TR 5 15 seconds, TE 5 25.5 ms, slice thickness 5 2 mm, FOV 5 20 3 20 mm 2 , and matrix size 5 64 3 64.…”

Section: T 1 and T 2 Measurements In Vivomentioning

confidence: 99%

PRO‐QUEST: a rapid assessment method based on progressive saturation for quantifying exchange rates using saturation times in CEST

Demetriou

Tachrount

Zaiß

et al. 2018

Magnetic Resonance in Med

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T ₁ : The Longitudinal Relaxation Time

Cited by 33 publications

References 72 publications

Chronic brain tissue remodeling after stroke in rat: A 1-year multiparametric magnetic resonance imaging study

Chronic brain tissue remodeling after stroke in rat: A 1-year multiparametric magnetic resonance imaging study

Effects of inflow and radiofrequency spoiling on the arterial input function in dynamic contrast‐enhanced MRI: A combined phantom and simulation study

PRO‐QUEST: a rapid assessment method based on progressive saturation for quantifying exchange rates using saturation times in CEST

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T 1 : The Longitudinal Relaxation Time

Cited by 33 publications

References 72 publications

Chronic brain tissue remodeling after stroke in rat: A 1-year multiparametric magnetic resonance imaging study

Chronic brain tissue remodeling after stroke in rat: A 1-year multiparametric magnetic resonance imaging study

Effects of inflow and radiofrequency spoiling on the arterial input function in dynamic contrast‐enhanced MRI: A combined phantom and simulation study

PRO‐QUEST: a rapid assessment method based on progressive saturation for quantifying exchange rates using saturation times in CEST

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T ₁ : The Longitudinal Relaxation Time