A general linear relaxometry model of R1 using imaging data. Issue 3 (3rd April 2014)

• Record Type: Journal Article
• Authors: Callaghan, Martina F.; Helms, Gunther; Lutti, Antoine; Mohammadi, Siawoosh; Weiskopf, Nikolaus
• Is Part Of: Magnetic resonance in medicine. Volume 73:Issue 3(2015:Mar.)
• Page Start: 1309
• Page End: 1314
• Publication Date: 2014-04-03
• Subjects: Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.25210
• Languages: English
• ISSNs: 0740-3194

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="mrm25210-sec-0001" sec-type="section"> <title>Purpose</title> <p>The longitudinal relaxation rate (R<sub>1</sub>) measured in vivo depends on the local microstructural properties of the tissue, such as macromolecular, iron, and water content. Here, we use whole brain multiparametric in vivo data and a general linear relaxometry model to describe the dependence of R<sub>1</sub> on these components. We explore a) the validity of having a single fixed set of model coefficients for the whole brain and b) the stability of the model coefficients in a large cohort.</p> </sec> <sec id="mrm25210-sec-0002" sec-type="section"> <title>Methods</title> <p>Maps of magnetization transfer (MT) and effective transverse relaxation rate (R<sub>2</sub>*) were used as surrogates for macromolecular and iron content, respectively. Spatial variations in these parameters reflected variations in underlying tissue microstructure. A linear model was applied to the whole brain, including gray/white matter and deep brain structures, to determine the global model coefficients. Synthetic R<sub>1</sub> values were then calculated using these coefficients and compared with the measured R<sub>1</sub> maps.</p> </sec> <sec id="mrm25210-sec-0003" sec-type="section"> <title>Results</title> <p>The model's validity was demonstrated by correspondence between the synthetic and measured R<sub>1</sub> values and by high stability of the model coefficients across a large cohort.</p> </sec> <sec id="mrm25210-sec-0004" sec-type="section"> <title>Conclusion</title> <p>A single set of global coefficients can be used to relate R<sub>1</sub>, MT, and R<sub>2</sub>* across the whole brain. Our population study demonstrates the robustness and stability of the model. Magn Reson Med, 2014. © 2014 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. <bold>Magn Reson Med 73:1309–1314, 2015. © 2014 Wiley Periodicals, Inc.</bold></p> </sec> </abstract>