Dependency of R2 and R2* relaxation on Gd-DTPA concentration in arterial blood: Influence of hematocrit and magnetic field strength |
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Authors: | Daniëlle van Dorth Krishnapriya Venugopal Dirk H J Poot Lydiane Hirschler Jeroen de Bresser Marion Smits Juan A Hernandez-Tamames Clément S Debacker Matthias J P van Osch |
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Institution: | 1. C. J. Gorter Center for High-Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands;2. Department of Radiology and Nuclear Medicine, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands;3. Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands;4. GHU Paris, Institut de Psychiatrie et Neurosciences, Hôpital Sainte-Anne, Paris, France |
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Abstract: | Dynamic susceptibility contrast (DSC) MRI is clinically used to measure brain perfusion by monitoring the dynamic passage of a bolus of contrast agent through the brain. For quantitative analysis of the DSC images, the arterial input function is required. It is known that the original assumption of a linear relation between the R2(*) relaxation and the arterial contrast agent concentration is invalid, although the exact relation is as of yet unknown. Studying this relation in vitro is time-consuming, because of the widespread variations in field strengths, MRI sequences, contrast agents, and physiological conditions. This study aims to simulate the R2(*) versus contrast concentration relation under varying physiological and technical conditions using an adapted version of an open-source simulation tool. The approach was validated with previously acquired data in human whole blood at 1.5 T by means of a gradient-echo sequence (proof-of-concept). Subsequently, the impact of hematocrit, field strength, and oxygen saturation on this relation was studied for both gradient-echo and spin-echo sequences. The results show that for both gradient-echo and spin-echo sequences, the relaxivity increases with hematocrit and field strength, while the hematocrit dependency was nonlinear for both types of MRI sequences. By contrast, oxygen saturation has only a minor effect. In conclusion, the simulation setup has proven to be an efficient method to rapidly calibrate and estimate the relation between R2(*) and gadolinium concentration in whole blood. This knowledge will be useful in future clinical work to more accurately retrieve quantitative information on brain perfusion. |
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Keywords: | arterial input function dynamic susceptibility contrast MRI hematocrit dependency magnetic field strength oxygen saturation simulations |
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