Bolus‐tracking MRI with a simultaneous T 1 ‐ and T ‐measurement

• Published in: Magnetic resonance in medicine 2009-09, Vol.62 (3), p.672-681
• Main Authors: Sourbron, S., Heilmann, M., Biffar, A., Walczak, C., Vautier, J., Volk, A., Peller, M.
• Format: Article
• Language: English
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.22042

The aim of this study was to propose and evaluate a methodology to analyze simultaneously acquired T ‐weighted dynamic susceptibility contrast (DSC) MRI and T 1 ‐weighted dynamic contrast enhanced (DCE) MRI data. Two generalized models of T ‐relaxation are proposed to account for tracer leakage, and a two‐compartment exchange model is used to separate tracer in intra‐ and extravascular spaces. The methods are evaluated using data extracted from ROIs in three mice with subcutaneously implanted human colorectal tumors. Comparing plasma flow values obtained from DCE‐MRI and DSC‐MRI data defines a practical experimental paradigm to measure T ‐relaxivities, and reveals a factor of 15 between values in tissue and blood. Comparing mean transit time values obtained from DCE‐MRI and DSC‐MRI without leakage correction, indicates a significant reduction of susceptibility weighting in DSC‐MRI during tracer leakage. A one‐parameter gradient correction model provides a good approximation for this susceptibility loss, but redundancy of the parameter limits the practical potential of this model for DSC‐MRI. Susceptibility loss is modeled more accurately with a variable T ‐relaxivity, which allows to extract new parameters that cannot be derived from DSC‐MRI or DCE‐MRI alone. They reflect the cellular and vessel geometry, and thus may lead to a more complete characterization of tissue structure. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.