Bolus-tracking MRI with a simultaneous T1- and T2-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
• Subjects: Algorithms; Animals; Cell Line, Tumor; Colorectal Neoplasms - diagnosis; Colorectal Neoplasms - metabolism; Computer Simulation; Contrast Media - pharmacokinetics; Diffusion Magnetic Resonance Imaging - methods; Humans; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; Meglumine - pharmacokinetics; Mice; Mice, Nude; Models, Biological; Organometallic Compounds - pharmacokinetics; Reproducibility of Results; Sensitivity and Specificity
• ISSN: 1522-2594
• DOI: 10.1002/mrm.22042

The aim of this study was to propose and evaluate a methodology to analyze simultaneously acquired T2*-weighted dynamic susceptibility contrast (DSC) MRI and T(1)-weighted dynamic contrast enhanced (DCE) MRI data. Two generalized models of T2*-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 T2*-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 T2*-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.