Can Contrast Extravasation be Separated from Intravascular Recirculation in DSC MRI of The Brain?

Introduction In dynamic susceptibility contrast (DSC) MRI, the concentration time curves commonly do not return to baseline after the first pass. In normal brain tissues with intact blood-brain barrier (BBB), the elevated concentration during the recirculation phase could be caused by the intravascular contrast agents. However, when the BBB is disrupted, as the case with brain tumor, both the intravascular component and the contrast extravasations contribute to the measured concentration time curves during recirculation. The recirculation behavior was studied in brain tumors and interpreted as the degree of vascular tortuosity and disturbances in blood flow within brain tumors (1, 2). However, contrast leakages in brain tumors were also investigated as T1 and T2 effects in the recirculation phase of the DSC curves, which were linked to vessel permeability (3, 4). The contrast leaked to the extravascular extracellular space (EES) can appear as additive (if T2) or subtractive (if T1) effects to the intravascular recirculation. The aim of this study is to investigate whether the contrast extravasation can be separated from intravascular recirculation in DSC MRI of the brain. Methods In DSC studies, the signal intensity time curve, S(t) can be approximated as: ( ) [ ] ( ) [ ]TE t C t C r R TR t C r R leakage nonleakage leakage e e ⋅ + ⋅ + − ⋅ ⋅ + − ⋅ − ⋅ = ) ( ) ( 2 ) ( 1 0 2 * 0 1 0 1 M S(t) [1]