The model used for calculating perfusion assumes that the gadolinium passes through the tissue, and then is removed (quickly). In cases where there is contrast-enhancement, at least some contrast remains in the tissue of interest. The result is that the signal intensity remains low, and does not return to baseline.

DR² of Enhancing Tissue versus Normal Tissues

Correction for Leakage

There are two ways commonly used to correct for contrast leakage:

1. Shorten the integration window so that the effect of leakage is small; or
2. Fit the "tail" of the signal intensity to match the baseline intensity, assuming the leakage began at the appearance of the peak, and was complete when the peak is nearly back at its baseline.

Neither of these corrections is entirely correct.