Why is it important to acquire precontrast and postcontrast images with the same imaging parameters

Why is it important to acquire precontrast and postcontrast images with the same imaging parameters?

Tissue SIs will change from precontrast to postcontrast images if the imaging parameters are changed but will also change if tissue enhancement following intravenous contrast administration is present. Thus, if the imaging parameters differ between precontrast and postcontrast image acquisitions, it would not be possible to determine whether an observed increase in tissue SI on postcontrast images is due to true enhancement or is artifactual in nature.