IDH1 and central nervous system cancer: ASL has proven utility as a noninvasive method of determining glioma grade and distinguishing between treatment effects and tumor recurrence in postoperative gliomas.65–67 CBF has also been shown to correlate with IDH and ATRX mutation status, which are of prognostic relevance.68 ASL has a low signal to noise ratio and, unlike DSC perfusion, does not require leakage correction.