This study is a diagnostic trial of fluorescein fluorescence as an intraoperative imaging biomarker during open cranial surgery for tumor resection of first-time (preoperatively) presumed high or low grade glioma. Subjects participate in a "one-time" event/visit (i.e, surgery) as part of this protocol. Images and data from the patient's pre- and post-operative MR scans are used for analysis in the study, but these acquisitions are part of the patient's standard-of-care, would occur independently of whether the participant is enrolled; and thus, are not considered to be research study visits. No post-surgical follow-up visit is part of the protocol data collection or analysis. Patients are monitored for possible adverse events through the routine follow-up under the care of the operating surgeon involved in the study procedures, post-operatively and subsequently through the medical record. Hence, this information is already being collected as part of standard-of-care and is available for adverse event surveillance. Patients receiving ALA who present with abnormally elevated LFTs beyond the peri-operative observation period are monitored on a regular basis until resolution and this blood testing is considered to be part of the study.