RecruitingPhase 2Drug trialInflammation in Primary and Secondary Malignancies of the Central Nervous System Using [C-11]-CS1P1Adult patients with primary or secondary central nervous system malignancies will be invited to undergo a baseline \[C-11\]-CS1P1 PET scan and a follow-up scan within 24 months of the baseline scan (preferably within 6-months post-treatment).The study will describe patterns of tracer uptake in tumors and normal brain and explore how these patterns relate to MRI findings, treatments received, and clinical outcomes.