Kristen W. Yeom
Brain tumors are the most common solid neoplasm of childhood and also a leading cause of cancer deaths in children. Unfortunately, these pediatric tumors can look bizarre, with a buffet of pathology that can be quite daunting when we first encounter them. For example, it’s not unusual for a scary-looking tumor with lots of blood, necrosis, and edema—one that might look just like a glioblastoma in an adult patient—to turn out to be a run-of-the-mill pilocytic tumor that’s totally curative. And it’s not just us radiologists. Pathologists can get confused, too. Not long ago, we saw a bland cerebellar tumor that was scooped out and called grade I pilocytic, just to see it recur like gangbusters in a matter of a few weeks after gross total resection. The pathology did get revised later to anaplastic pilocytic; regardless, the poor kid died.
Using diffusion imaging, we’re a lot savvier sorting out some these tumors, but there isn’t a whole lot of information on tumor perfusion in children. One reason might be the technical challenges of T2* DSC perfusion that require a large-bore IV access and high-flow contrast injection—potential barriers in babies and small kids. Arterial spin-labeling (ASL) perfusion, on the other hand, is well-suited for kids, as it doesn’t require contrast, has high labeling efficiency, and can be repeated in the case of motion.
Here we illustrate characteristic ASL perfusion patterns among diverse pediatric brain tumor pathologies, including astrocytic, neuronal-glial, and embryonal types, and a potential role for ASL in distinguishing high- and low-grade tumors. Perfusion differed significantly between medulloblastoma and pilocytic tumors of the posterior fossa; but more interestingly, we observed a uniquely wide perfusion range for medulloblastoma, which might reflect its diverse molecular makeup and clinical behavior, a hot topic in clinical neuro-oncology today.