Advances in the assessment of childhood brain tumors and treatment-related sequelae.

The assessment of children with brain tumors represents a unique challenge due to the difficulty in obtaining repeat tissue samples for evaluation. Over the past decade, magnetic resonance imaging has been the standard imaging modality utilized to follow tumor status and treatment effects in these children because of its sensitivity and ability to delineate tumor tissue. The information obtained from standard magnetic resonance imaging is primarily limited to structural changes. Newer techniques that noninvasively assess metabolic and physiologic characteristics of brain and tumor tissue are being developed and incorporated into clinical trials, particularly for the newer molecularly targeted agents, where physiologic changes rather than tumor size reduction may be an early determinant of activity. This article reviews some of these techniques and their role in the assessment of children with brain tumors.