In Reply
The letter by Dr Morton, addresses a concern to us all—the safety and well-being of human subjects in research studies, and in particular healthy pediatric populations. Zametkin and colleagues1 present a PET study of adolescents with ADHD and matched normal controls. That study was an attempt to further understand brain systems underlying a disorder that affects a significant number of children each year. The exposure of these minors to radiation was held to minimal levels. Given that ADHD is a significant and important psychiatric disorder to study, afflicting thousands of children each year, this study seemed warranted.Nevertheless, we share Dr Morton's concerns about the use of any invasive procedure in pediatric populations. In this regard, we are encouraged by the fact that an alternative, noninvasive approach to functional neuroimaging in developmental populations is now available. This is functional magnetic resonance imaging (fMRI), which can be used to