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Brain single-photon emission computed tomography for behavior disorders in children
1Department of Radiology, Children's Hospital Boston, MA.
Insights
Single-photon emission computed tomography (SPECT) brain imaging reveals functional abnormalities in childhood behavior disorders. Technetium-99m agents offer advantages over Xenon-133 for studying brain perfusion during cognitive tasks.
Area of Science:
- Neuroscience
- Medical Imaging
- Pediatrics
Background:
- Single-photon emission computed tomography (SPECT) is utilized to identify functional brain abnormalities in children.
- Two main categories of childhood disorders are studied: primary behavioral disorders and encephalopathies with neural dysfunction.
- Radiopharmaceuticals, primarily perfusion agents like Xenon-133 and Technetium-99m agents, are used for brain SPECT.
Purpose of the Study:
- To review the application of brain SPECT in evaluating functional abnormalities in childhood behavior disorders.
- To compare the utility of different radiopharmaceuticals, specifically Xenon-133 and Technetium-99m agents, for brain SPECT studies.
- To explore the potential of SPECT in understanding the neurophysiology of conditions like ADHD and cerebral palsy.
Main Methods:
- Brain SPECT imaging using perfusion agents such as Xenon-133 and Technetium-99m labeled compounds.
- Comparison of imaging methodologies, highlighting the advantages of Technetium-99m agents for capturing brain activity during behavioral events.
- Review of qualitative versus semiquantitative analysis of SPECT imaging data.
Main Results:
- SPECT studies with Xenon-133 in attention deficit disorder-hyperactivity (ADHD) suggest hypoperfusion in striatal and periventricular areas.
- Perfusional abnormalities in cerebral palsy correlate with clinical deficits, potentially aiding outcome prediction.
- Technetium-99m agents provide better spatial resolution and allow for imaging during cognitive tasks, unlike Xenon-133.
Conclusions:
- Brain SPECT, particularly with Technetium-99m agents, is a valuable tool for assessing functional brain abnormalities in childhood disorders.
- Standardization of the child's environment during SPECT is crucial for successful and reliable studies.
- Further research is needed, especially in childhood affective disorders, to fully leverage SPECT's diagnostic potential.
Abstract:
Single-photon emission computed tomography (SPECT) of the brain has been used to define functional abnormalities in two groups of childhood behavior disorders: (1) a "primary" category in which there is exclusive or predominant presentation with cognitive and/or behavioral dysfunction and (2) encephalopathies, often defined etiologically at the biochemical or molecular level, in which clinical expression includes, but is not confined to, neural dysfunction. Radiopharmaceuticals available for such studies are manifold, but those used to date have been predominantly perfusion agents, eg, Xenon-133 (133Xe) and technetium-99m (99mTc) hexamethylpropylene amine oxime, and studies with [99mTc]bicisate are eagerly awaited. Xenon-133 studies require that the patient be in the field of view of the detector while the tracer is administered. This renders it difficult for a subject to perform cognitive and other exercises while being imaged, because the environment is quite foreign. On the other hand, the 99mTc-labeled perfusion agents permit a scintigraphic "snapshot" of regional cerebral blood flow during a behavioral event without having to have the patient under the imaging instrument. Thus, one can separate the administration of the radiotracer, which can be done under more controlled and physiological conditions, from the actual imaging. In addition, greater spatial resolution is achieved with the technetium-based agents. Currently, multidetector or dedicated annular crystal-type cameras are the preferred brain SPECT devices, and they are essential to applications such as cortical "activation mapping" or tomographic detection of receptor systems. Close attention to technical detail and standardization of the child's behavioral environment during the investigation are critical to a successful study. The relative advantages and disadvantages of qualitative versus semiquantitative analysis of imaging date are reviewed. Among primary behavioral disorders, 133Xe SPECT studies in attention deficit disorder-hyperactivity (ADHD) have suggested a pattern of hypoperfusion of striatal and periventricular structures with sensorimotor cortical hyperperfusion. This pattern is consistent with some neurophysiological models of the disorder. In cerebral palsy, perfusional abnormalities have paralleled clinical deficits and may offer information to help predict outcome. The important field of childhood affective disorders (schizophrenia, juvenile autism, depression, etc) remains largely unstudied with SPECT. Finally, representative examples of the use of SPECT to study perfusion in encephalopathies with behavioral expression (phenylketonuria, MELAS (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes) syndrome, Wilson's disease, etc) are given.