fMRI: Imaging’s Next Frontier

 
 
 

ADHD to better understand how the ADHD brain behaves in response to the attention load.

Compared with healthy children, brain activation maps of children with ADHD showed increased involvement of the anterior cingulate cortex and decreased and disrupted functional connectivity between the frontal lobe and parietal lobe.

Li envisions a potential broad role for fMRI as the technology that could inform early diagnosis and perhaps targets for treatment. Although she predicts a role for fMRI in the diagnostic work-up of children suspected of having ADHD, the timeline is uncertain as the technology must be validated.

From structure to function, measurement to treatment

Carrie J. McAdams, MD, PhD, a neuroscientist at University of Texas Southwestern Medical Center in Dallas, and her colleague Dan Krawczyk, PhD, a cognitive neuroscientist at the Center for Brain Health in Dallas, are among the first to apply fMRI to patients with anorexia and bulimia.

The pair has been awarded a National Institutes of Mental Health grant to identify markers for the disorders using fMRI. “We’re interested in how the brain changes when people recover,” says McAdams.

During the study’s first phase, the researchers used fMRI to measure the responses of patients recovering from anorexia to two social cognition tasks. When patients were asked to think about themselves from a social perspective, there was less activation in the precuneous. When they were asked to think about themselves from a physical perspective, there were changes in the dorsal anterior cingulate.

In the next stage, the researchers will compare responses among patients currently struggling with anorexia with responses of patients who have recovered and maintained a healthy weight for one year.

McAdams and Krawczyk hypothesize that there may be changes in blood flow in certain areas of the brain among patients with anorexia. Potential treatments might activate that area. Thus, the model is not diagnostic. Instead, the researchers hope to use fMRI to identify general targets for therapy.

Roles for rads

Radiologists have been slow to wade into the unfamiliar territory of fMRI; most research and applications have been dominated by neurology and psychology. “The radiology profession needs to define the extent to which it wants to become involved in fMRI,” says Thomas T. Liu, PhD, director of the University of California San Diego Center for Functional MRI.  

McAdams and Krawczyk see potential roles in fMRI for radiologists. For example, radiologists could help develop techniques to analyze functional data, or they might offer input into an fMRI checklist that would help researchers gather basic functional data.

One roadblock to greater involvement among radiologists is lack of expertise. Many radiologists don’t know how to complete fMRI post-processing or assess the results. “This is out of the comfort zone for traditional radiologists, who are used to interpreting images rather than signals,” explains Hirsch.

This knowledge gap is tied to a lack of training. fMRI techniques have not been embedded into the mainstream radiology curriculum, so despite interest among residents, fMRI tends to fall under the educational radar, says Hirsch.

Another challenge relates to the difference between fMRI and other advanced imaging modalities, which provide results in units of physical measurement, such as diffusion rates of water, uptake of tracers or concentrations of metabolites. In contrast, fMRI results are based on the percentage difference between an active state and an empirically determined baseline characterized by a lack of activity.

Unlike radiologists, other members of the radiology team have established their expertise. At Boston Children’s, MR technologists play an important role in fMRI research. “It’s challenging because children are not sedated and have to remain still for 30 minutes,” says Gaab. The hospital constructed an MR simulator, a mock spaceship, to help children prepare for the exam. The goal is to help them adjust to the sounds of the scanner and understand the importance of remaining still during the scan. 

It is likely that these research projects will take several years or longer to bear clinical fruit. However, new possibilities will continue to emerge. If and how radiologists are involved remains to be seen. HI