Diffusion-tensor Imaging Aids in ADHD Diagnosis, Treatment
Diffusion-tensor-imaging (DTI) can be useful in both diagnosing attention deficit hyperactivity disorder (ADHD) and following up with patients during treatment, according to research presented Monday.
"The prevalence of ADHD around the world is about 7 percent of the population, and because of that it is considered a public health problem," said presenter Pilar Dies Suarez M.D., chief radiologist at Hospital Infantil de México Federico Gómez, in Mexico City. ADHD is diagnosed based on the presence of clinical symptoms, as no other accurate diagnosis is available, Dr. Dies Suarez said.
Researchers hypothesized the presence of a second neural tract involved in ADHD. They examined the frontocerebellar tract and fractional anisotropy (FA) difference between ADHD children and healthy controls. DTI provides information about the direction and integrity of neural fibre tracks in the brain in vivo.
"This is a new, different tract," Dr. Dies Suarez said. "Our radiology department tried to find that tract and then show its function. They used MR imaging as a quantitative tool for the diagnosis of ADHD; before that, there was only clinical diagnosis.
"We don't have a tool for the diagnosis," Dr. Dies Suarez continued. "We think MR imaging can be a quantitative tool for the diagnosis of ADHD."
Between May 2012 and May of this year, 23 children ages 7 to 12 (11 ADHD patients, 12 controls) were examined. Images were acquired on a Philips Intera-Achieva 1.5T imager.
Diffusion-tensor imaging (DTI) data were acquired using an SE-EPI sequence with the following parameters: TR/TE=9491/75ms, FOV= 230x230x140mm3, voxel size=1.60x1.60x2mm3, number of slices=70, fat suppressed. Diffusion weighted gradients were applied along 15 non-collinear directions with a b-value=800 s/mm2. High-resolution images were acquired using a 3DTI gradient sequence. Finally, researchers used FSL to correct eddy currents pre and post-motion correction and MedINRI to obtain FA and tracts. Segmentation of the cerebellum CB was manually drawn on midline sagittal 3D-T1 images.
"Along with methodology, I would add that a collaborative parent-medical physicist relationship is important," Dr. Dies Suarez said. "Generally those kids are very kinetic, so trying to get them inside the magnet without head movement is challenging. And sedation isn't recommended in order to avoid any risk implicit using anesthesia."
The study showed that the frontocerebellar circuit is present, and altered in ADHD patients; generalized fractional anisotropy is increased (p=0.08), in the ADHD group; and there are significant differences in the number of tracts between ADHD patients and control subjects, Dr. Dies Suarez said. The ADHD patients have fewer tracts and primarily left tracts.
Researchers found that the frontocerebellar tract responds better to behavioral therapy, Omega 3, and atomoxetine therapies, Dr. Dies Suarez said. Currently multidisciplinary therapy and pharmaceutical approaches are used to treat ADHD, she said.
"We propose diffusion tensor imaging as a quantitative tool for the diagnosis of ADHD," said Dr. Dies Suarez. "In the future, MR may be useful for follow-up patients with ADHD during their treatment.
"We hope to present the follow-up results next year," she concluded. "We think that maybe with treatment, the tracts can change and have better diffusion and connectivity."