SPECT goes 3D for improved diagnosis of ADHD

Reading a 3D thresholded SPECT vs. a conventional 2D SPECT has led to a dramatic improvement in sensitivity for the evaluation of attention deficit hyperactive disorder (ADHD), officials at Amen Clinics announced Dec. 9.

There is still a lot of debate over the value of perfusion imaging for psychiatric diagnoses. Neuroimaging researchers from Amen Clinics in Costa Mesa, Calif., wield the largest database of functional brain scans the world over—more than 90,000 scans from over 100 countries. Recent studies have indicated that previous literature may have been confounded by a lack of standardization between the SPECT techniques.

Howard Schneider, MD, from Sheppard Associates and colleagues from the department of nuclear medicine at Mount Sinai Hospital, affiliated with the University of Toronto, Ontario, Canada, conducted a retrospective study of 427 patients, with a concentration of 170 general psychiatry patients. Schneider and his team compared interpretations of 2D SPECT and 3D thresholded SPECT to see which was associated with better sensitivity and specificity for a clinical diagnosis of ADHD.

The brain perfusion studies were conducted using either Tc-99m hexamethylpropylene-amine oxime or Tc-99m ethyl cysteinate dimer molecular imaging agents. Researchers paid particular attention to signs of hypoperfusion of the orbitofrontal regions of the prefrontal cortex. Results of the study showed that, for the general psychiatry practice, 3D SPECT trumped 2D SPECT with sensitivities of 83 percent and 10 percent, respectively. The findings were published in the November 2014 issue of the Journal of Neuropsychiatry and Clinical Neurosciences.

“A 10 percent sensitivity hardly makes SPECT scans useful for clinical psychiatric applications, in keeping with the viewpoint of the opponents of this technology, whereas the 83 percent sensitivity for the 3D thresholded SPECT scans gives a diametrically opposite viewpoint, that with 3D thresholding, SPECT is indeed a useful procedure for certain psychiatric patients,” wrote Schneider et al.

Although, specificity and positive predictive values were a closer call with 3D SPECT having 76.9 percent specificity and 52.4 percent positive predictive value and the 2D SPECT data showed specificity and positive predictive values of 97.7 and 57.1, respectively.

“The thresholded images actually contain less data than the conventional images, but the experimental results in the present study show that this data transformation allows for a better sensitivity in the diagnosis of ADHD,” the researchers explained.

Functional imaging of the cerebral cortex could one day become a companion to clinical evaluation in the diagnosis of ADHD if future SPECT studies render similar findings.