Role of Hybrid Brain Imaging in Neuropsychiatric Disorders

Abstract

This is a focused review of imaging literature to scope the utility of hybrid brain imaging in neuropsychiatric disorders. The review focuses on brain imaging modalities that utilize hybrid (fusion) techniques to characterize abnormal brain molecular signals in combination with structural and functional changes that have been observed in neuropsychiatric disorders. An overview of clinical hybrid brain imaging technologies for human use is followed by a selective review of the literature that conceptualizes the use of these technologies in understanding basic mechanisms of major neuropsychiatric disorders and their therapeutics. Neuronal network abnormalities are highlighted throughout this review to scope the utility of hybrid imaging as a potential biomarker for each disorder.

Keywords: Alzheimer’s disease; affective disorders; brain disorders/diagnosis; humans; hybrid imaging; molecular imaging; neuroimaging; neuronal networks; neuropsychiatric disorders; schizophrenia.

Figure 1

Multiple factors contribute to neuropsychiatric disorder susceptibility. These factors include genetic predisposition, developmental insult, brain injury and natural (or disease-state) aging. Together these factors can influence the molecular, physiological and structural characteristics of the brain. Environmental (or external) factors, such as the demands of life, loss of a loved one or experiencing abuse can also have a negative impact on brain health. Taken together, neuropsychiatric disorder development is extremely cofounded with multiple variables, resulting in individualized trajectories to the same end point: a neuropsychiatric disorder.

Figure 2

PET and MR images of a 77-year-old male injected with 198 MBq of ¹⁸F-flurodeoxyglucose (FDG) while patient was lying supine in a Siemens Biograph mMR PET-MR hybrid scanner (Siemens Healthcare, Erlangen, Germany). A 60 min dynamic PET scan was acquired during multispectral MR imaging. These images illustrate the capacity to perform multi-parametric mapping in a single session simultaneously, to improve characterization of neuropsychiatric conditions. Axial images are from (top) left to right: T1-weighted (MRPAGE) for tissue-specific volumetric measurements, T2-weighted (FLAIR) for assessment of white matter lesions, and susceptibility-weighted imaging for detection of microbleeds and cerebral amyloid angiopathy; (bottom) left to right: fractional anisotropy image from diffusion tensor imaging for quantification of white matter structural integrity, perfusion weighted-imaging (ASL) for hemodynamic measurements and a PET-¹⁸F-FDG glucose consumption image. Images are presented with permission from patient and are courtesy of Lawson imaging, Lawson Health Research Institute (LHRI), London, ON, Canada.

Figure 3

Coronal high-resolution T1-weighted MR (left) and PET (center) images of two pulmonary carcinoma patients scanned at LHRI, London, Ontario, Canada using a Siemens Biograph mMR PET-MR hybrid scanner. The PET-¹⁸F-FDG and MR images were acquired simultaneously and, the PET was later superimposed onto the MR images (right). To illustrate the synergistic effect of PET’s high sensitivity and MR’s high spatial resolution to improve the specificity of characterizing neuropsychiatric disorders, two case studies are presented. (Top) row: A focal area of increased FDG-PET uptake in a metastatic lesion can be seen on the top row images that is well defined when the PET image is overlayed onto the MR image; (Bottom) row: Areas of hypometabolism in PET-¹⁸F-FDG images, a result of prior traumatic brain injury, are delineated in the fused PET and MR images. Images are presented with permission from patients.