Applying PET/MR for Dementia Applications

Dementia is a common disorder affecting about 50 million people worldwide with nearly 10 million cases every year . It is characterized by cognitive impairments as well as behavior disabilities. Cognitive impairments include difficulties with memory, attention, language and other higher cortical functions. Behavior disabilities may include apathy, aggressive behavior, hallucinations and changes in social interaction. The most common cause of dementia is Alzheimer disease (AD). To plan a proper treatment for the patient it is critical to evaluate accurately the type of dementia as well as obtain the earliest diagnosis possible. However, accurate differential diagnosis in dementia poses difficulties due overlapping phenotypes and limited understanding of the mechanism and pathologies . Diagnosis of the dementia is performed based on the combination of clinical symptoms and biomarkers that include imaging, genetic biomarkers, cerebrospinal fluid (CSF), and other objective markers of disease . The two main modalities used for dementia imaging are Magnetic Resonance Imaging (MRI) and molecular imaging including Single Photon Emission Tomography (SPECT) and Positron Emission Tomography (PET). MRI is performed with various of contrasts such as high resolution T1- weighted, T2- weighted and Diffusion Tensor Imaging (DTI) and functional MRI (fMRI) [2]. These methods give information about morphological modifications in the brain and atrophy characterizing the specific dementia type. In addition brain perfusion and diffusion pattern and assessment of the changing un the resting state functional connectivity network of the brain can be studied with MRI. PET with different tracer molecules allow diagnosis of metabolism pattern in the brain (18F-FDG-PET), modifications in the neurotransmitter system and detection of brain plaques associated with dementia such as amyloid β or Tau aggregates . Data acquired from both modalities allow the reliable and differential diagnosis, prediction of pre-dementia stages, monitoring therapy response and additional research information regarding the mechanism of the condition.