Clinical Use of Integrated Positron Emission Tomography-Magnetic Resonance Imaging for Dementia Patients Combining magnetic resonance imaging (MRI) with 2-deoxy-2-18F-fluoro-D-glucose positron emission tomography (FDG-PET) data improve the imaging accuracy for detection of Alzheimer disease and related dementias. Integrated FDG-PET-MRI is a recent technical innovation that allows both imaging modalities to be obtained simultaneously from individual patients with cognitive impairment. This report describes the practical benefits and challenges of using integrated FDG-PET-MRI to support the clinical diagnosis of various dementias. Over the past 7 years, we have performed integrated FDG-PET-MRI on >1500 patients with possible cognitive impairment or dementia. The FDG-PET and MRI protocols are the same as current conventions, but are obtained simultaneously over 25 minutes. An additional Dixon MRI sequence with superimposed bone atlas is used to calculate PET attenuation correction. A single radiologist interprets all imaging data and generates 1 report. The most common positive finding is concordant temporoparietal volume loss and FDG hypometabolism that suggests increased risk for underlying Alzheimer disease. Lobar-specific atrophy and FDG hypometabolism patterns that may be subtle, asymmetric, and focal also are more easily recognized using combined FDG-PET and MRI, thereby improving detection of other neurodegeneration conditions such as primary progressive aphasias and frontotemporal degeneration. Integrated PET-MRI has many practical benefits to individual patients, referrers, and interpreting radiologists. The integrated PET-MRI system requires several modifications to standard imaging center workflows, and requires training individual radiologists to interpret both modalities in conjunction. Reading MRI and FDG-PET together increases imaging diagnostic yield for individual patients; however, both modalities have limitations in specificity.

Overview of MR Imaging Volumetric Quantification in Neurocognitive Disorders This review article provides a general overview on the various methodologies for quantifying brain structure on magnetic resonance images of the human brain. This overview is followed by examples of applications in Alzheimer dementia and mild cognitive impairment. Other examples will include traumatic brain injury and other neurodegenerative dementias. Finally, an overview of general principles for protocol acquisition of magnetic resonance imaging for volumetric quantification will be discussed along with the current choices of FDA cleared algorithms for use in clinical practice.

Functional Connectivity in Neurodegenerative Disorders: Alzheimer's Disease and Frontotemporal Dementia Neurodegenerative disorders are a growing cause of morbidity and mortality worldwide. Onset is typically insidious and clinical symptoms of behavioral change, memory loss, or cognitive dysfunction may not be evident early in the disease process. Efforts have been made to discover biomarkers that allow for earlier diagnosis of neurodegenerative disorders, to initiate treatment that may slow the course of clinical deterioration. Neuronal dysfunction occurs earlier than clinical symptoms manifest. Thus, assessment of neuronal function using functional brain imaging has been examined as a potential biomarker. While most early studies used task-functional magnetic resonance imaging (fMRI), with the more recent technique of resting-state fMRI, “intrinsic” relationships between brain regions or brain networks have been studied in greater detail in neurodegenerative disorders. In Alzheimer's disease, the most common neurodegenerative disorder, and frontotemporal dementia, another of the common dementias, specific brain networks may be particularly susceptible to dysfunction. In this review, we highlight the major findings of functional connectivity assessed by resting state fMRI in Alzheimer's disease and frontotemporal dementia.

The Radiogenomics of Late-onset Alzheimer Disease Radiogenomics, defined as the integrated analysis of radiologic imaging and genetic data, is a well-established tool shown to augment neuroimaging in the clinical diagnosis, prognostication, and scientific study of late-onset Alzheimer disease (LOAD). Early work using candidate single nucleotide polymorphisms (SNPs) identified genetic variation in APOE, BIN1, CLU, and CR1 as key modifiers of brain structure and function using magnetic resonance imaging (MRI). More recently, polygenic risk scores used in conjunction with MRI and positron emission tomography have shown great promise as a risk-stratification tool for clinical trials and care-management decisions. In addition, recent work using multimodal MRI and positron emission tomography as proxies of LOAD progression has identified novel risk variants that are enhancing our understanding of LOAD pathophysiology and progression. Herein, we highlight key studies and trends in the radiogenomics of LOAD over the past two decades and their implications for clinical practice and scientific research.