The authors make a complete review of the potential clinical applications of traditional and novel magnetic resonance imaging (MRI) techniques in the evaluation of patients with Alzheimer's disease, including structural MRI, functional MRI, diffusion tension imaging and magnetization transfer imaging.

In this Part II review, as a complement to the Part I published in this supplement, the authors cover the imaging techniques that evaluates the Alzheimer's disease according to the different metabolic and molecular profiles. In this section MR spectroscopy, FDG-PET and amyloid PET are deeply discussed.

Positron Emission Tomography AnalysisThe PET analysis methods can be categorised into three main groups, as follows; a) Qualitative Analysis Visual assessment plays a vital role in the interpretation of PET studies in daily clinical practice. The interpretation relies on the comparison between metabolic activity in areas of interest and the adjoining background. This sort of assessment is especially appropriate to FDG-PET in recognising local glycolysis. Despite its simplicity, there may be inter-and intra-observer differences in PET interpretation due to the personal or subjective nature of visual assessment and the consequent lack of reproducibility, which becomes a cause of concern in diagnostic and therapeutic judgments and treatment monitoring where independent and neutral quantitative evaluation is needed. b) Quantitative Analysis Compartmental analysis models are a group of dynamic replicas that are used to evaluate the kinetics of materials quantitatively in physiological systems [1]. The constituents are the radiotracers or drugs and the kinetics processes to be measured can be the absorption, diffusion, transport and metabolism of substances such as glucose. Different compartment models can be used for quantitative PET analysis, for example, three tissue (four-compartment) compartment model, single tissue compartment model and two tissue (three-compartment) compartment model. Fourcompartment model has six parameters, and the statistical properties of the model may not estimate all parameters at once. Single tissue compartment model is a simple model and is mostly applied to measure blood flow by 15 O labelled AbstractThe advent of new neuroimaging modalities in recent decades, along with the increasing prevalence of neurological disorders and a rise in life expectancy over the past century, have collectively led to the numerous studies trying to explain the anatomical and functional changes in the human brain following the disease. Other investigators have attempted to find the differences in brain structures and functions following normal aging, since understanding age-related changes in the brain might be the first step to shed light on the pathophysiology of various neurological disorders. In this review, we describe the existing and novel quantitative approaches of functional positron emission tomography (PET) imaging. Moreover, we describe novel volumetric studies assessing global and regional volume changes based on advanced computerised techniques of magnetic resonance (MR) analysis such as voxel-based morphometry (VBM) and non-conventional MR techniques such as diffusion tensor imaging (DTI) and magnetization transfer imaging (MTI) followed by a brief review of arterial spin labeling (ASL) imaging.

Normal Aging Brain Normal aging is associated with a progressive decline in cognitive performance, including perception, attention, language and memory [1-3]. Age-related functional and biochemical changes in the brain include alterations in cerebral metabolism, cerebral blood flow and neurotransmitter function. With the advent of functional neuroimaging techniques, these biochemical changes can be measured in vivo throughout the life span of person. Because functional disturbances herald structural changes, imaging with positron emission tomography (PET) may yield abnormal results whereas the brain anatomy appears to be normal. Several positronlabeled tracers have been presented to discern the distribution and activity of age-related biochemical changes in the brain. Change of Cerebral Metabolism There is an inconsistency in 18-fluorodeoxyglucose (FDG)-PET findings for aging brain. A number of studies in normal aging subjects have shown significant decrease in whole brain glucose metabolism with advancing age, while others have noted no noticeable change. Although some decline in local glucose metabolism in the temporal, parietal, and frontal areas has been reported by some studies, others have revealed that the prefrontal cortex is the most important region affected by aging. The divergence in results may be due to different methodologies, screening criteria, range of subject ages, and especially sample size, which is one of the key factors for obtaining consistent statistical results. In addition, most early studies on age-related glucose metabolism used region of interest (ROI) analysis. However, recently voxel-based analysis such as Statistical Parametric Mapping (SPM) package, have been widely used to help detect the area missed in ROI analysis and avoid subjective variation. Several studies have now characterized the effect of aging on the distribution of glucose metabolism using FDG-PET. Kuhl et al. [4] reported the use of FDG-PET for determining patterns of local cerebral glucose utilization in 40 normal