Novel Quantitative Approach in Functional and Structural Imaging of Brain in Normal Ageing and Neurodegenerative Disorders: Part I. Basic Considerations in PET and MRI
Journal of Experimental and Clinical Neurosciences
Positron Emission Tomography Analysis The 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
... er-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 . 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 Abstract The 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.