F. Smaltino

Exploring brain function with magnetic resonance imaging.

Since its invention in the early 1990s, functional magnetic resonance imaging (fMRI) has rapidly assumed a leading role among the techniques used to localize brain activity. The spatial and temporal resolution provided by state-of-the-art MR technology and its non-invasive character, which allows multiple studies of the same subject, are some of the main advantages of fMRI over the other functional neuroimaging modalities that are based on changes in blood flow and cortical metabolism. This paper describes the basic principles and methodology of fMRI and some aspects of its application to functional activation studies. Attention is focused on the physiology of the blood oxygenation level-dependent (BOLD) contrast mechanism and on the acquisition of functional time-series with echo planar imaging (EPI). We also provide an introduction to the current strategies for the correction of signal artefacts and other image processing techniques. In order to convey an idea of the numerous applications of fMRI, we will review some of the recent results in the fields of cognitive and sensorimotor psychology and physiology.

A Biochemical Approach to the Interpretation of MRI Images: In Vitro Study on a Craniopharyngioma

Magnetic resonance imaging (MRI) provides very promising possibilities in tissue characterization. MRI signal intensity is a complex function of four independent tissue parameters (T1, T2, proton density, and proton flow) and it is influenced by the chosen acquisition sequence (Bradley 1987). The multiple factors that affect MRI signal intensity and the possibility of selecting the most effective acquisition parameters can emphasize tissue contrast. On the other hand, complexity of variables increases the difficulties in establishing a precise correlation between signal intensity and the biochemical composition of the examined tissue (Biagini 1986).

Biochemical analysis and MRI characterisation of craniopharyngiomas

The authors propose a two-step biochemical procedure able to provide information concerning T1 relaxation of biological systems. This method has been applied to the study of cystic craniopharyngiomas. The cyst fluid has been fractionated on a sucrose-gradient; the fractions have been examined by MRI and their composition has been determined. While fractions deriving from a control sucrose gradient showed a regular decrease of T1-weighted signal intensity, the tumour fractions have shown particular intensity patterns. The hyperintense fractions were believed to contain molecular components able to shorten T1 relaxation time. A significant correlation between signal intensity and molecular composition has been constant for haemoglobin, methaemoglobin and iron.

Differential diagnostic criteria in "plaque-like" MRI findings

A retrospective analysis of 197 multiple sclerosis (MS) and 197 chronic atherosclerotic encephalopathy (CAE) patients’ MR images has been performed. Site, number, morphology and distribution of lesions have been examined and provided valuable differential diagnostic criteria concerning symmetry and coexisting supra-and infratentorial localizations.