Mapping the motor cortex with BOLD functional magnetic resonance imaging

Abstract

Introduction – Functional magnetic resonance imaging (fMRI) is currently an essential tool for the study of human brain function, both in healthy volunteers and in patients suffering from multiple types of pathology. fMRI is a complex technique which needs to be applied in a careful and rigorous manner, requiring an understanding of its biophysical mechanisms so that reliable results with clinical acceptance can be obtained. The BOLD effect (Blood Oxygenation Level Dependent) is based on the magnetic properties of haemoglobin and it is the most used approach for measuring brain activity using MRI. Goals – To optimise a BOLD fMRI protocol on healthy volunteers for mapping the motor cortex, so that it can be applied to patients in the clinic. Methods – 34 healthy volunteers were divided into 2 study groups: BOLD 1 and BOLD 2. To optimise the acquisition, different paradigms were tested on sub-group BOLD 1. The influence of the echo time (TE) was studied on sub-group BOLD 2.The volume and activation level of the activated regions were compared under the different sets of conditions. Results/Discussion – It was possible to identify the motor cortex on all studied individuals. No significant statistical differences were detected when comparing the results obtained with the different acquisition parameters. Conclusion – The protocolwas optimised taking into account the level of comfort reported by the volunteers. Given that the goal is to use this protocol to study patients, comfort is a particularly important factor.

Keywords

• BOLD, córtex motor, paradigma, ressonância magnética funcional (RMf), TE (tempo de eco).