Distortion in 3T clinical fMRI data

Abstract: Functional MRI (fMRI) is a technique for determining which parts of the brain are activated when a subject experiences some type of physical sensation or performs an activity. This technique has during the past several years become a very useful tool for understanding functions of the nervous system, and the development of clinical applications is rapidly progressing. However, fMRI is not straightforward and attention must be paid to many details in the process. One necessity when performing an fMRI experiment is the use of very rapid imaging techniques. Images acquired with these techniques suffer from different types of artefacts such as geometric distortion, which could for example lead to misinterpretation of activation maps, or can be misleading when using fMRI for presurgical planning. The main objective of this work was to evaluate the effects of geometric distortion when performing fMRI experiments at the 3T dedicated head scanner (Siemens Magnetom Allegra) at Lund University Hospital. A correction method based on the evaluation technique was also implemented and applied to the distorted images.