Functional MRI for presurgical planning: problems, artefacts, and solutionstrategies

Ojectives - Presurgical mapping of motor function is a widely used clinical application of functional (f) MRI, employing the blood oxygenation level d ependent contrast. The aim of this study was to report on 3 years experienc e of 194 fMRI studies on the representation of motor function in 103 patien ts and to describe the problems and artefacts that were typically present. Methods - An evaluation was carried out to determine whether the patients' age, type or location of the tumourous lesion, severity of the paresis, or the tasks used during the investigation have an effect on artefacts of fMRI studies and how these artefacts are best overcome. Results - Functional MRI identified the motor regions in 85% of all investi gated paradigms. In 11% of the investigated patients no information at all on functional localisation was obtained. A draining vein within the central sulcus was present in all patients that showed activation within the paren chyma of the precentral gyrus but also in three patients in whom no parench ymal activation was present. Head movement artefacts were the most frequent cause for fMRI failure, followed by low signal to noise ratio. Motion arte facts were correlated with the degree of paresis and with the functional ta sk. Tasks involving more proximal muscles led to significantly more motion artefacts when compared with tasks that primarily involved distal muscles. Mean MR signal change during task performance was 2.5%. Conclusions - Most of the artefacts of functional MRI can be reliably detec ted and at least in part be reduced or eliminated with the help of mathemat ical algorithms, appropriate pulse sequences and tasks, and probably most i mportant-by evaluating the fMRI raw data - that is, the MR signal time cour ses.