How accurate is the electroencephalogram or fMRI as a lie detector?

Research shows that an electroencephalogram and the fMRI may achieve results of 87% accuracy. However, both test are invasive (the examinee is connected extensively to medical instruments or is inserted into a large tube). Both methods are very costly, require expensive equipment and extensive examiner training. For these reasons, neither is a viable lie detection solution for large groups of people, such as in pre-employment screening.