Quantification of fMRI artifact reduction by a novel plaster cast head holder

In light of artifact-induced high variability of activation in fMRI repeat studies, we developed and tested a clinically useful plaster cast head hold er (PCH) with improved immobilization, repositioning, and comfort. With PCH , there were considerably lower levels of translational and rotational head motion components compared to head fixation with conventional restraining straps (CRS). Rotational components cannot be fully compensated by realignm ent and lead to "false activations." In addition, task-correlated head moti on, which highly increases, the risk of artifacts, was considerably reduced with PCH, especially in a motion prone subject. Compared with PCH, head mo tion was 133% larger with CRS in a highly cooperative subject. With a motio n prone subject, head motion range was increased by 769% (PCH: 0.9 mm, CRS: 7.8 mm), which may indicate the usefulness of PCH for restless patients. I n functional activation maps, PCH alone yielded fewer residual motion artif acts than CRS + image registration. Subject tolerance of the head holder du ring the long measurement times of up to 2.5 hr was good, and slice orienta tion on different days confirmed the quality of repositioning. Hum. Brain M apping 12:207-213, 2000. (C) 2000 Wiley-Liss, Inc.