A NEW HEAD HOLDER FOR REDUCING AXIAL MOVEMENT AND REPOSITIONING ERRORS DURING PHYSIOLOGICAL CT IMAGING

Objective: We designed a new head holder for immobilization and reposi tioning in dynamic CT studies of the brain. Materials and Methods: A c ustomized thermoplastic face mask and foam head rest were made to rest rict movement of the head in all directions, but particularly out of t he axial plane (z-movement). Results: This design provided a rigid, de tailed mold of the face and back of the head that minimized motion dur ing lengthy CT studies and enabled accurate repositioning of the head for follow-up studies. Markers applied directly to the skin were used to quantify z-movement. Conclusion: When tested on 12 subjects, immobi lization was limited to <2.0 mm under worst-case conditions when the s ubject was asked to attempt forced movements. Repositioning was accura te to <1.5 mm when the subject was removed from the head holder and th en placed back into it.