A new tool fixation for external 3D head tracking using the Polaris Vicra system with the HRRT PET scanner

Objectives: The Polaris Vicra system (Northern Digital Inc.) is used for external 3D head registration with the Siemens HRRT brain PET. Our new tool fixation using a standard bandaid with a velcro-strap implies an improved frame repositioning. Methods: Head movements during serial PET 15O-water studies for up to 75 min (3-8 injections) were registered by the Polaris system in 4 volunteers. The tracking tool was fixed. Scans were divided into subframes based on the registered movements and reconstructed using the 3D-OSEM PSF method. The reconstructed subframes were repositioned to a reference position and pairwise similarity of subframes was evaluated before and after the repositioning. Results: Registered movements during scans were less than 4.3mm with. Images were compared before/after motion correction. Conclusions: Our new velcro band-aid fixation is suitable for clinical use: easy to use,disposable, comfortable, independent of head size and has low cost. It is reliable with only a limited contact area with the movable structures of the head. Registered movements corresponded to those seen on the PET images and correlations between scans were improved after repositioning based on the tracked head position.