Geometric accuracy of 3D coordinates of the Leksell stereotactic skull frame in 1.5 Tesla- and 3.0 Tesla-magnetic resonance imaging: A comparison of three different fixation screw materials

We assessed the geometric distortion of 1.5-tesla (t) and 3.0-t magnetic resonance (mr) images with the leksell skull frame system using three types of cranial quick fixation screws (qfss) of different materials-aluminum,aluminum with tungsten tip,and titanium-for skull frame fixation. two kinds of acrylic phantoms were placed on a leksell skull frame using the three types of screws,and were scanned with computed tomography (ct),1.5-t mr imaging and 3.0-t mr imaging. the 3d coordinates for both strengths of mr imaging were compared with those for ct. the deviations of the measured coordinates at selected points (x = 50,100 and 150; y = 50,100 and 150) were indicated on different axial planes (z = 50,75,100,125 and 150). the errors of coordinates with qfss of aluminum,tungsten-tipped aluminum,and titanium were <1.0,1.0 and 2.0 mm in the entire treatable area,respectively,with 1.5 t. in the 3.0-t field,the errors with aluminum qfss were <1.0 mm only around the center,while the errors with tungsten-tipped aluminum and titanium were >2.0 mm in most positions. the geometric accuracy of the leksell skull frame system with 1.5-t mr imaging was high and valid for clinical use. however,the geometric errors with 3.0-t mr imaging were larger than those of 1.5-t mr imaging and were acceptable only with aluminum qfss,and then only around the central region. © the author 2014. published by oxford university press on behalf of the japan radiation research society and japanese society for radiation oncology.