Geometric Error Of 3-dimensional Coordinates Of Leksell Stereotactic Skull Frame System In 1.5 Tesla- And 3.0 Tesla-mri

Hisato Nakazawa1, Kobayashi Tatsuya2, Mori Yoshimasa2, Uchiyama Yukio2, Hagiwara Masahiro2, Yamada Masami2

1Nagoya, Japan 2Nagoya Kyoritsu Hospital, Nagoya, Japan

Keywords: technique, magnetic resonance imaging, Imaging, gamma knife, stereotactic frame

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     Elekta provides some types of cranial screws of different materials, such as aluminum, titanium and aluminum with tungsten-tip for skull frame placement.   
     The aim of this study is to evaluate geometrical distortion produced by these screws.
     A grid-pattern acrylic box phantom filled with copper sulfate solution was placed on the Leksell skull frame using screws of titanium or those of aluminum with tungsten-tip. It was scanned with CT, 1.5T-MRI, and 3.0T-MRI. The 3-dimensional coordinates in 1.5T-MRI and 3.0T-MRI were compared with those in CT
     In both 1.5T- and 3.0T-MRI the errors of coordinates were least around the center, (x, y, z) = (100,100,100), with both 2 types of screws.   With tungsten-tipped aluminum screws errors of coordinates were less than 1 mm in 1.5T-MRI.   On the other hand, with titanium screws those were between 1 mm and 2 mm in 1.5T-MRI.   Using 3T-MRI, errors with screws of tungsten-tipped aluminum were less than 1.5 mm around the center and up to 3 mm around parietal area, and those with screws of titanium were between 1 mm and 2 mm around the center and up to 6 mm around parietal area.
     This is a retrospective study.
     Even in 1.5T-MRI, the errors of coordinates were more with titanium screws than with tungsten-tipped aluminum ones.   The distortion is more in 3T-MRI than in 1.5T-MRI with either type of screw.  
     3.0T-MRI is thought to be more susceptible to distortion by various conditions than 1.5T-MRI. We have to take image distortion into considerations, even if we use 3.0T-MRI by image fusion on CT.


Project Roles:

H. Nakazawa (), K. Tatsuya (), M. Yoshimasa (), U. Yukio (), H. Masahiro (), Y. Masami ()