For Avoiding The Skin Injury Through Performing Mri For Gamma Knife Surgery - Necessity Of Fixation Of Leksell G-frame By Using Insulated Fixation Posts And The Verification Of Reliability Of Them

Hiroyuki Kenai1, Masanori Yamashita2, Tomoshige Asano2, Akira Yamada2, Yukihiro Wakabayashi2, Hirofumi Nagatomi2

1Oita, Japan 2Nagatomi Neurosurgical Hospital, Oita, Japan

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

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     For preparing for Gamma Knife surgery(GKS), patients should undergo application of the Leksell G-frame with posts and quick fixation screws(QFSs) and high resolution MR imaging to obtain precise information of the target. In our institution, we had experienced the scars of QFSs in some cases became edematous and finally exulceration in severe cases at the early era of introducing Gamma Knife. After many investigations, we had finally found out that the cause was generation of heat of skin tissue surrounding QFS when performing MRI of the sequence of high specific absorption ratio(SAR) and reported that the generation of heat did not occur when QFS was insulated. And then the insulated fixation post (IFP) had been developed. Now when we use the ordinary posts, it is said that MRI should be performed in the sequence of SAR under 1W/kg for safety. But in the same sequence, SAR is different not only between the manufacturers, the models but also even individuals. Therefore for true safety, we have to confirm the SAR and the actual temperature rise in each sequence of each MRI system, but in fact it is arduous to do this.
     So practically, we can do nothing but using IFPs. But in Japan IFPs has not used generally until now, then we checked the reliability of the IFP and report about it and details of the development of IFP here.
     We used the aluminum pipe as dummy and fixed the frame to it with IFPs and QFSs, and confirmed the strength of the IFP itself and insert part by giving shocks on aluminum pipe. We also checked the reliability of the accuracy by comparing the coordinates before and after treatment in actual patients.
     Fixation of Leksell G-frame by IFP can avoid the skin injury by generation of heat in any sequence of MRI, and IFP is not different from ordinary post in strength and accuracy of fixation.
     This is a retrospective study.
     Now, high magnetic field MRI systems are getting widely spread.
     IFP should be used in GKS as a standard post.


Project Roles:

H. Kenai (), M. Yamashita (), T. Asano (), A. Yamada (), Y. Wakabayashi (), H. Nagatomi ()