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SU‐E‐T‐281: Quantitative Evaluation of the MRI Image Distortion in Gamma Knife Radiosurgery
Author(s) -
Feng W,
Xu Y,
Burri R,
Chen H,
Wuu C,
Isaacson S
Publication year - 2011
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3612232
Subject(s) - imaging phantom , image registration , scanner , radiosurgery , nuclear medicine , distortion (music) , magnetic resonance imaging , computer vision , medical imaging , computer science , artificial intelligence , medicine , image (mathematics) , radiology , radiation therapy , amplifier , computer network , bandwidth (computing)
Purpose: To quantify the spatial distortion of the MRI images in the Elekta Leksell GammaPlan version 9 planning system using different registration methods. Methods: The RPC SRS phantom was imaged using a GE Signa HDxt 1.5Tesla MR scanner and a GE LightSpeed VCT CT scanner. Both the T1 weighted MRI images and the fast imaging employing steady state acquisition (FIESTA) MRI images were acquired, along with the axial and helical CT images. The skull shell and the target in the phantom were contoured in all the four series of images acquired. The MRI images were registered in the planning system in three different ways: 1) using the fiduciary marks in the imaging box; 2) using a global co‐registration with FOV just covering skull shell; 3) using a local co‐registration to max 8.5cm FOV at image center. The target positions in all the four series of images were compared using the software tool in the planning system. Results: The target positions as obtained from the helical and the axial CT images agree within 0.1mm. For the registration method the fiduciary marks, the T1 weighted MRI images are shifted from the CT images 0.9mm in the anterior‐posterior direction, and 0.5mm in both the superior‐inferior and the left‐right directions. The corresponding displacements for the FIESTA images are 0.6mm, 0.5mm and 0.5mm respectively. The shifts of the target positions are significantly reduced in the global co‐registration approach, and all less than 0.2mm in the local co‐registration approach. Conclusions: MRI image distortion in GammaPlan version 9 is in the sub‐millimeter range for the central region of the MRI image. The spatial distortion in the FIESTA images is smaller than that in the T1 weighted images. Co‐registration to the central region of images can reduce MRI imaging distortion effect significantly.