Characteristics of geometric distortion correction with increasing field-of-view in open-configuration MRI.pdfVIP

Magnetic Resonance Imaging 32 (2014) 786–790 Contents lists available at ScienceDirect Magnetic Resonance Imaging journal homepage: Characteristics of geometric distortion correction with increasing ?eld-of-view in open-con?guration MRI Cheolpyo Hong a,?, Dong-Hoon Lee a,b, Bong Soo Han b a Center for Medical Metrology, Korea Research Institute of Standards and Science, Daejeon, Republic of Korea b Department of Radiological Science, College of Health Science, Yonsei University, Kwangwon-do, Republic of Korea article info Article history: Received 30 July 2013 Revised 3 February 2014 Accepted 3 February 2014 Keywords: Distortion correction Large ?eld-of-view Open MRI abstract Open-con?guration magnetic resonance imaging (MRI) systems are becoming increasingly desirable for musculoskeletal imaging and image-guided radiotherapy because of their non-claustrophobic con?guration. However, geometric image distortion in large ?elds-of-view (FOV) due to ?eld inhomogeneity and gradient nonlinearity hinders the practical applications of open-type MRI. We demonstrated the use of geometric distortion correction for increasing FOV in open MRI. Geometric distortion was modeled and corrected as a global polynomial function. The appropriate polynomial order was identi?ed as the minimum difference between the coordinates of control points in the distorted MR image space and those predicted by polynomial modeling. The sixth order polynomial function was found to give the optimal value for geometric distortion correction. The area of maximum distortion was b 1 pixel with an FOV of 285 mm. The correction performance error was increased at most 1.2% and 2.9% for FOVs of 340 mm and ~ 400 mm compared with the FOV of 285 mm. In particular, unresolved distortion was generated by local deformation near the gradient coil center. ? 2014 Elsevier Inc. All rights reserved. 1. Introduction The primary advantages of magnetic resonance imaging (MRI) for muscle morphology and radiotherapy are the e