Assessment of Reproducibility of Geometric Distortion in MRI using Phantom Measurements

Ashkanmehr, M. and Riyahi Alam, N. and Oghabian, M.A. and Ghasemzadeh, A. and Bakhtiary, M. and Ghanaati, H. and Hashemi, H. and Pakravan, M. and Shakeri, N. (2005) Assessment of Reproducibility of Geometric Distortion in MRI using Phantom Measurements. Iranian Journal of Medical Physics, 2 (3). pp. 1-8.

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Introduction:  Image  distortion  is  one  of  the  major  problems  of  magnetic  resonance  imaging (MRI) for use in 3DMRI, velocity MRI, FMRI and radiotherapy treatment planning (RTTP). It is widely known that the most obvious effect of the inhomogenity of the magnetic fields and the nonlinearity  of  the  gradient  is  the  Geometric  Distortion  of  MR  tomograms.  In  this  study,  the accuracy of MR images was considered by the phantom study and the reproducibility of images was evaluated by repeating the phantom measurements. Materials and Methods: MRI scans of the phantom with grid pattern inside it were performed using head coil in two 1.5 Tesla MRI systems (Picker VISTA TM HPQ, USA & GE Signa Echo Speed, USA). For the Geometric Distortion reproducibility evaluation the T1W, T2W and PDW SE  protocols  were  repeated  three  times.  The  Geometric  Distortion  was  measured  by  an  edge detection program in MATLAB.  Results: The geometric distortion in the peripheral area of the images tends to be generally larger than it in the central area in all images. The average displacement in Picker MRI was 3 pixels in the y and 1 pixel in the x direction and in GE MRI it was 1 pixel in both x and y direction for 24 cm FOV (pixel = 0.9 mm). Discussion and Conclusions: Since the positional variation was within 1 to 3 pixels for the head coil, it will be possible to use this MR system in 3DMRI, velocity MRI, FMRI and RTTP. To decrease the geometric distortion the use of suitable coil and protocol are expected. Â

Item Type: Article
Subjects: WN Radiology . Diagnostic Imaging
Divisions: Journals > Iranian J Medical Physics
Depositing User: ijmp ijmp
Date Deposited: 21 Jan 2018 15:49
Last Modified: 21 Jan 2018 15:49

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