Image distortion in MRI-based polymer gel dosimetry of Gamma Knife stereotactic radiosurgery systems

Yoichi Watanabe, Gerard M. Perera, Robertus B. Mooij

Research output: Contribution to journalArticlepeer-review

31 Scopus citations

Abstract

We have studied effects of MR (magnetic resonance) image distortion on polymer gel dosimetry of Gamma Knife stereotactic radiosurgery systems. MR images of BANG polymer gel phantoms were acquired by using a Hahn spin-echo sequence and a fast 3D imaging GRASS sequence. Image artifacts were studied by varying the directions of frequency encoding and the receiver bandwidth. The phantoms were also CT (computed tomography) scanned. The studies showed that the measured dose distributions are shifted by 1.8±0.5 mm (2 pixels) in the frequency encoding direction. The magnitude of the shift is inversely proportional to the receiver bandwidth in agreement with theory. Comparison of MRI with CT showed the same image shift. We concluded that the discrepancy is caused by MR image distortion due to a difference in susceptibility effects between the phantom and the fiducial markers of the Leksell localization box.

Original languageEnglish (US)
Pages (from-to)797-802
Number of pages6
JournalMedical Physics
Volume29
Issue number5
DOIs
StatePublished - 2002

Keywords

  • Absorbed dose
  • BANG-3 polymer gel
  • Gamma knife
  • MRI
  • Magnetic susceptibility

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