High-Pass-Filtered Phase Image: Left- versus Right-Handed MR Imaging Systems

Letters to the Editor Letters to the Editor

Published online before print March 28, 2013, doi: 10.3174/ajnr.A3571
AJNR 2013 34: E72

T.M. Mehemeda and A. Yamamotoa
aDepartment of Diagnostic Imaging and Nuclear Medicine
Kyoto University Graduate School of Medicine
Kyoto, Japan

We read with interest the article entitled “Detection of Intratumoral Calcification in Oligodendrogliomas by Susceptibility-Weighted MR Imaging”1 and would like to comment on the appearance of calcification on the high-pass-filtered phase images.

The authors reported that the paramagnetic (authors wrote “diamagnetic”) hemorrhagic component of the tumor would cause a negative phase shift and appear as dark signal on the high-pass-filtered phase images, while the diamagnetic (authors wrote “paramagnetic”) intratumoral calcifications would cause an opposite positive phase shift and appear as bright signal on the high-pass-filtered phase images. This description is true, but only in the case of right-handed MR imaging systems, while in left-handed MR imaging systems, the complete opposite signal would be seen: Paramagnetic substances would appear bright, while diamagnetic substances would appear dark.2,3

In Figs 2D and 3D of the above-mentioned article, the high-pass-filtered phase images are those of a left-handed MR imaging system, evident by the bright signal of the veins (paramagnetic deoxyhemoglobin).3

The article showed that high-pass-filtered phase images can depict intratumoral calcification in oligodendrogliomas better than conventional MR images; this finding has been reported before.4 Understanding the contrast appearance of high-pass-filtered phase images on left-handed versus right-handed MR imaging systems would make distinguishing diamagnetic calcification from paramagnetic hemorrhage a much easier task and prevent any possible confusion.

References

  1. Zulfiqar M, Dumrongpisutikul N, Intrapiromkul J, et al. Detection of intratumoral calcification in oligodendrogliomas by susceptibility-weighted MR imaging. AJNR Am J Neuroradiol 2012;33:858–64 » Abstract/FREE Full Text
  2. Duyn J, Speck O. Brain Anatomy with Phase. In: Haacke EM, ReichenbachJR. Susceptibility Weighted Imaging in MRI: Basic Concepts and Clinical Applications. Hoboken, New Jersey: John Wiley & Sons; 2011:121–36 » Search Google Scholar
  3. Mittal S, Thomas B, Wu Z, et al. Novel approaches to imaging brain tumors. In: Haacke EM, Reichenbach JR. Susceptibility Weighted Imaging in MRI: Basic Concepts and Clinical Applications. Hoboken, New Jersey: John Wiley & Sons; 2011:151–70 » Search Google Scholar
  4. Wu Z, Mittal S, Kish K, et al. Identification of calcification with MRI using susceptibility-weighted imaging: a case study. J Magn Reson Imaging 2009;29:177–82 » CrossRef » Medline
High-Pass-Filtered Phase Image: Left- versus Right-Handed MR Imaging Systems