A method to correct background phase offset for phase-contrast MRI in the presence of steady flow and spatial wrap-around artifact

Magn Reson Med. 2019 Apr;81(4):2424-2438. doi: 10.1002/mrm.27572. Epub 2018 Nov 15.

Abstract

Purpose: Background phase offsets in phase-contrast MRI are often corrected using polynomial regression; however, correction performance degrades when temporally invariant outliers such as steady flow or spatial wrap-around artifact are present. We describe and validate an iterative method called automatic rejection of temporally invariant outliers (ARTO), which excludes these outliers from the fitting process.

Methods: The ARTO method iteratively removes pixels with large polynomial regression errors analyzed by a Gaussian mixture model fitting of the residual distribution. A total of 150 trials of a simulated phantom (75 with wrap-around artifact) and 125 phase-contrast MRI cines from 22 healthy subjects (48 with wrap-around artifact) were used for validation. Background phase offsets were corrected using second-order weighted regularized least squares (WRLS) with and without ARTO. Flow volumes after WRLS and WRLS+ARTO corrections were compared with the known truth (phantom) and stationary phantom reference (in vivo) using Bland-Altman analysis. The ratio between the pulmonary flow and the systemic flow was also computed in a subset of 6 subjects.

Results: In the simulated phantom, compared with WRLS and no correction, correction with WRLS+ARTO produced superior agreement in volumetric flow quantification with the known truth. In vivo, WRLS+ARTO also produced superior agreement with stationary phantom-corrected volumetric flow compared with WRLS and no correction. In data sets with wrap-around artifact, WRLS produced significantly larger variance in the pulmonary flow and systemic flow ratio than stationary phantom correction (P = .0008).

Conclusion: The proposed method provides automatic exclusion of temporally invariant outliers and produces flow quantification results comparable to stationary phantom correction.

Keywords: background phase; background phase correction; cardiovascular MRI; eddy currents; flow quantification; phase contrast.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Algorithms
  • Aorta, Thoracic / diagnostic imaging
  • Artifacts
  • Computer Simulation
  • Healthy Volunteers
  • Hemodynamics
  • Humans
  • Image Processing, Computer-Assisted / methods*
  • Least-Squares Analysis
  • Magnetic Resonance Imaging*
  • Models, Theoretical
  • Normal Distribution
  • Phantoms, Imaging*
  • Prospective Studies
  • Pulmonary Artery / diagnostic imaging
  • Regression Analysis
  • Stroke Volume
  • Young Adult