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Correction of phase offset errors in main pulmonary artery flow quantification
Author(s) -
Lankhaar JanWillem,
Hofman Mark B.M.,
Marcus J. Tim,
Zwanenburg Jaco J.M.,
Faes Theo J.C.,
VonkNoordegraaf Anton
Publication year - 2005
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.20361
Subject(s) - imaging phantom , offset (computer science) , percentile , standard deviation , scanner , pixel , mathematics , nuclear medicine , biomedical engineering , physics , computer science , medicine , statistics , optics , programming language
Purpose To investigate whether an existing method for correction of phase offset errors in phase‐contrast velocity quantification is applicable for assessment of main pulmonary artery flow with an MR scanner equipped with a high‐power gradient system. Materials and Methods The correction method consists of fitting a surface through the time average of stationary pixels of velocity‐encoded phase images, and subtracting this surface from the velocity images. Pixels are regarded as stationary if their time standard deviation falls into the lowest percentile. Flow was measured in the main pulmonary artery of 15 subjects. Each measurement was repeated on a stationary phantom. The phase offset error in the phantom was used as a reference. Correction was applied with varying polynomial surface orders (0–5) and stationarity percentiles (5–50%). The optimal surface order and stationarity percentile were determined by comparing the fitted surface with the phantom. Results Using a first‐order surface and a (noncritical) 25% percentile, the correction method significantly reduced the phase offset error from 1.1 to 0.35 cm/second (RMS), which is equivalent to a reduction from 11% to 3.3% of mean volume flow. Phase error correction strongly affected stroke volume (range –11 to 26%). Conclusion The method significantly reduces phase offset errors in pulmonary artery flow. J. Magn. Reson. Imaging 2005;22:73–79. © 2005 Wiley‐Liss, Inc.