3D R2* mapping of the placenta during early gestation using free-breathing multiecho stack-of-radial MRI at 3T

Tess Armstrong, Dapeng Liu, Thomas Martin, Rinat Masamed, Carla Janzen, Cass Wong, Teresa Chanlaw, Sherin U. Devaskar, Kyunghyun Sung, Holden H. Wu

Research output: Contribution to journalArticlepeer-review


Background: Multiecho gradient-echo Cartesian MRI characterizes placental oxygenation by quantifying R* 2. Previous research was performed at 1.5T using breath-held 2D imaging during later gestational age (GA). Purpose: To evaluate the accuracy and repeatability of a free-breathing (FB) 3D multiecho gradient-echo stack-of-radial technique (radial) for placental R* 2 mapping at 3T and report placental R* 2 during early GA. Study Type: Prospective. Population: Thirty subjects with normal pregnancies and three subjects with ischemic placental disease (IPD) were scanned twice: between 14–18 and 19–23 weeks GA. Field Strength: 3T. Sequence: FB radial. Assessment: Linear correlation (concordance coefficient, ρc) and Bland–Altman analyses (mean difference, MD) were performed to evaluate radial R* 2 mapping accuracy compared to Cartesian in a phantom. Radial R* 2 mapping repeatability was characterized using the coefficient of repeatability (CR) between back-to-back scans. The mean and spatial coefficient of variation (CV) of R* 2 was determined for all subjects, and separately for anterior and posterior placentas, at each GA range. Statistical Tests: ρc was tested for significance. Differences in mean R* 2 and CV were tested using Wilcoxon Signed-Rank and Rank-Sum tests. P < 0.05 was considered significant. Z-scores for the IPD subjects were determined. Results: FB radial demonstrated accurate (ρc≥0.996; P < 0.001; |MD|<0.2s−1) and repeatable (CR<4s−1) R* 2 mapping in a phantom, and repeatable (CR≤4.6s−1) R* 2 mapping in normal subjects. At 3T, placental R* 2 mean ± standard deviation was 12.9s−1 ± 2.7s−1 for 14–18 and 13.2s−1 ± 1.9s−1 for 19–23 weeks GA. The CV was significantly greater (P = 0.043) at 14–18 (0.63 ± 0.12) than 19–23 (0.58 ± 0.13) weeks GA. At 19–23 weeks, the CV was significantly lower (P < 0.001) for anterior (0.49 ± 0.08) than posterior (0.67 ± 0.11) placentas. One IPD subject had a lower mean R* 2 than normal subjects at both GA ranges (Z<–2). Data Conclusion: FB radial provides accurate and repeatable 3D R* 2 mapping for the entire placenta at 3T during early GA. Level of Evidence: 2. Technical Efficacy: Stage 1. J. Magn. Reson. Imaging 2019;49:291–303.

Original languageEnglish (US)
Pages (from-to)291-303
Number of pages13
JournalJournal of Magnetic Resonance Imaging
Issue number1
StatePublished - Jan 2019
Externally publishedYes


  • 3D radial imaging
  • 3T
  • R2* mapping
  • early gestation
  • free-breathing MRI
  • placenta MRI

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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