3D [Formula: see text] 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

doi:10.1002/jmri.26203

3D $R_{2}^{*}$ mapping of the placenta during early gestation using free-breathing multiecho stack-of-radial MRI at 3T

J Magn Reson Imaging. 2019 Jan;49(1):291-303. doi: 10.1002/jmri.26203. Epub 2018 Aug 24.

Authors

Tess Armstrong^{1

2}, Dapeng Liu¹, Thomas Martin^{1

2}, Rinat Masamed¹, Carla Janzen³, Cass Wong¹, Teresa Chanlaw⁴, Sherin U Devaskar⁴, Kyunghyun Sung^{1

2}, Holden H Wu^{1

2}

Affiliations

¹ Department of Radiological Sciences, University of California Los Angeles, Los Angeles, California, USA.
² Department of Physics and Biology in Medicine, University of California Los Angeles, Los Angeles, California, USA.
³ Department of Obstetrics and Gynecology, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
⁴ Department of Pediatrics, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.

Abstract

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, ρ_c ) 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: ρ_c 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 (ρ_c ≥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.

Keywords: $R_{2}^{*}$ mapping; 3D radial imaging; 3T; early gestation; free-breathing MRI; placenta MRI.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Algorithms
Artifacts
Breath Holding*
Female
Humans
Image Enhancement / methods
Image Interpretation, Computer-Assisted / methods
Image Processing, Computer-Assisted
Imaging, Three-Dimensional / methods*
Magnetic Resonance Imaging*
Motion
Phantoms, Imaging
Placenta / diagnostic imaging*
Pregnancy
Prospective Studies
Reproducibility of Results
Respiration

Abstract

Publication types

MeSH terms

Grants and funding