Department of Radiological Sciences, University of California Los Angeles, 300 UCLA Medical Plaza, Ste. B119, Los Angeles, CA, 90095, USA.
Physics and Biology in Medicine, University of California Los Angeles, Los Angeles, CA, USA.
Pediatr Radiol. 2019 Jun;49(7):876-888. doi: 10.1007/s00247-019-04384-7. Epub 2019 Apr 17.
Body composition and hepatic fat correlate with future risk for metabolic syndrome. In children, many conventional techniques for quantifying body composition and hepatic fat have limitations. MRI is a noninvasive research tool to study body composition and hepatic fat in infants; however, conventional Cartesian MRI is sensitive to motion, particularly in the abdomen because of respiration. Therefore we developed a free-breathing MRI technique to quantify body composition and hepatic fat in infants.
In infants, we aimed to (1) compare the image quality between free-breathing 3-D stack-of-radial MRI (free-breathing radial) and 3-D Cartesian MRI in the liver and (2) determine the feasibility of using free-breathing radial MRI to quantify body composition and hepatic proton-density fat fraction (PDFF).
Ten infants ages 2-7 months were scanned with free-breathing radial (two abdominal; one head and chest) and Cartesian (one abdominal) MRI sequences. The median preparation and scan times were reported. To assess feasibility for hepatic PDFF quantification, a radiologist masked to the MRI technique scored abdominal scans for motion artifacts in the liver using a 3-point scale (1, or non-diagnostic, to 3, or no artifacts). Median visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT) and brown adipose tissue (BAT) volume and PDFF, and hepatic PDFF were measured using free-breathing radial MRI. We assessed repeatability of free-breathing radial hepatic PDFF (coefficient of repeatability) between back-to-back scans. We determined differences in the distribution of image-quality scores using McNemar-Bowker tests. P<0.05 was considered significant.
Nine infants completed the entire study (90% completion). For ten infants, the median preparation time was 32 min and scan time was 24 min. Free-breathing radial MRI demonstrated significantly higher image-quality scores compared to Cartesian MRI in the liver (radial scan 1 median = 2 and radial scan 2 median = 3 vs. Cartesian median = 1; P=0.01). Median measurements using free-breathing radial were VAT=52.0 cm, VAT-PDFF=42.2%, SAT=267.7 cm, SAT-PDFF=87.1%, BAT=1.4 cm, BAT-PDFF=26.1% and hepatic PDFF=3.4% (coefficient of repeatability <2.0%).
In this study, free-breathing radial MRI in infants achieved significantly improved liver image quality compared to Cartesian MRI. It is feasible to use free-breathing radial MRI to quantify body composition and hepatic fat in infants.
身体成分和肝脂肪与代谢综合征的未来风险相关。在儿童中，许多用于量化身体成分和肝脂肪的传统技术都存在局限性。MRI 是一种用于研究婴儿身体成分和肝脂肪的非侵入性研究工具；然而，传统的笛卡尔 MRI 对运动敏感，尤其是在腹部，因为呼吸。因此，我们开发了一种自由呼吸 MRI 技术来量化婴儿的身体成分和肝脂肪。
在婴儿中，我们旨在（1）比较自由呼吸 3D 堆叠径向 MRI（自由呼吸径向）和 3D 笛卡尔 MRI 在肝脏中的图像质量，（2）确定使用自由呼吸径向 MRI 定量身体成分和肝质子密度脂肪分数（PDFF）的可行性。
10 名 2-7 个月大的婴儿接受了自由呼吸径向（两个腹部；一个头部和胸部）和笛卡尔（一个腹部）MRI 序列扫描。报告了中位数准备和扫描时间。为了评估肝 PDFF 定量的可行性，一位放射科医生使用 3 分制（1 分，或不可诊断，至 3 分，或无伪影）对 MRI 技术进行了盲法评估，对肝脏的运动伪影进行了评分。使用自由呼吸径向 MRI 测量了内脏脂肪组织（VAT）、皮下脂肪组织（SAT）和棕色脂肪组织（BAT）的体积和 PDFF 以及肝 PDFF。我们评估了两次自由呼吸径向肝 PDFF 之间的可重复性（重复性系数）。我们使用 McNemar-Bowker 检验确定图像质量评分分布的差异。P<0.05 被认为具有统计学意义。
9 名婴儿完成了整个研究（完成率为 90%）。对于 10 名婴儿，中位数准备时间为 32 分钟，扫描时间为 24 分钟。与笛卡尔 MRI 相比，自由呼吸径向 MRI 在肝脏中显示出显著更高的图像质量评分（径向扫描 1 中位数=2 和径向扫描 2 中位数=3 与笛卡尔中位数=1；P=0.01）。使用自由呼吸径向测量的中位数分别为 VAT=52.0cm、VAT-PDFF=42.2%、SAT=267.7cm、SAT-PDFF=87.1%、BAT=1.4cm、BAT-PDFF=26.1%和肝 PDFF=3.4%（重复性系数<2.0%）。
在这项研究中，与笛卡尔 MRI 相比，婴儿的自由呼吸径向 MRI 显著提高了肝脏的图像质量。使用自由呼吸径向 MRI 定量婴儿的身体成分和肝脂肪是可行的。
