Ma Weijing, Sheikh Khadija, Svenningsen Sarah, Pike Damien, Guo Fumin, Etemad-Rezai Roya, Leipsic Jonathan, Coxson Harvey O, McCormack David G, Parraga Grace
Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London, Canada.
J Magn Reson Imaging. 2015 May;41(5):1465-74. doi: 10.1002/jmri.24680. Epub 2014 Jun 26.
To evaluate ultra-short-echo-time (UTE) MRI pulmonary signal-intensity measurements and reproducibility in chronic obstructive pulmonary disease (COPD).
A two-dimensional sequence (echo-time = 0.05 ms; acquisition-time = 13 s) with interleaved half-pulse excitation and radial ramp-sampling was used with compressed-sensing to reconstruct UTE images from under-sampled data. Five healthy volunteers and 15 subjects with COPD provided written informed consent to imaging and pulmonary-function-tests. Healthy volunteers underwent MRI at four lung volumes: full-expiration, functional-residual-capacity (FRC), FRC+1L, and full-inhalation; COPD patients underwent computed-tomography (CT) and MRI at FRC+1L. Three-week reproducibility was evaluated and the relative area of the density histogram ≤ -950 HU (RA950 ) was compared with mean MRI signal-intensity. The 15th percentile of signal-intensity-histogram (SI15 ) was compared with the 15th percentile of the CT-density-histogram (HU15 ).
In healthy subjects, signal-intensity correlated with the inverse of lung volume (r = 0.99; P = 0.007). Contrast-to-noise and signal-to-noise ratios were significantly improved for 32-channel UTE (P < 0.01). The coefficient of variation for 3-week repeated measurements was 4%. There were significant correlations for signal-intensity with RA950 (r = -0.71; P = 0.005), FEV1 /FVC (r = 0.59; P = 0.02), and for SI15 with HU15 (r = 0.62; P = 0.01).
Pulmonary signal-intensity is reproducible and related to tissue density. In COPD subjects with and without bronchiectasis, signal-intensity was also related to pulmonary function and CT measurements.
评估超短回波时间（UTE）MRI在慢性阻塞性肺疾病（COPD）中对肺信号强度的测量及可重复性。
采用二维序列（回波时间 = 0.05 ms；采集时间 = 13 s），通过交错半脉冲激发和径向斜坡采样，并结合压缩感知技术，从欠采样数据中重建UTE图像。5名健康志愿者和15名COPD患者签署了影像学检查和肺功能测试的书面知情同意书。健康志愿者在四个肺容量状态下接受MRI检查：完全呼气、功能残气量（FRC）、FRC + 1L和完全吸气；COPD患者在FRC + 1L状态下接受计算机断层扫描（CT）和MRI检查。评估了3周内的可重复性，并将密度直方图相对面积≤ -950 HU（RA950）与MRI平均信号强度进行比较。将信号强度直方图的第15百分位数（SI15）与CT密度直方图的第15百分位数（HU15）进行比较。
在健康受试者中，信号强度与肺容量的倒数相关（r = 0.99；P = 0.007）。32通道UTE的对比噪声比和信噪比显著提高（P < 0.01）。3周重复测量的变异系数为4%。信号强度与RA950（r = -0.71；P = 0.005）、FEV1 / FVC（r = 0.59；P = 0.02）显著相关，SI15与HU15（r = 0.62；P = 0.01）显著相关。
肺信号强度具有可重复性且与组织密度相关。在有和无支气管扩张的COPD受试者中，信号强度也与肺功能和CT测量相关。
