Department of Physics and Astronomy, Western University, London, ON, Canada.
Lawson Imaging, Lawson Health Research Institute, London, ON, Canada.
MAGMA. 2021 Feb;34(1):73-84. doi: 10.1007/s10334-020-00860-6. Epub 2020 Jul 6.
Diffusion-weighted, hyperpolarized Xe MRI is useful for the characterization of microstructural changes in the lung. A stretched exponential model was proposed for morphometric extraction of the mean chord length (L) from diffusion-weighted data. The stretched exponential model enables accelerated mapping of L in a single-breathhold using compressed sensing. Our purpose was to compare L maps obtained from stretched-exponential model analysis of accelerated versus unaccelerated diffusion-weighted Xe MRI data obtained from healthy/injured rat lungs.
L maps were generated using a stretched-exponential model analysis of previously acquired fully sampled diffusion-weighted Xe rat data (b values = 0 … 110 s/cm) and compared to L maps generated from retrospectively undersampled data simulating acceleration factors of 7/10. The data included four control rats and five rats receiving whole-lung irradiation to mimic radiation-induced lung injury. Mean L obtained from the accelerated/unaccelerated maps were compared to histological mean linear intercept.
Accelerated L estimates were similar to unaccelerated L estimates in all rats, and similar to those previously reported (< 12% different). L was significantly reduced (p < 0.001) in the irradiated rat cohort (90 ± 20 µm/90 ± 20 µm) compared to the control rats (110 ± 20 µm/100 ± 15 µm) and agreed well with histological mean linear intercept.
Accelerated mapping of L using a stretched-exponential model analysis is feasible, accurate and agrees with histological mean linear intercept. Acceleration reduces scan time, thus should be considered for the characterization of lung microstructural changes in humans where breath-hold duration is short.
扩散加权、超极化 Xe MRI 可用于肺部微结构变化的特征描述。提出了一种扩展指数模型，用于从扩散加权数据中提取平均弦长（L）的形态测量。扩展指数模型可在单次屏气中使用压缩感知加速 L 的映射。我们的目的是比较从健康/损伤大鼠肺部加速与非加速扩散加权 Xe MRI 数据的扩展指数模型分析获得的 L 图。
使用扩展指数模型分析先前获取的完全采样扩散加权 Xe 大鼠数据（b 值=0...110 s/cm）生成 L 图，并与模拟加速因子为 7/10 的回顾性欠采样数据生成的 L 图进行比较。数据包括 4 只对照大鼠和 5 只接受全肺照射以模拟放射性肺损伤的大鼠。从加速/非加速图中获得的平均 L 与组织学平均线性截距进行比较。
在所有大鼠中，加速 L 估计值与非加速 L 估计值相似，与之前报道的结果相似（<12%差异）。与对照大鼠（110 ± 20 µm/100 ± 15 µm）相比，照射大鼠组的 L 显著降低（p < 0.001）（90 ± 20 µm/90 ± 20 µm），与组织学平均线性截距吻合良好。
使用扩展指数模型分析加速 L 图是可行的、准确的，并且与组织学平均线性截距一致。加速可减少扫描时间，因此在人类中用于肺部微结构变化的特征描述时应考虑。
