The purpose of this study was to evaluate oxygen-enhanced pulmonary imaging at 0.55 T with 3D stack-of-spirals ultrashort-T_E (UTE) acquisition. Oxygen-enhanced pulmonary MRI offers the measurement of regional lung ventilation and perfusion using inhaled oxygen as a contrast agent. Low-field MRI systems equipped with contemporary hardware can provide high-quality structural lung imaging by virtue of the prolonged T₂*. Fortuitously, the T₁ relaxivity of oxygen increases at lower field strengths, which is expected to improve the sensitivity of oxygen-enhanced lung MRI. We implemented a breath-held T₁-weighted 3D stack-of-spirals UTE acquisition with a 7 ms spiral-out readout. Measurement repeatability was assessed using five repetitions of oxygen-enhanced lung imaging in healthy volunteers (n = 7). The signal intensity at both normoxia and hyperoxia was strongly dependent on lung tissue density modulated by breath-hold volume during the five repetitions. A voxel-wise correction for lung tissue density improved the repeatability of percent signal enhancement maps (coefficient of variation = 34 ± 16%). Percent signal enhancement maps were compared in 15 healthy volunteers and 10 patients with lymphangioleiomyomatosis (LAM), a rare cystic disease known to reduce pulmonary function. We measured a mean percent signal enhancement of 9.0 ± 3.5% at 0.55 T in healthy volunteers, and reduced signal enhancement in patients with LAM (5.4 ± 4.8%, p = 0.02). The heterogeneity, estimated by the percent of lung volume exhibiting low enhancement, was significantly increased in patients with LAM compared with healthy volunteers (11.1 ± 6.0% versus 30.5 ± 13.1%, p = 0.01), illustrating the capability to measure regional functional deficits.

中文翻译：

---

使用当代 0.55 T MRI 系统的氧增强功能性肺成像

本研究的目的是通过 3D 螺旋堆叠超短T _E (UTE) 采集评估 0.55 T 的氧增强肺成像。氧增强肺 MRI 使用吸入的氧气作为造影剂提供了局部肺通气和灌注的测量。配备现代硬件的低场 MRI 系统可以通过延长的T ₂ *提供高质量的肺结构成像。幸运的是，氧的T ₁弛豫率在较低的场强下增加，这有望提高氧增强肺 MRI 的灵敏度。我们实施了一个令人屏息的T ₁加权 3D 螺旋堆栈 UTE 采集，具有 7 ms 螺旋输出读数。在健康志愿者中使用五次重复氧增强肺成像评估测量重复性（n = 7)。常氧和高氧的信号强度强烈依赖于五次重复期间由屏气体积调节的肺组织密度。肺组织密度的体素校正提高了百分比信号增强图的可重复性（变异系数 = 34 ± 16%）。比较了 15 名健康志愿者和 10 名淋巴管平滑肌瘤病 (LAM) 患者的信号增强百分比图，这是一种已知会降低肺功能的罕见囊性疾病。我们测量了健康志愿者在 0.55 T 时的平均信号增强百分比为 9.0 ± 3.5%，而 LAM 患者的信号增强降低（5.4 ± 4.8%，p = 0.02)。与健康志愿者相比，LAM 患者的异质性（由肺体积显示低增强的百分比估计）显着增加（11.1 ± 6.0% 对 30.5 ± 13.1%，p  = 0.01），说明测量区域功能缺陷的能力。