Bannier Elise, Neyran Bruno, Cieslar Katarzyna, Rivoire Julien, Heidemann Robin M, Gaillard Sophie, Sulaiman Abdul Razzaq, Canet-Soulas Emmanuelle, Cremillieux Yannick
Université de Lyon, Villeurbanne, France.
Invest Radiol. 2009 Apr;44(4):185-91. doi: 10.1097/RLI.0b013e3181965d52.
Current clinical hyperpolarized He lung ventilation MR imaging protocols rely on the patient's ability to control inhalation and exhalation and hold their breath on demand. This is impractical for intensive care unit patients under ventilation or for pediatric populations under the age of 3 to 4 years. To address this problem, we propose a free-breathing protocol for hyperpolarized He lung ventilation spiral imaging. This approach was evaluated in vitro and on rabbits.
The protocol was implemented on a clinical 1.5-T magnetic resonance imaging scanner. Ventilation images were acquired using a spiral sequence, in vitro on a lung phantom and in vivo on rabbits, the animal breathing freely from a gas reservoir. Dynamic spiral ventilation images were reconstructed using retrospective Cine synchronization. Magnetic resonance (MR) signal dynamics was modeled taking account of gas inflow and outflow, radiofrequency depolarization and oxygen-induced relaxation.
Cine ventilation images acquired in spontaneously breathing rabbits were reconstructed with a temporal resolution of 50 milliseconds. Gas volume variations and time-to-maximum maps were obtained. The numerical model was validated in vitro and in vivo with various gas mixtures. Ventilation parameters (functional residual capacity, tidal volume, and alveolar pO2) were extracted from the MR signal dynamics.
Ventilation imaging can be performed at tidal volume using a simple experimental protocol, without any ventilation device or breath-hold period. Acquisition time, SNR and pO2 decay can be optimized using the developed numerical model. Free-breathing ventilation images can be obtained without artifacts related to motion or gas flow. Lastly, parametric maps can be derived from the time-resolved ventilation images and physiological parameters extracted from the global signal dynamics.
当前临床超极化氦气肺通气磁共振成像方案依赖于患者控制吸入和呼出以及按需屏气的能力。这对于接受通气治疗的重症监护病房患者或3至4岁以下的儿科患者来说是不切实际的。为了解决这个问题，我们提出了一种用于超极化氦气肺通气螺旋成像的自由呼吸方案。该方法在体外和兔子身上进行了评估。
该方案在临床1.5-T磁共振成像扫描仪上实施。使用螺旋序列采集通气图像，体外在肺部模型上进行，体内在兔子身上进行，动物从储气罐自由呼吸。使用回顾性电影同步重建动态螺旋通气图像。考虑气体流入和流出、射频去极化和氧诱导弛豫，对磁共振（MR）信号动力学进行建模。
以50毫秒的时间分辨率重建了自发呼吸兔子获得的电影通气图像。获得了气体体积变化和最大时间图。数值模型在体外和体内用各种气体混合物进行了验证。从MR信号动力学中提取通气参数（功能残气量、潮气量和肺泡pO2）。
使用简单的实验方案可以在潮气量下进行通气成像，无需任何通气设备或屏气期。使用开发的数值模型可以优化采集时间、信噪比和pO2衰减。可以获得无运动或气流相关伪影的自由呼吸通气图像。最后，可以从时间分辨通气图像中导出参数图，并从全局信号动力学中提取生理参数。
