Department of Radiology, University Hospital of Lausanne (CHUV), Lausanne, Switzerland.
JACC Cardiovasc Imaging. 2012 Dec;5(12):1231-9. doi: 10.1016/j.jcmg.2012.06.010.
This study sought to establish an accurate and reproducible T(2)-mapping cardiac magnetic resonance (CMR) methodology at 3 T and to evaluate it in healthy volunteers and patients with myocardial infarct.
Myocardial edema affects the T(2) relaxation time on CMR. Therefore, T(2)-mapping has been established to characterize edema at 1.5 T. A 3 T implementation designed for longitudinal studies and aimed at guiding and monitoring therapy remains to be implemented, thoroughly characterized, and evaluated in vivo.
A free-breathing navigator-gated radial CMR pulse sequence with an adiabatic T(2) preparation module and an empirical fitting equation for T(2) quantification was optimized using numerical simulations and was validated at 3 T in a phantom study. Its reproducibility for myocardial T(2) quantification was then ascertained in healthy volunteers and improved using an external reference phantom with known T(2). In a small cohort of patients with established myocardial infarction, the local T(2) value and extent of the edematous region were determined and compared with conventional T(2)-weighted CMR and x-ray coronary angiography, where available.
The numerical simulations and phantom study demonstrated that the empirical fitting equation is significantly more accurate for T(2) quantification than that for the more conventional exponential decay. The volunteer study consistently demonstrated a reproducibility error as low as 2 ± 1% using the external reference phantom and an average myocardial T(2) of 38.5 ± 4.5 ms. Intraobserver and interobserver variability in the volunteers were -0.04 ± 0.89 ms (p = 0.86) and -0.23 ± 0.91 ms (p = 0.87), respectively. In the infarction patients, the T(2) in edema was 62.4 ± 9.2 ms and was consistent with the x-ray angiographic findings. Simultaneously, the extent of the edematous region by T(2)-mapping correlated well with that from the T(2)-weighted images (r = 0.91).
The new, well-characterized 3 T methodology enables robust and accurate cardiac T(2)-mapping at 3 T with high spatial resolution, while the addition of a reference phantom improves reproducibility. This technique may be well suited for longitudinal studies in patients with suspected or established heart disease.
本研究旨在建立一种准确且可重复的 3T 心脏磁共振（CMR）T2 映射方法，并在健康志愿者和心肌梗死患者中进行评估。
心肌水肿会影响 CMR 的 T2 弛豫时间。因此，T2 映射已被用于在 1.5T 下描述水肿。一种旨在指导和监测治疗的、针对纵向研究设计的 3T 实现方法仍有待充分地进行特性描述和体内评估。
使用自由呼吸导航门控径向 CMR 脉冲序列，该序列具有绝热 T2 准备模块和用于 T2 定量的经验拟合方程，通过数值模拟进行了优化，并在 3T 进行了体模研究验证。然后在健康志愿者中确定该方法用于心肌 T2 定量的可重复性，并使用具有已知 T2 的外部参考体模进行改进。在一小部分已确诊心肌梗死的患者中，确定了局部 T2 值和水肿区域的范围，并与常规 T2 加权 CMR 和 X 射线冠状动脉造影进行了比较（如果有）。
数值模拟和体模研究表明，经验拟合方程在 T2 定量方面明显比更传统的指数衰减更准确。志愿者研究使用外部参考体模始终显示出低至 2±1%的可重复性误差，平均心肌 T2 为 38.5±4.5ms。志愿者的观察者内和观察者间变异性分别为-0.04±0.89ms（p=0.86）和-0.23±0.91ms（p=0.87）。在梗死患者中，水肿区的 T2 为 62.4±9.2ms，与 X 射线血管造影结果一致。同时，T2 映射的水肿区域范围与 T2 加权图像的范围很好地相关（r=0.91）。
新的、特征良好的 3T 方法能够在 3T 下以高空间分辨率实现稳健且准确的心脏 T2 映射，而添加参考体模可提高可重复性。该技术可能非常适合疑似或确诊心脏病患者的纵向研究。
