Kampf Thomas, Bauer Wolfgang Rudolf, Reiter Theresa
University of Wuerzburg, Department for Experimental Physics V, Am Hubland, 97074 Wuerzburg, Germany; Comprehensive Heart Failure Centre Wuerzburg, Germany.
University Hospital Wuerzburg, Department of Internal Medicine I, Oberduerrbacher Straße 6a, 97080 Wuerzburg, Germany; Comprehensive Heart Failure Centre Wuerzburg, Germany.
Z Med Phys. 2018 Feb;28(1):25-35. doi: 10.1016/j.zemedi.2017.07.003. Epub 2017 Aug 9.
Contrast and non-contrast MRI based characterization of myocardium by T-mapping will be of paramount importance to obtain biomarkers, e.g. fibrosis, which determines the risk of heart failure patients. T-mapping by the standard post-processing of the modified look-locker inversion recovery (MOLLI) lacks of accuracy when trying to reduce its duration, which on the other hand, is highly desirable in patients with heart failure. The recently suggested inversion group fitting (IGF) technique, which considers more parameters for fitting, has a superior accuracy for long T times despite a shorter duration. However, for short T values, the standard method has a superior precision. A conditional fitting routine is proposed which ideally takes advantage of both algorithms.
All measurements were performed on a 1.5T clinical scanner (ACHIEVA, Philips Healthcare, The Netherlands) using a MOLLI 5(n)3(n)3 prototype with n(heart beats) being a variable waiting time between inversion experiments. Phantom experiments covered a broad range of T times, waiting times and heart rates. A saturation recovery experiment served as a gold standard for T measurement. All data were analyzed with the standard MOLLI, the IGF fit and the conditional fitting routine and the obtained T values were compared with the gold standard. In vivo measurements were performed in a healthy volunteer and a total of 34 patients with normal findings, dilative cardiomyopathy and amyloidosis.
Theoretical analysis and phantom experiments provided a threshold value for an apparent IGF T determining processing with IGF post processing for values above, or switching to the standard technique for values below. This was validated in phantoms and patients measurements. A reduction of the waiting time to 1 instead of 3 heart beats between the inversion experiments showed reliable results. The acquisition time was reduced from 17 to 13 heart beats. The in vivo measurements showed ECV values between 25% (18-33%; SD 0.03) in the healthy, 30% (22-40%; SD 0.04) in patients with DCM and 45% (30-60%; SD 0.9) in patients with amyloidosis.
The adopted post-processing algorithm determines long T values with high accuracy and short T values while maintaining a high precision. Based on reduction of waiting time, and independence of heart rate, it shortens breath hold duration and allows fast T-mapping, which is frequently a prerequisite in patients with cardiac diseases.
基于T值映射的对比剂增强和非对比剂增强心脏磁共振成像对心肌特征的分析，对于获取生物标志物（如纤维化）至关重要，纤维化决定了心力衰竭患者的风险。在试图缩短改良Look-Locker反转恢复序列（MOLLI）标准后处理的时间时，其T值映射缺乏准确性，而另一方面，这对于心力衰竭患者是非常必要的。最近提出的反转组拟合（IGF）技术，在拟合时考虑了更多参数，尽管时间较短，但对于长T值具有更高的准确性。然而，对于短T值，标准方法具有更高的精度。本文提出了一种条件拟合程序，理想情况下可以利用两种算法的优势。
所有测量均在1.5T临床扫描仪（ACHIEVA，飞利浦医疗保健公司，荷兰）上进行，使用MOLLI 5(n)3(n)3原型序列，其中n（心跳数）为反转实验之间的可变等待时间。模型实验涵盖了广泛的T值、等待时间和心率范围。饱和恢复实验用作T值测量的金标准。所有数据均采用标准MOLLI、IGF拟合和条件拟合程序进行分析，并将获得的T值与金标准进行比较。对一名健康志愿者以及总共34例检查结果正常、患有扩张型心肌病和淀粉样变性的患者进行了体内测量。
理论分析和模型实验提供了一个表观IGF T值的阈值，用于确定高于该值时采用IGF后处理，低于该值时切换到标准技术。这在模型和患者测量中得到了验证。将反转实验之间的等待时间从3次心跳减少到1次心跳显示出可靠的结果。采集时间从每次心跳17次减少到13次。体内测量显示，健康人的细胞外容积（ECV）值为25%（18 - 33%；标准差0.03），扩张型心肌病患者为30%（22 - 40%；标准差0.04），淀粉样变性患者为45%（30 - 60%；标准差0.9）。
所采用的后处理算法在保持高精度的同时，能够高精度地确定长T值和短T值。基于等待时间的减少以及心率的独立性，它缩短了屏气时间并允许快速T值映射，这通常是心脏病患者的一个先决条件。
