Vassiliou Vassilios S, Heng Ee Ling, Gatehouse Peter D, Donovan Jacqueline, Raphael Claire E, Giri Shivraman, Babu-Narayan Sonya V, Gatzoulis Michael A, Pennell Dudley J, Prasad Sanjay K, Firmin David N
NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.
Imperial College, National Heart and Lung Institute, London, UK.
J Cardiovasc Magn Reson. 2016 Sep 22;18(1):62. doi: 10.1186/s12968-016-0275-9.
Magnetic resonance imaging (MRI) phantoms are routinely used for quality assurance in MRI centres; however their long term stability for verification of myocardial T1/ extracellular volume fraction (ECV) mapping has never been investigated.
Nickel-chloride agarose gel phantoms were formulated in a reproducible laboratory procedure to mimic blood and myocardial T1 and T2 values, native and late after Gadolinium administration as used in T1/ECV mapping. The phantoms were imaged weekly with an 11 heart beat MOLLI sequence for T1 and long TR spin-echo sequences for T2, in a carefully controlled reproducible manner for 12 months.
There were only small relative changes seen in all the native and post gadolinium T1 values (up to 9.0 % maximal relative change in T1 values) or phantom ECV (up to 8.3 % maximal relative change of ECV, up to 2.2 % maximal absolute change in ECV) during this period. All native and post gadolinium T2 values remained stable over time with <2 % change. Temperature sensitivity testing showed MOLLI T1 values in the long T1 phantoms increasing by 23.9 ms per degree increase and short T1 phantoms increasing by 0.3 ms per degree increase. There was a small absolute increase in ECV of 0.069 % (0.22 % relative increase in ECV) per degree increase. Variation in heart rate testing showed a 0.13 % absolute increase in ECV (0.45 % relative increase in ECV) per 10 heart rate increase.
These are the first phantoms reported in the literature modeling T1 and T2 values for blood and myocardium specifically for the T1mapping/ECV mapping application, with stability tested rigorously over a 12 month period. This work has significant implications for the utility of such phantoms in improving the accuracy of serial scans for myocardial tissue characterisation by T1 mapping methods and in multicentre work.
磁共振成像（MRI）体模常用于MRI中心的质量保证；然而，其用于验证心肌T1/细胞外容积分数（ECV）成像的长期稳定性从未得到研究。
采用可重复的实验室程序制备氯化镍琼脂糖凝胶体模，以模拟血液和心肌的T1和T2值，即T1/ECV成像中钆剂注射前后的数值。每周使用11心动周期MOLLI序列对体模进行T1成像，使用长TR自旋回波序列进行T2成像，以精心控制的可重复方式持续12个月。
在此期间，所有钆剂注射前后的T1值（T1值最大相对变化高达9.0%）或体模ECV（ECV最大相对变化高达8.3%，ECV最大绝对变化高达2.2%）仅有微小的相对变化。所有钆剂注射前后的T2值随时间保持稳定，变化<2%。温度敏感性测试显示，长T1体模的MOLLI T1值每升高1度增加23.9毫秒，短T1体模每升高1度增加0.3毫秒。ECV每升高1度有0.069%的微小绝对增加（ECV相对增加约0.22%）。心率变化测试显示，心率每增加10次，ECV有0.13%的绝对增加（ECV相对增加约0.45%）。
这是文献中首次报道的专门用于T1成像/ECV成像应用、模拟血液和心肌T1和T2值的体模，并在12个月期间进行了严格的稳定性测试。这项工作对于此类体模在提高T1成像方法对心肌组织特征进行系列扫描的准确性以及在多中心研究中的应用具有重要意义。
