Zhang Jeff L, Conlin Chris C, Carlston Kristi, Xie Luke, Kim Daniel, Morrell Glen, Morton Kathryn, Lee Vivian S
University of Utah School of Medicine, Department of Radiology, Salt Lake City, UT, USA.
NMR Biomed. 2016 Jul;29(7):969-77. doi: 10.1002/nbm.3553. Epub 2016 May 20.
Dynamic contrast-enhanced (DCE) MRI is widely used for the measurement of tissue perfusion and to assess organ function. MR renography, which is acquired using a DCE sequence, can measure renal perfusion, filtration and concentrating ability. Optimization of the DCE acquisition protocol is important for the minimization of the error propagation from the acquired signals to the estimated parameters, thus improving the precision of the parameters. Critical to the optimization of contrast-enhanced T1 -weighted protocols is the balance of the T1 -shortening effect across the range of gadolinium (Gd) contrast concentration in the tissue of interest. In this study, we demonstrate a Monte Carlo simulation approach for the optimization of DCE MRI, in which a saturation-recovery T1 -weighted gradient echo sequence is simulated and the impact of injected dose (D) and time delay (TD, for saturation recovery) is tested. The results show that high D and/or high TD cause saturation of the peak arterial signals and lead to an overestimation of renal plasma flow (RPF) and glomerular filtration rate (GFR). However, the use of low TD (e.g. 100 ms) and low D leads to similar errors in RPF and GFR, because of the Rician bias in the pre-contrast arterial signals. Our patient study including 22 human subjects compared TD values of 100 and 300 ms after the injection of 4 mL of Gd contrast for MR renography. At TD = 100 ms, we computed an RPF value of 157.2 ± 51.7 mL/min and a GFR of 33.3 ± 11.6 mL/min. These results were all significantly higher than the parameter estimates at TD = 300 ms: RPF = 143.4 ± 48.8 mL/min (p = 0.0006) and GFR = 30.2 ± 11.5 mL/min (p = 0.0015). In conclusion, appropriate optimization of the DCE MRI protocol using simulation can effectively improve the precision and, potentially, the accuracy of the measured parameters. Copyright © 2016 John Wiley & Sons, Ltd.
动态对比增强（DCE）磁共振成像（MRI）被广泛用于测量组织灌注和评估器官功能。使用DCE序列采集的磁共振肾造影可以测量肾脏灌注、滤过和浓缩能力。优化DCE采集方案对于将采集信号到估计参数的误差传播最小化很重要，从而提高参数的精度。对比增强T1加权方案优化的关键在于在感兴趣组织中钆（Gd）对比剂浓度范围内T1缩短效应的平衡。在本研究中，我们展示了一种用于优化DCE MRI的蒙特卡罗模拟方法，其中模拟了饱和恢复T1加权梯度回波序列，并测试了注射剂量（D）和时间延迟（TD，用于饱和恢复）的影响。结果表明，高D和/或高TD会导致动脉峰值信号饱和，并导致肾血浆流量（RPF）和肾小球滤过率（GFR）的高估。然而，使用低TD（例如100 ms）和低D会导致RPF和GFR出现类似误差，这是由于对比前动脉信号中的莱斯偏差。我们纳入22名受试者的患者研究比较了注射4 mL Gd对比剂后进行磁共振肾造影时100和300 ms的TD值。在TD = 100 ms时，我们计算出RPF值为157.2±51.7 mL/min，GFR为33.3±11.6 mL/min。这些结果均显著高于TD = 300 ms时的参数估计值：RPF = 143.4±48.8 mL/min（p = 0.0006）和GFR = 30.2±11.5 mL/min（p = 0.0015）。总之，使用模拟对DCE MRI方案进行适当优化可以有效提高测量参数的精度，并可能提高其准确性。版权所有©2016约翰威立父子有限公司。
