Zhang Jin, Winters Kerryanne, Reynaud Olivier, Kim Sungheon Gene
Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, USA.
NMR Biomed. 2017 Sep;30(9). doi: 10.1002/nbm.3737. Epub 2017 May 22.
The aim of this study was to assess the feasibility of combining dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) with the measurement of the radiofrequency (RF) transmit field B and pre-contrast longitudinal relaxation time T . A novel approach has been proposed to simultaneously estimate B and T from a modified DCE-MRI scan that actively encodes the washout phase of the curve with different amounts of T and B weighting using multiple flip angles and repetition times, hence referred to as active contrast encoding (ACE)-MRI. ACE-MRI aims to simultaneously measure B and T , together with contrast kinetic parameters, such as the transfer constant K , interstitial space volume fraction v and vascular space volume fraction v . The proposed method was tested using numerical simulations and in vivo studies with mouse models of breast cancer implanted in the flank and mammary fat pad, and glioma in the brain. In the numerical simulation study with a signal-to-noise ratio of 10, both B and T were estimated accurately with errors of 5.1 ± 3.5% and 12.3 ± 8.8% and coefficients of variation (CV) of 14.9 ± 8.6% and 15.0 ± 5.0%, respectively. Using the same ACE-MRI data, the kinetic parameters K , v and v were also estimated with errors of 14.2 ± 8.3% (CV = 13.5 ± 4.6%), 14.7 ± 9.9% (CV = 13.3 ± 4.5%) and 14.0 ± 9.3% (CV = 14.0 ± 4.5%), respectively. For the in vivo tumor data from 11 mice, voxel-wise comparisons between ACE-MRI and DCE-MRI methods showed that the mean differences for the five parameters were as follows: ΔK = 0.006 (/min), Δv = 0.016, Δv = 0.000, ΔB = -0.014 and ΔT = -0.085 (s), which suggests a good agreement between the two methods. When compared with separately measured B and T , and DCE-MRI estimated kinetic parameters as a reference, the mean relative errors of ACE-MRI estimation were B = -0.3%, T = -8.5%, K = 11.4%, v = 14.5% and v = 4.5%. This proof-of-concept study demonstrates that the proposed ACE-MRI method can be used to estimate B and T , together with contrast kinetic model parameters.
本研究的目的是评估将动态对比增强磁共振成像（DCE-MRI）与射频（RF）发射场B和对比前纵向弛豫时间T的测量相结合的可行性。已提出一种新方法，通过一种改进的DCE-MRI扫描同时估计B和T，该扫描使用多个翻转角和重复时间，以不同量的T和B加权对曲线的洗脱期进行主动编码，因此称为主动对比编码（ACE）-MRI。ACE-MRI旨在同时测量B和T，以及对比动力学参数，如转移常数K、间质空间体积分数v和血管空间体积分数v。所提出的方法通过数值模拟以及在植入侧腹和乳腺脂肪垫的乳腺癌小鼠模型和脑胶质瘤小鼠模型上的体内研究进行了测试。在信噪比为10的数值模拟研究中，B和T的估计均准确，误差分别为5.1±3.5%和12.3±8.8%，变异系数（CV）分别为14.9±8.6%和15.0±5.0%。使用相同的ACE-MRI数据，动力学参数K、v和v的估计误差分别为14.2±8.3%（CV = 13.5±4.6%）、14.7±9.9%（CV = 13.3±4.5%）和14.0±9.3%（CV = 14.0±4.5%）。对于来自11只小鼠的体内肿瘤数据，ACE-MRI和DCE-MRI方法之间的逐体素比较表明，五个参数的平均差异如下：ΔK = 0.006（/min），Δv = 0.016，Δv = 0.000，ΔB = -0.014，ΔT = -0.085（s），这表明两种方法之间具有良好的一致性。与单独测量的B和T以及作为参考的DCE-MRI估计的动力学参数相比，ACE-MRI估计的平均相对误差为：B = -0.3%，T = -8.5%，K = 11.4%，v = 14.5%，v = 4.5%。这项概念验证研究表明，所提出的ACE-MRI方法可用于估计B和T以及对比动力学模型参数。
