Brynolfsson Patrik, Yu Jun, Wirestam Ronnie, Karlsson Mikael, Garpebring Anders
Department of Radiation Physics, Umeå University, Umeå, Sweden.
Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden.
Magn Reson Med. 2015 Oct;74(4):1156-64. doi: 10.1002/mrm.25490. Epub 2014 Oct 16.
The purpose of this study was to investigate, using simulations, a method for improved contrast agent (CA) quantification in DCE-MRI.
We developed a maximum likelihood estimator that combines the phase signal in the DCE-MRI image series with an additional CA estimate, e.g. the estimate obtained from magnitude data. A number of simulations were performed to investigate the ability of the estimator to reduce bias and noise in CA estimates. Noise levels ranging from that of a body coil to that of a dedicated head coil were investigated at both 1.5T and 3T.
Using the proposed method, the root mean squared error in the bolus peak was reduced from 2.24 to 0.11 mM in the vessels and 0.16 to 0.08 mM in the tumor rim for a noise level equivalent of a 12-channel head coil at 3T. No improvements were seen for tissues with small CA uptake, such as white matter.
Phase information reduces errors in the estimated CA concentrations. A larger phase response from higher field strengths or higher CA concentrations yielded better results. Issues such as background phase drift need to be addressed before this method can be applied in vivo.
本研究的目的是通过模拟研究一种在动态对比增强磁共振成像（DCE-MRI）中改进造影剂（CA）定量的方法。
我们开发了一种最大似然估计器，它将DCE-MRI图像序列中的相位信号与额外的CA估计值相结合，例如从幅度数据获得的估计值。进行了多项模拟以研究该估计器减少CA估计中的偏差和噪声的能力。在1.5T和3T条件下，研究了从体线圈到专用头线圈的一系列噪声水平。
使用所提出的方法，对于相当于3T下12通道头线圈的噪声水平，在血管中团注峰值的均方根误差从2.24 mM降低到0.11 mM，在肿瘤边缘从0.16 mM降低到0.08 mM。对于造影剂摄取量小的组织，如白质，未观察到改善。
相位信息减少了估计的造影剂浓度中的误差。更高场强或更高造影剂浓度产生的更大相位响应产生了更好的结果。在该方法可应用于体内之前，需要解决诸如背景相位漂移等问题。
