Liu Ho-Ling, Chang Ting-Ting, Yan Feng-Xian, Li Cheng-He, Lin Yu-Shi, Wong Alex M
Department of Medical Imaging and Radiological Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
Department of Imaging Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX, USA.
NMR Biomed. 2015 Jun;28(6):642-9. doi: 10.1002/nbm.3297. Epub 2015 Apr 16.
The forward volumetric transfer constant (K(trans)), a physiological parameter extracted from dynamic contrast-enhanced (DCE) MRI, is weighted by vessel permeability and tissue blood flow. The permeability × surface area product per unit mass of tissue (PS) in brain tumors was estimated in this study by combining the blood flow obtained through pseudo-continuous arterial spin labeling (PCASL) and K(trans) obtained through DCE MRI. An analytical analysis and a numerical simulation were conducted to understand how errors in the flow and K(trans) estimates would propagate to the resulting PS. Fourteen pediatric patients with brain tumors were scanned on a clinical 3-T MRI scanner. PCASL perfusion imaging was performed using a three-dimensional (3D) fast-spin-echo readout module to determine blood flow. DCE imaging was performed using a 3D spoiled gradient-echo sequence, and the K(trans) map was obtained with the extended Tofts model. The numerical analysis demonstrated that the uncertainty of PS was predominantly dependent on that of K(trans) and was relatively insensitive to the flow. The average PS values of the whole tumors ranged from 0.006 to 0.217 min(-1), with a mean of 0.050 min(-1) among the patients. The mean K(trans) value was 18% lower than the PS value, with a maximum discrepancy of 25%. When the parametric maps were compared on a voxel-by-voxel basis, the discrepancies between PS and K(trans) appeared to be heterogeneous within the tumors. The PS values could be more than two-fold higher than the K(trans) values for voxels with high K(trans) levels. This study proposes a method that is easy to implement in clinical practice and has the potential to improve the quantification of the microvascular properties of brain tumors.
正向容积转移常数（K(trans)）是从动态对比增强（DCE）磁共振成像（MRI）中提取的生理参数，受血管通透性和组织血流量的影响。本研究通过结合伪连续动脉自旋标记（PCASL）获得的血流量和DCE MRI获得的K(trans)，估算了脑肿瘤中单位质量组织的通透性×表面积乘积（PS）。进行了分析分析和数值模拟，以了解血流和K(trans)估计中的误差如何传播到最终的PS。对14例患有脑肿瘤的儿科患者在临床3-T MRI扫描仪上进行扫描。使用三维（3D）快速自旋回波读出模块进行PCASL灌注成像以确定血流量。使用3D扰相梯度回波序列进行DCE成像，并使用扩展的Tofts模型获得K(trans)图。数值分析表明，PS的不确定性主要取决于K(trans)的不确定性，并且对血流相对不敏感。整个肿瘤的平均PS值范围为0.006至0.217 min⁻¹，患者之间的平均值为0.050 min⁻¹。平均K(trans)值比PS值低18%，最大差异为25%。当逐体素比较参数图时，肿瘤内PS和K(trans)之间的差异似乎是异质性的。对于具有高K(trans)水平的体素，PS值可能比K(trans)值高两倍以上。本研究提出了一种在临床实践中易于实施的方法，有可能改善脑肿瘤微血管特性的量化。
