Park Bumwoo, Choi Byung Se, Sung Yu Sub, Woo Dong-Cheol, Shim Woo Hyun, Kim Kyung Won, Choi Yoon Seok, Pae Sang Joon, Suh Ji-Yeon, Cho Hyungjoon, Kim Jeong Kon
Department of Radiology, Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea.
Center for Bioimaging of New Drug Development, Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea.
Korean J Radiol. 2017 Jul-Aug;18(4):585-596. doi: 10.3348/kjr.2017.18.4.585. Epub 2017 May 19.
To simulate the B-inhomogeneity-induced variation of pharmacokinetic parameters on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).
B-inhomogeneity-induced flip angle (FA) variation was estimated in a phantom study. Monte Carlo simulation was performed to assess the FA-deviation-induced measurement error of the pre-contrast R, contrast-enhancement ratio, Gd-concentration, and two-compartment pharmacokinetic parameters (K, v, and v).
B-inhomogeneity resulted in -23-5% fluctuations (95% confidence interval [CI] of % error) of FA. The 95% CIs of FA-dependent % errors in the gray matter and blood were as follows: -16.7-61.8% and -16.7-61.8% for the pre-contrast R, -1.0-0.3% and -5.2-1.3% for the contrast-enhancement ratio, and -14.2-58.1% and -14.1-57.8% for the Gd-concentration, respectively. These resulted in -43.1-48.4% error for K, -32.3-48.6% error for the v, and -43.2-48.6% error for v. The pre-contrast R was more vulnerable to FA error than the contrast-enhancement ratio, and was therefore a significant cause of the Gd-concentration error. For example, a -10% FA error led to a 23.6% deviation in the pre-contrast R, -0.4% in the contrast-enhancement ratio, and 23.6% in the Gd-concentration. In a simulated condition with a 3% FA error in a target lesion and a -10% FA error in a feeding vessel, the % errors of the pharmacokinetic parameters were -23.7% for K, -23.7% for v, and -23.7% for v.
Even a small degree of B-inhomogeneity can cause a significant error in the measurement of pharmacokinetic parameters on DCE-MRI, while the vulnerability of the pre-contrast R calculations to FA deviations is a significant cause of the miscalculation.
在动态对比增强磁共振成像（DCE-MRI）中模拟由B不均匀性引起的药代动力学参数变化。
在体模研究中估计B不均匀性引起的翻转角（FA）变化。进行蒙特卡罗模拟以评估由FA偏差引起的对比前R、对比增强率、钆浓度和双室药代动力学参数（K、v和v）的测量误差。
B不均匀性导致FA出现-23%-5%的波动（误差百分比的95%置信区间[CI]）。灰质和血液中依赖FA的误差百分比的95%CI如下：对比前R为-16.7%-61.8%和-16.7%-61.8%，对比增强率为-1.0%-0.3%和-5.2%-1.3%，钆浓度为-14.2%-58.1%和-14.1%-57.8%。这导致K的误差为-43.1%-48.4%，v的误差为-32.3%-48.6%，v的误差为-43.2%-48.6%。对比前R比对比增强率更容易受到FA误差的影响，因此是钆浓度误差的一个重要原因。例如，-10%的FA误差导致对比前R偏差23.6%，对比增强率偏差-0.4%，钆浓度偏差23.6%。在模拟条件下，目标病变处FA误差为3%，供血血管处FA误差为-10%，药代动力学参数的误差百分比为：K为-23.7%，v为-23.7%，v为-23.7%。
即使是小程度的B不均匀性也会在DCE-MRI上药代动力学参数测量中导致显著误差，而对比前R计算对FA偏差的易感性是计算错误的一个重要原因。
