Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Med Phys. 2010 Jun;37(6):2683-92. doi: 10.1118/1.3427487.
Calculation of the precontrast longitudinal relaxation times (T10) is an integral part of the Tofts-based pharmacokinetic (PK) analysis of dynamic contrast enhanced-magnetic resonance images. The purpose of this study was to investigate the interpatient and over time variability of T10 in head and neck primary tumors and involved nodes and to determine the median T10 for primary and nodes (T10(p,n)). The authors also looked at the implication of using voxel-based T10 values versus region of interest (ROI)-based T10 on the calculated values for vascular permeability (K(trans)) and extracellular volume fraction (v(e)).
Twenty head and neck cancer patients receiving concurrent chemoradiation and molecularly targeted agents on a prospective trial comprised the study population. Voxel-based T10's were generated using a gradient echo sequence on a 1.5 T MR scanner using the variable flip angle method with two flip angles [J. A. Brookes et al., "Measurement of spin-lattice relaxation times with FLASH for dynamic MRI of the breast," Br. J. Radiol. 69, 206-214 (1996)]. The voxel-based T10, K(trans), and v(e) were calculated using iCAD's (Nashua, NH) software. The mean T10's in muscle and fat ROIs were calculated (T10(m,f)). To assess reliability of ROI drawing, T10(p,n) values from ROIs delineated by 2 users (A and B) were calculated as the average of the T10's for 14 patients. For a subset of three patients, the T10 variability from baseline to end of treatment was also investigated. The K(trans) and v(e) from primary and node ROIs were calculated using voxel-based T10 values and T10(p,n) and differences reported.
The calculated T10 values for fat and muscle are within the range of values reported in literature for 1.5 T, i.e., T10(m) = 0.958 s and T10(f) = 0.303 s. The average over 14 patients of the T10's based on drawings by users A and B were T10(pA) = 0.804 s, T10(nA) = 0.760 s, T10(pB) = 0.849 s, and T10(nB) = 0.810 s. The absolute percentage difference between K(trans) and v(e) calculated with voxel-based T10 versus T10(p,n) ranged from 6% to 81% and from 2% to 24%, respectively.
There is a certain amount of variability in the median T10 values between patients, but the differences are not significant. There were also no statistically significant differences between the T10 values for primary and nodes at baseline and the subsequent time points (p = 0.94 Friedman test). Voxel-based T10 calculations are essential when quantitative Tofts-based PK analysis in heterogeneous tumors is needed. In the absence of T10 mapping capability, when a relative, qualitative analysis is deemed sufficient, a value of T10(p,n) = 0.800 s can be used as an estimate for T10 for both the primary tumor and the affected nodes in head and neck cancers at all the time points considered.
计算对比预增强纵向弛豫时间（T10）是基于 Tofts 的药代动力学（PK）分析动态对比增强磁共振图像的一个组成部分。本研究的目的是研究头颈部原发性肿瘤和受累淋巴结中 T10 的患者间和随时间的可变性，并确定原发性和淋巴结的中位数 T10（T10(p,n)）。作者还研究了使用体素 T10 值与基于感兴趣区域（ROI）的 T10 对计算的血管通透性（K(trans)）和细胞外体积分数（v(e)）值的影响。
20 名接受同期放化疗和分子靶向治疗的头颈部癌症患者组成了研究人群。使用 1.5 T 磁共振扫描仪上的梯度回波序列，使用可变翻转角方法（两个翻转角 [J. A. Brookes 等人，“用于动态 MRI 乳房的 FLASH 自旋-晶格弛豫时间测量”，英国放射学杂志 69,206-214（1996）]）生成体素 T10。使用 iCAD（Nashua，NH）软件计算体素 T10、K(trans) 和 v(e)。计算肌肉和脂肪 ROI 中的平均 T10（T10(m,f)）。为了评估 ROI 绘制的可靠性，计算了由 2 名用户（A 和 B）描绘的 ROI 中的 T10(p,n)值，方法是将 14 名患者的 T10 值的平均值。对于三名患者的子集，还研究了从基线到治疗结束时 T10 的可变性。使用基于体素 T10 值的原发性和淋巴结 ROI 计算 K(trans) 和 v(e)，并报告差异。
脂肪和肌肉的计算 T10 值在文献中报道的 1.5 T 的范围内，即 T10(m) = 0.958 s 和 T10(f) = 0.303 s。基于用户 A 和 B 的绘图，14 名患者的 T10 平均值为 T10(pA) = 0.804 s、T10(nA) = 0.760 s、T10(pB) = 0.849 s 和 T10(nB) = 0.810 s。基于体素 T10 与 T10(p,n) 计算的 K(trans) 和 v(e)之间的绝对百分比差异范围为 6%至 81%和 2%至 24%。
患者之间的中位数 T10 值存在一定程度的可变性，但差异并不显著。原发性和淋巴结的 T10 值在基线和随后的时间点之间也没有统计学上的显著差异（p = 0.94 Friedman 检验）。当需要对异质性肿瘤进行基于定量 Tofts 的 PK 分析时，体素 T10 计算是必不可少的。在没有 T10 映射功能的情况下，如果认为相对定性分析已经足够，则可以使用 T10(p,n) = 0.800 s 作为在考虑的所有时间点处头颈部癌症的原发性肿瘤和受累淋巴结的 T10 的估计值。
