Department of Radiation Oncology, Ann Arbor, MI 48109-0010, USA.
Phys Med Biol. 2013 Jun 21;58(12):4277-96. doi: 10.1088/0031-9155/58/12/4277. Epub 2013 Jun 4.
The purpose of this study is to evaluate repeatability coefficients of diffusion tensor indices to assess whether longitudinal changes in diffusion indices were true changes beyond the uncertainty for individual patients undergoing radiation therapy (RT). Twenty-two patients who had low-grade or benign tumors and were treated by partial brain radiation therapy (PBRT) participated in an IRB-approved MRI protocol. The diffusion tensor images in the patients were acquired pre-RT, week 3 during RT, at the end of RT, and 1, 6, and 18 months after RT. As a measure of uncertainty, repeatability coefficients (RC) of diffusion indices in the segmented cingulum, corpus callosum, and fornix were estimated by using test-retest diffusion tensor datasets from the National Biomedical Imaging Archive (NBIA) database. The upper and lower limits of the 95% confidence interval of the estimated RC from the test and retest data were used to evaluate whether the longitudinal percentage changes in diffusion indices in the segmented structures in the individual patients were beyond the uncertainty and thus could be considered as true radiation-induced changes. Diffusion indices in different white matter structures showed different uncertainty ranges. The estimated RC for fractional anisotropy (FA) ranged from 5.3% to 9.6%, for mean diffusivity (MD) from 2.2% to 6.8%, for axial diffusivity (AD) from 2.4% to 5.5%, and for radial diffusivity (RD) from 2.9% to 9.7%. Overall, 23% of the patients treated by RT had FA changes, 44% had MD changes, 50% had AD changes, and 50% had RD changes beyond the uncertainty ranges. In the fornix, 85.7% and 100% of the patients showed changes beyond the uncertainty range at 6 and 18 months after RT, demonstrating that radiation has a pronounced late effect on the fornix compared to other segmented structures. It is critical to determine reliability of a change observed in an individual patient for clinical decision making. Assessments of the repeatability and confidence interval of diffusion tensor measurements in white matter structures allow us to determine the true longitudinal change in individual patients.
本研究旨在评估弥散张量指数的重复性系数，以评估接受放射治疗（RT）的个体患者的弥散指数的纵向变化是否是真实的变化，而不是超出个体患者不确定性的变化。22 名患有低级别或良性肿瘤并接受部分脑放射治疗（PBRT）的患者参与了经机构审查委员会批准的 MRI 方案。在 RT 前、RT 期间的第 3 周、RT 结束时以及 RT 后 1、6 和 18 个月，对患者的弥散张量图像进行了采集。作为不确定性的度量，通过使用来自国家生物医学成像档案库（NBIA）数据库的测试-重测弥散张量数据集，估计了分割胼胝体、胼胝体和穹窿中的弥散指数的重复性系数（RC）。测试和重测数据中估计的 RC 的 95%置信区间的上限和下限用于评估个体患者分割结构中的弥散指数的纵向百分比变化是否超出不确定性范围，因此可以被认为是真正的放射诱导变化。不同的白质结构中的弥散指数显示出不同的不确定性范围。各向异性分数（FA）的估计 RC 范围为 5.3%至 9.6%，平均弥散度（MD）的 RC 范围为 2.2%至 6.8%，轴向弥散度（AD）的 RC 范围为 2.4%至 5.5%，径向弥散度（RD）的 RC 范围为 2.9%至 9.7%。总体而言，23%的 RT 治疗患者的 FA 发生了变化，44%的 MD 发生了变化，50%的 AD 发生了变化，50%的 RD 发生了变化，超出了不确定性范围。在穹窿中，85.7%和 100%的患者在 RT 后 6 个月和 18 个月时的变化超出了不确定性范围，这表明与其他分割结构相比，放射对穹窿有明显的迟发性影响。对于临床决策制定，确定个体患者中观察到的变化的可靠性至关重要。对白质结构中弥散张量测量的重复性和置信区间的评估使我们能够确定个体患者的真实纵向变化。
