Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
J Magn Reson Imaging. 2011 Jun;33(6):1510-6. doi: 10.1002/jmri.22553.
To evaluate the reduced transverse relaxation rate (RR2), a new relaxation index which has been shown recently to be primarily sensitive to intracellular ferritin iron, as a means of detecting short-term changes in myocardial storage iron produced by iron-chelating therapy in transfusion-dependent thalassemia patients.
A single-breathhold multi-echo fast spin-echo sequence was implemented at 3 Tesla (T) to estimate RR2 by acquiring signal decays with interecho times of 5, 9 and 13 ms. Transfusion-dependent thalassemia patients (N = 8) were examined immediately before suspending iron-chelating therapy for 1 week (Day 0), after a 1-week suspension of chelation (Day 7), and after a 1-week resumption of chelation (Day 14).
The mean percent changes in RR2, R2, and R2* off chelation (between Day 0 and 7) were 11.9 ± 8.9%, 5.4 ± 7.7% and -4.4 ± 25.0%; and, after resuming chelation (between Day 7 and 14), -10.6 ± 13.9%, -8.9 ± 8.0% and -8.5 ± 24.3%, respectively. Significant differences in R2 and RR2 were observed between Day 0 and 7, and between Day 7 and 14, with the greatest proportional changes in RR2. No significant differences in R2* were found.
These initial results demonstrate that significant differences in RR2 are detectable after a single week of changes in iron-chelating therapy, likely as a result of superior sensitivity to soluble ferritin iron, which is in close equilibrium with the chelatable cytosolic iron pool. RR2 measurement may provide a new means of monitoring the short-term effectiveness of iron-chelating agents in patients with myocardial iron overload.
评估新的弛豫率（RR2），RR2 是一种最近被证明主要对细胞内铁蛋白铁敏感的弛豫指数，作为检测依赖输血的地中海贫血患者铁螯合治疗引起的心肌储存铁短期变化的一种手段。
在 3 特斯拉（T）下实施单次屏气多回波快速自旋回波序列，通过采集间隔回波时间为 5、9 和 13 ms 的信号衰减来估计 RR2。在停止铁螯合治疗 1 周（第 0 天）之前、停止螯合治疗 1 周后（第 7 天）和恢复螯合治疗 1 周后（第 14 天），对依赖输血的地中海贫血患者（N=8）进行检查。
RR2、R2 和 RR2去螯合（第 0 天和第 7 天之间）的平均百分比变化分别为 11.9%±8.9%、5.4%±7.7%和-4.4%±25.0%；并且，在恢复螯合治疗（第 7 天和第 14 天之间）时，RR2 和 RR2的百分比变化分别为-10.6%±13.9%、-8.9%±8.0%和-8.5%±24.3%。第 0 天和第 7 天之间以及第 7 天和第 14 天之间的 R2 和 RR2 差异均有统计学意义，RR2 的比例变化最大。R2* 差异无统计学意义。
这些初步结果表明，在铁螯合治疗改变后仅一周即可检测到 RR2 的显著差异，这可能是由于其对可溶性铁蛋白铁的敏感性更高所致，铁蛋白铁与可螯合的细胞溶质铁池密切平衡。RR2 测量可能为监测心肌铁过载患者铁螯合剂短期疗效提供一种新方法。
