正常成人下直肌年龄相关性变化的MR动态增强观察

Age-related changes of normal adult inferior rectus muscle： analysis with dynamic contrast-enhanced magnetic resonance imaging

目的探讨正常成人下直肌血供及细胞外间隙体积随年龄增长的变化趋势，评估眼外肌组织内的微循环血流状态，为眼外肌疾病的诊断和治疗提供重要信息。方法选取2009年1月至2010年6月在北京同仁医院250例行鼻窦动态增强MR检查的受检者进行研究。按年龄划分为5组（320～30岁，330—40岁，340—50岁，350—60岁，≥60岁）。增强扫描采用三维快速扰相梯度回波序列，扫描时间为4min59s，共采集12个时相。在图像后处理工作站上获取下直肌眶侧、球侧和同侧颞肌的动态增强曲线，测出参数增强前的信号强度（Slpre）、增强后最大信号强度（Slmax）、第12个时相的信号强度（Slphase12），计算峰值信号强度（Slpeak）、Tpeak、流出率（WR），并进行统计学分析。结果各年龄组眶侧Slpeak分别为404．7±12．7，395．1±15．9，367．3±5．1，307．0±12．4，265．3±6．2；Tpeak分另0为（85．2±1．0）S，（93．2±8．1）s，（106．8±4．6），（122．8±8．6）S，（133．0±0．8）s；WR分别为（9．25±0．50）％，（8．25±0．50）％，（7．50±0．58）％，（4．75±1．26）％，（3．50±1．73）％。球俱4Slpeak分另0为261．9±2．1，256．6±1．1，243．8±3．3，225．4±4．9，219．8±5．3；Tpeak分另0为（157．8±1．7）S，（166．5±4．5）S，（173．2±7．2）S，（192．8±9．1）S，（200．5±2．4）s；WR分另0为（7．25±0．50）％，（6．27±0．00）％，（4．50±0．58）％，（3．75±0．50）％，（2．25±1．50）％。颞肌Slpeak、Tpeak及WR各年龄组间差异无统计学意义（P〉0．05）。随年龄增长，Tpeak值逐渐增大，Slpeak、WR值逐渐减小，眶侧Tpeak随年龄增长变化更敏感（P〈0．05）。结论MR动态增强成像可无创性反映随年龄增长下直肌血供、细胞外间隙体积发生的变化，为眼外肌疾病的诊断和治疗提供了重要信息。

Objective To explore the age-related changes of blood supply and extracellular space volume in normal adult inferior rectus muscle, evaluate the microcirculation in extraocular muscle and offer important information for the diagnosis and treatment of extraocular muscle disorders. Methods A total of 250 patients undergoing nose-sinus dynamic contrast-enhanced magnetic resonance imaging were studied. Five groups were divided according to age （20 -30 yr old, 30 -40 yr old, 40 -50 yr old, 50 -60 yr old and over 60 yr old）. The technique of 3 DFSPGR （3-dimensional fast spoiled gradient-recalled） was used in dynamic contrast-enhanced imaging scanning 4 minutes and 59 seconds and acquiring 12 phases. Time-intensity curves of orbital layer, global layer of inferior rectus muscle and temporal muscle ipsilaterally were drawn on post-process work station. From the curves, the values of SIpre, Slmax and SIphasel2 were obtained and then SIpeak （peak signal intensity）, Tpeak （time of peak enhancement） and WR （washout ratio） computed. The data were analyzed statistically. Results SIpeak of orbital layer in all groups was as follows： 404.7 ± 12.7,395.1 ± 15.9,367.3 ± 5.1,307.0 ± 12.4 and 265.3 ± 6.2 respectively. Tpeak： （85.2 ± 1.0） s, （93.2 ± 8.1 ） s, （ 106. 8 ± 4. 6）, （ 122. 8 ± 8.6） s and （ 133.0 ± 0. 8 ） s respectively. WR ： （9. 25 ±0. 50） %, （8.25 ± 0. 50） %, （7.50 ± 0. 58 ） %, （4. 75 ± 1.26） % and （3. 50 ± 1.73）% respectively. Slpeak of global layer in all groups was as follows：261.9 ± 2. 1,256. 6 ± 1.1,243.8 ± 3.3,225.4 ±4. 9 and 219.8 ± 5.3 respectively. Tpeak ： （ 157.8 ± 1.7 ） s, （ 166. 5 ± 4. 5 ） s, （173.2±7.2） s,（192.8±9.1） sand （200.5±2.4） srespectively. WR： （7.25±0.50）%, （6.27± 0.00）%, （4.50±0.58）%, （3.75 ±0.50）% and （2.25 ±1.50）% respectively. SIpeak, Tpeak and WR of temporal muscle in all groups showed no statistical significance （ P 〉 0. 05 ）. Tpeak increased while Slpeak and WR decreased with age. Furthermore the changes of Tpeak of orbital layer were more sensitive. Conclusion Dynamic contrast-enhanced magnetic resonance imaging can non-invasively reflect the age-related changes of blood supply and extracellular space volume in normal adult inferior rectus muscle so as to offer important information for the diagnosis and treatment of extraocular muscle disorders.