正常人踝关节屈伸运动时小腿肌肉的在体速度编码相位对比MRI研究

The velocity encoded phase contrast MRI study of normal calf muscle contractile function in vivo during ankle flexion and extension movement

目的探讨采用速度编码相位对比MRI（VE—PCMRI）技术研究正常人小腿肌肉在体运动生物力学特征的价值。方法24名健康受试者，按年龄分为青年组（30～40岁）和老年组（60～78岁）。所有受试者平卧于MR仓内，进行周期性踝关节主动屈伸运动。应用VE—PCMRI技术，采集左小腿胫骨前肌（TA）、腓肠肌内侧头（MG）和比目鱼肌（SOL）的运动图像，1个屈伸运动周期包括20个时相。通过软件分析小腿肌肉的收缩速度，采用Mann—Whitney U秩和检验比较两组受试者小腿肌肉在体收缩速度的差异。结果在踝关节进行周期性屈伸运动时，背伸阶段（1～10时相），2组受试者TA均表现为向心收缩；跖屈阶段（11—20时相），2组受试者MG及SOL均表现为向心收缩。在背伸阶段中的第3～6时相，青年组TA收缩速度（中位数值分别为：-37．66、-53．00、-60．66、-56．00mm／s）大于老年组（中位数值分别为：-30．33、-42．49、-53．00、-48．67mm／s），在跖屈阶段中的第13—15时相，青年组MG收缩速度（中位数值分别为：-47．66、-60．00、-66．33mm／s）大于老年组（中位数值分别为：-25．17、-37．99、-50．98mm／s），跖屈阶段中的第12—14时相，青年组SOL收缩速度（中位数值分别为：-27．21、-40．10、-49．13mm／s）大于老年组（中位数值分别为：-20．66、-29．61、-37．16mm／s），差异均有统计学意义（P值均〈0．05）。结论踝关节周期性屈伸运动时，老年组TA、MG及SOL收缩功能下降。VE—PCMRI技术可以反映小腿肌在体活动的生物力学特点，为肌肉功能在体评估提供依据。

Objective To explore the characteristics of calf muscle movement of the normal volunteer in vivo by velocity encoded phase contrast MRI （VE-PC MRI）. Methods Twenty four healthy subjects were divided into the young group （30-40 years ） and the elderly group （60-78 years ）. All subjects were positioned on the scanner table and did ankles flexion-extension voluntary movement, the moving images of tibialis anterior muscles （TA）, medial gastrocnemius （MG） and soleus muscle （SOL）on the left were scanned with VE-PC MRI. The calf muscles contraction velocity were analyzed by software. The Mann-Whitney U test was used for comparison of calf muscles contraction velocity in vivo between the young group and the elderly group. Results During cyclic ankle flexion-extension, dorsiflexion phase （1- 10 phases）in the two groups, TA showed concentric contraction, plantar flexion phase （11-20 phases） , MG and SOL did concentric contraction. At 3-6 phases during dorsiflexion, velocity of TA （M value： -37. 66, -53.00, -60. 66, -56. 00 mm/s ） in the young group is higher than in the elderly group （M-value： - 30. 33, - 42. 49, - 53.00, - 48.67 mm/s）, at 13--15 phases during plantar flexion, velocity of MG （M-value ： - 47.66, - 60. 00, - 66. 33 mm/s） in the young group showed higher velocity than in the elderly group （M-value： -25.17, -37.99, -50. 98 mm/s）, at 12-14 phases during plantarflexion, SOL showed higher velocity in the young group （M-value： -27.21, -40. 10, -49. 13 mm/s） than in the elderly group （M-value ： - 20. 66, - 29.61, - 37.16 mm/s） （ all P 〈 0. 05 ）. Conclusions During active ankle cyclic flexion-extension movement, velocity of TA, MG and SOL in the elderly group are decreased as compared to the young group. VE-PC MRI can reflect biomechanical characteristics of calf muscle in vivo, and provide a new kind of measurement for lower extremities.