Section on Experimental Radiology, Department of Diagnostic Radiology, University Hospital of Tübingen, Hoppe-Seyler-Str. 3, 72076 Tübingen, Germany.
MAGMA. 2011 Aug;24(4):201-9. doi: 10.1007/s10334-011-0254-y. Epub 2011 May 15.
Examination of blood perfusion in the masseter muscle in the course of repetitive isometric contraction by arterial spin-labeling (ASL) MR imaging and additional T2 relaxation time measurements during and after masseter muscle activation.
Anatomical and ASL imaging was performed (3 T) in the masseter muscle of seven healthy volunteers before and after sustained clenching (30s) at maximum voluntary contraction (MVC). Several cycles of clenching were repeated in an overall period of 11 min. ASL imaging was performed by an adapted FAIR-TrueFISP technique. Time to peak and time to baseline were systematically analyzed in recorded perfusion curves. T2 relaxation times were estimated using a multi-echo spin-echo sequence. The influence of MVC on T2 was statistically analyzed.
In all cases, perfusion imaging and assessment of T2 relaxation time was feasible. Mean perfusion values at rest calculated from all volunteers were 97.9 ± 17.1 ml/min/100 g (right masseter) and 83.0 ± 18.1 ml/min/100 g (left masseter). The percentage mean perfusion increase in all volunteers immediately after clenching ranged between 114 and 154%. Mean time to peak was 13.7 s (range: 8.0-26.7 s; SD 5.6 s), and mean time to baseline was 25.6 s (range: 18.7-37.0 s; SD 5.4 s). No significant influence of MVC on T2 relaxation time was found, although a tendency to T2 increase after each clenching stress was observed.
Clear contraction-related perfusion changes of the masseter muscle could be assessed in high spatial and temporal resolution by means of ASL. In contrast, no significant T2 changes were measured. ASL imaging could serve as supplementing tool for studying masticatory function and dysfunction.
通过动脉自旋标记（ASL）磁共振成像（MRI）检查在重复等长收缩过程中咀嚼肌的血液灌注，并在咀嚼肌激活过程中和之后测量 T2 弛豫时间，以评估咀嚼肌的血液灌注。
对 7 名健康志愿者的咀嚼肌进行解剖学和 ASL 成像（3T），在最大自主收缩（MVC）前和持续咬牙（30s）后进行。在总共 11 分钟的时间内重复多次咬牙周期。ASL 成像采用改良的 FAIR-TrueFISP 技术进行。在记录的灌注曲线中系统地分析达峰时间和基线时间。使用多回波自旋回波序列估计 T2 弛豫时间。统计分析 MVC 对 T2 的影响。
在所有情况下，均可行灌注成像和 T2 弛豫时间评估。所有志愿者静息状态下计算的平均灌注值为 97.9±17.1ml/min/100g（右侧咀嚼肌）和 83.0±18.1ml/min/100g（左侧咀嚼肌）。所有志愿者咬牙后即刻的平均灌注增加百分比在 114%至 154%之间。平均达峰时间为 13.7s（范围：8.0-26.7s；标准差 5.6s），平均基线时间为 25.6s（范围：18.7-37.0s；标准差 5.4s）。尽管在每次咬牙应激后观察到 T2 增加的趋势，但未发现 MVC 对 T2 弛豫时间有显著影响。
通过 ASL 可在高空间和时间分辨率评估咀嚼肌的清晰与收缩相关的灌注变化。相反，未测量到明显的 T2 变化。ASL 成像可以作为研究咀嚼功能和功能障碍的补充工具。
