通过咬紧牙关评估咬肌的顺序变化：对T1、T2以及平衡稳态自由进动信号强度的定量分析。

Chikui Toru, Shiraishi Tomoko, Tokumori Kenji, Inatomi Daisuke, Hatakenaka Masamitsu, Yuasa Kenji, Yoshiura Kazunori

Department of Oral and Maxillofacial Radiology, Faculty of Dental Science, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka, Japan.

Acta Radiol. 2010 Jul;51(6):669-78. doi: 10.3109/02841851003702180.

BACKGROUND

The persistent muscle contractions during clenching are thought to cause some temporomandibular disorders. However, no report has so far evaluated the effect of clenching on the masticatory muscles by magnetic resonance imaging (MRI).

PURPOSE

To investigate the effect of clenching with maximum voluntary contraction on the T(1), T(2), and signal intensity (SI) of the balanced fast field-echo (b FFE) of the masseter muscle.

MATERIAL AND METHODS

A total of 11 volunteers participated. Multi-echo spin-echo echo-planar imaging was used for T(2) measurements, and multi-shot Look-Locker sequence for T(1) measurements. The Look-Locker sequence has been used for fast T(1) mapping and this method has been applied for the imaging of various tissues. In addition, the b FFE was used due to the high temporal resolution. These three sequences lasted for 10 min and the participants were instructed to clench from 60 s to 80 s after the start of the data acquisition. T(2), T(1), and SI were normalized compared to pre-clenching values.

RESULTS

T(2) decreased by clenching, which reflected a decrease of tissue perfusion due to the mechanical pressure. It increased rapidly after the clenching (peak value, 1.11+/-0.03; peak time, 16.8+/-7.6 s after the clenching), which corresponded to the reactive hyperemia and later, it gradually returned to the initial values (half period, 2.22+/-0.84 min). The change in the SI of the b FFE was triphasic and similar to that of T(2) clenching. T(1) increased after the cessation of the clenching and later gradually decreased during the recovery periods. However, the change of T(1) was quite different from that of T(2), with a lower peak value (1.04+/-0.02), a later peak time (36.0+/-28.0 s), and a longer half period (4.76+/-3.40 min) (P<0.0001, 0.0066, 0.02, respectively).

CONCLUSION

The change in T(2) was triphasic and we considered that it predominantly reflected the tissue perfusion.

背景

紧咬牙时持续的肌肉收缩被认为会导致一些颞下颌关节紊乱症。然而，迄今为止尚无报告通过磁共振成像（MRI）评估紧咬牙对咀嚼肌的影响。

目的

研究最大自主收缩紧咬牙对咬肌的T1、T2以及平衡快速场回波（b FFE）信号强度（SI）的影响。

材料与方法

共有11名志愿者参与。多回波自旋回波平面回波成像用于T2测量，多激发Look-Locker序列用于T1测量。Look-Locker序列已用于快速T1成像，该方法已应用于各种组织的成像。此外，由于高时间分辨率而使用了b FFE。这三个序列持续10分钟，参与者被要求在数据采集开始后60秒至80秒内紧咬牙。将T2、T1和SI与紧咬牙前的值进行归一化比较。

结果

紧咬牙导致T2降低，这反映了由于机械压力导致的组织灌注减少。紧咬牙后T2迅速升高（峰值，1.11±0.03；峰值时间，紧咬牙后16.8±7.6秒），这对应于反应性充血，随后逐渐恢复到初始值（半衰期，2.22±0.84分钟）。b FFE的SI变化呈三相，与T2紧咬牙时相似。紧咬牙停止后T1升高，随后在恢复期间逐渐降低。然而，T1的变化与T2的变化有很大不同，峰值较低（1.04±0.02），峰值时间较晚（36.0±28.0秒），半衰期较长（4.76±3.40分钟）（分别为P<0.0001、0.0066、0.02）。