The intravoxel incoherent motion MRI of lateral pterygoid muscle: a quantitative analysis in patients with temporomandibular joint disorders.

Objectives: To quantitatively evaluate diffusion and perfusion status of lateral pterygoid muscle (LPM) in patients with temporomandibular joint disorder (TMD) by intravoxel incoherent motion (IVIM) imaging and to correlate with findings on temporomandibular joints (TMJs) by conventional MRI.

Methods: 42 patients with TMD underwent MRI. To assess IVIM parameters, diffusion-weighted imaging was obtained by spin-echo-based single-shot echoplanar imaging. Regions of interest were created on all diffusion-weighted images of the superior belly of the lateral pterygoid (SLP) and inferior belly of the lateral pterygoid (ILP) at b-values 0-500 s mm. Then, IVIM parameters, diffusion (D) and perfusion (f) were calculated using biexponential fittings. The correlation of these values with conventional MRI findings on TMJs was investigated.

Results: For SLP, the f parameter in TMJs with anterior disc displacement without reduction was significantly higher than that in normal ones (p = 0.015). It was also significantly higher in TMJs with joint effusion than in those without (p = 0.016). On the other hand, for both SLP and ILP, the D parameter significantly increased in TMJs with osteoarthritis compared with those without (p = 0.015 and p = 0.022, respectively).

Conclusions: Pathological changes of LPM in patients with TMD may be quantitatively evaluated by IVIM parameters.