The Value Of DCE-MRI In Evaluating Extraocular Muscle In Normal Human And Patients With Thyroid-associated Ophthalmopathy In Different Stage

Objective:To investigate the shape of time-intensity curve (TIC) in normal extraocular muscles by using dynamic contrast-enhanced MRI(DCE-MRI), and to find the most sensitive parameter among Ktrans、Kep and Ve in evaluation of normal extraocular muscles. To investigate the shape of TIC in extraocular muscles in patients with active and stable thyroid-associated ophthalmopathy (TAO), and to calculate the threshold between the two stages, and finally to evaluate the feasibility of DCE-MRI for assessing the stage of TAO.Materials and Methods:DCE-MRI examinations were performed on36healthy controls,12patients with active TAO and17patients with stable TAO. Quantitative parameters of extraocular muscles in patients and controls, including Ktrans、Kep and Ve, were produced by post process software. The difference between corresponding parameters were compared statistically.Results:(1) Normal extraocular muscles were enhanced rapidly and prominently after injecting contrast agent. The shape of TIC were type Ⅱ or type Ⅲ. Ktrans was the most sensitive parameter in evaluation of normal extraocular muscles. Microcirculatory status of medial rectus and inferior rectus were the most active.(2)89.6%of the shape of TIC of rectus in active TAO were type Ⅱ and95.6%of the shape of TIC in stable TAO were type Ⅰ. There were significant differences in Ktrans、Kep between active TAO and stable TAO(P<0.05), and mean values of parameters in patients with stable TAO were lower than patients with active TAO.(3) Ktrans value was the most sensitive parameter for differentiating stages of TAO.(4) Each extraocular muscle had different microcirculatory status in active TAO, and microcirculatory status of all extraocular muscles had a tendency to reach a consistency in stable TAO. Inferior rectus and medial rectus were involved most easily. The threshold for Ktrans of stable TAO compared with active TAO was under0.107for medial rectus、under0.121for inferior rectus、under0.103for lateral rectus and under0.137for superior rectus. Conclusion:Quantitative parameters of DCE-MRI can evaluate the microcirculatory status of extraocular muscles. And Ktrans is the most sensitive and reliable parameter for reflecting and differentiating the microcirculatory status of the four extraocular muscles. Ktrans can evaluate extraocular muscles involvement in patients with TAO, and it can be used in differentiating stages of TAO.