CEST MRI for diagnosing the activity of thyroid-associated ophthalmopathy: Added value to magnetization transfer imaging

Motivation: Thyroid-associated ophthalmopathy (TAO) progresses from active phase characterized by inflammatory cell infiltration and glycosaminoglycan production and follows by inactive phase marked by collagen deposition and fibrosis. It's unknown if the pathological change can be measured by chemical exchange saturation transfer (CEST) MRI. Goal(s): Investigate the value of CEST for distinguishing active from inactive TAO. Approach: 53 active and 35 inactive TAO were enrolled. Magnetic-transfer-ratio (MTR) and MTR-asymmetry (MTRasym) at 1ppm, 2ppm and 3.5 ppm of extraocular muscles (EOMs) were analyzed. Results: The MTR and MTRasym_1ppm can significantly distinguish the activity of TAO, and their combination can significantly improve the diagnostic performance. Impact: TAO is treated differently according to activity. Our results showed CEST may measure the pathological change which provided significant added value to magnetization transfer imaging for diagnosing TAO activity. The application of CEST would be beneficial for TAO treatment selection.