Quantitative MRI Assessment of Orbital Structures in Radioactive Iodine-131 Therapy for Inactive Graves'...

The understanding regarding the role of orbital magnetic resonance imaging (MRI) in predicting the prognosis of radioactive iodine-131 (I-131) therapy for patients with inactive Graves' ophthalmopathy (GO) is limited. Therefore, this study aimed to explore the application of MRI quantitative measurements of orbital structures in radioactive I-131 therapy for inactive GO.

This retrospective study included 41 patients (82 eyes) diagnosed with GO at Anhui Medical University Affiliated Fuyang Hospital and Anhui Medical University First Affiliated Hospital from January 2022 to October 2025 as the GO group, and 32 patients (64 eyes) with Graves' disease (GD) who were matched with the GO group in terms of gender and age were selected as the GD group. All patients were treated with radioactive I-131 using the calculated dose method. MRI conventional images and readout segmentation of long variable echo-trains diffusion-weighted imaging (RESOLVE DWI) were performed before and after I-131 treatment, as well as the thyroid technetium (^99mTcO4-) imaging using single-photon emission computed tomography/computed tomography (SPECT/CT), and a correlation analysis was conducted between the changes in orbital MRI parameters and thyroid weight in GO patients. All eyeball parameters are taken as the average of the two eyes.

Before radioactive I-131 treatment, there were statistically significant differences in the average values of apparent diffusion coefficient (ADC) of the lacrimal gland and the long diameter of the transverse lacrimal gland between the GO group and the GD group (p ≤ 0.01). However, there was no statistically significant difference in the coronal lacrimal gland parameters of MRI and the thyroid parameters of SPECT/CT (p > 0.01). There was a statistically significant difference in the MRI orbital parameters (lacrimal gland protrusion [13.65 ± 1.47 vs. 12.02 ± 1.25], the long diameter [17.21 ± 2.29 vs. 16.03 ± 228], and area [93.05 ± 15.66 vs. 84.68 ± 14.76] of the lacrimal gland in the cross-section; longitudinal diameter [17.99 ± 2.71 vs. 17.67 ± 2.61] and area [109.81 ± 20.52 vs. 104.50 ± 19.03] of the lacrimal gland in the coronal plane) between the GO group before and after radioactive I-131 treatment (all p < 0.001). In addition, thyroid weight (53.53 ± 27.28 vs. 48.22 ± 23.65, p < 0.001), thyroid area (28.08 ± 10.25 vs. 24.89 ± 8.74, p < 0.001), and thyroid technetium uptake (17.82 ± 11.34 vs. 15.14 ± 9.57, p < 0.001) measured by SPECT/CT were also decreased. The change values of lacrimal gland protrusion (r = 0.600), the mean ADC (r = 0.766), the long diameter (r = 0.748), and area (r = 0.678) of the transverse lacrimal gland and the long diameter (r = 0.683) and area (r = 0.560) of the coronal lacrimal gland in the GO group before and after radioactive I-131 treatment were positively correlated with the change values of thyroid weight (all p < 0.05).

In patients with GO, lacrimal gland protrusion, MRI lacrimal gland length and area, and mean lacrimal gland ADC value may be reliable imaging indicators for evaluating the I-131 treatment.