Radiological Staging of Thyroid-Associated Ophthalmopathy: Comparison of T1 Mapping with Conventional MRI

Abstract

Background: Accurate staging of patients with thyroid-associated ophthalmopathy (TAO) is crucial for clinical decision. Full cognition of pathologic changes and staging TAO using conventional T2-weighted imaging is still limited.

Purpose: To investigate the feasibility of using T1 mapping to evaluate changes of extraocular muscles (EOMs) in TAO patients, as well as to compare T1 mapping and conventional T2-weighted imaging in staging TAO.

Materials and methods: Forty TAO patients were retrospectively enrolled. "Hot spot" and "cold spot" T1 relaxation times (T1RT_HS and T1RT_CS) of EOMs, as well as conventionally applied highest signal intensity ratio (SIR) of EOMs, were measured and compared between active and inactive groups.

Results: T1RT_CS and SIR were significantly higher in active TAOs than in the inactive ones (P < 0.001), while T1RT_HS was not (P=0.093). Meanwhile, T1RT_CS and SIR were positively correlated with clinical activity score (r = 0.489, 0.540; P < 0.001). TIRT_CS and SIR showed no significant area under curve for staging TAO (0.830 vs. 0.852; P=0.748). T1RT_CS ≥ 1000 alone showed optimal staging specificity (90.0%), while integration of T1RT_CS ≥ 1000 and SIR ≥ 2.9 demonstrated optimal staging efficiency and sensitivity (area under curve, 0.900; sensitivity, 86.0%).

Conclusions: Our findings suggest that the T1-mapping technique holds the potency to be utilized in TAO. The derived T1RT_CS of EOMs, which may be associated with fat infiltration, could be a useful biomarker to stage the disease, serving added efficiency, sensitivity, and specificity to single usage of conventional SIR.

Figure 1

Methods for measurements of T1RT_HS, T1RT_CS, and SIR: coronal T1 mapping (a) and coronal fat-suppressed T2-weighted imaging (b) in a 52-year-old male with active TAO. Two circular regions of interest measuring 5–10 mm² were placed in the area with the highest (white) and lowest (black) signal intensity by naked eye, representing T1RT_HS and T1RT_CS, respectively (a). Meanwhile, two similar-sized regions of interest were manually placed in the area of the most inflamed EOM with the highest signal intensity as well as ipsilateral temporal muscle (b). T1RT_HS, T1RT_CS, and SIR values of the left/right eye were 2426/2006 ms, 1365/1422 ms, and 4.14/3.95, respectively. T1RT = T1 relaxation time; HS = hot spot; CS = cold spot; SIR = signal intensity ratio; TAO = thyroid-associated ophthalmopathy.

Figure 2

Box-plot showing the comparisons of T1RT values and SIR between groups. An asterisk indicates a significant difference (^∗P < 0.001).

Figure 3

Receiver operating characteristic curves of significant parameters for staging TAO.

Figure 4

A 33-year-old male with active TAO (a, b) and a 54-year-old female with inactive TAO (c, d) were presented. Taken the left eye for example, the values of T1RT_HS, T1RT_CS, and SIR were 2282 ms, 1340 ms, and 3.27 for the patient with active TAO (a, b) and 2166 ms, 1062 ms, and 1.62 for the patient with inactive TAO, respectively (c, d).