Objective:To investigate the feasibility and reproducibility of using three-dimensional arterial spin labeling (3D-ASL) technique to evaluate the thyroid blood flow (TBF) in healthy adults and compare the difference in TBF between subjects with different gender and age.Methods:In this prospective study, 100 healthy adult subjects were enrolled from November 2018 to June 2019 in Chinese Academy of Medical Sciences Cancer Hospital, Shenzhen Hospital. All subjects received thyroid 3D-ASL MRI scanning, but several subjects were excluded from analysis for reasons including intolerance to examination ( n=1), overt artifacts ( n=11), abnormality detected in thyroid gland during conventional MRI ( n=15), resulting in 73 subjects included. Two attending radiologists independently evaluated the quality of ASL images and measured the TBF in upper, middle and lower poles of each lobe in thyroid gland bilaterally. Cohen’s Kappa was used to test the agreement in image quality between 2 radiologists, while intraclass correlation (ICC) analysis was implemented to evaluate the consistency in TBF measurements. Univariate variance analysis was used to compare the TBF in upper, middle and lower pole of thyroid gland unilaterally, and student t-test was performed to test the difference in TBF between two lobes, or in the same lobe but between different gender or age groups. Results:For image quality, 2 radiologists have good agreement (Kappa=0.753, P<0.001). In terms of TBF, consistency was moderate in the lower pole of left lobe between 2 radiologists (ICC=0.648, P<0.001), but good in the remaining parts of thyroid gland (all ICC>0.75, P<0.001). Unilaterally, TBF in the middle pole was significantly higher than those in the upper or lower pole ( P<0.001), but no significant difference was found between the upper and lower pole ( P>0.05). Regardless of upper, middle or lower pole, TBF in the right lobe was higher than the counterpart in the left lobe ( t=6.182, 6.294, 4.896, P<0.001). Between male subjects ( n=31) and female subjects ( n=42), no significant difference was found in the corresponding upper, middle or lower pole of thyroid lobe unilaterally ( P>0.05). As for age group, TBF in the middle pole of thyroid gland was higher in the middle age group (45-59 years old, n=12) than that in the young adult group (18-44 years old, n=61) ( t=3.868, P=0.003 for the left lobe, and t=2.647, P=0.022 for the right lobe), but no significant difference was found in the upper or lower pole of the unilateral thyroid lobe ( P>0.05). Conclusion:ASL can accurately measure blood flow perfusion in the thyroid gland with good reproducibility.

Objective:To explore the value of multi-parametric MRI for thyroid gland in differentiating benign and malignant thyroid nodules.Methods:From December 2018 to May 2020, 78 patients with 91 post-surgically pathologically confirmed thyroid nodules were enrolled in Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College. For each patient, the following MRI findings were obtained including the nodules′ location, size, shape, margin, signal intensity, cystic change, degree and pattern of contrast enhancement, involvement of surrounding structure, and ADC values. The time-intensity curve (TIC) were plotted and subtyped based on dynamic contrast enhancement MRI. The MRI findings between the benign and malignant thyroid nodules were compared using Mann-Whitney U test, χ 2 test or Fisher exact test. Multiple logistic regression analysis was used to select independent predictive variables and build a combined model, and the ROC curve was used to evaluate the diagnostic performance of each MRI finding and the combined model. Results:Between the benign and malignant thyroid nodules, the significant differences were found in size, shape, margin, presence of cystic changes, T 1WI signal intensity, ADC value, enhancement homogeneity, TIC subtypes and presence of thyroid capsule involvement ( P<0.05). Multivariate logistic analysis showed that ill-defined margin (OR=77.61), no presence of cystic changes (OR=36.11) and difference between TIC subtypes (OR=83.41) were independent predictive variables, and the area under the ROC curve (AUC) was 0.879, 0.788, and 0.751, respectively. The AUC, sensitivity and specificity of the combined model were 0.977, 0.986, and 0.904, respectively. Conclusions:Thyroid multi-parametric MRI derived findings can be used for the differential diagnosis of benign and malignant nodules. Combined with the independent risk factors with ill-defined margin, no presence of cystic changes, TIC of type plateau or washout, the diagnostic model has a higher diagnostic efficiency.