| PartⅠ Quantitative analysis of normal adult thyroid at 3.0T MRObjective:To investigate the morphology,size and MR signal characteristics of normal adult thyroid.Methods:100 patients underwent head and neck MR examination from May 2015 to May 2018 in the Second Affiliated Hospital of Soochow University.Their date were retrospectively analyzed.The thyroid morphology was observed on MR image,and the quantitative parameters of size(outside angle,width,thickness,isthmus)in different age groups were measured on T2-weighted images.The signal intensity(SIs)of the thyroid gland were measured on T1WI,enhanced T1WI and T2WI,respectively.The relative signal intensity(RSIs)of thyroid gland was calculated with fat as control.The data of different age groups were statistically analyzed.Results:The width and thickness of the left lobe were(12.08±2.33)mm and(11.13±2.35)mm which were significantly shorter than those of the right lobe,which were(12.95±2.27)mm and(11.99±2.16)mm(t=-2.670,-2.743;P=0.008,0.007).The width and thickness of the right lobe and left lobe of the female group were(12.42 ± 2.19)mm,(11.47±2.10)mm and(11.55±2.18)mm,(10.71±2.26)mm,which were significantly shorter than those of the male group,which were(13.57±2.23)mm,(12.59±2.10)mm and(12.70±2.37)mm,(11.61±2.24)mm(t=-2.598,-2.661,-2.501,-1.999,respectively;P=0.011,0.009,0.014,0.048,respectively).The volume of thyroid in different age groups was(11.91±3.50)cm3,(13.18±3.69)cm3,(11.61±2.11)cm3,(10.88±2.41)cm3,(9.95±1.80)cm3,with statistically significant differences(t=2.227,4.452,2.677;P=0.034,0.000,0.011,respectively).There were statistically significant differences between the group of the 30-39 years old and the 40-59 years old(t=2.048,2.845;P=0.048,0.007).The width,thickness and outside angle of the thyroid were negatively correlated with age(r=-0.261,-0.247,-0.367,respectively;P=0.000 for all).After 50 years old,the dimension of thyroid gland decreased with age.Those MR signals of the thyroid were negatively correlated with age(r=-0.759,-0.895,-0.822 and-0.884,respectively;P=0.000 for all).Conclusion:MRI can quantitatively evaluate the shape and size of thyroid gland in normal adults,as well as MRI signal features and age-related changes,which can provide a baseline reference for the diagnosis and study of the thyroid diseases.Part Ⅱ Quantitative MRI analysis of radiation-induced changes of the thyroid in patients with nasopharyngeal carcinoma and exploration the correlation between MRI findings and doseObjective:To evaluate the value of MRI quantitative analysis in patients with nasopharyngeal carcinoma after IMRT.Methods:MRI and radiotherapy data of 32 patients who were first diagnosed with nasopharyngeal cancer and hospitalized in the Second Affiliated Hospital of Soochow University from April 2015 to April 2017 were retrospectively collected.Before,during and after radiotherapy,The thyroid morphology was observed on MR image,and the quantitative parameters of size(outside angle,width,thickness)in different age groups were measured on T2-weighted images.The signal intensity(SIs)of the thyroid gland were measured on T1WI,enhanced T1WI and T2WI,respectively.The relative signal intensity(RSIs)of thyroid gland was calculated with fat as control.The data of different age groups were statistically analyzed.Results:The width,thickness of the left and right lobes and volume of the thyroid decreased gradually before and after radiotherapy(P<0.05).The PTVs in the process of radiotherapy,in 6 months and 12 months after radiotherapy were(87.34+8.90)%,(66.47+8.68)%,(50.87+8.39)%.They were significantly negatively correlated with Dmean and V50 of the thyroid are(r=0.515,0.426,0.501 and 0.673,0.358,0.481;P=0.003,0.015,0.003 and 0.000,0.044,0.005).There was no significant correlation between PTV of the thyroid at each time point after radiotherapy and the Dmax,Dmin and V30 of the thyroid(P>0.05).There was no significant correlation between PTV of the thyroid and radiation dose of the pituitary at each time point after radiotherapy(P>0.05).The mean T1WI RSI,T2WI RSI and enhanced T1WI RSI of the thyroid decreased gradually before and after(P<0.05).At each time point after radiotherapy,thyroid T1WI RSI,T2WI RSI and enhanced TIWI RSI were negatively correlated with Dmean,V40,V45 and V50(P<0.05).There was no significant correlation between T1WI RSI,T2WI RSI,enhanced T1WI RSI and the Dmax,Dmin of the thyroid and radiation doses of the pituitary after radiotherapy(P>0.05).Conclusion:The changes of morphological,size and signal of the thyroid can be showed by quantitative analysis of MRI before and after radiotherapy in patients with NPC which reflected the changes of thyroid structural components and functions after radiotherapy.The volume,T1WI RSI and T2WI RSI of the thyroid had the most significant changes at each time point before and after radiotherapy,and had a high correlation with radiation dose,which had important clinical reference value for the evaluation and monitoring of the thyroid status in patients with nasopharyngeal cancer after radiotherapy. |
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