| ObjectivesThis study was designed to apply CT perfusion imaging(CTPI) in normal thyroid and solitary thyroid nodules, to explore the clinical value of different perfusion parameters and time density curves in diagnosis and differential diagnosis of benign and malignant thyroid nodules.Materials and Methods21 patients with normal thyroid and 65 patients with solitary thyroid nodule (25 patients with nodular goiter,24 patients with thyroid adenoma and 16 with thyroid carcinoma) underwent CT perfusion scanning. Time-density curves (TDC) of regions of interest as well as its perfusion images and parameters including blood flow (BF), blood volume (BV), time to peak (TTP) and permeability surface (PS) were created by Siemens Body PCT software. Relative enhancement value(REV) of thyroid nodule was got according to TDC.Compared the differences of time density curve and its per-fusion parameter in different pathological types of thyroid, Evalued of the value of different perfusion parameters in differential diagnosis of benign and malignant thyro-id nodule and determine a certain threshold of perfusion parameters in the diagnosis. Results1. Time density curves of CT perfusion imaging could be classified into 5 types:a rapid ascending and rapid descending (type I), a rapid ascending and long platform (typeⅡ), a rapid ascending and slow descending (typeⅢ), a slow ascending and long platform (typeⅣ), a slow ascending and slow descending (typeV). Normal thyroids appeared more type I (10/21,47.6%), malignant group presented more typeIV(8/16,50%), whereas benign group presented more type V. There were significant differences among normal thyroid group/benign group and normal thyroid group/malignant group. No statistically significant differences were found in the benign group and malignant group.2. CT perfusion imaging clearly showed the size and contour of tumor, and the perfu-sion status of the internal tissue of tumor.The mean values of BF, BV, TTP, PS, REV in the normal thyroid group were (273.26±53.85)ml·100ml-1·min-1, (319.12±±42.35) ml/1000ml, (130.26±12.06) 0.1s, (150.71±42.37) 0.5ml·100ml-1·min-1 (86.54±20.77)HU; In the benign group, these parameters were(209.16±59.32) ml·100ml-1·min-1, (281.17±43.27)ml/1000ml, (179.82±19.99)0.1s, (172.00±47.30) 0.5ml·100ml-1·min-1, (78.92±20.11) HU; And in the malignant group, these parparameters were (253.69±39.38) ml·100ml-1·min-1, (297.59±40.19) ml/1000ml, (148.29±19.98)0.1s, (204.71±65.06) 0.5ml·100ml-1·min-1, (75.94±21.14)HU.3. There were significant differences among above three groups (normal thyroid group, benign group and malignant group) in BF, BV, PS and TTP value (P= 0.000,0.004,0.007 and 0.002 respectively). On the other hand, REV had no significant difference in all groups. In pair wise comparison among 3 groups, the differences of BF and TTP value of benign group/normal group and benign group/malignant group were statistically significant (P=0.000,0.006; 0.000, 0.000 respectively), while there were not statistically significant differences among normal group and malignant group (P=0.286,0.104 respectively).There were significant differences of PS value among malignant group/normal group and malignant group/benign group (P=0.002,0.025 respectively), while no statistically significant differences were found in the normal group and benign group (P=0.106). There were significant differences of BV value in the normal group and benign group (P=0.001), while no statistically significant differences in the malignant group/normal group and malignant group/benign group (P=0.131,0.183 respectively)。4. In the benign group, the mean values of BF,BV,TTP,PS,REV in the nodular goiter group were (189.97±65.92)ml·100ml-1·min-1, (277.05±38.14)ml/1000ml, (176.47±19.90)0.1s, (168.76±40.41) 0.5ml·100ml-1·min-1, (79.49±15.23)HU; And in the thyroid adenoma group, these parameters were (229.15±44.64) ml·1OOml-1·min-1, (285.46±48.58)ml/1000ml, (183.31±19.90)0.1s, (175.39±54.23) 0.5ml·100ml-1·min-1, (78.32±24.52)HU. There were significant differences among three groups (nodular goiter group, thyroid adenoma group and malignant group) in BF and TTP value (P=0.001,0.000 respectively). On the other hand, BV, PS and REV had no significant differences in all groups (P=0.330,0.095 and 0.863 respectively). In pair wise comparison among 3 groups, the differences of BF value of nodular goiter group/thyroid adenoma group and goiter group/ malignant group were statistically significant (P=0.012,0.000 respectively), while there were not statistically significant differences among thyroid adenoma group and malignant group (P=0.156). There were significant differences of TTP value among malignant group/nodular goiter group and malignant group/ thyroid adenoma group (P=0.000,0.000 respectivel), while no statistically significant differences were found in the nodular goiter group and thyroid adenoma group (P=0.234)5. There were more significant value of BF and TTP in differential diagnosis of benign and malignant thyroid nodule. When BF>236.746ml·100ml-1·min-1 was set as a threshold in the differential diagnosis of benign and malignant thyroid nodule, its sensitivity, specificity, positive predictive value, negative predictive value, diagnostic index and accuracy were 75%,77.60%,52.17%,90.48%, 1.526,76.92%.When TTP<174.363 0.1s was set as a threshold in the differential diagnosis of benign and malignant thyroid nodule, its sensitivity, specificity, positive predictive value, negative predictive value, diagnostic index and accuracy were 93.80%,65.30%,46.88%,96.97%,1.591,72.31%.Conclusions1. CT perfusion imaging provided quantitative information about blood flow patterns of normal thyroids and thyroid nodules, and was an applicable diagnostic method for differentiating thyroid nodules.2. TDC could be used as an applicable diagnostic method for the differentiation of normal thyroids and thyroid nodule, whereas there was not valuable in the discrimination of benign and malignant thyroid nodule.3. CT perfusion imaging was useful in distinguishing benign and malignant thyroid nodule.BF, BV and PS values in the malignant group were higher than them in the benign group, while TTP and REV values in the malignant group were less than them in the benign group.4. There were more significant value of BF and TTP in differential diagnosis of benign and malignant thyroid nodule. When BF>236.746ml·100ml-1·min-1 or TTP < 174.363 0.1s should be considered as a high possibility for malignancy.
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