| Objective To investigate the value of MR diffusion weighted imaging (DWI) in differentiating malignant from benign lesions. Methods DWI studies using echo planner imaging (EPI) sequence with a b value of 0, 150, 300 and 500 s/mm2 respectively, as well as routine MRI, were performed in 20 healthy volunteers with normal thyroid (normal group) and 50 hyroid focal lesions (benign group n=36, including 21 cases of nodular goiter, 12 cases of thyroid adenoma and 3 cases of subacute thyroiditis; malignant group n=14, including 13 cases of thyroid carcinoma and one case of thyroid lymphoma) proved by operation or aspiration biopsy pathologically. The signal intensity(SI) and apparent diffusion coefficient (ADC) values were measured and their differences among three groups were compared. Results There was no statistical SI difference between benign and malignant group. The differences in the mean ADC values were statistically significant between benign and malignant group with a b value of 150, 300 and 500s/mm2, respectively. However the statistical differences between malignant or benign lesions and normal group were uncertain with different b values. The one-side upper limits of 95% confidence interval of mean ADC values were adopted as the thresholds to differentiate the malignant from benign lesions,and the thresholds were respectively 1.992×10-3 mm2/s,1.582×10-3mm2/s,1.410×10-3mm2/s with b values of 150, 300 and 500s/mm2. The best b value was 150 s/mm2 which was determined by receiver operating characteristic curve (ROC). The sensitivity, specificity, accuracy, positive predicative value and negative predicative value were 78.57%,84.62%,82.50%,73.33% and 88.00%, respectively. Conclusion The mean ADC value of malignant lesions is lower than that of benign lesions, and ADC value is valuable in differentiating malignant from benign lesions with a threshold of 1.992×10-3mm2/s and a b value of 150s/mm2. Objective To investigate the value of multi-slice computed tomography (MSCT) perfusion imaging in differentiating malignant from benign lesions. Methods 45 thyroid focal lesions (33 benign lesions including 21 cases of nodular goiter and 12 cases of thyroid adenoma, and 12 malignant lesions including 11 cases of thyroid carcinoma and one case of thyroid lymphoma) proved by operation or aspiration biopsy pathologically underwent MSCT perfusion imaging. The parameters of hemoperfusion such as blood flow(BF),blood volume(BV) and permeability surface area product(PS) were acquired by using a software package. The parameters of time to peak(TTP) and peak enhancement(PE) were also acquired by time-indensity curve(TDC). Results The mean values of BF, BV, PS, TTP and PE in the benign group were (147.633±68.432) ml.min-1.100g-1, (302.040±153.014) ml.100g-1, ( 103.453±55.092 ) ml.min-1.100g-1, ( 28.033±8.015 ) second and(82.313±30.468) HU , respectively. The mean values of BF, BV, PS, TTP and PE in the malignant group were (130.189±83.449) ml.min-1.100g-1,(275.444±241.932) ml.100g-1,( 74.256±50.606 ) ml.min-1.100g-1,( 28.833±12.550 ) second,(86.056±70.453) HU , respectively. The mean values of BF, BV and PS of the malignant group were slightly lower than those of the benign group, while the mean values of TTP and PE were slightly higher than those of the benign group, but there was no statistically significance between the two groups. The TDC of CT perfusion imaging could be classified into 4 types. The TDC of malgnant group presented more typeⅡappearing slow ascending and long platform, whereas benign group presented more typeⅢappearing slow ascending and slow descending. A case of thyroid lymphoma showed low platform curve (typeⅣ). Conclusion TDC can provide blood flow information for thyroid focal leisions to some extent and is an applicable diagnostic method for the differentiation of benign from malignant thyroid lesions. The parameters of MSCT perfusion is not valuable in the discrimination of thyroid focal lesions. |
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