| Part 1:Preliminary study on image quality optimization of thyroid diffusionweighted imaging,voxel incoherent motion and dynamic contrast enhanced MRI Purpose:To explore the methods of optimizing the image quality of diffusionweighted imaging(DWI),intra voxel incoherent motion(IVIM)and dynamic contrast enhanced MRI(DCE-MRI)Method:A total of 54 patients were included in the study.DWI?IVIM and DCEMRI scans were performed with head and neck coils and eight-channel cervical surface coils,respectively.The scanning positions included axial and coronal scans.The quality of DWI?IVIM?DCE images at different coils and scanning azimuth were compared.Ten patients were scanned by conventional DWI and resolve-DWI at the same time,and the difference of image quality between the two sequences was compared.Results: When using combined head and neck coils scan,the image quality scores of different sequences were:3 or more of DWI in 9 cases,accounting for 60%(9/15),8 case of IVIM images with 3 points and above,accounting for 53%(8/15),of DCE-MRI scans,18 cases with 3 or more points,accounting for 90%(18/20).When the cervical surface coil was used,the image quality scores of different sequences were: 3 or more points of DWI in 32 cases accounting for 94%(32/34),and IVIM images of 3 or more in 32 cases,accounting for 94%(32/34),and in 34 cases of DCE-MRI image with 3 points or more,accounting for 100%(34/34).The image quality scores of DWI and IVIM scanning with cervical surface coil were significantly higher than those with head and neck coils,and the difference was statistically significant(P < 0.05).For DCE-MRI,there was no significant difference in image quality between the two groups(P =0.320,>0.05).In axial scanning,the image quality scores of different sequences were: 1 points in all DWI and IVIM images,accounting for 100%(5/5).When coronal scan was used,9 cases with image quality score were 3 points or more on DWI,accounting for 60%(9/15),8 cases had 3 points or more on IVIM images,accounting for 53%(8/15).The image quality score of coronal scan was significantly higher than that of axial scan.The difference was statistically significant(P < 0.05).There were 8 cases(80%,8/10)of conventional DWI surface coil coronal images and 10 cases(100%,10/10)of high resolution DWI surface coil axial images,which image quality with 3 points or more.The quality score of high resolution DWI images was significantly higher than that of conventional DWI images(P < 0.05).Conclusion: In DWI and IVIM examination of thyroid lesions,coronal scan and surface coil could significantly improve the image quality.The image quality and lesion details of high-resolution DWI scan were significantly higher than that of conventional DWI.In DCE-MRI images,the signal-to-noise ratio(SNR)was high,and different coils have little effect on image quality.Part2:Application of functional MRI in differential diagnosis of benign and malignant thyroid lesions Purpose: To explore the value of diffusion-weighted imaging(DWI),intravoxel incoherent motion(IVIMI)and quantitative dynamic contrast enhanced Mr imaging(DCEMRI)in differential diagnosis of benign and malignant thyroid lesions.Methods: Among 54 patients with thyroid disease,21 cases were included in the study.All 21 cases were examined by DCE-MRI and 17 cases by DWI and IVIM.According to the results of pathological examination,all the pathological changes were divided into benign lesion group and malignant lesion group.The difference of quantitative parameters of DWI?IVIM and DCE-MRI in benign,malignant and normal tissues was analyzed and statistically analyzed.Results: There were 8 benign lesions,9 malignant lesions and 17 normal tissues in DWI and IVIM quantitative analysis.The standard ADC values in benign,malignant and normal thyroid tissues were respectively(1.608±0.232?1.463±0.434?1.357±0.249)x10-3mm2/s,D values were(1.789±0.335?1.360±0.260?1.275±0.179)x10-3mm2/s,D* values were(0.047±0.053?0.034±0.031?0.023±0.011)x10-3mm2/s,and f values were(0.228±0.081?0.192±0.079?0.313±0.096)?The difference of D value between benign and malignant thyroid lesions was statistically significant,the area under ROC curve was 0.819,the best diagnostic threshold was 0.514,the sensitivity and specificity were 0.889 and 0.625 respectively.And there were significant differences in D value between benign and normal thyroid tissues,and f values between malignant and normal thyroid tissues.In the DCE examination,there were 8 benign lesions,13 malignant lesions and 21 normal tissue,Ktrans values in benign,malignant and normal tissues were respectively(0.240±0.074?0.328±0.143?0.228±0.887)min-1,Kep values were(1.355±0.265?1.241±0.217?1.506±0.194)min-1?Ve values were(0.189±0.088?0.264±0.092?0.150±0.04).There was statistically significant difference between malignant lesions and normal group in kep ve values.There was no significant difference in the value of Ktrans?Kep?Ve between benign and malignant thyroid lesions(P > 0.05).Conclusion: The IVIM parameter D f can effectively distinguish benign and malignant thyroid lesions,and the sensitivity of D value is higher than the standard ADC value. |
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