The Study Of Intravoxel Incoherent Motion Diffusion-weighted Imaging And Dynamic Contrast-enhanced MRI In The Diagnosis Of Gastric Cancer

Part Ⅰ Value of Intravoxel Incoherent Motion（IVIM）Diffusion-weighted Imaging in the Diagnosis of Pathologic Grades for Gastric CancerObjective: To study the clinical significance of intravoxel incoherent motion diffusion-weighted imaging（IVIM-DWI）in the diagnosis of pathologic grade for gastric cancer,and to investigate the correlation between IVIM parameters and the degree of differentiation of gastric adenocarcinoma.Methods: A total of 97 patients with different pathologic grade of gastric adenocarcinoma which were diagnosed histologically from September 2014 to January 2017 in Affiliated Hospital of North Sichuan Medical College.All the patients were performed with a abdominal scans using the 3.0T（US GE Discovery 750）Magnetic Resonance Imaging Scanner,including conventional T1 WI,T2WI,multiple b-values IVIM-DWI sequences and T1WI-LAVA dynamic contrast enhanced scan sequence.The b values of the DWI sequence were 0,30,50,80,100,300,500,800,1000,1500 s / mm²,respectively.Regions of interest（ROIs）were selected on the DWI imaging through the Functool-MADC model of GE AW 4.4 workstation by two MRI readers.The standard apparent diffusion coefficient（ADCstd）map,the slow apparent diffusion coefficient（D）map,fast apparent diffusion coefficient（D*）map and perfusion fraction（f）were calculated by the workstation,then the ADCstd,D,D* and f values of the tumor areas were obtained.One-way analysis of variance was used to analysis the difference of the IVIM-DWI parameters among the three groups of patients with well,moderate and poor differentiation of gastric cancer.Results: Pathological types of the 97 patients included poorly differentiated adenocarcinoma（62 cases）,moderately differentiated adenocarcinoma（18 cases）,and well differentiated adenocarcinoma（17 cases）.The ADCstd,D,D* and f values of poorly differentiated gastric cancer were,respectively,（1.34±0.27）×10^-3 mm² /s,（0.95±0.13）×10^-3 mm² /s,（17.76±5.99）×10^-3 mm² /s,and（55.90±8.96）%.The ADCstd,D,D* and f values of moderately differentiated gastric cancer were,respectively,（1.56±0.24）×10^-3 mm² /s,（1.09±0.12）×10^-3 mm² /s,（19.18±3.66）×10^-3 mm² /s,and（50.79±7.11）%.The ADCstd,D,D* and f values of well differentiated gastric cancer were（1.93±0.46）×10^-3 mm² /s,（1.26±0.15）×10^-3 mm² /s,（19.05±9.50）×10^-3 mm² /s,and（49.75±6.93）%,respectively.the difference of ADCstd and D values in gastric cancers with different differentiation degrees were statistically significant（P <0.05）.The f value of poorly differentiated gastric cancer is significantly higher than that of moderate and well differentiated groups（P <0.05）,but there was no significant difference between moderately differentiated group and well differentiated group（P> 0.05）.The difference of D* value in different differentiation groups was not statistically significant（P> 0.05）.Conclusion: The IVIM-DWI parameters have certain value in the diagnosis of different pathological grades of gastric cancer.The ADCstd and D values are negatively correlated with the pathological grades of gastric cancer,and the f value of poorly differentiated gastric cancer is significantly higher than that of moderate and well differentiated groups.The diagnostic ability of D* value in different pathological grades of gastric cancer remains to be further studied.Part Ⅱ The Study of Dynamic Contrast-enhanced MRI Perfusion Parameters in the Diagnosis of Gastric CancerObjective: To study the clinical significance of dynamic contrastenhanced magnetic resonance imaging（DCE-MRI）in the diagnosis of gastric cancer,as well as to investigate the ability of DCE-MRI perfusion parameters to differentiate the gastric cancer tissues and paracancerours tissues and their ability to differentiate different pathological grades of gastric adenocarcinoma.Methods: A total of 30 patients with different pathologic grade of gastric adenocarcinoma which were diagnosed histologically from March 2016 to January 2017 in Affiliated Hospital of North Sichuan Medical College.All of the patients were performed with abdominal scans using the 3.0T（US GE Discovery 750）Magnetic Resonance Imaging Scanner.The scanning sequences include conventional T1 WI,T2WI,multiple b-value DWI,multiple flip angle T1WI-LAVA and T1WI-LAVA dynamic contrast enhanced scan sequence.The Qmitk-DCE-Tool of Omni-Kinetics software（GE）was used to analyze the multiple flip angle T1WI-LAVA and T1WI-LAVA dynamic contrast enhanced imagings by two MRI readers.The Ktrans map,Kep map,Ve map and i AUC map were calculated by the post-processing software,then the Ktrans,Kep,Ve and i AUC values of the gastric cancer tissues and paracancerours tissues were obtained.The perfusion parameters of gastric cancer and paracancerours tissues were compared by using independent-sample T test,and comparison of the perfusion parameters in different pathological grades of gastric cancer patients by using one-way analysis of variance.Results: Pathological types of the 30 patients included poorly differentiated adenocarcinoma（21 cases）,moderately differentiated adenocarcinoma（3 cases）,well differentiated adenocarcinoma（6 cases）.The Ktrans,Kep,Ve and i AUC values of gastric adenocarcinoma tissue were（0.37±0.15）min^-1,（0.58±0.22）min^-1,0.49±0.22,8.07±4.49,respectively.The Ktrans,Kep,Ve and i AUC values of paracancerours tissues were（0.16±0.07）min^-1,（0.31±0.18）min^-1,0.43±0.21,2.08±0.80,respectively.The perfusion parameters of gastric cancer were higher than those of paracancerours tissues,the difference of Ktrans,Kep,and i AUC values were statistically significant（P <0.05）,however,the Ve value was not statistically significant（P> 0.05）.There were no significant differences in the parameters of Ktrans,Kep,Ve and i AUC among the different gastric cancer groups（P> 0.05）.Conclusion: DCE-MRI has a certain diagnostic value for gastric cancer.The Ktrans,Kep,and i AUC values can make a identification of gastric cancer tissue and no cancerous invasion of the stomach wall with non-invasive method which can provide a certain reference value for the clinicians to develop gastric cancer treatment plan.DCE-MRI perfusion imaging can also reflect the changes of local microvascular perfusion and permeability in gastric cancer.But according to the tumor perfusion parameters to infer the degree of tumor differentiation is not reliable,more further studies are needed.