The Diagnostic Value Of Reduced Filed Of View Diffusion Weighted Imaging And Intravoxel Incoherent Motion Diffusion-Weighted Imaging In Pancreatic Tumors

Part I.The clinical value of reduced field of view(R-FOV)diffusion weighted imaging(DWI)in pancreatic tumorsObjective:To study the image quality(IQ)and apparent diffusion coefficient(ADC)of R-FOV DWI compared with F-FOV DWI obtained by single shot echo planar imaging,and to explore the application value of R-FOV DWI diffusion weighted imaging in pancreatic solid diseases.Methods:Ninety-seven patients with pancreatic solid diseases were enrolled after Ethics Committee approval and signing the informed consent.Conventional diffusion-weighted imaging and reduced field of view diffusion-weighted imaging were performed on the 3T magnetic resonance imaging equipment.Two experienced abdominal physicians independently assessed the image quality of the participants while the clinical condition of the participants and the use of MRI sequences were completely blinded.A consistency analysis on the subjective scores given by the two physicians was performed.The SNR and ADC values of the head,body,and tail of the pancreas were measured by another experienced diagnostician.The Wilcoxon signed rank test and t test were used to compare the qualitative scores and ADC between the two DWI sequences.Results:In the qualitative analysis,the subjective scores of R-FOV DWI(b=600 s/mm2)was better than that of F-FOV DWI(b=600 s/mm2,p<0.01)and it was better than F-FOV DWI in terms of anatomical clarity(2.87±0.63 vs 2.34±0.36),lesion display(3.23±0.52 vs 2.77±0.24),artifact and deformation(3.16±0.46 vs 2.56±0.29)and overall image quality score(9.26±1.61 vs 7.67±0.89).In the quantitative analysis,the ADC values of the head,body and tail of the pancreas obtained by the R-FOV DWI sequence were 1.68±0.32,2.12±0.43 and 1.89±0.37,and the SNR values were 9.46±2.56,10.56±2.98 and 8.35±3.68.The ADC values of the head,body and tail of the pancreas obtained by the F-FOV DWI sequence were 1.76±0.25,2.21±0.17 and 2.01±0.34,while the SNR was 10.26±2.52,11.23±1.73,and 8.97±2.21,and there was no statistical difference between SNR and ADC values in the two sequences(p>0.05).The ADC value of R-FOV DWI sequence(2.01±0.22)was significantly lower than that of normal substantive ADC value(1.67±0.14,t=-10.27,p<0.01).Conclusion:The overall imaging quality and lesion display of R-FOV DWI are better than that of F-FOV DWI,and R-FOV DWI can reduce image distortion and artifacts.There was no statistical difference between the ADC values obtained from each part of the pancreas in the F-FOV DWI sequence and that obtained from the R-FOV DWI sequence,indicating that the ADC measurement had stability and high resolution in the plane,and the R-FOV DWI sequence had a better clinical application value in pancreatic lesions.Part II.Application of intravoxel incoherent motion diffusion weighted imaging(IVIM-DWI)in predicting the pathological grade of pancreatic ductal adenocarcinomaObjective:The purpose of this study was to evaluate the application of intravoxel incoherent motion diffusion-weighted imaging(IVIM-DWI)for predicting the pathological grades of pancreatic ductal adenocarcinoma(PDAC)by studying the IVIM-DWI parameters such as the apparent diffusion coefficient standard(ADC standard),pure diffusion coefficient(D),false diffusion coefficient(D*),and perfusion fraction(f).Methods:Forty-two patients(28 males and 14 females,ages 18-72,mean age 59.4±11.2)were enrolled from our hospital.These patients were planned for biliopancreatic surgical resection but did not receive any chemotherapy or radiotherapy.Preoperative routine pancreatic MRI examination at 3.0T was performed,and multiple b-value DWI scan sequences were performed.Among the 42 patients,18 cases were well-moderately differentiated PDAC and 24 cases were poorly differentiated PDAC as confirmed by pathological diagnosis after the surgeries.Pancreatic multiple b-value DWI were performed at 15 b values of 0,50,70,100,150,200,300,500,800,1000,1500,2000,2500,3000 and 3500 s/mm2 using Simens Skyra 3.0T scanner.The ADC standard,D*and f values for all PDACs are calculated using monoexponential and biexponential models.The independent sample t test was used to compare the parameters of well-moderately differentiated PDACs and poorly differentiated PDACs.P<0.05 was considered statistically significant.Results:The mean D values of well-moderately differentiated pancreatic ductal adenocarcinoma is significantly lower than that of poorly differentiated pancreatic ductal adenocarcinoma[(0.563 ± 0.042)× 10-3 mm2/s and(0.679±0.051)× 10-3 mm2/s,t=7.851,P<0.001].The average f values of well-moderately differentiated pancreatic ductal adenocarcinoma was significantly higher than the average f values of poorly differentiated pancreatic ductal adenocarcinoma[(57.8±7.8)%and(39.9±9.7)%,t=6.42,P<0.001].The D*of well-moderately differentiated pancreatic ductal adenocarcinoma is slightly higher than that of poorly differentiated pancreatic ductal adenocarcinoma[(4.017±0.873)× 10-3 mm2/s and(4.221±0.611)× 10-3 mm2/s,t=0.863,p>0.05],the difference is not statistically significant There was no statistically significant difference in ADC values between well-moderately differentiated ductal adenocarcinoma and poorly differentiated ductal adenocarcinoma of the pancreas[(0.796±164)×10-3 mm2/s and(0.807±0.241)×10-3 mm2/s,t=0.869,p>0.05].D value had the highest diagnostic efficiency in differentiating well-moderately and poorly differentiated ductal adenocarcinoma of the pancreas,with an area under the ROC curve(AUC)of 0.841 and an f value of 0.724.When D value was less than 0.576×10-3 mm2/s,the sensitivity and specificity were 98.5%and 80.6%.When the f value is greater than 45.3%,the sensitivity and specificity are 96.3%and 74.6%,respectively.Conclusion:The IVIM-DWI-derived parameters can be used for the clinical classification of pancreatic ductal adenocarcinoma,where the D value and f value can be used to distinguish between well-moderately differentiated PDAC and poorly differentiated pancreatic ductal adenocarcinoma.The diagnostic performance of IVIM-DWI is expected to be a promising and non-invasive tool for predicting the pathological grades of PDAC.