Evaluation Of The Efficiency Of Different IVIM Exponential Model In The Diagnosis Of Pancreatic Carcinoma

Objective:To evaluate the clinical application value of the monoexponential model of diffusion-weighted imaging(DWI),biexponential and stretched-exponential models of intravoxel incoherent motion(IVIM)in the diagnosis of pancreatic cancer.Materials and Methods:Retrospective collect and analyse 30 pancreatic carcinomas proven bu histopathology and/or clinical history from September 2015 to January 2017 including male 15,female 15,age from 48～89,mean age 65.53 ±9.17 years old.At the same time,25 cases of normal pancreas were examined(male 14 and female 11,age from 45-76,mean age 59.92±9.55 years old).All the patients were performed MRI examination on an 3.0T scanner(GE-Signa HDXT,USA)in a protocol containing the routine T1WI,T2WI,LAVA,DWI(b=0,600s/mm2),eDWI(b=0,20,50,100,150,200,400,800,1200,2000,3000s/mm2)and HB DWI(b=0,1500,2000,3000,4000s/mm2).The author and one radiologist with radiologist with 5 years experience in abdominal MR imaging diagnosis observed the PC’s signal,extent and vascular invasion,lymph node metastasis two observers discuss when they have different opinnion.Two observers were blinded to the results and independently measured the data using a dedicated software in Functool on GE ADW4.4 workstation.For each region of interested(ROI),they measured the mean value of ADC in DWI,Standard ADC,D-mono,D*-mono,fmono,D-Bi、Da-Bi、fBi in eDWI,and DDC,a in HB DWI).ROI was larger than 1/3 of the whole lesion and placed in the local with homogeneous signal,trying to avoid the hemorrhage,necrosis,ROI lesions The average value of three measurements was used for the final statistical analysis.The ROIs of pancreas in NP group were drawn with the same sizes about 80～200 mm2 in the head,body and tail of the pancreas,then the average value was calculated for further statistical analysis.The data of two groups of the monoexponential model、biexponential and stretched-exponential models were measured and recorded.SPSS 17.0 statistical software was used to analyze the data.Chi-square test was used to analysis images features on T1WI,T2WI and DWI sequences.ICC test was used to examine the consistency of the measurements between two observers,if the data agreed with eachother,the average data from two observers were calculated for further statistical analysis.If the parameters fitted normal distribution,the student’s t-test was executed to compare the obtained parametric values,otherwise Mann-Whitney U test was executed to compare the values,there was a significant difference when P<0.05.Draw the ROC curve of each parameter and analyze its diagnostic efficiencyResults:There was no difference in gender and age distribution between the two groups.There was no significant difference in the T1WI signals between the two groups(P<0.05),and there was significant difference in DWI and T2WI signal(P>0.05).The ICC value of the DWI parameter(ADC),eDWI parameters(Standard ADC,D*-mono,D-mono,fmono,D*-Bi,D-Bi,fBi)and HB DWI(DDC,α)in the PC group and NP group were respectively,0.983,0.972,0.993,0.980,0.923,0.999,0.998 0.994,0.977,0.915 and 0.954、0.992、0.992、0.997、0.996、0.997、0.962、0.958、0.939、0.993,exhibiting an amenable consistency.The ADC,standard ADC of PC and NP were(1.58±0.26)X 10-3mm2/s vs.(1.83±0.28)X 10-3mm2/s、(1.13±0.12)X 10-3mm2/s vs.(1.15 ± 0.18)X 10-3mm2/s.The D-mono,D*-mono,fmono values of HCC and HH group were(0.55±0.12)X 10-3mm2/s and(0.72±0.10)X 10-3mm2/s、(5.18±3.19)X 10-3mm2/s and(15.07±8.49)× 10-3mm2/s、(0.65±0.16)and(0.62±0.13).The D-Bi,D*-Bi,fBi values of them were(1.01±0.73)×10-3mm2/s and(1.08±0.49)X10-3mm2/s、(17.75±10.75)× 10-3mm2/s and(46.23±31.03)X10-3mm2/s、(0.63±0.15)×10-3mm2/s and(0.51±0.13)×10-3mm2/s.The DDC and a values of PC and NP were(1.97±0.53)X 10-3mm2/s and(3.02±1.57)X 10-3mm2/s、(0.59±0.08)and(0.83±0.18),and the value of ADC、Standard ADC、D-mono、D*-mono、D*-Bi、DDC、a remained statistically significant(P<0.05).The area under the ROC curve was more than 0.9 and the AUC was 0.905,The area under the ROC curve of ADC、D-moono、D*-mono、D*-Bi、DDC was 0.725、0.873、0.899、0.773、0.767.The area under the standard ADC curve is greater than 0.5,AUC value of 0.536.ROC of alpha was the largest,the threshold was 0.72,sensitivity was 0.76,specificity was 0.967.Conclusion:In this study,multiple I VIM parameters have significant difference on the PC diagnosis from NP,and the diagnostic efficiency better than ADC value of DWI;the alpha value from I VIM sequence of the stretched exponential model is the best parameters in differential diagnosis of pancreatic carcinoma from normal tissue.The proposed method may held great promise for the non-invasive,noncontrast-enhanced imaging of pancreas lesions and may eventually become a screening tool for pancreatic carcinoma.