Intravoxel Incoherent Motion Histogram Analysis And Synthetic MRI In The Diagnosis And Grading Of Prostate Cancer

Purpose:To evaluate the diagnostic performance of histogram analysis of intravoxel incoherent motion(IVIM)parameters for differentiating prostate cancer(PCa)from benign prostatic hyperplasia(BPH),and compare with the monoexponential model,with in-bore MR-guided biopsy as pathological reference.Materials and Methods:From March 2017 and May 2018,thirty patients were included in this study.All the patients underwent prostate MRI examinations before biopsies.The scan protocol included T2-weighted imaging(T2WI),T1-weighted imaging(T1WI)and multiple b values DWI(b value=0?20?50?100?200?500?1000?1500?2000 s/mm2).DWI images were processed with Matlab R2015b software by IVIM and monoexponential model for quantitation of diffusion coefficient(D),pseudo diffusion coefficient(D*),perfusion fraction(f)and apparent diffusion coefficient(ADC).Regions of interest(ROIs)were placed manually on each MR-guided biopsy lesion on parametric maps by two observers,who were blinded to the pathological findings.After ROI placement,histogram analyses of IVIM parameters for each ROI were automatically generated.The following histogram parameters were derived from different parametric maps:mean,min,10th percentile,25th percentile,50th percentile,75th percentile,90th percentile,max,skew,and kurtosis.The multiparametric data were compared between PCa and BPH group.Correlations between parameters and Gleason scores of PCa were assessed with Spearman rank test.ROC analysis was used to evaluate and compare the diagnostic ability of each parameter for discriminating PCa from BPH.Logistic regression model was used to evaluate the diagnostic performance of combination of different histogram parameters.Results:Sixteen PCa lesions and 20 BPH nodules were analyzed in this study.For IVIM-derived D,the histogram mean,75th and 90th and max of PCa were significantly lower than BPH.PCa had significantly lower min and 10th D*than BPH.For f,histogram mean,min,10th,25th,50th,75th,90th,max and skew showed significant differences between PCa and BPH.For ADC,PCa were significantly lower than BPH in terms of histogram mean,min,10th,25th,50th,75th,90th,max and kurtosis.Histogram mean D and min,25th D*show significantly negative correlation with Gleason score(r=-0.582,-0.534,-0.554,respectively).Histogram max D and mean f and min ADC showed higher diagnostic performance than other parameters(AUC=0.925,0.881,0.969,respectively).The IVIM model(combined with max D,min D*and mean f)(AUC=0.950[0.821,0.995])didn't show significant difference from the monoexponential model(AUC=0.969[0.849,0.999],P=0.23).Besides,combination of the IVIM and monoexponential model didn't improve diagnostic performance compared with the single model(P=0.362 and 0.763,respectively).Conclusions:Histogram analyses of IVIM and monoexponential model were both useful methods for discriminating PCa from BPH.The diagnostic performance of IVIM model seemed to be not superior to that of monoexponential model.Combination of IVIM and monoexponential model didn't add significant information to the single model alone.Purpose:The interpretation system for prostate MRI is largely based on qualitative image contrast of different tissue types.Therefore,a fast,standardized and robust quantitative technique is necessary.Synthetic MRI is capable of quantifying multiple relaxation parameters,which might have the potential application in prostate cancer(PCa).The aim of the present study was to investigate the use of quantitative relaxation maps derived from synthetic magnetic resonance imaging(MRI)for the diagnosis and grading of PCa.Materials and Methods:From April 2018 to April 2019,46 PCa patients and 48 noncancerous patients were enrolled in this prospective study.All patients underwent prostate MRI examinations on a 3.0 Tesla MR scanner before biopsy or prostatectomy.The MRI exams included T1-weighted imaging(TIWI),T2-weighted imaging(T2WI),diffusion-weighted imaging(DWI)with b value=50,1400 s/mm2 and synthetic MRI.Quantitative maps including T1,T2,PD and apparent diffusion coefficient(ADC)maps were derived.Four kinds of tissue types were identified on pathology,including PCa,stromal hyperplasia(SH),glandular hyperplasia(GH),and noncancerous peripheral zone(PZ).PCa foci were grouped as low-grade(LG,Gleason score?6)and intermediate/high-grade(HG,Gleason score?7).Regions of interest were manually drawn by two radiologists in consensus on parametric maps according to the pathological results.T1,T2,PD and ADC values were compared between different pathologic conditions and PCa with different Gleason scores.The diagnostic effectiveness of each parameter in discriminating PCa from other benign conditions was evaluated and compared by using receiver operating characteristic(ROC)analysis.Results:T1 and T2 values of PCa were significantly lower than SH(P=0.015 and 0.002).PCa and SH did not show significant difference in PD value(P=0.948).GH had significantly higher T1,T2 and PD values than PCa(P?0.007).The differences of T1 and T2 values between PCa and noncancerous PZ were also significant(P?0.006).The AUC of T2 value was significantly higher than that of PD value in differentiating PCa from SH in the TZ(P=0.011).T1 and T2 values showed similar AUC(P=0.669)in differentiating PCa from noncancerous PZ.The AUC of ADC value was significantly higher than T1,T2 and PD values in discriminating PCa from SH and noncancerous PZ(P ? 0.025).The T2 value of PCa lesions with Gleason score 8 was significantly higher than that of PCa with Gleason score7(P=0.02).T2,PD and ADC values demonstrated similar diagnostic performance in discriminating LG from HG PCa(AUC=0.806[0.640-0.918],0.717[0.542-0.854],and 0.817[0.652-0.925],respectively;P? 0.535).Conclusions:Relaxation maps derived from synthetic MRI were practical tools for discriminating PCa from other benign pathologies in both TZ and PZ.Besides,we found that T2 and PD values had the potential for discriminating LG from HG PCa lesions.