MRI Diffusion Weighted Imaging Multi-model Analysis Of The Prostate

Part I Evaluation of Different Mathematical Models and Different B-value Ranges of Diffusion-weighted Imaging in Peripheral Zone Prostate Cancer Detection Using B-values up to 4500 s/mm2Objectives:To evaluate the diagnostic performance of different mathematical models and different b-value ranges of diffusion-weighted imaging(DWI)in peripheral zone prostate cancer(PZ PCa)detection.Methods:Fifty-six patients with histologically proven PZ PCa who underwent DWI-magnetic resonance imaging(MRI)using 21 b-values(0-4500 s/mm2)were included.The mean signal intensities of the regions of interest(ROIs)placed in benign PZs and cancerous tissues on DWI images were fitted using mono-exponential,bi-exponential,stretched-exponential,and kurtosis models.The b-values were divided into four ranges:0-1000,0-2000,0-3200,and 0-4500 s/mm2,grouped as A,B,C,and D,respectively.ADC,<D>,D*,f,DDC,a,Dapp,and Kapp were estimated for each group.The adjusted coefficient of determination(R2)was calculated to measure goodness-of-fit.Receiver operating characteristic curve analysis was performed to evaluate the diagnostic performance of the parameters.Results:All parameters except D*showed significant differences between cancerous tissues and benign PZs in each group.The area under the curve values(AUCs)of ADC were comparable in groups C and D(p=0.980)and were significantly higher than those in groups A and B(p<0.05 for all).The AUCs of ADC and Kapp in groups B and C were similar(p = 0.07 and p = 0.954),and were significantly higher than the other parameters(p<0.001 for all).The AUCs of ADC in group D was slightly higher than Kapp(p = 0.002).and both were significantly higher than the other parameters(p<0.001 for all).Conclusions:In terms of differentiating cancerous from benign tissue,there is no obvious advantage for bi-exponential-derived parameters.stretched-derived parameters.kurtosis-derived parameters compared to ADC.ADC derived from conventional mono-exponential high b-value(3200 s/mm2)models is an optimal parameter for PZ PCa detection.Part ? Effects of Echo Time on IVIM Quantification and Reproducibility of Normal ProstatePurpose:To investigate the effects of echo time(TE)on intravoxel incoherent motion(IVIM)diffusion-weighted imaging(DWI)-derived parameters and short-term test-retest reproducibility of the prostate at 3.0T.Materials and methods:In this prospective study.17 healthy volunteers underwent two repeat examinations at 3.0 T.Each scan included IVIM-DWI using 9 b values(0,10,20,50,100,200,500,800,and 1000 s/mm2),the IVIM-DWI data were scanned 6 times with variable TE values of 60,70,80,90,100,and 120 ms.The other parameters are consistent for all scans.Thus,in total,each volunteer underwent 12 IVIM-DWI image series.The apparent diffusion coefficient(ADC)map of mono-exponential model and the D,Dstar,f maps of IVIM model were calculated.For each of diffusion examination,regions of interest(ROIs)were drawn on b = 0 images with TE = 60 ms.On the three largest axial image at the midgland level,ROIs were drawn within the outer border of the peripheral zone(PZ)and central gland(CZ),respectively.Then the ROI was copied to the other series(TE = 70,80,90,100,120 ms)within one examination.ADC,D,Dstar,f values with variable TE were calculated.The repeat measures were assessed by calculating the coefficient of variation(CV)and Bland-Altman limits of agreement(BA-LA)for each parameter.Pearson correlation coefficients were used to analyse the relationships between diffusion indices and TE.Results:Both the ADC and D values exhibited good reproducibility in the PZ and CZ for different TE values(CV:1.641%and 6.661%;BA-LA:-4.965%to 4.263%and-24.413%to 21.284%).Poor measurement reproducibility was observed for f,with CVs of 12.337%and 25.108%and BA-LA values of-43.961%to 30.994%and-52.185%to 62.516%;Dstar was found to be the most unreliable parameter,with CVs of 11.640%and 33.644%and BA-LA values of-29.917%to 35.054%and-96.248%to 81.146%.The ADC and Dstar demonstrated a positive correlation with TE in both the PZ and CZ(p<0.05).The D value demonstrated a positive correlation with TE in the PZ(p<0.05),but no statistically significant correlation with TE in the CZ(p>0.05)was observed.The f value was positively correlated with TE in the CZ(p<0.05),while there was no correlation with TE in the PZ(p>0.05).Conclusion:Good reproducibility of ADC/D and poor reproducibility of Dstar/f were observed in the normal prostate.TE has no effect on reproducibility whereas TE influence diffusion quantification,which should be kept constant in each examination protocol.This may be helpful for guiding clinical research,especially for longitudinal studies.