Preliminary Study Of Intravoxel Incoherent Motion Diffusion-weighted Imaging For Diagnosing Prostate Cancer

ObjectiveTo investigate the diagnostic value of multi b-value intravoxel incoherent motion（IVIM）diffusion-weighted imaging for prostate cancer（PCa）and evaluate tumor malign ancy according to the results of biopsy.MethodsOne hundred and fifty-three patients with suspected prostatic disease according to the results of biopsy were recruited in the study.58 patients（age range 56-94 years;mean age74.83 years）with biopsy-proven PCa were included.All tumors were located in the peripheral zone（PZ）.The mean prostate-specific antigen（PSA）level in these 58 patients was 52.48ng/ml（range 5.49-234.23ng/ml）.Each lesion was characterized by its Gleason score（GS）,and its malignancy was defined as either high grade（GS≥7,n=35）or low grade（GS<7,n=23）.There were 71 patients with benign prostatic hyperplasia（BPH）（mean age 71.75 years,age range 49-90 years;mean PSA level 12.76 ng/ml,range 1.01-42.69ng/ml）and 24 cases with normal prostate tissue（mean age 63.52 years,age range 50-76years;mean PSA level 4.65 ng/ml,range 1.26-23.32 ng/ml）.All patients were performed on a Siemens Magnetom Skyra 3.0-T MR scanner using an eight-channel abdominal phased-array coil.The examinations included axial FS-T₁WI,axial FS-T₂WI,sagittal T₂WI,DWI and IVIM.The axial FS-T₁WI images were acquired for all patients with the following parameters:TR=500 ms,TE=12 ms,slice thickness/gap=3.0/0.5mm,FOV=250×250 mm²,matrix=218×256,NEX 2.The axial FS-T₂WI images were acquired with the following parameters:TR=5300ms,TE=85ms,slice thickness/gap=3.0/0.6 mm,FOV=230×230 mm²,matrix=256×256,NEX 1.The DWI images were acquired with b values of 50,800s/mm² with the following parameters:TR=4400 ms,TE=87 ms,slice thickness/gap=5.0/0.6 mm,FOV=360×360 mm²,matrix=230×256,NEX 3.The IVIM sequence was performed with seven b values（0,50,100,150,200,400,600s/mm²）,TR=3900ms,TE=95 ms,slice thickness/gap=2.0/0.24mm,FOV=280×280mm²,matrix=160×160,NEX 4.The total scan time for IVIM was5min10s.The IVIM data were post processed using the workstation of Siemens,ivimMain and ImageJ.Apparent diffusion coefficient（ADC）,diffusion coefficient（D）,pseudo-diffusion coefficient（D*）and perfusion fraction（f）were measured in the map of DWI and IVIM.Based on the findings in T₂WI and DWI,the same region of interest（ROI）was used to analyze the IVIM parameter maps.Results1.The values of ADC（0.89±0.13×10^-33 mm²/s）,D（0.78±0.26×10^-33 mm²/s）in the cancerous areas were significantly lower than those in the noncancerous areas（P=0.000）.The f values（3.73±1.56%）in the cancerous areas were higher than those of noncancerous areas（P<0.05）.The D*values(12.03±3.21×10^-3mm²/s)were higher than those of noncancerous areas,but there was no statistical difference among the three groups（P>0.05）.2.The areas under the ROC curve（AUC）,the sensitivity and the specificity for the detection of prostate cancer were 0.993,93.1%and 98.6%for ADC value,as the threshold was 0.923×10^-33 mm²/s;0.997,95.8%and 98.6%for D value,as the threshold was 0.874×10^-33 mm²/s;and 0.877,73.6%and 94.4%for f value,as the threshold was3.107%.The diagnosis efficiency of D value was the best.3.The values of ADC(0.83±0.07×10^-3mm²/s),D(0.70±0.09×10^-3mm²/s)in the high grade（GS≥7）group were lower than in the low grade（GS<7）group(1.02±0.08×10^-3mm²/s,0.87±0.08×10^-3mm²/s)（P<0.05）.The f values（4.39±1.11%）in the high grade group were higher than in the low grade group（3.27±1.38%）（P<0.05）.The D*values(11.39±4.45×10^-3mm²/s)in the high grade group were slightly lower than those of low grade group(11.48±4.71×10^-3mm²/s),but there was no statistical difference between the two groups（P>0.05）.4.The ADC and D values of PCa were negatively correlated with Gleason score（r=-0.905,P<0.05;r=-0.724,P<0.05）.The f values of PCa were positively correlated with Gleason score（r=0.465,P<0.05）.Conclusion1.Multi b-value IVIM-DWI can separately reflect the true water diffusion motion and microcirculation perfusion information in the prostate.It may be a feasible technology in the diagnosis and differential diagnosis of PCa.2.Multi b-value IVIM-DWI is helpful to evaluate tumor malignancy.3.The diagnosis efficiency of multi b-value IVIM-DWI is better than the technology of traditional DWI.