Diffusion-weighted And Dynamic Contrast Enhanced MR Imaging In Normal Prostate And Prostatic Diseases At 3.0 Tesla

【Objective】1.To analyze and compare apparent diffusion coefficients(ADC) value of peripheral zone(PZ) and central gland(CG) in normal prostate gland and changes at different age groups by 3.0T Diffusion-weighted MR imaging(DWI) with array spatial sensitivity encoding(ASSET) technique and using different b values.2.To evaluate the value of DWI in differential diagnosis between benign prostatic hyperplasia(BPH) and prostatic carcinoma(Pca) by quantitatively analyzing the ADC values.3.To evaluate the value of the dynamic contrast enhanced MR imaging(DCE-MRI) in differential diagnosis between BPH and Pca by using Liver Acquisition with Volume Acceleration(LAVA) technique and analyzing the pattern of signal intensity-time curve(SI-T) and the correlated parameters.Part one:Study of Diffusion-weighted MR imaging with ASSET in normal prostate and prostatic diseases【Materials and Methods】1.Subjects51 patients who underwent prostate DWI scanning during Sep.2007 to Apr. 2008 were selected for study.These patients were divided into four groups as followings:young adult normal group(age from 21 to 50 years old),14 cases; symptomless aged group(age from 51 to 79 years old),15 cases;BPH group,13 patients;and Pca group,10 patients.2.Instruments(1) 3.OT GE Signa Exite HD superconducting MR scanner with 8-channel phased array abdomen coil.(2) ADW4.3 workstation and GE Functool software for data analysis.3.Examination methodsDWI was acquired by a single shot spin-echo planar imaging sequence with ASSET technique.Totally 51 cases in four groups underwent DWI scanning,in which the b values were 300,600,800,1000 s/mm²,respectively in normal young adult group and were 800,1000 s/mm² in the other three groups.4.Data processing and imaging evaluationAll the primitive data were sent to ADW 4.3 workstation for post-processing. ADC imaging were automatically generated by using GE Functool software for subsequent analysis.ADC values were calculated in the PZ and the CG of the young adult group,the PZ of the aged group,the hyperplasic tissue and the region of cancer (in five local prostatic cancer,the adjacent tissue were contained).Except for young adult group,the ADC values of the obturator internus were calculated in the other three groups.5.Statistical MethodSPSS 11.5 software package was applied to statistical in both parts of study.All data were recorded as(mean±standard deviation).Statistical significance level was set as a=0.05,statistically significant difference was defined as P value less than 0.05. General linear model repeated measures was used to compare the ADC values between PZ and CG at different b values in normal young adult,and to compare the ADC values among different groups or different areas at different b values.Then one way ANOVA,independent-samples t test or paired-samples t test was used for two-two comparison.【Results】 1.Diffusion-weighed imaging(1) The signal intensity of DWI in the PZ was higher than that in the CG in normal young adult group.The hyperplasic tissue demonstrated mixed signal intensity,and cancer focus and the encroached tissues showed high signal intensity. The lager the b value was,the better SNR it contained.The signal intensity ratio of cancer focus to the adjacent tissue in higher b values(800,1000 s/mm²) was better than that in lower b values(300,600s/mm²).(2) When b value were 800 s/mm² and 1000 s/mm²,the signal ratio of cancer focus to the obturator internus in the same slice was significant different(t=—4.052,P=0.003),with the ratio in b was 1000 s/mm² was higher that at in b was 800 s/mm².2.ADC value(1) No statistically significant difference(F=0.860,P=0.432) was found in ADC value of obturator internus among the aged group,BPH group and Pca group.The ADC value of obturator internus was decreased as b value increased(F=51.165, P=0.000).(2) Statistically significant difference(F=10.737,P=0.003) was found in ADC values between the PZ and the CG in the normal young adult group.Statistically significant difference(F=69.102,P=0.000) was found in ADC values among four different b values.That was,the larger the b value was,and the lower the ADC value was.ADC value in the PZ was higher than that in the CG with same b value.(3) Statistically significant difference(F=29.786,P=0.000) was found in ADC values of the PZ between the young adult group and the aged group.The ADC value of PZ in aged group was higher than that in youth adult group.No significant difference(F=1.746,P=0.197) was found in ADC values of the CG between the young adult group and the aged group,although the ADC value of the CG in aged group was higher than that in youth adult group.Positive correlations existed between age and the ADC values of PZ and CG.(4) Statistically significant difference(F=216.052,P=0.000) was found in ADC values among the PZ,CG of aged group,hyperplastic group and cancer group,with the cancer focus the lowest,hyperplastic tissue or the CG of aged group the second, the PZ of agedness group the highest.Statistically significant difference (F=19.944,P=0.000) was found among three groups at different b values.When the b values are 800s/mm²,1000 s/mm²,the ADC values of the cancer focus were (0.80±0.11)x10^-3 mm²/s and(0.73±0.10)x10^-3 mm²/s;in hyperplastic tissue were (1.35±0.14)x10^-3 mm²/s and(1.32±0.09)x10^-3 mm²/s:while in the PZ of the aged group were(1.40±0.44)x10^-3 mm²/s and(1.33±0.42)x10^-3 mm²/s.,in the CG of the aged group were(1.37±0.10)x10^-3 mm²/s and(1.30±0.11)x10^-3 mm²/s.(5) In five cases of focal cancer,statistically significant difference(F=80.466,P= 0.000) was found in ADC value between cancer focus and the adjacent prostatic tissue.The ADC value in cancer focus was lower than that in the adjacent prostatic tissue.(6) The 95%confidence interval of ADC value in cancer focus was 0.88x10^-3 mm²/s(b=800 s/mm²) and 0.80x10^-3 mm²/s(b=1000 s/mm²) respectively,both of which were smaller than 1.0x10^-3 mm²/s.ADC value of 1.0x10^-3 mm²/s was used as a standard to distinguish malignant lesions from benign lesions.When the b values equal to 800s/mm² and 1000s/mm²,if any tissue's ADC value was less than 1.0x10^-3 mm²/s in prostate,malignant lesions should be considered.However,if the ADC value was ranged from(1.26～1.43) x10^-3 mm²/s,hyperplastic tissue should be considered.【Conclusions】1.3.OT DWI with ASSET technique and phased array abdomen coil can generate good quality DWI and ADC images.The structures of the PZ and the CG in normal prostate,and the prostate lesions were clearly displayed.The signal to noise ratio of DWI image was decreased when b value increased.2.The ADC value of the PZ is higher than that in the CG in normal prostate at same b value.The higher the b value is,the lower the ADC value is.The ADC value of the PZ in prostate increased as age increased.When using in the diagnosis of prostate cancer,age-related increases in ADC value need to be considered. 3.Diffusion-weighted imaging is an effective and feasible method in differential diagnosis between the BPH and Pca.The ADC value of Pca was obviously lower than that of BPH,and also,the ADC value of Pca was lower than that of the adjacent tissues.4.The DWI and ADC value with higher b value had more diagnostic value than that with lower b value.The b value which equals to 1000s/mm² is recommended for DWI in this study.If any tissue's ADC value is less than 1.0x10^-3 mm²/s in prostate, malignant lesions should be considered.Part Two:Study of LAVA dynamic contrast enhanced MR imaging in differential diagnosis between benign and malignant prostate lesions【Materials and Methods】1.Subjects10 patients of BPH and 10 patients of Pca in the Part one were performed with LAVA dynamic contrast enhanced MR scanning.2.Instruments(1) High pressure syringe(Ulrich medical,German)(2) GD-DTPA as MR contrast agent.(3)Others as same as part one.3.Examination technique:10 cases of BPH and 10 cases of Pca were performed with dynamic enhanced MR scanning,using LAVA technique.A mask imaging was obtained before injecting, then scanning was repeatedly obtained at the 0^th,1^th,2^th,3^th,4^th,6^th,8^th minute, which started at 5s delay time after injecting of contrast agent Gd-DTPA(flow rate of 2.0ml/s and dose of 0.2mmol/kg).4.Data processing and image evaluationThe dynamic enhanced data was post-processed using commercially available GE Functool SER(signal enhance ratio) software package.The SI-T curve was generated automatically.The characteristics of the curve in benign and malignant lesions were compared and the maximum intensity rate(%),the one-minute intensity rate(%),the two-minute intensity rate(%),wash-out score and time to peak were calculated respectively.5.Statistical MethodSPSS 11.5 software package was applied to statistical analysis.All data were recorded as(mean±standard deviation).Statistical significance level was set as a=0.05,statistically significant difference was defined as P value less than 0.05.The characteristics of SI-T curve,the time to peak value between benign and malignant lesions were compared with the rank test method.The maximum intensity rate(%),the one-minute intensity rate(%),and the two-minute intensity rate(%) between benign and malignant lesions were compared with general linear model repeated measures.The wash-out score between benign and malignant lesions were compared with independent-samples t test.【Results】1.10 cases of BPH developed in the CG,while two cases of Pea developed in CG.2.The SI-T curve in 10 cases of BPH appeared as type"â… "in 6 cases,type "â…¡" in 3 cases and only type "â…¢" in 1 case;however,the SI-T curve in 10 cases of Pea appeared as type "â…¡" in 3 cases and only type "â…¢" in 7 case.If standard C(that is type "â…¢" for Pea,type"â… "and"â…¡" for BPH) was taken as diagnostic standard,the diagnose sensitivity,specificity,accuracy,positive predictive value and negative predictive value were 70.0%,90.0%,80.0%,87.5%,85.0%,respectively.3.The reference parameters of LAVA DCE-MRI were as followings:in the BPH group,the maximum intensity rate%(111.33±19.35),the one-minute intensity rate% (97.50±20.43),the two-minute intensity rate%(105.44±20.05) and wash-out score (9.03±8.07);and in the Pca group,the maximum intensity rate%(140.88±35.72),the one-minute intensity rate%(137.03±34.69),the two-minute intensity rate% (136.10±39.98) and wash-out score(17.89±7.47).Statistically significant difference (F=6.480,P=0.002) was found between benign and malignant lesions in maximum intensity rate%,one-minute intensity rate%,two-minute intensity rate%.Also statistically significant difference(t=2.547,P=0.020) was found between benign and malignant lesions in wash-out score.Except for the one-minute intensity rate%,the maximum intensity rate%,two-minute intensity rate%and wash out score were overlapped in some degree.All these indexes above in the Pca group were higher than that in the BPH group.4.When using one minute(Z=-4.359,P=0.000) or two minute(Z=-2.854,P=0.023) as limit,statistically significant difference was found in time-to-peak between the BPH and Pea group.The time to peak in the Pea group was earlier than that in the BPH group.【Conclusions】1.Propeller LAVA DCE-MRI is an effective and useful method in differential diagnosis between BPH and Pca,as it can give more morphologic and hemodynamic information.2.The pattern of the SI-T curve played some value in differential diagnosing between BPH and Pca.Most of BPH showed type "â… " SI-T curve,however,most of Pca showed type "â…¢".Both of BPH and Pea could happen to type "â…¡".With the standards C as the diagnostic standards for Pca(type "â…¢" as Pca,type "â… "and "â…¡"as BPH),the diagnose sensitivity,specificity,positive predictive value,negative predictive value,and accuracy were 70.0%,90.0%,80.0%,87.5%,85.0% respectively.3.The reference parameters in DCE-MRI played some role in differential diagnosing between BPH and Pea.The maximum intensity rate%,one-minute intensity rate%, two-minute intensity rate%and wash-out score of Pca were higher than that of BPH.Except for the one-minute intensity rate%,there were some overlapping between benign and malignant lesions.Pca showed an early and fast enhancement, with the time to peak value earlier than that of BPH.