Three-dimensional Proton MR Spectroscopic Imaging Of Prostate Cancer: Preliminary Study

[Objective] In this study, we assessed the metabolic characteristic of prostate cancer(PCa) with three-dimensional proton MR spectroscopic imaging (3D ¹HMRSI), we also evaluated the value of 3D MRSI in the differential diagnosis of prostate cancer and in posttreatment followup of PCa.[Materials and Methods] In this study, patients included 23 previously untreated PCa (7 of PZ, 2 of CG origin, 14 with large turner invaded both PZ and CG), 6 PCa after hormone deprivation therapy, 2 recurrent PCa after TURP, 18 benign prostatic hyperplasia (BPH), 2 chronic prostatitis and 5 normal prostates. 23 previously untreated PCa and 2 recurrent PCa were proved by pathology of systemic sextant biopsy or operation, 18 BPH and 2 chronic prostatitis patients were proved pathologically by biopsy or operation or clinically. All subjects underwent combined general MR imaging and 3D MRSI before radical prostatectomy and biopsy excluded 6 PCa after hormone deprivation therapy. MR imaging/MR spectroscopic imaging studies were performed with a 1.5T Twin-Speed Infinity with Excite I (Signa; GE Medical System), The sequences included axial T₁WI (normal and bigger FOV), axial T₂WI (fat saturation and no fs), coronal fs T₂WI and 3D MRSI by PRESS and multi voxel spectroscopy. All the puncture locations of PCa were marked on the basis of sextants in MRSI and T2WI. The ratio (choline+creatine/citrate, choline/ creatine) in cancer pixtels of peripheral zone (PZ, 143 pixtels) and central gland (CG, 137 pixtels) were measured, The ratios (Cho+Cre/Cit, Cho/ Cre) in control group (BPH) of PZ (133)and CG (133) were random measured. The metabolite ratios (Cho+Cre/Cit, Cho/ Cre) of PCa and BPH respectively compared by student t test and ANOVA, P value less than 0.05 was considered as significant. PCa was considered by general MRI when there was an area of low signal intensity within the PZ on T2-weighted images, definite cancer was identified by MRS when the ratio of Cho+Cre/Cit was greater than 3 SD above normal (>0.86), The presence of cancer was identified when tPSA>4ng/ml or tPSA>10ng/ml. According to diagnosis standards mentioned above, descriptive statistical data including sensitivity, specificity, accuracy, positive predictive value (ppv) and negative predictive value (npv) were determined for general MRI, 3D MRSI and tPSA in detection of PCa. Receiver operating characteristic (ROC) analysis was used to compare the diagnosis efficacy of PCa by Cho+Cre/Cit with diagnosis efficacy by Cho/ Cre, in ROC curves the best threshold of Cho+Cre/Cit was choosed, accuracy, sensitivity and specificity according to the best threshold was determined. [Results]1. Normal prostate PZ showed homogenous high signal intensity (SI), 3D MRSI demonstrated a normal spectral pattern with citrate dominant and no abnormal elevation in Cho, Cho and Cre were lower than Cit.2. PCa and BPH spectral patternPZ of BPH showed dominant Cit, which was markedly higher than Cho and Cre. (Cho+Cre) /Cit<0.75. CG metablic patterns demonstrated the variability, in the glandular BPH region, the amount of Cit was high; while in the stromal region, the Cit level was much lower, (Cho+Cre) /Cit ratio may be bigger than 0.86, which was difficultly different from PCa. Significantly higher choline levels and significantly lower citrate levels were observed in PCa compared with BPH and normal peripheral zone tissues, (Cho+Cre) /Cit>0.86.3. Comparison of PCa and BPH 3D MRSI1) (Cho+Cre) /Cit and Cho/ Cre of PCa pixtels in PZ compared with BPH pixtels in PZ and CG143 PCa pixels were acquired from PZ, BPH pixels of PZ (133) and CG (133) were random measured. The (Cho+Cre) /Cit ratios of three groups were 3.52 + 1.68, 0.57 ±0.22 and 0.78 + 0.28 (mean + SD) respectively, which showed statistically significant differences ( 7^=368. 4, PO.001). It showed statistically significant differences between (Cho+Cre) /Cit ratio of PCa and BPH PZ (t=20. 82, PO.001) . PCa values had minimal overlap with BPH values. The Cho/Cre ratio of three groups were 2.87± 1.39, 1.10 + 0.49 and 1.47 + 0.64 (mean + SD) respectively, the significant difference was showed in PZ PCa group vs BPH PZ group (t=14. 22, PO.001), but there were some overlap between PCa and BPH. ROC analysis showed that diagnosis efficacy of PCa with Cho+Cre/Cit was better than with Cho/ Cre, the best threshold of Cho+Cre/Cit was 1.16, according to which sensitivity, specificity and accuracy of this PZ PCa group were 99.3 %, 99.2 % and 99.3 %, respectively.2) (Cho+Cre) /Cit and Cho/ Cre of PCa pixtels in CG compared with BPH pixtels in CG137 cancer pixtels were acquired from 2 PCa origined from CG and 14 PCa with large tumor invaded CG, 133 BPH pixtels were acquired from CG of BPH. (Cho+Cre) /Cit of PCa group and BPH group were 3.29 + 1.48 and 0.78 + 0.28 respectively, Cho/ Cre of PCa group and BPH group were 2.87+1.07 and 1.47± 0.64 respectively. The difference of (Cho+Cre) /Cit or Cho/ Cre between two groups were statistically significant respectively (t=19.56, PO.001; t=13.2, PO.001 ) , but there was some overlap between PCa and BPH if taking (Cho+Cre) /Cit or Cho/ Cre as diagnostic criterion.4. The general MRI and MRS pattern of chronic prostatitisOne of chronic prostatitis patents showed diffusely hypointensity of PZ inT2WI, the other appeared a local lower SI in the right PZ and diffusely hypointensity of the left PZ. MRS patterns of two chronic prostatitis patents were similar to PCa, which demonstrated elevated choline and reduced citrate, a pattern consistent with definite cancer.5. The general MRI and MRS pattern of PCa after hormone deprivation therapy1) After hormonal therapy, the prostate volume decreased, SI homogenous decrease in PZ were found in 6 patients.2) 3D MRSI of 4 patients demonstrated that Cit decreased obviously or dispeared and Cho was also high. Cit and Cho were all lower than the noise level.6. The prostate volume decreased, SI homogenous decrease in PZ were found in 2 recurrent PCa after TURP, the CG dispeared could be seen. 3D MRSI demonstrated the elevation of Cho and the reduction of Cit.7. The sensitivity, specificity, accuracy, ppv and npv for general 3D MRSI, MRI, and tPSA (>10ng/ml or >4ng/ml) in detection of PCa were 100%, 80%, 92.6%, 88.6%, 100%; 93.3%, 70%, 84.3%, 82.9%, 87.5%; 90.3%, 70%, 82.4 %, 82.4%, 82.4%; 93.5%, 25%, 66.7%, 67.4%, 71.4%, respectively.[Conclusion]1. 3D MRSI can reflect PCa metabolic pattern. 3D MRSI can be successfully applied to the diagnosis of cancer in the PZ on the basis of the elevation of Cho and the reduction Cit in cancerous tissue compared with normal, healthy PZ tissue. The ratio of (Cho+Cre)/Cit > 1.16 is a preferable threshold to differentiate PCa in PZ from BPH.2. Evaluation of the CG with imaging is difficult. CG cancer has a metabolic profile that is different from that of CG tissue and the (Cho+Cre) /Cit ratio of CG cancer is significantly higher than CG tissue, however, the broad range of metabolite ratios observed in CG cancer precludes the use of (Cho+Cre) /Cit ratio...