Pancreatic Adenocarcinoma:Diffusion Weighted Imaging And In Vivo Proton (~1H) Magnetic Resonance Spectroscopy

Part I: Pancreatic Adenocarcinoma：high resolution diffusion-weighted magneticresonance imaging using reduced field of viewObjective: To investigate the value of reduced field-of-view diffusion weighted magneticresonance imaging （RFOV DW-MRI） in the diagnosis of pancreatic adenocarcinoma.Methods:36healthy volunteers and49patients with pancreatic ductal adenocarcinoma（PDAC）,9patients with pancreatic adenosquamous carcinoma （PASC）,6patients withpancreatic neuroendocrine carcinoma （PNC）,3patients with mass-forming chronicpancreatitis （MFCP）,1patient with solid pseudopapillary tumor （SPT）（all proven bypathological results） underwent respiratory-triggered reduced FOV DWI and full FOVDWI at3.0T. Image quality was assessed for RFOV DWI and full FOV （FFOV） DWIwith diagnostic quality and artifacts. Apparent diffusion coefficient （ADC） values ofnormal pancreas and all types of pancreatic lesions were statistically analyzed andcompared with nonparametric test. ROC curve was used to analyze the diagnostic powerof ADC value.Results: Higher resolution （1.25x1.25mm²for axial images） diffusion weighted imagesof the pancreas were successfully acquired. The image quality scores for RFOV DWI wassignificantly higher than those for FFOV DWI （P=0.000）, and the artifacts scores forRFOV DWI was significantly lower than those of FFOV （P=0.000）. ADC values ofPDAC, PASC, PNC, MFCP and normal pancreas （NP） were （1.54±0.26） x10^-3、（1.77±0.12） x10^-3、（1.77±0.21） x10^-3、（1.27±0.19） x10^-3、（2.02±0.28） x10^-3mm²/s （χ2=51.835，P=0.000）. Nemenyi test showed there were significant statistical differences inADC values between PDAC and NP（χ²=45.98，P=0.00）, MFCP and NP（χ²=13.4，P=0.00）. ROC curve disclosed that the sensitivity and specificity were65.3%and89.1%,respectively, when ADC≤1.615x10^-3mm²/s was used as a cut off value for differentialdiagnosis of PDAC from other pancreatic neoplasms in our study and normal pancreaswith RFOV DWI. It also showed that the sensitivity and specificity were87.8%and61.8%, respectively, when ADC≤1.865x10^-3mm²/s was used as a cut off value for differential diagnosis with FFOV DWI.Conclusion: The image quality and resolution of respiratory-triggered RFOV DWI wassignificantly higher than normal SS-EPI DWI. The ADC values from RFOV DWI werewell related to pathological features of pancreatic entity, Thus RFOV DWI may behelpful in the early diagnosis of pancreatic adenocarcinoma.Part II:：Diffusion-weighted magnetic resonance imaging of pancreaticadenocarcinoma using multiple b-valuesObjective: To investigate the value of diffusion weighted magnetic resonance imagingwith multiple b-values in the diagnosis of pancreatic adenocarcinoma.Methods:20healthy volunteers and23patients with pancreatic ductal adenocarcinoma（PDAC）,5patients with pancreatic adenosquamous carcinoma （PASC）,3patients withpancreatic neuroendocrine carcinoma （PNC）,3patients with mass-forming chronicpancreatitis （MFCP）（all proven by pathological results） underwent respiratory-triggeredmultipl b-values （0，20s/mm²ï¼Œ50s/mm²ï¼Œ100s/mm²ï¼Œ200s/mm²ï¼Œ400s/mm²ï¼Œ600s/mm²ï¼Œ800s/mm²ï¼Œ1000s/mm²ï¼‰ DWI at3.0T. perfusion fraction （f）, pseudodiffudion coefficient（D^*）, pure diffusion coefficient （D） and Apparent diffusion coefficient （ADC_tot） werecalculated by IVIM-DWI. Parameters derived by IVIM-DWI were compared amongpancreatic lesions and normal pancreas. ROC curve was used to analyze the diagnosticpower of each parameter.Results: f of PDAC, PASC, PNC, MFCP and normal pancreas （NP） were （27.67±4.73）%,（28.20±5.35）%,（42.57±4.31）%,（23.83±13.17）%,（43.09±7.88）%,（χ²=34.073，P=0.000）.D^*of PDAC, PASC, PNC, MFCP and NP were3.87±1.65,3.50±0.85,5.18±1.60,4.64±1.21,9.12±4.23μm2/ms,（χ²=24.993, P=0.000）. D of PDAC, PASC, PNC, MFCPand NP were0.87±0.23,1.05±0.08,0.87±0.08,0.65±0.29,0.87±0.24μm²/ms,（χ²=6.212，P=0.184）. ADC_tot of PDAC, PASC, PNC, MFCP and NP were1.36±0.14,1.49±0.07,1.62±0.04,0.99±0.04,1.66±0.20μm²/ms,（χ²=28.092，P=0.000）. Nemenyi test showedthere were significant statistical differences in D^*between PDAC and NP, PASC and NP,in f between PDAC and PNC, PDAC and NP, PASC and NP, MFCP and NP, in ADC_tot between PDAC and NP, PNC and MFCP, MFCP and NP. There was no significantdifference berween each of two groups in D. ROC curve disclosed that the area undercurves （AUC） were0.925,0.898,0.854, and0.804,0.787,0.775for differential diagnosisof PDAC from NP, PDAC from other pancreatic neoplasms and normal pancreas with f,D^*and ADCtot, respectively. There was no diagnostic power for D.Conclusion: f proved to be the best paremeter for differentiation between PDAC from NP,PDAC from other pancreatic neoplasms cand normal pancreas. It was well related toperfusion status in microcirculation of pancreatic entity, Thus f may be helpful in theearly diagnosis of pancreatic adenocarcinoma.Part III：In vivo¹H Magnetic resonance spectroscopy of pancreatic adenocarcinomaObjective: To analyze the¹H-MRS features and to explore the value of metabolitequantification in diagnosis of in-vivo pancreatic adenocarcinoma, also to determinewhether there is a correlation of pancreatic metabolism with the Ki-67labling index.Methods:20healthy volunteers and22patients with pancreatic ductal adenocarcinoma（PDAC, proven by pathological results） underwent in-vivo¹H-MRS. The relative lipidcontent （rLip, the ratio of lipid peak area divided by peak areas from0to6ppm）,choline-containing metabolites （CCM） to glutamate and glutamine complex （Glx） ratio（CCM/Glx） were compared between two groups. CCM, rLip and Ki-67labling index oftumors with varied differentiating grades were compared, and the correlation of CCM,rLip and Ki-67labling index were determined using linear regression analysis. ROCcurve was used to analyze the diagnostic power of CCM and rLip.Results: CCM/Glx （0.570±0.065） and rLip （0.600±0.078） of NP were significantlyhigher than those of pancreatic adenocarcinoma （CCM/Glx0.444±0.095, rLip0.393±0.118）, P=0.000. The Ki-67labling index [（50.71±10.86）%], CCM/Glx（0.407±0.080） of well-to-moderately differentiated tumors were significantly lower thanthose of poorly differentiated [Ki67（63.37±7.73）%, CCM/Glx0.497±0.092], P=0.007,P=0.024, respectively. There was no significant statistical differences for rLip betweendifferent grade of tumors. There is a significant linear correlation （P=0.002） between CCM/Glx and Ki-67labling index, but no significant correlation between rLip and Ki-67（P=0.069）. ROC curve disclosed that the area under curves （AUC） were0.916,0.852,respectively, for differential diagnosis of PDAC from NP with rLip and CCM/Glx.Conclusion: In vivo¹H-MRS, pancreatic adenocarcinoma presented with a decrease ofCCM concentration and relative lipid content, and CCM/Glx was significantly correlatedwith Ki67labling index. Thus,¹H-MRS may have potential value in predicting thedifferentiation degree and proliferation activity of pancreatic adenocarcinoma.