A Comparative Study Of 3.0T MR Imaging Features And Pathology Of The Orthotopic Transplantation Nude Mouse Model Of Human Pancreatic Cancer

This study adopted Siemens Magnetom Trio Tim 3.0 Tesla superconductive MRI,enhancement scanning by means of injecting contrast agent intraperitoneally and clinical breast coil.Perform a comparative study of MR imaging and pathology of a orthotopic nude mouse model with human pancreatic cancer,which was divided into three parts.Part One:Establishment the Orthotopic Transplantation Nude Mouse Model with Human Pancreatic Cancer Celllines PANC-1Objective:To establish orthotopic transplantation nude mouse model of the human pancreatic cancer for the study of its biological characteristics.Materials and Methods:The subcutaneous tumors cells suspension made by the subcutaneous injection of human pancreatic cancer cell lines Panc-1 were used as the source of tissue for orthotopic implantation of tissue onto the pancreas of 20 nude mice.After implantation,the growth of the tumor was monitored noninvasively by Magnetic Resonance Imaging (MRI).Then the successful rate,time and the growth status of the tumor were monitored and recorded.At the end of the 7th week,all the specimens were examined by pathological methods.Result:Thirty-five percent(7/20) mice with implantation of primary human Panc-1 adenocarcinoma cells were accurately detected orthotopic implanted tumors by MRI after 15 days,and all the 20 nude mice developed pancreatic tumor within 27 days after operations.At last,the tumor formation of all mice were detected and confirmed histological as poorly differentiated adenocarcinoma.Conclusion:The orthotopic transplantation nude mouse model of the human pancreatic cancer render a useful,stable,ideal tools to expose the human pancreatic cancer in vivo furtherly.Part Two:Experimental study of injecting contrast agent intraperitoneally to nude mouse for MRI enhancement scanningObjective:To evaluate the feasibility of injecting contrast agent intraperitoneally to mouse for MRI enhancement scanning,and find the best phase and the imagines of enhancement.Materials and methods:Adopting Siemens Magnetom Trio Tim 3.0 Tesla superconductive MRI and breast coil,The 20 nude mouse were examined to acquire TSE-T1-weighted images of plain scanning and contrast enhancement scanning after injecting contrast agent intraperitoneally.The successive scanning was performed at 1.5min,3min,6min,9min,12 min after injection of Gadodiamide intraperitoneally with the same parameter.Signal intensities of Liver,left kidney,muscle of left-posterior limb were measured,plain scan and every phase's enhancement scanning images were measured respectively.Intensification rates of these three tissues were calculated. Result:Signal intensities of Liver,left kidney,muscle of left-posterior limb on every phase's enhancement scanning images were higher than plain scan's(Dunnett-t test,P value＜0.01).No statistically significant differences were found among intensification rates of Liver,left kidney,muscle of left-posterior limb among every phase's enhancement scanning images(analysis of variance,p value＞0.05)Conclusion:Mice's tissue and organ on T₁WI could be intensified after 1.5min injecting Gadobenate Dimeglumine intraperitoneally,and duration of intensification was long.It was confirmed that intraperitoneal injection was a simple and feasible means to perform MRI enhancement scanning in the experiment of the small rodent.Part Three:a Comparative Study of Pathology and MRI Ehancement Scanning Features of the Orthotopic Transplantation Nude Mouse Model with Human Pancreatic CancerObjective:To find 3.0T clinic MRI examination technique and the pathomechanism of MRI enhancement scanning features of the human pancreatic orthotopic transplanted tumor.Materials and Methods:Adopting Siemens Magnetom Trio Tim 3.0 Tesla superconductive MRI and breast coil,The 30 orthotopic transplantation nude mouse models of the human pancreatic cancer were sampling at 28 days after the operation to acquire TSE-T1-weighted and T2-weighted transverse axial images and contrast enhancement scanning. The successive scanning was performed at 1.5min,3min,6min,9min,12 min after injection of Gadodiamide intraperitoneally.MRI features of the tumor and its surrounding tissues were observed.Signal intensities of tumors were measured.Plain scan and every phase's enhancement scanning images were measured respectively.Intensification rates of tumors were calculated.Pathologic examination was done after MRI scanning.A comparative analysis was made between pathological and MRI results.Results:The successful rate of inoculation of 30 nude mice was 100%.the tumor formation of all mice were detected and confirmed histological as poorly differentiated adenocarcinoma.The MRI findings of the tumors were uniformly slightly hypointensity(90%,27/30),or unevenly(10%,3/30)on TSE-T₁WI,uniformly(20%,6/30)or unevenly (80%,24/30) hyperintensity with equal or more hyper signal spots on TSE-T2WI;during post-contrast dynamic scanning,all the tumors were demonstrated gradually obviously enhancement.Signal intensities and intensification rates of tumors on every phase's enhancement scanning images were higher than plain scan images(P＜0.01),and statistically significant differences were found among intensification rates of tumors on every phase's enhancement scanning.In a word,MRI could estimate pathologic exhibition of tumors according to tumor's internal signal.At the same time,the surrounding tissues invaded by tumor could be imaged. With comparison,It was demonstrated that MRI features of implanted tumors had corresponding pathomechanism.The area intensified significantly is on where the tumor cells grown actively with rich capillaries;signal intensity obviously was not observed on the central area, which corresponded to the area of necrotic tissue and(or) more densely packed cells on histologic sections.Conclusion:It was demonstrated that MRI features of implanted tumors had corresponding pathomechanism.