| PART ? build rat C6 glioma modle and observe the charactures of its functional magnetic resonance imagePurposeC6 glioma cells were stereotacically implanted into the right caudate nucleus of young male SD rats,The purpose was to explore the laboratory and prodecure,method and key point in establishing the rat gliomamodel for the further study,Precontrast T1 weighted spin-echo imaging?T1WI?,T2 weighted spin-echo imaging?T2WI?,Diffusion weighted imaging?DWI?,Perfusion weighted imaging?PWI?,Proton magnetic resonance spectroscopy?1HMRS?and Diffusion tensor imaging?DTI?were employed to explore the biological characteristics through MRI scanning.Methods 15 SD rats were cultured for exponential phase of growth in vitro were stereotaxically implanted into the right caudate nucleus for 5mm deep in the cranium in each of 14 SD rats in glioma group,after 2 weeks of implantation,The barin of each rat was imaged with T1WI,T2WI,DWI,PWI,1HMRS and DTI,MR examination of the rat brain was performed using PHLIPS?Achieva1.5T?and coil for wrist.The scanning direction was along the rat macroaxis.Transverse diameter value of the tumor was measure on both T2WI and postcontrast T1WI image.We rebuild the apparent diffusion coefficient?ADC?map and regional cerebral blood volume?rCBV?maps and estimate the ADC values and maximal rCBV values in the tumor area and contralateral area with the workstation equipped with Achieva1.5T.we observed the peak of N-acetylaspartate?NAA?,choline?CHO?,lipid?Lip?,lactate?LAC?,creatine compounds?CR?and glutamate and glutamine?Glu-n?and caltulated the specific value between peak area of the metabolite mentioned above and peak area of the CR.Results 15 rat were observed with tumor in the brain by MRI scanning of the 14 rats implanted with C6 cells.2 weeks after implantation,on DWIs,the signal intensity in the tumor area was significant higher than that in the contralateral white matter.On rCBV maps of the tumors were distributed homogeneously.The maximal rCBV values in tumoral regions were significantly higher than that in contralateral white matter.Lip level,Glu-nlevel and CHO level were significant higher in tumor region compared with the contralateral white matter;NAA level was significant lower in tumor region compared with the contralateral white matter 2weeks after implantation.FA images clearly showed that white matter fiber tracts in contralateral site were good.White matter fibers adjacent to tumor were compressed,partly invaded and destroyed.The FA value in tumor region was significant lower compared with the contralateral white matter.Conclusion SD rat C6 glioma model is stable and reliable.It grows fast;the vaccination success rate is high.The C6 rat glioma model 2 weeks after tumor cells implanted,can satisfy the experimental requirements for rat C6 glioma biological characteristics through MRI.Part ? quantitative assessment of diffusion in the cerebral extracullular space of rat C6 glioma modlePurpose 30 SD rat were randomized into two groups,glioma group and control group.Each group contained 15 rats and they were devided into5 cage.Build the C6 glioma rat in each rat of the glioma group by the method described in part I.To explore the drainage process of the brain interstitial fluid?ISF?and transport property in the interstitial space?ISS?in rat deep brain tissue by tracer-based magnetic resonance imaging?MRI?.On the basis of classical diffusion equation in porous media,to establish distribution and clearance model for local drug administration of brain,and compared the diffusion parameters at different time point after administration.Methods The present study employed magnetic resonance imaging for real-time visualization and quantitative assessment of drug diffusion in gliomas.Using gadolium-diethylenetriaminepentaacetic acid?Gd-DTPA?as a tracer,we considered diffusion in the agarose gel phantom as a reference and compared the diffusion and distribution patterns between the control group and C6 glioma-bearing rats after direct cerebral infusion.Results Gd-DTPA diffused unequally along different directions in the control group,but diffused equally along different directions in agar and glioma.The free diffusion coefficient?D?of Gd-DTPA in an agar phantom was 1.06×10-33 mm2/s.The maximal distribution volume of Gd-DTPA in agar was?242.8±17.6?L?and that in glioma was?66.4±9.1?L?.The effective diffusion coefficient?D*?in gliomas was much smaller than in the control group??6.50±1.81?×10-55 mm2/s vs.?2.95±0.30?×10-44 mm2/s,t=13.22,P<0.01?,resulting a higher tortuosity(l?28??7?DD*?8?12)??4.03±0.46?vs.?1.90±0.1 0?,t=9.54,P<0.01?.The clearance rate constant showed no significant differences between the experiment and control group(?7.94±3.97?×10-5/s vs.?4.71±1.10?×10-5/s,t=1.67,P=0.16).Conclusion Our findings confirmed that Gd-DTPA diffusion was severely impaired in gliomas and presented in an anisotropic pattern in the caudate nucleus.The proposed method provides a new approach for the real-time monitoring of interstitial drug delivery and quantitative assessment of biophysical structural variations in diseased tissue. |
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