A Study On Mr Perfusion With USPIO And Dynamic Monitoring In Rat C6 Brain Glioma

Object:? To compare the similarities and differences between ultrasmall superparamagnetic iron oxide (USPIO) perfusion-weighted imaging and Gd-DTPA Perfusion-weighted imaging and clarify the feasibility of USPIO PWI in evaluating tumor angiogenesis.Materials and Methods: Thirty male Sprague-Dawley rats, with age of 3-4 months and body weight of 200-250 g were used in this study. C6 glioma model in rat was established by stereotactic implantation.Thirty male SD rats were divided into two groups in random. MR imging of conventional examination and PWI were performed at 12 days of tumor age. USPIO PWI and Gd-DTPA PWI were performed respectively. Imaging sequences included: spin-echo T1 weighted imaging, fast spin-echo T2 weighted imaging, EPI-PWI after the injection of contrast agent through the rat tail vein. At last postcontrast spin-echo T1 weighted or fast spin-echo T2 weighted imaging were performed.Two regions of interest at the largest section of tumor were selected in each subject, one is in the center of tumor (enhanced region, necrotic area should be avoid of ), and the other one is in corresponding area of the contralateral normal brain. Based on signal-time curve from PWI, we can get the corresponding data. the raw data were input into computer and the maximum signal reduction ratio, regional blood volume and the ratio of each parameter between the two ROI were calculated.The tumor specimens were obtained from brian imediately after MR imaging.Histopathology was examined with hematoxylin and eosin(HE)staining and immunohistochemistry of GFAP.All data were analyzed by SPSS 11.0 statistical software package. Paired t test was performed , P values below 0.05 was considered to be statistically significant . P values below 0.01 was considered to be great different.Results: Great difference was found about the rBV and SSRmax between tumor tissue and normal brain tissue in both USPIO-PWI and Gd-DTPA-PWI group (P < 0.05). The rBV and SSRmax in tumor is higher. The rBV and SSRmax in USPIO-PWI group is higher than those in Gd-DTPA-PWI group.Great difference was also found about the QrBV and QSRRmax between the two groups.The MTT in tumor tissue was greatly different from that in normal brain tissue in both USPIO-PWI and Gd-DTPA-PWI group (P < 0.05),but there is no significant difference between USPIO-PWI group and Gd-DTPA-PWI group ( MTT)Conclusions: USPIO perfusion demonstrate more obvious perfusion effect than Gd-DTPA,which should be consider as the choice in evaluation of tumor microcirculation. Object: To observe the dynamic changes of USPIO in glioma and explore its significance in glioma.Materials and Methods: Ten male Sprague-Dawley rats, with age of 3-4 months and body weight of 200-250 g were selected in this part. C6 glioma model was established stereotactically.Gd-DTPA enhanced MR imaging was performed at day 12 after tumor implantation.USPIO was intervenouly administered the next day and monitored by MRI at hour 0,24,48,72 respectively. Imaging sequences including: precontrast spin-echo T1 weighted imaging, fast spin-echo T2 weighted imaging, and spin-echo postcontrast T1WI and T2WI after the injection of contrast agent through the rat tail vein.The signal dynamic change in the tumor area was observed. Two mirror symmetrical regions of interest were selected in each subject, one is the in center of tumor (enhanced region, avoid of necrotic area ), and the other is in the contralateral normal brain tissue. The third one is the corresponding background which is parallelled with the other two regions mentioned above.The mean area of the ROI is 4 mm2. Signal intensity from the three ROI was achieved, and then the contrast to noise ratio was calculated by (singal of the tumor–singal of the contralateral normal brain)/singal of the background.The CNR-time curve was drawn.Tumor specimen was obtained from their brian imediately after MR imaging, hematoxylin and eosin(HE)staining and prussian blue staining were performed for histopathology. Results: USPIO enhanced MR imaging demonstrated that USPIO stay in tumor longer than Gd-DTPA.The negative enhancing effect produced by USPIO presented at the border of the tumor at first, then infiltrated into the center of the tumor gradually. The peak time of the negative enhancing effect appeared at 24 hours after contrast agent administration,and then decreased with time went on(hour 48 and hour 72).Conclusions:This study further suggested that USPIO as a cell specific contrast medium stay in tumor longer and can be used to have repeat observation with one administration and maybe used to evaluate the immune reaction of the tumor.