Objective To explore the value of Gadofluorine M,a novel M RI enhancement agent,in the diagnosis the early radiation brain injury.Methods Seventy-two Wistar rats were randomly divided into 5 equal groups.To establish the radiation injury model,the rat's posterior brain was irradiated with 0(blank controls),25,35,45,55,and 65 Gy,respectively.After irradiation MR plain scanning and Gadofluorine M enhancement scanning (after the T1WI and T2WI scanning Gf at the dosage of 0.1 mmol/kg was injected intravenously and scanning was performed again 12 h later) were performed once a week for 8 weeks.Another 12 rats were randomly divided into 2 equal groups to exposure to 55 and 65Gy,respectively,and MR scanning was performed once a week for 8 weeks since the third week after MR.After T1WI and T2WI scanning Gd-DTPA was injected intravenously,MR was conducted again 30 min later,and Gf was injected intravenously (Gd-DTPAenhancement and Gf enhancement contrast).The MR image and the pixel count were compared.Since the third week 2 rats from the Gf enhancement scanning group and 1 rat from the Gd-DTPA enhancement and Gf enhancement contrast were killed after MR with their brains taken out to undergo pathological examination.Results No abnormal signal changes were found in MRI in 25 and 35 Gy groups within 2 months after irradiation.A high signal in the Gf enhancement T1 WI image was found in 45,55,and 65 Gy groups within the period of 4-6 weeks after radiation.The signal intensity was significantly higher than that of the control,25,and 35 Gy groups(F =2.15,P <0.05).The emerge time of this signal was negatively correlated with the dose of radiation(r =-0.62,P < 0.05).When there was no obvious change was found by Gd-DTPA enhancement,a high signal representing change of injury could be found in Gf enhancement in the same rat.The signal intensity was significantly enhanced in Gf enhancement compared to the Gd-DTPA enhancement (F = 2.74,P <0.01).Histopathology examination of the 65 Gy group showed frosted degeneration in part of the region,however,no obvious necrotic damage was found in other groups.Conclusions The Gf enhancement change appears before histopathological changes,it helps discover early radiation injury in brain.Compared to the regular MRI and Gd-DTPA enhancement,Gadofluorine M enhancement has obvious advantage and is worth further research and application.

Objective To detect the distribution of mesenchymal stem cells(MSCs) after total-body irradiation in rats. Methods MSCs were cultured and labeled with green fluorescent protein(GFP). Rats were exposed to total-body irradiation(TB1) or TBI plus total brain irradiation, and then MSCs were injected through the tail vein. The Fluorescent MSCs were observed by fluorescence microscope. The MSCs numbers in different organs were determined by quantitative RT-PCR method. Results GFP-labeled MSCs were ob-tained. After MSCs were infused to the rats,few of them were observed in the organs of nonirradiated group except for a very low number in the lungs,bone marrow(BM) and spleen. TBI of 6 Gy increased the engraft-ment of MSCs in almost all the organs, especially in early response tissues such as the small intestine and BM. TBI of 7 Gy further increased the number of MSCs. The MSCs numbers in the brain and other organs were significantly increased after 20 Gy total brain irradiation in addition to 6 Gy TBI. Conclusions Radi-ation injury can induce the aggregation of MSCs. With the increase of radiation dose and severity of radiation injury,a significant increase of MSCs in different organs were observed. Local irradiation can increase the MSCs distribution in the radiation field as well as other organs.