ABSTRACT
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.
ABSTRACT
Objective To analyse the ultrastructural and metabolic changes of brain injury after single-fraction high-dose radiation in rabbits by means of proton 1-hydrogen) magnetic resonance spectroscopy ~1H MRS) ,in order to provide the basic theory for early detection of radiation-induced brain injury.Methods Experimental model of single-fraction high-dose radiation-injured brain was established in 40 rabbits , which were randomly divided into 4 groups and underwent 10, 15, 20 Gy and 30 Gy radiation , respectively. Proton MRS in a clinical MR imager was used to ascertain the amount of whole-brain N-acetylaspartic acid NAA), lactic acid Lac), choline Cho), creatine Cr) before and within 8 weeks after focused single-fraction high-dose irradiation therapy. Metabolic maps of NAA, Lac, Cho and Cr were created from MRS data set. Detection of irradiation injury among the tested models was assessed by receiver operating characteristic analysis and by quantitative signal intensity changes. The peak values of NAA , Lac , Cho and Cr on MRS before and after radiation were measured. Histopathology and electron microscope were used to ascertain changes of the ultrastructural organization in the irradiated area.the results were compared and statisti-cally analyzed. Results Initially MRS was found a slightly decrease. Until obviously change was detected, statistical significance variation of MRS occurred. A significant decrease in~1H MRS occurred at the early stage of brain injury induced by single-fraction high-dose irradiation.Conclusion ~1H MRS may be regarded as a noninvasive and sensitive means for the detection of early radiation-induced brain injury.
ABSTRACT
Objective To evaluate the diagnostic values of diffusion tensor imaging(DTI)in early radiation-induced brain injury of the temporal lobes.Methods Conventional and MR diffusion tensor imaging examinations were performed in 23 patients following radiotherapy for nasopharyngeal carcinoma(NPC)and in 28 age-matched healthy controls.Isotropic apparent diffusion coefficient(ADCiso)and anisotropic index were measured in the white matter on both of the temporal lobes.Results The value of ADCiso,fractional anisotropy(FA),relative anisotropy(RA)and 1 minus volume ratio(1-VR)were(644.08?56.80)?10-6 mm2/s,0.394?0.074,0.344?0.075 and 0.182?0.072 respectively.In comparison with control group,these values were significant decreased(P