Diagnostic Value Of Magnetic Susceptibility-weighted Imaging In Diffuse Axonal Injury

Objective:To study the diagnostic value of Susceptibility Weighted Imaging(SWI) in diffuse axonal injury(DAI) and the relationship between SWI and clinical prognosis.Methods:Twenty patients(15 males and 5 females) with DAI were included in this study. Routine sequences(T₁WI,T₂WI and FLAIR) and SWI were performed on a 3.0 T MRI system.The cerebral injuries were caused by traffic accident in 16 cases,fall in 2 cases,heavy pound in 1 case and beating in 1 case.There were 8 cases whose Glasgow score Scale(GCS) ranged from 3 to 5,4 cases from 6 to 8 and 8 from 9 to 12. The interval time between injury and examination was between 3 hours to 20 days. The number and volume of lesions observed in SWI and routine sequence were compared.Results:Routine MRI scan found a total of 78 lesions,while SWI sequence detected 424 lesions.The number of the lesions found in SWI sequence was bigger than that of conventional MRI(u=-15.447,P＜0.01).DAI lesions showed high signal or a slightly lower signal on T₁WI and high or low signal on T₂WI.DAI lesions showed high signal on FLAIR and isointense or low signal in the central part of some lesions. Punctate or sheet lesions can be seen in conventional MRI and the boundaries of the majority of lesions were not clear.The lesions were punctate,beaded,patchy and cord-like significantly lower signal with various sizes on SWI.Some lesions merged into plate signal(lesion diameter＜2.0 cm).Distribution of lesions was multifocal with clear boundary.Lesions were punctate or linear mostly in the corticomedullary junction,beeded mostly in white matter and cerebellar and patchy mostly in basal ganglia,corpus callosum and brain stem.The total volume of the lesions measured in conventional MRI and SWI were 19,340 mm³ and 38,042 mm³,respectively.The total volume measured in SWI was bigger than that in routine MR(t = 5.870,P＜0.01).The number and volume of all lesions were negatively correlated with GCS(r =-0.802, P＜0.01 and r=-0.767,P＜0.01).Conclusion:SWI sequence can found more bleeding lesions than the routine MRI sequences. In particular,SWI has advantages in displaying small bleeding lesions with needle-like.The total volume measured in SWI was bigger than that in routine MR. At the same time SWI can show the location and extent of lesions clearly.The number and the volume of the lesions are closely related to GCS.Thus it can be said that SWI provide an important imaging basis for diagnosing DAI and evaluating the prognosis of patients.