MAGNETIZATION-TRANSFER IMAGING OF DIFFUSE AXONAL INJURY FOLLOWING EXPERIMENTAL BRAIN INJURY IN THE PIG - CHARACTERIZATION BY MAGNETIZATION-TRANSFER RATIO WITH HISTOPATHOLOGIC CORRELATION

Purpose: Our goal was to evaluate the use of the magnetization transfe r ratio (MTR) in the detection of diffuse axonal injury (DAI) resultin g from traumatic brain injury in a swine model, Method: DAI was create d by applying a nonimpact, coronal plane, rotational acceleration to t he heads of miniature swine (n = 4). GE imaging was performed with and without off-resonance MT saturation. Histologic correlation of axonal injury with MRI was performed 7 days postinjury, Thirty-one subcortic al white matter regions and 10 deep white matter regions were selected for the direct comparison of histologic data and MTR measurements, Re sults: Nineteen of 41 examined locations exhibited histologic evidence of axonal injury, The mean MTR in regions with axonal damage was sign ificantly less than in regions without axonal damage. These changes we re observed both in regions demonstrating high signal intensity on T2- weighted images (T2WI) (p < 0.0001, n = 6) and in regions with no sign al intensity change on T2WI (p < 0.05, n = 13). Conclusion: These resu lts suggest that the measurement of MTR may have the potential for eva luating axonal damage in DAI following traumatic brain injury even whe n conventional T2WI does not demonstrate the lesion.