RA-13
COMPARISON OF FINAL INTRA-OPERATIVE MR SCAN AND POST-OPERATIVE MRI PERFORMED 24 TO 72 HOURS AFTER BRAIN TUMOUR RESECTION

BACKGROUND: There is no published evidence comparing the utility of final intraoperative MRI (ioMRI) and early post-operative MRI (24-72 hours) as baseline scans following brain tumour resection. AIM: To evaluate the utility and validity of the final ioMRI scan as a post-operative baseline after paediatric brain tumour resections. METHOD: A prospective audit comparing the final ioMRI scan with standard immediate post-operative MRI scan performed between 24-72 hours post-surgery. The inclusion criteria were those patients undergoing brain tumour resection using ioMRI and were suitable for MRI scan without general anaesthesia. Standard post-operative MRI was performed 24- 72 hours (24HR) in addition to the final ioMRI scan. The scans were independently evaluated by a local and an external paediatric neuroradiologist. Identical sequences in the final ioMRI and post-24 hour MRI were compared to assess imaging characteristics of residual tumour. Both scans were compared for extent of surgically induced contrast enhancement, diffusion abnormalities and abnormalities that were equivocal for residual tumour. RESULTS: 19 patients underwent intraoperative and early post-operative MRI. There was no difference between ioMRI and 24 hour post op scans in identifying residual tumour. Surgically induced contrast enhancement was similar in both groups. There were more changes on diffusion imaging and more oedema around the surgical cavity on the 24HR scan. CONCLUSION: The final ioMRI may be safely used as the baseline postoperative scan provided the standard imaging guidelines are followed and is evaluated jointly by the operating neurosurgeon and neuroradiologist who are aware of potential pitfalls.