Postoperative diffusion weighted MRI and preoperative CT scan fusion for residual cholesteatoma localization

To evaluate the ability of preoperative mastoid high resolution Computerized tomography (CT Scan) fusion with the postoperative diffusion weighted magnetic resonance imaging (Non-EPI DWI) to accurately localize the residual cholesteatoma thus sparing an unnecessary postoperative CT scan radiation.

this is a prospective study performed in our tertiary care center. We followed up prospectively a consecutive group of patients presenting with middle ear cholesteatoma using preoperative mastoid CT scans, postoperative mastoid CT scan and mastoid diffusion weighted MRI (DWI) between 2012 and 2013. Postoperative DWI were fused to both: the preoperative and postoperative mastoid CT scans. Fused images were evaluated for their ability to detect accurately the location of residual cholesteatoma if any. Results were correlated to the surgical findings.

Twenty-eight patients were included in this study. Ten patients showed middle ear opacity on the postoperative CT scans; the remaining negatively patients were excluded. DWI detected residual cholesteatoma in 3 out of the ten patients. Both CT scans; the pre and postoperative were able to precisely localize the residual cholesteatoma when fused to the postoperative DWI. Intra-operatively, three patients had a residual cholesteatoma that corresponded to the fused radiological images while a fourth patient presenting low signal intensity on the Non-EPI DWI had no cholesteatoma.

Diffusion weighted MRI/CT scan fusion combines the advantages of residual cholesteatoma detection and precise localization. Preoperative CT scans performed before the first surgery can be used for the fusion with the Non-EPI DWI in order to spare the patient an unnecessary another CT scan and thus decreasing radiation exposure.