Preoperative mapping of fistula-in-ano: a new three-dimensional MRI-based modelling technique.

Abstract

We aimed to develop an intuitive, interactive, three-dimensional (3D) MRI modelling technique to produce a 3D image of fistula-in-ano. The 3D model was created from standard two-dimensional (2D) MRI sequences to produce an image that is anatomically correct. Individual muscle and soft-tissue layers were extracted from T1-weighted sequences and fistula pathology from short TI inversion recovery (STIR) sequences, to produce two separate volumes. These were then fused using postprocessing software (Vitrea Workstation version 6.3) to generate a 3D model. The final 3D model was incorporated into a PDF file that has an integrated computer aided design (CAD) viewer, allowing the surgeon to rotate it in any direction during preoperative planning or whilst in theatre. As an adjunct to 2D MRI images and the associated radiology report, this model communicates the fistula anatomy to the clinician more clearly and should be particularly useful in complex cases.