<title>Modified maximum intensity projections for surgical guidance</title>

Abstract

In interactive, image-guided surgery (IIGS) we use stacked slice tomographic image sets as 3D maps of the patient's anatomy. Such sets can provide exquisite information on bony anatomy, soft tissue structure and lesion definition or function. However, none of these tomographic sets clearly show the location and extent of vascular structures, which may be of critical importance to the surgical process. Conventional x-ray angiography (XRA) provides a high degree of spatial resolution but compresses 3D of tissue into a 2D image. New imaging modalities such as magnetic resonance angiography or computed tomography angiography can provide 3D information about the vascular location but in a format which makes vascular identification and location of vascular extremely difficult. Maximum intensity projection (MIP) is a post-processing technique which produces projection images using the maximum intensity value encountered on the projection line, as contrasted to the XRA process which uses the integral of line values for its projection. While each of the images are 2D representations of 3D volumes, the 3D ambiguities may be resolved by creating multiple projections angles and using motion parallax. Conventional MIP projections were developed for diagnostic purposes and radiology users. Intraoperative use in surgery brings with it a different set of constraints. In surgery, the surgeon cares about blood vessels in or near the surgical site. Projection images containing information from the contralateral side provide a superfluous distraction for the surgeon. We have developed a MIP procedure which is more appropriate for surgical applications.