gms | German Medical Science

Objective: Objects and image information supplied by the image-guidance system can be displayed by the head-up display of the operating microscope or on screen. Recently the contour of patients' cranium, image-injected in head-up displays of standard operating microscopes, have been used to check the registration accuracy of image-guidance. We propose the use of the brain surface relief and superficial vessels for real-time intraoperative visualization of brain shift or registration inaccuracies of image-guidance for intraoperative adjustment.

Method: A commercially available image-guidance system and a standard operating microscope were used. Segmentation of the brain surface and cortical blood vessel profile was performed manually on preoperative CT- and MR images. The overlay of segmented digital and operating-microscope images was used to monitor image-guidance accuracy. Adjustment for brainshift was performed by manually matching digital images on anatomical structures using a software module of the navigation system.

Results: Experimental use of a phantom demonstrated that the brain surface relief may be used to increase accuracy of registration and possibly brain shift. The technique was used to assist during surgery of five consecutive patients with seven intracerebral brain tumors. The brain surface relief was successfully used to monitor registration accuracy after craniotomy and during the whole procedure. If a certain degree of brainshift occurred following craniotomy (in four of the five cases enrolled) the accuracy could be restored and corticotomies were correctly centred over the tumors to be resected, which was assed by matching the segmented contours of the (in some cases deep seated) target lesion to the anatomical site.

Conclusions: The proposed method was easy to perform and augmented image-guidance accuracy when operating on small deep seated lesions.