Interactive image directed neurosurgery: patient registration employing the Laitinen stereo-adapter

Laser surface scanning for patient registration in intracranial image-guided surgery

OBJECTIVE

To report our clinical experience with a new laser scanning-based technique of surface registration. We performed a prospective study to measure the calculated registration error and the application accuracy of laser surface registration for intracranial image-guided surgery in the clinical setting.

METHODS

Thirty-four consecutive patients with different intracranial diseases were scheduled for intracranial image-guided surgery by use of a passive infrared surgical navigation system. Surface registration was performed by use of a Class I laser device that emits a visible laser beam. The Polaris camera system (Northern Digital, Waterloo, ON, Canada) detects the skin reflections of the laser, which the software uses to generate a virtual three-dimensional matrix of the anatomy of each patient. An advanced surface-matching algorithm then matches this virtual three-dimensional matrix to the three-dimensional magnetic resonance therapy data set. Registration error as calculated by the computer was noted. Application accuracy was assessed by use of the localization error for three distant anatomic landmarks.

RESULTS

Laser surface registration was successful in all patients. For the surgical field, application accuracy was 2.4 +/- 1.7 mm (range, 1-9 mm). Application accuracy was higher for the surgical field of frontally located lesions (mean, 1.8 +/- 0.8 mm; n = 13) as compared with temporal, parietal, occipital, and infratentorial lesions (mean, 2.8 +/- 2.1 mm; n = 21).

CONCLUSION

Laser scanning for surface registration is an accurate, robust, and easy-to-use method of patient registration for image-guided surgery.

Computer assisted oral and maxillofacial surgery--a review and an assessment of technology

Advances in the basic scientific research within the field of computer assisted oral and maxillofacial surgery have enabled us to introduce features of these techniques into routine clinical practice. In order to simulate complex surgery with the aid of a computer, the diagnostic image data and especially various imaging modalities including computer tomography (CT), magnetic resonance imaging (MRI) and Ultrasound (US) must be arranged in relation to each other, thus enabling a rapid switching between the various modalities as well as the viewing of superimposed images. Segmenting techniques for the reconstruction of three-dimensional representations of soft and hard tissues are required. We must develop ergonomic and user friendly interactive methods for the surgeon, thus allowing for a precise and fast entry of the planned surgical procedure in the planning and simulation phase. During the surgical phase, instrument navigation tools offer the surgeon interactive support through operation guidance and control of potential dangers. This feature is already available today and within this article we present a review of the development of this rapidly evolving technique. Future intraoperative assistance takes the form of such passive tools for the support of intraoperative orientation as well as so-called 'tracking systems' (semi-active systems) which accompany and support the surgeons' work. The final form are robots which execute specific steps completely autonomously. The techniques of virtual reality and computer assisted surgery are increasingly important in their medical applications. Many applications are still being developed or are still in the form of a prototype. It is already clear, however, that developments in this area will have a considerable effect on a surgeon's routine work.

Incorporation of ultrasonic imaging in an optically coupled frameless stereotactic system

Frameless stereotactic interactive tracking systems relate a point in the surgical field to a corresponding point on the patients MR or CT scans in multiple planes. A basic weakness with these systems is that they cannot compensate for movement of target points due to brain shift caused by CSF drainage or lesion removal. Real time images can be obtained using ultrasonic techniques but the poor quality and definition and the ill-defined scan plane make interpretation difficult and reduce the usefulness of this modality. The authors have combined these two modalities by mounting light emitting diodes (LEDs) on the ultrasonic probe, thus allowing a "virtual tip" to be developed in the centre of the ultrasonic beam, and tracked via an optically coupled frameless stereotactic system (Radionics, OTS). This has allowed a direct correlation between pre-operative MR and the per-operative ultrasonic images using reformatted MR images. Ultrasound images are obtained through a separate skull opening and the image plane is determined by the position of the virtual tip. The ultrasonic and MR images are presented side by side for visual comparison. Minimally invasive tumour resection or haematoma removal could be carried out under ultrasonic guidance with direct interactive relation to the preoperative MR scans. Alternatively interactive image directed surgical procedures can be up-dated in real time by dynamic ultrasonic images taken in clearly defined scan planes.