page_title: Patient registration
section_title: Surface registration
hierarchical_section_title: Patient registration / Application / Markerless patient registration / Surface registration
caption_attribution_description: Scheme of the SSN principles
context_page_description: Patient registration is used to correlate the reference position of a virtual 3D dataset gathered by computer medical imaging with the reference position of the patient. This procedure is crucial in computer assisted surgery, in order to insure the reproducitibility of the preoperative registration and the clinical situation during surgery.
  The use of the term "patient registration" out of this context can lead to a confusion with the procedure of registering a patient into the files of a medical institution.
  In computer assisted surgery, the first step is to gather a 3D dataset that reproduces with great accuracy the geometry of the normal and pathological tissues in the region that has to be operated on. This is mainly obtained by using CT or MRI scans of that region. The role of patient registration is to obtain a close-to-ideal reference reproducibility of the dataset – in order to correlate the position of the gathered dataset with the patient's position during the surgical intervention.
context_section_description: Since 1998, new procedures have been developed by Marmulla and co-workers, using a different approach to the problem. Both during CT dataset gathering and surgical intervention, the patient registration was made by registering complete areas and surfaces, instead of distinctive surface markers. This was achieved by using laser scanners and a small guiding transmitter. The precision of the patient registration was significantly improved with this method.
  Based on this concept, several registration and navigation systems were built by the same team. The Surgical Segment Navigator (SSN and SSN++) is such a system, developed for the first time for oral and maxillofacial surgery. This system correlates three different coordinate sets: CT data set, surface laser scan data set and the dataset produced by a small guiding transmitter, placed on the patient's head. The Laboratory Unit for Computer-Assisted Surgery (LUCAS) is used for planning surgery in the laboratory. This technological and surgical advance has permitted the elimination of mechanical guidance systems and improved the accuracy of the determinations, and thus the surgical act.
  A research group at Ryerson University developed a method to use optical topographical imaging (OTI) to create a 3D model of the surface of open surgical sites and perform surface registration to CT and MRI data sets for neurosurgical navigation. The OTI technology is being licensed by 7D Surgical for their navigation platform.
caption: Schematic representation of the SSN system
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