Analysis of Process Costing for the Use of Navigation Systems in Functional Endoscopic Sinus Surgery  
[PERSON]  
1 Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital of Regensburg, 93053 Regensburg, Germany; [EMAIL_ADDRESS] (C.T.S.); [EMAIL_ADDRESS] (C.H.); [EMAIL_ADDRESS] (C.R.)  
2 Department of Otorhinolaryngology, Head and Neck Surgery, Friedrich-Alexander University Erlangen-Nuremberg (FAU), 91054 Erlangen, Germany; [EMAIL_ADDRESS] (M.T.); [EMAIL_ADDRESS] (A.S.); [EMAIL_ADDRESS] (H.I.)  
3  
H.  
C.  
sphenoid sinuses [1]. Yet, economic efficiency can only be confirmed in exceptional cases. The available studies show higher costs incurred when using navigation systems [1; 2; 3; 4].  
Consequently, health insurance funds will only bear the costs of endoscopic endonasal sinus operations with intraoperative navigation in exceptional cases. Therefore, an accurate calculation of the investment involved in using a navigation system is required.  
The purpose of navigation is to improve intraoperative orientation by the localization of anatomical structures, which requires the ongoing development of imaging techniques and endoscopy. At the same time, intraoperative navigation is based on connecting data about the patient's position in space, as well as the position of the navigable surgical instruments and the dataset from computed tomography (CT) and/or magnetic resonance imaging (MRI) that has been recorded preoperatively under defined conditions [5].  
In 1989, [PERSON] was the first to describe computer-assisted surgery as a technique to support head and neck surgeons [6]. The technique was based on a three-dimensional volume model of the patient's skull, generated by CT or MRI. Body points could be marked in this 3D model by an intraoperative correlation of model and patient. A volume digitizer was used for the purpose. The real-time positioning of surgical instruments without visual control could, thus, be achieved. [PERSON] demonstrated the use of the system in the areas of the skull base, orbits, and paranasal sinuses [6].  
The navigation system manufactured by Fiagon (Henningsdorf) has been used in the ENT clinic of the University Hospital, Erlangen since 2007.  
This is an electromagnetic system and consists of a computing unit, a field generator built into the headrest, and a localizer. In addition, navigable instruments can be connected to the computing unit.  
Before navigation starts, registration of the patient and the calibration of the system take place. This involves correlating the location of instrument and patient with the CT data set. The localizer placed on the patient shows the exact position of the patient in the generated magnetic field. Precise alignment is achieved by surface registration. A point cloud is produced in the computing unit, and this is matched to the CT-imaging dataset [7].  
Figure 1a shows the main components and Figure 1b shows the instruments used for navigated sinus operations. The location of the pointer instrument being used is projected into the axial, coronal, and sagittal sectional planes of the CT on the screen and correlated with the endoscopy image that appears alongside on the screen. The instrument tip is highlighted in the view by crosshairs and a green arrow (see Figure 1c) [7; 8].  
Figure 1: _Cont_.