Radiation dose reduction in computer assisted navigation for functional endoscopic sinus surgery - cadaver head experiments and clinical implementation

Objectives: Computed tomography based navigation for endoscopic sinus surgery is inflationary used despite of major public concern about iatrogenic radiation induced cancer risk. Studies on dose reduction for CAS-CT are almost inexistent. We validate the use of radiation dose reduced CAS-CT for clinically applied surface registration. Methods: Dose reduced CAS-CT of mineral salt fixed, human cadaver heads with 9.6, 6, 4, 2 and 1.1 mGy were compared with the reference dose at 65 mGy CTDI (CT-Dose Index). For each CT dose with different surface resolution, the precision of the soft touch registration was measured with target registration error (TRE). In a practical step, dose reduced protocols were tested for 12 months. Results: Using surface registration at highest and lowest doses, TRE did not differ significantly for registration accuracy. Protocols tested preserved technical registration accuracy and the pragmatics of dose reduction was limited only by different needs for picture quality of the individual surgeon, use for uncomplicated or revision surgery, and reserve for other unexpected factors (movement artifacts). Conclusions: The accuracy of today's surface registration technology was not the limit for dose reduction. It is the amount of diminished picture quality tolerated by the individual surgeon and the question of how much of the ever refined radiological picture resolution is necessary at all. For the majority of operations, consensus for a significant 6-fold radiation dose reduction from 65 mGy to 9.6 mGy CTDI could be realized illustrating a big potential for similar approaches in other institutions.