## 4 Discussion  
Over the past decades, intraoperative navigation systems have evolved from 2D conventional C-arm fluoroscopy to 3D imaging, using the CT technique. Knowledge about radiation exposure to the operating staff is of great importance since the long-term effects of chronic low-dose exposure are still unclear [16; 17; 18; 19]. Our study results show a significant lower radiation exposure to the operating staff in procedures performed with iCT, compared to C-arm fluoroscopy. The surgeon's and the operating nurse's radiation dose respectively decreased thirteen and four times on average (Figures 2 and 3), while the radiation dose of the anesthesiologist (Figure 4) was almost eliminated with iCT. This can be explained by the ability to insert the pedicle screws using a single iCT scan and spinal navigation [8; 9; 20; 21]. During a procedure with iCT, prior to pedicle screw insertion, a scan is taken via a compact system pendant which can be held by an unsterile nurse behind a lead wall in the OR. The sterile surgeon and operating nurse also stand behind this lead wall. The generated image is then, together with navigation software, used to insert the screws in an accurate manner. Afterwards, a second iCT scan is obtained to evaluate the placement of the pedicle screws. If misplaced, the inaccurate screw(s) are relocated. In contrast, fluoroscopy-guided surgeries require real-time imaging of the surgical instruments in the region of interest [22]. Herewith, the surgeon and operating nurse stand at the contralateral side of the X-ray source when radiographic images are made, resulting in a higher radiation dose. During MI-PLIF surgeries assisted by iCT, an additional lateral C-arm fluoroscopy device was used to guide the insertion of a graft cage in the intervertebral space. Therefore, we believe that the ED of the staff members is mainly due to radiation exposure derived from the lateral C-arm fluoroscope. This thought is supported by [PERSON] et al. who could demonstrate that the radiation dose of the operating room staff could be completely eliminated during minimally invasive transforma  
Figure 8: Time efficiency of an MI-PLIF surgery. (**A**) Duration of pedicle screw insertion (in hh:mm:ss) compared between surgeries assisted by iCT (\(n\) = 24) and C-arm fluoroscopy (\(n\) = 18). (**B**) Total operation duration (in hh:mm:ss) compared between surgeries assisted by iCT (\(n\) = 29) and C-arm fluoroscopy (\(n\) = 43). Outliers are marked as “\({}^{\circ\prime}\)” on the boxplot. Significance (\(p\) < 0.001) is indicated with “***” above the two boxplots. LIF procedures guided by only an AIRO iCT device and 3D navigation [23]. In addition, [PERSON] et al. demonstrated that various spinal procedures can be performed with only iCT navigation, eliminating the use of a C-arm fluoroscope in 75% of the cases [24]. The greater interquartile range of surgeries performed with C-arm fluoroscopy, compared to iCT, suggest that the exposure of the operating room staff is dependent on the surgeon's experience and the complexity of the surgery, while the radiation output of the iCT is more standardized. Thus, AIRO iCT-based spinal instrumentation increases the safety of the OR personnel by decreasing or even eliminating radiation exposure. Consequently, surgeons can perform more image-guided surgeries per year when they use iCT before they reach the annual dose limit of 20 mSv. In addition, it is not necessary to wear a lead skirt during iCT-navigated surgery, since the operating room staff can leave the room while scanning [24,25]. Therefore, it can increase ergonomics by avoiding back pain or muscular fatigue caused by the weight of the lead apron after long-lasting procedures [26]. In contrary to the ED of the operating staff, the ED of the patient increased approximately four times on average during surgeries with iCT, compared to surgeries performed with C-arm fluoroscopy.