###### Abstract  
Navigation systems used during minimally invasive spine procedures have evolved from uniplanar, two-dimensional C-arm fluoroscopy to multiplanar, 3D intraoperative computed tomography (iCT). In this study, the radiation exposure to the patient and operating room staff in posterior intervertebral lumbar fusion procedures is compared between iCT and C-arm fluoroscopy. The effective dose of the surgeon, operating nurse, and anesthesiologist was measured during surgery with personal dosimeters, and the effective dose of the patient was measured with GafchromicTM films. The time efficiency of the procedure was evaluated by recording the duration of pedicle screw fixation and the duration of the total surgery time. A total of 75 patients participated in the study; 30 patients had surgery guided by iCT and 45 by C-arm fluoroscopy. The radiation dose of the surgeon, the operating nurse, and the anesthesiologist was thirteen fold lower with surgeries assisted by iCT compared to C-arm fluoroscopy. In contrast, the effective dose of the patient significantly increased with iCT. Using iCT, radiation exposure of the operating room staff can be significantly reduced. iCT increases the effective dose of the patient and prolongs the operative time.  
intraoperative computed tomography; radiation; posterior lumbar fusion +
Footnote †: journal: Medical Imaging, Ziekenhuis Oost-Limburg, 3600 Genk, Belgium; [EMAIL_ADDRESS] (A.H)  
Footnote †: journal: Medical Imaging, Ziekenhuis Oost-Limburg, 3600 Genk, Belgium; joris.  
source repetitively. While the patient is mainly exposed to the primary beam, the surgeon and the operating staff are exposed to scatter radiation. Exposure to ionizing radiation can potentially cause several pathologies. To minimize the occurrence of radiation associated pathologies, the ALARA (As Low As Reasonably Achievable) principle is used, which claims that the exposure to radiation must be kept as low as reasonably achievable [8; 9; 10; 11]. It is especially important for surgeons and the operating nurses, who are repetitively exposed to ionizing radiation during surgical procedures, to have knowledge about the radiation dose [8; 9; 10; 11].  
One of the procedures in which navigation systems are used is the lumbar interbody fusion (LIF), an effective treatment for patients with lumbar spinal disorders where conservative management fails [12; 13; 14; 15]. The spine can be approached in five main directions: posterior, transforminal, oblique, anterior, and lateral [12; 14]. The approach direction depends on the surgical indication, and all approaches can be performed in a minimally invasive way [12; 14; 15]. A posterior approach of the lumbar interbody fusion (PLIF) is used to treat degenerative conditions requiring a fusion procedure. A minimally invasive PLIF procedure (MI-PLIF) allows excellent visualization of the nerve roots and adequate interbody height restoration in order to decompress the nerves. Furthermore, this approach allows a 360-degree fusion through a single incision.  
As described above, navigation systems are used to increase the accuracy and safety of instrumentation during minimally invasive surgery. This study evaluates the use of a novel, 3D navigation system, iCT, during an MI-PLIF procedure with comparison to the golden standard technique, C-arm fluoroscopy, regarding radiation exposure to the patient and the operating staff. Furthermore, attention was focused on the length of both procedures because knowledge about clinical efficacy is important to outweigh the benefits for the patient with the potential harm of ionizing radiation.