Noninvasive patient tracker mask for spinal 3D navigation: does the required large-volume 3D scan involve a considerably increased radiation exposure?

OBJECTIVE Intraoperative 3D imaging and navigation is increasingly used for minimally invasive spine surgery. A novel, noninvasive patient tracker that is adhered as a mask on the skin for 3D navigation necessitates a larger intraoperative 3D image set for appropriate referencing. This enlarged 3D image data set can be acquired by a state-of-the-art 3D C-arm device that is equipped with a large flat-panel detector. However, the presumably associated higher radiation exposure to the patient has essentially not yet been investigated and is therefore the objective of this study. METHODS Patients were retrospectively included if a thoracolumbar 3D scan was performed intraoperatively between 2016 and 2019 using a 3D C-arm with a large 30 x 30-cm flat-panel detector (3D scan volume 4096 cm(3)) or a 3D C- arm with a smaller 20 x 20-cm flat-panel detector (3D scan volume 2097 cm(3)), and the dose area product was available for the 3D scan. Additionally, the fluoroscopy time and the number of fluoroscopic images per 3D scan, as well as the BMI of the patients, were recorded. RESULTS The authors compared 62 intraoperative thoracolumbar 3D scans using the 3D C- arm with a large flat-panel detector and 12 3D scans using the 3D C-arm with a small flat-panel detector. Overall, the 3D C-arm with a large flatpanel detector required more fluoroscopic images per scan (mean 389.0 +/- 8.4 vs 117.0 +/- 4.6, p < 0.0001), leading to a significantly higher dose area product (mean 1028.6 +/- 767.9 vs 457.1 +/- 118.9 cGy x cm(2), p = 0.0044). CONCLUSIONS The novel, noninvasive patient tracker mask facilitates intraoperative 3D navigation while eliminating the need for an additional skin incision with detachment of the autochthonous muscles. However, the use of this patient tracker mask requires a larger intraoperative 3D image data set for accurate registration, resulting in a 2.25 times higher radiation exposure to the patient. The use of the patient tracker mask should thus be based on an individual decision, especially taking into considering the radiation exposure and extent of instrumentation.