OR Staff Radiation Dose Exposure
The average staff exposure per procedure was 0.21 ± 0.06 μSv, with CBCT contributing to 83.8% of the total staff exposure dose (Figure 3). For 2D fluoroscopy, the average staff dose ranged from 0 to 0.025 μSv, compared with 0.004 to 9.167 μSv measured by the reference dosimeter (APD) attached to the C-arm (i.e., worst-case staff exposure situation). For 3D CBCT, the average staff dose ranged from 0 to 0.354 μSv, compared with 28.6 to 201.6 μSv measured by the reference APD (Figure 4). The average staff-to-reference dose ratio per procedure was 0.05 ± 0.01%. This ratio decreased to less than 0.01% after a few procedures had been performed. This was mainly due to the real-time feedback displayed by the personal dosimeters, enabling improved strategies for occupational radiation dose management and protection, resulting in a minimized staff exposure (Figure 5).
Average staff radiation dose measured for each performed procedure. The dose values correspond to the personal dose equivalent H p(10) measured in units of μSv.
Average staff radiation dose per performed procedure versus the corresponding reference radiation dose measured by an active personal dosimeter attached to the C-arm (i.e., a worst-case staff exposure situation) for each performed x-ray imaging event. The dose values correspond to the personal dose equivalent H p(10) measured in units of μSv.
Average staff-to-reference radiation dose ratio for each performed procedure. The reference radiation doses were measured by an active personal dosimeter attached to the C-arm (i.e., a worst-case staff exposure situation).
Patient Radiation Dose Exposure
The median amount of spinal levels treated was 8 [2–12]. An average of 43 ± 5 seconds of 2D x-ray imaging (fluoroscopy) was used for the identification of spinal level and iso-centering to locate the region of interest. For navigation planning and screw placement, a median of 2 [1–4] CBCT acquisitions was performed. An additional 2 [1–4] CBCT acquisitions were performed for verification, replacing postoperative CT (Table 2).
The average AK and DAP per procedure was 159 ± 16 mGy and 31.3 ± 2.8 Gy cm2; respectively. The average patient ED was 15.8 ± 1.8 mSv with CBCT contributing to 97 ± 1% of the total procedure ED. Figure 6 shows the ED per procedure, and the corresponding contribution from 2D and 3D imaging. As expected, the effective dose correlated with the number of vertebrae treated (ρ=0.59, P < 0.05) and the number of CBCT acquisitions (ρ=0.48, P < 0.05). It did not, however, correlate with patient characteristics such as body-mass index (ρ=0.10, P = 0.66), weight (ρ=0.04, P = 0.88), height (ρ=0, P = 1), or age (ρ=0.03, P = 0.91).
Patient radiation dose for each performed procedure. The dose values correspond to effective doses calculated in units of mSv using tissue weighting factors from ICRP 103 [REF ICRP 103]. ICRP indicates International Commission on Radiological Protection.
During the first 10 procedures, a total of 38 CBCT acquisitions were performed (19 small and 19 medium field-of-view). During the final 10 procedures, a total of 39 CBCT acquisitions were performed (1 small, 21 medium, and 17 large field-of-view). The decision to use a larger field-of-view for the final 10 procedures was due to the fact that more spinal levels could be treated with clinically sufficient image quality at a reduced patient exposure (per spinal level treated); a 52% reduction of DAP from 7.5 ± 1.3 to 3.6 ± 0.4 (P < 0.05) and a 32% reduction of ED from 3.0 ± 0.5 to 2.0 ± 0.3 (P = 0.08) per spinal level treated were observed. The satisfactory CBCT image quality for verification of screw placement made additional postoperative CT imaging unnecessary.
Spine. 2020;45(1):E45-E53. © 2020 Lippincott Williams & Wilkins