In this study, we systematically evaluated the reduction effect of radiation exposure sustained by the medical staff using protection equipment during fluoroscopic guided spinal procedures. We revealed concrete real exposure doses for each part of the surgeon, assistant surgeon, scrub nurse, and anesthesiologist with and without protection. The main results in this study are 1) the occupational exposure doses resulting from C-arm fluoroscopy at the under table are very low with appropriate protection, 2) the doses of surgeon’s optic lens and hand at the over table and lateral position are relatively still high even with appropriate protection though each protection seems to be effective.
Many previous studies demonstrated that the greater the distance the medical staff is from the X-ray source, the lower the radiation exposure to the medical staff. However, spine surgeons have difficulty to take enough distance from the irradiation field because they normally must stand beside the trunk of the patient during their spinal procedure[8]. Another important factor influencing exposure dose is the location of the radiation source. The level of occupational exposure dose also varies greatly depending on the location of the radiation source. There was much scatter radiation exposure to each part of the medical staff when the X-ray source was positioned over the table and laterally[9]. In this study, the exposure doses for the surgeon’s optic lens, thyroid gland, hand, and chest in lateral position were nearly 30 times higher compared with those of the under table (Table 2, 3).
When the radiation source is under the table, the patient's torso itself shields the medical staff, thus the occupational exposure is low except for the surgeon's hands and gonads. If the surgeon is properly protected, the occupational exposure for the surgeon's hands and gonads would be reduced to the acceptable level. The hands were exposed to 20 µSv in 3 minutes even with shielding (Table 2). This is not perfect, but it does not appear to exceed the annual permissible dose[10].
When the radiation source is over the table, radiation exposure to the surgeon's upper body, i.e., optic lens, thyroid gland, and hand, is high (Table 2). Furthermore, the radiation exposure to the source side was even higher during lateral fluoroscopy (Table 3). As for the shielding effect during lateral fluoroscopy, the radiation dose to all parts of the body except the hand was significantly reduced (Table 3). The Optic lens and hand were reduced by about half, but still relatively high. Calculated from the result of this study, the exposure dose of a surgeon’s optic lens without shielding when the X-ray source was positioned laterally was 73.7 µSv in 3 minutes, so it takes 833 minutes to reach the dose safety limit for the optic lens of one year. Similarly, it takes 1063 minutes to reach the dose limit for the hand of the year. This means that increasing the number of surgeries may exceed the dose limit. With proper shielding, it takes 1818 minutes and 1945 minutes, respectively, to reach the lens and hand dose safety limits.
Because scrub nurses and anesthesiologists are well away from the irradiation field, occupational exposure is low even without shielding in any radiation source positions. However, shielding is desirable to minimize stochastic effects such as cancer because the radiation dose is not completely zero[10][11]. Adverse events such as carcinogenesis and genetic abnormalities are considered stochastic effects without threshold, and efforts must be made to minimize radiation exposure as much as possible to prevent these harmful events.
This study had some limitations. First, in the current study, the occupational radiation exposure to each part of the medical staff using protection equipment was only the scatter radiation exposure not including direct exposure. Sometimes spine surgeons see their hand in the fluoroscopic monitor in spinal surgery, and the direct radiation exposure to the hand is much higher than that of scatter radiation exposure. Second, only one piece of protective equipment was used to investigate for each part. A comparative study of the effectiveness of other types of protective equipment for the eye and hand in reducing radiation exposure is needed. Despite these limitations, this is the first study to provide initial accurate radiation exposure data with appropriate protection in a simulated spinal surgical procedure with the X-ray source in different positions.
In conclusion, this study demonstrated that the effectiveness of the protective equipment in reducing occupational radiation exposure during spine surgery was generally satisfactory. In particular, shielding is essential when the radiation source is over the table or lateral position because the scattered radiation to the surgeon becomes large. However, wearing protective equipment does not necessarily mean that radiation exposure is completely eliminated. When the radiation source is over the table or lateral position, protective equipment which have a higher lead dose or additional protection techniques should be used to protect the hands and eyes.