Estimation of patient dose and associated radiogenic risks from fluoroscopically guided pedicle screw insertion

Study Design. An experimental model for the assessment of patient dose and associated radiogenic risks associated with pedicle screw internal fixation surgical procedures. Objectives. To provide data for the accurate determination of patient effective dose, gonadal dose, and entrance skin dose from fluoroscopically assisted pedicle screw insertion procedures and to investigate the potential of both stochastic and deterministic radiogenic effects to occur following such procedures. Summary of Background Data. There is increased concern on radiation exposure of patients undergoing fluoroscopically guided interventional procedures. Methods. The cumulative screening time and dose area product, for each fluoroscopic projection used, were monitored in 20 patients undergoing pedicle screw internal fixation. The dose absorbed by each radiosensitive organ/tissue was determined from direct measurements obtained using an anthropomorphic phantom appropriately loaded with thermoluminescence dosimeters. Results. An average pedicle screw insertion procedure requires 1.2 minutes and 2.1 minutes of fluoroscopic exposure along anteroposterior and lateral projections, respectively, resulting in a dose area product of 232 cGy cm(2) and 568 cGy cm(2), correspondingly. Gender-specific normalized data for the determination of effective, gonadal, and entrance skin dose to patients undergoing fluoroscopically guided pedicle screw internal fixation procedures were derived. The effective dose from an average procedure was 1.52 and 1.40 mSv and the gonadal dose 0.67 and 0.12 mGy for female and male patients, respectively. The average radiogenic risks for fatal cancer and genetic defects were 115 and 4 per million of patients treated, respectively. Induction of skin injuries might be induced when fluoroscopy along the lateral projection is highly extended and the source to skin distance is kept low. Conclusions. Patient dose and radiogenic risks associated with an average pedicle screw internal fixation procedure are tolerable. However, for young patients with complex spinal disorders requiring extended fluoroscopy, radiogenic risks may be considerable. Present data may be used for estimation of effective dose, gonadal dose, and entrance skin exposure and associated radiogenic risks to patients undergoing fluoroscopically guided pedicle screw insertion in any institution.