Radiation dose for pedicle screw insertion - Fluoroscopic method versus computer-assisted surgery

Study Design. Comparison of the radiation dose between the traditional fluo roscopic approach and computed tomography (CT)-based computer-assisted surg ery for pedicle screw placement was determined. Objectives. To evaluate the radiation dose delivered by fluoroscopy-control led pedicle screw placement versus insertion guided by computer. To define the CT computer-assisted protocol, involving lower radiation exposure for t he patient, that still provides acceptable image quality. Summary of Background Data. There are no published data describing the dose delivered in CT-based image-guided surgery, and there are few studies in w hich the;;organ dose and the effective dose delivered during pedicle screw insertion that is performed traditionally with fluoroscopic control are des cribed. Methods. Dose measurements were performed on two types (REMAB and RANDO) of anthropomorphic phantoms. Thermoluminescent dosimeters were used to measur e the organ dose. Both phantoms were exposed to the fluoroscopic x-ray beam . The representative intraoperative scenario was determined by observation of 20 consecutive surgical interventions featuring pedicle screw implantati on. For the CT dose measurement only, the REMAB phantom was used with two t ypes of CT scanners. Three scanning protocols were evaluated: sequential, s piral optimized, and sequential optimized. Optimization of the scanning pro tocol included changes of anode current. The CT images were subsequently pr ocessed to achieve three-dimensional reconstruction of the lumbar spine for the computer-assisted intervention. Results. Organ and effective doses were higher in any of the CT examination s than in the fluoroscopic procedure. There was a slight difference between doses registered during optimized spiral scanning and doses in the calcula ted optimized sequential CT protocol. Optimized sequential scanning was ass ociated with an effective dose 40% lower than that in nonoptimized sequenti al scanning. The small anatomic structures of the spine could be easily rec ognized on each of the three-dimensional reconstructions, and all of them w ere suitable for use in computer-assisted surgery. Conclusions. Percutaneous pedicle screw insertion in the lumbar region of t he spine, performed using fluoroscopic control, requires a lower radiation dose than do CT scans necessary for computer-assisted surgery. The CT radia tion dose can be significantly decreased by optimization of the scanner set tings for computer-assisted surgery. The advantages of computer-assisted su rgery justify CT scans, when based on correctly chosen indications.