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Low-Dose Radiation 3D Intraoperative Imaging: How Low Can We Go? An O-Arm, CT Scan, Cadaveric Study
Vishal Sarwahi1, Monica Payares2, Stephen Wendolowski1
1Department of Pediatric Orthopedics, Cohen Children's Medical Center, Northwell Health System, New Hyde Park, NY.
Abstract:
MINI: The objective of this study was to evaluate the accuracy and reliability of pedicle screw placement using O-Arm at dosages below the manufactured recommended dose. O-Arm at reduced dose showed a 90% accuracy when compared with computed tomography; however, about 30% medial breaches were misclassified.
Study Design:
Cadaveric study.
Objective:
The objective was to evaluate O-Arm's ability at low-dose (LD) settings to assess intraoperative screw placement.
Summary Of Background Data:
Accurate placement of pedicle screws is crucial because of proximity to vital structures. Malposition of screws may result in significant morbidity and potential mortality. O-arm provides real-time, intraoperative imaging of patient's anatomy and provides higher accuracy in scoliosis surgeries, avoiding risk to vital structures. We hypothesize using LD or ultra-low doses (ULDs) to obtain intraoperative images allow for accurate assessment of screw placement, both minimizing radiation exposure and preventing screw misplacement.
Methods:
Eight cadavers were instrumented with pedicle screws bilaterally from T1 to S1. Screws were randomly placed using O-arm navigation into three positions: contained within the bone, OUT-anterior/lateral, and OUT-medial. O-arm images were obtained at three dosage settings: LD (kVp120/mAs125-lowest manufacturer recommended), very-low dose (VLD) (kVp120/mAs63), and ULD (kVp120/mAs39). Computed tomography (CT) scan was performed using institution's LD protocol (kVp100/mAs50) and gross dissection to identify screw positions.
Results:
LD, VLD, ULD, and CT for identifying "IN" screws relative to gross dissection had, a mean (standard deviation) sensitivity of 84.2% (±5.7), specificity of 76.1% (±9.3), and accuracy of 79.9% (±3.1) from all three observers. Across the three observers, the interobserver agreement was 0.67 (0.61-0.72) for LD, 0.74 (0.69-0.79) for VLD, 0.61 (0.56-0.66) for ULD, and 0.79 (0.74-0.84) for CT. Effective doses of radiation (mSV) for LD O-arm scan was 2.16, VLD 1.08, ULD 0.68, and our LD CT protocol was 1.05.
Conclusion:
Accuracy of pedicle screw placement is similar for O-arm at all doses and CT compared to gross dissection. Interobserver reliability was substantial for VLD and CT. Approximately 30% of medial screw breaches are, however, misclassified. ULD and VLDs can be used for intraoperative navigation and evaluation purposes within these limitations.
Level Of Evidence:
N/A.
Insights
Low-dose O-arm imaging accurately assesses pedicle screw placement, comparable to CT scans. However, medial breaches may be misclassified, requiring careful interpretation of ultra-low dose images.
Area of Science:
- Spinal Surgery
- Medical Imaging
- Radiation Safety
Background:
- Accurate pedicle screw placement is critical in spinal surgery to prevent neurological damage and improve outcomes.
- O-arm technology offers real-time intraoperative imaging, enhancing surgical precision and safety.
- Reducing radiation exposure during intraoperative imaging is a key goal in minimizing patient risk.
Purpose of the Study:
- To evaluate the accuracy and reliability of O-arm imaging for pedicle screw placement at reduced radiation doses.
- To compare the diagnostic performance of low-dose (LD), very-low dose (VLD), and ultra-low dose (ULD) O-arm settings against computed tomography (CT) and gross dissection.
Main Methods:
- A cadaveric study involving bilateral pedicle screw instrumentation from T1 to S1.
- O-arm imaging was performed at LD, VLD, and ULD settings, with CT scans and gross dissection serving as references.
- Screw positions were categorized as within bone, anterior/lateral breach, or medial breach.
Main Results:
- O-arm imaging at all tested doses demonstrated comparable accuracy to CT in identifying pedicle screws, with overall accuracy around 80%.
- Interobserver agreement was substantial for VLD and CT, indicating good reliability in image interpretation.
- A significant finding was the misclassification of approximately 30% of medial screw breaches across O-arm dose settings.
Conclusions:
- O-arm imaging at reduced radiation doses (LD, VLD, ULD) is a viable tool for assessing pedicle screw placement accuracy, similar to CT.
- VLD and ULD settings offer a balance between radiation reduction and diagnostic utility for intraoperative navigation.
- Clinicians must be aware of the potential for misclassifying medial breaches, necessitating careful review of O-arm images.
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