The dangers of radiation exposure to patients and operating room staff are well-publicised. With the advent of minimally invasive spine surgery, both patient and operating room staff may undergo more radiation exposure to satisfy increased intraoperative imaging demands. According to research by Timothy Wang and others published in Spine, ultra-low radiation imaging enhanced by software could reduce the exposure of operating room staff to radiation by over 75% in comparison to using standard C-arm fluoroscopy.
LessRay image-enhancement software (Nuvasive, formally sold by SafeRay Spine) is designed to allow surgeons to reduce their reliance on radiation-releasing imaging during procedures. The technology uses “high-quality, full-dose preoperative baseline fluoroscopic images to form a composite image of the relevant spinal levels.” By recording “the spatial relationship between the anatomy and C-arm fluoroscope,” the system can provide a live viewfinder during surgery, enabling C-arm technicians to use less imaging for relocalisation.
“Subsequent low-quality ultra-low radiation images can then be mapped onto the preoperative high-quality baseline images,” the authors write. This allows for the visualisation of surgical instruments, and renders low-radiation images high enough quality for intraoperative use.
This IRB-approved, prospective, randomised single-surgeon trial catalogued the total radiation output and particular exposure to each member of staff during 24 minimally invasive transforaminal interbody fusion operations. Procedures were split into five intervals (“zero: presurgical baseline imaging and pedicle marking, one: left-sided pedicle cannulation and K-wire placement, two: right-sided pedicle cannulation and K-wire placement, three: bilateral pedicle screw placement and four: interbody graft placement). Half of the patients underwent standard-dose imaging during intervals zero, two and three (with ultra-low radiation imaging in intervals one and three), with the other half undergoing ultra-low radiation in intervals two and four.
Comparing the overall radiation dose for each interval, researchers found a decrease of 73.87% (39.15mGy vs. 10.23mGy) during intervals one and two when performed using the ultra-low imaging system. Similarly, interval three resulted in an 89.3% (39.76mGy vs 4.26mGy) reduction in radiation exposure for the ultra-low system, with interval 4 showing a 56.7% decrease (24.76mGy vs. 10.71mGy). Based on their results, the authors projected a total decrease of 75.5% in radiation exposure for a single-level MIS TLIF procedure when performed using ultra-low radiation imaging as opposed to standard C-arm fluoroscopy.
In terms of individual operating room staff, the greatest decreased cumulative radiation exposure was experienced by the surgeon, who was exposed to 83.5% less radiation overall when using ultra-low-radiation imaging (6.61mrem vs. 1.09mrem). The authors did not find any statistical difference in operative time across the procedures, and reported no complications related to imaging in any of the procedures.
While acknowledging that this research is limited by the relatively low number of procedures in the series (24), the authors state that, in spite of this, “the results are overwhelmingly demonstrative of significant reduction in radiation exposure.” They recommend that future research compares this technology with modalities such as navigation-assisted fluoroscopic imaging.
The authors state that this use of ultra-low radiation imaging shows that “radiation settings well lower than any prior published series can be utilised with resultant decrease in radiation exposure to all parties in the operating room suite.” Given the health risks associated with radiation exposure, they conclude that “computer-assisted image enhancement, coupled with wise use of ALARA (as low as reasonably achievable) should be considered during minimally invasive spinal fusion.
Commenting on the importance of the work, Wang told Spinal News International, “Our research demonstrates significant radiation reduction using ultra low radiation imaging protocols coupled with image enhancement software, without loss of quality. It is a significant step in improving the safety profile of increasingly popular minimally invasive approaches to the spine.”