Utilization of Magnetic Resonance Imaging-based Synthetic Computed Tomography for Pedicle Screw Navigation in...

Pedicle screw instrumentation using a fluoroscopy-assisted freehand technique (FAFT) or using navigation based on a preoperative traditional computed tomography (tCT) scan is a common practice. However, concerns remain regarding the long-term effects of repeated ionizing radiation exposure. In 2025, the first pediatric patients in the USA underwent navigated posterior spinal fusions (PSFs) using magnetic resonance imaging (MRI) converted to CT scan-like quality, known as synthetic CT (sCT). The purpose of this study is to report on the clinical, radiographic, and complication outcomes of this cohort and compare radiation exposure between sCT, tCT, and FAFT modalities.

Twenty patients received PSFs using sCT imaging and machine-vision image-guided surgical (MvIGS) navigation. Fluoroscopy was used in sCT cases to confirm the location of T12 and for small adjustments in alignment after rod insertion. To compare radiation exposure, the patients who received sCT were compared with a matched cohort of 135 patients receiving PSFs using the FAFT and 27 patients receiving PSFs using tCT imaging paired with MvIGS navigation. Radiation exposure was measured in mGy. Pedicle morphologies were measured and classified according to Sarwahi et al.

Twelve patients (63%) who received sCT had an idiopathic diagnosis. Mean age at surgery was 13.6 ± 4 years. Across 335 pedicles instrumented, 13% were type C or D in morphology. The mean radiation exposure to the 27 patients receiving a preoperative tCT scan combined with routine intraoperative fluoroscopy was 5.44 mGy. For the 20 sCT cases, the mean radiation exposure was 0.90 mGy, reflecting an 83.5% reduction in radiation (P = .001). In comparison, 3 surgeons utilized FAFT during PSFs, producing a mean radiation dose of 7 mGy. Thus, navigated sCT cases resulted in an 87.1% reduction in radiation exposure in comparison to FAFT cases (P < .001). Within the sCT cohort, there were no intraoperative neuromonitoring (IONM) changes, cerebrospinal fluid (CSF) leaks, or postoperative neurologic deficits.

Navigated PSFs utilizing sCTs paired with MvIGS navigation allow for instrumentation of small pedicles with an 83.5% reduction in radiation compared with tCTs and an 87.1% reduction in radiation compared with FAFT cases.

(1)In this study, synthetic CTs are created by taking MRIs and converting this imaging into CT-scan-like quality using a proprietary, artificial intelligence mediated algorithm.(2)Synthetic CTs, paired with MvIGS navigation, were used to navigate pedicle screws in idiopathic, syndromic, congenital, and neuromuscular scoliosis diagnoses.(3)Difficult type C and D pedicles were instrumented using MvIGS navigation based on sCT imaging.(4)There is an 83.5% reduction in radiation exposure to the patient for MvIGS navigation cases using synthetic CTs compared with MvIGS navigation cases using traditional CTs.(5)In comparison to patients receiving PSFs using a fluoroscopy-assisted freehand technique, MvIGS navigation cases using synthetic CTs resulted in an 87% reduction in radiation exposure for both the surgeon and the patient.

III, Retrospective Cohort Study.